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Cui X, Tang M, Zhu T. A water probe for direct pH measurement of individual particles via micro-Raman spectroscopy. J Environ Sci (China) 2025; 149:200-208. [PMID: 39181634 DOI: 10.1016/j.jes.2023.10.037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 10/26/2023] [Accepted: 10/26/2023] [Indexed: 08/27/2024]
Abstract
The acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health. We recently developed a novel and facile water-probe-based method for directly measuring of the pH for micrometer-size droplets, providing a promising technique to better understand aerosol acidity in the atmosphere. The complex chemical composition of fine particles in the ambient air, however, poses certain challenges to using a water-probe for pH measurement, including interference from interactions between compositions and the influence of similar compositions on water structure. To explore the universality of our method, it was employed to measure the pH of ammonium, nitrate, carbonate, sulfate, and chloride particles. The pH of particles covering a broad range (0-14) were accurately determined, thereby demonstrating that our method can be generally applied, even to alkaline particles. Furthermore, a standard spectral library was developed by integrating the standard spectra of common hydrated ions extracted through the water-probe. The library can be employed to identify particle composition and overcome the spectral overlap problem resulting from similar effects. Using the spectral library, all ions were identified and their concentrations were determined, in turn allowing successful pH measurement of multicomponent (ammonium-sulfate-nitrate-chloride) particles. Insights into the synergistic effect of Cl-, NO3-, and NH4+ depletion obtained with our approach revealed the interplay between pH and volatile partitioning. Given the ubiquity of component partitioning and pH variation in particles, the water probe may provide a new perspective on the underlying mechanisms of aerosol aging and aerosol-cloud interaction.
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Affiliation(s)
- Xiaoyu Cui
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China; BIC-ESAT and SKL-ESPC, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Mingjin Tang
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Tong Zhu
- BIC-ESAT and SKL-ESPC, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
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2
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Song W, Guo S, Li H. Size-dependent acidity of aqueous nano-aerosols. Phys Chem Chem Phys 2024. [PMID: 39189057 DOI: 10.1039/d4cp01752h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/28/2024]
Abstract
Understanding the accurate acidity of nano-aerosols is important for the research on atmospheric chemistry. Herein, we propose the contributions from both the aerosol size and multiphase buffer effect to the steady-state acidity of nano-aerosols at a constant aerosol water content (AWC) through molecular simulations. As increasing of the aerosol size, the solvation free energy (SFE, ΔGs) became more negative (decreasing by 3-130 kcal mol-1 for different types of species) and Henry's law constant (H) apparently increased (from e6 to e16 mol m-3 Pa-1) in the nano-aerosols compared to that in bulk solutions. The lower SFE led to lower solute pKa and pKb values; thus, the acidity of HSO4- and HNO3 and the alkalinity of NH3 showed positive relations with the aerosol size. The lower H also increased the pKa of gaseous solutes, leading to a decrease in the acidity of HNO3 and a shift from alkaline to acidic for the NH4+/NH3 buffer pair in the nano-aerosols. The present study revealed the relationship between aerosol acidity and solvent size from a microscopic perspective. Specifically, the acidity of aerosols containing HSO4-/SO42- and HNO3/NO3- decreased with an increase in their radii, whereas aerosols containing NH4+/NH3 exhibited an opposite trend. This phenomenon can be attributed to the disappearance of the interfacial effect with an increase in the size of the aerosols. The above conclusions are of great significance for studying the pH-dependent multi-phase chemical processes in aerosols.
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Affiliation(s)
- Wanrong Song
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
| | - Shaoxun Guo
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
| | - Hui Li
- Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
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3
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Wilson KR, Prophet AM. Chemical Kinetics in Microdroplets. Annu Rev Phys Chem 2024; 75:185-208. [PMID: 38382571 DOI: 10.1146/annurev-physchem-052623-120718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Micrometer-sized compartments play significant roles in driving heterogeneous transformations within atmospheric and biochemical systems as well as providing vehicles for drug delivery and novel reaction environments for the synthesis of industrial chemicals. Many reports now indicate that reaction kinetics are accelerated under microconfinement, for example, in sprays, thin films, droplets, aerosols, and emulsions. These observations are dramatic, posing a challenge to our understanding of chemical reaction mechanisms with potentially significant practical consequences for predicting the complex chemistry in natural systems. Here we introduce the idea of kinetic confinement, which is intended to provide a conceptual backdrop for understanding when and why microdroplet reaction kinetics differ from their macroscale analogs.
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Affiliation(s)
- Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA;
| | - Alexander M Prophet
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA;
- Department of Chemistry, University of California, Berkeley, California, USA;
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4
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Yoo H, Seo D, Shin D, Ro CU. Direct Observation of Particle-To-Particle Variability in Ambient Aerosol pH Using a Novel Analytical Approach Based on Surface-Enhanced Raman Spectroscopy. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:7977-7985. [PMID: 38664901 DOI: 10.1021/acs.est.4c00220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
The pH of atmospheric aerosols is a key characteristic that profoundly influences their impacts on climate change, human health, and ecosystems. Despite widely performed aerosol pH research, determining the pH levels of individual atmospheric aerosol particles has been a challenge. This study presents a novel analytical technique that utilizes surface-enhanced Raman spectroscopy to assess the pH of individual ambient PM2.5-10 aerosol particles in conjunction with examining their hygroscopic behavior, morphology, and elemental compositions. The results revealed a substantial pH variation among simultaneously collected aerosol particles, ranging from 3.3 to 5.7. This variability is likely related to each particle's unique reaction and aging states. The extensive particle-to-particle pH variability suggests that atmospheric aerosols present at the same time and location can exhibit diverse reactivities, reaction pathways, phase equilibria, and phase separation properties. This pioneering study paves the way for in-depth investigations into particle-to-particle variability, size dependency, and detailed spatial and temporal variations of aerosol pH, thus deepening our understanding of atmospheric chemistry and its environmental implications.
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Affiliation(s)
- Hanjin Yoo
- Department of Chemistry, Inha University, Incheon 22212, Republic of Korea
- Particle Pollution Management Center, Inha University, Incheon 21999, Republic of Korea
| | - Dongkwon Seo
- Department of Chemistry, Inha University, Incheon 22212, Republic of Korea
| | - Dongha Shin
- Department of Chemistry, Inha University, Incheon 22212, Republic of Korea
| | - Chul-Un Ro
- Department of Chemistry, Inha University, Incheon 22212, Republic of Korea
- Particle Pollution Management Center, Inha University, Incheon 21999, Republic of Korea
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5
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Devlin SW, Bernal F, Riffe EJ, Wilson KR, Saykally RJ. Spiers Memorial Lecture: Water at interfaces. Faraday Discuss 2024; 249:9-37. [PMID: 37795954 DOI: 10.1039/d3fd00147d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
In this article we discuss current issues in the context of the four chosen subtopics for the meeting: dynamics and nano-rheology of interfacial water, electrified/charged aqueous interfaces, ice interfaces, and soft matter/water interfaces. We emphasize current advances in both theory and experiment, as well as important practical manifestations and areas of unresolved controversy.
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Affiliation(s)
- Shane W Devlin
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Franky Bernal
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Erika J Riffe
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Richard J Saykally
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
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6
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Wu G, Wang H, Zhang C, Gong D, Liu X, Ristovski Z, Wang B. Anthropogenic pollutants induce enhancement of aerosol acidity at a mountainous background atmosphere in southern China. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 903:166192. [PMID: 37567283 DOI: 10.1016/j.scitotenv.2023.166192] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Revised: 08/08/2023] [Accepted: 08/08/2023] [Indexed: 08/13/2023]
Abstract
Aerosol acidity plays a crucial role in atmospheric physicochemical processes, climate change and human health, particularly in the formation of secondary organic aerosols (SOA). However, understanding the characteristics and driving factors of aerosol acidity in background mountains has been limited. In this study, we conducted intensive field measurements in the Nanling mountains during the dry and wet seasons to analyze aerosol pH characteristics and their driving factors using sensitivity tests. The mean aerosol pH in the background mountains was found to be 2.68 ± 0.55, with values ranging from 0.38 to 4.44, significantly lower than predicted values in northern China. Sensitivity tests revealed that aerosol acidity in the background atmosphere was more responsive to dominant chemical species (T-NH3 (= NH4+ + NH3) and SO42-) rather than relative humidity and temperature. Additionally, we observed that sulfate and ammonium, transported occasionally by dryer northern air masses, had a substantial impact on decreasing aerosol pH at the site. Similar to the southeastern United States, NH4+/NH3 also dominated the total buffer capacity of aerosol acidity in the Nanling mountains. The strong aerosol acidity in this area is expected to have adverse effects on regional air quality and climate by enhancing SOA formation and regulating the dry deposition of inorganic reactive nitrogen.
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Affiliation(s)
- Gengchen Wu
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China; Guangdong Provincial Observation and Research Station for Atmospheric Environment and Carbon Neutrality in Nanling Forests, China
| | - Hao Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China; Guangdong Provincial Observation and Research Station for Atmospheric Environment and Carbon Neutrality in Nanling Forests, China; JNU-QUT Joint Laboratory for Air Quality Science and Management, Jinan University, Guangzhou 511443, China.
| | - Chengliang Zhang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China; Guangdong Provincial Observation and Research Station for Atmospheric Environment and Carbon Neutrality in Nanling Forests, China
| | - Daocheng Gong
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China; Guangdong Provincial Observation and Research Station for Atmospheric Environment and Carbon Neutrality in Nanling Forests, China
| | - Xiaoting Liu
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China; Department of Ophthalmology, The First Affiliated Hospital, Jinan University, Guangzhou, China; JNU-QUT Joint Laboratory for Air Quality Science and Management, Jinan University, Guangzhou 511443, China
| | - Zoran Ristovski
- JNU-QUT Joint Laboratory for Air Quality Science and Management, Jinan University, Guangzhou 511443, China; International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane 4001, Australia
| | - Boguang Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China; Guangdong Provincial Observation and Research Station for Atmospheric Environment and Carbon Neutrality in Nanling Forests, China; JNU-QUT Joint Laboratory for Air Quality Science and Management, Jinan University, Guangzhou 511443, China.
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7
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Wallace BJ, Mongeau ML, Zuend A, Preston TC. Impact of pH on Gas-Particle Partitioning of Semi-Volatile Organics in Multicomponent Aerosol. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:16974-16988. [PMID: 37885068 DOI: 10.1021/acs.est.3c02894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
The partitioning of semivolatile organic compounds (SVOCs) between the condensed and gas phases can have significant implications for the properties of aerosol particles. In addition to affecting size and composition, this partitioning can alter radiative properties and impact cloud activation processes. We present measurements and model predictions on how activity and pH influence the evaporation of SVOCs from particles to the gas phase, specifically investigating aqueous inorganic particles containing dicarboxylic acids (DCAs). The aerosols are studied at the single-particle level by using optical trapping and cavity-enhanced Raman spectroscopy. Optical resonances in the spectra enable precise size tracking, while vibrational bands allow real-time monitoring of pH. Results are compared to a Maxwell-type model that accounts for volatile and nonvolatile solutes in aqueous droplets that are held at a constant relative humidity. The aerosol inorganic-organic mixture functional group activity coefficients thermodynamic model and Debye-Hückel theory are both used to calculate the activities of the species present in the droplet. For DCAs, we find that the evaporation rate is highly sensitive to the particle pH. For acidity changes of approximately 1.5 pH units, we observe a shift from a volatile system to one that is completely nonvolatile. We also observe that the pH itself is not constant during evaporation; it increases as DCAs evaporate, slowing the rate of evaporation until it eventually ceases. Whether a DCA evaporates or remains a stable component of the droplet is determined by the difference between the lowest pKa of the DCA and the pH of the droplet.
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Affiliation(s)
- Brandon J Wallace
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Michel Laforest Mongeau
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Andreas Zuend
- Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, Canada H3A 0B9
| | - Thomas C Preston
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
- Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, Canada H3A 0B9
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8
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Bustos NA, Ribbeck K, Wagner CE. The role of mucosal barriers in disease progression and transmission. Adv Drug Deliv Rev 2023; 200:115008. [PMID: 37442240 DOI: 10.1016/j.addr.2023.115008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 05/22/2023] [Accepted: 07/10/2023] [Indexed: 07/15/2023]
Abstract
Mucus is a biological hydrogel that coats and protects all non-keratinized wet epithelial surfaces. Mucins, the primary structural components of mucus, are critical components of the gel layer that protect against invading pathogens. For communicable diseases, pathogen-mucin interactions contribute to the pathogen's fate and the potential for disease progression in-host, as well as the potential for onward transmission. We begin by reviewing in-host mucus filtering mechanisms, including size filtering and interaction filtering, which regulate the permeability of mucus barriers to all molecules including pathogens. Next, we discuss the role of mucins in communicable diseases at the point of transmission (i.e. how the encapsulation of pathogens in emitted mucosal droplets externally to hosts may modulate pathogen infectivity and viability). Overall, mucosal barriers modulate both host susceptibility as well as the dynamics of population-level disease transmission. The study of mucins and their use in models and experimental systems are therefore crucial for understanding the mechanistic biophysical principles underlying disease transmission and the early stages of host infection.
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Affiliation(s)
- Nicole A Bustos
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Katharina Ribbeck
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Caroline E Wagner
- Department of Bioengineering, McGill University, Montreal, Quebec, Canada.
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9
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Tong YK, Ye A. Liquid-Liquid Phase Separation in Single Suspended Aerosol Microdroplets. Anal Chem 2023; 95:12200-12208. [PMID: 37556845 DOI: 10.1021/acs.analchem.2c05605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/11/2023]
Abstract
Liquid-liquid phase separation (LLPS) is ubiquitous in ambient aerosols. This specific morphology exerts substantial impacts on the physicochemical properties and atmospheric processes of aerosols, particularly on the gas-particle mass transfer, the interfacial heterogeneous reaction, and the surface albedo. Although there are many studies on the LLPS of aerosols, a clear picture of LLPS in individual aerosols is scarce due to the experimental difficulties of trapping a single particle and mimicking the suspended state of real aerosols. Here, we investigate the phase separation in individual contactless microdroplets by a self-constructed laser tweezer/Raman spectroscopy system. The dynamic transformation of the morphology of optically trapped droplets over the course of humidity cycles is detected by the time-resolved cavity-enhanced Raman spectra. The impacts of pH and inorganic components on LLPS in aerosols are discussed. The results show that the increasing acidity can enhance the miscibility between the hydrophilic and hydrophobic phases and decrease the separation relative humidity of aerosols. Moreover, the inorganic components also have various impacts on the aerosol phase state, whose influence depends on their different salting-out capabilities. It brings possible implications on the morphology of actual atmospheric particles, particularly for those dominated by internal mixtures of inorganic and organic components.
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Affiliation(s)
- Yu-Kai Tong
- Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China
| | - Anpei Ye
- Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China
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10
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Acharja P, Ghude SD, Sinha B, Barth M, Govardhan G, Kulkarni R, Sinha V, Kumar R, Ali K, Gultepe I, Petit JE, Rajeevan MN. Thermodynamical framework for effective mitigation of high aerosol loading in the Indo-Gangetic Plain during winter. Sci Rep 2023; 13:13667. [PMID: 37608151 PMCID: PMC10444748 DOI: 10.1038/s41598-023-40657-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 08/16/2023] [Indexed: 08/24/2023] Open
Abstract
The Indo-Gangetic Plain (IGP) experiences severe air pollution every winter, with ammonium chloride and ammonium nitrate as the major inorganic fractions of fine aerosols. Many past attempts to tackle air pollution in the IGP were inadequate, as they targeted a subset of the primary pollutants in an environment where the majority of the particulate matter burden is secondary in nature. Here, we provide new mechanistic insight into aerosol mitigation by integrating the ISORROPIA-II thermodynamical model with high-resolution simultaneous measurements of precursor gases and aerosols. A mathematical framework is explored to investigate the complex interaction between hydrochloric acid (HCl), nitrogen oxides (NOx), ammonia (NH3), and aerosol liquid water content (ALWC). Aerosol acidity (pH) and ALWC emerge as governing factors that modulate the gas-to-particle phase partitioning and mass loading of fine aerosols. Six "sensitivity regimes" were defined, where PM1 and PM2.5 fall in the "HCl and HNO3 sensitive regime", emphasizing that HCl and HNO3 reductions would be the most effective pathway for aerosol mitigation in the IGP, which is ammonia-rich during winter. This study provides evidence that precursor abatement for aerosol mitigation should not be based on their descending mass concentrations but instead on their sensitivity to high aerosol loading.
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Affiliation(s)
- Prodip Acharja
- Indian Institute of Tropical Meteorology, Ministry of Earth Sciences, Pune, India
- Laboratoire des Sciences du Climat et de l'Environnement, LSCE, CNRS, Gif-sur-Yvette, France
| | - Sachin D Ghude
- Indian Institute of Tropical Meteorology, Ministry of Earth Sciences, Pune, India.
| | - Baerbel Sinha
- Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sahibzada Ajit Singh Nagar, Punjab, India.
| | - Mary Barth
- National Center for Atmospheric Research, Boulder, CO, 80307, USA
| | - Gaurav Govardhan
- Indian Institute of Tropical Meteorology, Ministry of Earth Sciences, Pune, India
| | | | - Vinayak Sinha
- Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sahibzada Ajit Singh Nagar, Punjab, India
| | - Rajesh Kumar
- National Center for Atmospheric Research, Boulder, CO, 80307, USA
| | - Kaushar Ali
- Indian Institute of Tropical Meteorology, Ministry of Earth Sciences, Pune, India
| | - Ismail Gultepe
- Engineering and Applied Science, Ontario Technical University, Oshawa, ON, Canada
- Civil and Environment Eng and Earth Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Jean-Eudes Petit
- Laboratoire des Sciences du Climat et de l'Environnement, LSCE, CNRS, Gif-sur-Yvette, France
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11
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Wei Y, Nenes A, Gao J, Liang W, Liang D, Shi G, Feng Y, Russell AG. Abundant nitrogen oxide and weakly acidic environment synergistically promote daytime particulate nitrate pollution. JOURNAL OF HAZARDOUS MATERIALS 2023; 456:131655. [PMID: 37216807 DOI: 10.1016/j.jhazmat.2023.131655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 05/09/2023] [Accepted: 05/15/2023] [Indexed: 05/24/2023]
Abstract
Nitrate is formed through the chemical production of gas-phase nitric acid and subsequent partitioning to the aerosol phase during the daytime. Many studies in the past separated these two aspects, even though they occur simultaneously in the atmosphere. To better understand the nitrate formation mechanism and effectively mitigate its production, it is necessary to consider the synergy between these two mechanisms. For this, we analyze hourly-speciated ambient observations data, with EK&TMA (Empirical Kinetic & Thermodynamic Modeling Approach) map to comprehensively explore the factors controlling nitrate production. Results show that precursor NO2 concentration and aerosol pH, which are related to anthropogenic activities, are the two major factors for chemical kinetics production and gas/particle thermodynamic partitioning processes respectively. Abundant NO2 and weakly acidic environments are favorable conditions for daytime particulate nitrate pollution, thus collaborative control of coal source, vehicle source, and dust source is needed to alleviate nitrate pollution.
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Affiliation(s)
- Yuting Wei
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control, Tianjin Key Laboratory of Urban Transport Emission Research, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China; CMA-NKU Cooperative Laboratory for Atmospheric Environment-Health Research (CLAER), College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Athanasios Nenes
- Laboratory of Atmospheric Processes and their Impacts, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland; Center for the Study of Air Quality and Climate Change, Institute of Chemical Engineering Sciences, Foundation for Research and Technology Hellas, Patras GR-26504, Greece
| | - Jie Gao
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control, Tianjin Key Laboratory of Urban Transport Emission Research, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China; CMA-NKU Cooperative Laboratory for Atmospheric Environment-Health Research (CLAER), College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Weiqing Liang
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control, Tianjin Key Laboratory of Urban Transport Emission Research, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China; CMA-NKU Cooperative Laboratory for Atmospheric Environment-Health Research (CLAER), College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Danni Liang
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control, Tianjin Key Laboratory of Urban Transport Emission Research, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China; CMA-NKU Cooperative Laboratory for Atmospheric Environment-Health Research (CLAER), College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Guoliang Shi
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control, Tianjin Key Laboratory of Urban Transport Emission Research, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China; CMA-NKU Cooperative Laboratory for Atmospheric Environment-Health Research (CLAER), College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China.
| | - Yinchang Feng
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control, Tianjin Key Laboratory of Urban Transport Emission Research, College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China; CMA-NKU Cooperative Laboratory for Atmospheric Environment-Health Research (CLAER), College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Armistead G Russell
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
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12
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Li M, Kan Y, Su H, Pöschl U, Parekh SH, Bonn M, Cheng Y. Spatial homogeneity of pH in aerosol microdroplets. Chem 2023. [DOI: 10.1016/j.chempr.2023.02.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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13
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Estefany C, Sun Z, Hong Z, Du J. Raman spectroscopy for profiling physical and chemical properties of atmospheric aerosol particles: A review. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 249:114405. [PMID: 36508807 DOI: 10.1016/j.ecoenv.2022.114405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 12/05/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
Atmosphere aerosols have significant impact on human health and the environment. Aerosol particles have a number of characteristics that influence their health and environmental effects, including their size, shape, and chemical composition. A great deal of difficulty is associated with quantifying and identifying atmospheric aerosols because these parameters are highly variable on a spatial and temporal scale. An important component of understanding aerosol fate is Raman Spectroscopy (RS), which is capable of resolving chemical compositions of individual particles. This review presented strategic techniques, especially RS methods for characterizing atmospheric aerosols. The nature and properties of atmospheric aerosols and their influence on environment and human health were briefly described. Analytical methodologies that offer insight into the chemistry and multidimensional properties of aerosols were discussed. In addition, perspectives for practical applications of atmospheric aerosols using RS are featured.
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Affiliation(s)
- Cedeño Estefany
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Key Laboratory of Resources and Environmental System Optimization of Ministry of Education, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, China
| | - Zhenli Sun
- Key Laboratory of Resources and Environmental System Optimization of Ministry of Education, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, China
| | - Zijin Hong
- Key Laboratory of Resources and Environmental System Optimization of Ministry of Education, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, China
| | - Jingjing Du
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
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14
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Jing X, Chen Z, Huang Q, Liu P, Zhang YH. Spatiotemporally Resolved pH Measurement in Aerosol Microdroplets Undergoing Chloride Depletion: An Application of In Situ Raman Microspectrometry. Anal Chem 2022; 94:15132-15138. [PMID: 36251492 DOI: 10.1021/acs.analchem.2c03381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Acidity is a defining property of atmospheric aerosols that profoundly affects environmental systems, human health, and climate. However, directly measuring the pH of aerosol microdroplets remains a challenge, especially when the microdroplets' composition is nonhomogeneous or dynamically evolving or both. As a result, a pH measurement technique with high spatiotemporal resolution is needed. Here, we report a spatiotemporally resolved pH measurement technique in microdroplets using spontaneous Raman spectroscopy. Our target sample was the microdroplets comprising sodium chloride and oxalic acid─laboratory surrogates of sea spray aerosols and water-soluble organic compounds, respectively. Our measurements show that the chloride depletion from the microdroplets caused a continuous increase in pH by ∼0.5 units in 2 hours. Meanwhile, the surface propensity of chloride anions triggers a stable pH gradient inside a single droplet, with the pH at the droplet surface lower than that at the core by ∼ 0.4 units. The uncertainties arising from the Raman detection limit (±0.08 pH units) and from the nonideal solution conditions (-0.06 pH units) are constrained. Our findings indicate that spontaneous Raman spectroscopy is a simple yet robust technique for precise pH measurement in aerosols with high spatiotemporal resolution.
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Affiliation(s)
- Xinbo Jing
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing100081, China
| | - Zhe Chen
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing100081, China
| | - Qishen Huang
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing100081, China.,Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania16801, United States
| | - Pai Liu
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing100081, China
| | - Yun-Hong Zhang
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing100081, China
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15
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Milsom A, Squires AM, Quant I, Terrill NJ, Huband S, Woden B, Cabrera-Martinez ER, Pfrang C. Exploring the Nanostructures Accessible to an Organic Surfactant Atmospheric Aerosol Proxy. J Phys Chem A 2022; 126:7331-7341. [PMID: 36169656 PMCID: PMC9574911 DOI: 10.1021/acs.jpca.2c04611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
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The composition of atmospheric aerosols varies with time,
season,
location, and environment. This affects key aerosol properties such
as hygroscopicity and reactivity, influencing the aerosol’s
impact on the climate and air quality. The organic fraction of atmospheric
aerosol emissions often contains surfactant material, such as fatty
acids. These molecules are known to form three-dimensional nanostructures
in contact with water. Different nanostructures have marked differences
in viscosity and diffusivity that are properties whose understanding
is essential when considering an aerosol’s atmospheric impact.
We have explored a range of nanostructures accessible to the organic
surfactant oleic acid (commonly found in cooking emissions), simulating
variation that is likely to happen in the atmosphere. This was achieved
by changing the amount of water, aqueous phase salinity and by addition
of other commonly coemitted compounds: sugars and stearic acid (the
saturated analogue of oleic acid). The nanostructure was observed
by both synchrotron and laboratory small/wide angle X-ray scattering
(SAXS/WAXS) and found to be sensitive to the proxy composition. Additionally,
the spacing between repeat units in these nanostructures was water
content dependent (i.e., an increase from 41 to 54 Å in inverse
hexagonal phase d-spacing when increasing the water
content from 30 to 50 wt %), suggesting incorporation of water within
the nanostructure. A significant decrease in mixture viscosity was
also observed with increasing water content from ∼104 to ∼102 Pa s when increasing the water content
from 30 to 60 wt %. Time-resolved SAXS experiments on levitated droplets
of this proxy confirm the phase changes observed in bulk phase mixtures
and demonstrate that coexistent nanostructures can form in droplets.
Aerosol compositional and subsequent nanostructural changes could
affect aerosol processes, leading to an impact on the climate and
urban air pollution.
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Affiliation(s)
- Adam Milsom
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston B15 2TT, Birmingham, United Kingdom
| | - Adam M Squires
- Department of Chemistry, University of Bath, South Building, Soldier Down Ln, Claverton Down BA2 7AX, Bath, United Kingdom
| | - Isabel Quant
- School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Nicholas J Terrill
- Diamond Light Source, Diamond House, Harwell Science and Innovation Campus, OX11 0DE, Didcot, United Kingdom
| | - Steven Huband
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Ben Woden
- Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, United Kingdom
| | - Edna R Cabrera-Martinez
- Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, United Kingdom
| | - Christian Pfrang
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston B15 2TT, Birmingham, United Kingdom.,Department of Meteorology, University of Reading, Whiteknights, Earley Gate, RG6 6BB, Reading, United Kingdom
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16
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Li M, Su H, Zheng G, Kuhn U, Kim N, Li G, Ma N, Pöschl U, Cheng Y. Aerosol pH and Ion Activities of HSO 4- and SO 42- in Supersaturated Single Droplets. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:12863-12872. [PMID: 36047919 PMCID: PMC9494740 DOI: 10.1021/acs.est.2c01378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 08/23/2022] [Accepted: 08/25/2022] [Indexed: 06/15/2023]
Abstract
Accurate determination of acidity (pH) and ion activities in aqueous droplets is a major experimental and theoretical challenge for understanding and simulating atmospheric multiphase chemistry. Here, we develop a ratiometric Raman spectroscopy method to measure the equilibrium concentration of sulfate (SO42-) and bisulfate (HSO4-) in single microdroplets levitated by aerosol optical tweezers. This approach enables determination of ion activities and pH in aqueous sodium bisulfate droplets under highly supersaturated conditions. The experimental results were compared against aerosol thermodynamic model calculations in terms of simulating aerosol ion concentrations, ion activity coefficients, and pH. We found that the Extended Aerosol Inorganics Model (E-AIM) can well reproduce the experimental results. The alternative model ISORROPIA, however, exhibits substantial deviations in SO42- and HSO4- concentrations and up to a full unit of aerosol pH under acidic conditions, mainly due to discrepancies in simulating ion activity coefficients of SO42--HSO4- equilibrium. Globally, this may cause an average deviation of ISORROPIA from E-AIM by 25 and 65% in predicting SO42- and HSO4- concentrations, respectively. Our results show that it is important to determine aerosol pH and ion activities in the investigation of sulfate formation and related aqueous phase chemistry.
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Affiliation(s)
- Meng Li
- Minerva
Research Group, Max Planck Institute for
Chemistry, 55128 Mainz, Germany
| | - Hang Su
- Multiphase
Chemistry Department, Max Planck Institute
for Chemistry, 55128 Mainz, Germany
| | - Guangjie Zheng
- Minerva
Research Group, Max Planck Institute for
Chemistry, 55128 Mainz, Germany
| | - Uwe Kuhn
- Multiphase
Chemistry Department, Max Planck Institute
for Chemistry, 55128 Mainz, Germany
| | - Najin Kim
- Multiphase
Chemistry Department, Max Planck Institute
for Chemistry, 55128 Mainz, Germany
| | - Guo Li
- Minerva
Research Group, Max Planck Institute for
Chemistry, 55128 Mainz, Germany
| | - Nan Ma
- Minerva
Research Group, Max Planck Institute for
Chemistry, 55128 Mainz, Germany
- Institute
for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
| | - Ulrich Pöschl
- Multiphase
Chemistry Department, Max Planck Institute
for Chemistry, 55128 Mainz, Germany
| | - Yafang Cheng
- Minerva
Research Group, Max Planck Institute for
Chemistry, 55128 Mainz, Germany
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17
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Yoo H, Lee H, Park C, Shin D, Ro CU. Novel Single-Particle Analytical Technique for Submicron Atmospheric Aerosols: Combined Use of Dark-Field Scattering and Surface-Enhanced Raman Spectroscopy. Anal Chem 2022; 94:13028-13035. [DOI: 10.1021/acs.analchem.2c01696] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hanjin Yoo
- Department of Chemistry, Inha University, Incheon 22212, South Korea
- Particle Pollution Research and Management Center, Incheon 21999, South Korea
| | - Hayeong Lee
- Department of Chemistry, Inha University, Incheon 22212, South Korea
| | - Changmin Park
- Department of Chemistry, Inha University, Incheon 22212, South Korea
| | - Dongha Shin
- Department of Chemistry, Inha University, Incheon 22212, South Korea
| | - Chul-Un Ro
- Department of Chemistry, Inha University, Incheon 22212, South Korea
- Particle Pollution Research and Management Center, Incheon 21999, South Korea
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18
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Tackman EC, Grady RS, Freedman MA. Direct measurement of the pH of aerosol particles using carbon quantum dots. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2022; 14:2929-2936. [PMID: 35856566 DOI: 10.1039/d2ay01005d] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The pH of aerosol particles remains challenging to measure because of their small size, complex composition, and high acidity. Acidity in aqueous aerosol particles, which are found abundantly in the atmosphere, impacts many chemical processes from reaction rates to cloud formation. Only one technique - pH paper - currently exists for directly determining the pH of aerosol particles, and this is restricted to measuring average acidity for entire particle populations. Other methods for evaluating aerosol pH include filter samples, particle-into-liquid sampling, Raman spectroscopy, organic dyes, and thermodynamic models, but these either operate in a higher pH range or are unable to assess certain chemical species or complexity. Here, we present a new method for determining acidity of individual particles and particle phases using carbon quantum dots as a novel in situ fluorophore. Carbon quantum dots are easily synthesized, shelf stable, and sensitive to pH in the highly acidic regime from pH 0 to pH 3 relevant to ambient aerosol particles. To establish the method, a calibration curve was formed from the ratiometric fluorescence intensity of aerosolized standard solutions with a correlation coefficient (R2) of 0.99. Additionally, the pH of aerosol particles containing a complex organic mixture (COM) representative of environmental aerosols was also determined, proving the efficacy of using carbon quantum dots as pH-sensitive fluorophores for complex systems. The ability to directly measure aerosol particle and phase acidity in the correct pH range can help parametrize atmospheric models and improve projections for other aerosol properties and their influence on health and climate.
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Affiliation(s)
- Emma C Tackman
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.
| | - Rachel S Grady
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.
| | - Miriam Arak Freedman
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.
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19
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Lei Z, Chen Y, Zhang Y, Cooke ME, Ledsky IR, Armstrong NC, Olson NE, Zhang Z, Gold A, Surratt JD, Ault AP. Initial pH Governs Secondary Organic Aerosol Phase State and Morphology after Uptake of Isoprene Epoxydiols (IEPOX). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:10596-10607. [PMID: 35834796 DOI: 10.1021/acs.est.2c01579] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Aerosol acidity increases secondary organic aerosol (SOA) formed from the reactive uptake of isoprene-derived epoxydiols (IEPOX) by enhancing condensed-phase reactions within sulfate-containing submicron particles, leading to low-volatility organic products. However, the link between the initial aerosol acidity and the resulting physicochemical properties of IEPOX-derived SOA remains uncertain. Herein, we show distinct differences in the morphology, phase state, and chemical composition of individual organic-inorganic mixed particles after IEPOX uptake to ammonium sulfate particles with different initial atmospherically relevant acidities (pH = 1, 3, and 5). Physicochemical properties were characterized via atomic force microscopy coupled with photothermal infrared spectroscopy (AFM-PTIR) and Raman microspectroscopy. Compared to less acidic particles (pH 3 and 5), reactive uptake of IEPOX to the most acidic particles (pH 1) resulted in 50% more organosulfate formation, clearer phase separation (core-shell), and more irregularly shaped morphologies, suggesting that the organic phase transitioned to semisolid or solid. This study highlights that initial aerosol acidity may govern the subsequent aerosol physicochemical properties, such as viscosity and morphology, following the multiphase chemical reactions of IEPOX. These results can be used in future studies to improve model parameterizations of SOA formation from IEPOX and its properties, toward the goal of bridging predictions and atmospheric observations.
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Affiliation(s)
- Ziying Lei
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Yuzhi Chen
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Yue Zhang
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Madeline E Cooke
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Isabel R Ledsky
- Department of Chemistry, Carleton College, Northfield, Minnesota 55057, United States
| | - N Cazimir Armstrong
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Nicole E Olson
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Zhenfa Zhang
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Avram Gold
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Jason D Surratt
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Andrew P Ault
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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20
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Liu B, Huang Y, Zheng W, Wang D, Fan M. A SERS pH sensor for highly alkaline conditions and its application for pH sensing in aerosol droplets. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2022; 14:1856-1861. [PMID: 35510989 DOI: 10.1039/d2ay00387b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Surface-Enhanced Raman Scattering (SERS) has been widely used in pH sensing. However, SERS sensors capable of stably analysing pH under highly alkaline conditions are still scarce. In this work, a SERS pH sensor employing Alizarin Yellow R as the molecular probe was carefully developed for strong alkaline solutions. The results showed that the probe presented excellent sensing performance in the pH range of 10.04-14.04, including desirable stability and reversibility. Raman band assignments of the probe molecules with the protonated and deprotonated forms were calculated using Gaussian 09. To demonstrate the application, we measured the centroid pH of the phosphate buffer (PB) droplet and compared it to the value obtained with 4-mercaptobenzoic acid (4-MBA) as a probe.
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Affiliation(s)
- Boyu Liu
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 610031, China.
| | - Yuting Huang
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 610031, China.
| | - Wenxu Zheng
- College of Material and Energy, South China Agricultural University, Guangzhou, 510642, China
| | - Dongmei Wang
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 610031, China.
- State-province Joint Engineering Laboratory of Spatial Information Technology of High-Speed Rail Safety, Chengdu, 610031, China
| | - Meikun Fan
- Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 610031, China.
- State-province Joint Engineering Laboratory of Spatial Information Technology of High-Speed Rail Safety, Chengdu, 610031, China
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21
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Li LF, Chen Z, Liu P, Zhang YH. Direct Measurement of pH Evolution in Aerosol Microdroplets Undergoing Ammonium Depletion: A Surface-Enhanced Raman Spectroscopy Approach. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:6274-6281. [PMID: 35476405 DOI: 10.1021/acs.est.1c08626] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Accurately measuring the pH of atmospheric aerosols is a prerequisite for understanding the multiphase chemistry that profoundly affects the environment and climate systems. Despite the advancements of experimental techniques for in situ pH measurements in aerosols, current studies are limited to measuring the static pH of aerosol microdroplets with an unperturbed composition. This steady-state scenario, however, deviates from the real-world aerosols undergoing atmospheric aging reactions, specifically, those characterized with a spontaneous displacement of strong bases (or acids) with high volatility. Here, we introduce a continuous and in situ measurement of aerosol pH by using a 4-mercaptopyridine-functionalized silver nanoparticle probe and surface-enhanced Raman spectroscopy. We find that the ammonium depletion─a spontaneous displacement of ammonium by dicarboxylic acid salts─continuously acidifies aerosol water over time. The decaying trends of pH in the aerosols under various humidity conditions can be unified with a universal exponential function. Such an exponentially decaying function further indicates that the ammonium depletion reaction is a self-limiting process. Our technique can be applied to study the dynamic change of aerosol acidity during the complex atmospheric aging processes, toward elucidating their implications on atmospheric chloride, nitrate, and ammonium cycles.
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Affiliation(s)
- Lin-Fang Li
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Zhe Chen
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Pai Liu
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Yun-Hong Zhang
- Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
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22
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Cui X, Tang M, Wang M, Zhu T. Water as a probe for pH measurement in individual particles using micro-Raman spectroscopy. Anal Chim Acta 2021; 1186:339089. [PMID: 34756261 DOI: 10.1016/j.aca.2021.339089] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 09/16/2021] [Accepted: 09/20/2021] [Indexed: 10/20/2022]
Abstract
Atmospheric aerosol acidity impacts numerous physicochemical processes, but the determination of particle pH remains a significant challenge due to the nonconservative nature of the H+ concentration ([H+]). Traditional measurements have difficulty in describing the practical state of an aerosol because they comprise chemical components or hypotheses that change the nature of the particles. In this work, we present a direct pH measurement that uses water as a general probe to detect [H+] in individual particles by micro-Raman spectroscopy. Containing the vibrational bands of ions and water influenced by ions, the spectra of hydrated ion were decomposed from the solution spectra as standard spectra by multivariate curve resolution analysis. Meanwhile, ratios of hydrated ions were calculated between the Raman spectra and standard spectra to evaluate concentration profiles of each ion. It demonstrated that good quantitative models between the ratio and concentration for all ions including H+ can be built with correlation coefficients (R2) higher than 0.95 for the solutions. The method was further applied to individual particle pH measurement. The pH value of sulfate aerosol particles was calculated, and the standard error was 0.09 using pH values calculated from the [HSO4-]/[SO42-] as a reference. Furthermore, the applicability of the method was proven by detecting the pH value of chloride particles. Therefore, utilizing water, the most common substance, as the spectroscopic probe to measure [H+] without restriction of the ion system, this method has potential to measure the pH value of atmospheric particles with various compounds, although more work needs to be done to improve the sensitivity of the method.
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Affiliation(s)
- Xiaoyu Cui
- BIC-ESAT and SKL-ESPC, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
| | - Mingjin Tang
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
| | - Mingjin Wang
- BIC-ESAT and SKL-ESPC, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
| | - Tong Zhu
- BIC-ESAT and SKL-ESPC, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China.
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23
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Chang YP, Devi Y, Chen CH. Micro-droplet Trapping and Manipulation: Understanding Aerosol Better for a Healthier Environment. Chem Asian J 2021; 16:1644-1660. [PMID: 33999498 DOI: 10.1002/asia.202100516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Indexed: 11/09/2022]
Abstract
Understanding the physicochemical properties and heterogeneous processes of aerosols is key not only to elucidate the impacts of aerosols on the atmosphere and humans but also to exploit their further applications, especially for a healthier environment. Experiments that allow for spatially control of single aerosol particles and investigations on the fundamental properties and heterogeneous chemistry at the single-particle level have flourished during the last few decades, and significant breakthroughs in recent years promise better control and novel applications aimed at resolving key issues in aerosol science. Here we propose graphene oxide (GO) aerosols as prototype aerosols containing polycyclic aromatic hydrocarbons, and GO can behave as two-dimensional surfactants which could modify the interfacial properties of aerosols. We describe the techniques of trapping single particles and furthermore the current status of the optical spectroscopy and chemistry of GO. The current applications of these single-particle trapping techniques are summarized and interesting future applications of GO aerosols are discussed.
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Affiliation(s)
- Yuan-Pin Chang
- Department of Chemistry, National Sun Yat-sen University, No. 70 Lien-hai Rd., Kaohsiung, 80424, Taiwan.,Aerosol Science Research Center, National Sun Yat-sen University, No. 70 Lien-hai Rd., Kaohsiung, 80424, Taiwan
| | - Yanita Devi
- Department of Chemistry, National Sun Yat-sen University, No. 70 Lien-hai Rd., Kaohsiung, 80424, Taiwan
| | - Chun-Hu Chen
- Department of Chemistry, National Sun Yat-sen University, No. 70 Lien-hai Rd., Kaohsiung, 80424, Taiwan
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24
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Huang Q, Wei H, Marr LC, Vikesland PJ. Direct Quantification of the Effect of Ammonium on Aerosol Droplet pH. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:778-787. [PMID: 33296596 DOI: 10.1021/acs.est.0c07394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ammonium is an important atmospheric constituent that dictates many environmental processes. The impact of the ammonium ion concentration on 10-50 μm aerosol droplet pH was quantified using pH nanoprobes and surface-enhanced Raman spectroscopy (SERS). Sample solutions were prepared by mixing 1 M ammonium sulfate (AS), ammonium nitrate (AN), sodium sulfate (SS), or sodium nitrate (SN) solutions with 1 M phosphate buffer (PB) at different volume ratios. Stable pH values were measured for pure PB, AS, and AN droplets at different concentrations. The centroid pH of 1 M PB droplets was ∼11, but when PB was systematically replaced with ammonium (AS- or AN-PB), the centroid pH within the droplets decreased from ≈11 to 5.5. Such a decrease was not observed in sodium (SS- or SN-PB) droplets, and no pH differences were observed between sulfate and nitrate salts. Ammonia partitioning to the gas phase in ammonium-containing droplets was evaluated to be negligible. Raman sulfate peak (∼980 cm-1) intensity measurements and surface tension measurements were conducted to investigate changes in ion distribution. The pH difference between ammonium-containing droplets and ammonium-free droplets is attributed to the alteration of the ion distribution in the presence of ammonium.
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Affiliation(s)
- Qishen Huang
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States
- Virginia Tech Institute of Critical Technology and Applied Science (ICTAS) Sustainable Nanotechnology Center, Blacksburg, Virginia 24061, United States
| | - Haoran Wei
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Linsey C Marr
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States
- Virginia Tech Institute of Critical Technology and Applied Science (ICTAS) Sustainable Nanotechnology Center, Blacksburg, Virginia 24061, United States
| | - Peter J Vikesland
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States
- Virginia Tech Institute of Critical Technology and Applied Science (ICTAS) Sustainable Nanotechnology Center, Blacksburg, Virginia 24061, United States
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25
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Ault AP, Grassian VH, Carslaw N, Collins DB, Destaillats H, Donaldson DJ, Farmer DK, Jimenez JL, McNeill VF, Morrison GC, O'Brien RE, Shiraiwa M, Vance ME, Wells JR, Xiong W. Indoor Surface Chemistry: Developing a Molecular Picture of Reactions on Indoor Interfaces. Chem 2020; 6:3203-3218. [PMID: 32984643 PMCID: PMC7501779 DOI: 10.1016/j.chempr.2020.08.023] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Chemical reactions on indoor surfaces play an important role in air quality in indoor environments, where humans spend 90% of their time. We focus on the challenges of understanding the complex chemistry that takes place on indoor surfaces and identify crucial steps necessary to gain a molecular-level understanding of environmental indoor surface chemistry: (1) elucidate key surface reaction mechanisms and kinetics important to indoor air chemistry, (2) define a range of relevant and representative surfaces to probe, and (3) define the drivers of surface reactivity, particularly with respect to the surface composition, light, and temperature. Within the drivers of surface composition are the roles of adsorbed/absorbed water associated with indoor surfaces and the prevalence, inhomogeneity, and properties of secondary organic films that can impact surface reactivity. By combining laboratory studies, field measurements, and modeling we can gain insights into the molecular processes necessary to further our understanding of the indoor environment.
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Affiliation(s)
- Andrew P Ault
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Vicki H Grassian
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.,Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92037, USA.,Department of Nanoengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Nicola Carslaw
- Department of Environment and Geography, University of York, York, North Yorkshire YO10 5NG, UK
| | - Douglas B Collins
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada.,Department of Chemistry, Bucknell University, Lewisburg, PA 17837, USA
| | - Hugo Destaillats
- Indoor Environment Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - D James Donaldson
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada.,Department of Physical and Environmental Sciences, University of Toronto, Toronto, ON M1C 1A4, Canada
| | - Delphine K Farmer
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Jose L Jimenez
- Department of Chemistry and Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder, Boulder, CO 80309, USA
| | - V Faye McNeill
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
| | - Glenn C Morrison
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Rachel E O'Brien
- Department of Chemistry, College of William and Mary, Williamsburg, VA 23185, USA
| | - Manabu Shiraiwa
- Department of Chemistry, University of California Irvine, Irvine, CA 92697, USA
| | - Marina E Vance
- Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO 80309, USA
| | - J R Wells
- National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA
| | - Wei Xiong
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.,Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093, USA
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Su H, Cheng Y, Pöschl U. New Multiphase Chemical Processes Influencing Atmospheric Aerosols, Air Quality, and Climate in the Anthropocene. Acc Chem Res 2020; 53:2034-2043. [PMID: 32927946 PMCID: PMC7581287 DOI: 10.1021/acs.accounts.0c00246] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Atmospheric aerosols and fine particulate matter (PM2.5) are strongly affecting human health and climate in the Anthropocene,
that is, in the current era of globally pervasive and rapidly increasing
human influence on planet Earth. Poor air quality associated with high aerosol concentrations is among the
leading health risks worldwide, causing millions of attributable excess
deaths and years of life lost every year. Besides their health impact,
aerosols are also influencing climate through interactions with clouds
and solar radiation with an estimated negative total effective radiative
forcing that may compensate about half of the positive radiative forcing
of carbon dioxide but exhibits a much larger uncertainty. Heterogeneous
and multiphase chemical reactions on the surface and in the bulk of
solid, semisolid, and liquid aerosol particles have been recognized
to influence aerosol formation and transformation and thus their environmental
effects. However, atmospheric multiphase chemistry is not well understood
because of its intrinsic complexity of dealing with the matter in
multiple phases and the difficulties of distinguishing its effect
from that of gas phase reactions. Recently, research on atmospheric
multiphase chemistry received
a boost from the growing interest in understanding severe haze formation
of very high PM2.5 concentrations in polluted megacities
and densely populated regions. State-of-the-art models suggest that
the gas phase reactions, however, are not capturing the high concentrations
and rapid increase of PM2.5 observed during haze events,
suggesting a gap in our understanding of the chemical mechanisms of
aerosol formation. These haze events are characterized by high concentrations
of aerosol particles and high humidity, especially favoring multiphase
chemistry. In this Account, we review recent advances that we have
made, as well as current challenges and future perspectives for research
on multiphase chemical processes involved in atmospheric aerosol formation
and transformation. We focus on the following questions: what are
the key reaction pathways leading to aerosol formation under polluted
conditions, what is the relative importance of multiphase chemistry
versus gas-phase chemistry, and what are the implications for the
development of efficient and reliable air quality control strategies?
In particular, we discuss advances and challenges related to different
chemical regimes of sulfate, nitrate, and secondary organic aerosols
(SOAs) under haze conditions, and we synthesize new insights into
the influence of aerosol water content, aerosol pH, phase state, and
nanoparticle size effects. Overall, there is increasing evidence that
multiphase chemistry plays an important role in aerosol formation
during haze events. In contrast to the gas phase photochemical reactions,
which are self-buffered against heavy pollution, multiphase reactions
have a positive feedback mechanism, where higher particle matter levels
accelerate multiphase production, which further increases the aerosol
concentration resulting in a series of record-breaking pollution events.
We discuss perspectives to fill the gap of the current understanding
of atmospheric multiphase reactions that involve multiple physical
and chemical processes from bulk to nanoscale and from regional to
global scales. A synthetic approach combining laboratory experiments,
field measurements, instrument development, and model simulations
is suggested as a roadmap to advance future research.
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Affiliation(s)
- Hang Su
- Max Planck Institute for Chemistry, Mainz 55128, Germany
| | - Yafang Cheng
- Max Planck Institute for Chemistry, Mainz 55128, Germany
| | - Ulrich Pöschl
- Max Planck Institute for Chemistry, Mainz 55128, Germany
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27
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Ault AP. Aerosol Acidity: Novel Measurements and Implications for Atmospheric Chemistry. Acc Chem Res 2020; 53:1703-1714. [PMID: 32786333 DOI: 10.1021/acs.accounts.0c00303] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The pH of a solution is one of its most fundamental chemical properties, impacting reaction pathways and kinetics across every area of chemistry. The atmosphere is no different, with the pH of the condensed phase driving key chemical reactions that ultimately impact global climate in numerous ways. The condensed phase in the atmosphere is comprised of suspended liquid or solid particles, known as the atmospheric aerosol, which are differentiated from cloud droplets by their much smaller size (primarily <10 μm). The pH of the atmospheric aerosol can enhance certain chemical reactions leading to the formation of additional condensed phase mass from lower volatility species (secondary aerosol), alter the optical and water uptake properties of particles, and solubilize metals that can act as key nutrients in nutrient-limited ecosystems or cause oxidative stress after inhalation. However, despite the importance of aerosol acidity for climate and health, our fundamental understanding of pH has been limited due to aerosol size (by number >99% of particles are <1 μm) and complexity. Within a single atmospheric particle, there can be hundreds to thousands of distinct chemical species, varying water content, high ionic strengths, and different phases (liquid, semisolid, and solid). Making aerosol analysis even more challenging, atmospheric particles are constantly evolving through heterogeneous reactions with gases and multiphase chemistry within the condensed phase. Based on these challenges, traditional pH measurements are not feasible, and, for years, indirect and proxy methods were the most common way to estimate aerosol pH, with mixed results. However, aerosol pH needs to be incorporated into climate models to accurately determine which chemical reactions are dominant in the atmosphere. Consequently, experimental measurements that probe pH in atmospherically relevant particles are sorely needed to advance our understanding of aerosol acidity.This Account describes recent advances in measurements of aerosol particle acidity, specifically three distinct methods we developed for experimentally determining particle pH. Our acid-conjugate base method uses Raman microspectroscopy to probe an acid (e.g., HSO4-) and its conjugate base (e.g., SO42-) in individual micrometer-sized particles. Our second approach is a field-deployable colorimetric method based on pH indicators (e.g., thymol blue) and cell phone imaging to provide a simple, low-cost approach to ensemble average (or bulk) pH for particles in distinct size ranges down to a few hundred nanometers in diameter. In our third method, we monitor acid-catalyzed polymer degradation of a thin film (∼23 nm) of poly(ε-caprolactone) (PCL) on silicon by individual particles with atomic force microscopy (AFM) after inertially impacting particles of different pH. These measurements are improving our understanding of aerosol pH from a fundamental physical chemistry perspective and have led to initial atmospheric measurements. The impact of aerosol pH on key atmospheric processes, such as secondary organic aerosol (SOA) formation, is discussed. Some unique findings, such as an unexpected size dependence to aerosol pH and kinetic limitations, illustrate that particles are not always in thermodynamic equilibrium with the surrounding gas. The implications of our limited, but improving, understanding of the fundamental chemical concept of pH in the atmospheric aerosol are critical for connecting chemistry and climate.
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Affiliation(s)
- Andrew P. Ault
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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28
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Jia S, Chen W, Zhang Q, Krishnan P, Mao J, Zhong B, Huang M, Fan Q, Zhang J, Chang M, Yang L, Wang X. A quantitative analysis of the driving factors affecting seasonal variation of aerosol pH in Guangzhou, China. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 725:138228. [PMID: 32302828 DOI: 10.1016/j.scitotenv.2020.138228] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/25/2020] [Accepted: 03/25/2020] [Indexed: 06/11/2023]
Abstract
Aerosol acidity is of great interest due to its effects on atmospheric chemical processes and impact on human health; however, the driving factors of aerosol acidity have only been scarcely investigated. This study characterized the aerosol acidity during the wet and dry seasons in Guangzhou, China, and systematically analyzed the seasonal variation and the corresponding driving factors of aerosol acidity followed by the discussion of their impact on gas-aerosol partitioning of NH3 and HNO3. It was demonstrated that the pH of PM2.5 was 0.08 unit lower (more acidic) during wet season than during the dry season and the aerosol acidity varied less in South China than that in North China. Additionally, our results showed that the meteorological parameters including temperature and relative humidity have larger effect on aerosol pH variation than chemical species. Particularly, the lower temperature during dry season had the positive influence (0.38 pH unit) on aerosol pH compared to the wet season; however, the negative effect due to relative humidity (RH) and chemical species resulted in a smaller seasonal variation of aerosol pH between these two seasons. The sensitivity analysis showed that the increase of temperature has negative impact (reducing pH) on aerosol pH with an almost linear relationship, while RH and chemical species represented a two-phase linear and nonlinear effect, respectively. Finally, the calculation of gas-aerosol partitioning indicated that the temperature had the largest influence on the seasonal variation of gas-aerosol partitioning for both HNO3 and NH3 followed by liquid water content and non-ideality, while aerosol acidity imposed the lowest impact, which suggests that all the parameters including meteorological and chemical species should be comprehensively evaluated to devise a PM2.5 control strategy.
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Affiliation(s)
- Shiguo Jia
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Field Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Guangzhou 510275, PR China
| | - Weihua Chen
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Institute for Environmental and Climate Research, Jinan University, Guangzhou 510632, PR China
| | - Qi Zhang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou 510275, PR China
| | - Padmaja Krishnan
- Department of Civil & Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore 117576, Singapore
| | - Jingying Mao
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Institute for Environmental and Climate Research, Jinan University, Guangzhou 510632, PR China
| | - Buqing Zhong
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Institute for Environmental and Climate Research, Jinan University, Guangzhou 510632, PR China
| | - Minjuan Huang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Field Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Guangzhou 510275, PR China
| | - Qi Fan
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou 510275, PR China
| | - Jinpu Zhang
- Guangdong Environmental Monitoring Center, Guangzhou 510308, PR China
| | - Ming Chang
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Institute for Environmental and Climate Research, Jinan University, Guangzhou 510632, PR China
| | - Liming Yang
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 117576, Singapore.
| | - Xuemei Wang
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Institute for Environmental and Climate Research, Jinan University, Guangzhou 510632, PR China.
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29
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Nazaroff WW, Weschler CJ. Indoor acids and bases. INDOOR AIR 2020; 30:559-644. [PMID: 32233033 DOI: 10.1111/ina.12670] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 03/18/2020] [Accepted: 03/19/2020] [Indexed: 05/15/2023]
Abstract
Numerous acids and bases influence indoor air quality. The most abundant of these species are CO2 (acidic) and NH3 (basic), both emitted by building occupants. Other prominent inorganic acids are HNO3 , HONO, SO2 , H2 SO4 , HCl, and HOCl. Prominent organic acids include formic, acetic, and lactic; nicotine is a noteworthy organic base. Sources of N-, S-, and Cl-containing acids can include ventilation from outdoors, indoor combustion, consumer product use, and chemical reactions. Organic acids are commonly more abundant indoors than outdoors, with indoor sources including occupants, wood, and cooking. Beyond NH3 and nicotine, other noteworthy bases include inorganic and organic amines. Acids and bases partition indoors among the gas-phase, airborne particles, bulk water, and surfaces; relevant thermodynamic parameters governing the partitioning are the acid-dissociation constant (Ka ), Henry's law constant (KH ), and the octanol-air partition coefficient (Koa ). Condensed-phase water strongly influences the fate of indoor acids and bases and is also a medium for chemical interactions. Indoor surfaces can be large reservoirs of acids and bases. This extensive review of the state of knowledge establishes a foundation for future inquiry to better understand how acids and bases influence the suitability of indoor environments for occupants, cultural artifacts, and sensitive equipment.
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Affiliation(s)
- William W Nazaroff
- Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA
| | - Charles J Weschler
- Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ, USA
- International Centre for Indoor Environment and Energy, Technical University of Denmark, Lyngby, Denmark
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30
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Olson NE, Xiao Y, Lei Z, Ault AP. Simultaneous Optical Photothermal Infrared (O-PTIR) and Raman Spectroscopy of Submicrometer Atmospheric Particles. Anal Chem 2020; 92:9932-9939. [PMID: 32519841 DOI: 10.1021/acs.analchem.0c01495] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Physicochemical analysis of individual atmospheric aerosols at the most abundant sizes in the atmosphere (<1 μm) is analytically challenging, as hundreds to thousands of species are often present in femtoliter volumes. Vibrational spectroscopies, such as infrared (IR) and Raman, have great potential for probing functional groups in single particles at ambient pressure and temperature. However, the diffraction limit of IR radiation limits traditional IR microscopy to particles > ∼10 μm, which have less relevance to aerosol health and climate impacts. Optical photothermal infrared (O-PTIR) spectroscopy is a contactless method that circumvents diffraction limitations by using changes in the scattering intensity of a continuous wave visible laser (532 nm) to detect the photothermal expansion when a vibrational mode is excited by a tunable IR laser (QCL: 800-1800 cm-1 or OPO: 2600-3600 cm-1). Herein, we simultaneously collect O-PTIR spectra with Raman spectra at a single point for individual particles with aerodynamic diameters <400 nm (prior to impaction and spreading) at ambient temperature and pressure, by also collecting the inelastically scattered visible photons for Raman spectra. O-PTIR and Raman spectra were collected for submicrometer particles with different substrates, particle chemical compositions, and morphologies (i.e., core-shell), as well as IR mapping with submicron spatial resolution. Initial O-PTIR analysis of ambient atmospheric particles identified both inorganic and organic modes in individual sub- and supermicrometer particles. The simultaneous IR and Raman microscopy with submicrometer spatial resolution described herein has considerable potential both in atmospheric chemistry and numerous others fields (e.g., materials and biological research).
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Affiliation(s)
- Nicole E Olson
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Yao Xiao
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Ziying Lei
- Department of Environmental Health Sciences, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Andrew P Ault
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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31
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Pye HOT, Nenes A, Alexander B, Ault AP, Barth MC, Clegg SL, Collett JL, Fahey KM, Hennigan CJ, Herrmann H, Kanakidou M, Kelly JT, Ku IT, McNeill VF, Riemer N, Schaefer T, Shi G, Tilgner A, Walker JT, Wang T, Weber R, Xing J, Zaveri RA, Zuend A. The Acidity of Atmospheric Particles and Clouds. ATMOSPHERIC CHEMISTRY AND PHYSICS 2020; 20:4809-4888. [PMID: 33424953 PMCID: PMC7791434 DOI: 10.5194/acp-20-4809-2020] [Citation(s) in RCA: 155] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Acidity, defined as pH, is a central component of aqueous chemistry. In the atmosphere, the acidity of condensed phases (aerosol particles, cloud water, and fog droplets) governs the phase partitioning of semi-volatile gases such as HNO3, NH3, HCl, and organic acids and bases as well as chemical reaction rates. It has implications for the atmospheric lifetime of pollutants, deposition, and human health. Despite its fundamental role in atmospheric processes, only recently has this field seen a growth in the number of studies on particle acidity. Even with this growth, many fine particle pH estimates must be based on thermodynamic model calculations since no operational techniques exist for direct measurements. Current information indicates acidic fine particles are ubiquitous, but observationally-constrained pH estimates are limited in spatial and temporal coverage. Clouds and fogs are also generally acidic, but to a lesser degree than particles, and have a range of pH that is quite sensitive to anthropogenic emissions of sulfur and nitrogen oxides, as well as ambient ammonia. Historical measurements indicate that cloud and fog droplet pH has changed in recent decades in response to controls on anthropogenic emissions, while the limited trend data for aerosol particles indicates acidity may be relatively constant due to the semi-volatile nature of the key acids and bases and buffering in particles. This paper reviews and synthesizes the current state of knowledge on the acidity of atmospheric condensed phases, specifically particles and cloud droplets. It includes recommendations for estimating acidity and pH, standard nomenclature, a synthesis of current pH estimates based on observations, and new model calculations on the local and global scale.
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Affiliation(s)
- Havala O. T. Pye
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, 27711, USA
| | - Athanasios Nenes
- School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
- Institute for Chemical Engineering Sciences, Foundation for Research and Technology Hellas, Patras, GR-26504, Greece
| | - Becky Alexander
- Department of Atmospheric Science, University of Washington, Seattle, WA, 98195, USA
| | - Andrew P. Ault
- Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Mary C. Barth
- National Center for Atmospheric Research, Boulder, CO, 80307, USA
| | - Simon L. Clegg
- School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK
| | - Jeffrey L. Collett
- Department of Atmospheric Science, Colorado State University, Fort Collins, CO, 80523, USA
| | - Kathleen M. Fahey
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, 27711, USA
| | - Christopher J. Hennigan
- Department of Chemical, Biochemical, and Environmental Engineering, University of Maryland Baltimore County, Baltimore, MD, 21250, USA
| | - Hartmut Herrmann
- Leibniz Institute for Tropospheric Research (TROPOS), Atmospheric Chemistry Department (ACD), Leipzig, 04318, Germany
| | - Maria Kanakidou
- Department of Chemistry, University of Crete, Voutes, Heraklion Crete, 71003, Greece
| | - James T. Kelly
- Office of Air Quality Planning & Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC, 27711, USA
| | - I-Ting Ku
- Department of Atmospheric Science, Colorado State University, Fort Collins, CO, 80523, USA
| | - V. Faye McNeill
- Department of Chemical Engineering, Columbia University, New York, NY, 10027, USA
| | - Nicole Riemer
- Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois, 61801, USA
| | - Thomas Schaefer
- Leibniz Institute for Tropospheric Research (TROPOS), Atmospheric Chemistry Department (ACD), Leipzig, 04318, Germany
| | - Guoliang Shi
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control, Nankai University, Tianjin, 300071, China
| | - Andreas Tilgner
- Leibniz Institute for Tropospheric Research (TROPOS), Atmospheric Chemistry Department (ACD), Leipzig, 04318, Germany
| | - John T. Walker
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, 27711, USA
| | - Tao Wang
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Rodney Weber
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Jia Xing
- School of Environment, Tsinghua University, Beijing, 100084, China
| | - Rahul A. Zaveri
- Atmospheric Sciences & Global Change Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Andreas Zuend
- Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, H3A 0B9, Canada
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32
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Lackey HE, Nelson GL, Lines AM, Bryan SA. Reimagining pH Measurement: Utilizing Raman Spectroscopy for Enhanced Accuracy in Phosphoric Acid Systems. Anal Chem 2020; 92:5882-5889. [PMID: 32223185 DOI: 10.1021/acs.analchem.9b05708] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Measurement of pH is an integral component of chemical studies and process control; however, traditional pH probes are difficult to utilize in harsh or complex chemical systems. Optical spectroscopy-based online monitoring offers a powerful and novel route for characterizing system parameters, such as pH, and is well adapted to deployment in harsh environments or chemically complex systems. Specifically, Raman spectroscopy combined with chemometric analysis can provide an improved method of online p[H+] measurement. Multivariate curve resolution (MCR) analysis of Raman spectra can be utilized to determine speciation as a function of p[H+], and the MCR scores assigned to each species can be used to calculate p[H+]. Subsequent chemometric modeling can be used to correlate spectral response to p[H+]. This was demonstrated with phosphoric acid, a chemical system known to challenge traditional pH probes. Raman spectra exhibit clear changes with pH due to changing speciation, and chemometric modeling can be successfully utilized to correlate those fingerprints to p[H+]. With the use of this approach, p[H+] of the phosphoric acid system can be accurately measured without foreknowledge of system conditions such as ionic strength.
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Affiliation(s)
- Hope E Lackey
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Gilbert L Nelson
- Department of Chemistry, College of Idaho, 2112 Cleveland Boulevard, Caldwell, Idaho 83605, United States
| | - Amanda M Lines
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Samuel A Bryan
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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33
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Chang P, Chen Z, Zhang Y, Liu Y. Direct measurement of aerosol pH in individual malonic acid and citric acid droplets under different relative humidity conditions via Raman spectroscopy. CHEMOSPHERE 2020; 241:124960. [PMID: 31590017 DOI: 10.1016/j.chemosphere.2019.124960] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 09/14/2019] [Accepted: 09/23/2019] [Indexed: 06/10/2023]
Abstract
Acidity of aerosol particles plays important roles in atmospheric chemistry, in turn, impacting climate system and public health. Current knowledge of acidity in atmosphere aerosols remains fairly scarce largely because of difficulty in direct measurement. On the other hand, indirect methods for estimating aerosol pH are often inconsistent with pH values predicted by thermodynamic models. Recently, a direct Raman spectroscopy method has been reported to determine pH values of acid-conjugate base equilibria systems based on Raman intensity of distinct characteristic peaks of conjugate acid-base pair. Nevertheless, for pure carboxylic acid aerosol particles, such as malonic acid (MA), characteristic peak of its conjugate base cannot be clearly observed in Raman spectra owing to small Ka value (weak acid dissociation constant), which leads to little dissociation of weak acid and low concentration of its conjugated base. As a result, pH of carboxylic acid particles cannot be directly determined by calibrating concentrations of acid and its conjugated base using the above-mentioned method. To address such an issue, we demonstrate a new approach for determining pH values of malonic acid (MA) and citric acid (CA) droplets under different relative humidity (RH) based on calibration curves. We measure Raman intensity ratios of acid solutions at different concentrations and their pH values to establish a calibration curve, and then using the intensity ratio of MA and CA droplets under different RH to determine aerosol particle pH based on calibration curves. Results have shown that aerosol pH of MA droplet decreases with a decreasing RH and pH values ranges from 1.03 to -0.12, when RH value is reduced from 90% to 26%, in good agreement with model prediction values. In addition, we also, for the first time, report pH values of CA droplets under different RH conditions and its pH values range from 1.13 to -0.74 when RH is reduced from 91% to 28%.
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Affiliation(s)
- Pianpian Chang
- The Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, PR China
| | - Zhe Chen
- The Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, PR China
| | - Yunhong Zhang
- The Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, PR China.
| | - Yong Liu
- Department of Chemistry, University of Colorado Denver, Denver, CO, 80217, USA.
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34
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Boyer HC, Gorkowski K, Sullivan RC. In Situ pH Measurements of Individual Levitated Microdroplets Using Aerosol Optical Tweezers. Anal Chem 2020; 92:1089-1096. [PMID: 31760745 DOI: 10.1021/acs.analchem.9b04152] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The pH of microscale reaction environments controls numerous physicochemical processes, requiring a real-time pH microprobe. We present highly accurate real-time pH measurements of microdroplets using aerosol optical tweezers (AOT) and analysis of the whispering gallery modes (WGMs) contained in the cavity-enhanced Raman spectra. Uncertainties ranging from ±0.03 to 0.06 in pH for picoliter droplets are obtained through averaging Raman frames acquired at 0.5 Hz over 3.3 min. The high accuracy in pH determination is achieved by combining two independent measurements uniquely provided by the AOT approach: the anion concentration ratio from the spontaneous Raman spectra, and the total solute concentration from the refractive index retrieved from WGM analysis of the stimulated cavity-enhanced Raman spectra. pH can be determined over a range of -0.36 to 0.76 using the aqueous sodium bisulfate system. This technique enables direct measurements of pH-dependent chemical and physical changes experienced by individual microparticles and exploration of the role of pH in the chemical behavior of confined microenvironments.
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Affiliation(s)
- Hallie C Boyer
- Center for Atmospheric Particle Studies , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Kyle Gorkowski
- Department of Atmospheric and Oceanic Sciences , McGill University , Montreal , Quebec H3A 0B9 , Canada
| | - Ryan C Sullivan
- Center for Atmospheric Particle Studies , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
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Abstract
Airborne particles are very dynamic and highly reactive components of the Earth's atmosphere. Their high surface area and water content provide a unique reaction environment for multiphase chemistry that continually modifies particle composition and properties that consequently impact air quality as well as concentrations of gas-phase species. By absorbing and scattering solar and terrestrial radiation, particles directly influence the planet's radiative balance. Their indirect effects include modifying the nucleation, lifetime, and physical properties of clouds. Due to the sensitivity of the atmospheric environment to all these variables, fundamental studies of chemical transformations of atmospheric particles, their sources, continuously evolving composition, and physical properties are of highest research priority. Accurate descriptions of particles and their effects in the atmosphere require comprehensive information not only on the particle-type populations and their size distributions and concentrations, but also on the diversity and the spatial heterogeneity of chemical components within individual particles. Developments and applications of modern chemical imaging approaches for off-line characterization of atmospheric particles have been at the forefront of modern experimental studies and have resulted in a transformative impact in atmospheric chemistry and physics. This Account presents a synopsis of recent advances in chemical imaging of atmospheric particles collected on substrates during field and laboratory experiments. The unique advantage of chemical imaging methods is that they simultaneously provide two analytical measurements: imaging of particles to assess variability in their individual sizes and morphology, as well as particle-specific speciation of their composition and spatial heterogeneity of different chemical components within individual particles. We also highlight analytical chemistry approaches that enable chemical imaging of particles with different levels of elemental and molecular specificity, including applications of multimodal methodologies where the same or similar groups of particles are probed by two or more complementary techniques. These approaches provide unique experimental insights on the nature and sources of particles, understanding their physical properties, atmospheric reactivity, and transformations. Chemical imaging data provide unique experimental input for atmospheric models that simulate aging and changes in particle-type populations, internal composition, and their associated optical and cloud forming properties. We highlight applications of chemical imaging in selected recent studies, discuss their existing limitations, and forecast future research directions for this area.
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Affiliation(s)
- Alexander Laskin
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Ryan C. Moffet
- Meteorology and Air Quality Measurements, Sonoma Technology, Inc., Petaluma, California 94954, United States
| | - Mary K. Gilles
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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36
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Feng Y, Liu L, Yang Y, Deng Y, Li K, Cheng H, Dong X, Li W, Zhang L. The application of Raman spectroscopy combined with multivariable analysis on source apportionment of atmospheric black carbon aerosols. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 685:189-196. [PMID: 31174116 DOI: 10.1016/j.scitotenv.2019.05.367] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 05/19/2019] [Accepted: 05/24/2019] [Indexed: 06/09/2023]
Abstract
Source apportionment studies become increasingly crucial for black carbon (BC) in atmospheric particulate matters given its linkage with adverse public health and climate impacts. In this work, a facile and rapid method using Raman spectra combined with stepwise discriminant analysis (SDA) was proposed to identify and quantify the contributions of atmospheric BC sources. Four BC samples from biomass burning, coal combustion, gasoline and diesel vehicle emission were characterized by Raman spectra. The SDA model was established based on 10 parameters with significant differences (p < 0.05), giving an accuracy of 83% with a cross-validation rate of 80%. Utilizing four suggested discriminant variables from SDA model, vehicle emission was predicted as the dominant contributor to ambient BC particles, among which gasoline contributed much higher than diesel at an urban road intersection in Shanghai, China. This new method shows great potential to classify and investigate the sources of atmospheric BC aerosols and provide more effective information on air pollution control measures.
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Affiliation(s)
- Yiqing Feng
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
| | - Lei Liu
- Department of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou 310027, PR China; Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Yang Yang
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Yue Deng
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Kejian Li
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Hanyun Cheng
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Xu Dong
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Weijun Li
- Department of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou 310027, PR China
| | - Liwu Zhang
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China.
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37
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Peng X, Vasilakos P, Nenes A, Shi G, Qian Y, Shi X, Xiao Z, Chen K, Feng Y, Russell AG. Detailed Analysis of Estimated pH, Activity Coefficients, and Ion Concentrations between the Three Aerosol Thermodynamic Models. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:8903-8913. [PMID: 31294542 DOI: 10.1021/acs.est.9b00181] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this work, we utilize a rich set of simulated and ground-based observational data in Tianjin, China to examine and compare the differences in aerosol acidity and composition predicted by three popular thermodynamic equilibrium models: ISORROPIA II, the Extended Aerosol Inorganics Model vision IV (E-AIM IV), and the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients model (AIOMFAC). The species used to estimate aerosol acidity for both simulated and ambient data were NH4+, Na+, SO42-, NO3-, and Cl-. For simulated data, there is good agreement between ISORROPIA II and E-AIM IV predicted acidity in the forward and metastable mode, resulting from the hydrogen ion activity coefficient (γ(H+)) and the molality (m(H+)) showing opposite trends. While almost all other inorganic species concentrations are found to be similar among the three models, such is not the case for the bisulfate ion (HSO4-), which is linked to m(H+). We find that differences in predicted bisulfate between the three models primarily result from differences in the treatment of the HSO4- ↔ H+ + SO42- reaction for highly acidic conditions. This difference in bisulfate is responsible for much of the difference in estimated pH for the ambient data (average pH of 3.5 for ISORROPIA II and 3.0 for E-AIM IV).
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Affiliation(s)
- Xing Peng
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control & Center for Urban Transport Emission Research, College of Environmental Science and Engineering , Nankai University , Tianjin 300350 , P. R. China
- School of Civil and Environmental Engineering , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - Petros Vasilakos
- School of Chemical and Biomolecular Engineering , Georgia Institute of Technology , Atlanta , Georgia , 30332 , United States
- School of Civil and Environmental Engineering , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - Athanasios Nenes
- Laboratory of Atmospheric Processes and Their Impacts, School of Architecture, Civil & Environmental Engineering , Ecole Polytechnique Federale de Lausanne , CH-1015 , Lausanne , Switzerland
- Institute of Chemical Engineering Sciences , Foundation for Research and Technology Hellas , GR-26504 , Patras , Greece
| | - Guoliang Shi
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control & Center for Urban Transport Emission Research, College of Environmental Science and Engineering , Nankai University , Tianjin 300350 , P. R. China
| | - Yu Qian
- School of Civil and Environmental Engineering , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
| | - Xurong Shi
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control & Center for Urban Transport Emission Research, College of Environmental Science and Engineering , Nankai University , Tianjin 300350 , P. R. China
| | - Zhimei Xiao
- Tianjin Eco-Environmental Monitoring Center , Tianjin 300191 , P. R. China
| | - Kui Chen
- Tianjin Eco-Environmental Monitoring Center , Tianjin 300191 , P. R. China
| | - Yinchang Feng
- State Environmental Protection Key Laboratory of Urban Ambient Air Particulate Matter Pollution Prevention and Control & Center for Urban Transport Emission Research, College of Environmental Science and Engineering , Nankai University , Tianjin 300350 , P. R. China
| | - Armistead G Russell
- School of Civil and Environmental Engineering , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
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38
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Coddens EM, Angle KJ, Grassian VH. Titration of Aerosol pH through Droplet Coalescence. J Phys Chem Lett 2019; 10:4476-4483. [PMID: 31298863 DOI: 10.1021/acs.jpclett.9b00757] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The pH of aqueous aerosols, as well as cloud and fog droplets, has an important influence on the chemistry that takes place within these unique microenvironments. Utilizing conjugate acid/base pairs to infer pH changes, we investigate, for the first time, changes in aerosol pH upon coalescence. In particular, we show that the pH within individual aqueous aerosols that are ∼8 μm in diameter can be titrated via droplet coalescence in an aerosol optical tweezer. Using sulfate/bisulfate and carbonate/bicarbonate as model systems, the pH of trapped aerosols is determined before and after introduction of smaller aerosols containing a strong acid. The pH change upon coalescence with the smaller, acidic aerosol is calculated using specific ion interaction theory. Furthermore, we show that the pH of an individual aerosol can be altered along a fairly wide range of pH values, paving the way for future studies requiring rigorous pH control of an aqueous aerosol.
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Affiliation(s)
- Ellen M Coddens
- Department of Chemistry and Biochemistry , University of California San Diego , La Jolla , California 92093 , United States
| | - Kyle J Angle
- Department of Chemistry and Biochemistry , University of California San Diego , La Jolla , California 92093 , United States
| | - Vicki H Grassian
- Department of Chemistry and Biochemistry , University of California San Diego , La Jolla , California 92093 , United States
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39
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Marsh A, Rovelli G, Miles REH, Reid JP. Complexity of Measuring and Representing the Hygroscopicity of Mixed Component Aerosol. J Phys Chem A 2019; 123:1648-1660. [PMID: 30707027 DOI: 10.1021/acs.jpca.8b11623] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The validation of approaches to predict the hygroscopicity of complex mixtures of organic components in aerosol is important for understanding the hygroscopic response of organic aerosol in the atmosphere. We report new measurements of the hygroscopicity of mixtures of dicarboxylic acids and amino acids using a comparative kinetic electrodynamic balance (CK-EDB) approach, inferring the equilibrium water content of the aerosol from close to a saturation relative humidity (100%) down to 80%. We show that the solution densities and refractive indices of the mixtures can be estimated with an accuracy of better than ±2% using the molar refractive index mixing rule and densities and refractive indices for the individual binary organic-aqueous solutions. Further, we show that the often-used mass-, volume-, and mole-weighted mixing rules to estimate the hygroscopicity parameter κ can overestimate the hygroscopic parameter by a factor of as much as 3, highlighting the need to understand the specific nonideal interactions that may arise synergistically in mixtures and cannot be represented by simple models. Indeed, in some extreme cases the hygroscopicity of a multicomponent mixture can be very close to that for the least hygroscopic component. For mixtures of similar components for which no additional synergistic interactions need be considered, the hygroscopicity of the mixed component aerosol can be estimated with high accuracy from the hygroscopic response of the binary aqueous-organic aerosol. In conclusion, we suggest that the hygroscopicity of multicomponent organic aerosol can be highly nonadditive and that simple correlations of hygroscopicity with composition may often misrepresent the level of complexity essential to interpreting aerosol hygroscopicity.
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Affiliation(s)
- Aleksandra Marsh
- School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , U.K
| | - Grazia Rovelli
- School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , U.K
| | - Rachael E H Miles
- School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , U.K
| | - Jonathan P Reid
- School of Chemistry , University of Bristol , Cantock's Close , Bristol BS8 1TS , U.K
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40
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Marr LC, Tang JW, Van Mullekom J, Lakdawala SS. Mechanistic insights into the effect of humidity on airborne influenza virus survival, transmission and incidence. J R Soc Interface 2019. [PMID: 30958176 DOI: 10.6084/m9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023] Open
Abstract
Influenza incidence and seasonality, along with virus survival and transmission, appear to depend at least partly on humidity, and recent studies have suggested that absolute humidity (AH) is more important than relative humidity (RH) in modulating observed patterns. In this perspective article, we re-evaluate studies of influenza virus survival in aerosols, transmission in animal models and influenza incidence to show that the combination of temperature and RH is equally valid as AH as a predictor. Collinearity must be considered, as higher levels of AH are only possible at higher temperatures, where it is well established that virus decay is more rapid. In studies of incidence that employ meteorological data, outdoor AH may be serving as a proxy for indoor RH in temperate regions during the wintertime heating season. Finally, we present a mechanistic explanation based on droplet evaporation and its impact on droplet physics and chemistry for why RH is more likely than AH to modulate virus survival and transmission.
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Affiliation(s)
- Linsey C Marr
- 1 Civil and Environmental Engineering, Virginia Tech , Blacksburg, VA 24061 , USA
| | - Julian W Tang
- 2 Clinical Microbiology, University Hospitals Leicester NHS Trust , Leicester , UK
- 3 Infection, Immunity and Inflammation, University of Leicester , Leicester , UK
| | | | - Seema S Lakdawala
- 5 Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine , Pittsburgh, PA 15219 , USA
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41
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Marr LC, Tang JW, Van Mullekom J, Lakdawala SS. Mechanistic insights into the effect of humidity on airborne influenza virus survival, transmission and incidence. J R Soc Interface 2019; 16:20180298. [PMID: 30958176 PMCID: PMC6364647 DOI: 10.1098/rsif.2018.0298] [Citation(s) in RCA: 220] [Impact Index Per Article: 44.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 12/20/2018] [Indexed: 12/27/2022] Open
Abstract
Influenza incidence and seasonality, along with virus survival and transmission, appear to depend at least partly on humidity, and recent studies have suggested that absolute humidity (AH) is more important than relative humidity (RH) in modulating observed patterns. In this perspective article, we re-evaluate studies of influenza virus survival in aerosols, transmission in animal models and influenza incidence to show that the combination of temperature and RH is equally valid as AH as a predictor. Collinearity must be considered, as higher levels of AH are only possible at higher temperatures, where it is well established that virus decay is more rapid. In studies of incidence that employ meteorological data, outdoor AH may be serving as a proxy for indoor RH in temperate regions during the wintertime heating season. Finally, we present a mechanistic explanation based on droplet evaporation and its impact on droplet physics and chemistry for why RH is more likely than AH to modulate virus survival and transmission.
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Affiliation(s)
- Linsey C. Marr
- Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061, USA
| | - Julian W. Tang
- Clinical Microbiology, University Hospitals Leicester NHS Trust, Leicester, UK
- Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
| | | | - Seema S. Lakdawala
- Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA
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42
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Freedman MA, Ott EJE, Marak KE. Role of pH in Aerosol Processes and Measurement Challenges. J Phys Chem A 2019; 123:1275-1284. [PMID: 30586311 DOI: 10.1021/acs.jpca.8b10676] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
pH is one of the most basic chemical properties of aqueous solution, but its measurement in nanoscale aerosol particles presents many challenges. The pH of aerosol particles is of growing interest in the atmospheric chemistry community because of its demonstrated effects on heterogeneous chemistry and human health, as well as potential effects on climate. The authors have shown that phase transitions of aerosol particles are sensitive to pH, focusing on systems that undergo liquid-liquid phase separation. Currently, aerosol pH is calculated indirectly from knowledge of species present in the gas and aerosol phases through the use of thermodynamic models. From these models, ambient aerosol is expected to be highly acidic (pH ∼ 0-3). Direct measurements have focused on model systems due to the difficulty of this measurement. This area is one in which physical chemists should be encouraged to contribute because of the potential consequences for aerosol processes in the environment.
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Affiliation(s)
- Miriam Arak Freedman
- Department of Chemistry , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Emily-Jean E Ott
- Department of Chemistry , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Katherine E Marak
- Department of Chemistry , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
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43
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Tirella PN, Craig RL, Tubbs DB, Olson NE, Lei Z, Ault AP. Extending surface enhanced Raman spectroscopy (SERS) of atmospheric aerosol particles to the accumulation mode (150-800 nm). ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2018; 20:1570-1580. [PMID: 30124713 DOI: 10.1039/c8em00276b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Due to their small size, measurements of the complex composition of atmospheric aerosol particles and their surfaces are analytically challenging. This is particularly true for microspectroscopic methods, where it can be difficult to optically identify individual particles smaller than the diffraction limit of visible light (∼350 nm) and measure their vibrational modes. Recently, surface enhanced Raman spectroscopy (SERS) has been applied to the study of aerosol particles, allowing for detection and characterization of previously undistinguishable vibrational modes. However, atmospheric particles analyzed via SERS have primarily been >1 μm to date, much larger than the diameter of the most abundant atmospheric aerosols (∼100 nm). To push SERS towards more relevant particle sizes, a simplified approach involving Ag foil substrates was developed. Both ambient particles and several laboratory-generated model aerosol systems (polystyrene latex spheres (PSLs), ammonium sulfate, and sodium nitrate) were investigated to determine SERS enhancements. SERS spectra of monodisperse, model aerosols between 400-800 nm were compared with non-SERS enhanced spectra, yielding average enhancement factors of 102 for both inorganic and organic vibrational modes. Additionally, SERS-enabled detection of 150 nm size-selected ambient particles represent the smallest individual aerosol particles analyzed by Raman microspectroscopy to date, and the first time atmospheric particles have been measured at sizes approaching the atmospheric number size distribution mode. SERS-enabled detection and identification of vibrational modes in smaller, more atmospherically-relevant particles has the potential to improve understanding of aerosol composition and surface properties, as well as their impact on heterogeneous and multiphase reactions involving aerosol surfaces.
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Affiliation(s)
- Peter N Tirella
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
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44
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Werner J, Persson I, Björneholm O, Kawecki D, Saak CM, Walz MM, Ekholm V, Unger I, Valtl C, Caleman C, Öhrwall G, Prisle NL. Shifted equilibria of organic acids and bases in the aqueous surface region. Phys Chem Chem Phys 2018; 20:23281-23293. [PMID: 30191936 PMCID: PMC6146375 DOI: 10.1039/c8cp01898g] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Acid-base equilibria of carboxylic acids and alkyl amines in the aqueous surface region were studied using surface-sensitive X-ray photoelectron spectroscopy and molecular dynamics simulations. Solutions of these organic compounds were examined as a function of pH, concentration and chain length to investigate the distribution of acid and base form in the surface region as compared to the aqueous bulk. Results from these experiments show that the neutral forms of the studied acid-base pairs are strongly enriched in the aqueous surface region. Moreover, we show that for species with at least four carbon atoms in their alkyl-chain, their charged forms are also found to be abundant in the surface region. Using a combination of XPS and MD results, a model is proposed that effectively describes the surface composition. Resulting absolute surface concentration estimations show clearly that the total organic mole fractions in the surface region change drastically as a function of solution pH. The origin of the observed surface phenomena, hydronium/hydroxide concentrations in the aqueous surface region and why standard chemical equations, used to describe equilibria in dilute bulk solution are not valid in the aqueous surface region, are discussed in detail. The reported results are of considerable importance especially for the detailed understanding of properties of small aqueous droplets that can be found in the atmosphere.
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Affiliation(s)
- Josephina Werner
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
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45
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Craig RL, Peterson PK, Nandy L, Lei Z, Hossain MA, Camarena S, Dodson RA, Cook RD, Dutcher CS, Ault AP. Direct Determination of Aerosol pH: Size-Resolved Measurements of Submicrometer and Supermicrometer Aqueous Particles. Anal Chem 2018; 90:11232-11239. [DOI: 10.1021/acs.analchem.8b00586] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
| | | | - Lucy Nandy
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | | | | | | | | | | | - Cari S. Dutcher
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
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46
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Boreddy SKR, Kawamura K. Investigation on the hygroscopicity of oxalic acid and atmospherically relevant oxalate salts under sub- and supersaturated conditions. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2018; 20:1069-1080. [PMID: 29953162 DOI: 10.1039/c8em00053k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Oxalic acid (OxA) is an end product in the oxidation of many organic compounds, and therefore is ubiquitous in the atmosphere and is often the most abundant organic species in ambient aerosols. To better understand the hygroscopic properties of OxA under sub- and supersaturated conditions in the atmosphere, we investigated the hygroscopic growth and cloud condensation nuclei (CCN) activation ability of pure OxA and its salts using a hygroscopic tandem differential mobility analyzer (HTDMA) and cloud condensation nuclei counter (CCNC), respectively. OxA particles absorb water under >45% RH, suggesting that the initial phase state might be an amorphous solid. The measured hygroscopic growth factor (HGF) of OxA at 90% RH was 1.47. We found that the HGF of ammonium oxalate (NH4-Ox) was larger than that of OxA, whereas HGFs of sodium, calcium, and magnesium oxalates (Na-Ox, Ca-Ox, and Mg-Ox) were smaller than that of OxA particles. Potassium oxalate (K-Ox) behaved like a typical water-soluble inorganic salt, exhibiting deliquescence and efflorescence transitions at around 85% and 50% RH, respectively. Na-Ox exhibited strong activation capabilities among all the investigated salts, followed by NH4-Ox and K-Ox as inferred from the activation ratios (CCN/CN) against supersaturations (SS). On the other hand, Ca-Ox showed moderate activation ability and Mg-Ox showed poor CCN activation ability. We also observed significantly higher κCCN values compared to κHTDMA for pure OxA and its salts (NH4-Ox and Na-Ox), suggesting that the condensation of OxA into the aqueous phase occurs during water uptake. These findings improve the fundamental understanding of hygroscopic behaviors and phase states of oxalic acid and its salts under sub- and supersaturated conditions in the atmosphere and impacts of hygroscopicity on the direct and indirect effects of aerosol particles.
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Affiliation(s)
- Suresh K R Boreddy
- Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan.
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47
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Wei H, Vejerano EP, Leng W, Huang Q, Willner MR, Marr LC, Vikesland PJ. Aerosol microdroplets exhibit a stable pH gradient. Proc Natl Acad Sci U S A 2018; 115:7272-7277. [PMID: 29941550 PMCID: PMC6048471 DOI: 10.1073/pnas.1720488115] [Citation(s) in RCA: 100] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Suspended aqueous aerosol droplets (<50 µm) are microreactors for many important atmospheric reactions. In droplets and other aquatic environments, pH is arguably the key parameter dictating chemical and biological processes. The nature of the droplet air/water interface has the potential to significantly alter droplet pH relative to bulk water. Historically, it has been challenging to measure the pH of individual droplets because of their inaccessibility to conventional pH probes. In this study, we scanned droplets containing 4-mercaptobenzoic acid-functionalized gold nanoparticle pH nanoprobes by 2D and 3D laser confocal Raman microscopy. Using surface-enhanced Raman scattering, we acquired the pH distribution inside approximately 20-µm-diameter phosphate-buffered aerosol droplets and found that the pH in the core of a droplet is higher than that of bulk solution by up to 3.6 pH units. This finding suggests the accumulation of protons at the air/water interface and is consistent with recent thermodynamic model results. The existence of this pH shift was corroborated by the observation that a catalytic reaction that occurs only under basic conditions (i.e., dimerization of 4-aminothiophenol to produce dimercaptoazobenzene) occurs within the high pH core of a droplet, but not in bulk solution. Our nanoparticle probe enables pH quantification through the cross-section of an aerosol droplet, revealing a spatial gradient that has implications for acid-base-catalyzed atmospheric chemistry.
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Affiliation(s)
- Haoran Wei
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061
- Sustainable Nanotechnology Center, Virginia Tech Institute of Critical Technology and Applied Science, Blacksburg, VA 24061
- Center for the Environmental Implications of Nanotechnology, Duke University, Durham, NC 27708
| | - Eric P Vejerano
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061
- Sustainable Nanotechnology Center, Virginia Tech Institute of Critical Technology and Applied Science, Blacksburg, VA 24061
- Center for the Environmental Implications of Nanotechnology, Duke University, Durham, NC 27708
- Arnold School of Public Health, University of South Carolina, Columbia, SC 29208
| | - Weinan Leng
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061
- Sustainable Nanotechnology Center, Virginia Tech Institute of Critical Technology and Applied Science, Blacksburg, VA 24061
- Center for the Environmental Implications of Nanotechnology, Duke University, Durham, NC 27708
| | - Qishen Huang
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061
- Sustainable Nanotechnology Center, Virginia Tech Institute of Critical Technology and Applied Science, Blacksburg, VA 24061
- Center for the Environmental Implications of Nanotechnology, Duke University, Durham, NC 27708
| | - Marjorie R Willner
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061
- Sustainable Nanotechnology Center, Virginia Tech Institute of Critical Technology and Applied Science, Blacksburg, VA 24061
- Center for the Environmental Implications of Nanotechnology, Duke University, Durham, NC 27708
| | - Linsey C Marr
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061
- Sustainable Nanotechnology Center, Virginia Tech Institute of Critical Technology and Applied Science, Blacksburg, VA 24061
- Center for the Environmental Implications of Nanotechnology, Duke University, Durham, NC 27708
| | - Peter J Vikesland
- Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061;
- Sustainable Nanotechnology Center, Virginia Tech Institute of Critical Technology and Applied Science, Blacksburg, VA 24061
- Center for the Environmental Implications of Nanotechnology, Duke University, Durham, NC 27708
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48
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Losey DJ, Ott EJE, Freedman MA. Effects of High Acidity on Phase Transitions of an Organic Aerosol. J Phys Chem A 2018; 122:3819-3828. [DOI: 10.1021/acs.jpca.8b00399] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Delanie J. Losey
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Emily-Jean E. Ott
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Miriam Arak Freedman
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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49
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Vejerano EP, Marr LC. Physico-chemical characteristics of evaporating respiratory fluid droplets. J R Soc Interface 2018; 15:20170939. [PMID: 29491178 PMCID: PMC5832737 DOI: 10.1098/rsif.2017.0939] [Citation(s) in RCA: 169] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 02/05/2018] [Indexed: 11/12/2022] Open
Abstract
The detailed physico-chemical characteristics of respiratory droplets in ambient air, where they are subject to evaporation, are poorly understood. Changes in the concentration and phase of major components in a droplet-salt (NaCl), protein (mucin) and surfactant (dipalmitoylphosphatidylcholine)-may affect the viability of any pathogens contained within it and thus may affect the efficiency of transmission of infectious disease by droplets and aerosols. The objective of this study is to investigate the effect of relative humidity (RH) on the physico-chemical characteristics of evaporating droplets of model respiratory fluids. We labelled these components in model respiratory fluids and observed evaporating droplets suspended on a superhydrophobic surface using optical and fluorescence microscopy. When exposed to continuously decreasing RH, droplets of different model respiratory fluids assumed different morphologies. Loss of water induced phase separation as well as indication of a decrease in pH. The presence of surfactant inhibited the rapid rehydration of the non-volatile components. An enveloped virus, ϕ6, that has been proposed as a surrogate for influenza virus appeared to be homogeneously distributed throughout the dried droplet. We hypothesize that the increasing acidity and salinity in evaporating respiratory droplets may affect the structure of the virus, although at low enough RH, crystallization of the droplet components may eliminate their harmful effects.
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Affiliation(s)
- Eric P Vejerano
- Center for Environmental Nanoscience and Risk, Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, USA
| | - Linsey C Marr
- Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061, USA
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Pye HOT, Zuend A, Fry JL, Isaacman-VanWertz G, Capps SL, Appel KW, Foroutan H, Xu L, Ng NL, Goldstein AH. Coupling of organic and inorganic aerosol systems and the effect on gas-particle partitioning in the southeastern US. ATMOSPHERIC CHEMISTRY AND PHYSICS 2018; 18:357-370. [PMID: 29963078 PMCID: PMC6020690 DOI: 10.5194/acp-18-357-2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Several models were used to describe the partitioning of ammonia, water, and organic compounds between the gas and particle phases for conditions in the southeastern US during summer 2013. Existing equilibrium models and frameworks were found to be sufficient, although additional improvements in terms of estimating pure-species vapor pressures are needed. Thermodynamic model predictions were consistent, to first order, with a molar ratio of ammonium to sulfate of approximately 1.6 to 1.8 (ratio of ammonium to 2× sulfate, RN/2S ≈ 0.8 to 0.9) with approximately 70% of total ammonia and ammonium (NH x ) in the particle. Southeastern Aerosol Research and Characterization Network (SEARCH) gas and aerosol and Southern Oxidant and Aerosol Study (SOAS) Monitor for AeRosols and Gases in Ambient air (MARGA) aerosol measurements were consistent with these conditions. CMAQv5.2 regional chemical transport model predictions did not reflect these conditions due to a factor of 3 overestimate of the nonvolatile cations. In addition, gas-phase ammonia was overestimated in the CMAQ model leading to an even lower fraction of total ammonia in the particle. Chemical Speciation Network (CSN) and aerosol mass spectrometer (AMS) measurements indicated less ammonium per sulfate than SEARCH and MARGA measurements and were inconsistent with thermodynamic model predictions. Organic compounds were predicted to be present to some extent in the same phase as inorganic constituents, modifying their activity and resulting in a decrease in [H+]air (H+ in μgm-3 air), increase in ammonia partitioning to the gas phase, and increase in pH compared to complete organic vs. inorganic liquid-liquid phase separation. In addition, accounting for nonideal mixing modified the pH such that a fully interactive inorganic-organic system had a pH roughly 0.7 units higher than predicted using traditional methods (pH = 1.5 vs. 0.7). Particle-phase interactions of organic and inorganic compounds were found to increase partitioning towards the particle phase (vs. gas phase) for highly oxygenated (O : C≥0.6) compounds including several isoprene-derived tracers as well as levoglu-cosan but decrease particle-phase partitioning for low O: C, monoterpene-derived species.
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Affiliation(s)
- Havala O. T. Pye
- National Exposure Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USA
| | - Andreas Zuend
- Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Québec, Canada
| | - Juliane L. Fry
- Department of Chemistry, Reed College, Portland, Oregon, USA
| | - Gabriel Isaacman-VanWertz
- Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
| | - Shannon L. Capps
- Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, Pennsylvania, USA
| | - K. Wyat Appel
- National Exposure Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USA
| | - Hosein Foroutan
- National Exposure Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USA
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | - Lu Xu
- Department of Environmental Science and Engineering, California Institute of Technology, Pasadena, California, USA
| | - Nga L. Ng
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Allen H. Goldstein
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
- Department of Civil and Environmental Engineering, University of California, Berkeley, California, USA
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