1
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Kumar A, Kumar P. Dissociation of H 2O 2 on water surfaces (ice and water droplets). Phys Chem Chem Phys 2024; 26:11331-11339. [PMID: 38563356 DOI: 10.1039/d3cp04107g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
OH radicals are an important constituent of the atmosphere. Therefore, all reactions that act as a source of OH radicals are important. It is known that photo-dissociation of H2O2 is an important source of OH radicals in the atmosphere. In the present study, using Born-Oppenheimer molecular dynamics simulations, we have shown that the H2O2 molecule can dissociate thermally on water droplets, as well as on the surface of ice, to form OH radicals. Furthermore, the dissociation of H2O2 was found to be very fast (less than 50 fs) on the ice surface compared with on the water droplets. We believe this route for the formation of OH radicals could be more critical than photo-dissociation, as it can take place both during the day and at night, but further studies with more sophisticated theoretical approaches or experiments are required to confirm this hypothesis.
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Affiliation(s)
- Amit Kumar
- Department of Chemistry, Malaviya National Institute of Technology Jaipur, Jaipur, 302017, India.
| | - Pradeep Kumar
- Department of Chemistry, Malaviya National Institute of Technology Jaipur, Jaipur, 302017, India.
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2
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Jones SH, King MD, Rennie AR, Ward AD, Campbell RA, Hughes AV. Aqueous Radical Initiated Oxidation of an Organic Monolayer at the Air-Water Interface as a Proxy for Thin Films on Atmospheric Aerosol Studied with Neutron Reflectometry. J Phys Chem A 2023; 127:8922-8934. [PMID: 37830513 PMCID: PMC10614302 DOI: 10.1021/acs.jpca.3c03846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 09/12/2023] [Indexed: 10/14/2023]
Abstract
Neutron reflectometry has been used to study the radical initiated oxidation of a monolayer of the lipid 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) at the air-solution interface by aqueous-phase hydroxyl, sulfate, and nitrate radicals. The oxidation of organic films at the surface of atmospheric aqueous aerosols can influence the optical properties of the aerosol and consequently can impact Earth's radiative balance and contribute to modern climate change. The amount of material at the air-solution interface was found to decrease on exposure to aqueous-phase radicals which was consistent with a multistep degradation mechanism, i.e., the products of reaction of the DSPC film with aqueous radicals were also surface active. The multistep degradation mechanism suggests that lipid molecules in the thin film degrade to form progressively shorter chain surface active products and several reactive steps are required to remove the film from the air-solution interface. Bimolecular rate constants for oxidation via the aqueous phase OH radical cluster around 1010 dm3 mol-1 s-1. Calculations to determine the film lifetime indicate that it will take ∼4-5 days for the film to degrade to 50% of its initial amount in the atmosphere, and therefore attack by aqueous radicals on organic films could be atmospherically important relative to typical atmospheric aerosol lifetimes.
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Affiliation(s)
- Stephanie H. Jones
- Centre
of Climate, Ocean and Atmosphere, Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, U.K.
- STFC,
Central Laser Facility, Research Complex
at Harwell, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0FA, U.K.
| | - Martin D. King
- Centre
of Climate, Ocean and Atmosphere, Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, U.K.
| | - Adrian R. Rennie
- Department
of Chemistry, Angström Laboratory, Uppsala University, 75121 Uppsala, Sweden
| | - Andrew D. Ward
- STFC,
Central Laser Facility, Research Complex
at Harwell, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0FA, U.K.
| | - Richard A. Campbell
- Institut
Laue-Langevin, BP 156, 6, 71 avenue des Martyrs, CS 20156, F-38042
Cedex 9 Grenoble, France
| | - Arwel V. Hughes
- ISIS
Pulsed Neutron and Muon source, Rutherford
Appleton Laboratory, Harwell Oxford, Oxfordshire OX11 0QX, U.K.
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3
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Weatherly S, Lyons R. The photolytic conversion of 4-nonylphenol to 4-nonylcatechol within snowpack of the Palisade Glacier, Sierra Nevada, CA, USA. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 876:162835. [PMID: 36924957 DOI: 10.1016/j.scitotenv.2023.162835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/09/2023] [Accepted: 03/09/2023] [Indexed: 06/18/2023]
Abstract
4-Nonylphenol (4-NP), an environmental pollutant with potent ecotoxicological effects, has been discovered in significant quantities in glacial ice and snow of the Sierra Nevada Mountain Range, CA. Photolysis of 4-NP is suspected to be a major, if not the sole, breakdown pathway in snow. However, the photolysis process has yet to be characterized in detail for this unique environment. This study therefore seeks to (1) confirm the presence of the major photolysis product within snowpack and snowmelt samples from the Palisade Glacier, CA, (2) determine key photolysis parameters through laboratory assays in snow analogs, and (3) compute environmentally relevant photolysis rates in snowpack via a spectral solar irradiance model parameterized for the Palisade Glacier. The primary photooxidation product of 4-NP, 4-nonylcatechol (4-NC), was synthesized and characterized by NMR and GC-MS for use as a reference standard in the detection of 4-NC in environmental samples. 4-NP was detected in all snowpack (n = 4) and snowmelt (n = 5) samples, with concentrations of 1.05 (± 0.11) μg L-1 and 1.28 (± 0.12) μg L-1, respectively. 4-NC was detected in all snowmelt outflow samples and all but one snow samples (88 % detection frequency) but was below the limit of quantification for the given method. All samples were collected during a sampling regime at the Palisade Glacier in August of 2021. Quantum yields of photolysis at the 277 nm absorption band were determined to be 0.36 (±0.06) and 0.21 (±0.06) in ultrapure water and liquid snow, respectively. Under clear sky conditions at the Palisade Glacier, half-lives for 4-NP are estimated to range from 235 to 251 h (9.8-10.5 days) based on assays conducted in liquid snowmelt and irradiance modeling. These results suggest that the photolysis of 4-NP, and hence the production of 4-NC, is occurring at significant rates within the snowpack where 4-NC is inevitably released to downstream catchment areas via snowmelt. 4-NC is significantly more toxic than its precursor, thereby raising amplified concerns for downstream human and wildlife populations. Furthermore, the ubiquity of 4-NP among the Earth's environments presents this as an issue of potentially global concern.
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Affiliation(s)
- Shaun Weatherly
- University of Redlands, 1200 E Colton Ave., Redlands, CA 92373, United States of America.
| | - Rebecca Lyons
- University of Redlands, 1200 E Colton Ave., Redlands, CA 92373, United States of America
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4
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Xiao M, Tang X, Shi X, Zhang C. Indirect photodegradation of sulfadimidine and sulfapyridine: Influence of CDOM components and main seawater factors. CHEMOSPHERE 2023; 333:138821. [PMID: 37149098 DOI: 10.1016/j.chemosphere.2023.138821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Revised: 02/26/2023] [Accepted: 04/29/2023] [Indexed: 05/08/2023]
Abstract
This study investigated the indirect photodegradation of sulfadimidine (SM2) and sulfapyridine (SP) in the presence of chromophoric dissolved organic matter (CDOM), and studied the influences of main marine factors (salinity, pH, NO3- and HCO3-). Reactive intermediate (RI) trapping experiments demonstrated that triplet CDOM (3CDOM*) played a major role in the photodegradation of SM2 with a 58% photolysis contribution, and the contributions to the photolysis of SP were 32%, 34% and 34% for 3CDOM*, hydroxyl radical (HO·) and singlet oxygen (1O2), respectively. Among the four CDOMs, JKHA, with the highest fluorescence efficiency, exhibited the fastest rate of SM2 and SP photolysis. The CDOMs were composed of one autochthonous humus (C1) and two allochthonous humus (C2 and C3). C3, with the strongest fluorescence intensity, had the strongest capacity to generate RIs and accounted for approximately 22%, 11%, 9% and 38% of the total fluorescence intensity of SRHA, SRFA, SRNOM and JKHA, respectively, indicating the predominance of CDOM fluorescent components in the indirect photodegradation of SM2 and SP. These results demonstrated the photolysis mechanism: The photosensitization of CDOM occurred after its fluorescence intensity decreased, and a large number of RIs (3CDOM*, HO· and 1O2, etc.) were generated by energy and electron transfer, then these RIs reacted with SM2 and SP to cause photolysis. The increase in salinity stimulated the photolysis of SM2 and SP consecutively. The photodegradation rate of SM2 first increased and then decreased with increasing pH, whereas the photolysis of SP was remarkably promoted by high pH but remained stable at low pH. NO3- and HCO3- had little effect on the indirect photodegradation of SM2 and SP. This research may contribute to a better understanding of the fate of SM2 and SP in the ocean and provide new insights into the transformation of other sulfonamides (SAs) in marine ecological environments.
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Affiliation(s)
- Mingyan Xiao
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao, 266100, PR China
| | - Xinyu Tang
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao, 266100, PR China
| | - Xiaoyong Shi
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao, 266100, PR China; National Marine Hazard Mitigation Service, Beijing, 100194, China.
| | - Chuansong Zhang
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, 238 Songling Road, Qingdao, 266100, PR China.
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5
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Berrens ML, Bononi FC, Donadio D. Effect of sodium chloride adsorption on the surface premelting of ice. Phys Chem Chem Phys 2022; 24:20932-20940. [PMID: 36040383 DOI: 10.1039/d2cp02277j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We characterise the structural properties of the quasi-liquid layer (QLL) at two low-index ice surfaces in the presence of sodium chloride (Na+/Cl-) ions by molecular dynamics simulations. We find that the presence of a high surface density of Na+/Cl- pairs changes the surface melting behaviour from step-wise to gradual melting. The ions lead to an overall increase of the thickness and the disorder of the QLL, and to a low-temperature roughening transition of the air-ice interface. The local molecular structure of the QLL is similar to that of liquid water, and the differences between the basal and primary prismatic surface are attenuated by the presence of Na+/Cl- pairs. These changes modify the crystal growth rates of different facets and the solvation environment at the surface of sea-water ice with a potential impact on light scattering and environmental chemical reactions.
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Affiliation(s)
- Margaret L Berrens
- Department of Chemistry, University of California Davis, Davis, CA, 95616, USA.
| | - Fernanda C Bononi
- Department of Chemistry, University of California Davis, Davis, CA, 95616, USA.
| | - Davide Donadio
- Department of Chemistry, University of California Davis, Davis, CA, 95616, USA.
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6
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Sunlight-driven nitrate loss records Antarctic surface mass balance. Nat Commun 2022; 13:4274. [PMID: 35879324 PMCID: PMC9314437 DOI: 10.1038/s41467-022-31855-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 07/06/2022] [Indexed: 11/08/2022] Open
Abstract
Standard proxies for reconstructing surface mass balance (SMB) in Antarctic ice cores are often inaccurate or coarsely resolved when applied to more complicated environments away from dome summits. Here, we propose an alternative SMB proxy based on photolytic fractionation of nitrogen isotopes in nitrate observed at 114 sites throughout East Antarctica. Applying this proxy approach to nitrate in a shallow core drilled at a moderate SMB site (Aurora Basin North), we reconstruct 700 years of SMB changes that agree well with changes estimated from ice core density and upstream surface topography. For the under-sampled transition zones between dome summits and the coast, we show that this proxy can provide past and present SMB values that reflect the immediate local environment and are derived independently from existing techniques.
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7
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Hong J, Liu L, Zhang Z, Xia X, Yang L, Ning Z, Liu C, Qiu G. Sulfate-accelerated photochemical oxidation of arsenopyrite in acidic systems under oxic conditions: Formation and function of schwertmannite. JOURNAL OF HAZARDOUS MATERIALS 2022; 433:128716. [PMID: 35358816 DOI: 10.1016/j.jhazmat.2022.128716] [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: 01/08/2022] [Revised: 03/12/2022] [Accepted: 03/13/2022] [Indexed: 06/14/2023]
Abstract
The weathering of arsenopyrite is closely related to the generation of acid mine drainage (AMD) and arsenic (As) pollution. Solar radiation can accelerate arsenopyrite oxidation, but little is known about the further effect of SO42- on the photochemical process. Here, the photooxidation of arsenopyrite was investigated in the presence of SO42- in simulated AMD environments, and the effects of SO42- concentration, pH and dissolved oxygen on arsenopyrite oxidation were studied as well. SO42- could accelerate the photooxidation of arsenopyrite and As(III) through complexation between nascent schwertmannite and As(III). Fe(II) released from arsenopyrite was oxidized to form schwertmannite in the presence of SO42-, and the photooxidation of arsenopyrite occurred through the ligand-to-metal charge-transfer process in schwertmannite-As(III) complex along with the formation of reactive oxygen species in the presence of O2. The photooxidation rate of arsenopyrite first rose and then fell with increasing SO42- concentration. In the pH range of 2.0-4.0, the photooxidation rate of arsenopyrite progressively increased in the presence of SO42-. This study reveals how SO42- promotes the photooxidation of arsenopyrite and As release in the AMD environment, and improves the understanding of the transformation and migration of As in mining areas.
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Affiliation(s)
- Jun Hong
- Key Laboratory of Fertilization from Agricultural Wastes, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Soil Fertilizer, Hubei Academy of Agricultural Sciences, Wuhan 430070, Hubei Province, China; College of Resources and Environment, Interdisciplinary Sciences Institute, Huazhong Agricultural University, Wuhan 430070, Hubei Province, China
| | - Lihu Liu
- College of Resources and Environment, Interdisciplinary Sciences Institute, Huazhong Agricultural University, Wuhan 430070, Hubei Province, China
| | - Ziwei Zhang
- College of Resources and Environment, Interdisciplinary Sciences Institute, Huazhong Agricultural University, Wuhan 430070, Hubei Province, China
| | - Xiange Xia
- Key Laboratory of Fertilization from Agricultural Wastes, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Soil Fertilizer, Hubei Academy of Agricultural Sciences, Wuhan 430070, Hubei Province, China.
| | - Li Yang
- Key Laboratory of Fertilization from Agricultural Wastes, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Soil Fertilizer, Hubei Academy of Agricultural Sciences, Wuhan 430070, Hubei Province, China
| | - Zengping Ning
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, Guizhou Province, China
| | - Chengshuai Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, Guizhou Province, China
| | - Guohong Qiu
- College of Resources and Environment, Interdisciplinary Sciences Institute, Huazhong Agricultural University, Wuhan 430070, Hubei Province, China.
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8
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Zhong W, Fu W, Sun S, Wang L, Liu H, Wang J. Characterization of TiO 2 and an as-prepared TiO 2/SiO 2 composite and their photocatalytic performance for the reduction of low-concentration N-NO 3- in water. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:40585-40598. [PMID: 35084675 DOI: 10.1007/s11356-022-18793-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
Excessive N-NO3- water pollution has become a widespread and serious problem that threatens human and ecosystem health. Here, a TiO2/SiO2 composite photocatalyst was prepared via the sol-gel/hydrothermal method. TiO2 and TiO2/SiO2 were characterized by X-ray diffraction (XRD), UV-Vis differential reflectance spectroscopy (DRS), Fourier infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Afterward, the photocatalytic performance of TiO2 and TiO2/SiO2 to reduce low nitrate concentrations (30 mgN L-1) under UV light was evaluated and the effects of different factors on this process were investigated, after which the reaction conditions were optimized. Removal rates of up to 99.93% were achieved at a hole scavenger (formic acid) concentration of 0.6 mL L-1, a CO2 flow rate of 0.1 m3 h-1, and a TiO2 concentration of 0.9 g L-1. In contrast, TiO2/SiO2 at a 1.4 g L-1 concentration and a TiO2 load rate of 40% achieved a removal rate of 83.48%, but with more than 98% of nitrogen generation rate. NO2- and NH4+ were the minor products, whereas N2 was the main product.
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Affiliation(s)
- Wanzhen Zhong
- College of Resources and Environment, Shandong Agricultural University, Tai'an, 271018, People's Republic of China
- School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao, 266000, China
| | - Weizhang Fu
- College of Resources and Environment, Shandong Agricultural University, Tai'an, 271018, People's Republic of China.
| | - Shujuan Sun
- College of Resources and Environment, Shandong Agricultural University, Tai'an, 271018, People's Republic of China.
| | - Lingsheng Wang
- College of Resources and Environment, Shandong Agricultural University, Tai'an, 271018, People's Republic of China
| | - Huaihao Liu
- College of Resources and Environment, Shandong Agricultural University, Tai'an, 271018, People's Republic of China
| | - Junzhi Wang
- School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao, 266000, China
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9
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Wang Y, Huang DD, Huang W, Liu B, Chen Q, Huang R, Gen M, Mabato BRG, Chan CK, Li X, Hao T, Tan Y, Hoi KI, Mok KM, Li YJ. Enhanced Nitrite Production from the Aqueous Photolysis of Nitrate in the Presence of Vanillic Acid and Implications for the Roles of Light-Absorbing Organics. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:15694-15704. [PMID: 34784716 DOI: 10.1021/acs.est.1c04642] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A prominent source of hydroxyl radicals (•OH), nitrous acid (HONO) plays a key role in tropospheric chemistry. Apart from direct emission, HONO (or its conjugate base nitrite, NO2-) can be formed secondarily in the atmosphere. Yet, how secondary HONO forms requires elucidation, especially for heterogeneous processes involving numerous organic compounds in atmospheric aerosols. We investigated nitrite production from aqueous photolysis of nitrate for a range of conditions (pH, organic compound, nitrate concentration, and cation). Upon adding small oxygenates such as ethanol, n-butanol, or formate as •OH scavengers, the average intrinsic quantum yield of nitrite [Φ(NO2-)] was 0.75 ± 0.15%. With near-UV-light-absorbing vanillic acid (VA), however, the effective Φ(NO2-) was strongly pH-dependent, reaching 8.0 ± 2.1% at a pH of 8 and 1.5 ± 0.39% at a more atmospherically relevant pH of 5. Our results suggest that brown carbon (BrC) may greatly enhance the nitrite production from the aqueous nitrate photolysis through photosensitizing reactions, where the triplet excited state of BrC may generate solvated electrons, which reduce nitrate to NO2 for further conversion to nitrite. This photosensitization process by BrC chromophores during nitrate photolysis under mildly acidic conditions may partly explain the missing HONO in urban environments.
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Affiliation(s)
- Yalin Wang
- Department of Civil and Environmental Engineering, and Centre for Regional Oceans, Faculty of Science and Technology, University of Macau, Macau 999078, China
| | - Dan Dan Huang
- Shanghai Academy of Environmental Sciences, Shanghai 200233, China
| | - Wanyi Huang
- Department of Civil and Environmental Engineering, and Centre for Regional Oceans, Faculty of Science and Technology, University of Macau, Macau 999078, China
| | - Ben Liu
- Department of Civil and Environmental Engineering, and Centre for Regional Oceans, Faculty of Science and Technology, University of Macau, Macau 999078, China
| | - Qi Chen
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, BIC-ESAT and IJRC, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Rujin Huang
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
| | - Masao Gen
- Faculty of Frontier Engineering, Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | | | - Chak K Chan
- School of Energy and Environment, City University of Hong Kong, Hong Kong 999077, China
| | - Xue Li
- Institute of Mass Spectrometry and Atmospheric Environment, Jinan University, Guangzhou 510632, China
| | - Tianwei Hao
- Department of Civil and Environmental Engineering, and Centre for Regional Oceans, Faculty of Science and Technology, University of Macau, Macau 999078, China
| | - Yunkai Tan
- Department of Civil and Environmental Engineering, and Centre for Regional Oceans, Faculty of Science and Technology, University of Macau, Macau 999078, China
| | - Ka In Hoi
- Department of Civil and Environmental Engineering, and Centre for Regional Oceans, Faculty of Science and Technology, University of Macau, Macau 999078, China
| | - Kai Meng Mok
- Department of Civil and Environmental Engineering, and Centre for Regional Oceans, Faculty of Science and Technology, University of Macau, Macau 999078, China
| | - Yong Jie Li
- Department of Civil and Environmental Engineering, and Centre for Regional Oceans, Faculty of Science and Technology, University of Macau, Macau 999078, China
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10
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Gen M, Zhang R, Chan CK. Nitrite/Nitrous Acid Generation from the Reaction of Nitrate and Fe(II) Promoted by Photolysis of Iron-Organic Complexes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:15715-15723. [PMID: 34812628 DOI: 10.1021/acs.est.1c05641] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Gaseous nitrous acid (HONO) has the potential to greatly contribute to the atmospheric oxidation capacity. Increased attention has been paid to in-particle nitrite or nitrous acid, N(III), as one of the HONO sources. However, sources and formation mechanisms of N(III) remain uncertain. Here, we study a much less examined reaction of Fe(II) and nitrate as a source of N(III). The N(III) production was indirectly probed by its multiphase reaction with SO2 for sulfate production. Particles containing nitrate and Fe(III) were irradiated for generating Fe(II). Sulfate production was enhanced by the presence of UV and organic compounds likely because of the enhanced redox cycle between Fe(II) and Fe(III). Sulfate production rate increases with the concentration of iron-organic complexes in nitrate particles. Similarly, higher concentrations of iron-organic complexes yield higher nitrate decay rates. The estimated production rates of N(III) under simulated conditions in our study vary from 0.1 to 3.0 μg m-3 of air h-1. These values are comparable to HONO production rates of 0.2-1.6 ppbv h-1, which fall in the values reported in laboratory and field studies. The present study highlights a synergistic effect of the coexistence of iron-organic complexes and nitrate under irradiation as a source of N(III).
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Affiliation(s)
- Masao Gen
- Faculty of Frontier Engineering, Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong 999077, China
| | - Ruifeng Zhang
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong 999077, China
| | - Chak Keung Chan
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong 999077, China
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11
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Sršeň Š, Slavíček P. Optimal Representation of the Nuclear Ensemble: Application to Electronic Spectroscopy. J Chem Theory Comput 2021; 17:6395-6404. [PMID: 34542278 DOI: 10.1021/acs.jctc.1c00749] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nuclear densities are frequently represented by an ensemble of nuclear configurations or points in the phase space in various contexts of molecular simulations. The size of the ensemble directly affects the accuracy and computational cost of subsequent calculations of observable quantities. In the present work, we address the question of how many configurations do we need and how to select them most efficiently. We focus on the nuclear ensemble method in the context of electronic spectroscopy, where thousands of sampled configurations are usually needed for sufficiently converged spectra. The proposed representative sampling technique allows for a dramatic reduction of the sample size. By using an exploratory method, we model the density from a large sample in the space of transition properties. The representative subset of nuclear configurations is optimized by minimizing its Kullback-Leibler divergence to the full density with simulated annealing. High-level calculations are then performed only for the selected subset of configurations. We tested the algorithm on electronic absorption spectra of three molecules: (E)-azobenzene, the simplest Criegee intermediate, and hydrated nitrate anion. Typically, dozens of nuclear configurations provided sufficiently accurate spectra. A strongly forbidden transition of the nitrate anion presented the most challenging case due to rare geometries with disproportionately high transition intensities. This problematic case was easily diagnosed within the present approach. We also discuss various exploratory methods and a possible extension to dynamical simulations.
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Affiliation(s)
- Štěpán Sršeň
- Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, Prague 16628, Czech Republic
| | - Petr Slavíček
- Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, Prague 16628, Czech Republic
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12
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Ma L, Guzman C, Niedek C, Tran T, Zhang Q, Anastasio C. Kinetics and Mass Yields of Aqueous Secondary Organic Aerosol from Highly Substituted Phenols Reacting with a Triplet Excited State. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:5772-5781. [PMID: 33851829 DOI: 10.1021/acs.est.1c00575] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Biomass burning emits large amounts of phenols, which can partition into cloud/fog drops and aerosol liquid water (ALW) and react to form aqueous secondary organic aerosol (aqSOA). Triplet excited states of organic compounds (3C*) are likely oxidants, but there are no rate constants with highly substituted phenols that have high Henry's law constants (KH) and are likely important in ALW. To address this gap, we investigated the kinetics of six highly substituted phenols with the triplet excited state of 3,4-dimethoxybenzaldehyde. Second-order rate constants at pH 2 are all fast, (2.6-4.6) × 109 M-1 s-1, while values at pH 5 are 2-5 times smaller. Rate constants are reasonably described by a quantitative structure-activity relationship with phenol oxidation potentials, allowing rate constants of other phenols to be predicted. Triplet-phenol kinetics are unaffected by ammonium sulfate, sodium chloride, galactose (a biomass-burning sugar), or Fe(III). In contrast, ammonium nitrate increases the rate of phenol loss by making hydroxyl radicals, while Cu(II) inhibits phenol decay. Mass yields of aqueous SOA from triplet reactions are large and range from 59 to 99%. Calculations using our data along with previous oxidant measurements indicate that phenols with high KH can be an important source of aqSOA in ALW, with 3C* typically the dominant oxidant.
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Affiliation(s)
- Lan Ma
- Department of Land, Air, and Water Resources, University of California, Davis, California 95616, United States
| | - Chrystal Guzman
- Department of Land, Air, and Water Resources, University of California, Davis, California 95616, United States
| | - Christopher Niedek
- Department of Environmental Toxicology, University of California, Davis, California 95616, United States
| | - Theodore Tran
- Department of Land, Air, and Water Resources, University of California, Davis, California 95616, United States
| | - Qi Zhang
- Department of Environmental Toxicology, University of California, Davis, California 95616, United States
| | - Cort Anastasio
- Department of Land, Air, and Water Resources, University of California, Davis, California 95616, United States
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13
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Shi Q, Tao Y, Krechmer JE, Heald CL, Murphy JG, Kroll JH, Ye Q. Laboratory Investigation of Renoxification from the Photolysis of Inorganic Particulate Nitrate. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:854-861. [PMID: 33393757 DOI: 10.1021/acs.est.0c06049] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Nitrogen oxides (NOx) play a key role in regulating the oxidizing capacity of the atmosphere through controlling the abundance of O3, OH, and other important gas and particle species. Some recent studies have suggested that particulate nitrate, which is conventionally considered as the ultimate oxidation product of NOx, can undergo "renoxification" via photolysis, recycling NOx and HONO back to the gas phase. However, there are large discrepancies in estimates of the importance of this channel, with reported renoxification rate constants spanning three orders of magnitude. In addition, previous laboratory studies derived the rate constant using bulk particle samples collected on substrates instead of suspended particles. In this work, we study renoxification of suspended submicron particulate sodium and ammonium nitrate through controlled laboratory photolysis experiments using an environmental chamber. We find that, under atmospherically relevant wavelengths and relative humidities, particulate inorganic nitrate releases NOx and HONO less than 10 times as rapidly as gaseous nitric acid, putting our measurements on the low end of recently reported renoxification rate constants. To the extent that our laboratory conditions are representative of the real atmosphere, renoxification from the photolysis of inorganic particulate nitrate appears to play a limited role in contributing to the NOx and OH budgets in remote environments. These results are based on simplified model systems; future studies should investigate renoxification of more complex aerosol mixtures that represent a broader spectrum of aerosol properties to better constrain the photolysis of ambient aerosols.
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Affiliation(s)
- Qianwen Shi
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario M1C 1A4, Canada
| | - Ye Tao
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario M1C 1A4, Canada
| | - Jordan E Krechmer
- Center for Aerosol and Cloud Chemistry, Aerodyne Research Incorporated, Billerica, Massachusetts 01821, United States
| | - Colette L Heald
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Jennifer G Murphy
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Jesse H Kroll
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Qing Ye
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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14
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Bononi FC, Chen Z, Rocca D, Andreussi O, Hullar T, Anastasio C, Donadio D. Bathochromic Shift in the UV–Visible Absorption Spectra of Phenols at Ice Surfaces: Insights from First-Principles Calculations. J Phys Chem A 2020; 124:9288-9298. [DOI: 10.1021/acs.jpca.0c07038] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Fernanda C. Bononi
- Department of Chemistry, University of California Davis, Davis, California 95616-5270, United States
| | - Zekun Chen
- Department of Chemistry, University of California Davis, Davis, California 95616-5270, United States
| | - Dario Rocca
- Université de Lorraine, CNRS, LPTC, F-54000 Nancy, France
| | - Oliviero Andreussi
- Department of Physics, University of North Texas Denton, Texas 76203, United States
| | - Ted Hullar
- Department of Land, Air and Water Resources, University of California Davis Davis, California 95616-8627, United States
| | - Cort Anastasio
- Department of Land, Air and Water Resources, University of California Davis Davis, California 95616-8627, United States
| | - Davide Donadio
- Department of Chemistry, University of California Davis, Davis, California 95616-5270, United States
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15
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Xue H, Gao S, Li M, Wang Y, Liu B. Performance of ultraviolet/persulfate process in degrading artificial sweetener acesulfame. ENVIRONMENTAL RESEARCH 2020; 188:109804. [PMID: 32798943 DOI: 10.1016/j.envres.2020.109804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 06/06/2020] [Indexed: 06/11/2023]
Abstract
The degradation of the artificial sweetener acesulfame (ACE) was investigated using an ultraviolet (UV)365-activated peroxydisulfate (PDS) process. The results demonstrated that the ACE reaction rate with the UV/PDS process followed pseudo first-order kinetics (R2 > 0.9) under various conditions. A high dosage of PDS, alkaline condition, and the existence of NO3- and Cl- enhanced ACE degradation; however, a high dosage of ACE, the existence of HCO3-, humic acid, and fulvic acid, and a real water matrix did not facilitate the degradation of ACE. Four types of transformation products were detected in the degradation of ACE by UV/PDS, and the primary degradation pathways were oxidation, hydroxyl substitution, hydrolysis, and hydration. The hydroxyl radicals played a predominant role (71.31%) in the degradation of ACE by the UV/PDS process, followed by sulfate radicals (14.57%) and UV photolysis (8.83%). Both the degradation and mineralization rates of ACE using the UV/PDS process had significant advantages over that of the UV/H2O2 process regarding ACE degradation, indicating that the UV/PDS process is more promising for treating water containing ACE.
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Affiliation(s)
- Honghai Xue
- Key Laboratory of Songliao Aquatic Environment, Ministry of Education, Jilin Jianzhu University, Changchun, PR China.
| | - Siyu Gao
- Key Laboratory of Songliao Aquatic Environment, Ministry of Education, Jilin Jianzhu University, Changchun, PR China.
| | - Ming Li
- Key Laboratory of Songliao Aquatic Environment, Ministry of Education, Jilin Jianzhu University, Changchun, PR China.
| | - Ying Wang
- Key Laboratory of Songliao Aquatic Environment, Ministry of Education, Jilin Jianzhu University, Changchun, PR China.
| | - Binshuo Liu
- Graduate Student Department, Jilin Jianzhu University, Changchun, PR China.
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16
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Gen M, Zhang R, Li Y, Chan CK. Multiphase Photochemistry of Iron-Chloride Containing Particles as a Source of Aqueous Chlorine Radicals and Its Effect on Sulfate Production. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:9862-9871. [PMID: 32668147 DOI: 10.1021/acs.est.0c01540] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Photolysis of iron chlorides is a well-known photolytic source of Cl• in environmental waters. However, the role of particulate chlorine radicals (Cl• and Cl2•-) in their multiphase oxidative potential has been much less explored. Herein, we examine the effect of Cl•/Cl2•- produced from photolysis of particulate iron chlorides on atmospheric multiphase oxidation. As a model system, experiments on multiphase oxidation of SO2 by Cl•/Cl2•- were performed. Fast sulfate production from SO2 oxidation was observed with reactive uptake coefficients of ∼10-5, comparable to the values necessary for explaining the observations in the haze events in China. The experimental and modeling results found a good positive correlation between the uptake coefficient, γSO2, and the Cl• production rate, d[Cl•]/dt, as γSO2 = 5.3 × 10-6 × log(d[Cl•]/dt) + 4.9 × 10-5. When commonly found particulate dicarboxylic acids (oxalic acid or malonic acid) were added, sulfate production was delayed due to the competition of Fe3+ between chloride and the dicarboxylic acid for its complexation at the initial stage. After the delay, comparable sulfate production was observed. The present study highlights the importance of photochemistry of particulate iron chlorides in multiphase oxidation processes in the atmosphere.
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Affiliation(s)
- Masao Gen
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
- Faculty of Frontier Engineering, Institute of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Ruifeng Zhang
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
| | - Yongjie Li
- Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macau 999078, China
| | - Chak K Chan
- School of Energy and Environment, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
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17
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Hullar T, Bononi FC, Chen Z, Magadia D, Palmer O, Tran T, Rocca D, Andreussi O, Donadio D, Anastasio C. Photodecay of guaiacol is faster in ice, and even more rapid on ice, than in aqueous solution. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:1666-1677. [PMID: 32671365 DOI: 10.1039/d0em00242a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Snowpacks contain a wide variety of inorganic and organic compounds, including some that absorb sunlight and undergo direct photoreactions. How the rates of these reactions in, and on, ice compare to rates in water is unclear: some studies report similar rates, while others find faster rates in/on ice. Further complicating our understanding, there is conflicting evidence whether chemicals react more quickly at the air-ice interface compared to in liquid-like regions (LLRs) within the ice. To address these questions, we measured the photodegradation rate of guaiacol (2-methoxyphenol) in various sample types, including in solution, in ice, and at the air-ice interface of nature-identical snow. Compared to aqueous solution, we find modest rate constant enhancements (increases of 3- to 6-fold) in ice LLRs, and much larger enhancements (of 17- to 77-fold) at the air-ice interface of nature-identical snow. Our computational modeling suggests the absorption spectrum for guaiacol red-shifts and increases on ice surfaces, leading to more light absorption, but these changes explain only a small portion (roughly 2 to 9%) of the observed rate constant enhancements in/on ice. This indicates that increases in the quantum yield are primarily responsible for the increased photoreactivity of guaiacol on ice; relative to solution, our results suggest that the quantum yield is larger by a factor of roughly 3-6 in liquid-like regions and 12-40 at the air-ice interface.
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Affiliation(s)
- Ted Hullar
- Department of Land, Air and Water Resources, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
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18
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Bu L, Zhu N, Li C, Huang Y, Kong M, Duan X, Dionysiou DD. Susceptibility of atrazine photo-degradation in the presence of nitrate: Impact of wavelengths and significant role of reactive nitrogen species. JOURNAL OF HAZARDOUS MATERIALS 2020; 388:121760. [PMID: 31810806 DOI: 10.1016/j.jhazmat.2019.121760] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 11/20/2019] [Accepted: 11/25/2019] [Indexed: 06/10/2023]
Abstract
The role of reactive nitrogen species (RNS) formed from nitrate photolysis has aroused interests in transformation of contaminants of emerging concern. This study investigated the influence of UV wavelengths (255, 285 and 365 nm) on photolysis of nitrate for degradation of atrazine (ATZ). The UV285/nitrate system showed the fastest rate constant for degradation of ATZ with kobs of 0.0022 cm2 mJ-1. UV photolysis, RNS, and hydroxyl radical (HO) were identified as main contributors to ATZ degradation in UV/nitrate system. Among the contributors, RNS made the major contribution to degradation of ATZ in UV285/nitrate system, while HO is the predominant specie in UV255/nitrate system. Variance decomposition analysis showed that degradation of ATZ was slightly impacted by natural organic matter and carbonate/bicarbonate in UV285/nitrate system but was dramatically affected in UV255/nitrate system. Main transformation products of ATZ in UV285/nitrate system were identified and possible pathways were proposed. RNS were confirmed to be favorable for acceleration of ATZ photolysis through further reaction of RNS with hydroxyatrazine (with electron-rich moieties). Our study provides deep insights on the influence of UV wavelength on nitrate photolysis and ATZ degradation, and provides a novel method for remediation of water co-contaminated by nitrate and organic contaminants.
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Affiliation(s)
- Lingjun Bu
- Key Laboratory of Building Safety and Energy Efficiency, Ministry of Education, Department of Water Engineering and Science, College of Civil Engineering, Hunan University, Changsha, 410082, China; Department of Chemical and Environmental Engineering, 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012, USA
| | - Ningyuan Zhu
- Department of Chemical and Environmental Engineering, 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012, USA; Zigui Ecological Station for Three Gorges Dam Project, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Sciences, Chinese Academy of Sciences, 71 East Beijing Road, Nanjing 210008, China
| | - Chunquan Li
- Department of Chemical and Environmental Engineering, 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012, USA; School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
| | - Ying Huang
- Department of Chemical and Environmental Engineering, 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012, USA
| | - Minghao Kong
- Department of Chemical and Environmental Engineering, 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012, USA
| | - Xiaodi Duan
- Department of Chemical and Environmental Engineering, 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012, USA.
| | - Dionysios D Dionysiou
- Department of Chemical and Environmental Engineering, 705 Engineering Research Center, University of Cincinnati, Cincinnati, OH 45221-0012, USA
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19
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Hullar T, Magadia D, Anastasio C. Photodegradation Rate Constants for Anthracene and Pyrene Are Similar in/on Ice and in Aqueous Solution. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:12225-12234. [PMID: 30251528 DOI: 10.1021/acs.est.8b02350] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Snowpacks contain a variety of chemicals, including organic pollutants such as toxic polycyclic aromatic hydrocarbons (PAHs). While PAHs undergo photodegradation in snow and ice, the rates of these reactions remain in debate. Some studies report that photochemical reactions in snow proceed at rates similar to those expected in a supercooled aqueous solution, but other studies report faster reaction rates, particularly at the air-ice interface (i.e., the quasi-liquid layer, or QLL). In addition, one study reported a surprising nonlinear dependence on photon flux. Here we examine the photodegradation of two common PAHs, anthracene and pyrene, in/on ice and in solution. For a given PAH, rate constants are similar in aqueous solution, in internal liquid-like regions of ice, and at the air-ice interface. In addition, we find the expected linear relationship between reaction rate constant and photon flux. Our results indicate that rate constants for the photochemical loss of PAHs in, and on, snow and ice are very similar to those in aqueous solution, with no enhancement at the air-ice interface.
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Affiliation(s)
- Ted Hullar
- Department of Land, Air and Water Resources , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
| | - Danielle Magadia
- Department of Land, Air and Water Resources , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
- Now at California Department of Food and Agriculture , 3292 Meadowview , Sacramento , California 95832 , United States
| | - Cort Anastasio
- Department of Land, Air and Water Resources , University of California, Davis , One Shields Avenue , Davis , California 95616 , United States
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20
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McFall AS, Edwards KC, Anastasio C. Nitrate Photochemistry at the Air-Ice Interface and in Other Ice Reservoirs. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:5710-5717. [PMID: 29667816 DOI: 10.1021/acs.est.8b00095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The photolysis of snowpack nitrate (NO3-) is an important source of gaseous reactive nitrogen species that affect atmospheric oxidants, particularly in remote regions. However, it is unclear whether nitrate photochemistry differs between the three solute reservoirs in/on ice: in liquid-like regions (LLRs) in the ice; within the solid ice matrix; and in a quasi-liquid layer (QLL) at the air-ice interface, where past work indicates photolysis is enhanced. In this work, we explore the photoformation of nitrite in these reservoirs using laboratory ices. Nitrite quantum yields, Φ(NO2-), at 313 nm for aqueous and LLR ice samples agree with previous values, e.g., 0.65 ± 0.07% at -10 °C. For ice samples made via flash-freezing solution in liquid nitrogen, where nitrate is possibly present as a solid solution, the nitrite quantum yield is 0.57 ± 0.05% at -10 °C, similar to the LLR results. In contrast, the quantum yield at the air-ice interface is enhanced by a factor of 3.7 relative to LLRs, with a value of 2.39 ± 0.24%. These results indicate nitrate photolysis is enhanced at the air-ice interface, although the importance of this enhancement in the environment depends on the amount of nitrate present at the interface.
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Affiliation(s)
- Alexander S McFall
- Department of Land, Air, and Water Resources , University of California, Davis , Davis , California 95616 , United States
| | - Kasey C Edwards
- Department of Land, Air, and Water Resources , University of California, Davis , Davis , California 95616 , United States
| | - Cort Anastasio
- Department of Land, Air, and Water Resources , University of California, Davis , Davis , California 95616 , United States
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21
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Zhu Y, Kieber DJ. Wavelength- and Temperature-Dependent Apparent Quantum Yields for Photochemical Production of Carbonyl Compounds in the North Pacific Ocean. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:1929-1939. [PMID: 29286649 DOI: 10.1021/acs.est.7b05462] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Photolysis of dissolved organic matter is the main source of carbonyl compounds in sunlit seawater, but rates and photoefficiences are poorly constrained. Wavelength- and temperature-dependent apparent quantum yields (AQYs) were determined for photochemical production of acetaldehyde, glyoxal, and methylglyoxal in North Pacific Ocean seawater. Wavelength-dependent AQYs at 20 °C decreased exponentially with increasing wavelength between 290 and 380 nm, from 1.29 × 10-4 to 4.12 × 10-6, 2.52 × 10-5 to 6.89 × 10-7, and 4.37 × 10-6 to 1.25 × 10-7 mol (mol quanta)-1 for acetaldehyde, glyoxal, and methylglyoxal, respectively. AQYs decreased after 6 h irradiation at 310 nm, possibly due to depletion of photochemical precursors or carbonyl photolysis. Average activation energies (95% CI) for photochemical production at 320 nm were 9.31 (±9.3), 26.0 (±7.5), and 34.7 (±12.8) kJ mol-1 for acetaldehyde, glyoxal, and methylglyoxal, respectively. The peak response for photochemical production rates in surface seawater was ∼325 nm, with ∼30% contribution from UV-B and ∼70% from UV-A. Computed noontime wavelength-integrated photoproduction rates were 0.5-0.8, 0.04-0.2, and 0.03-0.06 nmol L-1 h-1 for acetaldehyde, glyoxal, and methylglyoxal, respectively, under cloudless conditions in August. Results can be used to determine regional-scale photochemical production rates for these compounds in the surface ocean.
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Affiliation(s)
- Yuting Zhu
- Department of Chemistry, State University of New York, College of Environmental Science and Forestry , 1 Forestry Drive, Syracuse, New York 13210, United States
| | - David J Kieber
- Department of Chemistry, State University of New York, College of Environmental Science and Forestry , 1 Forestry Drive, Syracuse, New York 13210, United States
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22
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Phan TTN, Nikoloski AN, Bahri PA, Li D. Adsorption and photo-Fenton catalytic degradation of organic dyes over crystalline LaFeO3-doped porous silica. RSC Adv 2018; 8:36181-36190. [PMID: 35558479 PMCID: PMC9088607 DOI: 10.1039/c8ra07073c] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 10/16/2018] [Indexed: 01/20/2023] Open
Abstract
LaFeO3 (LFO)-doped mesoporous silica (HPS) (HPS-xLFO with theoretical LFO/silica molar ratio x = 0.075, 0.15, 0.3) was successfully prepared via impregnation of metal ions into the porous silica HPS-0LFO support and subsequent calcination. The characterization studies suggest that increasing the doping of LFO, which exhibited a particle size of ∼10–15 nm, in the silica support led to a reduction in surface area and bandgap of the resulting catalyst. The use of HPS-0.15LFO yielded a superior removal rate (98.9%) of Rhodamine B (RhB), thanks to the effective dark adsorption and visible light-induced photo-Fenton degradation, both of which were greater than those of pure LFO crystals. This enhancement could be explained by the unique properties of the mesoporous silica support. In particular, the wide-opening mesopores created a large surface area to dope LFO as active sites and minimize diffusion of RhB into pores during the photo-Fenton reaction. The photo-Fenton catalytic degradation of RhB could reach 98.6% within 90 min exposure to visible light irradiation under optimized conditions: RhB concentration = 10 mg L−1, catalyst dosage = 1 g L−1, pH = 6 and H2O2 = 15 mM. Moreover, the recycle and reuse test proved the good stability and repetitive use of HPS-0.15LFO for high performance RhB removal. LFO-doped mesoporous silica yielded high removal rate of dye, due to the dark adsorption and visible light-induced photo-Fenton degradation.![]()
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Affiliation(s)
- Thi To Nga Phan
- Chemical and Metallurgical Engineering and Chemistry
- School of Engineering and Information Technology
- Murdoch University
- Australia
| | - Aleksandar N. Nikoloski
- Chemical and Metallurgical Engineering and Chemistry
- School of Engineering and Information Technology
- Murdoch University
- Australia
| | - Parisa Arabzadeh Bahri
- Chemical and Metallurgical Engineering and Chemistry
- School of Engineering and Information Technology
- Murdoch University
- Australia
| | - Dan Li
- Chemical and Metallurgical Engineering and Chemistry
- School of Engineering and Information Technology
- Murdoch University
- Australia
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23
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Tugaoen HO, Garcia-Segura S, Hristovski K, Westerhoff P. Challenges in photocatalytic reduction of nitrate as a water treatment technology. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 599-600:1524-1551. [PMID: 28531961 DOI: 10.1016/j.scitotenv.2017.04.238] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 04/28/2017] [Accepted: 04/29/2017] [Indexed: 06/07/2023]
Abstract
Management of ubiquitous nitrate contamination in drinking water sources is a major engineering challenge due to its negative impacts from eutrophication to immediate risk to human health. Several water treatment technologies exist to manage nitrate pollution in water sources. However, the most widely used technologies are phase separation treatments. In this context, nanoscale photocatalysis emerges as a highly promising transformative technology capable of reducing nitrate to innocuous nitrogen with noticeable selectivity. This critical review describes the photocatalytic reduction mechanisms of nitrate towards undesirable products (nitrite, ammonium) and the more desirable product (dinitrogen). The mechanisms are based on the standard reduction potential of each individual species and highlight the contribution of reducing species (e.g. CO2-) radicals formed from different hole scavengers. The strategic use of different pure, doped, and composite nanoscale photocatalysts is discussed on the basis of reduction mechanisms' overall conversion, kinetic rates, and selectivity towards N2. The choice of light source affects pathways and influences by-product selectivity because direct photolysis of N-intermediates, which has been overlooked in the literature. In addition, the re-oxidation of nitrite and ammonia as drawback process is explained. Finally, an exhaustive analysis presents the photocatalytic reduction applications for treating real water matrices and the competing effect of other species. Overall, this critical review aims to contribute to the understanding of the potential application/constraints of photocatalysis in inorganic nitrogen management, and guide researchers towards future efforts required for widespread implementation.
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Affiliation(s)
- Heather O'Neal Tugaoen
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-3005, USA
| | - Sergi Garcia-Segura
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-3005, USA
| | - Kiril Hristovski
- The Polytechnic School, Arizona State University, Mesa, AZ 85212, USA
| | - Paul Westerhoff
- School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85287-3005, USA.
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24
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Benedict KB, Anastasio C. Quantum Yields of Nitrite (NO2–) from the Photolysis of Nitrate (NO3–) in Ice at 313 nm. J Phys Chem A 2017; 121:8474-8483. [DOI: 10.1021/acs.jpca.7b08839] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Katherine B. Benedict
- Department of Land, Air,
and Water Resources, University of California—Davis, One Shields Avenue, Davis, California 95616, United States
| | - Cort Anastasio
- Department of Land, Air,
and Water Resources, University of California—Davis, One Shields Avenue, Davis, California 95616, United States
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25
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Kang C, Bao S, Chen B, Zhong Y, Huang D, Wang Y, Xue H, Tian T. Photoconversion of 2-Chloronaphthalene in Water. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2017; 99:415-421. [PMID: 28780636 DOI: 10.1007/s00128-017-2146-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Accepted: 07/28/2017] [Indexed: 06/07/2023]
Abstract
The photoconversion of 2-chloronaphthalene (CN-2) in water in a simulated sunlight system was investigated. The photoconversion efficiency, photoproducts and mechanisms were inspected, and the effects of inorganic ions (NO3-, NO2-) and fulvic acid (FA) were discussed. The results showed that CN-2 could be transformed in water under the irradiation. NO3- and NO2- promoted the photoconversion of CN-2 owing to ·OH generated by the photolysis of NO3- and NO2-; FA at a lower concentration promoted the photoconversion, but it had an inhibition effect at a higher concentration. It was demonstrated that the acidic conditions promoted the photoconversion of CN-2 by the active groups such as superoxide radical anion, hydrogen peroxide and hydroxyl radical produced in the system. Eight photoproducts of CN-2 were characterized by the GC-MS method and the possible photoconversion mechanisms were proposed accordingly.
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Affiliation(s)
- Chunli Kang
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130012, China
| | - Siqi Bao
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130012, China
| | - Baiyan Chen
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130012, China
| | - Yubo Zhong
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130012, China
| | - Dongmei Huang
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130012, China
| | - Yuhan Wang
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130012, China
| | - Honghai Xue
- Key Laboratory of Songliao Aquatic Environment, Ministry of Education, Jilin Jianzhu University, Changchun, 130118, China
| | - Tao Tian
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130012, China.
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26
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Duca C, Imoberdorf G, Mohseni M. Effects of inorganics on the degradation of micropollutants with vacuum UV (VUV) advanced oxidation. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2017; 52:524-532. [PMID: 28276889 DOI: 10.1080/10934529.2017.1282770] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This research focused on the effects of inorganic water constituents on the efficiency of vacuum UV (VUV) for the degradation of micropollutants in surface water supplies. Atrazine was used as a model miropollutant, and bicarbonate, sulphate, and nitrate were used as the most common inorganic constituents in the water matrix. First, the absorbance of radiation at 254 and 185 nm was measured in the presence of different ions. At 254 nm, only nitrate showed a measurable absorption coefficient of [Formula: see text] = 3.51 M[Formula: see text] cm[Formula: see text], and all other ions showed a molar absorption coefficient below the detection limit. However, at 185 nm, all the ions showed high absorption coefficients, with nitrate giving the highest absorption coefficient of [Formula: see text] = 5568 M[Formula: see text] cm[Formula: see text]. Second, the hydroxyl radical (HO[Formula: see text]) scavenging effects of the same inorganic ions were evaluated; nitrate and bicarbonate showed a negative effect during the UV/H2O2 and VUV advanced oxidation processes. Sulfate was photolyzed with 185 nm UV to form HO[Formula: see text], and for this reason, it assisted the degradation of the target micropollutant, as demonstrated by increases in the degradation rate constant. An additional component of this work involved developing a method for measuring the quantum yield of atrazine at 185 nm. This made it possible to distinguish the contribution of OH radical attach from that of direct photolysis towards the degradation of atrazine.
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Affiliation(s)
- Clara Duca
- a Department of Chemical and Biological Engineering , University of British Columbia , Vancouver , British Columbia , Canada
| | - Gustavo Imoberdorf
- a Department of Chemical and Biological Engineering , University of British Columbia , Vancouver , British Columbia , Canada
| | - Madjid Mohseni
- a Department of Chemical and Biological Engineering , University of British Columbia , Vancouver , British Columbia , Canada
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27
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Benedict KB, McFall AS, Anastasio C. Quantum Yield of Nitrite from the Photolysis of Aqueous Nitrate above 300 nm. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:4387-4395. [PMID: 28340298 DOI: 10.1021/acs.est.6b06370] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Photolysis of nitrate (NO3-) produces reactive nitrogen and oxygen species via three different channels, forming: (1) nitrogen dioxide (NO2) and hydroxyl radical (•OH), (2) nitrite (NO2-) and oxygen atom (O(3P)), and (3) peroxynitrite (ONOO-). These photoproducts are important oxidants and reactants in surface waters, atmospheric drops, and snowpacks. While the efficiency of the first channel, to form NO2, is well documented, a large range of values have been reported for the second channel, nitrite, above 300 nm. In part, this disagreement reflects secondary chemistry that can produce or destroy nitrite. In this study, we examine factors that influence nitrite production and find that pH, nitrate concentration, and the presence of an •OH scavenger can be important. We measure an average nitrite quantum yield (Φ(NO2-)) of (1.1 ± 0.2)% (313 nm, 50 μM nitrate, pH ≥ 5), which is at the upper end of past measurements and an order of magnitude above the smallest-and most commonly cited-value reported for this channel. Nitrite production is often considered a very minor channel in nitrate photolysis, but our results indicate it is as important as the NO2 channel. In contrast, at 313 nm we observe no formation of peroxynitrite, corresponding to Φ(ONOO-) < 0.26%.
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Affiliation(s)
- Katherine B Benedict
- Department of Land, Air, and Water Resources University of California Davis Davis, California 95616, United States
| | - Alexander S McFall
- Department of Land, Air, and Water Resources University of California Davis Davis, California 95616, United States
| | - Cort Anastasio
- Department of Land, Air, and Water Resources University of California Davis Davis, California 95616, United States
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28
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Morenz KJ, Donaldson DJ. Chemical Morphology of Frozen Mixed Nitrate–Salt Solutions. J Phys Chem A 2017; 121:2166-2171. [DOI: 10.1021/acs.jpca.6b12608] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Karen J. Morenz
- Department
of Chemistry and ‡Department of Physical and Environmental Sciences, University of Toronto, 27 King’s College Circle, Toronto ON M5S, Canada
| | - D. James Donaldson
- Department
of Chemistry and ‡Department of Physical and Environmental Sciences, University of Toronto, 27 King’s College Circle, Toronto ON M5S, Canada
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29
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Ianniello A, Spataro F, Salvatori R, Valt M, Nardino M, Björkman MP, Esposito G, Montagnoli M. Air-snow exchange of reactive nitrogen species at Ny-Ålesund, Svalbard (Arctic). RENDICONTI LINCEI 2016. [DOI: 10.1007/s12210-016-0536-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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30
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Zhang Q, Pei G, Liu G, Li H, Gao L. Distribution and Photochemistry of Polycyclic Aromatic Hydrocarbons in the Baotou Section of the Yellow River During Winter. ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2015; 69:133-142. [PMID: 25838210 DOI: 10.1007/s00244-015-0135-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 01/28/2015] [Indexed: 06/04/2023]
Abstract
In this study, ice and water samples were collected from seven sites along the Baotou section of the Yellow River during winter 2013. Total polycyclic aromatic hydrocarbon (PAH) concentrations in the ice and in the water under the ice ranged from 21.3 to 59.4 ng L(-1), and from 38.3 to 222.4 ng L(-1), respectively. The average concentration in water under the ice was approximately 2.5 times greater than the average concentration in the ice phase. Four-ring PAHs dominated and accounted for 68.2 and 76.0 % of the total PAHs in ice and water, respectively. PAH concentrations were highest at sampling site S2 and were also relatively high at sites S4 and S5. PAH sources in ice and in water under the ice were similar. Three components were selected to represent the coal-combustion sources of PAHs. Because it was the main pollutant, and its concentrations were the highest, we examined the photodegradation behavior of fluoranthene and investigated the effects of light-sensitive materials (H2O2, acetone, and sediment) on fluoranthene photodegradation in the ice phase. Results showed that low H2O2 concentrations promoted photoconversion in the initial stage of the reaction and that degradation rates decreased later in the reaction. Likewise, high H2O2 concentrations promoted photoconversion. As acetone concentrations increased, the rates of fluoranthene-degradation decreased. Sediments may also have decreased the degradation rate of fluoranthene.
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Affiliation(s)
- Qi Zhang
- College of Water Conservancy and Civil Engineering, Inner Mongolia Agricultural University, Hohhot, 010018, China
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31
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George C, Ammann M, D’Anna B, Donaldson DJ, Nizkorodov S. Heterogeneous photochemistry in the atmosphere. Chem Rev 2015; 115:4218-58. [PMID: 25775235 PMCID: PMC4772778 DOI: 10.1021/cr500648z] [Citation(s) in RCA: 279] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Indexed: 02/06/2023]
Affiliation(s)
- Christian George
- Université
de Lyon 1, Lyon F-69626, France
- CNRS, UMR5256,
IRCELYON, Institut de Recherches sur la Catalyse et
l’Environnement de Lyon, Villeurbanne F-69626, France
| | - Markus Ammann
- Laboratory
of Radiochemistry and Environmental Chemistry, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - Barbara D’Anna
- Université
de Lyon 1, Lyon F-69626, France
- CNRS, UMR5256,
IRCELYON, Institut de Recherches sur la Catalyse et
l’Environnement de Lyon, Villeurbanne F-69626, France
| | - D. J. Donaldson
- Department
of Chemistry and Department of Physical & Environmental Sciences, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Sergey
A. Nizkorodov
- Department
of Chemistry, University of California, Irvine, California 92697, United States
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32
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McKay G, Rosario-Ortiz FL. Temperature dependence of the photochemical formation of hydroxyl radical from dissolved organic matter. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:4147-4154. [PMID: 25719947 DOI: 10.1021/acs.est.5b00102] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The temperature dependence of the photochemical production of the hydroxyl radical (•OH) from dissolved organic matter (DOM) was investigated by measuring the apparent temperature dependence of the quantum yield (Φa) for this process. Temperature dependent Φa values were analyzed using the Arrhenius equation. Apparent activation energies obtained for DOM isolates purchased from the International Humic Substances Society ranged from 16 to 34 kJ mol(-1). Addition of 40 units mL(-1) catalase, used to hinder the hydrogen peroxide (H2O2)-dependent pathway to •OH, did not impact the observed activation energy. However, an increase in activation energy was observed in lower molecular weight DOM obtained by size fractionation. We also measured the temperature dependence of p-benzoquionone photolysis as a model compound for DOM and observed no temperature dependence (slope p = 0.41) for the formation of phenol from oxidation of benzene (the •OH probe used), but a value of about 10 kJ mol(-1) for p-benzoquinone loss, which is consistent with formation of a quinone-water exciplex. These data provide insight into DOM photochemistry as well as provide parameters useful for modeling steady state •OH concentrations in natural systems.
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Affiliation(s)
- Garrett McKay
- Department of Civil, Environmental and Architectural Engineering, 428 UCB, University of Colorado, Boulder, Colorado 80309, United States
| | - Fernando L Rosario-Ortiz
- Department of Civil, Environmental and Architectural Engineering, 428 UCB, University of Colorado, Boulder, Colorado 80309, United States
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33
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Marcotte G, Marchand P, Pronovost S, Ayotte P, Laffon C, Parent P. Surface-Enhanced Nitrate Photolysis on Ice. J Phys Chem A 2015; 119:1996-2005. [DOI: 10.1021/jp511173w] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Guillaume Marcotte
- Département
de Chimie, Université de Sherbrooke, 2500 boul. de l’Université, Sherbrooke, Québec, Canada J1K 2R1
| | - Patrick Marchand
- Département
de Chimie, Université de Sherbrooke, 2500 boul. de l’Université, Sherbrooke, Québec, Canada J1K 2R1
| | - Stéphanie Pronovost
- Département
de Chimie, Université de Sherbrooke, 2500 boul. de l’Université, Sherbrooke, Québec, Canada J1K 2R1
| | - Patrick Ayotte
- Département
de Chimie, Université de Sherbrooke, 2500 boul. de l’Université, Sherbrooke, Québec, Canada J1K 2R1
| | - Carine Laffon
- Aix-Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Philippe Parent
- Aix-Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
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34
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Richards-Henderson NK, Anderson C, Anastasio C, Finlayson-Pitts BJ. The effect of cations on NO2 production from the photolysis of aqueous thin water films of nitrate salts. Phys Chem Chem Phys 2015; 17:32211-8. [DOI: 10.1039/c5cp05325k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cations are shown to enhance nitrate photochemistry by changing the concentrations of nitrate ions in the interface region.
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Affiliation(s)
| | | | - Cort Anastasio
- Department of Land
- Air and Water Resources
- University of California – Davis
- Davis
- USA
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35
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Scharko NK, Berke AE, Raff JD. Release of nitrous acid and nitrogen dioxide from nitrate photolysis in acidic aqueous solutions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:11991-12001. [PMID: 25271384 DOI: 10.1021/es503088x] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Nitrate (NO3(-)) is an abundant component of aerosols, boundary layer surface films, and surface water. Photolysis of NO3(-) leads to NO2 and HONO, both of which play important roles in tropospheric ozone and OH production. Field and laboratory studies suggest that NO3¯ photochemistry is a more important source of HONO than once thought, although a mechanistic understanding of the variables controlling this process is lacking. We present results of cavity-enhanced absorption spectroscopy measurements of NO2 and HONO emitted during photodegradation of aqueous NO3(-) under acidic conditions. Nitrous acid is formed in higher quantities at pH 2-4 than expected based on consideration of primary photochemical channels alone. Both experimental and modeled results indicate that the additional HONO is not due to enhanced NO3(-) absorption cross sections or effective quantum yields, but rather to secondary reactions of NO2 in solution. We find that NO2 is more efficiently hydrolyzed in solution when it is generated in situ during NO3(-) photolysis than for the heterogeneous system where mass transfer of gaseous NO2 into bulk solution is prohibitively slow. The presence of nonchromophoric OH scavengers that are naturally present in the environment increases HONO production 4-fold, and therefore play an important role in enhancing daytime HONO formation from NO3(-) photochemistry.
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Affiliation(s)
- Nicole K Scharko
- School of Public and Environmental Affairs and the Department of Chemistry, Indiana University , Bloomington, Indiana 47405-2204, United States
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36
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Meusinger C, Berhanu TA, Erbland J, Savarino J, Johnson MS. Laboratory study of nitrate photolysis in Antarctic snow. I. Observed quantum yield, domain of photolysis, and secondary chemistry. J Chem Phys 2014; 140:244305. [DOI: 10.1063/1.4882898] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Affiliation(s)
- Carl Meusinger
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - Tesfaye A. Berhanu
- Univ. Grenoble Alpes, LGGE, F-38000 Grenoble, France
- CNRS, LGGE, F-38000 Grenoble, France
| | - Joseph Erbland
- Univ. Grenoble Alpes, LGGE, F-38000 Grenoble, France
- CNRS, LGGE, F-38000 Grenoble, France
| | - Joel Savarino
- Univ. Grenoble Alpes, LGGE, F-38000 Grenoble, France
- CNRS, LGGE, F-38000 Grenoble, France
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37
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Berhanu TA, Meusinger C, Erbland J, Jost R, Bhattacharya SK, Johnson MS, Savarino J. Laboratory study of nitrate photolysis in Antarctic snow. II. Isotopic effects and wavelength dependence. J Chem Phys 2014; 140:244306. [DOI: 10.1063/1.4882899] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Tesfaye A. Berhanu
- Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, F-38041 Grenoble, France
- Univ. Grenoble Alpes, LGGE, F-38041 Grenoble, France
| | - Carl Meusinger
- Copenhagen Center for Atmospheric Research (CCAR), Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - Joseph Erbland
- Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, F-38041 Grenoble, France
- Univ. Grenoble Alpes, LGGE, F-38041 Grenoble, France
| | - Rémy Jost
- Laboratoire de Interdisciplinaire de Physique (LIPHY) Univ. de Grenoble, Grenoble, France
| | - S. K. Bhattacharya
- Research Center for Environmental Changes, Academia Sinica, Nangang, Taipei 115, Taiwan
| | - Matthew S. Johnson
- Copenhagen Center for Atmospheric Research (CCAR), Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - Joël Savarino
- Laboratoire de Glaciologie et Géophysique de l’Environnement, CNRS, F-38041 Grenoble, France
- Univ. Grenoble Alpes, LGGE, F-38041 Grenoble, France
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38
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Svoboda O, Slavíček P. Is Nitrate Anion Photodissociation Mediated by Singlet-Triplet Absorption? J Phys Chem Lett 2014; 5:1958-1962. [PMID: 26273880 DOI: 10.1021/jz500713a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Photolysis of the nitrate anion is involved in the oxidation processes in the hydrosphere, cryosphere, and stratosphere. While it is known that the nitrate photolysis in the long-wavelength region proceeds with a very low quantum yield, the mechanism of the photodissociation remains elusive. Here, we present the quantitative modeling of singlet-singlet and singlet-triplet absorption spectra in the atmospherically relevant region around 300 nm, and we argue that a spin-forbidden transition between the singlet ground state and the first triplet state contributes non-negligibly to the nitrate anion photolysis. We further propose that the nitrate anion excited into the first singlet excited state relaxes nonradiatively into its ground state. The full understanding of the nitrate anion photolysis can improve modeling of the asymmetric solvation in the atmospheric processes, e.g., photolysis on the surfaces of ice or snow.
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Affiliation(s)
- Ondřej Svoboda
- Department of Physical Chemistry, Institute of Chemical Technology, Technická 5, 16628 Prague 6, Czech Republic
| | - Petr Slavíček
- Department of Physical Chemistry, Institute of Chemical Technology, Technická 5, 16628 Prague 6, Czech Republic
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39
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Kahan TF, Wren SN, Donaldson DJ. A pinch of salt is all it takes: chemistry at the frozen water surface. Acc Chem Res 2014; 47:1587-94. [PMID: 24785086 DOI: 10.1021/ar5000715] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chemical interactions at the air-ice interface are of great importance to local atmospheric chemistry but also to the concentrations of pollutants deposited onto natural snow and ice. However, the study of such processes has been hampered by the lack of general, surface-specific probes. Even seemingly basic chemical properties, such as the local concentration of chemical compounds, or the pH at the interface, have required the application of assumptions about solute distributions in frozen media. The measurements that have been reported have tended for the most part to focus on entire ice or snow samples, rather than strictly the frozen interface with the atmosphere. We have used glancing-angle laser spectroscopy to interrogate the air-ice interface; this has yielded several insights into the chemical interactions there. The linear fluorescence and Raman spectra thus measured have the advantage of easy interpretability; careful experimentation can limit their probe depth to that which is relevant to atmospheric heterogeneous processes. We have used these techniques to show that the environment at the interface between air and freshwater ice surfaces is distinct from that at the interface between air and liquid water. Acids such as HCl that adsorb to ice surfaces from the gas phase result in significantly different pH responses than those at liquid water surfaces. Further, the solvation of aromatic species is suppressed at freshwater ice surfaces compared with that at liquid water surfaces, leading to extensive self-association of aromatics at ice surfaces. Photolysis kinetics of these species are much faster than at liquid water surfaces; this can sometimes (but not always) be explained by red shifts in the absorption spectra of self-associated aromatics increasing the extent to which solar radiation is absorbed. The environment presented by frozen saltwater surfaces, in contrast, appears to be reasonably well-described by liquid water. The extent of hydrogen bonding and the solvation of adsorbed species are similar at liquid water surfaces and at frozen saltwater surfaces. Adsorbed acids and bases evoke similar pH responses at frozen saltwater ice surfaces and liquid water surfaces, and photochemical kinetics of at least some aromatic compounds at frozen saltwater ice surfaces are well-described by kinetics in liquid water. These differences are not observed in experiments that interrogate the entire ice sample (i.e., that do not distinguish between processes occurring in liquid regions within bulk ice and those at the air-ice interface). Our work has shown that in general, the chemistry occurring at salty frozen interfaces is well described as being cold aqueous chemistry, whereas that seen at the pure ice interface is not. These findings have significant implications for heterogeneous atmospheric processes in ice-covered environments.
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Affiliation(s)
- Tara F. Kahan
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 Canada
| | - Sumi N. Wren
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 Canada
| | - D. James Donaldson
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 Canada
- Department
of Physical and Environmental Science, University of Toronto at Scarborough, Toronto, Ontario M1C 1A4 Canada
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40
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Richards-Henderson NK, Callahan KM, Nissenson P, Nishino N, Tobias DJ, Finlayson-Pitts BJ. Production of gas phase NO2 and halogens from the photolysis of thin water films containing nitrate, chloride and bromide ions at room temperature. Phys Chem Chem Phys 2014; 15:17636-46. [PMID: 24042539 DOI: 10.1039/c3cp52956h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nitrate and halide ions coexist in particles generated in marine regions, around alkaline dry lakes, and in the Arctic snowpack. Although the photochemistry of nitrate ions in bulk aqueous solution is well known, there is recent evidence that it may be more efficient at liquid-gas interfaces, and that the presence of other ions in solution may enhance interfacial reactivity. This study examines the 311 nm photolysis of thin aqueous films of ternary halide-nitrate salt mixtures (NaCl-NaBr-NaNO3) deposited on the walls of a Teflon chamber at 298 K. The films were generated by nebulizing aqueous 0.25 M NaNO3 solutions which had NaCl and NaBr added to vary the mole fraction of halide ions. Molar ratios of chloride to bromide ions were chosen to be 0.25, 1.0, or 4.0. The subsequent generation of gas phase NO2 and reactive halogen gases (Br2, BrCl and Cl2) were monitored with time. The rate of gas phase NO2 formation was shown to be enhanced by the addition of the halide ions to thin films containing only aqueous NaNO3. At [Cl(-)]/[Br(-)] ≤ 1.0, the NO2 enhancement was similar to that observed for binary NaBr-NaNO3 mixtures, while with excess chloride NO2 enhancement was similar to that observed for binary NaCl-NaNO3 mixtures. Molecular dynamics simulations predict that the halide ions draw nitrate ions closer to the interface where a less complete solvent shell allows more efficient escape of NO2 to the gas phase, and that bromide ions are more effective in bringing nitrate ions closer to the surface. The combination of theory and experiments suggests that under atmospheric conditions where nitrate ion photochemistry plays a role, the impact of other species such as halide ions should be taken into account in predicting the impacts of nitrate ion photochemistry.
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41
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Jacobi HW, Kleffmann J, Villena G, Wiesen P, King M, France J, Anastasio C, Staebler R. Role of nitrite in the photochemical formation of radicals in the snow. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 48:165-172. [PMID: 24237312 DOI: 10.1021/es404002c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Photochemical reactions in snow can have an important impact on the composition of the atmosphere over snow-covered areas as well as on the composition of the snow itself. One of the major photochemical processes is the photolysis of nitrate leading to the formation of volatile nitrogen compounds. We report nitrite concentrations determined together with nitrate and hydrogen peroxide in surface snow collected at the coastal site of Barrow, Alaska. The results demonstrate that nitrite likely plays a significant role as a precursor for reactive hydroxyl radicals as well as volatile nitrogen oxides in the snow. Pollution events leading to high concentrations of nitrous acid in the atmosphere contributed to an observed increase in nitrite in the surface snow layer during nighttime. Observed daytime nitrite concentrations are much higher than values predicted from steady-state concentrations based on photolysis of nitrate and nitrite indicating that we do not fully understand the production of nitrite and nitrous acid in snow. The discrepancy between observed and expected nitrite concentrations is probably due to a combination of factors, including an incomplete understanding of the reactive environment and chemical processes in snow, and a lack of consideration of the vertical structure of snow.
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Affiliation(s)
- Hans-Werner Jacobi
- CNRS, Laboratoire de Glaciologie et Géophysique de l'Environnement LGGE, 38041 Grenoble, Rhône-Alpes, France
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42
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Svoboda O, Kubelová L, Slavíček P. Enabling Forbidden Processes: Quantum and Solvation Enhancement of Nitrate Anion UV Absorption. J Phys Chem A 2013; 117:12868-77. [DOI: 10.1021/jp4098777] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ondřej Svoboda
- Department of Physical Chemistry, Institute of Chemical Technology, Technická 5, 16628 Prague 6, Czech Republic
| | - Lucie Kubelová
- Department of Physical Chemistry, Institute of Chemical Technology, Technická 5, 16628 Prague 6, Czech Republic
| | - Petr Slavíček
- Department of Physical Chemistry, Institute of Chemical Technology, Technická 5, 16628 Prague 6, Czech Republic
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43
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Liu J, Wu JY, Kang CL, Peng F, Liu HF, Yang T, Shi L, Wang HL. Photo-Fenton effect of 4-chlorophenol in ice. JOURNAL OF HAZARDOUS MATERIALS 2013; 261:500-511. [PMID: 23988575 DOI: 10.1016/j.jhazmat.2013.07.040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2013] [Revised: 06/28/2013] [Accepted: 07/18/2013] [Indexed: 06/02/2023]
Abstract
The photoconversion of 4-chlorophenol (4-CP) in a simulated sunlight-Fenton system was investigated in ice and aqueous solution. It was found that the hydroxyl radical (OH) had an important effect on the photoconversion of 4-CP in both phases, but the effects of Cl(-), SO4(2-), NO3(-), and HCO3(-) were different. In aqueous solution, the photoconversion efficiency of 4-CP was proportional to the OH concentration, and hence, Cl(-) and HCO3(-) as OH scavengers prohibited the photoconversion; SO4(2-) had little effect; NO3(-) promoted the process under certain conditions owing to OH being generated by the photolysis of NO3(-). In ice, however, the photoconversion efficiency of 4-CP was not proportional to the concentration of OH. The photoconversion efficiency of 4-CP increased with increasing concentrations of all ions, although the OH remained almost constant, only increasing or decreasing slightly. This provides new evidence for the presence of a quasi-liquid layer (QLL). Hydroxylation products were detected in both phases. All photoproducts in aqueous solution contained only a single benzene ring, whereas in ice, dimers were also detected.
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Affiliation(s)
- Jia Liu
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China
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Bower JP, Anastasio C. Using singlet molecular oxygen to probe the solute and temperature dependence of liquid-like regions in/on ice. J Phys Chem A 2013; 117:6612-21. [PMID: 23841666 DOI: 10.1021/jp404071y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Liquid-like regions (LLRs) are found at the surfaces and grain boundaries of ice and as inclusions within ice. These regions contain most of the solutes in ice and can be (photo)chemically active hotspots in natural snow and ice systems. If we assume all solutes partition into LLRs as a solution freezes, freezing-point depression predicts that the concentration of a solute in LLRs is higher than its concentration in the prefrozen (or melted) solution by the freeze-concentration factor (F). Here we use singlet molecular oxygen production to explore the effects of total solute concentration ([TS]) and temperature on experimentally determined values of F. For ice above its eutectic temperature, measured values of F agree well with freezing-point depression when [TS] is above ∼1 mmol/kg; at lower [TS] values, measurements of F are lower than predicted from freezing-point depression. For ice below its eutectic temperature, the influence of freezing-point depression on F is damped; the extreme case is with Na2SO4 as the solute, where F shows essentially no agreement with freezing-point depression. In contrast, for ice containing 3 mmol/kg NaCl, measured values of F agree well with freezing-point depression over a range of temperatures, including below the eutectic. Our experiments also reveal that the photon flux in LLRs increases in the presence of salts, which has implications for ice photochemistry in the lab and, perhaps, in the environment.
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Affiliation(s)
- Jonathan P Bower
- Department of Land, Air, and Water Resources University of California, Davis, One Shields Avenue, Davis, California 95616, United States
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Domine F, Bock J, Voisin D, Donaldson DJ. Can We Model Snow Photochemistry? Problems with the Current Approaches. J Phys Chem A 2013; 117:4733-49. [DOI: 10.1021/jp3123314] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Florent Domine
- Takuvik Joint International
Laboratory, Université Laval (Canada) and CNRS (France), Pavillon Alexandre Vachon, 1045 Avenue de
La Médecine, Québec, QC G1V 0A6, Canada
- Department of Chemistry, Université Laval, Pavillon Alexandre Vachon,
1045 Avenue de La Médecine, Québec, QC G1V 0A6, Canada
| | - Josué Bock
- Université Joseph Fourier−Grenoble
1/CNRS, Laboratoire de Glaciologie et Géophysique de l’Environnement, UMR 5183, Grenoble, F-38041, France
| | - Didier Voisin
- Université Joseph Fourier−Grenoble
1/CNRS, Laboratoire de Glaciologie et Géophysique de l’Environnement, UMR 5183, Grenoble, F-38041, France
| | - D. J. Donaldson
- Department of Chemistry, University of Toronto, and Department of Physical and
Environmental Sciences, University of Toronto Scarborough, Scarborough, Toronto, ON, Canada
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Dilbeck CW, Finlayson-Pitts BJ. Hydroxyl radical oxidation of phospholipid-coated NaCl particles. Phys Chem Chem Phys 2013; 15:9833-44. [PMID: 23676928 DOI: 10.1039/c3cp51237a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Biological organic compounds mixed with NaCl and other inorganic compounds in sea-salt aerosol particles react in air with oxidants such as ozone and hydroxyl (OH) radicals. Laboratory studies of model systems can provide insight into these reactions. We report here studies of the kinetics and mechanism of oxidation of unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) on NaCl by gas phase OH in air at room temperature and 1 atm pressure using diffuse reflection infrared Fourier transform spectrometry (DRIFTS) and matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) to identify possible structures of surface-bound reaction products. For comparison, some studies were also carried out on the saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) on NaCl. The calculated concentration of hydroxyl radicals, generated by photolysis of isopropyl nitrite, was (1.6-6.4) × 10(8) radicals cm(-3). Surface-bound aldehydes, ketones, organic nitrates and nitrate ions were identified as products of these reactions and structures of potential products were proposed based on mechanistic considerations combined with the MALDI-TOF-MS and DRIFTS spectra. The loss rate of vinyl hydrogen, =C-H, at 3008 cm(-1) was used to obtain a lower limit for the rate constant (k1) for addition of OH to the double bond, k1 > (3 ± 1) × 10(-13) cm(3) molecule(-1) s(-1) (1s), corresponding to a reaction probability of γ(add) > (4 ± 1) × 10(-3) (1s). Assuming that abstraction from -CH2- groups in POPC is the same as for DPPC, the percentage of the reaction that occurs by addition is ~80%. This is similar to the percent addition predicted using structure-reactivity relationships for gas-phase reactions. Decreasing the amount of POPC relative to NaCl resulted in more nitrate ion formation and less relative loss of POPC, and increasing the OH concentration resulted in a more rapid loss of POPC and faster product formation. These studies suggest that under atmospheric conditions with an OH concentration of 5 × 10(6) radicals cm(-3), the lifetime of POPC with respect to OH is <6 days.
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Affiliation(s)
- Christopher W Dilbeck
- Department of Chemistry, University of California Irvine, Irvine, CA 92697-2025, USA
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Kriger LD, Miklin MB, Dyagileva EP, Anan’ev VA. Photolysis of alkaline-earth nitrates. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2013. [DOI: 10.1134/s0036024413020180] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Mostofa KMG, Liu CQ, Sakugawa H, Vione D, Minakata D, Saquib M, Mottaleb MA. Photoinduced Generation of Hydroxyl Radical in Natural Waters. PHOTOBIOGEOCHEMISTRY OF ORGANIC MATTER 2013. [DOI: 10.1007/978-3-642-32223-5_3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Richards NK, Finlayson-Pitts BJ. Production of gas phase NO₂ and halogens from the photochemical oxidation of aqueous mixtures of sea salt and nitrate ions at room temperature. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:10447-10454. [PMID: 22506935 DOI: 10.1021/es300607c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Nitrate and halide ions coexist in a number of environmental systems, including sea salt particles, the Arctic snowpack, and alkaline dry lakes. However, little is known about potential synergisms between halide and nitrate ions. The effect of sea salt on NO(3)(-) photochemistry at 311 nm was investigated at 298 K using thin films of deliquesced NaNO(3)-synthetic sea salt mixtures. Gas phase NO(2), NO, and halogen products were measured as a function of photolysis time using NO(y) chemiluminescence and atmospheric pressure ionization mass spectrometry (API-MS). The production of NO(2) increases with the halide-to-nitrate ratio, and is similar to that for mixtures of NaCl with NaNO(3). Gas phase halogen production also increased with the halide-to-nitrate ratio, consistent with NO(3)(-) photolysis yielding OH which oxidizes halide ions in the film. Yields of gas phase halogens and NO were strongly dependent on the acidity of the solution, while that of NO(2) was not. An additional halogen formation mechanism in the dark involving molecular HNO(3) is proposed that may be important in other systems such as reactions on surfaces. These studies show that the yield of Br(2) relative to NO(2) during photolysis of halide-nitrate mixtures could be as high as 35% under some atmospheric conditions.
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Affiliation(s)
- Nicole K Richards
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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