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Deng DD, Long B. Quantitative kinetics of the atmospheric reaction between isocyanic acid and hydroxyl radicals: post-CCSD(T) contribution, anharmonicity, recrossing effects, torsional anharmonicity, and tunneling. Phys Chem Chem Phys 2023; 26:485-492. [PMID: 38079149 DOI: 10.1039/d3cp04385a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Hydroxyl radicals (OH) are the most important atmospheric oxidant, initiating atmospheric reactions for the chemical transformation of volatile organic compounds. Here, we choose the HNCO + OH reaction as a prototype reaction because it contains the fundamental reaction processes for OH radicals: H-abstraction reaction by OH and OH addition reaction. However, its kinetics are unknown under atmospheric conditions. We investigate the reaction of HNCO with OH by using the GMM(P).L method close to the accuracy of single, double, triple, and quadruple excitations and noniterative quintuple excitations with a complete basis set (CCSDTQ(P)/CBS) as benchmark results and a dual-level strategy for kinetics calculations. The calculated rate constant of HNCO + OH is in good agreement with the experimental data available at the temperatures between 620 and 2500 K. We find that the rate constant cannot be correctly obtained by using experimental data to extrapolate the atmospheric temperature ranges. We find that the post-CCSD(T) contribution is very large for the barrier height with the value of -0.85 kcal mol-1 for the H-abstraction reaction, while the previous investigations were done up to the CCSD(T) level. Moreover, we also find that recrossing effects, tunneling, torsional anharmonicity, and anharmonicity are important for obtaining quantitative kinetics in the OH + HNCO reaction.
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Affiliation(s)
- Dai-Dan Deng
- College of Physics and Mechatronic Engineering, Guizhou Minzu University, Guiyang 550025, China.
| | - Bo Long
- College of Physics and Mechatronic Engineering, Guizhou Minzu University, Guiyang 550025, China.
- College of Materials Science and Engineering, Guizhou Minzu University, Guiyang 550025, China
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2
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Sha Q, Liu X, Yuan Z, Zheng J, Lou S, Wang H, Li X, Yu F. Upgrading Emission Standards Inadvertently Increased OH Reactivity from Light-Duty Diesel Truck Exhaust in China: Evidence from Direct LP-LIF Measurement. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:9968-9977. [PMID: 35770386 DOI: 10.1021/acs.est.2c02944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Vehicular exhaust is an important source of reactive gases responsible for the formation of ozone and secondary organic aerosols (SOAs) in the atmosphere. Although significant efforts have been made to characterize the chemical compounds associated with vehicular exhaust, there is still a wealth of compounds that are unable to be detected, posing uncertainties in estimating their contribution to atmospheric reactivity. In this study, by improving laser-induced fluorescence techniques, we achieved the first-ever direct measurement of the total OH reactivity (TOR) from light-duty diesel truck (LDDT) exhaust with different emission standards. We found that the TOR from the LDDT exhaust was 80-130 times the TOR from the gasoline exhaust measured in Japan. Unexpectedly, we discovered increased TOR emissions along with upgrading emission standards, possibly as a collective result of high combustion temperature in the engine and the oxidation catalysts in the exhaust after-treatment that favor production of highly oxidized organics in the stricter emission standard. Most of these oxidized organics are unable to be speciated by routine measurements, resulting in the missing OH reactivity increasing rapidly from 1.91% for China III to 42.0% for China V LDDT. Upgrading the emission standard failed to reduce the TOR from LDDT exhaust, which may inadvertently promote the contribution of LDDT to the formation of ozone and SOA pollution in China.
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Affiliation(s)
- Qing'e Sha
- Institute of Environmental and Climate Research, Jinan University, Guangzhou 510632, China
| | - Xuehui Liu
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
| | - Zibing Yuan
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
| | - Junyu Zheng
- Institute of Environmental and Climate Research, Jinan University, Guangzhou 510632, China
| | - Shengrong Lou
- State Environmental Protection Key Laboratory of the Cause and Prevention of Urban Air Pollution Complex, Shanghai Academy of Environmental Sciences, Shanghai 200233, China
| | - Hongli Wang
- State Environmental Protection Key Laboratory of the Cause and Prevention of Urban Air Pollution Complex, Shanghai Academy of Environmental Sciences, Shanghai 200233, China
| | - Xin Li
- College of Environmental Science and Engineering, Peking University, Beijing 100871, China
| | - Fei Yu
- Institute of Environmental and Climate Research, Jinan University, Guangzhou 510632, China
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3
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Wang C, Mattila JM, Farmer DK, Arata C, Goldstein AH, Abbatt JPD. Behavior of Isocyanic Acid and Other Nitrogen-Containing Volatile Organic Compounds in The Indoor Environment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:7598-7607. [PMID: 35653434 DOI: 10.1021/acs.est.1c08182] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Isocyanic acid (HNCO) and other nitrogen-containing volatile chemicals (organic isocyanates, hydrogen cyanide, nitriles, amines, amides) were measured during the House Observation of Microbial and Environmental Chemistry (HOMEChem) campaign. The indoor HNCO mean mixing ratio was 0.14 ± 0.30 ppb (range 0.012-6.1 ppb), higher than outdoor levels (mean 0.026 ± 0.15 ppb). From the month-long study, cooking and chlorine bleach cleaning are identified as the most important human-related sources of these nitrogen-containing gases. Gas oven cooking emits more isocyanates than stovetop cooking. The emission ratios HNCO/CO (ppb/ppm) during stovetop and oven cooking (mean 0.090 and 0.30) are lower than previously reported values during biomass burning (between 0.76 and 4.6) and cigarette smoking (mean 2.7). Bleach cleaning led to an increase of the HNCO mixing ratio of a factor of 3.5 per liter of cleaning solution used; laboratory studies indicate that isocyanates arise via reaction of nitrogen-containing precursors, such as indoor dust. Partitioned in a temperature-dependent manner to indoor surface reservoirs, HNCO was present at the beginning of HOMEChem, arising from an unidentified source. HNCO levels are higher at the end of the campaign than the beginning, indicative of occupant activities such as cleaning and cooking; however the direct emissions of humans are relatively minor.
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Affiliation(s)
- Chen Wang
- School of Environmental Science and Engineering, Southern University of Science and Technology and Guangdong Provincial Observation and Research Station for Coastal Atmosphere and Climate of the Greater Bay Area, Shenzhen, 518055, China
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - James M Mattila
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Delphine K Farmer
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Caleb Arata
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California 94720, United States
| | - Allen H Goldstein
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California 94720, United States
- Department of Civil and Environmental Engineering, University of California, Berkeley, California 94720, United States
| | - Jonathan P D Abbatt
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
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4
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Pham TV, Tran AV. Gas Phase Reaction of Isocyanic Acid: Kinetics, Mechanisms, and Formation of Isopropyl Aminocarbonyl. ACS OMEGA 2021; 6:34661-34674. [PMID: 34963950 PMCID: PMC8697403 DOI: 10.1021/acsomega.1c05063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 11/12/2021] [Indexed: 06/14/2023]
Abstract
Isocyanic acid, HNCO, mainly emitted by combustion processes, is doubted to be detrimental to human health if its concentration surpasses ∼1 ppbv. Very little information has been found regarding the HNCO loss in the gas phase. This study aims to close this knowledge gap by performing a theoretical kinetic study on the reaction of HNCO with the propargyl radical. The potential energy surface of the HNCO + C3H3 reaction was characterized utilizing high-level CCSD(T)/CBS(TQ5)//B3LYP/6-311++G(3df,2p) quantum-chemical approaches, followed by TST and RRKM/ME kinetic computations. The obtained results reveal that the reaction can proceed via H-abstraction, leading to the C3H4 + NCO bimolecular products with energy barriers of 23-25 kcal/mol, and/or addition, resulting in C4H4NO intermediates with 23-26 kcal/mol barrier heights. The C4H4NO adducts when formed can decompose to products and/or return to HNCO + C3H3 in which the reverse decompositions are found to be dominant with a branching ratio that accounts for nearly 100% at 300 K and 760 Torr. The calculated P-independent rate coefficients indicate that at low temperatures, the H-abstraction channels are insignificant. However, at high temperatures (T > 1500 K), the H-abstraction path leading to H3CCCH + NCO prevails with a branching ratio of ∼50-53% in the descending 1800-1500 K temperature range at 760 Torr, while the H-abstraction leading to H2CCCH2 + NCO is favorable at T > 1800 K, with the yield reaching above 50% at 760 Torr. In contrast to the H-abstraction rate constants, the calculated values for the additions and the C4H4NO decompositions show a positive pressure dependence. Both the total rate constants for the reactions HNCO + C3H3 → products and C4H4NO → products, which are, respectively, k _total_bimo(T) = 3.53 × 10-23 T 3.27 exp[(-21.35 ± 0.06 kcal/mol)/RT] cm3 molecule-1 s-1 and k _total_uni(T) = 1.13 × 1025 T -4.02 exp[(-11.77 ± 0.16 kcal/mol)/RT] s-1, increase with the increasing temperature in the 300-2000 K range at 760 Torr. The rate constant of HNCO + C3H3 → products is about 8 orders of magnitude smaller than the value of HCHO + C3H3 → products, showing that HCHO is more reactive toward the C3H3 free radicals than HNCO. The computed heats of formation for several species agree well with the available literature data with the deviation less than 1.0 kcal/mol, indicating that the methods used in this study are extremely reliable. With the given results, it is vigorously suggested that the predicted rate constants, together with the thermodynamic data of the species involved, can be confidently used for modeling HNCO-related systems under atmospheric and combustion conditions.
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5
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Zhou L, Salvador CM, Priestley M, Hallquist M, Liu Q, Chan CK, Hallquist ÅM. Emissions and Secondary Formation of Air Pollutants from Modern Heavy-Duty Trucks in Real-World Traffic-Chemical Characteristics Using On-Line Mass Spectrometry. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:14515-14525. [PMID: 34652131 PMCID: PMC8567417 DOI: 10.1021/acs.est.1c00412] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 08/02/2021] [Accepted: 09/09/2021] [Indexed: 06/13/2023]
Abstract
Complying with stricter emissions standards, a new generation of heavy-duty trucks (HDTs) has gradually increased its market share and now accounts for a large percentage of on-road mileage. The potential to improve air quality depends on an actual reduction in both emissions and subsequent formation of secondary pollutants. In this study, the emissions in real-world traffic from Euro VI-compliant HDTs were compared to those from older classes, represented by Euro V, using high-resolution time-of-flight chemical ionization mass spectrometry. Gas-phase primary emissions of several hundred species were observed for 70 HDTs. Furthermore, the particle phase and secondary pollutant formation (gas and particle phase) were evaluated for a number of HDTs. The reduction in primary emission factors (EFs) was evident (∼90%) and in line with a reduction of 28-97% for the typical regulated pollutants. Secondary production of most gas- and particle-phase compounds, for example, nitric acid, organic acids, and carbonyls, after photochemical aging in an oxidation flow reactor exceeded the primary emissions (EFAged/EFFresh ratio ≥2). Byproducts from urea-selective catalytic reduction systems had both primary and secondary sources. A non-negative matrix factorization analysis highlighted the issue of vehicle maintenance as a remaining concern. However, the adoption of Euro VI has a significant positive effect on emissions in real-world traffic and should be considered in, for example, urban air quality assessments.
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Affiliation(s)
- Liyuan Zhou
- School
of Energy and Environment, City University
of Hong Kong, Hong Kong, China
| | - Christian M. Salvador
- Department
of Chemistry and Molecular Biology, University
of Gothenburg, 412 96 Gothenburg, Sweden
| | - Michael Priestley
- Department
of Chemistry and Molecular Biology, University
of Gothenburg, 412 96 Gothenburg, Sweden
| | - Mattias Hallquist
- Department
of Chemistry and Molecular Biology, University
of Gothenburg, 412 96 Gothenburg, Sweden
| | - Qianyun Liu
- School
of Energy and Environment, City University
of Hong Kong, Hong Kong, China
| | - Chak K. Chan
- School
of Energy and Environment, City University
of Hong Kong, Hong Kong, China
| | - Åsa M. Hallquist
- IVL
Swedish Environmental Research Institute, 400 14 Gothenburg, Sweden
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6
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Hu D, Lu B, Song C, Zhu B, Wang L, Bernhardt E, Zeng X. Synthesis and characterization of phosphorous(III) diisocyanate and triisocyanate. Dalton Trans 2021; 50:3299-3307. [PMID: 33595037 DOI: 10.1039/d1dt00261a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two phosphorous(iii) isocyanates, ClP(NCO)2 and P(NCO)3 were isolated as neat substances and characterized with IR (gas-phase and Ne-matrix), Raman (solid), and 31P NMR spectroscopy. Their vibrational spectra were analyzed in terms of a single conformer with the aid of quantum chemical computations at the B3LYP/6-311+G(3df) level of theory. In line with the theoretically computed favorable syn-configuration of the NCO ligands with the sterically active lone-pair electrons on the central phosphorous atom (nP), low-temperature single-crystal X-ray diffraction (XRD) of solid ClP(NCO)2 reveals a Cs symmetric syn-configuration for both NCO ligands with weak CO (r = 2.9692(4) Å) van der Waals (vdW) interactions. In the binary isocyante P(NCO)3, all the three NCO ligands adopt similar syn-configuration with nP, leading to a propeller-shaped structure with slightly distorted C3v symmetry due to steric repulsion of the NCO ligands and the PO vdW interactions (r = 3.1901(1) Å) in the solid state.
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Affiliation(s)
- Dandan Hu
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Bo Lu
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Chao Song
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Bifeng Zhu
- Department of Chemistry, Fudan University, Shanghai, 200433, China.
| | - Lina Wang
- Department of Chemistry, Fudan University, Shanghai, 200433, China.
| | - Eduard Bernhardt
- FB C-Anorganische Chemie, Bergische Universität Wuppertal, Gaussstrasse 20, Wuppertal, 42119, Germany
| | - Xiaoqing Zeng
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China and Department of Chemistry, Fudan University, Shanghai, 200433, China.
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7
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Wang Z, Yuan B, Ye C, Roberts J, Wisthaler A, Lin Y, Li T, Wu C, Peng Y, Wang C, Wang S, Yang S, Wang B, Qi J, Wang C, Song W, Hu W, Wang X, Xu W, Ma N, Kuang Y, Tao J, Zhang Z, Su H, Cheng Y, Wang X, Shao M. High Concentrations of Atmospheric Isocyanic Acid (HNCO) Produced from Secondary Sources in China. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:11818-11826. [PMID: 32876440 DOI: 10.1021/acs.est.0c02843] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Isocyanic acid (HNCO) is a potentially toxic atmospheric pollutant, whose atmospheric concentrations are hypothesized to be linked to adverse health effects. An earlier model study estimated that concentrations of isocyanic acid in China are highest around the world. However, measurements of isocyanic acid in ambient air have not been available in China. Two field campaigns were conducted to measure isocyanic acid in ambient air using a high-resolution time-of-flight chemical ionization mass spectrometer (ToF-CIMS) in two different environments in China. The ranges of mixing ratios of isocyanic acid are from below the detection limit (18 pptv) to 2.8 ppbv (5 min average) with the average value of 0.46 ppbv at an urban site of Guangzhou in the Pearl River Delta (PRD) region in fall and from 0.02 to 2.2 ppbv with the average value of 0.37 ppbv at a rural site in the North China Plain (NCP) during wintertime, respectively. These concentrations are significantly higher than previous measurements in North America. The diurnal variations of isocyanic acid are very similar to secondary pollutants (e.g., ozone, formic acid, and nitric acid) in PRD, indicating that isocyanic acid is mainly produced by secondary formation. Both primary emissions and secondary formation account for isocyanic acid in the NCP. The lifetime of isocyanic acid in a lower atmosphere was estimated to be less than 1 day due to the high apparent loss rate caused by deposition at night in PRD. Based on the steady state analysis of isocyanic acid during the daytime, we show that amides are unlikely enough to explain the formation of isocyanic acid in Guangzhou, calling for additional precursors for isocyanic acid. Our measurements of isocyanic acid in two environments of China provide important constraints on the concentrations, sources, and sinks of this pollutant in the atmosphere.
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Affiliation(s)
- Zelong Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Bin Yuan
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Chenshuo Ye
- State Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - James Roberts
- NOAA Chemical Sciences Laboratory, Boulder, Colorado 80305, USA
| | - Armin Wisthaler
- Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
| | - Yi Lin
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Tiange Li
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Caihong Wu
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Yuwen Peng
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Chaomin Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Sihang Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Suxia Yang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Baolin Wang
- School of Environmental Science and Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China
| | - Jipeng Qi
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Chen Wang
- School of Environmental Science and Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China
| | - Wei Song
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Weiwei Hu
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Xinming Wang
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Wanyun Xu
- State Key Laboratory of Severe Weather & Key Laboratory for Atmospheric Chemistry of China Meteorology Administration, Chinese Academy of Meteorological Sciences, Beijing 100081, China
| | - Nan Ma
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Ye Kuang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Jiangchuan Tao
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Zhanyi Zhang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Hang Su
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany
| | - Yafang Cheng
- Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany
| | - Xuemei Wang
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
| | - Min Shao
- Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
- Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
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Agarwal AK, Singh AP, Gupta T, Agarwal RA, Sharma N, Pandey SK, Ateeq B. Toxicity of exhaust particulates and gaseous emissions from gasohol (ethanol blended gasoline)-fuelled spark ignition engines. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2020; 22:1540-1553. [PMID: 32573620 DOI: 10.1039/d0em00082e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In the last couple of decades, blending of oxygenated additives with gasoline has been advocated to reduce dependence on fossil fuels and to reduce hazardous health effects of gaseous emissions and particulate matter (PM) emitted by internal combustion (IC) engines in the transport sector worldwide. The primary objective of this research was to carry out a comparative analysis of exhaust PM emitted by gasohol (gasoline blended with 10% ethanol, v/v)-fulled spark ignition (SI) engine with that of baseline gasoline-fuelled SI engine. To assess the PM toxicity, physical, chemical and biological characterizations of PM were carried out using the state-of-the-art instruments and techniques. Measurements of regulated and unregulated gaseous species were also carried out at part/full loads. The results showed that the gasohol-fuelled engine emitted relatively lower concentrations of unregulated gaseous species such as sulfur dioxide (SO2), isocyanic acid (HNCO), etc. Physical characterization of exhaust particles revealed that the gasohol-fuelled engine emitted a significantly lower number of particles compared to the gasoline-fuelled engine. The presence of harmful polycyclic aromatic hydrocarbons (PAHs) and higher trace metal concentrations in PM emitted from the gasoline-fuelled engine was another important finding of this study. Biological characterizations showed that PM emitted from the gasohol-fuelled engine were less cytotoxic and had lower reactive oxygen species (ROS) generation potential. Mutagenicity of PM emitted from the gasohol-fuelled engine was also lower compared to that from the gasoline-fuelled engine. Overall, this study demonstrated that utilization of gasohol in SI engines led to the reduction in emissions, and lowering of PM toxicity, in addition to partial replacement of fossil fuels with renewable fuels.
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Affiliation(s)
- Avinash Kumar Agarwal
- Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, India
| | - Akhilendra Pratap Singh
- Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, India
| | - Tarun Gupta
- Environmental Engineering Laboratory, Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, India
| | | | - Nikhil Sharma
- Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur-208016, India
| | - Swaroop Kumar Pandey
- Department of Biological Sciences & Bioengineering, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| | - Bushra Ateeq
- Department of Biological Sciences & Bioengineering, Indian Institute of Technology Kanpur, Kanpur-208016, India.
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9
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Liu S, Xie Y, Song X. Accurate and rapid discrimination of cigarette and household decoration material ash residues by negative chemical ionization TOFMS via acid-enhanced evaporation. Sci Rep 2020; 10:5810. [PMID: 32242063 PMCID: PMC7118106 DOI: 10.1038/s41598-020-62814-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 03/19/2020] [Indexed: 11/10/2022] Open
Abstract
The detection and identification of cigarette ash in fire debris can be meaningful in fire investigations caused by burning cigarettes. In this work, a novel analytical method based on negative chemical ionization time-of-flight mass spectrometry (NCI/TOFMS) combined with a phosphoric-acid-enhanced evaporation strategy has been developed for the discrimination of cigarette ash samples (CAs) and common household decoration material ash samples (CHDMAs). A series of characteristic ions representing the acidified products HNCO and formic acid in the CAs were achieved, whose signal responses were enhanced with the help of mechanical agitation operation. To account for both the signal responses of the characteristic ions and acid corrosion of the ion source, the dynamic-purge gas was chosen to be 200 mL/min. The whole time for analysis was only 5 min, which is suitable for high-throughput measurements of large quantities of fire debris. As a result, a preliminary discrimination was achieved between the CAs and CHDMAs by virtue of the chemometric tool of principal components analysis (PCA) based on intensity differences of the characteristic ions. The results are encouraging and highlight the potential of NCI/TOFMS without complicated sample preparation steps for the accurate and high-throughput identification of cigarette ash on substrates in fire debris.
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Affiliation(s)
- Shujun Liu
- Liaoning Key Laboratory for Green Synthesis and Preparative Chemistry of Advanced Materials, College of Chemistry, Liaoning University, Shenyang, 110036, China.,Shenyang Fire Research Institute of MEM, Shenyang, 110034, China
| | - Yuanyuan Xie
- Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
| | - Ximing Song
- Liaoning Key Laboratory for Green Synthesis and Preparative Chemistry of Advanced Materials, College of Chemistry, Liaoning University, Shenyang, 110036, China.
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10
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Qin Y, Lu B, Rauhut G, Hagedorn M, Banert K, Song C, Chu X, Wang L, Zeng X. The Simplest, Isolable, Alkynyl Isocyanate HC≡CNCO: Synthesis and Characterization. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201911102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yuanyuan Qin
- College of ChemistryChemical Engineering and Materials ScienceSoochow University Suzhou 215123 China
| | - Bo Lu
- College of ChemistryChemical Engineering and Materials ScienceSoochow University Suzhou 215123 China
| | - Guntram Rauhut
- Institute for Theoretical ChemistryUniversity of Stuttgart Pfaffenwaldring 55 Stuttgart 70569 Germany
| | - Manfred Hagedorn
- Chemnitz University of TechnologyOrganic Chemistry Strasse der Nationen 62 Chemnitz 09111 Germany
| | - Klaus Banert
- Chemnitz University of TechnologyOrganic Chemistry Strasse der Nationen 62 Chemnitz 09111 Germany
| | - Chao Song
- College of ChemistryChemical Engineering and Materials ScienceSoochow University Suzhou 215123 China
| | - Xianxu Chu
- College of ChemistryChemical Engineering and Materials ScienceSoochow University Suzhou 215123 China
| | - Lina Wang
- Department of ChemistryFudan University Shanghai 200433 China
| | - Xiaoqing Zeng
- College of ChemistryChemical Engineering and Materials ScienceSoochow University Suzhou 215123 China
- Department of ChemistryFudan University Shanghai 200433 China
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11
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Qin Y, Lu B, Rauhut G, Hagedorn M, Banert K, Song C, Chu X, Wang L, Zeng X. The Simplest, Isolable, Alkynyl Isocyanate HC≡CNCO: Synthesis and Characterization. Angew Chem Int Ed Engl 2019; 58:17277-17281. [PMID: 31553514 DOI: 10.1002/anie.201911102] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Indexed: 11/08/2022]
Abstract
Alkynyl isocyanates have been postulated as highly reactive intermediates in synthetic chemistry. Herein, the parent molecule HC≡CNCO is isolated for the first time. In sharp contrast to the previously reported short lifetime (ca. 15 s) at room temperature, we found that HC≡CNCO has a lifetime of 55 h in the gas phase (2 mbar, 300 K) with a melting point of -79.5 °C and vaporization enthalpy (ΔHvap ) of 23.1(1) kJ mol-1 . Apart from the IR (gas, solid, and matrix), 1 H and 13 C NMR, and UV/Vis spectroscopic characterization, its photoisomerization with a acylnitrene HC≡CC(O)N and cyanoketene NCC(H)CO has been observed.
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Affiliation(s)
- Yuanyuan Qin
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Bo Lu
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Guntram Rauhut
- Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, Stuttgart, 70569, Germany
| | - Manfred Hagedorn
- Chemnitz University of Technology, Organic Chemistry, Strasse der Nationen 62, Chemnitz, 09111, Germany
| | - Klaus Banert
- Chemnitz University of Technology, Organic Chemistry, Strasse der Nationen 62, Chemnitz, 09111, Germany
| | - Chao Song
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Xianxu Chu
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Lina Wang
- Department of Chemistry, Fudan University, Shanghai, 200433, China
| | - Xiaoqing Zeng
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China.,Department of Chemistry, Fudan University, Shanghai, 200433, China
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12
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Hems RF, Wang C, Collins DB, Zhou S, Borduas-Dedekind N, Siegel JA, Abbatt JPD. Sources of isocyanic acid (HNCO) indoors: a focus on cigarette smoke. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2019; 21:1334-1341. [PMID: 30976776 DOI: 10.1039/c9em00107g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The sources and sinks of isocyanic acid (HNCO), a toxic gas, in indoor environments are largely uncharacterized. In particular, cigarette smoke has been identified as a significant source. In this study, controlled smoking of tobacco cigarettes was investigated in both an environmental chamber and a residence in Toronto, Canada using an acetate-CIMS. The HNCO emission ratio from side-stream cigarette smoke was determined to be 2.7 (±1.1) × 10-3 ppb HNCO/ppb CO. Side-stream smoke from a single cigarette introduced a large pulse of HNCO to the indoor environment, increasing the HNCO mixing ratio by up to a factor of ten from background conditions of 0.15 ppb. Although there was no evidence for photochemical production of HNCO from cigarette smoke in the residence, it was observed in the environmental chamber via oxidation by the hydroxyl radical (1.1 × 107 molecules per cm3), approximately doubling the HNCO mixing ratio after 30 minutes of oxidation. Oxidation of cigarette smoke by O3 (15 ppb = 4.0 × 1017 molecules per cm3) and photo-reaction with indoor fluorescent lights did not produce HNCO. By studying the temporal profiles of both HNCO and CO after smoking, it is inferred that gas-to-surface partitioning of HNCO acts as an indoor loss pathway. Even in the absence of smoking, the indoor HNCO mixing ratios in the Toronto residence were elevated compared to concurrent outdoor measurements by approximately a factor of two.
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Affiliation(s)
- Rachel F Hems
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
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13
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Brook JR, Cober SG, Freemark M, Harner T, Li SM, Liggio J, Makar P, Pauli B. Advances in science and applications of air pollution monitoring: A case study on oil sands monitoring targeting ecosystem protection. JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION (1995) 2019; 69:661-709. [PMID: 31082314 DOI: 10.1080/10962247.2019.1607689] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The potential environmental impact of air pollutants emitted from the oil sands industry in Alberta, Canada, has received considerable attention. The mining and processing of bitumen to produce synthetic crude oil, and the waste products associated with this activity, lead to significant emissions of gaseous and particle air pollutants. Deposition of pollutants occurs locally (i.e., near the sources) and also potentially at distances downwind, depending upon each pollutant's chemical and physical properties and meteorological conditions. The Joint Oil Sands Monitoring Program (JOSM) was initiated in 2012 by the Government of Canada and the Province of Alberta to enhance or improve monitoring of pollutants and their potential impacts. In support of JOSM, Environment and Climate Change Canada (ECCC) undertook a significant research effort via three components: the Air, Water, and Wildlife components, which were implemented to better estimate baseline conditions related to levels of pollutants in the air and water, amounts of deposition, and exposures experienced by the biota. The criteria air contaminants (e.g., nitrogen oxides [NOx], sulfur dioxide [SO2], volatile organic compounds [VOCs], particulate matter with an aerodynamic diameter <2.5 μm [PM2.5]) and their secondary atmospheric products were of interest, as well as toxic compounds, particularly polycyclic aromatic compounds (PACs), trace metals, and mercury (Hg). This critical review discusses the challenges of assessing ecosystem impacts and summarizes the major results of these efforts through approximately 2018. Focus is on the emissions to the air and the findings from the Air Component of the ECCC research and linkages to observations of contaminant levels in the surface waters in the region, in aquatic species, as well as in terrestrial and avian species. The existing evidence of impact on these species is briefly discussed, as is the potential for some of them to serve as sentinel species for the ongoing monitoring needed to better understand potential effects, their potential causes, and to detect future changes. Quantification of the atmospheric emissions of multiple pollutants needs to be improved, as does an understanding of the processes influencing fugitive emissions and local and regional deposition patterns. The influence of multiple stressors on biota exposure and response, from natural bitumen and forest fires to climate change, complicates the current ability to attribute effects to air emissions from the industry. However, there is growing evidence of the impact of current levels of PACs on some species, pointing to the need to improve the ability to predict PAC exposures and the key emission source involved. Although this critical review attempts to integrate some of the findings across the components, in terms of ECCC activities, increased coordination or integration of air, water, and wildlife research would enhance deeper scientific understanding. Improved understanding is needed in order to guide the development of long-term monitoring strategies that could most efficiently inform a future adaptive management approach to oil sands environmental monitoring and prevention of impacts. Implications: Quantification of atmospheric emissions for multiple pollutants needs to be improved, and reporting mechanisms and standards could be adapted to facilitate such improvements, including periodic validation, particularly where uncertainties are the largest. Understanding of baseline conditions in the air, water and biota has improved significantly; ongoing enhanced monitoring, building on this progress, will help improve ecosystem protection measures in the oil sands region. Sentinel species have been identified that could be used to identify and characterize potential impacts of wildlife exposure, both locally and regionally. Polycyclic aromatic compounds are identified as having an impact on aquatic and terrestrial wildlife at current concentration levels although the significance of these impacts and attribution to emissions from oil sands development requires further assessment. Given the improvement in high resolution air quality prediction models, these should be a valuable tool to future environmental assessments and cumulative environment impact assessments.
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Affiliation(s)
- J R Brook
- a Dalla Lana School of Public Health and Department of Chemical Engineering and Applied Chemistry, University of Toronto , Toronto , Ontario , Canada
| | - S G Cober
- b Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario , Canada
| | - M Freemark
- c National Wildlife Research Centre, Environment and Climate Change, Ottawa , Canada
| | - T Harner
- b Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario , Canada
| | - S M Li
- b Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario , Canada
| | - J Liggio
- b Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario , Canada
| | - P Makar
- b Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario , Canada
| | - B Pauli
- c National Wildlife Research Centre, Environment and Climate Change, Ottawa , Canada
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14
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Leslie MD, Ridoli M, Murphy JG, Borduas-Dedekind N. Isocyanic acid (HNCO) and its fate in the atmosphere: a review. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2019; 21:793-808. [PMID: 30968101 DOI: 10.1039/c9em00003h] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Isocyanic acid (HNCO) has recently been identified in ambient air at potentially concerning concentrations for human health. Since its first atmospheric detection, significant progress has been made in understanding its sources and sinks. The chemistry of HNCO is governed by its partitioning between the gas and liquid phases, its weak acidity, its high solubility at pH above 5, and its electrophilic chemical behaviour. The online measurement of HNCO in ambient air is possible due to recent advances in mass spectrometry techniques, including chemical ionization mass spectrometry for the detection of weak acids. To date, HNCO has been measured in North America, Europe and South Asia as well as outdoors and indoors, with mixing ratios up to 10s of ppbv. The sources of HNCO include: (1) fossil fuel combustion such as coal, gasoline and diesel, (2) biomass burning such as wildfires and crop residue burning, (3) secondary photochemical production from amines and amides, (4) cigarette smoke, and (5) combustion of materials in the built environment. Then, three losses processes can occur: (1) gas phase photochemistry, (2) heterogenous uptake and hydrolysis, and (3) dry deposition. HNCO lifetimes with respect to photolysis and OH radical oxidation are on the order of months to decades. Consequently, the removal of HNCO from the atmosphere is thought to occur predominantly by dry deposition and by heterogeneous uptake followed by hydrolysis to NH3 and CO2. A back of the envelope calculation reveals that HNCO is an insignificant global source of NH3, contributing only around 1%, but could be important for local environments. Furthermore, HNCO can react due to its electrophilic behaviour with various nucleophilic functionalities, including those present in the human body through a reaction called protein carbamoylation. This protein modification can lead to toxicity, and thus exposure to high concentrations of HNCO can lead to cardiovascular and respiratory diseases, as well as cataracts. In this critical review, we outline our current understanding of the atmospheric fate of HNCO and its potential impacts on outdoor and indoor air quality. We also call attention to the need for toxicology studies linking HNCO exposure to health effects.
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Affiliation(s)
- Michael David Leslie
- Department of Chemistry, University of Toronto, 80 St George Street, Toronto, Ontario M5S 3H6, Canada
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15
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Leanderson P, Krapi B. High levels of isocyanic acid in smoke generated during hot iron cauterization. ARCHIVES OF ENVIRONMENTAL & OCCUPATIONAL HEALTH 2019; 75:159-164. [PMID: 31070514 DOI: 10.1080/19338244.2019.1593920] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Pyrolysis of nitrogen containing biofuels generates isocyanic acid (ICA) and we here studied if ICA also is present in cauterization smoke. Air sampling was performed when animal technicians that had developed airway symptoms worked with dehorning. Tissue heated in a laboratory model was used to mimic cauterization. ICA in air at the workplace exceeded 10 times the national exposure limit. In the laboratory, the ICA generated per mg tissue from heated hair, horn and nail was 13.9 ± 7.8, 24.0 ± 4.1 and 32.0 ± 2.9 µg, respectively. Three workers were medically examined and two were diagnosed with asthma and a third had severe airway problem that resembled asthma. The study shows that high levels of ICA are generated during cauterization of nitrogen-containing tissue. If this could trigger airway symptoms deserves to be investigated further.
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Affiliation(s)
- Per Leanderson
- Occupational and Environmental Medicine Center, Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - Blerim Krapi
- Occupational and Environmental Medicine Center, Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
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16
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Leanderson P. Isocyanates and hydrogen cyanide in fumes from heated proteins and protein-rich foods. INDOOR AIR 2019; 29:291-298. [PMID: 30548495 DOI: 10.1111/ina.12526] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 11/07/2018] [Accepted: 12/05/2018] [Indexed: 06/09/2023]
Abstract
Toxic compounds in cooking fumes could cause respiratory problems. In the present study, the formation of isocyanic acid (ICA), methyl isocyanate (MIC), and hydrogen cyanide (HCN) was studied during the heating of proteins or frying of protein-rich foods. Heating was performed in an experimental setup using a tube oven set at 200-500°C and in a kitchen when foods with different protein content were fried at a temperature around 300°C. ICA, MIC, and HCN were all generated when protein or meat was heated. Individual amino acids were also heated, and there was a significant positive correlation between their respective nitrogen content and the formation of the measured compounds. Gas from heated protein or meat also caused carbamylation in albumin. ICA, MIC, and HCN were also present in fumes generated when meat, egg, and halloumi were fried in a kitchen pan. The levels of ICA were here twice that of the Swedish occupational exposure limit. If ICA, MIC, and HCN in fumes from heated protein-rich foods could contribute to the risk of airway dysfunction among those exposed is not clear, but it is important to avoid inhaling frying and grilling fumes and to equip kitchens with good exhaust ventilation.
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Affiliation(s)
- Per Leanderson
- Department of Clinical and Experimental Medicine, Occupational and Environmental Medicine Center, Linköping University, Linköping, Sweden
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17
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Agarwal AK, Singh AP, Gupta T, Agarwal RA, Sharma N, Rajput P, Pandey SK, Ateeq B. Mutagenicity and Cytotoxicity of Particulate Matter Emitted from Biodiesel-Fueled Engines. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:14496-14507. [PMID: 30512948 DOI: 10.1021/acs.est.8b03345] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Biodiesel engines produce several intermediate species, which can potentially harm the human health. The concentration of these species and their health risk potential varies depending on engine technology, fuel, and engine operating condition. In this study, experiments were performed on a large number of engines having different configurations (emissions norms/fuel used), which were operated at part load/full load using B20 (20% v/v biodiesel blended with mineral diesel) and mineral diesel. Experiments included measurement of gaseous emissions, and physical, chemical, and biological characterization of exhaust particulate matter (PM). Chemical characterization of PM was carried out for detecting polycyclic aromatic hydrocarbons (PAH's) and PM bound trace metals. The biological toxicity associated with PM was assessed using human embryonic kidney 293T cells (HEK 293T). The mutagenic potential of the PM was tested at three different concentrations (500, 100, and 50 μg/mL) using two different Salmonella strains, TA98 and TA100, with and without liver S9 metabolic enzyme fraction. PM samples exhibited cytotoxic effect on HEK 293T cells (IC50 < 100 μg/mL) and there was significant potential for reactive oxygen species (ROS) generation. Comparison of different engines showed that modern engines (Euro-III and Euro-IV compliant) produced relatively cleaner exhaust compared to older engines (Euro-II compliant). Biodiesel-fueled engines emitted lower number of particles compared to diesel-fueled engines. However, chemical characterization revealed that biodiesel-fueled engines exhaust PM contained several harmful PAHs and trace metals, which affected the biological activity of these PM, as reflected in the biological investigations. Mutagenicity and cytotoxicity of PM from biodiesel-fueled engines were relatively higher compared to their diesel counterparts, indicating the need for exhaust gas after-treatment.
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18
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Zhang ZG, Xin M, Wu YN, Zhao ST, Tang YJ, Chen Y. Imaging HNCO photodissociation at 201 nm: State-to-state correlations between CO (X1Σ+) and NH (a1Δ). CHINESE J CHEM PHYS 2018. [DOI: 10.1063/1674-0068/31/cjcp1808192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Zhi-guo Zhang
- School of Physics and Electronic Engineering, Fuyang Normal University, Fuyang 236041, China
| | - Min Xin
- School of Physics and Electronic Engineering, Fuyang Normal University, Fuyang 236041, China
| | - Yan-ning Wu
- School of Physics and Electronic Engineering, Fuyang Normal University, Fuyang 236041, China
| | - Shu-tao Zhao
- School of Physics and Electronic Engineering, Fuyang Normal University, Fuyang 236041, China
| | - Yi-jia Tang
- School of Physics and Electronic Engineering, Fuyang Normal University, Fuyang 236041, China
| | - Yang Chen
- Department of Chemical Physics and Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
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19
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Liggio J, Stroud CA, Wentzell JJB, Zhang J, Sommers J, Darlington A, Liu PSK, Moussa SG, Leithead A, Hayden K, Mittermeier RL, Staebler R, Wolde M, Li SM. Quantifying the Primary Emissions and Photochemical Formation of Isocyanic Acid Downwind of Oil Sands Operations. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:14462-14471. [PMID: 29210280 DOI: 10.1021/acs.est.7b04346] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Isocyanic acid (HNCO) is a known toxic species and yet the relative importance of primary and secondary sources to regional HNCO and population exposure remains unclear. Off-road diesel fuel combustion has previously been suggested to be an important regional source of HNCO, which implies that major industrial facilities such as the oil sands (OS), which consume large quantities of diesel fuel, can be sources of HNCO. The OS emissions of nontraditional toxic species such as HNCO have not been assessed. Here, airborne measurements of HNCO were used to estimate primary and secondary HNCO for the oil sands. Approximately 6.2 ± 1.1 kg hr-1 was emitted from off-road diesel activities within oil sands facilities, and an additional 116-186 kg hr-1 formed from the photochemical oxidation of diesel exhaust. Together, the primary and secondary HNCO from OS operations represent a significant anthropogenic HNCO source in Canada. The secondary HNCO downwind of the OS was enhanced by up to a factor of 20 relative to its primary emission, an enhancement factor significantly greater than previously estimated from laboratory studies. Incorporating HNCO emissions and formation into a regional model demonstrated that the HNCO levels in Fort McMurray (∼10-70 km downwind of the OS) are controlled by OS emissions; > 50% of the monthly mean HNCO arose from the OS. While the mean HNCO levels in Fort McMurray are predicted to be below the 1000 pptv level associated with potential negative health impacts, (∼25 pptv in August-September), an order of magnitude increase in concentration is predicted (250-600 pptv) when the town is directly impacted by OS plumes. The results here highlight the importance of obtaining at-source HNCO emission factors and advancing the understanding of secondary HNCO formation mechanisms, to assess and improve HNCO population exposure predictions.
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Affiliation(s)
- John Liggio
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Craig A Stroud
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Jeremy J B Wentzell
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Junhua Zhang
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Jacob Sommers
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Andrea Darlington
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Peter S K Liu
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Samar G Moussa
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Amy Leithead
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Katherine Hayden
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Richard L Mittermeier
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Ralf Staebler
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
| | - Mengistu Wolde
- National Research Council Canada , Flight Research Laboratory, Ottawa, Ontario Canada , K1A 0R6
| | - Shao-Meng Li
- Air Quality Research Division, Environment and Climate Change Canada , Toronto, Ontario Canada , M3H 5T4
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20
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Bock N, Baum MM, Anderson MB, Pesta A, Northrop WF. Dicarboxylic Acid Emissions from Aftertreatment Equipped Diesel Engines. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:13036-13043. [PMID: 28952310 DOI: 10.1021/acs.est.7b03868] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Dicarboxylic acids play a key role in atmospheric particle nucleation. Though long assumed to originate from primary sources, little experimental evidence exists directly linking combustion to their emissions. In this work, we sought definitive proof that dicarboxylic acids are produced in diesel engines and that they can slip through a modern aftertreatment system (ATS) at low exhaust temperatures. One difficulty in measuring dicarboxylic acid emissions is that they cannot be identified using conventional mass spectroscopy techniques. In this work, we refined a derivatization gas chromatography-mass spectroscopy technique to measure 11 mono- and dicarboxylic acids from plain and KOH impregnated quartz filters. Filters were loaded with exhaust from a modern passenger car diesel engine on a dynamometer sampled before and after an ATS consisting of an oxidation catalyst and diesel particulate filter. Our findings confirm that dicarboxylic acids are produced in diesel engine combustion, especially during low temperature combustion modes that emit significant concentrations of partially combusted hydrocarbons. Exhaust acids were largely removed by a fully warmed-up ATS, mitigating their environmental impact. Our results also suggest that dicarboxylic acids do not participate in primary particle formation in dilute engine exhaust as low quantities were collected on unimpregnated filters.
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Affiliation(s)
- Noah Bock
- University of Minnesota , 111 Church Street SE, Minneapolis, Minnesota 55455, United States
| | - Marc M Baum
- Oak Crest Institute of Science, 132 W. Chestnut Ave., Monrovia, California 91016, United States
| | - Mackenzie B Anderson
- Oak Crest Institute of Science, 132 W. Chestnut Ave., Monrovia, California 91016, United States
| | - Anaïs Pesta
- Oak Crest Institute of Science, 132 W. Chestnut Ave., Monrovia, California 91016, United States
| | - William F Northrop
- University of Minnesota , 111 Church Street SE, Minneapolis, Minnesota 55455, United States
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21
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Parandaman A, Tangtartharakul CB, Kumar M, Francisco JS, Sinha A. A Computational Study Investigating the Energetics and Kinetics of the HNCO + (CH3)2NH Reaction Catalyzed by a Single Water Molecule. J Phys Chem A 2017; 121:8465-8473. [DOI: 10.1021/acs.jpca.7b08657] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Arathala Parandaman
- Department
of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093, United States
| | - Chanin B. Tangtartharakul
- Department
of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093, United States
| | - Manoj Kumar
- Department
of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Joseph S. Francisco
- Department
of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Amitabha Sinha
- Department
of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093, United States
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22
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Friedman B, Link MF, Fulgham SR, Brophy P, Galang A, Brune WH, Jathar SH, Farmer DK. Primary and Secondary Sources of Gas-Phase Organic Acids from Diesel Exhaust. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:10872-10880. [PMID: 28825297 DOI: 10.1021/acs.est.7b01169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Organic acids have primary and secondary sources in the atmosphere, impact ecosystem health, and are useful metrics for identifying gaps in organic oxidation chemistry through model-measurement comparisons. We photooxidized (OH oxidation) primary emissions from diesel and biodiesel fuel types under two engine loads in an oxidative flow reactor. formic, butyric, and propanoic acids, but not methacrylic acid, have primary and secondary sources. Emission factors for these gas-phase acids varied from 0.3-8.4 mg kg-1 fuel. Secondary chemistry enhanced these emissions by 1.1 (load) to 4.4 (idle) × after two OH-equivalent days. The relative enhancement in secondary organic acids in idle versus loaded conditions was due to increased precursor emissions, not faster reaction rates. Increased hydrocarbon emissions in idle conditions due to less complete combustion (associated with less oxidized gas-phase molecules) correlated to higher primary organic acid emissions. The lack of correlation between organic aerosol and organic acid concentrations downstream of the flow reactor indicates that the secondary products formed on different oxidation time scales and that despite being photochemical products, organic acids are poor tracers for secondary organic aerosol formation from diesel exhaust. Ignoring secondary chemistry from diesel exhaust would lead to underestimates of both organic aerosol and gas-phase organic acids.
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Affiliation(s)
- Beth Friedman
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States
| | - Michael F Link
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States
| | - S Ryan Fulgham
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States
| | - Patrick Brophy
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States
| | - Abril Galang
- Department of Mechanical Engineering, Colorado State University , Fort Collins, Colorado 80523-1872, United States
| | - William H Brune
- Department of Meteorology, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Shantanu H Jathar
- Department of Mechanical Engineering, Colorado State University , Fort Collins, Colorado 80523-1872, United States
| | - Delphine K Farmer
- Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States
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23
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Jankowski MJ, Olsen R, Thomassen Y, Molander P. Comparison of air samplers for determination of isocyanic acid and applicability for work environment exposure assessment. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2017; 19:1075-1085. [PMID: 28762425 DOI: 10.1039/c7em00174f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Isocyanic acid (ICA) is one of the most abundant isocyanates formed during thermal decomposition of polyurethane (PUR), and other nitrogen containing polymers. Hot-work, such as flame cutting, forging, grinding, turning and welding may give rise to thermal decomposition of said polymers potentially forming significant amounts of ICA. A newly launched dry denuder sampler for airborne isocyanates using di-n-butylamine (DBA) demonstrated build-up of background ICA-DBA over time. Build-up of background ICA-DBA was not observed when stored at inert conditions (Ar atmosphere) for 84 days. Thus, freshly prepared denuders were used. The sampling efficiency of ICA using freshly prepared denuder samplers (0.2 L min-1), impinger + filter samplers (0.5 L min-1) using DBA and 1-(2-methoxyphenyl) piperazine (2MP)-impregnated filter cassette samplers (1 L min-1) was investigated. PTR-MS measurements of ICA were used as a quantitative reference. Dynamically generated standard ICA atmospheres covered the range 5.6 to 640 ppb at absolute humidities (AH) 4.0 and 16 g m-3. Recovered ICA was found to be 73-115% (denuder), 89-115% (impinger + filter) and 62-100% (2MP filter cassette). The method limit of detection (LOD) was equal to an amount of ICA of 24 ng (denuder), 8.9 ng (impinger + filter) and 9.4 ng (2MP filter cassette). The PTR-MS LOD for ICA was 1.8 and 2.8 ppb in atmospheres with an AH of 4 and 16 g m-3. Denuder samplers were used for personal (n = 176) and stationary (n = 31) air sampling during hot-work at six industrial sites (n = 23 workers). ICA was detected above method LOD in 66% and 58% of the personal and stationary samples, respectively. ICA workroom air concentrations were determined to be 1.8-320 ppb (median 12 ppb) (personal samples), and 1.5-44 ppb (median 6.6 ppb) (stationary samples).
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Drozd GT, Zhao Y, Saliba G, Frodin B, Maddox C, Weber RJ, Chang MCO, Maldonado H, Sardar S, Robinson AL, Goldstein AH. Time Resolved Measurements of Speciated Tailpipe Emissions from Motor Vehicles: Trends with Emission Control Technology, Cold Start Effects, and Speciation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:13592-13599. [PMID: 27993057 DOI: 10.1021/acs.est.6b04513] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Experiments were conducted at the California Air Resources Board Haagen-Smit Laboratory to understand changes in vehicle emissions in response to stricter emissions standards over the past 25 years. Measurements included a wide range of volatile organic compounds (VOCs) for a wide range of spark ignition gasoline vehicles meeting varying levels of emissions standards, including all certifications from Tier 0 up to Partial Zero Emission Vehicle. Standard gas chromatography (GC) and high performance liquid chromatography (HLPC) analyses were employed for drive-cycle phase emissions. A proton-transfer-reaction mass spectrometer measured time-resolved emissions for a wide range of VOCs. Cold-start emissions occur almost entirely in the first 30-60 s for newer vehicles. Cold-start emissions have compositions that are not significantly different across all vehicles tested and are markedly different from neat fuel. Hot-stabilized emissions have varying importance depending on species and may require a driving distance of 200 miles to equal the emissions from a single cold start. Average commute distances in the U.S. suggest the majority of in-use vehicles have emissions dominated by cold starts. The distribution of vehicle ages in the U.S. suggests that within several years only a few percent of vehicles will have significant driving emissions compared to cold-start emissions.
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Affiliation(s)
- Greg T Drozd
- Department of Environmental Science, Policy, and Management, University of California , Berkeley , California 94720, United States
| | - Yunliang Zhao
- Center for Atmospheric Particle Studies, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Georges Saliba
- Center for Atmospheric Particle Studies, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Bruce Frodin
- California Air Resources Board, Sacramento, California 95814, United States
| | - Christine Maddox
- California Air Resources Board, Sacramento, California 95814, United States
| | - Robert J Weber
- Department of Environmental Science, Policy, and Management, University of California , Berkeley , California 94720, United States
| | - M-C Oliver Chang
- California Air Resources Board, Sacramento, California 95814, United States
| | - Hector Maldonado
- California Air Resources Board, Sacramento, California 95814, United States
| | - Satya Sardar
- California Air Resources Board, Sacramento, California 95814, United States
| | - Allen L Robinson
- Center for Atmospheric Particle Studies, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Allen H Goldstein
- Department of Environmental Science, Policy, and Management, University of California , Berkeley , California 94720, United States
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Chandra BP, Sinha V. Contribution of post-harvest agricultural paddy residue fires in the N.W. Indo-Gangetic Plain to ambient carcinogenic benzenoids, toxic isocyanic acid and carbon monoxide. ENVIRONMENT INTERNATIONAL 2016; 88:187-197. [PMID: 26760716 DOI: 10.1016/j.envint.2015.12.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 12/17/2015] [Accepted: 12/19/2015] [Indexed: 06/05/2023]
Abstract
In the north west Indo-Gangetic Plain (N.W.IGP), large scale post-harvest paddy residue fires occur every year during the months of October-November. This anthropogenic perturbation causes contamination of the atmospheric environment with adverse impacts on regional air quality posing health risks for the population exposed to high concentrations of carcinogens such as benzene and toxic VOCs such as isocyanic acid. These gases and carbon monoxide are known to be emitted from biomass fires along with acetonitrile. Yet no long-term in-situ measurements quantifying the impact of this activity have been carried out in the N.W. IGP. Using high quality continuous online in-situ measurements of these gases at a strategic downwind site over a three year period from 2012 to 2014, we demonstrate the strong impact of this anthropogenic emission activity on ambient concentrations of these gases. In contrast to the pre-paddy harvest period, excellent correlation of benzenoids, isocyanic acid and CO with acetonitrile (a biomass burning chemical tracer); (r≥0.82) and distinct VOC/acetonitrile emission ratios were observed for the post-paddy harvest period which was also characterized by high ambient concentrations of these species. The average concentrations of acetonitrile (1.62±0.18ppb), benzene (2.51±0.28ppb), toluene (3.72±0.41ppb), C8-aromatics (2.88±0.30ppb), C9-aromatics (1.55±0.19ppb) and CO (552±113ppb) in the post-paddy harvest periods were about 1.5 times higher than the annual average concentrations. For isocyanic acid, a compound with both primary and secondary sources, the concentration in the post-paddy harvest period was 0.97±0.17ppb. The annual average concentrations of benzene, a class A carcinogen, exceeded the annual exposure limit of 1.6ppb at NTP mandated by the National Ambient Air Quality Standard of India (NAAQS). We show that mitigating the post-harvest paddy residue fires can lower the annual average concentration of benzene and ensure compliance with the NAAQS. Calculations of excessive lifetime cancer risk due to benzene amount to 25 and 10 per million inhabitants for children and adults, respectively, exceeding the USEPA threshold of 1 per million inhabitants. Annual exposure to isocyanic acid was close to 1ppb, the concentration considered to be sufficient to enhance risks for cardiovascular diseases and cataracts. This study makes a case for urgent mitigation of post-harvest paddy residue fires as the unknown synergistic effect of multi-pollutant exposure due to emissions from this anthropogenic source may be posing grave health risks to the population of the N.W. IGP.
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Affiliation(s)
- B P Chandra
- Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S.A.S. Nagar, Manauli PO, Punjab 140306, India
| | - Vinayak Sinha
- Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S.A.S. Nagar, Manauli PO, Punjab 140306, India.
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Brady JM, Crisp TA, Collier S, Kuwayama T, Forestieri SD, Perraud V, Zhang Q, Kleeman MJ, Cappa CD, Bertram TH. Real-time emission factor measurements of isocyanic acid from light duty gasoline vehicles. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:11405-11412. [PMID: 25198906 DOI: 10.1021/es504354p] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Exposure to gas-phase isocyanic acid (HNCO) has been previously shown to be associated with the development of atherosclerosis, cataracts and rheumatoid arthritis. As such, accurate emission inventories for HNCO are critical for modeling the spatial and temporal distribution of HNCO on a regional and global scale. To date, HNCO emission rates from light duty gasoline vehicles, operated under driving conditions, have not been determined. Here, we present the first measurements of real-time emission factors of isocyanic acid from a fleet of eight light duty gasoline-powered vehicles (LDGVs) tested on a chassis dynamometer using the Unified Driving Cycle (UC) at the California Air Resources Board (CARB) Haagen-Smit test facility, all of which were equipped with three-way catalytic converters. HNCO emissions were observed from all vehicles, in contrast to the idealized laboratory measurements. We report the tested fleet averaged HNCO emission factors, which depend strongly on the phase of the drive cycle; ranging from 0.46 ± 0.13 mg kg fuel(-1) during engine start to 1.70 ± 1.77 mg kg fuel(-1) during hard acceleration after the engine and catalytic converter were warm. The tested eight-car fleet average fuel based HNCO emission factor was 0.91 ± 0.58 mg kg fuel(-1), within the range previously estimated for light duty diesel-powered vehicles (0.21-3.96 mg kg fuel(-1)). Our results suggest that HNCO emissions from LDGVs represent a significant emission source in urban areas that should be accounted for in global and regional models.
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Affiliation(s)
- James M Brady
- Department of Chemistry and Biochemistry, University of California , San Diego, California 92093, United States
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Borduas N, da Silva G, Murphy JG, Abbatt JPD. Experimental and theoretical understanding of the gas phase oxidation of atmospheric amides with OH radicals: kinetics, products, and mechanisms. J Phys Chem A 2014; 119:4298-308. [PMID: 25019427 DOI: 10.1021/jp503759f] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Atmospheric amides have primary and secondary sources and are present in ambient air at low pptv levels. To better assess the fate of amides in the atmosphere, the room temperature (298 ± 3 K) rate coefficients of five different amides with OH radicals were determined in a 1 m(3) smog chamber using online proton-transfer-reaction mass spectrometry (PTR-MS). Formamide, the simplest amide, has a rate coefficient of (4.44 ± 0.46) × 10(-12) cm(3) molec(-1) s(-1) against OH, translating to an atmospheric lifetime of ∼1 day. N-methylformamide, N-methylacetamide and propanamide, alkyl versions of formamide, have rate coefficients of (10.1 ± 0.6) × 10(-12), (5.42 ± 0.19) × 10(-12), and (1.78 ± 0.43) × 10(-12) cm(3) molec(-1) s(-1), respectively. Acetamide was also investigated, but due to its slow oxidation kinetics, we report a range of (0.4-1.1) × 10(-12) cm(3) molec(-1) s(-1) for its rate coefficient with OH radicals. Oxidation products were monitored and quantified and their time traces were fitted using a simple kinetic box model. To further probe the mechanism, ab initio calculations are used to identify the initial radical products of the amide reactions with OH. Our results indicate that N-H abstractions are negligible in all cases, in contrast to what is predicted by structure-activity relationships. Instead, the reactions proceed via C-H abstraction from alkyl groups and from formyl C(O)-H bonds when available. The latter process leads to radicals that can readily react with O2 to form isocyanates, explaining the detection of toxic compounds such as isocyanic acid (HNCO) and methyl isocyanate (CH3NCO). These contaminants of significant interest are primary oxidation products in the photochemical oxidation of formamide and N-methylformamide, respectively.
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Affiliation(s)
- Nadine Borduas
- †Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Gabriel da Silva
- ‡Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia
| | - Jennifer G Murphy
- †Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Jonathan P D Abbatt
- †Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
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