156 results on '"Crilley, Leigh R."'
Search Results
2. Quantification of within-vehicle exposure to NOx and particles: Variation with outside air quality, route choice and ventilation options
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Matthaios, Vasileios N., Kramer, Louisa J., Crilley, Leigh R., Sommariva, Roberto, Pope, Francis D., and Bloss, William J.
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- 2020
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3. Predicting real-time within-vehicle air pollution exposure with mass-balance and machine learning approaches using on-road and air quality data
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Matthaios, Vasileios N., primary, Knibbs, Luke D., additional, Kramer, Louisa J., additional, Crilley, Leigh R., additional, and Bloss, William J., additional
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- 2023
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4. Impact of HO2 aerosol uptake on radical levels and O3 production during summertime in Beijing
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Dyson, Joanna E., primary, Whalley, Lisa K., additional, Slater, Eloise J., additional, Woodward-Massey, Robert, additional, Ye, Chunxiang, additional, Lee, James D., additional, Squires, Freya, additional, Hopkins, James R., additional, Dunmore, Rachel E., additional, Shaw, Marvin, additional, Hamilton, Jacqueline F., additional, Lewis, Alastair C., additional, Worrall, Stephen D., additional, Bacak, Asan, additional, Mehra, Archit, additional, Bannan, Thomas J., additional, Coe, Hugh, additional, Percival, Carl J., additional, Ouyang, Bin, additional, Hewitt, C. Nicholas, additional, Jones, Roderic L., additional, Crilley, Leigh R., additional, Kramer, Louisa J., additional, Acton, W. Joe F., additional, Bloss, William J., additional, Saksakulkrai, Supattarachai, additional, Xu, Jingsha, additional, Shi, Zongbo, additional, Harrison, Roy M., additional, Kotthaus, Simone, additional, Grimmond, Sue, additional, Sun, Yele, additional, Xu, Weiqi, additional, Yue, Siyao, additional, Wei, Lianfang, additional, Fu, Pingqing, additional, Wang, Xinming, additional, Arnold, Stephen R., additional, and Heard, Dwayne E., additional
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- 2023
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5. Radical chemistry and ozone production at a UK coastal receptor site.
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Woodward-Massey, Robert, Sommariva, Roberto, Whalley, Lisa K., Cryer, Danny R., Ingham, Trevor, Bloss, William J., Ball, Stephen M., Cox, Sam, Lee, James D., Reed, Chris P., Crilley, Leigh R., Kramer, Louisa J., Bandy, Brian J., Forster, Grant L., Reeves, Claire E., Monks, Paul S., and Heard, Dwayne E.
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RADICALS (Chemistry) ,PEROXY radicals ,BUDGET ,MEDIAN (Mathematics) ,METROPOLITAN areas ,OZONE ,SEISMIC anisotropy - Abstract
OH, HO 2 , total and partially speciated RO 2 , and OH reactivity (kOH′) were measured during the July 2015 ICOZA (Integrated Chemistry of OZone in the Atmosphere) project that took place at a coastal site in north Norfolk, UK. Maximum measured daily OH, HO 2 and total RO 2 radical concentrations were in the range 2.6–17 × 10 6 , 0.75–4.2 × 10 8 and 2.3–8.0 × 10 8 molec. cm -3 , respectively. kOH′ ranged from 1.7 to 17.6 s -1 , with a median value of 4.7 s -1. ICOZA data were split by wind direction to assess differences in the radical chemistry between air that had passed over the North Sea (NW–SE sectors) and that over major urban conurbations such as London (SW sector). A box model using the Master Chemical Mechanism (MCMv3.3.1) was in reasonable agreement with the OH measurements, but it overpredicted HO 2 observations in NW–SE air in the afternoon by a factor of ∼ 2–3, although slightly better agreement was found for HO 2 in SW air (factor of ∼ 1.4–2.0 underprediction). The box model severely underpredicted total RO 2 observations in both NW–SE and SW air by factors of ∼ 8–9 on average. Measured radical and kOH′ levels and measurement–model ratios displayed strong dependences on NO mixing ratios, with the results suggesting that peroxy radical chemistry is not well understood under high-NO x conditions. The simultaneous measurement of OH, HO 2 , total RO 2 and kOH′ was used to derive experimental (i.e. observationally determined) budgets for all radical species as well as total RO x (i.e. OH + HO 2 + RO 2). In NW–SE air, the RO x budget could be closed during the daytime within experimental uncertainty, but the rate of OH destruction exceeded the rate of OH production, and the rate of HO 2 production greatly exceeded the rate of HO 2 destruction, while the opposite was true for RO 2. In SW air, the RO x budget analysis indicated missing daytime RO x sources, but the OH budget was balanced, and the same imbalances were found with the HO 2 and RO 2 budgets as in NW–SE air. For HO 2 and RO 2 , the budget imbalances were most severe at high-NO mixing ratios, and the best agreement between HO 2 and RO 2 rates of production and destruction rates was found when the RO 2 + NO rate coefficient was reduced by a factor of 5. A photostationary-steady-state (PSS) calculation underpredicted daytime OH in NW–SE air by ∼ 35 %, whereas agreement (∼ 15 %) was found within instrumental uncertainty (∼ 26 % at 2 σ) in SW air. The rate of in situ ozone production (P (O x)) was calculated from observations of RO x , NO and NO 2 and compared to that calculated from MCM-modelled radical concentrations. The MCM-calculated P (O x) significantly underpredicted the measurement-calculated P (O x) in the morning, and the degree of underprediction was found to scale with NO. [ABSTRACT FROM AUTHOR]
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- 2023
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6. Extreme Concentrations of Nitric Oxide Control Daytime Oxidation and Quench Nocturnal Oxidation Chemistry in Delhi during Highly Polluted Episodes
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Nelson, Beth S., Bryant, Daniel J., Alam, Mohammed S., Sommariva, Roberto, Bloss, William J., Newland, Mike J., Drysdale, Will S., Vaughan, Adam R., Acton, W. Joe F., Hewitt, C. Nicholas, Crilley, Leigh R., Swift, Stefan J., Edwards, Pete M., Lewis, Alastair C., Langford, Ben, Nemitz, Eiko, Shivani, Gadi, Ranu, Gurjar, Bhola R., Heard, Dwayne E., Whalley, Lisa K., Şahin, Ülkü A., Beddows, David C. S., Hopkins, James R., Lee, James D., Rickard, Andrew R., Hamilton, Jacqueline F., Nelson, Beth S., Bryant, Daniel J., Alam, Mohammed S., Sommariva, Roberto, Bloss, William J., Newland, Mike J., Drysdale, Will S., Vaughan, Adam R., Acton, W. Joe F., Hewitt, C. Nicholas, Crilley, Leigh R., Swift, Stefan J., Edwards, Pete M., Lewis, Alastair C., Langford, Ben, Nemitz, Eiko, Shivani, Gadi, Ranu, Gurjar, Bhola R., Heard, Dwayne E., Whalley, Lisa K., Şahin, Ülkü A., Beddows, David C. S., Hopkins, James R., Lee, James D., Rickard, Andrew R., and Hamilton, Jacqueline F.
- Abstract
Delhi, India, suffers from periods of very poor air quality, but little is known about the chemical production of secondary pollutants in this highly polluted environment. During the postmonsoon period in 2018, extremely high nighttime concentrations of NOx (NO and NO2) and volatile organic compounds (VOCs) were observed, with median NOx mixing ratios of ∼200 ppbV (maximum of ∼700 ppbV). A detailed chemical box model constrained to a comprehensive suite of speciated VOC and NOx measurements revealed very low nighttime concentrations of oxidants, NO3, O3, and OH, driven by high nighttime NO concentrations. This results in an atypical NO3 diel profile, not previously reported in other highly polluted urban environments, significantly perturbing nighttime radical oxidation chemistry. Low concentrations of oxidants and high nocturnal primary emissions coupled with a shallow boundary layer led to enhanced early morning photo-oxidation chemistry. This results in a temporal shift in peak O3 concentrations when compared to the premonsoon period (12:00 and 15:00 local time, respectively). This shift will likely have important implications on local air quality, and effective urban air quality management should consider the impacts of nighttime emission sources during the postmonsoon period.
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- 2023
7. Extensive field evidence for the release of HONO from the photolysis of nitrate aerosols
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Andersen, Simone T., primary, Carpenter, Lucy J., additional, Reed, Chris, additional, Lee, James D., additional, Chance, Rosie, additional, Sherwen, Tomás, additional, Vaughan, Adam R., additional, Stewart, Jordan, additional, Edwards, Pete M., additional, Bloss, William J., additional, Sommariva, Roberto, additional, Crilley, Leigh R., additional, Nott, Graeme J., additional, Neves, Luis, additional, Read, Katie, additional, Heard, Dwayne E., additional, Seakins, Paul W., additional, Whalley, Lisa K., additional, Boustead, Graham A., additional, Fleming, Lauren T., additional, Stone, Daniel, additional, and Fomba, Khanneh Wadinga, additional
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- 2023
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8. Development and validation of a new in situ technique to measure total gaseous chlorine in air
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Furlani, Teles C., primary, Ye, RenXi, additional, Stewart, Jordan, additional, Crilley, Leigh R., additional, Edwards, Peter M., additional, Kahan, Tara F., additional, and Young, Cora J., additional
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- 2023
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9. Characteristics of ultrafine particle sources and deposition rates in primary school classrooms
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Laiman, Rusdin, He, Congrong, Mazaheri, Mandana, Clifford, Samuel, Salimi, Farhad, Crilley, Leigh R., Megat Mokhtar, Megat Azman, and Morawska, Lidia
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- 2014
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10. Measurement report: Interpretation of wide-range particulate matter size distributions in Delhi
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Harrison, Roy M., Alam, Mohammed S., Beddows, David C.S., Bousiotis, Dimitrios, Shi, Zongbo, Crilley, Leigh R., Bloss, William, Brean, James, Khanna, Isha, and Verma, Rulan
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Atmospheric Science - Abstract
Delhi is one of the world's most polluted cities, with very high concentrations of airborne particulate matter. However, little is known about the factors controlling the characteristics of wide-range particle number size distributions. Here, new measurements are reported from three field campaigns conducted in winter and pre-monsoon and post-monsoon seasons at the Indian Institute of Technology campus in the south of the city. Particle number size distributions were measured simultaneously, using a scanning mobility particle sizer and a GRIMM optical particle monitor, covering 15 nm to >10 ?m diameter. The merged, wide-range size distributions were categorized into the following five size ranges: nucleation (15-20 nm), Aitken (20-100 nm), accumulation (100 nm-1 ?m), large fine (1-2.5 ?m), and coarse (2.5-10 ?m) particles. The ultrafine fraction (15-100 nm) accounts for about 52 % of all particles by number (PN10 is the total particle number from 15 nm to 10 ?m) but just 1 % by PM10 volume (PV10 is the total particle volume from 15 nm to 10 ?m). The measured size distributions are markedly coarser than most from other parts of the world but are consistent with earlier cascade impactor data from Delhi. Our results suggest substantial aerosol processing by coagulation, condensation, and water uptake in the heavily polluted atmosphere, which takes place mostly at nighttime and in the morning hours. Total number concentrations are highest in winter, but the mode of the distribution is largest in the post-monsoon (autumn) season. The accumulation mode particles dominate the particle volume in autumn and winter, while the coarse mode dominates in summer. Polar plots show a huge variation between both size fractions in the same season and between seasons for the same size fraction. The diurnal pattern of particle numbers is strongly reflective of a road traffic influence upon concentrations, especially in autumn and winter, although other sources, such as cooking and domestic heating, may influence the evening peak. There is a clear influence of diesel traffic at nighttime, when it is permitted to enter the city, and also indications in the size distribution data of a mode < 15 nm, which is probably attributable to CNG/LPG vehicles. New particle formation appears to be infrequent and is, in this dataset, limited to 1 d in the summer campaign. Our results reveal that the very high emissions of airborne particles in Delhi, particularly from traffic, determine the variation in particle number size distributions.
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- 2022
11. Measurement report: Interpretation of wide-range particulate matter size distributions in Delhi
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Şahin, Ülkü Alver, primary, Harrison, Roy M., additional, Alam, Mohammed S., additional, Beddows, David C. S., additional, Bousiotis, Dimitrios, additional, Shi, Zongbo, additional, Crilley, Leigh R., additional, Bloss, William, additional, Brean, James, additional, Khanna, Isha, additional, and Verma, Rulan, additional
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- 2022
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12. Assessing the effectiveness of low-cost air quality monitors for identifying volcanic SO2 and PM downwind from Masaya volcano, Nicaragua
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Whitty, Rachel C. W., primary, Pfeffer, Melissa A., additional, Ilyinskaya, Evgenia, additional, Roberts, Tjarda J., additional, Schmidt, Anja, additional, Barsotti, Sara, additional, Strauch, Wilfried, additional, Crilley, Leigh R., additional, Pope, Francis D., additional, Bellanger, Harold, additional, Mendoza, Elvis, additional, Mather, Tamsin A., additional, Liu, Emma J., additional, Peters, Nial, additional, Taylor, Isabelle A., additional, Francis, Hilary, additional, Hernández Leiva, Xochilt, additional, Lynch, Dave, additional, Norbert, Sebastien, additional, and Baxter, Peter, additional
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- 2022
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13. Is the ocean surface a source of nitrous acid (HONO) in the marine boundary layer?
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Crilley, Leigh R., primary, Kramer, Louisa J., additional, Pope, Francis D., additional, Reed, Chris, additional, Lee, James D., additional, Carpenter, Lucy J., additional, Hollis, Lloyd D. J., additional, Ball, Stephen M., additional, and Bloss, William J., additional
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- 2021
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14. PM1 composition and source apportionment at two sites in Delhi, India, across multiple seasons
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Reyes-Villegas, Ernesto, Panda, Upasana, Darbyshire, Eoghan, Cash, James M., Joshi, Rutambhara, Langford, Ben, Di Marco, Chiara F., Mullinger, Neil J., Alam, Mohammed S., Crilley, Leigh R., Rooney, Daniel J., Acton, W. Joe F., Drysdale, Will, Nemitz, Eiko, Flynn, Michael, Voliotis, Aristeidis, McFiggans, Gordon, Coe, Hugh, Lee, James, Hewitt, C. Nicholas, Heal, Mathew R., Gunthe, Sachin S., Mandal, Tuhin K., Gurjar, Bhola R., Shivani, Gadi, Ranu, Singh, Siddhartha, Soni, Vijay, and Allan, James D.
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aerosol mass spectrometry ,Source apportionment ,urban air quality ,air pollution ,positive matrix factorization ,megacities ,atmospheric aerosol ,Atmospheric Sciences ,PM1 - Abstract
Air pollution in urban environments has been shown to have a negative impact on air quality and human health, particularly in megacities. Over recent decades, Delhi, India, has suffered high atmospheric pollution, with significant particulate matter (PM) concentrations as a result of anthropogenic activities. Organic aerosols (OAs) are composed of thousands of different chemical species and are one of the main constituents of submicron particles. However, quantitative knowledge of OA composition, their sources and their processes in urban environments is still limited. This is important particularly in India, as Delhi is a massive, inhomogeneous conurbation, where we would expect the apportionment and concentrations to vary depending on where in Delhi the measurements/source apportionment is performed, indicating the need for multisite measurements. This study presents the first multisite analysis carried out in India over different seasons, with a focus on identifying OA sources. The measurements were taken during 2018 at two sites in Delhi, India. One site was located at the India Meteorological Department, New Delhi (ND). The other site was located at the Indira Gandhi Delhi Technical University for Women, Old Delhi (OD). Non-refractory submicron aerosol (NR-PM1) concentrations (ammonium, nitrate, sulfate, chloride and organic aerosols) of four aerosol mass spectrometers were analysed. Collocated measurements of volatile organic compounds, black carbon, NOx and CO were performed. Positive matrix factorisation (PMF) analysis was performed to separate the organic fraction, identifying a number of conventional factors: hydrocarbon-like OAs (HOAs) related to traffic emissions, biomass burning OAs (BBOAs), cooking OAs (COAs) and secondary OAs (SOAs). A composition-based estimate of PM1 is defined by combining black carbon (BC) and NR-PM1 (C-PM1= BC + NR-PM1). No significant difference was observed in C-PM1 concentrations between sites, OD (142 ± 117 µg m−3) compared to ND (123 ± 71 µg m3), from post-monsoon measurements. A wider variability was observed between seasons, where pre-monsoon and monsoon showed C-PM1 concentrations lower than 60 µg m−3. A seasonal variation in C-PM1 composition was observed; SO42- showed a high contribution over pre-monsoon and monsoon seasons, while NO3- and Cl− had a higher contribution in winter and post-monsoon. The main primary aerosol source was from traffic, which is consistent with the PMF analysis and Aethalometer model analysis. Thus, in order to reduce PM1 concentrations in Delhi through local emission controls, traffic emission control offers the greatest opportunity. PMF–aerosol mass spectrometer (AMS) mass spectra will help to improve future aerosol source apportionment studies. The information generated in this study increases our understanding of PM1 composition and OA sources in Delhi, India. Furthermore, the scientific findings provide significant information to strengthen legislation that aims to improve air quality in India.
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- 2021
15. Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NOₓ in Beijing
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Whalley, Lisa K., Slater, Eloise J., Woodward-Massey, Robert, Ye, Chunxiang, Lee, James D., Squires, Freya, Hopkins, James R., Dunmore, Rachel E., Shaw, Marvin, Hamilton, Jacqueline F., Lewis, Alastair C., Mehra, Archit, Worrall, Stephen D., Bacak, Asan, Bannan, Thomas J., Coe, Hugh, Percival, Carl J., Ouyang, Bin, Jones, Roderic L., Crilley, Leigh R., Kramer, Louisa J., Bloss, William J., Vu, Tuan, Kotthaus, Simone, Grimmond, Sue, Sun, Yele, Xu, Weiqi, Yue, Siyao, Ren, Lujie, Acton, W. Joe F., Hewitt, C. Nicholas, Wang, Xinming, Fu, Pingqing, and Heard, Dwayne E.
- Abstract
Measurements of OH, HO2, complex RO2 (alkene- and aromatic-related RO2) and total RO2 radicals taken during the integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO) campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity, are presented. The concentrations of radicals were elevated, with OH reaching up to 2.8×107moleculecm−3, HO2 peaking at 1×109moleculecm−3 and the total RO2 concentration reaching 5.5×109moleculecm−3. OH reactivity (k(OH)) peaked at 89 s−1 during the night, with a minimum during the afternoon of ≈22s−1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbv h−1) under the very low NO conditions (
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- 2021
16. Chemical source profiles of fine particles for five different sources in Delhi
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Hama, Sarkawt, primary, Kumar, Prashant, additional, Alam, Mohammed S., additional, Rooney, Daniel J., additional, Bloss, William J., additional, Shi, Zongbo, additional, Harrison, Roy M., additional, Crilley, Leigh R., additional, Khare, Mukesh, additional, and Gupta, Sanjay Kumar, additional
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- 2021
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17. Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NOxin Beijing
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Whalley, Lisa K., Slater, Eloise J., Woodward-Massey, Robert, Ye, Chunxiang, Lee, James D., Squires, Freya, Hopkins, James R., Dunmore, Rachel E., Shaw, Marvin, Hamilton, Jacqueline F., Lewis, Alastair C., Mehra, Archit, Worrall, Stephen D., Bacak, Asan, Bannan, Thomas J., Coe, Hugh, Percival, Carl J., Ouyang, Bin, Jones, Roderic L., Crilley, Leigh R., Kramer, Louisa J., Bloss, William J., Vu, Tuan, Kotthaus, Simone, Grimmond, Sue, Sun, Yele, Xu, Weiqi, Yue, Siyao, Ren, Lujie, Joe, W., Nicholas Hewitt, C., Wang, Xinming, Fu, Pingqing, Heard, Dwayne E., Whalley, Lisa K., Slater, Eloise J., Woodward-Massey, Robert, Ye, Chunxiang, Lee, James D., Squires, Freya, Hopkins, James R., Dunmore, Rachel E., Shaw, Marvin, Hamilton, Jacqueline F., Lewis, Alastair C., Mehra, Archit, Worrall, Stephen D., Bacak, Asan, Bannan, Thomas J., Coe, Hugh, Percival, Carl J., Ouyang, Bin, Jones, Roderic L., Crilley, Leigh R., Kramer, Louisa J., Bloss, William J., Vu, Tuan, Kotthaus, Simone, Grimmond, Sue, Sun, Yele, Xu, Weiqi, Yue, Siyao, Ren, Lujie, Joe, W., Nicholas Hewitt, C., Wang, Xinming, Fu, Pingqing, and Heard, Dwayne E.
- Abstract
Measurements of OH, HO2, complex RO2 (alkene-and aromatic-related RO2) and total RO2 radicals taken during the integrated Study of AIR Pollution PROcesses in Beijing (AIRPRO) campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity, are presented. The concentrations of radicals were elevated, with OH reaching up to 2:8 × 107 molecule cm-3, HO2 peaking at 1 × 109 molecule cm-3 and the total RO2 concentration reaching 5:5×109 molecule cm-3. OH reactivity (k.OH/) peaked at 89 s-1 during the night, with a minimum during the afternoon of 22s-1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbvh-1) under the very low NO conditions (< 0:5ppbv) experienced in the afternoons, demonstrating a missing OH source consistent with previous studies under high volatile organic compound (VOC) emissions and low NO loadings. Under the highest NO mixing ratios (104 ppbv), the HO2 production rate exceeded the rate of destruction by 50ppbvh-1, whilst the rate of destruction of total RO2 exceeded the production by the same rate, indicating that the net propagation rate of RO2 to HO2 may be substantially slower than assumed. If just 10 % of the RO2 radicals propagate to HO2 upon reaction with NO, the HO2 and RO2 budgets could be closed at high NO, but at low NO this lower RO2 to HO2 propagation rate revealed a missing RO2 sink that was similar in magnitude to the missing OH source. A detailed box model that incorporated the latest Master Chemical Mechanism (MCM3.3.1) reproduced the observed OH concentrations well but over-predicted the observed HO2 under low concentrations of NO (< 1ppbv) and under-predicted RO2 (both the complex RO2 fraction and other RO2 types which we classify as simple RO2) most significantly at the highest NO concent
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- 2021
18. Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NOx in Beijing
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Whalley, Lisa, Slater, Eloise, Woodward-Massey, Robert, Ye, Chunxiang, Lee, James D., Squires, Freya, Hopkins, James R., Dunmore, Rachel E., Shaw, Marvin, Hamilton, Jacqueline F., Lewis, Alastair C., Mehra, Archit, Worrall, Stephen David, Bacak, Asan, Bannan, Thomas J., Coe, Hugh, Ouyang, Bin, Jones, Roderic L., Crilley, Leigh R., Kramer, Louisa J., Bloss, William J., Vu, Tuan, Kotthaus, Simone, Grimmond, Sue, Sun, Yele, Xu, Weiqi, Yue, Siyao, Ren, Lujie, Acton, W Joe F, Hewitt, C N, Wang, Xinming, Fu, Pingqing, Heard, Dwayne E., Whalley, Lisa, Slater, Eloise, Woodward-Massey, Robert, Ye, Chunxiang, Lee, James D., Squires, Freya, Hopkins, James R., Dunmore, Rachel E., Shaw, Marvin, Hamilton, Jacqueline F., Lewis, Alastair C., Mehra, Archit, Worrall, Stephen David, Bacak, Asan, Bannan, Thomas J., Coe, Hugh, Ouyang, Bin, Jones, Roderic L., Crilley, Leigh R., Kramer, Louisa J., Bloss, William J., Vu, Tuan, Kotthaus, Simone, Grimmond, Sue, Sun, Yele, Xu, Weiqi, Yue, Siyao, Ren, Lujie, Acton, W Joe F, Hewitt, C N, Wang, Xinming, Fu, Pingqing, and Heard, Dwayne E.
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- 2021
19. In situ ozone production is highly sensitive to volatile organic compounds in Delhi, India
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Nelson, Beth S., Stewart, Gareth J., Drysdale, Will S., Newland, Mike J., Vaughan, Adam R., Dunmore, Rachel E., Edwards, Pete M., Lewis, Alastair C., Hamilton, Jacqueline F., Acton, W. Joe, Hewitt, C. Nicholas, Crilley, Leigh R., Alam, Mohammed S., Şahin, Ülkü A., Beddows, David C.S., Bloss, William J., Slater, Eloise, Whalley, Lisa K., Heard, Dwayne E., Cash, James M., Langford, Ben, Nemitz, Eiko, Sommariva, Roberto, Cox, Sam, Gadi, Ranu, Gurjar, Bhola R., Hopkins, James R., Rickard, Andrew R., Lee, James D., Nelson, Beth S., Stewart, Gareth J., Drysdale, Will S., Newland, Mike J., Vaughan, Adam R., Dunmore, Rachel E., Edwards, Pete M., Lewis, Alastair C., Hamilton, Jacqueline F., Acton, W. Joe, Hewitt, C. Nicholas, Crilley, Leigh R., Alam, Mohammed S., Şahin, Ülkü A., Beddows, David C.S., Bloss, William J., Slater, Eloise, Whalley, Lisa K., Heard, Dwayne E., Cash, James M., Langford, Ben, Nemitz, Eiko, Sommariva, Roberto, Cox, Sam, Gadi, Ranu, Gurjar, Bhola R., Hopkins, James R., Rickard, Andrew R., and Lee, James D.
- Abstract
The Indian megacity of Delhi suffers from some of the poorest air quality in the world. While ambient NO2 and particulate matter (PM) concentrations have received considerable attention in the city, high ground-level ozone (O3) concentrations are an often overlooked component of pollution. O3 can lead to significant ecosystem damage and agricultural crop losses, and adversely affect human health. During October 2018, concentrations of speciated non-methane hydrocarbon volatile organic compounds (C2–C13), oxygenated volatile organic compounds (o-VOCs), NO, NO2, HONO, CO, SO2, O3, and photolysis rates, were continuously measured at an urban site in Old Delhi. These observations were used to constrain a detailed chemical box model utilising the Master Chemical Mechanism v3.3.1. VOCs and NOx (NO + NO2) were varied in the model to test their impact on local O3 production rates, P(O3), which revealed a VOC-limited chemical regime. When only NOx concentrations were reduced, a significant increase in P(O3) was observed; thus, VOC co-reduction approaches must also be considered in pollution abatement strategies. Of the VOCs examined in this work, mean morning P(O3) rates were most sensitive to monoaromatic compounds, followed by monoterpenes and alkenes, where halving their concentrations in the model led to a 15.6 %, 13.1 %, and 12.9 % reduction in P(O3), respectively. P(O3) was not sensitive to direct changes in aerosol surface area but was very sensitive to changes in photolysis rates, which may be influenced by future changes in PM concentrations. VOC and NOx concentrations were divided into emission source sectors, as described by the Emissions Database for Global Atmospheric Research (EDGAR) v5.0 Global Air Pollutant Emissions and EDGAR v4.3.2_VOC_spec inventories, allowing for the impact of individual emission sources on P(O3) to be investigated. Reducing road transport emissions only, a common strategy in air pollution abatement strategies worldwide, was found to inc
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- 2021
20. Interference from alkenes in chemiluminescent NOx measurements
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Alam, Mohammed S., Crilley, Leigh R., Lee, James D., Kramer, Louisa J., Pfrang, Christian, Vázquez-Moreno, Mónica, Ródenas, Milagros, Muñoz, Amalia, and Bloss, William J.
- Abstract
Nitrogen oxides (NOx=NO+NO2) are critical intermediates in atmospheric chemistry and air pollution. NOx levels control the cycling and hence abundance of the primary atmospheric oxidants OH and NO3 and regulate the ozone production which results from the degradation of volatile organic compounds (VOCs) in the presence of sunlight. They are also atmospheric pollutants, and NO2 is commonly included in air quality objectives and regulations. NOx levels also affect the production of the nitrate component of secondary aerosol particles and other pollutants, such as the lachrymator peroxyacetyl nitrate (PAN). The accurate measurement of NO and NO2 is therefore crucial for air quality monitoring and understanding atmospheric composition. The most commonly used approach for the measurement of NO is the chemiluminescent detection of electronically excited NO2 (NO2∗) formed from the NO + O3 reaction within the NOx analyser. Alkenes, ubiquitous in the atmosphere from biogenic and anthropogenic sources, also react with ozone to produce chemiluminescence and thus may contribute to the measured NOx signal. Their ozonolysis reaction may also be sufficiently rapid that their abundance in conventional instrument background cycles, which also utilises the reaction with ozone, differs from that in the measurement cycle such that the background subtraction is incomplete, and an interference effect results. This interference has been noted previously, and indeed, the effect has been used to measure both alkenes and ozone in the atmosphere. Here we report the results of a systematic investigation of the response of a selection of commercial NOx monitors to a series of alkenes. These NOx monitors range from systems used for routine air quality monitoring to atmospheric research instrumentation. The species-investigated range was from short-chain alkenes, such as ethene, to the biogenic monoterpenes. Experiments were performed in the European PHOtoREactor (EUPHORE) to ensure common calibration and samples for the monitors and to unequivocally confirm the alkene levels present (via Fourier transform infrared spectroscopy – FTIR). The instrument interference responses ranged from negligible levels up to 11 %, depending upon the alkene present and conditions used (e.g. the presence of co-reactants and differing humidity). Such interferences may be of substantial importance for the interpretation of ambient NOx data, particularly for high VOC, low NOx environments such as forests or indoor environments where alkene abundance from personal care and cleaning products may be significant.
- Published
- 2020
21. Observations of speciated isoprene nitrates in Beijing: implications for isoprene chemistry
- Author
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Reeves, Claire E., primary, Mills, Graham P., additional, Whalley, Lisa K., additional, Acton, W. Joe F., additional, Bloss, William J., additional, Crilley, Leigh R., additional, Grimmond, Sue, additional, Heard, Dwayne E., additional, Hewitt, C. Nicholas, additional, Hopkins, James R., additional, Kotthaus, Simone, additional, Kramer, Louisa J., additional, Jones, Roderic L., additional, Lee, James D., additional, Liu, Yanhui, additional, Ouyang, Bin, additional, Slater, Eloise, additional, Squires, Freya, additional, Wang, Xinming, additional, Woodward-Massey, Robert, additional, and Ye, Chunxiang, additional
- Published
- 2021
- Full Text
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22. Enhanced wintertime oxidation of VOCs via sustained radical sources in the urban atmosphere
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Sommariva, Roberto, primary, Crilley, Leigh R., additional, Ball, Stephen M., additional, Cordell, Rebecca L., additional, Hollis, Lloyd D.J., additional, Bloss, William J., additional, and Monks, Paul S., additional
- Published
- 2021
- Full Text
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23. Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NOx in Beijing
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Whalley, Lisa, Slater, Eloise, Woodward-Massey, Robert, Ye, Chunxiang, Lee, James D., Squires, Freya, Hopkins, James R., Dunmore, Rachel E., Marvin David Shaw, Hamilton, Jacqueline F., Lewis, Alastair C., Mehra, Archit, Worrall, Stephen David, Bacak, Asan, Bannan, Thomas J., Coe, Hugh, Ouyang, Bin, Jones, Roderic L., Crilley, Leigh R., Kramer, Louisa J., Bloss, William J., Vu, Tuan, Kotthaus, Simone, Grimmond, Sue, Sun, Yele, Xu, Weiqi, Yue, Siyao, Ren, Lujie, Acton, W. Joe F., Hewitt, C. N., Wang, Xinming, Fu, Pingqing, and Heard, Dwayne E.
- Abstract
Measurements of OH, HO2, RO2-complex (alkene and aromatic-related RO2) and total RO2 radicals taken during the AIRPRO campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity are presented. The concentrations of radicals were elevated with OH reaching up to 2.8 × 107 molecule cm−3, HO2 peaked at 1 × 109 molecule cm−3 and the total RO2 concentration reached 5.5 × 109 molecule cm−3. OH reactivity (k(OH)) peaked at 89 s−1 during the night, with a minimum during the afternoons of ~ 22 s−1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbv hr−1) under the very low NO conditions (2 production rate exceeded the rate of destruction by ~ 50 ppbv hr−1, whilst the rate of destruction of total-RO2 exceeded the production by the same rate indicating that the net propagation rate of RO2 to HO2 may be substantially slower than assumed. If just 10 % of the RO2 radicals propagate to HO2 upon reaction with NO, the HO2 and RO2 budgets could be closed at high NO, but at low NO this lower RO2 to HO2 propagation rate revealed a missing RO2 sink that was similar in magnitude to the missing OH source. A detailed box model that incorporated the latest MCM chemical mechanism (MCM3.3.1) reproduced the observed OH concentrations well, but over-predicted the observed HO2 under low concentrations of NO (2 (both the complex-RO2 fraction and other RO2 types which we classify as simple-RO2) most significantly at the highest NO concentrations. The model also under-predicted the observed k(OH) consistently by ~ 10 s−1 across all NOx levels highlighting that the good agreement for OH was fortuitous due to a cancellation of missing OH source and sink terms in its budget. Including heterogeneous loss of HO2 to aerosol surfaces did reduce the modelled HO2 concentrations in-line with the observations, but only at NO mixing ratios 2 concentration on several mornings when the Cl atom concentration was calculated to exceed 1 × 104 atoms cm−3 and could reconcile the modelled and measured RO2 concentrations at these times. However, on other mornings, when the Cl atom concentration was lower, large under-predictions in total RO2 remained. Furthermore, the inclusion of Cl atom chemistry did not enhance the modelled RO2 beyond the first few hours after sunrise and so was unable to resolve the modelled under-prediction in RO2 observed at other times of the day. Model scenarios, in which missing VOC reactivity was included as an additional reaction that converted OH to RO2, highlighted that the modelled OH, HO2 and RO2 concentrations were sensitive to the choice of RO2 product. The level of modelled to measured agreement for HO2 and RO2 (both complex and simple) could be improved if the missing OH reactivity formed a larger RO2 species that was able to undergo reaction with NO, followed by isomerisation reactions reforming other RO2 species, before eventually generating HO2. In this work an α-pinene-derived RO2 species was used as an example. In this simulation, consistent with the experimental budget analysis, the model underestimated the observed OH indicating a missing OH source. The model uncertainty, with regards to the types of RO2 species present and the radicals they form upon reaction with NO (HO2 directly or another RO2 species), leads to over an order of magnitude less O3 production calculated from the predicted peroxy radicals than calculated from the observed peroxy radicals at the highest NO concentrations. This demonstrates the rate at which the larger RO2 species propagate to HO2 or to another RO2 or indeed to OH needs to be understood to accurately simulate the rate of ozone production in environments such as Beijing where large multifunctional VOCs are likely present.
- Published
- 2020
24. A comparison of PM2.5-bound polycyclic aromatic hydrocarbons in summer Beijing (China) and Delhi (India)
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Elzein, Atallah, Stewart, Gareth J., Swift, Stefan J., Nelson, Beth S., Crilley, Leigh R., Alam, Mohammed S., Reyes-Villegas, Ernesto, Gadi, Ranu, Harrison, Roy M., Hamilton, Jacqueline F., and Lewis, Alastair C.
- Abstract
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in air, soil, and water and are known to have harmful effects on human health and the environment. The diurnal and nocturnal variations of 17 PAHs in ambient particle-bound PAHs were measured in urban Beijing (China) and Delhi (India) during the summer season using gas-chromatography–quadrupole time-of-flight mass spectrometry (GC-Q-TOF-MS). The mean concentration of particles less than 2.5 µm (PM2.5) observed in Delhi was 3.6 times higher than in Beijing during the measurement period in both the daytime and night-time. In Beijing, the mean concentration of the sum of the 17 PAHs (∑17 PAHs) was 8.2 ± 5.1 ng m−3 in daytime, with the highest contribution from indeno[1,2,3-cd]pyrene (12 %), while at night-time the total PAHs was 7.2 ± 2.0 ng m−3, with the largest contribution from benzo[b]fluoranthene (14 %). In Delhi, the mean ∑17 PAHs was 13.6 ± 5.9 ng m−3 in daytime and 22.7 ± 9.4 ng m−3 at night-time, with the largest contribution from indeno[1,2,3-cd]pyrene in both the day (17 %) and night (20 %). Elevated mean concentrations of total PAHs in Delhi observed at night were attributed to emissions from vehicles and biomass burning and to meteorological conditions leading to their accumulation from a stable and low atmospheric boundary layer. Local emission sources were typically identified as the major contributors to total measured PAHs in both cities. Major emission sources were characterized based on the contribution from each class of PAHs, with the four-, five- and six-ring PAHs accounting ∼ 95 % of the total PM2.5-bound PAHs mass in both locations. The high contribution of five-ring PAHs to total PAH concentration in summer Beijing and Delhi suggests a high contribution from petroleum combustion. In Delhi, a high contribution from six-ring PAHs was observed at night, suggesting a potential emission source from the combustion of fuel and oil in power generators, widely used in Delhi. The lifetime excess lung cancer risk (LECR) was calculated for Beijing and Delhi, with the highest estimated risk attributed to Delhi (LECR = 155 per million people), which is 2.2 times higher than the Beijing risk assessment value (LECR = 70 per million people). Finally, we have assessed the emission control policies in each city and identified those major sectors that could be subject to mitigation measures.
- Published
- 2020
25. Elevated levels of OH observed in haze events during wintertime in central Beijing
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Slater, Eloise, Whalley, Lisa K., Woodward-Massey, Robert, Ye, Chunxiang, Lee, James D., Squires, Freja, Hopkins, James R., Dunmore, Rachel E., Shaw, Marvin, Hamilton, Jacqueline F., Lewis, Alastair C., Crilley, Leigh R., Kramer, Louisa J., Bloss, William J., Vu, Tuan, Sun, Yele, Xu, Weiqi, Yue, Siyao, Ren, Lujie, Acton, W. Joe F., Hewitt, C N, Wang, Xinming, Fu, Pingqing, Heard, Dwayne E., Slater, Eloise, Whalley, Lisa K., Woodward-Massey, Robert, Ye, Chunxiang, Lee, James D., Squires, Freja, Hopkins, James R., Dunmore, Rachel E., Shaw, Marvin, Hamilton, Jacqueline F., Lewis, Alastair C., Crilley, Leigh R., Kramer, Louisa J., Bloss, William J., Vu, Tuan, Sun, Yele, Xu, Weiqi, Yue, Siyao, Ren, Lujie, Acton, W. Joe F., Hewitt, C N, Wang, Xinming, Fu, Pingqing, and Heard, Dwayne E.
- Abstract
Wintertime in situ measurements of OH, HO2 and RO2 radicals and OH reactivity were made in central Beijing during November and December 2016. Exceptionally elevated NO was observed on occasions, up to ∼250 ppbv. The daily maximum mixing ratios for radical species varied significantly day-to-day over the ranges 1–8×106 cm−3 (OH), 0.2–1.5×108 cm−3 (HO2) and 0.3–2.5×108 cm−3 (RO2). Averaged over the full observation period, the mean daytime peak in radicals was 2.7×106, 0.39×108 and 0.88×108 cm−3 for OH, HO2 and total RO2, respectively. The main daytime source of new radicals via initiation processes (primary production) was the photolysis of HONO (∼83 %), and the dominant termination pathways were the reactions of OH with NO and NO2, particularly under polluted haze conditions. The Master Chemical Mechanism (MCM) v3.3.1 operating within a box model was used to simulate the concentrations of OH, HO2 and RO2. The model underpredicted OH, HO2 and RO2, especially when NO mixing ratios were high (above 6 ppbv). The observation-to-model ratio of OH, HO2 and RO2 increased from ∼1 (for all radicals) at 3 ppbv of NO to a factor of ∼3, ∼20 and ∼91 for OH, HO2 and RO2, respectively, at ∼200 ppbv of NO. The significant underprediction of radical concentrations by the MCM suggests a deficiency in the representation of gas-phase chemistry at high NOx. The OH concentrations were surprisingly similar (within 20 % during the day) in and outside of haze events, despite j(O1D) decreasing by 50 % during haze periods. These observations provide strong evidence that gas-phase oxidation by OH can continue to generate secondary pollutants even under high-pollution episodes, despite the reduction in photolysis rates within haze.
- Published
- 2020
26. Insights into HONO sources from observations during a solar eclipse
- Author
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Singh, Ajit, primary, Crilley, Leigh R., additional, Pope, Francis D., additional, and Bloss, William J., additional
- Published
- 2021
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27. Elevated levels of OH observed in haze events during wintertime in central Beijing
- Author
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Slater, Eloise J., primary, Whalley, Lisa K., additional, Woodward-Massey, Robert, additional, Ye, Chunxiang, additional, Lee, James D., additional, Squires, Freya, additional, Hopkins, James R., additional, Dunmore, Rachel E., additional, Shaw, Marvin, additional, Hamilton, Jacqueline F., additional, Lewis, Alastair C., additional, Crilley, Leigh R., additional, Kramer, Louisa, additional, Bloss, William, additional, Vu, Tuan, additional, Sun, Yele, additional, Xu, Weiqi, additional, Yue, Siyao, additional, Ren, Lujie, additional, Acton, W. Joe F., additional, Hewitt, C. Nicholas, additional, Wang, Xinming, additional, Fu, Pingqing, additional, and Heard, Dwayne E., additional
- Published
- 2020
- Full Text
- View/download PDF
28. A comparison of PM<sub>2.5</sub>-bound polycyclic aromatic hydrocarbons in summer Beijing (China) and Delhi (India)
- Author
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Elzein, Atallah, primary, Stewart, Gareth J., additional, Swift, Stefan J., additional, Nelson, Beth S., additional, Crilley, Leigh R., additional, Alam, Mohammed S., additional, Reyes-Villegas, Ernesto, additional, Gadi, Ranu, additional, Harrison, Roy M., additional, Hamilton, Jacqueline F., additional, and Lewis, Alastair C., additional
- Published
- 2020
- Full Text
- View/download PDF
29. A portable, robust, stable, and tunable calibration source for gas-phase nitrous acid (HONO)
- Author
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Lao, Melodie, primary, Crilley, Leigh R., additional, Salehpoor, Leyla, additional, Furlani, Teles C., additional, Bourgeois, Ilann, additional, Neuman, J. Andrew, additional, Rollins, Andrew W., additional, Veres, Patrick R., additional, Washenfelder, Rebecca A., additional, Womack, Caroline C., additional, Young, Cora J., additional, and VandenBoer, Trevor C., additional
- Published
- 2020
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30. Radical chemistry at a UK coastal receptor site -- Part 1: observations of OH, HO2, RO2, and OH reactivity and comparison to MCM model predictions.
- Author
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Woodward-Massey, Robert, Sommariva, Roberto, Whalley, Lisa K., Cryer, Danny R., Ingham, Trevor, Bloss, William J., Cox, Sam, Lee, James D., Reed, Chris P., Crilley, Leigh R., Kramer, Louisa J., Bandy, Brian J., Forster, Grant L., Reeves, Claire E., Monks, Paul S., and Heard., Dwayne E.
- Abstract
OH, HO
2 , total and partially-speciated RO2 , and OH reactivity (k'OH) were measured during the July 2015 ICOZA (Integrated Chemistry of OZone in the Atmosphere) project that took place at a coastal site in North Norfolk, UK. Maximum measured daily OH, HO2 , and total RO2 radical concentrations were in the range 2.6-17 × 106, 0.75-4.2 × 108, and 2.3-8.0 × 108 molecule cm-3 , respectively. k'OH ranged from 1.7 to 17.6 s-1 with a median value of 4.7 s-1 . ICOZA data were split by wind direction to assess differences in the radical chemistry between air that had passed over the North Sea (NW-SE sectors) or major urban conurbations such as London (SW sector). A photostationary steady-state (PSS) calculation underpredicted daytime OH in NW-SE air by ~35%, whereas agreement (~15%) was found within instrumental uncertainty (~26% at 2σ) in SW air. A box model using MCMv3.3.1 chemistry was in better agreement with the OH measurements, but it overpredicted HO2 observations in NW-SE air in the afternoon by a factor of ~2-3, although slightly bet ter agreement was found for HO2 in SW air (factor of ~1.4-2.0 underprediction). The box model severely underpredicted total RO2 observations in both NW-SE and SW air by factors of ~8-9 on average. Measured radical and k'OH levels and measurement-to-model ratios displayed strong dependences on NO mixing ratios. The PSS calculation could capture OH observations at high NO but underpredicted the observations at low NO. The box model overpredicted HO2 concentrations at low NO in NW-SE air, whereas in SW air, the measurements and model results were in agreement across the full NO range. The box model underpredicted total RO2 at all NO levels, where the measurement-to-model ratio scaled with NO. This trend has been found in all previous field campaigns in which total RO2 was measured using the ROx LIF technique and suggests that peroxy radical chemistry is not well understood under high NOx conditions. [ABSTRACT FROM AUTHOR]- Published
- 2022
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31. Radical chemistry at a UK coastal receptor site - Part 2: experimental radical budgets and ozone production.
- Author
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Woodward-Massey, Robert, Sommariva, Roberto, Whalley, Lisa K., Cryer, Danny R., Ingham, Trevor, Bloss, William J., Ball, Stephen M., Lee, James D., Reed, Chris P., Crilley, Leigh R., Kramer, Louisa J., Bandy, Brian J., Forster, Grant L., Reeves, Claire E., Monks, Paul S., and Heard, Dwayne E.
- Abstract
In our companion paper (Woodward-Massey et al., 2022), we presented measurements of radical species and OH reactivity (k'OH) made in summer 2015 during the ICOZA (Integrated Chemistry of OZone in the Atmosphere) field campaign at the Weybourne Atmospheric Observatory, a site on the east coast of the UK. In the present work, we used the simultaneous measurement of OH, HO
2 , total RO2 , and k'OH to derive experimental (i.e., observationally determined) budgets for all radical species as well as total ROx (= OH + HO2 + RO2 ). Data were separated according to wind direction: prevailing SW winds (with influence from London and other major conurbations), and all other winds (NW-SE; predominantly marine in origin). In NW-SE air, the ROx budget could be closed during the daytime within experimental uncertainty but OH destruction exceeded OH production, and HO2 production greatly exceeded HO2 destruction while the opposite was true for RO2 . In SW air, the ROx budget analysis indicated missing daytime ROx sources but the OH budget was balanced, and the same imbalances were found with the HO2 and RO2 budgets as in NW-SE air. For HO2 and RO2 , the budget imbalances were most severe at high NO mixing ratios. We explored several mechanistic modifications to the experimental budgets to try to reconcile the HO2 and RO2 budget imbalances: (1) the addition of generic radical recycling processes, (2) reduction of the rate of RO2 x HO2 conversion, (3) inclusion of heterogeneous HO2 uptake, and (4) addition of chlorine chemistry. The best agreement between HO2 and RO2 production and destruction rates was found for option (2), in which we reduced the RO2 + NO rate constant by a factor of 5. The rate of in situ ozone production (P(Ox )) was calculated from observations of ROx , NO, and NO2 and compared to that calculated from MCM-modelled radical concentrations. The MCM-calculated P(Ox ) significantly 35 underpredicted the measurement-calculated P(Ox ) in the morning, and the degree of underprediction was found to scale with NO. [ABSTRACT FROM AUTHOR]- Published
- 2022
- Full Text
- View/download PDF
32. Nitrous acid (HONO) emissions under real-world driving conditions from vehicles in a UK road tunnel
- Author
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Kramer, Louisa J., primary, Crilley, Leigh R., additional, Adams, Thomas J., additional, Ball, Stephen M., additional, Pope, Francis D., additional, and Bloss, William J., additional
- Published
- 2020
- Full Text
- View/download PDF
33. An instrument for in situ measurement of total ozone reactivity
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Sommariva, Roberto, primary, Kramer, Louisa J., additional, Crilley, Leigh R., additional, Alam, Mohammed S., additional, and Bloss, William J., additional
- Published
- 2020
- Full Text
- View/download PDF
34. Effect of aerosol composition on the performance of low-cost optical particle counter correction factors
- Author
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Crilley, Leigh R., primary, Singh, Ajit, additional, Kramer, Louisa J., additional, Shaw, Marvin D., additional, Alam, Mohammed S., additional, Apte, Joshua S., additional, Bloss, William J., additional, Hildebrandt Ruiz, Lea, additional, Fu, Pingqing, additional, Fu, Weiqi, additional, Gani, Shahzad, additional, Gatari, Michael, additional, Ilyinskaya, Evgenia, additional, Lewis, Alastair C., additional, Ng'ang'a, David, additional, Sun, Yele, additional, Whitty, Rachel C. W., additional, Yue, Siyao, additional, Young, Stuart, additional, and Pope, Francis D., additional
- Published
- 2020
- Full Text
- View/download PDF
35. Intercomparison of nitrous acid (HONO) measurement techniques in a megacity (Beijing)
- Author
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Crilley, Leigh R., primary, Kramer, Louisa J., additional, Ouyang, Bin, additional, Duan, Jun, additional, Zhang, Wenqian, additional, Tong, Shengrui, additional, Ge, Maofa, additional, Tang, Ke, additional, Qin, Min, additional, Xie, Pinhua, additional, Shaw, Marvin D., additional, Lewis, Alastair C., additional, Mehra, Archit, additional, Bannan, Thomas J., additional, Worrall, Stephen D., additional, Priestley, Michael, additional, Bacak, Asan, additional, Coe, Hugh, additional, Allan, James, additional, Percival, Carl J., additional, Popoola, Olalekan A. M., additional, Jones, Roderic L., additional, and Bloss, William J., additional
- Published
- 2019
- Full Text
- View/download PDF
36. Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS
- Author
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Holzinger, Rupert, primary, Acton, W. Joe F., additional, Bloss, William J., additional, Breitenlechner, Martin, additional, Crilley, Leigh R., additional, Dusanter, Sébastien, additional, Gonin, Marc, additional, Gros, Valerie, additional, Keutsch, Frank N., additional, Kiendler-Scharr, Astrid, additional, Kramer, Louisa J., additional, Krechmer, Jordan E., additional, Languille, Baptiste, additional, Locoge, Nadine, additional, Lopez-Hilfiker, Felipe, additional, Materić, Dušan, additional, Moreno, Sergi, additional, Nemitz, Eiko, additional, Quéléver, Lauriane L. J., additional, Sarda Esteve, Roland, additional, Sauvage, Stéphane, additional, Schallhart, Simon, additional, Sommariva, Roberto, additional, Tillmann, Ralf, additional, Wedel, Sergej, additional, Worton, David R., additional, Xu, Kangming, additional, and Zaytsev, Alexander, additional
- Published
- 2019
- Full Text
- View/download PDF
37. Source apportionment of fine and coarse particles at a roadside and urban background site in London during the 2012 summer ClearfLo campaign
- Author
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Crilley, Leigh R., Lucarelli, Franco, Bloss, William J., Harrison, Roy M., Beddows, David C., Calzolai, Giulia, Nava, Silvia, Valli, Gianluigi, Bernardoni, Vera, and Vecchi, Roberta
- Subjects
Source apportionment ,PMF ,Health, Toxicology and Mutagenesis ,London ,Hourly temporal resolution ,Toxicology ,Pollution - Abstract
London, like many major cities, has a noted air pollution problem, and a better understanding of the sources of airborne particles in the different size fractions will facilitate the implementation and effectiveness of control strategies to reduce air pollution. Thus, the trace elemental composition of the fine and coarse fraction were analysed at hourly time resolution at urban background (North Kensington, NK) and roadside (Marylebone Road, MR) sites within central London. Unlike previous work, the current study focuses on measurements during the summer providing a snapshot of contributing sources, utilising the high time resolution to improve source identification. Roadside enrichment was observed for a large number of elements associated with traffic emissions (Al, S, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Rb and Zr), while those elements that are typically from more regional sources (e.g. Na, Cl, S and K) were not found to have an appreciable increment. Positive Matrix Factorization (PMF) was applied for the source apportionment of the particle mass at both sites with similar sources being identified, including sea salt, airborne soil, traffic emissions, secondary inorganic aerosols and a Zn-Pb source. In the fine fraction, traffic emissions was the largest contributing source at MR (31.9%), whereas it was incorporated within an “urban background” source at NK, which had contributions from wood smoke, vehicle emissions and secondary particles. Regional sources were the major contributors to the coarse fraction at both sites. Secondary inorganic aerosols (which contained influences from shipping emissions and coal combustion) source factors accounted for around 33% of the PM10 at NK and were found to have the highest contributions from regional sources, including from the European mainland. Exhaust and non-exhaust sources both contribute appreciably to PM10 levels at the MR site, highlighting the continuing importance of vehicle-related air pollutants at roadside.
- Published
- 2017
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38. Measurement Report: Interpretation of Wide Range Particulate Matter Size Distributions in Delhi.
- Author
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Şahin, Ülkü Alver, Harrison, Roy M., Alam, Mohammed S., Beddows, David C. S., Bousiotis, Dimitrios, Zongbo Shi, Crilley, Leigh R., Bloss, William, Brean, James, Khanna, Isha, and Verma, Rulan
- Abstract
Delhi is one of the world's most polluted cities, with very high concentrations of airborne particulate matter. However, little is known on the factors controlling the characteristics of particle number size distributions. Here, new measurements are reported from three field campaigns conducted in winter, pre-monsoon and post-monsoon seasons on the Indian Insitute of Technology campus in the south of the city. Particle number size distributions were measured simultaneously using a Scanning Mobility Particle Sizer and a Grimm optical particle monitor, covering 15 nm to >10 µm diameter. The merged, wide-range size distributions were categorised into five size ranges: nucleation (15-20 nm), Aitken (20-100 nm), accumulation (100 nm-1 µm), large fine (1-2.5 µm) and coarse (2.5-10 µm) particles. The ultrafine fraction (15-100 nm) accounts for about 52 % of all particles by number (PN
10 ), but just 1 % by PM10 volume (PV10 ). The measured size distributions are markedly coarser than most from other parts of the world, but are consistent with earlier cascade impactor data from Delhi. Our results suggest substantial aerosol processing by coagulation, condensation and water uptake in the heavily polluted atmosphere, which takes place mostly at nighttime and in the morning hours. Total number concentrations are highest in winter, but the mode of the distribution is largest in the post-monsoon (autumn) season. The accumulation mode particles dominate the particle volume in autumn and winter, while the coarse mode dominates in summer. Polar plots show a huge variation between both size fractions in the same season and between seasons for the same size fraction. The diurnal pattern of particle numbers is strongly reflective of a road traffic influence upon concentrations, especially in autumn and winter. There is a clear influence of diesel traffic at nighttime when it is permitted to enter the city, and also indications in the size distribution data of a mode <15 nm, probably attributable to CNG/LPG vehicles. New particle formation appears to be infrequent, and in this dataset is limited to one day in the summer campaign. Our results reveal that the very high emissions of airborne particles in Delhi, particularly from traffic, determine the variation of particle number size distributions. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
39. Intercomparison of nitrous acid (HONO) measurement techniques in a megacity (Beijing)
- Author
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Crilley, Leigh R., Kramer, Louisa J., Ouyang, Bin, Duan, Jun, Zhang, Wenqian, Tong, Shengrui, Ge, Maofa, Tang, Ke, Qin, Min, Xie, Pinhua, Shaw, Marvin D., Lewis, Alastair C., Mehra, Archit, Bannan, Thomas J., Worrall, Stephen D., Priestley, Michael, Bacak, Asan, Coe, Hugh, Allan, James, Percival, Carl J., Popoola, Olalekan A.M., Jones, Roderic L., Bloss, William J., Crilley, Leigh R., Kramer, Louisa J., Ouyang, Bin, Duan, Jun, Zhang, Wenqian, Tong, Shengrui, Ge, Maofa, Tang, Ke, Qin, Min, Xie, Pinhua, Shaw, Marvin D., Lewis, Alastair C., Mehra, Archit, Bannan, Thomas J., Worrall, Stephen D., Priestley, Michael, Bacak, Asan, Coe, Hugh, Allan, James, Percival, Carl J., Popoola, Olalekan A.M., Jones, Roderic L., and Bloss, William J.
- Abstract
Nitrous acid (HONO) is a key determinant of the daytime radical budget in the daytime boundary layer, with quantitative measurement required to understand OH radical abundance. Accurate and precise measurements of HONO are therefore needed; however HONO is a challenging compound to measure in the field, in particular in a chemically complex and highly polluted environment. Here we report an intercomparison exercise between HONO measurements performed by two wet chemical techniques (the commercially available a long-path absorption photometer (LOPAP) and a custom-built instrument) and two broadband cavity-enhanced absorption spectrophotometer (BBCEAS) instruments at an urban location in Beijing. In addition, we report a comparison of HONO measurements performed by a time-of-flight chemical ionization mass spectrometer (ToF-CIMS) and a selected ion flow tube mass spectrometer (SIFT-MS) to the more established techniques (wet chemical and BBCEAS). The key finding from the current work was that all instruments agree on the temporal trends and variability in HONO (r2 > 0.97), yet they displayed some divergence in absolute concentrations, with the wet chemical methods consistently higher overall than the BBCEAS systems by between 12 % and 39 %. We found no evidence for any systematic bias in any of the instruments, with the exception of measurements near instrument detection limits. The causes of the divergence in absolute HONO concentrations were unclear, and may in part have been due to spatial variability, i.e. differences in instrument location and/or inlet position, but this observation may have been more associative than casual.
- Published
- 2019
40. Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS
- Author
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Sub Atmospheric physics and chemistry, Marine and Atmospheric Research, Holzinger, Rupert, Acton, W. Joe F., Bloss, William J., Breitenlechner, Martin, Crilley, Leigh R., Dusanter, Sebastien, Gonin, Marc, Gros, Valerie, Keutsch, Frank N., Kiendler-Scharr, Astrid, Kramer, Louisa J., Krechmer, Jordan E., Languille, Baptiste, Locoge, Nadine, Lopez-Hilfiker, Felipe, Materic, Dusan, Moreno, Sergi, Nemitz, Eiko, Quelever, Lauriane L. J., Esteve, Roland Sarda, Sauvage, Stephane, Schallhart, Simon, Sommariva, Roberto, Tillmann, Ralf, Wedel, Sergej, Worton, David R., Xu, Kangming, Zaytsev, Alexander, Sub Atmospheric physics and chemistry, Marine and Atmospheric Research, Holzinger, Rupert, Acton, W. Joe F., Bloss, William J., Breitenlechner, Martin, Crilley, Leigh R., Dusanter, Sebastien, Gonin, Marc, Gros, Valerie, Keutsch, Frank N., Kiendler-Scharr, Astrid, Kramer, Louisa J., Krechmer, Jordan E., Languille, Baptiste, Locoge, Nadine, Lopez-Hilfiker, Felipe, Materic, Dusan, Moreno, Sergi, Nemitz, Eiko, Quelever, Lauriane L. J., Esteve, Roland Sarda, Sauvage, Stephane, Schallhart, Simon, Sommariva, Roberto, Tillmann, Ralf, Wedel, Sergej, Worton, David R., Xu, Kangming, and Zaytsev, Alexander
- Published
- 2019
41. Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS
- Author
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Holzinger, Rupert, Acton, W. Joe F., Bloss, William J., Breitenlechner, Martin, Crilley, Leigh R., Dusanter, Sébastien, Gonin, Marc, Gros, Valerie, Keutsch, Frank N., Kiendler-Scharr, Astrid, Kramer, Louisa J., Krechmer, Jordan E., Languille, Baptiste, Locoge, Nadine, Lopez-Hilfiker, Felipe, Materić, Dušan, Moreno, Sergi, Nemitz, Eiko, Quéléver, Lauriane L.J., Sarda Esteve, Roland, Sauvage, Stéphane, Schallhart, Simon, Sommariva, Roberto, Tillmann, Ralf, Wedel, Sergej, Worton, David R., Xu, Kangming, Zaytsev, Alexander, Holzinger, Rupert, Acton, W. Joe F., Bloss, William J., Breitenlechner, Martin, Crilley, Leigh R., Dusanter, Sébastien, Gonin, Marc, Gros, Valerie, Keutsch, Frank N., Kiendler-Scharr, Astrid, Kramer, Louisa J., Krechmer, Jordan E., Languille, Baptiste, Locoge, Nadine, Lopez-Hilfiker, Felipe, Materić, Dušan, Moreno, Sergi, Nemitz, Eiko, Quéléver, Lauriane L.J., Sarda Esteve, Roland, Sauvage, Stéphane, Schallhart, Simon, Sommariva, Roberto, Tillmann, Ralf, Wedel, Sergej, Worton, David R., Xu, Kangming, and Zaytsev, Alexander
- Abstract
In September 2017, we conducted a proton-transfer-reaction mass-spectrometry (PTR-MS) intercomparison campaign at the CESAR observatory, a rural site in the central Netherlands near the village of Cabauw. Nine research groups deployed a total of 11 instruments covering a wide range of instrument types and performance. We applied a new calibration method based on fast injection of a gas standard through a sample loop. This approach allows calibrations on timescales of seconds, and within a few minutes an automated sequence can be run allowing one to retrieve diagnostic parameters that indicate the performance status. We developed a method to retrieve the mass-dependent transmission from the fast calibrations, which is an essential characteristic of PTR-MS instruments, limiting the potential to calculate concentrations based on counting statistics and simple reaction kinetics in the reactor/drift tube. Our measurements show that PTR-MS instruments follow the simple reaction kinetics if operated in the standard range for pressures and temperature of the reaction chamber (i.e. 1–4 mbar, 30–120∘, respectively), as well as a reduced field strength E∕N in the range of 100–160 Td. If artefacts can be ruled out, it becomes possible to quantify the signals of uncalibrated organics with accuracies better than ±30 %. The simple reaction kinetics approach produces less accurate results at E∕N levels below 100 Td, because significant fractions of primary ions form water hydronium clusters. Deprotonation through reactive collisions of protonated organics with water molecules needs to be considered when the collision energy is a substantial fraction of the exoergicity of the proton transfer reaction and/or if protonated organics undergo many collisions with water molecules.
- Published
- 2019
42. Global impact of nitrate photolysis in sea-salt aerosol on NOx, OH, and O3 in the marine boundary layer
- Author
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Kasibhatla, Prasad, Sherwen, Tomás, Evans, Mathew J., Carpenter, Lucy J., Reed, Chris, Alexander, Becky, Chen, Qianjie, Sulprizio, Melissa P., Lee, James D., Read, Katie A., Bloss, William, Crilley, Leigh R., Keene, William C., Pszenny, Alexander A.P., and Hodzic, Alma
- Abstract
Recent field studies have suggested that sea-salt particulate nitrate (NITs) photolysis may act as a significant local source of nitrogen oxides (NOx) over oceans. We present a study of the global impact of this process on oxidant concentrations in the marine boundary layer (MBL) using the GEOS-Chem model, after first updating the model to better simulate observed gas-particle phase partitioning of nitrate in the marine boundary layer. Model comparisons with long-term measurements of NOx from the Cape Verde Atmospheric Observatory (CVAO) in the eastern tropical North Atlantic provide support for an in situ source of NOx from NITs photolysis, with NITs photolysis coefficients about 25-50 times larger than corresponding HNO3 photolysis coefficients. Short-term measurements of nitrous acid (HONO) at this location show a clear daytime peak, with average peak mixing ratios ranging from 3 to 6 pptv. The model reproduces the general shape of the diurnal HONO profile only when NITs photolysis is included, but the magnitude of the daytime peak mixing ratio is under-predicted. This under-prediction is somewhat reduced if HONO yields from NITs photolysis are assumed to be close to unity. The combined NOx and HONO analysis suggests that the upper limit of the ratio of NITs : HNO3 photolysis coefficients is about 100. The largest simulated relative impact of NITs photolysis is in the tropical and subtropical marine boundary layer, with peak local enhancements ranging from factors of 5 to 20 for NOx, 1.2 to 1.6 for OH, and 1.1 to 1.3 for ozone. Since the spatial extent of the sea-salt aerosol (SSA) impact is limited, global impacts on NOx, ozone, and OH mass burdens are small ( ∼ 1-3 %). We also present preliminary analysis showing that particulate nitrate photolysis in accumulation-mode aerosols (predominantly over continental regions) could lead to ppbv-level increases in ozone in the continental boundary layer. Our results highlight the need for more comprehensive long-term measurements of NOx, and related species like HONO and sea-salt particulate nitrate, to better constrain the impact of particulate nitrate photolysis on marine boundary layer oxidant chemistry. Further field and laboratory studies on particulate nitrate photolysis in other aerosol types are also needed to better understand the impact of this process on continental boundary layer oxidant chemistry.
- Published
- 2018
43. In situ Ozone Production is highly sensitive to Volatile Organic Compounds in the Indian Megacity of Delhi.
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Nelson, Beth S., Stewart, Gareth J., Drysdale, Will S., Newland, Mike J., Vaughan, Adam R., Dunmore, Rachel E., Edwards, Pete M., Lewis, Alastair C., Hamilton, Jacqueline F., Acton, W. Joe, Hewitt, C. Nicholas, Crilley, Leigh R., Alam, Mohammed S., §ahin, Ülkü A., Beddows, David C. S., Bloss, William J., Slater, Eloise, Whalley, Lisa K., Heard, Dwayne E., and Cash, James M.
- Abstract
The Indian megacity of Delhi suffers from some of the poorest air quality in the world. While ambient NO2 and particulate matter (PM) concentrations have received considerable attention in the city, high ground level ozone (O3) concentrations are an often overlooked component of pollution. O3 can lead to significant ecosystem damage, agricultural crop losses, and adversely affect human health. During October 2018, concentrations of speciated non-methane hydrocarbons volatile organic compounds (C2 -- C13), oxygenated volatile organic compounds (o-VOCs), NO, NO2, HONO, CO, SO2, O3, and photolysis rates, were continuously measured at an urban site in Old Delhi. These observations were used to constrain a detailed chemical box model utilising the Master Chemical Mechanism v3.3.1. VOCs and NOx (NO + NO2) were varied in the model to test their impact on local O3 production rates, P(O3), which revealed a VOC-limited chemical regime. When only NOx concentrations were reduced, a significant increase in P(O3) was observed, thus VOC co-reduction approaches must also be considered in pollution abatement strategies. Of the VOCs examined in this work, mean morning P(O3) rates were most sensitive to monoaromatic compounds, followed by monoterpenes and alkenes, where halving their concentrations in the model led to a 15.6 %, 13.1 % and 12.9 % reduction in P(O3), respectively. P(O3) was not sensitive to direct changes in aerosol surface area but was very sensitive to changes in photolysis rates, which may be influenced by future changes in PM concentrations. VOC and NOx concentrations were divided into emission source sectors, as described by the EDGAR v5.0 Global Air Pollutant Emissions and EDGAR v4.3.2_VOC_spec inventories, allowing for the impact of individual emission sources on P(O3) to be investigated. Reducing road transport emissions only, a common strategy in air pollution abatement strategies worldwide, was found to increase P(O3), even when the source was removed in its entirety. Effective reduction in P(O3) was achieved by reducing road transport along with emissions from combustion for manufacturing and process emissions. Modelled P(O3) reduced by ~ 20 ppb h-1 when these combined sources were halved. This study highlights the importance of reducing VOCs in parallel with NOx and PM in future pollution abatement strategies in Delhi. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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44. Evaluating the sensitivity of radical chemistry and ozone formation to 1ambient VOCs and NOx in Beijing.
- Author
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Whalley, Lisa K., Slater, Eloise J., Woodward-Massey, Robert, Chunxiang Ye, Lee, James D., Squires, Freya, Hopkins, James R., Dunmore, Rachel E., Shaw, Marvin, Hamilton, Jacqueline F., Lewis, Alastair C., Mehra, Archit, Worrall, Stephen D., Bacak, Asan, Bannan, Thomas J., Coe, Hugh, Ouyang, Bin, Jones, Roderic L., Crilley, Leigh R., and Kramer, Louisa J.
- Abstract
Measurements of OH, HO
2 , RO2 -complex (alkene and aromatic-related RO2 ) and total RO2 radicals taken during the AIRPRO campaign in central Beijing in the summer of 2017, alongside observations of OH reactivity are presented. The concentrations of radicals were elevated with OH reaching up to 2.8 x 107 molecule cm-3 , HO2 peaked at 1 x 109 molecule cm-3 and the total RO2 concentration reached 5.5 x 109 molecule cm-3 . OH reactivity (k(OH)) peaked at 89 s-1 during the night, with a minimum during the afternoons of ~22 s-1 on average. An experimental budget analysis, in which the rates of production and destruction of the radicals are compared, highlighted that although the sources and sinks of OH were balanced under high NO concentrations, the OH sinks exceeded the known sources (by 15 ppbv hr-1 ) under the very low NO conditions (<0.5 ppbv) experienced in the afternoons, demonstrating a missing OH source consistent with previous studies under high volatile organic compound (VOC), low NO loadings. Under the highest NO mixing ratios (104 ppbv), the HO2 production rate exceeded the rate of destruction by ~ 50 ppbv hr-1 , whilst the rate of destruction of total-RO2 exceeded the production by the same rate indicating that the net propagation rate of RO2 to HO2 may be substantially slower than assumed. If just 10% of the RO2 radicals propagate to HO2 upon reaction with NO, the HO2 and RO2 budgets could be closed at high NO, but at low NO this lower RO2 to HO2 propagation rate revealed a missing RO2 sink that was similar in magnitude to the missing OH source. A detailed box model that incorporated the latest MCM chemical mechanism (MCM3.3.1) reproduced the observed OH concentrations well, but over-predicted the observed HO2 under low concentrations of NO (<1 ppbv) and under-predicted RO2 (both the complex-RO2 fraction and other RO2 types which we classify as simple-RO2 ) most significantly at the highest NO concentrations. The model also under-predicted the observed k(OH) consistently by ~10 s-1 across all NO[sub x] levels highlighting that the good agreement for OH was fortuitous due to a cancellation of missing OH source and sink terms in its budget. Including heterogeneous loss of HO2 to aerosol surfaces did reduce the modelled HO2 concentrations in-line with the observations, but only at NO mixing ratios <0.3 ppbv. The inclusion of Cl atoms, formed from the photolysis of nitryl chloride, enhanced the modelled RO2 concentration on several mornings when the Cl atom concentration was calculated to exceed 1 x 104 atoms cm-3 and could reconcile the modelled and measured RO2 concentrations at these times. However, on other mornings, when the Cl atom concentration was lower, large under-predictions in total RO2 remained. Furthermore, the inclusion of Cl atom chemistry did not enhance the modelled RO2 beyond the first few hours after sunrise and so was unable to resolve the modelled under-prediction in RO2 observed at other times of the day. Model scenarios, in which missing VOC reactivity was included as an additional reaction that converted OH to RO2 , highlighted that the modelled OH, HO2 and RO2 concentrations were sensitive to the choice of RO2 product. The level of modelled to measured agreement for HO2 and RO2 (both complex and simple) could be improved if the missing OH reactivity formed a larger RO2 species that was able to undergo reaction with NO, followed by isomerisation reactions reforming other RO2 species, before eventually generating HO2 . In this work an α-pinene-derived RO2 species was used as an example. In this simulation, consistent with the experimental budget analysis, the model underestimated the observed OH indicating a missing OH source. The model uncertainty, with regards to the types of RO2 species present and the radicals they form upon reaction with NO (HO2 directly or another RO2 species), leads to over an order of magnitude less O3 production calculated from the predicted peroxy radicals than calculated from the observed peroxy radicals at the highest NO concentrations. This demonstrates the rate at which the larger RO2 species propagate to HO2 or to another RO2 or indeed to OH needs to be understood to accurately simulate the rate of ozone production in environments such as Beijing where large multifunctional VOCs are likely present. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
45. A comparison of PM2.5-bound polycyclic aromatic hydrocarbons in summer Beijing (China) and Delhi (India).
- Author
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Elzein, Atallah, Stewart, Gareth J., Swift, Stefan J., Nelson, Beth S., Crilley, Leigh R., Alam, Mohammed S., Reyes-Villegas, Ernesto, Gadi, Ranu, Harrison, Roy M., Hamilton, Jacqueline F., and Lewis, Alastair C.
- Abstract
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in air, soil and water and known to have harmful effects on human health and the environment. The diurnal and nocturnal variation of 17-PAHs in ambient particle-bound PAHs were measured in urban Beijing (China) and Delhi (India) during the summer season using GC-Q-TOF-MS. The mean concentration of particles less than 2.5 microns (PM
2.5 ) observed in Delhi was 3.6 times higher than in Beijing during the measurement period in both the day-time and night-time. In Beijing, the mean concentration of the sum of the 17 PAHs (Σ17-PAHs) was 8.2 ± 5.1 ng m-3 in daytime, with the highest contribution from Indeno[1,2,3-cd]pyrene (12 %), while at night-time the total PAHs was 7.2 ± 2.0 ng m-3 , with the largest contribution from Benzo[b]fluoranthene (14 %). In Delhi, the mean Σ17-PAHs was 13.6 ± 5.9 ng m-3 in daytime, and 22.7 ± 9.4 ng m-3 at night-time, with the largest contribution from Indeno[1,2,3-cd]pyrene in both the day (17 %) and night (20 %). Elevated mean concentrations of total PAHs in Delhi observed at night were attributed to emissions from vehicles and biomass burning and to meteorological conditions leading to their accumulation from a stable and low atmospheric boundary layer. Local emission sources were typically identified as the major contributors to total measured PAHs, however, in Delhi 25 % of the emissions were attributed to long-range atmospheric transport. Major emission sources were characterized based on the contribution from each class of PAHs, with the 4, 5, and 6 ring PAHs accounting ~ 95 % of the total PM2.5 -bound PAHs mass in both locations. The high contribution of 5 ring PAHs to total PAH concentration in summer Beijing and Delhi suggests a high contribution from petroleum combustion. In Delhi, a high contribution from 6 ring PAHs was observed at night, suggesting a potential emission source from the combustion of fuel and oil in power generators, widely used in Delhi. The lifetime excess lung cancer risk (LECR) was calculated for Beijing and Delhi, with the highest estimated risk attributed to Delhi (LECR = 155 per million people), 2.2 times higher than Beijing risk assessment value (LECR = 70 per million people). Finally, we have assessed the emission control policies in each city and identified those major sectors that could be subject to mitigation measures. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
46. Interference from alkenes in chemiluminescent NOx measurements.
- Author
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Alam, Mohammed S., Crilley, Leigh R., Lee, James D., Kramer, Louisa J., Pfrang, Christian, Vázquez-Moreno, Mónica, Muñoz, Amalia, Ródenas, Milagros, and Bloss, William J.
- Subjects
- *
AIR quality monitoring , *OZONIZATION , *PEROXYACETYL nitrate , *INTERMEDIATES (Chemistry) , *VOLATILE organic compounds , *HYGIENE products , *AIR pollutants - Abstract
Nitrogen oxides (NOx = NO + NO2) are critical intermediates in atmospheric chemistry. NOx levels control the cycling and hence abundance of the primary atmospheric oxidants OH and NO3, and regulate the ozone production which results from the degradation of volatile organic compounds (VOCs) in the presence of sunlight. They are also atmospheric pollutants, and NO2 is commonly included in air quality objectives and regulations. NOx levels also affect the production of the nitrate component of secondary aerosol particles and other pollutants such as the lachrymator peroxyacetyl nitrate (PAN). The accurate measurement of NO and NO2 is therefore crucial to air quality monitoring and understanding atmospheric composition. The most commonly used approach for measurement of NO is chemiluminescent detection of electronically excited NO2 (NO2*) from the NO + O3 reaction. Alkenes, ubiquitous in the atmosphere from biogenic and anthropogenic sources, also react with ozone to produce chemiluminescence and thus may contribute to the measured NOx signal. Their ozonolysis reaction may also be sufficiently rapid that their abundance in the instrument background cycle, which also utilises reaction with ozone, differs from the measurement cycle - such that the background subtraction is incomplete, and an interference effect results. This interference has been noted previously, and indeed the effect has been used to measure both alkenes and ozone in the atmosphere. Here we report the results of a systematic investigation of the response of a selection of commercial NOx monitors, ranging from systems used for routine air quality monitoring to atmospheric research instrumentation, to a series of alkenes. Alkenes investigated range from short chain alkenes, such as ethene, to the biogenic monoterpenes. Experiments were performed in the European Photoreactor (EUPHORE) to ensure common calibration and samples for the monitors, and to unequivocally confirm the alkene levels present (via FTIR). The instrument interference responses ranged from negligible levels up to 11% depending upon the alkene present and conditions used (e.g. presence of co-reactants and differing humidity). Such interferences may be of substantial importance for the interpretation of ambient NOx data, particularly for high-VOC, low-NOx environments such as forests, or indoor environments where alkene abundance from personal care and cleaning products may be significant. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
47. Observations of speciated isoprene nitrates in Beijing: implications for isoprene chemistry.
- Author
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Reeves, Claire E., Mills, Graham P., Whalley, Lisa K., Acton, W. Joe F., Bloss, William J., Crilley, Leigh R., Grimmond, Sue, Heard, Dwayne E., Hewitt, C. Nicholas, Hopkins, James R., Kotthaus, Simone, Kramer, Louisa J., Jones, Roderic L., Lee, James D., Yanhui Liu, Bin Ouyang, Slater, Eloise, Squires, Freya, Xinming Wang, and Woodward-Massey, Robert
- Abstract
Isoprene is the most important biogenic volatile organic compound in the atmosphere. Its calculated impact on ozone (O
3 ) is critically dependent on the model isoprene oxidation chemical scheme, in particular the way the isoprene-derived nitrates (IN) are treated. By combining gas chromatography with mass spectrometry, we have developed a system capable of separating, and unambiguously measuring, individual IN isomers. In this paper we report measurements from its first field deployment, which took place in Beijing as part of the Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) programme, along with box model simulations using the Master Chemical Mechanism (MCM) (v.3.3.1) to assess the key processes affecting the production and loss of the IN. Seven individual isoprene nitrates were identified and quantified during the summer campaign: two β-isoprene hydroxy nitrates (IHN); four δ isoprene carbonyl nitrates (ICN); and propanone nitrate. Whilst we had previously demonstrated that the system can measure the four δ-IHN, we found no evidence of them in Beijing. The two β-IHN mixing ratios are well correlated with an R² value of 0.85. The mean for their ratio ((1-OH, 2-ONO2 )-IHN : (4-OH, 3-ONO2 )-IHN) is 3.4 and exhibits no clear diel cycle (the numbers in the names indicate the carbon (C) atom in the isoprene chain to which the radical is added). Examining this in a box model demonstrates its sensitivity to nitric oxide (NO), with lower NO mixing ratios favouring (1-OH, 2-ONO2 )-IHN over (4-OH, 3-ONO2 )-IHN. This is largely a reflection of the modelled ratios of their respective precursor peroxy radicals which, at NO mixing ratios of less than 1 part per billion (ppb), increase substantially with decreasing NO. Interestingly, this ratio in the peroxy radicals still exceeds the kinetic ratio (i.e. their initial ratio based on the yields of the adducts from OH addition to isoprene and the rates of reaction of the adducts with oxygen (O2 )) even at NO mixing ratios as high as 100 ppb. The relationship of the observed β-IHN ratio with NO is much weaker than modelled, partly due to far fewer data points, but it agrees with the model simulation in so far as there tend to be larger ratios at sub 1 ppb amounts of NO. Of the δ-ICN, the two trans (E) isomers are observed to have the highest mixing ratios and the mean isomer ratio (E-(4-ONO2 , 1-CO)-ICN to E-(1-ONO2 , 4-CO)-ICN)) is 1.4, which is considerably lower than the expected ratio of 6 for addition of NO3 in the C1 and C4 carbon positions in the isoprene chain. The MCM produces far more δ-ICN than observed, particularly at night and it also simulates an increase in the daytime δ-ICN that greatly exceeds that seen in the observations. Interestingly, the modelled source of δ-ICN is predominantly during the daytime, due to the presence in Beijing of appreciable daytime amounts of NO3 along with isoprene. The modelled ratios of δ-ICN to propanone nitrate are very different to the observed. This study demonstrates the value of speciated IN measurements to test our understanding of the isoprene degradation chemistry. Our interpretation is limited by the uncertainties in our measurements and relatively small data set, but highlights areas of the isoprene chemistry that warrant further study, in particular the NO3 initiated isoprene degradation chemistry. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
48. Nitrous acid (HONO) emissions under real-world driving conditions from vehicles in a UK road tunnel.
- Author
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Kramer, Louisa J., Crilley, Leigh R., Adams, Thomas J., Ball, Stephen M., Pope, Francis D., and Bloss, William J.
- Abstract
Measurements of atmospheric boundary layer nitrous acid (HONO) and nitrogen oxides (NO
x ) were performed in summer 2016 inside a city centre road tunnel in Birmingham, United Kingdom. HONO and NOx mixing ratios were strongly correlated with traffic density, with peak levels observed during the early evening rush hour as a result of traffic congestion in the tunnel. A daytime ΔHONO / ΔNOx ratio of 0.85 % (0.72–1.01 %, 95 % CI) was calculated using reduced major axis regression as the overall fleet-average (comprising 59 % diesel-fuelled vehicles). A comparison with previous tunnel studies and analysis on composition of the fleet suggest that goods-vehicles have a large impact on the overall HONO vehicle emissions; however, new technologies aimed at reducing exhaust emissions, particularly for diesel vehicles, may have reduced the overall direct HONO emission in the UK. This result suggests that in order to accurately represent urban atmospheric emissions and OH radical budget, fleet-weighted HONO / NOx ratios may better quantify HONO vehicle emissions in models, compared with use of a single emissions ratio for all vehicles. The contribution of the direct vehicular source of HONO to total ambient HONO concentrations is also investigated and results show that, in areas with high traffic density, vehicle exhaust emissions are likely to be the dominant HONO source to the boundary layer. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
49. Global impact of nitrate photolysis in sea-salt aerosol on NO<sub><i>x</i></sub>, OH, and O<sub>3</sub> in the marine boundary layer
- Author
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Kasibhatla, Prasad, primary, Sherwen, Tomás, additional, Evans, Mathew J., additional, Carpenter, Lucy J., additional, Reed, Chris, additional, Alexander, Becky, additional, Chen, Qianjie, additional, Sulprizio, Melissa P., additional, Lee, James D., additional, Read, Katie A., additional, Bloss, William, additional, Crilley, Leigh R., additional, Keene, William C., additional, Pszenny, Alexander A. P., additional, and Hodzic, Alma, additional
- Published
- 2018
- Full Text
- View/download PDF
50. Evaluation of a low-cost optical particle counter (Alphasense OPC-N2) for ambient air monitoring
- Author
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Crilley, Leigh R., primary, Shaw, Marvin, additional, Pound, Ryan, additional, Kramer, Louisa J., additional, Price, Robin, additional, Young, Stuart, additional, Lewis, Alastair C., additional, and Pope, Francis D., additional
- Published
- 2018
- Full Text
- View/download PDF
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