Measurements of carbonyl compounds around the Arabian Peninsula indicate large missing sources of acetaldehydeстатья
Аннотация: Abstract. Volatile organic compounds (VOCs) were measured around the Arabian Peninsula using a research vessel during the AQABA campaign (Air Quality and Climate Change in the Arabian Basin) from June to August 2017. In this study we examine carbonyl compounds (CxHyO), measured by a proton transfer reaction mass spectrometer (PTR-ToF-MS), and present both a regional concentration distribution and a budget assessment for these key atmospheric species. Among the aliphatic carbonyls, acetone had the highest mixing ratios in most of the regions traversed, varying from 0.43 ppb over the Arabian Sea to 4.5 ppb over the Arabian Gulf, followed by formaldehyde (measured by Hantzsch monitor, 0.82 ppb over the Arabian Sea and 3.8 ppb over the Arabian Gulf) and acetaldehyde (0.16 ppb over the Arabian Sea and 1.7 ppb over the Arabian Gulf). Unsaturated carbonyls (C4–C9) varied from 10 to 700 ppt during the campaign, and followed similar regional mixing ratio dependence as aliphatic carbonyls, which were identified as oxidation products of cycloalkanes over polluted areas. An empirical method based on hydrocarbon ratios was applied to investigate the photochemical source strength of the aliphatic carbonyls. While the distribution and relative concentration enhancements of the C3–C8 aliphatic carbonyls could be explained by this method, that of acetaldehyde could not. A smaller but still significant discrepancy was found when comparing measurements to global chemistry-transport model (EMAC) results, with the model underestimating the measured acetaldehyde mixing ratio up to an order of magnitude. Implementing a photolytically driven marine source of acetaldehyde significantly improved the agreement between measurements and model, particularly over the remote regions (e.g. Arabian Sea). However, the newly introduced acetaldehyde source was still insufficient to describe the observations over the most polluted regions (Arabian Gulf and Suez), where model underestimation of primary emissions and biomass burning events are possible reasons.
Год издания: 2020
Авторы: Nijing Wang, Achim Edtbauer, Christof Stönner, Andrea Pozzer, Efstratios Bourtsoukidis, Lisa Ernle, Dirk Dienhart, Bettina Hottmann, Horst Fischer, Jan Schuladen, John N. Crowley, Jean-Daniel Paris, Jos Lelieveld, Jonathan Williams
Ключевые слова: Atmospheric chemistry and aerosols, Air Quality and Health Impacts, Air Quality Monitoring and Forecasting
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