A146-0007
Isoprene secondary organic aerosol in summertime Beijing: the effect of anthropogenic emissions on organosulfate and nitrooxy organosulfate formation
Monday, 14 December 2020
Poster
Daniel Bryant1, James R Hopkins2, Rachel Dunmore2, Kelly Louise Pereira1, Pete Edwards3, Marvin Shaw3, Freya Anne Squires2, Tom Bannan4, Archit Mehra4, Stephen D Worrall5, Asan Bacak6, Hugh Coe7, Carl Percival8, Lisa Whalley9, Dwayne E Heard9, Eloise Slater10, Bin Ouyang11, Tianqu Cui12, Jason D Surratt13, Di Liu14, Zongbo Shi15, Roy M Harrison16, Yele Sun17, Weiqi Xu18, Claire Reeves19, Graham Mills20, Sue B Grimmond21, Alastair C Lewis3, James D Lee22, Andrew R Rickard23 and Jacqueline Hamilton2, (1)University of York, York, United Kingdom, (2)University of York, Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, York, United Kingdom, (3)Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, United Kingdom, (4)University of Manchester, Manchester, United Kingdom, (5)Aston University, Chemical Engineering and Applied Chemistry, Birmingham, United Kingdom, (6)University of Manchester, Centre for Atmospheric Science, School of Earth, Atmospheric and Environmental Sciences, Manchester, United Kingdom, (7)Department of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom, (8)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (9)University of Leeds, School of Chemistry, Leeds, LS2, United Kingdom, (10)University of Leeds, School of Chemsitry, Leeds, AL, United Kingdom, (11)University of Cambridge, Cambridge, United Kingdom, (12)University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, (13)UNC-Environment Sci & Eng, Chapel Hill, NC, United States, (14)State Key Laboratory of Organic Geochemistry and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou, China, (15)Institute of Surface-Earth System Science, Tianjin University, Tianjin, China, (16)University of Birmingham, School of Geography, Earth and Environmental Sciences, Birmingham, United Kingdom, (17)Institute of Atmospheric Physics, Chinese Academy of Sciences, State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Beijing, China, (18)Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China, (19)National Centre for Atmospheric Science, Leeds, United Kingdom, (20)University of East Anglia, Norwich, United Kingdom, (21)University of Reading, Meteorology, Reading, RG6, United Kingdom, (22)National Centre for Atmospheric Science, University of York, York, United Kingdom, (23)National Centre for Atmospheric Science, York, United Kingdom
Abstract:
Urban environments such as Beijing present highly complex mixtures of emissions from both biogenic and anthropogenic sources, emitted both locally and more regionally. Recent studies have shown that on average 87 % of organic aerosol (OA) is comprised of modern carbon (MC), even in urban environments where fossil fuel species would be expected to dominate. Isoprene is the highest emitted volatile organic compound globally as such understanding the importance of isoprene in highly polluted urban areas will help elucidate the urban sources of MC. Isoprene secondary organic aerosol (iSOA) has been extensively studied in chambers but limited ambient studies in urban areas have taken place, where it has been shown that, Isoprene organosulfates (OSs) and nitrooxy organosulfates (NOSs) are key OA constituents generally formed from biogenic-anthropogenic interactions.
Offline filter samples were collected as part of the joint UK-China Air Pollution and Human Health (APHH-Beijing) campaign, alongside a comprehensive suite of complementary gas and aerosol phase measurements at an urban site in Beijing during summertime 2017. This study presents ultra-high performance liquid chromatography, high-resolution mass spectrometry measurements of iSOA OS and NOS species in ambient PM2.5 samples.
iSOA OS formation was found to be dependant on both photochemistry and the availability of particulate sulfate for reactive uptake, with a strong correlation towards the product of ozone and particulate sulfate. Several iSOA NOS species were quantified alongside the OS species and represented both day and night-time formation mechanisms. Two mono-nitrated NOS species which peaked during the day are proposed to form from sequential reactions of isoprene with NO3 and OH radicals. While Di and Tri-nitrated iSOA NOS species peaked during the night and are proposed to form from multiple NO3 oxidation steps. Overall, tentatively assigned iSOA OS and NOS species contributed on average 2.2 % to the oxidised organic aerosol measured by aerosol mass spectrometry but increased to 10.5 % on certain days. These measurements indicate that iSOA can make a substantial contribution to OA in urban Beijing and formation is strongly controlled by anthropogenic emissions with heterogenous reactions resulting in extensive conversion to OS products.
