Strong anthropogenic control of secondary organic aerosol formation from isoprene in Beijing

Abstract

Isoprene-derived secondary organic aerosol (iSOA) is a significant contributor to organic carbon (OC) in some forested regions, such as tropical rainforests and the Southeastern US. However, its contribution to organic aerosol in urban areas that have high levels of anthropogenic pollutants is poorly understood. In this study, we examined the formation of anthropogenically influenced iSOA during summer in Beijing, China. Local isoprene emissions and high levels of anthropogenic pollutants, in particular NOx and particulate SO2-4 , led to the formation of iSOA under both high- A nd low-NO oxidation conditions, with significant heterogeneous transformations of isoprene-derived oxidation products to particulate organosulfates (OSs) and nitrooxyorganosulfates (NOSs). Ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry was combined with a rapid automated data processing technique to quantify 31 proposed iSOA tracers in offline PM2.5 filter extracts. The co-elution of the inorganic ions in the extracts caused matrix effects that impacted two authentic standards differently. The average concentration of iSOA OSs and NOSs was 82.5 ngm-3, which was around 3 times higher than the observed concentrations of their oxygenated precursors (2-methyltetrols and 2-methylglyceric acid). OS formation was dependant on both photochemistry and the sulfate available for reactive uptake, as shown by a strong correlation with the product of ozone (O3) and particulate sulfate (SO2-4). A greater proportion of high-NO OS products were observed in Beijing compared with previous studies in less polluted environments. The iSOA-derived OSs and NOSs represented 0.62% of the oxidized organic aerosol measured by aerosol mass spectrometry on average, but this increased to ∼ 3% on certain days. These results indicate for the first time that iSOA formation in urban Beijing is strongly controlled by anthropogenic emissions and results in extensive conversion to OS products from heterogenous reactions.

Publication DOI: https://doi.org/10.5194/acp-2019-929
Divisions: Engineering & Applied Sciences > Chemical Engineering & Applied Chemistry
Additional Information: © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.
Uncontrolled Keywords: Atmospheric Science
Full Text Link:
Related URLs: https://www.atm ... t/20/7531/2020/ (Publisher URL)
http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2020-06-30
Accepted Date: 2020-05-15
Submitted Date: 2019-10-23
Authors: Bryant, Daniel J.
Dixon, William J.
Hopkins, James R.
Dunmore, Rachel E.
Pereira, Kelly L.
Shaw, Marvin
Squires, Freya A.
Bannan, Thomas J.
Mehra, Archit
Worrall, Stephen D. ( 0000-0003-1969-3671)
Bacak, Asan
Coe, Hugh
Percival, Carl J.
Whalley, Lisa K.
Heard, Dwayne E.
Slater, Eloise J.
Ouyang, Bin
Cui, Tianqu
Surratt, Jason D.
Liu, Di
Shi, Zongbo
Harrison, Roy
Sun, Yele
Xu, Weiqi
Lewis, Alastair C.
Lee, James D.
Rickard, Andrew R.
Hamilton, Jacqueline F.

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