Multifunctional Products of Isoprene Oxidation in Polluted Atmosphere and Their Contribution to SOA.

Isoprene (2‐methyl‐1, 3‐butadiene) is a nonmethane volatile organic compound (VOC) with the largest global emission and high reactivity. The oxidation of isoprene is crucial to atmospheric photochemistry and contributes significantly to the global formation of secondary organic aerosol. Here, we conducted comprehensive observations in polluted megacities of Nanjing and Shanghai during summer of 2018. We identified multiple functionalized isoprene oxidation products, of which 72% and 88% of the total mole concentration were nitrogen‐containing species with the dominant compound being C5 dihydroxyl dinitrate (C5H10N2O8). We calculated the volatility using the group‐contribution method and estimated the particle‐phase concentration by equilibrium gas/particle partitioning. The results showed that the multifunctional products derived from isoprene oxidation can contribute to 2.6% of the total organic aerosol mass (0.28 ± 0.27 μg/m3), highlighting the potential importance of isoprene oxidation in polluted regions. Plain Language Summary: Isoprene, as one of the most important precursors to form secondary organic aerosol (SOA) globally, has been extensively studied, most of which however focused in the pristine regions. In polluted urban areas, where isoprene would interact significantly with anthropogenic emissions, for example, NOx, the understanding of SOA formation potential of isoprene is rather controversial. Here, we used state‐of‐the‐art instruments to measure isoprene, highly functionalized intermediate compounds and organic aerosol simultaneously at two suburban sites in eastern China region and identify several tens of isoprene oxidation products with most of which identified as nitrogen‐containing species, confirming the significant interaction between the isoprene derived peroxy radicals and NOx. These multifunctional products are mostly semi‐volatile species and can contribute considerably to the observed SOA, highlighting an important role of biogenic volatile organic compounds oxidation on SOA formation under high‐NOx conditions, for example, anthropogenic emission dominant regions. Key Points: Simultaneous measurements of volatile organic compounds, highly functionalized intermediate compounds and organic aerosol were conductedOrganic nitrates dominated the C4‐C5 functionalized isoprene oxidation products detected by NO3− CIMSMost of the identified isoprene oxidation products were categorized as SVOC and can contributed to secondary organic aerosol [ABSTRACT FROM AUTHOR]