Biogenic organosulfates (OSs) are important markers of secondary organic aerosol (SOA) formation involving cross reactions of biogenic precursors (terpenoids) with anthropogenic pollutants. Until now, there has been rare information about biogenic OSs in the air of highly polluted areas. In this study, fine particle (PM 2.5 ) samples were separately collected in daytime and nighttime from summer to fall 2010 at a site in the central Pearl River Delta (PRD), South China. Pinene-derived nitrooxyorganosulfates (pNOSs) and isoprene-derived OSs (iOSs) were quantified using a liquid chromatograph (LC) coupled with a tandem mass spectrometer (MS/MS) operated in negative electrospray ionization (ESI) mode. The pNOSs with MW 295 exhibited higher levels in fall (151 ± 86.9 ng m −3 ) than summer (52.4 ± 34.0 ng m −3 ), probably owing to the elevated levels of NOx and sulfate in fall when air masses mainly passed through city clusters in the PRD and biomass burning was enhanced. In contrast to observations elsewhere where higher levels occurred at nighttime, pNOS levels in the PRD were higher during the daytime in both seasons, indicating that pNOS formation was likely driven by photochemistry over the PRD. This conclusion is supported by several lines of evidence: the specific pNOS which could be formed through both daytime photochemistry and nighttime NO 3 chemistry exhibited no day− night variation in abundance relative to other pNOS isomers; the production of the hydroxynitrate that is the key precursor for this specific pNOS was found to be significant through photochemistry but negligible through NO 3 chemistry based on the mechanisms in the Master Chemical Mechanism (MCM). For iOSs, 2-methyltetrol sulfate ester which could be formed from isoprene-derived epoxydiols (IEPOX) under low-NOx conditions showed low concentrations (below the detection limit to 2.09 ng m −3 ), largely due to the depression of IEPOX formation by the high NOx levels over the PRD. ■ INTRODUCTIONBiogenic volatile organic compounds (BVOCs) including isoprene and monoterpenes 1 contribute significantly to the global secondary organic aerosol (SOA) budget. 2 Recent studies have shown that the conversion of BVOCs to SOA can be significantly promoted in the presence of high anthropogenic emissions. 3−6 As notable SOA products of BVOCs reacting with anthropogenic pollutants under acidic conditions, organosulfates (OSs) have been detected in both laboratory-generated SOA 7−10 and ambient aerosols. 11−18 Moreover, OSs could contribute a significant fraction of fine particles, accounting for up to 30% of organic matter (OM) 9,19−23 and up to 10% of total sulfate. 24,25 The formation mechanisms of OSs are still unclear. Previous chamber studies have demonstrated that both OH-photooxidation and NO 3 dark reactions can form pinene-derived nitrooxy-organosulfates (pNOSs) on acidic particles. 9 The pNOSs were only detected in nighttime samples in northeastern Bavaria, Germany, suggesting a role for nighttime NO 3 chemistry in pNOS formation. 15 How...

The National Key Research and Development Program of China, the National Natural Science Foundation of China, the Fundamental Research Funds for the Central Universities, the Guangdong Province Natural Science Foundation, the Career Development Fellowship of Australian National Health and Medical Research Council, and the Early Career Fellowship of Australian National Health and Medical Research Council.

Our findings suggest that exposure to air pollutants increases the odds of sleep disorder in children and point to the need to make reducing exposure to air pollutants a public health priority.

Secondary organic aerosol (SOA) formation from biogenic precursors is affected by anthropogenic emissions, which are not well understood in polluted areas. In this study, we accomplished a year-round campaign at nine sites in polluted areas located in the Pearl River Delta (PRD) region during 2015. We measured typical biogenic SOA (BSOA) tracers from isoprene, monoterpenes, and β-caryophyllene, as well as major gaseous and particulate pollutants and investigated the impact of anthropogenic pollutants on BSOA formation. The concentrations of BSOA tracers were in the range of 45.4 to 109 ng m −3 with the majority composed of products from monoterpenes (SOA M , 47.2 ± 9.29 ng m −3 ), isoprene (SOA I , 23.1 ± 10.8 ng m −3 ), and β-caryophyllene (SOA C , 3.85 ± 1.75 ng m −3 ). We found that atmospheric oxidants, O x (O 3 plus NO 2 ), and sulfate correlated well with later-generation SOA M tracers, but this was not the case for first-generation SOA M products. This suggested that high O x and sulfate levels could promote the formation of later-generation SOA M products, which probably led to the relatively aged SOA M that we observed in the PRD. For the SOA I tracers, both 2-methylglyceric acid (NO/NO 2channel product) and the ratio of 2-methylglyceric acid to 2-methyltetrols (HO 2 -channel products) exhibit NO x dependence, indicating the significant impact of NO x on SOA I formation pathways. The SOA C tracer was elevated in winter at all sites and was positively correlated with levoglucosan, O x , and sulfate. Thus, the unexpected increase in SOA C in wintertime might be highly associated with the enhancement of biomass burning, O 3 chemistry, and the sulfate component in the PRD. The BSOAs that were estimated using the SOA tracer approach showed the highest concentration in fall and the lowest concentration in spring with an annual average concentration of 1.68 ± 0.40 µg m −3 . SOA M dominated the BSOA mass all year round. We also found that BSOA correlated well with sulfate and O x . This implied a significant effect from anthropogenic pollutants on BSOA formation and highlighted that we could reduce BSOA by controlling the anthropogenic emissions of sulfate and O x precursors in polluted regions.

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