Characteristics and contributions of biogenic secondary organic aerosol tracers to PM2.5 in Shanghai, China

To evaluate biogenic secondary organic aerosol (BSOA) tracers from biogenic precursors, fine particles (PM2.5) were collected using filter-based high-volume samplers from spring-summer of 2015 in the central part of Shanghai, China. The results showed that the isoprene SOA tracers exhibited the highest levels (17.64 +/- 9.75 ng m(-3)) and were always observed along with higher temperatures, which results in a higher tracer formation rate and isoprene emission strength. However, the isoprene SOA tracers showed a weak correlation with the relative humidity (p > 0.05). The isoprene SOA tracers showed remarkable correlations with the [H+] because of the enhanced formation of isoprene SOA in the acidic aerosols. On the basis of these results, 2-methylglyceric acid was determined to have weak correlations with other isoprene tracers, which indicated that it had different formation pathways from those of other isoprene SOA tracers. Cis-pinonic acid had negative correlations with other SOA tracers, indicating that it is the first product in the oxidation process. Furthermore, the isoprene-based tracers (SOCisoprene) 1 were, calculated to be 0.031-0.299 mu g C m(-3) (with an average of 0.114 +/- 0.062 mu g C m(-3)), which accounted for more than half of the biogenic SOA. The SOC estimation with SOA tracers (SOC tracer-based) averaged 0.155 +/- 0.066 mu g m(-3), with a range from 0.049 to 0.309 mu g m(-3) during the sampling period, which amounted to 2.73% OC. (C) 2018 Turkish National Committee for Air Pollution Research and Control. Production and hosting by Elsevier B.V. All rights reserved.