Characteristics and contributions of biogenic secondary organic aerosol tracers to PM2.5 in Shanghai, China
2017
Zhu, Wenfei | Luo, Lina | Cheng, Zhen | Yan, Naiqiang | Lou, Shengrong | Ma, Yongpeng
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) were calculated to be 0.031–0.299 μg C m−3 (with an average of 0.114 ± 0.062 μg 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 μg m−3, with a range from 0.049 to 0.309 μg m−3 during the sampling period, which amounted to 2.73% OC.
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