Abstract. 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 (SOAM, 47.2±9.29 ng m−3),
isoprene (SOAI, 23.1±10.8 ng m−3), and β-caryophyllene (SOAC, 3.85±1.75 ng m−3). We found that
atmospheric oxidants, Ox (O3 plus NO2), and sulfate
correlated well with later-generation SOAM tracers, but this was not the case for
first-generation SOAM products. This suggested that high Ox and
sulfate levels could promote the formation of later-generation SOAM products,
which probably led to the relatively aged SOAM that we observed in the PRD. For
the SOAI tracers, both 2-methylglyceric acid (NO/NO2-channel
product) and the ratio of 2-methylglyceric acid to 2-methyltetrols
(HO2-channel products) exhibit NOx dependence, indicating the
significant impact of NOx on SOAI formation pathways. The
SOAC tracer was elevated in winter at all sites and was positively correlated
with levoglucosan, Ox, and sulfate. Thus, the unexpected increase in
SOAC in wintertime might be highly associated with the enhancement of
biomass burning, O3 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. SOAM
dominated the BSOA mass all year round. We also found that BSOA correlated
well with sulfate and Ox. 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 Ox precursors in polluted regions.
Supplementary material to "Impact of anthropogenic emissions on biogenic secondary organic aerosol: Observation in the Pearl River Delta, South China"
