Impact of anthropogenic emissions on biogenic secondary organic aerosol: observation in the Pearl River Delta, southern China

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 (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.

Impact of the COVID-19 on the vertical distributions of major pollutants from a tower in the Pearl River Delta

“…During the lockdown, there was a significantly stronger correlation between PM 2.5 and O 3 , where R values for the 0, 120, 220, and 335 m scatter plots were significant at p < 0.1. In the PRD region, VOCs significantly contributed to the formation of fine particles ( Liu et al, 2008 ; Zheng et al, 2009 ), particularly secondary organic aerosols ( Huang et al, 2006 ; Chang et al, 2019 ; Zhang et al, 2019 ). Although the advent of COVID-19 did trigger reductions in the concentrations of NO x , SO 2 , and other primary pollutants, VOC emissions may not have experienced such dramatic changes ( Liu et al, 2021 , Liu et al, 2021 ).…”

Anthropogenic–Biogenic Interactions at Night: Enhanced Formation of Secondary Aerosols and Particulate Nitrogen- and Sulfur-Containing Organics from β-Pinene Oxidation

“…Aerosol particles in the atmosphere have negative impacts on regional air quality, climate change, and human health. , Secondary aerosols produced during the oxidation of volatile organic compounds (VOCs) or inorganic precursors, for example, NO x /SO 2 /NH 3 , represent a large fraction of the total aerosol particle mass. , Biogenic VOCs (BVOCs) are globally the main precursors for the secondary organic aerosol (SOA) budget due to their relatively high emission rates (about ten times higher than anthropogenic VOCs) and high reactivity toward atmospheric major oxidants. − When BVOCs mix with anthropogenic emissions, the oxidation of BVOCs and their SOA formation potential can be altered as highlighted by many field observations. − However, anthropogenic–biogenic interactions during SOA formation are more complex than their current representation in models, and consequently, uncertainties in the predicted SOA budget might be induced. − …”

Impact of the COVID-19 pandemic on the observed vertical distributions of PM&lt;sub&gt;2.5&lt;/sub&gt;, NO&lt;sub&gt;x&lt;/sub&gt;, and O&lt;sub&gt;3&lt;/sub&gt; from a tower in the Pearl River Delta

“…However, during the lockdown, both were likely to have a similar source. In the PRD region, VOCs contribute significantly to the formation of fine particles (Liu et al, 2008;Zheng et al, 2009), especially secondary organic aerosols (Huang et al, 2006;Chang et al, 2019;Zhang et al, 2019). Although the advent of the COVID-19 pandemic did result in reductions in the concentrations of NOx, SO2, and other primary pollutants, the VOCs emissions might not change as dramatically as NOx (Liu et al, 2021), which provided important precursors for both O3 and the secondary organic aerosols during the lockdown, and strengthened the correlation between the PM2.5 and O3 concentrations.…”