Insights into the formation and properties of secondary organic aerosol at a background site in Yangtze River Delta region of China: Aqueous-phase processing vs. photochemical oxidation. (15th October 2020)

• Record Type: Journal Article
• Authors: Huang, Dan Dan; Kong, Lin; Gao, Jie; Lou, Shengrong; Qiao, Liping; Zhou, Min; Ma, Yingge; Zhu, Shuhui; Wang, Hongli; Chen, Shiyi; Zeng, Limin; Huang, Cheng
• Is Part Of: Atmospheric environment. Volume 239(2020)
• Publication Date: 2020-10-15
• Subjects: Yangtze River Delta (YRD) -- Secondary organic aerosol (SOA) -- Biomass burning -- Aqueous-phase processing -- Photochemical oxidation; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2020.117716
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Physicochemical processes leading to secondary organic aerosol (SOA) formation in rural Yangtze River Delta (YRD) are poorly constrained. We present observation results on chemical characteristics, sources and contributions from different formation routes of organic aerosol (OA) at a background site of YRD region in summer. High-resolution aerosol mass spectrometric analysis revealed that SOA dominated the total OA in rural YRD with a mass fraction of higher than 70%, emphasizing more significant impacts of secondary formation than primary emission on air quality in summer. Positive matrix factorization identified two SOA types that respectively associated with aqueous-phase processing (aqueous OOA) and photochemical oxidation (photochemical OOA). One foggy period with strong biomass burning influence (BB) and one clean period (Clean) with strong local influence were chosen for detailed analysis. Aqueous OOA and photochemical OOA had average mass ratios of 1.5:1 and 0.18:1 respectively for foggy-BB and Clean, suggesting the relative importance of different atmospheric processes on SOA formation under different environmental conditions. High OA concentrations (>15 μg/m 3 ) were also associated with high fractional contributions from aqueous-phase processing in BB (40%) and photochemical processes in Clean (>60%). Furthermore, while aqueous-phase processing might promote the accumulation of OA, a better correlation between oxygenation levels of bulk OA with OX (O3 +NO2 ) concentrations than that with aerosol liquid water content suggests that photochemical gas-phase oxidation imposed larger impacts on the degree of oxygenation of bulk OA. Our results highlight the combined effects of different chemical transformation pathways on local air quality and aerosol properties. Highlights: SOA dominated the total OA in rural YRD in summer. Photochemical oxidation imposed significant impacts on the degree of oxygenation of OA. Both photochemical oxidation and aqueous-phase processing showed importance in accumulation of OA.