Chemical characterization of oxygenated organic compounds in gas-phase and particle-phase in the Pearl River Delta using iodide-CIMS with FIGAERO

Chemical characterization of oxygenated organic compounds in gas-phase and particle-phase in the Pearl River Delta using Iodide-CIMS with FIGAERO

Chenshuo Ye¹, Yi Lin², Zelong Wang², Tiange Li², Caihong Wu², Chaomin Wang², Weiwei Hu³, Shan Huang², Wei Song³, Xinming Wang³, Bin Yuan²*, Min Shao^2,1**

1 College of Environmental Sciences and Engineering, Peking University, Beijing

2 Institute for Environmental and Climate Research, Jinan University, Guangzhou

3 Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou

* e-mail: byuan@jnu.edu.cn

** e-mail: mshao@pku.edu.cn

Abstract

The Pearl River Delta region (PRD) is a highly industrialized and urbanized area in southeastern China, strongly influenced by both anthropogenic and biogenic emissions. The atmospheric processes in PRD involves the interactions between organics and inorganics, anthropogenic pollutants and natural emissions, leading to the formation of various  secondary products. The iodide chemical ionization time-of-flight mass spectrometer installed with FIGAERO inlet was applied at an urban site in PRD region during the autumn of 2018, to measure a number of oxygenated organic compounds in both gas phase and particle phase. Using the dataset, we find: (1) Oxygenated organic compounds and N-containing organics accounted for the majority of detected species. The most abundant organics were formic acid and multifunctional organics containing 3-6 oxygens. Nitrophenols, dinitrophenols and organic nitrates derived from isoprene and monoterpenes made a substantial contribution to N-containing organics. (2) Isoprene oxidation products peaked in the afternoon, while monoterpene oxidation products and oxidized aromatics had various diurnal patterns due to their different chemical pathways during their formation processes. (3) We detected many biomass burning tracers previously described in the literature, among which levoglucosan, along with other monosaccharide derivatives and serval guaiacol derivatives, were highly correlated with each other, with their concentrations peaked during the harvest season for local crops. (4) Photochemical processes generally create smaller products of higher oxidation states, whereas nighttime chemistry plays an important role in producing larger molecule but less oxidized products particularly nitrogen-containing oxygenated organics. The variations of dominant atmospheric processes as well as the emissions of precursors lead to the variations of the bulk properties of secondary products.