Characterization of organic aerosols and their precursors in southern China during a severe haze episode in January 2017

Di Chang; Zhe Wang; Jia Guo; Tao Li; Yiheng Liang; Lingyan Kang; Men Xia; Yaru Wang; Chuan Yu; Hui Yun; Dingli Yue; Tao Wang

doi:10.1016/j.scitotenv.2019.07.123

Characterization of organic aerosols and their precursors in southern China during a severe haze episode in January 2017

Sci Total Environ. 2019 Nov 15:691:101-111. doi: 10.1016/j.scitotenv.2019.07.123. Epub 2019 Jul 9.

Authors

Di Chang¹, Zhe Wang², Jia Guo³, Tao Li⁴, Yiheng Liang¹, Lingyan Kang¹, Men Xia¹, Yaru Wang¹, Chuan Yu⁴, Hui Yun¹, Dingli Yue⁵, Tao Wang¹

Affiliations

¹ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China.
² Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China. Electronic address: z.wang@polyu.edu.hk.
³ Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
⁴ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China; School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China.
⁵ Guangdong Environmental Monitoring Center, State Environmental Protection Key Laboratory of Regional Air Quality Monitoring, Guangzhou 510308, China.

PMID: 31319248
DOI: 10.1016/j.scitotenv.2019.07.123

Abstract

The rapid industrialization and economic development in the Pearl River Delta (PRD) region of southern China have led to a substantial increase in anthropogenic emissions and hence frequent haze pollution over the past two decades. In early January 2017, a severe regional haze pollution episode was captured in the PRD region, with a peak PM_2.5 concentration of around 400μgm^-3, the highest value ever reported at this site. During the haze episode, elevated concentrations of oxygenated volatile organic compounds (OVOCs, 33±16 ppbv) and organic matter (41±15μg m^-3) were observed, indicating the enhanced roles of secondary organic aerosols (SOAs) in the formation of haze pollution. Water-soluble organic carbon (WSOC, 12.8±5.5μg C m^-3) dominated the organic aerosols, with a WSOC/OC ratio of 0.63±0.12 and high correlation (R=0.85) with estimated secondary organic carbon (SOC), suggesting the predominance of a secondary origin of the measured organic aerosols during the haze episode. Four carboxylic acids (oxalic, acetic, formic, and pyruvic acids) were characterized in the aerosols (1.30±0.38μgm^-3) and accounted for 3.6±1.2% of WSOC in carbon mass, with oxalic acid as the most abundant species. The simultaneous measurements of volatile organic compounds (VOCs), OVOCs, and organic acids in aerosols at this site provided an opportunity to investigate the relationship between the precursors and the products, as well as the potential formation pathways. Water-soluble aldehydes and ketones, predominantly produced via the oxidation of anthropogenic VOCs (mainly propane, toluene, n-butane, and m, p-xylene), were the main contributors of the organic acids. The formation of OVOCs is largely attributed to gas-phase photochemical oxidation, whereas the WSOC and dicarboxylic acids were produced from both photochemistry and nocturnal heterogeneous reactions. These findings provided further insights into the oxidation and evolution of organic compounds during the haze pollution episode.

Keywords: Haze pollution; Organic acids; Oxygenated volatile organic compounds; Photochemistry; WSOC.