Intense secondary aerosol formation due to strong atmospheric photochemical reactions in summer: observations at a rural site in eastern Yangtze River Delta of China

Dongfang Wang; Bin Zhou; Qingyan Fu; Qianbiao Zhao; Qi Zhang; Jianmin Chen; Xin Yang; Yusen Duan; Juan Li

doi:10.1016/j.scitotenv.2016.06.212

Intense secondary aerosol formation due to strong atmospheric photochemical reactions in summer: observations at a rural site in eastern Yangtze River Delta of China

Sci Total Environ. 2016 Nov 15:571:1454-66. doi: 10.1016/j.scitotenv.2016.06.212. Epub 2016 Jul 12.

Authors

Dongfang Wang¹, Bin Zhou², Qingyan Fu³, Qianbiao Zhao¹, Qi Zhang⁴, Jianmin Chen², Xin Yang⁵, Yusen Duan⁶, Juan Li⁶

Affiliations

¹ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Shanghai Environmental Monitoring Center, Shanghai 200235, China.
² Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Fudan-Tyndall Center, Fudan University, Shanghai 200433, China.
³ Shanghai Environmental Monitoring Center, Shanghai 200235, China. Electronic address: qingyanf@semc.gov.cn.
⁴ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Department of Environmental Toxicology, University of California, Davis, California 95616, United States. Electronic address: dkwzhang@ucdavis.edu.
⁵ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Fudan-Tyndall Center, Fudan University, Shanghai 200433, China. Electronic address: yangxin@fudan.edu.cn.
⁶ Shanghai Environmental Monitoring Center, Shanghai 200235, China.

PMID: 27418517
DOI: 10.1016/j.scitotenv.2016.06.212

Abstract

High pollution episodes of PM2.5 and O3 were frequently observed at a rural site (N31.0935º, E120.978°) in eastern Yangtze River Delta (YRD) in summer. To study the impacts of photochemical reactions on secondary aerosol formation in this region, we performed real-time measurements of the mass concentration and composition of PM2.5, particle size distribution (13.6~736.5 nm), concentrations of gas pollutants including O3, SO2, NO2, CO, non-methane hydrocarbons (NMHC)), and nitrate radical in 2013. During the sampling period, the average concentration of PM2.5 was 76.1 (± 16.5) μg/m(3), in which secondary aerosol species including sulfate, nitrate, ammonium, and secondary organic aerosol (SOA) accounted for ~ 62%. Gas-phase oxidation of SO2 was mainly responsible for a fast increase of sulfate (at 1.70 μg/m(3)/h) in the morning. Photochemical production of nitric acid was intense during daytime, but particulate nitrate concentration was low in the afternoon due to high temperature. At night, nitrate was mainly formed through the hydrolysis of NO3 and/or N2O5. The correlations among NMHC, Ox (= O3 + NO2), and SOA suggested that a combination of high emission of hydrocarbons and active photochemical reactions led to the rapid formation of SOA. In addition, several new particle formation and fast growth events were observed despite high ambient aerosol loading. Since the onset of new particle events was accompanied by a rapid increase of H2SO4 and SOA, enhanced formation of sulfate and SOA driven by photochemical oxidation likely promoted the formation and growth of new particles. Together, our results demonstrated that strong atmospheric photochemical reactions enhanced secondary aerosols formation and led to the synchronous occurrence of high concentrations of PM2.5 and O3 in a regional scale. These findings are important for better understanding the air pollution in summer in YRD.

Keywords: Gaseous Precursors; PM(2.5); Photochemical Oxidation; Secondary Aerosol Formation; Yangtze River Delta.

MeSH terms

Aerosols / analysis*
Air Pollutants / analysis*
China
Environmental Monitoring
Ozone / analysis*
Particle Size
Particulate Matter / analysis*
Photochemical Processes
Seasons

Substances

Aerosols
Air Pollutants
Particulate Matter
Ozone