Abstract
The study of air quality over the Yangtze River is important for the pollution of urban agglomeration along the longest river in China. A comprehensive 15-day shipborne observation was conducted in the Yangtze River of the Jiangsu section in the summer of 2019. Through online observation and offline chemistry analysis of aerosol and gaseous pollutants, the result showed that the air pollution over the Yangtze River was more severe than that in surrounding cities. Sulfate, nitrate, and ammonium (SNA) dominated the water-soluble inorganic species and accounted for 35.0% ± 7.3% of the fine particle concentration (PM2.5) along the Yangtze River. The high concentration of sulfate in the droplet mode (0.56–1.0 μm) was due to the formation of sulfate through in-cloud processes under high sulfur dioxide (SO2) concentration by ship emission and high relative humidity along the river. The strong correlation between the measured mass absorption efficiency value by carbon analyzer and that simulated based on the assumption of core–shell suggested that the core–shell mode was the main composition form of aerosol in the Yangtze River. The scattering effect was the main part of the aerosol light extinction, and the scattering coefficient of 0.4- to 1.1-μm particles accounted for 85.0% of the total extinction coefficient. Positive matrix factorization model was applied for the source apportionment of particle size segment of main extinction contribution (0.4–2.1 μm), and the result showed that secondary nitrate, ship emission, coal combustion, fugitive dust, and biomass burning were the main sources of aerosols in the Yangtze River. After source reanalysis, the result indicated that the contribution of secondary nitrate from nitrogen oxide (NOx) by ship emission and coal combustion should not be ignored.
Highlights
The Yangtze River is the longest river in China and Asia, which geographically flows from Qinghai Province to eastern China at Shanghai
In order to better characterize air pollution over the Yangtze River, an intensive cruise campaign was conducted in the Yangtze River of the Jiangsu section from August 22 to September 6, 2019
Compared with internal and external mixing states, the simulated mass absorption efficiency (MAE) values based on the core–shell mixing assumption were much closer to the measured values, indicating that core–shell mixed particles widely existed in the air of the Yangtze River
Summary
The Yangtze River is the longest river in China and Asia, which geographically flows from Qinghai Province to eastern China at Shanghai. Chemical, Extinction, Yangtze River intensive and complicated sources of air pollutants (Xu et al, 2016). Many studies focused on the chemical compositions, optical properties, and source apportionment of ambient aerosol in the Yangtze River Delta cities. A previous study indicated that size distributions of nitrate and ammonium presented significant seasonal variations and distinctive characteristics in polluted days in Shanghai (Ding et al, 2017). Different from the urban regional studies (Li et al, 2014; Zhang et al, 2021), aerosol along the Yangtze River was largely affected by ship emissions (Li et al, 2018). Huang et al (2020) suggested that PM2.5 concentrations of five stations in Yantai were largely affected by ship emission in the ocean It showed that the Yangtze River is an important route of trade and travel in China. There are seldom data related to chemical characterization and optical properties of aerosol along the Yangtze River channel, and related shipborne observations for optical characteristics and source apportionment of aerosols along the Yangtze River remain insufficient
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