Measurement report: characterization and sources of the ambient secondary organic carbon in a Chinese megacity over five years from 2016 to 2020
- 1Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
- 2Shanghai Environmental Monitoring Center, Shanghai, China
- 3School of Physics, Ryan Institute's Centre for Climate & Air Pollution Studies, and Marine Renewable Energy Ireland, National University of Ireland Galway, University Road, Galway, H91 CF50, Ireland
- 4State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China
- 5Zhejiang Tianlan Environmental Protection Technology Co., Ltd., Hangzhou 311202, China
- 6Department of Environmental Engineering, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China
- 7State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China
- 8Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
Abstract. To investigate impact factors and source area of secondary organic aerosols in the Yangtze River Delta (YRD) region, a world-class urban agglomeration in China, long-term measurements of organic carbon (OC) and elementary carbon (EC) in particulate matter of less than 2.5 μm (PM2.5) with hourly time resolution were conducted at a regional site in Shanghai from 2016 to 2020. Based on the five-year measurements, the interannual, monthly, seasonal, and diurnal variations in OC and EC, as well as OC subtypes, i.e., secondary OC (SOC) and primary OC (POC), apportioned by the novel statistical model of the minimum R2 method, and the formation pathways of SOC, are presented. By examining the relationship between SOC and temperature, as well as relative humidity (RH), we show that SOC formation is greatly enhanced at high temperatures (>30 °C), while it is inversely correlated with RH. In particular, we show that the photochemical formation of SOC is the major formation pathway even in winter when solar radiation was supposedly less intense than in summer, which is different from that in north China plain where aqueous phase chemistry is found to be an important SOC formation pathway. Moreover, increased SOC concentrations are also found to be associated with high wind speed (>5 m s−1) in winter, which is increased by 29.1 % (2.62 μg m−3) when compared to that during lower winds, suggesting regional sources of SOC in winter. By analyzing the potential source regions using the concentration weighted trajectory (CWT), the geographic regions of SOC are found to be mainly associated with transport from outside Shanghai (SOC > 3.5 μg m−3) including central and southern Anhui, Zhejiang, and Fujian. The results from this study provide critical information about the long-term trend of carbonaceous aerosol, in particular SOC, in one of the largest megacities in the world and are helpful to develop pollution control measures from a long-term planning perspective.
Meng Wang et al.
Meng Wang et al.
Measurement report: characterization and sources of the ambient secondary organic carbon in a Chinese megacity over five years from 2016 to 2020 https://doi.org/10.5281/zenodo.6473085
Meng Wang et al.
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