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Characteristics of Air Pollutants and Greenhouse Gases at a Regional Background Station in Southwestern China

Category: Aerosol and Atmospheric Chemistry

Accepted Manuscripts
DOI: 10.4209/aaqr.2018.11.0397
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Linjun Cheng1, Dongsheng Ji 2,3, Jun He4, Liang Li1, Li Du1, Yang Cui2,5, Hongliang Zhang6, Luxi Zhou7, Zhiqing Li8, Yingxing Zhou9, Chengyuan Miao9, Zhengyu Gong1, Yuesi Wang2,3

  • 1 China National Environmental Monitoring Center, Beijing 100012, China
  • 2 State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100191, China
  • 3 Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
  • 4 International Doctoral Innovation Centre, Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, Ningbo 315100, China
  • 5 University of Chinese Academy of Sciences, Beijing 100049, China
  • 6 Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803, USA
  • 7 National Academies of Sciences, Engineering, and Medicine, Washington, DC 20001, USA
  • 8 Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
  • 9 Yunnan Wuyi Expressway Construction Headquarters, Yunnan, Kunming 650300, China

Abstract

The characteristics of air pollutants and greenhouse gases at regional background sites are important for assessing the impact of anthropogenic emissions on the atmospheric environment, ecosystems and climate change. However, observational studies are still scarce at such background sites. In this study, one-year continuous hourly observations of air pollutants (O3, CO, SO2, NOx, PM2.5 and PM10) and greenhouse gases (CO2, CH4 and N2O) were performed at the Gongga Mountain background station (GGS, 101°97′E, 29°55′N, elevation 3541 m) in southwestern China from January 1 to December 31, 2017. The concentrations and variations in these air pollutants and greenhouse gases were determined, and the effect of transboundary atmospheric transport on the air pollution at the study site was investigated. The results showed that the annual average concentrations (mixing ratios) of O3, CO, SO2, NO2, CO2, CH4, N2O, PM2.5 and PM10 were 74.7 ± 22.0 μg m-3, 0.3 ± 0.2 mg m-3, 0.5 ± 0.6 μg m-3, 1.7 ± 1.3 μg m-3, 406.1 ± 9.5 ppm, 1.941 ± 0.071 ppm, 324.5 ± 14.8 ppb, 6.5 ± 6.2 μg m-3 and 10.6 ± 11.2 μg m-3, respectively. The concentrations (mixing ratios) of the abovementioned substances at the GGS are comparable to those at other background sites in China and around the world. The slight differences among concentrations at different sites might be mainly associated with the impacts of anthropogenic emissions near the background sites and meteorological conditions. High values of O3 were observed in spring and summer and were related to stratospheric intrusions of O3. SO2 and PM2.5 showed higher concentrations in the summer than in autumn. Relatively high CO, NO2 and PM10 values were mostly observed in spring and winter. Relatively low CO2 concentrations were observed in summer due to the vigorous summertime photosynthesis of vegetation. The lowest CH4 concentrations were recorded in summer, while the CH4 levels in the other three seasons were similar to each other; in contrast, the highest N2O concentrations were observed in summer due to the enhanced microbial activity by the high ambient summer temperatures. A diurnal variation in O3 was observed, with early morning minima and afternoon maxima. CO and NO2 displayed higher concentrations in the daytime than in the nighttime. A slight increase in both PM2.5 and PM10 concentrations was also recorded in the daytime. These patterns were closely related to scattered anthropogenic emissions and regional atmospheric transport. CO2 showed lower concentrations in the daytime than in the nighttime, although CH4 had no obvious diurnal variation. The N2O concentration peaked at 10:00-12:00 (Local time), which could be ascribed to the enhancement of microbial activity by the increased soil temperature. The results based on the relationship between wind and the concentrations of air pollutants and greenhouse gases were almost consistent with those based on the potential contribution source function method. It appeared that O3 and its precursors in parts of Inner Mongolia and Gansu, Ningxia, Sichuan, Chongqing and Hubei Provinces as well as adjacent areas of Hunan, Guizhou and Guangxi Provinces contributed to the increase in O3 at the study site. The potential source areas for CO and SO2 were similar and were mainly distributed in India and Pakistan and areas of Inner Mongolia and Gansu and Guizhou Provinces of China. Potential source areas for NO2, PM2.5 and PM10 were even found in neighboring countries of South Asia, in addition to domestic regions, including Inner Mongolia, Gansu Province and the Cheng-Yu economic region. In addition, parts of Yunnan Province (China) as well as India and Pakistan were potential source areas for CO2, CH4 and N2O.

Keywords

Air pollutants Greenhouse gases Background station Southwestern China


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