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Fine Particulate Matter and Ozone Pollution in the 18 Cities of the Sichuan Basin in Southwestern China: Model Performance and Characteristics

Category: Air Pollution Modeling

Volume: 19 | Issue: 10 | Pages: 2308-2319
DOI: 10.4209/aaqr.2019.05.0235
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Xue Qiao1,2,3, Hao Guo3, Pengfei Wang3, Ya Tang4, Qi Ying5, Xing Zhao6, Wenye Deng7, Hongliang Zhang 3,8

  • 1 Institute of New Energy and Low-Carbon Technology and Healthy Food Evaluation Research Center, Sichuan University, Chengdu 610065, China
  • 2 State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, China
  • 3 Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, USA
  • 4 College of Architecture and Environment and Healthy Food Evaluation Research Center, Sichuan University, Chengdu 610065, China
  • 5 Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843, USA
  • 6 Department of Epidemiology and Biostatistics, West China School of Public Health, Sichuan University, Chengdu 610041, China
  • 7 Xinjiang Academy of Environmental Protection Science, Urumqi 830011, China
  • 8 Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China

Highlights

  • Hotspots of winter PM2.5 occur near the urban centers of Chengdu and Chongqing.
  • Summer O3 concentrations are higher in some rural areas than in urban areas.
  • Time-series patterns of 24-h PM2.5 and 8-h O3 are similar among the 18 cities.
  • Primary organic aerosols and SO42− are the top contributors to PM2.5 in winter.
  • Spatial changes of O3 and PM2.5 reflect trans-boundary transport of air pollutants.

Abstract

The Sichuan Basin (SCB) is located in southwestern China and has a total population of 108.1 million across 18 cities, including the 2 largest in western China (Chengdu and Chongqing). As most air quality monitoring stations are located in urban areas, we simulated the PM2.5 (i.e., particulate matter with an aerodynamic diameter < 2.5 µm) and ozone (O3) in the entire SCB during winter (December 2014–February 2015) and summer (June–August 2015) by using the Weather Research and Forecasting (WRF) and the Community Multi-scale Air Quality (CMAQ) models. The simulated concentrations of 24-h PM2.5 and its major components generally agree with observations during both seasons, but the simulated 1-h and 8-h O3 are acceptable only for summer. Increasing in severity from the rim of the SCB to its inner areas, the PM2.5, as well as its major components, exhibits hotspots near the central urban areas of Chongqing and Chengdu, with concentrations of 150–200 µg m–3 and 40–60 µg m–3 during winter and summer, respectively. The 1-h and 8-h O3 exhibit no hotspots in the urban centers of Chongqing and Chengdu but show elevated levels in some rural and suburban areas (55–70 ppb and 65–80 ppb, respectively), including those on the western and southwestern rim of the SCB, and downwind of the urban center of Chongqing. Despite the great spatial variations in the PM2.5 and O3 concentrations, the vast majority of the basin fails to meet the WHO guidelines for 24-h PM2.5 (25 µg m–3) and 8-h O3 (~47 ppb) on > 70% of the days during winter and > 40% of the days during summer, respectively. Based on the aforementioned spatial patterns of the PM2.5 and O3 concentrations, and the wind directions within the basin, strictly controlling emissions originating in the SCB may greatly reduce PM2.5 and O3 concentrations within the basin.

Keywords

Chengdu Chongqing Spatio-temporal variations Air pollution


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