Revealing the origin of fine particulate matter in the Sichuan Basin from a source-oriented modeling perspective

Abstract

The Sichuan Basin (SCB) with 18 cities is one of the regions that are greatly affected by PM2.5 (i.e., particulate matter (PM) with an aerodynamic equivalent diameter less than or equal to 2.5 μm) in China. In this study, we used the Weather Research Forecasting (WRF) model and a source-oriented version of the Community Multiscale Air Quality (CMAQ) model to quantify the contributions from different sectors and regions to PM2.5 for the SCB in 2015. The annual PM2.5 concentrations in the 18 SCB urban centers (i.e., the central urban areas) are 42–112 μg m−3, much higher than the World Health Organization (WHO) guideline (10 μg m−3) and having 20–86, 6–17, and 6–10 μg m−3 due to SCB, non-SCB, and unidentified emissions, respectively. Non-SCB emissions can contribute up to 87 μg m−3 to 24-h PM2.5 concentrations for an urban center. Industrial and residential activities are the largest sectors for annual PM2.5 concentrations in the urban centers, and each of them contributes ~25%–50%. The combined residential and industrial contributions (>~60%) are always much higher than that from each of the other sources on PM2.5 pollution and extreme pollution days (>75 and > 150 μg m−3, respectively). This study suggests that China's standard for annual PM2.5 (35 μg m−3) in most of the SCB cities might be achieved mainly through controlling SCB emissions (particularly those from industrial and residential activities); however, to meet the WHO guideline and to reduce PM2.5 pollution days and extreme pollution days, both SCB and non-SCB emissions should be greatly reduced.