Abstract. The Sichuan Basin (SCB) is one of the regions suffering from severe air
pollution in China, but fewer studies have been conducted for this region
than for the more developed regions in eastern and northern China. In this study,
a source-oriented version of the Community Multiscale Air Quality (CMAQ)
model was used to quantify contributions from nine regions to PM2.5
(i.e., particulate matter, PM, with an aerodynamic diameter less than 2.5 µm) and its components in the 18 cities within the SCB in the winter
(December 2014 to February 2015) and summer (June to August 2015). In the
winter, citywide average PM2.5 concentrations are 45–126 µg m−3, with 21 %–51 % and
39 %–66 % being
due to local and nonlocal emissions, respectively. In the summer,
15 %–45 % and 25 %–52 % of citywide average
PM2.5 (14–31 µg m−3) are due to local and
nonlocal emissions, respectively. Compared to primary PM (PPM), the
inter-region transport of secondary inorganic aerosols (SIA), including
ammonia, nitrate, and sulfate ions (NH4+, NO3-, and
SO42-, respectively), and their gas-phase precursors are greater.
The region to the east of SCB (R7, including central and eastern China
and others) is the largest contributor outside the SCB, and it can
contribute approximately 80 % of PM2.5 in the eastern, northeastern,
and southeastern rims of the SCB but only 10 % in other SCB regions in
both seasons. Under favorable transport conditions, regional transport of
air pollutants from R7 could account for up to 35–100 µg m−3 of PM2.5 in each of the SCB cities in the winter. This
study demonstrates that it is important to have joint emission control
efforts among cities within the SCB and regions to the east in order to
reduce PM2.5 concentrations and prevent high PM2.5 days for the
entire basin.
Characteristics and source origins of carbonaceous aerosol in fine particulate matter in a megacity, Sichuan Basin, southwestern China
