High Wet Deposition of Black Carbon over the Sichuan Basin of China

Abstract

The wet deposition flux of black carbon (BC) over the Sichuan Basin is studied on the basis of the MERRA-2 data from 1981 to 2020, aiming at investigating high BC wet deposition flux in China in terms of long-term spatial-temporal trends and influences of BC column mass density and precipitation. In China, the largest BC wet deposition flux with a regionally-averaged value of 1.00 × 10−2 μg m−2 s−1 over the Sichuan Basin is observed, especially in the western and southern regions of the Basin with values as high as 2.20 × 10−2 μg m−2 s−1. The seasonality of BC wet deposition flux over the Sichuan Basin depicts maximum levels in autumn, moderate levels in spring and winter, and minimum levels in summer. The monthly mean BC wet deposition flux varies almost twofold, ranging from the lowest average value of 8.05 × 10−3 μg m−2 s−1 in July to the highest 1.28 × 10−2 μg m−2 s−1 in October. This study suggests that BC column mass density and precipitation are two significant factors affecting high BC wet deposition flux, whereas BC wet deposition flux is more related to BC column mass density than to precipitation over the Sichuan Basin.