Long-Term Trend Of Ground-Level Pm2.5 Concentrations Over 2012-2017 In China

Ambient suspended fine particulate matter (PM2.5) is a greatest environmental risk factor for premature mortality. We adopted aerosol optical depth (AOD) retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument to produce annual-mean PM2.5 concentrations from 2012 to 2017 with a spatial resolution of 3km. A geographically weighted regression model was conducted using vertical- and hydroscopic-corrected AOD and meteorological data. The PM2.5 estimates were validated by the ground measurements, with R-2 and RMSE (MPE) of 0.79 and 18.26 (12.03) mu g/m(3). The results show that national average of PM2.5 concentration represented a 31% decline over five years, from 69.37 mu g/m(3) in 2013 to 43.85 mu g/m(3) in 2017, after a slightly rise (6%) during 2012-2013. Significant reduction was revealed in the Beijing-Tianjin-Hebei region, decreasing by 37.31% from 2013 to 2017. Despite low decline in some southeastern provinces, the national-mean PM2.5 concentration has decreased by 31%, indicating the effectiveness of the control policies issued by Chinese government in 2013. Nevertheless, efforts to improve air quality are still required to further reduce the mass concentration in China.