Spatiotemporal Distributions and Source Apportionment of PM2.5-Bound Antimony in Beijing, China

Antimony (Sb) is a toxic heavy metal, and PM2.5-bound Sb (Sb-PM2.5) in the air impacts human health via inhalation pathways. In this study, we analyzed multiyear measurements of ambient Sb-PM2.5 in Beijing to characterize its spatiotemporal distributions, identify main sources, and predict future trends. The results show that ambient Sb-PM2.5 has been decreasing with fluctuations from 2005 to 2012 and decreased rapidly after 2013, which was likely a result of the government's enhanced air pollution control plan that targeted main sources of industrial Sb. Across the city, average Sb-PM2.5 concentrations were relatively higher at nonemission locomotive traffic sampling sites and in densely populated areas (9.45-19.45 ng/m(3)) and lower in background areas (0.6-0.9 ng/m(3)). Regional-scale emissions and local human activities both affected the spatial distributions of Sb-PM2.5. Notably, Sb-PM2.5 concentration increased by 58.3% from 2006 to 2013 in one suburban background area, indicating the changing emission distributions and intensities over the study period. A neural network model was developed and tested to predict future Sb-PM2.5 levels, results from which showed that with simulated massive reductions in coal supplies and a rapid boom in the waste incineration industry, Sb-PM2.5 concentration would vary in a smaller range (from 4.08 to 4.38 ng/m(3)) over the next decade as compared to the observed range during 2011-2018 (19.0-5.44 ng/m(3)). The impact of the continued expansion of the waste incineration industry on Sb-PM2.5 pollution needs to be considered in future emission control policies.