Spatiotemporal distributions and source apportionment of PM2.5-bound antimony in Beijing, China

Abstract

Antimony (Sb) is a toxic heavy metal, and PM_2.5-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/m³) and lower in background areas (0.6–0.9 ng/m³). 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/m³) over the next decade as compared to the observed range during 2011–2018 (19.0–5.44 ng/m³). 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.