Different variations in PM2.5 sources and their specific health risks in different periods in a heavily polluted area of the Beijing-Tianjin-Hebei region of China.

The temporal variations in source-specific health risks of airborne particles and the differences in estimated source contributions to PM 2.5 mass and PM 2.5 exposure in severely polluted areas with the implementation of control measures remain unclear. In this study, PM 2.5 samples were collected from a city of heavy pollution in the Beijing-Tianjin-Hebei region of China in two autumn-winter seasons during 2017–2019. The dominant species of PM 2.5 was SNA (sum of sulfate, nitrate, and ammonium; 34 %), organic matter (OM; 23 %), and fine soil (15 %). PM 2.5 concentration decreased across the years, whereas trace elements and OM showed the largest increases. A positive matrix factorization model combined with a health risk assessment method identified six sources, and quantified their specific health risks. The major sources of PM 2.5 mass were secondary source (37 %) and coal combustion (20 %). The health risks (non-cancer risk for children, and cancer risk for children and adults) exceeded the guidelines, and were dominated by industrial processes (38 % and 40 %) and coal combustion (22 % and 52 %). The interannual decline in PM 2.5 concentration was mainly due to reductions in biomass burning and soil dust, but the significant increase in health risks was attributed to the enhancement of industrial processes and coal combustion. On clean days, both PM 2.5 mass and health risks were significantly affected by industrial processes and soil dust. As PM 2.5 pollution increased, secondary source and coal combustion contributed significantly to PM 2.5 mass. Coal combustion posed high health risks during pollution and the heating periods, especially in 2018–2019. Mn, Cr, and As were the dominant elements responsible for source-specific health risks. The quantitative result highlights the different responses of PM 2.5 mass and health risks to recent mitigation measures, and suggests that both source concentrations and source-specific health risks should be of concern in the future. [Display omitted] • The responses of PM 2.5 mass and health risks to mitigation measures were different. • Enhanced industry and coal combustion caused the interannual rise in health risks. • Coal combustion posed high health risks during heavy pollution and heating periods. • Industrial processes exhibited the highest non-cancer risk. • Mn, Cr, and As were the dominators of source-specific health risks. [ABSTRACT FROM AUTHOR]