[Source Apportionment of PM2.5 in Suburban Area of Beijing-Tianjin-Hebei Region in Autumn and Winter].

: To identify the main sources of PM2.5 in Beijing-Tianjin-Hebei (BTH) region, PM2.5 samples were collected at four suburban sites in BTH region during autumn and winter in 2014-2015. Source apportionment of PM2.5 was conducted using the chemical mass balance model (CMB). It shows that the main sources of PM2.5 in autumn and winter were secondary aerosols (36%-58%), traffic (8%-26%), residential coal combustion (8%-16%), and biomass burning (5%-16%). Secondary nitrate was the most important source of PM2.5 at most sites during autumn and winter (11%-27%). The source apportionment at different pollution levels indicates that the coherence of the increasing trend of different sources among the four sites were much more obvious in autumn than in winter. Also, the increasing contribution of secondary sources (47.2-115.7 μg·m-3) was much higher than that of primary sources (29.5-43.4 μg·m-3) in autumn, but such trend was not significant in winter. The total contribution of coal combustion at suburban sites was quite similar to that in urban sites, but in suburban areas residential coal combustion dominates the contribution from coal combustion. Thus, it is very necessary for suburban areas of the BTH region to control emissions from residential coal combustion.