Characteristics and sources of aerosol pollution at a polluted rural site southwest in Beijing, China.

Annual average PM concentration in south Beijing was 30% and 40% higher than the whole Beijing city in 2015 and 2016, respectively. Few studies have been conducted to investigate what leads to the characteristics and sources of heavy pollution in the south rural area of Beijing. This study conducted an observation with Aerosol Chemical Speciation Monitor (ACSM) at a southwest rural site (Liulihe) in Beijing during 2014-2016, to investigate the seasonal aerosol characteristics and their sources. Positive matrix factorization (PMF) algorithm was used to distinguish different components of organic aerosol measured by ACSM. Biomass burning is an important pollution source, mainly due to the open burning after harvest season in autumn, regional transport in spring, and local residential biofuel use in winter. Coal consumption is the largest primary organic aerosol source in winter. Heavy duty diesel trucks contributed significantly to organic aerosol at night-time in the rural area. Results of this study show residential solid fuel burning is the most important source of aerosol pollution in the rural area of Beijing and the results focusing on urban Beijing might have underestimate the contribution from residential emissions in the Beijing-Tianjin-Hebei region.