资源环境科技发展态势分析平台

Aerosol physiochemistry and sources in the background regions of North China Plain (NCP) remains poorly characterized. Here we present a comprehensive characterization of aerosol composition and sources at an NCP mountain site during heating periods (November 12 to December 24, 2018) using a Quadrupole Aerosol Mass Spectrometer (Q-AMS). The average mass concentration of non-refractory submicron aerosols (NR-PM₁) was 22.6 ± 29.9 μg/m³, in which organic aerosol (OA) and nitrate showed comparable contribution of 32.8% and 35.1%, respectively, followed by ammonium (15.3%), sulfate (13.9%) and chloride (2.6%). Secondary inorganic aerosol (SIA) was found to dominated in polluted days (70%) which the aerosol level is 15 times higher than that in clean days which dominated by organics (54%). In addition, organics, nitrate and sulfate showed similar unimodal size distributions peaked at 600–800 nm in polluted days, which appear to be internally mixed that originated from regional transportation of aged aerosol. Whereas, the different size distribution mode of organics with SIA that peaked at smaller particle size (200–300 nm) in cleans days suggested contributions from local emissions. Positive matrix factorization (PMF) and ME2 analysis showed oxidized organic aerosols (OOA) dominated the total OA (64%), while the contribution of the hydrocarbons-like OA (HOA) and biomass burning OA (BBOA) was comparable (15–21%). To evaluate the effect of air pollution control on the background aerosols chemistry, interannual variations in aerosol chemical compositions during heating periods in 2014–2018 were deduced combined with the trajectory cluster analysis. The results showed the aerosol source region was mainly from the urban agglomeration of NCP, which showed the largest decrease in aerosol mass concentration during the past five years. In addition, the aerosol compositions became to be SIA dominated gradually under different air mass influence condition, suggesting the air pollution control is more effective for the reduction of primary emissions than the secondary species.