加入SOA示踪的深圳大气PM_2.5受体模型源解析

In order to identify the contribution of all primary and secondary sources, including secondary organic aerosol (SOA), of PM_2.5 in the urban area of Shenzhen, PM_2.5 samples were collected continuously from 2nd September, 2017 to 29th August, 2018 at Shenzhen university town. The chemical components of PM_2.5 and mass spectrometry of water-soluble organic matter (WSOM) were measured, with 162 valid datasets obtained. During the observation period, the mean annual mass concentration of PM_2.5 was 26 µg/m³. Based on the experience of traditional source apportionment of PM_2.5, the carboxylic acid ion fragment (CO₂⁺) was added to the PMF model as a tracer of SOA. The water-soluble organic oxygen (WSOO) was also added to the PMF model for the calculation of the O/C of each factor, which was used to verify the apportionment of organic matter. The results show that SOA could be resolved independently, and the O/C was significantly higher than that of the organic matters in primary sources. Vehicle emissions, secondary sulfate, secondary nitrate and SOA were the four main sources, accounting 25%, 23%, 17% and 10% to the mass concentration of PM_2.5, respectively. While ships emissions, fugitive dust, aged sea salt, building dust, biomass burning, coal combustion and industry emissions each contributed less than 5%. The variations of vehicle emissions, secondary sulfate, secondary nitrate and SOA showed higher mass concentrations in winter and lower in summer, which was closely related to the pollution transport from inland under the winter monsoon. The contribution of secondary nitrate and SOA significantly increased during the polluted days, therefore, NO_x and volatile organic compounds were the keys of emission reduction.