加入SOA示踪的深圳大气PM2.5受体模型源解析

为厘清包括二次有机气溶胶（SOA）在内的深圳市区PM_2.5各种一次和二次来源贡献，本文于2017年9月2日~2018年8月29日在深圳市大学城点位开展PM_2.5样品采集，并进行化学组分和水溶性有机物（WSOM）质谱测量，共获得162组有效数据.观测期间深圳市大气PM_2.5平均质量浓度为26μg/m³，在传统PMF源解析的基础上加入羧基离子碎片（CO₂⁺）作为SOA的示踪物，加入水溶性有机氧（WSOO）用于计算各因子O/C，验证有机物解析效果.结果表明，SOA可以被独立解析出，其O/C明显高于其他一次污染源中有机物；机动车、二次硫酸盐、二次硝酸盐、SOA为最主要的4个源，对PM_2.5质量浓度的贡献分别为25%、23%、17%和10%，船舶、地面扬尘、老化海盐、建筑尘、生物质燃烧、燃煤和工业贡献均在5%以内.各个源的变化特征表明，机动车、二次硫酸盐、二次硝酸盐、SOA等源贡献呈现冬高夏低的季节特征，与冬季季风条件下源自内陆的污染传输密切相关.污染天气时，二次硝酸盐和SOA的贡献增加相对最显著，因此NOx和挥发性有机物是减排的关键.

Source apportionment of PM2.5 in Shenzhen based on receptor model with SOA tracer

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.