雾霾期间含氧/氮多环芳烃的形成机制、来源及健康风险评估

Oxygenate polycyclic aromatic hydrocarbons (OPAHs) and nitrated-PAHs (NPAHs) are semi- or low volatile pollutants as the derivatives of PAHs. They are more toxic than their parent PAHs and could be to important contributors to the high toxicity of particles at extremely low concentrations. OPAHs and NPAHs can also be formed in the atmosphere by the direct photolysis of parent-PAHs or homogeneous and heterogeneous reactions between parent-PAHs and atmospheric oxidants (e.g., O3, OH and NO3). However, the exact mechanisms of OPAHs and NPAHs formation are not very clear at present, and it is difficult to identification the first emission and secondary formations. Hence, this study will collected PM2.5 and gaseous samples simultaneous in Beijing, Guangzhou, and Xi'an, the three typical urban cities during haze episode and non-haze period by four sampling periods (07:00-11:00, 11:00-15:00, 15:00-19:00, and 19:00-07:00) each day in winter and summer. The temporal variations, spatial distributions and gas/particle partitioning will be obtained in different pollution conditions. Combined the source spectral data and different model calculations, the source contributions will determinate. The possible mechanisms of homogeneous and heterogeneous reactions will be explored by combining O3, NOX, SO2, CO data and simple model calculations. The inhalation exposure levels of PAHs, OPAHs and NPAHs by BaPeq equivalent concentrations and ILCR risks will also be estimated. This work will provide new dataset for haze study, and provide important information for the migration, transformation and fate of PAHs.

含氧、含氮多环芳烃是比其本体多环芳烃毒性更大的半挥发或低挥发性污染物，其中多环芳烃与大气氧化试剂（O3、OH、NO3等）的均相和非均相反应是其主要来源。但目前对其形成机理了解还不充分。本研究拟在北京、广州、西安三个典型城市冬季和夏季的雾霾期和非雾霾期同时采集气态、颗粒态样品。每天分4个时段：07：00-11:00，11：00-15：00，15:00-19:00，19:00-07:00。获得不同污染条件下，目标物的时空变化特征及气固分配比；结合源谱数据及模型判断其主要来源及贡献；结合O3、NOX、SO2和CO等在线监测及简单的模型计算，探讨其可能存在的均相和非均相反应的机理，并判断其影响因素；进行呼吸风险暴露评估。该研究为我国雾霾的研究提供基础数据，并为PAHs的迁移转化及归宿提供数据资料。

北京、广州、西安是我国大气污染的典型地区。本研究对三个城市开展冬季和夏季的雾霾期和非雾霾期采集气态、颗粒态样品。分白天和晚上进样样品采集。其中西安市颗粒物污染最重，其次为北京，广州最轻。且三地的组成特征明显存在差异性。研究发现相对湿度和扩散系数是影响污染物的两个主要气象条件。根据源谱数据及模型（PMF）获得颗粒物多环芳烃的主要来源，不同功能区来源略有不同，其中固体燃料燃烧和机动车排放仍然是主要的来源。而OPAHs和NPAHs则主要为二次生成。根据PAHs的含量进行了呼吸风险暴露评估，结果发现冬季存在较高的风险，尤其是成年人风险较大。采用蒙塔卡罗风险评估对其不确定性及敏感性进行分析。发现供暖季致癌斜率因子（CSF）是主要的评价因子，而在非供暖期每日的呼吸暴露量则为最主要的评价因子。根据气象条件和气体数据很难获得PAHs的转化与它们之间的关系。本研究初步开展了烟雾箱实验。采用高分辨率的在线仪器（PTR-MS,HR-AMS,SPMS），发现在某些条件下，排入大气中的气态PAHs可以快速的转化为颗粒态。生成大量的二次粒子。该研究为我国雾霾的研究提供基础数据，并为PAHs的迁移转化及归宿提供数据资料。

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