基于中国西部典型河谷盆地大气多环芳烃衍生物排放/演变的 污染过程识别及呼吸暴露风险

Lanzhou, a petrochemical industrialized city located in Northwest China with the typical valley-mountain topography where photochemical smog appeared earliest in China, is highly contaminated by PAHs pollution owning to its considerable high PAHs emissions.In addition,its typical mountain-valley topography and strong atmospheric inversion layer likely be bound to PAHs suffer from secondary transformation to their derivatives during photochemical processing.This project will investigate the seasonal variation and temporal and spatial distribution of parent PAHs and their derivatives in air, gas/particle partitioning,and particle size distribution characteristics based on the concentration of collected air samples.In this project,the samples including the gaseous and particulate matter samples（PM1.0、PM2.5、PM10）across Lanzhou valley-basin will be colledted with a diurnal interval for a period of one year, and the targeted parent PAHs and their derivatives such as oxy-, hydroxy- and nitro-PAH derivatives will be analysed. Based on above observational concentrations and automatic monitoring O3、NO2、NOx and meteorological data on the normal sites of local envirionmental monitoring, major efforts including the ratio of parent PAHs to their derivatives,the ratio of OC/EC and the ratio of PM2.5/PM10 will be made to identify the sources and processes of primary emission or secondary transformation of PAHs derivatives. In addition,this project will try to clarify the contributions of .PAHs derivatives to SOA, and secondary transformation mechanism by using online AMS analysis.Moreover, the inhalation cancer risk of local residents will be assessed based on the measured data of parent PAHs and their derivatives.Furthermore,this project will provide considerable insight into understanding those major factors that dominate local secondary transformation and inhalation risk of PAHs derivatives including primary emissions meteorology, topography and geography, and physical/chemical properties of individual PAH derivatives in a typical valley-basin.The scientific demostration of this project will contribute to the control and manegement and health risk of local air pollution to Lanzhou valley.

兰州为我国首个发生光化学烟雾的工业城市，其多环芳烃（PAHs）排放严重，封闭的河谷盆地和强逆温层为PAHs大气光化学氧化形成二次衍生物提供了特定的污染气象地理条件。本项目拟对比母体PAHs毒性更大的衍生物：硝基PAHs（Nitro-PAHs）、含氧PAHs（Oxy-PAHs）及羟基PAHs（OH-PAHs）大气气相及颗粒相（PM1.0、PM2.5、PM10）进行1年昼夜观测研究，拟阐明PAHs衍生物大气时空分布、气-固分配、粒径分布特征及其昼夜和季节差异；利用特征化合物比值、OC/EC比值、PM2.5/PM10比值、结合O3、NO2、NOx监测及气象数据识别一次排放或二次形成；结合在线AMS初步解析PAHs衍生物对SOA的贡献及其二次生成演变机制；基于观测数据对河谷盆地人群呼吸暴露风险进行评估；明确影响PAHs衍生物二次形成及健康风险主控因子，为区域大气污染整治及健康风险提供科学依据。

兰州是我国首个发生光化学烟雾的重工业城市，存在较高的VOCs、SVOCs（如PAHs）和NOx等O3前体物排放，较高NOx及O3可促进PAHs降解和PAHs衍生物二次形成，而其封闭的河谷盆地、高海拔、强逆温层又为光化学反应提供了特定的污染气象条件，使其成为识别二次过程的天然实验场。本课题研究了兰州大气PAHs及其衍生物污染季节差异，评估了呼吸暴露风险，识别了一次二次来源的贡献差异，主要结果如下：.1.∑16PAHs年均浓度为50.29±26.19 ng/m3，冬季较夏季高2.48倍，BaP冬夏季分别超出国标二级的3.13和1.38倍，冬季采暖燃烧造成较高的PAHs排放；2-3环主要在气相，5-6环主要在颗粒相；在国内外为中等污染水平，主要来自燃煤、汽车尾气、炼焦、生物质燃烧等排放，冬季燃煤、炼焦等排放贡献明显增加。.2.∑12NPAHs年均浓度为4.38±2.00 ng/m3，冬季较夏季高约1.26倍；∑12NPAHs/∑16PAHs比值表明：日较夜、夏较冬贡献更高二次NPAHs，冬季一次排放主导大粒径NPAHs浓度，夏季二次形成主导气相、细粒径NPAHs浓度；2+3N-FLA/1N-PYR比值表明：冬季存在较强光化学反应；在国内外处于中等污染水平。空间浓度：工业区>城区>背景区，工业区大气氧化性和一次排放最强。.3.∑8OPAHs年均浓度为9.47±3.72 ng/m3，冬季较夏季高1.65倍;工业和背景区均气相夏季高于冬季，表明夏季主控气相中OPAHs浓度为二次过程，而城区则冬季浓度明显高于夏季，表明一次排放主导城区冬季浓度；在国内外为较轻污染水平；气相和颗粒相中9-FLU均为贡献占比最大的组分（均约60%）。.4.气溶胶组成表明：碳质气溶胶主要来自机动车尾气和燃煤排放，冬夏季分别为燃煤和机动车尾气贡献较高占比；SOC的质量浓度冬季较夏季高，表明其浓度水平受一次排放的主导；冬季较夏季更高的OC/EC比值表明OC在冬季也为一次排放主导；WSOC在细粒径上分布更高占比，二次贡献为主导。.5.WRF-CMAQ模拟表明，城区较郊区、男性较女性、儿童较成人存在更高的PAHs呼吸致癌风险；大气母体PAHs较NPAHs会造成当地居民更高的健康风险。