重庆城区大气-水界面过程对PAHs及其衍生物收支的影响

Nitrated (NPAH) and oxygenated polycyclic aromatic hydrocarbons (OPAH) have caused great concern because of their ubiquitous occurrence and higher toxicities than parent PAHs. PAHs and related derivatives are important organic pollutants in the atmosphere in Chongqing urban area. Atmospheric processes over the Three Gorge Reservoir (TGR) in Chongqing may bring contaminants into water and consequently aquatic ecosystems while scavenging from the atmosphere. In addition, pollutants in previously contaminated water may reemit into the atmospheric environment. It’s crucial to study the atmospheric processes for understanding the cycling and fate of organic pollutants in the TGR area. However, comprehensive study about the atmospheric processes of PAH especially their derivatives in air-water interface is scarce, especially in the TGR area. Therefore, in this study, typical urban area along Yangtze River in Chongqing will be chosen as sampling site. Atmosphere, water, atmospheric dry and wet deposition samples will be collected to conduct systematic and in-depth study on the characterization of atmospheric dry and wet deposition and the air-water exchange mechanism of PAH and related derivatives. The aims of this project are to investigate the source and formation mechanism of PAH and related derivatives; to explore the migrating and transforming course of PAH and related derivatives in air and water environment; to study the impact of air-water interaction on PAH and related derivatives in air and water in Chongqing urban area. This study will be helpful to understand the source, transport, transformation and fate of PAH and related derivatives in the TGR area. This study could also provide insightful environmental geochemical datasets of PAHs and related derivatives for further understanding their globle cycling.

近年来，硝基及含氧多环芳烃由于广泛存在于生态系统中，且毒性较母体多环芳烃（PAHs）更强而备受关注。PAH类物质是三峡库区大气中最重要的一类有机污染物。库区水体既可能是大气污染物的汇也可能是源，研究大气-水界面过程对于认识污染物在库区的循环及归趋至关重要。然而目前对PAH类污染物特别是PAH衍生物在气-水界面间的迁移转化还极度缺乏认识，三峡库区更甚。鉴于此，本项目拟在长江重庆段沿岸选择典型城区设立观测点，通过采集大气、水体及干、湿沉降样品，对PAHs及其衍生物的大气干、湿沉降特征及水-气交换规律开展系统性研究，探讨PAHs及其衍生物的来源成因及在大气与水体间的迁移机制，揭示大气-水界面作用对重庆城区大气和水体中PAHs及其衍生物收支的影响。本研究有助于揭示三峡库区PAHs及其衍生物来源、迁移变化规律及归趋，对进一步认识PAHs及其衍生物在三峡库区甚至全球的环境地球化学循环有着重要科学意义。

近年来，硝基及含氧多环芳烃由于广泛存在于生态系统中，且毒性较母体多环芳烃（PAHs）更强而备受关注。PAH类物质是三峡库区大气中最重要的一类有机污染物。库区水体既可能是大气污染物的汇也可能是源，研究大气-水界面过程对于认识污染物在库区的循环及归趋至关重要。然而目前对PAH类污染物特别是PAH衍生物在气-水界面间的迁移转化还极度缺乏认识，三峡库区更甚。鉴于此，本项目在长江重庆段沿岸选择了三个典型城区设立了观测点，通过采集大气、水体及干、湿沉降样品，对PAHs及其衍生物的大气干、湿沉降特征及水-气交换规律开展了系统性研究，探讨了PAHs及其衍生物的来源成因及在大气与水体间的迁移规律，揭示了大气-水界面作用对重庆城区大气和水体中PAHs及其衍生物收支的影响。主要研究结果：（1）PACs，特别是PAHs主要通过干沉降从大气中去除；（2）PACs的湿沉降主要受到降雨导致的颗粒物沉降控制，也与化合物的化学性质有关；（3）干沉降受到许多因素的影响，如化合物在大气中的气粒分配状态，在大气颗粒物中的粒径分布状态以及PACs的化学性质等；（4）PACs在水体中溶解相及颗粒相的分配主要受到悬浮颗粒物含量及化合物辛醇水分配系数的影响；（5）采用概率风险评估模型和非概率风险评估模型对水体中PACs引起的人体健康风险估算结果变化趋势类似但绝对值有差异，两者均发现婴儿对水体中PACs的暴露非常敏感，特别是皮肤暴露途径；（6）水-气交换模型结果表明，重庆城区低分子量PAHs具有从水体挥发进入大气的趋势，且挥发通量主要受到温度控制，而高分子量PAHs和所有的OPAHs均表现为从大气进入水体；（7）综合考虑大气干湿沉降与水-气交换过程，在重庆城区，水体是大气中PACs的汇。本研究有助于揭示三峡库区PAHs及其衍生物来源、迁移变化规律及归趋，对进一步认识PAHs及其衍生物在三峡库区的环境地球化学循环有着重要科学意义。