典型表层岩溶泉域系统多环芳烃的迁移研究

It is well known that karst groundwater is very important in southwest China. Due to the innate vulnerability and sensitivity, a karst system is easily polluted by PAHs. Precipitation events is an important driving force of promoting transport of PAHs. The distribution and transport of PAHs are primarily controlled by physical/chemical properties of the individual PAH species, dissolved organic matter and suspended organic and inorganic particles. However, the environmental behavior and relevant mechanism is less known in epikarst spring system in Southwest China. This should be emergent to be researched. Three typical epikarst spring system located in Nanchuan District, Chongqing were chosen in this study. Regular monitoring, high resolution of rainfall monitoring and experiment analysis will be used in this research. Aim to discuss response process of different molecular weight and forms of PAHs to rainfall event, analysis the importance influence of DOM and suspend particle matter on the transport of PAHs, and then reveal the transport process and mechanism of PAHs in karst epikarst spring system (transport from atmosphere to soil, seepage water, and spring). In order to reveal the role of atmosphere deposition and soil in PAHs transfer and preservation, quantify the contribution of rainfall event to PAHs content of spring water, a mass balance that weighs input of PAHs versus output from a karst spring was established. Based on contrasting the different migration and mechanism among the three springs (on behalf of different land use activities), the ability to regulate PAHs pollution of different land use (rocky desertification) will be discussed. The research will help to enhance the understanding the mechanism of PAHs pollution in karst system, and will provide scientific basis for controlling karst groundwater pollution.

岩溶系统先天的脆弱性和敏感性，极易受到PAHs的污染。降水事件是促进PAHs迁移的重要驱动力。PAHs本身的理化性质、溶解性有机质和颗粒物是影响PAHs迁移的关键因子。然而有关PAHs在我国西南表层岩溶泉域系统的环境行为及相关机制不够清楚。本项目以重庆南川区的3个典型表层岩溶泉为例，通过野外定期监测、高分辨率监测与实验分析，探讨不同形态PAHs对降雨的响应过程以及DOM和颗粒物对PAHs迁移的影响，揭示PAHs在表层岩溶泉域系统(大气、土壤、地下水)的迁移过程及机理。通过PAHs输入与输出质量平衡分析，揭示大气沉降及土壤层对表层岩溶泉水PAHs输入的作用以及降雨事件对PAHs迁移的贡献。对比代表不同土地利用的3个泉域PAHs迁移差异及机理，探讨不同土地利用(石漠化)对PAHs在表层岩溶泉污染的调控能力。研究有助于提高PAHs在岩溶系统污染机理的认识，为控制岩溶地下水污染提供科学依据。

岩溶系统先天的脆弱性和敏感性，极易受到PAHs的污染。然而有关PAHs在中国西南岩溶系统尤其是表层岩溶泉域系统的环境行为及相关机制不够清楚。本项目对岩溶流域大气、土壤、土壤渗透水和地下水PAHs进行系统观测，基于降雨事件对PAHs在表层岩溶泉域和地下河系统的迁移过程和影响因素开展系统研究，探讨不同土地利用、大气输入及土壤层对岩溶地下水PAHs污染的调控机理。取得的主要结果有：（1）岩溶系统土壤中PAHs的垂直分布受土地利用、PAHs排放强度和土壤性质的影响，土壤有机质可能成为PAHs向下迁移的主要载体。（2）降雨可能通过促进土壤中PAHs的溶解，增加土壤渗透水溶解态PAHs的浓度，并促进其向下迁移，DOM可能是土壤渗透水中中高环PAHs向下迁移的重要载体。（3）土壤中低分子量PAHs向下迁移的能力较高分子量PAHs强。（4）明确了大气气相转移、大气沉降输入、土壤和渗透水的垂直迁移是表层岩溶地下水PAHs的主要来源，但由于土壤的截留效应，即使是脆弱的岩溶系统，高分子量PAHs也很难迁移至地下水。（5）揭示了水动力是促进PAHs在表层岩溶泉域和地下河系统迁移的重要驱动力，DOM和颗粒携带是促进降雨过程中PAHs迁移的两个主要机制。（6）输入输出质量平衡表明大气输入的PAHs被土壤层有效截留，使得地下水输出PAHs比例很小。不同表层岩溶泉域由于土地利用、土壤性质（土层厚度和有机质等）和泉水流量的差异影响输入输出的比例。（7）明确了岩溶地下河系统地表PAHs主要以落水洞+地下河管道快速流和土壤渗透水+裂隙的慢速流两种途径进入地下河，而在表层岩溶泉域系统主要以溶解态的形式通过土壤渗透水向下迁移，构建了岩溶系统PAHs迁移概念模型。（8）重庆典型岩溶地下水PAHs污染水平相对较高，存在一定的健康风险，但地下水PAHs健康风险呈下降的趋势。这些结果有助于提高PAHs在岩溶系统污染机理的认识，为控制岩溶地下水污染提供科学依据。