岩溶地下河系统水环境中多环芳烃污染特征

Pollution Characteristics of Polycyclic Aromatic Hydrocarbons in Water Environment of Karst Underground River System

地下河作为岩溶地区的主要饮用水源地,对当地的经济和社会发展具有重要的支撑作用,但由于岩溶地区特殊的含水结构,使得多环芳烃(PAHs)有机污染物极易进入岩溶地下水环境中造成严重污染,影响水质安全。该研究选择了南宁市清水泉地下河作为典型地下河的代表,利用含量与组成分析法、同分异构体比值法和逸度方法开展多环芳烃污染特征研究。结果表明,地下水和表层沉积物中∑16PAHs浓度范围分别为276.76~460.12 ng/L、332.17~977.96 ng/g,PAHs浓度整体处于中低等污染水平。污染物排放及PAHs的理化性质使得PAHs浓度从上游至下游逐渐减少,但高环PAHs的比例逐渐升高。根据同分异构体比值法的源解析结果,研究区地下水中PAHs来源主要为上游的生物质燃烧源、中游的石油源和下游的混合源,沉积物与其有一定差异,中上游表征为生物质燃烧源,中下游表征为混合源。随着环数的增加,PAHs由向地下水中扩散转变为向沉积物中扩散,且有机碳的增加也会导致PAHs向沉积物中扩散。研究结果可以为岩溶地下水环境中PAHs污染物防治提供科学依据。

As the main source of drinking water in southern karst areas,underground rivers play an important supporting role in local economic and social development.However,due to the special aquifer structure in karst areas in South China,polycyclic aromatic hydrocarbons(PAHs)can easily enter the karst water environment of underground river and cause serious pollution,which will affect the water quality safety.In this study,Qingshuiquan underground river in Nanning City was selected as the representative of the typical underground river in South China,and the pollution characteristics of PAHs were studied by content and composition analysis,isomer ratio method and fugacity method.The total concentration of PAHs in groundwater and surface sediments was in the range of 276.76~460.12 ng/L,332.17~977.96 ng/g,respectively,and the overall PAHs content was at a medium and low pollution level.Pollutant discharge and physical and chemical properties of PAHs caused the concentration of PAHs to decrease gradually from upstream to downstream,but the proportion of high-cyclic PAHs increased gradually.According to the source analysis results of the ratio method,PAHs sources in groundwater of the study area were mainly biomass combustion sources in the upstream,oil sources in the middle and mixed sources in the downstream.Sediment and groundwater had some differences.The middle and upper reaches were the source of biomass combustion,while the middle and lower reaches were the mixed source.With the increase of the number of rings,PAHs diffused from groundwater to sediments.The increase of organic carbon would lead to PAHs easily diffusing into sediments.The results can provide scientific basis for the prevention and control of PAHs pollutants in karst groundwater environment.