重庆老龙洞地下河间隙水重金属污染及毒性评估

为查明重庆岩溶地区老龙洞地下河重金属污染情况，于2013年9月采集了地下河上覆水体和表层沉积物间隙水共7组水样，用ICP-OES测定地下河上覆水体和表层沉积物间隙水中的Mn含量，ICP-MS测定Cu、Cd、Cr、As和Pb含量，分析了老龙洞地下河表层沉积物间隙水中各重金属元素的空间分布，对不同介质中的重金属元素进行相关性分析，并参考美国EPA推荐的“国家推荐水质标准”对间隙水中重金属可能产生的生物毒性进行评估。结果表明：老龙洞地下河上覆水体中Mn和Pb的浓度超过了GB 5749-2006规定的生活饮用水限值（Mn≤100 ug/L，Pb≤10 ug/L），不可作为饮用水源；间隙水中各重金属元素的浓度都比上覆水体高，有向上覆水体扩散的潜在可能性。除Pb、Mn外，间隙水中重金属的含量大小依次为上游>中游>下游。上覆水中除Mn与As、Cd与Cr外，其他金属元素之间的相关性不大；间隙水中Cr、Cu、As和Cd的相关系数分别为0.895～0.997，呈高度正相关。间隙水中金属元素除As不会对水生生态系统产生急性毒性外，Cr、Cu、Cd和Pb都会对水生生态系统产生急性毒性，尤以Cr、Cu、Cd最为严重。

Heavy metal pollution and toxicity assessment of interstitial water from Laolongdong subterranean river, Chongqing

With increasing urbanization and industrialization,karst subterranean river systems,an important source of drinking water in karst areas,have suffered from various degrees of pollution.Samples of overlying water and interstitial water from surface sediments were collected at the seven sampling sites along the Laolongdong subterranean river in Chongqing karst area during September 2013.Mn concentrations were measured by ICP-OES.and Cu,Cd,Cr,As and Pb were measured by ICP-MS,in order to determine the heavy metal pollution status.The spatial distribution of the heavy metals in the interstitial water and the relationships between metals in different media were studied.Meanwhile,the biological toxicity of the metals in interstitial water was assessed according to the National Recommended Water Quality Criteria released by the EPA.The results showed that the overlying water of Laolongdong subterranean river is not suitable for drinking,as the Mn and Pb levels were higher than limits（Mn≤100 ug/L,Pb≤10 ug/L） established by GB5749—2006.The concentrations of metals in the interstitial water samples were higher than those in the overlying water samples.This phenomenon probably indicates that the heavy metals may be released from the interstitial water into the overlying water.The concentrations of the studied metals（with the exception of Mn and Pb） in interstitial water decreased from upstream to midstream to downstream locations.Although statistical analysis suggested that there were no significant correlations between the concentrations of these metals occurring in overlying water,with the exception of Mn and As,as well as Cd and Cr,high correlations were found between Cu,Cd,Cr and As in interstitial water.Toxicity assessment of the interstitial water showed that Pb and especially Cr,Cu and Cd,pose acute toxicity to the aquatic ecosystem.However,As does not pose acute toxicity to the aquatic ecosystem.