岩溶地下河表层沉积物多环芳烃的污染及生态风险研究

为了解重庆南山老龙洞岩溶地下河表层沉积物中多环芳烃(polycyclic aromatic hydrocarbons,PAHs)的污染特征及生态风险,分析了地下河上游及出口表层沉积物样品中16种优先控制PAHs的含量和组成.结果表明,沉积物中PAHs总量在58.2~3 598 ng·g-1之间,大部分在100~5 000 ng·g-1之间,处于中等到高污染水平;从组成来看,老龙洞组成以2~4环为主,占到75.1%,仙女洞以4~6环相对富集,其比例为56.6%;老龙洞沉积物中PAHs主要来源于上游水体传输及地表土壤的输入,PAHs在地下河管道中的迁移表现为2~3环PAHs迁移距离远,4~6环的PAHs被强烈地吸附于沉积物中,迁移能力不足,从而富集于地下河管道中;生态风险评价结果表明,老龙洞沉积物PAHs很少产生负面生态效应,而仙女洞沉积物产生负面生态效应概率较大,一旦PAHs逐渐往下游迁移,将对下游的生态构成威胁.

Contamination and Ecological Risk Assessment of Polycyclic Aromatic Hydrocarbons in Surface Sediment in Karst Underground River

In order to understand pollution characteristics and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in surface sediment from Laolongdong underground river, the concentration and composition of 16 priority PAHs were analyzed. The results showed that the total concentrations of PAHs ranged from 58.2 to 3598 ng·g^-1, and most of the values were between 100 and 5000 ng·g^-1. It means that sediments in the river were moderately and heavily polluted by PAHs. The PAH composition were dominated by 2-4 rings (accounted for 75.1%) compounds in Laolongdong, while 4-6 rings PAHs accounted for 56.6% in Xiannvdong. Sediments in Laolongdong mainly came from the transportation of the upstream water and surface soil. 2-3 rings PAHs had higher transport capability with farther migration distance, while 4-6 rings PAHs had lower transport capability and shorter migration distance in the conduit, because 4-6 rings PAHs could be easily absorbed by sediments. The result of ecological assessment of PAHs showed that the ecological risk level in Laolongdong was low, leading to little negative ecological impact. However, the level in Xiannvdong was high. Once PAHs migrated from upstream to downstream, it would result in ecological threat for the downstream area.