[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 3 598 ng x g(-1), and most of the values were between 100 and 5 000 ng x 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.