青岛某燃煤电厂排污口邻近海域表层沉积物重金属生态风险评价

Ecological Risk Assessment of Heavy Metals in Surface Sediment near A Coal-fired Power Plant Sewage Outlet in Qingdao

沿海地区燃煤发电厂海水烟气脱硫系统长期、大量排放含有重金属的脱硫海水,可能会对排污口附近海域生态系统造成危害,然而目前关于这方面的研究尚少。本研究连续3年跟踪监测了该排污口附近海域表层沉积物中重金属As、Cd、Cr、Cu、Hg、Pb和Zn的含量,其平均浓度分别为3.54、0.36、26.22、18.04、0.04、24.37和47.21 mg·kg^(-1)。为降低传统沉积物重金属风险评价过程中的不确定性,分别采用Monte Carlo模拟与沉积物质量基准(SQGs)和潜在生态风险指数(PERI)相结合的概率方法对其生态危害进行了评价。SQGs结果显示,4次监测Cu、Pb和Cd分别以50%、65%和80%的概率处于低风险,其他4种重金属以90%以上的概率处于低风险。PERI结果显示,4次监测Hg分别以34.41%、79.72%、60.39%和85.91%的概率处于中等风险,其他6种重金属的潜在生态危害均以100%的概率为轻微程度,7种重金属的综合生态危害以90%以上的概率为轻微程度。总体来讲,4次监测沉积物中重金属污染程度均为轻微,表明燃煤电厂脱硫海水的长期排放并未造成排污口附近海域表层沉积物重金属的污染。同时,本文结果表明采用Monte Carlo模拟法与传统污染指数法相结合的概率方法能够更好地表征重金属的生态危害,为工业污染水域风险缓解提供更加详细的决策支持。

Large amounts of waste consisting of heavy metal-containing seawater are discharged from coal-fired power plants into adjacent seas daily,which is harmful to the ecosystem of the sea near the outfall.However,very few studies have been carried out on the ecological risk of these heavy metals.This study conducted a three-year continuous monitoring to the average concentrations of heavy metals in the surface sediments of the sea located near the outfall of a coal-fired power plant in Qingdao.The average concentrations of As,Cd,Cr,Cu,Hg,Pb and Zn were 3.54,0.36,26.22,18.04,0.04,24.37 and 47.21 mg·kg^(-1),respectively.In order to reduce the uncertainties in the traditional risk assessment of heavy metals in surface sediment,this study combined Monte Carlo simulations with sediment quality benchmarks(SQGs)and potential ecological risk index(PERI),respectively,to conduct the ecological risk assessment.The results of SQGs showed that,during the four sampling times,risk degrees of Cu,Pb and Cd were low with 50%,65%and 80%probability,respectively;As,Cr,Hg,and Zn were also at the low risk degree with more than 90%probability.The PERI results showed that,during the four sampling times,the risk de-gree of Hg was moderate with 34.41%,79.72%,60.39%and 85.91%probability,respectively;the potential eco-logical risk degree of the other six heavy metals were low with 100%probability.The combined ecological risk of these seven heavy metals was at the low degree with more than 90%probability.In general,the heavy metal con-tamination degree of sediment in the four monitoring times was low,indicating that the long-term discharge of des-ulfurized seawater from coal-fired power plants did not cause heavy metal contamination in the surface sediments near the outfall.Meanwhile,the results of this study revolved that the probabilistic approach combining Monte Carlo simulation and traditional pollution index method can better characterize the ecological risk of heavy metals and provide a detailed decision support for the risk mitigation of industrially polluted waters.