重金属对淡水生物生态风险的物种敏感性分布评估

Assessing acute ecological risks of heavy metals to freshwater organisms by species sensitivity distributions

应用生态风险评价中的物种敏感性分布(SSD)方法构建了6种常见重金属元素(Cd,Cu,Hg,Pb,Zn和Mn)对淡水生物的SSD曲线.在此基础上,计算了6种重金属对不同生物的5%危害浓度(HC5)及其不同暴露浓度对生物的潜在影响比例(PAF),比较了脊椎动物和无脊椎动物(包括鱼类,甲壳类等)对6种重金属的敏感性以及不同重金属的急性生态风险(简称生态风险),并且评价了3个典型水体中常见重金属的联合生态风险.结果表明,6种重金属元素的HC5值的大小顺序为Cu<Cd<Hg<Zn<Pb<Mn.浓度小于10μg/L时,Cu,Hg和Cd的生态风险差异不大.在10μg/L的暴露浓度下,Cu、Hg和Cd均使全部物种中超过5%受到影响.随着浓度升高,Hg和Cu的生态风险迅速增大并超过Cd.当浓度达到1000μg/L,分别有88.31%和86.32%的物种会受到Hg和Cu的损害.Zn在浓度为10μg/L时生态风险接近于Cd,随着浓度升高其生态风险要低于Cd.Pb和Mn的生态风险相对较小.当重金属元素的浓度在不同的范围时,不同生物的敏感性大小顺序会发生变化.Hg对脊椎动物和鱼类以及Cu对无脊椎动物和甲壳类的生态风险较大.典型水体重金属生态风险的评估结果表明,黄河口的重金属联合生态风险明显高于长江铜陵段和杭州西湖.

Species sensitivity distributions （SSD） method was used to assess the ecological risk of six heavy metals （Cd, Cu, Hg, Pb, Zn and Mn） to freshwater organisms. The acute toxicity data （LC50 or ECs0） were collected from ECOTOX database and SSD curves were fitted based on BurrlII function. The acute ecological risks of the heavy metals and the sensitivity of different freshwater species （vertebrate and invertebrate） to these heavy metals were compared by the hazardous concentrations for 5% of the species （HC5） and the potential affected fractions （PAF）. The the HC5 values of the six heavy metals were in the order： Cu〈Cd〈Hg〈Zn〈Pb〈Mn. When exposure concentration was lower than 10μg/L, no significant differences in the ecological risks of Cu, Hg and Cd was observed. However, Cu, Hg and Cd exceeded the threshhold of 5% （PAF） at the exposure level of 10μg/L. The ecological risks of Cu and Hg increased rapidly and exceeded that of Cd as the exposure concentration increased. When came up to 1000μg/L, 88.31% and 86.32% of freshwater species would be affected by Hg and Cu, respectively. The ecological risk of Zn was close to Cd at exposure concentration of 10μg/L and became smaller with higher concentration, while the risk of Pb and Mn were relatively low. The order of sensitivity to freshwater organisms varied with different concentration of heavy metals. High ecological risks were observed when vertebrates （and fish） were exposure to Hg and invertebrates （and crustaceans） were exposure to Cu. The case studies showed that the ecological risk of heavy metals in the Yellow River Estuary was significantly higher than that in the Tongling section of the Yangtze River and that in the West Lake in Hangzhou.