嘉陵江亭子口水库沉积物重金属分布特征及风险评价

Distribution of the heavy metal contaminants and the corresponding eco-hazard risk assessment in the sediment of Tingzikou Reservoir of Jialing River

为了解嘉陵江亭子口水库表层沉积物中重金属污染水平及生态风险,采集干流表层沉积物样品,分析其中重金属元素Pb、Cu、Cd、Cr和Zn的全量;采用改进BCR法提取各元素赋存形态;从重金属全量、赋存形态、生物毒性和生物可利用性角度出发,采用地累积指数法(Igeo)、次生相与原生相比值法(RSP)、对数回归模型法及风险评价编码法(RAC)全面评价各元素的污染程度与生态风险。结果表明:1)各元素质量比均高于全国土壤元素背景值,Cd质量比高达背景值的14.63倍;2)Cu-Cd、Cu-Cr、Cd-Cr之间表现为强相关(p<0.01),各元素与p H值呈负相关,而OM与元素Cu、Zn之间表现为显著相关(p<0.05);3)各元素有效态百分比由大到小依次为Cd、Pb、Zn、Cu、Cr,Cd有效态质量分数超过80%,迁移转化和生物可利用性的风险较大;4)Igeo评价显示,Cd达到强污染水平;5)RSP评价显示,Cd二次释放污染可能性最高;6)对数回归模型评价显示,各元素都可能对水生生物造成危害;7)RAC评价表明,Cd、Zn具有中风险水平的潜在生态风险。研究表明:亭子口水库表层沉积物存在以Cd为首要因子的重金属污染和潜在生态风险;多种评价方法综合运用,能比较全面地反映重金属污染及风险的真实水平。

The given paper is aimed at study and examine the pollution level and the ecological risk of the heavy metal contaminants at the surface sediments of Tingzikou Reservoir,along the Jialing river,Sichuan.For the above said purpose,we have analyzed the total amounts of heavy metal elements,including those of Pb,Cu,Cd,Cr and Zn in the integrated forms of each element.That is to say,we have collected and extracted the samples of the surface sediments along the main stream and,then,assessed comprehensively biotoxicity and bioavailability from the aspects of the total contents in ten integrated forms,with the methods of geoaccumulation index(Igeo)and the modified BCR method.And,furthermore,we have done the secondary phase and primary comparison(RSP),the logistic regression model and the risk assessment coding method(RAC)to trace the pollution degree and the ecological risk degree of the said heavy metal elements.The results of the above examination and comparison show that:(1)The mass ratio of each element turns out to be higher than the background value indicators of the soil elements as is stated in China national standard level.As to the Cd mass ratio,14.63 times is higher than that of the background value as stated in the national standard;(2)Our examination and comparison also show that the existence of Cu-Cd,Cu-Cr,and Cd-Cr also shows a strong Pearson correlation(p<0.01),with each of them negatively correlated with the p H value.And,so is OM,which is significantly correlated with those of Cu and Zn(p<0.05);(3)The available percentage of each element can be seen in the following descending order:Cd>Pb>Zn>Cu>Cr.Among them,the available percentage order of Cd can be over 80%.This may show that the migration,transformation and bioavailability of Cd risk turns out to be greater than those of other elements;(4)The Igeo evaluation also shows that the risk of Cd can be said to reach a strong pollution degree;(5)The RSP evaluation shows that the highest possibility of the pollution release is that of Cd;(6)The logarithmic regression model evaluation also prove that each element may cause its own harm to the aquatic organisms;(7)The RAC assessment shows that Cd and Zn are actually also potentially ecological risk factors,though at the moderate risk level.Thus,it can be seen that the given studies can help to determine that there indeed exist heavy metal pollution and potential ecological risks with Cd as the primary factor in the surface sediments of Tingzikou Reservoir.The practical application of various assessment has fully reflected and disclosed the real harms of the heavy metal pollution risks.