海口市南渡江流域河塘底泥重金属污染特征及评价

以基于内梅罗综合污染评价方法和GIS空间分析法,分析了海口市南渡江流域典型河塘底泥0-30cm层Cu、Zn、Pb、Cd、Cr、Ni、As、Hg等8种重金属元素含量、污染状况、空间分布特征及污染原因.结果发现：1）该河塘底泥重金属污染物主要为Cd和Cu,含量平均值分别为0.43mg·kg^-1和78.60mg·kg^-1,超标幅度分别为41.51％和36.71％.2）重金属综合污染指数评价表明该河塘底泥存重金属污染是以“轻微污染”和“中度污染”为主,轻微及以下等级的污染区域占总面积的74.20％,“中度污染”区域占总面积的25.80％;底泥重金属污染具有较强的空间异质性,上游6种重金属含量变异系数大于下游;上游底泥Pb、As含量均值高于下游,而Cr、Ni、Cu、Zn、Cd、Hg含量低于下游,下游污染等级、污染面积较上游大.3） Hakanson潜在生态危害指数法评价结果显示,Cd和Hg元素具有一定潜在生态风险,河塘底泥处于“轻微生态危害”等级.4）河塘周边土壤及成土母质重金属背景值高、河塘附近采石场的弃土石场重金属含量高,是该河塘底泥重金属超标的主要原因;应该根据底泥的污染等级来决定其农业土地利用.

The Characteristic and Assessment of the Heavy Metal Pollution in Ponds sediment of Nandu River in Haikou City

Using Nemero pollution evaluation method and GIS, the content, the pollution condition, the spatial distribution characteristics and the pollution reason of the 8 kind of different heavy metal elements （Cu,Zn, Pb, Cd, Cr, Ni, As, Hg） in ponds sediment of Nandu River in Haikou city were analyzed. The result shows： （1） Among the surveyed heavy metals, Cd and Cu account for the key pollutants. The average value is 0.43 mg·kg^-1 and 78.60 mg·kg^-1, respectively. The exceeded amplitude is 41.51% and 36.71%, respectively. （2） The overall evaluation result shows most of heavy metal pollution in the sediment is light pollution and moderate pollution. The area of the light pollution level and below account for a total area of 74.20%. The area of the moderate pollution level and below account for a total area of 25.80%. Sediment of heavy metal pollution has strong spatial heterogeneity; The variation coefficient of 6 kinds of heavy metal content in upstream is greater than the variation coefficient in downstream. The average values of Pb and As in upstream are higher than the average values in downstream, but the average values of Cr,Ni,Cu,Zn,Cd,Hg are the opposite, the Pollution degree and Pollution area in downstream are bigger than the in upstream. （3） The results of evaluation of Hakanson potential ecological risk show that, The Cd and Hg elements have some potential ecological risk, and the sediments are in ＂slight ecological risk＂ level. （4）High content of heavy metals of the nearby soil and the soil parent material in the area, high content of heavy metals of rubble in the quarry near the river are the key reasons that the sediment exceed normal. There we suggest making use of the sediment reasonably according to different soil pollution degrees.