湘江水系沉积物重金属元素分布特征及风险评价

Distribution characteristics and ecological risk assessment of heavy metals in sediments from Xiang River

对湘江流域水系沉积物中9种重金属(As?Cd?Cr?Cu?Hg?Ni?Pb?Sb?Zn)含量进行统计分析,以地累积指数(Igeo)为参数分析了1982年以来湘江流域重金属污染程度的变化趋势,采用富集因子法和对数回归模型评价了重金属污染程度和潜在水生生物风险,并采用主成分分析法判别了重金属的可能污染来源.结果表明:湘江流域水系沉积物中重金属的空间分布极不均匀,近30a以来重金属元素的Igeo大体呈缓慢上升的趋势,长株潭地区和衡阳地区大部分重金属元素的Igeo逐渐降低.湘江流域污染程度最高的重金属元素为Cd,其次为As和Hg,郴州地区呈现出以Cd为主,多种重金属复合污染特征,具有很强的潜在水生生物危害性,是湘江流域污染最严重的地区.水系沉积物中重金属可能的2个主要污染来源为采选?冶炼废水的排放和尾矿库的泄漏,岩石的化学风化和河流的搬运作用.

The total contents of nine heavy metals(As、Cd、Cr、Cu、Hg、Ni、Pb、Sb、Zn)in sediments from Xiang River were analyzed. Geoaccumulation index(Igeo) was used to analyze the trend of pollution since 1982. The degrees of heavy metals pollution and potential aquatic organism risk were evaluated by using enrichment factor(EF) and logarithm regression models, respectively.Possible pollution source of heavy metals were deduced according to the results of principal component analysis(PCA). The results showed that the spatial distribution of these heavy metals in sediments in Xiang River were highly heterogeneous. In general, the Igeo of most heavy metals from whole Xiang River had increased slowly in the past 30 years with the exception that it decreased in the Changsha-Zhuzhou-Xiangtan section and Hengyang section. In Xiang River, the most polluted heavy metal was Cd, followed by As and Hg. ChenZhou was the most polluted area and its pollution could be characterized as the combined pollution dominated by Cd.There were two possible pollution sources of heavy metals in sediments. One source was the discharge of industrial wastewater including selecting and smelting wastewater, as well as the leakage of tailings ponds. The other source was the chemical weathering of rocks and river transportation.