三峡库区云阳消落带土壤重金属形态及其在植物中的富集和转移

Soil heavy metal's form and their enrichment and transfer in plants in the water level fluctuating zone at Yunyang in Three Gorge reservoir area

三峡大坝建成蓄水以来,其夏涨秋消的调度方式使得每年5-10月份在海拔145～175m范围内形成291.1km2的消落带。本文通过分析云阳消落带土壤重金属含量及其形态和重金属在消落带植物体根、茎、叶的分布,以及植物对重金属的生物富集和转移系数,来研究消落带重金属污染情况及重金属在土壤-植被的富集和转移规律。研究结果表明,云阳消落带存在较为严重的Cd污染,单因子污染指数为5.02,内梅罗综合污染指数为3.637;Cd和Cr主要是生物毒性不强残渣态;Cu形态主要是金属可交换态和碳酸盐结合态,生物毒性比较强;Mn的形态主要是铁锰结合态;Pb的形态分配比例均匀,生物毒性较弱。可交换态与转移系数极显著正相关,相关系数为0.981;有机及硫化物结合态与富集系数显著正相关,相关系数为0.905;铁锰结合态、碳酸盐结合态和残渣晶格结合态对富集和转移系数贡献都不大。三峡库区消落带重金属在植物体内的富集、转移主要由土壤中重金属可交换态和有机及硫化物结合态的性质决定。

Caused by water level rise in summer and drop in autumn, 291.1 km2 of water level fluctuating zone （WLFZ） has formed in the region between 145 to 175 m above sea level from May to October after the Three Gorge Dam being built. Through analyzing on the soil heavy metal＇s content and form as well as dis- tribution in the root, stem and leaf of the plants, and on the heavy metal＇s enrichment and transfer coeffi- cients from soil to the plant in Yunyang WLFZ, the heavy metal pollution and the enrichment and transfer law are studied in the paper. The results show that there is heavy cadmium pollution in Yunyang WLFZ with the single factor pollution index and Nemerow comprehensive pollution index being 5.02 and 3. 637 respec- tively; that the pollutants cadmium and chromium assume residual form with weak bio-toxicity; the pollu- tant Cu assumes exchangeable form or combined form with carbonate with relatively strong bio-toxicity; the Mn the combined form with iron; and that the distribution ratio of Pb is quite uniform with weak bio-toxici- ty. The exchangeable form is highly positive correlated with the transfer coefficient and the related coeffi- cient is 0. 981. The combined form of organic matter and sulfide is highly positive correlated with the enrich- ment coefficient and the related coefficient is 0. 905. The contribute ratios of the Fe-Mn combined form and the carbonate as well as the residual combined form to the enrichment and transfer coefficients are small. The enrichment and transfer of heavy metals from soil to plant are mainly controlled by the properties of the heavy metals＇ exchangeable form and the combined form of organic matter and sulfide.