三峡澎溪河回水区消落带岸边土壤重金属污染分布特征

在对澎溪河回水区消落带及岸边土样品中重金属含量和样品理化性质测定的基础上,重点分析了该区域内重金属分布特征,并对重金属元素间的相关性展开研究.同时,应用地累积指数对研究区域污染现状进行评价.结果表明,消落带样品中Cu、Cr、Zn、As、Cd、Pb、Hg的平均含量分别为28.17、59.21、108.98、4.77、2.02、28.85、0.52mg·kg-1;岸边土样品中重金属的含量范围分别为22.32、54.90、98.05、7.87、0.77、22.97、0.94mg·kg-1.Cd是三峡库区污染较严重的重金属元素.相关性分析表明：在消落带样品中,Cd与Zn显著相关（p〈0.01）,Pb、Hg和Cu、As都存在显著的正相关关系,说明这4种重金属元素在接受外来污染时可能存在相似性;在岸边土样品中,Cd与Zn、Cr与Cu、As与Hg显著相关（p〈0.01）,Pb与Cu、Cr、Zn、Cd显著正相关,表明这几种重金属可能有着相似的来源.消落带样品重金属污染程度评价结果为：Cd〉Hg〉Zn〉Pb〉Cu〉As〉Cr,岸边土样品重金属污染程度评价结果为：Hg〉Cd〉Zn〉As〉Pb〉Cu〉Cr,Cd和Hg在个别站位达到了严重污染水平.消落带土壤受人为扰动后会成为水体的二次污染源,因此,消落带土壤重金属对水体的潜在影响不容忽视.

Distribution and characteristics of heavy metals in soils of water-level-fluctuating zone of Pengxi River, Three Gorge Reservoir

The distribution and the correlation of heavy metals (Cu, Cr, Zn, As, Cd, Pb, Hg) in the surface sediment and soils of the water-level-fluctuating zone in the backwater reaches of Pengxi river were studied based on examining the heavy metal concentration and analyzing geochemical characteristics of samples. The contamination level and potential ecological risk of these elements were evaluated using the Geo-accumulation Index and Potential Ecological Risk Index. The result indicated that the average concentration of Cu, Cr, Zn, As, Cd, Pb, Hg in the soil of water-level-fluctuating zone was 28.17, 59.21, 108.98, 4.77, 2.02, 28.85, 0.52 mg·kg^-1, respectively, and it was 22.32, 54.90, 98.05, 7.87, 0.77, 22.97, 0.94 mg·kg^-1 in the surface sediment, respectively. Cd was highly polluted element in the Three Gorges Reservoir (TGR). Correlation analysis indicated that Cd had a significant correlation with Zn at 0.01 level, while Pb and Hg were significantly positively correlated with Cu and As in the soil of the water-level-fluctuating zone, indicating that these four heavy metals may be similar in response to external pollution. Cd was significantly correlated to Zn at 0.01 level, and so were Cr and Cu, As and Hg. Whereas Cu, Cr, Zn, and Cd were significantly positively correlated with Pb in surface sediments, indicating that these five heavy metals may have similar sources. The contamination level for the seven metals followed a descending order of Cd>Hg>Zn>Pb>Cu>As>Cr in the soil of water-level-fluctuating zone, and Hg>Cd>Zn>As>Pb>Cu>Cr in the surface sediment. Of the seven elements, Cd and Hg reached serious pollution level at some stations. The soil in the water-level-fluctuating zone can become a potential pollution source for the water column with disturbance. Therefore, close attention should be paid to the potential impact of heavy metals in this zone.