黄河下游滩区开封段土壤重金属分布特征及其潜在风险评价

Study on Distribution Characteristics and Potential Ecological Risk of Soil Heavy Metals in the Yellow River Beach Region in Kaifeng City

按照土壤采样规范,对开封段黄河滩区及滩外土壤采样,表层0～20 cm样品48个,垂直剖面采样100 cm,2个;并按照土壤化学分析方法,对Pb、Cr、Hg、As和Cd这5种重金属进行分析;最后,按照国家土壤一级标准,采用单因子污染指数、内梅罗综合污染指数和Hkanson潜在生态危害指数法对开封市黄河滩区土壤重金属分布特征、污染状况和潜在生态危害进行了分析.结果表明:①开封市黄河滩区土壤Pb、Cr、Hg、As和Cd这5种重金属含量就平均值而言,Cr的平均含量最大,Pb、Hg的平均含量最小.除Hg之外,其它重金属元素的变异系数均较小,说明重金属Hg存在较大差异;滩区土壤的主要污染元素为Hg、As、Pb,其中Pb的污染为普遍性污染.Cr和Cd在各村间变化不大,且含量均在国家一级标准(自然保护区)以下.②土壤各重金属元素的空间分布特征研究区内上下段之间分异明显,上段呈清洁状态,中段有少量污染,下段表现出明显富集的分布状态;③以黄河大堤为界,滩区内外重金属分异与居民点分布密切相关,在滩区上段(西南部)居民集中,土壤各重金属浓度较高,表现为沿河区<大堤外,中下游段(滩区东北部)重金属含量大于大堤外土地,下游段东北趋向于污染富集.④以重金属平均单项潜在生态风险指数(Eri)评价表明,开封市黄河滩区土壤Hg的潜在生态风险达到强烈水平,Pb在重金属综合潜在生态风险的贡献率高达50.5%,是最主要的生态风险重金属,各个重金属的污染程度为Hg>Pb>As>Cd>Cr.⑤各重金属生态危害的次序为Hg>Cd>As>Pb>Cr.由RI值对应的潜在生态风险等级可知,开封市黄河滩区土壤存在中等级别重金属潜在生态危害.

The distributions,soil environment status and potential ecological risk of heavy metals were studied in beach soil of returning the cropland into Yellow River beach region in Kaifeng by the Nemerows and Hkansons methods.The results showed that ① as Among the average contents of the five heavy metals Pb,Cr,Hg,As and Cd,the highest was the average content of Cr,and the lowest was the average content of Pb and Hg.In addition to Hg,the coefficients of variation of other heavy metals were relatively small,indicating that the content of heavy metals was quite different at different sites,and to some extent,relecting that Hg,As and Pb were the major elements polluting the soil,among which,Pb pollution was the pollution with universality.There was little difference in the contents of Cr and Cd from village to village the coefficient of variation was small,and the contents were below the national standard level.②There was significant difference in the spatial distribution of soil heavy metal elements in the upper,the middle and lower sections of the study area.The upper section was clean,the middle section was slightly polluted,and the lower section was enriched with pollutants.③The distribution of heavy metals in the beach region inside and outside the levees of Yellow River was closely related to the distribution of the residential regions.In the upper section of the beach region（southwest）,the population was large and the contents of heavy metals were high.The contents of heavy metals were lower in the near river zone than outside the levees of Yellow River.And the heavy metal contents in the middle and lower section were higher than those outside the levees of Yellow River,while the lower section（northwest） showed a tendency of pollution enrichment.④ In the view of the average individual potential ecological risk index of heavy metals（E r i）,the potential ecological risk of Hg reached intense levels,and the potential ecological risk of Pb ＇s contribution to the integrated risk was 50.5%,which was the heavy metal with highest ecological risks.Cd and Pb had a moderate ecological risk,while As and Cr had minor ecological risk.Ecological hazards of heavy metals ranked in the ascending order of Hg Pb As Cd Cr.⑤ The ecological hazard of the heavy metals was ranked in the order Hg Cd As Pb Cr.Based on the potential ecological risk level corresponding to the RI values,it was shown that there was moderate potential ecological risks of heavy metals in the Yellow River beach region in Kaifeng.