农业区旱地垂直剖面土壤中重金属赋存形态与生态风险评价

Speciation and the Ecological Risk Assessment of Heavy Metals in Vertical Profile Soil of Agricultural Area

用ICP-OES测定了厦门市农业区某旱地垂直剖面土壤中10种重金属元素的含量,并用改进的BCR四步连续提取法分析了垂直剖面土壤中6种重金属的赋存形态。结果表明,剖面土壤中Cd富集较严重,Pb主要以还原态为主,而Mn、Cu、Fe、V、Zn主要以残渣态存在;重金属生物有效性系数排序为Pb(0.514)>Mn(0.398)>Cu(0.221)>Fe(0.165)>V(0.100)>Zn(0.059 7),Pb和Mn的生物有效性较高,对环境存在较大的潜在生态危害。次生相与原生相分布比值法对重金属潜在生态风险评价的结果表明,Co、Zn、Fe、V、Cu和Mn处于无污染水平,Pb处于中度污染水平。潜在生态危害指数表明,垂直剖面土壤中潜在生态危害顺序为Cd>Cu>Pb>Cr>Zn,Cd的生态危害系数对多元素综合潜在生态风险的贡献最大,即Cd表现为首要的潜在生态风险因子。

Contents of 10 heavy metals in a soil profile of agricultural area in Xiamen City,China were analyzed by ICP-OES. The chemical speciation of heavy metals（ Mn,Cu,Fe,V,Zn,and Pb） was determined using modified BCR-four step sequential extraction procedure. Results show that Cd is enriched considerably in the soil profile. Pb mainly exists in the reducible fraction,while Mn,Cu,Fe,V and Zn mainly exist in the residual fraction. The sequence of bioavailability factors of heavy metals is Pb（ 0. 514）〉 Mn（ 0. 398）〉 Cu（ 0. 221） 〉Fe（ 0. 165） 〉V（ 0. 100） 〉Zn（ 0. 059 7）. Pb and Mn exhibit higher bioavailability and potential risk to environment. The ratios of secondary phase to primary phase of heavy metals show that Co,Zn,Fe,V,Cu and Mn present no pollution,while Pb presents moderate pollution. The potential ecological risk of heavy metals shows the order of Cd〉Cu〉Pb〉Cr〉Zn in the profile soil. Cd shows the highest contribution to the comprehensive potential risk of multi-elements,indicating that Cd is the worst of potential ecological risk genes.