济南市污灌区土壤中Zn、As和Pb赋存形态特征及其风险评估

Chemical fractionation characteristic and risk assessment of Zn,As and Pb in sewage irrigation soils in Jinan city

污水作为一种替代性水资源曾经在我国缺水地区广泛应用到农田灌溉。因长期采用污水灌溉,导致污水中的重金属在土壤中累积,对农产品安全和区域生态造成严重影响。为探究典型污灌区土壤中重金属污染水平及空间分布特征,以济南市污灌区土壤作为研究对象,采用BCR连续提取法分析污灌区土壤中的Zn、As和Pb等重金属元素的赋存形态,同时通过地累积指数法、内梅罗综合指数法及潜在风险评价法系统评价济南市污灌区土壤中典型重金属的污染程度和生态风险。结果表明,济南市污灌区中Zn、As和Pb的平均含量分别为55.2、12.3和13.9 mg/kg,均高于背景值。化学赋存形态结果表明,土壤重金属Zn、As和Pb均以残渣态为主要赋存形态,其比例可分别高达51.4%、65.4%和55.4%。地累积污染指数结果表明,3种重金属元素均表现为无污染水平。通过使用潜在生态风险指数法进行评价,济南市污灌区土壤重金属生态风险均表现为轻微风险水平,其风险排序为As>Pb>Zn。综合潜在生态风险指数RI值范围为3.3~66.2,平均值为24.4,整体表现为中等风险水平。其中As为主要污染源,对综合潜在风险指数的贡献率达到58.4%。

Sewage,as an alternative water resource,was widely used in farmland irrigation in water-deficient areas in China.Because of long-term sewage irrigation,the heavy metals in sewage were accumulated in soil,which seriously threatened the safety of agricul⁃tural products and the regional ecological environment.To explore the pollution and distribution characteristics of typical heavy metals in sewage irrigated soil in Jinan,this study collected the soils from sewage irrigation areas in Jinan.The chemical fractionation of Zn,As and Pb was analyzed by using the improved BCR sequential extraction procedure,and the contamination status and ecological risk of Zn,As and Pb in the sewage irrigated soil was evaluated by utilizing the geo-accumulation index(Igeo).Nemerow index and poten⁃tial risk assessment methods.The results showed that the average contents of Zn,As and Pb in sewage irrigated soil were up to 55.2,12.3 and 13.9 mg/kg,respectively,which were higher than the background value.In terms of chemical fractionation,Zn,As and Pb were mainly in the form of residue fraction(F4),with an average proportion of 51.4%,65.4%and 55.4%,respectively.The Igeo showed that three heavy metal elements remained pollution-free.The potential ecological risk of the sewage irrigated soil was in the fol⁃lowing order As>Pb>Zn.The RI value of the comprehensive potential ecological risk index ranged from 3.3 to 66.2,with an average value of 24.4,which indicated that the sewage irrigated soil was at the level of medium risk.Arsenic was the main pollution source,with a contribution of 58.4%to the comprehensive potential risk index.