宁夏沿黄城市带土壤重金属分布特征及其生态风险评价

Distribution Characteristics and Ecological Risk Assessment of Soil Heavy Metals of the City Belt of Ningxia Along the Yellow River

宁夏沿黄城市带是黄河中上游重要的产业聚集区,其土壤健康状况对黄河流域生态保护和高质量发展先行区建设具有重要意义。为摸清沿黄城市带土壤重金属现状及生态风险,该研究取样检测了该区域682个样点的土壤重金属元素含量,分析了其生态风险,并进行了溯源。研究结果表明:(1)宁夏沿黄城市带0~20 cm土壤砷(As)、铬(Cr)、铜(Cu)、锰(Mn)、铅(Pb)、锌(Zn)、镍(Ni)和镉(Cd)8种重金属元素平均值分别为(3.11±1.88)、(60.66±15.64)、(17.86±6.10)、(509.92±186.74)、(17.62±11.10)、(57.36±25.33)、(25.23±4.95)和(0.77±0.49) mg/kg。0~20 cm土层重金属元素平均含量均低于土壤背景值,也低于农用地土壤污染风险筛选值。0~5 cm土层重金属元素含量高于0~20 cm土层,且Cr、Mn、Zn和Cd 4种元素含量超过了土壤背景值。(2)沿黄城市带中As、Cr、Cu、Mn、Pb、Zn和Ni这7种元素对环境污染风险极低。大部分区域土壤Cd含量明显高于背景值,污染风险较高。(3)沿黄城市带重金属元素有5种来源,其中母质源对重金属来源贡献率最高,其次为农业和工业复合源、交通运输源,农业源和工业源对重金属元素贡献小。研究结果表明宁夏沿黄城市带土壤重金属有较高等级的Cd生态风险,值得关注。

The City Belt of Ningxia along the Yellow River is an important industrial cluster in the middle and upper reaches of the Yellow River,and the soil health of this region is significance to the construction of the Yellow River Basin Ecological Protection and High-Quality Development Zone.In this study,we tested the heavy metal content of 682 soil samples along the Yellow River urban belt,and analyzed ecological risks,and conducted traceability.The results are as follow:(1)The mean content of As,Cr,Cu,Mn,Pb,Zn,Ni and Cd in 0~20 cm surface soil were(3.11±1.88),(60.66±15.64),(17.86±6.10),(509.92±186.74),(17.62±11.10),(57.36±25.33),(25.23±4.95)and(0.77±0.49)mg/kg,respectively.The average content of heavy metal in 0~20 cm soil layer was lower than the soil background value,and also lower than the Screening Value of Soil Pollution Risk in Agricultural Land.The content of heavy metal in 0~5 cm soil layer was higher than 0~20 cm soil layer,and the content of Cr,Mn,Zn and Cd exceeded the soil background value.(2)The risk of environmental pollution from the seven elements As,Cr,Cu,Mn,Pb,Zn,and Ni in the urban belt along the Yellow River is extremely low.In most parts of the region,the soil Cd content was higher than the soil background value,causing higher ecological pollution risk.(3)There are five sources of soil heavy metal along the Yellow City Belt,among which the contribution rate of parent material is the highest,followed by the combined sources of agriculture-industry,transportation sources.The results of the study indicate that soil heavy metals in the urban belt along the Yellow River in Ningxia have a high level of Cd ecological risk,which is worthy of attention.