湟水河沉积物重金属空间分布与污染评价

Distribution and Assessment of Heavy Metals in Sediments of Huangshui River

文章采集湟水河西宁段表层沉积物样品14个,利用火焰原子吸收分光光度法对其中Cr、As、Pb、Cd、Zn 5种重金属的含量进行分析,揭示了湟水河西宁段表层沉积物重金属的空间分布特征,并用地积累指数法和潜在生态危害指数法对该流域重金属污染状况进行评价。结果表明,湟水河西宁段沉积物中Pb、Zn、Cr浓度低于各重金属的农用地土壤污染风险筛选值(《土壤环境质量农用地土壤污染风险管控标准(试行)》(GB15618-2018))120、250、200 mg/kg。As浓度的平均值为508.13 mg/kg,是青海省土壤元素背景值的36.30倍,农用地土壤污染风险管制值的4.23倍;Cd浓度的平均值为4.93 mg/kg,分别为青海省土壤元素背景值的35.99倍和农用地土壤污染风险管制值的1.64倍,严重超标。在湟水河西宁段,重金属污染风险极高,2种评价方法得到的结果一致,污染严重程度为Cd>As>Pb>Cr>Zn。Cd和As是湟水河西宁段沉积物生态风险的主要贡献元素,应重点研究加以防范。

Fourteen bottom sediments samples were collected from the Xining Section of Huangshui River.The samples were analyzed for heavy metals(Cr,As,Pb,Cd and Zn)by a flame atomic absorption spectrophotometry.The pollution assessment of heavy metals in the sediments was carried out using the geo-accumulation index and the potential ecological risk index.The results indicated that the contents of Pb、Zn and Cr in the sediments of Huangshui River were lower than120、250、200 mg/kg,which was the risk screening value of each heavy metal for soil contamination of agricultural land(GB15618-2018).The average value of As contents was 508.13 mg/kg.It was 36.30 times background contents of elements in Qinghai soils,and 4.23 times risk intervention values for soil contamination of agricultural land(GB15618-2018).The average value of Cd contents was 4.93 mg/kg.It was 35.99 times background contents of elements in Qinghai soils,and 1.64times risk intervention values.They exceeded the limit severely.The risk of heavy metal pollution was extremely high in the sediments from Xining Section of Huangshui River,the results obtained by the potential ecological risk index and the geoaccumulation index were consistent.The pollution severity was Cd>As>Pb>Cr>Zn.Cd and As were the main contributing elements to the ecological risk of the sediments in the Xining Section of the Huangshui River,which should be mainly studied and prevented.