湟水河流域西宁段河流表层沉积物重金属空间分布及生态风险评估

Spatial Distribution and Ecological Risk Assessment of Heavy Metals in Surface Sediments from Xining Section of the Huangshui River Basin

采集湟水河流域西宁段16个表层沉积物样品,运用电感耦合等离子体质谱和测汞仪测定了沉积物中重金属含量,结合污染负荷指数法、潜在生态风险指数法、沉积物质量基准法查明了流域表层沉积物重金属(Hg、Cr、Zn、Cu、Cd)污染现状、空间分布特征、潜在生态风险,使用聚类分析和Pearson相关分析方法分析了五种重金属可能来源。结果表明:(1)污染负荷指数法显示流域内主要污染元素为Hg、Cd。Hg从上游到下游呈现先升高后降低的趋势,Cd从上游到下游总体呈现升高趋势。(2)各重金属的潜在生态风险指数(Ei)依次为Hg>Cd>Cu>Cr>Zn,而综合潜在生态风险指数(RI)结果表明,中等生态风险以上等级的样品约占87.5%,严重生态风险的样点主要集中在北川河及湟水河中下游等受工、农业以及交通源污染较重的采样点位,各重金属生态风险指数在综合指数中占主导地位的为Hg与Cd,表明湟水河流域西宁段表层沉积物中Hg与Cd具有极强的生态风险。(3)沉积物质量基准法表明,流域内沉积物中五种重金属的毒性效应均较低,Cr对底栖生物产生毒性效应的可能性较大。(4)相关分析及聚类分析表明,Cr、Cu、Zn主要受自然源影响,Hg、Cd主要受工业活动等人为源影响。

In order to evaluate the pollution status,spatial distribution characteristics,potential ecological risk and possible sources of heavy metals( Hg,Cr,Zn,Cu,Cd),16 surface sediments were collected from Xining section of the Huangshui River Basin. The concentrations of heavy metals were analyzed using Inductively Coupled Plasma-Mass Spectrometry( ICP-MS) and Mercury Analyzer. Pollution load index( Pijand PLI),Hkanson potential ecological risk index( Eiand RI) and sediment quality guideline( SQGs) were calculated to evaluate the pollution degree of heavy metals in sediments. Pearson correlation analysis( PCA) and cluster analysis( CA)were used to deduce the potential sources of these elements. The PLI results showed that Xining section of the Huangshui River Basin were significantly contaminated by Hg and Cd. Hg increased firstly and then decreased from upstream to downstream,and Cd generally increased from upstream to downstream. The ecological hazards( Ei) for each heavy metals in a descending order were Hg> Cd> Cu>Cr> Zn. The comprehensive index of potential ecological risks( RI) for heavy metals indicated that 87. 5% of the 16 sediments samples had more than moderate ecological risks,and the sites with high RIs were generally located in Beichuan River and the midstream and downstream of the Huangshui River,which were heavily polluted by industrial,agricultural and transportation sources. In addition,the Eiof Hg and Cd were predominant components of RI,indicating that Xining section of the Huangshui River Basin is an area with extremely high potential ecological risk of Hg and Cd.The SQGs results indicated the toxic effects of these five heavy metals were low in the sediments,and Cr had a higher possibility of toxic effects on benthos. The PCA and CA results showed that Cr,Cu and Zn were mainly affected by natural sources. The major source of Hg and Cd was human activities( e.g.,industrial activities).