贺江水系沉积物重金属空间分布特征、来源及潜在生态风险

摘要

以珠江一级支流——贺江水系沉积物为研究对象,通过系统采集表层沉积物样品,利用电感耦合等离子质谱仪(ICP-MS)和电感耦合光发射光谱仪(ICP-OES)测定As、Cd、Co、Cr、Cu、Mn、Ni、Pb、Sb、Tl、V、Zn和Fe等金属元素含量,查明流域沉积物中重金属空间分布特征,结合主成分分析和相关性分析等探讨贺江流域表层水系沉积物中重金属的来源,并利用地累积指数法、富集因子法和生态风险指数法评估了沉积物中重金属污染状况和潜在生态风险.结果表明:贺江流域表层水系沉积物中重金属受到不同程度的人为活动影响,As、Cd、Cu、Mn、Pb、Sb、Tl和Zn的平均含量高于我国西南五省水系沉积物中的重金属的平均值,而其它元素含量相对较低;地累积指数法(Igeo)和富集因子法(EF)污染评价结果表明,贺江流域表层水系沉积物污染程度大小依次为Sb>As>Cd>Pb>Zn>Tl>Cu>Mn>Co>V>Ni>Cr,其中,未受Co、Cr、Ni和V污染;各金属Hakanson潜在生态风险指数irE大小依次为Sb>Tl>As>Cd>Pb>Cu>Co>Ni>Zn>V>Mn>Cr,重金属综合潜在生态风险指数(RI)为65.63～1142,其中,As、Cd、Sb和Tl的生态风险指数irE之和占综合指数RI的平均百分比为88.30％,表明As、Cd、Sb和Tl等4种重金属具有极强的生态风险;主成分分析提取的两个主成分的累积贡献率达到79.80％,结合野外调查资料和Pearson相关性分析结果,表明As、Cd、Cu、Mn、Pb、Sb、Tl、Zn主要源于农业生产活动、城镇生活污水、鱼养殖业和矿业活动的贡献,而Fe、Co、Cr、Ni和V则主要源于岩石自然风化的贡献.%In order to investigate the spatial distribution characteristics of heavy metals, and to discriminate their sources and potential ecological risks in surface sediments of the Hejiang River, a sum of 41surface sediment samples were collected. Total contents of As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Tl, V, Zn and Fe in these samples were measured by the inductively coupled plasma mass spectrometry (ICP-MS) and the inductive plasma optical emission spectrometry (ICP-OES). Principal component analysis (PCA) and Pearson correlation analysis were used to deduce its potential emission sources of these elements. Geo-accumulation index (Igeo), enrichment factor (EF) and the Hakanson's potential ecological risk index (Eirand RI) were calculated to evaluate the pollution degree and ecological risk level of heavy metals in sediments, respectively. Results showed that the contents of heavy metals in sediments were impacted by human activities in different extent, only the average contents of As, Cd, Cu, Mn, Pb, Sb, Tl and Zn were higher than the background values. The calculatedIgeos and EFs also showed that the contaminated degree of heavy metals in a descending order were Sb > As > Cd > Pb > Zn > Tl > Cu > Mn > Co > V > Ni > Cr, besides, the Hejiang River was not contaminated by Co, Ni, V and Cr. The ecological risk indexes (Eir) for all selected metals in a descending order were Sb > Tl > As > Cd > Pb > Cu > Co >Ni > Zn > V > Mn > Cr. Compared with the assessment results of Geo-accumulation index (Igeo) and enrichment factor (EF),irEcan more scientifically reflect the aquatic environmental quality and ecological hazards of sediments. Moreover, the comprehensive indexes of potential ecological risks (RI) for heavy metals ranged from 65.63 to 1142, and the sumEirvalue of As, Cd, Sb and Tl accounted for 88.30％ of RI, suggesting that the Hejiang River occured high potential ecological risk of As, Cd, Sb and Tl. The PCA results showed that the cumulative proportion of the first two components accounted for 79.80％ of the total variables, suggesting that As, Cd, Cu, Mn, Pb, Sb, Tl and Zn were controlled by anthropogenic source including agricultural activities, urban wastewater, aquaculture and mining industry, and Fe, Co, Cr, Ni and V were mainly contributed by natural sources such as rock weathering.