城市重污染河流沉积物营养盐和重金属分布及潜在生态风险

Distribution and potential ecological risks of nutrient elements and heavy metals in sediments of a heavily polluted urban river

以南京市南河为研究对象,采集4个断面的沉积物柱状样(0~120 cm)分析其总氮(TN)、总磷(TP)、有机质(OM)及重金属(Cr、Ni、Cu、As、Cd、Hg、Pb和Zn)的含量,并采用潜在生态风险评价及相关性分析等方法,揭示黑臭河道底泥中营养元素和重金属的垂向分布特征及潜在生态风险。结果表明:南河沉积物中营养元素和重金属含量呈明显的空间差异特征,其中北部河段TN、TP和OM的含量明显高于南部;深度方向上,TN和TP均随深度先增加后减少,且在40~80 cm深度处含量最高。南河的南部和北部沉积物中重金属含量均较高,其中南部的Ni、Cd和Pb及北部的Cu、Hg和Zn的含量均为中部的2倍以上;深度方向上,除Hg和Zn外,各重金属含量在60 cm以内呈现随深度逐渐增加的趋势。潜在生态风险评价显示,各断面Hg和Cd均达到极强生态危害,其次是Ni和Zn,而As的危害程度相对较小。相关性分析显示,沉积物中Cu与TP、TN和OM呈极显著相关,Ni和Cr呈极显著正相关且都与Zn呈显著正相关,Cd、Pb、As和Zn之间两两呈显著正相关。总体上,南河底泥重金属及营养元素污染较严重,且存在复合污染的趋势。

To reveal the vertical distribution characteristics and potential ecological risk of nutrient elements and heavy metals in the sediment of a black and odorous urban river,taking the Nanhe River in Nanjing City as an example,sediment columnar samples(0~120 cm)from four sections were collected to analyze contents of total nitrogen(TN),total phosphorus(TP),organic matter(OM)and heavy metals(Cr,Ni,Cu,As,Cd,Hg,Pb,and Zn),and their potential ecological risk assessment and correlation analysis were studied.Results show that the nutrients and heavy metals in the sediment exhibited wide spatial differences,which is that the contents of TN,TP and OM in the sediments of northern section were significantly higher than those in the southern section.TN and TP increased with the depth and then decreased,with peaks at the depth of 40~80 cm.Contents of heavy metals in the southern and northern sections were higher,particularly the contents of Ni,Cd,and Pb in the sediments in the southern section and the contents of Cu,Hg,and Zn in the northern section reached more than twice of the middle section.Along the depth direction,except Hg and Zn,the content of heavy metals increased gradually with the depth within 60 cm.Potential ecological risk assessments showed that Hg and Cd in the sediments reached a very strong ecological hazard level,followed by Ni and Zn,while as showed little ecological hazard.Correlation analysis showed that Cu was significantly correlated with TP,TN,and OM,Ni and Cr were significantly positively correlated with Zn,and Cd,Pb,As,and Zn were significantly positively mutual-correlated.Heavy metals and nutrient elements in the sediment reached a high pollution level and showed a compound pollution trend.