沱江干流岸边土壤营养盐和重金属分布特征

Distribution Characteristic of Nutrients and Heavy Metals in Shore Soil of Tuojiang River

为了解沱江干流岸边土壤中营养盐及重金属含量分布和污染特征,对沱江干流岸边土壤中总氮(TN)、总磷(TP)和6种重金属元素(Cu、Pb、Zn、Ni、Cr、As)的含量及空间分布分别进行了研究,并对营养盐和重金属污染状况进行定量评价。结果表明,沱江干流岸边土壤中总氮(TN)和总磷(TP)的平均含量分别为863.68 mg/kg和956.38 mg/kg,下游TN含量高于上游和中游,上游TP含量高于中游和下游。15个点位的营养盐(TN、TP)含量多数超过了加拿大安大略省环境和能源部发布的沉积物中能引起水环境生态风险效应的营养物含量评价标准,但仍属于多数底栖生物可以承受的污染水平。重金属Cu、Pb、Zn、Ni、Cr、As的平均含量分别为13.26、25.19、27.43、17.75、24.32、1.78 mg/kg。6种重金属分布整体均表现为下游>中游>上游,除As外,其余5种重金属含量分布趋势较为相似。相关性分析结果表明除As外,其余5种重金属两两之间呈显著正相关性。沱江干流岸边土壤6种重金属潜在生态危害排序为Pb>Ni>Cu>As>Cr>Zn,Pb为最主要的生态风险贡献因子。

The aim of this article was to explore the spatial distribution and pollution level of nutrients and heavy metals in shore soil of Tuojiang mainstreams.The spatial distribution of TN,TP and Cu,Pb,Zn,Ni,Cr and As in shore soil of Tuojiang mainstreams were analyzed respectively.The pollution level of nutrients and heavy metals were evaluated.It was found that the average contents of TN and TP were 863.68 and 956.38 mg/kg,respectively.The content of TN in the downstream was higher than that in the upstream and the middle.TP content in the upstream was higher than that in the middle and the downstream.Compared with the relative standards of Otario in Canada,the situation of the TN and TP contents in 15 sampling crosssections was not good,exceeding the limits of evaluation standard set by the environment department of Ontario for controlling content of nutrients which will cause ecological risks.The average contents of Cu,Pb,Zn,Ni,Cr and As in samples were 13.26,25.19,27.43,17.75,24.32 and 1.78 mg/kg,respectively.The distribution of 6 heavy metals contents generally as follows:downstream>midstream>upstream.Similar patterns of spatial distribution of Cu,Pb,Zn,Ni and Cr were observed and significant positive correlations existed among these 6 elements except As.The assessment results showed that order of pollution level of heavy metals was Pb>Ni>Cu>As>Cr>Zn,Pb was the primary element with ecological risk in shore soil of Tuojiang mainstreams.