沘江流域土壤和农作物重金属污染分布特征

Distribution Characteristics of Heavy Metal Pollution in Soil and Crops in the Pijiang River Basin

通过实地调查和实验室检验,分析了2016—2018年云龙县沘江流域农田土壤和农作物重金属污染时空变化特征,探究重金属污染来源。结果显示:①云龙县沘江流域土壤重金属污染属于重污染,其中镉富集最为严重,其次为铅和锌,砷含量较低。2016—2018年土壤重金属污染程度有所减轻。②调查期间从入境上游到汇入澜沧江下游,农田土壤重金属含量先增后降,沿程污染特征分析与地质背景值及矿业活动相关。③调查区域内农作物的重金属存在不同程度的超标现象,其中以铅、镉含量超标最为普遍。在重金属的富集能力上表现为蔬菜类>谷物类>薯类。调查期间,农作物中的砷、锌元素未见明显富集现象;④相关性分析显示,土壤中的锌、铅、镉元素来源相近,农作物中的锌、铅、镉含量也受相似因素的影响,但土壤重金属污染只是农作物重金属富集的影响因素之一。

Through field surveys and laboratory tests,the characteristics of the spatiotemporal changes of heavy metal pollution in farmland soils and crops along the Pijiang River Basin in Yunlong County were analyzed from 2016 to 2018 to explore the sources of heavy metal pollution.The results showed that the heavy metal pollution in the soil of Pijiang River was heavy,of which cadmium was the most concentrated,followed by lead and zinc,and the arsenic content was low.From 2016 to 2018,the degree of heavy metal pollution in the soil has eased.During the survey,from the upper reaches of the county to the lower reaches of Lancang River,the heavy metal content in the farmland soil increased first and then decreased.The analysis of pollution characteristics along the way is related to geological background values and mining activities.Excessive levels of heavy metals in crops exist in the survey area,and lead and cadmium contents are the most common.The concentration of heavy metals is expressed as vegetables more than cereals,and more than potatoes.There was no obvious enrichment of arsenic and zinc in crops.Correlation analysis showed that the sources of zinc,lead,and cadmium in the soil are similar,and the content of zinc,lead,and cadmium in crops is also affected by similar factors,but soil heavy metal pollution is only one of the factors affecting the heavy metal enrichment of crops.