武清区典型蔬菜种植区土壤重金属的风险评估和空间分布特征

Risk assessment and spatial distribution characteristics of heavy metals in soil of typical vegetable planting areas in Wuqing

重金属污染已严重危害人类健康与粮食安全,为探明不同时期土壤重金属动态变化规律,采集了天津市武清区的95个农田表层土,并对样品中Pb、Cu、Cr、Ni、Zn、Cd和As的含量进行测定。基于地统计法分析农田土壤重金属空间分布规律,探讨2005年和2019年土壤重金属的累积、潜在生态风险以及土壤中重金属的空间分布特征。结果表明,除Ni以外,重金属Pb、Cu、Cr、Zn、Cd和As随着时间的推移累积污染不断增加。地累积指数和潜在生态风险指数结果表明,Cd和As是研究区生态风险的主要贡献者。2005年和2019年重金属空间特征表明,Cu、Cr、Ni、Zn和As具有相似的空间分布,高值区集中在研究区的西南部,Pb的高值区呈现面源污染,而Cd呈现明显的点源污染。研究区Cu主要受农业施肥的影响,Zn主要受农业施肥和污水灌溉的双重影响,As、Ni和Cr的污染主要来自成土母质,Cd可能来源于工业活动,Pb归因于交通尾气的排放。研究表明,武清区典型蔬菜种植土壤重金属累积的主要原因是工业排放以及污水灌溉。本研究明确了天津市武清区的土壤重金属空间分布特征及污染源,可为研究区污染控制和生态保护提供理论依据。

Heavy metal pollution has seriously endangered human health and food security.In order to explore the dynamic changes of heavy metals in soil in different periods,a total of 95 surface soil samples(bulk soil)were collected from Wuqing District,Tianjin,China.Then the heavy metals(i.e.,As,Cd,Cu,Cr,Ni,Pb,and Zn)concentrations in these simples were quantified.The spatial distribution of soil heavy metals in farmland was analyzed based on geostatistical analysis to explore the accumulation of heavy metals in soil,potential ecological risks and sources of heavy metals in soil.The results showed that the cumulative pollution of heavy metals Pb,Cu,Cr,Zn,Cd and As increased with time except Ni.The geoaccumulation index and potential ecological risk index indicated that Cd and As in the study area were the main contributors to the total ecological risk.The spatial characteristics of heavy metals in 2005 and 2019 showed that Cu,Cr,Ni,Zn and As had similar spatial distribution,the high-value areas were concentrated in the southwest of the study area.The highvalue areas of Pb showed non-point source pollution,while Cd showed obvious point source pollution.Cu was mainly affected by agricultural fertilization,Zn was mainly affected by agricultural fertilization and sewage irrigation.As,Ni and Cr was mainly caused by soil parent material.Cd might originate from industrial activities.Pb was attributed to traffic exhaust emissions.The study have shown that the main causes of heavy metal accumulation were industrial emissions and sewage irrigation.This study clarifies the spatial distribution characteristics and pollution sources of heavy metals in soil in Wuqing District,Tianjin,which can provide theoretical basis for pollution control and ecological protection in the study area.