葫芦岛东北部土壤重金属分布特征及来源解析

Distribution characteristics and sources of soil heavy metals in soils in the area of northeastern Huludao City

选择典型辽宁省工矿型城市葫芦岛,以东北部的龙岗区、连山区和南票区为研究区,基于1:25万土地质量调查获取的重金属数据,分析探讨土壤重金属的分布特征、赋存形态及污染来源.结果发现:研究区表层和深层土壤8项重金属平均含量均高于辽宁省背景值,其中表层土壤Cd、Cu、Pb、Zn、Hg、As空间上呈现出龙港区沿海及内陆局部浓集的特点,Ni、Cr高值区主要分布在下白垩统和中侏罗统火山岩地层区.各重金属富集系数平均值表现为Cd>Hg>Pb>Zn>As>Cu>Cr>Ni,其中,Cd3.41、Hg2.93,空间上表现为大面积强烈富集.土壤中Cd主要以离子交换态为主,占全量的54.38%,生态风险最高.土壤剖面中Cd、Pb、Hg、Zn总体呈现出"表聚性"特征,而Cu、As、Cr、Ni呈现出"平稳性"特征,且不同成土母质对重金属具有明显的控制.各重金属单项污染指数平均值表现为Cd>Zn>Cu>Pb>Cr>Ni>As>Hg,其中Cd污染水平较高.来源分析显示,Zn、Cu、Cd、As、Pb主要受工业、交通、生活、采矿等人类活动的综合影响,Cr、Ni主要受地质背景控制,而Hg更多来源于煤炭燃烧.

Land quality geochemical assessment at a scale of 1:250,000 was carried out in the Longgang,Lianshan and Nanpiao districts in the northeast Huludao city,which is a typical industrial and mining city in Liaoning Province.Topsoil,deep soil,and samples from vertical profile were collected in the study area.To determine the dynamics of the soil heavy metals distribution patterns,concentrations and species of eight elements in samples of seven different size fractions were used.The results show that the average content of eight soil heavy metals in the topsoil and deep soils of the study area was higher than the background values of them in Liaoning Province,and the high concentrations of Cd,Cu,Pb,Zn,Hg,As in topsoil were delineated along the coast and inland areas of Longgang District.The high-value areas of Ni and Cr were mainly distributed above the Lower Cretaceous and Middle Jurassic volcanic rock strata.The average value of the enrichment coefficient of each heavy metal was Cd>Hg>Pb>Zn>As>Cu>Cr>Ni.Cd and Hg were strongly enriched in large areas in the study area with the average value of the enrichment coefficient 3.41 and Hg 2.93 respectively.Cd in soil is mainly in ion exchange fraction with the highest ecological risk,accounting for 54.38%of the total amount.In the soil profile,Cd,Pb,Hg and Zn show the characteristics of surface aggregation,while Cu,As,Cr and Ni show curves with a steady change.The distribution of heavy metals in soil was spatially consistent with that of parent material.The average value of the single pollution index of each heavy metal is Cd>Zn>Cu>Pb>Cr>Ni>As>Hg,of which Cd pollution level is higher.It is indicated that the distribution of Zn,Cu,Cd,As and Pb in topsoil are mainly affected by human activities such as industry,transportation,life and mining.The distribution of Cr and Ni are mainly parallel with geological background.High concentrations of Hg in soil are primarily caused by coal combustion.