天津市城区不同功能区绿地土壤重金属分布特征及来源研究

Distribution and sources of heavy metals in greenbelt soil in different functional zones of Tianjin City

对天津市中心城区内居住文教区、交通绿化带、工业区、公园、河岸5类功能区的绿地土壤中As、Cd、Cr、Cu、Hg、Ni、Pb、Zn进行了调查研究。结果表明:天津市绿地土壤中重金属累积程度Hg>Cd>Pb>Zn>Cu;As、Cr、Ni平均含量接近背景值。Pb、Zn、Cu、As在工业区绿地土壤中含量最高,Cd、Hg、Ni、Cr在河岸绿地土壤中含量最高。大气沉降是重金属进入绿地土壤的主要途径;大气沉降物质重金属平均含量和土壤背景值的比值与绿地土壤重金属累积系数显著相关。大气重金属沉降量的差异是造成不同功能区绿地土壤重金属差异的主要原因;河岸绿地还受到河道污水灌溉和河道底泥的影响;生产和生活垃圾也可能造成重金属的局部累积。

This study investigated the elements of As,Cd,Cr,Cu,Hg,Ni,Pb,and Zn in greenbelt soil in five types of functional zones in the urban area of Tianjin City,namely residential and educational zones,traffic greenbelts,industrial zones,parks,and river banks.The results are as follows.The overall accumulationof heavy metals in the greenbelt soil is in the order Hg>Cd>Pb>Zn>Cu,with the average content of As,Cr,and niapproximating to the background values.Pb,Zn,Cu,and as have the highest content in the greenbelt soil in industrial zones,while Cd,Hg,Ni,and Cr have the highest content in river banks.Heavy metals mainly migrate intogreenbelt soil by means of atmospheric deposition.Moreover,the accumulation coefficient of heavy metals in greenbelt soil is significantly correlated with the ratio of the average content of heavy metals in atmospheric deposition and the background value of the heavy metals in the soil.Meanwhile,the difference in heavy metal content between the greenbelt soil in different functional zones are mainly caused bythe difference in the quantity of the heavy metals in the atmospheric deposition.Besides,the greenbelt soil on river banks is also affected by sewage irrigation and river sediments,and industrial and household waste may also cause local accumulation of heavy metals.