农用地土壤中7种重金属可提取态的测定

Determination of Seven Extractable Heavy Metals in Soil of Agricultural Land

该文以氯化钙溶液进行提取,采用电感耦合等离子体质谱法和原子荧光光谱法,测定农用地土壤中Cd,As,Pb,Cr,Cu,Zn,Ni等7种重金属可提取态,检出限在0.003~0.06 mg/kg之间。该方法用于4个可提取态质控样品的测定,测定值与推荐值基本相符,测定的相对标准偏差(n=8)在3.3%~9.1%之间。基于800余件农用地土壤样品的测定数据,对7种重金属可提取态与土壤pH值及重金属总量之间的关系进行了初步考察。结果表明,7个重金属可提取态和总量关系无明显相关性,仅在土壤酸性条件下可提取态Cd与总量Cd呈正相关性。7种重金属提取率大小顺序为Cd>Zn>Ni>Cu,As>Pb>Cr,其中Cd,Zn,Ni,Cu,Pb的提取率随土壤pH值的增大而迅速下降,而As,Cr在土壤碱性条件下的提取率略高于中酸性条件下的提取率。

In this paper,the extractable state of seven heavy metals,such as Cd,As,Pb,Cr,Cu,Zn and Ni in agricultural soil has been determined by using Inductively Coupled Plasma Mass Spectrometry and Atomic Fluorescence Spectrometry,and using calcium chloride solution as an extractant.The detection limits are between 0.003 and 0.06 mg/kg.The method is applied to the determination of four extractable quality control samples,and the measured values are basically consistent with the recommended values.The relative standard deviation(n=8)is between 3.3%and 9.1%.Based on the determination data of more than 800 samples of agricultural soil,the relationship between the extractable state of seven heavy metals and soil pH and total heavy metals has beem investigated.It is showed that there is no significant correlation between the extractable state and the total amount of the seven heavy metals,and the extractable Cd is positively correlated with the total Cd only under the acidic conditions of the soil.The order of extraction efficiency for seven heavy metals is Cd>Zn>Ni>Cu and As>Pb>Cr.The extraction efficiency of Cd,Zn,Ni,Cu and Pb will decrease rapidly accompanying with the increase of pH value in the soil.The extraction efficiency of As and Cr under alkaline conditions is slightly higher than that under medium and acidic conditions.