黄河下游滩区开封段土壤重金属空间分异规律

Spatial variation of soil heavy metals in the beach of Lower Yellow River: A case study in Kaifeng Section

对黄河下游滩区开封段及滩外土壤采样48个,按照土壤化学分析方法,对铅(Pb)、铬(Cr)、汞(Hg)、砷(As)和镉(Cd)5种重金属进行分析,采用单因子污染指数、普通克里格法和相关分析对研究区土壤重金属含量特征、污染状况和分布特征进行了计算。结果表明:①研究区土壤5种重金属Pb、Cr、Hg、As和Cd含量就平均值而言,Cr的平均含量最大,Pb、Hg的平均含量最小。Pb、Cr、Hg、As和Cd4种重金属元素的变异系数在0.13～0.28之间,属于中等变异强度,Hg变异系数较大,Hg的空间差异相对较大;②重金属元素Pb、Cr、Hg、As、Cd之间具有较强的线性关系,可能具有共同来源——水沙输入;③主要污染元素为Hg、As、Pb,其中Pb的污染为中度污染且范围较广,而As和汞Hg构成三级轻度污染。Cr和Cd在各村间变化不大,Cr,Cd没有构成污染,且Cd是全部清洁表现出污染没有积累;④土壤各重金属元素的空间分布特征在研究区内上下段之间分异明显,上段呈清洁状态,中段有少量污染,下段表现出明显富集的分布状态。

In this paper we collected 48 soil samples in the surface levels of soil from 0-20 cm inside and outside the Yellow River beach in Kaifeng City. Based on the standard analysis methods of soil chemical composition, five heavy metals contents, including Lead （Pb）, Chromium （Cr）, Mercury （Hg）, Arsenic （As） and Cadmium （Cd） in soil are analyzed. Three different models of single-factor pollution index, Ordinary Kriging and correlation analysis are adapted respectively, to quantificationally study soil heavy metals contents, and also to calculate their pollutants and the spatial distribution in the study area. Eventually we obtain the following results. （1） In terms of the average content level of the five heavy metals, the average content of Cr is the highest, while those of Pb and Hg are the lowest. However, the spatial variation analysis used by the coefficients of variation demonstrated that the spatial variety of Hg content is the largest for its large variety coefficient, and the other 4 heavy metals （Pb, Cr, As and Cd ） are at the similar medium levels （0.13-0.28）. （2） There is a strong linear relationship between the heavy metal Pb, Cr, Hg, As, and Cd, which implies that the 5 soil heavy metals may have a same origin of the Yellow River sediment and water input. （3） The main pollution elements are Hg, As and Pb, among them, the pollution degree of Pb is moderate and its pollution range is relatively wide; As and Hg are at the third level of light pollution degree. Both Cr and Cd contents, which have not been polluted, have little difference from village to village. Cd content is at a very low level without pollutant accumulation. （4） The spatial distribution of soil heavy metals is significantly different from the upper to lower beach within the study area. The upper beach soil is relatively clean, and the middle beach is lightly polluted; while the lower beach soil shows a significant concentration of heavy metals.