深圳市土壤重金属背景含量垂向分布与理化特征

为摸清深圳市6种常规重金属(Cd、Hg、Cr、Cu、Zn、Ni)在不同剖面层次的背景含量及垂向分布规律,探究土壤剖面重金属背景含量与理化参数的关系,在全市基本生态控制线区域布设土壤典型剖面样点50个,每个点位按A、B、C3层采集土壤样品共150个。结果表明,土壤剖面不同采样层次重金属背景含量存在显著差异,随着深度增加,Cr、Cu、Zn、Ni的背景含量呈现逐渐增加的规律,Cd和Hg的背景含量呈现先减少后增加的趋势。深圳市土壤剖面中6种重金属的背景含量相对较低,整体上略低于“七五”全国土壤环境背景值。土壤剖面理化参数存在典型的南方土壤特性,土壤pH值呈酸性,随着深度增加,土壤容重、Al₂O₃和Fe₂O₃含量逐渐增加,而有机质、CaO含量呈逐渐下降趋势,离子交换量呈先增加后减少趋势;土壤机械组成特征为砂粒最多、粉粒次之、粘粒最少。将土壤剖面重金属背景含量与理化参数进行相关性分析,发现Fe₂O₃、Al₂O₃和土壤机械组成与土壤重金属背景含量相关性最为显著。逐步多元线性回归分析表明,影响土壤重金属背景含量的理化参数依次为Fe₂O₃、Al₂O₃、机械组成和阳离子交换量。

Vertical distribution of background content of heavy metals and physicochemical parameters in soil of Shenzhen City

In order to find out the background content and vertical distribution of six conventional heavy metals (Cd, Hg, Cr, Cu, Zn and Ni), and to explore the relationship between the background content of heavy metals and the physicochemical parameters in different soil profile levels in Shenzhen, 50 typical soil profile sample points were laid out in the area of basic ecological control line, and 150 soil samples were collected at each point according to three layers A, B and C. The results showed that there were significant differences in the background contents of heavy metals in different sampling levels of soil profile. With the increase of depth, the background contents of Cr, Cu, Zn and Ni increased gradually, while Cd and Hg decreased first and then increased. The background contents of six heavy metals in Shenzhen soil profile were relatively low, which was slightly lower than the national soil environmental background values in the Seventh Five Year Plan. The physicochemical parameters of soil profile showed typical Southern soil characteristics. The pH values of soil were acidic. With the increased of depth, the soil bulk density, Al₂O₃and Fe₂O₃ contents increased gradually, while the contents of organic matter and CaO decreased gradually, and the cation exchange capacity increased first and then decreased; the characteristics of soil mechanical composition were that sand particles were the most, silt particles were the second, and clay particles were the least. The correlation between the background content of heavy metals and physicochemical parameters was analyzed, and it was found that Fe₂O₃, Al₂O₃ and soil mechanical composition had the most significant correlation with the background content of heavy metals in soil. The stepwise multiple linear regression analysis showed that the physicochemical parameters affecting the background content of heavy metals in soil were found to be Fe₂O₃, Al₂O₃, mechanical composition and cation exchange capacity.