重金属污染对土壤介电特性的影响规律研究

Study of the Impact of Heavy Metals Contamination on Dielectric Properties of Soils

研究重金属污染对土壤介电特性的影响规律,可为高频物探设备及地质雷达探测重金属污染以及评价提供重要的理论依据。以土壤铬(Cr)、镉(Cd)、铅(Pb)污染为例,在细砂、粉土、黏土3种土样中分别加入不同质量浓度的Cr、Cd、Pb污染液,利用介电常数仪测定不同含水率下土样的介电常数的变化特征,分析Cr、Cd、Pb污染液质量浓度、土壤含水率以及土壤颗粒粗细对介电常数的影响规律。结果表明,细砂、粉土、黏土在无污染条件下,控制介电常数变化的主导因素是土壤含水率和颗粒粒度径;在加入Cr、Cd、Pb污染液的情况下,当含水率大于15%,尤其是大于20%时,3种土样的介电常数均随重金属污染液质量浓度的增大而显著增大。土壤颗粒越细、越偏黏性,其介电常数对重金属污染质量浓度的变化越敏感。利用高频物探设备和地质雷达探测土壤重金属污染时,在黏性介质中,对Cr、Cd、Pb污染的探测效果好。

Dielectric properties of soils are the basis for using the high frequency geophysical equipment and ground penetrating radar to assesse and evaluate heavy metals incontaminated soils. Taking chromium （Cr）, cad- mium （Cd） and lead （Pb） as examples, this paper investigated the change in dielectric constants of three soil sam- ples - fine sand, silt and clay - using a dielectric constant instrument under different soil moisture contentafter add- ing Cr, Cd and Pb at different concentrations to the three soil samples. We analyzed the effect of Cr, Cd and Pb concentration, soil moisture, as well as soil particle size gradation on the dielectric constant. The results showed that without metal pollution, the dielectric constants of the three soils depended mainly on moisture and particle size gradation. After adding Cr, Cd and Pb, the dielectric constants of the soils increased significantly, especially when the soil moisture was higher than 20%. The dielectric constant is sensitive to soil texture, increasing with clay and silt contents. Therefore, the high frequency geophysical equipment and ground penetrating radar are more effective for detecting heavy medals in fine-texture soils dominated by clays and/or silts.