土壤中镉(Cd)被作物吸收的程度及其生态风险取决于土壤中Cd的赋存形态,基于Cd有效形态的污染土壤风险评价及在此基础上制订污染土壤修复安全阈值是Cd污染农田土壤风险评价和治理亟待解决的问题。目前针对土壤中重金属有效态的化学浸提方法较多,但缺乏针对不同性质土壤中有效态Cd的普适性浸提方法已成为Cd污染土壤风险评价技术瓶颈。本研究采集了全国9个不同性质农田土壤,以水稻、小白菜和玉米为测试作物,通过外源添加方法制备Cd污染土壤,结合土壤培养和盆栽实验,测定了5种常用化学浸提方法,包括中性无机盐浸提方法(CaCl₂浸提法)、弱酸浸提法(HCl浸提法)、络合螯合剂浸提方法(DTPA和ETPA浸提法)和组合浸提方法(Mehlich-3(M3)浸提法)对不同性质土壤中有效态Cd浸提效果及其与作物Cd吸收的量化关系,筛选适用于不同性质土壤中有效态Cd的通用浸提方法。结果表明,不同化学浸提法提取的土壤有效态Cd含量间具有显著差异,不同浸提方法对土壤中Cd的浸提率(%)为DTPA≈EDTA≈HCl> M3≈CaCl₂。不同化学浸提态Cd与作物Cd吸收的相关系数间具有显著差异,基于综合相关系数方法,得出5种不同浸提态Cd与作物Cd吸收的综合相关系数为I_M3=0.765,I_EDTA=0.641,I_DTPA=0.627,I_HCl=0.606,$I_{CaCl_{2}}=0.711$,M3浸提态Cd含量与不同性质土壤中水稻、小白菜和玉米植株地上部Cd相关性最高,可作为不同性质土壤中有效态Cd通用浸提方法。相关研究结果可为农田土壤中Cd有效态评价及Cd污染农田的修复提供理论依据。

The degree of cadmium (Cd) uptake and transport in plants and its ecological risk are largely determined by the chemical form it takes in soils. In risk assessment of Cd contaminated farmland soils two urgent issues need to be addressed: risk assessment based on the effective form of Cd in soil, and formulation of safety threshold values for heavy metal remediation. Currently, although many effective chemical extraction methods are available for heavy metal remediation, there lacks a versatile extraction method for bioavailable Cd in soils with different soil properties. In this study, farmland soil samples of nine soil types in China are collected for soil culture and pot experiments using rice, Chinese cabbage, and corn as test crops. Chromium contaminated soil samples are prepared by exogenous addition methods. Overall, five commonly used chemical extraction methods—neutral inorganic salt (CaCl₂), weak acid (HCl), chelating agent (DTPA, ETPA), and combined (Mehlich-3, or M3) extraction methods—are tested to quantitatively evaluate the effectiveness of these methods for Cd extraction under different soil types and the relationship between Cd extracted from soils and Cd accumulation in crops, with the goal of finding an extraction method that is widely applicable in different soil types. Chromium bioavailability determined by different methods differed significantly (p<0.05), and the extraction rates (%) followed the order of DTPA≈EDTA≈HCl>M3≈CaCl₂. Through comprehensive correlation analysis, the comprehensive correlation coefficients (I_p) between Cd extracted from soil and Cd uptake in the shoots of crops were calculated for each method, yielding I_M3=0.765, I_EDTA=0.641, I_DTPA=0.627, I_HCl=0.606, $I_{CaCl_{2}}=0.711$. Thus, M3 was considered a versatile extraction method which showed the highest I_p values for rice, Chinese cabbage, and corn in soils with different soil properties. The above results provide a theoretical basis for the evaluation of Cd bioavailability in farmland soils and remediation of Cd contaminated farmland.