基于梯度扩散薄膜技术评估稻田土壤中镉的生物有效性

为了给重金属污染农田土壤的安全性评估提供方法学指导,以稻田土壤-水稻体系为对象,通过比较化学提取法(土壤溶液法和0.01 mol·L~(-1)Ca Cl2提取法)和梯度扩散薄膜技术(DGT)所提取的有效态镉(Cd)含量与水稻谷粒中Cd含量(0.06~2.16 mg·kg~(-1))的相关关系,阐述DGT是否能更准确评估Cd的生物有效性及其作用机理。结果表明,土壤Cd全量与谷粒中Cd含量、几种有效态Cd提取量均未显示出显著相关性,不能真实反映Cd的生物有效性。DGT提取的Cd含量与谷粒Cd含量的相关性系数(R_(线性)~2=0.89和R_(曲线)~2=0.94)高于土壤溶液法(R_(线性)~2=0.87和R_(曲线)~2=0.92)和0.01 mol·L~(-1)Ca Cl2提取法(R_(线性)~2=0.80和R_(曲线)~2=0.83),R值分析表明DGT技术模拟了根部吸收土壤Cd过程中土壤固-液释放补给动态过程。因此,与传统化学提取法相比,DGT技术能更好地预测Cd污染土壤(0.31~10.64 mg·kg~(-1))中Cd的生物有效性。

Evaluation of cadmium bioavailability via diffusive gradients in thin film technology for agricultural soils

Risk assessment of heavy metal pollution is important in the study of soil environments, though there is no agreed-upon conclusion about assessment methods, until now. Assessment methods for the potential risk of cadmium-polluted agricultural soils urgently need to be confirmed. In this study, a soil-rice system was developed to compare the accuracy and feasibility of different methods, including diffusive gradients in thin film technology (DGT) and traditional chemical extraction methods. The mechanism of DGT for evaluating Cd bioavailability was also discussed. There were significantly positive relationships between Cd concentrations obtained by the three extraction procedures and Cd concentrations in rice grain (0.06~2.16 mg·kg^-1). The correlation coefficients obtained by DGT (R_Linear²=0.89 and R_Curvilinear²=0.94) were much larger than those obtained by the soil solution method (R_Linear²=0.87 and R_Curvilinear²=0.92) and 0.01 mol·L^-1 CaCl₂ extraction method (R_Linear²=0.80 and R_Curvilinear²=0.83). In addition, R values obtained using the 2D DIFS model showed that the solid-liquid dynamic process was rapid in bulk soils, and R experimental values indicated a sustained supply of cadmium from soil solid to liquid. In general, DGT showed a more scientific prediction of Cd bioavailability in paddy soils with long-range Cd concentrations (0.31~10.64 mg·kg^-1). If in situ measurement prediction is successful, DGT will be a good prospect in standard settings for evaluating Cd contamination of paddy soils.