土壤-甘蔗作物系统中镉的生物有效性研究

Cadmium Bioavailability in Soil-sugarcane System

采用田间调查及ICP-MS等技术手段结合,在广西采集田间甘蔗和甘蔗根际土,分别用乙酸(HAc)、乙二胺四乙酸二钠(EDTA-2Na)、氯化镁(MgCl2)3种化学提取方法和梯度扩散薄膜技术(DGT)提取甘蔗根际土中有效态镉(Cd)含量,研究其与甘蔗根、叶和茎中Cd含量之间的关系。简单相关分析表明,4种方法提取的有效态Cd含量都与甘蔗根和茎中Cd含量显著相关,但DGT的相关性优于化学提取方法。综合土壤pH、阳离子交换量(CEC)、有机质(OM%)和土壤颗粒组成等理化指标对土壤有效态Cd含量的影响,运用多元统计分析,确定两种主成分因子,建立了多元回归模型。结果表明,DGT技术模型融合了影响土壤Cd生物有效性的主要因子,预测结果几乎不受本研究所选取的土壤基本理化指标影响,因而是一种预测Cd生物有效性的较好方法。

The relationships between cadmium（Cd） bioavailability in soils and Cd concentrations in the roots, leaves and unpolished stalks of sugarcane were studied based on field investigation and the ICP-MS technique. Sugarcane samples and rhizosphere soils around them at 18 sites in Guangxi Province of China were collected and the concentrations of Cd were determined on acetic acid（HAc）, ethylenediaminetetraacetic acid disodium salt （EDTA-2Na）, magnesium chloride hexahydrate （MgCl2） extractions, and by diffusive gradients in thin films （DGT）. Although simple linear regression analyses between concentrations of Cd in plants and those in soils measured using DGT and chem- ical extractions showed very good fits in both roots and unpolished stalks, the correlation coefficients of those obtained by DGT were higher than those based on chemical extractions. Multivariate analyses were used to assess the impact of pH, cation exchanged capacity（CEC ）, soil organic matter（OM% ） and texture, two principal components were extracted and the linear regression models were established. These results indicated that the multiple linear regression of the DGT measurement quantitatively incorporates the main factors affecting the bioavailability of Cd in soils, predictions of the DGT model were hardly affected by the physical and chemical properties of soils chosen in this paper. The bioavailability of Cd in soils could be predicted more accurately by DGT than chemical extractions.