地质高背景农田土壤中水稻对重金属的富集特征及风险预测

为了解地质高背景农田重金属的行为特征,对两个不同地区(浙江北部丘陵地区和广西中部岩溶地区)土壤和水稻子实中As、Cd、Pb、Ni、Cu和Zn的含量进行了分析,研究重金属的迁移富集差异及其主要影响因素,并以土壤理化参数和有效态重金属(EDTA提取态)为变量,建立两个研究地区水稻子实中重金属含量的最优经验预测方程。结果表明,在浙江研究区土壤中Cd和As超标明显,广西研究区土壤Pb、As和Cd超标严重;但从水稻子实重金属含量结果来看,只有Cd在浙江研究区超标。两个研究区重金属元素在水稻中的生物富集因子均较低,明显低于人为污染的农田;相关性分析和回归预测表明,土壤有效态重金属、pH、有机质和CaO是影响水稻子实重金属含量的主要因子。

Enrichment characteristics and risk prediction of heavy metals for rice grains growing in paddy soils with a high geological background

In this study, we determined the concentrations of As, Cd, Pb, Ni, Cu and Zn in paddy soils and rice grains from two study areas(Zhejiang and Guangxi) and analyzed the bioaccumulation factors and influencing factors in the soil-rice system. The optimal empirical equations to predict heavy metals in rice grains were established, which include available heavy metals(EDTA-extractive content) and the physicochemical parameters of soils. The results showed that the main excessive elements in soils were Cd and As in Zhejiang, whereas Pb, As and Cd concentrations in soils markedly exceeded the background values in Guangxi. However, only the Cd contents in rice grains from Zhejiang were greater than the national standard level. The bioaccumulation factors of heavy metals in rice grains were fairly low, and were significantly different from those of farmlands contaminated by anthropogenic sources. Correlation analysis and the regression prediction equation showed that available heavy metals, along with the pH, organic matters, and CaO values in soils were the key factors affecting the bioaccumulation of heavy metals in rice grains of the study areas.