土壤-植物系统重金属镉、锌生物有效性的数学模型评价

植物对土壤中重金属的吸收是一个非线性的过程.由于土壤和植物参数测定具有相当难度,经验模型而非理论模型常被用于评价和预测土壤—植物系统中重金属的生物有效性.在已发表的文献中,弗兰德利希模型(Freundlich typemodel)已被一些学者实际应用于预测和评价植物对土壤中重金属的吸收.重金属的生物有效性与土壤中重金属的总量、pH和有机质含量具有极为密切的关系.然而,对同时建立于上述3个参数的重金属生物有效性的数学评价模型的实际应用还未得到验证.为此,在对已发表文献的数据进行分析的基础上,采用多元回归的方法,建立了基于土壤重金属全量、pH和有机质含量为参数的重金属生物有效性评价模型.实际分析表明,虽然模型中各参数的系数因土壤类型、气候和作物种类而不同,两模型均能很好地评价和预测作物对土壤重金属镉的吸收.与弗兰德利希模型相比较,所建数学模型能更精确地评价土壤—植物系统中重金属锌的生物有效性.

Cadmium and Zinc Transfer from Soil to Plant:Potential Use of Two Mathematical Models

Transfer of heavy metal from soils to plant is very important from both the agricultural and environmental viewpoints, and it is described as a nonlinear process. Generally due to difficultly determining soil and plant parameters, it was empirical models rather than mechanistic models that were practically used to predict plant heavy metal concentration from soils. Freundlich-type function (Cplant=b×Casoil) has been successfully used to predict heavy metal uptake from soils to plant in published literature. It is well understood that heavy metal bioavailability in soil has close relative to total soil metal content, soil pH and soil organic matter, however, actual prediction of metal uptake based simultaneously on these three soil parameters has not generally been tested. We therefore reanalyzed available data sets from published literature with the method of multiple regression analysis, aimed at evaluating the potential use of Freundlich-type functions and an equation in the form of log(Mplant)=a+b.(pHsoil)+c.log(MT/OM)to predict Cd and Zn concentration in plants. Results suggest that the equation, which based on soil pH (pHsoil),total soil metal content (MT) and organic matter (OM), was reasonably predictive of aboveground plant tissue Cd and Zn concentration, (Mplant), although the coefficients a, b, and c varied with the particular soil, climate and crop type. Both Equations were suitable to predict Cd uptake by plants. Compared with Freundlich-type functions, the equation including three soil parameters (soil pH, total soil metal content, organic matter) was more suitable to predict Zn transfer from soils to plant.