铅镉在土壤-青菜系统吸收累积的数值模拟

Numerical simulation of lead and cadmium transfer and accumulation in soil-rape system

选取湖北大冶重金属污染土壤,添加外源铅镉制备成铅镉复合污染土壤。采用盆栽试验,研究了青菜地上部铅镉质量比与土壤铅镉总量、土壤有机质、pH值等的关系,在此基础上建立了铅镉在青菜体内吸收累积预测模型,并考察青菜地上部铅镉质量比与生长时间的相关性。结果表明,青菜地上部铅镉质量比与土壤铅镉总量呈正相关性,与土壤pH值、有机质呈负相关性。通过多元线性回归获得的改进Freundlich模型,能够较好地预测青菜地上部对土壤重金属铅镉的吸收累积量。在青菜生长周期内,地上部重金属铅镉质量比与生长时间的关系可以通过对数型生长函数较好地拟合。

The transfer models and numerical simulation of lead and cadmium accumulation in the soil-rape system were studied by an out- door pot-culture experiment in the contaminated soils c／ollected from Daye County, Hubei Province. The relationships of the heavy metal amount in shoot parts with the total heavy metal amount in soils, pH and organic matter content were studied and the transfer models were established. It was found that Freundlich model can predict the accu- mulation of heavy metal in shoot well through the adsorption of heavy metal from the the soil. The modified Freundlich model, which intro- duced the effects of pH and organic matter contents could predict the accumulated heavy metal amount better. The heavy metal amount in the shoot parts were proportional to the total heavy metal amount and adversely correlated with the organic content and pH. The relation- ship of heavy metal amount in the shoot parts with the growth time was also examined by numerical simulation. It was found that the heavy metal amount in the shoot parts increased with the growth time. The data were fitted with linear equation and sigmoidal logistic function fit. In the growing period, the heavy metal amount in shoot parts can be fitted better by sigmoidal logistic function. The transfer model and numerical simulation are able to provide technical references for pre- dicting the heavy metal amount in rape to ensure the food safety.