Weng Liping, Lexmond Theo M, Wolthoorn Anke, Temminghoff Erwin J M, van Riemsdijk Willem H
Wageningen University, Department of Environmental Science, Subdepartment of Soil Quality, P.O. Box 8005, 6700 EC Wageningen, The Netherlands.
Environ Toxicol Chem. 2003 Sep;22(9):2180-7. doi: 10.1897/02-116.
The effect of pH on the bioaccumulation of nickel (Ni) by plants is opposite when using a nutrient solution or a soil as a growing medium. This paradox can be understood if the pH effect on the bioaccumulation, on the chemical speciation in the soil solution, and on the binding to the soil of Ni are all taken into account. Using simple equations to describe the individual relationships, it is possible to quantify these effects once the relationships have been established. Increased Ni uptake leads to reduced plant dry weight production for a certain growing period. The median effective concentration (EC50) decreased from 23 to 1.7 microM Ni in the nutrient solution for pH 4.0 to 7.0, whereas the EC50 of added Ni in a sandy soil increased from 0.72 to 9.95 mmol Ni/kg soil for pH 4.7 to 6.8. Bioaccumulation, binding to the soil solid phase, and binding to the dissolved organic matter all increase with increasing pH. However, the magnitude of the effect is the least for bioaccumulation as a function of pH, causing the apparent paradox.
当使用营养液或土壤作为生长介质时，pH值对植物镍（Ni）生物累积的影响是相反的。如果将pH值对生物累积、土壤溶液中化学形态以及镍与土壤结合的影响都考虑在内，那么这种矛盾就可以理解了。使用简单的方程式来描述各自的关系，一旦建立了这些关系，就可以对这些影响进行量化。在一定生长时期内，镍吸收量的增加会导致植物干物质产量降低。在营养液中，pH值从4.0变为7.0时，半数有效浓度（EC50）从23微摩尔镍降至1.7微摩尔镍；而在沙质土壤中，pH值从4.7变为6.8时，添加镍的EC50从0.72毫摩尔镍/千克土壤增加到9.95毫摩尔镍/千克土壤。生物累积、与土壤固相的结合以及与溶解有机物的结合均随pH值升高而增加。然而，作为pH值函数的生物累积效应的幅度最小，从而导致了明显的矛盾。
