Weng Li Ping, Wolthoorn Anke, Lexmond Theo M, Temminghoff Erwin J M, van Riemsdijk Willem H
Sub-department of Soil Quality, Department of Environmental Science, Wageningen University, P.O. Box 8005, 6700 EC Wageningen, The Netherlands. liping
Environ Sci Technol. 2004 Jan 1;38(1):156-62. doi: 10.1021/es030053r.
Acidity (pH) has been realized to be the most important soil characteristic that modulates bioavailability of heavy metals by affecting both the chemical speciation of metals in soil and the metal binding to the active sites on biota. In this work, we show that besides soil pH, metal bioavailability also depends to a certain extent on the type of soil. A better understanding of the role of soil type in regulating metal availability can be achieved with the analysis of soil composition and with calculations using chemical speciation models. Results of pot experiments, in which three different soils were spiked with nickel, show that the EC50 of total nickel in decreasing the biomass production of oats varies widely (0.7-22.5 mmol kg(-1) soil, more than 30 times). pH (4.7-7.0) is the most important factor, explaining up to a factor of 14 difference of nickel bioavailability in the soils. The remaining variation is caused by other differences in soil composition (soil type). The bioavailability and toxicity of nickel in the organic matter-rich soil studied is less than half of that in the sandy and clay soil studied at a similar pH. The chemical calculations using a multi-surface speciation model show that soil organic matter binds Ni much stronger than clay silicates and iron (hydr)oxides within the acidic pH range, which supports the experimental findings. In all three soils, the EC50 of Ni expressed in terms of Ni in 0.01 M CaCl2 soil extraction is rather stable (24-58 microM), suggesting the possibility to use this extraction as an estimation of metal availability in soil.
酸度（pH值）已被认为是最重要的土壤特性，它通过影响土壤中金属的化学形态以及金属与生物群活性位点的结合，来调节重金属的生物有效性。在这项研究中，我们表明，除了土壤pH值外，金属生物有效性在一定程度上还取决于土壤类型。通过分析土壤成分并使用化学形态模型进行计算，可以更好地理解土壤类型在调节金属有效性方面的作用。盆栽实验结果表明，在三种不同土壤中添加镍后，总镍降低燕麦生物量生产的半数有效浓度（EC50）差异很大（0.7 - 22.5 mmol kg(-1)土壤，超过30倍）。pH值（4.7 - 7.0）是最重要的因素，它解释了土壤中镍生物有效性高达14倍的差异。其余的变化是由土壤成分（土壤类型）的其他差异引起的。在相似pH值下，所研究的富含有机质土壤中镍的生物有效性和毒性不到所研究的砂土和粘土土壤的一半。使用多表面形态模型进行的化学计算表明，在酸性pH范围内，土壤有机质对镍的结合比粘土硅酸盐和铁（氢）氧化物强得多，这支持了实验结果。在所有三种土壤中，以0.01 M CaCl2土壤提取物中的镍表示的镍EC50相当稳定（24 - 58 microM），这表明有可能使用这种提取物来估算土壤中金属的有效性。
