Lin Zhongbing, Schneider André, Nguyen Christophe, Sterckeman Thibault
INRA, Laboratoire Sols et Environnement, UMR 1120, 2, avenue de la Forêt de Haye, TSA 40602, 54518, Vandoeuvre-lès-Nancy, France,
Environ Sci Pollut Res Int. 2014 Nov;21(22):12811-26. doi: 10.1007/s11356-014-3218-8. Epub 2014 Jun 28.
Phytoextraction is a potential method for cleaning Cd-polluted soils. Ligand addition to soil is expected to enhance Cd phytoextraction. However, experimental results show that this addition has contradictory effects on plant Cd uptake. A mechanistic model simulating the reaction kinetics (adsorption on solid phase, complexation in solution), transport (convection, diffusion) and root absorption (symplastic, apoplastic) of Cd and its complexes in soil was developed. This was used to calculate plant Cd uptake with and without ligand addition in a great number of combinations of soil, ligand and plant characteristics, varying the parameters within defined domains. Ligand addition generally strongly reduced hydrated Cd (Cd(2+)) concentration in soil solution through Cd complexation. Dissociation of Cd complex ([Formula: see text]) could not compensate for this reduction, which greatly lowered Cd(2+) symplastic uptake by roots. The apoplastic uptake of [Formula: see text] was not sufficient to compensate for the decrease in symplastic uptake. This explained why in the majority of the cases, ligand addition resulted in the reduction of the simulated Cd phytoextraction. A few results showed an enhanced phytoextraction in very particular conditions (strong plant transpiration with high apoplastic Cd uptake capacity), but this enhancement was very limited, making chelant-enhanced phytoextraction poorly efficient for Cd.
植物提取是一种用于清理镉污染土壤的潜在方法。向土壤中添加配体有望增强镉的植物提取效果。然而，实验结果表明这种添加对植物吸收镉具有矛盾的影响。开发了一个机理模型，用于模拟镉及其络合物在土壤中的反应动力学（在固相上的吸附、在溶液中的络合）、迁移（对流、扩散）以及根系吸收（共质体、质外体）过程。利用该模型计算了在大量土壤、配体和植物特性组合下添加和不添加配体时植物对镉的吸收情况，并在定义的范围内改变参数。添加配体通常会通过镉络合作用大幅降低土壤溶液中镉的水合态（Cd(2+)）浓度。镉络合物（[化学式：见原文]）的解离无法弥补这种降低，这极大地降低了根系对Cd(2+)的共质体吸收。[化学式：见原文]的质外体吸收不足以弥补共质体吸收的减少。这就解释了为什么在大多数情况下，添加配体导致模拟的镉植物提取量减少。少数结果表明在非常特殊的条件下（植物蒸腾作用强烈且质外体对镉的吸收能力高）植物提取量会增加，但这种增加非常有限，使得螯合剂强化植物提取对镉的效率很低。
