Evangelou Michael W H, Daghan Hatice, Schaeffer Andreas
Institut für Biologie V-Umweltchemie, RWTH Aachen, Worringerweg 1, Aachen D-52056, Germany.
Chemosphere. 2004 Oct;57(3):207-13. doi: 10.1016/j.chemosphere.2004.06.017.
Cadmium poses a major environmental and human health threat because of its constant release through anthropogenic activities. A need, therefore, exists for cost-effective remediation procedures. Phytoremediation, the use of plants to extract contaminants from soils and groundwater, has revealed great potential. However, it is limited by the fact that plants need time, nutrient supply and, moreover, have a limited metal uptake capacity. Synthetic chelators have shown positive effects in enhancing heavy metal extraction through phytoremediation, but they have also revealed a vast number of negative side-effects. The objective of this research was to investigate the use of humic acids as an alternative to synthetic chelators. Humic acids were applied to a cadmium-contaminated soil at various dosages, and the uptake of cadmium into Nicotiana tabacum SR-1 was determined in relation to the amounts of total and bioavailable cadmium in the soil. It was found that the theoretical bioavailability of cadmium, as determined by diethylenetriaminepentaacetic acid (DTPA) extraction, did not change, but its plant uptake was enhanced significantly, in some cases up to 65%. Humic acids added at a rate of 2 g kg(-1) soil increased the cadmium concentration in the shoots from 30.9 to 39.9 mg kg(-1). A possible reason for this enhancement is the decrease in pH, resulting in higher cadmium availability. Another possibility taken into account is that plants may take up cadmium complexes with humic acid fragments, which result from microbiological degradation or, self-dissociation.
镉因其通过人为活动不断释放而对环境和人类健康构成重大威胁。因此，需要具有成本效益的修复程序。植物修复，即利用植物从土壤和地下水中提取污染物，已显示出巨大潜力。然而，它受到植物需要时间、养分供应的限制，而且植物对金属的吸收能力有限。合成螯合剂在通过植物修复增强重金属提取方面已显示出积极效果，但它们也显示出大量负面副作用。本研究的目的是调查使用腐殖酸作为合成螯合剂的替代品。将腐殖酸以不同剂量施用于受镉污染的土壤，并根据土壤中总镉和生物可利用镉的含量测定镉在烟草SR-1中的吸收情况。结果发现，通过二乙烯三胺五乙酸（DTPA）提取测定的镉的理论生物有效性没有变化，但其植物吸收显著增强，在某些情况下高达65%。以2 g kg(-1)土壤的速率添加腐殖酸使地上部镉浓度从30.9 mg kg(-1)增加到39.9 mg kg(-1)。这种增强的一个可能原因是pH值降低，导致镉的有效性更高。考虑的另一种可能性是植物可能吸收与腐殖酸片段形成的镉络合物，这些络合物是由微生物降解或自解离产生的。
