模拟湿地植物根系分泌物对酸性矿山废水沉淀物中Fe、Mn释放及形态的影响

为研究人工湿地处理酸性矿山废水(acid mine drainage,AMD)系统中植物根系分泌物对根际环境沉淀物中Fe、Mn活性的影响,评估人工湿地处理AMD时对Fe、Mn固持作用的稳定性及可靠性,选用植物根系分泌物中常见的柠檬酸、苹果酸及草酸来模拟植物根系分泌物对沉淀物中Fe、Mn的释放及形态影响。结果表明:3种有机酸对根际环境沉淀物中Fe、Mn的释放均产生不同程度的影响,相同浓度下的有机酸对Fe的影响顺序为:柠檬酸>苹果酸>草酸,对Mn的影响顺序为:柠檬酸>草酸>苹果酸。随着有机酸浓度的增加,沉淀物中Fe、Mn的释放量逐渐增加,且Fe的释放量大于Mn。形态分析结果表明,在有机酸参与前沉淀物中Fe、Mn主要以可还原态形式存在,当添加3种不同浓度的有机酸后,沉淀物中的可还原态Fe、Mn极不稳定,易向可交换态发生转变,而残渣态与可氧化态则较为稳定,说明沉淀物中残渣态与可氧化态的Fe、Mn在人工湿地中是Fe、Mn去除的重要途径。

INFLUENCE OF ROOT EXUDATES TO METAL FORMS OF IRON AND MANGANESE OF AMD SEDIMENT IN RHIZOSPHERE ENVIRONMENT

For studying the influence of root exudates on the activities of Fe,Mn in the artificial wetland treatment AMD system,and evaluating the stability and reliability of Fe,Mn,effects of citric acid,malic acid and oxalic acid on Fe,Mn in root precipitate were investigated by simulated leaching experiment.Results indicated that three kinds of low molecular organic acids had effects on release of iron and manganese in root precipitate.The leaching trends of Fe,Mn in root precipitate were:Citric acid ＞ malic acid ＞ oxalic acid for Fe,citric acid ＞ oxalic acid ＞ malic acid for Mn.With the increase of organic acid concentration,releases of Fe,Mn in the precipitate were gradually increased.There was a good activation effect on Fe,Mn in precipitate when three kinds of organic acid added.Reducible fractions of Fe,Mn were main forms in the control group.With the increase of organic acid,there were an increasing trend in exchangeable fraction and a decreasing trend in reducible fractions of Fe,Mn,but changes of residual and oxidizable fractions were not obvious.Using the treatment of wetland for AMD,root exudate can affect exchangeable and reducible fraction of Fe,Mn,but have little influence to residual and oxidizable fractions.Above all,residual and oxidizable fractions of Fe,Mn in constructed wetland were an important way of Fe and Mn removal.