湿地植物凋落物对酸性矿山废水理化特征及沉积物中Fe、Mn稳定性的影响

为研究人工湿地处理酸性矿山废水(AMD)系统中植物凋落物腐解对其理化特征及沉积物中Fe、Mn稳定性的影响,明确人工湿地处理AMD系统中湿地植物的综合作用及持续效果,将质量分数为0(CK组)、2%(D1组)、20%(D2组)的植物凋落物添加至湿地沉积物中,采用下进上出的进水方式向沉积物中添加人工配制的AMD,同时设置水力停留时间为72h,研究不同量的湿地植物凋落物在腐解过程中对AMD中pH、氧化还原电位(Eh)、Fe、Mn等理化指标及沉积物中Fe、Mn形态的影响。结果表明:湿地植物凋落物的腐解能明显提高AMD的pH,且随着植物凋落物的持续腐解,D2组中pH上升幅度明显大于CK与D1组;植物凋落物的腐解可有效地降低AMD的Eh,植物凋落物腐解初期,D1、D2组中Eh急剧下降,且D2组Eh下降幅度大于CK与D1组,随植物凋落物在各处理组中的持续分解,各组中Eh继续呈下降趋势,但下降幅度明显小于试验初期Eh的下降幅度;植物凋落物的存在可明显抑制沉积物对AMD中Fe的吸附;植物凋落物腐解初期,植物凋落物的存在抑制了沉积物对Mn的吸附,而在植物凋落物腐解后期,植物凋落物促进了湿地沉积物对Mn的吸附;湿地沉积物Fe、Mn主要以可还原态形式存在,植物凋落物的腐解促进了沉积物中可还原态Fe、Mn向可氧化态Fe、Mn的转化,且Fe、Mn形态的转化量随着植物凋落物量的增加而增加,有利于沉积物中Fe、Mn稳定性的增加。

Effects of plant litter on characteristics of AMD and stability of Fe,Mn in sediments of constructed wetland

In order to study the effect of plant litter decomposition on physical and chemical characters of Acid Mine Drainage(AMD)and the stability of Fe and Mn in sediments in constructed wetland system,different mass ratio of plant litter named CK(0),D1(2%)and D2(20%)were added into the sediments.The artificial AMD was added into the sediments by entering at bottom and leaving at top.The hydraulic retention time was set as 72 hto analyze the effect of plant litter on pH,Eh,Fe,Mn of AMD and Fe,Mn forms in the sediments.The results indicated that plant litter improved the pH of AMD,with continuous decomposition of plant litter,the pH in D2 group was significantly greater than that in the CK and D1 groups.The decomposition of plant litter could effectively reduce the Eh of AMD.At the initial stage of litter decomposition,Eh decreased sharply in the D1 and D2 groups,and the decrease in the D2 treatment group was greater than that in the D1 group.Plant litter decomposition showed inhibitory effect on Fe adsorption by the sediments.At the initial stage of decomposition,plant litter inhibited the adsorption of Mn by sediments,but at the later stage of decomposition,plant litter promoted the adsorption of Mn by wetland sediments.Reducible Fe and Mn were the main forms in the sediments.Plant litter decomposition promoted the conversion of reducible Fe and Mn to oxidizable Fe and Mn of the sediments.The addition of plant litter increased the stability of Fe and Mn in sediments.In the constructed wetlands treating AMD,the natural regression of plant litter was beneficial to increase the stability of Fe and Mn in the sediments.