玉米秸秆对煤矸石中重金属释放及生物有效性的影响

Effects of Corn Straw on Heavy Metals Release and Bioavailability in Coal Gangue

为研究秸秆对煤矸石重金属释放及生物有效性的影响,向煤矸石中添加不同比例(0%、1%、2%、5%、10%)的玉米秸秆,研究其对煤矸石中铁(Fe)、锰(Mn)、铜(Cu)、锌(Zn)、铅(Pb)和镉(Cd)等重金属释放及赋存形态的影响。结果表明,玉米秸秆的添加促进了煤矸石中Fe、Mn的快速释放,且秸秆添加比例越高,浸出液中Fe、Mn的质量浓度越高,试验结束时(秸秆腐解180 d)秸秆添加量为10%的处理组中Fe、Mn的质量浓度分别达到459.30、47.30 mg/L;玉米秸秆的添加整体上促进了煤矸石中Cu、Zn的释放,抑制了煤矸石中Pb的溶出,对Cd的溶出影响不明显。总体上,秸秆添加促进了煤矸石中Fe、Mn由可还原态向可交换态及可氧化态转化,Cu由可交换态及可还原态向可氧化态转化,使Zn由可还原态转化为可交换态。重金属RAC风险评价结果显示,各重金属中活性形态占比大小依次为Mn>Zn>Cu>Fe>Cd>Pb,秸秆的添加使煤矸石中Mn、Zn活性形态占比升高,秸秆添加量为5%的处理组煤矸石中Cu、Cd活性形态占比最低。综上,玉米秸秆添加量为5%时对煤矸石中的Cu、Pb、Cd有固定作用,但同时会活化煤矸石中的Mn、Zn,在使用玉米秸秆对煤矸石进行修复改良时,应关注煤矸石中Mn、Zn活性的变化,以防对环境造成二次污染。

In order to study the effect of straw on the release and bioavailability of heavy metals in coal gangue,different proportions(0%,1%,2%,5%,10%)of corn straw were added to coal gangue to study their effects on the release and forms of heavy metals such as iron(Fe),manganese(Mn),copper(Cu),zinc(Zn),lead(Pb),and cadmium(Cd)in coal gangue.The results showed that the addition of corn straw promoted the rapid release of Fe and Mn in coal gangue,and the higher the proportion of straw addition,the higher the concentration of Fe and Mn in the leachate.At the end of the experiment(180 days of straw decomposition),the concentration of Fe and Mn in the treatment group with 10%straw addition reached 459.30 mg/L and 47.30 mg/L,respectively.The addition of corn straw overall promoted the release of Cu and Zn in coal gangue,inhibited the dissolution of Pb in coal gangue,but had no significant effect on the dissolution of Cd.Overall,the addition of straw promoted the transformation of Fe and Mn from reducible to exchangeable and oxidizable states in coal gangue,and the transformation of Cu from exchangeable and reducible states to oxidizable state,resulting in the transformation of Zn from reducible to exchangeable states.The heavy metal RAC risk assessment results showed that the proportion of active forms in each heavy metal was in the order of Mn>Zn>Cu>Fe>Cd>Pb.The addition of straw increased the proportion of Mn and Zn activity in coal gangue,and the treatment group with a straw addition of 5%had the lowest proportion of Cu and Cd activity in coal gangue.In summary,the addition of 5%corn straw has a fixing effect on Cu,Pb,and Cd in coal gangue,but it also activates Mn and Zn in coal gangue.When using corn straw for remediation and improvement of coal gangue,attention should be paid to the changes in Mn and Zn activity in coal gangue to prevent secondary pollution to the environment.