Metal-contaminated plants after phytoremediation provide organic matter and trace metals for anaerobic fermentation. In this study, alfalfa straw harvested from an abandoned iron mine was used for anaerobic fermentation. The variation of metal speciation during the anaerobic fermentation process and the influences on fermentation parameters were investigated. The results showed that the group adding alfalfa increased the peak daily biogas yield by 33.40 % compared to the group with cow dung only. Fe in the fermenter was predominated by the soluble and the residual fraction. Cu was transformed from soluble Cu to residual Cu with the fermentation progressed. On the 13^th day of fermentation, the percentage of soluble Fe decreased while the percentage of soluble Cu, Ni and Zn increased which induced the daily biogas yields peak. Metal speciation was correlated to the fermentation parameters. Daily biogas yields were negatively correlated to the acid-extractable fraction of Ni and Zn (p < 0.05). pH was negatively correlated to the soluble Cu, the acid-extractable fraction of Cu and Zn (p < 0.05), while positively correlated to the reducible and oxidizable Fe (p < 0.01). Further adding metals promoted the biogas production of alfalfa by bringing forward the daily biogas peak and increasing the peak yields. In particular, adding Cu only produced more biogas than adding other metals (single or multiple). Exogenous metals addition generally resulted in more acid-extractable fraction of Cu, Ni and Zn, i.e. the mobility of these metals increased. 19 % of Fe was activated into acid-extractable fraction after the addition of Ni. The results of this study are expected to provide references for the reutilization of contaminated biomass and optimizing the metal contained fermentation process.

植物修复后受金属污染的植物为厌氧发酵提供有机物和微量金属。在这项研究中，从废弃铁矿中收获的苜蓿秸秆用于厌氧发酵。研究了厌氧发酵过程中金属形态的变化及其对发酵参数的影响。结果表明，与仅添加牛粪的组相比，添加苜蓿的组将峰值日沼气产量提高了 33.40%。发酵罐中的铁主要是可溶部分和残留部分。随着发酵的进行，Cu从可溶性Cu转变为残留Cu。13^日发酵第 1 天，可溶性 Fe 的百分比下降，而可溶性 Cu、Ni 和 Zn 的百分比增加，导致日产沼气量达到峰值。金属形态与发酵参数相关。每日沼气产量与镍和锌的酸提取部分呈负相关（p < 0.05）。pH 值与可溶性 Cu、Cu 和 Zn 的酸可萃取部分呈负相关（p < 0.05），而与可还原和可氧化的 Fe 呈正相关（p < 0.01）。进一步添加金属促进了苜蓿的沼气产量，提前了每日沼气峰值，提高了峰值产量。特别是，与添加其他金属（单一或多种）相比，添加 Cu 只会产生更多的沼气。外源金属的添加通常会导致更多的 Cu、Ni 和 Zn 的酸可萃取部分，即 这些金属的流动性增加。添加 Ni 后，19% 的 Fe 被活化成酸可萃取部分。该研究结果有望为污染生物质的再利用和含金属发酵工艺的优化提供参考。