中文摘要：

地下水砷污染的形成机制目前尚不清楚,普遍认为,微生物对吸附于铁氧化物表面的As（Ⅴ）以及基质Fe（Ⅲ）的还原是砷释放的主要原因.本研究中以富集的混合菌群为接种微生物,以不同比例（Al∶Fe为1∶0、1∶1、0∶1）的铁铝氢氧化物为吸附剂,考察了微生物对吸附于这些载体上的As（Ⅴ）的还原和迁移作用.结果表明,接种微生物后,3种体系表现出不同程度的As释放,溶液中释放的As基本上是As（Ⅲ）.在氢氧化铁体系中,溶解态As（Ⅲ）浓度仅为60μg/L左右,微生物还原产生的As（Ⅲ）几乎全部存在于固相中;在Al∶Fe为1∶1的铁铝氢氧化物中,溶解态As（Ⅲ）大约为1.3 mg/L;氢氧化铝体系中,该值为7.8mg/L,约占微生物还原总As（Ⅲ）的82%.而未接种的对照组均未检测到As（Ⅲ）以及明显的As释放.本研究还考察了吸附基质铁氧化物的还原对砷迁移的影响,结果表明,砷的还原发生在铁还原之前,铁的还原并没有引起砷的明显释放.因此,根据本实验结果推断,氢氧化铁吸附的As（Ⅴ）的还原及Fe（Ⅲ）的还原很可能不是造成地下水系统中砷释放的主要原因,而吸附于铝氧化物或其它矿物表面的As（Ⅴ）的还原可能引起了砷向水相迁移.

英文摘要：

Ahhough the mechanisms of arsenic release into groundwater remain poorly characterized, microbial reduction of As（ Ⅴ ） adsorbed on the surface of iron oxides and the reductive dissolution of iron oxides are generally considered to play a key role in the mobilization of arsenic. We investigated the impact of bacterial reduction of adsorbed As（ Ⅴ ） on a AI： Fe （1：0, 1：1, O： 1） hydroxides on arsenic mobilization using the mixed bacterial culture. After inoculatien, the increase of dissolved As（Ⅲ ） concentration was observed, whereas As（ Ⅴ） was negligible in aqueous phase. Arenic release for the Al ： Fe （ 1 ： 0, 1 ： 1, 0 ： 1 ） hydroxides systems was 60 μg/L, 1.3 mg/L and 7.8 mg/L respectively. On the contrary, neither reduction nor release of arsenic was observed in the uninoculated groups. Furthermore, the introduction of aluminium may be responsible for the release of arsenic owing to its weaker affinity to As（ Ⅲ ）. In addition, our results showed that Fe reduction occurred far later than arsenic reduction and mobilization and obvious increase was not observed even after Fe reduction occurred. It suggested that in natural systems, the biotic reduction of As （ Ⅴ ） adsorbed on ferric oxides or Fe （Ⅲ ） may not the major cause of arsenic release in sediment or groundwater system as previous works proposed. The reduction of As（ Ⅴ ） bound to aluminum oxides or other minerals may play a key role.