水稻土中铁的厌氧生物氧化还原循环对砷的影响

The Effect of Anaerobic Redox Cycling of Iron on Arsenic Mobility in Paddy

应用砷污染水稻土的厌氧富集培养,探讨水稻土中潜在存在铁厌氧生物循环及其对氮和砷的耦合作用.富集培养直接证明了水稻土中铁的厌氧生物循环:三价铁(人工合成针铁矿)在厌氧条件下被逐渐还原成二价铁;铁还原过程结束并外源添加硝酸根时,培养基中新生的二价铁在依赖于硝酸根的铁氧化菌的作用下被氧化;当提供新的电子供体乙酸时,生物合成的铁矿重新被还原.在铁氧化还原循环过程中,随着铁的还原,培养基中砷的浓度不断增加,反之,当铁逐渐氧化的同时不断地吸附固定培养基中的砷.在铁的厌氧氧化阶段,铁氧化的同时硝酸根被还原,培养基中积累了NH4+和NO2-.因此,厌氧水稻土中可以进行完整的铁氧化还原循环,同时这个循环过程耦合了氮和砷的迁移转化.

An enrichment culture of arsenic polluted paddy microorganisms was used to investigate the potential microbially mediated anaerobic redox cycling of iron.The redox cycling of iron was simulated by the enrichment as follows：1）Goethite（Fe（Ⅲ））was reduced immediately following inoculation of Artificial Groundwater medium（AGW）with paddy under anaerobic condition;2）Addition of NO3-after Fe（Ⅲ）reduction ceased resulted in the immediate oxidation of Fe（Ⅱ）coupled to reduction of NO3-.3）The fresh Fe（Ⅲ）minerals originated from the nitrate dependent iron oxidation were reduced again when new electron donor of acetate was supplied to the enrichment.Arsenic was released when iron minerals were reduced,and it was immobilized by absorbing to minerals when Fe（Ⅱ）was oxidized.Nitrate reduction was coupled to Fe（Ⅱ）oxidation during anaerobic oxidation of Fe（Ⅱ）,which resulted in the accumulation of NH4＋ and NO2-.These results indicated that the paddy contained microorganisms which were capable of dissimilatory Fe（Ⅲ）and oxidation of Fe（II）with reduction of NO3-,which potentially drove the microbially mediated redox cycling of iron,and which significantly affected the transformation of N and As.