微生物介导下高砷地下水系统的氧化还原分带性概念模型

微生物活动对地下水水化学组分、氧化还原环境及砷的迁移转化有重要影响。研究高砷地下水系统的氧化还原分带性,有助于进一步理解微生物作用下地下水中砷的迁移转化规律,并为高砷地下水原位修复技术提供理论依据。在综述前人的研究成果的基础上,阐明了不同生物地球化学阶段砷的吸附、释放及固定过程,并刻画出高砷地下水系统的氧化还原分带性概念模型。在地下水环境中,微生物依次消耗(还原)溶解氧、NO-₃、Fe(Ⅲ)、SO2-₄和CO₂等组分,氧化有机物获取能量。在溶解氧和NO-3还原阶段,地下水处于偏氧化环境,此时Fe(Ⅲ)还原受到抑制,其负载的砷不会释放到地下水中;当Fe(Ⅲ)还原时,地下水处于还原环境,会导致与之共存的砷释放,形成高砷地下水;而当SO2-₄还原时,地下水处于强还原环境,产生的HS-与Fe2+形成的铁硫化物吸附或共沉淀砷,会降低地下水中的砷浓度。 

Conceptual Model of Redox Zonation in High Arsenic Groundwater System Under the Effect of Microorganisms

Microbial activities have important effects on chemical composition and redox condition of groundwater,and also migration and transformation of arsenic.Researches on redox zonation in high arsenic groundwater system can help people to further understand the migration and transformation of arsenic in groundwater under the effect of microorganisms,and provide the theoretical basis for in-situ remediation of high arsenic groundwater.By reviewing the results of previous studies,this paper elucidates the adsorption,release and readsorption of arsenic in different biogeochemical stages,and depicts the conceptual model of redox zonation in high arsenic groundwater system.Along the groundwater flow paths,the electron acceptors are consumed sequentially in the order as dissolved oxygen>nitrate>Fe(III)>sulfate>CO₂.In dissolved oxygen and nitrate reduction stage,groundwater is in partial oxidation environment,and the arsenic will not be released into the groundwater as the Fe(III) reduction is inhibited.In Fe(III) reduction stage,groundwater is in reduction environment and the reductive dissolution of Fe(III) is the main process,so the arsenic will be released into the groundwater.When SO2-₄reduction starts,groundwater is in strong reducing environment,and the sulfide that generated by combination of HS- and Fe2+will adsorb or coprecipitate the arsenic,thus decreasing arsenic concentration in the groundwater.