INSTAAR, University of Colorado, 450 UCB, Boulder, Colorado 80309, USA.
Environ Sci Technol. 2010 Jan 1;44(1):123-8. doi: 10.1021/es901472g.
Iron (Fe) and dissolved organic matter (DOM) cycling have been implicated in arsenic mobilization via microbially mediated Fe oxide reduction. To evaluate the sources and multiple roles of DOM in Bangladesh aquifers, we conducted spectroscopic analyses on various types of surface water and groundwater samples from a site representative of aquifer chemistry and hydrology. Surface water contained humic substances with oxidized quinone-like moieties and high concentrations of labile microbially derived DOM. In contrast, in shallow groundwater where dissolved iron and arsenic concentrations were high, the quinone-like moieties of humic substances were more reduced, with less abundant labile DOM than that of surface water. Instead, DOM at these depths was characterized by terrestrial (plant/soil) signatures. A sediment microcosm experiment demonstrated that Fe(II) and terrestrially derived DOM were released from sediment over time. The results provide new evidence to support a dual role of natural DOM in Bangladesh aquifers (1) as a labile substrate for Fe- and humic-reducing bacteria and (2) as an electron shuttle via humic substances to enhance microbial iron reduction. Fluorescence index, amino acid-like fluorescence, and redox index may serve as useful indicators of the type of DOM likely to be involved in Fe solubilization and potentially As mobilization reactions.
铁 (Fe) 和溶解的有机物质 (DOM) 的循环被认为通过微生物介导的氧化铁还原作用促使砷的迁移。为了评估 DOM 在孟加拉国含水层中的来源和多种作用，我们对一个具有代表性的含水层化学和水文学的地点的各种地表水和地下水样本进行了光谱分析。地表水含有具有氧化醌类部分和高浓度易生物降解的微生物衍生 DOM 的腐殖质物质。相比之下，在溶解铁和砷浓度较高的浅层地下水中，腐殖质物质的醌类部分还原程度更高，可生物降解的 DOM 比地表水少。相反，这些深度的 DOM 的特征是具有陆地（植物/土壤）特征。沉积物微宇宙实验表明，Fe(II) 和陆地衍生的 DOM 会随着时间从沉积物中释放出来。结果提供了新的证据，支持天然 DOM 在孟加拉国含水层中具有双重作用：（1）作为铁和腐殖质还原菌的易生物降解基质，（2）通过腐殖质作为电子穿梭体来增强微生物铁还原。荧光指数、氨基酸样荧光和氧化还原指数可作为可能参与铁溶解和潜在砷迁移反应的 DOM 类型的有用指标。
