Anawar H M, Akai J, Yoshioka T, Konohira E, Lee J Y, Fukuhara H, Tari Kul Alam M, Garcia-Sanchez A
Department of Environmental Geochemistry, IRNASA-CSIC, Cordel De Merinas 40-52, Aptdo 257, Salamanca 37008, Spain.
Environ Geochem Health. 2006 Dec;28(6):553-65. doi: 10.1007/s10653-006-9054-0. Epub 2006 Nov 21.
The extensive extraction of arsenic (As)-contaminated groundwaters for drinking, household and agricultural purposes represents a serious health concern in many districts of Bangladesh. This laboratory-based incubation study investigated the sources and mechanisms of As mobilization in these groundwaters. Several incubation studies were carried out using sediments collected from the Bangladesh aquifer that were supplemented, or not, with different nutrients, followed by an analysis of the sediment suspensions for pH, ORP (oxidation-reduction potential), EC (electrical conductivity) and As and Fe(II) concentrations. In the substrate-amended sediment suspensions incubated under anaerobic environment, there was a mobilization of As (maximum: 50-67 microg/l) and Fe(II) (maximum: 182 microg/l), while the ORP value decreased immediately and drastically (as much as -468 mV to -560 mV) within 5-6 days. In the sediment suspensions incubated under control and aerobic conditions, no significant As mobilization occurred. The simultaneous mobilization of As and Fe(II) from sediments is a strong indication that their mobilization resulted from the reduction of Fe oxyhydroxide by the enhanced activity of indigenous bacteria present in the sediments; this phenomenon also provides insights on the mobilization mechanism of As in groundwater. The concentrations of As in the sediments used in the incubation studies were strongly linked to the gradients of redox potential development that was stimulated by the quantity of organic nutrient (glucose) used. The penetration of surface-derived organic matter into the shallow aquifer may stimulate the activity of microbial communities, thereby leading to a reduction of iron oxyhydroxide and As release.
出于饮用、家庭及农业目的而大量抽取受砷污染的地下水，这在孟加拉国许多地区引发了严重的健康问题。这项基于实验室的孵化研究调查了这些地下水中砷的来源及迁移机制。利用从孟加拉国含水层采集的沉积物开展了多项孵化研究，这些沉积物添加或未添加不同养分，随后分析沉积物悬浮液的pH值、氧化还原电位（ORP）、电导率（EC）以及砷和亚铁离子（Fe(II)）浓度。在厌氧环境下孵化的添加了底物的沉积物悬浮液中，砷（最高达50 - 67微克/升）和亚铁离子（最高达182微克/升）出现了迁移，而氧化还原电位值在5 - 6天内立即大幅下降（多达 - 468毫伏至 - 560毫伏）。在对照和好氧条件下孵化的沉积物悬浮液中，未发生显著的砷迁移。沉积物中砷和亚铁离子的同时迁移有力表明，它们的迁移是由于沉积物中本土细菌活性增强，导致氢氧化铁还原所致；这一现象也为地下水中砷的迁移机制提供了见解。孵化研究中使用的沉积物中砷的浓度与因所用有机养分（葡萄糖）数量而激发的氧化还原电位发展梯度密切相关。源自地表的有机物渗入浅层含水层可能会刺激微生物群落的活性，从而导致氢氧化铁还原和砷释放。
