Role of microbiogeochemical processes in mobilization of As in the aquifer sediments of the Bengal Delta Plain (BDP): an experimental approach

在孟加拉三角洲平原(BDP)，由于长期饮用高砷含量的地下水，数百万人暴露在慢性砷中毒中。尽管在理解这场灾难背后的地球化学过程方面取得了进展，但地下水中砷浓度高的最终原因仍然不清楚，这阻碍了有效缓解措施的实施。有一种有根据的猜测认为，细菌和相关的生物地球化学过程可能在从含水层沉积物中动员As方面发挥关键作用，但这一假设的有效性至今仍未得到很大程度的探索。拟议的项目旨在通过微生物学家、地球化学家、地质学家和化学家在联合实验室和实地实验中的协同合作，评估和量化微生物在这一过程中的作用。从一个高砷和一个低砷地点的两个钻井中收集的含水层沉积物和地下水将进行地球化学和微生物特征分析，并将这些材料用于柱实验，以研究在不同微生物菌株介导的氧化还原过程中砷的动员。现场试验包括抽水和注水试验，以及两年多的水化学监测，目的是破译广泛开采水资源、含水层曝气、微生物活动和地下水中高砷含量之间的复杂相互作用。

In the Bengal Delta Plain (BDP) millions of people are exposed to chronic As poisoning due to prolonged consumption of groundwater with high As contents. Despite progresses in understanding the geochemical processes behind this calamity, the ultimate cause of the high As concentrations in groundwater is still unclear, impeding the implementation of efficient mitigation measures. There is an educated guess that bacteria and related biogeochemical processes may play a key role in the mobilization of As from the aquifer sediments, but the validity of this hypothesis remained largely unexplored until now. The proposed project aims to assess and quantify the role of microbes in this process by a synergetic co-operation among microbiologists, geochemists, geologists and chemists in joint laboratory and field experiments. Aquifer sediments and groundwater collected from two drillings at a high and a low As site will be geochemically and microbiologically characterized and the material will be used in column experiments to investigate the mobilization of As during redox processes mediated by different strains of microbes. Field experiments consisting of pumping and injection tests coupled with a hydrochemical monitoring over 2 years aim at deciphering the complex interaction among extensive water exploitation, aquifer aeration, microbial activity, and high As contents in groundwater.