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），数百万人由于长期饮用高砷含量的地下水而暴露于慢性砷中毒。尽管在了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，细菌和相关的生物地球化学过程可能在含水层沉积物中砷的动员中起关键作用，但这一假设的有效性至今仍未得到充分的探索。拟议的项目旨在通过微生物学家、地球化学家、地质学家和化学家之间的协同合作，在联合实验室和实地实验中评估和量化微生物在这一过程中的作用。在砷含量高和砷含量低的两个钻孔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学表征，这些材料将用于柱实验，以研究不同菌株介导的氧化还原过程中砷的动员。现场试验包括泵送和注入试验，加上2年多的水化学监测，旨在破译广泛的水开采、含水层通气性、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.