Arsenic-sulfur speciation - a potential key to understanding arsenic accumulation and mobilisation in sulfidic aquifers of Bangladesh

孟加拉国目前被认为是世界上饮用水砷中毒影响最大的国家。在过去的10年里，砷的总浓度筛选和家庭修复措施已经实施，但砷的来源仍然不清楚。在拟议的项目中，我们将筛选不同深度的井，挖掘不同的地质构造，主要关注pH值、氧化还原电位、氧化还原敏感物种和稳定同位素。在柱实验中，沉积物样品将暴露于O2、CO2、磷酸盐、腐植酸和呼吸抑制剂中，以阐明砷的不同动员机制。对不同深度的监测井进行连续取样将显示出化学成分随深度和时间的变化。与之前进行的所有其他研究相反，将进行无机As(ll)/As(V)形态以外的砷形态形成。本文将探讨富有机质地层中甲基化砷的重要性以及砷硫物质形成对硫化铁中砷的动员作用。砷硫化合物是研究含硫水体中砷化学的重要线索。建模将有助于更好地了解孟加拉国的情况，并预测世界其他国家的类似情况。

Bangladesh is currently the country believed to show the largest impact of arsenic poisoning worldwide from drinking water. Screening on total arsenic concentrations and householdbased remediation measures have been implemented over the past 10 years, but the origin of the arsenic is still not clear. During the proposed project we will screen wells of different depths tapping different geological formations with major focus on pH, redox potential, redox sensitive species, and stable isotopes. Sediment samples in column experiments will be exposed to O2, CO2, phosphate, humic acids, and respiratory inhibitors to illuminate different mechanisms of arsenic mobilization. Continuous sampling of monitoring wells of different depths will show depth and time dependent variations in chemistry. Contrary to all other studies conducted before, arsenic speciation beyond inorganic As(lll)/As(V) speciation will be done. The importance of methylated arsenic species in organic-rich strata and the potential of arsenic-sulfur species formation on the mobilization of arsenic from ironsulfides will be investigated. Arsenic-sulfur species have seldom been investigated so far but can be an important clue in arsenic chemistry in sulfidic waters. Modeling will help to better understand the situation in Bangladesh and predict similar scenarios in other countries worldwide.