Hydrogeochemical characteristics of the aquifers with variable arsenic concentrations

摘要

Arsenic (As) concentrations in groundwater range between ＞0.1 and 476 μl-1, with localized high concentrations in abandoned meander/channel deposits. The groundwater flow lines tend to be deflected away from the high As aquifer. This indicates both low permeability and low recharge rates, as well as an abundance of fine-grained sediments associated with high As areas. These factors allow for high groundwater residence time for sediment-water interaction to occur, thus facilitating the release of As from meander/channel deposits. Borehole lithology analysis confirms our assumption, where finer-sediments are associated with the high As concentrations. Moreover, the presence of silt/clay intercalations within the sandy aquifer at the sites showing high As seems to influence As mobility.