million people rely on groundwater contaminated with arsenic. The relevant processes occurring in aquifers vary according to the geological and hydrological conditions. Concentrations of dissolved arsenic are known to be particularly high in fluvial sediments with abundant organic material and limited oxygen supplies, e.g. in the deltas of the Ganges (Bangladesh) or the Red River (Vietnam); here, arsenic bound to iron oxides is released as a result of the chemically reducing environment. In Pakistan, however, though sediment layers are present along the Indus, reducing conditions are largely lacking. But the new study shows a strong correlation between elevated arsenic concentrations and high soil pH. Infiltration of irrigation water through alkaline topsoil and young alluvial sediments may thus contribute to arsenic enrichment in groundwater. First author Joel Podgorski, a geophysicist at Eawag, stresses that this is still a hypothesis. It is supported by the fact that irrigated areas largely coincide with regions where elevated arsenic concentrations were measured by co-author Ali Shah of COMSATS (Islamabad).
Read more at: https://phys.org/news/2017-08-arsenic-pakistan-greater.html#jCp
