Arsenic in Groundwater Worldwide

This special IGRAC project resulted in refining of (administrative) boundaries of regions which have been reported as having problem with high arsenic concentrations in groundwater. In this stage, more detailed mapping of global distribution of arsenic-rich groundwater by using existing geological maps is not yet possible.

Areas with arsenic-rich groundwater are often associated with unconsolidated alluvial sediments. As rivers eroded and silted up, sediments packets of varying composition and grain size were deposited and shifted along. Therefore, their arsenic content and release potential may vary, even within a distance of 10 m (Alaerts and Khouri, 2004). This makes it difficult to locate the precise arsenic contaminated area.

The depth of the arsenic contaminated groundwater was also not taken into account. Deeper groundwater can travel a longer distance through different aquifers. Consequently, deeper groundwater has a higher change to contain arsenic. The aquifer rocks found at the places where groundwater is contaminated with arsenic, do not necessarily have to be the source of the arsenic. The source can be just the layer on top, or a formation much further away upstream.

Input from regional experts will result in additional information and consequently more detailed specification of areas (aquifers, geological formations) contaminated with arsenic.