Spatial and Temporal Variation of Ground Water Arsenic in the Lower Mekong River Basin in Cambodia.

Groundwater across Southeast Asia is severely contaminated by arsenic, which is naturally derived from eroded Himalayan sediments.  Arsenic within the sediments can be released into groundwater after deposition in the large deltas upon burial and the onset of anaerobic conditions.  However, groundwater As varies spatially and temporally in the region due to changes in redox conditions oscillating hydrologic conditions coupled with ever intensifying land use change.  We established a field site with 3-dimmensional network of wells to monitor arsenic concentrations in the Lower Mekong River Basin, Cambodia.  This network was initiated in 2004.  Here we present data on the evolving spatial and temporal distribution of arsenic within the shallow to deep aquifer of the region.  Such information and analyses are vital for predicting where and when arsenic concentrations may exceed safe level for human consumption.