Improved groundwater geogenic arsenic hazard map for Cambodia

Arsenic is a known environmental chemical hazard in shallow groundwaters of Cambodia and is increasingly recognised as a major problem for public health. Notwithstanding this, accurate arsenic data are not available for many wells in potentially arsenic-prone areas, particularly around the Tonle Sap Great Lake (TSL) and in the coastal provinces (CP). We present here new data for shallow groundwater (16-120-m depth) arsenic in the TSL and CP regions as well as an improved regression-kriging (RK) based groundwater arsenic hazard map for the whole country. High arsenic levels (up to 100gL(-1)) were found in shallow groundwaters from the TSL and CP regions of Cambodia, but despite strong compositional similarities (near neutral, reducing, Na-Mg-Ca-HCO3 dominated) with high arsenic level groundwaters near the Mekong and Bassac rivers, groundwater arsenic levels in both the TSL and CP regions were most commonly low (interquartile range 0.09-1.2gL(-1)). The RK geostatistical model was highly successful, accounting for over 50% of the observed variation in arsenic concentrations countrywide and represents a potentially useful tool for policymakers and those responsible and with the interest and authority to prepare arsenic mitigation and safe water supply plans.