Another Geological Disaster besides Earthquakes in Nepal: The Challenge of Eliminating Arsenic from Contaminated Groundwater in the Lowlands of the Country

Abstract

The lowlands of Nepal are severely affected by the arsenic (As) crisis causing serious health issues to the inhabitants using As contaminated groundwater as drinking water. The problem in Nepal has been more or less disregarded – whereas in other countries (e. g,. Bangladesh) the problem had been recognized much earlier. There is clear evidence that the As concentration in groundwater is hardly dependent of climatic seasons whereas the concentration of Fe in groundwater is widely variable in pre- and post-monsoon. A substantial portion of this element is retained by clay minerals. During pre-monsoon clayey sediments are chemically weathered losing Na and K thus remaining relatively enriched in immobile compound like Fe and Al but as long as reduced conditions persist, As remains mobile. This article includes a brief overview on the overall situation concerning the issue of arsenic in groundwater as well as a discussion of the weak correlation or decoupling of aqueous As and Fe in the groundwater and the original reservoir of arsenic being incorporated in clay minerals and mitigation options. The study also shades light on some socio-economic impacts of such changes on the livelihood of marginal communities residing downstream the affected areas.