ABSTRACT
ABSTRACT: A study on arsenic (As) contamination of groundwater in the Gaur Municipality, Rautahat district of Nepal was undertaken during October, 2003. This study investigates the occurrences and distribution of As and its mechanism of release in groundwater in the affected areas. Our observations reveal that the groundwater was alkaline with high concentration of bicarbonates (562.8 mg/L), rich in iron, manganese, and silica Analyses of As in groundwater samples from 50 (both private as well as public) shallow tubewells revealed concentrations in the range between 1-62g/L. Among analyzed samples, 1 exceeded 50g/L concentration and 18 were between 10-50g/L concentrations and rest of samples (31) were below 10g/L concentration. However, the WHO guideline of maximum concentration limit of As in drinking water is 10g/L. The release of As from the sediments is related to: (i) the reduction of iron oxides and hydroxides, found to be the main mechanism of mobilization of As in the groundwater; (ii) desorption of As by phosphate and silica; and (iii) anion exchange with OH. Arsenic concentration found in tubewells indicates that people are consuming As contaminated water (without any pretreatment) at serious risk of As poisoning. However, there is no counter treatment of As diseases; As remediation is the only one option to save the lives of people.
