MECHANISM OF ARSENIC POLLUTION OF GROUNDWATER AND COUNTERMEASURES FOR THE POLLUTION IN BANGLADESH

90% of the tube wells in Samta village, where we have been investigating the causes of the arsenic contamination in groundwater and developing arsenic-free water supply systems since March 1997, had arsenic concentrations above the Bangladesh standard of 0.05mg/1. Tube wells with arsenic concentrations of over 0.50mg/l were distributed in the southern part with a belt-like shape from east to west and the arsenicconcentration was decreasing toward northern part of the village. In order to examine the characteristics of arsenic distribution in Samta, the arsenic pollution of groundwater in extensive area including Samta village was investigated and the distribution of arsenic pollution for the area was obtained in the paper. From some discussion about the examination and review of the geological survey results & change of arsenic concentration with time in Samta which have beenobtained in these years, we propose a model for explaining the characteristics of arsenic pollution in Samta in the paper. And the movements of countermeasures for arsenic pollution problems by us are introduced here, too.