Factors Influencing Arsenic Availability and Extraction from Groundwater in Bangladesh

Harold Hemond
Massachusetts Institute of Technology
P30ES02109

Background: In the past decade, Bangladesh has shifted its drinking water supply from surface water to groundwater through the drilling of 6-10 million private wells. This was done in an effort to curtail the severe and numerous waterborne disease outbreaks. The incidence of waterborne diarrheal diseases have dropped significantly during this period; however, many of the wells carry high concentrations of arsenic, a known human carcinogen. As a consequence, cancer rates and the rates of other diseases may be increasing in Bangladesh. The purpose of the current study was to determine the source of the arsenic in the groundwater and factors that mitigate its concentration.

Advance: The research team found that arsenic concentrations in the soil and sediment peak at a depth 30-40 meters and that deep wells, in general, are a better source of clean water. The influx of carbon from soil sediments and carbon rich surface water into the wells is also associated with higher levels of arsenic in the water. Thus, massive irrigation pumping, which draws water into the aquifer from surface water sources, may affect arsenic concentrations.

Implication: This study indicates that low arsenic containing water in deeper aquifers is the best source of water in Bangladesh. This could explain differences in arsenic concentrations found in wells of close proximity. However, the relationship of arsenic mobility to inflow of carbon raises important concerns about the proper depth and the proximity to high volume irrigation wells. Although this study does not provide immediate relief for the people of Bangladesh, it does provide public health officials the necessary information to identify the candidate wells to be used for drinking water.

Citation: Harvey CF, Swartz CH, Badruzzaman AB, Keon-Blute N, Yu W, Ali MA, Jay J, Beckie R, Niedan V, Brabander D, Oates PM, Ashfaque KN, Islam S, Hemond HF, Ahmed MF. Arsenic mobility and groundwater extraction in Bangladesh. Science. 2002 Nov 22;298(5598):1602-6.