Subsurface Arsenic Occurrence and Depth of Contamination in Bangladesh.

Abstract

Both soil and underground water of the southwestern Bangladesh has already been threatened with arsenic contamination affecting health of millions of people. An estimated 44% of total area of Bangladesh (34 districts) and 53 million rural people are at risk of arsenic poisoning. In the southwestern and some parts of eastern Bangladesh, arsenic content in soil and underground water has identified higher contamination. The experts at Bangladesh Council for Scientific and Industrial Research (BCSIR) found the highest contamination, 14mg/l of shallow tube well water in Pabna, a northern district and 220mg/kg of soil in Sylhet area of Bangladesh.1) The World Health Organization (WHO) standard for arsenic in drinking water is 0.01mg/l. However, the maximum permissible limit of arsenic in drinking water of Bangladesh is 0.05mg/l. Worsening contamination of groundwater aquifer and sufferings of the millions of people demand extensive research in this field. This study is a preliminary evaluation of our ongoing research on current state of the subsurface contamination of arsenic in Bangladesh. Last decade water resources management has been analyzed to cope with the problem in the source level. Possible geo-hydrological and geo-chemical occurrences of arsenic in subsurface are discussed. The concentration of arsenic and the stratigraphic occurrence are presented. It is observed that arsenic concentration in tubewell water of 31 districts of Bangladesh contain above the maximum permissible limit. And the concentration of arsenic in tubewell water decreases with the depth of subsurface.

A Review of Groundwater Arsenic in the Bengal Basin, Bangladesh and India: from Source to Sink

“…Harvey et al [38] further argued that irrigation-pumping-induced inflow of the young inorganic carbon through rice fields and organic-rich ponds and river bottoms mobilizes the older organic carbon (probably by release from iron hydroxide grains which are known to sequester organic carbon), which in turn drives the biogeochemical processes mobilizing arsenic, involving organic carbon-driven reduction or displacement by bicarbonate. McArthur et al [28] on the contrary, argued that the CH 4 in the aquifers (reported by Ahmed et al [122], Harvey et al [38] and Pal and Mukherjee [85]) proves the presence of subsurface organic matter around the study areas and claimed that the surface sources of organic matter proposed by Harvey et al [38] do not seem to be a likely redox driver controlling the fate of arsenic mobilization due to the following reasons: Firstly, if the surface sources of organic matter would have been the dominant source of carbon to the aquifers then neither would the arsenic enrichment be localized to only 25 % of the wells in Bangladesh and nor would the arsenic contaminated wells be limited to only the Holocene aquifers, leaving out the Pleistocene-aged Madhupur and Barind tracts [55,118]; secondly, nor would the arsenic concentrations be highest around ∼20-40 m deep groundwater of the Bengal basin [29,38,55,118,149]; and finally, the dissolved organic carbon (DOC) is highest around 30 m depth and remains moderately high upto 80 m depth, which indicates a deep source for the DOC.…”

Mechanism of arsenic release to groundwater, Bangladesh and West Bengal

“…Arsenic concentrations increase with depth in wells at Manikganj, Faridpur and Gopalganj (Fig. 3), but other trends are reported to occur elsewhere, in particular, a maximum As concentration at 20 to 40 m depth has been reported (Karim et al, 1997; S.K. Acharyya, pers.…”

Influence of soil type and properties on distribution and changes in arsenic contents of different paddy soils in Bangladesh

“…Currently, about three quarters of the population are seriously affected by drinking water from arsenic contaminated groundwater in this country. Many reports (Karim et al 1997;AAN 1999AAN ,2000Ishiga et al 2000;Nickson et al 2000) indicate the large variability of this groundwater As problem on both local and regional scales. According to Ali and Wakatsuki (2002), water analysis from 1762 tube wells revealed that 64% contained As levels higher than the acceptable limit set by the WHO (0.01 mg L -I).…”