agree that in Bangladesh the cause of the arsenic is natural
(geological) and that it is not introduced by human activity
such as mining. However, controversy persists over how the
arsenic ends up dissolved in the water; there are three main
1) Pyrite Oxidation
It poses that a lowering
groundwater table draws in oxygen, which oxidizes sulphides
and thus releases arsenic; this hypothesis implies that dams/barrages
built across rivers upstream deplete Bangladesh of water,
thus lowering the groundwater table, etc.
It shifts the blame to the use of phosphate
fertilizer by farmers in Bangladesh with the supposed effect of contaminating the soil with arsenic.
Drawing water from a
pond filter in Noakhali, Bangladesh (Photograph
courtesy, UNICEF/ Shehzad Noorani)
Oxihydroxide Reduction Process:
takes place in shallow (<150m)
younger deltaic sediments with large organic components
(high oxygen demand); this was concluded by the British
Geological Survey (BGS) and
their associates after an extensive survey of tubewells
throughout Bangladesh, reported June 2000. According to this
(>150m), older, "flushed" aquifers are much
less contaminated or not at all; this suggests a possible
Approaches to the Arsenic Problem
The Arsenic Problem in
Bangladesh is currrently tackled from three angles:
of patients already suffering. Though urgent and necessary,
this does not remove the cause of the problem.
of arsenic from the water. Many techniques are on offer, but
it remains unclear which one merits large-scale
introduction, and only those capable of purifying large
volumes of water would offer a modicum of relief.
of contaminated sources, based on our current understanding
of the mechanisms of deposition and remobilization of
arsenic, and the identification of safe sources.
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