Validity of the Latest Research Findings on Causes of Groundwater Arsenic Contamination in Bangladesh

Abstract

The groundwater arsenic contamination problem in Bangladesh is the worst in the world. Two hypotheses are prevailing as the cause (mobilization) of groundwater arsenic contamination in Bangladesh. One is called "pyrite oxidation" and the other is "oxy-hydroxide reduction." According to the first hypothesis, groundwater arsenic contamination is human-made, which has a relationship with excessive groundwater withdrawal. On the other hand, according to the second one, the contamination is natural. The British Geological Survey (BGS) conducted an investigation to identify the cause of groundwater arsenic contamination in Bangladesh. Based on their findings, they rejected the pyrite oxidation hypothesis and accepted the oxy-hydroxide reduction hypothesis. However, several experts are opposing their research findings. Therefore, a case study is undertaken to examine the validity of the BGS findings. Although we obtained results which are similar to the BGS, the errors in the estimates of percent of wells contaminated, the key parameter of these analyse show that the present as well as BGS results are not dependable to make any conclusion about the cause of contamination. Moreover, the validity test shows that space-dependent relationships among different hydro-geological parameters for the heterogeneous aquifer system are not valid to represent time-dependent phenomena. Therefore, the conclusion made by the BGS is not valid. Still, there is a possibility that the pyrite oxidation hypothesis could be accepted. For a final conclusion we must observe these relationships in a time domain by generating reliable time-dependent field data.

Arsenic Contamination in Groundwater: A Statistical Modeling

“…Time here is seen to be linked with arsenic also indicate the oxidative dissolution of arsenic mineral which may again be consider to release of arsenic in ground water as a time variable parameter. The same phenomenon is endorsed by Fazal et al (2001).…”

“…In West Bengal arsenic species in contaminated drinking water were found to be arsenate and arsenite in 1:1 ratio (De, 2008). Pyrite oxidation has been proven to be the most acceptable hypothesis to explain the occurrence of arsenic in ground level water (Fazal et al, 2001). Therefore, the occurrence of arsenic might be coupled with the presence of iron (Fe) in water.…”

“…This would strengthen the correlation between arsenic and iron concentration of ground water more rational. Though several authors also reported an interrelation of groundwater arsenic concentration with Static water level (SWL) (Welch & Stollenwerk, 2003), Depth (Chakraborti et al, 2009), pH (Saxena et al, 2004) and Age (time) of the wells (Fazal et al, 2001) at a regional level. Now a day, interest has been also grown in determining of antimony (Sb) in groundwater due to its similar chemio-toxicological properties (Gibel, 1997) with arsenic though Sb-induced toxicity is more violent vomiting in accompanied with watery diarrhea and sever weakness (Das, 2008).…”

Effect of arsenic on photosynthesis, growth and yield of five widely cultivated rice (Oryza sativa L.) varieties in Bangladesh

“…Arsenic is one of the toxic environmental pollutants which has recently attract attention because of its chronic and epidemic effects on human health through widespread water and crop contamination due to the natural release of this toxic element from aquifer rocks in Bangladesh (Fazal et a., 2001;Smith et al, 2000;Ahmed, 2000;Hopenhayn, 2006), West Bengal, India (Chakraborti and Das, 1997;Banerjee, 2000). Geogenic contamination of arsenic in aquifer rocks has also been reported in Thailand (Visoottiviseth et al, 2002), Vietnam, Inner Mongolia, Greece, Hungary, USA, Ghana, Chile, Argentina and Mexico (O'Neill, 1995;Smedley and Kinniburgh, 2002).…”

Arsenic contamination in groundwater and its proposed remedial measures

“…The toxicity of arsenic follows the order: Inorganic As (III) species > Organic As (III) species > Inorganic As (V) species > Organic As (V) species > Elemental Arsenic. Arsenite is 60 times more toxic than arsenate (Fazal et al, 2001a), and arsenopyrite has been identified as the prime source of As pollution in Bangladesh (Fazal et al, 2001b). Arsenic can be introduced to a groundwater system through various means, including surface water and precipitation as well as anthropogenic and naturally occurring sources (Urik et al, 2009;Reza and Singh, 2010).…”