AGE OF ARSENIC CONTAMINATION IN BANGLADESH
Scholars such as McArthur et al., Gunnar Jack et al. and Aggarwal et al. believe that the groundwater arsenic poisoning has been present in Bangladesh for thousands of years. They also believe that the groundwater arsenic poisoning is occurring by a natural process. We could not find any reliable evidence/data in their reports that support their findings. On the other hand, the available geological, hydrological, hydrogeological, geochemical, groundwater use data and historical medical data indicate that the groundwater arsenic poisoning in Bangladesh is a recent (post-1975/post Farakka) man-made disaster, and oxidation is most likely responsible for the mobilization of arsenic into groundwater.
The age of the arsenic poisoning is directly related to the source and the cause of the poisoning. The development of arsenic related diseases is directly related to the use of arsenic poisoned groundwater for drinking and cooking purposes. The lag time for the development of arsenic lesion in West Bengal is about 2-5 years (Dr. Shaha, dermatologist). The people of Bangladesh and West Bengal of India have similar food habits, they are physically alike, and their intake of drinking water is also similar. The lag time for the development of arsenic lesion in other parts of the world varies from 8 to 14 years.
In order to examine the age, source and cause of the groundwater arsenic poisoning in Bangladesh and West Bengal of India, we have developed the following questions. The answer and analysis of these questions do not support the source, cause and age of the groundwater arsenic poisoning in Bangladesh as proposed by BGS, McArthur et.al., Gunnar Jack et.al. and Aggarwal et.al.
The questions are:
1. If the Oxyhydroxide Reduction hypothesis is correct and if arsenic was present in an adsorbed form on iron hydroxide for thousands of years and existed in a solution for thousands of years in the aquifer groundwater of the Bengal Basin without being flushed out to sea, how did the people of Bangladesh and West Bengal of India avoid the arsenic poisoning when thousands of people drank water from dugwells for thousands of years and from thousands of tubewells for 60 to 70 years, prior to the 1970s?
2. Also please explain how millions of people in Bangladesh who had been drinking water from millions of tubewells during the interval between the 1960's and prior to 1975, before the construction of dams/barrages and diversion of surface water by India from the Ganges, Tista, and 28 other common rivers of Bangladesh and India, lack signs of arsenic poisoning?"
On January 24, 2001, Dr. Peter Ravenscroft, Chief Hydrogeologist of MML and consultant of BGS in his post in Arsenic-Source Group stated that "My earlier conclusions on the age of contamination were based on general geological reasoning. This interpretation has apparently been independently confirmed by isotopic dating reported by Dr. Pradeep Aggarwal of IAEA, Vienna and his co-workers. They conclude that the contaminated waters have been in the ground for between a few tens and a few thousands of years.
Those who suggest an exclusively recent (post-1975) origin would be well advised to examine the IAEA results, and take the argument forwards."
Dr. Bridge, and myself analyzed the various reports and their findings. The available data suggest that the source and cause of the arsenic poisoning is directly related to the abstruction of groundwater and diversion of river water. Dr. Del Fanning, Dr. Chakraborti and Dr.Quamruzzaman's teams also came up with similar conclusions.
Dr.Aggarwal's team consists of Drs. Pradeep K. Aggarwal of International Atomic Energy Agency, Vienna; Asish R. Basu, Robert J. Poreda of University of Rochester, New York, USA; K.M.Kulkarni of Bhabha Atomic Energy Center, India; K.Froehlich of IAEA, Vienna; S.A.Trafder, Mohammed Ali, Nasir Ahmed of Bangladesh Atomic Energy Commission, Bangladesh; and Alamgir Hussain, Mizanur Rahman, Syed Reazuddin Ahmed of Bangladesh Water Development Board, Bangladesh.
Dr Aggarwal and his team in their summary "Isotope Hydrology of Groundwater in Bangladesh: Implications for Characterization and Mitigation of Arsenic in Groundwater" stated that "The exponential increase in groundwater exploitation between 1979 and 1999 does not appear to have affected the overall hydrodynamics of shallow and deep aquifers and, by implication, the arsenic mobilization process. Currently favored mechanisms of arsenic mobilization are found to be inconsistent with isotope data. The most likely process of arsenic mobilization may involve desorption from the sediments as a result of the relatively rapid and continuing (natural) renewal of shallow aquifers with arsenic free water."
If the desorption theory is the mechanism for arsenic release, where are the samples with adsorbed arsenic? What is the lag time for the adsorption of arsenic by iron hydroxide, and what is the age of the ironhydroxide? Dr. Aggarwal and his team did not study the pre-Farakka (prior to 1975) surface water and groundwater data of the Bengal Basin. Their study is based on very limited post Farakka hydrological and groundwater data. As a result, Dr.Aggarwal and his team do not have a clear picture about the surface and groundwater conditions, as well as about the source and the cause of the groundwater arsenic poisoning in Bangladesh.
Dr. Aggarwal and his team did not find any impact on the groundwater level in Bangladesh due to river water diversion from Ganges, Tista and 28 other common rivers of Bangladesh and India. Dr. Aggarwal and his team should know that prior to 1975 in Bangladesh, the area which was underwater for thousands of years is now dry land due to 26 years of river water diversion from the above mentioned rivers.
I suggest Dr. Aggarwal and his team to collect pre and Post Farakka river water discharge data of the common rivers of Bangladesh and India, and adequate groundwater level data in Bangladesh to find the impact of India's 26 years of unilateral diversion of river water on the groundwater as well as the source and the cause of the groundwater arsenic poisoning in Bangladesh.
Like Dr. Aggarwal et al., BGS investigators could not find any impact of river water diversion and over pumping of groundwater on the cause of the arsenic poisoning in Bangladesh, because BGS did not collect adequate pre and post Farakka river water discharge data and groundwater level data. We would like to know from BGS investigators, why they collected pre-Farakka(prior to 1975) river water discharge data of three major rivers of Bangladesh(Ganges, Bhramhaputra and Meghna) and why they did not collect post-Farakka discharge data of these rivers.
We are requesting BGS, McArthur et.al, Gunnar Jack et.al., and Aggarwal et.al. to take a look at the attached hydrograph of the Ganges river (Hardinge bridge point) in Bangladesh (Source:G.Hebblethwaite's research entitled "The Impacts and Implications of the Farakka Barrage upon Bangladesh" B.S. thesis, University of New Castle upon Tyne, U.K.,1997), to understand the importance of adequate pre and post Farakka river water discharge data of the common rivers of Bangladesh and India, and groundwater level data in Bangladesh for the study of the source and the cause of the arsenic disaster in Bangladesh.
We do not disagree with Dr. Aggarwal's isotopic findings regarding the age of the groundwater, but we do not agree with the age of groundwater arsenic poisoning. The age of the water and the time arsenic entered the water are TWO DIFFERENT THINGS. If arsenic was tied up in minerals that were stable below the water table when the sediments were first deposited and released when oxidation occurred as the groundwater table was lowered at a later date, then the date of arsenic contamination relates to the groundwater lowering not the age of the water.
The fact that some of the wells were below the WHO limits for arsenic when they were first tested and later tests detected an increase in concentration of arsenic above safe limits is an indication that recent local changes in the environment caused the change. Oxidation of arsenic pyrite and other arsenic bearing minerals is one possibility for the change. If the water diversion from rivers and the over pumping of groundwater are continued, this process will contaminate both new and old uncontaminated water whether the water is 25 years of old, or thousands/millions of years of old.
For thousands of years Prior to 1975 and before the construction of dams/barrages by India and India's unilateral diversion of surface water from the Ganges, Tista, and 28 other common rivers of Bangladesh and India, the people of Bangladesh drank groundwater from dug wells. If arsenic were present in the ground water it may have been diluted by surface water and the addition of dissolved oxygen may have caused precipitation of some of the arsenic and dissolved iron. During a period of about 60-70 years prior to 1975 some several millions tubewells were installed in Bangladesh. In 1940, about 50,000 tube wells were in use in Bangladesh(former East Pakistan). Millions of people (infants, young and old) drank water from these wells. No occurrences of arsenic diseases were recorded for those people who drank water from these tube wells.
Arsenic-poisoned patients were first discovered in Bangladesh in the early 1990's and in West Bengal in the early 1980's. The historical medical evidence supports a recent origin for the mobilization of arsenic into the groundwater of Bangladesh and West Bengal of India. In our articles we have explained how arsenic pyrite oxidation is one mechanism that could be adding arsenic to the groundwater as a result of change in water table levels.
It appears that Dr.Ravenscroft, Dr. Aggarwal and others have been confused by Aggarwal et al. isotopic findings, and as a result have misinterpreted the "age of groundwater" as the "age of groundwater arsenic poisoning." The historical groundwater use data and the historical medical data are more reliable and dependable methods to determine the age of the groundwater arsenic poisoning rather than isotopic and other methods. The geological, hydrological, hydrogeological, geochemical, historical groundwater use data and historical medical data do not support the age, source and the oxyhydroxide reduction and the desorption theories for the mobilization of arsenic into the groundwater of Bangladesh as proposed by BGS, McArthur et al., Gunnar Jack et al. and Aggarwal et al.
We are respectfully requesting Dr. Aggarwal and his team to answer the following question:
Why should the "age of the groundwater arsenic poisoning" in Bangladesh, determined by Aggarwal et al. not be considered incorrect?
Source: Meer Husain, The Independent, June 19, 2002