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Meer Husain info@sos-arsenic.net 6/14/04 10:56 AM |
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? |
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SOS- Arsenic info@sos-arsenic.net 6/14/04 11:01 AM |
NATURAL ORIGIN OF ARSENIC BY WESTERN SCIENTISTS AND THEIR FOLLOWERS With funding comes control over the specific content of research projects. The British Overseas Department financed the British Geological Survey and MacDoland (UK) Ltd engaged to find out the origin of arsenic in Bangladesh. According to the British Geological Survey and MML (1998, 1999) predict that sources of arsenic are without any doubt geological, in other words, naturally occurring arsenic contaminated the groundwater. The result of their investigations are according to the requirements of the donors that do not want to take responsibility of arsenic poisoning in Bangladesh. British Geological Survey do not support aerobic hypotheses as proposed by Indian scientists. Their main arguments on the processes of arsenic mobilisation are proposed by Nickson (1997) in his M.Sc. thesis. The geological formations from 10.5 million years to recent do not show any abnormal amount of arsenic that can contaminate the ground water of Bangladesh. The Indian Geological Survey and others (1999) reports: Our observations indicate that arsenic-rich pyrite and other arsenic minerals that give rise to arsenic pollution are rare or even absent in the sediments of the Ganges delta. Where arsenopyrite is present in sulphide ores associated with sediment-hosted gold deposits, it tends to be the earliest-formed mineral, derived from hydrothermal solutions and formed at temperatures typically of 100ºC or more. Such deposit is unknown in Bengal Basin. The Ganges alluvial tract upstream of Rajmahal, in the state of Bihar and Uttar Pradesh does not suffer arsenic contamination on a large scale The relatively low values of dissolved iron (0 - 0.7 mg per litre) upstream of the Ganges delta (Utter Pradesh and Bihar) indicate that the environment may not be sufficiently reducing iron and arsenic. Datta and Subramanian (1997) found concentrations in sediments from the River Ganges averaging 2.0 mg kg–1 (range 1.2–2.6 mg kg–1), from the Brahmaputra River averaging 2.8 mg kg–1 (range 1.4–5.9 mg kg–1) and from the Meghna River averaging 3.5 mg kg–1 (range 1.3–5.6 mg kg–1). The copper belt of Bihar (India) contains small amounts of arseopyrite and the coal basins of the Damodar valley (India) contain moderate concentrations of arsenic are drained by rivers that flow far to the south of the Ganges tributary system. ARGUMENT AGAINST NATURAL ORIGIN It is a story about underground water: when the nectar turns into poison. When a daily task of drinking water from the handpump becomes the source of crippling disease and death. This is not a "natural" disaster - where natural arsenic or fluoride, present deep down, just happened to make their way into drinking water. It is about a deliberate poisoning. Created by successive governments and multilateral agencies: all well intentioned in their quest for safer, cleaner water supply; all investing in boring into the ground, till they brought the dark zone into the light (CSE, 13. 08. 03) The story begins many years ago, sometimes in the 1960s and 1970s, when national governments and international agencies drew up detailed plans to provide safe water to all. They understood, rightly, that bacteria in water kills more babies than any other substance in the world. They believed the water on the surface - in millions of ponds and tanks and other water harvesting structures - was contaminated and so invested quickly in new technologies to dig deeper and deeper into the ground. Drills, borepipes, tubewells and handpumps quickly became the triumphalistic instruments of public health missions. Then the water table started to fall. Investment were made to dig deeper. And here is where the story turns. More than three decades of application of registered and unregistered agrochemicals lead to a dramatic soil erosion in Bangladesh. To compensate for the soil's dwindling natural fertility, farmers must apply more and more fertilisers - but with the decreasing prospect that yields will increase. Bangladesh is a very sad example that a wrong agricultural policy was applied to save lives, now millions are exposed to death slowly and silently. Seed, fertiliser, pesticide and ground water power pumps have completely changed the nation. Virtually all modern seed varieties are bred prominently for one thing "high yield" since high yield means more profit. Donor countries are happy with financing that also determines the type of research, as it has been observed from millions of dollars research work by the British Geological Survey and McDoland Ltd (UK). Arsenic poisoning: man-made disaster Genesis of Arsenic in Ground Water Delta At the CGWB(ER) workshop of February 7, 2002, he explained the contamination as due to natural geological setting caused by Holocene sea level rise and Ganga Brahmaputra deltaic sedimentation (S K Acharya, Arsenic in Groundwater from Southern West Bengal: Influence of Holocene Deltaic and Biochemical Reduction Process). Now a CSIR emeritus scientist, Acharya refuted the hypothesis that arsenic-bearing pyrite and/or arsenopyrite in the rock formation are a source of arsenical toxicity. Sikdar and Banerjee, in a paper published in the Journal of Human Settlements and titled 'Genesis of Arsenic in Groundwater Delta - An Anthropogenic model', found that extensive use of lead arsenate and copper arsenite as rhodenticides and pesticides explained more logically the causation of toxicity of arsenic origin than geological or geomorphological settings. The arsenicals dissolved in rainwater and then percolated through the zone of aeration into the aquifer over several years, they noted, while in aquifers that contain ferrous iron and manganese the "reaction took place with the dissolved oxygen, precipitating hydrated ferric oxide and hydrated oxides of Mn+3 and Mn+4. These precipitate acted as scavengers and retained the arsenic present in pentavalent state through chemi-sorption." The redox balance tilted towards a reducing environment, due to the organic rich argillaceous sediments deposited in fluvio-deltaic marshes and "triggered by recent heavy groundwater abstraction and use of phosphate fertilisers". The new findings corroborate what Subrata Sinha, formerly deputy director general of GSI, said in the early 1990s, when differing with the GSI where he was still working then. The change in soil chemistry “obviously causes arsenic contamination. The contra-indications are due to zealous emphasis on summer paddy cultivation using excessive inorganic pesticides. The most disturbing aspect of the arsenic problem in groundwater is tendentious sensationalisation and panicking. Besides, technologists from other disciplines who seemed to have been driven by monetary greed have sidelined opinions of geologists. Right now the authorities should severely restrict the propensity of farmers in growing HYV paddy during summer. A recent study which finds that arsenic pollution in groundwater is caused by the indiscriminate use of chemicals in agriculture, challenges the conclusion reached by other parties that it is basically geologic in nature. However, despite valid concerns over arsenic contamination, scare mongering by certain interests as well by the media is unwarranted. The findings of Sikdar and Banerjee would demolish the myth – emanating from the School of Environmental Studies, Jadavpur University, and propagated by the media – that arsenic pollution is basically geologic. The two geoscientists concentrated their research investigations to lithostratigraphic and geochemical aspects. They say, “Most scientists postulate that arsenic pollution in the Ganga delta of Bengal basin is a natural phenomenon and the origin of arsenic is related to the geological setting of the Bengal basin caused by Holocene sea level rise and the Ganga-Brahmaputra deltaic sedimentation. But the geological origin and mechanism of transport of arsenic from the source to the sink cannot answer some field observations. This paper at first discusses briefly the geological origin and mobilisation of arsenic in groundwater and its drawback and then, to overcome the difficulty, presents an anthropogenic model of the genesis of arsenic in groundwater.” This inference seeks to reject the inference by the Geological Survey of India (GSI), which in the late 1980s suggested that arsenic was “occurring in shallow sandy origin within a particular geological/geomorphological unit (Sankar, 2003). The arsenic dissolved in rainwater and then percolated through the zone of aeration into the aquifer over several years, they noted, while in aquifers that contain ferrous iron and manganese the “reaction took place with the dissolved oxygen, precipitating hydrated ferric oxide and hydrated oxides of Mn+3 and Mn+4. These precipitate acted as scavengers and retained the arsenic present in pentavalent state through chemisorption.” The redox balance tilted towards a reducing environment, due to the organic rich argillaceous sediments deposited in fluvio-deltaic marshes and “triggered by recent heavy groundwater abstraction and use of phosphate fertilisers”. Sikdar and Banerjee(2003)) based their study on six lithostratigraphic drillings they made in North 24 Parganas, Hooghly and Murshidabad districts. Five of these were in areas that have a high concentration of arsenic. The sixth was a control block in a non-arsenious zone in North 24 Parganas. They found six heavy mineral sites in sedimentary rocks mainly belonging to the Bihar plateau, with a portion originating in the sedimentary segments of the Himalayan region. "XRD analysis reveals that illite is the dominant clay mineral in the clay/silty clay partings. No arsenic bearing mineral phase could be identified in the clay or in the sands in the arsenious zone. The concentration of arsenic in sediments generally decreases with depth and arsenic has high positive correlation with iron, manganese, copper and lead and low correlation with zinc based on multiple correlation analysis. The mobility of arsenic from the sedimentary pyrite layer into the aquifers due to large-scale withdrawal of groundwater for agriculture and drinking purposes is due to the green revolution and outbreak of cholera in the 1960s in south Bengal. This followed rapid intake of O2(oxygen) within the pore spaces of the sediments and are believed to be due to the following geochemical processes: FeS2 + 2H2O + 5O2 ® FeSO4 + 2H2SO4 …(1) (Pyrite) (Ferrous sulphate) FeSO4 + O2 + 2H2SO4 2Fe (SO4)3 …(2) (Ferric sulphate) FeS2+7Fe2 (SO4)3+8H2O ®15FeSO4+8H2SO4 …(3) Needless to say, the ferric ion thus released acts as a catalyst in further decomposition of pyrite. Sikdar and Banerjee doubt the validity of this geochemical explanation. Taking a cue from an unpublished paper by K S Subramaninan et al, they point out a conceptual anomaly in the physico-chemical understanding of geologists of yesteryear and also of S K Acharya, former director-general GSI.5 "First, equations (1) and (3) may proceed chemically, but equation (2) cannot proceed chemically in acid solution and can occur via microbial oxidation, possibly caused by the microorganism of the ferrobacillus-thiobacillus group. Second, under the above oxidising condition arsenic will be mostly in As+5 oxidation state, but in nature As+3 is dominant in groundwater as observed by the authors in groundwater samples of North 24 Parganas district Third, the mechanism does not take into account the physico-chemical characteristics of the groundwater samples. In general, the pH and bicarbonate values of groundwater samples in arsenic affected areas are above 7 and 500 mg/l respectively. Under these conditions, it is doubtful whether reactions (2) and (3) would proceed, and consequently, to what extent leaching of arsenic would occur," the two earth-scientists explained. The findings of Sikdar and Banerjee would demolish the myth - emanating from the School of Environmental Studies, Jadavpur University, and propagated by the media - that arsenic pollution is basically geologic. The two geoscientists concentrated their research investigations to lithostratigraphic and geochemical aspects. They say, "Most scientists postulate that arsenic pollution in the Ganga delta of Bengal basin is a natural phenomenon and the origin of arsenic is related to the geological setting of the Bengal basin caused by Holocene sea level rise and the Ganga-Brahmaputra deltaic sedimentation. |
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Life Sciences Centre hasanat@interchange.ubc.ca 10/01/05 4:36 PM |
Arsenic in Groundwater: Bangladesh Experience Arsenic in Groundwater: Bangladesh Experience October 24, 2005 2.00 PM-8.00 PM LSC3, Life Sciences Centre, University of British Columbia, Vancouver Session I: 2-4:30 Chemistry, Epidemiology & Toxicology of Arsenic Dr. William Cullen, Dept of Chemistry, UBC Dr. David L. Eaton, School of Public Health, University of Washington Dr. Allan H. Smith, School of Public Health, University of California, Berkeley Dr. David A. Kalman, School of Public Health, University of Washington Dr. Ray Copes, BC Centre for Disease Control; BC Ministry of Health Session I Chair: Dr. Susan Kennedy, Health Care & Epidemiology, UBC 4.30-5: Coffee Break Session II: 5-7:30 Measurement & Mitigation of Arsenic in Groundwater Dr. Richard Wilson, Dept of Physics, Harvard University & The Arsenic Foundation Dr. Roger Beckie, Dept of Earth and Ocean Sciences, UBC Dr. Adele Buckley, Ontario Centre for Environmental Technology Advancement Dr. Ken J. Hall, Dept of Civil Engineering, UBC Dr. Steve Reiber, HDR Consulting, Seattle & Dept of Civil Engineering, University of Washington Session II Chair: Dr. Michael Brauer, School of Occupational and Environmental Hygiene, UBC 7.30 Refreshments Organized by: Bangladesh Students Association at UBC http://www.ams.ubc.ca/clubs/bsa/ Sponsored by: University of British Columbia - Dept. of Health Care and Epidemiology School of Occupational and Environmental Hygiene Centre for Health and Environment Research Centre for India and South Asia Research American Industrial Hygiene Association, BC & Yukon Contact: Hasanat Alamgir President, Bangladesh Students Association at UBC hasanat@interchange.ubc.ca 604-822-0839 ------------------------------------------------------------------------ Natural arsenic contamination is a cause for concern in many countries of the world including Argentina, Bangladesh, Chile, China, India, Mexico, Thailand and the United States of America. In Bangladesh, 27 % of shallow tube-wells have been shown to have high levels of arsenic (above 0.05mg/l). It has been estimated that 35 - 77 million of the total population of 125 million of Bangladesh are at risk of drinking contaminated water (WHO bulletin, volume 78, (9):page 1096). Approximately 1 in 100 people who drink water containing 0.05 mg arsenic per litre or more for a long period may eventually die from arsenic related cancers. Because of the delayed health effects, poor reporting, and low levels of awareness in some communities, the extent of the adverse health problems caused by arsenic in drinking water is unclear and not well documented. WHO has described the situation in Bangladesh as the largest mass poisoning of a population in history. |
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