NATURAL ORIGIN OF ARSENIC BY WESTERN SCIENTISTS AND THEIR FOLLOWERS
Arsenic poisoning: man-made disaster
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.
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).
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 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.
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".
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
FeOOH is microbially reduced and releases its sorbed load of arsenic to groundwater
In the deltaic plain of the Ganges-Meghna-Brahmaputra rivers, arsenic concentrations in groundwater commonly exceed regulatory limits (>50 ug l-1) because FeOOH is microbially reduced and releases its sorbed load of arsenic to groundwater. Neither pyrite oxidation nor competitive exchange with fertilizer-phosphate contribute to arsenic pollution. The most intense reduction, and so severest pollution, is driven by microbial degradation of buried deposits of peat. Concentrations of ammonium up to 23 mg l-1 come from microbial fermentation of buried peat and organic waste in latrines. Concentrations of phosphorus of up to 5 mg l-1 come from the release of sorbed phosphorus when FeOOH is reductively dissolved, and from degradation of peat and organic waste from latrines. Calcium and barium in groundwater come from dissolution of detrital (and possibly pedogenic) carbonate, whilst magnesium is supplied by both carbonate dissolution and weathering of mica. The 87Sr/86Sr values of dissolved strontium define a two component mixing trend between monsoonal rainfall (0.711 ± 0.001) and detrital carbonate (< 0.735) (J.M. McArthur, Water Resources Research, 37(1), 109-117. ).
But within the same geological formation 60 percent of the tubewells are arsenic contaminated but 40 percent are below arsenic standard or arsenic free!!!
"Arsenic Mobility and Groundwater Extraction in Bangladesh (II), SCIENCE VOL 300, 25 APRIL 2003"
"...A recent report from the International Atomic Energy Agency(8) lists eight samples with significantly elevated arsenic levels that do not contain any detectable 3H. We have collected and analyzed an additional 49 groundwater samples from other wells in Bangladesh that include a set of 5 paired arsenic and 3H analyses indicating high arsenic levels without detectable 3H (9, 10). The implication of the combined data set is that over a dozen carefully analyzed samples indicate that Bangladesh groundwater was elevated in arsenic well before the onset of massive irrigation. We therefore believe that increased irrigation over the past 25 years is unlikely to have caused widespread arsenic mobilization in Bangladesh groundwater through the sequence of steps proposed by Harvey et.al. in their otherwise very valuable contribution".
We already explained why your and Aggarwal et.al. isotopic studies for the determination of age of the groundwater arsenic poisoning in Bangladesh and West Bengal of India are not acceptable. We also strongly disagree with you and Harvey et.al regarding the reduction mechanism as the principal mechanism for releasing arsenic into groundwater because both you and Aggarwal et.al., McArthur et.al., and BGS investigators have rejected the recent Oxidation mechanism without any proper investigation. we could not find any data and evidence in your articles/reports that reject the recent oxidation mechanism as the principal cause for releasing arsenic into groundwater of Bangladesh and West Bengal of India.
Although Harve et.al. have failed to examine the oxidation and reduction mechanism with adequate data, they have properly noted and observed the significant draw down of water level in their study area that is linked to the recent over pumping of groundwater and diversion of river water, which is one of the three principal conditions for oxidation mechanism for releasing arsenic into groundwater. A significant lowering of the water table that occurred after 1975 was also reported by British geological Survey, Bangladesh Water Development Board and Bangladesh Agricultural Development Corporation.
In 2003, in order to disprove the Harvey et.al's groundwater draw down data, Aggarwal et.al. in their "Comment on Arsenic Mobility and Groundwater Extraction in Bangladesh, SCIENCE VOL 300, 25 APRIL, 2003" presented a groundwater hydrograph ( Observation well FA-01F) located in Faridpur, which does not show any draw down of water table after 1975 i.e., after the diversion of river water from the Ganges, Tista and 28 other common rivers of Bangledsh and India at all.
Many scientists around the world have probably accepted Aggarwal et.al. data as you have. We can not accept Aggarwal et.al's water level draw down data because Harvey et.al., Bangladesh Water Development Board, Bangladesh agricultural Development Corporation, British geological Survey and others' data show a significant lowering of the water table that occurred after 1975.
Please take a look at the attached hydrograph (Observation well FA-01F) that Aggarwal et.al. presented to disprove the post 1975/1960 draw down of groundwater level linked to agricultural irrigation and harvesting of river water from the Ganges, Tista and 28 other common rivers of Bangladesh and India in the up stream territory of India.
In follow-up e-mails I will Present some groundwater hydrological data that reject Aggarwal et.al. data. (Meer Husain, P.G. Environmental Geologist,Kansas Dept. of Health & Environment and Cowley County Community College Kansas, USA.. June 2005)
Arsenic is correlated to the colour of the sediment. Red or brownish sediments have been found to have low conentration of As
Elevated concentration of arsenic (As) in the groundwater of the shallow Holocene aquifers in Bangladesh is a major health concern. The levels of As in the groundwater is often above the national drinking water guideline value of 50 µg/L.
Arsenic is a naturally occurring element in the sediment-water system and is bound to different oxide minerals. Recent studies have revealed that the As concentration of the groundwater is correlated to the colour of the sediment. Red or brownish sediments have been found to have low conentration of As, possibly due to the adsorption of As on Fe(III)-oxyhydroxides (which gives the sediment its colour) and/or that these sediments have been weathered during the late Holocene age. The present study describes the adsorp-tion behaviour of the oxidised sediments as these sediments could be a potential source of As-safe drinking water for millions of rural villagers in Bangladesh. The study area was located in Matlab Upazila, SE Bangladesh, which is one of the hotspots for As-contamination of groundwater. Twenty tube wells were sampled to establish the water chemistry and to determine the age of the water. Two boreholes were drilled to prepare lithologs as well as to collect oxidised sediments. Batch experiments were performed in columns with flushing of reduced water through oxidised sediments to study the adsorption behaviour of the sediments, and the impact of redox reactions was studied though the addition of organic matter (lactose) to some of the columns. The concentration of As in the tubewells ranged between (less than) 5-400 µg/L. Groundwater age range between 1 and 12 kyr and reveal a linear correlation, the depth of the tubewells.as well as restricted movement of water both in the reduced and oxidised aquifers. The sediment chemistry analyses revealed a low amount of As, below 5 mg/kg, in the oxidised sediments ( HÄLLER, Sara1 et. al., 2007 GSA Denver Annual Meeting (28-31 October 2007) .
1. ARSENIC POISONING - ARGUMENT AGAINST NATURAL ORIGIN ?
2. AGE OF ARSENIC CONTAMINATION IN BANGLADESH
3. Genesis of arseniferous groundwater in the alluvial aquifers of Bengal Delta Plains and strategies for low-cost remediation
4. VIEWS ON SOURCE OF ARSENIC POISONING
5. Arsenic in Groundwater: Research and Rhetoric
6. ARSENIC AND OTHER TOXIC METALS IN BANGLADESH’S DRINKING WATER
7. Contamination of soil due to irrigation with arsenic laden water and its impact on phosphorus leading to crop production in Bangladesh
Last Modified March 14, 2008