|The Daily Star||
Volume 3 Number 236 Fri. April 28, 2000
Arsenification: Searching for an Alternative Theory
By Miah M. Adel
They do not admit that upstream water diversion has caused shortage of recharging water, and consequently, the shortage of oxygen in the recharging water to let occur water's natural purification process, although they admit that in presence of oxygen in groundwater, arsenic will be scavenged by iron hydroxide
THE author, a PhD, is Professor, Interdiscipli-nary Sciences Research Centre, University of Arkansas
The groundwater poisoning in the Bengal basin is the worst disaster in the history of human civilization. More than 75,000,000 people live under the threat of cancer due to drinking arsenic contaminated water.
My comments are on the article entitled " Mechanism of arsenic release to groundwater, Bangladesh and West Bengal" authored by R T Nickson, J M McArthur, P Ravenscroft, W G Burgess, and K M Ahmed and published in Applied Geochemistry, 1999. It seemed to me that the author group was introducing unrepresentative facts and figures for Bangladesh as representative ones into the world scientific community, which being recorded in the scientific literature might mislead scientists.
Facts about organic carbon are these: About 1 per cent of soil matter is organic. And about 60 per cent of organic matter is organic carbon. Or in other word, about 0.6 per cent of soil matter is organic carbon. Soil scientists from agricultural extension centers say that a 1 per cent organic matter or 0.6 per cent of organic carbon is equivalent to 20,000 pounds of organic matter in an acre of land that is six inches deep and that 90 per cent of organic matter lies in soil surface within the top six inches. Organic matter in soil comes from dead plants, animals, and insects. Leaching beneath the soil surface occurs for organic carbon from sugars and starch.
Surprisingly enough, the author group mentions that the organic carbon content in aquifer sediment is 6 per cent. Out of their ten samples, they find only in one sample above 6 per cent. Out of the rest, four are below 1 per cent in organic carbon content. Nothing has been said about the other five. Although, this 6 per cent would be much less than the 10 per cent found below the top six inches of the soil, if it is taken to be 10 per cent, the 90 per cent which lies within the top six inches becomes 54 per cent of the original. With the above clue of 0.6 per cent of organic carbon in 20,000 organic matter in a six-inch deep one-acre land, the Nickson group's finding suggests 1,800,000 lbs of organic matter within the top six inches of an acre of land in Bangladesh whereas the total soil content up to this depth in one acre of land is about 2,992,504 lbs. The Nickson group overly emphasizes on this data point. In their own words "This process is driven by the microbial oxidation of organic C, concentration of which reach 6 per cent C in aquifer sediment". The author group's fascination for this unfounded number goes beyond the boundary of scientific ethics. Their one sample 6.2 per cent organic carbon is being publicized as representative of the delta. Even if it is at all true for a specific site, a site-specific information cannot be representative for the whole country. Under normal procedure, the data should not be shown because of being 10 to 30 times more deviated from the average trend of the four other datapoints.
Even in a country like the USA which has got 55 per cent forest cover, about 1 per cent of organic matter lies in the soil. In a country like Bangladesh which is not even 9 per cent forested, how can such astronomical magnitude of organic matter be present?
In a recent response, Mr. Nickson pointed to the fact that one apple was enough to convince Newton. He should understand that Nickson's arsenic investigation and Newton's gravity meditation are two separate issues. They are not like even apples and oranges in shape. His group's 6 per cent organic carbon point is not tenable at all.
They think that organic carbon takes oxygen from iron hydroxide and arsenic is released in water with the production of carbon dioxide. However, they have not supplied any measured amount of carbon dioxide to that depth. They say that this reaction has been occurring for thousands of years. To the question of why arsenic contamination was detected in the nineties if organic carbon has been taking oxygen from time immemorial, their answer is not specific, rather vacillating.
They totally disregard the fact that people of the delta had been using groundwater for thousands of years. In 1941, there had been 50,000 villages and a population of 38,807,000 in the delta what is called Bangladesh today. The number of villages is now 87,000 and the population has risen to about 120,000,000. From the forties to the seventies, the number of open wells in a village varied from 5 to 10, on the average. The risk factor for the people living in the past can be calculated using the average individual weight, individual daily water intake, and the arsenic concentration.
The risk factor associated with the drinking of arsenic-contaminated water for an adult weighing 60 kg with a daily intake of 5 liters of water is 0.05 multiplied by the concentration of arsenic in water measured in mg per liter. It means if the concentration is 0.1 mg per liter, the risk factor becomes 0.05 x 0.1 = 0.005. This implies that five individuals out of 1,000 has the possibility of being affected with arsenic. If the concentration is 1 mg per liter, then there will be 5 patients out of 100, and for 2 mg per liter, there will be 10 patients out of 100.
If the age and the water intake are different, then the risk factor is the product of 1.75 arsenic concentration in water in mg per liter, and daily water intake in liter per day, and divided by the weight of the person. Today, the effect of arsenic contamination has broken out like an epidemic. Why is it happening now? Why did it not happen in the past? Here, again, come their myths and legends - people, possibly, had it but were wrongly diagnosed.
Furthermore, the scholars cannot deny the fact that today's tubewells are lifting the same water as was lifted from open wells in the past. Ravenscroft, one of his co-authors, finally admitted that water in open wells is neither in oxic (in contact with oxygen) nor anoxic (out of contact with oxygen) condition. Under this condition, how can an open well water cleanse itself of the heavy concentration of arsenic 1-2 mg per liter in matters of hours, the intervals between lifting of well water by its users? So, the current epidemic form should be existing in the past, too. Only exposure was not as such.
Concerns are raised for the authors for not admitting the fact that during the wet season the recharging groundwater carried 8-16 ppm of oxygen, which reacted with iron oxide to produce the scavenger (ferric hydroxide) for arsenic. However, the authors do admit the scavenging activity of iron oxide to pick up arsenic in presence of oxygen from a different source. They totally ignore the effect of surface water shortage. In no places do the authors mention the roles played by the lost surface water resources. Why is this negligence?
Groundwater flows from one part to another part in intervals of days, weeks, years, and even decades. These flows are classified as local, intermediate, and regional. Other than these flow systems, groundwater flows from higher elevation to lower elevation.
Mr Nickson refers to the Swedish group as supportive of their speculation. A Mr Prasam Banarjee from the Swedish group holds the opinion (New York Wagner College Conference, 1999) that the floodplain water in Bangladesh is void of oxygen. If that is true, how can fish be raised in floodplains? How can rice be cultivated in floodplains? And even how can deep water rice cultivation project work? Neither fish can live nor rice plants can grow without oxygen.
For information of others, let us take a trip around the Bangladesh land border with India. The great ring of dams and barrages and other water diversion arrangements include the ones upon the Madhumati, the Ichamati, the Betna-Kodalia, the Bhairab-Kabodak the Ganges, the Khukshi, the Atrai, the Punarbhaba, the Mahananda, the Karatoa, the Talma, the Ghoramara, the Seonai-Jamuneshwari, the Buri Teesta, the Tista, the Sangil, the Dharla, the Jinjiram, the Bhogai, the Piyan, the Kushiyara, the Sonai-Bardal, the Juri, the Manu, the Dhalai, the Khowai, the Sonai, the Gomti, the Selonia, the Muhuri, and the Feni. Each of these rivers played a unique role in their virgin state for the delta. The water diversion has reduced both the duration and the area of recharging surface water resources. The authors may point to "plenty" of surface water, or "winter rainfalls", the important point is to compare the current spatial and temporal availability of water to that at some base line year in the past. If water availability is reduced to one-half of the one that set up and thrived a wetland ecosystem for thousands of years, can that ecosystem survive? Outside investigators, although, may find water around, cannot think of the lost water resources to link them to the dilapidated ecosystems. This is what the author group is facing.
There are also major dams and barrages built around West Bengal. These include the Ajoy, the Mayurakshi, the Panchet Reservoir, the Maithon Reservoir, the Durgapur, the Tilaiya Reservoir, the Konar Reservoir, the Subarnarekha Multipurpose, and the Kansabati. The world's single most tampering of the water resources has taken place in the Bengal basin.
The major arsenic contaminated area falls between the Hoogli and the Padma and beside them. Plateus lie to the west of West Bengal. It is not unlikely that arsenic contaminated water from West Bengal seeps into Bangladesh groundwater because of higher elevation in West Bengal.
The Nickson group also states that "Under today's wet and oxidizing (21 per cent O2) atmosphere, pyrite does not survive the natural weathering process and so does not occur naturally as a detrital material". How can such a statement be made for the delta? Have they tested the major part of the delta to make this statement? Why do they make such a statement without investigation? Once again, they may be befooling the scientific community.
The important thing is that any conclusion they make must be consistent
in all respects. Water diversion has affected many sectors. The problem
has become an interdisciplinary one. The authors must do an integrated
investigation of the problem. The quality control of the work they do stands
questionable. They seem to be teamed up with the Swedish and Indian groups
to establish their got-up speculation in an environment where it cannot
be fit. They do not admit that upstream water diversion has caused shortage
of recharging water, and consequently, the shortage of oxygen in the recharging
water to let occur water's natural purification process, although they
admit that in presence of oxygen in groundwater, arsenic will be scavenged
by iron hydroxide. In the process they happen to be playing ducks and drakes
with the misfortune of more than 75,000,000 of the world's poorest people.
An integrated investigation alone can lead to find proper solution.