As the surface of the earth is covered with 70 % of water, it looks like a blue ball from far above. The well known fact is that water is the most valuable natural resource that exists and without which survival of life is impossible. About 97 % of the earth’s water is in the oceans or locked away as ice. Groundwater is the major source of freshwater accounting for about 0.6 per cent of the total. Only about 0.01 per cent of freshwater is present as lakes, streams lochs, reservoirs, ponds, rivers canals, ditches, coastal waters and estuaries (Vale, 2006).
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Specifically, the groundwater is present below the surface of the ground in the saturation zone which is located below the water table and is in direct contact with the ground or subsoil. Unfortunately, these are the only fresh sources available for humans and other terrestrial organisms. Pollution of this precious resource is a major problem globally.
Arsenic abbreviated as “As” occurs in the rocks present in the earth’s crust. It is also present in soil, all natural sources of exposure. For instance, arsenic can be traced to subterranean water brines that are used to produce oil and natural gas. It is in general through the drinking of contaminated water arsenic exposure occurs in humans and other terrestrial organisms. Exposure to arsenic at elevated levels poses serious health effects as the element itself is a well known carcinogen.
Besides, arsenic has been reported to affect the vascular system. Several researchers have also linked this to the cause of diabetes. The over-exploitation of groundwater results in the dissolution of naturally occurring arsenic from the rocks present in earth. This is a major source of arsenic pollutant in the groundwater. Additionally, arsenic is an element that is present in the pesticides, fungicides, and also industrial wastes that leach into the ground water (Wilkes University, N.D.).
Arsenic Pollution a Global Concern
Arsenic has been recognized as causing serious problems only in the recent decades. It was only in the 80s that the World Health Organization (WHO) had set specific standards for drinking water as 10 μg/l or 0.01 mg/l. Presently, there are many countries that have reported high levels of arsenic in part of their groundwater resources. For instance, it is a major problem in the Asian countries such as Afghanistan, Bangladesh, Cambodia, China, India, Myanmar, Nepal, etc. There are several studies from these regions that reported and published results of arsenic contamination in the ground water (Mandal and Suzuki, 2002; Polya et al., 2005).
Researchers also have found that the increased concentration of arsenic in ground waters the Asian region is considered to be of mainly geogenic origin. The main chemical reaction that results in the release of arsenic into the ground water is the reductive suspension of iron (hydr)oxides abbreviated as FeOOH. This reaction occurs due to the stimulation by microbial activity and organic materials present in the soil. Studies by researchers such as Ahmed et al. (2004) and McArthur et al. (2004), have proven beyond doubt that this is the main channel in which arsenic reaches the aquifers.
Combating Arsenic Water Pollution
The status of groundwater arsenic contamination in different parts of the world especially in Bangladesh is so serious that the instant plans and strategies need to be taken in order to solve this problem. It is essential to deliver adequate drinkable water to all seriously affected areas. Though there is yet no proper channel to decontaminate the arsenic contaminated ground water, the following are a few measures that need to be employed based on the cost effectiveness:
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- Provide a substitutive source of drinking water especially in the heavily contaminated regions. Methods such as pond sand filters, infiltration galleries, or Ranney wells, and even rainwater harvesting can be of great help.
- In places where good source of surface water are available, it can be used after purification by filtration and chlorination. There are also methods such as ultraviolet disinfection or solar radiation that can be utilized to purify drinking water.
- There are chemical methods to remove the arsenic from the contaminated water. For instance, arsenic can be removed by chemical precipitation using coagulants such as the salts of aluminium and iron. However, this method cannot be used in a large scale. Arsenic can also be removed by the process of oxidation. The use of oxidants such as free chlorine, ozone, permanganate, hypo-chlorite, and Fenton reagent (H2O2/Fe2+) aid in removing arsenic from the contaminated drinking water.
- One of the best ways to avoid arsenic in drinking water is drawing out arsenic free groundwater from deep aquifers.
- Filtration is yet another method by which arsenic can be removed from contaminated water. This filtration can be at the household level of at community level.
- Government need to take action to remove arsenic from the existing water sources. Additionally, it is also important to control the anthropogenic sources of water contamination through stringent law.
- In-situ remediation of arsenic contaminated groundwater by the use of iron filings permeable walls (Safiuddin and Karim, 2001).
Additionally, the implementation of some of the proper mitigation measures such as intensive water quality monitoring, need to be taken up in order to prevent the health hazards. It is important to supply arsenic free drinking water in the affected areas by following any of the above mentioned cost effective methods. It is also important to diagnosis and treat patients initially in order to avoid serious health problems.
There is a need to create awareness especially in the third world countries regarding arsenic poisoning. Research and development is another are that need financial support and motivation. Epidemiological studies in regions where the contamination of arsenic in water is high need to be taken up on priority basis. Additionally it is also essential to take up hydro -geological that will aid in assessing the extent of leaching of arsenic in ground water (Majumder, 2008).
Arsenic pollution particularly in the ground water and its impact on health is a global issue. Though there are no universal methods to decontaminate the polluted water, various methods need to be employed depending on the region and cost effectiveness. Since arsenic pollution occurs more due to the natural reasons when compared to anthropogenic activities, the control of this is difficult.
One of the important steps that can be taken up is by reducing the contamination through anthropogenic sources especially from the agricultural and industrial activities by following sustainable development. Awareness and education will also play important role in avoiding the use of arsenic contaminated water for drinking purposes. If these measures are not taken up seriously in the heavily polluted regions of the world, human health will be jeopardized.
Ahmed K.M., Bhattacharya P., Hasan M.A., Akhter S.H., Alam S.M.M., Bhuyian M.A.H., Imam M.B., Khan A.A. & Sracek O. (2004). Arsenic enrichment in groundwater of the alluvial aquifers in Bangladesh: an overview. Appl Geochem, 19: 181-200.
Majumder, A. (2008) Mitigation of Arsenic Contamination in Groundwater – Experiences. Web.
Mandal B.K. & Suzuki K.T. 2002. Arsenic around the world: a review. Talanta, 58: 201-235.
McArthur J.M., Banjeree D.M., Hudson-Edwards K.A., Mishra R., Purohit R., Ravenscroft P., Cronin A., Howarth R.J., Chatterjee A., Talukder T., Lowry D., Houghton S. & Chadha D.K. (2004). Natural organic matter in sedimentary basins and its relation to arsenic in anoxic ground water: the example of West Bengal and its worldwide implications. Appl Geochem, 19: 1255-1293.
Polya D.A., Gault A.G., Diebe N., Feldman P., Rosenboom J.W., Gilligan E., Fredericks D., Milton A.H., Sampson M., Rowland H.A.L., Lythgoe P.R., C. J.J., Middleton C. & Cooke D.A. (2005). Arsenic hazard in shallow Cambodian groundwaters. Mineral Mag, 69: 807-823.
Safiuddin, M. and Karim, M.M. (2001) Groundwater Arsenic Contamination In Bangladesh: Causes, Effects And Remediation. Proceedings of the 1st IEB international conference and 7th annual paper meet; Chittagong, Bangladesh: Institution of Engineers, Bangladesh. Web.
Vale, J., (2006). Water Quality, The Environment Agency. Web.
Wilkes University, (N.D.) Arsenic in Drinking Water and Groundwater, Center for Environmental Quality. Web.