The source of arsenic in India's groundwater continues to elude scientists more than a decade after the toxin was discovered in the water supply of the Bengal delta in India. But a recent study with a Kansas State University geologist and graduate student, as well as Tulane University, has added a twist - and furthered the mystery.
The environmental crisis began after large traces of the element were detected in the groundwater in the Bengal Basin - an area inhabited by more than 60 million residents. This has caused a water shortage, illness and death in the region, leaving residents unable to even use the water for ordinary tasks like washing dishes or ablution. Arsenic pollution causes skin lesions, respiratory failure and cancer when present in high concentrations in drinking water.
"It's an awful situation," said Saugata Datta, a Kansas State University assistant professor of geology. "This is one of the worst mass poisoning cases in this history of mankind."
Though no definitive arsenic source has been determined, many geologists have claimed that recent man-made ponds in the region are a major contributor, as the heavy rainfall and erosion have created high amounts of organic material - containing arsenic - in the ponds. From there the pond's water and organic material seep into the groundwaters.
Datta and colleagues recently completed a study looking at the ponds. Their findings, "Perennial ponds are not an important source of water or dissolved organic matter to groundwaters with high arsenic concentration in West Bengal, India," was published in Geophysical Research Letters in late October, and it also appeared in the journal Nature.
Their study suggests that ponds are not contributing substantial amount of water or this old organic matter into the groundwaters in the shallow aquifer in this region. According to study findings, these very high arsenic levels are actually coming from something else, possibly from within the organic matter contained in these Holocene sedimentary basins. Datta, along with Tulane University colleague Karen Johannesson - the study's other lead investigator - came to this conclusion after modeling the transport of the pond's organic matter through the meters of sand and clay to the aquifers below. Because of the organic matter's highly reactive nature to minerals - like arsenic - researchers found that this organic matter actually serves as a retardant and causes minerals to absorb more slowly into the aquifer sediments.
According to their model, it would take thousands of years to reach roughly 30 meters into the aquifers in the Bengal delta, which is where we see this peak of arsenic. "These high arsenic waters at the 30 meter depth are approximately 50 years old," Datta said. "Since the ponds that supply the organic matter have been around for thousands of years, the current ponds would not be the source of this organic matter."
The team created their model based on stable isotope data at Kansas State University's Stable Isotope Spectrometry Laboratory. The lab is operated by Troy Ocheltree, a biology researchassistant who co-authored the study. In the near future, Datta, Sankar Manalikada Sasidharan, a geology graduate student, India, and Sophia Ford, a geology undergraduate student, Wilson, will travel to the region to collect groundwater and aquifer sediment samples for an extensive study that accounts for various valleys and ponds.
In addition to arsenic, the team will also monitor for high concentrations of manganese, as scientists are finding that the two metals often appear together. (TerraDaily)
Scientists believe that about 140 million people, especially in developing countries, are being continuously poisoned by arsenic in their drinking water. Arsenic is very poisonous metalloid that is often used in pesticides, herbicides and insecticides. Despite the fact that this has become major problem, governments still failed to give proper significance and the priority that this problem, especially considering numbers of possible victims, deserves. It looks like those reports of poisonous communities in Bangladesh from 80s are being easily forgotten. (Gangajal)
Arsenic pollution of groundwater is a natural occurring high concentration of arsenic in deeper levels of groundwater, which became a high-profile problem in recent years due to the use of deep tubewells for water supply in the Ganges Delta, causing serious arsenic poisoning to large numbers of people. A 2007 study found that over 137 million people in more than 70 countries are probably affected by arsenic poisoning of drinking water.Arsenic contamination of ground water is found in many countries throughout the world, including the USA.
“In Bangladesh, West Bengal (India), and some other areas most drinking-water used to be collected from open dug wells and ponds with little or no arsenic, but with contaminated water transmitting diseases such as diarrhoea, dysentery, typhoid, cholera, and hepatitis. Programmes to provide ‘safe’ drinking-water over the past 30 years have helped to control these diseases, but in some areas they have had the unexpected side-effect of exposing the population to another health problem—arsenic.” WHO
US arsenic pollutionThere are many locations across the United States where the groundwater contains naturally high concentrations of arsenic. Cases of groundwater-caused acute arsenic toxicity, such as those found in Bangladesh, are unknown in the United States where the concern has focused on the role of arsenic as a carcinogen. The problem of high arsenic concentrations has been subject to greater scrutiny in recent years because of changing government standards for arsenic in drinking water.
Some locations in the United States, such as Fallon, Nevada, have long been known to have groundwater with relatively high arsenic concentrations (in excess of 0.08 mg/L). Even some surface waters, such as the Verde River in Arizona, sometimes exceed 0.01 mg/L arsenic, especially during low-flow periods when the river flow is dominated by groundwater discharge. In Arizona, an estimated 35 percent of water-supply wells were put out of compliance by the new regulation; in California, the percentage was 38 percent. A study of private water wells in the Appalachian mountains found that six percent of the wells had arsenic above the U.S. MCL of 0.010 mg/L. (Wikipedia)
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