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.
"Characteristically the organic matter is very sticky and likes to glom onto mineral surfaces," Datta said. "So it takes much longer for the organic matter to move the same distance along a groundwater flow path than it does through just the water itself."
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 research assistant 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 ap
|Contact: Saugata Datta|
Kansas State University