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K-State Today

May 16, 2012

An invisible predator: International planning visit to examine high amounts of arsenic in Botswanan groundwater

Submitted by Communications and Marketing

A trip to Botswana this summer for a team of researchers from Kansas State University and the University of Colorado at Boulder will examine the increased presence of arsenic in the groundwater of deltaic regions worldwide. The implications are significant as many people rely on this groundwater as other water sources are too polluted to drink.

Natalie Mladenov, assistant professor of civil engineering, and her student Hersy Enriquez, master's student in civil engineering, will join Ganga Hettiarachchi, associate professor of agronomy, in this research visit to Botswana, scheduled for July and August. The team's visit is funded by a $19,943 grant from the National Science Foundation.

Arsenic is colorless, odorless and tasteless in water and carries considerable health risks. It can be lethal in very high concentrations. Long-term, chronic exposure in drinking water is known to cause cancer and other severe health issues. Tens of millions of people worldwide often resort to drinking arsenic-contaminated water in the absence of clean drinking water. Some regions of the U.S. also contain high concentrations of arsenic in groundwater. The arsenic is typically geogenic or naturally occurring in many instances, but the mechanism by which it is released is not always consistent.

Botswana is the focus of the research for a variety of reasons. Mladenov has been working on water issues in the country on and off since 1998. She lived in the southern African country from 1998-1999 and worked with the Botswana Department of Water Affairs to study the water quality of a wastewater effluent-dominated river near the capital city of Gaborone. She also spent considerable time working in the Okavango Delta, a large inland delta.

"It represents a unique setting in which to study arsenic contamination because it is a pristine wetland that is home to rare and endangered animals," Mladenov said. "Yet the groundwater has naturally-occurring arsenic in high concentrations."

The site enables researchers to study the mechanisms for arsenic mobilization without the effects of anthropogenic pollution. The groundwater hydrology has also been well studied. In contrast, in other regions, such as Southeast Asia, the complex monsoon-influenced hydrology can complicate research on arsenic mobilization.

The American researchers will be working with scientists from the Okavango Research Institute and the University of Botswana to select field sites, collect samples and draft a new proposal that will be submitted to the National Science Foundation.

Much of the science around the arsenic contamination issue has focused on the influence of groundwater flow, geologic conditions, and inorganic chemistry. Mladenov's previous research in Bangladesh has demonstrated that organic chemistry and the involvement of microbes is really a driver for arsenic mobilization from the sediments to the water. In the Okavango, very little is known about the involvement of organic matter and microbes, yet that wetland is so abundant in organic matter that the surface water is a yellow-brown color.

"We anticipate that the high arsenic concentrations are linked to accumulation of dissolved organic matter in the groundwater and microbial processing of that organic material," Mladenov said.

The research team will also explore whether the quality of organic matter makes it better suited to mobilizing and keeping the arsenic in solution.

The new proposal will include a request for K-12 teachers to join in on future project research. Mladenov previously received funding to bring four middle and high school teachers with her to conduct research in Botswana. The teachers were able to meet with Botswana science teachers and examine their classrooms.

"Those research visits made a real impression on the U.S. teachers and their students through photos and videos," Mladenov said. "We hope to do the same when and if the larger project is funded."

After visiting Botswana, the researchers are planning to present about their travel and research to students in middle school classrooms.

Mladenov believes that the team's research will fill a critical knowledge gap of how arsenic is mobilized under different conditions. Once the information is established, water treatment or remediation strategies can be devised.

"A lot of time and money is spent trying to remove arsenic from drinking water supplies or to develop remediation strategies," Mladenov said. "What we learn about arsenic mobilization in Botswana can potentially be applied toward remediation strategies that seek to reverse that mobilization process."