DNA-based tracers to help researchers map aquifer for groundwater modeling

(Aug. 7, 2018) -- Researchers from The University of Texas at San Antonio (UTSA) and Southwest Research Institute (SwRI) are using unique DNA-based tracers to characterize the recharge and flow patterns in the Edwards Aquifer. The work, led by Vikram Kapoor of the UTSA College of Engineering and Ronald Green of SwRI’s Space Science and Engineering Division, is supported by a $125,000 grant from the organizations’ Connecting through Research Partnerships (Connect) Program.

The Edwards Aquifer is the primary source of drinking water for a vast number of people living in central and south Texas. As a natural water resource, it’s vulnerable to contamination from storm water runoff, leaking septic tanks and municipal waste. When a contamination occurs, it’s vital to detect the source quickly, which can be challenging.

“It’s very difficult to discern flow paths in the Edwards Aquifer,” Green said. “The bed of the waterway is made up of limestone, which has partially dissolved over time, creating a honeycomb structure that makes it impossible to visually identify the water’s path.”

To remedy this, local researchers are using a new class of DNA-based tracers to map the flow path of the aquifer. The tracers will be capsules made of environmentally safe material to ensure protection from environmental degradation while also permitting detection. The DNA material stored inside the capsule will be a synthetic, double-stranded DNA that is unique to each tracer.

“Scientists currently rely on fluorescent dyes and streamflow gain and loss measurements to discern flow pathways, but these methods don’t allow us to identify specific pollutant sources or individual flowpaths of concern, particularly in complex landscapes,” said Kapoor. “Because DNA is made of the four basic molecules that can be combined in any random order, the DNA-based tracer system allows for the fabrication of thousands of unique tracers.”

In addition to being cost-effective, the DNA-based tracers the researchers develop will allow for a large number of individual tracers to be simultaneously distinguished from one another.

After the tracers are released at different points in the water source, samples from throughout the aquifer will be collected and examined. The team will note which tracer has appeared in each sample and how many are present, to determine their path through the aquifer. This new mapping method differs starkly from the traditional approach of using fluorescent dyes to visually trace flow paths.

The method is expected to aid in the rapid detection of the source of contaminations by offering a clear, unique understanding of the complex flow paths of the aquifer. The team also plans to use the data results to create a robust database to calibrate surface water and ground water modeling, and support other hydrogeological studies.

“Ultimately, our goal is to improve the hydrological and biogeochemical models that are currently used to predict the transport of pollutants, aquifer recharge and other hydrological processes,” said Kapoor.

The Connecting through Research Partnerships (Connect) Program, sponsored by the UTSA Office of the Vice President for Research, Economic Development and Knowledge Enterprise (VPREDKE) and the SwRI Executive Office, is a grant opportunity offered to enhance greater scientific collaboration between the two institutions and to increase both UTSA’s and SwRI’s research-funding base with cross-campus collaborative programs.

— Staff Report

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