Student Field Research, Student Research

ENVS Lester Grant supports student research on DDT levels in soil

My name is Kathryn Barr. I am a junior in Emory College of Arts and Sciences, majoring in chemistry and minoring in environmental science. I am conducting research with Dr. Eri Saikawa, which is funded by a Lester grant from the Department of Environmental Sciences. I am studying the levels of DDT and the rate of decomposition of DDT into its metabolites in historical cotton farms in Walton County, Georgia. DDT was a common household and commercial pesticide from the 1940s to when it was banned in 1972. DDT degrades into DDE and DDD. All these compounds affect sexual development of wildlife, including softening bird eggshells. DDT and its metabolites are also carcinogenic and cause cancer in humans. While DDT has not been sprayed for half a century, DDT, DDE, and DDD remain in the environment for decades and continue to have adverse effects. Furthermore, cotton farms were one of the most sprayed areas of DDT, so we decided to detect the levels of DDT and its metabolites on historic cotton farms. Previous studies have concluded that external factors can speed up the degradation of DDT, and some have suggested that various farming techniques can affect the speed of degradation. Therefore, I hope to determine the correlation between recent agricultural practices and the rate of decomposition of DDT.

I arrived at Emory knowing I wanted to be involved in the environmental science department. All my life, I have visited the Adirondack Mountains and awed at the beauty of our Earth. As I investigated research opportunities in the department, I was exceedingly interested in Dr. Saikawa’s work detecting metal contaminants in soil. After I decided to enroll in the environmental science research class, I began brainstorming ideas for a project, keeping in mind soil contaminants. Then it dawned on me. I live on an old cotton farm, which was active while DDT was spayed. I wanted to be able to test the soil I live on for DDT, so I began researching what affects DDT degradation. While there are multiple factors- climate, soil composition, microbiomes- the most intriguing idea was that agricultural practices can affect DDT degradation. Practices that are happening to the soil now, like tillage, irrigation, fertilizers, have a large impact on the levels of DDT still in the soil. Therefore, I began this project.

I began sampling the summer of 2021. We drive the hour and a half to Walton County, an area that has many historic cotton farms that are owned by many different farmers. Once we arrive, I speak to the farmers about what agricultural practices the various fields have undergone, and we separate the sampling by agricultural techniques applied to the area. We take about 90 samples for each field that composite into 3 large samples, making multiple robust samples, and do this for every area that has undergone different agricultural practices. While the insects are obnoxious and the Georgia heat makes us very sweaty, we often grab a nice refreshing lunch after sampling! It was very surprising to me how much the farmers cared about the DDT contamination in their soils. They are exceedingly helpful by giving me a detailed history of the land, and they are extremely interested in the results and how to reduce their DDT contamination. It is comforting that the farmers care so much about the health of their workers, livestock, and those who consume their produce.

Throughout the next year, I will continue to sample farms and analyze the soil for DDT levels. I want to use this project as my senior thesis, and I want to publish a paper on the findings! I am so excited to see what the conclusions are for how agricultural practices affect degradation of DDT.