Sophie Sward, senior at the University of Arkansas majoring in Environmental, Soil, and Water Science in the Bumpers Honors College

Author: Sophie Sward | Major: Environmental, Soil, and Water Science | Semester: Spring 2025

Sophie Sward, a senior at the University of Arkansas majoring in Environmental, Soil, and Water Science in the Bumpers Honors College, defended her undergraduate thesis this past November on phytoremediation of contaminated soils. Her project specifically evaluates the capacity of industrial hemp (Cannabis sativa L.) coupled with Douglas fir (Pseudotsuga menziesii)- derived biochar to remediate a gradient of soils contaminated with cadmium (Cd), lead (Pb), and zinc (Zn). She worked with Dr. Kristofor Brye, University Professor of Applied Soil Physics and Pedology in the Crop, Soil, and Environmental Sciences department to conduct this research and develop a completed thesis. She conducted her research during the summer of 2023 and her future plans are to obtain advanced degrees in the field of environmental sciences.

The objective of this study was to evaluate the effects of soil-contamination level (i.e., low, medium, and high), industrial hemp cultivar (i.e., ‘Carmagnola’ and ‘Jinma’), biochar rate (i.e., 0, 2, 5, and 10% by volume) and their interactions on root tissue Cd, Pb, and Zn concentrations and uptakes, whole-plant Cd, Pb, and Zn uptakes, and translocation factors after 90 days of hemp growth in contaminated soil from the Tar Creek Superfund Site near Picher, Oklahoma. Hemp removal of Cd, Pb, and Zn differed among soil contamination levels and total Zn uptake was affected by biochar rate. Results from this study demonstrate that hemp has the potential to successfully remove heavy metals from the soil and translocate them into aboveground tissue, and that biochar amendment has the potential to enhance hemp’s remediation capability. This has important implications in the field of environmental restoration because traditional engineering-based forms of remediation are expensive and highly disruptive to the environment.

I knew I wanted to conduct my research on phytoremediation after taking Plants and Environmental Restoration in the Fall 2022 semester – I found the idea that plants could be used to remove contaminants interesting and I wanted to learn more about it. I asked Dr. Brye to be my thesis mentor because our research interests aligned on soil science and the promotion of soil health, and I knew that I enjoyed working with him after joining the soil judging team he coaches. Dr. Brye had worked with a masters’ student the previous year on a project utilizing industrial hemp and biochar in soil remediation that had a gap in research that I was able to fill, using already established data to calculate translocation factors and whole-plant uptakes, as well as generating my own data using root and biochar samples from this existing study.

Dr. Brye, along with Dr. David Miller, Professor of Soil Chemistry in the Crop, Soil, and Environmental Sciences department and Mr. Dietrich von Thurston, M.S. Crop, Soil and Environmental Sciences, developed and conducted the initial study and formulated the modified procedure I used to digest the root samples in the current project. Mr. Dietrich von Thurston and Dr. Miller taught me the procedures and helped me set up a test run of my samples to determine whether or not the mechanical removal of biochar had any significant effect on the heavy metal concentrations reported after analysis by atomic absorption spectrometry. That was the most challenging part of this research, the mechanical removal of biochar from ground root samples using tweezers and a magnifying glass, which thankfully had no significant effect on my results and I did not have to remove biochar from 80+ samples. Dr. Brye introduced me to Dietrich and got me started in the lab, provided insightful editing and direction throughout the drafting process, and was instrumental in helping me to understand the results and statistics. I learned so much about the mechanisms of phytoremediation and the challenges of environmental restoration, ways to improve technology to more efficiently restore ecosystems and protect communities.

Now that I have defended my thesis, the next steps for me are refining my thesis for submission within the Honors College, as well as working with Dr. Brye on developing a manuscript to submit to a peer-reviewed journal.