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Category: News

Holding On or Letting Go: How Freshwater Species Manage Radiocesium Exposure

By Tyjaha Steele

Katie Quinlin is seen releasing mosquitofish into R-Canal enclosure to start the uptake experiment. (Photo courtesy of Katie Quinlin)
Katie Quinlin is seen releasing mosquitofish into R-Canal enclosure to start the uptake experiment. (Photo courtesy of Katie Quinlin)

As legacy nuclear sites shift toward long-term stewardship, understanding how contaminants behave in the environment is critical for informed cleanup and monitoring decisions. Radiocesium (137Cs), a byproduct of nuclear fission, remains a concern due to its persistence and mobility through food webs. New research from the University of Georgia’s Savannah River Ecology Laboratory (SREL) and the Warnell School of Forestry and Natural Resources enhances our understanding of how freshwater aquatic species absorb and eliminate this contaminant, supporting future risk assessment and remediation strategies.  

Led by former SREL and Warnell graduate student Kathryn Quinlin, the study was conducted at R-Canal, a waterway historically affected by reactor operations at the Savannah River Site (SRS). Researchers focused on four freshwater species: bullfrog tadpoles, red swamp crayfish, eastern mosquitofish, and American white-water lilies.   

“These species were selected for their availability and because they represent distinct ecological roles such as primary producers, benthic omnivores, and pelagic carnivores,” says Quinlin. “Together, they provide a broader picture of how radiocesium moves through freshwater systems.” 

To monitor contaminant uptake, researchers enclosed each species in mesh cages within the contaminated canal. After exposure, they transferred the organisms to a clean reference pond to observe elimination rates. 

Bullfrog tadpoles absorbed radiocesium the fastest, reaching equilibrium in under nine days. Crayfish followed at just over 50 days, and mosquitofish took around 86 days to reach steady levels. Despite the slower uptake, mosquitofish and tadpoles reached similar radiocesium activity concentrations, both higher than those found in crayfish.  

“These findings challenge the idea that sediment-dwellers always accumulate more contamination,” states Xiaoyu Xu, an associate research scientist at SREL and co-author on this study. “Tadpoles likely absorb more radiocesium due to their vascularized skin and higher metabolic rates, while crayfish have hardened exoskeletons and a slower metabolism, which may limit uptake.” 

Once in the clean pond, tadpoles shed half their burden in under eight days, and water lilies cleared 137Cs at a similar rate (around 12 days). Crayfish eliminated the contaminant more slowly, with a half-life of 69 days, while mosquitofish took about 43 days.  

Xu notes that, “Slower elimination in crayfish and mosquitofish is likely tied to traits like lower metabolism and less permeable surfaces. Tadpoles, kept in warm indoor tanks, were more active, whereas crayfish were outdoors in cooler weather and unable to molt, a pathway hypothesized to be important for shedding contaminants.” 

Differences in radiocesium storage pools also affect how long species retain radiocesium and influence its persistence in aquatic systems. Tadpoles and water lilies likely store more radiocesium in short-term reservoirs, resulting in rapid cycling, which contrasts with the longer-term reservoirs where crayfish and mosquitofish are thought to be storing this contaminant. 

Radiocesium’s persistence, even at very low concentrations, can quietly influence aquatic communities over time. By capturing these subtle effects, the research contributes to a deeper understanding of radioactive contaminants and their long-term consequences for ecosystem function. 

“This study offers a direct comparison of radiocesium uptake and elimination for a variety of species under natural conditions. By documenting how species absorb and eliminate contaminants over time, the findings inform selection of bioindicator species, improve environmental modeling, and help guide monitoring and remediation at contaminated freshwater sites,” explains Beasley, a professor at SREL and co-author on this study. “This research also adds to the growing body of evidence that radiocesium cycling within aquatic food webs is complex and influenced by a myriad of biotic and abiotic attributes of ecological systems.” 

The full study, Uptake and elimination of 137Cs in aquatic biota inhabiting a contaminated effluent canal, was published in the Journal of Environmental Radioactivity. Authors include Kathryn A. Quinlin, Danielle Hill, Xiaoyu Xu, and James C. Beasley. 

Headlights and Hesitation: How Vehicle Lighting Affects Deer Behavior in Imminent Collision Scenarios

By Tyjaha Steele

Carson is pictured with a fawn at UGA's captive deer facility in Athens, Georgia. (Photo courtesy of Carson Pakula)
Carson is pictured with a fawn at UGA’s captive deer facility in Athens, Georgia. (Photo courtesy of Carson Pakula)

There’s a reason the phrase “deer caught in headlights” is so well-known. It captures a split-second moment with very real consequences, often at the expense of the driver and the animal themselves. With thousands of injuries and billions of dollars in damages reported each year, researchers are now asking whether changes to vehicle headlights could significantly alter how deer respond, potentially reducing the risk of collisions.

 Carson Pakula, a doctoral graduate research assistant and lead author of the study, conducted 174 trials at the Whitehall Deer Research Facility in Athens, Georgia, through his work with the University of Georgia’s Savannah River Ecology Laboratory and Warnell School of Forestry and Natural Resources. The team worked with 23 captive, wild-type female deer, testing eight lighting combinations using an oncoming electric golf cart outfitted with halogen or LED headlights (set to high or low beam), with or without a rear-facing lightbar. 

We chose these eight treatments to explore how vehicle lighting might affect deer behavior by testing different headlight types, since halogen and LED give off different colors of light,” explains Pakula. “We also compared low and high beams to see if brightness changes how deer react, and added a rear-facing lightbar to find out if lighting up the front of the vehicle makes it easier for deer to notice.  

The study focused on short-range encounters, which ranged just 95 meters between the deer and the vehicle, designed to simulate the final seconds before a potential collision. Using infrared cameras, researchers tracked alert behavior, when a deer stopped or reoriented in response to the vehicle, and flight behavior, when it made an apparent attempt to escape. 

Carson is seen setting up an infrared camera on a field vehicle. (Photo courtesy of Carson Pakula)
Carson is seen setting up an infrared camera on a field vehicle. (Photo courtesy of Carson Pakula)

Across all trials, deer alerted in 73% of cases and fled in just 52%. Halogen headlights on high beam with the lightbar off produced the most alerts, yet no lighting treatment reliably triggered flight behaviors. 

“Many deer showed no flight behavior and stayed in the vehicle’s path, regardless of lighting treatment. It’s a ‘freezing in the headlights’ response familiar to many drivers,” says DeVault. “Deer reactions seemed driven more by individual personality than lighting. Their dark-adapted vision may not align well with modern headlights.”

Carson smiles alongside the golf cart used to test how variations in vehicle lighting impacted deer responses to an approaching vehicle. (Photo courtesy of Carson Pakula)
Carson smiles alongside the golf cart used to test how variations in vehicle lighting impacted deer responses to an approaching vehicle. (Photo courtesy of Carson Pakula)

This is the first study to test how vehicle lighting affects the behavior of a moving deer during an imminent head-on collision. Previous research has focused on roadside deer or longer-range interactions. These findings establish a baseline for future studies that may explore lighting effects in free-ranging deer or longer-distance approaches, especially as 86% of new vehicles are built with LED systems by default. 

Although LED headlights emit blue wavelengths that correspond to what deer’s eyes are most sensitive to, halogen high beams still prompted the strongest alert responses. It’s unclear whether LED lights overwhelm the deer’s vision, mask movement cues, or simply fail to appear threatening under certain conditions. 

While lighting may influence how deer perceive an oncoming vehicle, it doesn’t appear to change the outcome of a close encounter. Broader mitigation efforts, such as fencing, road design, or population control, remain more consistent and scalable solutions for reducing deer-vehicle collisions. 

The full study, Caught in headlights: Captive white-tailed deer responses to variations in vehicle lighting during imminent collision scenarios, was published in Applied Animal Behaviour Science and was authored by Carson J. Pakula, Gino J. D’Angelo, Adrianna Mowrer, Olin E. Rhodes Jr., and Travis L. DeVault. 

Augusta University Students Wade Into the Wetlands

By Tyjaha Steele

Amanda Hurst smiles as she proudly displays a tadpole and newt that students from the Wetland Ecology course caught. (Photo courtesy of Tyjaha Steele)

Amanda Hurst, an Augusta University alum and acting Community Engagement Specialist at the Savannah River Ecology Laboratory (SREL), recently returned to her alma mater as a guest speaker in Dr. Robert Cromer’s Wetlands class. During her visit, Hurst led a discussion on the ecological importance of wetlands, emphasizing their role in supporting biodiversity, regulating water flow, and serving as critical habitats for different species. She also touched on the real-world challenges these ecosystems face, from habitat loss to climate stressors, offering students a broader perspective on the relevance of wetland conservation.

Austin Plagens is intently observing a plant using a botany hand lens. (Photo courtesy Tyjaha Steele)

“I really enjoyed having the opportunity to return to Augusta University and connect with students who are now sitting in the same spot that I once was,” said Hurst. “The energy and curiosity they bring as they immerse themselves into the fieldwork shows they’re building a genuine understanding of why these habitats matter.”

The class later joined Hurst and a team of SREL outreach professionals for a field experience at Dry Bay, one of the lab’s wetland research sites. Upon arrival, students were given a safety briefing and a short history of the area by Dr. Kurt Buhlmann, who helped set the stage for the day’s hands-on activities. The class was then divided into smaller groups, each led by SREL staff with specialized expertise: Linda Lee guided the plant and soil group, Katrina Ford introduced students to regional bird species, and Sean Poppy covered amphibians and fish. Hurst oversaw the reptile-focused group and assisted wherever needed. The students actively observed wildlife and collected data about the environment around them.

“When students are able to move from the classroom and into the environment, where they can step into the shoes of an ecologist, taking samples, recording data, seeing plants and animals in their natural environment, they are able to go beyond the textbook,” states Ford, Assistant Director for Outreach and Education at SREL. “From former students, I often hear how experiences like these impacted their final career choice.” 

Peyton Lee Allen is seen holding a YSI handheld water quality meter. (Photo courtesy of Tyjaha Steele)

Throughout the experience, students were able to directly apply classroom concepts in a research-rich environment. Turtles collected during the session were safely returned to SREL’s herpetology lab for ongoing research. For many, this trip not only reinforced their understanding of wetland systems, but also introduced them to the kinds of careers and fieldwork opportunities available in environmental science. 

Thanks to the coordination of Amanda Hurst, Dr. Cromer, and the SREL outreach team, the visit offered a blend of instruction, exploration, and collaboration. Opportunities like this strengthen the connection between students and the natural world, while showcasing the valuable role of field-based education in preparing the next generation of conservationists.

 

2025 Palmetto Alligator Research and Management Symposium Held at SREL Conference Center

Participants from the 2025 Palmetto Alligator Research and Management Symposium smile with a cut-out of Stumpy at the SREL Conference Center. (Photo courtesy of Ben Parrott)

The 2025 Palmetto Alligator Research and Management Symposium (PARMS) was hosted at the Savannah River Ecology Laboratory’s Conference Center, where researchers, wildlife managers, and students gathered to share current work in alligator and crocodilian research. The two-day event featured presentations on movement ecology, environmental stress, microplastic ingestion, and more, culminating in a keynote by Dr. Steven Platt, who reflected on over four decades of crocodilian conservation around the world.

The symposium was coordinated in part by SREL’s own Dr. Ben Parrott, whose efforts helped ensure a smooth and engaging experience for all attendees. With a packed schedule of talks, poster sessions, and discussions, PARMS 2025 created an inviting space for collaboration, learning, and future research planning in the field of herpetology.

Wild Pig Management and the Science Behind Trapping

By Tyjaha Steele

A sounder (group) of wild pigs foraging next to a wetland. (Photo courtesy of Jim Beasley)

Across the United States, there is a battle unfolding between wild pigs and farmers, landowners, and wildlife managers. These fast-breeding animals are an invasive species in North America whose adaptability to different environments has allowed them to thrive in novel areas, while causing extensive ecological and economic damage. Wild pigs in particular harm natural habitats, spread disease, and destroy crops and property as their populations and ranges continue to expand. Scientists are working to evaluate and improve methods for managing wild pig populations to slow their expansion and reduce the costly damage that they cause.  

 Leading this effort is Jim Beasley, a researcher and professor from the University of Georgia’s Savannah River Ecology Laboratory (SREL) and Warnell School of Forestry and Natural Resources. In their most recent study, Jim and members of his lab analyzed data from 867 capture events carried out by 31 professional trappers across four southeastern U.S. states. This research evaluated the effectiveness of the three most common trap designs used today to capture wild pigs, corral, drop, and passive net traps, under varying environmental conditions.  

Wild pig sow and piglets are rooting in the leaf litter for food. (Photo courtesy of Jim Beasley)

“The USDA estimates that wild pigs cause $2.5 billion in annual damage and control costs to U.S. agriculture while also significantly impacting native habitats and wildlife across their invasive range,” explains Beasley. “While there are many tools for managing wild pigs, trapping is one of the most widespread methods of wild pig control, especially by agencies and wildlife management professionals.” 

 This research examined how each trap type performed across different landscapes and seasons by reviewing factors like capture efficiency, bait usage, and time to first capture. Previous studies on wild pig trapping have often been limited in scope, location, and scale, so this study was designed to provide a comprehensive evaluation of trapping strategies by incorporating data from multiple ecoregions and a robust multi-year dataset. 

“We believed these to be the most important distinguishing factors when choosing a trap type,” states Chuck Taylor, a former SREL graduate student under Beasley and first author on this study. “By including multiple factors that covered the vast majority of concerns when buying or building a wild pig trap, and monitoring those factors over multiple years, and in multiple states, we were able to thoroughly evaluate each trap type and their strengths and weaknesses.” 

The team found that all of the trap types evaluated in this study were highly effective in capturing entire social groups of wild pigs, achieving at least an 88% success rate in removing all targeted individuals in each capture event. Drop traps had the shortest time to a capture event and performed the best during challenging masting seasons, when natural food resources are abundant, providing wild pigs with natural food sources that make bait less effective.  Corral traps and net traps also performed very well, capturing nearly all targeted wild pigs in 2-3 weeks, on average.  Net traps showed the most consistent results across seasons but required slightly more bait due to their passive nature. However, the few differences found between trap types were deemed to be insignificant, and each trap type was highly effective at capturing wild pigs. 

Researchers (from left to right) Sarah Chinn, Jacob Ashe, and Jim Beasley, are seen attaching a GPS tracking collar to a wild pig to better understand the movement behavior of this invasive species. (Photo courtesy of Jim Beasley)

“One important finding was that all evaluated trap types performed similarly and were highly effective in catching and removing entire social groups of pigs. This is important for developing a successful wild pig management program under various conditions because each of these trap types vary in cost, maneuverability, and effort to monitor and maintain,” says Beasley. “This suggests that managers have numerous options for optimizing trapping programs without sacrificing performance depending on local conditions, resources, and wild pig populations within their management areas.” 

Details of the study can be found in the Wildlife Society Bulletin, under the title “Evaluation of common trap types for capturing wild pigs.” The study was authored by Charles R. Taylor, Lauren Buxton, and James C. Beasley.  

Following the Flow: How water movement impacts ecosystems and contaminants in a riparian wetland

By Tyjaha Steele and Katrina Ford

A student researcher can be seen conducting wetland research at SRS. (Photo courtesy of Daniel Kaplan)

Researchers at the University of Georgia’s Savannah River Ecology Laboratory studied water movement in wetlands and its role in filtering contaminants in the Tims Branch watershed, a riparian wetland on the Savannah River Site in Aiken, South Carolina.

“We chose this area specifically to understand how water moves. This allows us to predict how wetlands hold onto contaminants,” explains Daniel Kaplan, a senior research scientist at SREL, associate director of the University of Georgia’s Research Institute, and lead investigator of this study.

The research team collected monthly water samples from rainfall, streams, and groundwater at different sites within the watershed. By analyzing stable isotopes of hydrogen (δ²H) and oxygen (δ¹⁸O), they traced how different water sources mixed over time. Additional measurements were collected and helped determine how groundwater chemistry influenced stream water quality.

The study found that groundwater renewed at 2–4% per day, taking about two to four weeks to mix fully. Groundwater contributed up to 4% of stream water in some areas, while stream water comprised nearly 70% of groundwater in others.

These exchanges shifted seasonally, with groundwater flowing into streams more in winter and stream water seeping into the soil in summer, influencing water quality and contaminate movement.

The movement of water within the environment is a key factor in assessing the distribution of various heavy metals and contaminants, including uranium, throughout a riparian wetland. Effective environmental management is crucial to ensuring the health and safety of the Central Savannah River Area.

“For future work, we hope to utilize this hydrological model with other studies to improve contaminant management and reduce risks to both human and environmental health across the CSRA and DOE Complex,” states Kaplan.

The original study titled, “Hydrological controls of a riparian wetland based on stable isotope data and model simulations,” was published in the journal Isotopes in Environmental and Health Studies (IEHS) and was written by Peter H. Santschi, Chen Xu, Peng Lin, Chris M. Yeager, Pieter Hazenberg, and Daniel I. Kaplan. This work was completed in collaboration with researchers from Texas A&M University, Florida International University, and the Argonne National Laboratory, and the University of Georgia’s Savannah River Ecology Laboratory.

SREL Comes Together to Cleanup for their Annual Volunteer Day

Anya Weiss (left) and Mary Beard (right) are all smiles at the Eco-Litter Cleanup. (Photo courtesy of Tyjaha Steele)

The Savannah River Ecology Laboratory (SREL) recently came together for its annual Volunteer Day, a tradition that celebrates environmental stewardship, collaboration, and community spirit. This year’s Eco-Litter Cleanup centered around clearing out old, unusable enclosures near Rainbow Bay, opening up the space to benefit native wildlife in the area. Armed with shovels, gloves, and plenty of determination, lab volunteers worked side by side to remove metal flashing and other materials that no longer served a purpose. It was a tough job, but the momentum never wavered thanks to the collective effort. Events like these reflect SREL’s ongoing commitment to hands-on conservation and habitat restoration. By dedicating time and resources to projects like this, the lab continues to protect critical environments and support the long-term health of wildlife across the Savannah River Site and beyond.

SREL Brings Attention to Nonnative Species in the CSRA for National Invasive Species Awareness Week

By Tyjaha Steele

Displayed is a cluster of Nandina domestica berries. (Photo courtesy of Tyjaha Steele)

Invasive species, also known as non-native species, can pose a significant and costly threat to agriculture and native wildlife. These introduced animals and plants are disruptive due to no natural predators, allowing them to spread aggressively, displace native species, disrupt food webs, spread disease, and alter habitats in ways that are difficult, if not impossible, to reverse. Their presence and rapid expansion require active management to prevent further destruction. 

Numerous invasive species have established themselves throughout the Central Savannah River Area (CSRA). For instance, the Cuban tree frog preys on native frogs, lizards, and snakes, impacting the entire food chain as it competes with native species for resources. Brown marmorated stink bugs, native to Asia, serve as severe agricultural pests by consuming vegetables and fruit. Nandina domestica, also known as heavenly bamboo, produces toxic berries for birds and outcompetes through crowding with native plants. However, few species cause as much destruction as feral pigs. 

Wild pigs are among the most destructive invasive species in North America. Their rapid reproduction and adaptability allow them to thrive in nearly any environment, making them difficult to control. They root through forests, wetlands, and farmland, destroying crops, eroding soil, and competing with native species for food. They also carry diseases that threaten livestock, wildlife, and even humans. As their populations grow, the economic and environmental damage escalates. 

A spotted pig forages in the soil at the Savannah River Site, a behavior that can disturb native habitats and contribute to ecological changes. (Photo courtesy UGA/SREL)

At the Savannah River Ecology Laboratory, Jim Beasley, professor at SREL,  is leading efforts to develop science-based solutions for managing invasive species, with a particular focus on wild pigs. His research examines how these species move through and adapt to changing landscapes, using field studies and laboratory techniques to track their behavior, population growth, and ecological impact. His work on wild pigs evaluates factors such as trapping methods, habitat conditions, and food availability to help landowners and wildlife managers determine the most effective strategies for controlling pig populations and reducing their impact. 

Managing invasive species requires ongoing research efforts to slow their spread and reduce their impact. As the challenges posed by these species continue to escalate, proactive measures are necessary to prevent invasive species from expanding their range and causing irreparable damage.  

Seeking Stability: How soft-release can improve outcomes for captive turtles released into fragmented environments

By Tyjaha Steele

Displayed is a trail camera aimed at the temporary release pens to monitor the turtles’ movements and behavior during their soft-release period. (Photo courtesy of Tracey Tuberville)
Displayed is a trail camera aimed at the temporary release pens to monitor the turtles’ movements and behavior during their soft-release period. (Photo courtesy of Tracey Tuberville)

For species rescued from captivity from illegal pet trade or wildlife trafficking, reintroduction into the wild goes beyond relocation. It requires reestablishing behaviors and instincts necessary for survival in nature. Animals with diminished natural instincts often struggle to adapt to unfamiliar environments. This leaves them vulnerable to threats like human activity and reduces their chances of thriving in their natural habitat.

Recognizing this challenge, researchers at the University of Georgia’s Savannah River Ecology Laboratory worked to boost the survival rates of 26 long-term captive Eastern Box Turtles (Terrapene carolina carolina) by releasing them to the Savannah River Site in Aiken, South Carolina, using a method called soft-release.

“Soft-release is frequently used in wildlife reintroductions and involves gradually acclimating animals to their release site before allowing them to roam freely,” states Tracey Tuberville, senior research scientist at SREL and lead scientist for this study.

Of the 26 turtles reintroduced, 16 were soft-released and slowly introduced to their new environment, while 10 were hard-released and placed directly into their new habitat. An additional 10 resident turtles served as a control group for comparison. A key metric of success that was tracked throughout the study was settling time.

“Settling time is the amount of time that was required for an animal to establish their home range and was an important metric used to determine whether soft-release was effective,” explains Ryan Rimple, a recently graduated UGA SREL master’s student and now PhD student at New Mexico State University, who was a lead contributor on this paper.

Soft-released turtles showed first-year survival rates of 87.5%, closely following those of their resident counterparts, and their chances of survival are likely to improve in subsequent years, as they continue to become acclimated to their new habitat. They settled into their new environment 21 days earlier than hard-released turtles, stayed closer to their release site, and showed reduced wandering after acclimation. By reducing these risky behaviors, soft-release is
likely to help promote high survivorship in turtles following release.

Marked for monitoring, this Eastern Box Turtle played a key role in understanding soft-release effectiveness. (Photo courtesy of Tracey Tuberville)
Marked for monitoring, this Eastern Box Turtle played a key role in understanding soft-release effectiveness. (Photo courtesy of Tracey Tuberville)

Tuberville asserts, “A key component of acclimation is confining turtles to a temporary enclosure at the release site to help curb their initial flight response that might occur when placed in an unfamiliar environment.” This helps to ease the stress of relocation. Temporary penning allows turtles to adjust to their surroundings, giving them the opportunity to locate necessary resources. The soft-release method is ideal for smaller or fragmented habitats, where limiting movement reduces the risks of road crossings, urban development, and exposure to predators.

The behavior and survival rates of hard-released turtles followed a different pattern throughout the study. They displayed slightly higher first-year survival rates, ranging from 90% to 100%, but established home ranges farther from the release site due to greater exploratory movements. Research indicates that this increased movement could be harmful in fragmented release sites, where animals may face higher mortality rates during the exploratory phase. “Being active on the surface is riskier to turtles than being hidden under leaf litter or other shelter sites. Obviously, turtles need to move to find food and mates. The more active they are on the surface, the greater the risk of encountering potential hazards such as roads or predators.” Tuberville explains.

Despite higher initial survival rates, the increased movement of hard-released turtles and associated risks highlight the need for a stabilized long-term approach. The findings from this study suggest that soft-release offers such stability for animals reintroduced after challenges like illegal trade or habitat loss.

Ryan Rimple can be seen holding an Eastern Box Turtle he helped reacclimate to its new environment. (Photo courtesy of Tracey Tuberville)
Ryan Rimple can be seen holding an Eastern Box Turtle he helped reacclimate to its new environment. (Photo courtesy of Tracey Tuberville)

Reflecting on the broader impact, Rimple adds, “the reduction we observed in the post-release exploratory phase is important as most studies have shown that this phase of post-release behavior is when turtles are most vulnerable to mortality. By reducing the risk of wandering, soft-release can increase survival rates, allowing released turtles the opportunity to add to their new population over time.”

The original study titled, “Translocation of Long-Term Captive Eastern Box Turtles and the Efficacy of Soft-Release: Implications for Turtle Confiscations,” was published in the Northeastern Naturalist and was written by Ryan Rimple, Michel Kohl, Kurt Buhlmann, and Tracey Tuberville.

Turning Trash Into Treasure: How scientists are using peanut shells and rice husks to clean up toxic mercury in our environment

By Tyjaha Steele

An image of a sulfur-modified rick husk used in this study as seen under a scanning electron microscope. (Photo courtesy of Valentine Nzengung)

In the wake of Hurricane Helene and the recent flooding across the Southeast, it is crucial to understand the environmental impact of such events. Flooding historically causes sediment disruption which spreads harmful contaminants like mercury. These events can allow for toxic levels of mercury to enter the food web, posing serious risks to wildlife and humans. Researchers at the University of Georgia’s Savannah River Ecology Laboratory (SREL) have developed a promising solution to remediate this issue using biochar, a carbonized byproduct of organic waste. When added to contaminated soil, biochar can reduce the harmful effects of mercury, especially in flooded areas. 

Natural soil samples were collected for testing from the Phinizy Center for Water Sciences and Phinizy Swamp Nature Park in Augusta, Georgia. Mesocosms, enclosed environments designed to replicate natural ecosystem conditions, were used to simulate flooding conditions on a smaller scale. The soil sediment was then enriched with inorganic mercury, mercury that has been combined with other chemical elements, to mimic a pollution event before it was left to sit for 28 days.  

Different types of biochar, either rice husk or peanut hull, unmodified or modified with sulfur, were added to the soil, and the mesocosms were flooded to observe the effects of water on the polluted soil.  

“Peanut hull and rice husk were chosen due to their wide availability and established background research,” explains Xiaoyu Xu, an assistant research scientist at the University of Georgia’s Savannah River Ecology Laboratory and lead researcher for this study.  

The soil then sat to adjust again for 28 days. Afterward, the soil’s chemical properties were measured to see how they changed, and samples were collected to see how much total mercury, labile mercury, and organic mercury (toxic methylmercury) remained. Researchers then reviewed how each type of biochar, applied at different application rates, affected the amount of mercury that became more toxic over time.  

The measurements were repeated at 28-day intervals (56 and 84 days after biochar application) to monitor changes in its effectiveness over time and to determine the most efficient application method. Researchers discovered that sulfur-modified rice husks, applied between 56 and 84 days, worked best in stabilizing labile mercury in contaminated floodplains. Success was determined based on decreases in total mercury and labile mercury concentrations, and a reduction in methylmercury.  

“Overall, we found that adding biochar reduced the amount of mercury that can easily move and react in the environment by bonding with smaller particles, making the mercury more stable and less harmful,” states Xu. “However, adding large amounts of sulfur-modified biochar unexpectedly increased the production of toxic methylmercury.”  

The ability of biochar to stabilize mercury is especially critical as extreme weather events like Hurricane Helene highlight the risks associated with flooding. Heavy rainfall and floodwaters can redistribute harmful metals like mercury that are associated with health concerns in humans. The research findings suggest that using biochar could offer a sustainable and scalable solution for remediating contaminated sites. This method repurposes agricultural waste that would otherwise be discarded and reduces the mobility and toxicity of mercury. As a result, it lowers the risk of mercury entering the food chain and causing health issues. 

More research is needed to understand how sulfur-modified biochar affects methylmercury levels over time. “This approach shows promise as an environmentally friendly and cost-effective way to use organic byproducts to tackle mercury contamination,” Xu adds. 

The original article was published in the Journal of Environmental Quality by Brittany E. Jensen, Breanna Spencer, and Xiaoyu Xu.