Category: News

By: Tyjaha Steele

Elise Webb is seen smiling alongside a redfin pickerel (Esox americanus) specimen for trophic transfer study at Beaver Dam Creek. (Photo courtesy of Elise Webb)

The Savannah River Ecology Laboratory (SREL) works closely with the U.S. Department of Energy as an independent evaluator of the ecological effects of DOE’s missions at the Savannah River Site (SRS). That role includes building a better understanding of the site’s ecosystems, providing the scientific information needed to track environmental conditions over time, and investigating emerging environmental questions. 

Researchers from the University of Georgia’s Savannah River Ecology Laboratory conducted the first comprehensive assessment of per- and polyfluoroalkyl substances (PFAS) across aquatic ecosystems at the SRS. The study was led by Elise Webb, who conducted the research as a master’s student at SREL, alongside Xiaoyu Xu, associate research scientist at SREL, and Benjamin B. Parrott, associate professor at SREL and the University of Georgia Odum School of Ecology. The team examined PFAS in surface water, sediment, and aquatic wildlife to better understand how these compounds move through freshwater ecosystems and establish the first site-wide baseline for the SRS. 

Per- and polyfluoroalkyl substances, commonly known as PFAS, are a large family of manufactured chemicals that have been used in industrial applications, including firefighting foams, for decades. Their persistence in the environment has made them an increasing focus of scientific research, particularly as researchers work to better understand their presence and movement in natural ecosystems. However, before this study, relatively little was known about their distribution across the SRS or how they moved through its aquatic ecosystems. 

“Rather than focusing on a single location or environmental medium, we collected water, sediment, and fish samples from more than 30 sites across multiple watersheds. That allowed us to evaluate PFAS in both the environment and aquatic organisms, providing a more complete picture of their distribution, bioavailability, and potential for bioaccumulation,” states Webb. “By sampling across the landscape, we could also examine how watershed characteristics, such as land development, metal co-contamination, and sediment composition, influenced PFAS concentrations. This allowed us to establish the first site-wide baseline for PFAS and identify potential sources of contamination and the environmental factors that affect PFAS transport and accumulation.”

See are PFAS extractions of water samples at the University of Florida with Dr. John Bowden. (Photo courtesy of Elise Webb)

Researchers collected water, sediment, and eastern mosquitofish from 30 locations across the site. The sampling locations spanned multiple watersheds, allowing the team to compare streams with different surrounding landscapes and environmental conditions. They also evaluated watershed characteristics, measured metals and metalloids, and analyzed a freshwater food web. 

PFAS was detected throughout the SRS, although concentrations varied among watersheds and sample types. Those differences showed that PFAS was not evenly distributed across the site, with certain compounds occurring more frequently or at higher concentrations in some watersheds than others.

The surrounding landscape offered additional clues about those patterns. Watersheds with more developed land generally had higher PFAS concentrations in surface water, while several long-chain PFAS compounds were positively associated with metals measured in sediments. 

At Beaver Dam Creek, eastern mosquitofish contained the highest PFAS concentrations measured during the study despite relatively modest concentrations in sediment. This finding demonstrates that biological samples can reveal patterns that water and sediment alone may miss. 

Samples collected from algae, crayfish, fish, and watersnakes in Beaver Dam Creek allowed the researchers to examine how PFAS moves through a freshwater food web. Several PFAS compounds became more concentrated in organisms occupying higher trophic levels, providing evidence that those compounds have the potential to biomagnify in freshwater ecosystems. 

“Our findings that PFAS concentrations are higher in predator species when compared to their prey is concerning as it means that as these contaminants move through the food web they are more likely to reach levels that end up impacting the health of certain species,” explains Parrott. “We ultimately need to better understand the health impacts of PFAS exposure in a variety of species to really understand the potential risk these contaminants convey in our ecosystems.” 

The study establishes the first comprehensive picture of PFAS across aquatic ecosystems at the SRS, documenting their distribution across the site, variation among watersheds, and movement through freshwater food webs. It also establishes the first comprehensive site-wide baseline, creating a benchmark for future environmental monitoring. 

The full study, PFAS on the U.S. Department of Energy’s Savannah River Site: Spatial Distribution, Bioavailability, Co-occurrence with Metals, and Potential Biomagnification, was published in Environmental Toxicology and Chemistry and authored by Elise M. Webb, Alina Timshina, Dylan Ricke, Dean E. Fletcher, John A. Bowden, Xiaoyu Xu, and Benjamin B. Parrott. 

By: Tyjaha Steele

When rain falls in a forest, not all of it reaches streams or is taken up by trees. Some returns to the atmosphere through evaporation, while some remains in the soil, providing the moisture plants and wildlife need to survive. Although scientists have long known that forests help conserve water, it has been difficult to determine whether the shade created by the canopy or the layer of fallen leaves covering the forest floor does more to slow water loss. 

One reason that question has been difficult to answer is that canopy shade and leaf litter naturally change together as forests grow, recover from disturbances, and respond to management practices. That makes it difficult to determine how much each contributes to slowing water loss on its own. To attempt to answer that question, the team developed a series of experimental simulations that separated the effects of canopy shade and leaf litter.  

Using those simulations, researchers from the University of Georgia’s Savannah River Ecology Laboratory (SREL), including Doug P. Aubrey, associate professor at SREL and the UGA Warnell School of Forestry and Natural Resources, recreated different levels of canopy shade and leaf litter under controlled conditions. By changing one while holding the other constant, they were able to isolate the role each plays in slowing evaporation from the forest floor, something that is difficult to accomplish in an intact forest.  

“In earlier research, our group found that the amount of water evaporating from the forest floor of very young forest stands was quite a bit higher than we had expected. We made those measurements for a few years as canopy leaf area increased and forest floor leaf litter accumulated through early stand development. We saw that the decline in forest floor evaporation through those first few years could be explained by the cumulative amount of leaf litter inputs, but the forest canopies had been damaged from a disturbance, so we couldn’t perform an inclusive analysis and attribute the response to just litter,” shares Aubrey. “Although it seemed intuitive that the litter layer would exert stronger controls than canopy shading, we didn’t have conclusive data, so we conducted this experiment. So, why were we interested in understanding the relative importance of these factors? Well, this type of fundamental knowledge regarding the relative influence of different forest structural components on hydrologic fluxes can inform forest management and perhaps lead to innovative approaches for minimizing water losses that don’t contribute to forest productivity.” 

The study found that both canopy shade and leaf litter helped reduce water loss, but the layer of fallen leaves had the greater effect. As more leaf litter accumulated on the forest floor, water was retained for longer, suggesting that the leaves form a protective layer that slows moisture loss from the soil. 

As forests change over time, so do the conditions that influence evaporation. Trees grow, storms open the canopy, leaf litter builds up and decomposes, and management activities alter both the forest floor and the trees above it. 

“When enough fallen leaves accumulate on the soil surface, they essentially form a barrier and the environmental conditions under that barrier are different than above it. Evaporation is a physical process, and its rate is largely determined by the atmospheric demand for water,” says Aubrey. “When the air is hot and dry, evaporation is high. When the air is less hot and less dry, evaporation is lower. Forest structure, both the canopy and the leaf litter, modify the atmospheric demand for water. The leaf litter layer creates a microclimate that is less hot and less dry than the microclimate above the layer so the atmospheric demand for water is muted and evaporation is much lower.” 

That understanding could have practical applications for forest management. Practices such as pine straw harvesting or clear-cutting remove much of the protective layer covering the forest floor, which the study found can increase water loss. Maintaining that natural layer may help forests retain more moisture, while the findings can also improve models used to predict how forests use water as they grow, are managed, and recover from natural disturbances. 

The full study, Exploring Forest Structural Controls on Soil and Litter Evaporation via Experimental Simulations, was published in Agricultural and Forest Meteorology and authored by Tyler E. McIntosh, C. Rhett Jackson, Caren C. Mendonca, Seth E. Younger, and Doug P. Aubrey. 

By: Tyjaha Steele

Wild pig sounder consuming bait at bait site. (Photo courtesy: Sydney Brewer and James Beasley)

Although bait is one of the most widely used tools for managing invasive wild pigs, its success depends on something that has long frustrated wildlife managers: getting pigs to find it in the first place. Some bait sites are discovered almost immediately, while others remain untouched, even in areas where pigs are known to be active. For managers relying on bait to trap, monitor, or remove wild pigs, knowing why those differences occur could make management efforts more effective and resources go further.  

Researchers have tested different bait types, scent attractants, and deployment methods for years, but relatively little research has examined the factors that determine whether pigs locate a bait site. Seeking to answer that question, researchers from the University of Georgia’s Savannah River Ecology Laboratory (SREL) and Warnell School of Forestry and Natural Resources, in collaboration with the U.S. Department of Agriculture’s National Wildlife Research Center, examined how bait placement, presentation, and social behavior influence bait visitation by individual wild pigs. 

Led by Sydney Brewer while completing her master’s degree at UGA, the study offers new insight into the behaviors that shape bait visitation and guides wildlife managers who depend on bait to support trapping, toxic baiting, disease surveillance, and population monitoring.  

“Wild pigs are extensively managed in their native and invasive range, with the goal of population reduction or eradication due to their damage to native and anthropogenic ecosystems. Wild pig management includes trapping, aerial gunning, toxic baiting, and free ranging all rely on or are improved by bait sites,” states Brewer. “Bait is expensive, and it takes time and personnel to maintain bait sites; therefore, managers are seeking ways to be the most efficient. Results from our research can directly inform managers on how to most effectively attract wild pigs to a site for management purposes to aid in the reduction of this invasive species and mitigation of their damage.”

Sydney Brewer sits with an anesthetized GPS collared wild pig. (Photo courtesy: Sydney Brewer).

To separate the effects of different baiting strategies, researchers fitted 52 wild pigs with GPS collars at the Savannah River Site (SRS) in South Carolina and conducted 325 experimental baiting trials over nearly two years. During each trial, a collared pig was monitored at a single bait site, allowing researchers to compare bait placed in different portions of the animal’s home range and to evaluate whether bait presentation (in a central pile or a pile with radiating trails of bait) or a commercially available sow-in-heat scent attractant influenced visitation.  

By comparing each of those factors, one pattern became clear. Even when bait was placed within a wild pig’s home range, pigs visited only 42% of bait sites, highlighting how difficult it can be to get pigs to locate bait in the first place. Bait placement had a greater influence on visitation than any other variable researchers evaluated. Wild pigs were 30.6% more likely to visit bait placed within the areas they used most frequently, and they reached those sites much sooner than bait located near the edges of their home ranges. Researchers also found that pigs became less likely to find bait as the distance between the animal and the bait site increased, reinforcing that understanding how pigs use their home range is more important than changing the way bait is presented. 

“Despite the numerous baits and lures available for attracting wild pigs, this study adds to the growing body of evidence that where bait sites are placed within the landscape is more important than the specific bait or lure used for determining the probability and timing of wild pig detection,” states Beasley. “Because wild pigs are poor thermoregulators, they often concentrate their activity near wetlands or streams with dense understory vegetation. Locating bait sites in these areas, particularly where fresh tracks, scat, or other sign are present, even if not conveniently near roads, should maximize detection rates and improve trapping efficiency.” 

The study also addressed a question that has practical implications for wildlife managers: can changing the baiting method improve success when placement is less than ideal?  

Based on the results, the answer appears to be no. Adding a sow-in-heat scent attractant did not increase the likelihood that pigs would visit bait, and spreading corn along trails rather than placing it in a single pile offered no measurable advantage. Rather than relying on different attractants or presentation methods, the findings suggest managers are more likely to improve bait visitation by selecting locations where pigs already spend their time.  

Researchers also found that the animals’ social behavior influenced bait visitation. Female wild pigs typically live in family groups, known as sounders, while adult males often spend much of their time alone and can be larger and more dominant at bait sites. During the study, females were less likely to visit bait sites after an adult male had already been there, and when they did, they generally arrived several days later. This finding indicates that social interactions among wild pigs can influence bait visitation in ways that may affect management efforts. Specifically, when dominant males are visiting trap/bait sites managers may be more effective at removing social groups if they first remove the dominant male.  

“Previous research has documented that both solitary males and sounders are semi-territorial, but there was a need to understand how this behavior influences bait site visitation. Understanding that females were less likely to visit sites after an adult male visited provides important management implications,” shares Brewer. “Females and sounders are typically targeted for management activity due to their high reproductive potential. Our results suggest removal of adult males may facilitate detection of sounders at bait sites, especially in areas where males may be monopolizing access to bait.”

For wildlife managers, the practical application is straightforward. If pigs fail to visit a bait site, changing the bait or waiting longer may do little to improve success. Instead, the authors recommend placing bait as close as possible to areas where there is clear evidence pigs are currently active, using fresh rooting, tracks, wallows, and other signs of recent activity to guide site selection. If a bait site remains undiscovered after an extended period, relocating it may be a more effective strategy than leaving it in place.  

Sounder of wild pigs are seen in a trap. (Photo courtesy: Sydney Brewer and James Beasley).

While the study focused on bait visitation, its findings could extend beyond a single management technique. Trapping, toxic baiting, disease surveillance, and many monitoring programs all rely on attracting pigs to a specific location, making bait placement one of the first decisions managers face. By identifying the factors that most strongly influence whether pigs discover bait, the research provides information that can help improve a wide range of wild pig management efforts.  

“The time and effort required to maintain trap and bait sites represent one of the greatest costs of wild pig management, so we hope this study will improve both the efficiency and effectiveness of wild pig management programs. Specifically, our results demonstrate that even when wild pigs are known to occur in an area, bait sites should be relocated if no activity is detected within 1–2 weeks,” says Beasley. “Because most management programs prioritize the removal of sounders to maximize population reduction, our findings further suggest that when large males discover bait sites before sounders, removing those males first may increase the efficiency of subsequent sounder trapping.”

The full study, Proximity to Bait and Social Interactions Influence Individual Wild Pig (Sus scrofa) Visitation at Bait Sites, was published in the Journal of Wildlife Management. Authors include Sydney M. Brewer, Nathan P. Snow, and James C. Beasley. 

By Tyjaha Steele

Peng Lin is shown working hands-on with cement in the lab (Photo courtesy of Peng Lin),

Although concrete is often seen as a stable barrier used to contain waste, it does not remain unchanged over time, and as it breaks down, it releases chemicals that can alter the surrounding groundwater. What happens when the materials designed to trap contaminants like uranium and strontium begin to change the conditions around them, and could those changes affect whether pollutants stay put or begin to move? 

To answer this question, researchers from the University of Georgia’s Savannah River Ecology Laboratory (SREL), including Peng Lin, an assistant research scientist, and Daniel I. Kaplan, a senior research scientist, worked with collaborators from Savannah River Mission Completion (SRMC) and Closure & Disposal Determinations to examine how aging cement materials influence the movement of metals and radioactive elements in subsurface environments. Using sediments collected from the Savannah River Site (SRS) in Aiken, South Carolina, specifically from a subsurface low-level radioactive waste disposal area, the study explored how groundwater chemistry shifts as cement degrades and how those shifts affect contaminants such as uranium, cesium, and cobalt over time. 

“People often assume these materials behave in a simple, predictable way underground, but that’s not the case. As cement-based materials age, they change the chemistry of the surrounding water, especially things like pH,” Lin shares. “These changes can strongly affect contaminants: some become tightly trapped, sometimes even forming solid minerals, while others can actually move more easily. Because of this, their behavior isn’t fixed over time and can vary depending on the type of contaminant and the surrounding soil.”

By recreating different stages of cement aging in laboratory experiments, the research team simulated how conditions change from newly formed cement to older, degraded material, and each stage reflected a different chemical environment. Newly formed cement creates highly alkaline conditions, meaning the water becomes more basic than natural groundwater, while older cement produces conditions that are closer to typical environmental levels. Using sediments collected several meters below ground, the team tested how contaminants, including uranium and strontium, responded across these different stages.   

As these conditions changed, the behavior of contaminants shifted as well, and in many cases, they became less mobile under high pH conditions. Metals and radionuclides such as uranium, strontium, cesium, and cobalt were more likely to attach to sediment particles, a process known as sorption, which reduces their ability to move with groundwater. In some cases, these conditions also caused contaminants to form solid mineral phases, further limiting their movement. Compared to natural groundwater conditions, the results showed much stronger retention of several contaminants in the presence of cement-related leachates, in some cases increasing by orders of magnitude depending on the element and conditions. 

“Many people might expect pollutants to simply dissolve and spread out, especially ones similar to common salts. But the results showed that some contaminants were actually trapped much more strongly in the presence of cement,” Lin states. “A particularly surprising finding was with cesium, a type of contaminant that behaves like familiar elements such as sodium or potassium and is usually expected to stay dissolved and mobile in water. Instead, the study found that cesium could become much more strongly retained in certain conditions, especially as the chemistry changed with cement aging.”

While this trend was consistent for many elements, responses varied depending on the type of contaminant, and not all showed the same level of change. Positively charged elements, such as uranium and cobalt, generally showed increased retention, while negatively charged contaminants, such as certain forms of technetium or iodine, responded differently and in some cases remained mobile. These differences are linked to chemical properties such as how easily an element dissolves in water or binds to particle surfaces, which means that each contaminant reacts differently even under similar environmental conditions. 

 As the cement continued to age, the strength of these effects shifted, and the ability of sediments to hold contaminants like cesium and strontium changed over time. Early-stage conditions, which are the most chemically extreme, often led to the strongest retention, while later stages produced more moderate effects as the chemistry moved closer to natural groundwater conditions. This progression highlights how contaminant behavior evolves alongside the materials meant to contain it.   

Because sediment type also plays a role, the researchers observed that clay-rich soils tended to hold contaminants such as uranium and cesium more consistently, while sandy sediments showed greater variability depending on surrounding conditions. These differences influence how far contaminants might travel and how quickly they could move through the subsurface. 

“When you look at all the findings together, they show that these underground systems are not static, which means they change a lot over time. As materials like cement age, they gradually alter the surrounding water chemistry, which in turn changes how contaminants behave,” Kaplan says. “What this helps us understand is that contaminants might not stay mobile forever, or stay trapped forever. Some may become more contained over time, while others could become easier to move depending on the conditions.”

By examining how cement materials, groundwater chemistry, and sediment type interact, the study provides insight into how contaminants behave in real-world disposal systems, and it helps improve predictions of long-term environmental risk. The findings also represent one of the more comprehensive efforts to quantify how cement aging influences the retention of metals and radionuclides like uranium, strontium, and cesium across a range of environmental conditions.  

The full study, Age-dependent cementitious leachate effects on metal and radionuclide sorption to sediments from a subsurface waste-disposal site, was published in Applied Geochemistry. Authors include Peng Lin, Karah Greene, Wei Xing, Steven Simner, Christina Logan, Richard Henry, and Daniel I. Kaplan.