Jonathan Remo, associate faculty in the School of Earth Systems and Sustainability left, works alongside Cecilia Albert Black, an undergraduate student, and Joseph Krienert, a doctoral student, to collect samples along the Mississippi River. Remo and Liliana Leaveicariu, Southern Illinois University Carbondale associate professors of geology, are leading a team to quantify and identify the processes that reduce nitrogen pollution in several floodplains. wetlands along the Middle Mississippi River. (Photo provided)
February 1, 2022
SIU researchers investigate how Mississippi wetlands could benefit human life as well as the environment
CARBONDALE, Ill. – Researchers at Southern Illinois University Carbondale are trying to find out if a key to mitigating an ongoing environmental threat lies along the banks of the mighty Mississippi River.
Liliana Lefticariu, associate Professor of Geology in the School of Earth Systems and Sustainability is leading a team to quantify and identify the processes that reduce nitrogen contamination in several floodplains. wetlands along the Middle Mississippi River. The region stretches for 190 miles from the confluence with the Missouri River at St. Louis to its confluence with the Ohio River at Cairo.
If nitrogen is too high in water, it can make life-giving nitrogen toxic for wildlife and humans. However, studies from other parts of the world have shown that wetland areas play an important role in reducing nitrogen pollution by supporting microbes that convert nitrogen pollutants into harmless gas.
The chemical is used by farmers and gardeners on thousands of acres. It can be found in groundwater and streams and eventually reaches the Mississippi River, where it will wash into the Gulf of Mexico. Livestock waste, septic effluent and Earth’s own atmosphere also provide such environmental inputs.
At high water concentrations, nitrogen can squeeze the oxygen out of the water while also giving rise to algae blooms that further choke the life out of the ocean near the river’s mouth.
Jonathan Remo, associate Professor of Geography and team co-leader, Joseph Krienert (doctoral student) and Cecilia Albert Black (undergraduate student in geology), are all part of the interdisciplinarity SIU team. A partnership among The Nature Conservancy, American Rivers and the U.S. Department of Agriculture’s Natural Resources Conservation Service and other groups is funding the work.
But how does it work?
Wetlands have been shown to be up to five times more efficient at reducing nitrate pollution than the best available land-based nitrogen mitigation strategies, Lefticariu said. The team’s main goal is quantifying the nitrogen removal efficiency while identifying key factors that limit nitrogen removal in such riverine wetlands.
To do this, the team will examine hydrological characteristics using geochemical attributes such as the levels of various nitrogen types, including nitrates, nitrites, ammonia, and particulate nitrogen, as well as their measuring their stable isotope signatures. Additional members will also be investigating the dynamics of the local microbiome to determine their role in the processing and cycling of nitrogen.
The stakes are high as the work to understand and reverse the so-called “Secret” is aimed at ensuring that everyone benefits. “hypoxic zone,” an oxygen-depleted “dead zone” of the Gulf of Mexico stretching from eastern Texas into Louisiana. Its current size is 6,334 sq. miles. This would be equivalent to more than 4,000,000 acres of habitat that could be inaccessible to fish and bottom species.
“The Mississippi River epitomizes this crisis,” Lefticariu said. Human-made nitrogen runoff is a major cause of economic and ecological damage. It causes more than $70 Billion in economic loss annually. But it’s also a worldwide problem.
“Developing this knowledge base will provide critical information to river managers as they try to specify the type and area of wetlands needed to help mitigate environmental problems related to elevated nitrogen loads,” she said.
To better understand how it all works, the team uses both field and laboratory studies along with computer modeling. There are many challenges.
The area is complex and this study is the first to examine it. It also means that there are many unknowns. To deal with these factors, the team designed a step-by-step approach to studying various processes individually before assembling a self-contained test system within the larger wetland system.
They are also examining how hydrologically connected lands directly along the river deal in nitrogen, as opposed those wetlands that are separated from the river by levees. The river floods the wetlands often, most often in spring when snow melts downstream, but flooding can occur at any point during the year depending on weather conditions.
“In other places, there are levees that protect the land from flooding,” Lefticariu said. “But behind the levees, we can still find wetlands, which in these cases are not directly connected to the river, but we study them as well. And we have observed differences in term of hydrological and bio-geochemical processes between these two types of wetlands, and we hope to learn more about efficiency of nitrate pollution reduction in these two types of wetlands.”
Important for the planet
Lefticariu said that nitrogen runoff, which is a worldwide problem, and the environmental problems it causes, pose a risk of irreversible damage. The Mississippi River has seen an increase in average nutrient levels. It is necessary to coordinate efforts to stop this trend.
“Our research is very important and timely since increasing nitrogen pollution can led to an environmental catastrophe,” she said, “and we need to develop strategies to prevent it.”