Wetlands Reduce Farm Runoff and Water Pollutants

By Blake Jackson

A study by the University of Kentucky’s Martin-Gatton College of Agriculture, Food and Environment highlights how small-scale wetlands - one soil-based and the other floating - can significantly reduce harmful pollutants from farm runoff and household waste.

These wetlands proved effective in lowering nutrient levels and filtering out “forever chemicals” from Kentucky waterways.

Led by Tiffany Messer, the Bill Gatton Foundation Endowed Chair and associate professor in the Department of Biosystems and Agricultural Engineering, the research focused on mesocosms - controlled environments that mimic real-world ecosystems.

“Mesocosms are a powerful tool because they let us isolate key variables while still mimicking field conditions,” said Messer. “It’s an essential step when trying to understand how these systems perform outside the lab.”

The team constructed 40 waist-high tanks resembling treatment wetlands. Half were filled with soil and bulrush, while the others used polyethylene rafts to suspend vegetation roots in water.

Each tank received doses of common pollutants - glyphosate, atrazine, caffeine, PFOS - along with nitrate, simulating runoff commonly found near rivers.

“Those four contaminants turn up again and again in our stream surveys,” said Messer. The researchers wanted to determine if these substances would interfere with nitrogen removal and if plants could absorb them.

Initially, the soil-based tanks slightly outperformed the floating ones, cutting nearly 50% of nitrate and reducing PFOS and atrazine by about one-third. But as temperatures rose, the floating wetlands excelled, eliminating almost all nitrate and reducing herbicides by 70%.

“The mat systems become living filters,” Messer noted. As roots extend, the water passes through a microbial-rich environment, improving purification.

Chemical analysis revealed most glyphosate and PFOS accumulated in plant stems and leaves, indicating that trimming could prevent re-release. Atrazine was found mainly in roots, requiring full plant removal for effective mitigation.

Though wetlands require more space than traditional treatment systems, Messer hopes to collaborate with local engineers to expand their use. “They’re pretty, but they aren’t fishing ponds,” she said. “The goal is to protect aquatic life in the receiving stream.”

For more details, visit bae.ca.uky.edu.

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