The wetland, which was built in an agricultural area, reduced levels of phosphorus by nearly 60 percent and nitrates by 40 percent. Phosphorus and nitrates are prime ingredients in both fertilizers and in water pollution.
High levels of these nutrients can cause algae to flourish, often to the detriment of fish and other animals that depend on waterways for survival. Algae essentially rob oxygen from water in a pond, lake and even the ocean.
"We saw a pretty significant reduction in phosphorus and nitrate concentrations close to the kind of decrease we typically see in a natural wetland," said William Mitsch, a study co-author and director of the Olentangy River Wetland Research Park at Ohio State University. "The water was cleaner when it left the wetland than when it came in."
The results appear in the current issue of the journal Ecological Engineering. Mitsch conducted the study with Daniel Fink, a student in the environmental science graduate program at Ohio State.
Often called the "kidneys" of the environment, wetlands act as buffer zones between land and waterways. They also act as sinks wetlands filter out chemicals in water that runs off from farm fields, roads, parking lots and other surfaces, and hold on to them for years to come.
But the jury is still out on how long a wetland can remain a sink for certain nutrients, Mitsch said. For example, phosphorus doesn't degrade, so after 30 or 40 years, the wetland in this study could possibly become a phosphorus source.
"Wetlands' capacity to store phosphorus declines with time," Mitsch said. "But a wetland that reaches that point has extremely rich soil, which could be harvested and spread over a farm field. Or the wetland itself could be turned into a field again,
Contact: William Mitsch
Ohio State University