The story isn't quite the same with nitrates ?a nitrogen-based compound found in fertilizer.
"As a wetland gets older, it gets better at handling and storing nitrogen," Mitsch said. "The idea is not to overload wetlands in the first place."
The three-acre wetland in the study was roughly the size of three football fields and drained a watershed about 14 times that large. It is located in prime agricultural territory in west central Ohio ?on the shores of Great Miami River, a tributary that flows into a local lake and then on to the Ohio River, which drains to the Mississippi River.
The researchers studied the wetland for two years, collecting and analyzing water samples twice each month. They tested the samples for concentrations of phosphorus, nitrates and several other chemicals.
The researchers also gathered data on water flowing into the wetland from rain and snowfall and from ground sources. They wanted to know if the design of this experimental wetland would work.
Apparently, it did.
"It was a relatively simple, inexpensive way to create a wetland, and it worked," said Mitsch, who is a professor of natural resources at Ohio State. The wetland was constructed by bulldozing a series of basins into the field. The five basins sloped downward toward the river ?the second basin was at a slightly lower elevation than the first, the third basin was slightly lower than the second, and so on. Surface water would come into the first basin and slowly seep toward the other basins. All of the basins were connected by water flowing beneath the surface.
No plants were planted in the wetland; rather, the builders let nature take its course, Mitsch said. Stands of trees surrounded part of the wetland.
"This area once was a wetland," Mitsch said. "So it reverted pretty quickly to that kind of ecosystem when it had the chance."
Over the two-year study, the w
Source:Ohio State University