CINCINNATI, Ohio, May 15, 2002 (ENS) - Wetlands can be a valuable asset in helping to clean up an unfortunate legacy of mining operations: acidic runoff. Geologists from the University of Cincinnati have found that a few key factors can determine whether a wetland area can successfully reduce the impact from acid mine drainage.

A stream of acid mine drainage. The minerals carried by the water turn it red. (All photos courtesy Professor Barry Maynard, University of Cincinnati)

While water supplies can be turned acidic by natural rock formations, the mounds of rock and rubble produced by mining increase the rock surface available to react with water, accelerating the process.

Highly acidic water can harm ecosystems, wildlife and cultural resources. The water can also etch away portions of mine rubble, releasing heavy metals and other toxins, and it leaves behind a difficult to clean mess in mine waste pits and open dumps. One of the worst cases of acid mine drainage, the Berkeley Pit in Montana, has contaminated 23 square miles with arsenic and heavy metals.

These toxins led to the 1995 deaths of 342 snow geese, who mistook the contaminated water for a safe migratory drinking stop.

Some manmade wetlands perform better than others at cleaning up acid mine drainage, the researchers found.

To accelerate this process, some manmade wetlands use a system known as an anoxic limestone drain. The limestone performs the same function as the microbes, decreasing the acidity of the water flowing through the wetlands.

Geology Professor Barry Maynard and graduate student Adam Flege, both from the McMicken College of Arts and Sciences, studied the effectiveness of constructed and natural wetlands in six sites affected by acid mine drainage in Indiana and Ohio.

Maynard and Flege found that some of these constructed wetlands worked very efficiently to reduce the impact of acid mine drainage, but others were less effective at cleanup.

Protecting marsh vegetation may help wetlands act as natural filters for mine drainage.

Though not all manmade wetlands were successful, Maynard emphasized that the research helps points the way toward designing better bioremediation systems in the future.

"There are several implications," said Maynard. "First of all, constructed wetlands need regular maintenance. Second, they should be larger. Third, and most important, the problem of clogging of the limestone drains needs to be solved."

Maintaining wetlands may require routine trapping of the wildlife that damages marsh plants, Maynard added. "It's not hard. It just requires a continuing expense," he said.

Maynard and Fledge reported their research, funded by the Indiana Division of Reclamation, during a joint meeting of the North-Central and Southeastern Sections of the Geological Society of America meeting in Lexington, Kentucky. target="_blank">http://www.epa.gov/region09/air