GYPSUM FORMATION IN ACID MINE DRAINAGE AFFLICTED STREAMS IN PERRY COUNTY, OHIO

An unknown white precipitant can be observed armoring limestone rocks in acid mine drainage (AMD) affected streams in Perry County, located in southeastern Ohio on the Appalachian Plateau. It can also be found on the banks of an unnamed stream that flows into a wetland remediation site. The white precipitant has been described as aluminum by local water quality specialists but quantitative tests have yet to be performed on it. Aluminum will precipitate out at a pH higher than 5 and will become soluble again at a pH greater than 9. The pH of the water at the mouth of the unnamed stream averages at 3.5. This pH is too low for aluminum to precipitate out of the stream. The same white precipitant can be observed at the Essex mine entrance located in New Straightsville, Ohio. The pH is less than 5 and the dissolved aluminum concentrations are 3.2 mg/liter according to published water quality data processed by the Ohio Department of Natural Resources. The sulfate concentrations are between 400 mg/liter and 500 mg/liter. There is also calcium present in the mine discharge at 40 to 50 mg/liter. The acidic water and presence of high sulfate concentrations and calcium may allow for gypsum formation on limestone rocks and along the banks of these streams. Gypsum may be forming under acidic water conditions as long as sulfate and calcium is sufficient in the environment. The acidic conditions and the high sulfate concentrations in the surface water is caused by pyrite oxidization. The pyrite can oxidize in open mines or in gob piles left by the former miners. Quantitative tests will be performed to determine if the precipitant is indeed gypsum or another sulfate mineral.