Explaining conductivity

(Photo of Big Clear Creek by Stephanie Ferrell)

Evidence that conductivity causes harm in Appalachian streams has only been discovered recently, thanks to a growing body of research demonstrating that conductivity levels are highly correlated with degradation of a stream’s ability to support aquatic life.

Dr. Margaret Palmer, director of the National Socio-Environmental Synthesis Center and a professor at University of Maryland’s Department of Entomology who has done much of the research on this issue, said the measure of a stream’s specific conductivity – how well it conducts electricity – turns out to be a better way of measuring the impact of a wide array of pollutants common in streams below mine sites.

When coal is mined, rock and other material is exposed to air and water for the first time in hundreds of thousands, perhaps even millions, of years. That material is broken up and reacts with oxygen and water. Many natural elements dissolve and run off in the water.

This creates a toxic soup. Alone, many of these elements aren’t at high enough concentrations to cause problems. “But the net effect of those together is what becomes dangerous,” Palmer said.

Conductivity is the best way to determine when those net effects can impact life in an Appalachian stream impacted by mining. “It’s a measure of the combined effect of all those constituents,” Palmer said.

The alternative would be to run hundreds or thousands of experiments trying to determine which exact combinations of individual elements and in what quantity cause problems. But there are so many different possible combinations, that’s simply not practical, or necessary.

“Measuring conductivity is an excellent way to measure the level of impacts in this setting,” she said.

That’s why the U.S. Environmental Protection Agency determined that conductivity above a certain level hurts aquatic life in Appalachian streams. Its water quality guidance is designed to help coal companies and state and federal regulators minimize the harmful effects of mountaintop removal mining.

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