What's turning Charlotte's drinking water acidic?

Part of Mountain Island Lake, the main water source for Charlotte and Gastonia, has for the first time made North Carolina's list of "impaired" waters.

For reasons experts don't yet know, water readings in the lower lake turned slightly acidic. Five other places on the Catawba River, and four in the Yadkin basin east of Charlotte, also made this year's bad-water list for the same reason.

Acidic water isn't harmful to drink, but it threatens fish and other aquatic life.

"In a large way, it's showing that our primary drinking water source is being impacted by more troubles," said Catawba Riverkeeper David Merryman.

Acid rain is among the suspects that might explain the Catawba and Yadkin readings. Industry emissions, largely from coal-burning power plants, form acidic compounds in the atmosphere that fall to the earth's surface. North Carolina's attorney general successfully sued the Tennessee Valley Authority in 2006 for power-plant pollution blowing into his state.

But Viney Aneja, an air-pollution scientist at N.C. State University, points to what he believes is a likelier culprit: drought.

A record dry spell hammered the Charlotte region from early 2007 to late 2008. Low water in streams and lakes could have concentrated sulfate and nitrate, Aneja says, making the water temporarily more acidic. The water samples that led to most of the Catawba's bad-water listings were collected in 2008.

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