'Rivers on Rolaids:' Alkalinity in Waterways on the Rise

  • Eastern waterways are showing increases in their alkalinity levels, which researchers believe is a legacy of acid rain dissolving limestone. The Susquehanna River, pictured here, was included on a list of sites that had increases in alkalinity. Photo: Nicholas A. Tonelli, via Wikimedia Commons

September 20, 2013

'Rivers on Rolaids': this is how one researcher described an increase in the alkaline condition of dozens of streams in the eastern United States.

The reason? Acid rain.

Although efforts such as the passage of the Clean Air Act have greatly mitigated acidic precipitation resulting from coal-fired power plants, the rise in alkalinity now being seen may be a legacy of a more polluted past.

"What we're seeing right now may just in fact be a delayed response of the watersheds to the severe degradation we observed in the 70s and 80s," says environmental scientist Rick Utz. "It's the same with any number of other phenomena like climate change. Some of the effects from climate change we may not see for decades or 50 years."

Utz works for the National Ecological Observatory Network and contributed to a study that looked at 97 sites from New Hampshire to Florida. Expecting to find that urban waterways would have the largest increases in alkalinity levels, he and fellow researchers were surprised to find that this upward trend was not limited to just urban areas. The work was published in Environmental Science & Technology.

"What we expected at first was that the sites where we would see the most rising alkalinity values would be urban sites where degrading cement, which has a lot of calcium carbonate in it, would be contributing to the rising levels," Utz says. "What we found though, is a large number of sites, not just urban sites, are exhibiting the trends."

Sixty-two out of the 97 sites examined saw increases in alkalinity. Watersheds that are high in elevation, have a lot of carbonate (limestone), and were subjected to the most acidic precipitation in the past have the fastest rising levels.

In Pennsylvania, large rivers such as the Susquehanna and Delaware rivers have increased alkalinity, although lower levels than creeks like Antietam and Conococheague creeks.

According to Utz, it is reasonable to believe that there are more waterways in Pennsylvania that also have increased alkalinity levels.