Balancing Acidity
4:00 am
Tue September 3, 2013

Rivers on Rolaids

U.Va. environmental scientist Michael Pace and former U.Va. student Carol Yang conduct a water study.
U.Va. environmental scientist Michael Pace and former U.Va. student Carol Yang conduct a water study.
Credit University of Virginia

Something surprising is happening to rivers in the eastern part of the United States.  Scientists from the Universities of Virginia and Maryland say human activities are changing the basic chemistry of the water.

In a survey of 97 rivers from Florida to New Hampshire over up to six decades, scientists have discovered the water becoming less acidic – a surprise in light of how much acid rain has fallen in this part of the world.

“Our initial thought was it must be the concrete – that all these heavily developed Eastern rivers with cities and what not, the concrete is essentially dissolving into the river," said  Michael Pace, a professor of environmental sciences at UVA.  After further analysis, he and his colleagues concluded that at some point the water was acidic and began dissolving rocks along the banks and river beds.

“We think what’s going on is essentially the watersheds – the landscapes around these rivers –are being weathered, and if they have carbonate rocks, which contain calcium carbonate, it essentially converts to baking soda.”

It is, he says, like rivers on Rolaids – with the carbonate balancing any acidity.  That’s good news for aquatic life, but troublesome for water treatment plants.  

“You get fouling of the pipes and scaling and things like that, and homeowners who have wells and certain kinds of waters would have had this kind of experience and know that you have to treat the water with water softeners and things like that.”

In other words, more treatment is needed – and that means more expense.  Some of the rivers studied flow into the Chesapeake Bay, but Pace says this trend is probably not an issue there:

“The bay is already sort of naturally alkaline, because it’s marine salty water, and so it would diminish the tendency of the bay to become more acidic.”

What’s more, the Clean Air Act has led to less acid rain, so the Ph of rivers may swing back toward a balance.  What scientists don’t know is how long that might take.  It could be a decade or a century.