Lead Scientist(s): Dr Gene E Likens
Human activities are changing the water chemistry of many streams and rivers in the Eastern U.S., with consequences for water supplies and aquatic life. [Kaushal, S. S., G. E. Likens, R. Utz, M. L. Pace, M. Grese and M.Yepsen. 2013. Increased river alkalinization in the Eastern U.S. Environmental Science and Technology, DOI: 10.1021/es401046s].
In the first survey of its kind, Dr. Likens and colleagues evaluated long-term alkalinity trends in 97 streams and rivers from Florida to New Hampshire. Sites ranged from small headwater streams to some of the nation’s largest rivers. Over the past 25 to 60 years, two-thirds became significantly more alkaline.
Alkalinity is a measure of water’s ability to neutralize acid. In excess, it can cause ammonia toxicity and algal blooms, alter water quality and harm aquatic life. Increasing alkalinity adds hardness to water supplies, causing pipe scaling and costly infrastructure problems. In addition, it can exacerbate the salinization of fresh water.
Human activities that create acid conditions are accelerating the problem. This acceleration occurs because acid rain, acidic mining waste, and agricultural fertilizers speed the breakdown of limestone, other carbonate rocks, and even concrete and cement.
Dr. Likens and colleagues found that watershed geology was the strongest predictor of river alkalinization, with rivers receiving water from porous limestone, and other carbonate rocks being more alkaline. Topography and pollution were also important. The most rapid rates of alkalinization were at high elevation sites that were chronically exposed to acid precipitation.
Among the rivers impacted by higher alkalinity are those that provide water for Washington, D.C., Philadelphia, Baltimore and Atlanta. This change results, in part, from acid rain exposure, urbanization, and the extent of land covered by cement and concrete.
Also affected are rivers that flow into water bodies already harmed by excess algae, such as the Chesapeake Bay, where managers are struggling to contain algal blooms that are toxic to fish, oysters, and crabs. Appalachian Mountain streams are also vulnerable. In that region, thin soils and steep slopes cause erosion, and there is persistent exposure to emissions such as sulfur and nitrogen oxides from industrial activity.
The research was funded by NASA Carbon Cycle & Ecosystems, the National Science Foundation’s Long Term Ecological Research Program, and The Andrew W. Mellon Foundation.
Sujay S. Kaushal, Gene E. Likens, Ryan M. Utz, Michael L. Pace, Melissa Grese, and Metthea Yepsen, “Increased river alkalization in the Eastern U.S,” in Environmental Science and Technology, August 26, 2013. View the article at: http://pubs.acs.org/doi/abs/10.1021/es401046s
The full research team included:
Sujay S. Kaushal, University of Maryland, College Park
Gene E. Likens, Cary Institute of Ecosystem Studies & University of Connecticut
Ryan M. Utz, National Ecological Observatory Network
Michael L. Pace, University of Virginia
Melissa Grese, University of Maryland, College Park
Metthea Yepsen, University of Maryland, College Park