title: Increased river alkalinization in the Eastern U.S.
abstract: The interaction between human activities and watershed geology is accelerating long-term changes in the carbon cycle of rivers. We evaluated changes in bicarbonate alkalinity, a product of chemical weathering, and tested for long-term trends at 97 sites in the eastern United States draining over 260,000 km(2). We observed statistically significant increasing trends in alkalinity at 62 of the 97 sites, while remaining sites exhibited no significant decreasing trends. Over 50% of study sites also had statistically significant increasing trends in concentrations of calcium (another product of chemical weathering) where data were available. River alkalinization rates were significantly related to watershed carbonate lithology, acid deposition, and topography. These three variables explained ~40% of variation in river alkalinization rates. The strongest predictor of river alkalinization rates was carbonate lithology. The most rapid rates of river alkalinization occurred at sites with highest inputs of acid deposition and highest elevation. The rise of alkalinity in many rivers throughout the Eastern U.S. suggests human-accelerated chemical weathering, in addition to previously documented impacts of mining and land use. Increased river alkalinization has major environmental implications including impacts on water hardness and salinization of drinking water, alterations of air-water exchange of CO2, coastal ocean acidification, and the influence of bicarbonate availability on primary production.
authors.affiliation: College Park Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland , College Park, Maryland 20740, United States.
authors.forename: Sujay S
authors.initials: SS
authors.lastname: Kaushal
authors.forename: Gene E
authors.initials: GE
authors.lastname: Likens
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Utz
authors.forename: Michael L
authors.initials: ML
authors.lastname: Pace
authors.forename: Melissa
authors.initials: M
authors.lastname: Grese
authors.forename: Metthea
authors.initials: M
authors.lastname: Yepsen
mesh_terms: D015258:Acid Rain; D002254:Carbonates / Q000737:chemistry; D004784:Environmental Monitoring; D055593:Geological Phenomena; D006802:Human Activities; D006863:Hydrogen-Ion Concentration; D045483:Rivers / Q000737:chemistry*; D014481:United States
chemical_list: D015258:Acid Rain; D002254:Carbonates