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GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 10, 1495, doi:10.1029/2003GL017056, 2003

Long-term decline in carbon dioxide supersaturation in rivers across the contiguous United States

Jeremy B. Jones Jr.

Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska, USA

Emily H. Stanley

Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA

Patrick J. Mulholland

Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA

Abstract

The partial pressure CO₂ (pCO₂) in streams and rivers reflects both internal carbon dynamics and external biogeochemical processes in terrestrial ecosystems. CO₂ is typically supersaturated in streams because rates of organic matter decomposition exceed photosynthetic uptake, and because of inflow of CO₂ supersaturated ground waters. Using the U.S. Geological Survey's NASQAN database, we calculated pCO₂ and dissolved inorganic carbon (DIC) concentration in 417 streams and rivers distributed across the contiguous United States over a 22-year period. In addition to demonstrating widespread supersaturation and distinct regional variation in pCO₂ across the U.S., our analysis revealed that pCO₂ significantly declined 78.4 ppmv y⁻¹ from 1973 to 1994. This decline is not attributable to changes in terrestrial weathering or in-stream processes, but instead suggests large-scale declines in terrestrial CO₂ production and import into aquatic ecosystems during this 22-year period.

Received 4 February 2003; accepted 11 April 2003; published 17 May 2003.

Index Terms: 1615 Global Change: Biogeochemical processes (4805); 1806 Hydrology: Chemistry of fresh water; 1886 Hydrology: Weathering (1625); 1803 Hydrology: Anthropogenic effects.

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Citation: Jones, J. B., Jr., E. H. Stanley, and P. J. Mulholland (2003), Long-term decline in carbon dioxide supersaturation in rivers across the contiguous United States, Geophys. Res. Lett., 30(10), 1495, doi:10.1029/2003GL017056.

Copyright 2003 by the American Geophysical Union.