9 research outputs found
Increased River Alkalinization in the Eastern U.S.
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<sup>2</sup>. 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 CO<sub>2,</sub> coastal ocean acidification, and the influence of bicarbonate
availability on primary production
Appendix D. Hydrogen (δD), carbon (δ13C), and nitrogen (δ15N) stable isotope ratios of consumers from each lake.
Hydrogen (δD), carbon (δ13C), and nitrogen (δ15N) stable isotope ratios of consumers from each lake
Appendix A. Taxa sampled in each lake, and their assumed mean trophic positions.
Taxa sampled in each lake, and their assumed mean trophic positions
Appendix E. Description of the methods and results for simulations that we ran in order to validate the mixing model that we use in this paper, by testing the ability of the model to recover the true parameters from simulated data.
Description of the methods and results for simulations that we ran in order to validate the mixing model that we use in this paper, by testing the ability of the model to recover the true parameters from simulated data
Appendix F. Prior distributions and posterior distributions of the total water contribution to tissue H and the total trophic fractionation of N between sources and consumers.
Prior distributions and posterior distributions of the total water contribution to tissue H and the total trophic fractionation of N between sources and consumers
Appendix C. Hydrogen (δD), carbon (δ13C), and nitrogen (δ15N) stable isotope ratios of basal resources and water in each lake.
Hydrogen (δD), carbon (δ13C), and nitrogen (δ15N) stable isotope ratios of basal resources and water in each lake
Appendix D. Information about goodness of fit of the models.
Information about goodness of fit of the models