John Wiley & Sons, Ltd.

Climate change and watershed mercury export: A multiple projection and model analysis

Future shifts in climatic conditions may impact watershed mercury (Hg) dynamics and transport. We apply an ensemble of watershed models to simulate and evaluate the responses of hydrological and total Hg (HgT) fluxes from the landscape to the watershed outlet and in‐stream HgT concentrations to two contrasting climate change projections for a watershed in the southeastern Coastal Plain of the US. Simulations are conducted under stationary atmospheric deposition and land cover conditions to explicitly evaluate the effect of projected precipitation and temperature on watershed Hg export (i.e., the flux of Hg at the watershed outlet). Based on downscaled inputs from two global circulation models that capture extremes of projected wet (CCSM3) and dry (ECHO) conditions for this region, we estimate an approximate 19% decrease in ensemble‐averaged mean annual watershed HgT fluxes using the ECHO climate change model and an approximate 5% increase in HgT fluxes with the CCSM3 model. Ensemble‐averaged mean annual ECHO in‐stream HgT concentrations increased 20%, while those of CCSM3 decreased by 9%, between the baseline and projected simulation periods. Watershed model simulation results using both climate change models suggest that monthly watershed HgT fluxes increase during the summer, when projected flow is higher than baseline conditions. Our multiple watershed model approach underscores the uncertainty associated with climate change response projections and their use in climate‐change management decisions. Thus, single‐model predictions can be misleading, particularly in developmental stages of watershed Hg modeling. Environ Toxicol Chem © 2013 SETAC

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