MAGIC Model Estimates of Critical Load of Sulfur Deposition to Protect Acid-Sensitive Resources in the Adirondack Mountains, New York

T.J. Sullivan1, B.J. Cosby2, T.C. McDonnell3, C.T. Driscoll4, A.T. Herlihy5, D.A. Burns6

The MAGIC model was applied to 97 lake watersheds in the Adirondack Mountains, New York, to estimate the critical load (CL) of sulfur deposition required to protect aquatic and terrestrial resources against acidification. The sensitive receptors that were evaluated included lake acid neutralizing capacity (ANC), soil base saturation (BS), soil solution nutrient base cation-toaluminum ratio (Bc:Al), and soil solution calcium-to-aluminum ratio (Ca:Al).Varying critical criteria thresholds and endpoint years were examined. Critical load and exceedance results were extrapolated numerically to the broader population of Adirondack lakes using the mathematical frame from EPA?s Environmental Monitoring and Assessment Program (EMAP). Spatial extrapolation and mapping were performed using the Adirondack Lakes Survey as the basis for extrapolating MAGIC-simulated CL values to the regional population of surveyed lakes. Resulting critical loads were compared to reveal patterns related to selection of sensitive receptor, critical criterion threshold, and endpoint year. This information will be of substantial importance for natural resource management in the Adirondack Mountain region.

1 E&S Environmental Chemistry, Inc., P.O. Box 609, Corvallis, OR 97339;
2 Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22903;
3 E&S Environmental Chemistry, Inc., P.O. Box 609, Corvallis, OR 97339;
4 Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY 13244;
5 Department of Fish and Wildlife, Oregon State University, Corvallis, OR 97331;
6 U.S. Geological Survey, Troy, NY 12180;