Response of Soil Water Chemistry to Simulated Changes in Acid Deposition in the Great Smoky Mountains

Cai, Meijun; Johnson, Amy; Schwartz, John; Fasce, P; Moore, Stephen; Kulp, Matt

cmicibiteratoand meters were used tonse to simuion. Con-3, and n experiments, e 4.4 among five nitial pInfluentuggest nte adsorption occurred when SO4-below 15 μmol L-1, which would eon levels. Base cation depletionnd 24–27 μmol L-1 Mg+2 reductionrily caused by soil cation exchange and not weathering. In theseletion was estimated as 90 to 140 years. Protons released by SO4base cation depletion, thereby delaying watershed recovery. Fieletics and hydrologic interflow rates, illustrating how precipitating watershed recovery in the future and suggest needs for further research.ABSTRACT: Watershed recovery from acidic deposition, such as the Noland Divide Watershed in the Great Smoky Mountains National Park, isdifficult to predict because of omplex biogeocheal processes exhd in soils. Labory soil columns in situ pan lysio investigate soil solution resplated reductions in acid deposittrolling for influent SO4-2, NONH4+ concentrations in the columffluent pH declined similarly toexperimental scenarios from an iH of approximately 4.7 and 6.1. -effluent chemical comparisons sitrification and/or SO4-2 desorption controls effluent pH. Sulfa2 influent was greater than 25 μmol L-1 and desorption occurred quate to approximately a 61% reduction in current SO4-2 depositi occurred in column experiments, in which 64–60 μmol L-1 Ca+2 as were measured. Cation depletion rates were pH dependent, prima soils with base saturation below 7%, complete Ca+2 and Mg+2 dep-2 desorption via ligand exchange are expected to cause further d experiments found SO4-2 sorption dynamics to be limited by kintion intensity can influence ion transport from soil to stream. Results from this study provide important information for predic