Modeling the hydrogeochemical response of a stream to acid deposition using the enhanced trickle-down model

Summarization: The enhanced trickle-down model was applied to White Oak Run, a second-order stream located in Shenandoah National Park in Virginia. Calibration of the model was performed using 5 years of field data. Simulation results indicate that 29% of the incoming sulfate is retained in the upper soil horizons and 22% is retained in the lower soil horizons. The alkalinity concentrations in the stream exhibited a seasonal variation, with increased values during low flow and decreased values during high flow. Ion exchange in the upper soil neutralized 39% of the incoming acidity and weathering accounted for 14% of the neutralization in the lower soil horizons. Long-term simulations indicated that White Oak Run is a delayed response system primarily due to high sulfate sorption capacity. Sulfate desorbed from the soils after 40 to 50 years, assuming no reductions in the current deposition. This has significant policy implications because reduction in deposition levels will not result in a quick recovery of the system.Presented on: Journal - Water Pollution Control Federatio