Computer Simulation of Soil Sensitivity to Acid Rain
- Elissa R. Levine and
- Edward J. Ciolkosz
A two-horizon (A and B) simulation model was used to determine the sensitivity of Pennsylvania soils to acid deposition. The model simulated changes in the soild phase of soils in humid, temperate climates undergoing acidification and cation leaching. The Pennsylvania State Univ. Soils Data Base, and precipitation data provided input to the model. Soils were grouped into sensitivity classes based on the amount of time required for bare, uncultivated, and unlimed soils to reach critical threshold values. Simulation results showed most Pennsylvania soils were either very sensitive or nonsensitive. Sensitive soils were already at the threshold values at the beginning of the simulation run. Nonsensitive soils contained sufficient buffer capacity to withstand present inputs of acid deposition for at least 90 yr. According to the model, changes in soil properties occur in the upper horizons first, and after a lag period, occur in the lower horizons. The number of exchangeable bases was the soil parameter most highly correlated with soil sensitivity due to the acid buffering ability of exchangeable cations. Adding CaCO3 to the simulation of slightly sensitive and very sensitive soils changed them to nonsensitive status by increasing the number of exchangeable bases available for buffering.
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