Solute transport in soil under the influence of acid rain

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1.Simulation model of pH in equilibrium soil water were composed of aluminum dissolution, formation of the three aluminum species, aluminum-dominant divalent base cations exchange, bicarbobnate formation, sulfuric ion adsorption, charge balance and mass balance of sulfuric ion and base cations respectively. Aluminum-base cations exchange were lumped togerher with mineral weathering as neutralization effects in the model. pH of soil water could estimate with standard error less than (]SY.+-。[)pH0.2 by this model.2.Aggregate dispersion was enhanced for pH<4 in nitric acid solutions, whereas not significant for all pH ranges in sulfuric acid solutions. Hydraulic conductivity of packed soil was decreased instantaneously due to aggregate dispersion when the nitric acid solutions were applied.Permeability and buffering capacity of allophanic soil were influenced by the species of acid solutions as well as the concentration of hydrogen ion of percolating acid solutions.3.pH profile following sulfuric acid solution diffusion into soil were predicted by the method of mixing cell model which were combined with chemical equilibrium equations established in batch experiments. The results of simulations, with reduced proportion of active soil and sulfuric ion adsorption, for pH profile after 15 days had a sharp pH change similar to measured profile. Simulations were succeeded in error less than (]SY.+-。[)pH0.1 compared with measured value.