Solute transport in soil under the influence of acid rain

1.土壤水平衡pH模拟模型包括铝的溶解、三种铝形态的形成、以铝为主的二价碱阳离子交换、重碳酸盐的形成、硫酸离子的吸附、硫酸离子和碱阳离子的电荷平衡和质量平衡。在该模型中，铝基阳离子交换被归结为矿物风化的中和效应。土壤水pH值可估算，标准误差小于(]sy.+-。2.在硝酸溶液中，pH和lt；4的聚集体分散性增强，而在硫酸溶液中的所有pH范围内，聚集态分散性并不显著。在硝酸溶液作用下，堆积土壤的水力传导性由于团聚体的分散而瞬间降低，不透水土壤的渗透性和缓冲能力受到酸溶液种类和渗酸溶液中氢离子浓度的影响。3.采用混合池模型结合间歇实验中建立的化学平衡方程，预测了硫酸溶液扩散到土壤中后的pH分布。在活性土壤比例和硫酸根离子吸附比例降低的情况下，模拟15天后的pH剖面的结果与实测剖面相似。模拟成功的误差小于(]sy.+-。[]pH值与实测值比较为0.1。

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.