Solute transport in soil under the influence of acid rain

1.平衡土壤水体pH模拟模型分别由铝的溶解、三种铝的形成、以铝为主的二价碱阳离子交换、碳酸氢盐的形成、硫离子的吸附、硫离子和碱阳离子的电荷平衡和质量平衡组成。在模型中，铝基阳离子交换与矿物风化作为中和效应集中在一起。利用该模型可估算出土壤水分pH值，其标准误差小于（]SY.+- [）pH0.2。在pH<4的硝酸溶液中，骨料分散增强，而在所有pH范围内的硫酸溶液中不显著。当施加硝酸溶液时，由于团聚体的分散，填充土的水力导电性立即降低。2 .酸性溶液种类和渗滤酸溶液中氢离子浓度对渗滤土的渗透性和缓冲能力均有影响。采用混合池模型，结合批量实验建立的化学平衡方程，对硫酸溶液扩散到土壤中的pH曲线进行了预测。模拟结果表明，随着活性土壤比例的减少和硫离子的吸附，15 d后的pH值变化与实测值相似。模拟成功，与实测值相比误差小于(]0.5±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.