The effects of principal constituents of acid rain on volcanic ash soil.

研究了在火山灰土壤中反复加入不同硝酸盐与硫酸盐当量比的酸溶液，预测土壤溶液中离子浓度的方法。预测方法由化学平衡方程、电平衡方程和土壤溶液质量守恒定理组成。结果总结如下：1)在相同土壤溶液ph下，HNO_3溶液> (NO_3^-和SO_4^2^->) H_2SO_4溶液混合溶液对铝的溶解量有一定的影响趋势。2)模型不能很好地模拟碱性阳离子的浓度变化。然而，它充分描述了碱性阳离子的累积释放。这表明它能够估计阳离子交换和矿物风化的酸缓冲能力。3)加入酸性混合溶液后，模型估计的SO_4^2^-浓度比实测值更低，NO_3^-: SO_4^2^-为0.75:0.25。但较好地描述了碱性阳离子的pH下降过程和浓度变化。因此，NO_3^-和SO_4^2^-等酸雨沉积在火山灰土壤中，对土壤碱性阳离子的释放和pH的降低起主导作用，而NO_3^-在土壤中很难被吸附。4)模拟结果与pH值和碱性阳离子累积释放量的测量值吻合较好。这些都是酸沉积对土壤最严重的影响。因此，该模拟模型中所使用的参数对于预测酸沉降对关东壤土的主要影响是有用的。

The prediction method of ion concentration in soil solutions with repetitive addition of acid solutions that vary in equivalent ratios of nitrate to sulfate in volcanic ash soil was examined in this study. The method for prediction was composed of chemical equilibrium equation, electrical balance and conservation of mass in soil solutions. The results were summarized in the following.1) There was a tendency of HNO_3 solution > acid mixed solution including NO_3^- and SO_4^2^->H_2SO_4 solution on the quantity of dissolved aluminum with equal soil solution pH.2) The model could not simulate well concentration change of basic cations. However, it adequately described cumulative release of basic cations. This shows it is ability to estimate acid buffering capacity of cation exchange and mineral weathering.3) The model less estimated concentration of SO_4^2^- further than the measured value with addition of acid mixed solution, NO_3^- : SO_4^2^- is 0.75 : 0.25. However, it adequately described pH decreasing process and concentration change of basic cations. Therefore, it seemed that NO_3^-, which is difficult to be adsorbed in soil, is dominantly affected release of basic cations and pH decreasing in soil when acid rain including NO_3^- and SO_4^2^- deposited to volcanic ash soil.4) The simulation results agreed well with the measured values of pH and cumulative release of basic cations. These represent the most serious effects of the acid deposition on the soil. Therefore, parameters used in this simulation model are useful for predicting the main effects of the acid deposition on the Kanto loam subsoil.