求解干旱地区土壤溶液Ca2+浓度和pH的逐步逼近算法

在土壤碳酸钙淋溶淀积过程的建模中,需要根据土壤碳酸钙化学热力学平衡原理求解土壤溶液中的Ca2 浓度和pH值,其中有些参数难以获得（如有关离子的活度系数）,不能直接求解,导致无法实现其过程的计算机模拟。本文针对这一难题,提出了一种逐步逼近算法,在已知土壤空气中的二氧化碳分压和土壤温度的情况下,可求得干旱地区土壤溶液中的Ca2 浓度和pH值,为土壤碳酸钙淋溶淀积过程的计算机模拟提供了重要的技术支持。本算法理论依据充分、结果稳定精度高、程序简便易实现,并在CAEDP模型中已得到了应用和验证。

AN ALGORITHM OF SUCCESSIVE APPROXIMATIONUSED TO CALCULATE Ca2+ CONCENTRATION AND pH VALUEIN SOIL SOLUTIONS OF ARID AREAS

In modeling the processes of soil CaCO3 eluviation and deposition, the Ca2 concentration and the pH value in soil solution must be calculated based on the principles of the soil chemical thermo-dynamic equilibrium. But it is difficult to calculate them directly, for some parameters ( e . g. ionic activity coefficients in soil solutions) are hardly available, which leads to unrealizability of computer simulation of the process. Focused on this problem, this paper presents an algorithm of successive approximation . With known CO2 partial pressures in soil air and soil temperatures, the algorithm enables computation of Ca2 concentrations and pH values in soil solutions at arid area, which provides a significant supporting technology for computer to simulate the process of soil CaCO3 eluviation and deposition. This method has been applied and verified in CAEDP model (A model for CaCO3 eluviation and deposition process in arid area soils) . The results show that the method is solidly grounded in theory with results accurate and stable, and process simple and easy to follow.