一类描述完全混合水体pH长时变化的缓冲动态数学模型

A MATHEMATICAL DYNAMIC BUFER MODEL FOR THE LONG-TERM VARIATION OF pH IN COMPLETE-MIXING WATERS

天然水体含有多种酸碱缓冲体系,以大气—水体—岩石构成的碳酸盐复合平衡体系为例,引入“缓冲系数”的概念,表达缓冲体系中各种缓冲组分对缓冲作用的贡献.缓冲系数由热力学平衡常数及其关系推导得出,是pH的函数.从物质守恒原则出发,融合水化学反应和水力学过程,建立一种含有缓冲项的描述完全混合水体酸度长时变化的动态模型(微分方程型).模型可用微分方程的数值方法求解.举例说明了模型的具体应用过程和计算结果的表现形式.

There are many acid-base buffer systems in natural waters. Based on the analysis of an illustrative air-water-rock carbonate equilibrium system, the conception of buffer coefficient is raised to express the buffer capacity of buffer components in buffer system. Buffer coefficients can be deduced from thermodynamic equilibrium constants, and their relations. Buffer coefficients are functions of pH. In combination of the chemical reactions in waters with hydraulic process and in accordance with the principle of substance balance, consequently, a dynamic buffer model (differential equation)for the long-term variation of pH in waters is established. The model can be solved, with numerical solution. The specific applied way of the model and the form of the calculated results are illustrated with an example.