The partition of materials that react with soil between the solid and the solution phase, and how this changes with time, can often be described by a simple equation: S = a c^b1t^b2 where S is the amount sorbed, c is the solution concentration, t the time of contact, and a, b₁ and b₂ are parameters. However, when the range of values for sorption is large, it is apparent that both b₁ and b₂ increase with decreasing sorption. At low values for sorption, b₁ approaches 1, and sorption plots are nearly linear. These observations are consistent with a mechanistic model in which it is postulated that the materials react with heterogenous sites. As the amount of sorption decreases, the heterogeneity of the occupied sites decreases. This is why b₁ increases. Because there is heterogeneity of occupied sites, there is a range of rates for the subsequent reaction. This is why the rates are proportional to a fractional index of time. It is better to describe the effects of time this way than by using several first-order equations.

中文翻译：

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描述吸附量和吸附速率的方程式

与土壤反应的材料在固相和溶液相之间的分配，以及这种情况如何随时间变化，通常可以用一个简单的方程式来描述：S  =  ac ^{b 1} t ^{b 2}其中S是吸附量，c是溶液浓度、接触时间t和a、b ₁和b ₂是参数。然而，当吸附值的范围很大时，很明显b ₁和b ₂都随着吸附的减少而增加。在低吸附值时，b₁接近 1，吸附图几乎呈线性。这些观察结果与假设材料与异质位点发生反应的机械模型一致。随着吸附量的减少，占据位点的异质性降低。这就是b ₁增加的原因。由于占据的位置存在异质性，因此后续反应的速率范围很广。这就是为什么利率与时间的分数指数成正比的原因。以这种方式描述时间的影响比使用几个一阶方程更好。