Interactions studied included adsorption and desorption of atrazine by Ca2+, Mg2+, and Na+ saturated soil material and the effect of chloride salts of the above cations on solubility of crystalline atrazine. It was found that adsorption isotherms follow the Freundlich equation. The desorption isotherm had the same shape as the adsorption isotherm but followed a different path back to the starting point. This hysteresis effect encountered indicates that adsorption and desorption of atrazine are irreversible reactions. The desorption isotherm was also found to fit the Freundlich equation where the exponential desorption coefficient was equal to the exponential adsorption coefficient divided by 2.3.The effect of exchangeable cations was found to be within experimental error, and the solubility of crystalline atrazine was found to be exponentially related to the ionic strength of the solution. Using the equation developed, a computerized model for predicting atrazine distribution and movement in soil systems was prepared. Predicted breakthrough and elution curves were in agreement with those found for effluents from soil columns. It was concluded that the skewed nature of the experimental curve was primarily due to differences in the adsorption and desorption of atrazine.

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