Hydrolysis of Propazine by the Surface Acidity of Organic Matter

Propazine [2‐chloro‐4, 6‐bis (isopropylamino)‐ s ‐triazine] hydrolysis in acidic aqueous soil‐free systems was pH dependent, increasing with lower pH values. At a given pH, degradation followed first‐order kinetics. At 23.5C, the relationship was log t ½ (days) = 0.59 pH −0.21. Adsorption of propazine by organic matter prepared from Michigan peat was also pH dependent, but both molecular and cationic adsorption occurred. An increased rate of degradation in the presence of organic matter was postulated as due to hydrolysis by ionized surface hydrogen. Increasing the calcium saturation resulted in decreased hydrolysis. Increasing the CaCl 2 concentration of the propazine‐organic matter‐aqueous system had no effect on acid hydrolysis. In the salt‐amended systems, an increased hydrolysis, to be expected from the lower pH in the ambient solution, was apparently offset by a decreased hydrolysis due to the lowered amounts of ionized surface hydrogen.