About a half century ago the introduction of 2, 4-dichlorophenoxyacetic acid (2, 4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) started the widespread use of pesticides in Canada . Since then, the increases in crop yields have largely been due to the use of enormous quantities of pesticides each year . As the demand of yield and quality of food and fiber increases with the world’s increasing population, the application of pesticides in agricultural environments to control weeds, pests or diseases continues to grow. However, pesticide residues may constitute a significant source of contamination of air, water, soil and food. Attention has increasingly been paid to the adverse effects of certain pesticides on environmental quality and ecosystem health in recent years [3,4]. The fate of a pesticide in the environment is governed by transformation and transport processes and the interaction of these processes . Regardless of the method of application, large amounts of pesticides ultimately reach the soil. As a result, soils are accumulating ever increasing amounts of residues of a wide variety of pesticides, which then volatilize into the air, move into water through leaching and surface run-off, are absorbed by organisms, and are broken down into other products. Therefore, the fate of pesticides in soils is of major interest to environmental scientists.