ABSTRACT
A wide variety of approaches has been developed to assess the distribution and fate of pesticides in the environment. One of the uses of unsaturated zone models is to estimate the potential of a pesticide to move through the soil profile and into groundwater. The use of simulation models may indicate the optimal use of pesticides, the establishment of well-setback distances, and the identification of vulnerable areas to be protected. The need for prevention and, as a consequence, for predictive a priori approaches, was recognized not only by the scientific community but also by politicians and legislators. Thus, predictive approaches appear to be extremely useful and promising tools to replace expensive field research or, at least, to enhance the understanding and extend the interpretation of experimental data. Mounting concern in the 1960s regarding environmental pollution resulted in the first major attempts to monitor the environment.
