Models for pesticide behavior in terrestrial environments

Abstract

Agricultural, industrial, and regulatory needs exist for quantitative descriptions of the fate or transport of chemicals in terrestrial environments. This paper provides a sketch of the art of mathematical modeling techniques intended to fulfill those needs. Before we examine either the theory or applications of approaches such as these, let us establish just what a model is, in general terms. Just as physical scale models replicate system functions in miniature, mathematical models mimic these functions through prescribed quantitative relationships. The relationship may be as simple as a graph of pesticide concentration vs. time for a given application rate, or it may be as complicated as a digital computer program designed to track a chemical through time, space, or transformations. In either case, its utility lies in its ability to provide a needed value (such as concentration) if it is operated using measurable input data such as application rate, rainfall, sunlight intensity, and wind vector. A set of rules, called an algorithm, establishes the numerical procedure used to estimate the needed values in cases of computational models.