The environmental behavior of chemicals in soil: atrazine as an example

In this work a mathematical model has been developed and used to estimate the soil vertical distribution of Atrazine dispersed in the environment. Water transport, rise due to capillarity, and partition among soil-contained water, air, and organic matter, as well as degradation processes, are considered. As far as the vertical mobility in soil is concerned, the model has been derived from that proposed by P. H. Nichols, A. Walker, and R. J. Baker [1982). Pestic. Sci. 12, 484-494). Such a model has been extended to include a procedure which takes into account the Atrazine mobility due to gravitational water flow. The organic carbon (O.C.) concentration gradient in soil was also considered in the evaluation when assessing partition processes, according to models by P. J. McCall et al. [1983). Residue Rev. 13, 231-241) and D. McKay and S. Paterson [1982). Environ. Sci. Technol. 16, 12, 654). The degradation processes are assumed to be first order, linearly related with O.C. content in soil. The application of this model to two sets of soil data demonstrated that Atrazine requires a long time (2 years or more, depending on soil features) in order to percolate at a depth comparable with those of a groundwater source.