Assessment groundwater contamination potential by pesticides: comparison among methods of leaching prediction

This work has as objective to compare some methods described in the literature (EPA screening criteria, indices GUS and LIX, and simple models RF, AF and TLPI) for evaluation of pesticide leaching potential and possibilities of groundwater contamination. Initially, the symbols and the mathematical equations were organized in order to facilitate the identification and the understanding of the factors considered during the construction of each model. The application and the comparison of the models were accomplished using literature data (physical and chemical properties of pesticides, soil characteristics, and weather conditions) for nine herbicides (2,4-D, Alachlor, Atrazine, Clomazone, Fluazifop-p-butylic, Metribuzin, Picloram, Simazine, Trifluralin) registered and extensively used in sugar-cane cultures in Brazil. Leaching potential results were not the same for all herbicides; however, the general classification was very similar for the methods studied. Differences found can be explained by singularities and limitations inherent to the conception of each method. The results showed that simpler models can be helpful for assessment of potential of groundwater contamination in extends areas of monoculture, where a large number of pesticides is applied, providing, thus, subsidies for making decisions more quickly and efficiently by the competent authorities.