AVALIAÇÃO DA LIBERAÇÃO CONTROLADA E FOTODEGRADAÇÃO DE ATRAZINA NO CULTIVO DE MILHO

Abstract

There are several methods to control and combat weeds in a crop, however, due to its fast action and efficiency, chemical control ends up being the most used. There are innumerable problems caused by the inappropriate use of these substances, including contamination of surface and groundwater, soil, microorganisms, among others. As a way of reducing the negative impacts caused by these pesticides, several techniques have been studied, among them, controlled release and ways to accelerate their degradation. Thus, the aim of this work was to study the environmental behavior of the controlled release of herbicide atrazine when anchored to the chitosan polymer and to evaluate its degradation. For the degradation, a titanium dioxide (TiO2) catalyst was used, prepared by the method proposed by Pechini and Adams, through a titanium precursor resin, standardized by gravimetry, the catalyst was prepared by calcination through the resin plus carbon junction (Vulcan xc72) and used in the form of ultrafine powder. The material characterization was performed by scanning electron microscopy (SEM) and x-ray diffraction (XRD). The anchoring potential and the controlled release of atrazine from the biopolymer were evaluated for a period of 90 days. Photocatalysis was evaluated considering the degradation reaction until the complete herbicide degradation. Both using spectroscopy in the UV-vis region. The soil persistence of the atrazine herbicide formulations anchored to the chitosan polymer and TiO2 catalyst was compared to the commercial herbicide formulation. For that, a randomized block design was used, with three repetitions, in a scheme (3 x 3) + 1, totalling 30 blocks. Chromatographic analyses were performed to identify atrazine in the different blocks after 10, 30 and 60 days of herbicide application. Through the obtained results it was possible to observe that adsorption and release of atrazine to the biopolymer occurred in all studied concentrations. Another important fact observed is that during the analysis period, the herbicide was released and adsorbed to the solution several times. Which is very beneficial to the environment. It was also observed that photodegradation using the TiO2 catalyst was extremely beneficial, since it degraded the herbicide faster when compared to direct photolysis. The same can be seen in the field experiment, where the herbicide had its maximum concentration found in the first 10 days, followed by adsorption at 30 days and the soil solution being released again at 60 days. Such results demonstrate that this technique is beneficial to the environment, since it can reduce the impacts caused by its leaching in addition to increasing the time that the herbicide can be available without losing its efficiency.