OCORRÊNCIA DE PESTICIDAS EM SOLOS ARGILOSOS E ARENOSOS APÓS APLICAÇÃO EM PASTAGENS E CANA-DE-AÇÚCAR

OCCURRENCE OF PESTICIDES IN CLAY AND SANDY SOILS AFTER APPLICATION IN PASTURE AND SUGARCANE CROPS.

Sugarcane is considered one of the greatest alternatives for the biofuels sector due to the high potential in the production of ethanol and its respective by-products. Processes of converting degraded pastures into sugarcane crops have been increasingly common in Brazil, as well as the use of pesticides to control plant diseases and pests in several crops. The objective of this work was to evaluate the occurrence of 2,4-D, ametryn, tebuthiuron, fipronil and its degradation products (fipronil sulfide and fipronil sulfone) in clay and sandy soils when applied to pasture and sugarcane management. Solid-liquid extraction and liquid chromatography coupled to mass spectrometry were used to quantify the compounds. The optimized method was validated with the following parameters: linear range from 0.5 to 300 µg L^-1; linearity (r) > 0.99; precision with CV from 1.0 to 15.0%; accuracy of 60 to 117%, instrumental limit of detection (LOD) from 0.1 to 1.0 µg L^-1 and instrumental limit of quantification (LOQ) of 0.5 µg L^-1 for all pesticides, except 2,4-D (5.0 µg L^-1). Pesticides concentrations of the experimental farms ranged from 0.1 to 266 µg kg^-1, with the highest concentrations found in the months of pesticide’s application. The results showed the persistence of some pesticides in the soils even after months of use.