Efeitos da aplicação de atrazina em três solos representativos do sudoeste do Paraná

Abstract

The continuous use of agrochemicals can cause irreparable environmental damage, and also impacts on living beings. The field of observation and study of this research is focused on the evaluation of the permanence rate and possible environmental impacts generated by the agrochemical atrazine, commonly applied in corn crops in the Southwest region of Paraná - Brazil. Samples from three types of soils most representative of the region were investigated: Red Latosol, Red Nitosol and Litholic Neosol. Physical, chemical and biological attributes of the samples were determined in laboratory tests. Close to planting areas, Latosol and Nitosol were denser and less humid, while the Neosol, which was less anthropogenically impacted, was less dense and more humid. Basal soil respiration indices pointed to Latosol equal to 0.95 ± 0.43 mg. C-CO2 kg-1hour1, Nitosol equal to 0.69 ± 0.21 mg. C-CO2 kg-1hour-1 and Neosol equal to 0.71 ± 0.32 mg. C-CO2 kg-1hour-1. Measurements of atrazine concentrations in soil samples were performed by liquid chromatography, indicating variability regarding the permanence of atrazine in the three types of soils studied. In the period of 60 days, the degradation rate was lower in Latosol, 23.39% degraded; intermediate in Nitosol, 55.02%degraded; and higher in Neosol, 66.73% degraded in relation to the initial mass added to the samples, therefore, soils witch more clayey textures, Latosol and Nitosol, showed lower degradation rates, while Neosol with greater acidity (pH = 4.90) showed a higher rate of degradation. As for the half-life estimate of atrazine in the studied soils, the calculated values were 146 to 194 days in Oxisol, 43 to 52 days in Nitosol and 33 to 42 days in Neosol.