Influência do regime de umidade do solo na toxicidade de imidacloprid sobre as espécies e. andrei e f. candida, em três tipos de solos tropicais

Abstract

Studying the tolerance limits of edaphic organisms exposed to contaminants is of fundamental importance for the evaluation of the negative effectS of pesticides on the soil ecosystem and its various functions. Considering that variations in precipitation patterns are predicted due to climatic changes, it is expected that the bioavailability and, consequently, the toxicity of pesticides will change according to the soil moisture regime. The objective of this study was to evaluate the toxicity of increasing concentrations of imidacloprid (a.i.) for earthworms Eisenia andrei and collembolans Folsomia candida in three types of soil: Tropical Artificial Soil (TAS), Oxisol and Entisol, which were submitted to adequate moisture conditions (60% of WHC) and soil water restriction (30% or 45% of WHC). The experiments were carried out in the Laboratory of Botany, Ecology and Entomology of the Federal University of the South Frontier, Campus Chapecó (SC) and were set up according to the norms of toxicity control carried out with earthworms (ISO 11268-2 / 2012 and OECD 207/1984) and collembolans (ISO 11267/1999). In both moisture regimes of all evaluated soils, mortality and reduction effects on the reproduction of the tested species were observed when in the presence of a.i. However, the values ​​of the end points obtained in soils with lower moisture content for springtails tests indicated that the toxicity of a.i. was potentiated in situations of reduced soil water. In addition, for Latosol and Neosol, some toxicity values ​​were significantly lower than the predicted values ​​in the environment for imidacloprid, indicating a potential risk to soil ecosystem. The results obtained could reflect the responses of the organisms when submitted to the combination of these natural and chemical stressors, indicating that soil moisture significantly influences the toxicity of imidacloprid.