Synergism and antagonism in environmental behavior of tebuthiuron and thiamethoxam in soil with vinasse by natural attenuation

Abstract

Full-scale farming systems rely on tebuthiuron and thiamethoxam to manage sugarcane for controlling weeds and insects, respectively. Both are effective pesticides, but they can harm the surroundings. Moreover, an additional level of routine management, such as spreading vinasse onto field for fertigation, can impact the environmental pollution/contamination positively or negatively. Therefore, we hypothesized the environmental behavior in and analyzed if it could be possible for natural attenuation to effectively dissipate them from the soil. The respirometric bioassay to quantify the microbial metabolism upon the pesticides in association with vinasse or not lasted for 130 days. Vinasse acted similar to an organic source of metabolizable energy. Hence, it enhanced the microbial transformation of target-pesticides into CO2. Soil samples respirometers, where vinasse and pesticides co-existed, became less toxic over a sensitive organism. Therefore, ecotoxicological bioassay cross-validated the synergism of vinasse towards the natural attenuation of tebuthiuron with the opposite true for thiamethoxam. The sigmoidal Gompertz function was more adequate to describe the microbial mineralization of tebuthiuron-thiamethoxam-vinasse associations in soil. This model presented more adequate to describe microbiological degradation than first-order functions. Plainly, analytical insights into microbiological-ecotoxicological ramifications of our exploratory study are timely and provided forward knowledge in naturally remediating agroecosystems.