Treatment of veterinary insecticide residues using biomixtures: performance, degradation kinetics, and ecotoxicological assessment
摘要
The intensification of livestock production involves the regular use of veterinary pharmaceuticals, which may enter the environment through handling, accidental spills, and other routes. The development of simple and effective in situ treatment technologies is essential to mitigate the associated environmental risks. This study aimed to assess the efficiency of biomixtures for treating residues from commercial pesticide formulations. Two biomixtures were prepared using soil, peat, and either rice husk (SPH) or barley bagasse (SPB). They were contaminated with 471 and 680 mg kg−1 of fipronil and fluazuron, respectively. Insecticide concentrations were periodically measured and modelled using single first-order kinetics, Gustafson and Holden, and bi-exponential models. The SPB biomixture degraded approximately 153 mg kg−1 of fipronil and 210 mg kg−1 of fluazuron within ~ 30 days, after which degradation appeared to plateau. In contrast, the SPH biomixture reduced fipronil concentrations by only around 56 mg kg−1. Biphasic kinetic models adequately described the degradation of both compounds. Control assays in soil showed no significant degradation over 30 days, highlighting the central role of microorganisms in insecticide dissipation. Although co-application promoted the development of bacterial and fungal populations compared with individual treatments, this increase was not associated with improved degradation performance. Ecotoxicological assays using Rhinella arenarum revealed a reduction in the toxicity of SPB-treated residues.