Ecotoxicidade de um herbicida à base de flumioxazina em organismos modelos terrestres e aquáticos

Abstract

Flumioxazin is an active ingredient in herbicides commonly used to control broad-leaved weeds in agriculture. Due to its effectiveness, the use of commercial products containing flumioxazin has significantly increased in recent years, raising concerns about environmental risks. The objective of this study was to assess the sublethal effects of a commercial formulation of flumioxazin on various model organisms representative of terrestrial and aquatic ecosystems, through an integrated approach to environmental toxicity analysis. In the first place, the study investigaed five plant models, four of which were used to analyze germination and initial plant development (Lactuca sativa L., Raphanus sativus L., Pennisetum glaucum L., and Triticum aestivum L.), while one (Allium cepa L.) was used to evaluate the genotoxicity of the herbicide. Germination was found to be the least sensitive parameter assessed, with the P. glaucum species showing the greatest sensitivity to herbicide toxicity, exhibiting reductions in root, aerial part, and fresh weight. Although mutagenic potential was identified, it occurred at doses significantly higher than those recommended for field use (0.005 g L-1

to 0.025 g L-1

), suggesting a low risk of the commercial formulation of flumioxazin for terrestrial environments. Toxicity tests were also conducted on aquatic models, including a green microalga (Raphidocelis subcapitata) and two zooplankton organisms (Ceriodaphnia silvestrii and Daphnia magna). Results revealed high sensitivity of microalgae to the herbicide, with phytotoxic effects observed at concentrations as low as 2.726 μg L-1

, leading to carbohydrate accumulation in response to flumioxazin. Cladocerans were also negatively impacted by the herbicide, showing inhibition of immobility in acute tests from a dose of 47.2 mg L-1

, and inhibition of immobility and reproduction in chronic exposure, with C. silvestrii affected at concentrations as low as 3.5 mg L -1 of flumioxazin. Species-specific responses were observed in filtration and ingestion rates, with D. magna reducing food filtration and C. silvestrii increasing ingestion. Chronic exposure of D. magna to contaminated microalgae resulted in 100% inhibition of egg production and reduced life expectancy by 13 days, along with developmental delays between life stages. In contrast to the relatively low toxicity observed in terrestrial environments, flumioxazin poses a environmental risk in aquatic ecosystems. These findings underscore the urgent need for mitigation and regulatory measures to protect aquatic environments from the adverse effects of flumioxazina.