Weed control and environmental risk assessment of herbicides in a Brazilian Atlantic forest railway ecosystem.

Weeds along railway lines pose serious operational and environmental challenges, particularly in protected natural areas where vegetation management must balance efficacy and ecological safety. The objective of this study was to select herbicides that are effective in controlling weeds and to evaluate the associated environmental risks. The experiment was conducted on a stretch of railway line in the Serra do Mar State Park, São Paulo, Brazil, with the application of single and mixed herbicides (glyphosate, indaziflam, imazapyr and saflufenacil). A phytosociological survey of the weed flora was performed, and the overall weed control and the control of the most common species (Glycine max, Paspalum spp, Commelina spp. and Digitaria spp.) were evaluated at 15, 30, 60, 90, 120, 150 and 180 days after application. For the analysis of possible environmental risks associated with the use of these herbicides, quantification of the active ingredients and their most important metabolites in soil and water was performed. The weed community on the railroad was predominantly composed of exotic species. The combination of pre- and postemergent herbicides provided the highest percentages of control with the longest weed-free period. The herbicide concentrations detected in the soil and water on the railway line and in the immediate vicinity were much lower than the initial concentrations, with no observed effect concentration (NOEC) for the most sensitive organisms found in the literature. The use of these herbicides, under the conditions evaluated, was efficient in the management of weeds and was environmentally safe.