Water polluted with glyphosate formulations: effectiveness of a decontamination process using Chlorella vulgaris growing as bioindicator

The environmental pollution caused by pesticides is considered a major problem worldwide. Glyphosate is one of the herbicides most widely used, and its use has increased sharply in the last years. In this work, the toxicity of four commercial glyphosate formulations (Eskoba^®, Panzer Gold^®, Roundup Ultramax^® and Sulfosato Touchdown^®) was assessed by determining the median effective concentration at 96 h (96 h-EC₅₀) using the microalga Chlorella vulgaris as the biological model. Although the formulations tested are moderately to slightly toxic to C. vulgaris according to the World Health Organization’s toxicity categories for aquatic and terrestrial organisms, this research shows that the four formulations are toxic, with Eskoba^® the least toxic and Roundup Ultramax^® the most toxic one. A UV/H₂O₂ remediation process for the detoxification of the samples was tested also. Its effectiveness was evaluated using a C. vulgaris growth inhibition test. Growth inhibition of C. vulgaris did not reach 18.2 %, indicating the efficacy of the UV/H₂O₂ remediation process to reduce glyphosate toxicity. In some of the samples tested within the first 48 h of the assay, C. vulgaris growth was even increased. The results of the present work suggest that the selected species was a good indicator to determine the toxicity level of glyphosate formulations and shows the relevance of the ecotoxicological tests to evaluate a physicochemical remediation process.