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Effectiveness evaluation of glyphosate oxidation employing the H2O2/UVC process: Toxicity assays with Vibrio fischeri and Rhinella arenarum tadpoles

Junges, Celina M., Vidal, Eduardo E., Attademo, Andrés M., Mariani, Melisa L., Cardell, Leandro, Negro, Antonio C., Cassano, Alberto, Peltzer, Paola M., Lajmanovich, Rafael C., Zalazar, Cristina S.
Journal of environmental science and health 2013 v.48 no.3 pp. 163-170
Vibrio fischeri, acetylcholinesterase, bacteria, ecotoxicology, enzyme inhibition, glyphosate, hydrogen peroxide, oxidation, photolysis, sublethal effects, tadpoles, water pollution
The H₂O₂/UVC process was applied to the photodegradation of a commercial formulation of glyphosate in water. Two organisms (Vibrio fischeri bacteria and Rhinella arenarum tadpoles) were used to investigate the toxicity of glyphosate in samples M₁, M₂, and M₃ following different photodegradation reaction times (120, 240 and 360 min, respectively) that had differing amounts of residual H₂O₂. Subsamples of M₁, M₂, and M₃ were then used to create samples M₁,E, M₂,E and M₃,E in which the H₂O₂ had been removed. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in tadpoles to determine possible sub-lethal effects. In V. fischeri, M₁,E, which was collected early in the photodegradation process, caused 52% inhibition, while M₃,E, which was collected at the end of the photodegradation process, caused only 17% inhibition. Survival of tadpoles was 100% in samples M₂, M₃, and in M₁,E, M₂,E and M₃,E. The lowest percentages of enzymatic inhibition were observed in samples without removal of H₂O₂: 13.96% (AChE) and 16% (BChE) for M₂, and 24.12% (AChE) and 13.83% (BChE) for M₃. These results show the efficiency of the H₂O₂/UVC process in reducing the toxicity of water or wastewater polluted by commercial formulations of glyphosate. According to the ecotoxicity assays, the conditions corresponding to M₂ (11 ± 1 mg a.e. L⁻¹ glyphosate and 11 ± 1 mg L⁻¹ H₂O₂) could be used as a final point for glyphosate treatment with the H₂O₂/UV process.