Glyphosate degradation in water employing the H2O2/UVC process: an

CARDELL, L.; VIDAL, A.; NEGRO, A.; CASSANO, A.; ZALAZAR, C.; JUNGES, C. M.; ATTADEMO, A.M.; PELTZER, P.M.; LAJMANOVICH, R.C.

San Diego, California

Conferencia; The17th International Conference on Advanced Oxidation Technologies for Treatment of Water, Air and Soil (AOTs-17); 2011

Organophosphorus pesticides are widely used in agriculture. Glyphosate is a nonselective, post-emergence, broad-spectrum organophosphate herbicide. Due to its extensive use in agriculture, it has become a major pollutant and studies of its impact on the environment have become more pertinent. Different biological tests were used for toxicity assessment of individual chemicals or complex effluents. Recent studies have shown that amphibians are one of the most sensitive vertebrate groups to the toxicological effects of the herbicide glyphosate. Exposure to these herbicides induced sublethal effects, such as malformation (craniofacial and mouth deformities, eye abnormalities, and bent or curved tails) in the South American species Scinax nasicus after exposure to glyphosate. Its sensitivity justifies the use of amphibian tadpoles for the examination the toxicity of samples of commercial formulated of glyphosate after H2O2/UVC treatment. The photodegradation of commercial glyphosate was carried out in an annular photoreactor, which was coupled with a centrifugal pump, a storage tank, and connecting tubing. Experiments were performed under batch mode, by recycling the reactants in a closed loop. A germicidal lamp (Philips 15 W), which was longitudinally placed at the axial center of the reactor, was used as the source of UV radiation (254 nm). The total volume was 2500 cm3. Experiments were carried out changing the initial glyphosate and hydrogen peroxide concentrations. Glyphosate was analyzed by ion chromatography with a suppressed conductivity detector employing an Ion Pac AS4A-SC analytical column and a solution of Na2CO3 (9 mM) and NaOH (4 mM) as eluent. Hydrogen peroxide was analysed with spectrophotometric methods at 350 nm.Short-term (24, and 48-h) static tests were performed in Rhinella arenarum tadpoles (N = 84), to evaluate the toxicity of samples of glyphosate employing the H2O2/UVC at 120, 240, and 360 min of time. The product degraded was Eskoba®, a commercial herbicide containing 48 % as monoisopropylamine salt. Control and animals at all treatments that had a survival at 48 h were euthanized and acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured. The combined effects of glyphosate (26-28 mg/L) and hydrogen peroxide (42 mg/l) of a treated sample for 120 min produced 100% mortality of tadpoles exposed for 48h; however after hydrogen peroxide removed no acute toxicity towards R. arenarum was detected. The mean values of the AChE activities in the control tadpoles was 16.62 ± 1.32 nmol min-1mg-1 of protein at 48 h. AChE activities varied significantly at 240 min of H2O2/UVC process with hydrogen peroxide extracted (p < 0.05) with a percentage of AChE inhibition was 26.5 %. Control BChE activities where 4.23 ± 0.45 nmol min-1mg-1 of protein at 48 h. BChE activities varied significantly at 120 (p