Gamma Irradiation Was Able to Degrade the Glyphosate and Aminomethylphosphonic Acid (AMPA) from Drinking Water Analyzed by LC-MS/MS

Glyphosate is the most widely used systemic herbicide in the world, applied post-emergence to control weeds and is non-selective. However, due to its toxicity to aquatic organisms and high persistence in water, it is necessary to conduct studies on the decontamination of water resources with glyphosate residues and its metabolite aminomethylphosphonic acid (AMPA). The objective of this study was to evaluate the degradation of glyphosate and AMPA in drinking water using gamma irradiation. First, the drinking water sample was found to be free of the herbicide and its metabolite, and then three concentrations of glyphosate and AMPA alone were added (0.5, 5.0, and 50.0 mg L-1). The samples were then exposed to different doses of gamma irradiation (0, 0.5, 1.0, 2.5, 5.0, and 10 kGy) in a cobalt-60 (60Co) source. The procedure was performed at room temperature with a dose of 0.08 kGy h-1 from the irradiator (source power: 215.95 Ci). Glyphosate and AMPA were quantified by Liquid Chromatography coupled to tandem Mass Spectrometry (LC-MS/MS). A pseudo-first order model was fitted from the kinetic study of the degradation of the chemicals. The irradiation doses required to degrade 50% of glyphosate (D0.5=8.97, 12.03, and 9.73 kGy) and the value for complete degradation (90%) of the herbicide (D0.9=29.82, 39.97, and 32.34 kGy), as the value of the dose constant (k), were 0.0772, 0.0576, and 0.0712 kGy-1 at concentrations of 0.5, 5.0, and 50.0 mg L-1, respectively. The increase in gamma irradiationgradually decreased of glyphosate and AMPA in drinking water. Thus, this study showed that the use of gamma irradiation can decontaminate drinking water with glyphosate and AMPA residues and be used in treatment plants, but it is necessary to use higher doses of radiation.