Glyphosate [N-(phosphonomethyl) glycine] is an active ingredient of common herbicide Roundup. The production and usage of glyphosate has steadily increased over the last few decades, particularly since the emergence of glyphosate-tolerant genetically modified crops, and its utility in no-till farming, urban household and recreational areas. Increasing presence of glyphosate and its major metabolites in the environment has raised concern on potential harm to environment. In this research, we investigated the abiotic degradation of glyphosate by birnessite under various mineral:glyphosate ratios to unravel degradation kinetics and potential bias in the pathways of degradation. Multi nuclei NMR (1H, 13C and 31P) spectroscopy was utilized to identify the composition of metabolites formed during degradation. Our results showed that abiotic degradation of glyphosate follows largely through the glycine pathway, forming glycine as the major metabolite, rather than AMPA (aminomethylphosphonic acid), which is common under biotic degradation of glyphosate. Intriguingly sarcosine, the common intermediate product before glycine, was not detected in all sets of experiments. Since the half-life of sarcosine is long (&gt;&gt;3 h), apparent absence of sarcosine in the product suggestted that it most likely did not form during degradation. In that case, preferential cleavage of C−N bond formed glycine directly. Overall, these results provide a reference for further investigation to bias glyphosate degradation towards less harmful products in the environment.

Role of Mn-oxide controlling the pathways of glyphosate degradation

253rd National Meeting (2017)

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