Abstract
We demonstrate for the first time that the broad-spectrum herbicide glyphosate is a stable transformation product during manganese-driven oxidation of diethylenetriamine penta(methylenephosphonate) (DTPMP), a complexing agent widely used in household and industry applications. Glyphosate formation was observed at circumneutral pH (i) in the presence of MnO2 (with and without dissolved O2) as well as (ii) in the presence of Mn2+ and O2. Maximum glyphosate yields varied with reaction conditions and ranged from 0.06 to 0.16 mol-%. Given the ubiquitous presence of manganese in the environment and wastewater treatment systems, Mn-driven transformation of DTPMP likely contributes to glyphosate formation under environmentally relevant conditions. Our results support recent reports of municipal wastewater as a previously neglected source of glyphosate in European surface waters with aminopolyphosphonates as suspected precursors. Therefore, the current approach to protecting water resources from glyphosate contamination needs to be revised, which has significant environmental, legal and economic implications.