TY - JOUR
T1 - Degradation of Glyphosate by Mn-Oxide May Bypass Sarcosine and Form Glycine Directly after C-N Bond Cleavage
AU - Li, Hui
AU - Wallace, Adam F.
AU - Sun, Mingjing
AU - Reardon, Patrick
AU - Jaisi, Deb P.
N1 - Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/2/6
Y1 - 2018/2/6
N2 - Glyphosate is the active ingredient of the common herbicide Roundup. The increasing presence of glyphosate and its byproducts has raised concerns about its potential impact on the environment and human health. In this research, we investigated abiotic pathways of glyphosate degradation as catalyzed by birnessite under aerobic and neutral pH conditions to determine whether certain pathways have the potential to generate less harmful intermediate products. Nuclear magnetic resonance (NMR) spectroscopy and high-performance liquid chromatography (HPLC) were utilized to identify and quantify reaction products, and density functional theory (DFT) calculations were used to investigate the bond critical point (BCP) properties of the C-N bond in glyphosate and Mn(IV)-complexed glyphosate. We found that sarcosine, the commonly recognized precursor to glycine, was not present at detectable levels in any of our experiments despite the fact that its half-life (∼13.6 h) was greater than our sampling intervals. Abiotic degradation of glyphosate largely followed the glycine pathway rather than the AMPA (aminomethylphosphonic acid) pathway. Preferential cleavage of the phosphonate adjacent C-N bond to form glycine directly was also supported by our BCP analysis, which revealed that this C-N bond was disproportionately affected by the interaction of glyphosate with Mn(IV). Overall, these results provide useful insights into the potential pathways through which glyphosate may degrade via relatively benign intermediates.
AB - Glyphosate is the active ingredient of the common herbicide Roundup. The increasing presence of glyphosate and its byproducts has raised concerns about its potential impact on the environment and human health. In this research, we investigated abiotic pathways of glyphosate degradation as catalyzed by birnessite under aerobic and neutral pH conditions to determine whether certain pathways have the potential to generate less harmful intermediate products. Nuclear magnetic resonance (NMR) spectroscopy and high-performance liquid chromatography (HPLC) were utilized to identify and quantify reaction products, and density functional theory (DFT) calculations were used to investigate the bond critical point (BCP) properties of the C-N bond in glyphosate and Mn(IV)-complexed glyphosate. We found that sarcosine, the commonly recognized precursor to glycine, was not present at detectable levels in any of our experiments despite the fact that its half-life (∼13.6 h) was greater than our sampling intervals. Abiotic degradation of glyphosate largely followed the glycine pathway rather than the AMPA (aminomethylphosphonic acid) pathway. Preferential cleavage of the phosphonate adjacent C-N bond to form glycine directly was also supported by our BCP analysis, which revealed that this C-N bond was disproportionately affected by the interaction of glyphosate with Mn(IV). Overall, these results provide useful insights into the potential pathways through which glyphosate may degrade via relatively benign intermediates.
UR - http://www.scopus.com/inward/record.url?scp=85041471033&partnerID=8YFLogxK
U2 - 10.1021/acs.est.7b03692
DO - 10.1021/acs.est.7b03692
M3 - Article
C2 - 29298390
AN - SCOPUS:85041471033
SN - 0013-936X
VL - 52
SP - 1109
EP - 1117
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 3
ER -