Insight of UV-vis spectra and atmospheric implication for the reaction of ˙OH radical towards glyphosate herbicide and its hydrates

Olivier Holtomo; Manain Derrick Mbigah; Mama Nsangou; Ousmanou Motapon

doi:10.1039/d1ra01591e

Insight of UV-vis spectra and atmospheric implication for the reaction of ˙OH radical towards glyphosate herbicide and its hydrates

RSC Adv. 2021 May 4;11(27):16404-16418. doi: 10.1039/d1ra01591e. eCollection 2021 Apr 30.

Authors

Olivier Holtomo^{1

2}, Manain Derrick Mbigah¹, Mama Nsangou^{3

4}, Ousmanou Motapon^{2

5}

Affiliations

¹ Department of Physics, Faculty of Science, University of Bamenda Bambili P. O. Box 39 Cameroon holtomoo@gmail.com.
² Department of Physics, Faculty of Science, University of Maroua Maroua P. O. Box 814 Cameroon.
³ Department of Physics, Higher Teacher's Training College, University of Maroua Maroua P. O. Box 46 Cameroon.
⁴ Department of Physics, Faculty of Science, University of Ngaoundéré Ngaoundéré P. O. Box 454 Cameroon.
⁵ Laboratory of Fundamental Physics, Faculty of Science, University of Douala Douala P. O. Box 24157 Cameroon.

Abstract

The rate constant of the reactions of ˙OH radicals with glyphosate (GPS) and its hydrates (GPS(H₂O) _n=1-3) were evaluated using the dual method M06-2X/6-311++G(df,p)//6-31+G(df,p) over the temperature range of 200-400 K. The results served to estimate the atmospheric lifetime along with the photochemical ozone creation potential (POCP). The calculations yielded an atmospheric lifetime of 2.34 hours and a POCP of 24.7 for GPS. Upon addition of water molecules, there is an increase of lifetime and decrease of POCP for water monomer and water dimer. The POCP for water trimer is slightly above the gaseous GPS. However, the POCPs of GPS and its hydrates are comparable to that of alkanes. The GPS and its hydrates were found to be a potential reservoir of CO₂. The acidification potential (AP) of GPS was found to be 0.189 and decreases upon addition of water molecules. This shows negligible contribution to rain acidification as the AP is less than that of SO₂. The UV-vis spectra were attained using the M06-L/6-311++G(3df,3pd) method and cover the range 160-260 nm which fits well with experiment.