title: Photodegradation of the herbicide imazethapyr in aqueous solution: effects of wavelength, pH, and natural organic matter (NOM) and analysis of photoproducts.
abstract: The photodegradation of imazethapyr, 5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-4,5-dihydroimidazol-1H-3-yl)nicotinic acid, has been investigated in phosphate buffers and in buffered solutions containing natural organic matter (NOM). Imazethapyr degrades most quickly under 253.7 nm light and at pH values >4. The presence of NOM in solution caused the reaction rate constants for the photodegradation to decrease, with higher concentrations of NOM having a larger effect. Calculations suggest light screening is the major effect of the NOM. Seven photoproducts have been identified, and a photodegradation mechanism is proposed.
authors.affiliation: Gustavus Adolphus College, MN 56082, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Espy
authors.forename: Emily
authors.initials: E
authors.lastname: Pelton
authors.forename: Annie
authors.initials: A
authors.lastname: Opseth
authors.forename: Jonathan
authors.initials: J
authors.lastname: Kasprisin
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Nienow
mesh_terms: D006540:Herbicides / Q000528:radiation effects*; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D008027:Light; D009539:Nicotinic Acids / Q000737:chemistry / Q000528:radiation effects*; D010782:Photolysis; D012996:Solutions; D014867:Water
chemical_list: D006540:Herbicides; D006812:Humic Substances; D009539:Nicotinic Acids; D012996:Solutions; D014867:Water; C093630:imazethapyr