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Fate and kinetics of carfentrazone‐ethyl herbicide in California, USA, flooded rice fields
Author(s) -
Ngim Kenley K.,
Crosby Donald G.
Publication year - 2001
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620200305
Subject(s) - chemistry , hydrolysis , benzoic acid , kinetics , dilution , stereochemistry , organic chemistry , physics , quantum mechanics , thermodynamics
Little is known of the environmental fate of the aryltriazolinone herbicide carfentrazone‐ethyl (compound I). Rice field applications of Shark® 40D commercial formulation to duplicate 5.7 m 2 rings (119 g a.i./ha) and 464 m 2 commercial basins (224 g a.i./ha) produced pseudo–first‐order half‐lives ( t ½ ) of 6.5 to 11.1 h in water and 37.9 to 174 h in sediment. The rapid dissipation from water was due to its hydrolysis to the chloropropionic acid (compound II), which further degraded to its propionic, cinnamic, and benzoic acids. Compound I degraded similarly in soil, but propionic and cinnamic acid levels were higher. Compound I was only weakly adsorbed, but lateral movement of compound II through soil occurred. Laboratory hydrolysis produced quantitative yields of compound II, t ½ values of 131 h at pH 7 and 3.36 h at pH 9, and slow dissipation at pH 5 (43% at 830 h). Ultraviolet (UV) irradiation of compound I in pH 7 buffer gave dissipation rates similar to those in dark controls ( t ½ 113 h vs 128 h), while compound II was comparatively stable to photolysis ( t ½ 765 h) and also did not volatilize from water. Ester hydrolysis followed by off‐site movement of the acid (compound II) account for the dissipation of compound I.