title: Heterogeneous oxidation of terbuthylazine by "dark" OH radicals under simulated atmospheric conditions in a flow tube.
abstract: In order to investigate the heterogeneous oxidation kinetics of the herbicide terbuthylazine (TERB), a stable and reproducible generation system of "dark" hydroxyl radical in the gas phase was developed and optimized using a PTR-MS. TERB was adsorbed on silica particles, which were coated on the walls of a flow tube. The hydroxyl radical was produced in the dark through the ozonolysis of 2,3-dimethyl-2-butene (DMB). The radical concentration was determined applying two different methods of calculation based on the monitoring of (i) a gaseous compound used as a tracer, m-xylene; (ii) one of the OH radical precursors, DMB. The obtained gaseous OH radical concentration in the reactor was (9.0 ± 4.0) × 10(7) radical cm(-3). Exposing TERB to the oxidant for 1-14 h, a heterogeneous kinetic constant of kOH = (1.5 ± 0.8) × 10(-13) cm(3) molecule(-1) s(-1) was found at 26 °C and RH < 1%. As a result, the heterogeneous oxidation of TERB by OH radicals seems to be much slower (by a factor of 63) when the organic compound is present in the particulate phase than when it reacts in homogeneous gas phase.
authors.affiliation: Aix Marseille Université , CNRS, LCE, FRE 3416, Case Courrier 29, 3 Place Victor Hugo, 13331 Marseille Cedex 03, France. maryline.pflieger@gmail.com
authors.forename: Maryline
authors.initials: M
authors.lastname: Pflieger
authors.forename: Anne
authors.initials: A
authors.lastname: Monod
authors.forename: Henri
authors.initials: H
authors.lastname: Wortham
mesh_terms: D017665:Hydroxyl Radical / Q000737:chemistry*; D010084:Oxidation-Reduction; D014227:Triazines / Q000737:chemistry*
chemical_list: D014227:Triazines; D017665:Hydroxyl Radical; C037565:terbutylazine