Abstract
This study investigates the heterogeneous OH oxidation of folpet and dimethomorph, two fungicides identified in the atmosphere of the Champagne-Ardenne region. Kinetic experiments were conducted in the relative mode, using terbuthylazine as a reference compound. The experimental method employed makes use of a simulation chamber coupled to a GC/MS analytical system. Meanwhile, the identification of (4-chlorophenyl)(3,4-dimethoxyphenyl)methanone (CPMPM), a degradation product of the OH oxidation of dimethomorph, is achieved using SPME/GC/MS. Moreover, a degradation mechanism of dimethomorph is proposed, and the heterogeneous OH reactivity of CPMPM is evaluated. The obtained OH reaction rate constants (cm(3) molecule(-1) s(-1)) are: k(z)-dimethomorph = (2.0 +/- 1.2) 10(-14), k(E)-dimethomorph = (1.7 +/- 1.2) 10(-14) k(Folpet) = (1.6 +/- 0.9) 10(-13) and k(CMPM) = (1.9 +/- 1.0) 10(-12). The implicated tropospheric life-times are up to 2 months, which shows that the investigated pesticides are relatively persistent towards oxidation removal processes. CPMPM, the identified product of OH oxidation of dimethomorph, is less persistent with a life time of only 6 days relative to heterogeneous oxidation by OH radicals. (C) 2013 Elsevier Ltd. All rights reserved.