Kinetics of the atmospherically important gas-phase reactions of a series of trimethyl phosphorothioates

Abstract

The kinetics of the gas-phase reactions of the trimethyl phosphorothioates (CH3O)3PS, (CH3O)2P(S)SCH3, (CH3O)2P(O)SCH3 and (CH3S)2P(O)OCH3 with OH and NO3 radicals and with O3 have been experimentally investigated. The rate constants obtained for reactions with OH radicals, NO3 radicals, and O3 at 298±2 K were, respectively (in cm3 molecule−1 s−1 units): for (CH3O)3PS, (6.97±0.39)×10−11: <2×10−14, and <3×10−19; for (CH3O)2P(S)SCH3, (5.60±0.17) ×10−11, <3×10−14, and <2×10−19; for (CH3O)2P(O)SCH3, (9.15±0.67) × 10−12, <1× 10−15 and <2×10−19; and for (CH3S)2P(O)OCH3 (9.45±0.74) × 10−12, ≤2 × 10−15 and <1× 10−19. These kinetic data, when combined with measured or estimated atmospheric concentrations of OH and NO3 radicals and O3, show that the dominant gas-phase atmospheric removal process for these trimethyl phosphorothioates is via the OH radical reaction, with calculated lifetimes ranging from a few hours to a few days.