Uptake of nopinone by water: Comparison between aqueous-and gas-phase oxidation of organic compounds in the atmosphere

The uptake of nopinone by liquid water at room temperature has been studied in a wetted-wall reactor coupled to a chemical ionization mass spectromete r and was found to be reversible and bulk-specific. A Henry's law constant of H(296 +/-3 K) = (176 +/- 50) Matm(-1) was obtained. Measuring the solubi lity using a bubble column technique resulted in a value of H(296 +/- 1 K) = (200 +/- 40) Matm(-1). We recommend an average value of H(296 +/- 2 K) = (195 +/- 60) Matm(-l). The temperature dependence of this coefficient has b een measured between 274 and 298 K and corresponds to an enthalpy of solvat ion of Delta H-soln = - (98 +/- 30) kJ/mol. The Henry's law coefficients me asured in this work are large enough that, in the presence of clouds, aqueo us-phase sinks of nopinone might compete with its gas-phase sinks. The poss ibility of such competition for other organic compounds in the atmosphere i s discussed.