In this work, a dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube was used to experimentally determine the Henry's Law Constants (HLC) of phenol and cresols. The measurements were conducted over the range 278-298 K in both deionized water and 35 g L -1°/°° solution of NaCl. At 293 K and in pure water, HLC were found to be equal to (in units of M atm -1 ): phenol, HLC = (1005 270); ocresol, HLC = (690 95); m-cresol, HLC = (1324 172); p-cresol, HLC = (1742 ± 360). The obtained data were used to derive the following Arrhenius expressions: HLC = (4.1 ± 0.6) 10 -9 exp((7684 ± 874)/T), HLC = (1.5 ± 0.1) 10 -10 exp((8544 ± 512)/T), HLC = (5.5 ± 0.4) 10 -11 exp((9028 ± 508)/T) and HLC = (3.3 ± 0.4) 10 -11 exp((9258 ± 818)/T) for phenol, ocresol, m-cresol and p-cresol, respectively. All of the values for HLC in 35 g L -1 salt solution were 10 to 30% lower than their respective values in deionised water, depending on the compound and the temperature. These data were then used to estimate the fractions of phenol or of cresols in atmospheric aqueous phase. In order to evaluate the impact of a cloud on the atmospheric chemistry of phenol and cresols, we compare also their atmospheric lifetimes under clear sky (τgas), and cloudy conditions (τmultiphase). The calculated multiphase lifetimes (in units of days) are 2 significantly lower than those in gas phase at a cumulus temperature of 283 K (in parentheses): phenol, 0.26 (0.45); o-cresol, 0.17 (0.24); m-cresol, 0.13 (0.22); p-cresol, 0.11 (0.23).
The OH-initiated oxidation of dichlorvos (a widely used insecticide) has been investigated under atmospheric conditions at the large outdoor European photoreactor (EUPHORE) in Valencia, Spain. The rate constant of OH reaction with dichlorvos, k, was measured by using a conventional relative rate technique where 1,3,5-trimethylbenzene (TMB) and cyclohexane were taken as references. With the use of the rate constants of 5.67 x 10(-11) and of 6.97 x 10(-12) cm3 molecule(-1) s(-1) for the reactions OH + TMB and OH + cyclohexane, respectively, the resulting value of the OH reaction rate constant with dichlorvos was derived to be k = (2.6 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1). The tropospheric lifetime of dichlorvos with respect to reaction with OH radical has been estimated to be around 11 h. The major carbon-containing products observed for the OH reaction with dichlorvos in air under sunlight condition were phosgene and carbon monoxide. The formation of a very stable toxic primary product such as phosgene associated with the relatively short lifetime of dichlorvos may make the use of this pesticide even more toxic for humans when released into the atmosphere.
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