Uptake of Gas-Phase Species by 1-Octanol. 1. Uptake of α-Pinene, γ-Terpinene, p-Cymene, and 2-Methyl-2-hexanol as a Function of Relative Humidity and Temperature

Abstract

With use of a droplet train apparatus, the uptake by 1-octanol of gas-phase α-pinene, γ-terpinene, p-cymene, and 2-methyl-2-hexanol was measured as a function of relative humidity and temperature (263−293 K). 1-Octanol was selected as a surrogate for hydrophobic oxygenated organic compounds found in tropospheric aerosols. The mass accommodation coefficients (α) of γ-terpinene, p-cymene, and 2-methyl-2-hexanol obtained from these measurements exhibit negative temperature dependences. The upper and lower values of α at 265 and 290 K, respectively, are as follows: for γ-terpinene 0.12 and 0.076; for p-cymene 0.20 and 0.097; and for 2-methyl-2-hexanol 0.25 and 0.11. The uptake of α-pinene is solubility limited, yielding values for the product HDl1/2 for α-pinene in 1-octanol (H = Henry's law constant, Dl = liquid-phase diffusion coefficient). With use of estimated values of Dl the Henry's law constant is obtained as ln H (M/atm) = −(6.59 ± 1.16) + (3.80 ± 0.31) × 103/T. The presence of water vapor does not a...