Temperature dependence of Henry's law constants of thirteen polycyclic aromatic hydrocarbons between 4°C and 31°C

An understanding of the temperature dependence of the Henry's law constant for organic contaminants is critical when modeling the transport and fate of these contaminants in the environment. The Henry's law constants for 13 polycyclic aromatic hydrocarbons (PAHs) were experimentally determined between 4 and 31 degrees C using a gas-stripping apparatus. The Henry's law constants ranged between 0.02 +/- 0.01 Pa m(3)/mol for chrysene at 4 degrees C and 73.3 +/- 20 Pa m(3)/mol for 2-methylnaphthalene at 31 degrees C. The temperature dependence of each PAH was modeled using the van't Hoff equation to calculate the enthalpy and entropy of phase change. For nine of the PAHs, the present study reports the first experimental measured temperature dependence of their Henry's law constant. The enthalpies of phase change ranged between 35.4 +/- 1.9 kJ/mol for 1-methylphenanthrene and 100 +/- 8 kJ/mol for chrysene. These data can be used to extrapolate Henry's law values within the experimental temperature ranges. For all PAHs except benzo[a]fluorene, the temperature dependence can be predicted within a relative standard error <10%.