Thermodynamics and kinetics of the solid solution of HNO3 in ice

The diffusion and solubility of gaseous HNO3 in ice have been measured as a function of temperature and HNO3 partial pressure between -8 and -35 degrees C. The diffusion coefficient of HNO3, follows the Arrhenius expression D = 1.37 x 10(-2610/T) cm(2) s(-1), but these values probably represent upper limits because of the existence of diffusion short circuits. The solubility of HNO3 in ice, X-HNO3(0), is about 5 x 10(-7) mole fraction at -15 degrees C and P-HNO3 = 10(-3) Pa, and its temperature and partial pressure dependences are X-HNO3(0) = 2.37 x 10(-12) e((3532.2/T))(P-HNO3)(1/2.3) mole fraction, where PHNO3 is the HNO3 partial pressure in Pa, and T is the temperature in Kelvin. These solubility data have been used to build the partial pressure versus inverse temperature phase diagram and to calculate the solidus of the temperature-composition phase diagram and the ice-to-water partition coefficient K. K varies with temperature between 3 x 10(-6) and 1.6 x 10(-5) Implications for ice cloud chemistry and for the interpretation of ice core analyses are briefly discussed.