Ks. Carslaw et al., STRATOSPHERIC AEROSOL GROWTH AND HNO3 GAS-PHASE DEPLETION FROM COUPLED HNO3 AND WATER-UPTAKE BY LIQUID PARTICLES, Geophysical research letters, 21(23), 1994, pp. 2479-2482
Aqueous sulphuric acid droplets, which constitute the background strat
ospheric aerosol, strongly absorb HNO3 and HCl under cold conditions.
A thermodynamic model is used to predict partitioning of HNO3, HCl and
H2O between gas and aerosol phases, and show that a 50-fold increase
in aerosol volume, observed in the Arctic stratosphere as temperature
approached the frost point (188.9 K), can be explained in terms of upt
ake of HNO3 and H2O by liquid aerosols. Calculated degrees of saturati
on of the droplets with respect to solid hydrates, taking into account
the reduction in vapour phase HNO3, suggest that the droplets remain
liquid to the frost point. Near this temperature, they can yield large
r aerosol volumes than would have been the case for solid NAT (HNO3.3H
2O) particles. The depletion of gas phase HNO3 into enhanced volumes o
f liquid aerosols resulting from volcanic eruptions may hamper NAT for
mation.