Interaction of HNO4 with ice surfaces

COLL 269

Thorsten Bartels-Rausch, thorsten.bartels-rausch@psi.ch, Thomas Huthwelker, Josep Graell, and Markus Ammann, markus.ammann@psi.ch. Laboratory for Radiochemistry and Environmental Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
It has been proposed that HNO4 might be an important reservoir species of nitrogen oxides in colder regions of the atmosphere. Here we present studies to investigate the adsorption of HNO4 on snow or ice surfaces, which might present an important sink of HNO4 and thus of atmospheric NOx.

For this a gas-phase synthesis of HNO4 has been set-up based on the reaction of NO2 with HO2. Also a detection scheme was developed to simultaneously determine HNO4 as well as important side products such as H2O2, O3, and HNO3, as well as NO2 using a chemical ionization mass spectrometer.

The adsorption behavior of HNO4 was investigated using coated wall flow tube at atmospheric pressure. The retention of HNO4 on ice films frozen from liquid water was determined at different temperatures from which the adsorption thermodynamics can be derived.