laboratory study; dissociation of acids; grain boundaries; flow tube; heterogeneous chemistry; adsorption kinetics; snow-air partitioning; adsorption thermodynamics; nitrogen oxides
Bartels-Rausch Thorsten, Wren S N, Schreiber Sepp, Riche Fabienne, Schneebeli M., Ammann Markus (2013), Diffusion of volatile organics through porous snow: impact of surface adsorption and grain boundaries, in Atmospheric Chemistry and Physics
, 13(14), 6727-6739.
Bartels-Rausch Thorsten (2013), Chemistry: Ten things we need to know about ice and snow, in Nature
, 494(7435), 27-29.
Krepelova Adela, Bartels-Rausch Thorsten, Brown Matthew A, Bluhm Hendrik, Ammann Markus (2012), Adsorption of Acetic Acid on Ice Studied by Ambient-Pressure XPS and Partial-Electron-Yield NEXAFS Spectroscopy at 230--240 K, in J. Phys. Chem. A
, 117(2), 401-409.
Donaldson D James, Ammann Markus, Bartels-Rausch Thorsten, Pöschl Ulrich (2012), Standard States and Thermochemical Kinetics in Heterogeneous Atmospheric Chemistry, in J. Phys. Chem. A
, 116(24), 6312.
The presence of ice or snow can significantly alter the composition of the surrounding air either because of chemistry or because the ice or snow scavenges atmospheric trace gases and removes them from the gas-phase. In this project, we focus on the uptake of trace gases as loss process. For the first time the uptake of peroxynitric acid (HNO4) was characterized. HNO4 is an important atmospheric nitrogen oxide species. Its removal from the gas-phase directly effects the concentration of hydroxyl radicals and thus the oxidizing capacity of the atmosphere. There is a growing interest in HNO4 and its interaction with ice and snow in the atmospheric and cryospheric science communities. Only recently the first wintertime measurements of HNO4 in Antarctica were presented, indicating that loss of HNO4 to the surface snow is an important process. Our results will now enable modelers to look at the large-scale impact of HNO4 adsorption to surface snow.The uptake of trace gases to ice or snow is complex with different processes operating at specific time-scales each. To allow extrapolations of laboratory findings to environmental settings the individual processes need to be characterized, because time-scales in the environment and during the laboratory experiments might differ. In this project we focus on the role of grain boundaries on the uptake process. Grain boundaries have been proposed to act as reservoir to which trace gases can diffuse an in which they accumulate over longer timescales. But direct and sound experimental evidence is missing. The uptake measurements with focus on the role of grain boundaries required the development of a new experimental approach. This is the reason to kindly ask for extension of the project by one year. The goal of the third task of this project is to characterize the dissociation of acids on ice surfaces. Until now a long-term uptake has been most dominantly been found for highly acidic trace gases, but it is currently unclear weather their high solubility or acidity causes this. A new instrument has been successfully tested. While the task related to the characterization of HNO4 uptake to ice has been finished within the first two years of the preceding project, we would like to apply for funds for an additional year to complete the analysis of the acid dissociation data set and complete the grain boundaries experiments and their analysis.