Partitioning Acetone between the Surface of Artificial Snow and the Gas Phase

In this project, we have assessed the decay rate of acetone, a representative pollutant, from the surface of snow of differing temperatures. Previous studies and models have described the partitioning of gases between the surface of snow using Henry’s law of solubility by assuming that the surface of snow has a microscopic layer of liquid water covering the surface. These studies do not account for the actual surface of snow, which, as it warms, becomes more disordered, having both crystalline ice surfaces and patches of water. Using a bubbler and compressed air, a flow of gaseous acetone was flowed through artificial snow for a period of time and then stopped. Acetone in the outflow was monitored using a mass spectrometer, and the rate of decay analyzed. The same process was done to assess the helium decay rate from snow, as helium does not interact with the surface of snow as strongly as acetone. The decay rate of acetone from the surface of an acetone-snow solution was measured. The decay rate of acetone in snow relies upon the temperature of the snow, as well as the volume of the snow and flow rate of air moving through the snow. From -20 to -7 degrees Celsius, desorption rates increased. However, at temperatures approaching the melting point of snow, the decay rate changes due to the dissolution of acetone that does not occur at colder temperatures. A more comprehensive model is needed to determine the effect of the specific surface area of the snow on the decay rate.