A preliminary experiment to examine chemical exchange at the soil-snow interface

Exchange of soil gases with the atmosphere is of current interest to researchers in several fields of geophysics and geochemistry. We have begun to examine the exchange of organic vapor at the soil-snow interface. The insights gained from this study may contribute to the general understanding of interfacial exchange processes. Soil specimens, spiked with organic solids having a great range of vapor pressure and aqueous solubility, were placed in shallow trays in contact with the surface prior to snowfall. Snow was allowed to accumulate over the trays and the temperature profiles within the adjacent snow and soil were recorded. Snow specimens were collected above the trays, with a height resolution of 1–5 cm, after exposure periods ranging from days to months. The snow specimens were analyzed with respect to density, particle size and chemical concentration. The preliminary results presented here indicate that organic materials with vapor pressure of the order of 10−3 to 10−6 torr achieved orderly concentration profiles coordinated with the distance from the source. Materials with greater or lesser vapor pressure were less orderly and refinement of the experimental method is necessary to understand this behavior. The experiment indicates that snowpack provides temporary storage for organic contaminants, which may exchange with air or groundwater. More extensive experiments are necessary to define the processes regulating organic exchange in snow. We propose that analysis of overlying snow may provide a non-invasive method of surveying soil contamination.