14. Semi-Volatile Organic Compounds in Snowmobile Exhaust and in the Snowpack

(1)Atmospheric Science Program, University of Nevada, Reno

(2)Organic Analytical Laboratory, Desert Research Institute, Reno, NV

Two-stroke snowmobiles emit high levels of PM, over 90% of which is classified as organic carbon. Analysis for semi-volatile organic compounds (SVOC) identified 86 species of polynuclear aromatic hydrocarbons (PAH) and 36 species of hopanes and steranes in snowmobile exhaust and in snow taken from the snowmobile trail. Evolution of SVOC deposited to the snowpack is documented for four days following snowmobile activity. Environmental parameters such as ultraviolet radiation, snowpack and ambient air temperature, and the accumulation of new snow over the snowmobile trail were monitored. Species of SVOC found to be the most stable include the hopanes, steranes, and some species of PAH with 5 or 6 aromatic rings. Those found to be the least stabile are typically species with 2 or 3 aromatic rings, and are suspected of loss by volatilization. Additionally, photo-reactive compounds such as anthracene, phenanthrene, or fluorene may be readily photolyzed when exposure to UV radiation remains high. Accumulation of fresh snow over the snowmobile trail isolates contaminants from UV radiation incident on the snow surface and from gas exchange with boundary layer air, effectively reducing the degradation by photolysis and losses by volatilization.