Air Toxic Emissions from Snowmobiles in Yellowstone National Park

Zhou, Yong; Shively, David; Mao, Huiting; Russo, Rachel; Pape, Bruce; Mower, Richard; Talbot, Robert; Sive, Barkley

A study on emissions associated with oversnow travel in Yellowstone National Park (YNP) was conducted for the time period of February 13-16, 2002 and February 12-16, 2003. Whole air and exhaust samples were characterized for 85 volatile organic compounds using gas chromatography. The toxics including benzene, toluene, ethylbenzene, xylenes (p-, m-, and o-xylene), and n-hexane, which are major components of twostroke engine exhaust,showlargeenhancementsduring sampling periods resulting from increased snowmobile traffic. Evaluation of the photochemical history of air masses sampled in YNP revealed that emissions of these air toxics were (i) recent, (ii) persistent throughout the region, and (iii) consistent with the two-stroke engine exhaust sample fingerprints. The annual fluxes were estimated to be 0.35, 1.12, 0.24, 1.45, and 0.36 Gg yr-1 for benzene, toluene, ethylbenzene, xylenes, and n-hexane, respectively, from snowmobile usage in YNP. These results are comparable to the flux estimates of 0.23, 0.77, 0.17, and 0.70 Gg yr-1 for benzene, toluene, ethylbenzene, and xylenes, respectively,thatwerederivedonthebasisof(i)actualsnowmobile counts in the Park and (ii) our ambient measurements conducted in 2003. Extrapolating these results, annual emissions from snowmobiles in the U.S. appear to be significantly higher than the values from theEPANational Emissions Inventory (1999). Snowmobile emissions represent a significant fraction (∼14-21%)ofairtoxicswithrespecttoEPAestimatesofemissions by nonroad vehicles. Further investigation is warranted to more rigorously quantify the difference between our estimates and emission inventories.

Air Toxic Emissions from Snowmobiles in Yellowstone National Park

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