Atmospheric volatile organic compound measurements: Distributions and effects on air quality in coastal marine, rural and remote continental environments
A detailed description of the analytical methods employed for whole air sampling and analysis of atmospheric volatile organic compounds is presented. The system described in this thesis produced high precision measurements for a large suite of nonmethane hydrocarbons, halocarbons, and alkyl nitrates, from part per billion by volume (ppbv) to part per trillion by volume (pptv) levels. The measurement precision for most gases ranged from 1-10%. Results from two subsequent field campaigns (2002 and 2003) conducted in Yellowstone National Park (YNP) are presented. The findings indicate that 2-stroke snowmobile engine emissions furnish large quantities of air toxics to the YNP air shed. Air toxics, which are major components of 2stroke engine exhaust, show large enhancements between the high traffic and low traffic sampling periods. Evaluation of the photochemical history of air masses sampled in the Park reveals that the air toxic emissions were recent and persistent throughout the region and consistent with the 2-stroke exhaust sample fingerprints. Using a box model, the emission fluxes from snowmobile usage in the Park are estimated to be 0.35, 1.12, 0.24, 1.45, and 0.36 Gg/yr for benzene, toluene, ethyl benzene, xylenes, and hexane, respectively. The U.S. annual emissions from snowmobile usage are significant (&sim;14-21%) with respect to EPA estimates. Results of the atmospheric measurements of short-lived halocarbons are presented from the New England Air Quality Study 2002 campaign, summer 2003 at Thompson Farm (TF) and Great Bay, and the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) 2004 campaign. Elevated levels of bromoform (CHBr3) were frequently observed, with maxima of 37.9 pptv and 47.4 pptv for TF and Appledore Island (AI), respectively. During the ICARTT 2004 campaign, the average levels of CHBr3 and dibromomethane (CH2Br2) were higher at AI (CHBr3 = 14.3 pptv, CH2Br2 = 3.2 pptv) compared to Thompson Farm (CHBr3 = 6.3 pptv, CH2Br2 = 2.3 pptv). Wind conditions play a very important role in controlling the distributions of these gases. Emission flux estimates for CHBr3, CH2Br 2, methyl iodide, and ethyl iodide were 26 +/- 57, 4.7 +/- 5.4, 5.9 +/- 4.6, and 0.065 +/- 0.20 nmol m-2 h -1, respectively.
Environmental Sciences, Atmospheric Sciences
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