Multi-year (2004-2008) record of nonmethane hydrocarbons and halocarbons in New England: Seasonal variations and regional sources
Multi-year time series records of C(2)-C(6) alkanes, C(2)-C(4) alkenes, ethyne, isoprene, C(6)-C(8) aromatics, trichloroethene (C(2)HCl(3)), and tetrachloroethene (C(2)Cl(4)) from canister samples collected during January 2004-February 2008 at the University of New Hampshire (UNH) AIRMAP Observatory at Thompson Farm (TF) in Durham, NH are presented. The objectives of this work are to identify the sources of nonmethane hydrocarbons (NMHCs) and halocarbons observed at TF, characterize the seasonal and interannual variability in ambient mixing ratios and sources, and estimate regional emission rates of NMHCs. Analysis of correlations and comparisons with emission ratios indicated that a ubiquitous and persistent mix of emissions from several anthropogenic sources is observed throughout the entire year. The highest C(2)-C(8) anthropogenic NMHC mixing ratios were observed in mid to late winter. Following the springtime minimums, the C(3)-C(6) alkanes, C(7)-C(8) aromatics, and C(2)HCl(3) increased in early to mid summer, presumably reflecting enhanced evaporative emissions. Mixing ratios of C(2)Cl(4) and C(2)HCl(3) decreased by 0.7 +/- 0.2 and 0.3 +/- 0.05 pptv/year, respectively, which is indicative of reduced usage and emissions of these halogenated solvents. Emission rates of C(3)-C(8) NMHCs were estimated to be 10(9) to 10(10) molecules cm(-2) s(-1) in winter 2006. The emission rates extrapolated to the state of New Hampshire and New England were similar to 2-60 Mg/day and similar to 12-430 Mg/day, respectively. Emission rates of benzene, toluene, ethylbenzene, xylenes, and ethyne in the 2002 and 2005 EPA National Emissions Inventories were within +/- 50% of the TF emission rates.