Spatial Variation, Sources and Emission Rates of Volatile Organic Compounds Over the Northeastern U.S.

Abstract

Ambient air samples were collected in 2 liter canisters along four ~250-300 mile (~400-480 km) loops radiating out from UNH in Durham, NH and included portions of western Maine (ME), eastern Vermont (VT), northern and eastern Massachusetts (MA), extreme northeastern Connecticut (CT), and northern Rhode Island (RI) (Fig. 1b). During each survey, four pairs of researchers collected samples every 10-15 miles (16-24 km) for a total of 24 samples on each route. The time of sample collection and the geospatial coordinates were recorded at each sampling location using a global positioning sensor (GPS). The sampling sites were generally open areas (i.e., fields, public parks) upwind of major sources and were chosen during the first sampling trip (June 21, 2006) which was conducted during the daytime (~09:00-19:00 EDT). The three subsequent surveys were conducted at night (~19:00-05:00 EDT) when winds were predicted to be low (<5 m s-1) to minimize the influence of photochemistry and to capture local nighttime emissions. The four sampling routes covered a wide geographic area that spanned considerable variation in altitude, land use, and population density. Moreover, the four surveys provide information on the seasonal variation of VOC sources. In order to characterize the diurnal variation of VOCs throughout the region, hourly ambient canister samples were collected over 24 hour periods on

Carbon monoxide isotopic measurements in Indianapolis constrain urban source isotopic signatures and support mobile fossil fuel emissions as the dominant wintertime CO source

“…We used an ‰; this change is insignificant relative to our measurement errors and can therefore be ignored (Table S2, Methane and non-methane hydrocarbon (NMHC) oxidation accounts for approximately half of the global CO budget (Duncan et al, 2007) and we estimate the contribution of these to the wintertime Indianapolis urban CO budget. Compounds such as OH and O 3 readily oxidize CH 4 and many NMHCs (Sander et al, 2006; Warneke et al, 2013;Russo et al, 2011;Khan et al, 2015) making them seasonally-varying sources of CO (Duncan et al, 2007). However, the relatively low wintertime NMHC and OH mole fractions (Helmig et al, 2013; Hu et al, 2015) mean that CH 4 and NMHC oxidation may be unimportant for our study.…”

“…However, the relatively low wintertime NMHC and OH mole fractions (Helmig et al, 2013; Hu et al, 2015) mean that CH 4 and NMHC oxidation may be unimportant for our study. Not all NMHC species capable of impacting CO are measured at INX; therefore some of the NMHC mole fractions are estimated using other urban studies in the literature (Warneke et al, 2013;Russo et al, 2011;Khan et al, 2015) (Table S2, supplemental material). Reaction rates with OH were calculated using k OH from Warneke et al (2013) if available, and if not, k OH was calculated using parameters from Sander et al (2006), and Atkinson et al, (1999, 2006.…”