Effects of biomass burning on summertime nonmethane hydrocarbon concentrations in the Canadian wetlands

Abstract

Approximately 900 whole air samples were collected and assayed for selected C2‐C10 hydrocarbons and seven halocarbons during the 5‐week Arctic Boundary Layer Expedition (ABLE) 3B conducted in eastern Canadian wetland areas. In more than half of the 46 vertical profiles flown, enhanced nonmethane hydrocarbon (NMHC) concentrations attributable to plumes from Canadian forest fires were observed. Urban plumes, also enhanced in many NMHCs, were separately identified by their high correlation with elevated levels of perchloroethene. Emission factors relative to ethane were determined for 21 hydrocarbons released from Canadian biomass burning. Using these data for ethane, ethyne, propane, n‐butane, and carbon monoxide enhancements from the literature, global emissions of these four NMHCs were estimated. Because of its very short atmospheric lifetime and its below detection limit background mixing ratio, 1,3‐butadiene is an excellent indicator of recent combustion. No statistically significant emissions of nitrous oxide, isoprene, or CFC 12 were observed in the biomass‐burning plumes encountered during ABLE 3B. The presence of the short‐lived biogenically emitted isoprene at altitudes as high as 3000 m implies that mixing within the planetary boundary layer (PBL) was rapid. Although background levels of the longer‐lived NMHCs in this Canadian region increase during the fire season, isoprene still dominated local hydroxyl radical photochemistry within the PBL except in the immediate vicinity of active fires. The average biomass‐burning emission ratios for hydrocarbons from an active fire sampled within minutes of combustion were, relative to ethane, ethene, 2.45; ethyne 0.57; propane, 0.25; propene, 0.73; propyne, 0.06; n‐butane, 0.09; i;‐butane, 0.01; 1‐butene, 0.14; cis‐2‐butene, 0.02; trans‐2‐butene, 0.03; i‐butylene, 0.07; 1,3‐butadiene, 0.12; n‐pentane, 0.05; i‐pentane, 0.03; 1‐pentene, 0.06; n‐hexane, 0.05; 1‐hexene, 0.07; benzene, 0.37; toluene, 0.16.

Observations of nonmethane organic compounds during ARCTAS − Part 1: Biomass burning emissions and plume enhancements

“…Using the same WAS data set, but with different plume selection and averaging, Simpson et al (2011) reported an ethane to CO ER for Canadian BB during ARC-TAS of 4.6 ± 0.9 pptv ppbv −1 , consistent with the mean ethane NEMR determined in this work. Simpson and co-authors also reported an ethane to CO ER from a Siberian boreal forest fire plume interception on 29 June (4.63 ± 0.08 pptv ppbv −1 , corresponding to plume 19 in this work: 4.5 ± 0.5 pptv ppbv −1 ), which combined with findings from a previous study (ABLE-3B, Blake et al, 1994) led the authors to conclude that there may be a characteristic boreal forest fire emission signature. However, our plume 7 was also traced to the Siberian boreal forest region and has an ethane to CO NEMR of 15 ± 2 pptv ppbv −1 .…”

Spatial and temporal variability of nonmethane hydrocarbon mixing ratios and their relation to photochemical lifetime

“…Sample canisters were evacuated to 10-2 torr and shipped to the site for sample collection. Although most canisters have shown reliability and stability in the containment of various halocarbons and hydrocarbons, some have also displayed growth of light olefins with time [Blake et al, 1994]. Ambient air rebaking of these canisters has helped to resolve the olefin growth problem.…”

Measuring OVOCs and VOCs by PTR-MS in an urban roadside microenvironment of Hong Kong: relative humidity and temperature dependence, and field intercomparisons

“…All canisters used in this study were pre-cleaned and evacuated by the Rowland-Blake group at the University of California, Irvine (UCI). Detailed information of the preparation and pre-conditioning of the canisters can be found elsewhere (Blake et al, 1994;Simpson et al, 2010). After sampling, canisters with air samples were sent back to the laboratory at UCI for VOC analysis by a GC-MSD/FID/ECD system within 1 week of collecting the canister samples.…”