Centre for Atmospheric Chemistry
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Browsing Centre for Atmospheric Chemistry by Author "Anlauf, K.G."
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Item Open Access Measurements of C2-C7 hydrocarbons during the polar sunrise experiment 1994: Further evidence for halogen chemistry in the troposphere(AGU, 1998) Ariya, P.A.; Jobson, B.T.; Sander, R.; Niki, H.; Harris, G.W.; Anlauf, K.G.; Hopper, J.F.Air samples for nonmethane hydrocarbon (NMHC) analysis were collected at two ground‐based sites: Alert, Northwest Territories (82.5°N, 62.3°W) and Narwhal ice camp, an ice floe 140 km northwest of Alert, from Julian days 90 to 117, 1994, and on a 2‐day aerial survey conducted on Julian days 89 and 90, 1994 over the Arctic archipelago. Several ozone depletion events and concurrent decreases in hydrocarbon concentrations relative to their background levels were observed at Alert and Narwhal ice camp. At Narwhal, a long period (≥7 days) of ozone depletion was observed during which a clear decay of alkane concentration occurred. A kinetic analysis led to a calculated Cl atom concentration of 4.5 × 103 cm−3 during this period. Several low‐ozone periods concurrent with NMHC concentration decreases were observed over a widespread region of the Arctic region (82°–85°N, and 51°–65°W). Hydrocarbon measurements during the aerial survey indicated that the low concentrations of these species occurred only in the boundary layer. In all ozone depletion periods, concentration changes of alkanes and toluene were consistent with Cl atom reactions. The changes in ethyne concentration from its background level were in excess of those expected from Cl atom kinetics alone and are attributed to additional Br atom reactions. A box modeling exercise suggested that the Cl and particularly Br atom concentrations required to explain the hydrocarbon behavior are also sufficient to destroy ozone.Item Open Access Nighttime Chemistry at a Rural Site in the Lower Fraser Valley(Elsevier, 2004) McLaren, R.; Salmon, R.A.; LIggio, J.; Hayden, K.L.; Anlauf, K.G.; Leaitch, R.NO3 was measured at the Sumas Eagle Ridge Site during the Pacific 2001 Air Quality Study. The average maximum levels ( average) observed on four nights was . NO3 at these levels can play a significant role in oxidation of volatile oxidation compounds (VOC), particularly biogenic monoterpenes. N2O5 levels were calculated on two nights presuming that the equilibrium, NO2+NO3N2O5, was maintained. Peak N2O5 levels were 200–. NO3 and N2O5 were found to contribute 7–9% of the total gaseous NOy on these two nights. Homogeneous and heterogeneous hydrolysis rates of N2O5 were calculated to estimate the nighttime production of gaseous and particulate nitric acid, respectively. Ignoring losses, the overnight total accumulated production of nitric acid was found to be 1.4–. In a comparison, it was found that the calculated heterogeneous production of fine particle nitrate can account for most of that which was observed experimentally on the two nights, indicating that this process is significant. Particulate pinonaldehyde measured throughout the study showed a significant night/day enhancement, in contrast to other carbonyls, indicating that NO3 also plays a role in formation of secondary organic aerosols at the site.