The role of carbonyl compounds in tropospheric ozone chemistry

The atmospheric concentrations of a variety of carbonyl compounds and some of their atmospheric oxidation precursor hydrocarbons were measured in several different Canadian environments. Air samples were collected and analyzed in situ on an hourly basis using an automated adsorbent-based preconcentration system coupled to a gas chromatograph for separation of the collected species, followed by a mass selective detector for their detection.;As part of the Pacific 93 Oxidants Study in the summer of 1993 in the Lower Fraser Valley, BC, measurements of isoprene, methyl vinyl ketone (MVK), methacrolein (MACR), acetone, propanal, butanal, and methyl ethyl ketone were conducted at a surface site located about 40 km east of Vancouver. The data provided evidence for substantial contributions of the biogenic hydrocarbon isoprene to ozone production in this region during an observed oxidant episode. An analysis of the relationship between ozone and isoprene's oxidation products MVK and MACR allowed the estimation that isoprene oxidation was responsible for ;To investigate the non-photochemical source of MVK and MACR, measurements of these compounds and CO were made in Toronto in the late winter of 1996, in the absence of biogenic isoprene emissions, and again in the summer of 1996. The concentrations of MVK and MACR were significant in the winter and were highly correlated with CO concentrations, which indicated that these compounds are emitted by automotive sources. Emission factors of MVK and MACR relative to CO were estimated through linear regression analysis to be ;Measurements of acetone, propanal, MEK, butanal, n-butane, and i-butane were conducted at Alert, NWT in the spring of 1995 as part of Polar Sunrise Experiment 1995 to further investigate the phenomenon of boundary layer ozone depletion in the Arctic. Ketone concentrations showed negative correlations with ozone, with significant increases during ozone depletion events which were difficult to account for from model simulations of hydrocarbon oxidation during the same periods with the expected low NO...