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Free keywords:
H2O2; organic peroxides; carbonyl compounds; city plume; photosmog
Abstract:
Gas-phase H2O2, organic peroxides and carbonyl compounds were determined at various sites from Mid-July to early August 1998 during the BERLIOZ campaign in Germany. The sites were located northwest of Berlin and were chosen to determine pollutants downwind of the city emissions during a summer smog episode. Hydrogen peroxide (H2O2), methyl hydroperoxide (MHP, CH3OOH) and occasionally hydroxymethyl hydroperoxide (HMHP, HOCH2OOH) were quantified in air samples by commercial fluorimetric methods and classical HPLC with post-column derivatisation by horseradish peroxidase/p-hydroxyphenyl acetic acid and fluorimetric detection. Carbonyl compounds were determined in ambient air by a novel method based on O-pentafluorobenzyl hydroxylamine as derivatisation agent. Mixing ratio profiles of the hydroperoxides and the carbonyl compounds are reported for the intensive phase of the campaign, 20-21 July, 1998. Peroxides showed pronounced diurnal variations with peak mixing ratios in the early afternoon. At times, a second maximum was observed in the late afternoon. The major part of the H2O2 was formed through recombination reactions of HO2 radicals, but there is some evidence that H2O2 is also formed from ozonolysis of anthropogenic and/or biogenic alkenes. Diurnal variations of mixing ratios of various carbonyl compounds are reported: alkanals (C-2 to C-10, isobutanal), unsaturated carbonyl compounds (methacrolein, methylvinylketone, acrolein), hydroxycarbonyl (glycolaldehyde, hydroxyacetone) and dicarbonyl compounds (glyoxal, methylglyoxal, biacetyl), aromatic compounds (benzaldehyde, o- and m-tolylaldehyde) and pinonaldehyde.
