Measurements of hydrogen peroxide and individual organic peroxides in the marine troposphere

Concentrations of gas-phase H2O2 and organic peroxides were measured in the marine boundary layer, during the FIELDVOC 93-campaign at the Pointe de Penmarcʹh (Brittany, France), from 14 May to 10 June, 1993. Air samples were collected by the scrubber sampling method. Precipitation samples were taken during different rain events. Analysis was performed with a reversed-phase high-performance liquid chromatography system (HPLC) using the p-hydroxyphenyl ethanoic acid/peroxidase fluorescence reaction for detection. Gaseous H2O2 mixing ratios were found to be < 0.1–1.2 ppbv. No significant diurnal variations of H2O2 concentrations were observed. The highest levels of H2O2 were measured during a period of pure maritime influence (30 May to 3 June), corresponding to local winds from western and southwestern directions. No organic peroxides were observed in the air samples. Rain water samples showed H2O2 concentrations of 1.4–134.8 μmol l−1. The highest concentration was measured on 27 May during a heavy thunderstorm. Organic peroxides, HOCH2OOH (HMHP) and CH3CH(OH)OOH (1-HEHP), were detected in rain samples with concentrations in the range of 0.4–0.8 μmol l−1. Meteorological parameters and trace gas concentrations, measured by other groups participating in the campaign, were taken into account to study their correlation with atmospheric peroxide concentrations. The results from the correlation analysis showed that the concentration of gaseous H2O2 is strongly dependent on the ambient concentration of NOx.