MEASUREMENTS OF HYDROGEN-PEROXIDE AND INDIVIDUAL ORGANIC PEROXIDES INTHE MARINE TROPOSPHERE

Concentrations of gas-phase H2O2 and organic peroxides were measured i n the marine boundary layer, during the FIELDVOC 93-campaign at the Po inte de Penmarc'h (Brittany, France), from 14 May to 10 June, 1993. Ai r samples were collected by the scrubber sampling method. Precipitatio n samples were taken during different rain events. Analysis was perfor med with a reversed-phase high-performance liquid chromatography syste m (HPLC) using the p-hydroxyphenyl ethanoic acid/peroxidase fluorescen ce reaction for detection. Gaseous H2O2 mixing ratios were found to be < 0.1-1.2 ppbv. No significant diurnal variations of H2O2 concentrati ons were observed. The highest levels of H2O2 were measured during a p eriod of pure maritime influence (30 May to 3 June), corresponding to local winds from western and southwestern directions. No organic perox ides were observed in the air samples. Rain water samples showed H2O2 concentrations of 1.4-134.8 mu moll(-1). The highest concentration was measured on 27 May during a heavy thunderstorm. Organic peroxides, HO CH2OOH (HMHP) and CH3CH(OH)OOH (1-HEHP), were detected in rain samples with concentrations in the range of 0.4-0.8 mu moll(-1). Meteorologic al parameters and trace gas concentrations, measured by other groups p articipating in the campaign, were taken into account to study their c orrelation 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. (C) 1997 E lsevier Science Ltd.