H202 and CH300H Transport and Chemical Evolution over the Pacific

H₂O₂ and CH₃OOH Transport and Chemical Evolution over the Pacific

Brian G. Heikes
Graduate School of Oceanography
University of Rhode Island
South Ferry Rd
Narragansett, RI 02882-1197
zagar@,notos.gso.uri.edu
voice: 401.874.6638
fax: 401.874.6898

High-pressure liquid chromatography is used to separate and quantify hydrogen peroxide, methy1hydroperoxide and other organic hydroperoxides. First gaseous hydroperoxides are collected in an aqueous solution. Then, retention time and enzyme specificity are used to distinguish the different hydroperoxides. Last, the hydroperoxides are quantified using the development of a fluorescence product. The chromatographic separation sets the minimum sample-time resolution. With two HPLC systems, this is 2+ minutes and allows H₂O₂ and CH₃OOH to be uniquely determined. Hydroxymethy1hydroperoxide, HOCH₃OOH, is also quantified within this interval if present. To date this has been the case only in highly polluted near surface environments. Each sample represents a 30-second collection period. Hence, we will report a 30-second observation every 120 seconds. The detection limits for H₂O₂and CH₃OOH are 15 and 25 ppt, respectively. A third HPLC system may be employed. This remains to be determined. The third system can be used to either improve sample time resolution or to qualitatively determine the presence of other organic hydroperoxides, such as, ethy1hydroperoxide or peroxyacetic acid.

The hydroperoxides are primary products of biomass burning and are secondary photochemical products of hydrocarbon oxidation and odd-hydrogen chemistry. Highest concentrations of H₂O₂, >3 ppb, have been observed in outflow from Asia associated with biomass burning and urban pollution and appears more sensitive to general pollutant levels than CH₃OOH. Both peroxides are sensitive to the relative concentrations of hydrocarbons and reactive oxides of nitrogen. Meteorological factors (e.g., water vapor, temperature, cloud, precipitation, sunlight), impact hydroperoxide concentrations, too. Measurements of the hydroperoxides aid in understanding the photochemical oxidant environments and the meteorological enviromnents encountered during the TRACE-P mission.