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 H2O2 and
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.
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