MEASUREMENTS AND CHEMISTRY OF SELECTED REACTIVE NITROGEN AND

OXYGENATED SPECIES OVER THE TROPICAL PACIFIC OCEAN (PEM-TROPICS-B)

H. B. Singh,

NASA Ames Research Center,

Moffett Field, CA 94035

We aim to deploy on the DC-8 aircraft, a three channel instrument package in its PAN/Aldehyde/Ketone (PANAK) configuration. A heated Teflon lined probe is used for sampling, and all calibrations, are done inflight in a manner that mimic ambient air sampling. In this configuration, PAN (Peroxyacetyl nitrate), PPN (Peroxypropionyl nitrate), tetrachloroethylene (tracer of urban air), and select alkyl nitrates (methyl, ethyl, and i-propyl nitrates) are separated on two EC-GC channels allowing a measurement every 4 to 5 minutes to a sensitivity of 1 ppt or better. The third channel equipped with a coupled Reduction Gas detector and a photoionization detector (to be added) uses capillary chromatography and is currently focused on the measurement of select oxygenated compounds. We plan to prepare, integrate and test the PANAK instrument aboard the DC-8, and participate in the PEM-Tropics-B deployment (March.-April, 1999) to perform measurements of PAN, PPN, methyl nitrate, ethyl/i-propyl nitrates, tetrachloroethylene, acetone, methanol, ethanol, and acetaldehyde to low ppt levels. We also plan to validate, process and analyze all data collected during PEM-Tropics, and interpret these to ascertain sources and chemistry of oxygenated hydrocarbons, reactive nitrogen species, atmospheric free radicals, and ozone.