| Abstract
| - Significant changes have occurred in the anthropogenicemissions of many compounds related to the Kyoto andMontreal Protocols within the past 20 years and many oftheir atmospheric abundances have responded dramatically. Additionally, there are a number of related naturalcompounds with underdetermined source or sink budgets. A new instrument, Medusa, was developed to makethe high frequency in situ measurements required for thedetermination of the atmospheric lifetimes and emissionsof these compounds. This automated system measures awide range of halocarbons, hydrocarbons, and sulfurcompounds involved in ozone depletion and/or climateforcing, from the very volatile perfluorocarbons (PFCs,e.g., CF4 and CF3CF3) and hydrofluorocarbons (HFCs,e.g., CH3CF3) to the higher-boiling point solvents (suchas CH3CCl3 and CCl2CCl2) and CHBr3. A network ofMedusa systems worldwide provides 12 in situ ambientair measurements per day of more than 38 compoundsof part per trillion mole fractions and precisions up to0.1% RSD at the five remote field stations operated bythe Advanced Global Atmospheric Gases Experiment(AGAGE). This custom system couples gas chromatography/mass spectrometry (GC/MSD) with a novel schemefor cryogen-free low-temperature preconcentration (−165°C) of analytes from 2 L samples in a two-trap processusing HayeSep D adsorbent.
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