C7-C11 aromatic and n-alkane hydrocarbons measured by a comprehensive gas chromatography
(GCxGC) system during the MINOS Campaign
Xiaobin Xu1, Jonathan Williams1, Christian Plass-Duelmer2,
Harald Berresheim2, Gavin Salisbury1, Lutz Lange1 and
Jos Lelieveld1
1 Max Planck Institute for Chemistry, Mainz, Germany
2 German Weather Service, Meteorological Observatory Hohenpeissenberg, Germany
During the MINOS campaign in August 2001 atmospheric organic compounds were measured using
the comprehensive two-dimensional gas chromatography (GCxGC) technique at the Finokalia
ground station, Crete. The measurement system was optimised to resolve C7-C14 hydrocarbons
and the other organic components eluting in the optimum temperature range. Details about the
system are described in a separate paper submitted to this conference (Xu et al.). This
paper focuses on the interpretation of data from measurements of about 20 C7-C11 aromatic
and n-alkane compounds, which have been identified and quantified. The observed day-to-day
and diurnal variations of mixing ratios are discussed. The role of the OH radical in the
day-to-day and diurnal variations is studied using a simple box model, measured OH concentrations,
and assuming constant sources. Under the constant source assumption, mean rate constants for the
reactions of the hydrocarbons with OH are estimated from the in-situ measurements of OH and the
hydrocarbons, and compared to the corresponding rate constants from the literature. Possible
factors other than OH reactions for the observed hydrocarbon variations are discussed.