Comparison of a Quadrupole and a Time-of-Flight Aerosol Mass Spectrometer during the Feldberg Aerosol Characterization Experiment 2004

Abstract

The Feldberg Aerosol Characterization Experiment (FACE-2004) took place from July 13–August 4, 2004 at the Taunus Observatory on the “Kleiner Feldberg” (825 m a.m.s.l.) in Central Germany. The experiment included (amongst others) size-resolved chemical characterization of non-refractory aerosol components. One of the experiment's objectives was to better understand and to characterize recently developed aerosol measurement instrumentation by intercomparison with other co-located instruments. One of these instruments was the Aerodyne Time-of-Flight Aerosol Mass Spectrometer (ToF-AMS).

Here we compare the datasets obtained by the ToF-AMS with those obtained by the well-characterized co-located Quadrupole Aerosol Mass Spectrometer (Q-AMS). A good agreement between the recently developed ToF-AMS with the established Q-AMS is reported here for all species measured with the two instruments for a time period where both instruments operated under well-calibrated conditions. During measurements with reduced detector gain after a pump failure changed species concentrations were measured with the ToF-AMS that did not agree with those measured with the Q-AMS. These changes were different for the individual species and could be attributed to the influence of the ion detection threshold as was shown by model calculations.

For efficient and user-friendly processing of ToF-AMS raw data a data processing software package was developed. Since this is the first time this software was used for field data, it is described in some detail here.

We thank the Johann-Wolfgang-Goethe University in Frankfurt/ Main for providing the facilities at the Taunus Observatory at Kleiner Feldberg. Special thanks goes to Heinz Bingemer for all the help and cooperation concerning this campaign. We thank the German Weather Service (DWD) for providing meteorological data as well as back trajectory calculations. Also, we would like to thank Jose-Luis Jimenez and Peter DeCarlo for providing the ToF-AMS data acquisition software. Silke Hings and Saskia Walter thank the International Max Planck Research School on Atmospheric Chemistry and Physics for funding of their participation in this work.