Ground based particle measurement during MINOS (Crete, August 2001): Size distribution and inorganic chemical composition

Johannes Schneider1, Stephan Borrmann1,2, Adam Wollny3, Martin Bläsner3, Nikos Mihalopoulos4, Haido Bardouki4 and Jean Sciare5

1 Max Planck Institute for Chemistry, Mainz, Germany
2 University Mainz, Germany
3 Research Center Jülich, Germany
4 University of Crete, Heraklion, Crete
5 LSCE, Bat 709, CEA Orme des Merisiers, Gif/Yvette, France


Chemical composition analysis of aerosol particles in the size range between 50 nm and 2 µm was performed using different analytical methods at a ground station at Finokalia (160 m asl), Crete, during August 2002. These measurements were part of the MINOS (Mediterranean Intensive Oxidant Study) campaign. The measurements include on-line mass spectrometric analysis using the aerosol mass spectrometer (AMS, Aerodyne Research Inc.), ion chromatographic analysis of filter samples (3-h averages) as well as single particle laser ablation technique. Additionally, the total concentration and the size distribution were also measured using commercial CN counters, differential mobility sizers and optical particle counters. Parallel measurements of the on-line mass spectrometers and the filter samplers are available between August 16 and 23, a time period on which we will focus here.
At the ground station, the total number concentration (particles with diameter larger than 3 nm) varied between 2000 and 5000 cm-3. The total surface area density ranged between 100 and 300 µm2cm-3. A large particle mode around 10 µm dominated the total volume density. This mode consisted most likely of local originating dust or sand particles, an assumption which is supported by single particle analysis made with the laser ablation instrument. The surface area density as well as the number density was dominated by a particle mode with a median radius around 100 nm, which consisted mostly of ammonium sulfate and organic material, while the nitrate content was very low. This mode also dominated the optical properties. Most likely these particles originate from sulfur emissions by fossil fuel combustion in eastern Europe, followed by gas-to-particle conversion and condensational growth during the transport to Crete, on a time scale of about 4 days.
The results obtained with the different measurements techniques, as well as the variations in the relative abundances of sulfate, ammonium, and organics will be discussed in relation to air mass origin.