Studies of aerosol at a coastal site using two aerosol mass spectrometry instruments and identification of biogenic particle types

Abstract

During August 2004 an Aerosol Time-of-Flight Mass Spectrometer (TSI ATOFMS Model 3800-100) and an Aerodyne Aerosol Mass Spectrometer (AMS) were deployed at Mace Head during the NAMBLEX campaign. Single particle data (size, positive and 5 negative mass spectra) from the ATOFMS were imported into ART 2a, a neural net- work algorithm, which assigns individual particles to clusters on the basis of their mass spectral similarities. Results are very consistent with previous time consuming man- ual classifications (Dall’Osto et al., 2004). Three broad classes were found: sea-salt, dust and carbon-containing particles, with a number of sub-classes within each. The 1 Aerodyne (AMS) instrument was also used during NAMBLEX, providing online, real 0 time measurements of the mass of non-refractory components of aerosol particles as function of their size. The ATOFMS detected a type of particle not identified in our earlier analysis, with a strong signal at m/z 24, likely due to magnesium. This type of particle was detected 1 during the same periods as pure unreacted sea salt particles and is thought to be 5 biogenic, originating from the sea surface. AMS data are consistent with this interpre- tation, showing an additional organic peak in the corresponding size range at times when the Mg-rich particles are detected. The work shows the ATOFMS and AMS to be largely complementary, and to provide a powerful instrumental combination in studies 2 of atmospheric chemistry.