ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-6-4601-2006 Cluster analysis of the organic peaks in bulk mass spectra obtained during the 2002 New England Air Quality Study with an Aerodyne aerosol mass spectrometer Marcolli C. 1 Canagaratna M. R. 2 Worsnop D. R. 2 Bahreini R. 3 4 de Gouw J. A. 3 4 Warneke C. 3 4 Goldan P. D. 3 Kuster W. C. 3 Williams E. J. 3 4 Lerner B. M. 3 4 Roberts J. M. 3 Meagher J. F. 3 Fehsenfeld F. C. 3 Marchewka M. L. 5 Bertman S. B. 5 Middlebrook A. M. 3 Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland Aerodyne Research Incorporated, Billerica, MA, USA National Oceanic and Atmospheric Administration, Earth System Research Laboratory, Chemical Sciences Division, Boulder, CO, USA Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA Department of Chemistry, Western Michigan University, Kalamazoo, MI, USA 12 06 2006 6 3 4601 4641 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/6/4601/2006/acpd-6-4601-2006.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/6/4601/2006/acpd-6-4601-2006.pdf

We applied hierarchical cluster analysis to an Aerodyne aerosol mass spectrometer (AMS) bulk mass spectral dataset collected aboard the NOAA research vessel Ronald H. Brown during the 2002 New England Air Quality Study off the east coast of the United States. Emphasizing the organic peaks, the cluster analysis yielded a series of categories that are distinguishable with respect to their mass spectra and their occurrence as a function of time. The differences between the categories mainly arise from relative intensity changes rather than from the presence or absence of specific peaks. The most frequent category exhibits a strong signal at <i>m/z</i> 44 and represents oxidized organic matter most probably originating from both, anthropogenic as well as biogenic sources. On the basis of spectral and trace gas correlations, the second most common category with strong signals at <i>m/z</i> 29, 43, and 44 contains contributions from isoprene oxidation products. The third through the fifth most common categories have peak patterns characteristic of monoterpene oxidation products and were most frequently observed when air masses from monoterpene rich regions were sampled. Taken together, the second through the fifth most common categories represent as much as 5 &micro;g/m<sup>3</sup> organic aerosol mass &ndash; 17% of the total organic mass &ndash; that can be attributed to biogenic sources. These numbers have to be viewed as lower limits since the most common category was attributed to anthropogenic sources for this calculation. The cluster analysis was also very effective in identifying a few contaminated mass spectra that were not removed during pre-processing. This study demonstrates that hierarchical clustering is a useful tool to analyze the complex patterns of the organic peaks in bulk aerosol mass spectra from a field study.