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

Abstract

Abstract. We applied hierarchical cluster analysis to an Aerodyne aerosol mass spectrometer (AMS) bulk mass spectral dataset collected aboard the NOAA research vessel R. 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 m/z 44 and represents oxidized organic matter 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 m/z 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 on average 17% of the total organic mass that stems likely from biogenic sources during the ship's cruise. 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 thatCorrespondence to: C. Marcolli (claudia.marcolli@env.ethz.ch) 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.

Biogenic VOC oxidation and organic aerosol formation in an urban nocturnal boundary layer: aircraft vertical profiles in Houston, TX

“…The ratio of m/z 30 to m/z 46 in the AMS mass spectra for this missed approach at Hooks was 3.6 ± 0.5, which is slightly higher than measured during calibration with pure ammonium nitrate particles (2.3 ± 0.3). While the higher ratio does not preclude ammonium nitrate in the aerosol phase, it does indicate the presence of either an organic nitrate, an oxygenated organic fragment, an amine, or another cation with inorganic nitrate (Marcolli et al, 2006;Farmer et al, 2010). On the basis of the available data from these profiles, it is difficult to assign the source of the lowaltitude nitrate aerosol enhancement to either the organic or the inorganic nighttime pathway.…”

Effect of oxidant concentration, exposure time, and seed particles on secondary organic aerosol chemical composition and yield

“…al., 2003;Marcolli et al, 2006). Using this approach, each mass spectral signal is normalized to the square root of the sum of the squares of all signals in the mass spectrum.…”

Loading-dependent elemental composition of α-pinene SOA particles

“…When taken together, the implication of those studies and ours is that the differences in the AMS UMR spectra are not large for SOA particles generated from anthropogenic and biogenic precursors. Therefore, in a regulatory context the attribution from mass spectra alone (e.g., by factor analysis) of biogenic compared to anthropogenic SOA particle mass and hence source controls must be approached cautiously (Zhang et al, 2005a, b;Marcolli et al, 2006;Lanz et al, 2007Lanz et al, , 2008. In particular, the library mass spectra to which results from factor analysis are compared must be collected under conditions similar to those occurring in the atmosphere.…”