Qualitative and quantitative assessment of UCM in PM2.5 of Bakersfield, CA.

Fine particulate matter (PM ₂.₅ ) was collected in Bakersfield, CA during the CalNex 2010 field experiment and was analyzed for primary organics using a gas chromatograph – mass spectrometer (GC-MS). Substantial presence of unresolved complex mixture (UCM) was observed in the collected PM ₂.₅ . To quantify the overlapping UCM peaks, a method was developed for the deconvolution (peak separation) of the UCM. This enabled unique quantification of each UCM peak. The developed method was tested on several runs of a standard reference material for urban dust, which yielded consistent values with a standard deviation of ~16%. The UCMs in the Bakersfield sample were quantified separately and qualitatively assessed for possible emission sources. The average spectrum from the UCM suggested the presence of alkanes, alkenes, and alkynes in the low-molecular weight UCM; and the presence of linear, branched, and cyclic alkanes in the high-molecular weight UCM. The method developed in the current study has the potential for application to a variety of environmental media.