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NATURE OF UNRESOLVED COMPLEX MIXTURE IN SIZE-DISTRIBUTED EMISSIONS FROM RESIDENTIAL WOOD COMBUSTION AS MEASURED BY THERMAL DESORPTION-GAS CHROMATOGRAPHY-MASS SPECTROMETRY
Citation:
Hays, M D., N D. Smith*, AND Y. Dong. NATURE OF UNRESOLVED COMPLEX MIXTURE IN SIZE-DISTRIBUTED EMISSIONS FROM RESIDENTIAL WOOD COMBUSTION AS MEASURED BY THERMAL DESORPTION-GAS CHROMATOGRAPHY-MASS SPECTROMETRY. JOURNAL OF GEOPHYSICAL RESEARCH: ATMOSPHERES. American Geophysical Union, Washington, DC, 109(D16S04):13 p, (2004).
Impact/Purpose:
Published Journal Article
Description:
In this study, the unresolved complex mixture (UCM) in size resolved fine aerosol emissions from residential wood combustion (RWC) is examined. The aerosols are sorted by size in an electrical low-pressure impactor (ELPI) and subsequently analyzed by thermal desorbtion/gas chromatography/mass spectrometry (TD/GC/MS). A semiquantitative system for predicting the branched alkane, cycloakane, alkylbenzene, C3-,C4-,C5-alkylbenzene, methynaphthanlene, C3-, C4-, C5-alkylnaphthalene, methylphenathrene C2-, C3-alkylphenathrene and dibenzothiophene concentrations in the UCM is introduced. Analysis by TD/GS/MS detects UCM on each ELPI stage for all six combustion tests. The UCM baseline is distinguished by fuel type; compared with Quercus sp., UCM of Pseudotsuga sp. assimilates more nonvolatile organics. Elution patterns tend to vary in shape and retention time expanse by and within molecular class. A high level of reproductibility is achieved in determing UCM areas. ELPI stage UCM fractions over the entire test set return a relative standard deviation of 19.1% indicating a highly consistent UCM/total area ratio across the ELPI size boundaries. Branched alkane (m/z 57) and dibenzothiophene (m/z 212 and 226) constituents are most abundant in UCM emissions from RWC, collectively accounting for 64-95% of the targeted chemical species. The total UCM emissions span 446-756 mg/kg and correspond to an upper limit of 7.1% of the PM2.5 mass. The UCM emissions are primarily accumulation mode, with a geometric mean diameter (dg) range of 120.3-518.4 nm. UCM in PM2.5 is chemically asymmetric (shifted to finer aerodynamic diameters [da]), typically clustering at da equal to or less than 1 micrometer. Measurable shifts in dg and changes in distribution widths (sigma g) on an intra-test basis suggest that the particle density is a function of size within PM1. The potential effects these results have on regulatory affairs, human health studies, and the state of the analytical science convering organics in PM2.5 is discussed.
