A new direct thermal desorption-GC/MS method: Organic speciation of ambient particulate matter collected in Golden, BC Luyi C. Ding * , Fu Ke, Daniel K.W. Wang, Tom Dann, Claire C. Austin Analysis & Air Quality Section, Air Quality Research Division, Environment Canada, 335 River Road, Ottawa, ON, Canada K1A 0H3 article info Article history: Received 25 March 2009 Received in revised form 10 July 2009 Accepted 11 July 2009 Keywords: Direct thermal desorption GC/MS Organic speciation PM2.5 OC/EC abstract Particulate matter having an aerodynamic diameter less than 2.5 mm (PM2.5) is thought to be implicated in a number of medical conditions, including cancer, rheumatoid arthritis, heart attack, and aging. However, very little chemical speciation data is available for the organic fraction of ambient aerosols. A new direct thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) method was developed for the analysis of the organic fraction of PM2.5. Samples were collected in Golden, British Columbia, over a 15-month period. n-Alkanes constituted 33–98% by mass of the organic compounds identified. PAHs accounted for 1–65% and biomarkers (hopanes and steranes) 1–8% of the organic mass. Annual mean concentrations were: n-alkanes (0.07–1.55 ng m 3 ), 16 PAHs (0.02–1.83 ng m 3 ), and biomarkers (0.02–0.18 ng m 3 ). Daily levels of these organics were 4.89–74.38 ng m 3 , 0.27–100.24 ng m 3 , 0.14–4.39 ng m 3 , respectively. Ratios of organic carbon to elemental carbon (OC/ EC) and trends over time were similar to those observed for PM2.5. There was no clear seasonal variation in the distribution of petroleum biomarkers, but elevated levels of other organic species were observed during the winter. Strong correlations between PAHs and EC, and between petroleum biomarkers and EC, suggest a common emission source – most likely motor vehicles and space heating. Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved. 1. Introduction Particulate matter having an aerodynamic diameter less than 2.5 mm (PM2.5) are of great concern because they are inhaled deep into the lungs carrying along with them adsorbed toxic organic substances (Kampa and Castanas, 2008). PM2.5 are thought to be implicated in a number of medical conditions, including cancer, rheumatoid arthritis, heart attack, and aging (Chow et al., 2007; Delfino et al., 2005; Lewtas, 2007; Mauderly and Chow, 2008), and they have been associated with increased daily morbidity and mortality (Schwartz, 1997; Schwartz et al., 1996). PM2.5 has contribution to poor visibility in both urban and rural areas, and has also had an impact on global climate change due to the light absorbing properties of elemental carbon (Jacobson et al., 2000; Watson et al., 2004). Elemental carbon (EC) emitted from combustion processes is a primary pollutant and a major absorber of light in the atmo- sphere (Jacobson et al., 2000). The organic carbon (OC) fraction of ambient PM2.5 comprises a wide variety of organic substances such as aliphatic compounds (n-alkanes, hopanes, and steranes), aromatic compounds, polycyclic aromatic hydrocarbons, carbox- ylic acids (alkanoic acids) and water-soluble organic compounds, including high-molecular-weight compounds, such as HULIS (humic-like substances) (Turpin et al., 2000). The principle sour- ces are combustion of fossil fuels and biomass burning, biological particles, plant fragments, and soil derived HULIS materials (Turpin et al., 2000). Organic carbon speciation remains largely unresolved due to the analytical complexity and high cost of the instrumentation (Brown et al., 2002). The standard solvent extraction method typically used for the determination of organic carbons in source and ambient particulate matter is a time-consuming procedure requiring a relatively large quantity of sample material (Hays and Lavrich, 2007; Waterman et al., 2000). Thermal/dual-optical carbon analysis is routinely used as a bulk-level chemical analysis method for the determination of organic carbon and elemental carbon fractions both in source and ambient particulate samples (Chow et al., 2004, 2001). However, it provides very little insight into the species of organic compounds adsorbed onto the particles. Thermal desorp- tion-gas chromatography/mass spectrometry (TD-GC/MS) is a molecular-level chemical analysis technique currently used for the rapid analysis of adsorbed volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) in particulate matter (Chow et al., 2007; Hays and Lavrich, 2007). It has proven to be an * Corresponding author. Tel.: þ1 613 991 1442; fax: þ1 613 990 8568. E-mail address: luyi.ding@ec.gc.ca (L.C. Ding). Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ – see front matter Crown Copyright Ó 2009 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2009.07.016 Atmospheric Environment 43 (2009) 4894–4902