Method Development For Concentration Measurements of SVOCs and Analysis of Ambient Samples

Semi-volatile organic compounds (SVOCs) comprise a wide range of toxic pollutants in the atmosphere. Phenols, polycyclic aromatic hydrocarbons (PAHs) and n-alkanes are specific examples of SVOCs that are the focus of this project. SVOCs are compounds with intermediate vapour pressures and can exist in the atmosphere in both gas phase and in particulate matter (PM), which makes their quantification in the atmosphere challenging. Therefore, developing a well-characterized analytical technique for accurate concentration measurement of the selected classes of SVOCs is essential in order to gain more insight into their ambient yield and environmental fate. Recently, a new methodology that allows sampling and analysis of the total (gas phase and PM) concentration of SVOCs in the atmosphere has been developed and tested on a class of SVOCs, namely, nitrophenols (Busca, 2010; Moukhtar et al., 2011; Saccon et al., 2013). This method is based on a sorbent impregnated filter (SIF) technique using conventional high volume air samplers, extraction and analysis by GC-MS. In this project, the newly developed XAD-4TM SIF was modified, developed and tested to determine its suitability for ambient concentration measurements of other classes of SVOCs like PAHs and n-alkanes. The results of the method validation tests show that the XAD-4TM SIF technique can be used for quantitative measurements of PAHs and n-alkanes in the atmosphere. Atmospheric samples were collected in Toronto as well as in the Alberta Oil Sands region and analyzed using the modified analytical technique. Preliminary results obtained from the Oil Sands samples showed relatively high concentrations for the three classes of SVOCs, particularly in samples impacted by the plume suspected to originate from the Syncrude and/or Suncor mining and upgrading sites. The carbon preference index (CPI) values obtained for these Oil Sands samples also indicated a substantial anthropogenic impact, even for the samples that were not significantly influenced by nearby emissions from upgrading/refining facilities. The CPI values for some samples were also consistent with some biogenic impact. A comparison of the phase distribution measurements of the three classes of SVOCs demonstrated a systematic dependence between the phase partitioning and vapour pressure for all n-alkanes and most PAHs. However, most of the nitrophenols did not follow this pattern, consistent with findings reported by Facca (2013) and Saccon et al. (2013). Some PAHs with intermediate vapour pressures also did not follow the partitioning expected from their vapour pressure. This indicates that factors other than vapour pressure play a major role in the partitioning of these SVOCs in the atmosphere.