Improved spatiotemporal polycyclic aromatic hydrocarbon (PAH) characterization and assessment in small craft harbour sediments in Nova Scotia  Emily Davisa, Dr. Tony Walkera, Dr. Michelle Adamsa, Rob Wilisb aSchool for Resource and Environmental Studies bDillon Consulting Limited Results Introduction Discussion Harbour sediments across the globe are notorious “sinks” for a large suite of environmental contaminants1. Polycyclic aromatic hydrocarbons (PAHs) represent one class of pollutants that find their way into these aquatic systems and subsequently, in to sediments1. The current assessment of PAHs within small craft harbour (SCH) sediment in Nova Scotia focuses on bulk concentration but demonstrates a disregard for source apportionment of these compounds. This is particularly important as PAHs can be derived from multiple sources including pyrolytic (combustion), petrogenic (petroleum derived), and natural sources2. More importantly, different PAH sources differ in their toxicological impacts and their bioavailability in aquatic environments, making their source apportionment important for both liability and sustainability of SCH systems3. There is overwhelming evidence that PAHs found within SCH sediment of the Gulf region of Nova Scotia are produced primarily from combustion processes, with wood combustion as the largest emission source (Fig. 1-3). Residential fireplaces, controlled burning, and forest fires all represent possible contributors. The small contribution of coal/coke (7%) in Fig. 2 is very likely from historical steel mill/coke oven processes that occurred in other areas of the province and is present with the Gulf region due to atmospheric movement and subsequent deposition into harbour systems. Pictou Landing harbour differs slightly from other SCHs as it reflects direct petroleum inputs and petroleum combustion sources, as reflected in Fig. 1. This suggests a greater likelihood of point source emissions surrounding the harbour (petroleum spills, exhaust from local boats). Objective To characterize and assess source apportionment of PAH compounds using PAH diagnostic ratios for nine SCHs across the Gulf region of Nova Scotia. Fig. 1. Double ratio plot of (anthracene/anthracene + phenanthrene) against (fluoranthene/fluoranthene + pyrene) (Yunker et al. 2002) for nine Gulf region SCHs for 2000-present. Of the ratios produced (n=112), 95% reflect combustion processes, while 5% suggest petroleum and/or petroleum combustion process inputs. Pleasant Bay Harbour, N.S. Photo credit: Branimir Photo Research Strategy Federal Marine Sediment Sampling Program (MSSP) data from 2000 to present Gulf region of Nova Scotia: Selection of nine SCHs Application of PAH diagnostic ratios to determine PAH emission sources Conclusions Of the nine harbours evaluated, there is a strong combustion signature across the region Of possible combustion sources, wood combustion represents the greatest contributor, with coal and automobile sources to a lesser extent PAH diagnostic ratios are creative management tools for establishing source apportionment of PAHs for harbour decision makers Fig. 2. Application of (Dickhut et al. 2000) benz[a]anthracene/chrysene (BaA/Chr) single ratio transition values to Gulf region SCH sediment data. Of the (n=118) ratios produced, 45% suggest wood combustion as a PAH source. PAHs are always released as mixtures and within these mixtures they contain molecular concentration ratios4. The proportional integrity of PAH mixtures is maintained over time, therefore, the application of PAH diagnostic ratios can provide insight to emission sources5. PAH diagnostic ratios have been studied extensively within the academic literature as an indicator of PAH sources. Acknowledgements Public Services and Procurement Canada (PSPC) and Dillon Consulting Limited have been instrumental in helping to gather historical sediment data to make this study possible. Thank you to the Nova Scotia Graduate Scholarship (NSGS) and the SRES Legacy Scholarship for funding this research. References Lima et al. 2005. Combustion-derived polycyclic aromatic hydrocarbons in the environment—a review. Environ Forensics, 6(2), 109-131. McCready et al. 2000. The distribution of polycyclic aromatic hydrocarbons in surficial sediments of Sydney Harbour, Australia. Mar Pollut Bull, 40(11), 999-1006. Bright et al. 2012. Practical Methods for the Discrimination of PAH Sources to Sediments at Fisheries and Oceans Small Craft Harbours: Creosote Inputs Versus Petroleum or Combustion Based Releases. Presented to: RPIC 2012 Federal Contaminated Sites Workshop. Retrieved from: http://www.rpic-ibic.ca/documents/2012_fcs_presentations/Bright_E.pdf (Accessed 02.14.16) Tobiszewski, M., & Namieśnik, J. 2012. PAH diagnostic ratios for the identification of pollution emission sources. Environ Pollut, 162, 110-119. Zemo, D.A. 2009. Use of parent polycyclic aromatic hydrocarbon (PAH) proportions to attribute PAH sources in sediments: a case study from the Pacific Northwest. Environ Forensics, 10(3), 229-239. Yunker et al. 2002. PAHs in the Fraser River basin: a critical appraisal of PAH ratios as indicators of PAH source and composition. Org Geochem, 33(4), 489-515 Dickhut et al. 2000. Automotive sources of carcinogenic polycyclic aromatic hydrocarbons associated with particulate matter in the Chesapeake Bay region. Environ Sci Technol, 34(21), 4635-4640.  Image credits: http://www.lounatale.com/travel-writing/view/maritimes-cape-breton https://chem.libretexts.org/Core/Organic_Chemistry/Arenes/Properties_of_Arenes/Polycyclic_Aromatics http://www.branimirphoto.ca/stock/pop_html/canada/atlantic/NS-1010-2701.html Watermark photo: http://tasteofnovascotia.com/member-profile-sharla-cameron-halls-harbour-lobster-pound-restaurant/ Fig. 3. Application of (Dickhut et al. 2000) benzo[b]fluoranthene/benzo[k]fluoranthene (Bbf/Bkf) single ratio transition values to Gulf region SCH sediment data. Of the (n=101) ratios produced, 63% suggest wood combustion as a PAH source.