Differential accumulation of PAHs, elements, and Pb isotopes by five lichen species from the Athabasca Oil Sands Region in Alberta, Canada

Abstract

A 2014 case study investigated the relative accumulation efficiency of polycyclic aromatic hydrocarbons (PAHs), total sulfur (S), total nitrogen (N), major and minor elements and Pb isotopes in five common lichen species at three boreal forest sites in the Athabasca Oil Sands Region (AOSR) in northeastern Alberta, Canada to identify the optimum lichen species for future biomonitoring. Differences in concentrations of PAHs, multiple elements, and Pb isotopes in fruticose (Bryoria furcellata, Cladina mitis, Evernia mesomorpha) and foliose (Hypogymnia physodes and Tuckermannopsis americana) lichens were found along a 100 km distance gradient from the primary oil sands operations. Integration of insights from emission source samples and oil sands mineralogy in consort with aerosol collection indicates incorporation of more fine particulate matter (PM) into foliose than fruticose lichen biomass. Contrasting PAH with element concentrations allowed lichen species specific accumulation patterns to be identified. The ability of lichen species to incorporate different amounts of gas phase (S and N), petrogenic (V, Ni, Mo), clay (low Si/Al and more rare earth elements), and sand (higher Si/Al and Ti) components from the oil sand operations reflects aerosol particle size and lichen physiology differences that translate into differences in PM transport distances and lichen accumulation efficiencies. Based on these findings Hypogymnia physodes is recommended for future PAH biomonitoring and source attribution studies.

Keywords: Foliose and fruticose lichens; Major and minor elements; Oil sands; PAHs; Pb isotopes.