Trace elements associated with the coarse and fine aerosol fractions in Sphagnum moss within the Athabasca Bituminous Sands region

Abstract

The Athabasca Bituminous Sands industry in Alberta has dramatic impacts on the economy of the province. Nevertheless, with increasing industrial operations, environmental concerns are also raised regarding the contamination of air and water with trace elements (TEs). To better assess the influence of the industry to the surrounding ecosystems, it is crucial to determine the TEs associated with the coarse and fine aerosols which differ in their size and chemical composition. Here, Sphagnum mosses were used as biomonitors of atmospheric deposition, and contributions from bulk deposition and fine aerosols were estimated by determining the abundance of TEs in bulk moss and acid soluble ash (ASA). The ash content of moss clearly increased with decreasing distance towards industry, reflecting increasing mineral dust input. Total concentrations of almost all the elements increased towards industry, while the acid soluble concentrations of the elements varied. Exhibiting high acid soluble proportions, Al, Y, and the elements enriched in bitumen (V and Ni) might be largely contributed by the ultrafine clay minerals such as kaolinite and illite. In contrast, Th, Mo (enriched in bitumen), Pb, Sb, and Tl showed low acid soluble proportions, which could be more influenced by the deposition of larger minerals such as feldspars and heavy minerals (e.g., monazite, zircon) from bituminous sands. Silver and Cd, behaving more like micronutrients such as Cu and Zn, were more impacted by plant uptake than mineral dust deposition. The above results were supported by the calculated enrichments of TEs, particle size distribution, X-ray diffraction, and principal component analysis. The study highlights the importance and necessity to determine the chemical reactivity of TEs in atmospheric dusts when evaluating their associated health risks to living organisms.