Establishing baseline levels of extractable trace metals in marine surface sediment of the Canadian Arctic

A comprehensive spatial assessment of extractable trace metal, including rare earth element (REE), distribution in the Canadian Arctic was conducted based on terrestrial and marine surface sediment samples to evaluate the current state of metal contamination. Major and trace element concentrations were determined by HNO₃-HCl partial digestion and triple quadrupole inductively coupled plasma mass spectrometer measurements. Results revealed significant regional variations in trace metal concentrations (e.g., Cr = 5-96 μg/g; Zn = 9-139 μg/g; ΣREE = 21-358 μg/g), with a clear West-East gradient. The highest non-REE metal concentrations are observed in Beaufort Sea and Amundsen Gulf, highlighting the influence of the Mackenzie River. Conversely, the REEs are concentrated near the coasts underlain by Canadian Shield rocks in the south-central and eastern Canadian Arctic. Normalized REE distribution patterns show an enrichment in light REEs compared to heavy REEs. The pollution indices indicate generally low enrichment or contamination, although few samples exhibit moderate arsenic enrichment/contamination in the Beaufort Shelf and Jones Sound. Based on the Canadian sediment quality guidelines, most samples had metal concentrations below the Probable Effects Level. However, concentrations exceeding this threshold were measured for arsenic (> 41.6 μg/g) and nickel (> 42.8 μg/g) in the Amundsen and Coronation gulfs, Jones Sound and Baffin Bay. Despite localized contamination, the trace metal distribution exhibit natural concentrations influenced by the regional geology and sedimentary processes. This geochemical baseline offers new insights from previously uncharacterized areas, improving our understanding of the sources and fate of trace metals and the accuracy of environmental monitoring of the Canadian Arctic.