Regional geochemical survey of Canadian Arctic sediments: insights into provenance, sediment dynamics and trace metal enrichment

Abstract

Major and trace element contents, grain size distribution and total organic carbon contents were measured in 141 marine surface and terrestrial sediment samples to study modern sediment dynamics in the Canadian Arctic (CA) and to provide an assessment of metal enrichment for V, Zn, Mn and Fe. Samples were collected from different areas between Baffin Bay and the Beaufort Sea during the ArcticNet 2016–2022 expeditions onboard the Canadian Coast Guard icebreaker Amundsen. Geochemical data combined with multivariate statistical analyses allowed the division of the CA into three chemical clusters (CC) and four regional provinces. Central CA (CC#1) and southeastern CA (CC#2) are mainly composed of relatively coarse sediments rich in detrital carbonates (Ca, Mg) and siliciclastic elements (Si, K, Zr), respectively, reflecting coastal erosion of surrounding land (e.g., Victoria Island, Baffin Island) and transport of sediment-laden sea ice. The sediments of CC#3, comprising western and eastern CA, are characterized by organic carbon and Fe–Mn oxyhydroxides. Western CA, which is also characterized by fine-grained aluminosilicates, is influenced by the Mackenzie River discharge, while eastern CA is shaped by polynyas and glacial erosion. The highest concentrations of V and Zn are recorded in the western CA. Over the whole region, significant positive correlations of Al with Zn, V and Fe suggest that lithogenic-derived inputs influence the distribution of these metals in sediments from the CA and that Fe oxides represent the main carrier phase. In western CA, Mn displays positive but weaker relationships with Al and Fe, suggesting a mixed source of Mn oxyhydroxides linked to both detrital fractions and authigenic processes near the sediment-water interface. High terrestrial Mn oxyhydroxide inputs from the Mackenzie River are remobilized and transported to areas with lower oxygen consumption in sediment, i.e., the Amundsen Gulf and Banks Island coasts, which leads to surface sediment enrichment in Mn. The enrichment factor and the geo-accumulation index, two pollution indices commonly used for identifying anthropogenic metal inputs, were also studied to evaluate their suitability in the context of this study. Discrepancies from the normalization of metals with a geochemical background and a normalizing element revealed that pollution indices should be used with caution. Overall, according to the pollution indices and the regional survey, the surface sediments of the CA show minor enrichment in trace metals and thus present natural concentrations relative to regional background values.