Evidence of long- range transport of toxic metals in High Arctic wetlands

High Arctic peatlands are among the most remote and climate- sensitive ecosystems on Earth. While they are globally recognised as important carbon sinks, their capacity to accumulate and archive atmospheric pollutants remains underexplored. This study investigates the deposition and accumulation of trace metals in peat cores from four sites across the Canadian High Arctic (Axel Heiberg Island, Banks Island, Ellesmere Island, and Kugaaruk) to assess the influence of long- range atmospheric transport on contaminant inputs.

Peat cores were collected from wetlands and analysed using inductively coupled plasma mass spectrometry (ICP-MS) for lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), chromium (Cr), and nickel (Ni). Concentration profiles were evaluated alongside enrichment factors (EFs), calculated relative to crustal reference elements, to distinguish anthropogenic contributions from natural lithogenic sources.

Across all sites, distinct enrichment of Pb, Cd, and Zn was observed in the upper peat layers, with enrichment factors exceeding 5 at several depths, particularly on Axel Heiberg and Ellesmere Island. In contrast, Cr and Ni displayed near-crustal EF values (close to 1), suggesting primarily natural origins. The enrichment patterns for Pb and Cd indicate deposition peaks likely corresponding to periods of heightened industrial emissions in the mid- to late 20th century, consistent with known global trends in atmospheric metal fallout. The widespread detection of anthropogenic metals across geographically isolated High Arctic wetlands underscores the efficacy of long- range atmospheric transport processes in dispersing contaminants from lower- latitude industrial regions.

These findings demonstrate that Arctic peatlands serve as dual-function environmental archives: they sequester both carbon and anthropogenic pollutants over millennial timescales. However, as climate warming intensifies permafrost thaw and alters hydrological and biogeochemical conditions, these historically sequestered metals risk remobilisation into Arctic freshwater systems. Such release could have cascading effects on sensitive ecosystems and local food webs, further illustrating the interconnectedness of global human activity and polar environmental change.

By coupling concentration and enrichment factor analyses across multiple Arctic sites, this study provides the first regional- scale evidence of widespread metal enrichment in High Arctic peatlands attributable to atmospheric transport. It highlights the necessity of incorporating contaminant storage and release processes into broader models of Arctic biogeochemical cycling. Understanding how these systems mediate both carbon and pollutant fluxes under a warming climate is critical for predicting future Arctic ecosystem responses and for developing effective environmental protection strategies.