Influence of climate change on the distribution of mercury and selected toxic metals in an Arctic Fjord

• Geochemical indices and toxic metals levels classify Kongsfjorden into inner and outer zones. • Toxic metals stem from long-range, natural, and climate-induced sources. • Glacial melt, permafrost thaw, and sea ice loss add toxic metals to the fjord. • Ecological risk in Kongsfjorden indicates a system under a moderate risk level. Toxic metals (TM) originating from diverse sources undergo regional and long-range oceanic transport into Arctic fjord ecosystems, profoundly impacting ecosystem health. Despite the ecological sensitivity of the Kongsfjorden ecosystem, comprehensive studies on TM distribution remain scarce. This study investigates TM concentrations in Kongsfjorden surface sediments from 2017 to 2019, emphasizing spatial distribution, source identification, and ecological risk assessment. Sedimentological and geochemical analyses delineate the fjord into two distinct zones: inner and outer, driven by the complex interplay of oceanic inflow, glacial discharge, and sediment deposition, which creates pronounced environmental gradients. TM concentrations were generally higher in the outer fjord, with several metals exceeding established reference thresholds, indicating remobilization of historically accumulated contaminants. Statistical analyses demonstrate that natural sources, long-range transport, and climate-related factors collectively influence TM accumulation. Positive Matrix Factorization modeling reveals that long-range transport, via atmospheric and oceanic pathways, predominantly contributes mercury (Hg) and lead (Pb) to the fjord sediments. Ecological risk assessments identify arsenic (As) and cadmium (Cd) as contaminants of moderate concern, posing substantial environmental risks corroborated by integrated risk indices. These findings underscore the critical need to implement a long-term monitoring program to evaluate TM ecological impacts and support effective environmental management in Kongsfjorden, thereby advancing the Arctic Council’s objectives for environmental protection and sustainable development.