Accumulation and secondary release of legacy Pb in high Arctic glaciers of Svalbard: Insights from Pb isotopes

Thanks largely to the ban on leaded gasoline, anthropogenic lead (Pb) emissions have decreased rapidly. However, global warming-induced glacier melting may release legacy Pb, emerging as a secondary pollution source that could adversely impact downstream ecosystems. This study analyzed Pb concentrations and isotopes across various environmental media in Ny-Ålesund, and compiled Pb datasets from Svalbard to quantify Pb sources and investigate potential re-mobilization of Pb due to glacier melting. The Pb concentrations in cryoconite, terrestrial sediments, and fjord sediments are significantly higher than those in local rocks, highlighting the contribution of long-range atmospheric transport. According to the MixSIAR model based on Pb isotopes, 34% of Pb in downstream ecosystems originates from long-range atmospheric transport, whereas atmospheric deposition of cryoconite accounts for up to 51%. We conservatively estimate that approximately 167 t yr^-1 of Pb are discharged into the fjord ecosystem through glacial runoff in Svalbard, predominantly in particulate form (>97%). Fine particulate matter enriched with Pb may pose broader environmental risks. Our study reveals that the re-mobilization of Pb due to glacier melting could become an increasingly significant source of Pb pollution, even in the remote high Arctic.