Evidence for contemporary soil mercury contamination from late 1700s North American fur trade

Soils from Grand Portage National Monument, MN, are locally higher in mercury (Hg) than those of the western Great Lakes region, with enrichment up to 21-fold at its fur trade depots compared to off-site locations. A potential historical source was the trade of vermilion (containing HgS) along the Grand Portage Trail during the 17–19th centuries. Mercury stable isotope values in trade site soils coincided with curated museum vermilion and relevant global cinnabar mines. We suggest that soil Hg enrichment may serve as a tracer for exchange networks and colonial expansion through this period and an indicator of Anthropocene environmental impact.