This study evaluates ore transport and other mining activities on metal levels in the remote Arctic ecosystem of Cape Krusenstern National Monument (CAKR) in northwestern Alaska. This monument is 50 km SW of Red Dog Mine, one of the world’s largest Pb–Zn mines. The Delong Mountain Transportation System (DMTS) haul road traverses approximately 32 km through CAKR and is used for ore concentrate to be transported from the mining and milling site to the port site. Metal concentrations and Pb isotopic compositions were measured in soil and porewater samples at 30 sites from six transects perpendicular to the mining haul road. Geochemical signatures were used to determine spatial patterns of mining-associated metals in peat soils and to assess the relative importance of metals in these soils from mining operations and from local parent material.
This study provides evidence of mining associated metals (e.g., ore concentrate) in peat soils collected along the haul road in CAKR. Metals originating from mining activities are observed up to 1000 m from the haul road and at depths approaching 30 cm in the soil profile. The highest metal concentrations were observed at sites closest to the haul road. Metal concentrations decrease with distance from the haul road in both bulk soil and porewater samples. Enrichment factors utilizing metal to titanium ratios were employed to distinguish anthropogenic metal sources from natural sources. The co-emission of road material derived from local rock with ore concentrates from the haul road results in similar enrichment factors for samples collected near the road and at 1000 m. Lead isotope ratios indicate a linear trend such that there are two dominant sources of metals in CAKR, ore concentrates and natural geology. Although global emissions from fossil fuel consumption and industrial activities may contribute to metal levels in the region, metal levels from those distant sources are not expected to vary across CAKR, especially in relation to the haul road.