Mixed trends in heavy metal-enriched fugitive dust on National Park Service lands along the Red Dog Mine haul road, Alaska, 2006-2017.

This study presents the status and trends of long-term monitoring of the elemental concentrations of zinc (Zn), lead (Pb), and cadmium (Cd) in Hylocomium splendens moss tissue in Cape Krusenstern National Monument (CAKR), Alaska, adjacent to the Red Dog Mine haul road. Spatial patterns of the deposition of these metals were re-assessed for the period from 2006-2017 following an identical study that assessed trends between 2001-2006. In contrast to the widespread and steep declines in Zn and Pb levels throughout most of the study area between 2001-2006, this study showed more mixed results for 2006-2017. At distances within 100 m of the haul road, only Pb decreased between 2006-2017. At distances between 100-5,000 m, however, both Zn and Cd decreased between 2006-2017, with high probabilities of decrease and percent decreases of 11-20% and 46-52% respectively. Lead did not decrease in any of the more distant areas. Following earlier work on lichen species richness in the study area, it appears that 2017 Zn levels are approaching those associated with "background" lichen species richness throughout a relatively large proportion of the study area at least 2,000 m from the haul road and several km from the port site. The findings in this study may be used to plan additional mitigation measures to reduce Zn deposition related to impacts on lichen communities.

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The authors have declared that no competing interests exist.