A Continental and Marine-Influenced Tree-Ring Mercury Record in the Old Crow Flats, Yukon, Canada

Abstract

Gaseous elemental mercury (Hg0) concentrations in the atmosphere have been increasing due to anthropogenic activities since the onset of colonial mining in the 17th century. However, accurate measurements of atmospheric Hg, including temporal trends, are mostly limited to recent decades. Natural environmental archives including tree rings show promise for reconstructing atmospheric concentrations of Hg0. In this paper, we present a new white spruce (Picea glauca) tree-ring Hg record (1696–2005) from the Old Crow Flats in northern Yukon. The record we present shows an increase in tree-ring Hg concentration (a proxy for gaseous Hg0 concentration) between 1748 and 1990 at a rate of +3.3% per year. A decrease in measured Hg is observed at the end of the record between 1990 and 2005, which may reflect the success of international regulations to reduce emissions including Hg. When compared with two other sites (a continental and marine location) in northwest Canada, there is not only some coherence in Hg trends at the regional scale but also some unique differences, suggesting that the location may influence atmospheric Hg0 available for assimilation. Further local factors within a site, such as soil moisture, may also affect the efficiency of this uptake. Results from this study highlight the need to better understand intra-site and inter-site differences in measured tree-ring Hg, and we recommend the continued development of a spatially resolved tree-ring Hg network in the northern boreal forest. Such records will be useful for developing better atmospheric Hg and global Hg models.

The Multi-Compartment Hg Modeling and Analysis Project (MCHgMAP): Mercury modeling to support international environmental policy

“…Since lakes and forested areas are widely distributed around the world, sediment core and tree-ring Hg data allow for the potential development of a global network of multi-century Hg timeseries (Eccles et al, 2020) to evaluate global atmospheric Hg emissions, as well as the spatial footprint and environmental impact of local Hg(0) emissions from point sources (Clackett et al, 2021;Navrátil et al, 2017Navrátil et al, , 2018Perone et al, 2018;Schneider et al, 2019;McLagan et al, 2022).…”

Critical Analysis of the Past, Present, and Future of Dendrochemistry: A Systematic Literature Review

“…Recently, more research has emphasized specific elements with more promising results from elements like mercury (Hg). Several studies have been published on the ability of trees to be used as recorders of Hg emissions in both regional and national settings [9,32,77,78,[123][124][125]. However, comparing any of these studies can be difficult due to site-and region-specific influences and individual studies using different species of trees.…”