Long-Term Changes in Global and Local Atmospheric Mercury as Recorded in White Spruce Tree-Rings in Central Yukon Territory

摘要

This thesis on Picea glauca trees in central Yukon Territory makes progress toward understanding the use of tree-rings as a natural archive for atmospheric mercury (Hg) over long time-scales, a perspective needed to better understand Hg cycling. Unlike other tree-ring properties, tree-ring Hg appears to be independent of age and incremental growth variations, thereby eliminating the need to correct tree-ring Hg for biological trends. This is the first study in northern Canada to develop a multi-century (1606-2014 CE) tree-ring Hg reconstruction, and corroborates observations from other Hg reconstructions in North America, such as low 17thCE Hg concentrations relative to the post-Industrial era and peak values in the 20th CE. Finally, analysis of a control site and an industrial site where Hg emissions were elevated for ~6 decades demonstrates that local Hg emissions are additive to regional atmospheric Hg concentrations, and retained in tree-ring records proximal to emission sources.