Using epiphytic lichens as biomonitors of atmospheric mercury and dust at a historical gold mine tailings site in Nova Scotia, Canada

Abstract

Historic gold mining in Nova Scotia, Canada, produced mercury (Hg)-contaminated tailings from the 1860s to 1940s that were deposited into the environment and subsequently abandoned upon mine closures. Today, these degraded landscapes are potential sources of contaminated dust, posing risks to human and ecosystem health. The primary objective of this thesis was to use epiphytic lichens (<i>Usnea</i> and <i>Platismatia</i> spp.) as biomonitors of airborne Hg in the Montague Gold District. Spatial distribution patterns of Hg in lichens showed hotspots near tailings deposits, reflecting greater inputs of Hg from windblown tailings, volatilization processes, throughfall, and/or stemflow. The Hg in the lichens was assessed in two ways, including surface-deposited and absorbed Hg fractions. These results suggested that gaseous Hg from the tailings was a more important source of the element compared to particulate-bound Hg. These lichens proved to be effective biomonitoring tools at Montague for assessing Hg pollution and identifying risk areas.