Biogeochemical cycling of mercury in terrestrial environments: Emphasis on mercury uptake by black spruce (Picea mariana) in peatlands and impacts of invasive earthworms on soil mercury cycling

Abstract

Mercury (Hg) is a naturally occurring element but has become an important environmental pollutant mostly due to human activities. This thesis focuses on deposition of mercury to terrestrial environments where vegetation and soil act as important sinks of mercury. The first study, focuses on the uptake of elemental mercury by black spruce trees in peatland environments to assess their potential ability to be used as passive atmospheric biomonitors. The second study, focuses on the impacts of invasive earthworms to mercury cycling in the soil. Earthworms feed primarily on organic rich forest floor which coincidentally complexes the largest amounts of mercury. Heavy earthworm invasions result in the complete consumption of the forest floor, which likely alters mercury cycling in forest soils. Two mass balance approaches are used to assess the mercury dynamics of these soils.