Abinash Agrawal (Committee Member), Don Cipollini (Committee Member), Chad.R Hammerschmidt (Advisor)
Master of Science (MS)
Cycling of mercury (Hg) and monomethylmercury (MMHg) in forest ecosystems can affect exposures of terrestrial and aquatic wildlife within the watershed. Litterfall has been posited to be a major source of MMHg and total Hg to the forest floor; however, the origin of MMHg associated with tree foliage is largely unknown. I tested the hypothesis that leaf MMHg would be controlled by root uptake and thereby proportional to levels in soil. Fresh leaves and associated soil samples were sampled from nine tree species (deciduous and coniferous) at 30 locations spanning a 1145 km2 area in southwest Ohio, a region presumed to have relatively homogeneous atmospheric deposition of Hg and MMHg. Concentrations of Hg species in tree leaves were unrelated to those in soil. In contrast, tree genera and trunk diameter were dominant variables influencing Hg levels in tree foliage. The fraction of total Hg as MMHg was relatively constant among all genera and averaged 0.4%. Results of this study suggest that uptake of gaseous Hg0 from the atmosphere is the dominant source of total Hg in foliage and that MMHg is formed by in vivo transformation of Hg(II) in proportion to the concentration accumulated. Via litterfall, it appears that processes associated with tree leaves are a major source of total Hg and MMHg to the forest floor.
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
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