Student Research Projects

Atmospheric Mercury Deposition to Ilex opaca: A comparison of deposition based on foliage location on the tree

Student Emily Brooks, '16
Faculty Mentor(s)
Department Biology
Course CHEM 270: Environmental Chemistry

Abstract

Once released into the environment, through natural and anthropogenic sources, inorganic mercury can convert to methylmercury, a known neurotoxin, that may biomagnify and bioaccumulate in aquatic food chains causing substantial consequences to humans. Leaf and needle surfaces adsorb atmospheric Hg species that are washed off during rain events, which leads to elevated deposition of Hg in throughfall when compared to open precipitation (Graydon et al. 2008; Rea et al. 2001). Our investigation sought to find if the location of the leaf on the tree, based on height and/or distance from the tree trunk, would affect the levels of mercury (Hg) deposited on the foliage of a Ilex opaca. Dry deposition was removed from leaves using deionized water, which was then analyzed for Hg content using a Tekran 2500 Hg analyzer. Overall, the samples contained low levels of mercury indicating minimal Hg deposition during our study. The leaves containing the highest deposition levels were from the bottom outer location and leaves located at the top of the tree contained higher mercury deposition than leaves in the bottom center region. These findings support our hypothesis that the more exposed foliage would have a higher deposition of Hg. Further investigation is needed to determine if the distance of the foliage from the tree trunk affects the Hg levels.