Congratulations to Patrick Donovan who successfully defended his dissertation May 11, 2015.
Advisor: Joel D. Blum

Abstract: Mercury (Hg) is a neurotoxic pollutant that exists in inorganic (Hg0, Hg2+) and organo-metallic (monomethyl mercury: MMHg) chemical forms. Hg has been released to aquatic environments during its many uses (for gold mining, consumer products and industrial processes), where it can be converted to MMHg. MMHg is a developmental neurotoxin that biomagnifies in the food web, posing a risk to humans and wildlife. Therefore, identifying the distribution of legacy Hg sources, and understanding its transformation to MMHg is of great interest. In this dissertation, we report Hg stable isotope ratios in sediment and food webs from North American streams contaminated by legacy mining and industrial Hg sources. In Chapter 2 and 3, we use Hg isotopes in sediment to fingerprint multiple Hg sources and trace their transport and deposition in streams and estuaries. In Chapters 4 and 5, we use Hg isotopes in biota to identify MMHg formation, degradation and exposure pathways in environments contaminated by historical gold and mercury mining. This dissertation demonstrates that Hg stable isotope measurements can be used to trace the spatial and temporal distribution of Hg sources and investigate biogeochemical processes leading to MMHg bioaccumulation in aquatic environments.