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Brittany Huhmann
Washington University in St. Louis
Advisor: Jeffrey G. Catalano
Abstract
Much of the hematite on the surface of Mars is believed to have formed in acid sulfate conditions. However, the presence of Ni(II) in Martian hematite spherules may suggest a different origin for these features. Ni(II) adsorption, a key step required for incorporation in aqueous conditions, is expected to be unfavorable under acidic conditions, and thus Ni-rich hematite is not expected under the postulated acid sulfate conditions that formed the associated sulfate mineral deposits. The present study addresses this issue by investigating the effects of pH on Ni(II) adsorption to hematite powder. The results show that Ni(II) adsorption increases with pH, with >50% adsorption occurring at about pH 5 and near-100% adsorption beyond pH 6. Ongoing studies are investigating whether sulfate enhances nickel adsorption at low pH, as has been observed with other divalent cations. Finally, Fe(II) may also have been present if hematite spherule formation occurred via an oxidative pathway, and future work will investigate its effect on Ni(II) incorporation into hematite. These studies will place constraints on the chemical conditions under which Ni-bearing hematite may form.
Brittany Huhmann is currently pursuing a bachelor's degree in Earth and Planetary Sciences at Washington University in Saint Louis. She is part of the four-year Pathfinder Program in Environmental Sustainability, which has allowed her to collaborate with other students from biology, anthropology, and environmental studies to apply concepts from their coursework to interdisciplinary case studies. She has also served as a teaching assistant for the program's freshman courses, which has enabled her to mentor other students interested in the field. Within her major, she has chosen to focus on geochemistry, and she hopes that this focus will allow her to work at the interface between the basic materials of ecosystems and the organisms that inhabit those ecosystems. In accordance with these interests, she has worked for the Missouri Department of Conservation studying gene flow in endangered fish species and for the US Geological Survey to evaluate Least Tern habitat on the Platte River.
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