Reactivity of Biogenic Manganese Oxides Associated with an Environmental Remediation System at a Superfund Site.

Environmental remediation of contaminated sites requires a detailed understanding of the biogeochemical processes occurring within remediation systems. In the Farm Lot 86 Superfund site (Raleigh, NC), dissolved manganese from influent groundwater is being microbially oxidized and precipitated, resulting in manganese oxide sludge formation in system components throughout the pump-and-treat system. To better understand manganese oxide formation, we conducted a multipronged spectroscopic and microbiolocial investigation of the sludge, which revealed the presence of layer type Mn(IV) oxides containing significant concentrations of cobalt(III), zinc(II), and barium(II) adsorbed to specific crystallographic sites. Efforts to isolate manganese oxidizing organisms resulted in isolation of phylogenetically diverse array of fungi. These organism produce layer-type Mn(IV) oxides that have structural characteristics, including association with organic matter and quamtity of crystallographic vacancies, that distinguish them from other Mn oxides and affect their sorption and redox reactivity. Electrochemical investigations of these mycogenic oxides reveal relationships between the incorporation of metals, mineral structure, and the redox reactivity.