EIGER FELLOW SINCE AUGUST 2005

Hiking in Panama

EDUCATION

Virginia Tech, Blacksburg, VA                             
M.S., Civil Engineering/Geotechnical Engineering (Geoenvironmental concentration), May 2003

University of Tennessee, Knoxville, TN
B.S., Civil and Environmental Engineering, August 2000

ADVISOR

Professor John Little, Department of Civil and Environmental Engineering

EIGER INTERSHIP

July 2007 to May 2008
Swiss Federal Institute for Aquatic Science and Technology (Eawag), Kastanienbaum, Switzerland
Interactions at the Sediment/Water Interface: Studied how oxygen fluxes at the sediment/water interface are affected by variable turbulence levels (wind-induced seiching in lakes), working with Drs. Alfred Wuest and Dan McGinnis. Also studied how microbial populations (specifically, Mn-reducing bacteria) vary with depth as a function of the sediment oxic zone location, working with Dr. Helmut Buergmann.

CURRENT RESEARCH

Transient sediment oxygen demand and biogeochemical cycling as a function of oxygen concentration and turbulence

Aquatic ecosystems, drinking water quality and hydropower plants are all negatively impacted by depleted levels of dissolved oxygen (DO). Hypolimnetic oxygen depletion may result in the release of iron (Fe) and manganese (Mn) from the sediments, thereby decreasing water quality and increasing drinking water treatment costs. To address these issues, hypolimnetic oxygenation diffuser systems are being used increasingly by drinking water utilities to replenish DO while preserving stratification.

This project focuses on how the cycling of DO, Fe and Mn at the sediment-water interface is impacted by diffuser-induced variations in turbulence and DO levels in the water column. Experiments are being performed using a network of measurements at a drinking-water-supply reservoir (Carvin’s Cove) equipped with an oxygenation diffuser system near Roanoke, Virginia, USA. In-situ porewater analyzers (“peepers”) are being used to obtain soluble (<0.45 micron) Fe and Mn profiles.  A profiling lander is currently being used in-situ to track how DO, temperature, pH and redox potential are changing at the sediment-water interface as a function of oxygenation. Fe2+ and Mn2+ microelectrode and DO microsensor profiles of sediment cores are also being obtained in coordination with peeper deployments and lander measurements. Preliminary data show that sediment-water fluxes of DO, Fe and Mn vary significantly as a result of diffuser operations. Our results indicate that hypolimnetic oxygenation may be successfully used to improve drinking water quality by increasing DO levels and subsequently decreasing Fe and Mn levels within the bulk water column. This research will be used to gain further understanding of how DO and turbulence levels impact mechanisms of oxygen transport, changes in sediment microbial populations and corresponding sediment-water biogeochemical fluxes.

CONTACT INFORMATION

lebryan1@vt.edu

Page last updated 11/10/09