Physical Sciences and Mathematics Commons^™

Biogeochemical Evolution Of Cryoconite Holes On Canada Glacier, Taylor Valley, Antarctica, Elizabeth A. Bagshaw, Martyn Tranter, Andrew G. Fountain, Kathleen A. Welch, Hassan J. Basagic, W. Berry Lyons

Geography Faculty Publications and Presentations

The cryoconite holes of the McMurdo Dry Valleys are simple, closed biogeochemical systems involving water, ice, mineral and organic debris, which serve as ecosystems for consortia of microorganisms. This study is the first to document the seasonal and annual chemical evolution of solutes in cryoconite holes. Samples of glacier ice, frozen cryoconite holes and those containing water were collected during the austral summer of 2005–2006. The isolation age was calculated from the excess Cl‾ in the holes, and varied from 0 to 5 years (a), consistent with the last hot summer when the cryoconite holes were open to the atmosphere. …

Pend Oreille River Model: Model Scenario Simulations, Robert Leslie Annear, Chris Berger, Scott A. Wells

Civil and Environmental Engineering Faculty Publications and Presentations

The Idaho Department of Environmental Quality is interested in developing a temperature and water quality Total Maximum Daily Load (TMDL) allocation for the Pend Oreille River between the Long Bridge near the historical Lake Pend Oreille outlet and Albeni Falls Dam (U.S. Army Corps of Engineer’s reservoir) as shown in Figure 1.

This management scenario report is an update of a prior report. The management scenarios had to be rerun because of a modeling error made with the outflows rate of Albeni Falls Dam. The new calibration error statistics were compared with the old statistics in Appendix B: Model Calibration …

Environmental Controls On The Landscape-Scale Biogeography Of Stream Bacterial Communities, Noah Fierer, Jennifer L. Morse, Sean T. Berthrong, Emily S. Bernhardt, Robert B. Jackson

Environmental Science and Management Faculty Publications and Presentations

We determined the biogeographical distributions of stream bacteria and the biogeochemical factors that best explained heterogeneity for 23 locations within the Hubbard Brook watershed, a 3000-ha forested watershed in New Hampshire, USA. Our goal was to assess the factor, or set of factors, responsible for generating the biogeographical patterns exhibited by microorganisms at the landscape scale. We used DNA fingerprinting to characterize bacteria inhabiting fine benthic organic matter (FBOM) because of their important influence on stream nutrient dynamics. Across the watershed, streams of similar pH had similar FBOM bacterial communities. Streamwater pH was the single variable most strongly correlated with …

Pend Oreille River, Box Canyon Model: Model Scenario Simulations, Chris Berger, Robert Leslie Annear, Scott A. Wells

Civil and Environmental Engineering Faculty Publications and Presentations

The Washington Department of Ecology is interested in developing a temperature Total Maximum Daily Load (TMDL) allocation for the Pend Oreille River between the Albeni Falls Dam (U.S. Army Corps of Engineer’s reservoir) and Box Canyon Dam as shown in Figure 1. The Pend Oreille drainage basin is shown in Figure 2. An existing model of the Box Canyon reach was updated from CE-QUALW2 Version 3.0 to Version 3.5. This current research involves improving the calibration of the original model (1997 and 1998) and expanding the model using 2004 as an additional data set for calibration.

The use of field …

Modeling Effects Of Channel Complexity And Hyporheic Flow On Stream Temperatures, Chris Berger, Scott A. Wells

Civil and Environmental Engineering Faculty Publications and Presentations

Stream temperatures are affected by multiple forcing functions, including surface heat exchange (including solar radiation, evaporation, conduction, and net long wave radiation) and hyporheic flows. Each of these forcing functions is directly influenced by the level of channel complexity in the stream channel and riparian shading. The interrelationship between channel complexity, hyporheic flow and stream temperature is highly complex, and efforts to manage for habitat diversity by managing channel complexity could result in unintended consequences on stream temperature. When planning modifications to stream channel complexity, consideration should be given to the effects such moderations could have on stream temperatures.

Urbanization …

Biogeochemical Stoichiometry Of Antarctic Dry Valley Ecosystems, John E. Barrett, Ross A. Virginia, W. Berry Lyons, Diane M. Mcknight, John Charles Priscu, Peter T. Doran, Andrew G. Fountain, Diana H. Wall, D. L. Moorhead

Geography Faculty Publications and Presentations

Among aquatic and terrestrial landscapes of the McMurdo Dry Valleys, Antarctica, ecosystem stoichiometry ranges from values near the Redfield ratios for C:N:P to nutrient concentrations in proportions far above or below ratios necessary to support balanced microbial growth. This polar desert provides an opportunity to evaluate stoichiometric approaches to understand nutrient cycling in an ecosystem where biological diversity and activity are low, and controls over the movement and mass balances of nutrients operate over 10–10⁶ years. The simple organisms (microbial and metazoan) comprising dry valley foodwebs adhere to strict biochemical requirements in the composition of their biomass, and when activated …

Observation Of Microslip Dynamics At High-Speed Microcontacts, Brian Borovsky, Adam M. Booth, Erin Manlove

Geology Faculty Publications and Presentations

The high-speed tribological properties of microscale contacts are studied using an indenter probe and quartz crystal microbalance. Elastic and dissipative shear forces are monitored as a function of contact radius for sapphire/gold interfaces with an adsorbed octadecanethiol monolayer. We observe shear force transitions understood as taking the interface from slipping to stuck conditions. We relate this behavior to the presence of interfacial microslip. Dynamic modeling shows that our observations are consistent with an interface that, when sliding, experiences full slip during half of each cycle. We discuss the implications for this technique as a sensitive probe of sliding friction.