Bacteria are ubiquitous in the environment and are known to affect metal transport and speciation through surface adsorption reactions. Under environmental stress, certain bacteria form a tough, dormant cell type known as a spore. In natural systems, these spore cells may also participate in adsorption reactions; however, their reactivity is likely different than vegetative cells due to their differentiated cell structure. In this research we develop a method to determine the proportions of active bacterial cells and spores in natural and lab grown samples. Using fluorescent and bright field microscopy we imaged laboratory grown Bacillus subtilis cultures and quantified the vegetative and spore cell abundances in each image. We performed total cell counts for the fluorescent microscopy images using the program CellC. Through differential staining with malachite green and safranin the vegetative cells were easily discerned by color in bright-field microscopy images and counted manually. This research develops an efficient method to quantify proportions of vegetative and spore cells grown within laboratory cultures or natural systems which is essential for investigating spore adsorption reactions.

The use of single-walled carbon nanotubes (SWCNT) within commercial and research-oriented industries is likely to increase in the future. This study aims to understand any potential threats or hazards to localized microbial ecosystems that may arise from the use and subsequent contamination of SWCNT’s. We use isothermal calorimetry to monitor effects of SWCNT on microbial growth. This approach monitors the heat produced by microbes during growth; the amount of heat released is directly proportional to the extent of microbial growth. Isothermal calorimetry is nonspecific and highly sensitive, thus making it possible to monitor growth of natural samples as well as pure cultures. We used three experimental systems to assess the effects of SWCNT on microbes. In the defined system, we grew Bacillus subtilis in a nutrient broth, both in the presence and absence of SWCNT’s, while monitoring heat flow. In the undefined systems, we inoculated water and soils samples with glucose to stimulate growth and monitored heat flow in the presence and absence of SWCNTs. Undefined samples were collected from various representative environments within the King county area. Preliminary results suggest that SWCNT’s are harmful to pure culture. SWCNT interactions with environmental media influence the extent of toxicity to natural microbial communities.

Grain size trends in tsunami deposits, if flow velocities and depths are known, can be used as guides for interpreting similar trends found in paleo-tsunami deposits. Tsunami deposits typically fine inland and upward because the maximum grain size that a tsunami can entrain decreases as the flow loses momentum. Coarsening grain size trends found locally within tsunami deposits are typically interpreted as the result of increased flow velocity due to flow over variations in local topography, or temporal accelerations as multiple waves pass by. A deposit from the 2004 Indian Ocean tsunami on Phra Thong Island, Thailand, provides an alternate explanation for coarsening, both landward and upward. Sediments from tin mining tailing piles left on the beach-ridge plain of the island were entrained by the tsunami and redeposited down-flow (toward land). The tailings are composed of coarser sand than the rest of the sediment transported by the tsunami, so an abrupt increase in grain-size is found behind the tailing piles. I performed grain size analysis on vertical subsamples collected from the 2004 tsunami deposit along a one-kilometer coastal transect, including before and after the tailings. My findings corroborate basic field observations of inland and upward fining, with coarsening at the tailing piles. Using basic sediment transport equations, I can estimate the minimum tsunami depth-velocity product required to suspend sediments from the tailing piles and compare these values to the observed flow characteristics. Vertical fining and coarsening trends within the deposit provide clues for determining temporal changes within the flow and the timing of entrainment of sediments from the tailing piles. In paleo-environments, the natural representation of tailing piles could be sand volcanoes (created by seismic liquefaction of saturated sand under confining pressure), and the flow of a tsunami over these structures might create similar grain size trends.

The retreat of Arctic sea ice extent during summer has attracted considerable attention from the public and science communities, especially since the record shattering minimum set during the summer of 2007. The estimates of sea ice extent are primarily based on retrievals of sea ice concentration (SIC) from passive microwave satellites. These estimates of SIC suffer from contamination from the overlying atmosphere and differences in surface emissivity between first-year and multi-year sea ice. Aerial radiometer data and ship observations have been used to validate SIC estimates and find that these errors vary seasonally. Melt-ponding, water vapor, clouds, wind, rough sea surface, and instrumentation error all contribute to errors in the SIC analyses, and as a result, SIC retrievals from passive microwave tend to be lower than the in-situ observations. Weather systems cause large brightness temperature fluctuations over short time scales spanning a few days. To address these issues, we have been developing numerical weather filters to improve the analysis of SIC from Scanning Multichannel Microwave Radiometer, Special Scanning Microwave Imager, and Advanced Microwave Scanning Radiometer to produce more accurate fields of SIC. Preliminary results show that our methods are able to remove SIC analysis errors due to changes in clouds, relative humidity, and varying surface conditions. Briefly, the weather filter improves SIC estimates due to passing weather systems by: 1) removing spurious SIC estimates over areas of open water; 2) increasing SIC estimates under clouds, and 3) decreasing SIC estimates under relatively dry air. Over first-year sea ice, the corrections to the SIC estimates range from –10% to as much as 30% during summer, while during winter and over multi-year sea ice the corrections are on the order of ±10%. These numerical weather filters may be used to improve retrievals of SIC for the Antarctic, and retrievals of surface temperature.

 Gathering reliable data about the rapidly shrinking sea ice cover of the Arctic is crucial to the study of climate change. Expanding our knowledge of processes beneath sea ice would expand our knowledge of features that significantly affect the global environment, such as ice thickness, melt rate, and ice and ocean temperatures. Yet we currently have no means of deploying instrumentation beneath sea ice short of landing on the ice and operating it manually, which is not practical for long-term measurements. To meet the demand for long-term data on sub-ice processes, our research team is developing an autonomous ice-penetrating probe. We will use the same deployment method as previous researchers, who have succeeded in deploying instrumentation on the ice surface via airplane. Other researchers have developed electrically powered ice penetrating probes, which were successfully deployed in glaciers on land to depths of hundreds of meters. However, these probes required manual operation and were inefficient because of their large size, which was limited by the size of the electronics available at the time. Advances in technology have greatly reduced the size of the electronics required to make useful measurements, enabling our research team to construct an electrically powered ice-penetrating probe that is smaller, more efficient, and autonomous. We are constructing such a probe by creating and testing a succession of design prototypes that are providing insight into the dynamics of ice penetration. Our successful first test article is faster and more efficient than previous models, penetrating through about 40 centimeters of saline ice at a rate of 6.6 meters per hour with an average power input of 500 watts. The final probe design will be capable of deployment via airplane and will autonomously penetrate through sea ice to reach the ocean beneath, enabling the study of sub-ice processes.

The expansion and retreat of the Antarctic ice sheet has a major impact on global sea level. It is difficult to model the extent of the ice sheet earlier than the most recent glaciation, but cosmic ray-produced isotopes in bedrock can be used to place limits on the extent of the ice sheet during past glaciations. Cosmic rays interact with the minerals in bedrock to produce unstable radioactive isotopes. We will measure the relative concentrations of two radioisotopes, aluminum-26 and beryllium-10, both of which are produced in quartz when exposed to cosmic rays. These isotopes increase in concentration when rock surfaces are exposed during interglacial periods, and decay at different rates when bedrock surfaces are shielded by ice during times of glacial cover. The ratio of these two isotopes is therefore sensitive to the length of exposure and burial of the bedrock. One possible complication is subglacial erosion, which can remove pre-exposed surfaces. However, by measuring concentrations of chlorine-36, which has a different production profile, we should be able to separate the effect of subglacial erosion from the glacial history of the surface. For this project, seven bedrock samples were collected on an elevation transect of Mt. Rigby in the Transantarctic Mountains. We separated minerals from whole rock samples and extracted the isotopes by ion-exchange chemistry. Isotope concentrations will be determined by Accelerator Mass Spectrometry.

Episodic Tremor and Slip is a recently discovered spatiotemporal correlation between subtle seismic signals, and slow slip events on subduction zones. Understanding ETS could be a valuable tool as a real time indicator of stress loading in the Cascadia earthquake zone and help predict times of high probabilities for large earthquakes near Seattle [Dagert and Rogers, 2003]. Further, understanding the character and locations of tremor epicenters could facilitate locating the locked segments of the Juan de Fuca plate [Wech and Creager, 2008]. We analyze data from 5 major ETS episodes since 2004 in Northern Washington on the Cascadia subduction zone. They occur every 13-16 months and persist for 15-20 days. During an ETS episode, a reversal in direction of the displacement of the tectonic plate revealed by GPS data is accompanied by weak seismic waves (tremor). Although ETS differs qualitatively from regular earthquakes, the total amount of slip in major ETS episodes corresponds to a magnitude 6.6-6.7 earthquake spread out over 15-20 days. In Cascadia this coupled process of tremor and slip migrates slowly along the interface between the subducting Juan de Fuca plate and the overriding North American plate. Our analysis of 16000 individual tremor locations reveals a new feature of ETS, termed “Rapid Tremor Reversal” (RTR). Occasionally pulses of tremor reverse direction from the general migration and zip backwards over already ruptured regions of the plate interface with velocities 10-20 times greater than the average propagation speed. We suggest that fluid pressure fluctuations can move faster through previously ruptured regions than they can advance through a region that has not yet tremored and slipped. Our preliminary results appear consistent with a fluid mechanism of tremor generation.