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Oak Ridge (oak + ridge)
Selected AbstractsGeoChip-based analysis of functional microbial communities during the reoxidation of a bioreduced uranium-contaminated aquiferENVIRONMENTAL MICROBIOLOGY, Issue 10 2009Joy D. Van Nostrand Summary A pilot-scale system was established for in situ biostimulation of U(VI) reduction by ethanol addition at the US Department of Energy's (DOE's) Field Research Center (Oak Ridge, TN). After achieving U(VI) reduction, stability of the bioreduced U(IV) was evaluated under conditions of (i) resting (no ethanol injection), (ii) reoxidation by introducing dissolved oxygen (DO), and (iii) reinjection of ethanol. GeoChip, a functional gene array with probes for N, S and C cycling, metal resistance and contaminant degradation genes, was used for monitoring groundwater microbial communities. High diversity of all major functional groups was observed during all experimental phases. The microbial community was extremely responsive to ethanol, showing a substantial change in community structure with increased gene number and diversity after ethanol injections resumed. While gene numbers showed considerable variations, the relative abundance (i.e. percentage of each gene category) of most gene groups changed little. During the reoxidation period, U(VI) increased, suggesting reoxidation of reduced U(IV). However, when introduction of DO was stopped, U(VI) reduction resumed and returned to pre-reoxidation levels. These findings suggest that the community in this system can be stimulated and that the ability to reduce U(VI) can be maintained by the addition of electron donors. This biostimulation approach may potentially offer an effective means for the bioremediation of U(VI)-contaminated sites. [source] Long-term successional forest dynamics: species and community responses to climatic variabilityJOURNAL OF VEGETATION SCIENCE, Issue 4 2010Paul Kardol Abstract Question: Are trees sensitive to climatic variability, and do tree species differ in their responses to climatic variability? Does sensitivity of forest communities to climatic variability depend on stand composition? Location: Mixed young forest at Walker Branch Watershed near Oak Ridge, East Tennessee, USA. Methods: Using a long-term dataset (1967,2006), we analyzed temporal forest dynamics at the tree and species level, and community dynamics for forest stands that differed in initial species composition (i.e., chestnut oak, oak,hickory, pine, and yellow poplar stands). Using summer drought and growing season temperature as defined climate drivers, we evaluated relationships between forest dynamics and climate across levels of organization. Results: Over the four-decade study period, forest communities underwent successional change and substantially increased in biomass. Variation in summer drought and growing season temperature contributed to temporal biomass dynamics for some tree species, but not for others. Stand-level responses to climatic variability were related to the responses of component species, except in pine stands. Pinus echinata, the dominant species in pine stands, decreased over time due to periodic outbreaks of pine bark beetle (Dendroctonus frontalis). These outbreaks at Walker Branch could not be directly related to climatic conditions. Conclusions: The results indicate that sensitivity of developing forests to climatic variability is stand type-dependent, and hence is a function of species composition. However, in the long term, direct effects of climatic variability on forest dynamics may be small relative to autogenic successional processes or climate-related insect outbreaks. Empirical studies testing for interactions between forest succession and climatic variability are needed. [source] Mortality of older construction and craft workers employed at department of energy (DOE) nuclear sitesAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 9 2009John M. Dement PhD Abstract Background The U.S. Department of Energy (DOE) established medical screening programs at the Hanford Nuclear Reservation, Oak Ridge Reservation, the Savannah River Site, and the Amchitka site starting in 1996. Workers participating in these programs have been followed to determine their vital status and mortality experience through December 31, 2004. Methods A cohort of 8,976 former construction workers from Hanford, Savannah River, Oak Ridge, and Amchitka was followed using the National Death Index through December 31, 2004, to ascertain vital status and causes of death. Cause-specific standardized mortality ratios (SMRs) were calculated based on US death rates. Results Six hundred and seventy-four deaths occurred in this cohort and overall mortality was slightly less than expected (SMR,=,0.93, 95% CI,=,0.86,1.01), indicating a "healthy worker effect." However, significantly excess mortality was observed for all cancers (SMR,=,1.28, 95% CI,=,1.13,1.45), lung cancer (SMR,=,1.54, 95% CI,=,1.24,1.87), mesothelioma (SMR,=,5.93, 95% CI,=,2.56,11.68), and asbestosis (SMR,=,33.89, 95% CI,=,18.03,57.95). Non-Hodgkin's lymphoma was in excess at Oak Ridge and multiple myeloma was in excess at Hanford. Chronic obstructive pulmonary disease (COPD) was significantly elevated among workers at the Savannah River Site (SMR,=,1.92, 95% CI,=,1.02,3.29). Conclusions DOE construction workers at these four sites were found to have significantly excess risk for combined cancer sites included in the Department of Labor' Energy Employees Occupational Illness Compensation Program (EEOCIPA). Asbestos-related cancers were significantly elevated. Am. J. Ind. Med. 52:671,682, 2009. © 2009 Wiley-Liss, Inc. [source] Leaf age affects the seasonal pattern of photosynthetic capacityand net ecosystem exchange of carbon in a deciduous forestPLANT CELL & ENVIRONMENT, Issue 6 2001K. B. Wilson Abstract Temporal trends in photosynthetic capacity are a critical factorin determining the seasonality and magnitude of ecosystem carbonfluxes. At a mixed deciduous forest in the south-eastern United States (Walker Branch Watershed, Oak Ridge, TN, USA), we independently measured seasonal trends in photosynthetic capacity (using single-leaf gas exchange techniques) and the whole-canopycarbon flux (using the eddy covariance method). Soil respiration was also measured using chambers and an eddy covariance system beneath the canopy. These independent chamber and eddy covariance measurements, along with a biophysical model (CANOAK), areused to examine how leaf age affects the seasonal pattern of carbon uptake during the growing season. When the measured seasonality in photosynthetic capacity is representedin the CANOAK simulations, there is good agreement with the eddy covariance data on the seasonal trends in carbon uptake. Removing the temporal trends in the simulations by using the early season maximum value of photosynthetic capacity over the entire growing season over estimates the annual carbon uptake by about 300 g C m,2 year,1, halfthe total estimated annual net ecosystem exchange. Alternatively, use of the mean value of photosynthetic capacity incorrectly simulates the seasonality in carbon uptake by the forest. In addition to changes related to leaf development and senescence, photosynthetic capacitydecreased in the middle and late summer, even when leaf nitrogenwas essentially constant. When only these middle and late summer reductions were neglected in the model simulations, CANOAK still overestimated the carbon uptake by an amount comparable to 25% ofthe total annual net ecosystem exchange. [source] Evaluation of a vertical frozen soil barrier at oak ridge national laboratoryREMEDIATION, Issue 3 2000Stanley W. Lynn Arctic Foundations, Inc. (AFI), of Anchorage, Alaska, has developed a freeze barrier system designed to hydraulically isolate a contaminant source area. The system can be used for long-term or temporary containment of groundwater until appropriate remediation techniques can be applied. The technology was evaluated under the United States Environmental Protection Agency's (EPA's) Superfund Innovative Technology Evaluation (SITE) program at the United States Department of Energy's (DOE's) Oak Ridge National Laboratory (ORNL) facility in Oak Ridge, Tennessee. For the demonstration, an array of freeze pipes called "thermoprobes" was installed to a depth of 30 feet below ground surface around a former waste collection pond and keyed into bedrock. The system was used to establish an impermeable frozen soil barrier to hydraulically isolate the pond. Demonstration personnel collected independent data to evaluate the technology's performance. A variety of evaluation tools were used,including a groundwater dye tracing investigation, groundwater elevation measurements, and subsurface soil temperature data,to determine the effectiveness of the freeze barrier system in preventing horizontal groundwater flow beyond the limits of the frozen soil barrier. Data collected during the demonstration provided evidence that the frozen soil barrier was effective in hydraulically isolating the pond. [source] | |||||||||||||