Bursian S.J.,Michigan State University |
Moore J.,Michigan State University |
Newsted J.L.,Cardno Entrix |
Link J.E.,Michigan State University |
And 9 more authors.
Environmental Toxicology and Chemistry | Year: 2012
This study assessed the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and 2,3,7,8 tetrachlorodibenzofuran (TCDF) on the incidence of jaw lesions and on hepatic cytochrome P4501A (CYP1A) endpoints in mink (Mustela vison). Adult female mink were assigned randomly to one of 13 dietary treatments (control and four increasing doses of TCDD, PeCDF, or TCDF) and provided spiked feed for approximately 150 d (60 d prior to breeding through weaning of offspring at 42 d post-parturition). Offspring were maintained on their respective diets for an additional 150 d. Activity of hepatic CYP1A enzymes in adult and juvenile mink exposed to TCDD, PeCDF, or TCDD was generally greater compared with controls, but changes in other CYP1A endpoints were less consistent. Histopathology of the mandible and maxilla of juvenile mink suggested a dose-related increase in the incidence of jaw lesions. The dietary effective doses (ED) for jaw lesions in 50% of the population (ED50) were estimated to be 6.6, 14, and 149ng/kg body weight (bw)/d for TCDD, PeCDF, and TCDF, respectively. The relative potencies of PeCDF and TCDF compared with TCDD based on ED10, ED20, and ED50 values ranged from 0.5 to 1.9 and 0.04 to 0.09, respectively. These values are within an order of magnitude of the World Health Organization toxic equivalency factor (TEFWHO) values of 0.3 and 0.1 for PeCDF and TCDF, respectively. © 2012 SETAC.
Zheng S.,Tsinghua University |
Zheng S.,Wuhan University |
Wu B.,Tsinghua University |
Thorne C.R.,University of Nottingham |
Simon A.,Cardno Entrix
Geomorphology | Year: 2014
The North Fork Toutle River (NFTR) has undergone extensive morphological changes following the catastrophic eruption of Mount St. Helens, Washington, in 1980, especially the upper reaches affected by a 2.5-km3 debris-avalanche deposit caused by the eruption. This paper reports analysis and interpretation of vertical adjustments to the thalweg long-profile at some 33km river reaches redeveloped on the debris-avalanche deposit during the 30-year period since the eruption. The results confirm that adjustments in the upper part of the study reaches have generally been led by degradation, while that in the lower reaches have been led by aggradation, with the middle reaches acting as a hinge zone. Trends of change in the thalweg long profile and bedslope reveal that channel gradients have decreased nonlinearly through time and with distance downstream from the volcano. Values of stream power have decreased with time commensurately owing to reductions in slope and channel widening (while the bed has coarsened) so that rates of erosion of the debris-avalanche deposit in the upper NFTR have slowed to the point that the long profile, now perched and slightly steeper, is relaxing toward a new equilibrium or graded condition. Thirty-year relaxation paths for thalweg elevation were simulated at seven key cross sections using newly developed, comprehensive rate law models based on nonlinear decay in rates of morphological response to perturbation. The results indicate that both single- and multistep rate law models can simulate the observed records. Consequently, the rate law approach provides an effective method for studying and simulating morphological response of the fluvial system to a major, instantaneous disturbance, such as a volcanic eruption. © 2013 Elsevier B.V.
Dayton P.K.,University of California at San Diego |
Kim S.,Moss Landing Marine Laboratories |
Jarrell S.C.,University of California at San Diego |
Oliver J.S.,Moss Landing Marine Laboratories |
And 8 more authors.
PLoS ONE | Year: 2013
Polar ecosystems are sensitive to climate forcing, and we often lack baselines to evaluate changes. Here we report a nearly 50-year study in which a sudden shift in the population dynamics of an ecologically important, structure-forming hexactinellid sponge, Anoxycalyx joubini was observed. This is the largest Antarctic sponge, with individuals growing over two meters tall. In order to investigate life history characteristics of Antarctic marine invertebrates, artificial substrata were deployed at a number of sites in the southern portion of the Ross Sea between 1967 and 1975. Over a 22-year period, no growth or settlement was recorded for A. joubini on these substrata; however, in 2004 and 2010, A. joubini was observed to have settled and grown to large sizes on some but not all artificial substrata. This single settlement and growth event correlates with a region-wide shift in phytoplankton productivity driven by the calving of a massive iceberg. We also report almost complete mortality of large sponges followed over 40 years. Given our warming global climate, similar system-wide changes are expected in the future. © 2013 Dayton et al.
Roberts-Ashby T.L.,University of South Florida |
Roberts-Ashby T.L.,U.S. Geological Survey |
Stewart M.T.,University of South Florida |
Ashby B.N.,Cardno Entrix
Environmental Geosciences | Year: 2013
The Cretaceous rocks of Florida have been recognized as potentially suitable reservoirs for geologic carbon dioxide (CO2) sequestration. Specifically, the upper member of the Upper Cretaceous Lawson Formation, together with the lower part of the Paleocene Cedar Keys Formation, is presented here as a potential composite CO2 storage reservoir that ismainly composed of porous dolostone sealed by thick anhydrites of the overlying middle Cedar Keys Formation. Many of the porous intervals within the Cedar Keys-Lawson storage reservoir display lateral continuity and have an average porosity range of 20%-30%. The estimated CO2 storage capacity for the reservoir is approximately 97 billion t of CO2, which means the Lawson and Cedar Keys Formations composite reservoir could potentially support CO2 sequestration for hundreds of large-scale power plants in the southeastern United States for their entire 40-yr lifespan. Because most of the previous research on the Lawson Formation is concentrated in north-central and northeastern Florida and southern Georgia, this study further characterizes the formation and its CO2 sequestration potential in south-central and southern Florida. Copyright © 2013. The American Association of Petroleum Geologists/Division of Environmental Geosciences.
Peck S.,Cardno ENTRIX
Environmental Connection Conference 2015 | Year: 2015
Located on the border of California and Nevada, Lake Tahoe (the Lake) is the largest alpine lake in North America. It is known for its scenic beauty and outstanding lake clarity. However, the clarity of the Lake has been declining since the mid-1960s because of the deposition of fine particles and nutrients from urban runoff and the growth of aquatic organisms that feed off the nutrients in the runoff (U.C. Davis, 2010). A program to restore the clarity of Lake Tahoe was initiated in the 1990's and involves the development, implementation and construction of numerous projects to control the quality of storm water runoff entering the Lake. One such project is the Bijou Area Erosion Control Project (Project). The Project included a planning-level process that analyzed runoff patterns in the watershed at the south end of Lake Tahoe and proposed methods to treat storm water runoff generated in the community before it reached Lake Tahoe. Because of the close proximity of the state highway and heavily developed commercial areas in the lower watershed adjacent to the Lake, the quality of storm water runoff entering the Lake is one of the lowest (highest constituent loading) of any outfall in the Lake Tahoe Basin. However, the Project area is different from other watersheds and outfalls with high constituent loading as the ability to effectively treat storm water runoff adjacent to the outfall is constrained by limited publicly owned land, available open space, high groundwater and high land values in the area. The planning process for the Project evaluated the storm water runoff and effluent loading (with primary objective/evaluation on sediment loading) to the Lake. Several alternatives were developed and the selected alternative was to implement a "pump and treat" system. This pump and treat system collects runoff from the state highway and commercial areas in this approximately 75% covered (impervious area) sub-watershed of the Bijou Creek watershed. The storm water runoff is then routed, in underground storm water pipes to approximately 180,000 gallons of sediment and storage vaults and discharges the storm water to a wet well and submersible pumping system (pumping system). The pumping system then discharges the storm water effluent through a force main uphill to a series of five dry infiltration basins about 1 mile to the south of the Lake. A treatment train for the urban storm water runoff was implemented and consists of a sediment vault, then "treatment" vaults, followed by infiltration basins, and if engaged, the grass-lined swale system. The use of both standard sediment vaults, which encompass "dead" storage to remove gross sediment, and "treatment" vaults, which are intended primarily to attenuate the flows for the pumping system, were developed, determined and designed through an iterative design process. The design process took into account available land space, private property negotiations (as over 80% of the storage is on private property) and modeling results. Large material drops out in the initial sediment vault followed by finer material in the treatment vaults. The infiltration basins will retain the inflow for all events up to a 100-year, 1-hour rainfall event. Except for extreme events or multiple events when the basins are full, the basins will completely trap the fine sediment and prevent discharge to the lake. If runoff were to occur from the basins, treatment would still occur through infiltration and adsorption in the grass-lined swale, and the natural channel of the Bijou Creek ecosystem. The Project completed final design and in 2012 was constructed over a two year/season period (2013 and 2014) and is scheduled for "turn on" in the early winter of 2014/2015.
Czarnomski N.M.,Utah State University |
Tullos D.D.,Oregon State University |
Thomas R.E.,University of Hull |
Simon A.,Cardno ENTRIX
Journal of Hydraulic Engineering | Year: 2012
Vegetation growing on the surface of a streambank has been shown to alter the shear stresses applied to the boundary, but basic questions remain regarding the influence of vegetation and streambank configurations on near-bank hydraulics. In the present study, Froudescaled flume experiments were used to investigate how changes in vegetation density (ratio of frontal area to channel area, including both stems and leaves) and bank surface angle influence near-bank turbulence intensities (RMSu;v;w) and Reynolds stresses (tuv and tuw) estimated using velocities obtained with an acoustic Doppler velocimeter positioned beneath the canopy. Results illustrate how, with increasing vegetation density, turbulence intensities and Reynolds stresses decreased along the sloped bank surface but increased at the base of the slope and within the main channel. The steeper bank angle resulted in greater vertical stresses on the bank surface than the shallower angle, but lateral momentum exchange was larger than vertical exchange along the base of the slope, regardless of bank angle. Leaves were an important influence on near-bank turbulence intensities and Reynolds stresses, whereas the influence of bank slope was small relative to the influence of vegetation density. © 2012 American Society of Civil Engineers.