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At least 307 records · Page 17Linked to original sources
USGS2008

Dissolved oxygen transfer to sediments by sweep and eject motions in aquatic environments

Dissolved oxygen (DO) concentrations were quantified near the sediment-water interface to evaluate DO transfer to sediments in a laboratory recirculating flume and open channel under varying fluid-flow conditions. DO concentration fluctuations were observed within the diffusive sublayer, as defined by the time-averaged DO concentration gradient near the sediment-water interface. Evaluation of the DO concentration fluctuations along with detailed fluid-flow characterizations were used to quantify quasi-periodic sweep and eject motions (bursting events) near the sediments. Bursting events dominated the Reynolds shear stresses responsible for momentum and mass fluctuations near the sediment bed. Two independent methods for detecting bursting events using DO concentration and velocity data produced consistent results. The average time between bursting events was scaled with wall variables and was incorporated into a similarity model to describe the dimensionless mass transfer coefficient (Sherwood number, Sh) in terms of the Reynolds number, Re, and Schmidt number, Sc, which described transport in the flow. The scaling of bursting events was employed with the similarity model to quantify DO transfer to sediments and results showed a high degree of agreement with experimental data. ?? 2008, by the American Society of Limnology and Oceanography, Inc.

Limnology and Oceanography↗
USGS1974

Activity-product constants of aragonite at 90° and 51°C

The activity-product constants of aragonite, K A =[Ca 2+ ][CO 3 2- ] (where the brackets denote activities), were determined experimentally at 90°C and at 51°C. Results at 90°C were obtained from four separate dolomite dissolution runs, in which aragonite precipitated and came to equilibrium with the aqueous phase (from the direction of. supersaturation), and from two runs starting with aragonite suspended in dilute MgCl 2 solutions (from the direction of undersaturation). The average values of K A from the six runs were in excellent agreement; for the negative logarithm of K A , P K A , they yield a value of 8.95±0.05. One run was made at 51° C starting with aragonite suspended in dilute MgCl 2 solution; the value of p K A at 51°C is 8.61±0.05. No X-ray detectable calcite was found at the conclusion of any of the runs, including a dolomite dissolution run at 90°C (D-10) that was sampled over a period of 10,268 h and toward the end had a concentration of approximately 0.002 molal total dissolved magnesium.

Journal of Research of the U.S. Geological Survey↗
USGS2026

The Sand AbrasioN Device for Aeolian Research (SANDAR): A new experimental device for investigating how wind transport affects sand on Earth and Mars

On Earth and Mars, aeolian transport causes sand grains to become abraded, resulting in mineralogic and textural changes. Understanding how sands evolve, or mature, with transport via experimental studies is important for understanding the origins, geologic history, and cycling of sediments, as well as dust production. Previous experimental works have used a variety of methods to simulate aeolian transport in the laboratory, but practical limitations and similitude concerns have limited such research. Here, we present and validate the Sand AbrasioN Device for Aeolian Research (SANDAR), a modified air mill that uses pressurized air to circulate sand around a small abrasion chamber, simulating the effects of aeolian transport. This device is re-circulating to simulate long-distance transport, and it allows for repeated analyses of well-constrained sediment samples, revealing their evolution over time. It is compatible with the grain sizes (74–500 μm) and grain impact velocities (∼0.6–3.7 m/s) typically expected for natural aeolian environments, and is also adaptable for diverse applications simulating different wind conditions. We show that the SANDAR achieves similitude of kinetic energy with respect to saltating sand on both Earth and Mars. SEM and optical microscope imaging reveal that the SANDAR produces microtextures on the surfaces of sand grains similar to those found with natural aeolian transport, demonstrating that it effectively simulates the mechanical effects of aeolian processes. Thus, the SANDAR is a valid tool for use in experimental research to improve our understanding of sedimentary processes across the Solar System.

Aeolian Research↗
USGS1962

Constant-head pumping test of a multiaquifer well to determine characteristics of individual aquifers

This report describes the theory and field procedures for determining the transmissibility and storage coefficients and the original hydrostatic head of each aquifer penetrated by a multiaquifer well. The procedure involves pumping the well in such a manner that the drawdown of water level is constant while the discharges of the different aquifers are measured by means of borehole flowmeters. The theory is developed by analogy to the heat-flow problem solved by Smith. The internal discharge between aquifers after the well is completed is analyzed as the first step. Pumping at constant, drawdown constitutes the second step. Transmissibility and storage coefficients are determined by a method described by Jacob and Lohman, after the original internal discharge to or from the aquifer has been compensated for in the calculations. The original hydrostatic head of each aquifer is then determined by resubstituting the transmissibility and storage coefficients into the first step of the analysis. The method was tested on a well in Chester County, Pa., but the results were not entirely satisfactory, owing to the lack of sufficiently accurate methods of flow measurement and, probably, to the effects of entrance losses in the well. The determinations of the transmissibility coefficient and static head can be accepted as having order-of-magnitude significance, but the determinations of the storage coefficient, which is highly sensitive to experimental error, must be rejected. It is felt that better results may be achieved in the future, as more reliable devices for metering the flow become available and as more is learned concerning the nature of entrance losses. If accurate data can be obtained, recently developed techniques of digital or analog computation may permit determination of the response of each aquifer in the well to any form of pumping.

Water Supply Paper↗
USGS1998

Interactions between pool geometry and hydraulics

An experimental and computational research approach was used to determine interactions between pool geometry and hydraulics. A 20-m-long, 1.8-m-wide flume was used to investigate the effect of four different geometric aspects of pool shape on flow velocity. Plywood sections were used to systematically alter constriction width, pool depth, pool length, and pool exit-slope gradient, each at two separate levels. Using the resulting 16 unique geometries with measured pool velocities in four-way factorial analyses produced an empirical assessment of the role of the four geometric aspects on the pool flow patterns and hence the stability of the pool. To complement the conclusions of these analyses, a two-dimensional computational flow model was used to investigate the relationships between pool geometry and flow patterns over a wider range of conditions. Both experimental and computational results show that constriction and depth effects dominate in the jet section of the pool and that pool length exhibits an increasing effect within the recirculating-eddy system. The pool exit slope appears to force flow reattachment. Pool length controls recirculating-eddy length and vena contracta strength. In turn, the vena contracta and recirculating eddy control velocities throughout the pool.

Water Resources Research↗
USGS2009

Relations between hydrology and velocity of a continuously moving landslide-evidence of pore-pressure feedback regulating landslide motion?

We measured displacement, pore-water pressure, and climatic conditions for 3 years at the continuously moving Slumgullion landslide in Colorado, USA. The landslide accelerated when pore-water pressure increased within the landslide body, but this occurred as pore-water pressure decreased along the landslide margin. The decrease probably occurred in response to shear-induced soil dilation at rates greater than pore-pressure diffusion and likely increased resistance to shear displacement and resulted in landslide deceleration. This dilative strengthening has been experimentally observed and explained theoretically, but not previously identified during field studies. Although landslide displacement should have exceeded that required to achieve critical-state density of shear boundaries, observed relocation of these boundaries indicates that shearing is episodic at fixed locations, so it permits renewed dilative strengthening when "fresh" soil is sheared. Thus, dilatant strengthening may be a considerable mechanism controlling landslide velocity, even for landslides that have continuously moved great distances. ?? Springer-Verlag 2009.

Landslides↗
USGS1996

Semivariogram modeling by weighted least squares

Permissible semivariogram models are fundamental for geostatistical estimation and simulation of attributes having a continuous spatiotemporal variation. The usual practice is to fit those models manually to experimental semivariograms. Fitting by weighted least squares produces comparable results to fitting manually in less time, systematically, and provides an Akaike information criterion for the proper comparison of alternative models. We illustrate the application of a computer program with examples showing the fitting of simple and nested models. Copyright ?? 1996 Elsevier Science Ltd.

Computers & Geosciences↗
USGS2026

Competition between invasive round goby and native slimy sculpin in a coldwater laboratory setting

Slimy sculpin ( Cottus cognatus ) abundance has substantially declined in many regions of the Laurentian Great Lakes coincident with the arrival and range expansions of invasive round goby ( Neogobius melanostomus ). Previous studies have shown that round goby can outcompete native mottled sculpin ( C. bairdii ) for shelter and negatively affect native spoonhead sculpin ( C. ricei ) growth, but direct behavioral interactions of slimy sculpin and round goby have not been observed. We conducted a laboratory experiment in which a pair of slimy sculpin were placed in an aquarium that contained an artificial spawning shelter and one round goby (treatment, n = 10) or no other fish (control, n = 10) for at least 30 days at temperatures reflective of their potential offshore overlap. We measured slimy sculpin egg deposition, aggressive interactions, artificial shelter occupancy, growth, and survival. Slimy sculpin were less likely to occupy shelters and experienced increased intraspecific competition when a round goby was present. In contrast, round goby rarely chased slimy sculpin, slimy sculpin were more likely to chase round goby, and slimy sculpin growth, egg deposition, and survival were not significantly different between groups. Differences in density between treatments and the relative size of fish could confound our observations. However, the dominant slimy sculpin occupied the shelter at similar rates between experimental groups if the round goby was smaller. Our results indicate that larger round goby overlapping with slimy sculpin could affect slimy sculpin shelter and space use, but the Great Lakes environment may create more stress for slimy sculpin than we observed.

Lake Michigan, Lake Superior↗
USGS2026

Lake trout colonization of artificial reefs: Who’s interested, and how long does it take?

Restoring self-sustaining lake trout ( Salvelinus namaycush ) populations has been a major management objective for decades across the species’ native range. Reproduction has been observed but recruitment has been limited in many areas of the Laurentian Great Lakes. Reef restoration and construction have been proposed to increase recruitment, leading to the construction of experimental spawning reefs in Thunder Bay, Lake Huron, during 2009–2010. Research shortly after reef construction demonstrated lake trout quickly colonized those reefs during spawning. We revisited this site after 10 years to evaluate lake trout encounter rate and residency on each reef over time and relative to an adjacent historical, anthropogenic reef complex using fine-scale acoustic telemetry. Encounter frequency increased at most experimental reefs since reef construction, but changes in residency were dependent on lake trout origin (hatchery or wild). Hatchery-produced fish increased their residency on the experimental reefs and spent more time on these reefs collectively than the historical reef; wild lake trout continued to primarily use the historical reef. We expected younger wild fish to have increased residency on the experimental reefs assuming these individuals could have originated from those reefs and were therefore more likely to return to them; however, residency on experimental reefs remained low (< 50%) for these fish. These results indicate that reef construction provided additional habitat used by spawning lake trout, but wild individuals continue to prefer older habitat including naive wild fish born after reef construction.

Michigan↗
USGS2010

Use of a reactive gas transport model to determine rates of hydrocarbon biodegradation in unsaturated porous media

A mathematical model is presented that simulates the transport and reaction of any number of gaseous phase constituents (e.g. CO 2 , O 2 , N 2 , and hydrocarbons) in unsaturated porous media. The model was developed as part of a method to determine rates of hydrocarbon biodegradation associated with natural cleansing at petroleum product spill sites. The one-dimensional model can be applied to analyze data from column experiments or from field sites where gas transport in the unsaturated zone is approximately vertical. A coupled, non-Fickian constitutive relation between fluxes and concentration gradients, together with the capability of incorporating heterogeneity with respect to model parameters, results in model applicability over a wide range of experimental and field conditions. When applied in a calibration mode, the model allows for the determination of constituent production/consumption rates as a function of the spatial coordinate. Alternatively, the model can be applied in a predictive mode to obtain the distribution of constituent concentrations and fluxes on the basis of assumed values of model parameters and a biodegradation hypothesis. Data requirements for the model are illustrated by analyzing data from a column experiment designed to determine the aerobic degradation rate of toluene in sediments collected from a gasoline spill site in Galloway Township, New Jersey.

Water Resources Research↗
USGS2014

Interrelations among the soil-water retention, hydraulic conductivity, and suction-stress characteristic curves

The three fundamental constitutive relations that describe fluid flow, strength, and deformation behavior of variably saturated soils are the soil-water retention curve (SWRC), hydraulic conductivity function (HCF), and suction-stress characteristic curve (SSCC). Until recently, the interrelations among the SWRC, HCF, and SSCC have not been well established. This work sought experimental confirmation of interrelations among these three constitutive functions. Results taken from the literature for six soils and those obtained for 11 different soils were used. Using newly established analytical relations among the SWRC, HCF, and SSCC and these test results, the authors showed that these three constitutive relations can be defined by a common set of hydromechanical parameters. The coefficient of determination for air-entry pressures determined independently using hydraulic and mechanical methods is >0.99, >0.98 for the pore size parameter, and 0.94 for the residual degree of saturation. One practical implication is that one of any of the four experiments (axis-translation, hydraulic, shear-strength, or deformation) is sufficient to quantify all three constitutive relations.

Journal of Geotechnical and Geoenvironmental Engin↗
USGS1984

Effect of excess dietary riboflavin on growth of rainbow trout

Fingerling rainbow trout were fed semipurified diets containing graded levels of supplemental riboflavin (3, 35, 42, 49, 56, 63, 70, 100 and 600 mg/kg of diet) to determine if dietary riboflavin in excess of requirements decreases growth. In three trials with three sizes of fish (mean initial weights, 0.5, 3.2 and 4.3 g) and two water temperatures (8.3° and 15°C), no significant diet-related growth inhibition was detected. The results suggest that rainbow trout, like other animals, are insensitive to excesses of dietary riboflavin and that the growth depression reported by other workers was the result of some other dietary influence or of faulty experimental design.

Journal of Nutrition↗
USGS2018

Measuring SO2 emission rates at Kīlauea Volcano, Hawaii, using an array of upward-looking UV spectrometers, 2014-2017

Retrieving accurate volcanic sulfur dioxide (SO 2 ) gas emission rates is important for a variety of purposes. It is an indicator of shallow subsurface magma, and thus may signal impending eruption or unrest. SO 2 emission rates are significant for accurately assessing climate impact, and providing context for assessing environmental, agricultural, and human health effects during volcanic eruptions. The U.S. Geological Survey Hawaiian Volcano Observatory uses an array of ten fixed, upward-looking ultraviolet spectrometer systems to measure SO 2 emission rates at 10-s sample intervals from the Kīlauea summit. We present Kīlauea SO 2 emission rates from the volcano’s summit and middle East Rift Zone during 2014–2017 and discuss the major sources of error for these measurements. Due to the wide range of SO 2 emissions encountered at the summit vent, we used a variable wavelength spectral analysis range to accurately quantify both high and low SO 2 column densities. We compare measured emission rates from the fixed spectrometer array to independent road and helicopter-based traverse measurements and evaluate the magnitudes and sources of uncertainties for each method. To address the challenge of obtaining accurate plume speed measurements, we examine ground-based wind-speed, plume speed tracking via spectrometer, and SO 2 camera derived plume speeds. Our analysis shows that: (1) the summit array column densities calculated using a dual fit window, are within -6 to +22% of results obtained with a variety of other conventional and experimental retrieval methods; (2) emission rates calculated from the summit array located ∼3 km downwind provide the best, practical estimate of summit SO 2 release under normal trade wind conditions; (3) ground-based anemometer wind speeds are 22% less than plume speeds determined by cross-correlation of plume features; (4) our best estimate of average Kīlauea SO 2 release for 2014–2017 is 5100 t/d, which is comparable to the space-based OMI emissions of 5518 t/d; and (5) short-term variability of SO 2 emissions reflects Kīlauea lava lake dynamics.

Hawaii↗
USGS1993

Aspects of numerical and representational methods related to the finite-difference simulation of advective and dispersive transport of freshwater in a thin brackish aquifer

The simulation of the transport of injected freshwater in a thin brackish aquifer, overlain and underlain by confining layers containing more saline water, is shown to be influenced by the choice of the finite-difference approximation method, the algorithm for representing vertical advective and dispersive fluxes, and the values assigned to parametric coefficients that specify the degree of vertical dispersion and molecular diffusion that occurs. Computed potable water recovery efficiencies will differ depending upon the choice of algorithm and approximation method, as will dispersion coefficients estimated based on the calibration of simulations to match measured data. A comparison of centered and backward finite-difference approximation methods shows that substantially different transition zones between injected and native waters are depicted by the different methods, and computed recovery efficiencies vary greatly. Standard and experimental algorithms and a variety of values for molecular diffusivity, transverse dispersivity, and vertical scaling factor were compared in simulations of freshwater storage in a thin brackish aquifer. Computed recovery efficiencies vary considerably, and appreciable differences are observed in the distribution of injected freshwater in the various cases tested. The results demonstrate both a qualitatively different description of transport using the experimental algorithms and the interrelated influences of molecular diffusion and transverse dispersion on simulated recovery efficiency. When simulating natural aquifer flow in cross-section, flushing of the aquifer occurred for all tested coefficient choices using both standard and experimental algorithms.

Journal of Hydrology↗
USGS2020

Development and evaluation of an improved TFM formulation for use in feeder stream treatments

The binational Great Lakes Fishery Commission sponsored Sea Lamprey Control Program effectively utilizes a variety of lampricide tools to keep populations of parasitic sea lampreys in the Great Lakes at levels that do not cause undue economic or ecological damage. The most widely used toxicant used in lampricide formulations is 3-trifluoromethyl-4-nitrophenol (TFM). In typical treatments, a liquid TFM formulation is applied to lamprey producing streams continuously for 10–14 hours to produce a moving block of lampricide-treated water that kills larval lamprey before they metamorphose into their parasitic lifestage. In many smaller tributaries of dendritic streams a solid bar formulation of TFM is used to supplement the mainstem treatment block. These supplemental TFM bar applications are coordinated with the arrival of the mainstem lampricide to prevent larval sea lamprey from seeking refuge in untreated waters and surviving the treatment. TFM bars are produced from formulated surfactants and designed to release TFM over an 8–10-hour period, depending on water temperature and velocity. However, some of the surfactants have been discontinued resulting in the reformulation of the TFM bars multiple times. As a result of these reformulations, TFM bar performance has declined. An experimental surfactant-free solid TFM tablet formulation was developed as a potential replacement for TFM bars. Release of TFM from the experimental tablets was evaluated using replicated laboratory dissolution trials conducted at three water temperatures and three water velocities. A continuous-flow laboratory flume was used for the dissolution trials and the decay of the tablets was modeled using logistic decay curves. Time required for the TFM tablet to decay 50 and 99% were compared among the groups using a two-way analysis of variance. Post-hoc Tukey Honest Significant Difference tests indicated that both water temperature and water velocity influenced the decay of the tablet; however, neither water temperature or water velocity appeared to dramatically influence TFM release. Results from this laboratory study indicate that the next stage of evaluating the TFM tablets using field tests is warranted.

Project Completion Report↗
USGS2025

Detroit River becoming a crucible for boundary organization experimentation

The Detroit River has a long history of human use and abuse, resulting in public outcry over water pollution and resource degradation. This public outcry helped catalyze the enactment of many laws and the Canada-U.S. Great Lakes Water Quality Agreement which led to enhanced research, monitoring, and water pollution control. As pollution from industries and municipal wastewater treatment plants came under control and progress was made in management of single species, the focus shifted to a more comprehensive ecosystem approach that accounted for all the sources of pollution and targeted restoring ecosystem health with resilience. Over time, the Detroit River became a “proving ground” or crucible for experimenting with boundary organizations to overcome geographical, political, institutional, and disciplinary boundaries and strengthen science-policy-management linkages for ecosystem-based management. This study identified 15 boundary organizations functioning in the Detroit River watershed and evaluated two case studies – St. Clair-Detroit River System Initiative and State of the Strait Conferences. Key lessons learned from this study include: 1) establishing boundary organizations, promoting cooperative learning, and building capacity for boundary-spanning are essential for use of an ecosystem approach; 2) boundary spanning requires specific skills, experience, and improved linkages between research and practice; 3) the 15 boundary organizations provide a unique opportunity to collaborate in a community of practice to share knowledge, foster cooperative learning, enhance problem-solving, build trust, and demonstrate leadership; and 4) continued actionable science, investment in capacity building, and cooperative learning are essential to meet long-term goals of sustainability.

Detroit River↗
USGS2000

Effects of lead in nestling black-crowned night-herons (Nycticorax nycticorax) experimentally dosed in the field

Lead is a known environmental toxicant, and poisoning resulting from the ingestion of lead shot has been well-documented in many species of waterfowl. However, much less is known regarding exposure and effects of free environmental lead in species of birds other than waterfowl. In an attempt to evaluate toxicity of lead to herons and to determine the usefulness of feathers as a non-invasive exposure-monitoring tool, black-crowned night-heron nestlings were dosed with lead to determine its distribution among tissues, and its effects on biochemical biomarkers, growth, and survival. Five-day-old heron nestlings (one per nest) at Chincoteague Bay, Virginia were given a single intra-peritoneal injection of dosing vehicle (control; N=7) or one of three lead solutions (as lead nitrate) (10, 50, or 250 mg/kg body weight of nestling; N=7 per dose) chosen to represent levels below, at, and above those found in moderately-polluted environments. All nestlings treated with lead exhibited dose-dependent inhibition of delta-aminolevulinic acid dehydratase (ALAD) activity compared to controls, and nestlings treated with the highest concentration showed a reduced carcass weight compared to controls. Of several measures of oxidative stress that were analyzed, significant differences were found between low- and high-dosed nestlings in hepatic total thiol and protein-bound sulfhydryl concentrations. No differences in survival were detected between dosed nestlings, controls, or uninjected siblings. Lead concentrations in several matrices, including feathers, are being determined to assess distribution among tissues and will also be examined for relationships with measures of effect.

Society of Environmental Toxicology and Chemistry,↗
USGS2019

Xenon hydrate as an analogue of methane hydrate in geologic systems out of thermodynamic equilibrium

Methane hydrate occurs naturally under pressure and temperature conditions that are not straightforward to replicate experimentally. Xenon has emerged as an attractive laboratory alternative to methane for studying hydrate formation and dissociation in multiphase systems, given that it forms hydrates under milder conditions. However, building reliable analogies between the two hydrates requires systematic comparisons, which are currently lacking. We address this gap by developing a theoretical and computational model of gas hydrates under equilibrium and nonequilibrium conditions. We first compare equilibrium phase behaviors of the Xe·H 2 O and CH 4 ·H 2 O systems by calculating their isobaric phase diagram, and then study the nonequilibrium kinetics of interfacial hydrate growth using a phase field model. Our results show that Xe·H 2 O is a good experimental analog to CH 4 ·H 2 O, but there are key differences to consider. In particular, the aqueous solubility of xenon is altered by the presence of hydrate, similar to what is observed for methane; but xenon is consistently less soluble than methane. Xenon hydrate has a wider nonstoichiometry region, which could lead to a thicker hydrate layer at the gas‐liquid interface when grown under similar kinetic forcing conditions. For both systems, our numerical calculations reveal that hydrate nonstoichiometry coupled with hydrate formation dynamics leads to a compositional gradient across the hydrate layer, where the stoichiometric ratio increases from the gas‐facing side to the liquid‐facing side. Our analysis suggests that accurate composition measurements could be used to infer the kinetic history of hydrate formation in natural settings where gas is abundant.

Geochemistry, Geophysics, Geosystems↗