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At least 55 records · Page 3Linked to original sources
USGS2002

Groundwater contamination downstream of a contaminant penetration site. II. Horizontal penetration of the contaminant plume

Part I of this study (Rubin, H.; Buddemeier, R.W. Groundwater Contamination Downstream of a Contaminant Penetration Site Part 1: Extension-Expansion of the Contaminant Plume. J. of Environmental Science and Health Part A (in press).) addressed cases, in which a comparatively thin contaminated region represented by boundary layers (BLs) developed within the freshwater aquifer close to contaminant penetration site. However, at some distance downstream from the penetration site, the top of the contaminant plume reaches the top or bottom of the aquifer. This is the location of the "attachment point," which comprises the entrance cross section of the domain evaluated by the present part of the study. It is shown that downstream from the entrance cross section, a set of two BLs develop in the aquifer, termed inner and outer BLs. It is assumed that the evaluated domain, in which the contaminant distribution gradually becomes uniform, can be divided into two sections, designated: (a) the restructuring section, and (b) the establishment section. In the restructuring section, the vertical concentration gradient leads to expansion of the inner BL at the expense of the outer BL, and there is almost no transfer of contaminant mass between the two layers. In the establishment section, each of the BLs occupies half of the aquifer thickness, and the vertical concentration gradient leads to transfer of contaminant mass from the inner to the outer BL. By use of BL approximations, changes of salinity distribution in the aquifer are calculated and evaluated. The establishment section ends at the uniformity point, downstream from which the contaminant concentration profile is practically uniform. The length of the restructuring section, as well as that of the establishment section, is approximately proportional to the aquifer thickness squared, and is inversely proportional to the transverse dispersivity. The study provides a convenient set of definitions and terminology that are helpful in visualizing the gradual development of uniform contaminant concentration distribution in an aquifer subject to contaminant plume penetration. The method developed in this study can be applied to a variety of problems associated with groundwater quality, such as initial evaluation of field data, design of field data collection, the identification of appropriate boundary conditions for numerical models, selection of appropriate numerical modeling approaches, interpretation and evaluation of field monitoring results, etc.

Journal of Environmental Science and Health - Part↗
USGS2006

Effects of temperature on biochemical reactions and drug resistance of virulent and avirulent Aeromonas salmonicida

Incubation temperatures of 11°, 18° and 28° did not substantially affect biochemical reactions of either virulent or avirulent forms of Aeromonas salmonicida subspecies salmonicida. The only change observed, amygdalin fermentation, was positive at 11° and 18° but negative at 28°C. Several isolates utilized sucrose, a characteristic not normally recognized for A. salmonicida subspecies salmonicida. Antimicrobial susceptibility screening indicated resistance to novobiocin increased at the higher incubation temperatures. Standardized drug sensitivity testing procedures and precise zone diameter interpretive standards for bacterial fish pathogens are needed.

Journal of Fish Diseases↗
USGS1987

Dehydration of seabird prey during transport to the colony: Effects on wet weight energy densities

We present evidence to indicate that dehydration of prey transported by seabirds from capture sites at sea to chicks at colonies inflates estimates of wet weight energy densities. These findings and a comparison of wet and dry weight energy densities reported in the literature emphasize the importance of ( i ) accurate measurement of the fresh weight and water content of prey, ( ii ) use of dry weight energy densities in comparisons among species, seasons, and regions, and ( iii ) cautious interpretation and extrapolation of existing data sets.

Canadian Journal of Zoology↗
USGS2010

Short-term effects of experimental fires on a Mojave Desert seed bank

A Mojave Desert shrub community was experimentally burned to understand changes in seed bank of desert annual plant species in response to wildfire. Seed mortality ranged from 55 to 80%, and fire caused significant losses of native and alien annual seeds. Schismus arabicus , Schismus barbatus , Bromus madritensis , Bromus tectorum , Erodium cicutarium and Plantago spp. made up >95% of the seed bank. Bromus spp. and Plantago spp. had proportionately greater mortality of seeds than did Schismus spp. and E. cicutarium . Schismus spp. can be lodged into soil cracks thus avoiding lethal temperatures. E. cicutarium has a self-drilling mechanism that places the seeds at greater depth in the soil. Greater seed mortality occurred beneath shrub canopies than interspaces for most species ( Plantago , spp., Bromus spp., and E. cicutarium ), but microsite had little effect on Schismus spp. Fire reduced the perennial Ambrosia dumosa densities under canopies. Fire reduced the mean number of species found in samples by about one species per plot and no species was extirpated on experimental plots. The relative abundances of common species did not change dramatically as a result of fire or microsite, however; seed densities varied by treatment and affected interpretations of species compositions.

Mojave Desert↗
USGS1989

Late Quaternary paleolimnology of Walker Lake, Nevada

Diatoms, crustaceans, and pollen from sediment cores, in conjunction with dated shoreline tufas provide evidence for lake level and environmental fluctuations of Walker Lake in the late Quaternary. Large and rapid changes of lake chemistry and level apparently resulted from variations in the course and discharge of the Walker River. Paleolimnological evidence suggests that the basin contained a relatively deep and slightly saline to freshwater lake before ca. 30 000 years B.P. During the subsequent drawdown, the Walker River apparently shifted its course and flowed northward into the Carson Sink. As a result, Walker Lake shallowed and became saline. During the full glacial, cooler climates with more effective moisture supported a shallow brine lake in the basin even without the Walker River. As glacial climates waned after 15 000 years ago, Walker Lake became a playa. The Walker River returned to its basin 4700 years ago, filling it with fresh water in a few decades. Thereafter, salinity and depth increased as evaporation concentrated inflowing water, until by 3000 years ago Walker Lake was nearly 90 m deep, according to dated shoreline tufas. Lake levels fluctuated throughout this interval in response to variations in Sierra Nevada precipitation and local evaporation. A drought in the Sierras between 2400 and 2000 years ago reduced Walker Lake to a shallow, brine lake. Climate-controlled refilling of the lake beginning 2000 years ago required about one millennium to bring Walker lake near its historic level. Through time, lake basins in the complex Lake Lahontan system, fill and desiccate in response to climatic, tectonic and geomorphic events. Detailed, multidisciplinary paleolimnologic records from related subbasins are required to separate these processes before lake level history can be reliably used to interpret paleoclimatology. ?? 1989 Kluwer Academic Publishers.

Journal of Paleolimnology↗
USGS2010

Using noble gases measured in spring discharge to trace hydrothermal processes in the Norris Geyser Basin, Yellowstone National Park, U.S.A.

Dissolved noble gas concentrations in springs are used to investigate boiling of hydrothermal water and mixing of hydrothermal and shallow cool water in the Norris Geyser Basin area. Noble gas concentrations in water are modeled for single stage and continuous steam removal. Limitations on boiling using noble gas concentrations are then used to estimate the isotopic effect of boiling on hydrothermal water, allowing the isotopic composition of the parent hydrothermal water to be determined from that measured in spring. In neutral chloride springs of the Norris Geyser Basin, steam loss since the last addition of noble gas charged water is less than 30% of the total hydrothermal discharge, which results in an isotopic shift due to boiling of ?? 2.5% ??D. Noble gas concentrations in water rapidly and predictably change in dual phase systems, making them invaluable tracers of gas-liquid interaction in hydrothermal systems. By combining traditional tracers of hydrothermal flow such as deuterium with dissolved noble gas measurements, more complex hydrothermal processes can be interpreted. ?? 2010 Elsevier B.V.

Journal of Volcanology and Geothermal Research↗
USGS1997

Geochemical characteristics and K-Ar ages of rare-metal bearing pegmatites from the Birimian of southeastern Ghana

The pegmatite-aplite rocks at Mankwadzi (Ejisimanku Hills) in southeastern Ghana are part of the pegmatite district that extends from Cape Coast to Winneba along the Atlantic coastline. The pegmatites are associated with the Cape Coast granite complex and were intruded during the waning phase of the Eburnian Orogeny (∼2.0 Ga). Three muscovite separates from pegmatite give KAr retention ages of 1909 ± 13 Ma , 1965 ± 13 Ma and 2019 ± 14 Ma. A biotite separate from granite yields a KAr age of 1907 ± 13 Ma. These ages are similar to KAr dates previously reported for the Cape Coast granites, indicating that the granites and pegmatites are coeval and probably genetically linked. The pegmatites are enriched in Li, Be, Nb and Sn and considerably impoverished in Rb, Th, Y and REEs. Microscopic examination of quartz from the pegmatites shows a large number of low salinity fluid inclusions that can be divided into two types: (1) one-phase liquid or gas-filled inclusions; and (2) two-phase liquid-vapour inclusions, with the vapour occupying 2–5% of the volume. The homogenisation temperature of the fluid inclusions clusters between 129 and 144°C. These homogenisation temperatures lead to an inferred entrapment temperature of ∼300°C at a pressure of ∼2.5 kbar, which is estimated for the metamorphism of host hornblende schists. The pegmatite fluid inclusions are interpreted as being secondary to the quartz hosts.

Journal of African Earth Sciences↗
USGS2012

Geometry and subsidence history of the Dead Sea basin: A case for fluid-induced mid-crustal shear zone?

Pull‐apart basins are narrow zones of crustal extension bounded by strike‐slip faults that can serve as analogs to the early stages of crustal rifting. We use seismic tomography, 2‐D ray tracing, gravity modeling, and subsidence analysis to study crustal extension of the Dead Sea basin (DSB), a large and long‐lived pull‐apart basin along the Dead Sea transform (DST). The basin gradually shallows southward for 50 km from the only significant transverse normal fault. Stratigraphic relationships there indicate basin elongation with time. The basin is deepest (8–8.5 km) and widest (∼15 km) under the Lisan about 40 km north of the transverse fault. Farther north, basin depth is ambiguous, but is 3 km deep immediately north of the lake. The underlying pre‐basin sedimentary layer thickens gradually from 2 to 3 km under the southern edge of the DSB to 3–4 km under the northern end of the lake and 5–6 km farther north. Crystalline basement is ∼11 km deep under the deepest part of the basin. The upper crust under the basin has lower P wave velocity than in the surrounding regions, which is interpreted to reflect elevated pore fluids there. Within data resolution, the lower crust below ∼18 km and the Moho are not affected by basin development. The subsidence rate was several hundreds of m/m.y. since the development of the DST ∼17 Ma, similar to other basins along the DST, but subsidence rate has accelerated by an order of magnitude during the Pleistocene, which allowed the accumulation of 4 km of sediment. We propose that the rapid subsidence and perhaps elongation of the DSB are due to the development of inter‐connected mid‐crustal ductile shear zones caused by alteration of feldspar to muscovite in the presence of pore fluids. This alteration resulted in a significant strength decrease and viscous creep. We propose a similar cause to the enigmatic rapid subsidence of the North Sea at the onset the North Atlantic mantle plume. Thus, we propose that aqueous fluid flux into a slowly extending continental crust can cause rapid basin subsidence that may be erroneously interpreted as an increased rate of tectonic activity.

Dead Sea shoreline↗
USGS2019

Surface imaging functions for elastic reverse time migration

Reverse time migration is often used to interpret acoustic or three‐component seismic recordings by creating an image of subsurface seismic reflectors. Here I describe elastic reverse time migration imaging functions that are cast as waveform misfit sensitivity kernels of contrasts in material parameters across hypothetical seismic discontinuities, that is, specular reflectors. The proposed “surface” imaging functions are theoretically applicable to either reflected or converted waves in order to estimate the location and reflectivity of these discontinuities. The surface imaging functions, as well as volumetric sensitivity kernels that target point diffractors, are tested on sets of synthetic surface array recordings that sample the 3‐D seismic wavefield on simple 2‐D structures generated using a 2.5‐D spectral element method. These tests illustrate that in contrast with the volumetric sensitivity kernels, the reflectivity is generally dominated by a high‐amplitude peak that coincides with input locations of discontinuities. Passive recordings of microseismicity, shot gathers, or a combination thereof can be potentially interpreted with the new surface imaging functions to yield useful reflectivity images.

Journal of Geophysical Research Solid Earth↗
USGS2012

The Steens Mountain (Oregon) geomagnetic polarity transition: 3. Its regional significance

Study of the variations of direction and intensity of the geomagnetic field as recorded by the Miocene lava flows on Steens Mountain, southeastern Oregon, has resulted in a detailed description of total field behavior during a reversal in polarity. In addition to information about the polarity reversal itself, the detailed paleomagnetic record includes several thousand years of geomagnetic history preceding and following the polarity transition at 15.5 Ma. In order to test the feasibility of using this record as a means of correlation in this part of the western United States, comparisons are made of reconnaissance and previously published paleomagnetic records obtained from what has been thought to be the Steens Basalt or rocks of equivalent age. Despite the fact that many of these earlier studies were not done in detail and were not intended for correlation purposes, convincing similarities among some of the records are evident. The Steens Basalt paleomagnetic record does, indeed, have potential as a correlation tool during this time of widespread basaltic volcanism. Additionally, paleomagnetic data from flows that were sampled in detail yield a middle Miocene paleomagnetic pole at 88.3°N, 209.0° (α 95 = 6.3°) for the High Lava Plains of Oregon. This pole position is statistically indistinguishable from the earth's rotational axis and implies that no tectonic rotation of this region has occurred since these lava flows were erupted. Data from selected sites within the coeval part of the Columbia River Basalt Group yield a paleomagnetic pole at 88.7°N, 171.6°E (α 95 = 4.0°). The Columbia River Basalt Group pole is statistically indistinguishable from either the rotational axis or from the High Lava Plains pole. These findings indicate no post‐20 Ma differential rotation between south‐eastern Washington and south‐central Oregon, in contrast to previous interpretations.

Journal of Geophysical Research B: Solid Earth↗
USGS2012

Relation of the spectroscopic reflectance of olivine to mineral chemistry and some remote sensing implications

Using high-resolution visible and near-infrared diffuse spectral reflectance, we have systematically investigated apparent wavelength shifts as a function of mineral chemistry in the Fe/Mg olivine series from Fo 11 to Fo 91 . The study also shows that trace amounts of nickel can be spectrally detected in the olivine structure. We show that significant compositional information can only be extracted at relatively high resolution, because the overall spectral characteristics of the olivines change only subtly as a function of the Fe/Mg ratio. Significant spectral variation as a function of grain size is also demonstrated, adding a further complication to the interpretation of remotely sensed data from olivine-rich surfaces. This laboratory study is expected to aid in the interpretation of remotely sensed data from both terrestrial and extraterrestrial bodies. Terrestrial applications may include the recognition of ultramafic, ultrabasic, and basaltic terrains which in themselves may have mineral potential. Among extraterrestrial applications, the asteroids are obvious candidates for further examination if instrumentation can provide the necessary wavelength coverage, resolution, and signal-to-noise ratio so that spectra can be compared to those laboratory data discussed here. Some permutations of Fe-Mg-Ni relations in olivines are discussed as they apply to the interpretation of asteroid surfaces and other extraterrestrial bodies.

Journal of Geophysical Research Solid Earth↗
USGS2000

Observations of health indices used to monitor a tailwater trout fishery

Health of the population of rainbow trout Oncorhynchus mykiss in the San Juan River tailwater was monitored to determine the effects of potential crowding from a reduced winter flow test at Navajo Dam, northwestern New Mexico. A systematic necropsy-based health profile provided a rapid method to detect gross changes in the health of the fish population. The health assessment index (HAI) was calculated to quantify the necropsy system and allow statistical comparisons of data sets. Other suborganismic indices were selected to encompass a range of responses specific to the stress of environmental alterations: physiology assessment using total protein and percent muscle lipids, an immune assessment using serum lysozyme, and a cellular-based evaluation using histology. The HAI values showed no clear trend in fish health, although significant differences occurred among fish samples during the test. Significant declines in condition factors and percent muscle lipids throughout the study suggested a seasonal effect. Total protein and lysozyme levels were variable, showing no discernible patterns. Most histological observations appeared to be incidental during the study. Although there was no clear demonstrable effect of altered flow on fish health, this study revealed the sensitivities of various health indicators, which may help in designing future studies and supporting or interpreting results using these approaches.

New Mexico↗
USGS2003

Latitudinal comparisons of walleye growth in North America and factors influencing growth of walleyes in Kansas reservoirs

We compared the growth of walleyes Stizostedion vitreum in Kansas to that of other populations throughout North America and determined the effects of the abundance of gizzard shad Dorosoma cepedianum and temperature on the growth of walleyes in Kansas reservoirs. Age was estimated from scales and otoliths collected from walleyes (N = 2,072) sampled with gill nets from eight Kansas reservoirs during fall in 1991-1999. Age-0 gizzard shad abundance was indexed based on summer seining information, and temperature data were obtained from the National Oceanic and Atmospheric Administration. Parameter estimates of von Bertalanffy growth models indicated that the growth of walleyes in Kansas was more similar to that of southern latitude populations (e.g., Mississippi and Texas) than to that of northern (e.g., Manitoba, Minnesota and South Dakota) or middle latitude (e.g., Colorado and Iowa) populations. Northern and middle latitude populations had lower mean back-calculated lengths at age 1, lower growth coefficients, and greater longevity than southern and Kansas populations. A relative growth index (RGI; [Lt/Ls ] ?? 100, where Lt is the observed length at age and Ls is the age-specific standard length derived from a pooled von Bertalanffy growth model) and standardized percentile values (percentile values of mean back-calculated lengths at age) indicated that the growth of walleyes in Kansas was above average compared with that of other populations in North America. The annual growth increments of Kansas walleyes were more variable among years than among reservoirs. The growth increments of age-0 and age-1 walleyes were positively related to the catch rates of gizzard shad smaller than 80 mm, whereas the growth of age-2 and age-3 walleyes was inversely related to mean summer air temperature. Our results provide a framework for comparing North American walleye populations, and our proposed RGI provides a simple, easily interpreted index of growth.

North American Journal of Fisheries Management↗
USGS2013

A bibliography of all known publications & reports on the Gulf sturgeon, Acipenser oxyrinchus desotoi

This functional bibliography is meant to be a complete and comprehensive bibliography of all discoverable reports containing information on the Gulf Sturgeon (GS). This bibliography contains all known reports presenting, documenting, summarizing, listing, or interpreting information on the GS through 31 December 2013. Report citations are organized into four sections. Section I includes published scientific journal articles, books, dissertations and theses, published and unpublished technical reports, published harvest prohibitions, and online articles reporting substantive scientific information. Section II includes newspaper, newsletter, magazine, book, agency news releases, and online articles reporting on GS occurrences, mortalities, captures, jumping, boat collisions, aquaculture, historical photographs, and other largely non-scientific or anecdotal issues. Section III consists of books, theses, ecotour-guides, media articles, editorials, and blogs reporting a mix of anecdotal information, historical information, and opinion on GS conservation, habitat issues, exploitation, aquaculture, and human interaction - but presenting very limited or no substantive scientific information. Section IV includes videos, films and audio recordings documenting GS life history and behavior.

Report↗
USGS2016

Elements in whole blood of Northwestern Crows ( Corvus caurinus ) in Alaska: No evidence for an association with beak deformities

A recent outbreak of beak deformities among resident birds in Alaska has raised concern about environmental contamination as a possible underlying factor. We measured whole blood concentrations of 30 essential and nonessential elements to determine whether any were associated with beak deformities in Northwestern Crows ( Corvus caurinus ). We tested for differences between 1) adults with versus those without beak deformities and 2) unaffected adults versus juveniles. Crows with beak deformities had slightly higher levels of barium, molybdenum, and vanadium (all P <0.05), but concentrations were generally low and within the range of values reported from other apparently healthy wild birds. Concentrations of several elements, including selenium, were higher in birds without versus birds with beak deformities (all P <0.05), a difference that may be explained in part by compromised foraging ability associated with the deformities. Adult crows had higher concentrations of cadmium, silicon, and zinc than juveniles (all P <0.05), although differences were relatively small and values were similar to those from other wild birds. Our results suggest that neither selenium nor other tested elements are likely to be causing beak deformities in Alaskan crows. We also provide the first data on elemental concentrations in Northwestern Crows. Levels of selenium far exceeded those typically found in passerine birds and were similar to those in marine-associated waterfowl, suggesting that background levels should be interpreted relative to a species's environment.

Alaska↗
USGS1989

An introduction to quiet daily geomagnetic fields

On days that are quiet with respect to solar-terrestrial activity phenomena, the geomagnetic field has variations, tens of gamma in size, with major spectral components at about 24, 12, 8, and 6 hr in period. These quiet daily field variations are primarily due to the dynamo currents flowing in the E region of the earth's ionosphere, are driven by the global thermotidal wind systems, and are dependent upon the local tensor conductivity and main geomagnetic field vector. The highlights of the behavior and interpretation of these quiet field changes, from their discovery in 1634 until the present, are discussed as an introduction to the special journal issue on Quiet Daily Geomagnetic Fields. ?? 1989 Birkha??user Verlag.

Pure and Applied Geophysics PAGEOPH↗
USGS2007

Structure of the California Coast Ranges and San Andreas Fault at SAFOD from seismic waveform inversion and reflection imaging

[1] A seismic reflection and refraction survey across the San Andreas Fault (SAF) near Parkfield provides a detailed characterization of crustal structure across the location of the San Andreas Fault Observatory at Depth (SAFOD). Steep-dip prestack migration and frequency domain acoustic waveform tomography were applied to obtain highly resolved images of the upper 5 km of the crust for 15 km on either side of the SAF. The resulting velocity model constrains the top of the Salinian granite with great detail. Steep-dip reflection seismic images show several strong-amplitude vertical reflectors in the uppermost crust near SAFOD that define an ∼2-km-wide zone comprising the main SAF and two or more local faults. Another prominent subvertical reflector at 2–4 km depth ∼9 km to the northeast of the SAF marks the boundary between the Franciscan terrane and the Great Valley Sequence. A deep seismic section of low resolution shows several reflectors in the Salinian crust west of the SAF. Two horizontal reflectors around 10 km depth correlate with strains of seismicity observed along-strike of the SAF. They represent midcrustal shear zones partially decoupling the ductile lower crust from the brittle upper crust. The deepest reflections from ∼25 km depth are interpreted as crust-mantle boundary.

Journal of Geophysical Research B: Solid Earth↗