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At least 217 records · Page 12Linked to original sources

USGS2005

Early concepts of the role of microorganisms in hydrogeology

Hydrogeologists and geochemists have made great progress in the past few decades in understanding the water/rock interaction that are major controls on the chemical character of ground water. We also recognize that, for many reactions, we do not understand the specific mechanisms generating these reactions, such as those involved in the generation of gases, dissolution of some minerals, and some aspects of isotopic fractionation. Additional understanding will be gained only by study of the interaction of organic material, minerals, and microorganisms in the water and in the pore space of the aquifer material.

Ground Water↗

USGS1966

Isotopic study of galenas from the upper Mississippi Valley, the Illinois-Kentucky, and some Appalachian Valley mineral districts

Analyses of lead isotopes in galena in carbonate rock ore deposits collected from several mineralized districts in the Central and Eastern Interior of the United States support previous studies in establishing that the galena is anomalously radiogenic ("J"type")- This study , using care-fully selected samples to test some géologie relationships, shows region-wide and distrietwide systematic variations in isotope ratios. The genetic implications of thèse variations are discussed. Two mechanisms of origin are considered to explain thèse variations in isotopic ratios. One involves mixing of leads from multiple sources, the other calls for variable lead-isotope ratios originating from a single source. Several source materials for the lead ores have been suggested; whether a single source has predominated, or two or more main sources have predominated is still unresolved. Slopes from Pb206/Pb204 versus Pb207/Pb204 plot are compatible with a contribution of lead by the 1300 ± 300 m.y. basement rocks that underlie the deposits. The spatial relationships of alkaline igneous rocks to several of the minerai districts in the Mississippi Valley région suggest a possible mag-matic source for the lead. Isotopic analyses of galenas closely associated with several of the intrusive rocks are similar in isotopic composition to adjacent ore leads, but genetic implications are ambiguous. Galena oc-curring in shales in the Mississippi Valley région outside mineralized districts contains ordinary lead. Théories that call upon such shales to be the major source of the lead in the depoaits of the Mississippi Valley type must explain this distinct différence in isotopic compositions. Galena collected from districts within the Appalachian Ridge and Valley Province contains notably less radiogenic lead than that from the Mississippi Valley minerai districts , and the lead is of the ordinary type.

Illinois, Kentucky↗

USGS2021

The Confocal Laser Scanning Microscopy Working Group of the ICCP: Final report 2021

This report summarizes the activities and results of the Confocal Laser Scanning Microscopy (CLSM) working group (WG) of the International Committee for Coal and Organic Petrology (ICCP), from its inception in September, 2015, to the present day (September, 2021). The purpose of this report is to document the history of the working group and to compile and evaluate its results. The CLSM WG examined an immature, organic-rich sample of Kimmeridge Clay, which was characterized via CLSM imaging and spectroscopy. In addition, mechanically polished and broad ion beam (BIB) milled sample preparations were characterized via atomic force microscopy. Highlights of findings from the CLSM WG include: the interpreted presence of Botryococcus; incomplete blocking of laser light from highly reflective materials; surface roughening and surface flattening induced by differential BIB milling dependent on location and scale of measurement; substitution of uranium for iron in sulfides; red-shift of reflectance and auto-fluorescence from below the sample surface; positive alteration from laser-induced photo-oxidation of the sample surface including fluorescence blue-shift; blueshift associated to higher fluorescence intensity regions in amorphous organic matter; need for fluorescence spectroscopy standardization as applied via CLSM; and the suitability of CLSM to predict solid bitumen reflectance via calibration to an extant data set. Due to the inability of WG members to continue participating in a WG format, the CLSM WG is hereby finalized. This report represents the final product of WG activity, with the aim to summarize the information included herein for a future peer-reviewed manuscript.

Final Report↗

USGS1987

EFFECT OF AN ACID RAIN ENVIRONMENT ON LIMESTONE SURFACES.

Salem limestone samples were exposed to weathering for 1 y in several urban and one rural environments. Samples exposed in the rural location were chemically indistinguishable from the freshly quarried limestone, whereas all samples collected from urban exposure sites developed gypsum stains on the ground-facing surfaces where the stones were not washed by precipitation. The gas-solid reaction of SO//2 with calcite was selected for detailed consideration. It appears from the model that under arid conditions, the quantity of stain deposited on an unwashed surface is independent of atmospheric SO//2 concentration once the surface has been saturated with gypsum. Under wet conditions, surface sulfation and weight loss are probably dominated by mechanisms involving wet stone. However, if the rain events are frequent and delimited by periods of dryness, the quantity of gypsum produced by a gas-solid reaction mechanism should correlate with both the frequency of rain events and the atmospheric SO//2 level.

Materials Performance↗

USGS1966

Electron microscope study of Sarcocystis sp

Sarcocystis sp. obtained from wild populations of grackles, Quiscalus quiscula (Linn.), were examined to clarify the effect of the parasite on the host. Electron micrographs are presented to show areas of muscle destruction adjacent to the parasite which appear to be mechanically produced by the parasite. The microtubules within the villus-like projections of the cyst suggest that their possible function is absorptive and/or conductive with regard to the production of a toxin or the conveyance of nutritive material to the developing cells. The proposed function of submembranous filaments and their relation to the conoid is discussed. Similarities in the ultrastructure to Toxoplasma and other protozoa tend to negate the relegation of Sarcocystis to the fungi and further emphasize its protozoan nature.

Experimental Parasitology↗

USGS1995

A summary of the effects of mining and related activities on the sediment-trace element geochemistry of Lake Coeur d'Alene, Idaho, USA

During 1989 and 1990 a series of 12 gravity cores, and 150 surface grab samples were collected in Lake Coeur d'Alene, Idaho to determine trace element concentrations, partitioning and surface and subsurface distribution patterns in the bed sediments of the lake. In addition, selected subsamples from one core were analyzed for 117 Cs activity to begin to establish a trace element geochemical history for the lake. The intent was to try and relate the trace element concentrations and distributions in the sediment column to past and present mining and mining related activities in the area. Substantial portions of the surface and near-surface sediments in Lake Coeur d'Alene are markedly enriched in Ag, As, Cd, Hg, Pb, Sb and Zn, and somewhat enriched in Cu, Fe and Mn. Surface distribution patterns, as well as variations in the thickness of the trace element-rich subsurface sediments, indicate that the source of much of this enriched material is the Coeur d'Alene River. The similarity between the trace element-rich surface and subsurface sediments with respect to: their location, their bulk chemistry, and their trace element partitioning indicate that the sources and/or concentrating mechanisms causing the trace element enrichment in the lake sediments probably have been the same throughout their depositional history. An estimated 75 million metric tons of trace element-rich sediments have been deposited on or in the lakebed. Based on a Mt. St. Helens' ash layer from the 1980 eruption, ages estimated from 137 Cs activity, and the presence of 80 discernible and presumably annual layers in a core collected near the Coeur d'Alene River delta, indicate that the deposition of trace element-rich sediments began, at least in the Coeur d'Alene River delta, some time between 1895 and 1910, dates consistent with the onset of mining and ore-processing activities that began in the area in the 1880's.

Journal of Geochemical Exploration↗

USGS2010

Zinc isotopic composition of particulate matter generated during the combustion of coal and coal + tire-derived fuels

Atmospheric Zn emissions from the burning of coal and tire-derived fuel (TDF) for power generation can be considerable. In an effort to lay the foundation for tracking these contributions, we evaluated the Zn isotopes of coal, a mixture of 95 wt % coal + 5 wt % TDF, and the particulate matter (PM) derived from their combustion in a power-generating plant. The average Zn concentrations and δ(66)Zn were 36 mg/kg and 183 mg/kg and +0.24‰ and +0.13‰ for the coal and coal + TDF, respectively. The δ(66)Zn of the PM sequestered in the cyclone-type mechanical separator was the lightest measured, -0.48‰ for coal and -0.81‰ for coal+TDF. The δ(66)Zn of the PM from the electrostatic precipitator showed a slight enrichment in the heavier Zn isotopes relative to the starting material. PM collected from the stack had the heaviest δ(66)Zn in the system, +0.63‰ and +0.50‰ for the coal and coal + TDF, respectively. Initial fractionation during the generation of a Zn-rich vapor is followed by temperature-dependent fractionation as Zn condenses onto the PM. The isotopic changes of the two fuel types are similar, suggesting that their inherent chemical differences have only a secondary impact on the isotopic fractionation process.

Environmental Science & Technology↗

USGS2009

The source of infrasound associated with long-period events at mount St. Helens

During the early stages of the 2004-2008 Mount St. Helens eruption, the source process that produced a sustained sequence of repetitive long-period (LP) seismic events also produced impulsive broadband infrasonic signals in the atmosphere. To assess whether the signals could be generated simply by seismic-acoustic coupling from the shallow LP events, we perform finite difference simulation of the seismo-acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere. The effects of topography, velocity structure, wind, and source configuration are considered. The simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of P/SV and Rayleigh wave energy converted locally along the propagation path, and acoustic energy originating from , the source epicenter. Although the horizontal acoustic velocity of the latter is consistent with our data, the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations, and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source. The observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic LP events. The observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated, highly permeable material. Heating by magmatic activity causes pressure to rise, periodically reaching the pressure threshold for rupture of the "valve" sealing the crack. Sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack, initiating resonance of the remaining fluid. Subtle waveform and amplitude variability of the infrasonic signals as recorded at an array 13.4 km to the NW of the volcano are attributed primarily to atmospheric boundary layer propagation effects, superimposed upon amplitude changes at the source.

Washington↗

USGS2011

Volcanic plume height measured by seismic waves based on a mechanical model

In August 2008 an unmonitored, largely unstudied Aleutian volcano, Kasatochi, erupted catastrophically. Here we use seismic data to infer the height of large eruptive columns such as those of Kasatochi based on a combination of existing fluid and solid mechanical models. In so doing, we propose a connection between a common, observable, short-period seismic wave amplitude to the physics of an eruptive column. To construct a combined model, we estimate the mass ejection rate of material from the vent on the basis of the plume height, assuming that the height is controlled by thermal buoyancy for a continuous plume. Using the estimated mass ejection rate, we then derive the equivalent vertical force on the Earth through a momentum balance. Finally, we calculate the far-field surface waves resulting from the vertical force. The model performs well for recent eruptions of Kasatochi and Augustine volcanoes if v , the velocity of material exiting the vent, is 120-230 m s -1 . The consistency between the seismically inferred and measured plume heights indicates that in these cases the far-field ~1 s seismic energy radiated by fluctuating flow in the volcanic jet during the eruption is a useful indicator of overall mass ejection rates. Thus, use of the model holds promise for characterizing eruptions and evaluating ash hazards to aircraft in real time on the basis of far-field short-period seismic data. This study emphasizes the need for better measurements of eruptive plume heights and a more detailed understanding of the full spectrum of seismic energy radiated coeruptively.

Journal of Geophysical Research B: Solid Earth↗

USGS2000

Volatile organic compounds in storm water from a parking lot

A mass balance approach was used to determine the most important nonpoint source of volatile organic compounds (VOCs) in storm water from an asphalt parking lot without obvious point sources (e.g., gasoline stations). The parking lot surface and atmosphere are important nonpoint sources of VOCs, with each being important for different VOCs. The atmosphere is an important source of soluble, oxygenated VOCs (e.g., acetone), and the parking lot surface is an important source for the more hydrophobic VOCs (e.g., benzene). VOCs on the parking lot surface appear to be concentrated in oil and grease and organic material in urban particles (e.g., vehicle soot). Except in the case of spills, asphalt does not appear to be an important source of VOCs. The uptake isotherm of gaseous methyl tert -butyl ether on urban particles indicates a mechanism for dry deposition of VOCs from the atmosphere. This study demonstrated that a mass balance approach is a useful means of understanding non-point-source pollution, even for compounds such as VOCs, which are difficult to sample.

Journal of Environmental Engineering↗

USGS2017

Shallow repeating seismic events under an alpine glacier at Mount Rainier, Washington, USA

We observed several swarms of repeating low-frequency (1–5 Hz) seismic events during a 3 week period in May–June 2010, near the summit of Mount Rainier, Washington, USA, that likely were a result of stick–slip motion at the base of alpine glaciers. The dominant set of repeating events ('multiplets') featured >4000 individual events and did not exhibit daytime variations in recurrence interval or amplitude. Volcanoes and glaciers around the world are known to produce seismic signals with great variability in both frequency content and size. The low-frequency character and periodic recurrence of the Mount Rainier multiplets mimic long-period seismicity often seen at volcanoes, particularly during periods of unrest. However, their near-surface location, lack of common spectral peaks across the recording network, rapid attenuation of amplitudes with distance, and temporal correlation with weather systems all indicate that ice-related source mechanisms are the most likely explanation. We interpret the low-frequency character of these multiplets to be the result of trapping of seismic energy under glacial ice as it propagates through the highly heterogeneous and attenuating volcanic material. The Mount Rainier multiplet sequences underscore the difficulties in differentiating low-frequency signals due to glacial processes from those caused by volcanic processes on glacier-clad volcanoes.

Washington↗

USGS2026

Thermal and dielectric properties of Juno’s regolith at one millimeter wavelength

We present the modeling results of the thermal lightcurve of asteroid (3) Juno at the wavelength of λ = 1.3 mm measured by the Atacama Large Millimeter-submillimeter Array. A thermophysical model together with a radiative transfer model suggests a thermal inertia of 13 ± 10 [J m −2 K −1 s −0.5 ], an equivalent emissivity of 0.8 ± 0.1, a loss tangent of 0.4 ± 0.3, and an index of refraction 1.8 ± 0.3. Based on previous laboratory measurements, the modeled index of refraction suggests a regolith porosity of about 45%. However, thermal inertia models using the material parameters of ordinary chondrite indicate a grain size of ∼10 μ m and require a high porosity of ∼90% to explain the low thermal inertia. In order to explain such a contradiction, we postulate that some repulsive mechanism might be in effect to reduce the contact of grains and therefore the thermal inertia. The loss tangent of Juno’s regolith corrected for the modeled thermal skin depth is in the order of 0.5, much higher than that of the lunar regolith and indicating an electrical skin depth of L = 0.1–1.4 mm that is within the thermal skin depth. The shape of the rotational lightcurve of Juno in the millimeter wavelengths is dominated by its irregular shape, but rotational variations in the thermal and/or dielectric properties cannot be ruled out. Our results demonstrate that millimeter-wavelength observations of asteroids provide an extra dimension of constraints to the porosity and grain size of asteroid regolith compared to the thermal infrared observations.

Planetary Science Journal↗

USGS2008

Elevated CO 2 enhances biological contributions to elevation change in coastal wetlands by offsetting stressors associated with sea-level rise

1. Sea-level rise, one indirect consequence of increasing atmospheric CO 2 , poses a major challenge to long-term stability of coastal wetlands. An important question is whether direct effects of elevated CO 2 on the capacity of marsh plants to accrete organic material and to maintain surface elevations outweigh indirect negative effects of stressors associated with sea-level rise (salinity and flooding). 2. In this study, we used a mesocosm approach to examine potential direct and indirect effects of atmospheric CO 2 concentration, salinity and flooding on elevation change in a brackish marsh community dominated by a C 3 species, Schoenoplectus americanus, and a C 4 grass, Spartina patens. This experimental design permitted identification of mechanisms and their role in controlling elevation change, and the development of models that can be tested in the field. 3. To test hypotheses related to CO 2 and sea-level rise, we used conventional anova procedures in conjunction with structural equation modelling (SEM). SEM explained 78% of the variability in elevation change and showed the direct, positive effect of S. americanus production on elevation. The SEM indicated that C 3 plant response was influenced by interactive effects between CO 2 and salinity on plant growth, not a direct CO 2 fertilization effect. Elevated CO 2 ameliorated negative effects of salinity on S. americanus and enhanced biomass contribution to elevation. 4. The positive relationship between S. americanus production and elevation change can be explained by shoot-base expansion under elevated CO 2 conditions, which led to vertical soil displacement. While the response of this species may differ under other environmental conditions, shoot-base expansion and the general contribution of C 3 plant production to elevation change may be an important mechanism contributing to soil expansion and elevation gain in other coastal wetlands. 5. Synthesis. Our results revealed previously unrecognized interactions and mechanisms contributing to marsh elevation change, including amelioration of salt stress by elevated CO 2 and the importance of plant production and shoot-base expansion for elevation gain. Identification of biological processes contributing to elevation change is an important first step in developing comprehensive models that permit more accurate predictions of whether coastal marshes will persist with continued sea-level rise or become submerged. ?? 2008 The Authors.

Journal of Ecology↗

USGS2021

Evaluation of techniques for mitigating snowmelt infiltration-induced landsliding in a highway embankment

Infiltration-induced landslides threaten transportation infrastructure around the world, and impose both direct costs through repair and remediation work and indirect costs through lost economic activity. Therefore, finding the most cost-effective techniques to mitigate slope failures that can impact critical infrastructure links is desirable. The Straight Creek landslide, which affects a segment of Interstate 70 in Summit County, Colorado (USA), has experienced seasonal failure driven by rapid springtime snowmelt infiltration since the early 1970s, allowing changes in its stability to be studied. Past studies have established that seasonal failure is driven by pore-water pressure increase caused by the rapid infiltration of snowmelt and the hydraulic conductivity contrast between upper slope materials and the highway embankment. Two remediation designs have been applied to the site, including lightweight caissons beneath the highway surface in 2011 and 2012, and horizontal drains near the slide toe in 2012. The effects of the lightweight caissons and horizontal drains, as well as an alternative drain design that would extend into the hillslope above the highway embankment, are evaluated within a rigorous hydro-mechanical simulation framework along with a method to generate a field of local factor of safety. Model results show that the effect of the lightweight caissons on the factor of safety is no more than 1% during times of critical instability, as they do not affect the seasonal changes in hydrology that cause destabilizing decreases in effective stress along the failure surface. Horizontal drains are intended to reduce pore-water pressures, but the location of existing drains limit their efficacy due to the low hydraulic conductivity of subsurface materials underneath the highway. Model results indicate that these drains are only partially responsible for a reduction in movement rate since their installation, which is also due to lower annual cumulative snowmelt infiltration levels since 2012. Results also show that an alternative drain design could result in increased stability during critical periods by intercepting downslope subsurface flow before it arrives at the hydraulic conductivity contrast at the embankment.

Colorado↗

USGS1986

A new model for humic materials and their interactions with hydrophobic organic chemicals in soil-water or sediment-water systems

A generalized model of humic materials in soils and sediments, which is consistent with their observed properties, is presented. This model provides a means of understanding the interaction of hydrophobic pollutants with humic materials. In this model, it is proposed that the humic materials in soils and sediments consist of a number of different oligomers and simple compounds which result from the partial degradation of plant remains. These degradation products are stabilized by incorporation into humic aggregates bound together by weak bonding mechanisms, such as hydrogen bonding, pi bonding, and hydrophobic interactions. The resulting structures are similar to micelles or membranes, in which the interiors of the structures are hydrophobic and the exteriors are hydrophilic. Hydrophobic compounds will partition into the hydrophobic interiors of the humic micelles or "membrane-like" structures. ?? 1986.

Journal of Contaminant Hydrology↗

USGS2020

Submarine landslide kinematics derived from high-resolution imaging in Port Valdez, Alaska

Submarine landslides caused by strong ground shaking during the M9.2 1964 Great Alaska earthquake generated a tsunami that destroyed much of the old town of Valdez, Alaska, and was responsible for 32 deaths at that location. We explore structural details of the 1964 landslide deposit, as well as landslide deposits from earlier events, in order to characterize kinematics of the landslide process. We present a new high‐resolution seismic reflection data set that images the 1964 landslide deposit and six pre‐1964 deposits with great detail. These deposits are represented by thick packages (~7–23 m) of debris within >500 m of fjord sedimentation above basement. Internal slide structures are associated with distinctive landslide failure mechanisms, including detailed erosional and depositional features and structures resolved within both landslide blocks and distal debris flow layers. Based on comparisons of deposit volume from subbottom structure and differenced bathymetry, we refine prior interpretations of the source of failed material. New data show evidence for basal erosion and reworking of fjord‐floor sedimentation. Additionally, material comprising the 1964 landslide appears to have been translated and deformed by lateral thrusting, rather than having been sourced entirely from upslope evacuation zones. Taking into account these complexities in depositional patterns, we show variations in slide size through Holocene time and relate the history of landslides to the paleoseismic record. Collectively, these new observations demonstrate that Port Valdez has a repeated history of large submarine landslides, which are likely associated with large megathrust earthquakes.

Alaska↗

USGS2012

Invasive zebra mussels ( Driessena polymorpha ) and Asian clams ( Corbicula fluminea ) survive gut passage of migratory fish species: implications for dispersal

The introduction and spread of invasive species is of great concern to natural resource managers in the United States. To effectively control the spread of these species, managers must be aware of the multitude of dispersal methods used by the organisms. We investigated the potential for survival through the gut of a migrating fish (blue catfish, Ictalurus furcatus ) as a dispersal mechanism for two invasive bivalves: zebra mussel ( Driessena polymorpha ) and Asian clam ( Corbicula fluminea ). Blue catfish (N = 62) were sampled over several months from Sooner Lake, Oklahoma, transported to a laboratory and held in individual tanks for 48 h. All fecal material was collected and inspected for live mussels. Survival was significantly related to water temperature in the lake at the time of collection, with no mussels surviving above 21.1 C°, whereas 12 % of zebra mussels (N = 939) and 39 % of Asian clams (N = 408) consumed in cooler water survived gut passage. This research demonstrates the potential for blue catfish to serve as a dispersal vector for invasive bivalves at low water temperatures.

Biological Invasions↗

USGS2010

Late Hesperian plains formation and degradation in a low sedimentation zone of the northern lowlands of Mars

The plains materials that form the martian northern lowlands suggest large-scale sedimentation in this part of the planet. The general view is that these sedimentary materials were transported from zones of highland erosion via outflow channels and other fluvial systems. The study region, the northern circum-polar plains south of Gemini Scopuli on Planum Boreum, comprises the only extensive zone in the martian northern lowlands that does not include sub-basin floors nor is downstream from outflow channel systems. Therefore, within this zone, the ponding of fluids and fluidized sediments associated with outflow channel discharges is less likely to have taken place relative to sub-basin areas that form the other northern circum-polar plains surrounding Planum Boreum. Our findings indicate that during the Late Hesperian sedimentary deposits produced by the erosion of an ancient cratered landscape, as well as via sedimentary volcanism, were regionally emplaced to form extensive plains materials within the study region. The distribution and magnitude of surface degradation suggest that groundwater emergence from an aquifer that extended from the Arabia Terra cratered highlands to the northern lowlands took place non-catastrophically and regionally within the study region through faulted upper crustal materials. In our model the margin of the Utopia basin adjacent to the study region may have acted as a boundary to this aquifer. Partial destruction and dehydration of these Late Hesperian plains, perhaps induced by high thermal anomalies resulting from the low thermal conductivity of these materials, led to the formation of extensive knobby fields and pedestal craters. During the Early Amazonian, the rates of regional resurfacing within the study region decreased significantly; perhaps because the knobby ridges forming the eroded impact crater rims and contractional ridges consisted of thermally conductive indurated materials, thereby inducing freezing of the tectonically controlled waterways associated with these features. This hypothesis would explain why these features were not completely destroyed. During the Late Amazonian, high-obliquity conditions may have led to the removal of large volumes of volatiles and sediments being eroded from Planum Boreum, which then may have been re-deposited as thick, circum-polar plains. Transition into low obliquity ~5. myr ago may have led to progressive destabilization of these materials leading to collapse and pedestal crater formation. Our model does not contraindicate possible large-scale ponding of fluids in the northern lowlands, such as for example the formation of water and/or mud oceans. In fact, it provides a complementary mechanism involving large-scale groundwater discharges within the northern lowlands for the emplacement of fluids and sediments, which could have potentially contributed to the formation of these bodies. Nevertheless, our model would spatially restrict to surrounding parts of the northern plain either the distribution of the oceans or the zones within these where significant sedimentary accumulation would have taken place. ?? 2010 Elsevier Inc.

Icarus↗