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At least 703 records · Page 39Linked to original sources

USGS2017

Nanoscale geochemical and geomechanical characterization of dispersed organic matter in shale by infrared nanoscopy

Solid organic matter (OM) plays an essential role in the generation, migration, storage, and production of hydrocarbons from economically important shale rock formations. Electron microscopy images have documented spatial heterogeneity in the porosity of OM at nanoscale, and bulk spectroscopy measurements have documented large variation in the chemical composition of OM during petroleum generation. However, information regarding the heterogeneity of OM chemical composition at the nanoscale has been lacking. Here we demonstrate the first application of atomic force microscopy-based infrared spectroscopy (AFM-IR) to measure the chemical and mechanical heterogeneity of OM in shale at the nanoscale, orders of magnitude finer than achievable by traditional chemical imaging tools such as infrared microscopy. We present a combination of optical microscopy and AFM-IR imaging to characterize OM heterogeneity in an artificially matured series of New Albany Shales. The results document the evolution of individual organic macerals with maturation, providing a microscopic picture of the heterogeneous process of petroleum generation.

Nature Communications↗

USGS2021

A global dataset of inland fisheries expert knowledge

Inland fisheries and their freshwater habitats face intensifying effects from multiple natural and anthropogenic pressures. Fish harvest and biodiversity data remain largely disparate and severely deficient in many areas, which makes assessing and managing inland fisheries difficult. Expert knowledge is increasingly used to improve and inform biological or vulnerability assessments, especially in data-poor areas. Integrating expert knowledge on the distribution, intensity, and relative influence of human activities can guide natural resource management strategies and institutional resource allocation and prioritization. This paper introduces a dataset summarizing the expert-perceived state of inland fisheries at the basin (fishery) level. An electronic survey distributed to professional networks (June-September 2020) captured expert perceptions (n = 536) of threats, successes, and adaptive capacity to fisheries across 93 hydrological basins, 79 countries, and all major freshwater habitat types. This dataset can be used to address research questions with conservation relevance, including: demographic influences on perceptions of threat, adaptive capacities for climate change, external factors driving multi-stressor interactions, and geospatial threat assessments.

Scientific Data↗

USGS2019

Population connectivity of pelagic megafauna in the Cuba-Mexico-United States triangle

The timing and extent of international crossings by billfishes, tunas, and sharks in the Cuba-Mexico-United States (U.S.) triangle was investigated using electronic tagging data from eight species that resulted in >22,000 tracking days. Transnational movements of these highly mobile marine predators were pronounced with varying levels of bi- or tri-national population connectivity displayed by each species. Billfishes and tunas moved throughout the Gulf of Mexico and all species investigated (blue marlin, white marlin, Atlantic bluefin tuna, yellowfin tuna) frequently crossed international boundaries and entered the territorial waters of Cuba and/or Mexico. Certain sharks (tiger shark, scalloped hammerhead) displayed prolonged periods of residency in U.S. waters with more limited displacements, while whale sharks and to a lesser degree shortfin mako moved through multiple jurisdictions. The spatial extent of associated movements was generally associated with their differential use of coastal and open ocean pelagic ecosystems. Species with the majority of daily positions in oceanic waters off the continental shelf showed the greatest tendency for transnational movements and typically traveled farther from initial tagging locations. Several species converged on a common seasonal movement pattern between territorial waters of the U.S. (summer) and Mexico (winter).

Scientific Reports↗

USGS2020

Morphological, elemental, and boron isotopic insights into pathophysiology of diseased coral growth anomalies

Growth anomalies (GAs) impact both coral skeleton and soft tissues and are detrimental to reef health. This tumor-like disease is increasingly found throughout the tropics and is commonly associated with high human population density, yet little is known about the etiology, pathology, or calcification behavior of the disease. Here, we investigate potential mechanisms involved in the development of GAs through chemical and morphological characterization of GA skeletons in Porites compressa from a site of high disease prevalence (Coconut Island, Hawaii). A comprehensive suite of trace elements and boron isotopes (δ11B) were measured in skeletal GAs to assess calcification behavior and uptake of essential and toxic metals. Scanning electron microscopy of GA skeleton revealed it to be highly porous consisting of a matrix with a disorganized crystal structure, in contrast to the dense well-organized normal skeleton of P. compressa. Elemental analyses revealed decreased Mg/Ca and increased U/Ca in GA skeletons relative to paired unaffected samples, suggesting a decreased abundance of rapidly accreting microstructures “centers of calcification” in the GAs. Estimates of carbonate system parameters based on δ11B and B/Ca measurements indicate reduced pH (–0.05 units) and [CO32–] within the calcifying fluid of GAs, which may have implications for GA calcification. Higher levels of essential (V/Ca and Mo/Ca) elements in GAs potentially indicate increased abundance of holobiont-associated, nitrogen-fixing bacteria and higher Sb/Ca and Nd/Ca indicate alteration in the accumulation/depuration of these toxic metals. In aggregate, our findings show that dystrophic calcification processes could explain structural differences seen in GA vs unaffected skeletons and highlight the use of approaches herein to shed light on disease pathophysiology in corals.

Scientific Reports↗

USGS2024

Cathodoluminescence differentiates sedimentary organic matter types

High-resolution scanning electron microscopy (SEM) visualization of sedimentary organic matter is widely utilized in the geosciences for evaluating microscale rock properties relevant to depositional environment, diagenesis, and the processes of fluid generation, transport, and storage. However, despite thousands of studies which have incorporated SEM methods, the inability of SEM to differentiate sedimentary organic matter types has hampered the pace of scientific advancement. In this study, we show that SEM-cathodoluminescence (CL) properties can be used to identify and characterize sedimentary organic matter at low thermal maturity conditions. Eleven varied mudstone samples with a broad array of sedimentary organic matter types, ranging from the Paleoproterozoic to Eocene in age, were investigated. Sedimentary organic matter fluorescence intensity and CL intensity showed an almost one-to-one correspondence, with certain exceptions in three samples potentially related to radiolytic alteration. Therefore, because CL emission can be used as a proxy for fluorescence emission from sedimentary organic matter, CL emission during SEM visualization can be used to differentiate fluorescent from non-fluorescent sedimentary organic matter. This result will allow CL to be used as a visual means to quickly differentiate sedimentary organic matter types without employing correlative optical microscopy and could be widely and rapidly adapted for SEM-based studies in the geosciences.

Scientific Reports↗

USGS2024

Discovery of giant and conventional magnetofossils bookending Cretaceous Oceanic Anoxic Event 2

Conventional magnetofossils are the remains of magnetotactic bacteria and giant magnetofossils are the remains of iron biomineralizing organisms that have not yet been identified. We report the oldest robust conventional and giant magnetofossil records, ~97 Ma, from marine sediments drilled in Holland Park, Virginia, USA. The Holland Park core records the Cenomanian-Turonian boundary and Oceanic-Anoxic Event 2 (OAE2). Magnetic datasets indicate single domain magnetite within the clay-rich sediments bookending OAE2. Electron microscopy images from these intervals highlight conventional and giant magnetofossil morphologies, including three potentially new giant magnetofossil morphologies: seeds, squash, and spades. There is an overall high abundance and morphological disparity of magnetofossils at Holland Park. However, we observe abundance, disparity, and preservation changes between the magnetofossil assemblages bookending OAE2. Our observations provide clues toward understanding the ecological thresholds of the enigmatic organisms that produce giant magnetofossils and evidence that magnetofossils may be widely distributed in the geologic record.

Virginia↗

USGS2000

Polyoxometalates from heteropoly "brown" precursors. A new structural class of mixed valence heteropolytungstates, [(XO4)W3IVW17VIO 62Hx]n-

Reduction of the α-Keggin anion [X n + O 4 W 12 O 36 ] [8 − n]− (X = H 2 2+ , B 3+ , Si 4+ ) by six electrons results in the known tungsten “brown” species [X n + O 4 (H 2 O) 3 W IV 3 W VI 9 O 33 ] [8 − n ]− in which three W atoms have been reduced from W VI to W IV , forming a metal–metal bonded triad. The W IV atoms have terminal water coordinated in place of terminal oxo groups. Additional tungstate can condense onto these water molecules in aqueous solution between pH = 4 and 6.5 to form the species reported here, [(XO 4 )W IV 3 W VI 17 O 62 H x ] y − . The boron derivative (X = B 3+ ) is more stable than the metatungstate (X = H 2 2+ ), both of which have been characterized by elemental analysis, 183 W NMR and X-ray crystal structure analysis. Eight additional tungstate groups condense in the form of a partial Keggin structure containing two triads and one dyad which is rotated 60° relative to a hypothetical α-isomer.

Journal of the Chemical Society, Dalton Transactio↗

USGS2011

LA-ICP-MS of magnetite: Methods and reference materials

Magnetite (Fe 3 O 4 ) is a common accessory mineral in many geologic settings. Its variable geochemistry makes it a powerful petrogenetic indicator . Electron microprobe ( EMPA ) analyses are commonly used to examine major and minor element contents in magnetite . Laser ablation ICP-MS ( LA-ICP-MS ) is applicable to trace element analyses of magnetite but has not been widely employed to examine compositional variations. We tested the applicability of the NIST SRM 610, the USGS GSE-1G, and the NIST SRM 2782 reference materials (RMs) as external standards and developed a reliable method for LA-ICP-MS analysis of magnetite . LA-ICP-MS analyses were carried out on well characterized magnetite samples with a 193 nm, Excimer, ArF LA system. Although matrix -matched RMs are sometimes important for calibration and normalization of LA-ICP-MS data, we demonstrate that glass RMs can produce accurate results for LA-ICP-MS analyses of magnetite . Cross-comparison between the NIST SRM 610 and USGS GSE-1G indicates good agreement for magnetite minor and trace element data calibrated with either of these RMs. Many elements show a sufficiently good match between the LA-ICP-MS and the EMPA data; for example, Ti and V show a close to linear relationship with correlation coefficients, R 2 of 0.79 and 0.85 respectively.

Journal of Analytical Atomic Spectrometry↗

USGS2013

TanA: a fluorogenic probe for thiaminase activity

A fluorogenic thiamine analogue is presented as a fluorescent probe for thiaminase activity. The emission of the fluorophore is quenched by photoinduced electron transfer (PET) to the N-substituted pyridinium portion of the probe. Action of the enzyme releases the free pyridine group causing a substantial increase in fluorescence.

Analytical Methods↗

USGS2019

Emerging investigator series: Atmospheric cycling of indium in the northeastern United States

Indium is critical to the global economy and is used in an increasing number of electronics and new energy technologies. However, little is known about its environmental behavior or impacts, including its concentrations or cycling in the atmosphere. This study determined indium concentrations in air particulate matter at five locations across the northeastern United States over the course of one year, in 1995. Historical records from a Massachusetts bog core showed that indium atmospheric concentrations in this region changed only modestly between 1995 and 2010. Atmospheric indium concentrations varied significantly both geographically and temporally, with average concentrations in PM 3 of 2.1 ± 1.6 pg m −3 (1 standard deviation), and average particle-normalized concentrations of 0.2 ± 0.2 μg In per g PM 3 . Peaks in the particle-normalized concentrations in two New York sites were correlated with wind direction; air coming from the north contributed higher concentrations of indium than air coming from the west. This correlation, along with measurements of indium in zinc smelter emissions and coal fly ash, suggests that indium in the atmosphere in the northeastern United States comes from a relatively constant low-level input from coal combustion in the midwest, and higher but more sporadic contributions from the smelting of lead, zinc, copper, tin, and nickel north of the New York sample sites. Understanding the industrial sources of indium to the atmosphere and how they compare with natural sources can lead to a better understanding of the impact of human activities on the indium cycle, and may help to establish a baseline for monitoring future impacts as indium use grows.

Massachusetts, New York↗

USGS2008

Low-Level detections of halogenated volatile organic compounds in groundwater: Use in vulnerability assessments

Concentrations of halogenated volatile organic compounds (VOCs) were determined by gas chromatography (GC) with an electron-capture detector (GC-ECD) and by gas chromatography with mass spectrometry (GC-MS) in 109 groundwater samples from five study areas in the United States. In each case, the untreated water sample was used for drinking-water purposes or was from a monitoring well in an area near a drinking-water source. The minimum detection levels (MDLs) for 25 VOCs that were identified in GC-ECD chromatograms, typically, were two to more than four orders of magnitude below the GC-MS MDLs. At least six halogenated VOCs were detected in all of the water samples analyzed by GC-ECD, although one or more VOCs were detected in only 43% of the water samples analyzed by GC-MS. In nearly all of the samples, VOC concentrations were very low and presented no known health risk. Most of the low-level VOC detections indicated post-1940s recharge, or mixtures of recharge that contained a fraction of post-1940s water. Concentrations of selected halogenated VOCs in groundwater from natural and anthropogenic atmospheric sources were estimated and used to recognize water samples that are being impacted by nonatmospheric sources. A classification is presented to perform vulnerability assessments at the scale of individual wells using the number of halogenated VOC detections and total dissolved VOC concentrations in samples of untreated drinking water. The low-level VOC detections are useful in vulnerability assessments, particularly for samples in which no VOCs are detected by GC-MS analysis.

Journal of Hydrologic Engineering↗

USGS2022

Assessing human resources development in volcano observatories using the knowledge, attitude, and practice survey

The purpose of this study was to assess the role played by the International Training Course, given by the Center for the Study of Active Volcanoes (CSAV) at the University of Hawai’i at Hilo, in the development of human resources for volcano observatory staff around the world. The study design included a literature review, interviews with representatives from 10 national volcano observatories, and electronic surveys designed and conducted by Florida International University, targeting graduates of training courses sponsored by the Volcano Disaster Assistance Program (VDAP), a cooperative partnership between the US Agency for International Development (USAID) and the US Geological Survey (USGS). The knowledge, attitude, and practice (KAP) method was used to develop a survey and a composite KAP index. Of the 92 individuals who answered the survey, 47 had completed the CSAV course. Two groups were formed from the survey respondents: (1) 47 people who were CSAV graduates; and (2) 45 people who did not take CSAV training. An independent samples t "> t t test and a one-way multivariate analysis were conducted to compare the KAP index and the three subindices. The heads of the volcano observatories identified the CSAV International Training as one of the most useful educational offerings relevant to volcano observatory operations available worldwide. The statistical analysis showed significant differences in the KAP index, knowledge subindex, and practice subindex between the two study groups. Results indicate that CSAV graduates are in a better position to attain self-sufficiency in studying and monitoring volcanoes, and by doing so, contribute more effectively to mitigation efforts for volcanic unrest and eruptions.

Natural Hazards Review↗

USGS1973

A pneumatic sample changer for gamma-ray spectroscopy

A gravity‐feed, pneumatic‐ejection sample changer has been developed. The changer is suitable for both flat and well‐type detectors and permits the continuous use of gamma‐ray spectroscopy equipment 24 h a day, 7 days a week. The electronic circuitry has a fail‐safe feature which stops the operation of the changer if a malfunction occurs.

Review of Scientific Instruments↗

USGS1962

Temperature dependence of decay time and intensity of alpha pulses in pure and thallium-activated cesium iodide

The intensity and decay time of Po 210 alpha particle scintillations produced in pure and thallium‐activated cesium iodide have been measured with a fast electronic system as a function of temperature down to 77°K. Three modes of decay due to alpha excitation have been observed for CsI(Tl), and two for CsI. Other than the 7‐ and 0.55‐μsec modes (at room temperature) reported in the literature for CsI(Tl), an additional temperature‐independent mode of about 1.3 μsec has been detected between 77 and 150°K. In CsI a fast temperature‐dependent mode of decay (≈100 nsec) was observed between 100–200°K in addition to the known principal mode.

Review of Scientific Instruments↗

USGS2008

Magnetic monitoring of earth and space

For centuries, navigators of the world’s oceans have been familiar with an effect of Earth’s magnetic field: It imparts a directional preference to the needle of a compass. Although in some settings magnetic orientation remains important, the modern science of geomagnetismhas emerged from its romantic nautical origins and developed into a subject of great depth and diversity. The geomagnetic field is used to explore the dynamics of Earth’s interior and its surrounding space environment, and geomagnetic data are used for geophysical mapping, mineral exploration, risk mitigation, and other practical applications. A global distribution of ground-based magnetic observatories supports those pursuits by providing accurate records of the magnetic-field direction and intensity at fixed locations and over long periods of time. Magnetic observatories were first established in the early 19th century in response to the influence of Alexander von Humboldt and Carl Friedrich Gauss. Since then, magnetic measurement has advanced significantly, progressing from simple visual readings of magnetic survey instruments to include automatic photographic measurement and modern electronic acquisition. To satisfy the needs of the scientific community, observatories are being upgraded to collect data that meet ever more stringent standards, to achieve higher acquisition frequencies, and to disseminate data in real time. To appreciate why data from magnetic observatories can be used for so many purposes, one needs only to recall that the geomagnetic field is a continuum, connecting the different parts of Earth to each other and to nearby space. Beneath our feet and above our heads, electric currents generate magnetic fields that contribute to the totality of the geomagnetic field measured at an observatory on Earth’s surface. The many physical processes that operate in each geophysical domain give rise to a complicated field that exhibits a wide variety of time-dependent behavior. In this article I review the status of the global community of magnetic observatories, show how Earth and space can be monitored for purposes of scientific understanding and practical application, and highlight the role played by magnetic observatories in the history of geomagnetism research.

Physics Today↗

USGS2013

Focused ion beam and field-emission microscopy of metallic filaments in memory devices based on thin films of an ambipolar organic compound consisting of oxadiazole, carbazole, and fluorene units

We report on the mechanism of operation of organic thin film resistive memory architectures based on an ambipolar compound consisting of oxadiazole, carbazole, and fluorene units. Cross-sections of the devices have been imaged by electron microscopy both before and after applying a voltage. The micrographs reveal the growth of filaments, with diameters of 50 nm–100 nm, on the metal cathode. We suggest that these are formed by the drift of aluminium ions from the anode and are responsible for the observed switching and negative differential resistance phenomena in the memory devices.

Applied Physics Letters↗

USGS2009

Fractionation of stable isotopes in perchlorate and nitrate during in situ biodegradation in a sandy aquifer

An in situ experiment was performed in a shallow alluvial aquifer in Maryland to quantify the fractionation of stable isotopes in perchlorate (Cl and O) and nitrate (N and O) during biodegradation. An emulsified soybean oil substrate that was previously injected into this aquifer provided the electron donor necessary for biological perchlorate reduction and denitrification. During the field experiment, groundwater extracted from an upgradient well was pumped into an injection well located within the in situ oil barrier, and then groundwater samples were withdrawn for the next 30 h. After correction for dilution (using Br– as a conservative tracer of the injectate), perchlorate concentrations decreased by 78% and nitrate concentrations decreased by 82% during the initial 8.6 h after the injection. The observed ratio of fractionation effects of O and Cl isotopes in perchlorate (e18O/e37Cl) was 2.6, which is similar to that observed in the laboratory using pure cultures (2.5). Denitrification by indigenous bacteria fractionated O and N isotopes in nitrate at a ratio of ~0.8 (e18O/e15N), which is within the range of values reported previously for denitrification. However, the magnitudes of the individual apparent in situ isotope fractionation effects for perchlorate and nitrate were appreciably smaller than those reported in homogeneous closed systems (0.2 to 0.6 times), even after adjustment for dilution. These results indicate that (1) isotope fractionation factor ratios (e18O/e37Cl, e18O/e15N) derived from homogeneous laboratory systems (e.g. pure culture studies) can be used qualitatively to confirm the occurrence of in situ biodegradation of both perchlorate and nitrate, but (2) the magnitudes of the individual apparent e values cannot be used quantitatively to estimate the in situ extent of biodegradation of either anion.

Environmental Chemistry↗

USGS2020

Surficial geochemistry and bioaccessibility of tellurium in semi-arid mine tailings

Tellurium (Te) is a critical element due to its use in solar technology. However, some forms are highly toxic. Few studies have examined Te behavior in the surficial environment, thus little is known about its potential human and environmental health impacts. This study characterizes two physicochemically distinct Te-enriched mine tailings piles (big and flat tailings) deposited by historic gold (Au) mining in the semi-arid Delamar mining district, Nevada. The big tailings are characterized by smaller particle size and higher concentrations of potentially toxic elements (up to 290 mg Te kg-1), which are enriched at the tailings surface. In contrast, the flat tailings have larger particle size and properties that are relatively invariant with depth. Based on the sulfate to sulfide ratio, the tailings were determined to be sulfate dominated suggesting a high degree of weathering, although the flat tailings did contain significant amounts of sulfides (~40%). Tellurium x-ray absorption spectroscopy of the big tailings indicates that tellurate, the less toxic Te species, is the principal form of Te. Electron microscopy indicates that most of the Te present at the site is associated with iron (oxy)hydroxides, sometimes with other potentially toxic elements, especially lead and antimony. Physiologically-based extraction tests indicate that substantially more Te is solubilized in synthetic stomach fluids than in lung fluids, with gastric bioaccessibility ranging from 13-31% of total Te. This points to low to medium bioaccessibility, which is common for iron (oxy)hydroxide associated elements. Together, these results represent a preliminary assessment of Te surficial behavior in a semi-arid environment and indicate that Te in these tailings represent a moderate health concern.

Environmental Chemistry↗