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At least 1,513 records · Page 84Linked to original sources
USGS2012

A collaborative approach for estimating terrestrial wildlife abundance

Accurately estimating abundance of wildlife is critical for establishing effective conservation and management strategies. Aerial methodologies for estimating abundance are common in developed countries, but they are often impractical for remote areas of developing countries where many of the world's endangered and threatened fauna exist. The alternative terrestrial methodologies can be constrained by limitations on access, technology, and human resources, and have rarely been comprehensively conducted for large terrestrial mammals at landscape scales. We attempted to overcome these problems by incorporating local peoples into a simultaneous point count of Asiatic wild ass (Equus hemionus) and goitered gazelle (Gazella subgutturosa) across the Great Gobi B Strictly Protected Area, Mongolia. Paired observers collected abundance and covariate metrics at 50 observation points and we estimated population sizes using distance sampling theory, but also assessed individual observer error to examine potential bias introduced by the large number of minimally trained observers. We estimated 5671 (95% CI = 3611–8907) wild asses and 5909 (95% CI = 3762–9279) gazelle inhabited the 11,027 km 2 study area at the time of our survey and found that the methodology developed was robust at absorbing the logistical challenges and wide range of observer abilities. This initiative serves as a functional model for estimating terrestrial wildlife abundance while integrating local people into scientific and conservation projects. This, in turn, creates vested interest in conservation by the people who are most influential in, and most affected by, the outcomes.

Biological Conservation↗
USGS2013

Rediscovering traditional vegetation management in preserves: trading experiences between cultures and continents

Land managers are grappling with massive changes in vegetation structure, particularly in protected areas formerly subjected to fire and grazing. The objective of this review was to compare notes on the historical and current management of ecosystems around the world (especially in wet to dry grasslands in the Americas, Australia, Africa, Europe and Asia) with respect to the usage of fire, grazing and cutting to reduce dominance and support the biodiversity of rare species. This review suggests that former disturbances, which are now often lost, may have once kept tall vegetation from pushing out rarer subdominant species. In cases where prehistoric biodiversity depended on fire or large ungulate grazing, traditional agricultural and indigenous practices may have carried biodiversity forward to historical times by mimicking pre-cultural disturbances (e.g., lightning fire and bison grazing). Ironically, biodiversity related to species richness, landscape heterogeneity and function may decline in preserves, especially if traditional management once maintained this biodiversity. Managers can benefit from a cross-continental comparison of the full arsenal of management techniques used to control encroaching vegetation.

Biological Conservation↗
USGS2014

Modeling effects of conservation grassland losses on amphibian habitat

Amphibians provide many ecosystem services valued by society. However, populations have declined globally with most declines linked to habitat change. Wetlands and surrounding terrestrial grasslands form habitat for amphibians in the North American Prairie Pothole Region (PPR). Wetland drainage and grassland conversion have destroyed or degraded much amphibian habitat in the PPR. However, conservation grasslands can provide alternate habitat. In the United States, the Conservation Reserve Program (CRP) is the largest program maintaining grasslands on agricultural lands. We used an ecosystem services model (InVEST) parameterized for the PPR to quantify amphibian habitat over a six-year period (2007–2012). We then quantified changes in availability of amphibian habitat under various land-cover scenarios representing incremental losses (10%, 25%, 50%, 75%, and 100%) of CRP grasslands from 2012 levels. The area of optimal amphibian habitat in the four PPR ecoregions modeled (i.e., Northern Glaciated Plains, Northwestern Glaciated Plains, Lake Agassiz Plain, Des Moines Lobe) declined by approximately 22%, from 3.8 million ha in 2007 to 2.9 million ha in 2012. These losses were driven by the conversion of CRP grasslands to croplands, primarily for corn and soybean production. Our modeling identified an additional 0.8 million ha (26%) of optimal amphibian habitat that would be lost if remaining CRP lands are returned to crop production. An economic climate favoring commodity production over conservation has resulted in substantial losses of amphibian habitat across the PPR that will likely continue into the future. Other regions of the world face similar challenges to maintaining amphibian habitats.

Prairie Pothole Region↗
USGS2016

Impacts of climate change and renewable energy development on habitat of an endemic squirrel, Xerospermophilus mohavensis , in the Mojave Desert, USA

Predicting changes in species distributions under a changing climate is becoming widespread with the use of species distribution models (SDMs). The resulting predictions of future potential habitat can be cast in light of planned land use changes, such as urban expansion and energy development to identify areas with potential conflict. However, SDMs rarely incorporate an understanding of dispersal capacity, and therefore assume unlimited dispersal in potential range shifts under uncertain climate futures. We use SDMs to predict future distributions of the Mojave ground squirrel, Xerospermophilus mohavensis Merriam, and incorporate partial dispersal models informed by field data on juvenile dispersal to assess projected impact of climate change and energy development on future distributions of X. mohavensis . Our models predict loss of extant habitat, but also concurrent gains of new habitat under two scenarios of future climate change. Under the B1 emissions scenario- a storyline describing a convergent world with emphasis on curbing greenhouse gas emissions- our models predicted losses of up to 64% of extant habitat by 2080, while under the increased greenhouse gas emissions of the A2 scenario, we suggest losses of 56%. New potential habitat may become available to X. mohavensis , thereby offsetting as much as 6330 km 2 (50%) of the current habitat lost. Habitat lost due to planned energy development was marginal compared to habitat lost from changing climates, but disproportionately affected current habitat. Future areas of overlap in potential habitat between the two climate change scenarios are identified and discussed in context of proposed energy development.

California↗
USGS2016

Future frequencies of extreme weather events in the National Wildlife Refuges of the conterminous U.S.

Climate change is a major challenge for managers of protected areas world-wide, and managers need information about future climate conditions within protected areas. Prior studies of climate change effects in protected areas have largely focused on average climatic conditions. However, extreme weather may have stronger effects on wildlife populations and habitats than changes in averages. Our goal was to quantify future changes in the frequency of extreme heat, drought, and false springs, during the avian breeding season, in 415 National Wildlife Refuges in the conterminous United States. We analyzed spatially detailed data on extreme weather frequencies during the historical period (1950–2005) and under different scenarios of future climate change by mid- and late-21st century. We found that all wildlife refuges will likely experience substantial changes in the frequencies of extreme weather, but the types of projected changes differed among refuges. Extreme heat is projected to increase dramatically in all wildlife refuges, whereas changes in droughts and false springs are projected to increase or decrease on a regional basis. Half of all wildlife refuges are projected to see increases in frequency (> 20% higher than the current rate) in at least two types of weather extremes by mid-century. Wildlife refuges in the Southwest and Pacific Southwest are projected to exhibit the fastest rates of change, and may deserve extra attention. Climate change adaptation strategies in protected areas, such as the U.S. wildlife refuges, may need to seriously consider future changes in extreme weather, including the considerable spatial variation of these changes.

Biological Conservation↗
USGS2026

Wildfire smoke reduces the vocal activity of imperiled grassland birds in New York State

Smoke from new fire regimes driven by climate change may affect biodiversity in new regions of the world. Wildfires that occurred in eastern Canada in 2023 burned nearly 7.8 million hectares of forest, sending smoke throughout the northeastern United States. We leveraged passive acoustic monitoring to investigate real-time effects of wildfire smoke on vocalization behavior of globally imperiled grassland birds during the breeding season in open land covers across New York State. We determined an overall negative effect of elevated smoke levels on breeding grassland bird vocal activity. We observed the strongest vocalization responses in Bobolink ( Dolichonyx oryzivorus ) – a colonial breeding, grassland-obligate species; Bobolink vocal activity sharply dropped during intense smoke early in the breeding season, yet increased during a milder smoke event later in the breeding season. Our results indicate that wildfire smoke can present an additive stressor to already imperiled grassland bird species via potential fitness reductions from decreased communication. While some aspects of smoke exposure may be uncontrollable, our results suggest that increased attention to conservation practices that promote grassland birds in the Northeast could be prioritized to offset negative effects of increased smoke associated with global change.

New York↗
USGS2006

Nonlinear inversion of potential-field data using a hybrid-encoding genetic algorithm

Using a genetic algorithm to solve an inverse problem of complex nonlinear geophysical equations is advantageous because it does not require computer gradients of models or "good" initial models. The multi-point search of a genetic algorithm makes it easier to find the globally optimal solution while avoiding falling into a local extremum. As is the case in other optimization approaches, the search efficiency for a genetic algorithm is vital in finding desired solutions successfully in a multi-dimensional model space. A binary-encoding genetic algorithm is hardly ever used to resolve an optimization problem such as a simple geophysical inversion with only three unknowns. The encoding mechanism, genetic operators, and population size of the genetic algorithm greatly affect search processes in the evolution. It is clear that improved operators and proper population size promote the convergence. Nevertheless, not all genetic operations perform perfectly while searching under either a uniform binary or a decimal encoding system. With the binary encoding mechanism, the crossover scheme may produce more new individuals than with the decimal encoding. On the other hand, the mutation scheme in a decimal encoding system will create new genes larger in scope than those in the binary encoding. This paper discusses approaches of exploiting the search potential of genetic operations in the two encoding systems and presents an approach with a hybrid-encoding mechanism, multi-point crossover, and dynamic population size for geophysical inversion. We present a method that is based on the routine in which the mutation operation is conducted in the decimal code and multi-point crossover operation in the binary code. The mix-encoding algorithm is called the hybrid-encoding genetic algorithm (HEGA). HEGA provides better genes with a higher probability by a mutation operator and improves genetic algorithms in resolving complicated geophysical inverse problems. Another significant result is that final solution is determined by the average model derived from multiple trials instead of one computation due to the randomness in a genetic algorithm procedure. These advantages were demonstrated by synthetic and real-world examples of inversion of potential-field data. ?? 2005 Elsevier Ltd. All rights reserved.

Computers & Geosciences↗
USGS2008

Geolocation of man-made reservoirs across terrains of varying complexity using GIS

The Reservoir Sedimentation Survey Information System (RESIS) is one of the world's most comprehensive databases of reservoir sedimentation rates, comprising nearly 6000 surveys for 1819 reservoirs across the continental United States. Sediment surveys in the database date from 1904 to 1999, though more than 95% of surveys were entered prior to 1980, making RESIS largely a historical database. The use of this database for large-scale studies has been limited by the lack of precise coordinates for the reservoirs. Many of the reservoirs are relatively small structures and do not appear on current USGS topographic maps. Others have been renamed or have only approximate (i.e. township and range) coordinates. This paper presents a method scripted in ESRI's ARC Macro Language (AML) to locate the reservoirs on digital elevation models using information available in RESIS. The script also delineates the contributing watersheds and compiles several hydrologically important parameters for each reservoir. Evaluation of the method indicates that, for watersheds larger than 5 km2, the correct outlet is identified over 80% of the time. The importance of identifying the watershed outlet correctly depends on the application. Our intent is to collect spatial data for watersheds across the continental United States and describe the land use, soils, and topography for each reservoir's watershed. Because of local landscape similarity in these properties, we show that choosing the incorrect watershed does not necessarily mean that the watershed characteristics will be misrepresented. We present a measure termed terrain complexity and examine its relationship to geolocation success rate and its influence on the similarity of nearby watersheds. ?? 2008 Elsevier Ltd. All rights reserved.

Computers & Geosciences↗
USGS2020

Acoustic Sediment Estimation Toolbox (ASET): A software package for calibrating and processing TRDI ADCP data to compute suspended-sediment transport in sandy rivers

Quantifying suspended-sediment transport is critical for a variety of disciplines related to the management of water resources. However, the number of gauging stations and monitoring networks in most rivers around the world is insufficient to improve understanding of river dynamics and support water resource management decisions. This is mainly due to the high operational costs and intensive labor involved in traditional sediment measurement techniques, especially in sand bed rivers where coarse material varies spatially in the river cross section. Recently, the acoustic surrogate method has received attention as a potentially accurate surrogate technology for estimating suspended-sediment concentrations. In addition, the acoustic surrogate method, through use of acoustic Doppler current profilers (ADCPs), has the advantage of being able to simultaneously measure the flow velocity field and cross-sectional area when moving-boat measurements are performed. In spite of the important advances made in the implementation of this technique, there are no widely-available, free tools for processing the ADCP acoustic signal cross section measurements which include options to extrapolate velocity and sediment in unmeasured ADCP zones and develop calibrations with physical samples. This paper presents a new software called Acoustic Sediment Estimation Toolbox (ASET), which enables the user to develop a calibration between the acoustic signal collected with a down-looking Teledyne RD Instruments ADCP and sediment concentrations determined using traditional sediment sampling techniques. Moreover, ASET software uses dynamic ADCP measurements to estimate the total suspended-sediment transport through a river cross section. The theoretical framework and data processing routines applied by each module in ASET are presented. Finally, a comparison is made between the results obtained by ASET and by traditional methodologies for computing suspended-sediment transport in a large river system (Paraná River, Argentina).

Computers & Geosciences↗
USGS2024

Hybrid CPU-GPU solution to regularized divergence-free curl-curl equations for electromagnetic inversion problems

The Curl-Curl equation is the foundation of time-harmonic electromagnetic (EM) problems in geophysics. The efficiency of its solution is key to EM simulations, accounting for over 95% of the computation cost in geophysical inversions for magnetotelluric or controlled-source EM problems. However, most published EM inversion codes are still central processing unit (CPU)-based and cannot utilize recent computational developments on the graphic processing units (GPUs). Based on a previously proposed divergence-free algorithm developed on CPUs, this study demonstrates the current limits of the CPU-based inversion procedure. To exploit the high throughput capability of GPUs, we propose a hybrid CPU-GPU framework to solve forward and adjoint problems required for EM inversions. The large sparse linear systems arising from the staggered-grid finite difference approximation of the Curl-Curl equation are solved with a mixed-precision Krylov subspace solver implemented on a GPU. The algorithm is then tested in EM forward and adjoint calculations, with real-world three-dimensional numerical examples. Test results show promising 30× kernel-level speed-ups over the conventional CPU algorithm. This approach may further take the complex frequency domain EM inversions onto the next, practical stage on small affordable GPU platforms.

Computers and Geosciences↗
USGS2026

3D semantic mapping of surface geological features

Semantic mapping in 3D is fundamental to a wide range of geoscientific studies and applications, including geomorphology, hazard assessment, and environmental monitoring. However, automatically segmenting geological features from large-scale photogrammetric datasets remains a significant challenge. We present a methodology to address this gap. Using overlapping images collected over environments of interest, Structure-from-Motion (SfM) produces georeferenced point clouds and estimates camera poses. Existing large vision models, such as Segment Anything Model, segment objects in the images, generating pixel-segmentation associations. To produce pixel-point associations, we project the points back onto the camera image planes. As objects are independently segmented across multiple images with different perspectives, we develop a segmentation mosaicking algorithm to build probabilistic point-segmentation associations that combines the pixel-segmentation associations and pixel-point associations. Our methodology is validated using both synthetic data generated by Kubric and real-world UAV-SfM data. The implementation is designed to be compatible with existing SfM software, including Agisoft and OpenDroneMap, for photogrammetry mapping in geoscience studies. As a case study, we apply our method to the semantic mapping of precariously balanced rocks (PBRs), which provide upper-bound constraints on historical ground motion shaking intensity. To support object-level identification of PBRs, we additionally integrated Grounding DINO, enabling text-prompted segmentation of features of interest within UAV imagery. This case study demonstrates the effectiveness of our method in generating a 3D semantic map of PBRs, enabling spatial distribution of PBR fragility for earthquake hazard analysis.

Computers & Geosciences↗
USGS2017

Sediment deposition and sources into a Mississippi River floodplain lake; Catahoula Lake, Louisiana

Floodplain lakes are important wetlands on many lowland floodplains of the world but depressional floodplain lakes are rare in the Mississippi River Alluvial Valley. One of the largest is Catahoula Lake, which has existed with seasonally fluctuating water levels for several thousand years but is now in an increasingly hydrologically altered floodplain. Woody vegetation has been encroaching into the lake bed and the rate of this expansion has increased since major human hydrologic modifications, such as channelization, levee construction, and dredging for improvement of navigation, but it remains unknown what role those modifications may have played in altering lake sedimentation processes. Profiles of thirteen 137 Cs sediment cores indicate sedimentation has been about 0.26 cm y − 1 over the past 60 years and has been near this rate since land use changes began about 200 years ago ( 210 Pb, and 14 C in Tedford, 2009). Carbon sequestration was low (10.4 g m − 2 y − 1 ), likely because annual drying promotes mineralization and export. Elemental composition (high Zr and Ti and low Ca and K) and low pH of recent (<~60 y) or surface sediments suggest Gulf Coastal Plain origin, but below the recent sediment deposits, 51% of sediment profiles showed influence of Mississippi River alluvium, rich in base cations such as K + , Ca 2 + , and Mg 2 + . The recent shift to dominance of Coastal Plain sediments on the lake-bed surface suggests hydrologic modification has disconnected the lake from sediment-bearing flows from the Mississippi River. Compared to its condition prior to hydrologic alterations that intensified in the 1930s, Catahoula Lake is about 15 cm shallower and surficial sediments are more acidic. Although these results are not sufficient to attribute ecological changes directly to sedimentological changes, it is likely the altered sedimentary and hydrologic environment is contributing to the increased dominance of woody vegetation.

Louisiana↗
USGS2004

A modern vs. Permian black shale - the hydrography, primary productivity, and water-column chemistry of deposition

The sediment currently accumulating in the Cariaco Basin, on the continental shelf of Venezuela, has an elevated organic-carbon content of approximately 5%; is accumulating under O2-depleted bottom-water conditions (SO42- reduction); is composed dominantly of foraminiferal calcite, diatomaceous silica, clay, and silt; and is dark greenish gray in color. Upon lithification, it will become a black shale. Recent studies have established the hydrography of the basin and the level of primary productivity and bottom-water redox conditions. These properties are used to model accumulation rates of Cd, Cr, Cu, Mo, Ni, V, and Zn on the seafloor. The model rates agree closely with measured rates for the uppermost surface sediment.The model is applied to the Meade Peak Phosphatic Shale Member of the Phosphoria Formation, a phosphate deposit of Permian age in the northwest United States. It too has all of the requisite properties of a black shale. Although the deposit is a world-class phosphorite, it is composed mostly of phosphatic mudstone and siltstone, chert, limestone, and dolomite. It has organic-carbon concentrations of up to 15%, is strongly enriched in several trace elements above a terrigenous contribution and is black. The trace-element accumulation defines a mean primary productivity in the photic zone of the Phosphoria Basin as moderate, at 500 g m-2 year-1 organic carbon, comparable to primary productivity in the Cariaco Basin. The source of nutrient-enriched water that was imported into the Phosphoria Basin, upwelled into the photic zone, and supported primary productivity was an O2 minimum zone of the open ocean. The depth range over which the water was imported would have been between approximately 100 and 600 m. The mean residence time of bottom water in the basin was approximately 4 years vs. 100 years in the Cariaco Basin. The bottom water was O2 depleted, but it was denitrifying, or NO3- reducing, rather than SO42- reducing. Published by Elsevier B.V.

Chemical Geology↗
USGS2006

The geochemical record of the last 17,000 years in the Guaymas Basin, Gulf of California

Sediments deposited on the western slope of the Guaymas Basin in the central Gulf of California are composed predominantly of detrital clastic material and biogenic silica (biopal), with minor organic material (average of 2.8% organic carbon) and calcium carbonate. The CaCO 3 is derived from calcareous plankton and is highly variable ranging from 0% to 16%. In general, the CaCO 3 content of the sediments varies inversely with the biopal content, reflecting the relative abundance of calcareous and siliceous plankton in the photic zone. Siliceous plankton dominate when winds are predominantly out of the northwest producing strong upwelling. Calcareous plankton indicates weak southeasterly winds that bring warm, tropical Pacific surface water into the Gulf. Based mainly on relative abundances of biopal and CaCO 3 , the sediments deposited over the last 17,000 years in the western Guaymas Basin can be divided into five intervals. In general, the sediments in the intervals with high biopal and low CaCO 3 are laminated, but this is not always true. Unlike most other continental margins of the world with well-developed oxygen minimum zones where highest concentrations of organic carbon and redox-sensitive trace metals occur in laminated sediments, the laminated sediments on the anoxic slope of the western Guaymas Basin do not always have the highest concentrations of organic carbon and trace metals such as Mo and Cd.

Guaymas Basin, Gulf of California↗
USGS2010

River solute fluxes reflecting active hydrothermal chemical weathering of the Yellowstone Plateau Volcanic Field, USA

In the past few decades numerous studies have quantified the load of dissolved solids in large rivers to determine chemical weathering rates in orogenic belts and volcanic areas, mainly motivated by the notion that over timescales greater than ~100kyr, silicate hydrolysis may be the dominant sink for atmospheric CO2, thus creating a feedback between climate and weathering. Here, we report the results of a detailed study during water year 2007 (October 1, 2006 to September 30, 2007) in the major rivers of the Yellowstone Plateau Volcanic Field (YPVF) which hosts Earth's largest "restless" caldera and over 10,000 thermal features. The chemical compositions of rivers that drain thermal areas in the YPVF differ significantly from the compositions of rivers that drain non-thermal areas. There are large seasonal variations in river chemistry and solute flux, which increases with increasing water discharge. The river chemistry and discharge data collected periodically over an entire year allow us to constrain the annual solute fluxes and to distinguish between low-temperature weathering and hydrothermal flux components. The TDS flux from Yellowstone Caldera in water year 2007 was 93t/km2/year. Extensive magma degassing and hydrothermal interaction with rocks accounts for at least 82% of this TDS flux, 83% of the cation flux and 72% of the HCO3- flux. The low-temperature chemical weathering rate (17t/km2/year), calculated on the assumption that all the Cl- is of thermal origin, could include a component from low-temperature hydrolysis reactions induced by CO2 ascending from depth rather than by atmospheric CO2. Although this uncertainty remains, the calculated low-temperature weathering rate of the young rhyolitic rocks in the Yellowstone Caldera is comparable to the world average of large watersheds that drain also more soluble carbonates and evaporates but is slightly lower than calculated rates in other, less-silicic volcanic regions. Long-term average fluxes at Yellowstone are likely ~20% higher than those in the abnormally dry water year 2007, but the protocol used in this study can be easily adaptable to track future changes in low-temperature weathering and hydrothermal flux components, which could provide better monitoring of magmatic unrest. ?? 2010.

Chemical Geology↗
USGS2013

Mercury isotope fractionation during ore retorting in the Almadén mining district, Spain

Almadén, Spain, is the world's largest mercury (Hg) mining district, which has produced over 250,000 metric tons of Hg representing about 30% of the historical Hg produced worldwide. The objective of this study was to measure Hg isotopic compositions of cinnabar ore, mine waste calcine (retorted ore), elemental Hg (Hg 0 (L)), and elemental Hg gas (Hg 0 (g)), to evaluate potential Hg isotopic fractionation. Almadén cinnabar ore δ 202 Hg varied from − 0.92 to 0.15‰ (mean of − 0.56‰, σ = 0.35‰, n = 7), whereas calcine was isotopically heavier and δ 202 Hg ranged from − 0.03‰ to 1.01‰ (mean of 0.43‰, σ = 0.44‰, n = 8). The average δ 202 Hg enrichment of 0.99‰ between cinnabar ore and calcines generated during ore retorting indicated Hg isotopic mass dependent fractionation (MDF). Mass independent fractionation (MIF) was not observed in any of the samples in this study. Laboratory retorting experiments of cinnabar also were carried out to evaluate Hg isotopic fractionation of products generated during retorting such as calcine, Hg 0 (L), and Hg 0 (g). Calcine and Hg 0 (L) generated during these retorting experiments showed an enrichment in δ 202 Hg of as much as 1.90‰ and 0.67‰, respectively, compared to the original cinnabar ore. The δ 202 Hg for Hg 0 (g) generated during the retorting experiments was as much as 1.16‰ isotopically lighter compared to cinnabar, thus, when cinnabar ore was roasted, the resultant calcines formed were isotopically heavier, whereas the Hg 0 (g) generated was isotopically lighter in Hg isotopes.

Almad�n District↗
USGS2014

Quantifying biomineralization of zinc in the Rio Naracauli (Sardinia, Italy), using a tracer injection and synoptic sampling

Streams draining mined areas throughout the world commonly have high concentrations of Zn. Because Zn is not easily removed from stream water and because it can be toxic to aquatic organisms, its presence is a persistent problem. The discovery of biomineralization of Zn-bearing solids in the mine drainage of Rio Naracauli, in Sardinia, Italy, provides insights into strategies for removing Zn and improving water quality in streams affected by mine drainage. Until now, the transport and attenuation of Zn has not been quantified in this stream setting. A continuous tracer injection experiment was conducted to quantify the biomineralization process and to identify the loading of constituents that causes a change from precipitation of hydrozincite [Zn 5 (CO 3 ) 2 (OH) 6 ] in the upstream reach to precipitation of a Zn-silicate phase downstream. Based on the mass-load calculations derived from the tracer experiment, about 1.2 kg/day of Zn is sequestered in hydrozincite. This biomineralization represents nearly 90% removal of Zn. Other elements such as Pb and Cd also are sequestered, either in the hydrozincite, or in a separate phase that forms simultaneously. In the lower 600 m of the stream, where the Zn-silicate forms, as much as 0.7 kg/day Zn are sequestered in this solid, but additions of Zn to the stream from groundwater discharge lead to an overall increase in load in that portion of the Rio Naracauli.

Sardinia↗
USGS2026

Rhyolitic and basaltic reference materials for TC/EA analysis: Investigation of water extraction and D/H ratios

Increasingly, water and D/H ratios of silicic and basaltic glasses are used to investigate magmatic degassing and secondary hydration, as well as for study these parameters in the mantle and crustal magmas. The advent of the High Temperature Conversion Element Analyzer (TC/EA) continuous flow mass spectrometry made the determination of hydrogen isotopes relatively quick and precise (±0.04 wt% H 2 O and 1–3‰ δ 2 H). Many labs around the world have such systems, thus there is a need to develop both silicic and basaltic volcanic glass reference materials (RMs) that can be used for interlaboratory comparison by bulk and microanalytical methods. Here, we report results of such investigation run against solid RMs (USGS micas) and water RMs (including VSMOW) in three different labs and describe analytical protocols. We report on the effects of glass size fraction, the mass of aliquots measured, and yield dependency for two glasses: UOR (drill cutting of IDDP-1 rhyolite, Iceland) and UOB (an E -MORB basalt from the East Pacific Rise). Proposed RM values are: UOB rhyolitic glass ( n = 31): H 2 O = 1.84 ± 0.06 wt% (1 s.d.), and δ 2 H = −115.5 ± 2.6‰ (1 s.d.). UOB basaltic glass ( n = 60): H 2 O = 0.37 ± 0.03 wt% (1 s.d.), and δ 2 H = −82.1 ± 5.7‰ (1 s.d.). Glass reference materials are available in 100 mg quantities from the Stable Isotope Laboratory at the University of Oregon for a nominal fee.

Chemical Geology↗