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At least 235 records · Page 13Linked to original sources
USGS2026

Correcting a systematic bias in an ocean drilling project site 882 alkenone sea surface temperature record

Reconstructions of sea surface temperature (SST) in the geologic record are fundamental to our understanding of Earth's climate history and the evaluation of Earth's climate sensitivity to greenhouse gas forcing. SSTs are reconstructed with a variety of methods, including alkenone biomarker lipids produced by certain coccolithophore algae. One such alkenone SST reconstruction from the subpolar northwest Pacific Ocean Drilling Program (ODP) Site 882 (50.21° N, 167.35° E, 3244 m water depth) has played a large role in shaping the paleoclimate science community's view of global climate warmth during the Late Pliocene (3.6–2.6 million years ago) and the subsequent cooling that characterized the intensification of Northern Hemisphere Glaciation (Haug, 1995; Haug et al., 2005; Martínez-Garcia et al., 2010). First, we have found that the values reported in the PANGAEA archive for this ODP Site 882 alkenone dataset were inaccurately reported as U K' 37 values when they are instead U K 37 ( https://doi.org/10.1594/PANGAEA.315092 , Haug and Sarnthein, 2005). This error in the archived data table resulted in the incorporation of inaccurate absolute SST estimates by several studies that applied U K' 37 calibrations to this ODP Site 882 dataset (e.g., Brennan et al., 2022; Clark et al., 2024, 2025; Tierney et al., 2019, 2025b). Second, using other published data from ODP Site 882 (Studer et al., 2012) and nearby Site 883 (51.11° N, 167.46° E, 2384 m water depth; Herbert et al., 2016; Novak et al., 2024), we show that the original Haug (1995) alkenone SST record at ODP Site 882 systematically reports an amplified range of absolute SST values compared to the more recently generated data. This observation is consistent with the known concentration-dependent biases of the gas chromatography chemical ionization mass spectrometry (GC-CI-MS) analytical method used by the original ODP Site 882 study (Chaler et al., 2000, 2003; Haug, 1995; Hefter, 2008; Rosell-Mele et al., 1995). These concentration-dependent analytical biases complicate applying a uniform correction to the entire Haug (1995) dataset. However, we are able to leverage the published datasets to propose a correction and quantification of uncertainty for a subset of the Haug (1995) dataset measured at similar on-column analyte abundance. For these samples, we find an average analytical uncertainty equivalent to ±2.05 °C , which is greater than and in addition to the typical ±1.4 °C 1 σ prediction uncertainty of the U K' 37 sea surface temperature proxy. We then discuss the implications of the corrected dataset for our understanding of late Neogene and Quaternary climate in the Kuroshio Extension region.

Climate of the Past↗
USGS2025

In situ Re-Os geochronology of Re-rich Palaeogene molybdenite by LA-ICP-MS/MS

In situ Re–Os geochronology by LA-ICP-MS/MS was previously demonstrated by reacting Os with CH 4 or N 2 O reaction gasses. However, for both reactions, a minor proportion of the Re parent isotope also reacts, potentially leading to significant isobaric interferences of 187 Re on 187 Os, especially for young samples with little radiogenic in-growth. Here we present an interlaboratory comparison and compare three reaction gas mixtures (CH 4 + H 2 + He, N 2 O and N 2 O + He) with the aim to robustly date Palaeogene (66–23 Ma) molybdenite from the Bingham Canyon and Henderson deposits. CH 4 mixed with H 2 gas gives the highest sensitivity, while N 2 O and He gas buffer Re reaction. On balance, the analytical method involving N 2 O + He reaction gas is most suitable for dating Palaeogene molybdenite, resulting in age precision of 2.6% for Bingham and 5.8% for Henderson. For older, >1 Ga molybdenite, CH 4 + H 2 + He may give comparatively better age precision.

Colorado, Utah↗
USGS2018

Computing under-ice discharge: A proof-of-concept using hydroacoustics and the Probability Concept

Under-ice discharge is estimated using open-water reference hydrographs; however, the ratings for ice-affected sites are generally qualified as poor. The U.S. Geological Survey (USGS), in collaboration with the Colorado Water Conservation Board, conducted a proof-of-concept to develop an alternative method for computing under-ice discharge using hydroacoustics and the Probability Concept. The study site was located south of Minturn, Colorado (CO), USA, and was selected because of (1) its proximity to the existing USGS streamgage 09064600 Eagle River near Minturn, CO, and (2) its ease-of-access to verify discharge using a variety of conventional methods. From late September 2014 to early March 2015, hydraulic conditions varied from open water to under ice. These temporal changes led to variations in water depth and velocity. Hydroacoustics (tethered and uplooking acoustic Doppler current profilers and acoustic Doppler velocimeters) were deployed to measure the vertical-velocity profile at a singularly important vertical of the channel-cross section. Because the velocity profile was non-standard and cannot be characterized using a Power Law or Log Law, velocity data were analyzed using the Probability Concept, which is a probabilistic formulation of the velocity distribution. The Probability Concept-derived discharge was compared to conventional methods including stage-discharge and index-velocity ratings and concurrent field measurements; each is complicated by the dynamics of ice formation, pressure influences on stage measurements, and variations in cross-sectional area due to ice formation. No particular discharge method was assigned as truth. Rather one statistical metric (Kolmogorov-Smirnov; KS), agreement plots, and concurrent measurements provided a measure of comparability between various methods. Regardless of the method employed, comparisons between each method revealed encouraging results depending on the flow conditions and the absence or presence of ice cover. For example, during lower discharges dominated by under-ice and transition (intermittent open-water and under-ice) conditions, the KS metric suggests there is not sufficient information to reject the null hypothesis and implies that the Probability Concept and index-velocity rating represent similar distributions. During high-flow, open-water conditions, the comparisons are less definitive; therefore, it is important that the appropriate analytical method and instrumentation be selected. Six conventional discharge measurements were collected concurrently with Probability Concept-derived discharges with percent differences (%) of −9.0%, −21%, −8.6%, 17.8%, 3.6%, and −2.3%. This proof-of-concept demonstrates that riverine discharges can be computed using the Probability Concept for a range of hydraulic extremes (variations in discharge, open-water and under-ice conditions) immediately after the siting phase is complete, which typically requires one day. Computing real-time discharges is particularly important at sites, where (1) new streamgages are planned, (2) river hydraulics are complex, and (3) shifts in the stage-discharge rating are needed to correct the streamflow record. Use of the Probability Concept does not preclude the need to maintain a stage-area relation. Both the Probability Concept and index-velocity rating offer water-resource managers and decision makers alternatives for computing real-time discharge for open-water and under-ice conditions.

Colorado↗
USGS2016

Estimating black bear density in New Mexico using noninvasive genetic sampling coupled with spatially explicit capture-recapture methods

During the 2004–2005 to 2015–2016 hunting seasons, the New Mexico Department of Game and Fish (NMDGF) estimated black bear abundance (Ursus americanus) across the state by coupling density estimates with the distribution of primary habitat generated by Costello et al. (2001). These estimates have been used to set harvest limits. For example, a density of 17 bears/100 km2 for the Sangre de Cristo and Sacramento Mountains and 13.2 bears/100 km2 for the Sandia Mountains were used to set harvest levels. The advancement and widespread acceptance of non-invasive sampling and mark-recapture methods, prompted the NMDGF to collaborate with the New Mexico Cooperative Fish and Wildlife Research Unit and New Mexico State University to update their density estimates for black bear populations in select mountain ranges across the state. We established 5 study areas in 3 mountain ranges: the northern (NSC; sampled in 2012) and southern Sangre de Cristo Mountains (SSC; sampled in 2013), the Sandia Mountains (Sandias; sampled in 2014), and the northern (NSacs) and southern Sacramento Mountains (SSacs; both sampled in 2014). We collected hair samples from black bears using two concurrent non-invasive sampling methods, hair traps and bear rubs. We used a gender marker and a suite of microsatellite loci to determine the individual identification of hair samples that were suitable for genetic analysis. We used these data to generate mark-recapture encounter histories for each bear and estimated density in a spatially explicit capture-recapture framework (SECR). We constructed a suite of SECR candidate models using sex, elevation, land cover type, and time to model heterogeneity in detection probability and the spatial scale over which detection probability declines. We used Akaike’s Information Criterion corrected for small sample size (AICc) to rank and select the most supported model from which we estimated density. We set 554 hair traps, 117 bear rubs and collected 4,083 hair samples. We identified 725 (367 M, 358 F) individuals; the sex ratio for each study area was approximately equal. Our density estimates varied within and among mountain ranges with an estimated density of 21.86 bears/100 km2 (95% CI: 17.83 – 26.80) for the NSC, 19.74 bears/100 km2 (95% CI: 13.77 – 28.30) in the SSC, 25.75 bears/100 km2 (95% CI: 13.22 – 50.14) in the Sandias, 21.86 bears/100 km2 (95% CI: 17.83 – 26.80) in the NSacs, and 16.55 bears/100 km2 (95% CI: 11.64 – 23.53) in the SSacs. Overall detection probability for hair traps and bear rubs, combined, was low across all study areas and ranged from 0.00001 to 0.02. We speculate that detection probabilities were affected by failure of some hair samples to produce a complete genotype due to UV degradation of DNA, and our inability to set and check some sampling devices due to wildfires in the SSC. Ultraviolet radiation levels are particularly high in New Mexico compared to other states where NGS methods have been used because New Mexico receives substantial amounts of sunshine, is relatively high in elevation (1,200 m – 4,000 m), and is at a lower latitude. Despite these sampling difficulties, we were able to produce density estimates for New Mexico black bear populations with levels of precision comparable to estimated black bear densities made elsewhere in the U.S. Our ability to generate reliable black bear density estimates for 3 New Mexico mountain ranges is attributable to our use of a statistically robust study design and analytical method. There are multiple factors that need to be considered when developing future SECR-based density estimation projects. First, the spatial extent of the population of interest and the smallest average home range size must be determined; these will dictate size of the trapping array and spacing necessary between hair traps. The number of technicians needed and access to the study areas will also influence configuration of the trapping array. We believe shorter sampling occasions could be implemented to reduce degradation of DNA due to UV radiation; this might help increase amplification rates and thereby increase both the number of unique individuals identified and the number of recaptures, improving the precision of the density estimates. A pilot study may be useful to determine the length of time hair samples can remain in the field prior to collection. In addition, researchers may consider setting hair traps and bear rubs in more shaded areas (e.g., north facing slopes) to help reduce exposure to UV radiation. To reduce the sampling interval it will be necessary to either hire more field personnel or decrease the number of hair traps per sampling session. Both of these will enhance detection of long-range movement events by individual bears, increase initial capture and recapture rates, and improve precision of the parameter estimates. We recognize that all studies are constrained by limited resources, however, increasing field personnel would also allow a larger study area to be sampled or enable higher trap density. In conclusion, we estimated the density of black bears in 5 study areas within 3 mountains ranges of New Mexico. Our estimates will aid the NMDGF in setting sustainable harvest limits. Along with estimates of density, information on additional demographic rates (e.g., survival rates and reproduction) and the potential effects that climate change and future land use may have on the demography of black bears may also help inform management of black bears in New Mexico, and may be considered as future areas for research.

New Mexico↗
USGS2025

Combining scanning electron microscopy, X-ray diffraction, and X-ray fluorescence to characterize shear zones at the Pogo gold deposit, Alaska

This study employs a multi-method analytical approach to characterize the mineralogical, geochemical, and textural properties of fault rocks from the Pogo gold mine in the Yukon-Tanana Upland, central Alaska. Specifically, we examine cataclasites, to document the structural and geochemical evolution of shear zones and their associations with gold mineralization. To investigate the shear zone, we integrate portable X-ray fluorescence (pXRF), scanning electron microscopy-based automated mineralogy (SEM-AM), X-ray diffraction (XRD), and high-resolution micro-X-ray fluorescence (micro-XRF) mapping. These methods collectively provide insights into bulk and trace element chemistry, mineralogical composition, and deformation-related textures across multiple scales. Handheld pXRF enables rapid geochemical screening, guiding SEM-AM and XRD analyses to ensure consistent mineralogical interpretation. X-ray diffraction identifies and quantifies crystalline phases, while SEM-AM produces high-resolution mineral maps, revealing mineral abundances, grain-scale textures, and gold associations. Micro-XRF mapping further refines our understanding by showing visual trace element distributions at sub-millimetre resolution. By integrating these techniques, we improve our understanding of the nature and geochemistry of Pogo shear zones, their role in gold mineralization, and support metallurgical processing strategies. This approach enhances exploration models and resource characterization for structurally complex gold deposits.

Alaska↗
USGS1989

Can we determine the biological availability of sediment-bound trace elements?

It is clear from available data that the susceptibility of biological communities to trace element contamination differs among aquatic environments. One important reason is that the bioavailability of metals in sediments appears to be altered by variations in sediment geochemistry. However, methods for explaining or predicting the effect of sediment geochemistry upon metal bioavailability are poorly developed. Experimental studies demonstrate that ingestion of sediments and uptake from solution may both be important pathways of metal bioaccumulation in deposit/detritus feeding species. Relative importance between the two is geochemistry dependent. Geochemical characteristics of sediments also affect metal concentrations in the tissues of organisms collected from nature, but the specific mechanisms by which these characteristics influence metal bioavailability have not been rigorously demonstrated. Several prerequisites are necessary to better understand the processes that control metal bioavailability from sediments. 1) improved computational or analytical methods for analyzing distribution of metals among components of the sediments; 2) improved computational methods for assessing the influences of metal form in sediments on sediment-water metal exchange; and 3) a better understanding of the processes controlling bioaccumulation of metals from solution and food by metazoan species directly exposed to the sediments. Such capabilities would allow mechanistic explanations essential to the development of practical tools sought for determining sediment quality criteria for metals.

Hydrobiologia↗
USGS2022

Special section overview: Effects of ecosystem change on North American percid populations.

Walleye Sander vitreus , Sauger S. canadensis , and Yellow Perch Perca flavescens (referred to as percids herein) are collectively among the most culturally and ecologically important fish species in North America. As ecosystems change in response to environmental drivers, such as climate change, nutrient loading, and invasive species, there is a need to understand how percid populations respond to these changes. To address this need, a symposium was held during the 81st Annual Midwest Fish and Wildlife Conference to bring fishery scientists and managers together to describe and discuss percid population responses to ecosystem change. Prevailing symposium themes included the challenge of identifying mechanisms responsible for population-level changes, developing strategies to adaptively manage for resilient fisheries, and consideration of scale, context, and methods when interpreting variable results. Given the uncertainty of how ecosystem changes affect percid populations, participants emphasized the importance of communicating uncertainties to stakeholders, implementing data-driven management strategies, setting realistic goals, and revising management actions in an adaptive framework. There was universal agreement on both the challenge and necessity of facilitating constructive engagement among stakeholders in cooperative decision making. Symposium participants identified knowledge gaps and discussed future efforts to build on our current understanding of percid populations, including continuation of long-term monitoring, improved standardization of evaluation metrics, implementing adaptive management experiments to identify causal relationships, development of more robust analytical methods, use of historical data sources, and refining techniques to realistically convey management options to stakeholders.

North American Journal of Fisheries Management↗
USGS2023

Improving ecological data science with workflow management software

Pressing environmental research questions demand the integration of increasingly diverse and large-scale ecological datasets as well as complex analytical methods, which require specialized tools and resources. Computational training for ecological and evolutionary sciences has become more abundant and accessible over the past decade, but tool development has outpaced the availability of specialized training. Most training for scripted analyses focuses on individual analysis steps in one script rather than creating a scripted pipeline, where modular functions comprise an ecosystem of interdependent steps. Although current computational training creates an excellent starting place, linear styles of scripting can risk becoming labor- and time-intensive and less reproducible by often requiring manual execution. Pipelines, however, can be easily automated or tracked by software to increase efficiency and reduce potential errors. Ecology and evolution would benefit from techniques that reduce these risks by managing analytical pipelines in a modular, readily parallelizable format with clear documentation of dependencies. Workflow management software (WMS) can aid in the reproducibility, intelligibility and computational efficiency of complex pipelines. To date, WMS adoption in ecology and evolutionary research has been slow. We discuss the benefits and challenges of implementing WMS and illustrate its use through a case study with the targets r package to further highlight WMS benefits through workflow automation, dependency tracking and improved clarity for reviewers. Although WMS requires familiarity with function-oriented programming and careful planning for more advanced applications and pipeline sharing, investment in training will enable access to the benefits of WMS and impart transferable computing skills that can facilitate ecological and evolutionary data science at large scales.

Methods in Ecology and Evolution↗
USGS2017

Methods used to characterize the chemical composition and biological activity of environmental waters throughout the United States, 2012-14

A vast array of chemical compounds are in wide commercial use in the United States, and the potential ecological and human-health effect of exposure to chemical mixtures has been identified as a high priority in environment health science. Awareness of the potential effects of low-level chemical exposures is rising. The U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, conducted a study in which samples were collected from 38 streams in 25 States to provide an overview of contaminants found in stream water across the Nation. Additionally, biological screening assays were used to help determine any potential ecological and human-health effects of these chemical mixtures and to prioritize target chemicals for future toxicological studies. This report describes the site locations and the sampling and analytical methods and quality-assurance procedures used in the study.

Open-File Report↗
USGS2010

Understanding beach health throughout the Great Lakes-Entering a new era of investigations

For over a decade, the U.S. Geological Survey (USGS) has been a leader in the science of beach health. The overall mission of this work is to provide science-based information and methods that will allow beach managers to more accurately make beach closure and advisory decisions, understand the sources and physical processes affecting beach contaminants, and understand how science-based information can be used to mitigate and restore beaches and protect the public. The work consists of four science elements-real-time assessments; pathogens and microbial source tracking; coastal processes; and data analysis, interpretation, and communication - which are described in this fact sheet. Some of the key questions for USGS beach research are the following: Are there better ways to inform the public whether they can use a beach without risking their health? How do new rapid analytical methods compare to traditional methods for determining concentrations of fecal-indicator bacteria at beaches? Are pathogens present at beaches and, if so, how do they get to the beach, and what is their source? How do sand movement and wave action on the beach affect fecal-indicator-bacteria and pathogen concentrations in the lake water? What are the best indicators of pathogenic microorganisms? With so many potential sources of fecal contamination at a beach, what methods can be used to distinguish the contributions from humans? What characteristics of beaches contribute most to influencing bacterial indicator and pathogen concentrations in beach sands and groundwater?

Fact Sheet↗
USGS2025

Effects of nonmotorized recreation on ungulates in the western United States—A science synthesis to inform National Environmental Policy Act analyses

The U.S. Geological Survey is working with Federal land management agencies to develop a series of science syntheses to support National Environmental Policy Act (NEPA) analyses. This report synthesizes science information about the potential effects of nonmotorized recreation on ungulates in the western United States. We conducted a structured literature search to find published science, data, and analysis methods about the characteristics of nonmotorized recreation, ungulate exposure and response to nonmotorized recreation, and approaches to mitigate negative effects of nonmotorized recreation on ungulates. The sections of the report align with standard elements of the NEPA analysis process. We found that timing, intensity, duration, and spatial distribution of nonmotorized recreation are important factors to understand when assessing effects of recreation on ungulates. Several aspects of ungulate biology, which vary by species, population, and individual, affect ungulate susceptibility to effects from recreation, including diet, migration and movement, and seasonal biology. Techniques for assessing effects include basic spatial analyses based on buffers around trails and recreation sites and more technical analytical methods based on displacement or avoidance of recreation sites. Options for mitigating negative effects of nonmotorized recreation on ungulates include timing and type-of-use restrictions, recreator education, and project design features to avoid human-ungulate conflicts. Public land managers can use this report by incorporating it by reference in NEPA analyses or as a general reference to find literature or identify gaps in the literature about the effects of noise from nonmotorized recreation on ungulates.

Scientific Investigations Report↗
USGS2025

The importance of method selection when estimating diet composition with quantitative fatty acid signature analysis

Quantitative fatty acid signature analysis (QFASA) is a common method of estimating the composition of prey species in the diets of consumers from polar and temperate ecosystems in which lipids are an important source of energy. A key characteristic of QFASA is that the large number of fatty acids that typically comprise lipids permits the dietary contributions of a correspondingly large number of prey types to be estimated. Several modifications to the original QFASA methods have been suggested in the literature and a significant extension of the original model published in 2017 allows simultaneous estimation of both diet proportions and calibration coefficients, which are metabolic constants in the model whose values must otherwise be estimated in independent feeding experiments. However, comparisons of diet estimates obtained using different estimation options have been limited. QFASA has been used to estimate the diet composition of several polar bear ( Ursus maritimus ) subpopulations, including the Southern Beaufort Sea (SBS) subpopulation. Prior QFASA estimates of SBS polar bear diet composition have most often been obtained using variations of the original QFASA model. We investigated the influence of variations in QFASA analytical methods on diet estimates by re-estimating the diet composition of polar bears from the Alaska portion of the SBS using three different methods and found that differences among the three sets of estimates were substantial. Our results illustrate how important the careful and deliberate selection of QFASA methods can be and we provide some guidance on techniques one might use to evaluate options.

PLoS ONE↗
USGS2010

Long-term frozen storage of stream water samples for dissolved orthophosphate, nitrate plus nitrite, and ammonia analysis

Many researchers have used freezing as an effective, short-term, water sample preservation method for subsequent nutrient analysis. In this study, filtered samples held at −16±2°C for 4–8 years were reanalyzed for orthophosphate, nitrate plus nitrite, and ammonia. Orthophosphate and ammonia concentrations decreased by 0.2 μg P/L and 5 μg N/L, respectively, at mean concentrations of 69.4 μg P/L and 246 μg N/L. Nitrate plus nitrite increased by 1.1 μg N/L at a mean concentration of 139.1 μg N/L. An anaerobic well sample proved to be unsuitable for freezing because it lost significant amounts of orthophosphate during the freezing process. None of the differences observed over long periods of frozen storage were more than twice the estimated standard deviation of the analytical methods used in the study. The small changes observed demonstrate the effectiveness of frozen storage as a means of nutrient preservation in water samples that are unaffected by the freezing process itself.

Water Resources Research↗
USGS1948

Application of Brianchon's theorem to construction of geologic profiles

Brianchon's theorem states that the three diagonals joining opposite vertices of a hexagon circumscribed about a conic are concurrent. A corollary of this theorem applies to a pentagon so that the points of tangency of an inscribed conic may be located. Any five non-concurrent straight lines in a plane, no three of which are parallel, will ordinarily form some kind of a pentagon; and if considered as tangents to a conic, they will define its shape and position. If these five lines are also normals to the traces of parallel stratigraphic surfaces having a constant strike, the derived conic may be regarded as an evolute, from which a set of involutes can be drawn that will constitute a structural profile. A method is thus afforded for constructing a profile normal to the strike of the rocks, and for measuring stratigraphic thickness, by the utilization of five observations of dip along a suitable linear traverse. Graphical methods are also given for constructing a parabolic evolute from four observations and a circular evolute from three observations. Additional points on the conic evolutes are obtained by the application of Pascal's theorem. A mathematical analysis is presented of the relationship between a conic and five of its tangents; and the conic evolute, rather than its involutes, is recommended as a satisfactory record of the structure of a parallel fold. To obtain the equation of this evolute, the equations of the five tangents are first derived, using trilinear coordinates. Thereafter the tangential and trilinear equations of the general conic are deduced. Criteria are given for classifying the conic as a hyperbola, ellipse, parabola, or circle. These graphical and analytical methods are adaptations of the general method of evolute and involutes. They are offered, not as substitutes for the general method, but as quicker, though somewhat less accurate, means of obtaining similar results, where structural conditions justify their use. © 1948, The Geological Society of America, Inc.

Geological Society of America Bulletin↗
USGS2007

Methods and data used to investigate polonium-210 as a source of excess gross-alpha radioactivity in ground water, Churchill County, Nevada

Ground water is the major source of drinking water in the Carson River Basin, California and Nevada. Previous studies have shown that uranium and gross-alpha radioactivities in ground water can be greater than U.S. Environmental Protection Agency Maximum Contaminant Levels, particularly in the Carson Desert, Churchill County, Nevada. Studies also have shown that the primary source of the gross-alpha radioactivity and alpha-emitting radionuclides in ground water is the dissolution of uranium-rich granitic rocks and basin-fill sediments that have their origins in the Sierra Nevada. However, ground water sampled from some wells in the Carson Desert had grossalpha radioactivities greater than could be accounted for by the decay of dissolved uranium. The occurrence of polonium-210 (Po-210) was hypothesized to explain the higher than expected grossalpha radioactivities. This report documents and describes the study design, field and analytical methods, and data used to determine whether Po-210 is the source of excess gross-alpha radioactivity in ground water underlying the Carson Desert in and around Fallon, Nevada. Specifically, this report presents: 1) gross alpha and uranium radioactivities for 100 wells sampled from June to September 2001; and 2) pH, dissolved oxygen, specific conductance, and Po-210 radioactivity for 25 wells sampled in April and June 2007. Results of quality-control samples for the 2007 dataset are also presented.

Open-File Report↗
USGS2026

Three new calcium formate reference materials for δ13C measurements and a redetermination of the R(13C/12C) ratio for VPDB based on proton nuclear magnetic resonance measurements

Rationale Isotope ratio mass spectrometry (IRMS) and proton nuclear magnetic resonance ( 1 H NMR) spectroscopy are independent techniques for determining the isotope ratio R ( 13 C/ 12 C) in organic compounds. However, the lack of suitable reference materials has limited intercalibration of results from these methods. Methods Three high-purity calcium formate isotopic reference materials were developed, each ideal for accurate isotope ratio measurements by both 1 H NMR and isotope-ratio mass spectrometry (IRMS). For each material, R ( 13 C/ 12 C) was determined by 1 H NMR, and the relative isotope abundance ( δ 13 C VPDB-LSVEC ) by IRMS. The combined IRMS and NMR results were used to determine the R ( 13 C/ 12 C) value of Vienna Peedee belemnite (VPDB). Results The combined datasets yield a value for R ( 13 C/ 12 C) of 0.0111050 ± 0.0000047 ( k = 2) for VPDB, which is 6.7‰ lower than the commonly cited value of 0.011180, but similar to other recent determinations. These three calcium formate reference materials exhibit high accuracy across both analytical methods and provide robust tools for instrument calibration, method validation, and inter-laboratory comparison in carbon stable isotope ratio analysis. Conclusions An accurate R ( 13 C/ 12 C) value for VPDB strengthens the link between relative ( δ 13 C VPDB-LSVEC ) values from IRMS and R ( 13 C/ 12 C) isotope ratios from NMR and other techniques. These three calcium formate isotopic reference materials (USGS106, USGS107, and USGS108) are available from the US Geological Survey and provide reference materials for calibration, method validation, and inter-laboratory comparison in carbon isotope ratio analysis.

Rapid Communications in Mass Spectrometry↗
USGS2008

Estimating sediment discharge: Appendix D

Sediment-discharge measurements usually are available on a discrete or periodic basis. However, estimates of sediment transport often are needed for unmeasured periods, such as when daily or annual sediment-discharge values are sought, or when estimates of transport rates for unmeasured or hypothetical flows are required. Selected methods for estimating suspended-sediment, bed-load, bed- material-load, and total-load discharges have been presented in some detail elsewhere in this volume. The purposes of this contribution are to present some limitations and potential pitfalls associated with obtaining and using the requisite data and equations to estimate sediment discharges and to provide guidance for selecting appropriate estimating equations. Records of sediment discharge are derived from data collected with sufficient frequency to obtain reliable estimates for the computational interval and period. Most sediment- discharge records are computed at daily or annual intervals based on periodically collected data, although some partial records represent discrete or seasonal intervals such as those for flood periods. The method used to calculate sediment- discharge records is dependent on the types and frequency of available data. Records for suspended-sediment discharge computed by methods described by Porterfield (1972) are most prevalent, in part because measurement protocols and computational techniques are well established and because suspended sediment composes the bulk of sediment dis- charges for many rivers. Discharge records for bed load, total load, or in some cases bed-material load plus wash load are less common. Reliable estimation of sediment discharges presupposes that the data on which the estimates are based are comparable and reliable. Unfortunately, data describing a selected characteristic of sediment were not necessarily derived—collected, processed, analyzed, or interpreted—in a consistent manner. For example, bed-load data collected with different types of bed-load samplers may not be comparable (Gray et al. 1991; Childers 1999; Edwards and Glysson 1999). The total suspended solids (TSS) analytical method tends to produce concentration data from open-channel flows that are biased low with respect to their paired suspended-sediment concentration values, particularly when sand-size material composes more than about a quarter of the material in suspension. Instantaneous sediment-discharge values based on TSS data may differ from the more reliable product of suspended- sediment concentration values and the same water-discharge data by an order of magnitude (Gray et al. 2000; Bent et al. 2001; Glysson et al. 2000; 2001). An assessment of data comparability and reliability is an important first step in the estimation of sediment discharges. There are two approaches to obtaining values describing sediment loads in streams. One is based on direct measurement of the quantities of interest, and the other on relations developed between hydraulic parameters and sediment- transport potential. In the next sections, the most common techniques for both approaches are briefly addressed.

Book chapter↗
USGS2009

Gas chromatographic–mass spectrometric fragmentation study of phytoestrogens as their trimethylsilyl derivatives: Identification in soy milk and wastewater samples

An analytical method for the identification of eight plant phytoestrogens (biochanin A, coumestrol, daidzein, equol, formononetin, glycitein, genistein and prunetin) in soy products and wastewater samples was developed using gas chromatography coupled with ion trap mass spectrometry (GC/MS–MS). The phytoestrogens were derivatized as their trimethylsilyl ethers with trimethylchlorosilane (TMCS) and N,O- bis (trimethylsilyl)trifluoroacetamide (BSTFA). The phytoestrogens were isolated from all samples with liquid–liquid extraction using ethyl acetate. Daidzein-d 4 and genistein-d 4 labeled standards were used as internal standards before extraction and derivatization. The fragmentation patterns of the phytoestrogens were investigated by isolating and fragmenting the precursor ions in the ion-trap and a typical fragmentation involved the loss of a methyl and a carbonyl group. Two characteristic fragment ions for each analyte were chosen for identification and confirmation. The developed methodology was applied to the identification and confirmation of phytoestrogens in soy milk, in wastewater effluent from a soy-milk processing plant, and in wastewater (influent and effluent) from a treatment plant. Detected concentrations of genistein ranged from 50,000 μg/L and 2000 μg/L in soy milk and in wastewater from a soy-plant, respectively, to 20 μg/L and <1 μg/L for influent and effluent from a wastewater treatment plant, respectively.

Journal of Chromatography A↗