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USGS1996

Hydrologic evaluation methodology for estimating water movement through the unsaturated zone at commercial low-level radioactive waste disposal site

This report identifies key technical issues related to hydrologic assessment of water flow in the unsaturated zone at low-level radioactive waste (LLW) disposal facilities. In addition, a methodology for incorporating these issues in the performance assessment of proposed LLW disposal facilities is identified and evaluated. The issues discussed fall into four areas: Estimating the water balance at a site (i.e., infiltration, runoff, water storage, evapotranspiration, and recharge); Analyzing the hydrologic performance of engineered components of a facility; Evaluating the application of models to the prediction of facility performance; and Estimating the uncertainty in predicted facility performance. An estimate of recharge at a LLW site is important since recharge is a principal factor in controlling the release of contaminants via the groundwater pathway. The most common methods for estimating recharge are discussed in Chapter 2. Many factors affect recharge; the natural recharge at an undisturbed site is not necessarily representative either of the recharge that will occur after the site has been disturbed or of the flow of water into a disposal facility at the site. Factors affecting recharge are discussed in Chapter 2. At many sites engineered components are required for a LLW facility to meet performance requirements. Chapter 3 discusses the use of engineered barriers to control the flow of water in a LLW facility, with a particular emphasis on cover systems. Design options and the potential performance and degradation mechanisms of engineered components are also discussed. Water flow in a LLW disposal facility must be evaluated before construction of the facility. In addition, hydrologic performance must be predicted over a very long time frame. For these reasons, the hydrologic evaluation relies on the use of predictive modeling. In Chapter 4, the evaluation of unsaturated water flow modeling is discussed. A checklist of items is presented to guide the evaluation. Several computer simulation codes that were used in the examples (Chapter 6) are discussed with respect to this checklist. The codes used include HELP, UNSAT-H, and VAM3DCG. To provide a defensible estimate of water flow in a LLW disposal facility, the uncertainty associated with model predictions must be considered. Uncertainty arises because of the highly heterogeneous nature of most subsurface environments and the long time frame required in the analysis. Sources of uncertainty in hydrologic evaluation of the unsaturated zone and several approaches for analysis are discussed in Chapter 5. The methods of analysis discussed include a bounding approach, sensitivity analysis, and Monte Carlo simulation. To illustrate the application of the discussion in Chapters 2 through 5, two examples are presented in Chapter 6. The first example is of a below ground vault located in a humid environment. The second example looks at a shallow land burial facility located in an arid environment. The examples utilize actual site-specific data and realistic facility designs. The two examples illustrate the issues unique to humid and arid sites as well as the issues common to all LLW sites. Strategies for addressing the analytical difficulties arising in any complex hydrologic evaluation of the unsaturated zone are demonstrated. The report concludes with some final observations and recommendations.

Report↗

USGS2005

A finite-volume ELLAM for three-dimensional solute-transport modeling

A three-dimensional finite-volume ELLAM method has been developed, tested, and successfully implemented as part of the U.S. Geological Survey (USGS) MODFLOW-2000 ground water modeling package. It is included as a solver option for the Ground Water Transport process. The FVELLAM uses space-time finite volumes oriented along the streamlines of the flow field to solve an integral form of the solute-transport equation, thus combining local and global mass conservation with the advantages of Eulerian-Lagrangian characteristic methods. The USGS FVELLAM code simulates solute transport in flowing ground water for a single dissolved solute constituent and represents the processes of advective transport, hydrodynamic dispersion, mixing from fluid sources, retardation, and decay. Implicit time discretization of the dispersive and source/sink terms is combined with a Lagrangian treatment of advection, in which forward tracking moves mass to the new time level, distributing mass among destination cells using approximate indicator functions. This allows the use of large transport time increments (large Courant numbers) with accurate results, even for advection-dominated systems (large Peclet numbers). Four test cases, including comparisons with analytical solutions and benchmarking against other numerical codes, are presented that indicate that the FVELLAM can usually yield excellent results, even if relatively few transport time steps are used, although the quality of the results is problem-dependent.

Ground Water↗

USGS2005

Determination of total mercury in biological and geological samples

The analytical chemist is faced with several challenges when determining mercury in biological and geological materials. These challenges include widespread mercury contamination, both in the laboratory and the environment, possible losses of mercury during sample preparation and digestion, the wide range of mercury values commonly observed, ranging from the low nanogram per gram or per liter for background areas to hundreds of milligrams per kilogram in contaminated or ore-bearing areas, great matrix diversity, and sample heterogeneity1. These factors can be naturally occurring or anthropogenic, but must be addressed to provide a precise and accurate analysis. Although there are many instrumental methods available for the successful determination of mercury, no one technique will address all problems or all samples all of the time. The approach for the determination of mercury used at the U.S. Geological Survey, Crustal Imaging and Characterization Team, Denver Laboratories, utilizes a suite of complementary instrumental methods when approaching a study requiring mercury analyses. Typically, a study could require the analysis of waters, leachates or selective digestions of solids, vegetation, and biological materials such as tissue, bone, or shell, soils, rocks, sediments, coals, sludges, and(or) ashes. No one digestion or sample preparation method will be suitable for all of these matrices. The digestions typically employed at our laboratories include: (i) a closed-vessel microwave method using nitric acid and hydrogen peroxide, followed by digestion/dilution with a nitric acid/sodium dichromate solution, (ii) a robotic open test-tube digestion with nitric acid and sodium dichromate, (iii) a sealed Teflon? vessel with nitric acid and sodium dichromate, (iv) a sealed glass bottle with nitric acid and sodium dichromate, or (v) open test tube digestion with nitric and sulfuric acids and vanadium pentoxide. The common factor in all these digestions is that they are very oxidative to ensure the conversion of all mercury forms into Hg (II). Each method of digestion has its advantages and limitations. The method of detection used in our laboratories involves a combination of an in-house, custom, classic continuous-flow cold-vapor atomic absorption spectrometry (CVAAS), a commercially available, automated, flow-injection and a continuous flow cold-vapor atomic fluorescence spectrometry (CV-AFS) systems, and a relatively new, automated and integrated approach where solid or liquid samples are thermally decomposed under an oxygen atmosphere (a nitrogen atmosphere is used for coals) and the released mercury vapor trapped onto a gold gauze and then thermally released into an AAS system. Other less frequently used instrumental methods available for the determination of mercury include inductively coupled plasma ? optical emission spectrometry (ICP-OES), inductively couple plasma ? mass spectrometry (ICP-MS) (both solution nebulization and laser ablation), and instrumental neutron activation analysis (INAA). Results from two case studies involving the determination of mercury in the challenging matrices of biological materials will be presented. These will include fillet, liver and stomach-content samples from grayling for a baseline/background study in Alaska, and samples of meat tissue and shell material from Tanner crabs from Glacier Bay, Alaska. These studies show that the method of digestion is more important than a very sensitive detection limit for mercury.

Open-File Report↗

USGS2024

Low-flow statistics computed for streamflow gages and methods for estimating selected low-flow statistics for ungaged stream locations in Ohio, water years 1975–2020

A study was conducted by the U.S. Geological Survey, in cooperation with the Ohio Water Development Authority and the Ohio Environmental Protection Agency, to compute low-flow frequency, flow-duration, and harmonic mean flow statistics for long-term streamflow gages and to develop regression equations to estimate those statistics at unregulated, ungaged stream locations in Ohio. The flow statistics were computed with data collected after the 1974 water year because upward trends and statistically significant step changes (occurring after the late 1960s but before 1975) in annual flow statistics were detected at many candidate gages in Ohio. A total of 180 continuous-record gages in Ohio and bordering States were identified as having at least 10 years of daily flow records during the analytical period (water years 1975–2020). Also identified were five low-flow partial-record gages in Ohio that had instantaneous low flows that correlated strongly with daily streamflows at one of the continuous-record gages (also referred to as index gages). For continuous-record gages, the following flow statistics were computed: annual and seasonal minimum 1-, 7-, 30-, and 90-day flows with 2-, 5-, 10-, 20-, and 50-year recurrence intervals; annual and seasonal 98-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, 50-, 40-, 30-, 20-, and 10-percent duration flows; and the harmonic mean flow. For partial-record gages, estimates were made for annual and seasonal minimum 1-, 7-, 30-, and 90-day low flows with 2-, 10-, and 20-year recurrence intervals and annual and seasonal 98-, 95-, 90-, 85-, and 80-percent duration flows. The drainage basin of each gage was inspected for anthropogenic or karst features that could appreciably affect or regulate low flows. That inspection resulted in data from 53 of the 180 continuous-record gages and the 5 low-flow partial-record gages being categorized as “unregulated” and subsequently used in regression analyses to develop equations for estimating low-flow statistics. Two hundred and sixty potential explanatory variables were tested for this study. In most cases, a streamflow-variability index (SVI) was chosen as the sole explanatory variable for the regression analyses to predict the harmonic mean and annual and seasonal low-flow yields. The exceptions were for one of the September–November low-flow yield statistics and all the December–February yield statistics. Drainage area, decimal longitude, and usually SVI were chosen as the explanatory variables for those exceptions and to predict the 80-percent duration flows. The SVI values used in the model were estimated from a geospatial grid of SVI values developed for this study by using an empirical Bayesian kriging regression prediction. Observations for continuous-record gages used in the regression analyses were weighted as a function of their record length. Weights for partial-record gages were estimated based on the weights determined for their index gages. Equations for low-flow yields were developed by using censored regressions with a censoring level of 0.00001 cubic foot per second per square mile. Numerical constraints were placed on the yield equations if they could compute yields less than the yield censoring level or if the yields did not monotonically decrease with increasing SVI. Logistic-regression equations were developed, with SVI and drainage area as explanatory variables, to estimate the probability that the low-flow statistics were greater than the flow censoring level (0.01 cubic foot per second). The regression equations presented in this report were developed for implementation in the Ohio StreamStats application. The equations are applicable to unregulated streams in Ohio and are not applicable to streams with karst drainage features, diversions, regulation, or other anthropogenic activities that can appreciably affect low flow. The equations were developed by using observations with a range of SVI values from 0.41 to 1.23 log10 cubic foot per second and a range of drainage areas from 0.21 to 540 square miles. The applicability of the equations outside these ranges is not known.

Ohio↗

USGS2022

Spatially explicit management of genetic diversity using ancestry probability surfaces

1. Ecological restoration and conservation efforts are increasing worldwide and the management of intraspecific genetic variation in plants and animals, an important component of biodiversity, is increasingly valued. As a result, tailorable, spatially explicit approaches to map genetic variation are needed to support decision-making and management frameworks related to the recovery of threatened and endangered species and the maintenance of genetic resources in species utilized by humans, such as for restoration or agricultural purposes. 2. Here, we describe and demonstrate a workflow to spatially interpolate patterns of genetic differentiation using novel functions in the R package POPMAPS ( Pop ulation M anagement using A ncestry P robability S urfaces). Our approach uses empirical genetic data to estimate ancestry coefficients across a user-defined landscape correlated with patterns of differentiation in the focal species. The resulting surface, which we term the ancestry probability surface, includes two components: hard population boundaries and estimations of uncertainty that represent confidence in population assignments (i.e., ancestry probabilities). 3. An ancestry probability surface developed for Hilaria jamesii , an important graminoid utilized in restoration across the western United States, demonstrates the functionality of POPMAPS . Genetic distances among empirical sites correlated better with least-cost distances across suitable habitat than with geographic distances, informing the surface over which the interpolation was conducted (i.e., a model indicating habitat suitability). A jackknifing procedure identified parameter values resulting in robust population assignments across the species’ range, which were utilized in downstream analyses to estimate ancestry coefficients from empirical data. Ancestry coefficients were translated into ancestry probabilities, which tended to be low for cells that were intermediate in distance between empirical sampling locations representing different populations or when influenced by empirical sampling locations with mixed genetic ancestry. 4. POPMAPS allows users to tailor parameter values and analytical approaches and thereby incorporate species-specific biological characteristics and desired levels of uncertainty into maps illustrating patterns of genetic differentiation. Ancestry probability surfaces may be used to guide management or investigate further ecological or evolutionary hypotheses. We discuss how maps produced by POPMAPS can inform multiple management challenges including species recovery planning and the utilization of commonly used species in restoration.

Methods in Ecology and Evolution↗

USGS2013

Integrated geophysical imaging of a concealed mineral deposit: a case study of the world-class Pebble porphyry deposit in southwestern Alaska

We combined aeromagnetic, induced polarization, magnetotelluric, and gravity surveys as well as drillhole geologic, alteration, magnetic susceptibility, and density data for exploration and characterization of the Cu-Au-Mo Pebble porphyry deposit. This undeveloped deposit is almost completely concealed by postmineralization sedimentary and volcanic rocks, presenting an exploration challenge. Individual geophysical methods primarily assist regional characterization. Positive chargeability and conductivity anomalies are observed over a broad region surrounding the deposit, likely representing sulfide minerals that accumulated during multiple stages of hydrothermal alteration. The mineralized area occupies only a small part of the chargeability anomaly because sulfide precipitation was not unique to the deposit, and mafic rocks also exhibit strong chargeability. Conductivity anomalies similarly reflect widespread sulfides as well as water-saturated glacial sediments. Mineralogical and magnetic susceptibility data indicate magnetite destruction primarily within the Cu-Au-Mo mineralized area. The magnetic field does not show a corresponding anomaly low but the analytic signal does in areas where the deposit is not covered by postmineralization igneous rocks. The analytic signal shows similar lows over sedimentary rocks outside of the mineralized area, however, and cannot uniquely distinguish the deposit. We find that the intersection of positive chargeability anomalies with analytic signal lows, indicating elevated sulfide concentrations but low magnetite at shallow depths, roughly delineates the deposit where it is covered only by glacial sediments. Neither chargeability highs nor analytic signal lows are present where the deposit is covered by several hundred meters of sedimentary and volcanic rocks, but a 3D resistivity model derived from magnetotelluric data shows a corresponding zone of higher conductivity. Gravity data highlight geologic features within the deposit, including shallow diorite sills that locally contain higher-grade mineralization. The results thus show ways in which an integrated survey approach might be used to distinguish zones of potentially economic mineralization.

Alaska↗

USGS2005

Establishing an analytical framework for calculating consistent and sensitive measures of the rate of biodiversity change

The Convention on Biological Diversity’s (CBD) VIth Conference of the Parties (COP) and the World Summit on Sustainable Development agreed to a target to achieve a significant reduction of the rate of biodiversity loss by 2010. The VIIth COP adopted a conceptual framework to facilitate the assessment of global progress toward 2010 and to encourage national and regional targets and indicators. However, most of the indicators identified are not and will not be adequately quantified at desired accuracy and with desired frequency by 2010. What is possible is the establishment of an analytic framework that can provide guidelines and baselines for biodiversity estimates that can steadily improve with time. A judicious combination of remotely sensed data, Geographic Information System data, ground samples, and expert knowledge of species trends and species’ use of habitats form a solid basis for assessing biodiversity. National development of sensitive, consistent, and affordable indicators that can contribute to the CBD global indicators requires access to a baseline set of global ecosystem, climate, topography, land cover, and human impact information. Fortunately, over the last ten years, a number of relevant information sources have become available. Such information, as well as appropriate methods for use, should be promoted and made highly accessible to countries and organizations that support the CBD. The NASA-Non-Governmental Organization (NGO) Conservation Working Group is collaborating to evaluate and demonstrate the meaningful role remote sensing can play in developing biodiversity indicators to meet the targets specified. The Working Group members are evaluating indicators across a range of biomes and scales. The results are being synthesized in a handbook describing the use of remote sensing for monitoring the 2010 target to be published in 2006.

Conference Paper↗

USGS1984

Heating rates in furnace atomic absorption using the L'vov platform

Heating rate profiles for the furnace tube wall, the furnace atmosphere, and a L'vov platform were established for a range of conditions in a cyclically heated graphite atomizer. The tube wall profile was made by direct observation with a recording optical pyrometer. The sodium line reversal method was used to establish the heating rate of the furnace atmosphere, and appearance temperatures for a series metals of differing volatility was used to establish platform profiles. The tube wall heating rate was nearly linear at 2240°C s − until the desired temperature was reached after which the temperature remained constant. The furnace atmosphere reached a given temperature 0.2–0.4 s later than the tube wall through most of the atomize cycle. The platform lagged the tube wall 0.5–0.8 s. Under typical operating conditions the furnace atmosphere was 100–200°C cooler than the tube wall and at nearly constant temperature when the analyte vaporized from the platform. The L'vov platform causes the cyclically heated commercial furnace to approximate the behavior of a constant temperature furnace during atomization.

Spectrochimica Acta Part B: Atomic Spectroscopy↗

USGS1951

Summary of the research work of the Trace Elements Section, Geochemistry and Petrology Branch, for the period April 1, 1948-December 31, 1950

This report summarizes the research work of the Trace Elements Section, Geochemistry and Petrology Branch, from the organization of the Section in April 1948 to December 31, 1950. The research undertaken thus far consists of laboratory and related field studies in the following fields: 1. Mineralogic and petrologic investigations of radioactive rocks, minerals, and ores. 2. Investigations of chemical methods of analysis for uranium, thorium, and other elements and compounds in radioactive materials, and related chemical problems. 3. Investigations of spectrographic methods of analysis for a wide variety of elements in radioactive materials. 4. Investigations of radiometric methods of analysis as applied to radioactive materials. It should be emphasized that the work undertaken thus far, described under the headings "Future work", is almost entirely in the nature of investigations supporting the field appraisal of known important uraniferous deposits. A comprehensive program of more fundamental research was submitted in April 1949 in a report entitled "Proposed program of desirable research in the geochemistry of uranium," but funds for this work have not been authorized. It is hoped, however, that funds to support basic research of the type indicated in that report may be available in the future. This report does not cover the analytical work of the Section nor the public-sample program. The analytical work has been summarized for the fiscal year 1950 in the report, "Numerical summary of the analytical work of the Trace Elements Section, Geochemistry and Petrology Branch, for the fiscal year 1950," by John C. Rabbit, U.S. Geol. Survey Trace Elements Memorandum Rept. 174, October 1950. A report on the public-sample program is in preparation. Much of the material in this report has been paraphrased from reports prepared by members of the Section. My special thanks are due them; to Earl Ingerson, chief of the Geochemistry and Petrology Branch of the Survey, for his critical review; to my secretary, Marie Woolihan, for her aid in collecting material; and to Virginia Layne of the editorial staff of the Section for typing the manuscript and the multilith mats.

Trace Elements Investigations↗

USGS2014

Using a Bayesian Network to predict shore-line change vulnerability to sea-level rise for the coasts of the United States

Sea-level rise is an ongoing phenomenon that is expected to continue and is projected to have a wide range of effects on coastal environments and infrastructure during the 21st century and beyond. Consequently, there is a need to assemble relevant datasets and to develop modeling or other analytical approaches to evaluate the likelihood of particular sea-level rise impacts, such as coastal erosion, and to inform coastal management decisions with this information. This report builds on previous work that compiled oceanographic and geomorphic data as part of the U.S. Geological Survey’s Coastal Vulnerability Index (CVI) for the U.S. Atlantic coast, and developed a Bayesian Network to predict shoreline-change rates based on sea-level rise plus variables that describe the hydrodynamic and geologic setting. This report extends the previous analysis to include the Gulf and Pacific coasts of the continental United States and Alaska and Hawaii, which required using methods applied to the USGS CVI dataset to extract data for these regions. The Bayesian Network converts inputs that include observations of local rates of relative sea-level change, mean wave height, mean tide range, a geomorphic classification, coastal slope, and observed shoreline-change rates to calculate the probability of the shoreline-erosion rate exceeding a threshold level of 1 meter per year for the coasts of the United States. The calculated probabilities were compared to the historical observations of shoreline change to evaluate the hindcast success rate of the most likely probability of shoreline change. Highest accuracy was determined for the coast of Hawaii (98 percent success rate) and lowest accuracy was determined for the Gulf of Mexico (34 percent success rate). The minimum success rate rose to nearly 80 percent (Atlantic and Gulf coasts) when success included shoreline-change outcomes that were adjacent to the most likely outcome. Additionally, the probabilistic approach determines the confidence in calculated outcomes as the probability of the most likely outcome. The confidence was highest along the Pacific coast and it was lowest along the Alaskan coast.

Open-File Report↗

USGS2002

Spectrochemical method for the determination of selenium

Selenium can be determined in pyrite, chalcocite, and marcasite by a simple and rapid spectrochemical method that requires no complicated arrangement of spectrographic equipment or chemical pretreatment of samples. Advantage is taken of the new short wave length radiation plates (Eastman) and the addition of copper oxide to enhance the selenium lines 2039.85 and 2062.78 A. The possibility exists of determining many other elements on the same exposure of the sample. The method is applicable in the range of 0.0015 to 2% selenium. Tests indicate an average difference from the chemical results of 0.07% in the few per cent range, 0.03% in the 0.1 to 1.0% range, 0.005% in the 0.01 to 0.1% range, and 0.00075% in the 0.001 to 0.01% range. The relative accuracy over the entire range is to about 7% of the concentration.

Analytical Chemistry↗

USGS1985

Topographic mapping of the Moon

Contour maps of the Moon have been compiled by photogrammetric methods that use stereoscopic combinations of all available metric photographs from the Apollo 15, 16, and 17 missions. The maps utilize the same format as the existing NASA shaded-relief Lunar Planning Charts (LOC-1, -2, -3, and -4), which have a scale of 1:2 750 000. The map contour interval is 500m. A control net derived from Apollo photographs by Doyle and others was used for the compilation. Contour lines and elevations are referred to the new topographic datum of the Moon, which is defined in terms of spherical harmonics from the lunar gravity field. Compilation of all four LOC charts was completed on analytical plotters from 566 stereo models of Apollo metric photographs that cover approximately 20% of the Moon. This is the first step toward compiling a global topographic map of the Moon at a scale of 1:5 000 000. ?? 1985 D. Reidel Publishing Company.

Earth, Moon and Planets↗

USGS2009

Description and Analytical Results for Deposited Dust Samples from a Two-Year Monitoring Program Near Deer Trail, Colorado, USA, 2006-2007

Biosolids reclaimed from municipal wastewater have been applied since 1993 on nonirrigated farmland and rangeland east of Deer Trail, Colo., by Metro Wastewater Reclamation District of Denver. The U.S. Geological Survey has monitored ground water at this site since 1993, and began monitoring the biosolids, soils, and stream sediments in 1999. To investigate the possible effects of airborne dust blowing from the application fields, passive dust samplers were deployed in 2006 and 2007. These samplers measured the quantity and composition of dust being deposited downwind of a farmed field where biosolids had been applied, compared to a farmed field upwind of the application area. The dust-deposition rates and dust compositions measured at the two study sites are consistent with rates and compositions measured elsewhere in Utah, Nevada, and California using the same methods and equipment. Higher deposition rates were measured at the biosolids site compared to the control site during 2006. Higher deposition rates at both sites appear to be associated with episodes of cultivation and harvest during dry periods. No consistent differences in elements likely to be associated with biosolids disposal were detected between the sites. However, the contents of copper, lead, and zinc in the dust samples are generally much higher than average values of these elements in crustal rocks and sediments. Such values for dust samples are consistent with measurements on modern dust samples from southern Nevada and California and probably reflect inputs from regional urban and manufacturing activities.

Open-File Report↗

USGS2012

A general theory of multimetric indices and their properties

1. Stewardship of biological and ecological resources requires the ability to make integrative assessments of ecological integrity. One of the emerging methods for making such integrative assessments is multimetric indices (MMIs). These indices synthesize data, often from multiple levels of biological organization, with the goal of deriving a single index that reflects the overall effects of human disturbance. Despite the widespread use of MMIs, there is uncertainty about why this approach can be effective. An understanding of MMIs requires a quantitative theory that illustrates how the properties of candidate metrics relates to MMIs generated from those metrics. 2. We present the initial basis for such a theory by deriving the general mathematical characteristics of MMIs assembled from metrics. We then use the theory to derive quantitative answers to the following questions: Is there an optimal number of metrics to comprise an index? How does covariance among metrics affect the performance of the index derived from those metrics? And what are the criteria to decide whether a given metric will improve the performance of an index? 3. We find that the optimal number of metrics to be included in an index depends on the theoretical distribution of signal of the disturbance gradient contained in each metric. For example, if the rank-ordered parameters of a metric-disturbance regression can be described by a monotonically decreasing function, then an optimum number of metrics exists and can often be derived analytically. We derive the conditions by which adding a given metric can be expected to improve an index. 4. We find that the criterion defining such conditions depends nonlinearly of the signal of the disturbance gradient, the noise (error) of the metric and the correlation of the metric errors. Importantly, we find that correlation among metric errors increases the signal required for the metric to improve the index. 5. The theoretical framework presented in this study provides the basis for understanding the properties of MMIs. It can also be useful throughout the index construction process. Specifically, it can be used to aid understanding of the benefits and limitations of combining metrics into indices; it can inform selection/collection of candidate metrics; and it can be used directly as a decision aid in effective index construction.

Methods in Ecology and Evolution↗

USGS2009

The Restoration Rapid Assessment Tool: An Access/Visual Basic application

Managers of parks and natural areas are increasingly faced with difficult decisions concerning restoration of disturbed lands. Financial and workforce resources often limit these restoration efforts, and rarely can a manager afford to address all concerns within the region of interest. With limited resources, managers and scientists have to decide which areas will be targeted for restoration and the restoration treatments to use in these areas. A broad range of approaches are used to make such decisions, from well-researched expert opinions (Cipollini et al. 2005) to gut feeling, with variable degrees of input from site visits, data collection, and data analysis used to support the decision. A standardized approach including an analytical assessment of site characteristics based on the best information available, with a written or electronic record of all the steps taken along the way, would make comparisons among a group of sites easier and lend credibility through use of common, documented criteria at all sites. In response to these concerns, we have developed the Restoration Rapid Assessment Tool (RRAT). RRAT is based on field observations of key indicators of site degradation, stressors influencing the site, value of the site with respect to larger management objectives, likelihood of achieving the management goals, and logistical constraints to restoration. The purpose of RRAT is not to make restoration decisions or prescribe methods, but rather to ensure that a basic set of pertinent issues are considered for each site and to facilitate comparisons among sites. Several concepts have been central to the development of RRAT. First, the management goal (also known as desired future condition) of any site under evaluation should be defined before the field evaluation begins. Second, the evaluation should be based upon readily observable indicators so as to avoid cumbersome field methods. Third, the ease with which site stressors can be ameliorated must be factored into the evaluation. Fourth, intrinsic site value must be assessed independently of current condition. Finally, logistical considerations must also be addressed. Our initial focus has been on riparian areas because they are among the most heavily impacted habitat types, and RRAT indicators reflect this focus.

Report↗

USGS1958

Operator's manual on the visual-accumulation tube method for sedimentation analysis of sands

The visual-tube method for sedimentation analysis of sands was developed as a part of the general investigation titled "A Study of Methods Used in Measurement and Analysis of Sediment Loads in Streams." The method is one answer to the need for a simple, rapid, and inexpensive means of determining the sedimentation-size frequency analysis of sand samples containing particles less than one millimeter in size. For analysis of coarser sands see the Appendix, Section 13, Report No. 11 "The Development and Calibration of the Visual-Accumulation-Tube" is available for those who have further interest in this analysis. The personnel who will be operating these units may have little or no previous knowledge of either the principles involved or the details of opera.ting procedure. This manual is intended as an aid to them in setting up the apparatus, learning the analytical procedure, interpreting the results, and understanding the primary principles encountered.

Report↗

USGS2016

Bounded fractional diffusion in geological media: Definition and Lagrangian approximation

Spatiotemporal Fractional-Derivative Models (FDMs) have been increasingly used to simulate non-Fickian diffusion, but methods have not been available to define boundary conditions for FDMs in bounded domains. This study defines boundary conditions and then develops a Lagrangian solver to approximate bounded, one-dimensional fractional diffusion. Both the zero-value and non-zero-value Dirichlet, Neumann, and mixed Robin boundary conditions are defined, where the sign of Riemann-Liouville fractional derivative (capturing non-zero-value spatial-nonlocal boundary conditions with directional super-diffusion) remains consistent with the sign of the fractional-diffusive flux term in the FDMs. New Lagrangian schemes are then proposed to track solute particles moving in bounded domains, where the solutions are checked against analytical or Eularian solutions available for simplified FDMs. Numerical experiments show that the particle-tracking algorithm for non-Fickian diffusion differs from Fickian diffusion in relocating the particle position around the reflective boundary, likely due to the non-local and non-symmetric fractional diffusion. For a non-zero-value Neumann or Robin boundary, a source cell with a reflective face can be applied to define the release rate of random-walking particles at the specified flux boundary. Mathematical definitions of physically meaningful nonlocal boundaries combined with bounded Lagrangian solvers in this study may provide the only viable techniques at present to quantify the impact of boundaries on anomalous diffusion, expanding the applicability of FDMs from infinite do mains to those with any size and boundary conditions.

Water Resources Research↗

USGS2024

Spaceborne imaging spectroscopy enables carbon trait estimation in cover crop and cash crop residues

Purpose Cover crops and reduced tillage are two key climate smart agricultural practices that can provide agroecosystem services including improved soil health, increased soil carbon sequestration, and reduced fertilizer needs. Crop residue carbon traits (i.e., lignin, holocellulose, non-structural carbohydrates) and nitrogen concentrations largely mediate decomposition rates and amount of plant-available nitrogen accessible to cash crops and determine soil carbon residence time. Non-destructive approaches to quantify these important traits are possible using spectroscopy. Methods The objective of this study was to quantify cash and cover crop residue nitrogen and carbon traits using partial least squares regression models and a combination of 1) the band equivalent reflectance (BER) of the PRecursore IperSpettrale della Missione Applicativa (PRISMA) imaging spectroscopy sensor derived from laboratory collected ASD spectra (n = 296) of 11 cover crop species and three cash crop species, and 2) spaceborne PRISMA imagery that coincided with destructive crop residue collections in the spring of 2022 (n = 65). Spectral range was constrained to 1200 to 2400nm to reduce the likelihood of confounding relationships in wavelengths sensitive to plant pigments or those related to canopy structure for both analytical approaches. Results Models using laboratory BER of PRISMA all demonstrated high accuracies and low errors for estimation of nitrogen and carbon traits (adj. R2 = 0.86 – 0.98; RMSE = 0.24 – 4.25%) and results suggest that a single model may be used for a given trait across all species. Models using spaceborne imaging spectroscopy demonstrated that crop residue carbon traits can be successfully estimated using PRISMA imagery (adj. R2 = 0.65 – 0.75; RMSE = 2.71 – 4.16%). We found moderate relationships between nitrogen concentration and PRISMA imagery (adj. R2 = 0.52; RMSE = 0.25%), which is partly related to the range of nitrogen in these senesced crop residues (0.38 – 1.85%). PRISMA imagery models were also impacted by atmospheric absorption, variability in surface moisture content, and some presence of green vegetation. Conclusion As spaceborne imaging spectroscopy data become more widely available from upcoming missions, crop residue trait estimates could be regularly generated and integrated into decision support tools to calculate decomposition rates and associated nitrogen credits to inform precision field management, as well as to enable measurement, monitoring, reporting, and verification of net carbon benefits from climate smart agricultural practice adoption in an emerging carbon marketplace.

Maryland↗