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At least 1,243 records · Page 69Linked to original sources
USGS2008

Analysis of a spatial point pattern: Examining the damage to pavement and pipes in Santa Clara Valley resulting from the Loma Prieta earthquake

This report describes some simple spatial statistical methods to explore the relationships of scattered points to geologic or other features, represented by points, lines, or areas. It also describes statistical methods to search for linear trends and clustered patterns within the scattered point data. Scattered points are often contained within irregularly shaped study areas, necessitating the use of methods largely unexplored in the point pattern literature. The methods take advantage of the power of modern GIS toolkits to numerically approximate the null hypothesis of randomly located data within an irregular study area. Observed distributions can then be compared with the null distribution of a set of randomly located points. The methods are non-parametric and are applicable to irregularly shaped study areas. Patterns within the point data are examined by comparing the distribution of the orientation of the set of vectors defined by each pair of points within the data with the equivalent distribution for a random set of points within the study area. A simple model is proposed to describe linear or clustered structure within scattered data. A scattered data set of damage to pavement and pipes, recorded after the 1989 Loma Prieta earthquake, is used as an example to demonstrate the analytical techniques. The damage is found to be preferentially located nearer a set of mapped lineaments than randomly scattered damage, suggesting range-front faulting along the base of the Santa Cruz Mountains is related to both the earthquake damage and the mapped lineaments. The damage also exhibit two non-random patterns: a single cluster of damage centered in the town of Los Gatos, California, and a linear alignment of damage along the range front of the Santa Cruz Mountains, California. The linear alignment of damage is strongest between 45° and 50° northwest. This agrees well with the mean trend of the mapped lineaments, measured as 49? northwest.

California↗
USGS1997

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory-Use of a modified ultrasonic nebulizer for the analysis of low ionic-strength water by inductively coupled optical emission spectrometry

The U.S. Geological Survey National Water Quality Laboratory has developed a method for the determination of dissolved calcium, iron, magnesium, manganese, silica, and sodium using a modified ultrasonic nebulizer sample-introduction system to an inductively coupled plasma-optical emission spectrometer. The nebulizer's spray chamber has been modified to avoid carryover and memory effects common in some conventional ultrasonic designs. The modified ultrasonic nebulizer is equipped with a high-speed rinse cycle to remove previously analyzed samples from the spray chamber without excessive flush times. This new rinse cycle decreases sample washout times by reducing carryover and memory effects from salt or analytes in previously analyzed samples by as much as 45 percent. Plasma instability has been reduced by repositioning the argon carrier gas inlet on the spray chamber and by directly pumping waste from the chamber, instead of from open drain traps, thereby maintaining constant pressure to the plasma. The ultrasonic nebulizer improves signal intensities, which are 8 to 16 times greater than for a conventional cross-flow pneumatic nebulizer, without being sensitive to clogging from salt buildup as in cross-flow nebulizers. Detection limits for the ultrasonic nebulizer are 4 to 18 times less than detection limits achievable using a cross-flow pneumatic nebulizer, with equivalent sample analysis time.

Open-File Report↗
USGS2022

Quantifying streamflow depletion from groundwater pumping: A practical review of past and emerging approaches for water management

Groundwater pumping can cause reductions in streamflow (“streamflow depletion”) that must be quantified for conjunctive management of groundwater and surface water resources. However, streamflow depletion cannot be measured directly and is challenging to estimate because pumping impacts are masked by streamflow variability due to other factors. Here, we conduct a management-focused review of analytical, numerical, and statistical models for estimating streamflow depletion and highlight promising emerging approaches. Analytical models are easy to implement, but include many assumptions about the stream and aquifer. Numerical models are widely used for streamflow depletion assessment and can represent many processes affecting streamflow, but have high data, expertise, and computational needs. Statistical approaches are a historically underutilized tool due to difficulty in attributing causality, but emerging causal inference techniques merit future research and development. We propose that streamflow depletion-related management questions can be divided into three broad categories (attribution, impacts, and mitigation) that influence which methodology is most appropriate. We then develop decision criteria for method selection based on suitability for local conditions and the management goal, actionability with current or obtainable data and resources, transparency with respect to process and uncertainties, and reproducibility.

Journal of the American Water Resources Associatio↗
USGS1997

U-Pb age of zircon crystals from the upper banner tonstein (Middle Pennsylvanian), Virginia: Absolute age of the Lower Pennsylvanian-Middle Pennsylvanian boundary and depositional rates for the Middle Pennsylvanian, central appalachian basin

The Upper Banner tonstein, a kaolinized volcanic ash bed that occurs about 90 m above the base of the Middle Pennsylvanian Series in Virginia, is the oldest known Middle Pennsylvanian tonstein in the Appalachian basin. On the basis of palynostratigraphy, the Upper Banner coal bed correlates approximately with the Langsettian-Duckmantian (ex Westphalian A-B) boundary in Europe. Stratigraphically, the Upper Banner tonstein occurs 440-480 m below the Fire Clay tonstein, which in turn is 25-50 m below the marine Magoffin Member of the Breathitt Formation, the approximate correlative of the Agir Marine Band that marks the Dunckmantian-Bolsovian (ex Westphalian C) boundary in Europe. Six single-crystal U-Pb zircon ages were determined for the Upper Banner tonstein. Of these, four overlap concordia within uncertainties and have 206Pb/238U ages that range from 306 to 310??1 Ma. Another analysis falls in the same group but plots slightly to the right of the curve, whereas a single analysis of a low uranium zircon grain gives an age of 316??1 Ma. Variation in ages is outside of analytical uncertainty; hence, variable amounts of recent Pb loss is implied, and the most probable (minimum) depositional age is given by the oldest value at 316??1 Ma - an age consistent with a mean sanidine 40Ar/39Ar plateau age of 311.2??0.7 Ma for the stratigraphically younger Fire Clay tonstein. Thus, the Upper Banner tonstein-Fire Clay tonstein interval is about 5 ?? 1 m.y. This period of time for the Dunckmantian Stage is in good agreement with the Hess and Lippolt (1986) and Hess et al. (1988) chronology for the Duckmantian based on 40Ar/39Ar plateau methods for Westphalian tonsteins. Also, on the basis of this period of time, calculated sedimentation rates (decompacted) od 66-165 m/m.y. were determined for the lower part of the Middle Pennsylvanian Series in the central Appalachian basin. These rates are consistent with the sedimentation rates for shallow-water marine siliciclastic sediments and passive-margin foreland sediments.

Prace - Panstwowego Instytutu Geologicznego↗
USGS1996

Quality control considerations for the determination of acid-volatile sulfide and simultaneously extracted metals in sediments

The determination of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEMs) in sediment by treatment with dilute HCl shows promise as a tool for predicting the potential for metal toxicity to sediment-dwelling organisms. Effective quality control measures must be developed if this method is to become a reliable procedure and to ensure comparability of data. However, establishing quality control measures that assess procedural errors for an operationally defined method can be problematic. For example, preextraction spikes added for assessing the accuracy of AVS and SEMs may be poorly recovered due to adsorption or reaction with sediment constituents. For a variety of sediment types, we found preextraction spikes of sulfide, mercury, and copper to be prone to variable recoveries for the AVS/SEM procedure; recoveries averaged 76.3% (SD, 20.9) for sulfide, 61.9% (39.6) for Hg, and 90.1% (12.7) for Cu. The average recovery was near 100% for preextraction spikes of sediments for Cd, Ni, Pb, and Zn, and the recoveries of preextraction blank spikes for all analytes were consistently 95 to 105%. Binding of Cu or Hg with sulfides is sufficiently strong that 1 N hydrochloric acid will not necessarily keep the spiked metal in the dissolved state. This does not mean that the SEM procedure is invalid for these metals, only that the quality control of procedural error is difficult to assess. However, Hg will generally not be detected when measured as an SEM because of its tendency to adsorb onto sulfide minerals even at extremely low pH. Some reference sediments may be useful for assessing consistency of AVS determinations; we measured 5.97 ± 0.65 μmol/g in National Institute of Standards and Technology (NIST) 1645 and 1.34 ± 0.14 μmol/g in NIST 2704 for repeated determinations conducted over the past 3 years. Apparently, some sediments may contain an oxidation-resistant sulfide component that can release low to moderate AVS when treated with dilute HCl.

Environmental Toxicology and Chemistry↗
USGS2025

A generalized design flood estimation framework under stationary and non-stationary scenarios

With the ever-ongoing debate over the death of stationarity in flood time series, developing methods for flood frequency analysis that can address both stationarity and non-stationarity simultaneously has become increasingly important for design flood estimation. Existing non-stationary flood frequency analysis (NFFQ) methods are either limited to providing time-varying conditional flood quantile estimates or lack closed-form expression to estimate the design flood over the planning period. We propose a novel framework, MM-NFFQ, that introduces marginal moments (MM) estimation techniques to provide a closed-form expression to estimate design flood under non-stationarity. We demonstrate MM-NFFQ using the LP3 distribution for estimating conditional moments, but in principle, it can work for any 3-parameter distribution. We first show the proposed MM-NFFQ collapses to stationary flood frequency analysis analytically using synthetic data and then demonstrate the MM-NFFQ approach for two basins exhibiting non-stationarity in their flood time series. We further extend the analysis to selected 40 basins across CONUS and find that arid basins exhibit higher deviation from stationarity. Thus, the proposed MM-NFFQ framework can estimate traditional flood frequency curves for both, stationary and non-stationary flood processes, and can also be utilized to analyze the changes in conditional moments and marginal moments over different planning horizons.

Journal of Hydrology X↗
USGS2024

De facto water reuse: Investigating the fate and transport of chemicals of emerging concern from wastewater discharge through drinking water treatment using non-targeted analysis and suspect screening

Wastewater is a source for many contaminants of emerging concern (CECs), and surface waters receiving wastewater discharge often serve as source water for downstream drinking water treatment plants. Nontargeted analysis and suspect screening methods were used to characterize chemicals in residence-time-weighted grab samples and companion polar organic chemical integrative samplers (POCIS) collected on three separate hydrologic sampling events along a surface water flow path representative of de facto water reuse. The goal of this work was to examine the fate of CECs along the study flow path as water is transported from wastewater effluent through drinking water treatment. Grab and POCIS samples provided a comparison between residence-time-weighted single-point and integrative sample results. This unique and rigorous study design, coupled with advanced analytical chemistry tools, provided important insights into chemicals found in drinking water and their potential sources, which can be used to help prioritize chemicals for further study. K -means clustering analysis was used to identify patterns in chemical occurrences across both sampling sites and sampling events. Chemical features that occurred frequently or survived drinking water treatment were prioritized for identification, resulting in the probable identification of over 100 CECs in the watershed and 28 CECs in treated drinking water.

Environmental Science & Technology↗
USGS2012

Ash3d: A finite-volume, conservative numerical model for ash transport and tephra deposition

We develop a transient, 3-D Eulerian model (Ash3d) to predict airborne volcanic ash concentration and tephra deposition during volcanic eruptions. This model simulates downwind advection, turbulent diffusion, and settling of ash injected into the atmosphere by a volcanic eruption column. Ash advection is calculated using time-varying pre-existing wind data and a robust, high-order, finite-volume method. Our routine is mass-conservative and uses the coordinate system of the wind data, either a Cartesian system local to the volcano or a global spherical system for the Earth. Volcanic ash is specified with an arbitrary number of grain sizes, which affects the fall velocity, distribution and duration of transport. Above the source volcano, the vertical mass distribution with elevation is calculated using a Suzuki distribution for a given plume height, eruptive volume, and eruption duration. Multiple eruptions separated in time may be included in a single simulation. We test the model using analytical solutions for transport. Comparisons of the predicted and observed ash distributions for the 18 August 1992 eruption of Mt. Spurr in Alaska demonstrate to the efficacy and efficiency of the routine.

Journal of Geophysical Research↗
USGS2018

Trace element characterisation of MAD‐559 zircon reference material for ion microprobe analysis

We document the composition of a natural zircon gemstone sourced from Madagascar, MAD‐559 – a new reference material for calibrating trace element mass fractions in zircon measured by SIMS. The composition of MAD‐559 was quantified by calibration relative to the well‐documented zircon reference material 91500, for which we compiled existing published data (Mg, Al, Y, rare earth elements, Hf, U, Th) and performed new measurements to characterise the mass fraction of less commonly measured elements (Li, Be, B, F, Na, P, K, Ca, Sc, Ti, Fe, Nb). Measurement results of SL13, CZ3 and MAD‐1 zircons and NIST SRM glasses were performed as quality control materials to test measurement bias and repeatability. We show the intermediate precision for most trace element measurement results of MAD‐559 to be between ± 3% and ± 5% RSD based on 139 measurements by SIMS on twenty‐five individual polished zircon chips measured during a 24‐h period, as well as repeat measurements performed over five separate analytical sessions. Trace element mass fractions were also measured by LA‐ICP‐MS in two different laboratories, and major element compositions measured by electron microprobe, to compare with results measured by SIMS. Based on laser Raman and hyperspectral cathodoluminescence spectroscopy, we show MAD‐559 to have high crystal disorder due to radiation damage relative to crystalline zircon (e.g., SL13 and 91500 zircon). Although the high cumulative alpha dose of MAD‐559 zircon makes it a poor reference material for geochronology, the consistency of the trace element mass fraction results measured in multiple sessions and by various measurement methods shows that it is an ideal reference material for microanalytical trace element mass fraction quantification of zircon.

Geostandards and Geoanalytical Research↗
USGS2024

Wildland fire effects on sediment, salinity, and selenium yields in a basin underlain by Cretaceous marine shales near Rangely, Colorado

Understanding and quantifying soil erosion from rangelands is a high priority for land managers, especially in areas underlain by Cretaceous Mancos Shale, which is a natural source of sediment, salinity, and selenium to surface waters in many areas of western Colorado and eastern Utah. The purpose of this report is to present the results of a U.S. Geological Survey study that assessed sediment, salinity, and selenium yields after the Dead Dog wildfire (fire began June 11, 2017) in northwestern Colorado. Two methodologies were used to quantify erosion, with different data requirements and analytical complexity. The first approach was the use of a process-based erosion model, the Watershed Erosion Prediction Project, which uses inputs of climate, topography, vegetation, and soils data from existing datasets to predict erosion, making this approach easily extensible to other areas. The second approach required more complex data collection and was used to measure erosion and deposition by differencing digital elevation models created from uncrewed aerial vehicle imagery collected in 2016 (pre-fire) and 2021 (post-fire). Sediment, salinity, and selenium yields were calculated from the volumetric estimates of erosion from both methods, and a discussion of factors that may have contributed to overall findings, including vegetation, fire effects, and soil characteristics, is included. The two approaches yielded different outputs. Results from the Watershed Erosion Prediction Project model indicated that almost no erosion occurred after the Dead Dog fire. However, morphological changes in the study basin after the Dead Dog fire were visible in the pre- and post-fire imagery and measured in the digital elevation model differencing technique, with net erosion occurring in channel and landscape extents, though calculated erosion rates and salinity and selenium yields were relatively small. Visible and measured morphological changes consisted primarily of incision and deposition within stream channels and rill incision and expansion on steeper slopes. Widespread sheet erosion was not evident. Much of the new erosion originated within, and immediately below, previously vegetated areas that were then burned by the wildfire. Greater erosion rates and salinity and selenium yields were measured in the channel extent relative to the landscape extent. Calculated erosion rates ranged from 0.24 to 0.45 megagrams per hectare per year. These results indicate that the Dead Dog fire resulted in increased erosion in the study basin, yet these effects were relatively small based on the overall magnitude of modeled and measured erosion from the Watershed Erosion Prediction Project and the digital elevation model differencing technique. Minimal erosion in the basin is likely due to local site characteristics typical of soils derived from Mancos Shale, including the presence of robust physical crusts and biological soil crusts, and limitations of the methods based on data availability. Focusing uncrewed aerial vehicle flights on key areas (individual steep slopes, high-intensity burn areas, specific stream reaches) could likely increase understanding of erosional process with less effort and error than doing landscape-level flights.

Colorado↗
USGS1975

Analysis for tellurium in rocks to 5 parts per billion

In the proposed method, a 12.5-g sample is digested with nitric acid and evaporated to dryness; the excess nitric acid is removed by reaction with formic acid. Tellurium is extracted from the dried residue into hydrobromic acid and is then coprecipitated with arsenic, using hypophosphorous acid as the reducing agent. The precipitate is dissolved in a solution of hydrobromic acid and bromine, from which the tellurium is extracted into 0.6 ml of methyl isobutyl ketone. Tellurium content is estimated by atomic absorption spectrophotometry. Recovery of tellurium from nitric acid solutions carried through the procedure approached 100 percent through the analytical range 5-200 ppb. The relative standard deviation of five consecutive analyses of USGS standard rock GSP-1 was 5.26 percent at a mean concentration of 20.8 ppb. Under optimum conditions an average of 20 samples may be analyzed per man-day.

Colorado↗
USGS2008

Trace analysis of antidepressant pharmaceuticals and their select degradates in aquatic matrixes by LC/ESI/MS/MS

Treated wastewater effluent is a potential environmental point source for antidepressant pharmaceuticals. A quantitative method was developed for the determination of trace levels of antidepressants in environmental aquatic matrixes using solid-phase extraction coupled with liquid chromatography-electrospray ionization tandem mass spectrometry. Recoveries of parent antidepressants from matrix spiking experiments for the individual antidepressants ranged from 72 to 118% at low concentrations (0.5 ng/L) and 70 to 118% at high concentrations (100 ng/L) for the solid-phase extraction method. Method detection limits for the individual antidepressant compounds ranged from 0.19 to 0.45 ng/L. The method was applied to wastewater effluent and samples collected from a wastewater-dominated stream. Venlafaxine was the predominant antidepressant observed in wastewater and river water samples. Individual antidepressant concentrations found in the wastewater effluent ranged from 3 (duloxetine) to 2190 ng/L (venlafaxine), whereas individual concentrations in the waste-dominated stream ranged from 0.72 (norfluoxetine) to 1310 ng/L (venlafaxine).

Analytical Chemistry↗
USGS2008

Evaluation of unsaturated zone air permeability through pneumatic tests

Predicting the steady state distribution of air pressure in the unsaturated zone resulting from a pneumatic test provides a method for determining air-phase permeability. This technique is analogous to the inverse problem of well hydraulics; however, air flow is more complicated than ground water flow because of air compressibility, the Klinkenberg effect, variations in air density and viscosity that result from temperature fluctuations in the unsaturated zone and the possibility of inducing water movement during the pneumatic test. An analysis of these complicating factors reveals that, when induced water movement can be neglected, a linear version of the airflow equation can provide an appropriate approximation for the purpose of determining air-phase permeability. Two analytical solutions for steady state, two-dimensional, axisymmetric airflow to a single well partially screened in the unsaturated zone are developed. One solution applies where there is a stratum of relatively low air permeability, separating the stratum in which the well is completed, from the atmosphere. The other solution applies where there is no separating stratum between the domain and atmosphere. In both situations the water table forms the lower horizontal boundary. Applications of both solutions to determine air permeability from data collected during pneumatic tests are presented.

Water Resources Research↗
USGS2009

Analytical Results for Agricultural Soils Samples from a Monitoring Program Near Deer Trail, Colorado (USA)

Since late 1993, Metro Wastewater Reclamation District of Denver (Metro District, MWRD), a large wastewater treatment plant in Denver, Colorado, has applied Grade I, Class B biosolids to about 52,000 acres of nonirrigated farmland and rangeland near Deer Trail, Colorado, USA. In cooperation with the Metro District in 1993, the U.S. Geological Survey (USGS) began monitoring groundwater at part of this site. In 1999, the USGS began a more comprehensive monitoring study of the entire site to address stakeholder concerns about the potential chemical effects of biosolids applications to water, soil, and vegetation. This more comprehensive monitoring program has recently been extended through 2010. Monitoring components of the more comprehensive study include biosolids collected at the wastewater treatment plant, soil, crops, dust, alluvial and bedrock groundwater, and stream bed sediment. Soils for this study were defined as the plow zone of the dry land agricultural fields - the top twelve inches of the soil column. This report presents analytical results for the soil samples collected at the Metro District farm land near Deer Trail, Colorado, during three separate sampling events during 1999, 2000, and 2002. Soil samples taken in 1999 were to be a representation of the original baseline of the agricultural soils prior to any biosolids application. The soil samples taken in 2000 represent the soils after one application of biosolids to the middle field at each site and those taken in 2002 represent the soils after two applications. There have been no biosolids applied to any of the four control fields. The next soil sampling is scheduled for the spring of 2010. Priority parameters for biosolids identified by the stakeholders and also regulated by Colorado when used as an agricultural soil amendment include the total concentrations of nine trace elements (arsenic, cadmium, copper, lead, mercury, molybdenum, nickel, selenium, and zinc), plutonium isotopes, and gross alpha and beta activity (Colorado Department of Public Health and Environment, Hazardous Materials and Waste Management Division, 1997; Colorado Department of Public Health and Environment,1998; U.S. Environmental Protection Agency, 1993). Since these were the identified priority parameters for the biosolids, the soils have the same set of priority parameters. Although the composite soils' priority analytes have been reported earlier to Metro District, the remaining elemental datasets for both the composite soils samples and selected fields' individual subsamples' data are presented here for the first time. More information about the other monitoring components is presented elsewhere in the literature (http://co.water.usgs.gov/projects/CO406/CO406.html). In general, the objective of each component of the study was to determine whether concentrations of priority parameters (1) were higher than regulatory limits, (2) were increasing with time, and(or) (3) were significantly higher in biosolids-applied areas than in a similar farmed area where biosolids were not applied. The method chosen for sampling the soils proved to be an efficient and reliable representation of the average composition of each field. This was shown by analyzing individual subsamples, averaging the resulting values, and then comparing the values to the composited samples' values. The soil chemistry shows distinct differences between the two sites, most likely due to the different underlying parent material. Biosolids data were used to compile an inorganic-chemical biosolids signature that can be contrasted with the geochemical signature of the agricultural soils for this site. The biosolids signature and an understanding of the geology and hydrology of the site can be used to separate biosolids effects from natural geochemical effects. Elements of particular interest for a biosolids signature after application in the soils include bismuth, copper, silver, mercury, and phosphorus. This signat

Open-File Report↗
USGS1993

Hydrogeology, ground-water quality, and potential for water-supply contamination near an abandoned wood-preserving plant site at Jackson, Tennessee

Hydrogeologic and ground-water-quality data were collected near an abandoned wood-preserving plant site at Jackson, Tennessee to determine the extent and magnitude of ground-water contamination in offsite areas and to assess the potential for contamination of nearby water-supply wells. New methods were used to collect ground-water samples from the alluvial aquifer at six offsite stations at depths of less than about 40 feet below land surface. In addition, 36 offsite wells were installed at these stations to collect samples from the alluvial aquifer and to depths of about 150 feet in the deeper Fort Pillow aquifer. Ground-water samples collected by the new methods and from the 36 offsite wells were analyzed for selected volatile and semi-volatile compounds. The samples collected from the 36 wells also were analyzed for major and trace inorganic constituents. Naphthalene and some volatile organic compounds were detected at low concentrations in samples from both the alluvial aquifer and the Fort Pillow aquifer. To assess the potential for water-supply contamination from the site, four water-supply wells to the east (upgradient) and three wells to the west (down- gradient) of the abandoned plant site were sampled. These samples were analyzed for the same analytes as the samples from the 36 wells. Although volatile organic compounds and elevated concentrations of trace and major inorganic constituents were measured in samples from some wells east of the site, no organic compounds associated with the wood- preserving process were detected. No contaminants from the site were detected in samples from wells west of the site.

Water-Resources Investigations Report↗
USGS2012

Groundwater-quality and quality-control data for two monitoring wells near Pavillion, Wyoming, April and May 2012

In June 2010, the U.S. Environmental Protection Agency installed two deep monitoring wells (MW01 and MW02) near Pavillion, Wyoming, to study groundwater quality. During April and May 2012, the U.S Geological Survey, in cooperation with the Wyoming Department of Environmental Quality, collected groundwater-quality data and quality-control data from monitoring well MW01 and, following well redevelopment, quality-control data for monitoring well MW02. Two groundwater-quality samples were collected from well MW01—one sample was collected after purging about 1.5 borehole volumes, and a second sample was collected after purging 3 borehole volumes. Both samples were collected and processed using methods designed to minimize atmospheric contamination or changes to water chemistry. Groundwater-quality samples were analyzed for field water-quality properties (water temperature, pH, specific conductance, dissolved oxygen, oxidation potential); inorganic constituents including naturally occurring radioactive compounds (radon, radium-226 and radium-228); organic constituents; dissolved gasses; stable isotopes of methane, water, and dissolved inorganic carbon; and environmental tracers (carbon-14, chlorofluorocarbons, sulfur hexafluoride, tritium, helium, neon, argon, krypton, xenon, and the ratio of helium-3 to helium-4). Quality-control sample results associated with well MW01 were evaluated to determine the extent to which environmental sample analytical results were affected by bias and to evaluate the variability inherent to sample collection and laboratory analyses. Field documentation, environmental data, and quality-control data for activities that occurred at the two monitoring wells during April and May 2012 are presented.

Wyoming↗
USGS2003

Data model and relational database design for the New Jersey Water-Transfer Data System (NJWaTr)

The New Jersey Water-Transfer Data System (NJWaTr) is a database design for the storage and retrieval of water-use data. NJWaTr can manage data encompassing many facets of water use, including (1) the tracking of various types of water-use activities (withdrawals, returns, transfers, distributions, consumptive-use, wastewater collection, and treatment); (2) the storage of descriptions, classifications and locations of places and organizations involved in water-use activities; (3) the storage of details about measured or estimated volumes of water associated with water-use activities; and (4) the storage of information about data sources and water resources associated with water use. In NJWaTr, each water transfer occurs unidirectionally between two site objects, and the sites and conveyances form a water network. The core entities in the NJWaTr model are site, conveyance, transfer/volume, location, and owner. Other important entities include water resource (used for withdrawals and returns), data source, permit, and alias. Multiple water-exchange estimates based on different methods or data sources can be stored for individual transfers. Storage of user-defined details is accommodated for several of the main entities. Many tables contain classification terms to facilitate the detailed description of data items and can be used for routine or custom data summarization. NJWaTr accommodates single-user and aggregate-user water-use data, can be used for large or small water-network projects, and is available as a stand-alone Microsoft? Access database. Data stored in the NJWaTr structure can be retrieved in user-defined combinations to serve visualization and analytical applications. Users can customize and extend the database, link it to other databases, or implement the design in other relational database applications.

Open-File Report↗
USGS2021

Occurrence and distribution of PFAS in sampled source water of public drinking-water supplies in the surficial aquifer in Delaware, 2018; PFAS and groundwater age-dating results

The U.S. Geological Survey, in cooperation with the Delaware Department of Natural Resources and Environmental Control and the Delaware Geological Survey, conducted a groundwater-quality investigation to (1) describe the occurrence and distribution of PFAS, and (2) document any changes in groundwater quality in the Columbia aquifer public water-supply wells in the Delaware Coastal Plain between 2000 and 2008 and between 2008 and 2018. Thirty public water-supply wells located throughout the Columbia aquifer of the Delaware Coastal Plain were sampled from August through November 2018. Groundwater collected from the wells was analyzed for the occurrence and distribution of 18 per- and polyfluorinated alkyl substances (PFAS) as well as groundwater age. Descriptive statistical analyses were performed to assess PFAS analytical results within the well network and the combined perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) concentrations were compared to the U.S. Environmental Protection Agency’s (EPA) health advisory level (HAL) for informational purposes only and not for evidence of compliance or noncompliance with Federal regulations. The EPA’s HAL is a health-based reference level for public drinking water as supplied to customers and is not applied to source (raw) water. Groundwater-age data were compared for sites sampled in 2000, 2008, and 2018 to document any changes. All samples were analyzed for 18 PFAS using EPA Method 537 (modified). Forty-four percent of the analyzed PFAS were detected in the study well network. Sixteen of the sampled wells have one or more PFAS detections, and as many as eight different PFAS were found in a single sample. Wells with a higher number of PFAS detected (five or more) were in New Castle and Sussex Counties. The PFAS most frequently detected were PFOA, with 47 percent detection; perfluorohexanoic acid (PFHxA), with 33 percent detection; and PFOS and perfluorohexane sulfonate (PFHxS), with 27 percent detection each. PFAS concentrations were below 1,000 parts per trillion (ppt). Two wells exceeded the EPA’s lifetime-drinking water health advisory level of 70 ppt for combined concentrations of PFOA and PFOS. The average age of groundwater entering the screens of the supply wells sampled in 2018 ranged from 8.2 to 45.8 years, with a median groundwater age of 25.7 years. Groundwater age was positively correlated with well depth and negatively correlated with dissolved oxygen. Groundwater age and PFAS concentrations were negatively correlated in the Columbia aquifer. Data from the 23 resampled wells indicate a significant positive difference in the average modeled groundwater-sample-age results. The average groundwater age from samples collected in 2018 was generally 5 years older than the average groundwater age from samples collected in 2008. The same pattern was found during cycle two (2008) of this study, where the 2008 groundwater age was on average 7 years older than the samples collected in 2000. The distribution of groundwater sample ages among the 17 trend wells and during the three study cycles (2000, 2008, and 2018) indicates that sample-age medians were statistically different from zero; well-water sample-age data show a slight increase in groundwater sample age.

Delaware↗