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At least 1,423 records · Page 79Linked to original sources
USGS1995

Areal distribution of selected trace elements, salinity, and major ions in shallow ground water, Tulare Basin, Southern San Joaquin Valley, California

The distribution of salinity and selected trace elements in shallow ground water in the Tulare Basin, California, was assessed to evaluate potential problems related to disposal in evaporation ponds of irrigation drain water containing elevated concentrations of selenium and other trace elements. The constituents of primary concern were selenium, arsenic, and salinity; uranium, boron, and molybdenum also were evaluated. Samples from 117 shallow wells were analyzed, and the results for samples from 110 of the wells were interpreted in relation to surficial geology, sediment depositional environment, soil characteristics, and hydrologic processes to determine the geochemical and hydrologic factors affecting the distribution of these constituents in ground water. In general, shallow ground water in areas where concentrations of salinity and most trace elements are elevated is influenced primarily by sediments derived from marine sedimentary rocks originating in the Coast Range, San Emigdio Mountains, and Tehachapi Mountains, and probably by unusual exposures of similar marine formations in the Sierra Nevada. Ground water in areas where concentrations of salinity and trace elements are significantly lower generally is influenced by igneous and metamorphic rocks exposed in the Sierra Nevada. In addition to sources of sediments, evaporation of shallow ground water, as indicated by isotopic enrichment of oxygen-18 and deuterium, increases salinity and concentrations of conservative trace elements such as selenium (under oxidizing conditions) and boron. Redox conditions affect the oxidation state of all trace elements of concern, except boron, and were found to be a major influence on trace-element solubility. Under oxidized conditions, selenate predominates and behaves conservatively, and arsenate predominates and is affected by sorption reactions that can limit arsenic solubility. Under reduced conditions, selenium is reduced to insoluble elemental selenium and arsenite predominates and generally is more soluble than arsenate. Elevated concentrations of uranium in shallow ground water probably are associated with uranium deposits in Kern County and other parts of the basin where oxidized conditions cause the more soluble uranyl species to predominate. Boron was correlated with salinity and behaved conservatively, whereas adsorption and precipitation of molybdenum minerals probably limited molybdenum solubility. Interrelations among constituents were examined with principal component analysis. The first two principal components explained 50.7 percent of the variance in the data. The first principal component was related to salinity, and the second principal component was related to redox conditions, reflecting two of the major influences on shallow groundwater quality found in this study.

California↗
USGS1996

Water quality of surficial aquifers in the Georgia-Florida Coastal Plain

The National Water Quality Assessment Program of the U.S. Geological Survey established the Georgia-Florida Coastal Plain study unit in 1991. The ground-water study-unit survey was conducted in 1993 to provide a broad overview of water quality in surficial aquifers. Three land resource provinces were included in the Georgia-Florida Coastal Plain study-unit survey: the Central Florida Ridge, the Coastal Flatwoods, and the Southern Coastal Plain. The U.S. Geological Survey sampled 37 wells in surficial aquifers, 18 in the Coastal Flatwoods and 19 in the Southern Coastal Plain. The Florida Department of Environmental Protection sampled 27 wells tapping surficial aquifers in the Central Florida Ridge as part of the background ground-water quality monitoring network from 1985 through 1989. The data were used to characterize water quality in surficial aquifers of the Central Florida Ridge. Results of the study-unit survey indicated that dissolved solids concentrations in ground water were mostly less than 100 mg/L (milligrams per liter). Higher medians of pH, specific conductance, and concentrations of calcium, bicarbonate, and dissolved solids were measured in samples from the Central Florida Ridge compared to the Southern Coastal Plain and Coastal Flatwoods, probably because of a greater percentage of carbonate minerals in aquifer materials. The U.S. Environmental Protection Agency secondary maximum contaminant level for iron of 300 ug/L (micrograms per liter) in drinking water was exceeded in 15 of 45 samples. Concentrations of nitrate as nitrogen were less than 3.0 mg/L in most samples (74 percent), indicating little or no influence from human activity. Only five samples (9 percent) had concentrations above 10 mg/L, the U.S. Environmental Protection Agency maximum contaminant level for nitrate concentration in drinking water. Significantly lower median concentrations of nitrate were measured in samples from polyvinyl chloride monitoring wells with diameters less than 6 inches than in large diameter, uncased, or iron-cased wells. The median nitrate concentration was 0.05 mg/L in water from monitoring wells, 1.0 mg/L in samples from iron cased wells, and 2.0 mg/L in samples from uncased wells. Concentrations of volatile organic compounds were mostly less than the detection levels and exceeded 1 ug/L in only four samples. Compounds detected at concentrations greater than 1 ug/L were: tetrachloroethane (8.77 ug/L), toluene (23 ug/L) and chloromethane (21 ug/L). Atrazine, desethyl-atrazine, and metolachlor were the only pesticides detected; concentrations were less than 0.02 ug/L, except for metolachlor (2.5 ug/L). Detection of organic compounds in surficial aquifers may be associated with specific activities or sources near the well. Concentrations of radon exceeded the U.S. Environmental Protection Agency proposed maximum contaminant level of 300 picocuries per liter (pCi/L) in 33 samples from wells on the Coastal Flatwoods and the Southern Coastal Plain. Concentrations as high as 13,000 pCi/L were detected in northern Florida. Although uranium concentrations were less than 1 ug/L in all but one sample (1.3 ug/L) from the Southern Coastal Plain, elevated radon concentrations indicate that uranium is present in aquifer material. Uranium is most likely sorbed to iron oxides and clays in subsurface materials. Tritium concentrations indicated that ground water was recharged by precipitation during the past 40 years. Higher concentrations of tritium in ground water were found in the northern part of the study area and may be related to Savannah River Nuclear Facility.

Florida, Georgia↗
USGS1996

Radon in ground water of the lower Susquehanna and Potomac River basins

Ground-water samples collected from 267 wells were analyzed for radon as part of a water-quality reconnaissance of subunits of the Lower Susquehanna and Potomac River Basins conducted by the United States Geological Survey (USGS) as part of the National Water-Quality Assessment (NAWQA) program. Radon is a product of the radioactive decay of uranium. Airborne radon has been cited by the Surgeon General of the United States as the second-leading cause of lung cancer and the United States Environmental Protection Agency (USEPA) has identified ground-water supplies as possible contributing sources of indoor radon. Eighty percent of ground-water samples collected for this study were found to contain radon at activities greater than 300 pCi/L (picocuries per liter), the USEPA's proposed Maximum Contaminant Level for radon in drinking water, and 31 percent of samples contained radon at activities greater than 1,000 pCi/L. The 10 subunits where samples were collected were grouped into three classes - median ground-water radon activity less than 300 pCi/L, between 300 pCi/L and 1,000 pCi/L, and greater than 1,000 pCi/L. Subunits underlain by igneous and metamorphic rocks of the Piedmont Physiographic Province typically have the highest median ground-water radon activities (greater than 1,000 pCi/L); although there is a large variation in radon activities within most of the subunits. Lower median radon activities (between 300 pCi/L and 1,000 pCi/L) were found in ground water in subunits underlain by limestone and dolomite. Of three subunits underlain by sandstone and shale, one fell into each of the three radon-activity classes. The large variability within these subunits may be attributed to the fact that the uranium content of sandstone and shale is related to the uranium content of the sediments from which they formed.

lower Susquehanna and Potomac River basins↗
USGS1997

Water-quality assessment of the Rio Grande Valley, Colorado, New Mexico and Texas: Ground-water quality in the Rio Grande flood plain, Cochiti Lake, New Mexico, to El Paso, Texas, 1995

From March to May of 1995, water samples were collected from 30 wells located in the flood plain of the Rio Grande between Cochiti Lake, New Mexico, and El Paso, Texas. These samples were analyzed for a broad host of constituents, including field parameters, major constituents, nutrients, dissolved organic carbon, trace elements, radiochemicals, pesticides, and volatile organic compounds. The main purpose of this study was to observe the quality of ground water in this part of the Rio Grande Valley study unit of the U.S. Geological Survey National Water-Quality Assessment program. The sampling effort was limited to the basin- fill aquifer beneath the above-defined reach of the Rio Grande flood plain because of the relative homogeneity of the hydrogeology, the large amount of ground-water use for public supply, and the potential for land-use activities to affect the quality of ground water. Most of the wells sampled for the study are used for domestic purposes, including drinking water. Depths to the tops of the sampling intervals in the 30 wells ranged from 10 to 345 feet below land surface, and the median was 161.5 feet; the sampling intervals in most of the wells spanned about 10 feet or less. Quality-control data were collected at three of the wells. A significant amount of variation was found in the chemical composition of ground water sampled throughout the study area, but the water generally was found to be of suitable chemical quality for use as drinking water, according to current enforceable standards established by the U.S. Environmental Protection Agency (EPA). Nutrients generally were measured at concentrations near or below their method reporting limits. The most dominant nutrient species was nitrite plus nitrate, at a maximum concentration of 1.9 milligrams per liter (as N). Only eight of the trace elements analyzed for had median concentrations greater than their respective minimum reporting levels. Water from one well exceeded the lifetime health advisory established by the EPA for molybdenum; water from a different well exceeded the proposed EPA maximum contaminant level for uranium. Gross alpha and gross beta particle activities generally appeared to strongly correlate with quantities of uranium and potassium, respectively, detected in ground water. However, water from one well exceeded the EPA maximum contaminant level for gross alpha particle activity and may exceed the EPA maximum contaminant level for beta particle and photon activity, although current data on gross beta particle activities are not conclusive on this point. Radon concentrations did not appear to directly correlate with uranium concentrations. The herbicide prometon was the only synthetic organic compound detected in ground water in the study area, and was detected in only one well, at a concentration of 0.038 microgram per liter. This well is shallow and is not used for drinking water. With the exception of the one detection of prometon, no strong evidence was found of effects on ground-water quality from human activities. Therefore, most of the water sampled probably recharged at the margins of the alluvial basins or recharged through the flood plain before human development began. With respect to major constituents, the concentrations of dissolved solids ranged from 209 to 3,380 milligrams per liter, and the median concentration was 409.5 milligrams per liter. There is evidence that the overall chemical composition of ground water in the study area may be affected by several processes, including cation exchange, feldspar weathering, calcite dissolution and precipitation, dissolution of volcanic glass, and microbial activity. Several chemical constituents in ground water showed relatively distinct spatial patterns that appear to be related to one or more of these processes.

Texas↗
USGS2022

Potential for critical mineral deposits in Maine, USA

An analysis of the potential for deposits of critical minerals and elements in Maine presented here includes data and discussions for antimony, beryllium, cesium, chromium, cobalt, graphite, lithium, manganese, niobium, platinum group elements, rhenium, rare earth elements, tin, tantalum, tellurium, titanium, uranium, vanadium, tungsten, and zirconium. Deposits are divided into two groups based on geological settings and common ore-deposit terminology. One group consists of known deposits (sediment-hosted manganese, volcanogenic massive sulphide, porphyry copper-molybdenum, mafic- and ultramafic-hosted nickel-copper [-cobalt-platinum group elements], pegmatitic lithium-cesium-tantalum) that are in most cases relatively large, well-documented, and have been explored extensively in the past. The second, and much larger group of different minerals and elements, comprises small deposits, prospects, and occurrences that are minimally explored or unexplored. The qualitative assessment used in this study relies on three key criteria: (1) the presence of known deposits, prospects, or mineral occurrences; (2) favourable geologic settings for having certain deposit types based on current ore deposit models; and (3) geochemical anomalies in rocks or stream sediments, including panned concentrates. Among 20 different deposit types considered herein, a high resource potential is assigned only to three: (1) sediment-hosted manganese, (2) mafic- and ultramafic-hosted nickel-copper(-cobalt-platinum group elements), and (3) pegmatitic lithium-cesium-tantalum. Moderate potential is assigned to 11 other deposit types, including: (1) porphyry copper-molybdenum (-rhenium, selenium, tellurium, bismuth, platinum group elements); (2) chromium in ophiolites; (3) platinum group elements in ophiolitic ultramafic rocks; (4) granite-hosted uranium-thorium; (5) tin in granitic plutons and veins; (6) niobium, tantalum, and rare earth elements in alkaline intrusions; (7) tungsten and bismuth in polymetallic veins; (8) vanadium in black shales; (9) antimony in orogenic veins and replacements; (10) tellurium in epithermal deposits; and (11) uranium in peat.

Maine↗
USGS2006

Testing the concept of drift shadow at Yucca Mountain, Nevada

If proven, the concept of drift shadow, a zone of reduced water content and slower ground-water travel time beneath openings in fractured rock of the unsaturated zone, may increase performance of a proposed geologic repository for high-level radioactive waste at Yucca Mountain, To test this concept under natural-flow conditions present in the proposed repository horizon, isotopes within the uranium-series decay chain (uranium-238, uranium-234, and thorium-230, or 238U-234U-230Th) have been analyzed in samples of rock from beneath four naturally occurring lithophysal cavities. All rock samples show 234U depletion relative to parent 238U indicating varying degrees of water-rock interaction over the past million years. Variations in 234U/238U activity ratios indicate that depletion of 234U relative to 238U can be either smaller or greater in rock beneath cavity floors relative to rock near cavity margins. These results are consistent with the concept of drift shadow and with numerical simulations of meter-scale spherical cavities in fractured tuff. Differences in distribution patterns of 234U/ 238U activity ratios in rock beneath the cavity floors are interpreted to reflect differences in the amount of past seepage into lithophysal cavities, as indicated by the abundance of secondary mineral deposits present on the cavity floors.

Conference Paper↗
USGS2015

In-situ arsenic removal during groundwater recharge through unsaturated alluvium

OBJECTIVES The purpose of this study was to determine the feasibility and sustainability of in-situ removal of arsenic from water infiltrated through unsaturated alluvium. BACKGROUND Arsenic is naturally present in aquifers throughout the southwestern United States and elsewhere. In January 2006, the U.S. Environmental Protection Agency (EPA) lowered the Maximum Contaminant Level (MCL) for arsenic from 50 to 10 micrograms per liter (g/L). This raised concerns about naturally-occurring arsenic in groundwater. Although commercially available systems using sorbent iron or aluminum oxide resins are available to treat high-arsenic water, these systems are expensive to build and operate, and may generate hazardous waste. Iron and aluminum oxides occur naturally on the surfaces of mineral grains that compose alluvial aquifers. In areas where alluvial deposits are unsaturated, these oxides may sorb arsenic in the same manner as commercial resins, potentially providing an effective low-cost alternative to commercially engineered treatment systems. APPROACH The Antelope Valley within the Mojave Desert of southern California contains a shallow water-table aquifer with arsenic concentrations of 5 g/L, and a deeper aquifer with arsenic concentrations of 30 g/L. Water was pumped from the deep aquifer into a pond and infiltrated through an 80 m-thick unsaturated zone as part of field-scale and laboratory experiments to treat high-arsenic groundwater and recharge the shallow water table aquifer at the site. The field-scale recharge experiment included the following steps: 1) construction of a recharge pond 2) test drilling for sample collection and instrument installation adjacent to the pond 3) monitoring downward migration of water infiltrated from the pond 4) monitoring changes in selected trace-element concentrations as water infiltrated through the unsaturated zone Data from instruments within the borehole adjacent to the pond were supplemented with borehole and surface geophysical data to evaluate the lateral spreading of water as it moved downward through the unsaturated zone. Three laboratory studies were undertaken. Sequential extraction was used to evaluate the abundance of iron, aluminum, and manganese oxides and selected trace elements on operationally defined sites on the surfaces of mineral grains collected before and after infiltration from the pond. Secondly, radio-labeled arsenic-73 microcosm experiments evaluated the potential for incorporation of arsenic sorbed to exchange sites on mineral grains into less reactive crystalline mineral structures with time. Finally, column studies evaluated arsenic sorption and the pH dependence of sorption for selected unsaturated zone materials. RESULTS/CONCLUSIONS Between December 2010 and July 2012, more than 120,000 cubic meters (m3 ) (about 97 acre-feet) of high-arsenic groundwater was pumped from the deep aquifer into a 0.11 hectare (about 0.27 acres) pond and infiltrated though an 80-meter (about 260 feet) thick unsaturated zone to recharge a water-table aquifer. Arsenic concentrations were lowered from 30 to 2 g/L as water infiltrated though the unsaturated zone at the site. Some uranium, possibly associated with past agricultural land use at the site, was mobilized to concentrations as high as 66 g/L within the unsaturated zone during the experiment. Uranium was resorbed and the high uranium concentrations did not reach the water table at the site. Concentrations of other trace elements, including antimony, chromium, vanadium, and selenium were low throughout the study. Infiltration rates from the pond were as high as 0.4 meters per day (1.1 feet per day, ft/d), and the wetting front moved downward about 25 centimeters per day (cm/d) (0.8 ft/d) to a depth of about 50 m (about 165 feet). Clay layers at that depth slowed the downward movement of the wetting front to about 5 cm/d (0.16 ft/d). Lateral movement of the wetting front was monitored using sequential direct-current (DC) surface and sequential electromagnetic (EM) and DC borehole resistivity. Most lateral movement occurred on a clay layer about 50 m (about 165 feet) below land surface. Infiltrated water reached the water table in January 2013. At the water table, the “wetted footprint” of water infiltrated from the pond, indicated by surface resistivity data, was about 13 hectares (about 32 acres). On the basis of data collected at the site, there is enough sorbent material to operate this pond and treat groundwater having an arsenic concentration of 30 g/L to 2 g/L for about 500 years. Toxicity Characteristic Leaching Procedure (TCLP) data showed arsenic concentrations to be below hazardous levels beneath the pond after the experiment. Pond maintenance may be required to keep infiltration rates high, and prevent accumulation of organic material on the pond bottom, although organic material on the pond bottom may increase removal of other trace elements in infiltrated water including chromium, selenium, and vanadium. Laboratory results are consistent with the field data and show sorption of arsenic in 10 cm (0.3 feet) columns to about 2 g/L over a pH range of 6 to 8, and at influent arsenic concentrations as high as 300 g/L, without breakthrough in 50 pore volumes. Column results suggest that the insitu treatment may remove arsenic in a range of hydrogeologic settings, and would not necessarily be restricted to alkaline alluvial aquifers common throughout the southwestern United States. Radiolabeled arsenic-73 experiments show that although arsenic is initially weakly sorbed (and potentially mobile), with time arsenic is incorporated into amorphous materials. One year after sorption onto surface exchange sites, most sorbed arsenic is incorporated into crystalline oxide minerals on the surfaces of primary mineral grains and is less mobile. Results of the study suggest that long-term land use restrictions on sites used for in-situ treatment of arsenic may not be needed to control water applied to surface materials. This minimizes some regulatory concerns about future land use at sites used for in-situ arsenic treatment. However, future land uses that may alter reduction-oxidation conditions in the subsurface should be avoided, such as infiltration of stormwater recharge or recharge with other water having high organic carbon concentrations (including unsewered residential land use, dairy or other confined animal operations).

Report↗
USGS1975

An occurrence of disseminated uraninite in Wheeler Basin, Grand County, Colorado

Disseminated uraninite occurs in Wheeler Basin, Grand County, Colo., about 5 mi (8 km) southeast of Monarch Lake, in Precambrian metamorphic rocks consisting of migmatized gneiss and mixed gneiss and pegmatite. An intrusion of Precambrian Y Silver Plume Granite lies within 400 ft (122 m) of the occurrence. The disseminated uraninite is confined to parts of the host rock that are rich in biotite; highest grade found was 0.73 percent uranium. The disseminated uraninite occurs as cubes and grains, generally from 0.1 to 0.3 mm across. Unit cell edge of the uraninite, ≈ 5.48 A, suggests its pegmatitic origin. The origin of the uraninite disseminations is attributed by us to remobilization and concentration of elements during metamorphism caused by the intrusion of Silver Plume Granite. Uranium and lead isotopic analyses by K. R. Ludwig of uraninite and monazite from biotite concentrations confirm an apparent age of 1,450±20 m.y. for these minerals. This age is equivalent to that reported for the Silver Plume Granite. Although the Wheeler Basin occurrence is small in size, it has many similarities to the Rossing uranium deposit in South-West Africa.

Colorado↗
USGS1977

Effect of initial radioactive-daughter disequilibrium on U-Pb isotope apparent ages of young minerals

Most calculations of U-Pb isotope apparent ages are made by use of equations that assume initial secular equilibrium of the uranium decay-chains. The possible error in calculated Pb/U isotope ratios arising from this assumption (especially for ores of sandstone uranium deposits) can be over 10 percent at 1 million years and exceed analytical error even at a 30 m.y. apparent age. Use of the more general equations (adapted from the Bateman equations) is desirable for calculation and interpretation of U-Pb isotope apparent ages of both open and closed systems in the range of 2 to 20 m.y. and is essential for apparent ages less than about 2 m^y. For very young sandstone uranium deposits, a significant uncertainty in the 208 Pb/ 238 U systematics may still persist owing to the uncertainty in the initial value of 234 U/ 238 U.

Journal of Research of the U.S. Geological Survey↗
USGS2015

Long-term anoxia and release of ancient, labile carbon upon thaw of Pleistocene permafrost

The fate of permafrost carbon upon thaw will drive feedbacks to climate warming. Here we consider the character and context of dissolved organic carbon (DOC) in yedoma permafrost cores from up to 20 m depth in central Alaska. We observed high DOC concentrations (4 to 129 mM) and consistent low molecular weight organic acid concentrations in three cores. We estimate a DOC production rate of 12 µmol DOC m −2 yr −1 based on model ages of up to ~200 kyr derived from uranium isotopes. Acetate C accounted for 24 ± 1% of DOC in all samples. This proportion suggests long-term anaerobiosis and is likely to influence thaw outcomes due to biolability of acetate upon release in many environments. The combination of uranium isotopes, ammonium concentrations, and calcium concentrations explained 86% of the variation in thaw water DOC concentrations, suggesting that DOC production may be related to both reducing conditions and mineral dissolution over time.

Geophysical Research Letters↗
USGS2006

Sea-cave temperature measurements and amino acid geochronology of British Late Pleistocene Sea stands

‘Calibrating’ amino acid ratios with uranium-series dates requires an accurate knowledge of current mean annual temperatures (CMATs) over the region studied. To measure these, test-tube sized ‘diffusion sensors’ were emplaced for 1 year (in 1984, 1985 and 1986), both outside and inside Minchin Hole sea-cave in South Wales and Belle Hougue sea-cave in Jersey, both of which have yielded Oxygen Isotope Substage 5e uranium-series ages on speleothems. Our outside temperatures agreed with meteorological ones. Our inside temperatures were over 1°C lower. To allow for this, a mean of ‘empirical’, ‘linear’ and ‘parabolic’ epimerisation calculations suggests that ratios from molluscs inside the caves should be multiplied by over 1.1 for comparison with outside ratios. This raises Bowen et al .'s ‘Pennard’ stage ratios from inside Minchin (and Bacon) Hole up towards the ‘Unnamed’ stage ratios outside, and suggests that the Unnamed sites are also from Oxygen Isotope Substage 5e, as proposed by Proctor and Smart. The same conclusion is reached more strongly by comparisons with the ratios and temperatures inside Belle Hougue to the south, and at Eemian (assumed 5e) sites in The Netherlands, Germany and Denmark to the east. The Pennard ratios from outside sites may provide further evidence for global sea stands close to the present level later in Oxygen Isotope Stage 5.

Journal of Quaternary Science↗
USGS1991

Timing of the last highstand of Lake Lahontan

Radiocarbon and uranium-series ages of a variety of materials from the Lahontan basin indicate that the last highstand lake occurred between 14 500 and 13 000 yr B.P. Although few in number, existing radiocarbon and uranium-series age data also indicate that lakes in the western Lahontan subbasins were small or moderate in size between 30 000 and 25 000 yr B.P. Existing data do not support the conclusions of Bradbury et al. (1989) who did not find evidence of a 14 000??yr B.P. highstand lake in the sediments of the Walker Lake subbasin. These data also do not support the existence of a highstand lake in the Walker Lake subbasin between 30 000 and 25 000 yr B.P. ?? 1991 Kluwer Academic Publishers.

Journal of Paleolimnology↗
USGS1992

Sampling and analysis for radon-222 dissolved in ground water and surface water

Radon-222 is a naturally occurring radioactive gas in the uranium-238 decay series that has traditionally been called, simply, radon. The lung cancer risks associated with the inhalation of radon decay products have been well documented by epidemiological studies on populations of uranium miners. The realization that radon is a public health hazard has raised the need for sampling and analytical guidelines for field personnel. Several sampling and analytical methods are being used to document radon concentrations in ground water and surface water worldwide but no convenient, single set of guidelines is available. Three different sampling and analytical methods-bubbler, liquid scintillation, and field screening-are discussed in this paper. The bubbler and liquid scintillation methods have high accuracy and precision, and small analytical method detection limits of 0.2 and 10 pCi/l (picocuries per liter), respectively. The field screening method generally is used as a qualitative reconnaissance tool.

Environmental Monitoring and Assessment↗
USGS1994

An integrated data-directed numerical method for estimating the undiscovered mineral endowment in a region

An integrated data-directed numerical method has been developed to estimate the undiscovered mineral endowment within a given area. The method has been used to estimate the undiscovered uranium endowment in the San Juan Basin, New Mexico, U.S.A. The favorability of uranium concentration was evaluated in each of 2,068 cells defined within the Basin. Favorability was based on the correlated similarity of the geologic characteristics of each cell to the geologic characteristics of five area-related deposit models. Estimates of the undiscovered endowment for each cell were categorized according to deposit type, depth, and cutoff grade. The method can be applied to any mineral or energy commodity provided that the data collected reflect discovered endowment. ?? 1994 Oxford University Press.

Nonrenewable Resources↗
USGS1997

Concentration, distribution, and comparison of selected trace elements in bed sediment and fish tissue in the South Platte River Basin, USA, 1992- 1993

During August–November 1992 and August 1993, bed sediment and fish liver were sampled in the South Platte River Basin and analyzed for 45 elements in bed sediment and 19 elements in fish liver. The results for aluminum, arsenic, cadmium, chromium, copper, iron, lead, manganese, selenium, silver, uranium, and zinc are presented here. All 12 trace elements were detected in bed sediment, but not all were detected in fish liver or in all species of fish. A background concentration of trace elements in bed sediment was calculated using the cumulative frequency curves of trace element concentrations at all sites. Arsenic, cadmium, copper, lead, manganese, silver, uranium, and zinc concentrations were greater than background concentrations at sites in mining areas or at sites that have natural sources of these elements. Trace element concentrations in fish liver generally did not follow the same patterns as concentrations in bed sediment, although concentrations of aluminum and cadmium were higher in fish liver collected at mountain sites that had been disturbed by mining. Concentrations of aluminum, arsenic, cadmium, chromium, copper, iron, lead, silver, and zinc increased in bed sediments in urban areas. Iron, silver, and zinc concentrations in fish liver also increased in urban areas. Concentrations of cadmium, copper, silver, and zinc in fish liver increased in the agricultural areas of the basin. Downstream changes in trace element concentrations may be the result of geological changes in addition to changes in land use along the river.

Archives of Environmental Contamination and Toxico↗
USGS2009

Unconventional energy resources: 2007-2008 review

This paper summarizes five 2007–2008 resource commodity committee reports prepared by the Energy Minerals Division (EMD) of the American Association of Petroleum Geologists. Current United States and global research and development activities related to gas hydrates, gas shales, geothermal resources, oil sands, and uranium resources are included in this review. These commodity reports were written to advise EMD leadership and membership of the current status of research and development of unconventional energy resources. Unconventional energy resources are defined as those resources other than conventional oil and natural gas that typically occur in sandstone and carbonate rocks. Gas hydrate resources are potentially enormous; however, production technologies are still under development. Gas shale, geothermal, oil sand, and uranium resources are now increasing targets of exploration and development, and are rapidly becoming important energy resources that will continue to be developed in the future.

Natural Resources Research↗
USGS2020

Sediment record of mining legacy and water quality from a drinking-water reservoir, Aztec, New Mexico, USA

The record of mining legacy and water quality was investigated in sediments collected in 2018 from four trenches in the Aztec, New Mexico, drinking-water reservoir #1. Bulk chemical analysis of sediments with depth in the reservoir revealed variable trace-element (uranium, vanadium, arsenic, copper, sulfur, silver, lead, and zinc) concentrations, which appear to coincide with historical mining and milling operations. Cesium-137 age dating, which identified the location of the 1963 radioactive fallout maximum, combined with the known age of the bottom and top of the sediment trenches, was used to estimate a polynomial sedimentation rate (average rate = 1.7 cm/yr). The clay size fraction (< 0.004 mm) was the dominant grain-size fraction of the sediments. Abundant fine-grained phyllosilicate (clay) minerals, predominantly montmorillonite and kaolinite, may explain sorption properties of trace elements. Scanning electron microscopy evaluation of sediments from two trenches showed copper and zinc associated with sulfur, and arsenic associated with iron and aluminum oxides. Results from laboratory batch experiments indicated that uranium, vanadium, and arsenic were released when sediments were reacted with a 150 mg/L sodium bicarbonate solution whereas copper was released when sediments were reacted with 2 mMol/L acetic acid. Observed concentrations from the two leach tests were below regulatory thresholds for delivery of solids to a landfill and were below drinking-water standards. Diatom relative abundance indicates that the water quality in the reservoir was not impaired by high metal concentrations.

Colorado, New Mexico↗
USGS1986

Correlation between electron spin resonance spectra and oil yield in eastern oil shales

Organic free radical spin concentrations were measured in 60 raw oil shale samples from north Alabama and south Tennessee and compared with Fischer assays and uranium concentrations. No correlation was found between spin concentration and oil yield for the complete set of samples. However, for a 13 sample set taken from a single core hole, a linear correlation was obtained. No correlation between spin concentration and uranium concentration was found.

Alabama, Tennessee↗