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Michael S. Lico

Publications and source records attributed to Michael S. Lico.

At least 19 recordsLinked to original sources
USGS2014

Preliminary geochemical assessment of water in selected streams, springs, and caves in the Upper Baker and Snake Creek drainages in Great Basin National Park, Nevada, 2009

Water in caves, discharging from springs, and flowing in streams in the upper Baker and Snake Creek drainages are important natural resources in Great Basin National Park, Nevada. Water and rock samples were collected from 15 sites during February 2009 as part of a series of investigations evaluating the potential for water resource depletion in the park resulting from the current and proposed groundwater withdrawals. This report summarizes general geochemical characteristics of water samples collected from the upper Baker and Snake Creek drainages for eventual use in evaluating possible hydrologic connections between the streams and selected caves and springs discharging in limestone terrain within each watershed. Generally, water discharging from selected springs in the upper Baker and Snake Creek watersheds is relatively young and, in some cases, has similar chemical characteristics to water collected from associated streams. In the upper Baker Creek drainage, geochemical data suggest possible hydrologic connections between Baker Creek and selected springs and caves along it. The analytical results for water samples collected from Wheelers Deep and Model Caves show characteristics similar to those from Baker Creek, suggesting a hydrologic connection between the creek and caves, a finding previously documented by other researchers. Generally, geochemical evidence does not support a connection between water flowing in Pole Canyon Creek to that in Model Cave, at least not to any appreciable extent. The water sample collected from Rosethorn Spring had relatively high concentrations of many of the constituents sampled as part of this study. This finding was expected as the water from the spring travelled through alluvium prior to being discharged at the surface and, as a result, was provided the opportunity to interact with soil minerals with which it came into contact. Isotopic evidence does not preclude a connection between Baker Creek and the water discharging from Rosethorn Spring. The residence time of water discharging into the caves and from selected springs sampled as part of this study ranged from 10 to 25 years. Within the upper Snake Creek drainage, the results of this study show geochemical similarities between Snake Creek and Outhouse Spring, Spring Creek Spring, and Squirrel Spring Cave. The strontium isotope ratio ( 87 Sr/ 86 Sr) for intrusive rock samples representative of the Snake Creek drainage were similar to carbonate rock samples. The water sample collected from Snake Creek at the pipeline discharge point had lower strontium concentrations than the sample downstream and a similar 87 Sr/ 86 Sr value as the carbonate and intrusive rocks. The chemistry of the water sample was considered representative of upstream conditions in Snake Creek and indicates minimal influence of rock dissolution. The results of this study suggest that water discharging from Outlet Spring is not hydrologically connected to Snake Creek but rather is recharged at high altitude(s) within the Snake Creek drainage. These findings for Outlet Spring largely stem from the relatively high specific conductance and chloride concentration, the lightest deuterium (δD) and oxygen-18 (δ 18 O) values, and the longest calculated residence time (60 to 90 years) relative to any other sample collected as part of this study. With the exception of water sampled from Outlet Spring, the residence time of water discharging into Squirrel Spring Cave and selected springs in the upper Snake Creek drainage was less than 30 years.

Nevada↗
USGS2008

Technical Review of Water-Resources Investigations of the Tule Desert, Lincoln County, Southern Nevada

The Nevada State Engineer in Ruling No. 5181 required Lincoln County and Vidler Water Company, Inc., to provide results from additional water-resources studies of Tule Desert in southern Nevada to support water-rights application 64692. As outlined by the ruling, the additional studies were to include the determination of the amount of ground water available from the Tule Desert basin, ground-water recharge to the Tule Desert, and the direction of ground-water flow. Results of these additional studies were published in five reports prepared for Lincoln County and Vidler Water Company, Inc. The National Park Service formally requested that the U.S. Geological Survey provide technical reviews of these five reports. The Nevada State Engineer in Ruling No. 5181 required Lincoln County and Vidler Water Company, Inc., to provide results from additional water-resources studies of Tule Desert in southern Nevada to support water-rights application 64692. As outlined by the ruling, the additional studies were to include the determination of the amount of ground water available from the Tule Desert basin, ground-water recharge to the Tule Desert, and the direction of ground-water flow. Results of these additional studies were published in five reports prepared for Lincoln County and Vidler Water Company, Inc. The National Park Service formally requested that the U.S. Geological Survey provide technical reviews of these five reports.

Open-File Report↗
USGS2007

Gasoline-Related Compounds in Lakes Mead and Mohave, Nevada, 2004-06

The distribution of man-made organic compounds, specifically gasoline-derived compounds, was investigated from 2004 to 2006 in Lakes Mead and Mohave and one of its tributary streams, Las Vegas Wash. Compounds contained in raw gasoline (benzene, toluene, ethylbenzene, xylenes; also known as BTEX compounds) and those produced during combustion of gasoline (polycyclic aromatic hydrocarbon compounds; also known as PAH compounds) were detected at every site sampled in Lakes Mead and Mohave. Water-quality analyses of samples collected during 2004-06 indicate that motorized watercraft are the major source of these organic compounds to the lakes. Concentrations of BTEX increase as the boating season progresses and decrease to less than detectable levels during the winter when few boats are on the water. Volatilization and microbial degradation most likely are the primary removal mechanisms for BTEX compounds in the lakes. Concentrations of BTEX compounds were highest at sampling points near marinas or popular launching areas. Methyl tert-butyl ether (MTBE) was detected during 2004 but concentrations decreased to less than the detection level during the latter part of the study; most likely due to the removal of MTBE from gasoline purchased in California. Distribution of PAH compounds was similar to that of BTEX compounds, in that, concentrations were highest at popular boating areas and lowest in areas where fewer boats traveled. PAH concentrations were highest at Katherine Landing and North Telephone Cove in Lake Mohave where many personal watercraft with carbureted two-stroke engines ply the waters. Lake-bottom sediment is not a sink for PAH as indicated by the low concentrations detected in sediment samples from both lakes. PAH compounds most likely are removed from the lakes by photochemical degradation. PAH compounds in Las Vegas Wash, which drains the greater Las Vegas metropolitan area, were present in relatively high concentrations in sediment from the upstream reaches. Concentrations of PAH compounds were low in water and sediment samples collected farther downstream, thus the bottom sediment in the upstream part of the wash may be an effective trap for these compounds. Bioavailable PAH compounds were present in all samples as determined using the Fluoroscan method. Microtox acute toxicity profiles indicated that Callville Bay in Lake Mead and the two Lake Mohave sites had only minor evidence that toxic compounds are present.

Scientific Investigations Report↗
USGS2006

Arsenic in ground water of the Western United States

Natural occurrences of ground water with moderate (10 to 50 micrograms per liter) to high (greater than 50 micrograms per liter) concentrations of arsenic are common throughout much of the Western United States. High concentrations of arsenic are generally associated with one of four geochemical environments: (1) basin-fill deposits of alluvial-lacustrine origin, particularly in semiarid areas, (2) volcanic deposits, (3) geothermal systems, and (4) uranium and gold-mining areas. These findings are based on an extensive literature review, compilation of unpublished reports and data, and the review of data bases containing more than 7,000 analyses of ground-water samples for arsenic. In the first two environments, arsenic appears to be associated with sediments derived, in part, from volcanic rocks of intermediate to acidic composition. Dissolved arsenic concentrations in water from volcanic aquifers in the same regions, however, may be low (less than 10 micrograms per liter). Solid phases (minerals, amorphous solids, and sedimentary organic matter) that supply the dissolved arsenic have not been identified in most areas. Alluvial and lacustrine sedimentary deposits appear to be an important source of arsenic in volcanic areas (such as Lane County, Oregon) and in areas underlain by basin-fill deposits (such as Carson Desert in Nevada and the Tulare Lake basin in California). Mobilization of arsenic in sedimentary aquifers may be, in part, a result of changes in the geochemical environment due to agricultural irrigation. In the deeper subsurface, elevated arsenic concentrations are associated with compaction caused by groundwater withdrawals.

Groundwater↗
USGS2005

Characterization of surface-water quality in the S-Line Canal and potential geochemical reactions from storage of surface water in the Basalt aquifer near Fallon, Nevada

The Fallon basalt aquifer serves as the sole source of municipal water supply for the Lahontan Valley in west-central Nevada. Principal users include the City of Fallon, Naval Air Station Fallon, and the Fallon Paiute-Shoshone Tribe. Pumpage from the aquifer increased from about 1,700 acre-feet per year in the early 1970's to more than 3,000 acre-feet per year in the late 1990's, and has been accompanied by declines in water levels and changes in water quality. Storage of surface water in the basalt may mitigate the effects of pumpage, but may cause undesirable changes in water chemistry. In May 2001, the U.S. Geological Survey began a study, in cooperation with the Fallon Paiute-Shoshone Tribe, to characterize the surface-water quality of the S-Line Canal, a likely source of water for augmenting recharge. Because arsenic concentrations in ground water of the basalt aquifer exceed drinking water standards, the potential for arsenic release to artificial recharge was explored by using geochemical modeling. Model results suggest that arsenic release may increase concentrations to levels that could limit the use of artificial recharge. Field-based experiments are needed to evaluate the underlying model assumptions.

Scientific Investigations Report↗
USGS2005

Potential for formation of disinfection by-products from storage of chlorinated surface water in the Basalt aquifer near Fallon, Nevada

Increased pumpage from a basalt aquifer near Fallon, Nevada, has caused its water levels to decline and has induced changes in the quality of water pumped from the basalt. The aquifer is the sole source of water for municipal supply to the city of Fallon, the Naval Air Station Fallon, and the Fallon Paiute-Shoshone Tribe. These changes may be mitigated by storage of surface water in the basalt for subsequent use. Because chlorination of the surface water may be required for storage, the U.S. Geological Survey, in cooperation with the Fallon Paiute-Shoshone Tribe, made laboratory tests using laboratory carbon-organic-free water, surface-water, ground-water, and basaltic-rock samples to determine the potential for formation of disinfection by-products. Experiments with water samples only (no rock and no chlorine) indicated no change in dissolved-organic-carbon (DOC) concentrations over a 20-day reaction period; whereas, all experiments using rock, water, and no chlorine indicated an increase in DOC concentrations. The greatest increase in DOC concentrations for all three water samples occurred in experiments with the rock samples from outcrops on Rattlesnake Hill. Experiments with water only and chlorine yielded a total trihalomethane (THM) concentration of 97.4 ?g/L for the ground-water sample and 347 ?g/L for the surface-water sample. Experiments with mixtures of water, rocks, and chlorine indicated that reactions with the rock consumed chlorine and released significant amounts of organic carbon from the rock, increasing the DOC concentration in the water. The organic carbon in the rocks likely is associated with the secondary clay minerals that line vesicles and fractures in the rocks. THM concentrations were greatest, from 335 to 909 ?g/L, for surface water equilibrated with rock samples from Rattlesnake Hill. However, the concentration of chlorine required to produce these high THM concentrations ranged from 18 to 84 mg/L. The results of the experiments suggest that the amount of organic carbon released from the rocks during successive cycles of recharge, storage, and recovery of chlorinated surface water may be relatively small. The chlorine demand of the rocks is so large that all of the free chlorine in the entire volume of recharged water likely would be consumed by only a very small volume of the aquifer surrounding an injection well, or beneath an infiltration bed. The majority of the volume of the aquifer filled by the stored water likely would never come in contact with free chlorine, and the increases in concentration of DOC observed in these experiments likely would occur in a very small volume of the stored water. For this reason, increases in concentration of THMs for the entire volume of water stored also likely would be considerably less than those measured in these experiments. To test this hypothesis, additional laboratory experiments using varying levels of chlorination, varying lengths of reaction periods, and repeated cycles of chlorination would be useful. A field experiment made at a small scale in an isolated part of the basalt aquifer would aid in the design of an operational system.

Scientific Investigations Report↗
USGS2004

Nutrient concentrations in Upper and Lower Echo, Fallen Leaf, Spooner, and Marlette Lakes and associated outlet streams, California and Nevada, 2002-03

Five lakes and their outlet streams in the Lake Tahoe Basin were sampled for nutrients during 2002-03. The lakes and streams sampled included Upper Echo, Lower Echo, Fallen Leaf, Spooner, and Marlette Lakes and Echo, Taylor, and Marlette Creeks. Water samples were collected to determine seasonal and spatial concentrations of dissolved nitrite plus nitrate, dissolved ammonia, total Kjeldahl nitrogen, dissolved orthophosphate, total phosphorus, and total bioreactive iron. These data will be used by Tahoe Regional Planning Agency in revising threshold values for waters within the Lake Tahoe Basin. Standard U.S. Geological Survey methods of sample collection and analysis were used and are detailed herein. Data collected during this study and summary statistics are presented in graphical and tabular form.

Open-File Report↗
USGS2004

Mercury in the Walker River Basin, Nevada and California: Sources, distribution, and potential effects on the ecosystem

Mercury is one of the most serious contaminants of water, sediment, and biota in Nevada because of its use during 19th century mining activities to recover gold and silver from ores. In 1998, mercury problems were discovered in the Walker River Basin of California and Nevada when blood drawn from three common loons from Walker Lake was analyzed and found to have severely elevated mercury levels. From 1999 to 2001, the U.S. Geological Survey and the U.S. Fish and Wildlife Service collected water, sediment, and biological samples to determine mercury sources, distribution, and potential effects on the Walker River Basin ecosystem. Total-mercury concentrations ranged from 0.62 to 57.11 ng/L in streams from the Walker River system and ranged from 1.02 to 26.8 ng/L in lakes and reservoirs. Total-mercury concentrations in streambed sediment ranged from 1 to 13,600 ng/g, and methylmercury concentrations ranged from 0.07 to 32.1 ng/g. The sediment-effects threshold for mercury for fresh-water invertebrates is 200 ng/g, which was exceeded at nine stream sites in the Walker River Basin. The highest mercury concentrations were in streams with historic mines and milling operations in the watershed. The highest mercury concentration in sediment, 13,600 ng/g, was found in Bodie Creek near Bodie, Calif., a site of extensive gold mining and milling activities during the 19th century. Sediment cores taken from Walker Lake show total-mercury concentrations exceeding 1,000 ng/g at depths greater than 15 cm below lake bottom. The presence of 137Cs above 8 cm in one core indicates that the upper 8 cm was deposited sometime after 1963. The mercury peak at 46 cm in that core, 2,660 ng/g, likely represents the peak of mining and gold extraction in the Bodie and Aurora mining districts between 1870 and 1880. Mercury concentrations in aquatic invertebrates at all sites downstream from mining activities in the Rough Creek watershed, which drains the Bodie and Aurora mining districts, were elevated (range 0.263 to 0.863 ?g/g, dry weight). Mercury concentrations in the Walker Lake tui chub, the most abundant and likely prey for common loons, ranged from approximately 0.09 ?g/g to approximately 0.9 ?g/g (wet weight). Larger tui chub in the lake, which are most likely older, had the highest mercury concentrations. Blood samples from 94 common loons collected at Walker Lake between 1998 and 2001 contained a mean mercury concentration of 2.96 ?g/g (standard deviation 1.72 ?g/g). These levels were substantially higher than those found in more than 1,600 common loons tested across North America. Among the 1,600 common loons, the greatest blood mercury concentration, 9.46 ?g/g, was from a loon at Walker Lake. According to risk assessments for northeastern North America, blood mercury concentrations exceeding 3.0 ?g/g cause behavioral, reproductive, and physiological effects. At least 52 percent of the loons at Walker Lake are at risk for adverse effects from mercury on the basis of their blood-mercury concentrations. The larger loons staging in the spring are the most at risk group. The elevated mercury levels found in tui chub and common loons indicate that there is a potential threat to the well being and reproduction of fish and wildlife that use Walker Lake. Wildlife that use Weber Reservoir may also be at risk because it is the first reservoir downstream from mining activities in the Bodie and Aurora areas and mercury concentrations in sediment were elevated. Additional data on mercury concentrations in top level predators, such as piscivorous fish and birds, are needed to assess public health and other environmental risks.

California, Nevada↗
USGS2000

Data on stream-water and bed-sediment quality in the vicinity of Leviathan Mine, Alpine County, California, and Douglas County, Nevada, September 1998

The U.S. Geological Survey (USGS) con- ducted a chemical assessment of streams in the Leviathan Mine and adjacent areas in September 1998. On-site measurements of streamflow, pH, dissolved oxygen, temperature, specific conductance, and at most sites alkalinity, bicarbonate, and carbonate were made at 14 sites. Water samples were collected for chemical analyses of nutrients, major ions, trace elements, and organic carbon. Bed-sediment samples of fine-grained sediment in representative depositional areas at each sampling location were collected for chemical analyses of major and trace elements, total carbon, inorganic carbon, and organic carbon.

California,Nevada↗
USGS1999

Concentrations and distribution of manmade organic compounds in the Lake Tahoe Basin, Nevada and California, 1997-99

The U.S. Geological Survey, in cooperation with the Tahoe Regional Planning Agency and the Lahontan Regional Water-Quality Control Board, sampled Lake Tahoe, major tributary streams to Lake Tahoe, and several other lakes in the Lake Tahoe Basin for manmade organic compounds during 1997-99. Gasoline components were found in all samples collected from Lake Tahoe during the summer boating season. Methyl tert -butyl ether (MTBE), benzene, toluene, ethylbenzene, and xylenes (BTEX) were the commonly detected compounds in these samples. Most samples from tributary streams and lakes with no motorized boating had no detectable concentrations of gasoline components. Motorized boating activity appears to be directly linked in space and time to the occurrence of these gasoline components. Other sources of gasoline components to Lake Tahoe, such as the atmosphere, surface runoff, and subsurface flow, are minor compared to the input by motorized boating. Water sampled from Lake Tahoe during mid-winter, when motorized boating activity is low, had no MTBE and only one sample had any detectable BTEX compounds. Soluble pesticides rarely were detected in water samples from the Lake Tahoe Basin. The only detectable concentrations of these compounds were in samples from Blackwood and Taylor Creeks collected during spring runoff. Concentrations found in these samples were low, in the 1 to 4 nanograms per liter range. Organochlorine compounds were detected in samples collected from semipermeable membrane devices (SPMD's) collected from Lake Tahoe, tributary streams, and Upper Angora Lake. In Lake Tahoe, SPMD samples collected offshore from urbanized areas contained the largest number and highest concentrations of organochlorine compounds. The most commonly detected organochlorine compounds were cis- and trans-chlordane, p , p' -DDE, and hexachlorobenzene. In tributary streams, SPMD samples collected during spring runoff generally had higher combined concentrations of organochlorine compounds than those collected during baseflow conditions. Upper Angora Lake had the fewest number of organochlorine compounds detected of all lake samples. Dioxins and furans were not detected in SPMD samples from two sites in Lake Tahoe or from two tributary streams. The number of polycyclic aromatic hydrocarbon (PAH) compounds and their combined concentrations generally were higher in samples from Lake Tahoe than those from tributary streams. Areas of high-motorized boating activity at Lake Tahoe had the largest number and highest concentrations of PAH's. PAH compounds were detected in samples from SPMD's in four of six tributary streams during spring runoff, all tributary streams during baseflow conditions, and at all lake sites. The most commonly detected PAH's in tributary streams during spring runoff were phenanthrene, fluoranthene, pyrene, and chrysene, and during baseflow conditions were phenanthrene, 1-methylphenanthrene, diethylnaphthalene, and pyrene. Upper Truckee River, which has an urban area in its drainage basin, had the largest number and highest combined concentration of PAH's of all stream samples. Bottom-sediment from Lake Tahoe had detectable concentrations of p-cresol, a phenol, in all but one sample. A sample collected near Chambers Lodge contained phenol at an estimated concentration of 4 micrograms per kilogram (µg/kg). Bottom-sediment samples from tributary streams had no detectable concentrations of organochlorine or PAH compounds. Several compounds were detected in bottom sediment from Upper Angora Lake at high concentrations. These compounds and their concentrations were p , p' -DDD (10 µg/kg), p , p' -DDE (7.4 µg/kg), 2,6-dimethylnaphthalene (estimated at 190 µg/kg), pentachlorophenol (3,000 µg/kg), and p-cresol (4,400 µg/kg).

California, Nevada↗
USGS1997

Water-quality assessment of the Las Vegas Valley area and the Carson and Truckee River basins, Nevada and California: Nutrients, pesticides, and suspended sediment, October 1969-April 1990

The U.S. Geological Survey National Water-Quality Assessment Program (NAWQA) is designed to provide long-term, consistent information on water quality that can be used to describe local, regional, and national conditions. The full-scale NAWQA Program, initiated in 1991, includes both study-unit and national synthesis activities. Study-unit investigations provide scientific data and interpretations that will be integrated by national synthesis studies to assess the quality of the Nation's water resources. The Nevada Basin and Range (NVBR) study unit is one of 60 proposed NAWQA study units in the United States. These riverbasin-scale areas were selected to represent large proportions of the Nation's water use and population served by public supplies, and the Nation's geographic diversity. The NVBR study unit includes the Las Vegas Valley area, approximately 1,640 mi in southern Nevada, and the Carson River Basin (3,970 mi 2 ) and Truckee River Basin (3,230 mi 2 ) in northwestern Nevada and northeastern California. The areas are typical of Basin and Range physiography. Snowfall in high mountains provides streamflow and ground-water recharge in adjacent basins. Unconsolidated basin-fill deposits commonly exceed 1,000 ft in thickness and are principal aquifers in the study unit. The study-unit climate varies from humid continental in the Sierra Nevada where the Carson and Truckee Rivers originate (annual precipitation exceeds 30 in.) to desert in terminal parts of the basins, including the Carson Desert and lower altitudes in Las Vegas Valley, where annual precipitation is less than 5 in. In 1990, Nevada had the greatest population growth rate and the fourth greatest percentage of population residing in urban areas in the Nation. More than 90 percent of Nevada's population (about 1,090,000 in 1990) resided in the study unit; the Las Vegas Valley area (about 710,000) was the most populous area. In 1990, water use in the study unit was about 1,117,000 acre-ft. Water use in the Las Vegas Valley area was about 317,000 acre-ft; 91 percent was for public supplies. Las Vegas Valley was 79 percent range land, but the 5 percent urban land use has significantly affected water resources. Water use in the Carson River Basin was 538,000 acre-ft in 1990. About 95 percent of the water was used for irrigation, although only 5 percent of the land was used for irrigated agriculture. Water use in the Truckee River Basin was 262,000 acre-ft in 1990. Public supply used about 36 percent of the water, although only 3 percent of the land was urban. Nutrients, pesticides, and suspended sediments are important water-quality issues in the study unit. Urban runoff and treated sewage effluent contribute these constituents to Las Vegas Wash and the Truckee River. Urban and agricultural activities in the Carson and Truckee River Basins are also sources of these constituents.

California, Nevada↗
USGS1997

Ground-water quality assessment of the Carson River basin, Nevada and California — Results of investigations, 1987–91

Using existing Nevada State drinking-water standards as a measure of the overall water quality, ground-water quality in principal aquifers of the upper Carson River basin is generally excellent. Ground-water quality in the Carson Desert, the distal end of the Carson River basin, displays extremes in concentrations of major and minor inorganic constituents, with dissolved solids reaching concentrations exceeding sea water. More than 10 percent of sampled ground water in the principal aquifers contain concentrations of arsenic, dissolved solids, and manganese greater than the drinking-water standards. Nearly all sampled ground water in the basin had radon-222 activities greater than the proposed Federal maximum contaminant level of 300 picocuries per liter. Uranium concentrations greater than the proposed Federal maximum contaminant level of 20 micrograms per liter were found in ground water in the adjacent Sierra Nevada.

California, Nevada↗
USGS1994

Ground-water quality and geochemistry, Carson Desert, western Nevada

Aquifers in the Carson Desert are the primary source of drinking water, which is highly variable in chemical composition. In the shallow basin-fill aquifers, water chemistyr varies from a dilute calcium bicarbonate-dominated water beneath the irrigated areas to a saline sodium chloride- dominated water beneath unirrigated areas. Water samples from the shallow aquifers commonly have dissolved solids, chloride, magnesium, sulfate, arsenic, and manganese concentrations that exceed State of Nevada drinking-water standards. Water in the intermediante basin-fill aquifers is a dilute sodium bicarbonate type in the Fallon area and a distinctly more saline sodium chloride type in the Soda Lake-Upsal Hogback area. Dissolved solids, chloride, arsenic, fluoride, and manganese concen- trations commonly exceed drinking-water standards. The basalt aquifer contains a dilute sodium bicarbonate chloride water. Arsenic concentrations exceed standards in all sampled wells. The concen- trations of major constituents in ground water beneath the southern Carson Desert are the result of evapotranspiration and natural geochemical reactions with minerals derived mostly from igneous rocks. Water with higher concentrations of iron and manganese is near thermodynamic equilibrium with siderite and rhodochrosite and indicates that these elements may be limited by the solubility of their respective carbonate minerals. Naturally occurring radionuclides (uranium and radon-222) are present in ground water from the Carson Desert in concen- tratons higher than proposed drinking-water standards. High uranium concentrations in the shallow aquifers may be caused by evaporative concentration and the release of uranium during dissolution of iron and manganese oxides or the oxidation of sedimentary organic matter that typically has elevated uranium concentrations. Ground water in the Carson Desert does not appear to have be contaminated by synthetic organic chemicals.

Open-File Report↗