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At least 199 records · Page 11Linked to original sources
USGS2004

Importance of storm events in controlling ecosystem structure and function in a Florida Gulf Coast estuary

From 8/95 to 2/01, we investigated the ecological effects of intra- and inter-annual variability in freshwater flow through Taylor Creek in southeastern Everglades National Park. Continuous monitoring and intensive sampling studies overlapped with an array of pulsed weather events that impacted physical, chemical, and biological attributes of this region. We quantified the effects of three events representing a range of characteristics (duration, amount of precipitation, storm intensity, wind direction) on the hydraulic connectivity, nutrient and sediment dynamics, and vegetation structure of the SE Everglades estuarine ecotone. These events included a strong winter storm in November 1996, Tropical Storm Harvey in September 1999, and Hurricane Irene in October 1999. Continuous hydrologic and daily water sample data were used to examine the effects of these events on the physical forcing and quality of water in Taylor Creek. A high resolution, flow-through sampling and mapping approach was used to characterize water quality in the adjacent bay. To understand the effects of these events on vegetation communities, we measured mangrove litter production and estimated seagrass cover in the bay at monthly intervals. We also quantified sediment deposition associated with Hurricane Irene's flood surge along the Buttonwood Ridge. These three events resulted in dramatic changes in surface water movement and chemistry in Taylor Creek and adjacent regions of Florida Bay as well as increased mangrove litterfall and flood surge scouring of seagrass beds. Up to 5 cm of bay-derived mud was deposited along the ridge adjacent to the creek in this single pulsed event. These short-term events can account for a substantial proportion of the annual flux of freshwater and materials between the mangrove zone and Florida Bay. Our findings shed light on the capacity of these storm events, especially when in succession, to have far reaching and long lasting effects on coastal ecosystems such as the estuarine ecotone of the SE Everglades.

Journal of Coastal Research↗
USGS2024

Network connectivity contributes to native small-bodied fish assemblages in the upper Mississippi River system

Effective management and conservation of fishes requires understanding habitat use across multiple life stages while ensuring necessary habitats are both available and accessible. Tributary habitats may play an important role in recruitment and dispersal of fishes in anthropogenically modified rivers such as the Mississippi and Illinois Rivers of the Midwest U.S.A. Identifying source locations that contribute to recruitment of fish populations can determine the importance of connectivity within river networks and pinpoint critical habitats that sustain fish populations. In the Upper Mississippi River System (UMRS), the environments that fish use in early life stages (i.e., natal origin) can be identified using otolith trace element analysis due to stability and distinctness in water chemistry (strontium: calcium [Sr:Ca]) among water bodies that is reflected in otoliths. Here, we used trace element analysis to determine natal origin of six small-bodied fishes including bullhead minnow ( Pimephales vigilax ), emerald shiner ( Notropis atherinoides ), gizzard shad ( Dorosoma cepedianum ), bluegill ( Lepomis macrochirus ), orangespotted sunfish ( Lepomis humilis ), and yellow perch ( Perca flavescens ) across six reaches of the UMRS (Pools 4, 8, 13, 26, the Open River of the Middle Mississippi River, and the La Grange Pool of the Illinois River). Otolith core Sr:Ca for fishes was quantified using laser ablation inductively coupled plasma mass spectrometry. Using the resulting Sr:Ca chemical signatures of otolith cores, natal origin (tributary, immigrant, or potential resident) was determined for individual fish based on family-specific relationships between otolith and water chemistries. We found that all species originated from tributaries and other reaches (i.e., were immigrants) to varying extents, which acted as evidence for network connectivity. Specifically, tributaries contributed up to 48% of individuals at a given reach. In certain reaches, Pool 26 and the Open River reach, up to 80% of individuals in a species immigrated from another mainstem river reach. Network connectivity was also important in both upstream and downstream directions. Contributions from network connectivity varied among species: bullhead minnow used less whereas orangespotted sunfish used more network connectivity than when all species were combined. Further, the use of network connectivity varied spatially where individuals captured in Pool 8 and the La Grange Pool less often and those from Pool 26 and the Open River more often originated from network connectivity compared to the whole assemblage across reaches. These results indicate that species' life history traits probably interacted with the physical environment, which differs spatially, to yield observed recruitment source patterns. Our results show that network connectivity contributes to established assemblages of native small-bodied fishes throughout the UMRS and underscore the role of interjurisdictional management in maintaining network connectivity to sustain fish populations.

Illinois, Iowa, Minnesota, Missouri, Wisconsin↗
USGS2018

Linking the agricultural landscape of the Midwest to stream health with structural equation modeling

Multiple physical and chemical stressors can simultaneously affect the biological condition of streams. To better understand the complex interactions of land-use practices, water quality, and ecological integrity of streams, the U.S. Geological Survey National Water Quality Assessment Project is conducting regional-scale assessments of stream condition across the United States. In the summer of 2013, weekly water samples were collected from 100 streams in the Midwestern United States. Employing watershed theory, we used structural equation modeling (SEM) to represent a general hypothesis for how 16 variables (previously identified to be important to stream condition) might be inter-related. Again, using SEM, we evaluated the ability of this “stressor network” to explain variations in multimetrics of algal, invertebrate, and fish community health, trimming away any environmental variables not contributing to an explanation of the ecological responses. Seven environmental variables—agricultural and urban land use, sand content of soils, basin area, percent riparian area as forest, channel erosion, and relative bed stability—were found to be important for all three-community metrics. The algal and invertebrate models included water-chemistry variables not included in the fish model. Results suggest that ecological integrity of Midwest streams are affected by both agricultural and urban land uses and by the natural geologic setting, as indicated by the sand content of soils. Chemicals related to crops (pesticides and nutrients) and residential uses (pyrethroids) were found to be more strongly related to ecological integrity than were natural factors (riparian forest, watershed soil character).

Environmental Science & Technology↗
USGS1989

The geology, botany and chemistry of selected peat-forming environments from temperate and tropical latitudes

Peat has been studied in several geologic settings: (1) glaciated terrain in cold temperate Maine and Minnesota, U.S.A.; (2) an island in the Atlantic Ocean off the coast of Maine, where sea level is rising; (3) the warm temperate U.S. Atlantic and Gulf Coastal Plains, where sea level has changed often; and (4) the tropical coast of Sarawak, Malaysia, and the tropical delta of the Batang Hari River, Sumatra, Indonesia. Most of these deposits are domed (ombrotrophic or partly ombrotrophic) bogs in which peat accumulation continued above the surface of the surrounding soil. However, the bogs of the U.S. Atlantic and Gulf Coastal Plains are comparatively not as domed, and many have almost level surfaces. In some bogs, aquatic or semi-aquatic plant materials accumulated, replaced water in the depressions, and formed a surface on which marsh or swamp vegetation could subsequently live, die, and accumulate. In others, the plant materials accumulated initially on level silt or sand surfaces supporting marshes or swamps. As the peat dome formed, plants growing on it changed from luxuriant ones near the base of the dome, where nutrients were brought into the bog by surface and ground water, to stunted ones at the top of the dome, where the raised bogs are fed by nutrient-poor precipitation. The physical and chemical changes that take place in the sequence of environments from the pond stage of deposit development, through the grassy marsh stage, through the forested swamp stage, and finally through the heath dome stage can be measured in terms of acidity and ash, volatile matter, carbon, hydrogen, nitrogen, sulfur and oxygen contents, as well as in the kind and distribution of trace elements. The organic and inorganic contents of the deposits relate to geomorphology, and geomorphology relates to their settings. As models of coal formation, some domed peat deposits may help in solving problems of distribution and character of ancient coal beds. But clearly not all peat deposits are precursors of coal. Most Holocene peat deposits are subject to destruction by erosion, fire and decomposition through microbial and chemical oxidation before burial. The best environments for coal precursors have biomass accumulation, a continuously rising water table within the mass, and minimum influx of clay and silt until preservation by burial. The most suitable settings for future economic coal deposits are domed bogs that accumulate thick, widespread peat having low ash and low sulfur contents. The ombrotrophic peat deposits of tropical Sarawak and Sumatra are thick and extensive, contain low-ash and low-sulfur peat, and have high heating values. They are considered to be the best tropical coal analogs because of their extent and chances of preservation; the base of the peat is below adjacent river levels, and chemical and structural conditions are favorable for accumulation.

International Journal of Coal Geology↗
USGS2000

A hydrologic primer for New Jersey watershed management

The U.S. Geological Survey (USGS) and the N.J. Department of Environmental Protection (NJDEP), and many other agencies and organizations are striving to educate the public about New Jersey’s water resources. In 1996, the NJDEP began implementing a “watershed management approach” to maintain the physical, chemical, and biological integrity of New Jersey’s waters. This approach concentrates on managing individual watershed areas by (1) defining the physical geographic boundaries of the watersheds, (2) basing water policy on sound scientific principles, and (3) developing partnerships with the public--the people most affected by watershed-management policies. New Jersey can be divided into five water regions as defined by the NJDEP: the Northeast, Raritan, Northwest, Lower Delaware, and Atlantic Coastal water regions (fig. 1). Each water region has been divided into three to five “watershed-management areas,” each of which encompasses a particular group of major rivers (fig. 2a-e). Each watershed management area consists of many smaller watersheds. Hydrologic data collected by Federal and State government agencies are invaluable as resources to policymakers who make decisions that affect the use of water in a particular watershed. The purpose of this report is to educate water-resource managers, policymakers, government officials, and the public about hydrologic concepts and the water-resource data needed to make informed decisions about water-management issues. (“Hydrologic” means relating to the occurrence, distribution, movement, and chemistry of all waters of the Earth (Fetter, 1980)). The first part of the report describes basic hydrologic concepts and includes explanations of the hydrologic cycle, the water budget, the surfacewater and ground-water flow systems, water-quality concepts and standards, and water use. The second part of the report summarizes the types of waterresource data that are available from Federal and State government agencies. Instructions on how to obtain the data and contact the appropriate Federal and State agencies, as well as suggestions for additional reading, also are included.

New Jersey↗
USGS1997

Comparison of phytoplankton succession in two lakes of different mixing regimes

The influence of frequent water-column mixing on phytoplankton succession and species composition was studied by comparing plankton dynamics in two lakes (Lake Opinicon and Upper Rock Lake) which have similar water chemistry, but differ widely in their basin morphometries: Opinicon is shallow and frequently-mixed during the ice-free season, whereas nearby Upper Rock is deep and dimictic. The species composition and the seasonal succession of phytoplankton were broadly similar in both lakes over the three years of study. The spring phytoplankton in both lakes consisted of diatoms that were replaced in the summer and fall by cyanobacteria. Diatom peaks in Opinicon preceded similar peaks in Upper Rock. Loss of diatoms from the phytoplankton in Upper Rock appeared to be related to sedimentation; in contrast, zooplankton herbivory may have resulted, partly, in loss of diatoms in Opinicon. Lightly-silicified and spindle-shaped diatoms (Rhizosolenia and single-celled Fragilaria) were more abundant in the dimictic lake, whereas heavily-silicified diatoms (Aulacoseira) were more abundant in the frequently-mixed lake. Zooplankton taxa and their seasonal patterns were similar in both lakes, but populations were considerably denser in the frequently-mixed lake. The results of canonical correspondence analysis and detrended correspondence analysis (multivariate ordination techniques) indicated that, although phytoplankton growth was influenced by similar physical and chemical variables in both lakes, the influence of chemical variables was stronger in Upper Rock. A frequently-mixed system, such as Lake Opinicon, appeared to provide a similar environment for plankton development to a well-mixed epilimnion of a typical dimictic lake, such as Upper Rock Lake.

Archiv fur Hydrobiologie↗
USGS1989

Terrestrial population models for ecological risk assessment: A state-of-the-art review

Few attempts have been made to formulate models for predicting impacts of xenobiotic chemicals on wildlife populations. However, considerable effort has been invested in wildlife optimal exploitation models. Because death from intoxication has a similar effect on population dynamics as death by harvesting, these management models are applicable to ecological risk assessment. An underlying Leslie-matrix bookkeeping formulation is widely applicable to vertebrate wildlife populations. Unfortunately, however, the various submodels that track birth, death, and dispersal rates as functions of the physical, chemical, and biotic environment are by their nature almost inevitably highly species- and locale-specific. Short-term prediction of one-time chemical applications requires only information on mortality before and after contamination. In such cases a simple matrix formulation may be adequate for risk assessment. But generally, risk must be projected over periods of a generation or more. This precludes generic protocols for risk assessment and also the ready and inexpensive predictions of a chemical's influence on a given population. When designing and applying models for ecological risk assessment at the population level, the endpoints (output) of concern must be carefully and rigorously defined. The most easily accessible and appropriate endpoints are (1) pseudoextinction (the frequency or probability of a population falling below a prespecified density), and (2) temporal mean population density. Spatial and temporal extent of predicted changes must be clearly specified a priori to avoid apparent contradictions and confusion.

Environmental Toxicology and Chemistry↗
USGS2007

Role of sediment resuspension in the remobilization of particulate-phase metals from coastal sediments

The release of particulate-phase trace metals due to sediment resuspension has been investigated by combining erosion chamber experiments that apply a range of shear stresses typically encountered in coastal environments with a shear stress record simulated by a hydrodynamic model. Two sites with contrasting sediment chemistry were investigated. Sediment particles enriched in silver, copper, and lead, 4−50 times greater than the bulk surface-sediment content, were the first particles to be eroded. As the shear-stress level was increased in the chamber, the total mass eroded increased, but the enrichment of these trace metals fell, approaching the bulk-sediment content. From the temporal distribution of shear stress generated by the hydrodynamic model for a site in Boston Harbor, resuspension fluxes were estimated. The erosion threshold of this site is exceeded during spring tides, releasing the particles enriched in trace metals into the water column. Due to the higher trace metal content and the regularity of resuspension, low-energy resuspension events (up to a shear stress of 0.2 N/m 2 ) contribute up to 60% of the resuspension metal flux in an average year. The estimated annual quantity of copper and lead resuspended into the water column is higher than estimates of the total riverine flux for these metals. These results indicate that sediment resuspension is a very important mechanism for releasing metals into the water column and provide new insight into the chemical and physical processes controlling the long-term fate of trace metals in contaminated sediments.

Massachusetts↗
USGS1986

Trace metal seasonal variations in Texas marine sediments

Trace elements in coastal environments are derived from three major sources: (1) the bordering watershed; (2) the offshore marine environment; and (3) industrial and/or urban effluent. The site of deposition, however, is controlled by physical and chemical processes in the coastal zone. In many cases, these processes are controlled by climate and can vary seasonally. In the harbor at Corpus Christi, Texas, the summer climate creates an oxygen-poor environment in the water column near the sediment-water interface. This causes chalcophilic metals to precipitate from the water, resulting in high concentrations in the sediments near the source. During the winter, turbulence created by strong winds causes the entire water mass to become aerated and oxidizing, and remobilization of some metals results. In addition, this turbulence accelerates circulation which transports the metal-enriched waters from the harbor. On the outer continental shelf of south Texas, the infaunal activity varies seasonally with bottom water temperatures. As this infaunal activity has an effect on the chemical environment within the sediment near the sediment-water interface, the observed trace metal content at the interface also appears to change with the seasons.

Texas↗
USGS2021

Growth and defense characteristics of whitebark pine (Pinus albicaulis) and lodgepole pine (Pinus contorta var latifolia) in a high-elevation, disturbance-prone mixed-conifer forest in northwestern Montana, USA

Recent, widespread tree mortality in the western U.S. resulting from changes in climate, pathogens, insect activity, and forest management practices has led to concerns for many ecologically and culturally important species. Within conifers, resin-based defenses have long been recognized as a primary defense mechanism against a variety of insects and pathogens. Oleoresin produced by trees contain complex mixtures of terpenoids that have numerous insecticidal and fungicidal properties. Research has also identified links between resin duct characteristics and increased probability of survival during bark beetle outbreaks. Whitebark pine ( Pinus albicaulis ) is a culturally significant high elevation species that provides numerous ecological services within subalpine and alpine ecosystems. Whitebark pine has co-evolved with a suite of biotic and abiotic disturbances. Individual trees allocate resources towards growth and resin-based defenses, making it a good candidate species to evaluate growth and defense relationships and tradeoffs. In this study we compared constitutive resin chemistry, tree growth and resin duct anatomy between similarly aged whitebark and lodgepole pine ( P. contorta var latifolia ) growing in proximity within a disturbance-prone, mixed-conifer forest in northwestern Montana. These two host species have varying degrees of historical exposure to mountain pine beetle. Our research yields four important findings. First, we did not find evidence of a tradeoff between tree growth and tree defenses (resin duct morphology and resin chemistry). This suggests that trees growing under favorable field conditions can experience high growth rates and still allocate ample resources towards defense. Second, we found that resin ducts and constitutive mono- and sesqui- terpenes were not correlated in lodgepole pine while duct production and area were positively related to constitutive monoterpenes, and duct size and area were positively related to constitutive sesquiterpenes, in whitebark pine. The lack of distinct, consistent relationships between these defensive features suggests that both whitebark and lodgepole pine trees present beetles with numerous, complex combinations of resin-based defenses. Third, based on constitutive terpene profiles, bark beetles are more likely to enter lodgepole pine but more likely to successfully elicit mass attacks in whitebark pine, which agrees with beetle attack and success patterns observed in the field. Fourth, overstory competition, particularly by Engelmann spruce ( Picea engelmannii ), can influence tree defenses, specifically by reducing constitutive terpene concentrations in lodgepole and whitebark pine. Competitive tree interactions could lead to altered bark beetle-conifer interactions as host and nonhost species migrate in response to changing climate. Our results suggest that strategies designed to support whitebark pine populations can benefit from better understanding interactions among growth, competition and physical and chemical defenses in response to multiple disturbance.

Montana↗
USGS2021

Water and sediment chemistry of selected existing and potential habitats of the Mohave tui chub, Mojave National Preserve, California, 2018

The Mohave tui chub ( Siphateles bicolor mohavensis ) was nearly extirpated from the Mojave River drainage in California by the mid-twentieth century and was listed as endangered in 1970. A source population of Mohave tui chub exists at MC Spring in Zzyzx, California, and has been used for several re-establishment efforts in previous decades. Two potential habitats in the Mojave National Preserve with perennial sources of water were identified by the National Park Service as candidates for additional Mohave tui chub re-establishment: West Pond and Rainbow Wells Pond. West Pond, an artificial pond at Zzyzx near MC Spring, contained a population of Mohave tui chub that died off in 1985 because of changes in water quality. The pond was rehabilitated in the past several years through re-excavation and by pumping fresh groundwater into the pond. Rainbow Wells Pond is an abandoned excavated mine site in the Cima Dome area. The bottom of the excavation intersects the water table, forming a pond. In cooperation with the National Park Service, the U.S. Geological Survey monitored water-quality conditions at West Pond and Rainbow Wells Pond for 1 year to characterize the suitability of spring habitat for re-establishment of Mohave tui chub populations. Data were also collected at three existing Mohave tui chub habitats in Mojave National Preserve to provide further information on the range of acceptable physical and chemical conditions. Initial water-quality results at West Pond indicate the pond has similar water quality as existing Mohave tui chub habitats. Initial water-quality results at Rainbow Wells Pond indicate the dissolved oxygen concentrations and springtime water temperatures are less than the long-term tolerable ranges for Mohave tui chub.

California↗
USGS2004

Age and source of water in springs associated with the Jacksonville Thrust Fault Complex, Calhoun County, Alabama

Water from wells and springs accounts for more than 90 percent of the public water supply in Calhoun County, Alabama. Springs associated with the Jacksonville Thrust Fault Complex are used for public water supply for the cities of Anniston and Jacksonville. The largest ground-water supply is Coldwater Spring, the primary source of water for Anniston, Alabama. The average discharge of Coldwater Spring is about 32 million gallons per day, and the variability of discharge is about 75 percent. Water-quality samples were collected from 6 springs and 15 wells in Calhoun County from November 2001 to January 2003. The pH of the ground water typically was greater than 6.0, and specific conductance was less than 300 microsiemens per centimeter. The water chemistry was dominated by calcium, carbonate, and bicarbonate ions. The hydrogen and oxygen isotopic composition of the water samples indicates the occurrence of a low-temperature, water-rock weathering reaction known as silicate hydrolysis. The residence time of the ground water, or ground-water age, was estimated by using analysis of chlorofluorocarbon, sulfur hexafluoride, and regression modeling. Estimated ground-water ages ranged from less than 10 to approximately 40 years, with a median age of about 18 years. The Spearman rho test was used to identify statistically significant covariance among selected physical properties and constituents in the ground water. The alkalinity, specific conductance, and dissolved solids increased as age increased; these correlations reflect common changes in ground-water quality that occur with increasing residence time and support the accuracy of the age estimates. The concentration of sodium and chloride increased as age increased; the correlation of these constituents is interpreted to indicate natural sources for chloride and sodium. The concentration of silica increased as the concentration of potassium increased; this correlation, in addition to the isotopic data, is evidence that silicate hydrolysis of clay minerals occurred. The geochemical modeling program NETPATH was used to investigate possible mixing scenarios that could yield the chemical composition of water collected from springs associated with the Jacksonville Thrust Fault Complex. The results of NETPATH modeling suggest that the primary source of water in Coldwater Spring is a deep aquifer, and only small amounts of rainwater from nearby sources are discharged from the spring. Starting with Piedmont Sports Spring and moving southwest along a conceptual ground-water flow path that parallels the Jacksonville Thrust Fault Complex, NETPATH simulated the observed water quality of each spring, in succession, by mixing rainwater and water from the spring just to the northeast of the spring being modeled. The percentage of rainwater and ground water needed to simulate the quality of water flowing from the springs ranged from 1 to 25 percent rainwater and 75 to 99 percent ground water.

Scientific Investigations Report↗
USGS1997

Physical and chemical characteristics of Terrace Reservoir, Conejos County, Colorado, May 1994 through May 1995

Terrace Reservoir receives drainage of low-pH, metal-enriched water from mineralized areas, including the Summitville Mine, within the Alamosa River Basin. Drainage from the Summitville Mine has contributed a substantial part of the metal load to Terrace Reservoir. From May 1994 through May 1995, a study was done by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to evaluate the physical and chemical characteristics of Terrace Reservoir. Terrace Reservoir was thermally stratified from about mid-May through August 1994. Thermal stratification was absent from September\x111994through March 1995. During periods of stratification, underflow of the Alamosa River was predominant, and residence times of the underflow were shortened by 40 to 75\x11percent of the theoretical residence times for a well-mixed reservoir. Transport and deposition of suspended solids in Terrace Reservoir varied spatially and temporally. Most of the suspended solids were deposited in Terrace Reservoir. The concentration of dissolved oxygen in the reservoir varied little spatially or temporally and generally was within a few tenths of the dissolved-oxygen concentration of the inflow. The pH of water in the reservoir generally ranged from about 4.0 to about 7.0, depending on date, depth, and location. The largest pH values were measured during May. A markeddecrease of about 1.5\x11pH units occurred at site T5 in the reservoir about mid-June. The pH of the reservoir remained at or below 5.5 from mid-June through November. Dissolved-metal concentrations varied spatially and temporally in response to several factors, which included inflow characteristics, reservoir stratification and mixing, inflow-routing and flow-through patterns, residence times, sedimentation, dissolved oxygen, and pH.Inflow chemistry is the dominant controlling factor of metal chemistry within Terrace Reservoir.During periods of stratification, large vertical variations in metal concentrations occurred. The highest metal concentrations in the reservoir generally were measured in the hypolimnion between June and August. During June, epilimnetic water of the reservoir had pH values greater than 6.0, and metal concentrations were lower than hypolimnetic concentrations. In the hypolimnion, pH values were less than 5.5. The difference between the chemistry of the epilimnion and the hypolimnion was due to differences in flow routing and residence times of water in those respective layers. The dissolved-metal concentrations were larger during July and August than during June.During September, small vertical variations in metalconcentrations occurred, and the dissolved-metal concentrations were nearly equivalent to the average August metal concentrations, indicatingthat the metal concentrations measured during September resulted largely from reservoir mixing.During March, the largest metal concentrationsoccurred in the epilimnion, where pH was about 5.5; in the hypolimnion, where the pH was about 6.0, dissolved-metal concentrations were substantially lower and reflected inflow concentrations.

Colorado↗
USGS1996

Physical and chemical characteristics of Terrace Reservoir, Conejos County, Colorado, May 1994 through May 1995; interim report

Terrace Reservoir receives drainage of low-pH, metal-enriched water from mineralized areas, including the Summitville Mine, within the Alamosa River Basin. Drainage from the Summitville Mine has contributed a substantial part of the metal load to Terrace Reservoir. From May 1994 through May 1995, a study was done by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to evaluate the physical and chemical characteristics of Terrace Reservoir. Terrace Reservoir was thermally stratified from about mid-May through August 1994. Thermal stratification was absent from September\x111994through March 1995. During periods of stratification, underflow of the Alamosa River was predominant, and residence times of the underflow were shortened by 40 to 75\x11percent of the theoretical residence times for a well-mixed reservoir. Transport and deposition of suspended solids in Terrace Reservoir varied spatially and temporally. Most of the suspended solids were deposited in Terrace Reservoir. The concentration of dissolved oxygen in the reservoir varied little spatially or temporally and generally was within a few tenths of the dissolved-oxygen concentration of the inflow. The pH of water in the reservoir generally ranged from about 4.0 to about 7.0, depending on date, depth, and location. The largest pH values were measured during May. A markeddecrease of about 1.5\x11pH units occurred at site T5 in the reservoir about mid-June. The pH of the reservoir remained at or below 5.5 from mid-June through November. Dissolved-metal concentrations varied spatially and temporally in response to several factors, which included inflow characteristics, reservoir stratification and mixing, inflow-routing and flow-through patterns, residence times, sedimentation, dissolved oxygen, and pH. Inflow chemistry is the dominant controlling factor of metal chemistry within Terrace Reservoir. During periods of stratification, large vertical variations in metal concentrations occurred. The highest metal concentrations in the reservoir generally were measured in the hypolimnion between June and August. During June, epilimnetic water of the reservoir had pH values greater than 6.0, and metal concentrations were lower than hypolimnetic concentrations. In the hypolimnion, pH values were less than 5.5. The difference between the chemistry of the epilimnion and the hypolimnion was due to differences in flow routing and residence times of water in those respective layers. The dissolved-metal concentrations were larger during July and August than during June. During September, small vertical variations in metal concentrations occurred, and the dissolved-metal concentrations were nearly equivalent to the average August metal concentrations, indicatingthat the metal concentrations measured during September resulted largely from reservoir mixing.During March, the largest metal concentrationsoccurred in the epilimnion, where pH was about 5.5; in the hypolimnion, where the pH was about 6.0, dissolved-metal concentrations were substantially lower and reflected inflow concentrations.

Colorado↗
USGS1977

A crystal-chemical classification of borate structures with emphasis on hydrated borates

The rules governing formation of hydrated borate polyanions that were proposed by C.L. Christ in 1960 are critically reviewed and new rules added on the basis of recent crystal structure determinations. Principles and classifications previously published by others are also critically reviewed briefly. The fundamental building blocks from which borate polyanions can be constructed are defined on the basis of the number n of boron atoms, and the fully hydrated polyanions are illustrated. Known structures are grouped accordingly, and a shorthand notation using n and symbols ?? = triangle, T = tetrahedron is introduced so that the polyanions can be easily characterized. For example, 3:??+2T describes [B3O3(OH)5]2-. Correct structural formulas are assigned borates with known structures whereas borates of unknown structure are grouped separately. ?? 1977 Springer-Verlag.

Physics and Chemistry of Minerals↗
USGS2023

Soil and geomorphic patterns within relict charcoal hearths could represent unique ecosystem niches

Hearths used for 19th and 20th century charcoal manufacturing have been found to have unique plant communities or to produce unique growth characteristics for some species but not others. Given known differences in hearth morphology, within hearth physical and chemical differences may exist and result in unique ecologic niches. We examined soil stratigraphy across 8 relict charcoal hearths (RCH) and control soils on different landforms near a 19th century furnace complex (Greenwood Furnace, northcentral Appalachians USA). Soils were analyzed for particle size, total and trace elements, and fertility. Platform creation resulted in soils from upslope RCH positions mixed with subsurface materials on the downslope side to create a stabilized platform. The thin, uniform thickness of charcoal surface horizons (Ac) suggests that RCHs were not used more than once for charcoal manufacturing or that charcoal was always removed very efficiently. While rubification of soil or rock from high heat was seen in 6 of 8 sites sampled, it was not extensive across sampled areas of any one hearth, which suggests hearth use may not have frequent, hot enough, or spatially disparate. Soil fertility characteristics change within RCHs but also by landscape position. Downslope RCH positions are enriched in some parameters compared to control soils (total C, Mehlich 3 Mg, Ca, and Aquia Regia digestion Mn) and that enrichment often is from the surface downward. Downslope enrichment within RCH soils may have occurred from charcoal and released ions, slope erosion and accumulation, or transportation of constructed materials during RCH creation. Landscape position may accentuate or mute soil chemistry differences. Greenwood Furnace RCHs have unique patterns of chemistry, which could result in unique niches for flora and maybe fauna within RCH. Future research should more closely investigate whether hearths support unique species assemblages and how they may play a role in enhancing today’s forest biodiversity.

Pennsylvania↗
USGS2006

Processes affecting transport of uranium in a suboxic aquifer

At the Naturita site in Colorado, USA, groundwaters were sampled and analyzed for chemical composition and by culture and culture-independent microbiological techniques. In addition, sediments were extracted with a dilute sodium carbonate solution to determine quantities of labile uranium within the sediments. Samples from the upgradient portion of the contaminated aquifer , where very little dissolved Fe(II) is found in the groundwater, have uranium content that is controlled by U(VI) adsorption and few metal-reducing bacteria are observed. In the extreme downgradient portion of the aquifer, where dissolved Fe(II) is observed, uranium content of the sediments includes significant quantities of reduced U(IV) and diverse populations of Fe(III)-reducing bacteria were present in the subsurface with the potential of reducing U(VI) to U(IV).

Physics and Chemistry of the Earth↗
USGS2014

Variation in the terrestrial isotopic composition and atomic weight of argon

The isotopic composition and atomic weight of argon (Ar) are variable in terrestrial materials. Those variations are a source of uncertainty in the assignment of standard properties for Ar, but they provide useful information in many areas of science. Variations in the stable isotopic composition and atomic weight of Ar are caused by several different processes, including (1) isotope production from other elements by radioactive decay (radiogenic isotopes) or other nuclear transformations (e.g., nucleogenic isotopes), and (2) isotopic fractionation by physical-chemical processes such as diffusion or phase equilibria. Physical-chemical processes cause correlated mass-dependent variations in the Ar isotope-amount ratios ( 40 Ar/ 36 Ar, 38 Ar/ 36 Ar), whereas nuclear transformation processes cause non-mass-dependent variations. While atmospheric Ar can serve as an abundant and homogeneous isotopic reference, deviations from the atmospheric isotopic ratios in other Ar occurrences limit the precision with which a standard atomic weight can be given for Ar. Published data indicate variation of Ar atomic weights in normal terrestrial materials between about 39.7931 and 39.9624. The upper bound of this interval is given by the atomic mass of 40 Ar, as some samples contain almost pure radiogenic 40 Ar. The lower bound is derived from analyses of pitchblende (uranium mineral) containing large amounts of nucleogenic 36 Ar and 38 Ar. Within this interval, measurements of different isotope ratios ( 40 Ar/ 36 Ar or 38 Ar/ 36 Ar) at various levels of precision are widely used for studies in geochronology, water–rock interaction, atmospheric evolution, and other fields.

Pure and Applied Chemistry↗