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Sample records for geochemistry water dynamics

  1. Geochemistry

    ERIC Educational Resources Information Center

    Ailin-Pyzik, Iris B.; Sommer, Sheldon E.

    1977-01-01

    Enumerates some of the research findings in geochemistry during the last year, including X-ray analysis of the Mars surface, trace analysis of fresh and esterarine waters, and analysis of marine sedements. (MLH)

  2. Geochemistry.

    ERIC Educational Resources Information Center

    Fyfe, William S.

    1979-01-01

    Techniques in geochemistry continue to improve in sensitivity and scope. The exciting areas of geochemistry still include the classical fields of the origin of the elements and objects in space, but environmental crisis problems are important as well. (Author/BB)

  3. Geochemistry of water in the Fort Union formation of the northern Powder River basin, southeastern Montana

    USGS Publications Warehouse

    Lee, Roger W.

    1981-01-01

    Shallow water in the coal-bearing Paleocene Fort Union Formation of southeastern Montana was investigated to provide a better understanding of its geochemistry. Springs, wells less than 200 feet deep, and wells greater than 200 feet deep were observed to have different water qualities. Overall, the ground water exists as two systems: a mosaic of shallow, chemically dynamic, and localized recharge-discharge cells superimposed on a deeper, chemically static regional system. Water chemistry is highly variable in the shallow system; whereas, waters containing sodium and bicarbonate characterize the deeper system. Within the shallow system, springs and wells less than 200 feet deep show predominantly sodium and sulfate enrichment processes from recharge to discharge. These processes are consistent with the observed aquifer mineralogy and aqueous chemistry. However, intermittent mixing with downward moving recharge waters or upward moving deeper waters, and bacterially catalyzed sulfate reduction, may cause apparent reversals in these processes.

  4. Geochemistry of water in the Fort Union Formation of the northern Powder River basin, southeastern Montana

    USGS Publications Warehouse

    Lee, Roger W.

    1980-01-01

    Shallow water in the coal-bearing Fort Union Formation of southeastern Montana was investigated to provide a better understanding of the geochemistry. Springs, wells less than 200 feet deep, and wells greater then 200 feet deep were observed to have different water qualities. Overall, the ground water exists as two systems: a mosaic of shallow, chemically dynamic, and localized recharge-discharge cells superimposed on a deeper, chemically static regional system. Water chemistry is highly variable in the shallow system, whereas sodium and bicarbonate waters characterize the deeper system. Within the shallow system , springs, and wells less than 200 feet deep show predominantly sodium and sulfate enrichment processes from recharge to discharge. These processes are consistent with the observed aquifer mineralogy and aqueous chemistry. However, intermittent mixing with downward moving recharge waters or upward moving deeper waters, and bacterially catalyzed sulfate reduction, may cause apparent reversals in these processes. (USGS)

  5. GEOCHEMISTRY OF SULFUR IN IRON CORROSION SCALES FOUND IN DRINKING WATER DISTRIBUTION SYSTEMS

    EPA Science Inventory

    Iron-sulfur geochemistry is important in many natural and engineered environments, including drinking water systems. In the anaerobic environment beneath scales of corroding iron drinking water distribution system pipes, sulfate reducing bacteria (SRB) produce sulfide from natu...

  6. Relating salt marsh pore water geochemistry patterns to vegetation zones and hydrologic influences

    NASA Astrophysics Data System (ADS)

    Moffett, Kevan B.; Gorelick, Steven M.

    2016-03-01

    Physical, chemical, and biological factors influence vegetation zonation in salt marshes and other wetlands, but connections among these factors could be better understood. If salt marsh vegetation and marsh pore water geochemistry coorganize, e.g., via continuous plant water uptake and persistently unsaturated sediments controlling vegetation zone-specific pore water geochemistry, this could complement known physical mechanisms of marsh self-organization. A high-resolution survey of pore water geochemistry was conducted among five salt marsh vegetation zones at the same intertidal elevation. Sampling transects were arrayed both parallel and perpendicular to tidal channels. Pore water geochemistry patterns were both horizontally differentiated, corresponding to vegetation zonation, and vertically differentiated, relating to root influences. The geochemical patterns across the site were less broadly related to marsh hydrology than to vegetation zonation. Mechanisms contributing to geochemical differentiation included: root-induced oxidation and nutrient (P) depletion, surface and creek-bank sediment flushing by rainfall or tides, evapotranspiration creating aerated pore space for partial sediment flushing in some areas while persistently saturated conditions hindered pore water renewal in others, and evapoconcentration of pore water solutes overall. The concentrated pore waters draining to the tidal creeks accounted for 41% of ebb tide solutes (median of 14 elements), including being a potentially toxic source of Ni but a slight sink for Zn, at least during the short, winter study period in southern San Francisco Bay. Heterogeneous vegetation effects on pore water geochemistry are not only significant locally within the marsh but may broadly influence marsh-estuary solute exchange and ecology.

  7. Dynamic groundwater flows and geochemistry in a sandy nearshore aquifer over a wave event

    NASA Astrophysics Data System (ADS)

    Malott, Spencer; O'Carroll, Denis M.; Robinson, Clare E.

    2016-07-01

    Dynamic coastal forcing influences the transport of pollutants in nearshore aquifers and their ultimate flux to coastal waters. In this study, field data are presented that show, for the first time, the influence of a period of intensified wave conditions (wave event) on nearshore groundwater flows and geochemistry in a sandy beach. Field measurements at a freshwater beach allow wave effects to be quantified without other complex forcing that are present along marine shorelines (e.g., tides). Pressure transducer data obtained over an isolated wave event reveal the development of transient groundwater flow recirculations. The groundwater flows were simulated in FEFLOW using a phase-averaged wave setup approach to represent waves acting on the sediment-water interface. Comparison of measured and simulated data indicates that consideration of wave setup alone is able to adequately capture wave-induced perturbations in groundwater flows. While prior studies have shown sharp pH and redox spatial zonations in nearshore aquifers, this study reveals rapid temporal variations in conductivity, pH, and redox (ORP) in shallow sediments (up to 0.5 m depth) in response to varying wave conditions. Comparison of head gradients with calculated conductivity and pH mixing ratios indicates the controlling effect of the wave-induced water exchange and flows in driving the observed geochemical dynamics. While we are not able to conclusively determine the extent to which temporal variations are caused by conservative mixing versus reactive processes, the pH and ORP variations observed will have significant implications for the fate of reactive pollutants discharging through sandy nearshore aquifers.

  8. Geochemistry and the understanding of ground-water systems

    NASA Astrophysics Data System (ADS)

    Glynn, Pierre D.; Plummer, L. Niel

    2005-03-01

    Geochemistry has contributed significantly to the understanding of ground-water systems over the last 50 years. Historic advances include development of the hydrochemical facies concept, application of equilibrium theory, investigation of redox processes, and radiocarbon dating. Other hydrochemical concepts, tools, and techniques have helped elucidate mechanisms of flow and transport in ground-water systems, and have helped unlock an archive of paleoenvironmental information. Hydrochemical and isotopic information can be used to interpret the origin and mode of ground-water recharge, refine estimates of time scales of recharge and ground-water flow, decipher reactive processes, provide paleohydrological information, and calibrate ground-water flow models. Progress needs to be made in obtaining representative samples. Improvements are needed in the interpretation of the information obtained, and in the construction and interpretation of numerical models utilizing hydrochemical data. The best approach will ensure an optimized iterative process between field data collection and analysis, interpretation, and the application of forward, inverse, and statistical modeling tools. Advances are anticipated from microbiological investigations, the characterization of natural organics, isotopic fingerprinting, applications of dissolved gas measurements, and the fields of reaction kinetics and coupled processes. A thermodynamic perspective is offered that could facilitate the comparison and understanding of the multiple physical, chemical, and biological processes affecting ground-water systems. La géochimie a contribué de façon importante à la compréhension des systèmes d'eaux souterraines pendant les 50 dernières années. Les avancées ont portées sur le développement du concept des faciès hydrochimiques, sur l'application de la théorie des équilibres, l'étude des processus d'oxydoréduction, et sur la datation au radiocarbone. D'autres concepts, outils et

  9. Scale-dependent temporal variations in stream water geochemistry

    USGS Publications Warehouse

    Nagorski, S.A.; Moore, J.N.; McKinnon, T.E.; Smith, D.B.

    2003-01-01

    A year-long study of four western Montana streams (two impacted by mining and two "pristine") evaluated surface water geochemical dynamics on various time scales (monthly, daily, and bi-hourly). Monthly changes were dominated by snowmelt and precipitation dynamics. On the daily scale, post-rain surges in some solute and particulate concentrations were similar to those of early spring runoff flushing characteristics on the monthly scale. On the bi-hourly scale, we observed diel (diurnal-nocturnal) cycling for pH, dissolved oxygen, water temperature, dissolved inorganic carbon, total suspended sediment, and some total recoverable metals at some or all sites. A comparison of the cumulative geochemical variability within each of the temporal groups reveals that for many water quality parameters there were large overlaps of concentration ranges among groups. We found that short-term (daily and bi-hourly) variations of some geochemical parameters covered large proportions of the variations found on a much longer term (monthly) time scale. These results show the importance of nesting short-term studies within long-term geochemical study designs to separate signals of environmental change from natural variability.

  10. Geochemistry and the understanding of ground-water systems

    NASA Astrophysics Data System (ADS)

    Glynn, Pierre D.; Plummer, L. Niel

    2005-03-01

    Geochemistry has contributed significantly to the understanding of ground-water systems over the last 50 years. Historic advances include development of the hydrochemical facies concept, application of equilibrium theory, investigation of redox processes, and radiocarbon dating. Other hydrochemical concepts, tools, and techniques have helped elucidate mechanisms of flow and transport in ground-water systems, and have helped unlock an archive of paleoenvironmental information. Hydrochemical and isotopic information can be used to interpret the origin and mode of ground-water recharge, refine estimates of time scales of recharge and ground-water flow, decipher reactive processes, provide paleohydrological information, and calibrate ground-water flow models. Progress needs to be made in obtaining representative samples. Improvements are needed in the interpretation of the information obtained, and in the construction and interpretation of numerical models utilizing hydrochemical data. The best approach will ensure an optimized iterative process between field data collection and analysis, interpretation, and the application of forward, inverse, and statistical modeling tools. Advances are anticipated from microbiological investigations, the characterization of natural organics, isotopic fingerprinting, applications of dissolved gas measurements, and the fields of reaction kinetics and coupled processes. A thermodynamic perspective is offered that could facilitate the comparison and understanding of the multiple physical, chemical, and biological processes affecting ground-water systems. La géochimie a contribué de façon importante à la compréhension des systèmes d'eaux souterraines pendant les 50 dernières années. Les avancées ont portées sur le développement du concept des faciès hydrochimiques, sur l'application de la théorie des équilibres, l'étude des processus d'oxydoréduction, et sur la datation au radiocarbone. D'autres concepts, outils et

  11. Geochemistry of surface and pore water at USGS coring sites in wetlands of South Florida, 1994 and 1995

    USGS Publications Warehouse

    Orem, William H.; Lerch, Harry E.; Rawlik, Peter

    2002-01-01

    In this report, we present preliminary data on surface and pore water geochemistry from 22 sites in south Florida sampled during 1994 and 1995. These results are part of a larger study designed to evaluate the role of biogeochemical processes in sediments in the cycling of carbon, nitrogen, phosphorus, and sulfur in the south Florida ecosystem. The data are briefly discussed in regard to regional trends in the concentrations of chemical species, and general diagenetic processes in sediments. These results are part of a larger study designed to evaluate the role of biogeochemical processes in sediments in the cycling of carbon, nitrogen, phosphorus, and sulfur in the south Florida ecosystem. These elements play a crucial role in regulating organic sedimentation, nutrient dynamics, redox conditions, and the biogeochemistry of mercury in the threatened wetlands of south Florida. Pore water samples for chemical analyis were obtained using a piston corer/squeezer designed to avoid compression of the sediment and avoid oxidation and contamination of the pore water samples. Results show distinct regional trends in both surface water and pore water geochemistry. Most chemical species in surface and pore water show peak concentrations in Water Conservation Area 2A, with diminishing concentrations to the south and west into Water Conservation Area 3A, and Everglades National Park. The largest differences observed were for phosphate and sulfide, with concentrations in pore waters in Water Conservation Area 2A up to 500x higher than concentrations observed in freshwater marsh areas of Water Conservation Area 3A and Everglades National Park. Sites near the Hillsboro Canal in Water Conservation Area 2A are heavily contaminated with both phosphorus and sulfur. Pore water profiles for dissolved reactive phosphate suggest that recycling of phosphorus at these contaminated sites occurs primarily in the upper 20 cm of sediment. High levels of sulfide in pore water in Water

  12. Geochemistry of water at Cajon Pass, California: preliminary results

    USGS Publications Warehouse

    Kharaka, Y.K.; Ambats, G.; Evans, William C.; White, A.F.

    1988-01-01

    Samples of water and associated gases were collected from the Cajon Pass well using downhole samplers, and from the pipe stands at the completion of drill stem tests. Results of chemical analysis indicate major differences in the composition of water from different fracture systems. The differences in water composition indicate different evolutionary paths and isolation of water within relatively proximal fracture systems. -from Authors

  13. The lipid geochemistry of interstitial waters of recent marine sediments

    SciTech Connect

    Saliot, A.; Brault, M.; Boussuge, C. )

    1988-04-01

    To elucidate the nature of biogeochemical processes occurring at the water-sediment interface, the authors have analyzed fatty acids, n-alkanes and sterols contained in interstitial waters collected from oxic and anoxic marine sediments in the eastern and western intertropical Atlantic Ocean and in the Arabian Sea. Lipid concentrations in interstitial waters vary widely and are generally much higher than concentrations encountered in the overlying sea water. Higher concentrations in interstitial water are observed in environments favorable for organic input and preservation of the organic matter in the water column and in the surficial sediment. The analysis of biogeochemical markers in the various media of occurrence of the organic matter such as sea water, suspended particles, settling particles and sediment is discussed in terms of differences existing between these media and bio-transformations of the organic matter at the water-sediment interface.

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

    USGS Publications Warehouse

    Lico, Michael S.; Seiler, R.L.

    1994-01-01

    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.

  15. Geochemistry of formation water, Pliocene-Pleistocene reservoirs, offshore Louisiana

    SciTech Connect

    Land, L.S.; MacPherson, G.L. )

    1989-09-01

    The total dissolved solids content of formation water from Pliocene-Pleistocene reservoirs, offshore Louisiana, is dominated by NaCl derived from the dissolution and recrystallization of diapiric salt. Other solutes, and the water itself, are derived from primary pore water (originally seawater, subsequently modified by sulfate reduction and methanogenesis) from mineralogically immature late Cenozoic marine clastics. {sup 18}O values between 0 and +2 {per thousand} (SMOW), coupled with nonradiogenic {sup 87}Sr/{sup 86}Sr ratios, demonstrate that the water has undergone little interaction with detrital silicates (smectite or detrital feldspars) prior to emplacement in the reservoirs. Water from Pliocene-Pleistocene reservoir rocks contrasts with water from nearby, onshore Miocene reservoirs, which is largely derived from more mineralogically mature Cenozoic clastic sediments. Low Ca, Ba, Li, B, and Br in both Miocene and Pliocene-Pleistocene water samples from offshore Louisiana indicate little contribution from Ca-rich water characteristic of deep-seated Mesozoic reservoirs. A few samples of formation water associated with diapiric salt structures could contain up to about 10% solutes derived from deep-seated Mesozoic sources, however.

  16. Geochemistry of spring water, southeastern Uinta Basin, Utah and Colorado

    USGS Publications Warehouse

    Kimball, Briant A.

    1981-01-01

    The chemical quality of water in the southeastern Uinta Basin, Utah and Colorado, is important to the future development of the abundant oil-shale resources of the area. This report examines the observed changes in chemistry as water circulates in both shallow and deep ground-water systems. Mass-balance and mass-transfer calculations are used to define reactions that simulate the observed water chemistry in the mixed sandstone, siltstone, and carbonate lithology of the Green River Formation of Tertiary age. The mass-transfer calculations determine a reaction path particular to this system. The early dominance of calcite dissolution produces a calcium carbonate water. After calcite saturation, deeper circulation and further rock-water interaction cause the reprecipitation of calcite, the dissolution of dolomite and plagioclase, and the oxidation of pyrite; all combining to produce a calcium magnesium sodium bicarbonate sulfate water. The calculations suggest that silica concentrations are controlled by a kaolinite-Ca-montmorillonite phase boundary. Close agreement of mineral-saturation indices calculated by both an aqueous-equilibrium model and the mass-transfer model support the selection of reactions from the mass-transfer calculations.

  17. Geochemistry of Standard Mine Waters, Gunnison County, Colorado, July 2009

    USGS Publications Warehouse

    Verplanck, Philip L.; Manning, Andrew H.; Graves, Jeffrey T.; McCleskey, R. Blaine; Todorov, Todor; Lamothe, Paul J.

    2009-01-01

    In many hard-rock-mining districts water flowing from abandoned mine adits is a primary source of metals to receiving streams. Understanding the generation of adit discharge is an important step in developing remediation plans. In 2006, the U.S. Environmental Protection Agency listed the Standard Mine in the Elk Creek drainage basin near Crested Butte, Colorado as a superfund site because drainage from the Standard Mine enters Elk Creek, contributing dissolved and suspended loads of zinc, cadmium, copper, and other metals to the stream. Elk Creek flows into Coal Creek, which is a source of drinking water for the town of Crested Butte. In 2006 and 2007, the U.S. Geological Survey undertook a hydrogeologic investigation of the Standard Mine and vicinity and identified areas of the underground workings for additional work. Mine drainage, underground-water samples, and selected spring water samples were collected in July 2009 for analysis of inorganic solutes as part of a follow-up study. Water analyses are reported for mine-effluent samples from Levels 1 and 5 of the Standard Mine, underground samples from Levels 2 and 3 of the Standard Mine, two spring samples, and an Elk Creek sample. Reported analyses include field measurements (pH, specific conductance, water temperature, dissolved oxygen, and redox potential), major constituents and trace elements, and oxygen and hydrogen isotopic determinations. Overall, water samples collected in 2009 at the same sites as were collected in 2006 have similar chemical compositions. Similar to 2006, water in Level 3 did not flow out the portal but was observed to flow into open workings to lower parts of the mine. Many dissolved constituent concentrations, including calcium, magnesium, sulfate, manganese, zinc, and cadmium, in Level 3 waters substantially are lower than in Level 1 effluent. Concentrations of these dissolved constituents in water samples collected from Level 2 approach or exceed concentrations of Level 1 effluent

  18. Geochemistry of oil-field water from the North Slope

    SciTech Connect

    Kharaka, Y.K.; Carothers, W.W.

    1989-01-01

    Knowledge of the chemical composition of oil-field water is important in understanding the origin and migration of petroleum as well as the water mineral reactions that affect the porosity and permeability of the reservoir rocks. This knowledge is essential in interpreting electric logs and in determining potential pollution, corrosion, and disposal problems of water produced with oil and gas. Finally, the chemical composition of water is an important factor in determining the conditions (temperature, pressure) for the formation of clathrates. This chapter reports detailed chemical analyses of seven formation-water samples from wells within the NPRA and one surface-and two formation-water samples from the Prudhoe Bay oil field. The authors also report {delta}D and {delta}{sup 18}O values for eight of the water samples as well as analyses for gases from six wells. The formation-water samples were obtained from depths ranging from about 700 to 2800 m and from reservoir rocks ranging in age from Mississippian (Lisburne Group) to Triassic. The reservoir rocks are sandstone except for sample 79-AK-5, which was obtained from a limestone interbedded with sandstone. Generally, the pre-Cretaceous sandstone reservoir rocks on the North Slope have a similar mineral composition. Van de Kamp (1979) gave the following description of these sandstones: Quartz (usually monocrystalline) and chert are the major components; carbonate and clay are variable. Carbonate occurs as detrital grains and as cement, siderite being the most common type. Siderite can form as much as 30 percent of the rock. Clay occurs as a common matrix, generally making up less than 10 percent of the rock. Accessory minerals include pyrite, plagioclase, microcline, glauconite, zircon, sphene, tourmaline, and muscovite.

  19. Coral skeletal geochemistry as a monitor of inshore water quality.

    PubMed

    Saha, Narottam; Webb, Gregory E; Zhao, Jian-Xin

    2016-10-01

    Coral reefs maintain extraordinary biodiversity and provide protection from tsunamis and storm surge, but inshore coral reef health is degrading in many regions due to deteriorating water quality. Deconvolving natural and anthropogenic changes to water quality is hampered by the lack of long term, dated water quality data but such records are required for forward modelling of reef health to aid their management. Reef corals provide an excellent archive of high resolution geochemical (trace element) proxies that can span hundreds of years and potentially provide records used through the Holocene. Hence, geochemical proxies in corals hold great promise for understanding changes in ancient water quality that can inform broader oceanographic and climatic changes in a given region. This article reviews and highlights the use of coral-based trace metal archives, including metal transported from rivers to the ocean, incorporation of trace metals into coral skeletons and the current 'state of the art' in utilizing coral trace metal proxies as tools for monitoring various types of local and regional source-specific pollution (river discharge, land use changes, dredging and dumping, mining, oil spills, antifouling paints, atmospheric sources, sewage). The three most commonly used coral trace element proxies (i.e., Ba/Ca, Mn/Ca, and Y/Ca) are closely associated with river runoff in the Great Barrier Reef, but considerable uncertainty remains regarding their complex biogeochemical cycling and controlling mechanisms. However, coral-based water quality reconstructions have suffered from a lack of understanding of so-called vital effects and early marine diagenesis. The main challenge is to identify and eliminate the influence of extraneous local factors in order to allow accurate water quality reconstructions and to develop alternate proxies to monitor water pollution. Rare earth elements have great potential as they are self-referencing and reflect basic terrestrial input. PMID

  20. Coral skeletal geochemistry as a monitor of inshore water quality.

    PubMed

    Saha, Narottam; Webb, Gregory E; Zhao, Jian-Xin

    2016-10-01

    Coral reefs maintain extraordinary biodiversity and provide protection from tsunamis and storm surge, but inshore coral reef health is degrading in many regions due to deteriorating water quality. Deconvolving natural and anthropogenic changes to water quality is hampered by the lack of long term, dated water quality data but such records are required for forward modelling of reef health to aid their management. Reef corals provide an excellent archive of high resolution geochemical (trace element) proxies that can span hundreds of years and potentially provide records used through the Holocene. Hence, geochemical proxies in corals hold great promise for understanding changes in ancient water quality that can inform broader oceanographic and climatic changes in a given region. This article reviews and highlights the use of coral-based trace metal archives, including metal transported from rivers to the ocean, incorporation of trace metals into coral skeletons and the current 'state of the art' in utilizing coral trace metal proxies as tools for monitoring various types of local and regional source-specific pollution (river discharge, land use changes, dredging and dumping, mining, oil spills, antifouling paints, atmospheric sources, sewage). The three most commonly used coral trace element proxies (i.e., Ba/Ca, Mn/Ca, and Y/Ca) are closely associated with river runoff in the Great Barrier Reef, but considerable uncertainty remains regarding their complex biogeochemical cycling and controlling mechanisms. However, coral-based water quality reconstructions have suffered from a lack of understanding of so-called vital effects and early marine diagenesis. The main challenge is to identify and eliminate the influence of extraneous local factors in order to allow accurate water quality reconstructions and to develop alternate proxies to monitor water pollution. Rare earth elements have great potential as they are self-referencing and reflect basic terrestrial input.

  1. Geochemistry of extremely alkaline (pH>12) ground water in slag-fill aquifers.

    PubMed

    Roadcap, George S; Kelly, Walton R; Bethke, Craig M

    2005-01-01

    Extremely alkaline ground water has been found underneath many shuttered steel mills and slag dumps and has been an impediment to the cleanup and economic redevelopment of these sites because little is known about the geochemistry. A large number of these sites occur in the Lake Calumet region of Chicago, Illinois, where large-scale infilling of the wetlands with steel slag has created an aquifer with pH values as high as 12.8. To understand the geochemistry of the alkaline ground water system, we analyzed samples of ground water and the associated slag and weathering products from four sites. We also considered several potential remediation schemes to lower the pH and toxicity of the water. The principal cause of the alkaline conditions is the weathering of calcium silicates within the slag. The resulting ground water at most of the sites is dominated by Ca2+ and OH- in equilibrium with Ca(OH)2. Where the alkaline ground water discharges in springs, atmospheric CO2 dissolves into the water and thick layers of calcite form. Iron, manganese, and other metals in the metallic portion of the slag have corroded to form more stable low-temperature oxides and sulfides and have not accumulated in large concentrations in the ground water. Calcite precipitated at the springs is rich in a number of heavy metals, suggesting that metals can move through the system as particulate matter. Air sparging appears to be an effective remediation strategy for reducing the toxicity of discharging alkaline water.

  2. Geochemistry of clathrate-derived methane in Arctic Ocean waters

    SciTech Connect

    Elliott, S.M.; Reagan, M.T.; Moridis, G.J.; Cameron-Smith, P.J.

    2010-03-15

    Alterations to the composition of seawater are estimated for microbial oxidation of methane from large polar clathrate destabilizations, which may arise in the coming century. Gas fluxes are taken from porous flow models of warming Arctic sediment. Plume spread parameters are then used to bracket the volume of dilution. Consumption stoichiometries for the marine methanotrophs are based on growth efficiency and elemental/enzyme composition data. The nutritional demand implied by extra CH{sub 4} removal is compared with supply in various high latitude water masses. For emissions sized to fit the shelf break, reaction potential begins at one hundred micromolar and falls to order ten a thousand kilometers downstream. Oxygen loss and carbon dioxide production are sufficient respectively to hypoxify and acidify poorly ventilated basins. Nitrogen and the monooxygenase transition metals may be depleted in some locations as well. Deprivation is implied relative to existing ecosystems, along with dispersal of the excess dissolved gas. Physical uncertainties are inherent in the clathrate abundance, patch size, outflow buoyancy and mixing rate. Microbial ecology is even less defined but may involve nutrient recycling and anaerobic oxidizers.

  3. Long-term agricultural non-point source pollution loading dynamics and correlation with outlet sediment geochemistry

    NASA Astrophysics Data System (ADS)

    Ouyang, Wei; Jiao, Wei; Li, Xiaoming; Giubilato, Elisa; Critto, Andrea

    2016-09-01

    Some agricultural non-point source (NPS) pollutants accumulate in sediments in the outlet sections of watersheds. It is crucial to evaluate the historical interactions between sediment properties and watershed NPS loading. Therefore, a sediment core from the outlet of an agricultural watershed was collected. The core age was dated using the 210Pb method, and sedimentation rates were determined using the constant rate of supply (CRS) model. The total nitrogen (TN), total phosphorus (TP), Cd, Pb, Cu, Ni and Cr accumulations in the sediment generally showed fluctuating increases, with the highest sedimentation fluxes all occurring in approximately 1998. The measurement of specific mass sedimentation rates reflected a record of watershed soil erosion dynamics. Using SWAT (Soil and Water Assessment Tool) to simulate long-term watershed agricultural NPS pollution loadings, the historical interactions between sediment properties and NPS loadings were further evaluated. The N leaching process weakened these interactions, but the historical accumulations of TP and heavy metals in sediments generally correlated well with watershed NPS TP loading. The regression analysis suggested that Pb and Cr were the most suitable indexes for assessing long-term NPS TN and TP pollution, respectively. Assessing the NPS loading dynamics using the vertical characteristics of sediment geochemistry is a new method.

  4. Environmental geochemistry for surface and subsurface waters in the Pajarito Plateau and outlying areas, New Mexico

    SciTech Connect

    Blake, W.D.; Goff, F.; Adams, A.I.; Counce, D.

    1995-05-01

    This report provides background information on waters in the Los Alamos and Santa Fe regions of northern New Mexico. Specifically, the presented data include major element, trace element, and isotope analyses of 130 water samples from 94 different springs, wells, and water bodies in the area. The region considered in this study extends from the western edge of the Valles Caldera to as far east as Santa Fe Lake. For each sample, the presented analysis includes fourteen different major elements, twenty-six trace elements, up to five stable isotopes, and tritium. In addition, this data base contains certain characteristics of the water that are calculated from the aforementioned raw data, including the water`s maximum and minimum residence times, as found from tritium levels assuming no contamination, the water`s recharge elevation, as found from stable isotopes, and the charge balance of the water. The data in this report are meant to provide background information for investigations in groundwater hydrology and geochemistry, and for environmental projects. For the latter projects, the presented information would be useful for determining the presence of contamination it any one location by enabling one to compare potential contaminant levels to the background levels presented here. Likely locations of interest are those possibly effected by anthropogenic activities, including locations in and around Los Alamos National Laboratory, White Rock Canyon, and developed areas in the Rio Grande Valley.

  5. Low Methane Concentrations in Sediment Along the Siberian Slope: Inference From Pore Water Geochemistry

    NASA Astrophysics Data System (ADS)

    Miller, C.; Dickens, G. R.; Jakobsson, M.

    2015-12-01

    The Eastern Siberian Arctic Ocean (ESAO) is experiencing some of the fastest rates of climate warming. Additionally, the ESAO hosts 80% of the world's subsea permafrost, and presumably holds large amounts of methane in sediments as gas hydrate and free gas. Despite these vast stores of vulnerable carbon, the ESAO is sparingly explored. Here, we present pore water geochemistry results from cores taken during the SWERUS-C3 international expedition and along five transects. Four of these are along the slopes of Arlis Spur, Central East Siberia, Henrietta Island-Makarov Basin, and Eastern Lomonosov Ridge; one is along the shelf in Herald Trough.Upward methane flux toward the seafloor, as inferred from dissolved sulfate and alkalinity profiles, is negligible on slopes the Arlis Spur, Central East Siberia, and Eastern Lomonosov Ridge. Methane flux from slopes near Henrietta Island and Makarov Basin ranged from 13.7 (367 m water depth) to 16.2 mmol/m2-kyr (964 m water depth). The highest flux on the slope, located at the intersection with Lomonosov Ridge, is 25.8 mmol/m2-kyr. In contrast to the generally low methane fluxes of the continental slope, the shelf sediments in Herald Trough have high upward methane fluxes, with measured rates up to 156.9 mmol/m2-kyr. These methane results are the first of their kind in this climatically sensitive region, and contradict previous assumptions regarding high methane flux rates along the slope.

  6. Salt marsh pore water geochemistry does not correlate with microbial community structure

    NASA Astrophysics Data System (ADS)

    Koretsky, Carla M.; Van Cappellen, Philippe; DiChristina, Thomas J.; Kostka, Joel E.; Lowe, Kristi L.; Moore, Charles M.; Roychoudhury, Alakendra N.; Viollier, Eric

    2005-01-01

    Spatial and temporal trends in pore water geochemistry and sediment microbial community structure are compared at three intertidal sites of a saltmarsh on Sapelo Island, GA. The sites include a heavily bioturbated, unvegetated creek bank, a levee with dense growth of Spartina alterniflora, and a more sparsely vegetated ponded marsh site. The redox chemistry of the pore waters ranges from sulfide-dominated at the ponded marsh site to suboxic at the creek bank site. At the three sites, the vertical redox stratification of the pore waters is more compressed in summer than in winter. The trends in redox chemistry reflect opposing effects of sediment respiration and pore water irrigation. Intense and deep burrowing activity by fiddler crabs at the creek bank site results in the efficient oxidation of reduced byproducts of microbial metabolism and, hence, the persistence of suboxic conditions to depths of 50 cm below the sediment surface. Increased supply of labile organic substrates at the vegetated sites promotes microbial degradation processes, leading to sharper redox gradients. At the levee site, this is partly offset by the higher density and deeper penetration of roots and macrofaunal burrows. Surprisingly, the microbial community structure shows little correlation with the variable vertical redox zonation of the pore waters across the saltmarsh. At the three sites, the highest population densities of aerobic microorganisms, iron- plus manganese-reducing bacteria, and sulfate reducers coexist within the upper 10 cm of sediment. The absence of a clear vertical separation of these microorganisms is ascribed to the high supply of labile organic matter and intense mixing of the topmost sediment via bioturbation.

  7. Geochemistry of Surface and Ground Water in Cement Creek from Gladstone to Georgia Gulch and in Prospect Gulch, San Juan County, Colorado

    USGS Publications Warehouse

    Johnson, Raymond H.; Wirt, Laurie; Manning, Andrew H.; Leib, Kenneth J.; Fey, David L.; Yager, Douglas B.

    2007-01-01

    In San Juan County, Colo., the effects of historical mining continue to contribute metals to ground water and surface water. Previous research by the U.S. Geological Survey identified ground-water discharge as a significant pathway for the loading of metals to surface water in the upper Animas River watershed from both acid-mine drainage and acid-rock drainage. In support of this ground-water research effort, Prospect Gulch was selected for further study and the geochemistry of surface and ground water in the area was analyzed as part of four sampling plans: (1) ten streamflow and geochemistry measurements at five stream locations (four locations along Cement Creek plus the mouth of Prospect Gulch from July 2004 through August 2005), (2) detailed stream tracer dilution studies in Prospect Gulch and in Cement Creek from Gladstone to Georgia Gulch in early October 2004, (3) geochemistry of ground water through sampling of monitoring wells, piezometers, mine shafts, and springs, and (4) samples for noble gases and tritium/helium for recharge temperatures (recharge elevation) and ground-water age dating. This report summarizes all of the surface and ground-water data that was collected and includes: (1) all sample collection locations, (2) streamflow and geochemistry, (3) ground-water geochemistry, and (4) noble gas and tritium/helium data.

  8. Organic geochemistry and pore water chemistry of sediments from Mangrove Lake, Bermuda

    USGS Publications Warehouse

    Hatcher, P.G.; Simoneit, B.R.T.; MacKenzie, F.T.; Neumann, A.C.; Thorstenson, D.C.; Gerchakov, S.M.

    1982-01-01

    Mangrove Lake, Bermuda, is a small coastal, brackish-water lake that has accumulated 14 m of banded, gelatinous, sapropelic sediments in less than 104 yr. Stratigraphic evidence indicates that Mangrove Lake's sedimentary environment has undergone three major depositional changes (peat, freshwater gel, brackish-water gel) as a result of sea level changes. The deposits were examined geochemically in an effort to delineate sedimentological and diagenetic changes. Gas and pore water studies include measurements of sulfides, ammonia, methane, nitrogen gas, calcium, magnesium, chloride, alkalinity, and pH. Results indicate that sulfate reduction is complete, and some evidence is presented for bacterial denitrification and metal sulfide precipitation. The organic-rich sapropel is predominantly algal in origin, composed mostly of carbohydrates and insoluble macromolecular organic matter called humin with minor amounts of proteins, lipids, and humic acids. Carbohydrates and proteins undergo hydrolysis with depth in the marine sapropel but tend to be preserved in the freshwater sapropel. The humin, which has a predominantly aliphatic structure, increases linearly with depth and composes the greatest fraction of the organic matter. Humic acids are minor components and are more like polysaccharides than typical marine humic acids. Fatty acid distributions reveal that the lipids are of an algal and/or terrestrial plant source. Normal alkanes with a total concentration of 75 ppm exhibit two distribution maxima. One is centered about n-C22 with no odd/even predominance, suggestive of a degraded algal source. The other is centered at n-C31 with a distinct odd/even predominance indicative of a vascular plant origin. Stratigraphic changes in the sediment correlate to observed changes in the gas and pore water chemistry and the organic geochemistry. ?? 1982.

  9. One-carbon (bio?)geochemistry in subsurface waters of the serpentinizing Coast Range Ophiolite

    NASA Astrophysics Data System (ADS)

    Hoehler, T. M.; McCollom, T.; Schrenk, M. O.; Kubo, M.; Cardace, D.

    2011-12-01

    Serpentinization - the aqueous alteration of ultramafic rocks - typically imparts a highly reducing and alkaline character to the reacting fluids. In turn, these can influence the speciation and potential for metabolism of one-carbon compounds in the system. We examined the aqueous geochemistry and assessed the biological potential of one-carbon compounds in the subsurface of the McLaughlin Natural Reserve (Coast Range Ophiolite, California, USA). Fluids from wells sunk at depths of 25-90 meters have pH values ranging from 9.7 to 11.5 and dissolved inorganic carbon (DIC concentrations) generally below 60 micromolar. Methane is present at concentrations up to 1.3 millimolar (approximately one-atmosphere saturation), and hydrogen concentrations are below 15 nanomolar, suggesting active consumption of H2 and production of CH4. However, methane production from CO2 is thermodynamically unfavorable under these conditions. Additionally, the speciation of DIC predominantly into carbonate at these high pH values creates a problem of carbon availability for any organisms that require CO2 (or bicarbonate) for catabolism or anabolism. A potential alternative is carbon monoxide, which is present in these waters at concentrations 2000-fold higher than equilibrium with atmospheric CO. CO is utilized in a variety of metabolisms, including methanogenesis, and bioavailability is not adversely affected by pH-dependent speciation (as for DIC). Methanogenesis from CO under in situ conditions is thermodynamically favorable and would satisfy biological energy requirements with respect to both Gibbs Energy yield and power.

  10. One-carbon (bio ?) Geochemistry in Subsurface Waters of the Serpentinizing Coast Range Ophiolite

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; Mccollom, Tom; Schrenk, Matt; Cardace, Dawn

    2011-01-01

    Serpentinization - the aqueous alteration of ultramafic rocks - typically imparts a highly reducing and alkaline character to the reacting fluids. In turn, these can influence the speciation and potential for metabolism of one-carbon compounds in the system. We examined the aqueous geochemistry and assessed the biological potential of one-carbon compounds in the subsurface of the McLaughlin Natural Reserve (Coast Range Ophiolite, California, USA). Fluids from wells sunk at depths of 25-90 meters have pH values ranging from 9.7 to 11.5 and dissolved inorganic carbon (DIC concentrations) generally below 60 micromolar. Methane is present at concentrations up to 1.3 millimolar (approximately one-atmosphere saturation), and hydrogen concentrations are below 15 nanomolar, suggesting active consumption of H2 and production of CH4. However, methane production from CO2 is thermodynamically unfavorable under these conditions. Additionally, the speciation of DIC predominantly into carbonate at these high pH values creates a problem of carbon availability for any organisms that require CO2 (or bicarbonate) for catabolism or anabolism. A potential alternative is carbon monoxide, which is present in these waters at concentrations 2000-fold higher than equilibrium with atmospheric CO. CO is utilized in a variety of metabolisms, including methanogenesis, and bioavailability is not adversely affected by pH-dependent speciation (as for DIC). Methanogenesis from CO under in situ conditions is thermodynamically favorable and would satisfy biological energy requirements with respect to both Gibbs Energy yield and power.

  11. The Dynamics of Flowing Waters.

    ERIC Educational Resources Information Center

    Mattingly, Rosanna L.

    1987-01-01

    Describes a series of activities designed to help students understand the dynamics of flowing water. Includes investigations into determining water discharge, calculating variable velocities, utilizing flood formulas, graphing stream profiles, and learning about the water cycle. (TW)

  12. An assessment of hydrogeochemical computer codes applied toward modeling and predicting post-mining pit water geochemistry

    SciTech Connect

    Bird, D.A.; Lyons, W.B. . Hydrology Program); Miller, G.C. . Dept. of Environmental Resource Sciences)

    1993-04-01

    Geochemists for the mining industry utilize a variety of computer codes to model and predict post-mining pit water chemogenesis. This study surveys several of the PC-supported hydrogeochemical codes, applies them to specific open pit mine scenarios, and evaluates their suitability to predicting post-mining pit and groundwater hydro-geochemistry. The prediction of pit water geochemistry is important because of the potential adverse effects of mine drainage, which include acidity, trace metal contamination, pit water stratification, and sludge accumulation. The WATEQ codes of the USGS can calculate speciation and saturation states of a pit water or groundwater sample, but are not designed to model forward rock/water reactions. NETPATH can calculate the chemical mass transfer (inverse modeling) that has occurred during rock/water interaction, but again is not designed to model forward pit water chemogenesis. Several mining industry modelers use EPA's MINTEQA2 code, which has shown to be very flexible with its large database and ability to model adsorption. Reaction path codes, like PHREEQE and EQ3/6, can model reactions on an incremental basis as the pit fills over time, but also may require much user manipulation. New coupled codes like PHREEQM and HYDROGEOCHEM can simulate movement and reaction of groundwater through the aquifer as it approaches and inundates the pit. One aspect of post-mining hydrogeochemical modeling that has received little attention is the effect groundwater will have down gradient after it flows from the pit into the aquifer.

  13. Geochemistry and isotope geochemistry of the Monfalcone thermal waters (northern Italy): inference on the deep geothermal reservoir

    NASA Astrophysics Data System (ADS)

    Petrini, R.; Italiano, F.; Ponton, M.; Slejko, F. F.; Aviani, U.; Zini, L.

    2013-09-01

    Geochemical investigations were carried out to define the origin of the low- to moderate-temperature thermal waters feeding the Monfalcone springs in northern Italy. Chemical data indicate that waters approach the composition of seawater. Mixing processes with cold low-salinity waters are highlighted. The δ18O and δD values are in the range -5.0 to -6.4 ‰, and -33 to -40 ‰, respectively, suggesting the dilution of the saline reservoir by karst-type freshwaters. A surplus of Ca2+ and Sr2+ ions with respect to a conservative mixing is ascribed to diagenetic reactions of the thermal waters with Cretaceous carbonates at depth. The measured Sr isotopic composition (87Sr/86Sr ratio) ranges between 0.70803 and 0.70814; after correction for the surplus Sr, a 87Sr/86Sr ratio indicating Miocene paleo-seawater is obtained. The dissolved gases indicate long-lasting gas-water interactions with a deep-originated gas phase of crustal origin, dominated by CO2 and marked by a water TDIC isotopic composition in the range -5.9 to-8.8 and helium signature with 0.08 < R/Ra < 0.27, which is a typical range for the crust. A possible scenario for the Monfalcone thermal reservoir consists of Miocene marine paleowaters which infiltrated through the karstic voids formed within the prevalently Cretaceous carbonates during the upper Eocene emersion of the platform, and which were entrapped by the progressive burial by terrigenous sediments.

  14. Stable isotope geochemistry of pore waters from the New Jersey shelf - No evidence for Pleistocene melt water

    NASA Astrophysics Data System (ADS)

    van Geldern, Robert; Hayashi, Takeshi; Böttcher, Michael E.; Mottl, Michael J.; Barth, Johannes A. C.; Stadler, Susanne

    2013-04-01

    Ocean Drilling Program, Volume 313, Tokyo, available at: http://publications.iodp.org/proceedings/313/313toc.htm. van Geldern, R., Hayashi, T., Böttcher, M. E., Mottl, M. J., Barth, J. A. C., and Stadler, S., 2013, Stable isotope geochemistry of pore waters and marine sediments from the New Jersey shelf: Methane formation and fluid origin: Geosphere, v. 9, no. 1, p. in press.

  15. Sulfur and iron geochemistry of the dynamic sedimentary system at the Costa Rica margin, IODP Expedition 344

    NASA Astrophysics Data System (ADS)

    Gott, C.; Riedinger, N.; Formolo, M.; Solomon, E. A.; Torres, M. E.; Bates, S. M.; Lyons, T. W.; 344 Scientific Party, I.

    2013-12-01

    One of the major targets of the CRISP (Costa Rica Seismogenesis Project) was to explore diagenetic processes, including fluid flow, related to the complex sedimentary and tectonic behavior of the Costa Rica margin system. Here we present preliminary results of the iron and sulfur geochemistry from sediments collected during the IODP Expedition 344 at Holes U1413B and U1414A. Our specific goal was to investigate the impact of this dynamic system on biogeochemical processes - especially regarding the sulfur cycle - and how minerals record these processes in the geologic record. The sediments at both investigated locations display non-steady state pore water conditions. Specifically, the deposits at Hole U1413B are characterized by a shallow sulfate-methane transition zone (SMTZ; approximately 15 mbsf), where released hydrogen sulfide reacts with reactive iron minerals to form iron sulfides. At Hole U1414A pore water sulfate is present at several hundreds of meters sediment depth, while the concentration of hydrogen sulfide is low (<4 μM). The measured concentrations of solid phase iron sulfides in the sediments indicate that pyrite is the main sulfur-bearing phase, reaching concentrations of 2 and 3 wt.%, in U1413B and U1414A, respectively. Sequential extractions of iron oxides reveal the presence of reactive iron phases, although in low concentrations (total iron oxides are below 1.1 wt.%), indicating ongoing alteration of iron oxides. The occurrence of these reactive iron minerals in the deeply buried sediments at Hole U1414A has implications for the deep biosphere - as those minerals can still be utilized by the microbial community. The non-steady state condition of the sedimentary system at both locations is also mirrored in the S-isotopic signal in the pore fluids as well as solid phase. The 34S-enriched sulfate (δ34S >+60 ‰) in the deeper sediment column is reflected in the δ34S profile of the in situ formed iron sulfides - the results can have

  16. Ground-water geochemistry of Kwajalein Island, Republic of the Marshall Islands, 1991. Water resources investigations

    SciTech Connect

    Tribble, G.W.

    1997-12-31

    The purpose of this report is to describe the chemical characteristics of ground water at Kwajalein Island. This characterization includes the overall chemical composition of aquifer water, the extent of non-conservative chemical reactions in the aquifer, and factors that influence of fate of organic contaminants, although the breakdown of specific contaminants is not addressed. A total of 116 ground-water samples were collected from the aquifer and shallow unsaturated zone during two periods in 1991. Because ground water on the islands is derived from rainwater and seawater, eight rain and eight seawater samples also were collected.

  17. Geochemistry of water in aquifers and confining units of the Northern Great Plains in parts of Montana, North Dakota, South Dakota, and Wyoming

    USGS Publications Warehouse

    Busby, J.F.; Kimball, B.A.; Downey, J.S.; Peter, K.D.

    1995-01-01

    The geochemistry of water in five aquifers and two confining units in the Williston Basin of the Northern Great Plains is similar and is controlled by halite dissolution. In areas outside the Williston Basin ground-water is fresh and controlled by the solution chemistry of carbonate and sulfate minerals.

  18. SeamountFlux: Pore water geochemistry and sediment characteristics (Guatemala Basin, East Pacific)

    NASA Astrophysics Data System (ADS)

    Pichler, T.; Poonchai, W.; Schmidt-Schierhorn, F.; Villinger, H. W.

    2011-12-01

    The scientific goal of the project "SeamountFlux" is to study a process, which can possibly contribute significantly to large scale cooling of the oceanic crust. The focus of the study is to investigate the exchange of matter and energy between the ocean and the upper young oceanic crust in the vicinity of unexplained circular depressions in the sedimentary cover, which are widely spread in the equatorial Pacific. A possible model for the formation of these so-called "hydrothermal pits" is the dissolution of calcium carbonate (CaCO3) minerals by upward flowing warm fluids, which are under-saturated in CaCO3. Seamounts are suspected to act as an entrance point for cold seawater, which then equilibrates with the basaltic oceanic crust prior to exiting through the pits. Such a process should affect the thermal structure in and around the pits as well as the geochemistry of the pore water. During cruise SO207 (June/July 2010 on the German RV Sonne) in the vicinity of ODP/IODP Site 1256 and ODP site 844 (Guatemala Basin, eastern equatorial Pacific) we collected 24 gravity cores varying in length between 3.3 m and 10.6 m from 3 distinct working areas. The cores were generally taken along a transect, starting in the center of a pit, across the pit slope to the surrounding seafloor. From these cores a total of 451 pore water samples were collected and analyzed onboard (pH, Eh, Fe, NH4 and alkalinity), as well as in the laboratory (Cl, SO4, Na, Mg, K, Ca, Sr and Mn). First results do not show any obvious evidence for the "hydrothermal" hypotheses. Pore water profiles were more or less identical, whether collected from within or from outside a pit. Chloride, SO4, Na, Mg, K, Ca, and Sr concentrations were identical to those in seawater. Particularly higher Ca and Sr concentrations were to be expected if calcium carbonate dissolution took place within the sediments. With respect to sediment composition and physico-chemical conditions in the pore waters, we observed larger

  19. Dynamics of protein hydration water.

    PubMed

    Wolf, M; Emmert, S; Gulich, R; Lunkenheimer, P; Loidl, A

    2015-09-01

    We present the frequency- and temperature-dependent dielectric properties of lysozyme solutions in a broad concentration regime, measured at subzero temperatures, and compare the results with measurements above the freezing point of water and on hydrated lysozyme powder. Our experiments allow examining the dynamics of unfreezable hydration water in a broad temperature range. The obtained results prove the bimodality of the hydration shell dynamics. In addition, we find indications of a fragile-to-strong transition of hydration water. PMID:26465518

  20. Sulfur geochemistry of hydrothermal waters in Yellowstone National Park: IV Acid-sulfate waters

    USGS Publications Warehouse

    Kirk, Nordstrom D.; Blaine, McCleskey R.; Ball, J.W.

    2009-01-01

    Many waters sampled in Yellowstone National Park, both high-temperature (30-94 ??C) and low-temperature (0-30 ??C), are acid-sulfate type with pH values of 1-5. Sulfuric acid is the dominant component, especially as pH values decrease below 3, and it forms from the oxidation of elemental S whose origin is H2S in hot gases derived from boiling of hydrothermal waters at depth. Four determinations of pH were obtained: (1) field pH at field temperature, (2) laboratory pH at laboratory temperature, (3) pH based on acidity titration, and (4) pH based on charge imbalance (at both laboratory and field temperatures). Laboratory pH, charge imbalance pH (at laboratory temperature), and acidity pH were in close agreement for pH ??10%, a selection process was used to compare acidity, laboratory, and charge balance pH to arrive at the best estimate. Differences between laboratory and field pH can be explained based on Fe oxidation, H2S or S2O3 oxidation, CO2 degassing, and the temperature-dependence of pK2 for H2SO4. Charge imbalances are shown to be dependent on a speciation model for pH values 350 mg/L Cl) decrease as the Cl- concentration increases from boiling which appears inconsistent with the hypothesis of H2S oxidation as a source of hydrothermal SO4. This trend is consistent with the alternate hypothesis of anhydrite solubility equilibrium. Acid-sulfate water analyses are occasionally high in As, Hg, and NH3 concentrations but in contrast to acid mine waters they are low to below detection in Cu, Zn, Cd, and Pb concentrations. Even concentrations of SO4, Fe, and Al are much lower in thermal waters than acid mine waters of the same pH. This difference in water chemistry may explain why certain species of fly larvae live comfortably in Yellowstone's acid waters but have not been observed in acid rock drainage of the same pH.

  1. Application of Hydrogen Isotope Geochemistry to Volcanology: Recent Perspective on Eruption Dynamics

    NASA Astrophysics Data System (ADS)

    Nakamura, M.; Kasai, Y.; Sato, N.; Yoshimura, S.

    2008-02-01

    Degassing of magma is central to understand the dynamics of volcanic eruption. Hydrogen isotopic composition of volcanic rocks reflects degassing processes. The natural obsidian samples in some eruptions typically show a gently and then rapidly decreasing δD trends with decreasing water content; this led to the two-stage degassing model, with closed-system volatile exsolution (batch fractionation of hydrogen isotope) during the explosive phase followed by open-system degassing (Rayleigh fractionation) to produce the low δD value of the dome and flow lavas[1,2]. However, the relationship between pattern of degassing (and fractionation) and mode of eruption is controversial[3]. Based on the CO2/H2O ratio of the obsidians, Rust et al.[4] suggested that the analyzed samples with relatively constant δD value and high water content were buffered (re-equilibrated) with vapor of relatively constant isotopic composition, assuming that silicic magma along conduit wall is fragmented and highly permeable. However, the timing and mechanism of the shift to open system degassing (Rayleigh fractionation) has not been clarified. To further constrain the eruption dynamics, experimental study on the hydrogen isotope fractionation during degassing would be helpful, although common noble metals used as sample capsules, including Au, are permeable to hydrogen at magmatic temperature, and even to water molecule in the prolonged run, probably due to the change of grain boundary properties such as thermal grooving.

  2. Application of Hydrogen Isotope Geochemistry to Volcanology: Recent Perspective on Eruption Dynamics

    SciTech Connect

    Nakamura, M.; Kasai, Y.; Sato, N.; Yoshimura, S.

    2008-02-25

    Degassing of magma is central to understand the dynamics of volcanic eruption. Hydrogen isotopic composition of volcanic rocks reflects degassing processes. The natural obsidian samples in some eruptions typically show a gently and then rapidly decreasing {delta}D trends with decreasing water content; this led to the two-stage degassing model, with closed-system volatile exsolution (batch fractionation of hydrogen isotope) during the explosive phase followed by open-system degassing (Rayleigh fractionation) to produce the low {delta}D value of the dome and flow lavas. However, the relationship between pattern of degassing (and fractionation) and mode of eruption is controversial. Based on the CO{sub 2}/H{sub 2}O ratio of the obsidians, Rust et al. suggested that the analyzed samples with relatively constant {delta}D value and high water content were buffered (re-equilibrated) with vapor of relatively constant isotopic composition, assuming that silicic magma along conduit wall is fragmented and highly permeable. However, the timing and mechanism of the shift to open system degassing (Rayleigh fractionation) has not been clarified. To further constrain the eruption dynamics, experimental study on the hydrogen isotope fractionation during degassing would be helpful, although common noble metals used as sample capsules, including Au, are permeable to hydrogen at magmatic temperature, and even to water molecule in the prolonged run, probably due to the change of grain boundary properties such as thermal grooving.

  3. Temporal variation of trace metal geochemistry in floodplain lake sediment subject to dynamic hydrological conditions.

    PubMed

    van Griethuysen, Corine; Luitwieler, Marloes; Joziasse, Jan; Koelmans, Albert A

    2005-09-01

    Climate change and land use may significantly influence metal cycling in dynamic river systems. We studied temporal variation of sediment characteristics in a floodplain lake, including concentrations of dissolved organic carbon, acid volatile sulfide and trace metals. The sampling period included a severe winter inundation and a dramatic water level drop during summer. Temporal changes were interpreted using multivariate analysis and chemical equilibrium calculations. Metal concentrations in sediment increased with depth, indicating a gradual improvement of sediment quality. In contrast, dissolved metal concentrations were highest in top layers due to mobilization from oxyhydroxides and precipitation with sulfides in deeper layers. Inundation had a mobilizing effect as it stimulated resuspension and oxygenation of sediment top layers. Water table lowering combined with organic matter decomposition led to immobilization due to sulfide formation. The chemistry of the sediments was consistent with model calculations, especially for macro-elements. The results illustrate the importance of seasonality for metal risk assessment.

  4. Maps showing water geochemistry of the Buffalo Peaks Wilderness Study Area, Lake, Park, and Chaffee Counties, Colorado

    USGS Publications Warehouse

    Nowlan, G.A.; Ficklin, Walter H.; Dover, Robert A.

    1985-01-01

    This report presents results of geochemical studies carried out in June and July of 1982 in the Buffalo Peaks Wilderness Study Area, Colo. (see index map). Samples of water were collected from 84 streams and 18 springs draining the study area. Tabulations of the analyses and a sample locality map are in Ficklin and others (1984). The geochemistry of stream sediments and panned concentrates of the study area is in Nowlan and Gerstel (1985). The geology of the study area and vicinity is in Hedlund (1985). The mineral resource potential of the study area is described in Hedlund and others (1983). This report (1) assists in the assessment of the mineral resource potential of the Buffalo Peaks Wilderness Study Area; and (2) compares analyses of water samples with analyses of stream-sediment and panned-concentrate samples (Nowlan and Gerstel, 1985).

  5. Sediment and water column geochemistry related to methane seepage along the northern US Atlantic margin

    NASA Astrophysics Data System (ADS)

    Pohlman, J.; Ruppel, C. D.; Colwell, F. S.; Krause, S.; Treude, T.; Graw, M.; Casso, M.; Boze, L. G.; Buczkowski, B.; Brankovits, D.

    2015-12-01

    Many of the more than 550 gas plumes recently identified along the northern US Atlantic margin (USAM) using multibeam water-column backscatter data lie at, or shallower than, the upper limit of gas hydrate stability on the continental slope. Important questions remain unanswered regarding the gas sources feeding these seeps, the export of carbon from the seafloor and the fundamental biogeochemical processes that regulate the flux and transformation of carbon along this margin. In addition, few programs have ever systematically studied the dynamics across the upper slope transition from no hydrate to hydrate. In September 2015, the US Geological Survey, Oregon State University, Geomar and UCLA conducted a multidisciplinary study aboard the R/V Sharp that included piston coring, multicoring, seafloor heat flow measurements, imaging of sub-seafloor sediments and water column methane plumes, and sampling of methane plumes in the water column. This presentation provides some of the basic geochemical results from the cruise, focusing on the pore water characteristics in upper slope gas hydrate provinces that will be used to constrain the fundamental biogeochemical processes operating at methane seeps, including data on the origin of seep methane at sites with and without a possible association with gas hydrate degradation. Water column profiling of methane and other biogeochemically relevant species (e.g., dissolved inorganic and organic carbon) are also used to establish how carbon exported from the seeps affects ocean chemistry and carbon availability in the deep ocean.

  6. Distribution and geochemistry of contaminated subsurface waters in fissured volcanogenic bed rocks of the Lake Karachai Area, Chelyabinsk, Southern Urals

    SciTech Connect

    Solodov, I.N.; Belichkin, V.I.; Zotov, A.V.; Kochkin, B.T.; Drozhko, E.G.; Glagolev, A.V.; Skokov, A.N.

    1994-06-01

    The present investigation is devoted to the study of the distribution and geochemistry of contaminated subsurface waters, beneath the site of temporary storage of liquid radioactive waste known as Lake Karachai. For this purpose a method of hydrogeochemical logging (HGCL) together with standard hydrogeochemical and geophysical methods of uncased hole logging were used. The distribution of sodium nitrate brine plumes in the subsurface was determined by the physical and physico-chemical properties of these brines and by the petrochemical composition of enclosing rocks and the structural setting of the flow paths. The latter is represented by fractures and large faults in the bedrock of volcanogenic and volcanogenic-sedimentary rocks of intermediate-to-basic composition. The volcanogenic rocks are overlain in some places by a thin cover of unconsolidated sediments, i.e., by loams and relatively impermeable silts. Contaminated waters flow-in accordance with the eluvium bottom relief towards local areas of natural (Mishelyak and Techa rivers) and artificial (Novogomenskii water intake) discharge of subsurface waters. The large Mishelyak fault, southwest of Lake Karachai and under fluvial sediments of the Mishelyak, is assumed to significantly influence the flow pattern of contaminated waters, diverting them from an intake of drinking water.

  7. Impact of Phosphogypsum waste on the Geochemistry of the coastal water of Ghannouche -Gabes (SE of Tunisia).

    NASA Astrophysics Data System (ADS)

    Ben Amor, R.; Fathallah, S.; Gueddari, M.

    2009-04-01

    Impact of Phosphogypsum waste on the Geochemistry of the coastal water of Ghannouche -Gabes (SE of Tunisia). R. Ben Amor, S. Fathallah, M. Gueddari (R.U. of Geochemistry and of Environmental Geology, Faculty of Sciences of Tunis, Department of Geology, 2092 Manar I) Corresponding author: R. Ben Amor; E-mail:magba_rim@yahoo.fr The littoral Ghannouche - Gabes (SE of Tunisia), has been known since the 1970's, an important industrialization especially after the installation of the chemical complex for the treatment of phosphates. These industries are at the origin of various waste materials, the most significant one is phosphogypsum (PG) which is released into the sea. The aim of this paper is to identify and to analyze the different entropic and natural factors, which govern the chemical composition in major elements, dissolved oxygen, pH and temperature of Ghannouche -Gabes coastal water, while studying, in particular, the impact of PG waste on the spatial distribution of these parameters. The result of the chemical analyses of the samples taken in June 2003, show that Na, K and Cl are conserved in solution and they evolve with constant Na/Cl and K/Cl ratio. The values of these ratios are similar to sea water average. The concentration of the other elements are controlled, first, by processes of precipitation or dissolution of the carbonated (Ca, Mg and HCO3) or sulphated (Ca and SO4) minerals, and second, by dilution or evaporation phenomena and by the phosphogypsum waste. The spatial distribution of these elements, of the pH, the dissolved oxygen and the temperature and the result of the saturation index with respect to calcite, gypsum and fluorite, by using of the PhreeqC program, show that the zone, located at north of the study area, between the commercial and the fishing port, is highly influenced by the PG waste. In this area, where the PG is released and which is relatively sheltered by the dams of the commercial and fishing port, waters are characterised by

  8. Applicability of Electrical and Electroanalytical Techniques to Detect Water and Characterize the Geochemistry of Undisturbed Planetary Soils

    NASA Technical Reports Server (NTRS)

    Seshadri, S.; Buehler, M. G.; Anderson, R. C.; Kuhlman, G. M.; Keymeulen, D.; Cheung, I. W.; Schaap, M. G.

    2005-01-01

    The search for life is a primary goal of NASA s planetary exploration program. The search is, of necessity, tiered in both the detection approach (looking for evidence of microbial fossils or the presence of water in the geological history of a planetary body and/or looking for evidence of water, energy sources, precursors to life, signatures of life and/or life itself in the present day planetary environment) and in the survey method (scale, range, specificity) employed. Terrestrial investigations suggests that life as we know it requires water. Thus, the search for extant microbial life and habitats requires identifying water-bearing soils. Determining Reduction-Oxidation (REDOX) couples present in water, once it is found, provides information on soil geochemistry and identifies potential chemical energy sources for life. Mars offers a near-term target for conducting this search. The identification of gully formation [1], layered deposits [2] and elemental ratios of bromine and chlorine [3] present indirect evidence that water was abundant locally in the Martian past. Additionally, Viking images of polar ice and frost formation on the surface of Mars demonstrate that water can exist in at least some near-surface regions of present-day Mars. Atmospheric pressure data further suggest that liquid water may be stable for short periods of time in the mid-latitudes of the Martian surface. [4] Measurements of the global distribution of hydrogen in the Martian regolith offer tantalizing indirect evidence that water may at least exist in near-surface soils. [5] Evidently, any water to be found is likely to exist as soil mixtures at levels ranging between approx.0.5% and approx.5 %.

  9. Occurrence and geochemistry of radium in water from principal drinking-water aquifer systems of the United States

    USGS Publications Warehouse

    Szabo, Z.; dePaul, V.T.; Fischer, J.M.; Kraemer, T.F.; Jacobsen, E.

    2012-01-01

    competing ions Ca, Mg, Ba and Sr, and occasionally of dissolved solids, K, SO 4 and HCO 3. The other water type to frequently contain elevated concentrations of the Ra radioisotopes was acidic (low pH), and had in places, high concentrations of NO 3 and other acid anions, and on occasion, of the competing divalent cations, Mn and Al. One or the other of these broad water types was commonly present in each of the PAs in which elevated concentrations of combined Ra occurred. Concentrations of 226Ra or 228Ra or combined Ra correlated significantly with those of the above listed water-quality constituents (on the basis of the non-parametric Spearman correlation technique) and loaded on principal components describing the above water types from the entire data set and for samples from the PAs with the highest combined Ra concentrations.Concentrations of 224Ra and 226Ra were significantly correlated to those of 228Ra (Spearman's rank correlation coefficient, +0.236 and +0.326, respectively). Activity ratios of 224Ra/ 228Ra in the water samples were mostly near 1 when concentrations of both isotopes were greater than or equal to 0.037Bq/L (1pCi/L), the level above which analytical results were most reliable. Co-occurrence among these highest concentrations of the Ra radionuclides was most likely in those PAs where chemical conditions are most conducive to Ra mobility (e.g. acidic North Atlantic Coastal Plain). The concentrations of 224Ra were occasionally greater than 0.037Bq/L and the ratios of 224Ra/ 228Ra were generally highest in the PAs composed of alluvial sands and Cretaceous/Tertiary sandstones from the western USA, likely because concentrations of 224Ra are enhanced in solution relative to those of 228Ra by alpha recoil from the aquifer matrix. Rapid adsorption of the two Ra isotopes (controlled by the alkaline and oxic aquifer geochemistry) combined with preferential faster recoil of 224Ra generates a 224Ra/ 228Ra ratio much greater than

  10. Water quality and geochemistry of the mountain fynbos ecosystem in the vicinity of Citrusdal, South Africa

    NASA Astrophysics Data System (ADS)

    Compton, J.; Soderberg, K.

    2003-12-01

    % clay). TMG ground waters studied have low ionic strength (0.2-1 mM) and electrical conductivity (2.5-12 mS/m). The low pH helps to keep trace metals in solution, particularly iron and manganese, which tend to precipitate in the presence of oxygen near the surface. The presence of metals in solution contributes to the ability of the ground waters studied to buffer the addition of hydroxyl ion (Base Neutralizing Capacity) in the acidity titration. The Acid Neutralizing Capacity, or the ability to buffer acid, increases downstream along the main valley as agricultural runoff increases. The size of the major elemental reservoirs and the fluxes among them are approximated from chemical analyses of the bedrock, soil, vegetation, and waters of the ecosystem. These estimates are used in a simplified box model to discuss the element dynamics within the fynbos ecosystem of a headwater catchment underlain by the Peninsula Formation. The data support the idea that soil and vegetation act as a filter, selectively retaining elements from the water, particularly K and Mn, but also including Ca, Mg, Fe, and Al. The properties of the ecosystem that allow for this retention of elements could be disrupted by human activities.

  11. Exploration Geochemistry.

    ERIC Educational Resources Information Center

    Closs, L. Graham

    1983-01-01

    Contributions in mineral-deposit model formulation, geochemical exploration in glaciated and arid environments, analytical and sampling problems, and bibliographic research were made in symposia held and proceedings volumes published during 1982. Highlights of these symposia and proceedings and comments on trends in exploration geochemistry are…

  12. Hydrology and geochemistry of thermal ground water in southwestern Idaho and north-central Nevada

    SciTech Connect

    Young, H.W.; Lewis, R.E.

    1980-12-01

    The study area occupies about 14,500 square miles in southwestern Idaho and north-central Nevada. Thermal ground water occurs under artesian conditions, in discontinuous or compartmented zones, in igneous or sedimentary rocks of Tertiary age. Ground-water movement is generally northward. Temperatures of the ground water range from about 30/sup 0/ to more than 80/sup 0/C. Chemical analyses of water from 12 wells and 9 springs indicate that nonthermal waters are a calcium bicarbonate type; thermal waters are a sodium bicarbonate type. Chemical geothermometers indicate probable maximum reservoir temperatures are near 100/sup 0/C. Concentration of tritium in the thermal water water is near zero.

  13. The Dynamics of Supercooled Water

    NASA Astrophysics Data System (ADS)

    Mallamace, Francesco

    2011-03-01

    We present an overview of recent experiments performed on transport properties of water in the deeply supercooled region, a temperature region of fundamental importance in the science of water. We report data of nuclear magnetic resonance, quasi-elastic neutron scattering, Fourier-transform infrared spectroscopy, and Raman spectroscopy, studying water confined in nano-meter-scale environments (nano-tubes and the protein hydration water) and in bulk solutions. When contained within small pores, water does not crystallise, and can be supercooled well below its homogeneous nucleation temperature Th. On this basis it is possible to carry out a careful analysis of the well known thermodynamical anomalies of water. Studying the temperature and pressure dependencies of water dynamics, we show that the liquid-liquid phase transition (LLPT) hypothesis represents a reliable model for describing liquid water. In this model, water in the liquid state is a mixture of two different local structures, characterised by different densities, namely the low density liquid (LDL) and the high-density liquid (HDL). The LLPT line should terminate at a special transition point: a low-T liquid-liquid critical point. In particular We discuss the following experimental findings on liquid water: (i) a crossover from non-Arrhenius behaviour at high T to Arrhenius behaviour at low T in transport parameters; (ii) a breakdown of the Stokes-Einstein relation; (iii) the existence of a Widom line, which is the locus of points corresponding to maximum correlation length in the p-T phase diagram and which ends in the liquid-liquid critical point; (iv) the direct observation of the LDL phase; (v) a minimum in the density at approximately 70K below the temperature of the density maximum. In our opinion these results represent the experimental proofs of the validity of the LLPT hypothesis.

  14. Sediment Microbial Community Dynamics and Geochemistry During Oxic and Hypoxic Periods in the Gulf of Mexico

    EPA Science Inventory

    Seasonal hypoxia in the benthic waters of the Louisiana Coastal Shelf contributes to the Gulf of Mexico "dead zone" phenomena. Limited information is available on sedimentary biogeochemical interactions during periods of hypoxia.

  15. Combine the soil water assessment tool (SWAT) with sediment geochemistry to evaluate diffuse heavy metal loadings at watershed scale.

    PubMed

    Jiao, Wei; Ouyang, Wei; Hao, Fanghua; Huang, Haobo; Shan, Yushu; Geng, Xiaojun

    2014-09-15

    Assessing the diffuse pollutant loadings at watershed scale has become increasingly important when formulating effective watershed water management strategies, but the process was seldom achieved for heavy metals. In this study, the overall temporal-spatial variability of particulate Pb, Cu, Cr and Ni losses within an agricultural watershed was quantitatively evaluated by combining SWAT with sediment geochemistry. Results showed that the watershed particulate heavy metal loadings displayed strong variability in the simulation period 1981-2010, with an obvious increasing trend in recent years. The simulated annual average loadings were 20.21 g/ha, 21.75 g/ha, 47.35 g/ha and 21.27 g/ha for Pb, Cu, Cr and Ni, respectively. By comparison, these annual average values generally matched the estimated particulate heavy metal loadings at field scale. With spatial interpolation of field loadings, it was found that the diffuse heavy metal pollution mainly came from the sub-basins dominated with cultivated lands, accounting for over 70% of total watershed loadings. The watershed distribution of particulate heavy metal losses was very similar to that of soil loss but contrary to that of heavy metal concentrations in soil, highlighting the important role of sediment yield in controlling the diffuse heavy metal loadings.

  16. Geochemistry of waters in the Valley of Ten Thousand Smokes region, Alaska

    NASA Astrophysics Data System (ADS)

    Keith, T. E. C.; Thompson, J. M.; Hutchinson, R. A.; White, L. D.

    1992-02-01

    Meteoric waters from cold springs and streams outside of the 1912 eruptive deposits filling the Valley of Ten Thousand Smokes (VTTS) and in the upper parts of the two major rivers draining the 1912 deposits have similar chemical trends. Thermal springs issue in the mid-valley area along a 300-m lateral section of ash-flow tuff, and range in temperature from 21 to 29.8°C in early summer and from 15 to 17°C in mid-summer. Concentrations of major and minor chemical constituents in the thermal waters are nearly identical regardless of temperature. Waters in the downvalley parts of the rivers draining the 1912 deposits are mainly mixtures of cold meteoric waters and thermal waters of which the mid-valley thermal spring waters are representative. The weathering reactions of cold waters with the 1912 deposits appear to have stabilized and add only subordinate amounts of chemical constituents to the rivers relative to those contributed by the thermal waters. Isotopic data indicate that the mid-valley thermal spring waters are meteoric, but data is inconclusive regarding the heat source. The thermal waters could be either from a shallow part of a hydrothermal system beneath the 1912 vent region or from an incompletely cooled, welded tuff lens deep in the 1912 ash-flow sheet of the upper River Lethe area. Bicarbonate-sulfate waters resulting from interaction of near-surface waters and the cooling 1953-1968 southwest Trident plug issue from thermal springs south of Katmai Pass and near Mageik Creek, although the Mageik Creek spring waters are from a well-established, more deeply circulating hydrothermal system. Katmai caldera lake waters are a result of acid gases from vigorous drowned fumaroles dissolving in lake waters composed of snowmelt and precipitation.

  17. Geochemistry of waters in the Valley of Ten Thousand Smokes region, Alaska

    USGS Publications Warehouse

    Keith, T.E.C.; Thompson, J.M.; Hutchinson, R.A.; White, L.D.

    1992-01-01

    Meteoric waters from cold springs and streams outside of the 1912 eruptive deposits filling the Valley of Ten Thousand Smokes (VTTS) and in the upper parts of the two major rivers draining the 1912 deposits have similar chemical trends. Thermal springs issue in the mid-valley area along a 300-m lateral section of ash-flow tuff, and range in temperature from 21 to 29.8??C in early summer and from 15 to 17??C in mid-summer. Concentrations of major and minor chemical constituents in the thermal waters are nearly identical regardless of temperature. Waters in the downvalley parts of the rivers draining the 1912 deposits are mainly mixtures of cold meteoric waters and thermal waters of which the mid-valley thermal spring waters are representative. The weathering reactions of cold waters with the 1912 deposits appear to have stabilized and add only subordinate amounts of chemical constituents to the rivers relative to those contributed by the thermal waters. Isotopic data indicate that the mid-valley thermal spring waters are meteoric, but data is inconclusive regarding the heat source. The thermal waters could be either from a shallow part of a hydrothermal system beneath the 1912 vent region or from an incompletely cooled, welded tuff lens deep in the 1912 ash-flow sheet of the upper River Lethe area. Bicarbonate-sulfate waters resulting from interaction of near-surface waters and the cooling 1953-1968 southwest Trident plug issue from thermal springs south of Katmai Pass and near Mageik Creek, although the Mageik Creek spring waters are from a well-established, more deeply circulating hydrothermal system. Katmai caldera lake waters are a result of acid gases from vigorous drowned fumaroles dissolving in lake waters composed of snowmelt and precipitation. ?? 1992.

  18. Hydrology and geochemistry of thermal ground water in southwestern Idaho and north-central Nevada

    SciTech Connect

    Young, H.W.; Lewis, R.E.

    1982-01-01

    Chemical analyses of water from 12 wells and 9 springs indicate that nonthermal waters are a calcium bicarbonate type; thermal waters are a sodium carbonate or bicarbonate type. Chemical geothermometers indicate probable maximum reservoir temperatures are near 100/sup 0/ Celsius. Concentration of tritium in the thermal water is near zero. Depletion of stable isotopes in the hot waters relative to present-day meteoric waters indicates recharge to the system probably occurred when the climate averaged 3/sup 0/ to 5/sup 0/ Celsius colder than at present. Temperatures about 3.5/sup 0/ Celsius colder than at present occurred during periods of recorded Holocene glacial advances and indicate a residence time of water in the system of at least several thousand years. Residence time calculated on the basis of reservoir volume and thermal-water discharge is 3400 to 6800 years for an effective reservoir porosity of 0.05 and 0.10, respectively. Preliminary analyses of carbon-14 determinations indicate an age of the hot waters of about 18,000 to 25,000 years. The proposed conceptual model for the area is one of an old system, where water has circulated for thousands, even tens of thousands, of years. Within constraints imposed by the model described, reservoir thermal energy for the geothermal system in southwestern Idaho and north-central Nevada is about 130 x 10/sup 18/ calories.

  19. Geochemistry for Chemists.

    ERIC Educational Resources Information Center

    Hostettler, John D.

    1985-01-01

    A geochemistry course for chemists is described. Includes: (1) general course information; (2) subject matter covered; and (3) a consideration of the uses of geochemistry in a chemistry curriculum, including geochemical "real world" examples, geochemistry in general chemistry, and geochemistry as an elective. (JN)

  20. Geochemistry and origins of mineralized waters in the Floridan aquifer system, northeastern Florida

    USGS Publications Warehouse

    Phelps, G.G.

    2001-01-01

    Increases in chloride concentration have been observed in water from numerous wells tapping the Floridan aquifer system in northeastern Florida. Although most increases have been in the eastern part of Duval County, Florida, no spatial pattern in elevated chloride concentrations is discernible. Possible sources of the mineralized water include modern seawater intrusion; unflushed Miocene-to-Pleistocene-age seawater or connate water in aquifer sediments; or mineralized water from deeper zones of the aquifer system or from formations beneath the Floridan aquifer system. The purpose of this study was to document the chemical and isotopic characteristics of water samples from various aquifer zones, and from geochemical and hydrogeologic data, to infer the source of the increased mineralization. Water samples were collected from 53 wells in northeastern Florida during 1997-1999. Wells tapped various zones of the aquifer including: the Fernandina permeable zone (FPZ), the upper zone of the Lower Floridan aquifer (UZLF), the Upper Floridan aquifer (UFA), and both the UFA and the UZLF. Water samples were analyzed for major ions and trace constituents and for isotopes of carbon, oxygen, hydrogen, sulfur, strontium, chlorine, and boron. Samples of rock from the aquifer were analyzed for isotopes of oxygen, carbon, and strontium. In general, water from various aquifer zones cannot be differentiated based on chemistry, except for water from FPZ wells. Major-ion concentrations vary as much within the upper zone of the Lower Floridan aquifer and the Upper Floridan aquifer as between these two zones. Simple models of mixing between fresh ground water and either modern seawater or water from the FPZ as a mineralized end member show that many water samples from the UZLF aquifer and the UFA are enriched in bicarbonate, calcium, magnesium, sulfate, fluoride, and silica and are depleted in sodium and potassium (as compared to concentrations predicted by simple mixing). Chemical mass

  1. Flow and geochemistry along shallow ground-water flowpaths in an agricultural area in southeastern Wisconsin

    USGS Publications Warehouse

    Saad, D.A.; Thorstenson, D.C.

    1998-01-01

    Ground water recharging at mid- and downgradient wells is oxic and contains dissolved nitrate, whereas the ground water discharging to the stream is anoxic and contains dissolved ammonium. Redox environments were defined at each well on the basis of relative concentrations of various dissolved redox-active species. Chemically permissible flowpaths inferred from the observed sequence of redox environments at well sites are consistent with flowpaths in the ground-water flow model. The transition from nitrate in recharging groun

  2. Isotope Geochemistry and Chronology of Offshore Ground Water Beneath Indian River Bay, Delaware

    USGS Publications Warehouse

    Böhlke, John Karl; Krantz, David E.

    2003-01-01

    Results of geophysical surveys in Indian River Bay, Delaware, indicate a complex pattern of salinity variation in subestuarine ground water. Fresh ground-water plumes up to about 20 meters thick extending hundreds of meters offshore are interspersed with saline ground water, with varying degrees of mixing along the salinity boundaries. It is possible that these features represent pathways for nutrient transport and interaction with estuarine surface water, but the geophysical data do not indicate rates of movement or nutrient sources and reactions. In the current study, samples of subestuarine ground water from temporary wells with short screens placed 3 to 22 meters below the sediment-water interface were analyzed chemically and isotopically to determine the origins, ages, transport pathways, and nutrient contents of the fresh and saline components. Apparent ground-water ages determined from chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), tritium (3H), and helium isotopes (3He and 4He) commonly were discordant, but nevertheless indicate that both fresh and saline ground waters ranged from a few years to at least 50 years in age. Tritium-helium (3H-3He) ages, tentatively judged to be most reliable, indicate that stratified offshore freshwater plumes originating in distant recharge areas on land were bounded by relatively young saline water that was recharged locally from the overlying estuary. Undenitrified and partially denitrified nitrate of agricultural or mixed origin was transported laterally beneath the estuary in oxic and suboxic fresh ground water. Ammonium produced by anaerobic degradation of organic matter in estuarine sediments was transported downward in suboxic saline ground water around the freshwater plumes. Many of the chemical and isotopic characteristics of the subestuarine ground waters are consistent with conservative mixing of the fresh (terrestrial) and saline (estuarine) endmember water types. These data indicate that freshwater plumes

  3. Effects of slow recovery rates on water column geochemistry in aquitard wells

    USGS Publications Warehouse

    Schilling, K.E.

    2011-01-01

    Monitoring wells are often installed in aquitards to verify effectiveness for preventing migration of surface contaminants to underlying aquifers. However, water sampling of aquitard wells presents a challenge due to the slow recovery times for water recharging the wells, which can take as long as weeks, months or years to recharge depending on the sample volume needed. In this study, downhole profiling and sampling of aquitard wells was used to assess geochemical changes that occur in aquitard wells during water level recovery. Wells were sampled on three occasions spanning 11years, 1year and 1week after they were purged and casing water showed substantial water chemistry variations. Temperature decreased with depth, whereas pH and specific conductance increased with depth in the water column after 11years of water level recovery. Less stable parameters such as dissolved O2 (DO) and Eh showed strong zonation in the well column, with DO stratification occurring as the groundwater slowly entered the well. Oxidation of reduced till groundwater along with degassing of CO2 from till pore water affects mineral solubility and dissolved solid concentrations. Recommendations for sampling slowly recovering aquitard wells include identifying the zone of DO and Eh stratification in the well column and collecting water samples from below the boundary to better measure unstable geochemical parameters. ?? 2011 Elsevier Ltd.

  4. Ground-water quality and geochemistry in Carson and Eagle Valleys, western Nevada and eastern California

    USGS Publications Warehouse

    Welch, Alan H.

    1994-01-01

    Aquifers in Carson and Eagle Valleys are an important source of water for human consumption and agriculture. Concentrations of major constituents in water from the principal aquifers on the west sides of Carson and Eagle Valleys appear to be a result of natural geochemical reactions with minerals derived primarily from plutonic rocks. In general, water from principal aquifers is acceptable for drinking when compared with current (1993) Nevada State drinking-water maximum contaminant level standards. Water was collected and analyzed for all inorganic constituents for which primary or secondary drinking-water standards have been established. About 3 percent of these sites had con- stituents that exceeded one or more primary or secondary drinking-water standards have been established. About 3 percent of these sites had con- stituents that exceeded one or more primary standards and water at about 10 percent of the sites had at least one constituent that surpassed a secondary standard. Arsenic exceeded the standard in water at less than 1 percent of the principal aquifer sites; nitrate surpassed its standard in water at 3 percent of 93 sites. Water from wells in the principal aquifer with high concentrations of nitrate was in areas where septic systems are used; these concentrations indicate that contamination may be entering the wells. Concentrations of naturally occurring radionuclides in water from the principal aquifers, exceed the proposed Federal standards for some constituents, but were not found t be above current (1993) State standards. The uranium concen- trations exceeded the proposed 20 micrograms per liter Federal standard at 10 percent of the sites. Of the sites analyzed for all of the inorganic constituents with primary standards plus uranium, 15 percent exceed one or more established standards. If the proposed 20 micrograms per liter standard for uranium is applied to the sampled sites, then 23 percent would exceed the standard for uranium or some other

  5. Integrating geophysics and geochemistry to evaluate coalbed natural gas produced water disposal, Powder River Basin, Wyoming

    NASA Astrophysics Data System (ADS)

    Lipinski, Brian Andrew

    Production of methane from thick, extensive coalbeds in the Powder River Basin of Wyoming has created water management issues. More than 4.1 billion barrels of water have been produced with coalbed natural gas (CBNG) since 1997. Infiltration impoundments, which are the principal method used to dispose CBNG water, contribute to the recharge of underlying aquifers. Airborne electromagnetic surveys of an alluvial aquifer that has been receiving CBNG water effluent through infiltration impoundments since 2001 reveal produced water plumes within these aquifers and also provide insight into geomorphologic controls on resultant salinity levels. Geochemical data from the same aquifer reveal that CBNG water enriched in sodium and bicarbonate infiltrates and mixes with sodium-calcium-sulfate type alluvial groundwater, which subsequently may have migrated into the Powder River. The highly sodic produced water undergoes cation exchange reactions with native alluvial sediments as it infiltrates, exchanging sodium from solution for calcium and magnesium on montmorillonite clays. The reaction may ultimately reduce sediment permeability by clay dispersion. Strontium isotope data from CBNG wells discharging water into these impoundments indicate that the Anderson coalbed of the Fort Union Formation is dewatered due to production. Geophysical methods provide a broad-scale tool to monitor CBNG water disposal especially in areas where field based investigations are logistically prohibitive, but geochemical data are needed to reveal subsurface processes undetectable by geophysical techniques. The results of this research show that: (1) CBNG impoundments should not be located near streams because they can alter the surrounding hydraulic potential field forcing saline alluvial groundwater and eventually CBNG water into the stream, (2) point bars are poor impoundment locations because they are essentially in direct hydraulic communication with the associated stream and because plants

  6. Seasonal nutrient dynamics in the Anacostia River (D.C., USA): geochemistry and hydrocarbon biomarkers

    NASA Astrophysics Data System (ADS)

    Sarraino, S.; Frantz, D. E.; Macavoy, S. E.

    2010-12-01

    The seasonal biogeochemistry of the urban Anacostia River (Washington D.C. USA) was investigated. Chemical parameters examined include: inorganics (Ca, Mg, Na, S, K, P, NO3, NH4, PO4, B, Ba, Ni, Co); fatty acids and other hydrocarbons; C, N and S stable isotopes; and other water chemistry indicators (hardness, salinity, alkalinity, soluble salts, SAR, TDS). Between April and July 2010, water and sediment were sampled from three tidal freshwater sites along the Anacostia River (UP, MID, and DWN). Two of the selected sites, UP and DWN, are located next to a combined sewage outflow. Water column nutrient analysis shows increasing availability of ammonium (NH4) and nitrate (NO3) at all sites between April and July. At MID, the site showing the highest rates of nutrient growth over the sampling period, NH4 concentrations increase from 0.13 to 1.49 µg/L and NO3 concentrations increase from 0.71 to 2.88 mg/L. A marked NO3 pulse is observed at the DWN site in early May; NO3 concentrations jump from 0.68 to 3.36 mg/L between April 5 and May 6, decreasing to 1.22 mg/L by May 20. Unlike UP and MID, which show NH4 and NO3 increasing concurrently, this NO3 pulse at DWN is accompanied with a decline in NH4 levels, suggestive of an allochthonous NO3 source. Forthcoming stable isotope data are expected to characterize the source of such nitrogen inputs, as well as organic material, throughout the year. Preliminary GC-MS analysis of isolated fatty acids does not explicitly suggest bacterial or higher plant dominance in the spring; however, some notable compounds were identified, such as the PAH fluoranthene, naphthoquinone, and testosterone, as well as a number of cholesterols and other steroids. Higher proportions of bacterial fatty acid biomarkers are expected during the summer. Principle Component Analysis (PCA) of the chemistry data suggests geochemical variables, rather than nutrients, are the driving forces of observed trends. PCA, along with fatty acid characterization and

  7. Change in Magma Dynamics at Okataina Rhyolite Caldera revealed by Plagioclase Textures and Geochemistry

    NASA Astrophysics Data System (ADS)

    Shane, P. A. R.

    2015-12-01

    A fundamental reorganization of magma dynamics at Okataina volcano, New Zealand, occurred at 26 ka involving a change from smaller volume, high-temperature rhyodacite magmas to a lower eruptive tempo of larger volume, low-temperature, rhyolite magmas. Zircon studies demonstrate the presence of a periodically active, long-lived (100,000 yr) magmatic reservoir. However, there is little correlation between periods of zircon crystallization and eruption events. In contrast, the changing magmatic dynamics is revealed in plagioclase growth histories. Crystals from the ~0.7 ka Kaharoa eruption are characterized by resorbed cores displaying a cellular-texture of high-An (>40) zones partially replaced by low-An (<30) zones, surrounded by a resorption surface and a prominent normal-zoned rim (An50-20). Elevated An, Fe, Mg, Sr and Ti follow the resorption surface and display rimward depletion trends, accompanied by Ba and REE enrichment. The zonation is consistent with fractional crystallization and cooling. The cores display wide trace element diversity, pointing to crystallization in a variety of melts, before transport and mixing into a common magma where the rims grew. Plagioclase from the ~36 ka Hauparu eruption display several regrowth zones separated by resorption surfaces, which surround small resorbed cores with a spongy cellular texture of variable An content (An 40-50). The crystals display step-wise re-growth of successively higher An, Fe, Mg and Ti content, consistent with progressive mafic recharge. Two crystal groups are distinguished by trace element chemistry indicating growth in separate melts and co-occurrence via magma-mingling. The contrasting zoning patterns in plagioclase correspond to the evolutionary history of magmatism at Okataina. Emptying of the magma reservoir following caldera eruption at 46 ka reduced barriers to mafic magma ascent. This is recorded by the frequent resorption and recharge episodes in Hauparu crystals. Subsequent re

  8. Isotope geochemistry of thermal and nonthermal waters in the Valles caldera, Jemez Mountains, northern New Mexico

    SciTech Connect

    Vuataz, F.D.; Goff, F.

    1986-02-10

    Over 100 stable isotope and 45 tritium analyses from thermal and nonthermal waters of the Jemez Mountains region, New Mexico, have been used to define the hydrodynamics of the Valles caldera (Baca) geothermal system and related geothermal fluids of the region. Evaluation of 36 cold meteoric waters yields an equation for the Jemez Mountains meteoric water line of deltaD = 8delta/sup 18/O+12, while further evaluation of nine cold meteoric waters yields an equation relating recharge elevation to deuterium content of E(meters) = -44.9 (deltaD)-1154. Based on the deuterium content of five Baca well waters (223/sup 0/--294/sup 0/C), the average recharge elevation of the Valles geothermal system ranges from 2530 to 2890 m. This range of elevations falls between the elevations of the lowest point of the caldera floor (2400 m) and the summit of the resurgent dome inside the caldera (3430 m). Thus stable isotopes indicate that the caldera depression probably serves as a recharge basin for the deep geothermal system. Although cold spring waters of the Jemez Mountains region consist of meteoric water, tritium analyses show that most of them contain water between 20 and 75 years old.

  9. The occurrence and geochemistry of fluoride in some natural waters of Kenya

    NASA Astrophysics Data System (ADS)

    Gaciri, S. J.; Davies, T. C.

    1993-03-01

    In recent years the acquisition of considerable additional data on the hydrogeochemical behaviour of fluoride in natural waters of Kenya has been made possible by extensive surface-water and groundwater sampling campaigns as well as by improvements in analytical techniques. Ultimately, the principal source of fluoride relates to emissions from volcanic activity associated with the East African Rift System. Through various intermediate steps, but also directly, fluoride passes into the natural water system and components of the food chain. Ingestion by man is mainly through drinking water and other beverages. River waters in Kenya generally have a fluoride concentration lower than the recommended level (1.3 ppm) for potable water, thus promoting susceptibility to dental caries. Groundwaters and lake waters show considerably higher fluoride contents, resulting in the widespread incidence of fluorosis in areas where groundwater is the major source of drinking water, and lake fish is a regular component of the diet. This paper presents a synthesis of the data so far obtained on the sources and distribution of fluoride in the hydrological system of Kenya, examines the extent of fluorine toxicity and puts forward recommendations to combat or minimise the problem.

  10. A Classroom Simulation of Water-Rock Interaction for Upper-Level Geochemistry Courses.

    ERIC Educational Resources Information Center

    Cercone, Karen Rose

    1988-01-01

    Describes a simple hands-on model of water-rock interaction that can be constructed in the classroom using styrofoam bowls and foil-wrapped candies. This interactive simulation allows students to vary the factors which control water-rock interaction and to obtain immediate results. (Author/CW)

  11. Flow and geochemistry along shallow ground-water flowpaths in an agricultural area in southeastern Wisconsin

    USGS Publications Warehouse

    Saad, D.A.; Thorstenson, D.C.

    1998-01-01

    Ground water recharging at mid- and downgradient wells is oxic and contains dissolved nitrate, whereas the ground water discharging to the stream is anoxic and contains dissolved ammonium. Redox environments were defined at each well on the basis of relative concentrations of various dissolved redox-active species. Chemically permissible flowpaths inferred from the observed sequence of redox environments at well sites are consistent with flowpaths in the ground-water flow model. The transition from nitrate in recharging ground water to ammonium in ground water discharging to the stream suggests the possibility of nitrate reduction along the flowpath. None of the techniques employed in this study, however, were able to prove the occurrence of this reaction.

  12. The aqueous geochemistry of neptunium: Dynamic control of soluble concentrations with applications to nuclear waste disposal

    SciTech Connect

    Kaszuba, J.P.; Runde, W.H.

    1999-12-15

    The valence state of neptunium, one of the most important radionuclides of concern for long-term emplacement of nuclear waste, primarily defines its geochemical reactions and migration behavior. The authors evaluate how redox potential and solid-phase stability interact and influence neptunium solubility and aqueous speciation in natural systems. Neptunium thermodynamic data for the most important valence states for natural waters, +IV and +V, are updated to correct database inconsistencies. The most significant changes are as follows: (1) Np{sub 2}O{sub 5}(cr) is 2 orders of magnitude more stable than reported previously, (2) the stability of NpO{sub 2}OH(aq) is reduced, (3) NpO{sub 2}(OH){sub 2}{sup {minus}} and mixed Np(V) hydroxo-carbonato species become important at high pH, and (4) Np(OH){sub 5{minus}} is disregarded as a valid species. As a result, Np{sub 2}O{sub 5} and Np(OH){sub 4}(am) are the stable solids in aquifers of low ionic strength, neptunium solubility decreases in the pH range 10--12 and increases at pH above 12, and both redox potential and Np(OH){sub 4}(am) solubility product control soluble neptunium concentrations at neutral pH and Eh between {minus}0.2 and 0.3. these relationships are important for effective nuclear waste package design, such as including cement as an engineered barrier and evaluating impacts of discharged solutions on natural waters in release scenarios at nuclear waste storage facilities.

  13. Deep subsurface drip irrigation using coal-bed sodic water: part II. geochemistry

    USGS Publications Warehouse

    Bern, Carleton R.; Breit, George N.; Healy, Richard W.; Zupancic, John W.

    2013-01-01

    Waters with low salinity and high sodium adsorption ratios (SARs) present a challenge to irrigation because they degrade soil structure and infiltration capacity. In the Powder River Basin of Wyoming, such low salinity (electrical conductivity, EC 2.1 mS cm-1) and high-SAR (54) waters are co-produced with coal-bed methane and some are used for subsurface drip irrigation(SDI). The SDI system studied mixes sulfuric acid with irrigation water and applies water year-round via drip tubing buried 92 cm deep. After six years of irrigation, SAR values between 0 and 30 cm depth (0.5-1.2) are only slightly increased over non-irrigated soils (0.1-0.5). Only 8-15% of added Na has accumulated above the drip tubing. Sodicity has increased in soil surrounding the drip tubing, and geochemical simulations show that two pathways can generate sodic conditions. In soil between 45-cm depth and the drip tubing, Na from the irrigation water accumulates as evapotranspiration concentrates solutes. SAR values >12, measured by 1:1 water-soil extracts, are caused by concentration of solutes by factors up to 13. Low-EC (-1) is caused by rain and snowmelt flushing the soil and displacing ions in soil solution. Soil below the drip tubing experiences lower solute concentration factors (1-1.65) due to excess irrigation water and also contains relatively abundant native gypsum (2.4 ± 1.7 wt.%). Geochemical simulations show gypsum dissolution decreases soil-water SAR to 14 and decreasing EC in soil water to 3.2 mS cm-1. Increased sodicity in the subsurface, rather than the surface, indicates that deep SDI can be a viable means of irrigating with sodic waters.

  14. Water geochemistry of the Lucero Uplift, New Mexico: geothermal investigation of low-temperature mineralized fluids

    SciTech Connect

    Goff, F.; McCormick, T.; Gardner, J.N.; Trujillo, P.E.; Counce, D.; Vidale, R.; Charles, R.

    1983-04-01

    A detailed geochemical investigation of 27 waters of the Lucero uplift, central New Mexico, was performed to determine if the fluids originate from a high-temperature geothermal system along the Rio Grande rift. Two types of mineralized water issue from the Lucero region: a relatively saline (high-Cl, high-SO/sub 4/) type and a relatively dilute (low-Cl, high-SO/sub 4/) type. Emergence temperatures of both types range from 12 to 26/sup 0/C. Chemical data and thermodynamic and geothermometer calculations all indicate that both water types are in equilibrium with carbonate and evaporite minerals found in local Colorado Plateau rocks at surface temperatures or slightly higher. Stable isotope data do not indicate high-temperature rock-water interaction. Although evidence is seen for mixing between mineralized waters and dilute surface waters, no evidence for mixing of a deep hot fluid and surface waters is seen. Dilute mineral waters, which issue from a large area of Chinle Formation on the west side of the Lucero uplift, may be useful for low-temperature geothermal applications with appropriate design of equipment. Saline mineral waters, which leak from a zone of faulted and folded rocks along the Comanche fault zone, do not appear to have much, if any, geothermal potential due to their low-temperature, restricted distribution, and high concentration of dissolved solids. No evidence that saline mineral waters are associated with Quaternary faults of the Rio Grande rift or Quaternary basaltic volcanism within the immediate area is seen.

  15. The marine geochemistry of actinium-227: Evidence for its migration through sediment pore water

    SciTech Connect

    Nozaki, Yoshiyuki; Yamada, Masatoshi ); Nikaido, Hirofumi )

    1990-10-01

    {sup 227}Ac with a half life of 21.8 years has a potential utility as a tracer of deep water circulation and mixing studies on time scales less than 100 years. Here the authors present the first measurement of {sup 227}Ac profile in the pore water of Northwest Pacific deep-sea sediment and in the {approximately}10,000 m long water column of Izu-Ogasawara Trench. The results clearly show that {sup 227}Ac is supplied from the sediment to the overlying water through migration in the pore water. The model calculation indicates that the molecular diffusion alone through sediment porewater can support only a half of the standing crop of excess {sup 227}Ac in the water column and the enhanced supply of {sup 227}Ac by particle mixing is necessary to account for the remainder. Thus, bioturbation in the deep sea plays an important role in controlling the flux of some short-lived radionuclides such as {sup 227}Ac and {sup 228}Ra across the sediment-water interface.

  16. Radium isotope geochemistry of thermal waters, Yellowstone National Park, Wyoming, USA

    SciTech Connect

    Sturchio, N.C.; Bohlke, J.K.; Markun, F.J. )

    1993-03-01

    Radium isotope activities ([sup 226]Ra, [sup 228]Ra, and [sup 224]Ra), chemical compositions, and sulfur isotope ratios in sulfate were determined for water samples from thermal areas in Yellowstone National Park, Wyoming. Activities of [sup 226]Ra in these waters range from <0.2 to 37.9 dpm/kg. Activity ratios of [sup 228]Ra/[sup 226]Ra range from 0.26 to 14.2, and those of [sup 224]Ra/[sup 228]Ra range from 0.73 to 3.1. Radium concentrations are inversely correlated with aquifer equilibration temperatures (estimated from dissolved silica concentrations), while [Ra/Ba][sub aq] and [sup 228]Ra/[sup 226]Ra activity ratios depend upon U/Ba and Th/U ratios in aquifer rocks. Major controls on Ra concentration in Yellowstone thermal waters are inferred to be (1) barite saturation (at Norris Geyser Basin, Mammoth Hot Springs, and other northern areas) and (2) zeolite-water ion exchange (at Upper Geyser Basin). The data are consistent with a model in which (1) radium and barium are supplied to water by bulk dissolution of aquifer rock, and (2) chemical equilibration of water with rock is rapid relative to the 1602 year half-life of [sup 226]Ra. The [sup 228]Ra/[sup 226]Ra activity ratios of the waters may in some cases reflect surface enrichments of [sup 232]Th and/or may indicate that [alpha]-recoil input of [sup 228]Ra is rapid relative to water-rock chemical equilibration. Activity ratios of [sup 224]Ra/[sup 228]Ra indicate a nearly ubiquitous [sup 224]Ra excess that generally increases with decreasing pH. Near-surface ([le]100 m) thermal water flow velocities at Mammoth Hot Springs are estimated from [sup 224]Ra/[sup 228]Ra variation to be [ge]1 m h[sup [minus]1]. 73 refs., 4 figs., 4 tabs.

  17. Arsenic in ground water of the United States: occurrence and geochemistry

    USGS Publications Warehouse

    Welch, Alan H.; Westjohn, D.B.; Helsel, Dennis R.; Wanty, Richard B.

    2000-01-01

    Concentrations of naturally occurring arsenic in ground water vary regionally due to a combination of climate and geology. Although slightly less than half of 30,000 arsenic analyses of ground water in the United States were ≤ 1 µg/L, about 10% exceeded 0 µg/L. At a broad regional scale, arsenic concentrations exceeding 10 µg/L appear to be more frequently observed in the western United States than in the eastern half. Arsenic concentrations in ground water of the Appalachian Highlands and the Atlantic plain generally are very low (≤ 1 µg/L). Concentrations are somewhat greater in the Interior Plains and the Rocky Mountain System, investigations of ground water in New England, Michigan, Minnesota, South Dakota, Oklahoma, and Wisconsin within the last decade suggest that arsenic concentrations exceeding 10 µg/L are more widespread and common than previously recognized. Arsenic release from iron oxide appears to be the most common cause of widespread arsenic concentrations exceeding 10 µg/L a ground water. This can occur in response to different geochemical conditions, including release of arsenic to ground water through reaction of iron oxide with either natural or anthropogenic (i.e., petroleum products) organic carbon. Iron oxide also can release arsenic to alkaline ground water, such as that found in some felsic volcanic rocks and alkaline aquifers of the Western United States. Sulfide minerals are both a source and sink for arsenic. Geothermal water and high evaporation rates also are associated with arsenic concentrations ≥ 10g/L in ground and surface water, particularly in the west.

  18. Hydro geochemistry Study of Yamama formation water in southern Iraqi oil Fields, Migration,Diagensis

    NASA Astrophysics Data System (ADS)

    Ali, A. A.; SOC Team

    2013-05-01

    Yamama Formation (Lower Cretaceous) form one of the main oil reservoir in southern Iraq, the present study deals with the general physical and chemical characteristics of Yamama formation water in selected oil fields - southern Iraq. Via the collecting the available water analysis data in in selected 10 wells in southern Iraqi oil fields, Well Logs, as well as, the technical final well reports. The task of this study is to illustrate the chemical and physical variation among the study oil wells, and their relation with the depositional environment, the grading of temperature and pressure, the reason behind of over pressure phenomenon, besides the delineation of oil migration and water reservoir movement direction. The study confirms the occurrences of two types of formation water; the first one is the connate water, which is brine, hypersaline, and marine in nature reflects the possibility of hydrocarbon accumulations. And the second is mixing water reflects the mixing of original marine water with percolating meteoric water for various degree. Regarding the hydrochemical ratios, the direction of water movement and oil migration is from northeast toward west and south west starting from Messan oil Fields, moreover, the secondary migration of oil is in the same direction. The western migration of oil and water attributed to the enhancement of porosity and permeability in this direction, which in turn means the possibility of finding new stratigraphic traps in this direction mainly western of Nasiriya and Garraf areas. The relationship between depositional environment and diagenetic processes in one hand, and the sediment logical units; tidal lime granular unit revealed the occurrences of khidar al-may which extends up to Al-Managish in Kuwait and Nahar Umar - Majnoon, Nasiriya - Abu Amood, as well as the clayey units represented by isolated and semi isolated lagoonal deposits. Based on the ionic ratios in AlZubair, Nahar Umer and Al-Kifil oil fields, outer shelf

  19. Hydrogeology, water quality, and geochemistry of the Rush Springs aquifer, western Oklahoma

    USGS Publications Warehouse

    Becker, M.F.; Runkle, D.L.

    1998-01-01

    The Rush Springs aquifer, in western Oklahoma, is equivalent to the Permian-age Rush Springs Formation. It is composed of very fine-grained to fine-grained sandstone that is massive to highly cross-bedded and is underlain by less-permeable Marlow Formation. Reported irrigation well yields exceed 1,000 gallons per minute; yields reported on 89 drillers' logs ranged from 11 to 850 gallons per minute. Transmissivities range from 670 to 1,870 feet squared per day. Specific yields for core samples range from 0.13 to 0.34. Estimates of hydraulic conductivities at one site ranged from 1.05 to 5.62 feet per day. The Rush Springs aquifer is recharged by infiltration of precipitation, ranging from 0.2 to more than 2 inches per year. Discharge is primarily to streams and rivers where the Rush Springs aquifer crops. Estimated total withdrawal was 54.7 million gallons per day in 1990. Over 42 million gallons per day, or 77.8 percent of water withdrawn, was used for irrigation of crops. Thirty-five of the 64 wells sampled produced nitrate concentration that equaled or exceeded drinking water standards. Sulfate concentration also exceeds the drinking water standards in some areas. Two major water types occur in the aquifer, a calcium-magnesium bicarbonate type and a calcium sulfate type. Dissolved solids concentrations in water samples from the aquifer ranged from 52 to 1,840 milligrams per liter. The chemical composition of ground water in the Rush Springs aquifer is the result of chemical reactions between the recharge waters and minerals in the overlying soils and rocks in the Rush Springs and Marlow Formations. Saturation indices of minerals were calculated for 64 water-quality analyses using the geochemical computer model WATEQF. Mass transfer rates were calculated using the mass-balance model NETPATH.

  20. Rare earth element geochemistry in cold-seep pore waters of Hydrate Ridge, northeast Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Himmler, Tobias; Haley, Brian A.; Torres, Marta E.; Klinkhammer, Gary P.; Bohrmann, Gerhard; Peckmann, Jörn

    2013-07-01

    The concentrations of rare earth elements (REEs), sulphate, hydrogen sulphide, total alkalinity, calcium, magnesium and phosphate were measured in shallow (<12 cm below seafloor) pore waters from cold-seep sediments on the northern and southern summits of Hydrate Ridge, offshore Oregon. Downward-decreasing sulphate and coevally increasing sulphide concentrations reveal sulphate reduction as dominant early diagenetic process from ~2 cm depth downwards. A strong increase of total dissolved REE (∑REE) concentrations is evident immediately below the sediment-water interface, which can be related to early diagenetic release of REEs into pore water resulting from the re-mineralization of particulate organic matter. The highest pore water ∑REE concentrations were measured close to the sediment-water interface at ~2 cm depth. Distinct shale-normalized REE patterns point to particulate organic matter and iron oxides as main REE sources in the upper ~2-cm depth interval. In general, the pore waters have shale-normalized patterns reflecting heavy REE (HREE) enrichment, which suggests preferential complexation of HREEs with carbonate ions. Below ~2 cm depth, a downward decrease in ∑REE correlates with a decrease in pore water calcium concentrations. At this depth, the anaerobic oxidation of methane (AOM) coupled to sulphate reduction increases carbonate alkalinity through the production of bicarbonate, which results in the precipitation of carbonate minerals. It seems therefore likely that the REEs and calcium are consumed during vast AOM-induced precipitation of carbonate in shallow Hydrate Ridge sediments. The analysis of pore waters from Hydrate Ridge shed new light on early diagenetic processes at cold seeps, corroborating the great potential of REEs to identify geochemical processes and to constrain environmental conditions.

  1. Geochemistry of formation waters from the Lower Silurian Clinton Formation (Albion Sandstone), eastern Ohio

    SciTech Connect

    Sanders, L.L. )

    1991-10-01

    Waters of the petroleum-bearing Clinton formation (Albion Sandstone) of eastern Ohio are highly concentrated brines with average total dissolved solids (TDS) of 250,000 ppm. Sodium, calcium, and chloride account for 97% of the TDS. Distribution of divalent metal chlorides (MCl{sub 2}) allows inference of an up-dip paleoflow direction, although present-day flow is probably down-dip paleoflow direction, although present-day flow is probably down-dip. Solute distribution may have been emplaced during early basin development; it thus provides a snapshot of paleoflow. Formation structure alone can not explain MCl{sub 2} trends; they probably also are controlled by regional variation in salt thickness. Major constituent data do not indicate that membrane filtration affected the waters. High bromide content (mean = 1,860 ppm) of the water indicates that they originated from evaporating seawater. They probably are related genetically to the Salina evaporite group. Calculations show that several subsequent diagenetic reactions can account for the observed major ion composition. Recrystallization of aragonite and dolomitization of calcite probably occurred as the waters moved through the big Lime and/or the Packer Shell carbonates. Cation exchange and chlorite formation probably altered water composition during interaction with shales of the Cabot Head formation and within the Clinton. Minor constituents of the waters appear to be controlled by reactions with clays.

  2. [Geochemistry of surface and ground water in the Lijang basin, Northwest Yunnan].

    PubMed

    Pu, Tao; He, Yuan-Qing; Zhu, Guo-Feng; Zhang, Wei; Cao, Wei-Hong; Chang, Li; Wang, Chun-Feng

    2012-01-01

    The study focused on the chemical element compositions of river water and groundwater in Lijiang Basin. Water samples were collected in Baishui, Sanshu, Geji and Shuhe rivers in Lijiang Basin to analyze pH, conductivity and ion concentration, in order to understand the contributions of anthropogenic activities and rock weathering to river solutes. The results show that all water samples are mildly alkaline and are rich in Ca2+ and HCO3-, which account for 54.8 and 92.4 percentage of total ion concentration respectively. Obvious variations have been perceived during monsoon and westward wind season. The ion concentration of river water is lower than that of groundwater. With decreasing elevation, the ion concentrations are found to increase considerably in the study region. According to source study of major ions, water chemistry is mainly influenced by precipitation rock weathering and dissolving processes. In addition, precipitation is an important factor in monsoon seasons whereas the anthropogenic inputs have lead to light pollution on water in residential district.

  3. Ground-water quality and geochemistry in Dayton, Stagecoach, and Churchill Valleys, western Nevada

    USGS Publications Warehouse

    Thomas, James M.; Lawrence, Stephen J.

    1994-01-01

    The U.S. Geological Survey investigated the quality of ground water in the Dayton, Stagecoach, and Churchill Valleys as part of the Carson River Basin National Water-Quality Assessment (NAWQA) pilot study. Four aquifer systems have been de- lineated in the study area. Principal aquifers are unconsolidated deposits at altitudes of less than 4,900 feet above sea level and more than 50 feet below land surface. Shallow aquifers are at altitudes of less than 4,900 feet and less than 50 feet below land surface. Upland aquifers are above 4,900 feet and provide recharge to the principal aquifers. Thermal aquifers, defined as those having a water temperature greater than 30 degrees Celsius, are also present. Ground water used in Dayton, Stagecoach, and Churchill Valleys is pumped from principal aquifers in unconsolidated basin-fill deposits. Ground water in these aquifers originates as precipitation in the adjacent mountains and is recharged by the Carson River and by underflow from adjacent upstream valleys. Ground-water flow is generally parallel to the direction of surface-water flow in the Carson River. Ground water is discharged by pumping, evapo- transpiration, and underflow into the Carson River. The results of geochemical modeling indicate that as ground water moves from upland aquifers in mountainous recharge areas to principal aquifers in basin-fill deposits, the following processes probably occur: (1) plagioclase feldspar, sodium chloride, gypsum (or pyrite), potassium feldspar, and biotite dissolve; (2) calcite precipitates; (3) kaolinite forms; (4) small amounts of calcium and magnesium in the water exchange for potassium on aquifer minerals; and (5) carbon dioxide is gained or lost. The geochemical models are consistent with (1) phases identified in basin- fill sediments; (2) chemical activity of major cations and silica; (3) saturation indices of calcite and amorphous silica; (4) phase relations for aluminosilicate minerals indicated by activity diagrams; and

  4. Hydrogeophysics and geochemistry reveal heterogeneity and water quality improvements in aquifer recharge and recovery (ARR) (Invited)

    NASA Astrophysics Data System (ADS)

    Parsekian, A.; Regnery, J.; Wing, A.; Knight, R. J.; Drewes, J. E.

    2013-12-01

    Aquifer recharge and recover (ARR) is the process of infiltrating water into the ground for storage and withdrawal through wells at a later time. Two significant challenges faced during the design of ARR systems are 1) evaluating aquifer heterogeneity and 2) understanding the rock fluid interactions; these knowledge gaps may have profound impacts on the volume of recoverable water and the improvement in water quality in comparison with the source-water. Our objective in this research is to leverage the advantages of hydrogeophysical measurements and geochemical sampling to reveal the properties of an aquifer through which ARR water travels with the goal of informing current operations and future design decisions. Combined geophysical and geochemical investigations reveal subsurface heterogeneity, indicate possible flow paths though the aquifer and quantify specific reductions in contaminant concentrations. Ground penetrating radar (GPR), electromagnetic induction (EMI) and electrical resistivity tomography (ERT) were used to image the subsurface throughout two key infiltration/extraction areas of an ARR site in Colorado, USA. The most valuable results came from 2.5D ERT revealing the structural patterns and suggesting the distribution of textural composition of unconsolidated sediments. Geochemical measurements on transects intersecting the geophysical measurements resolved bulk parameters (i.e. total organic carbon, cations, anions) and trace organic contaminants (e.g. trace organic compounds) and were also used to estimate mixing and water travel times and assess the performance of the ARR site regarding water quality and quantity. Our results indicate that the subsurface is highly heterogeneous at our study site and that the coarse-grained sedimentary units, acting as the best conduit for transporting water, are likely discontinuous. The electrical resistivity measurements indicate certain areas of the infiltration basins may have good hydraulic connections to

  5. Isotope geochemistry of waters affected by acid mine drainage in old labour sites (SE, Spain).

    NASA Astrophysics Data System (ADS)

    Pérez-Sirvent, Carmen; Martinez-Sanchez, Maria Jose; Garcia-Lorenzo, Maria Luz; Agudo, Ines; Hernandez-Cordoba, Manuel; Recio, Clemente

    2015-04-01

    The ore deposits of this zone have iron, lead and zinc as the main metal components. Iron is present in oxides, hydroxides, sulfides, sulfates, carbonates, and silicates; lead and zinc occur in sulfides (galena and sphalerite, respectively), carbonates, sulfates, and lead or zinc-bearing (manganese, iron) oxides. Mining started with the Romans and activity peaked in the second half of the 19th century and throughout the 20th century until the 1980's. From 1940 to 1957, mineral concentration was made by froth flotation and, prior to this, by gravimetric techniques. The mining wastes, or tailings, with a very fine particle size were deposited inland (tailings dams) and, since 1957, huge releases were made in directly the sea coast. The objective of this work was to evaluate processes affecting waters from abandoned mine sites by way of stable isotopic analysis, particularly H and O stable isotopes from water and S and O from dissolved sulfates. Several common chemical and physical processes, such as evaporation, water-rock interaction and mixing could alter water isotopic composition. Evaporation, which causes an enrichment in δD and δ18O in the residual water, is an important process in semiarid areas. The results obtained indicate that, for sites near the coast, waters are meteoric, and marine infiltration only takes place in the deepest layers near the shore or if water remains stagnated in sediments with low permeability. The main source of sulfate was the oxidation of sulfides, resulting in the liberation of acid, sulfate and metals. In order to assess the mechanism responsible for sulfide oxidation, the stoichiometric isotope balance model and the general isotope balance model were tested, suggesting that the oxidation via Fe3+ was predominant in the surface, and controlled by A. ferrooxidans, while at depth, sulfate reduction occurred.

  6. Hydrogeology, Aquifer Geochemistry, and Ground-Water Quality in Morgan County, West Virginia

    USGS Publications Warehouse

    Boughton, Carol J.; McCoy, Kurt J.

    2006-01-01

    Private and public wells throughout Morgan County, W. Va., were tested to determine aquifer hydraulic, geochemical, and water-quality characteristics. The entire study area is located in the Valley and Ridge Physiographic Province, a region of complex geologic structure and lithology. Aquifers in the study area are characterized by thin to thick bedded formations with interbedding among the various limestones, shales, sandstones, and siltstones that are folded into a series of steeply dipping north-south trending anticlines and synclines. Zones of ground-water production typically consist of one to two fracture sets, with little to no production from unfractured bedrock matrix. Measurements of transmissivity range from 2 to 1,490 feet squared per day, with the larger transmissivities occurring near bedding contacts and in zones with cross-faulting or jointing. Ground water flows from recharge areas in the uplands to local drainages and to deeper flow systems that appear to be controlled by regional geologic structure. The overall flow direction is from south to north within the study area. Ground water within the study area is predominantly a calcium-bicarbonate type water reflecting contact with carbonate rocks. Sodium-bicarbonate and calcium-magnesium-sulfate end-members also exist, with many samples exhibiting mixing, which may be the result of flow between the differing rock types or within units containing both carbonate rocks and shales. Values of water-quality characteristics that were greater than U.S. Environmental Protection Agency drinking-water standards included radon-222, pH, turbidity, iron, manganese, aluminum, and total- and fecal-coliform and Escherichia coli (E. coli) bacteria. Concentrations of radon-222 were detected in all samples from all units, with the largest concentrations (1,330 and 2,170 picocuries per liter) from the Clinton Formation.

  7. Cryptic Role of Zero-Valent Sulfur in Metal and Metalloid Geochemistry in Euxinic Waters

    NASA Astrophysics Data System (ADS)

    Helz, G. R.

    2014-12-01

    Natural waters that are isolated from the atmosphere in confined aquifers, euxinic basins and sediment pore waters often become sulfidic. These waters are conventionally described simply as reducing environments. But because nature does not constrain their exposure to reducing equivalents (e.g. from organic matter) and oxidizing equivalents (e.g. from Fe,Mn oxides), these reducing environments in fact vary cryptically in their redox characteristics. The implications for trace metal and metalloid cycles are only beginning to be explored. The activity of zero-valent sulfur (aS0), a virtual thermodynamic property, is a potentially useful index for describing this variation. At a particular temperature and ionic strength, aS0 can be quantified from knowledge of pH and the total S(0) to total S(-II) ratio. Although data are incomplete, the deep waters of the Black Sea (aS0 ca. 0.3) appear to be more reducing than the deep waters of the Cariaco Basin (aS0 ca. 0.5) even though both are perennially sulfidic. An apparent manifestation is a greater preponderance of greigite relative to mackinawite in the Cariaco Basin. Interestingly, greigite is stable relative to mackinawite in both basins but predominates only at the higher aS0. Values of aS0 in sulfidic natural waters span the range over which Hg-polysulfide complexes gain predominance over Hg sulfide complexes. Competition between these ligands is thought to influence biological methylation, mercury's route into aquatic and human food chains. In sulfidic deep ground waters, the redox state and consequent mobility of As, a global human hazard, will depend on aS0. At intermediate sulfide concentrations, higher aS0 favors more highly charged and thus less mobile As(V) species relative to As(III) species despite the overall reducing characteristics of such waters. Helz, G.R. (2014) Activity of zero-valent sulfur in sulfidic natural waters. Geochem. Trans. In press.

  8. Hydrology and geochemistry of thermal ground water in southwestern Idaho and north-central Nevada

    USGS Publications Warehouse

    Young, H.W.; Lewis, R.E.

    1980-01-01

    In southwestern Idaho and north-central Nevada, thermal groundwater occurs under artesian conditions in igneous or sedimentary rocks of Tertiary age. Temperatures of the groundwater range from 30 degrees to more than 80 degrees Celsius. Thermal waters are a sodium carbonate or bicarbonate type; nonthermal waters are a calcium bicarbonate. Chemical geothermometers indicate maximum reservoir temperatures near 100 degrees Celsius. Stable-isotope data indicate recharge to the system occurred when climate averaged 3 degrees to 5 degrees Celsius colder than at present; such conditions existed during Holocene glacial advances 3,000 and more than 8,000 years ago. Residence time calculated on the basis of reservoir volume and thermal-water discharge is 3,400 to 6,800 years. Considering estimates of heat flux in and heat discharged by conduction and convection, about 25.0 cubic feet per second, or about 18,000 acre-feet per year, of 50 degrees Celsius water is required to transport excess heat from the system advectively in groundwater. The conceptual model is one where water has circulated thousands, even tens of thousands, of years. Within model constraints, reservoir thermal energy for this geothermal system is 130x10 to the 18th power calories. (USGS)

  9. Implications of formation water movement based on isotopic data and elemental geochemistry, southwestern Ontario

    SciTech Connect

    Frape, S.K.; Dollar, P.; Fritz, P.; Travail, R.A.; McNutt, R.H.; MacQueen, R.W.

    1986-08-01

    Formation waters in Paleozoic sediments analyzed for /sup 2/H, /sup 18/O, /sup 87/Sr//sup 86/Sr, tritium, and major/minor contents show the following. (1) The stable isotope contents are typical for formation brines, but have /sup 18/O and /sup 2/H values that group according to formation age, with waters in Cambrian strata being most depleted; and the most concentrated brines do not compare well to known Michigan basin brines. Many waters are Ca-Na-Cl brines similar to typical Canadian shield brines, although the origin of the various chemical species may be masked by intense rock-water interaction. (2) The /sup 87/Sr//sup 86/Sr values for Cambrian brines range from 0.7095 to 0.7102. In one detailed study, the brine and calcite cement had the same value (0.7095), which is slightly higher than Cambrian seawater (0.7091-0.7092), and indicates that the cement precipitated from the brine during diagenesis. The reservoir rock has a /sup 87/Sr//sup 86/Sr value of 0.7330, indicating little or no water/rock exchange. Sr isotopic values for Ordovician brines range from 0.7095 to 0.7103, which is higher than Ordovician seawater (0.7085). In contrast, the Silurian Salina Formation brines and Silurian seawater values are the same (0.7085-0.7087). Despite an active tectonic history, causing considerable faulting and movement within Paleozoic and Precambrian rock strata, the isotopic results for the Cambrian indicate isotopic equilibrium between brine and cement; therefore, these formation waters have not moved since the calcite formed.

  10. Effects of acid mine effluent on sediment and water geochemistry, Ruttan Cu-Zn mine

    USGS Publications Warehouse

    Shilts, W.W.

    1996-01-01

    Waters were collected from the surface and bottom of four lakes as well as from the Churchill River and approximately 20 small ponds beside the Leaf Rapids-Ruttan mine-South Indian Lake road to determine geochemical variations related to tailings and waste rock disposal from the Ruttan Cu-Zn VHMS deposit. Using sonar profiling as a guide, grab samples and cores of sediments were also collected in Ruttan, Brehaut, Rusty, and Alto lakes to investigate the geochemical and sedimentological effects of liming the acid (pH 2.5) outflow from Ruttan Lake. Preliminary results indicate that metals anthropogenically enriched in Ruttan Lake (Zn, Cd, and Hg in particular) are scavenged and precipitated at the inflow end of Brehaut Lake as a result of adding lime solutions to the Vermilion River, midway through the 500 m reach that connects Ruttan Lake and Brehaut Lake. Zn in Ruttan Lake water (up to 17 ppm) is precipitated in the limey sediment. Zn is not enriched in waters of Rusty Lake, the next lake downstream from Brehaut Lake. Rusty Lake has Zn concentrations comparable to background water from Alto Lake (<10 ppb Zn). At present, liming appears to be controlling metal migration effectively, but a body of Zn-Cd-Hg-rich carbonate precipitate occupies the south end of Brehaut Lake which, without liming, would be receiving water of pH 2.5 from Ruttan Lake, resulting in a remobilization of metals. The related study also showed that Zn concentrations are elevated in water in contact with waste rock used to upgrade sections of the Leaf Rapids-South Indian Lake and Brehaut Lake roads.

  11. Ground-Water Geochemistry of Kwajalein Island, Republic of the Marshall Islands, 1991

    USGS Publications Warehouse

    Tribble, Gordon W.

    1997-01-01

    Ground water on Kwajalein Island is an important source of drinking water, particularly during periods of low rainfall. Fresh ground water is found as a thin lens underlain by saltwater. The concentration of dissolved ions increases with depth below the water table and proximity to the shoreline as high-salinity seawater mixes with fresh ground water. The maximum depth of the freshwater lens is 37 ft. Chloride is assumed to be non-reactive under the range of geochemical conditions on the atoll. The concentration of chloride thus is used as a conservative constituent to evaluate freshwater-saltwater mixing within the aquifer. Concentrations of sodium and for the most part, potassium and sulfate, also appear to be determined by conservative mixing between saltwater and rain. Concentrations of calcium, magnesium, and strontium are higher than expected from conservative mixing; these higher concentrations are a result of the dissolution of carbonate minerals. An excess in dissolved inorganic carbon results from carbonate-mineral dissolution and from the oxidation of organic matter in the aquifer; the stoichiometric difference between excess dissolved inorganic carbon and excess bivalent cations is used as a measure of the amount of organic-matter oxidation. Organic-matter oxidation also is indicated by the low concentration of dissolved oxygen, high concentrations of nutrients, and the presence of hydrogen sulfide in many of the water samples. Low levels of dissolved oxygen indicate oxic respiration, and sulfate reduction is indicated by hydrogen sulfide. The amount of dissolved inorganic carbon released during organic-matter oxidation is nearly equivalent to the amount of carbonate-mineral dissolution. Organic-matter oxidation and carbonate-mineral dissolution seem to be most active either in the unsaturated zone or near the top of the water table. The most plausible explanation is that high amounts of oxic respiration in the unsaturated zone generate carbon dioxide

  12. Geohydrology and ground-water geochemistry at a sub-arctic landfill, Fairbanks, Alaska

    USGS Publications Warehouse

    Downey, J.S.

    1990-01-01

    The Fairbanks-North Star Borough, Alaska, landfill is located on silt, sand, and gravel deposits of the Tanana River flood plain, about 3 miles south of the city of Fairbanks water supply wells. The landfill has been in operation for about 25 years in this sub-arctic region of discontinuous permafrost. The cold climate limits biological activity within the landfill with corresponding low gas and leachate production. Chloride concentrations, specific conductance, water temperature, and earth conductivity measurements indicate a small plume of leachate flowing to the northwest from the landfill. The leachate remains near the water table as it flows northwestward toward a drainage ditch. Results of computer modeling of this local hydrologic system indicate that some of the leachate may be discharging to the ditch. Chemical data show that higher-than-background concentrations of several ions are present in the plume. However, the concentrations appear to be reduced to background levels within a short distance along the path of groundwater flow from the landfill, and thus the leachate is not expected to affect the water supply wells. (USGS)

  13. Water-rock interaction and geochemistry of groundwater from the Ain Azel aquifer, Algeria.

    PubMed

    Belkhiri, Lazhar; Mouni, Lotfi; Tiri, Ammar

    2012-02-01

    Hydrochemical, multivariate statistical, and inverse geochemical modeling techniques were used to investigate the hydrochemical evolution within the Ain Azel aquifer, Algeria. Cluster analysis based on major ion contents defined 3 main chemical water types, reflecting different hydrochemical processes. The first group water, group 1, has low salinity (mean EC = 735 μS/cm). The second group waters are classified as Cl-HCO(3)-alkaline earth type. The third group is made up of water samples, the cation composition of which is dominated by Ca and Mg with anion composition varying from dominantly Cl to dominantly HCO(3) plus SO(4). The varifactors obtained from R-mode FA indicate that the parameters responsible for groundwater quality variations are mainly related to the presence and dissolution of some carbonate, silicate, and evaporite minerals in the aquifer. Inverse geochemical modeling along groundwater flow paths indicates the dominant processes are the consumption of CO(2), the dissolution of dolomite, gypsum, and halite, along with the precipitation of calcite, Ca-montmorillonite, illite, kaolinite, and quartz.

  14. Occurrence and Geochemistry of Polonium-210 in Ground Water, Lahontan Valley, Nevada

    NASA Astrophysics Data System (ADS)

    Seiler, R. L.

    2008-12-01

    Substantially more gross alpha radioactivity than could be explained by the presence of uranium led to the discovery of polonium-210 in numerous domestic wells in Lahontan Valley, Nevada. Polonium-210 activities in water from 30 domestic wells ranged from <1 mBq/L to 2,800±95 mBq/L, with a median activity of 350 mBq/L. The source of the polonium is radioactive decay of uranium in sediments eroded from granitic rocks in the Sierra Nevada that has been transported into the valley. In the United States, polonium-210 activities greater than these have been reported for only a few wells in Florida and one well in Louisiana. Polonium-210 activities in ground water rarely exceed about 40 mBq/L because it strongly binds to sediments. On-going research in Lahontan Valley is aimed at identifying the biological and geological factors responsible for mobilization of the polonium. Preliminary results indicate that elevated polonium-210 activities (>400 mBq/L) are associated with anoxic (DO <0.1 mg/L), high pH (>8.5) water. Iron, but not manganese, increases monotonically with polonium. δ34SSO4 values indicate that sulfate reduction has occurred in all of the wells with elevated polonium-210 activities. However, sulfide concentrations were low (≤0.02 mg/L) in all but one well containing >130 mBq/L of polonium-210. This is consistent with previous investigations which have shown that polonium-210 is mobilized by sulfate- reducing bacteria and can remain in solution as long as sulfides do not accumulate. The polonium-210 in the water is not supported by lead-210. In Lahontan Valley ground water, uranium, radon, and polonium are the only significant alpha emitters. Radon and polonium activities are not statistically correlated and wells with elevated polonium-210 activities almost always have uranium concentrations <3 μg/L.

  15. Geochemistry and source waters of rock glacier outflow, Colorado Front Range

    USGS Publications Warehouse

    Williams, M.W.; Knauf, M.; Caine, N.; Liu, F.; Verplanck, P.L.

    2006-01-01

    We characterize the seasonal variation in the geochemical and isotopic content of the outflow of the Green Lake 5 rock glacier (RG5), located in the Green Lakes Valley of the Colorado Front Range, USA. Between June and August, the geochemical content of rock glacier outflow does not appear to differ substantially from that of other surface waters in the Green Lakes Valley. Thus, for this alpine ecosystem at this time of year there does not appear to be large differences in water quality among rock glacier outflow, glacier and blockslope discharge, and discharge from small alpine catchments. However, in September concentrations of Mg2+ in the outflow of the rock glacier increased to more than 900 ??eq L-1 compared to values of less than 40 ??eq L-1 at all the other sites, concentrations of Ca2+ were greater than 4,000 ??eq L-1 compared to maximum values of less than 200 ??eq L-1 at all other sites, and concentrations of SO42- reached 7,000 ??eq L-1, compared to maximum concentrations below 120 ??eq L-1 at the other sites. Inverse geochemical modelling suggests that dissolution of pyrite, epidote, chlorite and minor calcite as well as the precipitation of silica and goethite best explain these elevated concentrations of solutes in the outflow of the rock glacier. Three component hydrograph separation using end-member mixing analysis shows that melted snow comprised an average of 30% of RG5 outflow, soil water 32%, and base flow 38%. Snow was the dominant source water in June, soil water was the dominant water source in July, and base flow was the dominant source in September. Enrichment of ?? 18O from - 10??? in the outflow of the rock glacier compared to -20??? in snow and enrichment of deuterium excess from +17.5??? in rock glacier outflow compared to +11??? in snow, suggests that melt of internal ice that had undergone multiple melt/freeze episodes was the dominant source of base flow. Copyright ?? 2005 John Wiley & Sons, Ltd.

  16. Geochemistry and Hydrogeology of Water-Filled Sinkholes at Bitter Lake NWR, Roswell, NM

    NASA Astrophysics Data System (ADS)

    Premo, Z. E.; Crossey, L. J.

    2008-12-01

    Bitter Lake NWR in southeast (Roswell) New Mexico is located at the convergence of the Pecos River and the surface discharge region in the Roswell Artesian Basin (shallow alluvial aquifer and carbonate aquifer). The Refuge hosts approximately 50 water-filled sinkholes, which each support a unique and diverse aquatic ecosystem. An initial survey of water chemistries indicates that each sink has a unique chemical identity and neutral to alkaline pH. Sinkholes are filled by one or more artesian springs, groundwater seepage and possible hydrothermal water sources. We present results of water and gas analyses of 10 representative sinkholes, sampled during spring and summer, 2008. Analytical results, including major ions, metals (arsenic, selenium, iron), and gas chemistries are compared with monitoring well data from wells found to the north of the Refuge, along the Pecos River, and to the west, along the Pecos Slope - the regional aquifer recharge area. Well samples representative of regional groundwater provide potential end member perspectives for sources of sinkhole waters. Samples were collected incrementally from the surface to sinkhole floor to profile the limnological structure and to assess chemical variation and mixing through the water column. A sonde was deployed to measure and record physical parameters. Results of the analysis are used to describe the geochemical mixing that is occurring within the sinks. As each sink behaves as an independent unit, those separated by less than 10 meters can have dramatic variability in chemical signature and biological influence. For example, among the 29 sinks sampled during the initital survey, chloride concentrations range from 1.912x10-3 to 1.405 mol/kg; sulfate from 7.204x10-4 to 0.1364 mol/kg; and fluoride from 3.579x10-4 to 3.453x10-3 mol/kg. Along the Pecos Slope, groundwater chloride concentrations increase from less than 1.410x10-3 mol/kg near the major recharge area in the Sacramento Mountains to 0.141 mol

  17. Uranium-thorium isotope geochemistry of saline ground waters from central Missouri

    SciTech Connect

    Banner, J.L.; Chen, J.H.; Wasserburg, G.J.

    1989-03-01

    The isotopic and elemental distributions of uranium and thorium were examined in a suite of saline ground waters from central Missouri using mass spectrometric techniques. The waters were sampled from natural springs and artesian wells in Mississippian and Ordovician aquifers and have a wide range in salinity (5 to 26 /per thousand/), deltaD (/minus/108 to /minus/45 /per thousand/), and delta/sup 18/O (/minus/14.7 to /minus/6.5 /per thousand/) values. The suite of samples has a large range in /sup 238/U (50 to 200 x 10/sup /minus/12/g/g) and /sup 232/Th (0.3 to 9.1 x 10/sup /minus/12/g/g) concentrations and extremely high /sup 234/U//sup 238/U activity ratios ranging from 2.15 to 16.0. These isotopic compositions represent pronounced uranium-series disequilibrium compared with the value of modern seawater (1.15) or the equilibrium value (1.00). For such /sup 234/U-enriched waters, /sup 234/U//sup 238/U isotope ratios can be determined with a precision of /+-/ 10 /per thousand/ (2sigma) on 10 mL of sample and less than /+-/5 /per thousand/ on 100 mL. In contrast to the large /sup 234/U enrichments, /sup 230/Th//sup 238/U activity ratios in the ground waters are significantly lower than the equilibrium value. The more saline samples have markedly higher /sup 234/U//sup 238/U activity ratios and lower deltaD and delta/sup 18/O values. Unfiltered and filtered (< 0.1 ..mu..m) aliquots of a saline sample have the same isotopic composition and concentration of uranium, indicating uranium essentially occurs entirely as a dissolved species. The filtered/unfiltered concentration ratio for thorium in this sample is 0.29, demonstrating the predominant association of thorium with particulates.

  18. Gas and water geochemistry of geothermal systems in Dominica, Lesser Antilles island arc

    NASA Astrophysics Data System (ADS)

    Joseph, Erouscilla P.; Fournier, Nicolas; Lindsay, Jan M.; Fischer, Tobias P.

    2011-09-01

    Four of the nine potentially active volcanoes on the island of Dominica in the Lesser Antilles volcanic island arc have associated active volcanic-hydrothermal systems. Between 2000 and 2006 the gas and thermal waters from these systems were investigated to geochemically characterise the fluids, gain insight into the temperature and equilibrium state of the underlying reservoirs, and evaluate the feasibility of monitoring geothermal features as a volcano surveillance tool in Dominica. The geothermal gases are typical of those found in arc-type settings, with N 2 excess and low amounts of He and Ar. The dry gas is dominated by CO 2 (ranging from 492 to 993 mmol/mol), and has a hydrothermal signature with hydrogen sulphide as the main sulphurous gas. The waters are predominantly acid-sulphate (SO 4 = 100-4200 mg/L, pH ≤ 4), and likely formed as a result of dilution of acidic gases in near surface oxygenated groundwater. Enrichment in both δ 18O and δD with respect to the global meteoric water line (GMWL) confirms that the waters are of primarily meteoric origin, but have been affected by evaporation processes. Quartz geothermometers gave equilibrium temperatures of 83 °C-203 °C. These temperatures contrast with the higher equilibrium temperature ranges (170 °C-350 °C) obtained for the gases using the H 2/Ar*-CH 4/CO 2 gas ratios plot, suggesting that the quartz geothermometers are affected by non-attainment of equilibrium. This may be a result of precipitation of the dissolved silica and/or dilution by relatively cold shallow aquifers of the thermal fluids. Generally, no significant variations in fluid gas chemistry of the hydrothermal systems were observed during the study period, and we propose that there were no changes in the state of volcanic activity in this period. One exception to this occurred in a feature known as the Boiling Lake, which underwent a month-long period of significant compositional, temperature and water level fluctuations ascribed to

  19. Fluoride geochemistry of thermal waters in Yellowstone National Park: I. Aqueous fluoride speciation

    USGS Publications Warehouse

    Deng, Y.; Nordstrom, D.K.; Blaine, McCleskey R.

    2011-01-01

    Thermal water samples from Yellowstone National Park (YNP) have a wide range of pH (1-10), temperature, and high concentrations of fluoride (up to 50mg/l). High fluoride concentrations are found in waters with field pH higher than 6 (except those in Crater Hills) and temperatures higher than 50??C based on data from more than 750 water samples covering most thermal areas in YNP from 1975 to 2008. In this study, more than 140 water samples from YNP collected in 2006-2009 were analyzed for free-fluoride activity by ion-selective electrode (ISE) method as an independent check on the reliability of fluoride speciation calculations. The free to total fluoride concentration ratio ranged from <1% at low pH values to >99% at high pH. The wide range in fluoride activity can be explained by strong complexing with H+ and Al3+ under acidic conditions and lack of complexing under basic conditions. Differences between the free-fluoride activities calculated with the WATEQ4F code and those measured by ISE were within 0.3-30% for more than 90% of samples at or above 10-6 molar, providing corroboration for chemical speciation models for a wide range of pH and chemistry of YNP thermal waters. Calculated speciation results show that free fluoride, F-, and major complexes (HF(aq)0, AlF2+, AlF2+ and AlF30) account for more than 95% of total fluoride. Occasionally, some complex species like AlF4-, FeF2+, FeF2+, MgF+ and BF2(OH)2- may comprise 1-10% when the concentrations of the appropriate components are high. According to the simulation results by PHREEQC and calculated results, the ratio of main fluoride species to total fluoride varies as a function of pH and the concentrations and ratios of F and Al. ?? 2011.

  20. Cr(VI) occurrence and geochemistry in water from public-supply wells in California

    USGS Publications Warehouse

    Izbicki, John; Wright, Michael; Seymour, Whitney A.; McCleskey, R. Blaine; Fram, Miranda S.; Belitz, Kenneth; Esser, Bradley K.

    2015-01-01

    Hexavalent chromium, Cr(VI), in 918 wells sampled throughout California between 2004 and 2012 by the Groundwater Ambient Monitoring and Assessment-Priority Basin Project (GAMA-PBP) ranged from less than the study reporting limit of 1 microgram per liter (μg/L) to 32 μg/L. Statewide, Cr(VI) was reported in 31 percent of wells and equaled or exceeded the recently established (2014) California Maximum Contaminant Level (MCL) for Cr(VI) of 10 μg/L in 4 percent of wells. Cr(VI) data collected for regulatory purposes overestimated Cr(VI) occurrence compared to spatially-distributed GAMA-PBP data. Ninety percent of chromium was present as Cr(VI), which was detected more frequently and at higher concentrations in alkaline (pH ≥ 8), oxic water; and more frequently in agricultural and urban land uses compared to native land uses. Chemical, isotopic (tritium and carbon-14), and noble-gas data show high Cr(VI) in water from wells in alluvial aquifers in the southern California deserts result from long groundwater-residence times and geochemical reactions such as silicate weathering that increase pH, while oxic conditions persist. High Cr(VI) in water from wells in alluvial aquifers along the west-side of the Central Valley results from high-chromium in source rock eroded to form those aquifers, and areal recharge processes (including irrigation return) that can mobilize chromium from the unsaturated zone. Cr(VI) co-occurred with oxyanions having similar chemistry, including vanadium, selenium, and uranium. Cr(VI) was positively correlated with nitrate, consistent with increased concentrations in areas of agricultural land use and mobilization of chromium from the unsaturated zone by irrigation return.

  1. Cr(VI) Occurrence and Geochemistry in Water From Public-Supply Wells in California

    SciTech Connect

    Izbicki, John A.; Wright, Michael T.; Seymour, Whitney A.; McCleskey, R. Blaine; Fram, Miranda S.; Belitz, Kenneth; Esser, Bradley K.

    2015-08-18

    Hexavalent chromium, Cr(VI), in 918 wells sampled throughout California between 2004 and 2012 by the Groundwater Ambient Monitoring and Assessment Program—Priority Basin Project (GAMA—PBP) ranged from less than the study reporting limit (SRL) of 1 microgram per liter (μg/L) to 32 μg/L. Statewide, Cr(VI) was reported in 31 percent of sampled wells and equaled or exceeded the recently established (2014) California Maximum Contaminant Level (MCL) for Cr(VI) of 10 μg/L in 4 percent of sampled wells. Cr(VI) data collected for regulatory purposes overestimate Cr(VI) occurrence. Ninety percent of chromium was present as Cr(VI), which was detected more frequently and at higher concentrations in alkaline (pH > 8), oxic water, and more frequently in agricultural and urban land uses compared to native land uses. Chemical, isotopic (tritium and carbon-14), and noble-gas data show high Cr(VI) in water from wells in alluvial aquifers in the southern California deserts result from long groundwater-residence times and geochemical reactions such as silicate weathering that increase pH, while oxic conditions persist. High Cr(VI) in water from wells in alluvial aquifers along the west-side of the Central Valley results from high-chromium abundance in source rock eroded to form those aquifers, and areal recharge processes (including irrigation return) that mobilize chromium from the unsaturated zone. Cr(VI) co-occurred with oxyanions having similar chemistry, including vanadium, selenium, and uranium. Cr(VI) was positively correlated with nitrate, consistent with increased concentrations in areas of agricultural land use and mobilization of chromium from the unsaturated zone by irrigation return.

  2. Cr(VI) Occurrence and Geochemistry in Water From Public-Supply Wells in California

    DOE PAGES

    Izbicki, John A.; Wright, Michael T.; Seymour, Whitney A.; McCleskey, R. Blaine; Fram, Miranda S.; Belitz, Kenneth; Esser, Bradley K.

    2015-08-18

    Hexavalent chromium, Cr(VI), in 918 wells sampled throughout California between 2004 and 2012 by the Groundwater Ambient Monitoring and Assessment Program—Priority Basin Project (GAMA—PBP) ranged from less than the study reporting limit (SRL) of 1 microgram per liter (μg/L) to 32 μg/L. Statewide, Cr(VI) was reported in 31 percent of sampled wells and equaled or exceeded the recently established (2014) California Maximum Contaminant Level (MCL) for Cr(VI) of 10 μg/L in 4 percent of sampled wells. Cr(VI) data collected for regulatory purposes overestimate Cr(VI) occurrence. Ninety percent of chromium was present as Cr(VI), which was detected more frequently and atmore » higher concentrations in alkaline (pH > 8), oxic water, and more frequently in agricultural and urban land uses compared to native land uses. Chemical, isotopic (tritium and carbon-14), and noble-gas data show high Cr(VI) in water from wells in alluvial aquifers in the southern California deserts result from long groundwater-residence times and geochemical reactions such as silicate weathering that increase pH, while oxic conditions persist. High Cr(VI) in water from wells in alluvial aquifers along the west-side of the Central Valley results from high-chromium abundance in source rock eroded to form those aquifers, and areal recharge processes (including irrigation return) that mobilize chromium from the unsaturated zone. Cr(VI) co-occurred with oxyanions having similar chemistry, including vanadium, selenium, and uranium. Cr(VI) was positively correlated with nitrate, consistent with increased concentrations in areas of agricultural land use and mobilization of chromium from the unsaturated zone by irrigation return.« less

  3. Geochemistry of summit fumarole vapors and flanking thermal/mineral waters at Popocatepetl Volcano, Mexico

    SciTech Connect

    Werner, C.; Goff, F.; Janik, C.J.

    1997-06-01

    Popocatepetl Volcano is potentially devastating to populations living in the greater Mexico City area. Systematic monitoring of fumarole gases and flanking thermal/mineral springs began in early 1994 after increased fumarolic and seismic activity were noticed in 1991. These investigations had two major objectives: (1) to determine if changes in magmatic conditions beneath Popocatepetl might be reflected by chemical changes in fumarolic discharges and (2) to determine if thermal/mineral spring waters in the vicinity of Popocatepetl are geochemically related to or influences by the magmatic system. This report summarizes results from these two discrete studies.

  4. Mineralogy and geochemistry of efflorescent minerals on mine tailings and their potential impact on water chemistry.

    PubMed

    Grover, B P C; Johnson, R H; Billing, D G; Weiersbye, I M G; Tutu, H

    2016-04-01

    In the gold mining Witwatersrand Basin of South Africa, efflorescent mineral crusts are a common occurrence on and nearby tailings dumps during the dry season. The crusts are readily soluble and generate acidic, metal- and sulphate-rich solutions on dissolution. In this study, the metal content of efflorescent crusts at an abandoned gold mine tailings dump was used to characterise surface and groundwater discharges from the site. Geochemical modelling of the pH of the solution resulting from the dissolution of the crusts was used to better understand the crusts' potential impact on water chemistry. The study involved two approaches: (i) conducting leaching experiments on oxidised and unoxidised tailings using artificial rainwater and dilute sulphuric acid and correlating the composition of crusts to these leachates and (ii) modelling the dissolution of the crusts in order to gain insight into their mineralogy and their potential impact on receiving waters. The findings suggested that there were two chemically distinct discharges from the site, namely an aluminium- and magnesium-rich surface water plume and an iron-rich groundwater plume. The first plume was observed to originate from the oxidised tailings following leaching with rainwater while the second plume originated from the underlying unoxidised tailings with leaching by sulphuric acid. Both groups of minerals forming from the respective plumes were found to significantly lower the pH of the receiving water with simulations of their dissolution found to be within 0.2 pH units of experimental values. It was observed that metals in a low abundance within the crust (for example, iron) had a stronger influence on the pH of the resulting solutions than metals in a greater abundance (aluminium or magnesium). Techniques such as powder X-ray diffraction (PXRD) and in situ mineral determination techniques such as remote sensing can effectively determine the dominant mineralogy. However, the minerals or metals

  5. Helium and neon isotope geochemistry of some ground waters from the Canadian Precambrian Shield

    NASA Astrophysics Data System (ADS)

    Bottomley, D. J.; Ross, J. D.; Clarke, W. B.

    1984-10-01

    Ground waters in a Precambrian granitic batholith at the Whiteshell Nuclear Research Establishment (WNRE) in Pinawa, Manitoba contain between 5 × 10 -5 and 10 -1 cc STP/g H 2O of radiogenic helium-4 but have relatively uniform 3He/ 4He ratios of between 0.6 × 10 -8 and 2.3 × 10 3. The highest helium samples also contain radiogenic 21,22Ne produced by (α, n) or ( n,α) reactions with other isotopes. As much as 1.8 × 10 -9ccSTP/ gH2O of excess 21Ne and 3.8 × 10 -9ccSTP/ gH2O of excess 22Ne have been measured. Helium and 21Ne ages of these ground waters, calculated on the basis of known crustal production rates of 4He and 21Ne, are unreasonably high (up to 2 × 10 5 years) and incompatible with the 14C ages and other isotopic and hydrogeologic data. Uranium enrichment in the flow porosity of the granite may dominate 4He and 21,22Ne production in this granite and mask the contributions from more typical U and Th concentrations in the rock matrix. At the Chalk River Nuclear Laboratories in Ontario helium concentrations in ground waters in a Precambrian monzonitic gneiss range from 1.5 × 10 -7 to 8.7 × 10 -4ccSTP/ gH2O with the 3He/ 4He ratios ranging from 2.0 × 10 -3 to 1.5 × 10 -7. The highest helium concentrations may be attributable to the presence of a thick uraniferous pegmatite vein and yield helium ages more than two orders of magnitude higher than the 14C ages. Application of He age dating equations to ground waters from Precambrian granitic rocks requires knowledge of the nature of uranium and thorium enrichment in the subsurface in order to select appropriate values for porosity and uranium and thorium concentration in the rock.

  6. Mineralogy and geochemistry of efflorescent minerals on mine tailings and their potential impact on water chemistry.

    PubMed

    Grover, B P C; Johnson, R H; Billing, D G; Weiersbye, I M G; Tutu, H

    2016-04-01

    In the gold mining Witwatersrand Basin of South Africa, efflorescent mineral crusts are a common occurrence on and nearby tailings dumps during the dry season. The crusts are readily soluble and generate acidic, metal- and sulphate-rich solutions on dissolution. In this study, the metal content of efflorescent crusts at an abandoned gold mine tailings dump was used to characterise surface and groundwater discharges from the site. Geochemical modelling of the pH of the solution resulting from the dissolution of the crusts was used to better understand the crusts' potential impact on water chemistry. The study involved two approaches: (i) conducting leaching experiments on oxidised and unoxidised tailings using artificial rainwater and dilute sulphuric acid and correlating the composition of crusts to these leachates and (ii) modelling the dissolution of the crusts in order to gain insight into their mineralogy and their potential impact on receiving waters. The findings suggested that there were two chemically distinct discharges from the site, namely an aluminium- and magnesium-rich surface water plume and an iron-rich groundwater plume. The first plume was observed to originate from the oxidised tailings following leaching with rainwater while the second plume originated from the underlying unoxidised tailings with leaching by sulphuric acid. Both groups of minerals forming from the respective plumes were found to significantly lower the pH of the receiving water with simulations of their dissolution found to be within 0.2 pH units of experimental values. It was observed that metals in a low abundance within the crust (for example, iron) had a stronger influence on the pH of the resulting solutions than metals in a greater abundance (aluminium or magnesium). Techniques such as powder X-ray diffraction (PXRD) and in situ mineral determination techniques such as remote sensing can effectively determine the dominant mineralogy. However, the minerals or metals

  7. Integration of ground-water and vadose-zone geochemistry to investigate hydrochemical evolution

    SciTech Connect

    Fisher, R.S.; Mullican, W.F.

    1990-01-01

    This paper summarizes the results of an extensive groundwater-sampling program conducted in the Hueco Bolson and Diablo Plateau area of West Texas. The origin, hydrochemical evolution, and age of groundwater in arid lands of Trans-Pecos Texas were investigated by combining mineralogic analyses of soils and aquifer matrix, chemical analyses of readily soluble materials in soils and water extracted from the thick, unsaturated zone, and chemical and isotopic analyses of groundwater from three principal aquifers, the Diablo Plateau, Hueco Bolson, and Rio Grande alluvial aquifers. Repeated groundwater sampling over a 3-year period and quarterly sampling of selected wells revealed no significant short-term chemical or isotopic variability. Groundwater ages range from recent to nearly 28,000 years; the distribution of ages reflects relative permeability (transmissivity) of the aquifers. Most groundwaters evolve from calcium-bicarbonate to sodium-sulfate types because of carbonate and sulfate mineral dissolution coupled with exchange of aqueous calcium and magnesium for sodium on clay minerals. Water in the Rio Grande alluvial aquifer evolved to a sodium-chloride type as a result of extensive evapotranspiration on irrigated fields. The appendices list detailed results of field measurements of temperature, pH, Eh, dissolved oxygen, and major ion concentrations.

  8. Water and gas geochemistry of the Calatrava Volcanic Province (CVP) hydrothermal system (Ciudad Real, central Spain)

    NASA Astrophysics Data System (ADS)

    Vaselli, Orlando; Nisi, Barbara; Tassi, Franco; Giannini, Luciano; Grandia, Fidel; Darrah, Tom; Capecchiacci, Francesco; del Villar, Pèrez

    2013-04-01

    An extensive geochemical and isotopic investigation was carried out in the water and gas discharges of the Late Miocene-Quaternary Calatrava Volcanic Province (CVP) (Ciudad Real, Spain) with the aim reconstruct the fluid circulation in the area. CVP consists of a series of scattered (monogenetic) vents from where alkaline lava flows and pyroclastic deposits formed in two different periods. The first stage (8.7-6.4 Ma) mainly included ultra-potassic mafic extrusives, whilst the second stage (4.7-1.75 Ma) prevalently originated alkaline and ultra-alkaline volcanics. Both stages were followed by a volcanic activity that extended up to 1.3 and 0.7 Ma, respectively. This area can likely be regarded as one of the most important emitting zones of CO2 in the whole Peninsular Spain along with that of Selva-Emporda in northeastern Spain (Cataluña) and it can be assumed as one of the best examples of natural analogues of CO2 leakages in Spain. This latter aspect is further evidenced by the relatively common water-gas blast events that characterize the CCVF. In the last few years the presence of a CO2-pressurized reservoir at a relatively shallow level as indeed caused several small-sized explosion particularly during the drilling of domestic wells. The fluid discharging sites are apparently aligned along well-defined directions: NW-SE and NNW-SSE and subordinately, ENE-WSW, indicating a clear relationship between the thermal discharges and the volcanic centers that also distribute along these lineaments. The CVP waters are mostly hypothermal (up to 33 °C) and are generally Mg(Ca)-HCO3 in composition and occasionally show relatively high concentrations of Fe and Mn, with pH and electrical conductivity down to 5.5 and up to 6.5 mS/cm, respectively. The oxygen and hydrogen isotopes suggest a meteoric origin for these waters. The mantle source of these volcanic products is apparently preserved in the many CO2-rich (up to 990,000 mmol/mol) gas discharges that characterize CVP

  9. Hydrogeologic framework and geochemistry of the Edwards aquifer saline-water zone, south-central Texas

    USGS Publications Warehouse

    Groschen, George E.; Buszka, Paul M.

    1997-01-01

    Estimated in-place temperature of the samples collected indicates an increase with depth and (or) distance from the downdip limit of freshwater. The pH of the samples decreases with increasing distance from the downdip limit of freshwater, but the decrease is caused partly by the increase in temperature. Dissolved major ions and dissolved solids concentrations all indicate a progressive but monotonic increase in salinity from updip to downdip. The alkalinity of the water samples is predominantly bicarbonate because the low-molecular weight aliphatic-acid anion concentrations are small relative to the bicarbonate concentrations. The dissolved organic carbon concentrations also are lower than expected for an aquifer with economic amounts of oil and gas hydrocarbons.

  10. Organic geochemistry of deep ground waters from the Palo Duro Basin, Texas: implications for radionuclide complexation, ground-water origin, and petroleum exploration

    SciTech Connect

    Means, J.L.; Hubbard, N.J.

    1985-05-01

    This report describes the organic geochemistry of 11 ground-water samples from the Palo Duro Basin, Texas and discusses the implications of their organic geochemical compositions in terms of radionuclide complexation, ground-water origin, and the petroleum potential of two candidate repository sites in Deaf Smith and Swisher Counties. Short-chain aliphatic acid anions are the principal organic constituents present. Stability constant data and simple chemical equilibria calculations suggest that short-chain aliphatic acids are relatively weak complexing agents. The extent of complexation of a typical actinide by selected inorganic ligands present in these brines is expected to far outweigh actinide complexation by the aliphatic acid anions. Various lines of evidence suggest that some portion of the bromide concentrations in the brines is derived from the same source as the short-chain aliphatic acid anions. When the postulated organic components are subtracted from total bromide concentrations, the origins of the Palo Duro brines, based on chloride versus bromide relationships, appear largely consistent with origins based on isotopic evidence. The short-chain aliphatic acid anion content of the Palo Duro brines is postulated to have been much greater in the geologic past. Aliphatic acid anions are but one of numerous petroleum proximity indicators, which consistently suggest a greater petroleum exploration potential for the area surrounding the Swisher County site than the region encompassing the candidate site in Deaf Smith County. Short-chain aliphatic acid anions appear to provide a useful petroleum exploration tool as long as the complex reactions that may dimish their concentrations in ground water are recognized. 71 refs., 10 figs., 10 tabs.

  11. World water dynamics: global modeling of water resources.

    PubMed

    Simonovic, Slobodan P

    2002-11-01

    The growing scarcity of fresh and clean water is among the most important issues facing civilization in the 21st century. Despite the growing attention to a chronic, pernicious crisis in world's water resources our ability to correctly assess and predict global water availability, use and balance is still quite limited. An attempt is documented here in modeling global world water resources using system dynamics approach. Water resources sector (quantity and quality) is integrated with five sectors that drive industrial growth: population; agriculture; economy; nonrenewable resources; and persistent pollution. WorldWater model is developed on the basis of the last version of World3 model. Simulations of world water dynamics with WorldWater indicate that there is a strong relationship between the world water resources and future industrial growth of the world. It is also shown that the water pollution is the most important future water issue on the global level. PMID:12448404

  12. Spatial and temporal dynamics of sediment in contrasted mountainous watersheds (Mexican transvolcanic belt and French Southern Alps) combining river gauging, elemental geochemistry and fallout radionuclides

    NASA Astrophysics Data System (ADS)

    Evrard, O.; Navratil, O.; Gratiot, N.; Némery, J.; Duvert, C.; Ayrault, S.; Lefèvre, I.; Legout, C.; Bonté, P.; Esteves, M.

    2009-12-01

    In mountainous environments, an excessive fine sediment supply to the rivers typically leads to an increase in water turbidity, contaminant transport and a rapid filling of reservoirs. This situation is particularly problematic in regions where water reservoirs are used to provide drinking water to large cities (e.g. in central Mexico) or where stream water is used to run hydroelectric power plants (e.g. in the French Southern Alps). In such areas, sediment source areas first need to be delineated and sediment fluxes between hillslopes and the river system must be better understood before implementing efficient erosion control measures. In this context, the STREAMS (« Sediment Transport and Erosion Across MountainS ») project funded by the French National Research Agency (ANR) aims at understanding the spatial and temporal dynamics of sediment at the scale of mountainous watersheds (between 500 - 1000 km2) located in contrasted environments. This 3-years study is carried out simultaneously in a volcanic watershed located in the Mexican transvolcanic belt undergoing a subhumid tropical climate, as well as in a sedimentary watershed of the French Southern Alps undergoing a transitional climate with Mediterranean and continental influences. One of the main specificities of this project consists in combining traditional monitoring techniques (i.e. installation of river gauges, turbidimeters and sediment samplers in several sub-catchments) and sediment fingerprinting using elemental geochemistry (measured by Instrumental Neutron Activation Analysis - INAA - and Inductively Coupled Plasma - Mass Spectrometry - ICP-MS) and fallout radionuclides (measured by gamma spectrometry). In the French watershed, geochemical analysis allows outlining different sediment sources (e.g. the contribution of calcareous vs. marl-covered sub-watersheds). Radionuclide ratios (e.g.Be-7/Cs-137) allow identifying the dominant erosion processes occurring within the watershed. Areas mostly

  13. Geochemistry of Precambrian carbonates: II. Archean greenstone belts and Archean sea water.

    PubMed

    Veizer, J; Hoefs, J; Lowe, D R; Thurston, P C

    1989-01-01

    Carbonate rocks with geological attributes of marine sediments are a minor component of the Archean greenstone belts. Despite their relative scarcity, these rocks are important because they record chemical and isotopic properties of coeval oceans. The greenstones containing such carbonates appear to cluster at approximately 2.8 +/- 0.2 and approximately 3.5 +/- 0.1 Ga ago. The samples for the younger group are from the Abitibi, Yellowknife, Wabigoon (Steep Rock Lake), Michipicoten and Uchi greenstone belts of Canada and the "Upper Greenstones" of Zimbabwe. The older group includes the Swaziland Supergroup of South Africa, Warrawoona Group of Australia and the Sargur marbles of India. Mineralogically, the carbonates of the younger greenstones are mostly limestones and of the older ones, ferroan dolomites (ankerites); the latter with some affinities to hydrothermal carbonates. In mineralized areas with iron ores, the carbonate minerals are siderite +/- ankerite, irrespective of the age of the greenstones. Iron-poor dolomites represent a later phase of carbonate generation, related to post-depositional tectonic faulting. The original mineralogy of limestone sequences appears to have been an Sr-rich aragonite. The Archean carbonates yield near-mantle Sr isotopic values, with (87Sr/86Sr)o of 0.7025 +/- 0.0015 and 0.7031 +/- 0.0008 for younger and older greenstones, respectively. The best preserved samples give delta 13C of +1.5 +/- 1.5% PDB, comparable to their Phanerozoic counterparts. In contrast, the best estimate for delta 18O is -7% PDB. Archean limestones, compared to Phanerozoic examples, are enriched in 16O as well as in Mn2+ and Fe2+, and these differences are not a consequence of post-depositional alteration phenomena. The mineralogical and chemical attributes of Archean carbonates (hence sea water) are consistent with the proposition that the composition of the coeval oceans may have been buffered by a pervasive interaction with the "mantle", that is, with

  14. Influence of rock composition on the geochemistry of stream and spring waters from mountainous watersheds in the Gunnison, Uncompahgre, and Grand Mesa National Forests, Colorado

    USGS Publications Warehouse

    Miller, William Roger

    2002-01-01

    The ranges of geochemical baselines for stream and spring waters were determined and maps were constructed showing acid-neutralizing capacity and potential release of total dissolved solids for streams and spring waters for watersheds underlain by each of ten different rock composition types in the Gunnison, Uncompahgre, and Grand Mesa National Forests, Colorado (GMUG). Water samples were collected in mountainous headwater watersheds that have comparatively high precipitation and low evapotranspiration rates and that generally lack extensive ground-water reservoirs. Mountainous headwaters react quickly to changes in input of water from rain and melting snow and they are vulnerable to anthropogenic impact. Processes responsible for the control and mobility of elements in the watersheds were investigated. The geochemistry of water from the sampled watersheds in the GMUG, which are underlain by rocks that are relatively unmineralized, is compared to the geochemistry of water from the mineralized Redcloud Peak area. The water with the highest potential for release of total dissolved solids is from watersheds that are underlain by Paleozoic sedimentary rocks; that high potential is caused primarily by gypsum in those rocks. Water that has the highest acid-neutralizing capacity is from watersheds that are underlain by Paleozoic sedimentary rocks. The water from watersheds underlain by the Mancos Shale has the next highest acid-neutralizing capacity. Water that has the lowest acid-neutralizing capacity is from watersheds that are underlain by Tertiary ash-flow tuff. Tertiary sedimentary rocks containing oil shale, the Mesavede Formation containing coal, and the Mancos Shale all contain pyrite with elevated metal contents. In these mountainous head-water areas, water from watersheds underlain by these rock types is only slightly impacted by oxidation of pyrite, and over-all it is of good chemical quality. These geochemical baselines demonstrate the importance of rock

  15. Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. III. An anion-exchange resin technique for sampling and preservation of sulfoxyanions in natural waters

    USGS Publications Warehouse

    Druschel, G.K.; Schoonen, M.A.A.; Nordstorm, D.K.; Ball, J.W.; Xu, Y.; Cohn, C.A.

    2003-01-01

    A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange resin Bio-Rad??? AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with 1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five pools in Yellowstone National Park between on-site IC analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern) and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin were made using HCl solutions, but were unsuccessful. Bio-Rad??? AG2-X8, an anion-exchange resin with weaker binding sites than the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl. Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions using AG2-X8 resin columns. ?? The Royal Society of Chemistry and the Division of Geochemistry of the American Chemical Society 2003.

  16. Dynamics of deeply supercooled interfacial water

    NASA Astrophysics Data System (ADS)

    Swenson, Jan; Cerveny, Silvina

    2015-01-01

    In this review we discuss the relaxation dynamics of glassy and deeply supercooled water in different types of systems. We compare the dynamics of such interfacial water in ordinary aqueous solutions, hard confinements and biological soft materials. In all these types of systems the dielectric relaxation time of the main water process exhibits a dynamic crossover from a high-temperature non-Arrhenius temperature dependence to a low-temperature Arrhenius behavior. Moreover, at large enough water content the low-temperature process is universal and exhibits the same temperature behavior in all types of systems. However, the physical nature of the dynamic crossover is somewhat different for the different types of systems. In ordinary aqueous solutions it is not even a proper dynamic crossover, since the water relaxation decouples from the cooperative α-relaxation of the solution slightly above the glass transition in the same way as all secondary (β) relaxations of glass-forming materials. In hard confinements, the physical origin of the dynamic crossover is not fully clear, but it seems to occur when the cooperative main relaxation of water at high temperatures reaches a temperature where the volume required for its cooperative motion exceeds the size of the geometrically-confined water cluster. Due to this confinement effect the α-like main relaxation of the confined water seems to transform to a more local β-relaxation with decreasing temperature. Since this low-temperature β-relaxation is universal for all systems at high water content it is possible that it can be considered as an intrinsic β-relaxation of supercooled water, including supercooled bulk water. This possibility, together with other findings for deeply supercooled interfacial water, suggests that the most accepted relaxation scenarios for supercooled bulk water have to be altered.

  17. Sulfur geochemistry of hydrothermal waters in Yellowstone National Park: I. The origin of thiosulfate in hot spring waters

    USGS Publications Warehouse

    Xu, Y.; Schoonen, M.A.A.; Nordstrom, D.K.; Cunningham, K.M.; Ball, J.W.

    1998-01-01

    Thiosulfate (S2O2-3), polythionate (SxO2-6), dissolved sulfide (H2S), and sulfate (SO2-4) concentrations in thirty-nine alkaline and acidic springs in Yellowstone National Park (YNP) were determined. The analyses were conducted on site, using ion chromatography for thiosulfate, polythionate, and sulfate, and using colorimetry for dissolved sulfide. Thiosulfate was detected at concentrations typically less than 2 ??mol/L in neutral and alkaline chloride springs with low sulfate concentrations (C1-/SO2-4 > 25). The thiosulfate concentration levels are about one to two orders of magnitude lower than the concentration of dissolved sulfide in these springs. In most acid sulfate and acid sulfate-chloride springs (Cl-/SO2-4 < 10), thiosulfate concentrations were also typically lower than 2 ??mol/L. However, in some chloride springs enriched with sulfate (Cl-/SO2-4 between 10 to 25), thiosulfate was found at concentrations ranging from 9 to 95 ??mol/L, higher than the concentrations of dissolved sulfide in these waters. Polythionate was detected only in Cinder Pool, Norris Geyser basin, at concentrations up to 8 ??mol/L, with an average S-chain-length from 4.1 to 4.9 sulfur atoms. The results indicate that no thiosulfate occurs in the deeper parts of the hydrothermal system. Thiosulfate may form, however, from (1) hydrolysis of native sulfur by hydrothermal solutions in the shallower parts (<50 m) of the system, (2) oxidation of dissolved sulfide upon mixing of a deep hydrothermal water with aerated shallow groundwater, and (3) the oxidation of dissolved sulfide by dissolved oxygen upon discharge of the hot spring. Upon discharge of a sulfide-containing hydrothermal water, oxidation proceeds rapidly as atmospheric oxygen enters the water. The transfer of oxygen is particularly effective if the hydrothermal discharge is turbulent and has a large surface area.

  18. Optimal Dynamics of Intermittent Water Supply

    NASA Astrophysics Data System (ADS)

    Lieb, Anna; Wilkening, Jon; Rycroft, Chris

    2014-11-01

    In many urban areas of the developing world, piped water is supplied only intermittently, as valves direct water to different parts of the water distribution system at different times. The flow is transient, and may transition between free-surface and pressurized, resulting in complex dynamical features with important consequences for water suppliers and users. These consequences include degradation of distribution system components, compromised water quality, and inequitable water availability. The goal of this work is to model the important dynamics and identify operating conditions that mitigate certain negative effects of intermittent water supply. Specifically, we will look at valve parameters occurring as boundary conditions in a network model of transient, transition flow through closed pipes. Optimization will be used to find boundary values to minimize pressure gradients and ensure equitable water availability.

  19. Water losses dynamic modelling in water distribution networks

    NASA Astrophysics Data System (ADS)

    Puleo, Valeria; Milici, Barbara

    2015-12-01

    In the last decades, one of the main concerns of the water system managers have been the minimisation of water losses, that frequently reach values of 30% or even 70% of the volume supplying the water distribution network. The economic and social costs associated with water losses in modern water supply systems are rapidly rising to unacceptably high levels. Furthermore, the problem of the water losses assumes more and more importance mainly when periods of water scarcity occur or when not sufficient water supply takes part in areas with fast growth. In the present analysis, a dynamic model was used for estimating real and apparent losses of a real case study. A specific nodal demand model reflecting the user's tank installation and a specific apparent losses module were implemented. The results from the dynamic model were compared with the modelling estimation based on a steady-state approach.

  20. Sulfur geochemistry of hydrothermal waters in Yellowstone National Park. 1: The origin of thiosulfate in hot spring waters

    SciTech Connect

    Xu, Y.; Schoonen, M.A.A.; Nordstrom, D.K.; Cunningham, K.M.; Ball, J.W.

    1998-12-01

    Thiosulfate (S{sub 2}O{sub 3}{sup 2{minus}}), polythionate (S{sub x}O{sub 6}{sup 2{minus}}), dissolved sulfide (H{sub 2}S), and sulfate (SO{sub 4}{sup 2{minus}}) concentrations in thirty-nine alkaline and acidic springs in Yellowstone National Park (YNP) were determined. The analyses were conducted on site, using ion chromatography for thiosulfate, polythionate, and sulfate, and using colorimetry for dissolved sulfide. Thiosulfate was detected at concentrations typically less than 2 {micro}mol/L in neutral and alkaline chloride springs with low sulfate concentrations (Cl{sup {minus}}/SO{sub 4}{sup 2{minus}} > 25). The thiosulfate concentration levels are about one to two orders of magnitude lower than the concentration of dissolved sulfide in these springs. In most acid sulfate and acid sulfate-chloride springs (Cl{sup {minus}}/SO{sub 4}{sup 2{minus}} < 10), thiosulfate concentrations were also typically lower than 2 {micro}mol/L. However, in some chloride springs enriched with sulfate (Cl{sup {minus}}/SO{sub 4}{sup 2{minus}} between 10 and 25), thiosulfate was found at concentrations ranging from 9 to 95 {micro}mol/L, higher than the concentrations of dissolved sulfide in these waters. Polythionate was detected only in Cinder Pool, Norris Geyser basin, at concentrations up to 8 {micro}mol/L, with an average S-chain-length from 4.1 to 4.9 sulfur atoms. The results indicate that no thiosulfate occurs in the deeper parts of the hydrothermal system. Thiosulfate may form, however, from (1) hydrolysis of native sulfur by hydrothermal solutions in the shallower parts (<50 m) of the system, (2) oxidation of dissolved sulfide upon mixing of a deep hydrothermal water with aerated shallow groundwater, and (3) the oxidation of dissolved sulfide by dissolved oxygen upon discharge of the hot spring. Upon discharge of a sulfide-containing hydrothermal water, oxidation proceeds rapidly as atmospheric oxygen enters the water. The transfer of oxygen is particularly effective if the

  1. Medical geochemistry of tropical environments

    NASA Astrophysics Data System (ADS)

    Dissanayake, C. B.; Chandrajith, Rohana

    1999-10-01

    Geochemically, tropical environments are unique. This uniqueness stems from the fact that these terrains are continuously subjected to extreme rainfall and drought with resulting strong geochemical fractionation of elements. This characteristic geochemical partitioning results in either severe depletion of elements or accumulation to toxic levels. In both these situations, the effect on plant, animal and human health is marked. Medical geochemistry involves the study of the relationships between the geochemistry of the environment in which we live and the health of the population living in this particular domain. Interestingly, the relationships between geochemistry and health are most marked in the tropical countries, which coincidentally are among the poorest in the world. The very heavy dependence on the immediate environment for sustainable living in these lands enables the medical geochemist to observe correlations between particular geochemical provinces and the incidence of certain diseases unique to these terrains. The aetiology of diseases such as dental and skeletal fluorosis, iodine deficiency disorders, diseases of humans and animals caused by mineral imbalances among others, lie clearly in the geochemical environment. The study of the chemistry of the soils, water and stream sediments in relation to the incidence of geographically distributed diseases in the tropics has not only opened up new frontiers in multidisciplinary research, but has offered new challenges to the medical profession to seriously focus attention on the emerging field of medical geochemistry with the collaboration of geochemists and epidemiologists.

  2. Structure and dynamics of complex liquid water: Molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    S, Indrajith V.; Natesan, Baskaran

    2015-06-01

    We have carried out detailed structure and dynamical studies of complex liquid water using molecular dynamics simulations. Three different model potentials, namely, TIP3P, TIP4P and SPC-E have been used in the simulations, in order to arrive at the best possible potential function that could reproduce the structure of experimental bulk water. All the simulations were performed in the NVE micro canonical ensemble using LAMMPS. The radial distribution functions, gOO, gOH and gHH and the self diffusion coefficient, Ds, were calculated for all three models. We conclude from our results that the structure and dynamical parameters obtained for SPC-E model matched well with the experimental values, suggesting that among the models studied here, the SPC-E model gives the best structure and dynamics of bulk water.

  3. Geochemistry driven trends in microbial diversity and function across a temperature transect of a shallow water hydrothermal system off Milos (Greece)

    NASA Astrophysics Data System (ADS)

    Bühring, Solveig I.; Amend, Jan P.; Gómez Sáez, Gonzalo V.; Häusler, Stefan; Hinrichs, Kai-Uwe; Pichler, Thomas; Pop Ristova, Petra; Price, Roy E.; Santi, Ioulia; Sollich, Miriam

    2014-05-01

    The shallow water hydrothermal vents off Milos Island, Greece, discharge hot, slightly acidic, reduced fluids into colder, slightly alkaline, oxygenated seawater. Gradients in temperature, pH, and geochemistry are established as the two fluids mix, leading to the formation of various microbial microniches. In contrast to deep-sea hydrothermal systems, the availability of sun light allows for a combination of photo- and chemotrophic carbon fixation. Despite the comparably easy accessibility of shallow water hydrothermal systems, little is known about their microbial diversity and functioning. We present data from a shallow hydrothermal system off Milos Island, one of the most hydrothermally active regions in the Mediterranean Sea. The physico-chemical changes from ambient seafloor to hydrothermal area were investigated and documented by in situ microsensor profiling of temperature, pH, total reduced sulfur and dissolved oxygen alongside porewater geochemistry. The spatial microbial diversity was determined using a combination of gene- and lipid-based approaches, whereas microbial functioning was assessed by stable isotope probing experiments targeting lipid biomarkers. In situ microprofiles indicated an extreme environment with steep gradients, offering a variety of microniches for metabolically diverse microbial communities. We sampled a transect along a hydrothermal patch, following an increase in sediment surface temperature from background to 90°C, including five sampling points up to 20 cm sediment depth. Investigation of the bacterial diversity using ARISA revealed differences in the community structure along the geochemical gradients, with the least similarity between the ambient and highly hydrothermally impacted sites. Furthermore, using multivariate statistical analyses it was shown that variations in the community structure could be attributed to differences in the sediment geochemistry and especially the sulfide content, and only indirectly to shifts in

  4. Estancia Basin dynamic water budget.

    SciTech Connect

    Thomas, Richard P.

    2004-09-01

    The Estancia Basin lies about 30 miles to the east of Albuquerque, NM. It is a closed basin in terms of surface water and is somewhat isolated in terms of groundwater. Historically, the primary natural outlet for both surface water and groundwater has been evaporation from the salt lakes in the southeastern portion of the basin. There are no significant watercourses that flow into this basin and groundwater recharge is minimal. During the 20th Century, agriculture grew to become the major user of groundwater in the basin. Significant declines in groundwater levels have accompanied this agricultural use. Domestic and municipal use of the basin groundwater is increasing as Albuquerque population continues to spill eastward into the basin, but this use is projected to be less than 1% of agricultural use well into the 21st Century. This Water Budget model keeps track of the water balance within the basin. The model considers the amount of water entering the basin and leaving the basin. Since there is no significant surface water component within this basin, the balance of water in the groundwater aquifer constitutes the primary component of this balance. Inflow is based on assumptions for recharge made by earlier researchers. Outflow from the basin is the summation of the depletion from all basin water uses. The model user can control future water use within the basin via slider bars that set values for population growth, water system per-capita use, agricultural acreage, and the types of agricultural diversion. The user can also adjust recharge and natural discharge within the limits of uncertainty for those parameters. The model runs for 100 years beginning in 1940 and ending in 2040. During the first 55 years model results can be compared to historical data and estimates of groundwater use. The last 45 years are predictive. The model was calibrated to match to New Mexico Office of State Engineer (NMOSE) estimates of aquifer storage during the historical period by

  5. Subseabed Disposal Project annual report, FY85 to termination of project: Physical Oceanography and Water Column Geochemistry Studies, October 1984 through May 1986

    SciTech Connect

    Kupferman, S.L.

    1987-05-01

    This report covers the work of the Physical Oceanography and Water Column Geochemistry (POWCG) Studies Group of the Subseabed Disposal Project (SDP) from October 1984 to termination of the project in May 1986. The overview of the work includes an introduction, general descriptions of the activities, and a summary. Detailed discussions are included as appendices. During the period of this report the POWCG Studies Group held a meeting to develop a long-term research plan for the Nares Abyssal Plain, which was recently designated as a study area for the Environmental Study Group of the SDP. The POWCG Studies Group has also planned and participated in two interdisciplinary oceanographic missions to the Nares which have resulted in the acquisition of data and samples which can be used to begin to understand the workings of the ecosystem at the site, and for developing a preliminary site assessment. The papers in the appendices have been processed for inclusion in the Energy Data Base.

  6. Fluid dynamics: How water explodes

    NASA Astrophysics Data System (ADS)

    Allen, Susan Davis

    2016-10-01

    Micro-explosions triggered by the absorption of X-ray laser light in drops and jets of water result in shock waves and in rapid heating and expansion of the liquid -- as now revealed in state-of-the-art experiments.

  7. Dynamic characteristics of gas-water interfacial plasma under water

    SciTech Connect

    Zheng, S. J.; Zhang, Y. C.; Ke, B.; Ding, F.; Tang, Z. L.; Yang, K.; Zhu, X. D.

    2012-06-15

    Gas-water interfacial plasmas under water were generated in a compact space in a tube with a sandglass-like structure, where two metal wires were employed as electrodes with an applied 35 kHz ac power source. The dynamic behaviors of voltage/current were investigated for the powered electrode with/without water cover to understand the effect of the gas-water interface. It is found that the discharge exhibits periodic pulsed currents after breakdown as the powered electrode is covered with water, whereas the electrical current reveals a damped oscillation with time with a frequency about 10{sup 6} Hz as the powered electrode is in a vapor bubble. By increasing water conductivity, a discharge current waveform transition from pulse to oscillation presents in the water covering case. These suggest that the gas-water interface has a significant influence on the discharge property.

  8. Vibrational Spectroscopy and Dynamics of Water.

    PubMed

    Perakis, Fivos; Marco, Luigi De; Shalit, Andrey; Tang, Fujie; Kann, Zachary R; Kühne, Thomas D; Torre, Renato; Bonn, Mischa; Nagata, Yuki

    2016-07-13

    We present an overview of recent static and time-resolved vibrational spectroscopic studies of liquid water from ambient conditions to the supercooled state, as well as of crystalline and amorphous ice forms. The structure and dynamics of the complex hydrogen-bond network formed by water molecules in the bulk and interphases are discussed, as well as the dissipation mechanism of vibrational energy throughout this network. A broad range of water investigations are addressed, from conventional infrared and Raman spectroscopy to femtosecond pump-probe, photon-echo, optical Kerr effect, sum-frequency generation, and two-dimensional infrared spectroscopic studies. Additionally, we discuss novel approaches, such as two-dimensional sum-frequency generation, three-dimensional infrared, and two-dimensional Raman terahertz spectroscopy. By comparison of the complementary aspects probed by various linear and nonlinear spectroscopic techniques, a coherent picture of water dynamics and energetics emerges. Furthermore, we outline future perspectives of vibrational spectroscopy for water researches.

  9. The effect of water on protein dynamics.

    PubMed Central

    Zaccai, G

    2004-01-01

    Neutron diffraction and spectroscopy were applied to describe the hydration and dynamics of a soluble protein and a natural membrane from extreme halophilic Archaea. The quantitative dependence of protein motions on water activity was clearly illustrated, and it was established that a minimum hydration shell is required for the systems to access their functional resilience, i.e. a dynamics state that allows biological activity. PMID:15306381

  10. Geochemistry of and radioactivity in ground water of the Highland Rim and Central Basin aquifer systems, Hickman and Maury counties, Tennessee

    USGS Publications Warehouse

    Hileman, G.E.; Lee, R.W.

    1993-01-01

    A reconnaissance of the geochemistry of and radioactivity in ground water from the Highland Rim and Central Basin aquifer systems in Hickman and Maury Counties, Tennessee, was conducted in 1989. Water in both aquifer systems typically is of the calcium or calcium magnesium bicarbonate type, but concentrations of calcium, magnesium, sodium, potassium, chloride, and sulfate are greater in water of the Central Basin system; differences in the concentrations are statistically significant. Dissolution of calcite, magnesium-calcite, dolomite, and gypsum are the primary geochemical processes controlling ground-water chemistry in both aquifer systems. Saturation-state calculations using the computer code WATEQF indicated that ground water from the Central Basin system is more saturated with respect to calcite, dolomite, and gypsum than water from the Highland Rim system. Geochemical environments within each aquifer system are somewhat different with respect to dissolution of magnesium-bearing minerals. Water samples from the Highland Rim system had a fairly constant calcium to magnesium molar ratio, implying congruent dissolution of magnesium-bearing minerals, whereas water samples from the Central Basin system had highly variable ratios, implying either incongruent dissolution or heterogeneity in soluble constituents of the aquifer matrix. Concentrations of radionuclides in water were low and not greatly different between aquifer systems. Median gross alpha activities were 0.54 picocuries per liter in water from each system; median gross beta activities were 1.1 and 2.3 picocuries per liter in water from the Highland Rim and Central Basin systems, respectively. Radon-222 concentrations were 559 and 422 picocuries per liter, respectively. Concentrations of gross alpha and radium in all samples were substantially less than Tennessee?s maximum permissible levels for community water-supply systems. The data indicated no relations between concentrations of dissolved

  11. ISOGENIE: Linking geochemistry, isotopic chemistry and microbial dynamics & community composition in a thawing permafrost peatland, Stordalen Mire, Abisco, Sweden.

    NASA Astrophysics Data System (ADS)

    Chanton, J.; Crill, P. M.; Rich, V.; McCalley, C. K.; Hodgkins, S. B.; Tyson, G.; Logan, T.; Wehr, R.; Mondav, R.; Li, C.; Frolking, S.; Saleska, S. R.

    2011-12-01

    As permafrost thaws, increasing CH4 emissions from northern wetlands are likely to cause positive feedback to atmospheric warming. One of the over-arching goals of this project is to connect geochemical processes, particularly focusing on methane production, to underlying microbial population dynamics and genomics. Recent transformative technical advances in both high throughput investigations of microbial communities and high temporal resolution biogeochemical isotope measurements now permit a uniquely comprehensive approach to opening the microbial "black boxes" that impact carbon cycling on global scales. This project links detailed microbial sampling with detailed geochemical and isotopic sampling on seasonal and diel timescales and has an extensive modeling component. Gas exchange is monitored across the wetland gradients in a series of automated chambers and isotopes of emitted and belowground methane and carbon dioxide are measured with a QC laser system. The mire is in a state of partial thaw. With this thaw is an apparent ecological session in wetland community structure and associated changes in organic matter lability, rates of methane production and microbial community. Our group's study sites range from palsa with underlying permanently frozen peat, to recently collapsed and flooded palsa, to flooded palsa colonized by Sphagnum, to flooded eriophorum sites, to sites populated by Carex, to open water lakes. Across this environmental gradient pH ranges from 4 to 6.5. This change is driven by changes in hydrology as the surface of the thawing permafrost subsides and an adjacent lake drains into the mire. Along this environmental gradient, from palsa to Carex, the lability of the peat increases significantly as determined in incubations of peat material and monitoring of methane and carbon dioxide production rates. Coincident with this environmental gradient is a decrease in the apparent fractionation factor between methane and carbon dioxide and methane

  12. Temporal changes in microbial ecology and geochemistry in produced water from hydraulically fractured Marcellus shale gas wells.

    PubMed

    Cluff, Maryam A; Hartsock, Angela; MacRae, Jean D; Carter, Kimberly; Mouser, Paula J

    2014-06-01

    Microorganisms play several important roles in unconventional gas recovery, from biodegradation of hydrocarbons to souring of wells and corrosion of equipment. During and after the hydraulic fracturing process, microorganisms are subjected to harsh physicochemical conditions within the kilometer-deep hydrocarbon-bearing shale, including high pressures, elevated temperatures, exposure to chemical additives and biocides, and brine-level salinities. A portion of the injected fluid returns to the surface and may be reused in other fracturing operations, a process that can enrich for certain taxa. This study tracked microbial community dynamics using pyrotag sequencing of 16S rRNA genes in water samples from three hydraulically fractured Marcellus shale wells in Pennsylvania, USA over a 328-day period. There was a reduction in microbial richness and diversity after fracturing, with the lowest diversity at 49 days. Thirty-one taxa dominated injected, flowback, and produced water communities, which took on distinct signatures as injected carbon and electron acceptors were attenuated within the shale. The majority (>90%) of the community in flowback and produced fluids was related to halotolerant bacteria associated with fermentation, hydrocarbon oxidation, and sulfur-cycling metabolisms, including heterotrophic genera Halolactibacillus, Vibrio, Marinobacter, Halanaerobium, and Halomonas, and autotrophs belonging to Arcobacter. Sequences related to halotolerant methanogenic genera Methanohalophilus and Methanolobus were detected at low abundance (<2%) in produced waters several months after hydraulic fracturing. Five taxa were strong indicators of later produced fluids. These results provide insight into the temporal trajectory of subsurface microbial communities after "fracking" and have important implications for the enrichment of microbes potentially detrimental to well infrastructure and natural gas fouling during this process.

  13. Temporal changes in microbial ecology and geochemistry in produced water from hydraulically fractured Marcellus shale gas wells.

    PubMed

    Cluff, Maryam A; Hartsock, Angela; MacRae, Jean D; Carter, Kimberly; Mouser, Paula J

    2014-06-01

    Microorganisms play several important roles in unconventional gas recovery, from biodegradation of hydrocarbons to souring of wells and corrosion of equipment. During and after the hydraulic fracturing process, microorganisms are subjected to harsh physicochemical conditions within the kilometer-deep hydrocarbon-bearing shale, including high pressures, elevated temperatures, exposure to chemical additives and biocides, and brine-level salinities. A portion of the injected fluid returns to the surface and may be reused in other fracturing operations, a process that can enrich for certain taxa. This study tracked microbial community dynamics using pyrotag sequencing of 16S rRNA genes in water samples from three hydraulically fractured Marcellus shale wells in Pennsylvania, USA over a 328-day period. There was a reduction in microbial richness and diversity after fracturing, with the lowest diversity at 49 days. Thirty-one taxa dominated injected, flowback, and produced water communities, which took on distinct signatures as injected carbon and electron acceptors were attenuated within the shale. The majority (>90%) of the community in flowback and produced fluids was related to halotolerant bacteria associated with fermentation, hydrocarbon oxidation, and sulfur-cycling metabolisms, including heterotrophic genera Halolactibacillus, Vibrio, Marinobacter, Halanaerobium, and Halomonas, and autotrophs belonging to Arcobacter. Sequences related to halotolerant methanogenic genera Methanohalophilus and Methanolobus were detected at low abundance (<2%) in produced waters several months after hydraulic fracturing. Five taxa were strong indicators of later produced fluids. These results provide insight into the temporal trajectory of subsurface microbial communities after "fracking" and have important implications for the enrichment of microbes potentially detrimental to well infrastructure and natural gas fouling during this process. PMID:24803059

  14. Water dynamics in glass ionomer cements

    NASA Astrophysics Data System (ADS)

    Berg, M. C.; Jacobsen, J.; Momsen, N. C. R.; Benetti, A. R.; Telling, M. T. F.; Seydel, T.; Bordallo, H. N.

    2016-07-01

    Glass ionomer cements (GIC) are an alternative for preventive dentistry. However, these dental cements are complex systems where important motions related to the different states of the hydrogen atoms evolve in a confined porous structure. In this paper, we studied the water dynamics of two different liquids used to prepare either conventional or resin-modified glass ionomer cement. By combining thermal analysis with neutron scattering data we were able to relate the water structure in the liquids to the materials properties.

  15. Microbial Sulfur Geochemistry in Mine Systems (Invited)

    NASA Astrophysics Data System (ADS)

    Warren, L. A.; Norlund, K. L.; Hitchcock, A.

    2010-12-01

    Acid mine drainage (AMD), metal laden, acidic water, is the most pressing mining environmental issue on a global scale. While it is well recognized that the activity of autotrophic Fe and S bacteria amplify the oxidation of the sulfidic wastes, thereby generating acidity and leaching metals; the underlying microbial geochemistry is not well described. This talk will highlight results revealing the importance of microbial cooperation associated with a novel sulfur-metabolizing consortium enriched from mine waters. Results generated by an integrated approach, combining field characterization, geochemical experimentation, scanning transmission X-ray microscopy (STXM), and fluorescence in situ hybridization (FISH) [1]describing the underlying ecological drivers, the functionally relevant biogeochemical architecture of the consortial macrostructure as well as the identities of this environmental sulphur redox cycling consortium will be presented. The two common mine bacterial strains involved in this consortium, Acidithiobacillus ferroxidans and Acidiphilium sp., are specifically spatially segregated within a macrostructure (pod) of extracellular polymeric substance (EPS) that enables coupled sulphur oxidation and reduction reactions despite bulk, oxygenated conditions. Identical pod formation by type culture strains was induced and linked to ecological conditions. The proposed sulphur geochemistry associated with this bacterial consortium produces 40-90% less acid than expected based on abiotic AMD models, with implications for both AMD mitigation and AMD carbon flux modeling. We are currently investigating the implications of these sulphur-processing pods for metal dynamics in mine systems. These results demonstrate how microbes can orchestrate their geochemical environment to facilitate metabolism, and underscore the need to consider microbial interactions and ecology in constraining their geochemical impacts. [1] Norlund, Southam, Tyliszcczak, Hu, Karunakaran, Obst

  16. Geochemistry, Comparative Analysis, and Physical and Chemical Characteristics of the Thermal Waters East of Hot Springs National Park, Arkansas, 2006-09

    USGS Publications Warehouse

    Kresse, Timothy M.; Hays, Phillip D.

    2009-01-01

    rock collapse for uncased wells completed in highly fractured rock. However, the propagation of newly formed large fractures that potentially could damage well structures or result in pirating of water from production wells appears to be of limited possibility based on review of relevant studies. Characteristics of hydraulic conductivity, storage, and fracture porosity were interpreted from flow rates observed in individual wells completed in the Bigfork Chert and Stanley Shale; from hydrographs produced from continuous measurements of water levels in wells completed in the Arkansas Novaculite, the Bigfork Chert, and Stanley Shale; and from a potentiometric-surface map constructed using water levels in wells throughout the study area. Data gathered from these three separate exercises showed that fracture porosity is much greater in the Bigfork Chert relative to that in the Stanley Shale, shallow groundwater flows from elevated recharge areas with exposures of Bigfork Chert along and into streams within the valleys formed on exposures of the Stanley Shale, and there was no evidence of interbasin transfer of groundwater within the shallow flow system. Fifteen shallow wells and two cold-water springs were sampled from the various exposed formations in the study area to characterize the water quality and geochemistry for the shallow groundwater system and for comparison to the geochemistry of the hot springs in Hot Springs National Park. For the quartz formations (novaculite, chert, and sandstone formations), total dissolved solids concentrations were very low with a median concentration of 23 milligrams per liter, whereas the median concentration for groundwater from the shale formations was 184 milligrams per liter. Ten hot springs in Hot Springs National Park were sampled for the study. Several chemical constituents for the hot springs, including pH, total dissolved solids, major cations and anions, and trace metals, show similarity with the shale formations

  17. Aquifer geochemistry and effects of pumping on ground-water quality at the Green Belt Parkway Well Field, Holbrook, Long Island, New York

    USGS Publications Warehouse

    Brown, Craig J.; Colabufo, Steven; Coates, John D.

    2002-01-01

    Geochemistry, microbiology, and water quality of the Magothy aquifer at a new supply well in Holbrook were studied to help identify factors that contribute to iron-related biofouling of public-supply wells. The organic carbon content of borehole sediments from the screen zone, and the dominant terminal electron-accepting processes (TEAPs), varied by depth. TEAP assays of core sediments indicated that iron reduction, sulfate reduction, and undetermined (possibly oxic) reactions and microbial activity are correlated with organic carbon (lignite) content. The quality of water from this well, therefore, reflects the wide range of aquifer microenvironments at this site. High concentrations of dissolved iron (3.6 to 6.4 micromoles per liter) in water samples from this well indicate that some water is derived from Fe(III)-reducing sediments within the aquifer, but traces of dissolved oxygen indicate inflow of shallow, oxygenated water from shallow units that overlie the local confining units. Water-quality monitoring before and during a 2-day pumping test indicates that continuous pumping from the Magothy aquifer at this site can induce downward flow of shallow, oxygenated water despite the locally confined conditions. Average concentrations of dissolved oxygen are high (5.2 milligrams per liter, or mg/L) in the overlying upper glacial aquifer and at the top of the Magothy aquifer (4.3 mg/L), and low (<0.1 mg/L) in the deeper, anaerobic part of the Magothy; average concentrations of phosphate are high (0.4 mg/L) in the upper glacial aquifer and lower (0.008 mg/L) at the top of the Magothy aquifer and in the deeper part of the Magothy (0.013 mg/L). Concentrations of both constituents increased during the 2 days of pumping. The d34S of sulfate in shallow ground water from observation wells (3.8 to 6.4 per mil) was much heavier than that in the supplywell water (-0.1 per mil) and was used to help identify sources of water entering the supply well. The d34S of sulfate in a

  18. Optimality and soil water-vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Schymanski, S. J.

    2007-12-01

    Soil moisture is an important factor for nearly all hydrological and biogeochemical processes. Antecedent soil moisture impacts on infiltration and runoff generation, the soil moisture distribution within the soil together with other factors determines the soil carbon and nutrient cycling and the amount of soil moisture within the rooting zone often constitutes a major constraint for plant growth and evapo-transpiration. The main processes determining soil moisture dynamics are infiltration, percolation, evaporation and root water uptake. Therefore, modelling soil moisture dynamics requires an interdisciplinary approach that links hydrological and biological processes. Previous approaches treat either root water uptake rates or root distributions and transpiration rates as a given, and calculate the soil moisture dynamics based on the theory of flow in unsaturated media. The present study introduces a different approach to linking soil water and vegetation dynamics, based on optimality. Assuming that plants aim at minimising the costs related to the maintenance of the root system while meeting their demand for water, a model was formulated that dynamically adjusts the vertical root distribution in the soil profile to meet this objective. The model was used to compute the soil moisture dynamics in a tropical savanna over 12 months, which showed a better resemblance with the observed time series of surface soil moisture than models based on fixed root distributions. The optimality-based approach to modelling soil-vegetation interactions requires a new level of interdisciplinary synthesis, as biological and hydrological knowledge needs to be combined to derive the very basis of the model, namely the costs and benefits of different root properties. On the other hand, this approach has the potential to reduce the number of unknowns in a model (e.g. the vertical root distribution), which makes it a valuable alternative to more empirically-based approaches.

  19. Dynamic ionization of water under extreme conditions

    SciTech Connect

    Goncharov, A F; Goldman, N; Fried, L E; Crowhurst, J C; Kuo, I W; Mundy, C J; Zaug, J M

    2004-07-19

    Raman spectroscopy has been used to study fluid water at approximately 1000 K and 2 to 60 GPa in a laser heated diamond anvil cell. First principles molecular dynamics (MD) simulations have also been employed to simulate water under similar conditions. The experimental Raman intensity of the O-H stretch mode was observed to decrease with pressure, and beyond 50 GPa this mode was no longer visible. At approximately the same pressure we inferred a change in the slope of the melting curve. Consistent with these experimental observations, the MD simulations show that water under these conditions forms a dynamically ionized liquid state, which is dominated by very short lived (<10 fs) H{sub 2}O, H{sub 3}O{sup +} and O{sup 2-} species.

  20. Geochemistry and origin of formation waters in the western Canada sedimentary basin-I. Stable isotopes of hydrogen and oxygen

    USGS Publications Warehouse

    Hitchon, B.; Friedman, I.

    1969-01-01

    Stable isotopes of hydrogen and oxygen, together with chemical analyses, were determined for 20 surface waters, 8 shallow potable formation waters, and 79 formation waters from oil fields and gas fields. The observed isotope ratios can be explained by mixing of surface water and diagenetically modified sea water, accompanied by a process which enriches the heavy oxygen isotope. Mass balances for deuterium and total dissolved solids in the western Canada sedimentary basin demonstrate that the present distribution of deuterium in formation waters of the basin can be derived through mixing of the diagenetically modified sea water with not more than 2.9 times as much fresh water at the same latitude, and that the movement of fresh water through the basin has redistributed the dissolved solids of the modified sea water into the observed salinity variations. Statistical analysis of the isotope data indicates that although exchange of deuterium between water and hydrogen sulphide takes place within the basin, the effect is minimized because of an insignificant mass of hydrogen sulphide compared to the mass of formation water. Conversely, exchange of oxygen isotopes between water and carbonate minerals causes a major oxygen-18 enrichment of formation waters, depending on the relative masses of water and carbonate. Qualitative evidence confirms the isotopic fractionation of deuterium on passage of water through micropores in shales. ?? 1969.

  1. Geochemistry of formation waters from the Wolfcamp and “Cline” shales: Insights into brine origin, reservoir connectivity, and fluid flow in the Permian Basin, USA

    USGS Publications Warehouse

    Engle, Mark A.; Reyes, Francisco R.; Varonka, Matthew S.; Orem, William H.; Lin, Ma; Ianno, Adam J.; Westphal, Tiffani M.; Xu, Pei; Carroll, Kenneth C.

    2016-01-01

    Despite being one of the most important oil producing provinces in the United States, information on basinal hydrogeology and fluid flow in the Permian Basin of Texas and New Mexico is lacking. The source and geochemistry of brines from the basin were investigated (Ordovician- to Guadalupian-age reservoirs) by combining previously published data from conventional reservoirs with geochemical results for 39 new produced water samples, with a focus on those from shales. Salinity of the Ca–Cl-type brines in the basin generally increases with depth reaching a maximum in Devonian (median = 154 g/L) reservoirs, followed by decreases in salinity in the Silurian (median = 77 g/L) and Ordovician (median = 70 g/L) reservoirs. Isotopic data for B, O, H, and Sr and ion chemistry indicate three major types of water. Lower salinity fluids (<70 g/L) of meteoric origin in the middle and upper Permian hydrocarbon reservoirs (1.2–2.5 km depth; Guadalupian and Leonardian age) likely represent meteoric waters that infiltrated through and dissolved halite and anhydrite in the overlying evaporite layer. Saline (>100 g/L), isotopically heavy (O and H) water in Leonardian [Permian] to Pennsylvanian reservoirs (2–3.2 km depth) is evaporated, Late Permian seawater. Water from the Permian Wolfcamp and Pennsylvanian “Cline” shales, which are isotopically similar but lower in salinity and enriched in alkalis, appear to have developed their composition due to post-illitization diffusion into the shales. Samples from the “Cline” shale are further enriched with NH4, Br, I and isotopically light B, sourced from the breakdown of marine kerogen in the unit. Lower salinity waters (<100 g/L) in Devonian and deeper reservoirs (>3 km depth), which plot near the modern local meteoric water line, are distinct from the water in overlying reservoirs. We propose that these deep meteoric waters are part of a newly identified hydrogeologic unit: the Deep Basin Meteoric Aquifer System

  2. Water transport dynamics in trees and stands

    SciTech Connect

    Pallardy, S.G.; Cermak, J.; Ewers, F.W.; Kaufmann, M.R.; Parker, W.C.; Sperry, J.S.

    1995-07-01

    Water transport dynamics in trees and stands of conifers have certain features that are characteristic of this group and are at least rare among angiosperms. Among these features is the xylem transport system that is dependent on tracheids for long-distance water transport. Tracheid-containing xylem is relatively inefficient, a property that can reduce submaximum allowable rates of gas exchange, but tracheids also offer substantial capacity for water storage and high resistance to freezing-induced dysfunction. Thus, they are quite compatible with the typical evergreen habit and long transpiration season of conifers. At the stand level, canopy transpiration in conifers is primarily controlled by stomatal conductance. In contrast, in dense canopies of angio-sperms, particularly those of tropical forests with limited air mixing, stand transpiration is limited by radiation input rather than by stomatal control. Because of their evergreen habit a greater proportion of evapotranspiration in conifer forests is associated with evaporation of water intercepted by the tree crowns. Other features of transport dynamics are characteristic of most conifers, but are not unique to this group. Among these features are typically shallow root systems that often must supply water in winter to replace transpiration needs of evergreen species, common occurrence of mycorrhizae that enhance mineral and water uptake, and drought tolerance adaptations that include elements of both dehydration avoidance (e.g., stomatal closure under water stress, shifts in allocation of dry matter to below-ground sinks) and dehydration tolerance (e.g., capacity for acclimation of photosynthetic apparatus to drought, osmotic adjustment). Transpiration rates from conifer foliage often are lower than those of deciduous angiosperms, probably because of the lower maximum capacity of tracheid-bearing xylem to transport water.

  3. Vibrational Spectroscopy and Dynamics of Water.

    PubMed

    Perakis, Fivos; Marco, Luigi De; Shalit, Andrey; Tang, Fujie; Kann, Zachary R; Kühne, Thomas D; Torre, Renato; Bonn, Mischa; Nagata, Yuki

    2016-07-13

    We present an overview of recent static and time-resolved vibrational spectroscopic studies of liquid water from ambient conditions to the supercooled state, as well as of crystalline and amorphous ice forms. The structure and dynamics of the complex hydrogen-bond network formed by water molecules in the bulk and interphases are discussed, as well as the dissipation mechanism of vibrational energy throughout this network. A broad range of water investigations are addressed, from conventional infrared and Raman spectroscopy to femtosecond pump-probe, photon-echo, optical Kerr effect, sum-frequency generation, and two-dimensional infrared spectroscopic studies. Additionally, we discuss novel approaches, such as two-dimensional sum-frequency generation, three-dimensional infrared, and two-dimensional Raman terahertz spectroscopy. By comparison of the complementary aspects probed by various linear and nonlinear spectroscopic techniques, a coherent picture of water dynamics and energetics emerges. Furthermore, we outline future perspectives of vibrational spectroscopy for water researches. PMID:27096701

  4. Geohydrology, water quality, and nitrogen geochemistry in the saturated and unsaturated zones beneath various land uses, Riverside and San Bernardino counties, California, 1991-93

    USGS Publications Warehouse

    Rees, Terry F.; Bright, D.J.; Fay, R.G.; Christensen, A.H.; Anders, R.B.; Baharie, B.S.; Land, M.T.

    1995-01-01

    The U.S. Geological Survey, in cooperation with the Eastern Municipal Water District, the Metropolitan Water District of Southern California, and the Orange County Water District, has completed a derailed study of the Hemet groundwater basin. The quantity of ground water stored in the basin in August 1992 is estimated to be 327,000 acre-feet. Dissolved-solids concentration ranged from 380 to 700 mg/L (milligrams per liter), except in small areas where the concentration exceeded 1,000 mg/L. Nitrate concentrations exc__*'ded the U.S. Environmental Protection Agency Maximum Contaminant Level (MCL) of 10 mg/L nitrate (its nitrogen) in the southeastern part of the basin, in the Domenigoni Valley area, and beneath a dairy in the Diamond Valley area. Seven sites representing selected land uses-residential, tuff grass irrigated with reclaimed water, citrus grove, irrigated farm, poultry farm, and dairy (two sites)--were selected for detailed study of nitrogen geochemistry in the unsaturated zone. For all land uses, nitrate was the dominant nitrogen species in the unsaturated zone. Although nitrate was seasonally present in the shallow unsaturated zone beneath the residential site, it was absent at moderate depths, suggesting negligible migration of nitrate from the surface at this time. Microbial denitrification probably is occurring in the shallow unsaturated zone. High nitrate concentrations in the deep unsaturated zone (greater than 100 ft) suggest either significantly higher nitrate loading at some time in the past, or lateral movement of nitrate at depth. Nitrate also is seasonally present in the shallow unsaturated zone beneath the reclaimed-water site, and (in contrast with the residential site), nitrate is perennially present in the deeper unsaturated zone. Mictobial identification in the unsaturated zone and in the capillary fringe above the water table decreases, the concentrations of nitrate in pore water to below the MCL before reaching the water table. Pore

  5. Water dynamics in different biochar fractions.

    PubMed

    Conte, Pellegrino; Nestle, Nikolaus

    2015-09-01

    Biochar is a carbonaceous porous material deliberately applied to soil to improve its fertility. The mechanisms through which biochar acts on fertility are still poorly understood. The effect of biochar texture size on water dynamics was investigated here in order to provide information to address future research on nutrient mobility towards plant roots as biochar is applied as soil amendment. A poplar biochar has been stainless steel fractionated in three different textured fractions (1.0-2.0 mm, 0.3-1.0 mm and <0.3 mm, respectively). Water-saturated fractions were analyzed by fast field cycling (FFC) NMR relaxometry. Results proved that 3D exchange between bound and bulk water predominantly occurred in the coarsest fraction. However, as porosity decreased, water motion was mainly associated to a restricted 2D diffusion among the surface-site pores and the bulk-site ones. The X-ray μ-CT imaging analyses on the dry fractions revealed the lowest surface/volume ratio for the coarsest fraction, thereby corroborating the 3D water exchange mechanism hypothesized by FFC NMR relaxometry. However, multi-micrometer porosity was evidenced in all the samples. The latter finding suggested that the 3D exchange mechanism cannot even be neglected in the finest fraction as previously excluded only on the basis of NMR relaxometry results. X-ray μ-CT imaging showed heterogeneous distribution of inorganic materials inside all the fractions. The mineral components may contribute to the water relaxation mechanisms by FFC NMR relaxometry. Further studies are needed to understand the role of the inorganic particles on water dynamics. PMID:25594163

  6. The dynamic crossover in water does not require bulk water.

    PubMed

    Turton, David A; Corsaro, Carmelo; Martin, David F; Mallamace, Francesco; Wynne, Klaas

    2012-06-14

    Many of the anomalous properties of water may be explained by invoking a second critical point that terminates the coexistence line between the low- and high-density amorphous states in the liquid. Direct experimental evidence of this point, and the associated polyamorphic liquid-liquid transition, is elusive as it is necessary for liquid water to be cooled below its homogeneous-nucleation temperature. To avoid crystallization, water in the eutectic LiCl solution has been studied but then it is generally considered that "bulk" water cannot be present. However, recent computational and experimental studies observe cooperative hydration in which case it is possible that sufficient hydrogen-bonded water is present for the essential characteristics of water to be preserved. For femtosecond optical Kerr-effect and nuclear magnetic resonance measurements, we observe in each case a fractional Stokes-Einstein relation with evidence of the dynamic crossover appearing near 220 K and 250 K respectively. Spectra obtained in the glass state also confirm the complex nature of the hydrogen-bonding modes reported for neat room-temperature water and support predictions of anomalous diffusion due to "worm-hole" structure.

  7. Coal Formation and Geochemistry

    NASA Astrophysics Data System (ADS)

    Orem, W. H.; Finkelman, R. B.

    2003-12-01

    Coal is one of the most complex and challenging natural materials to analyze and to understand. Unlike most rocks, which consist predominantly of crystalline mineral grains, coal is largely an assemblage of amorphous, degraded plant remains metamorphosed to various degrees and intermixed with a generous sprinkling of minute syngenetic, diagenetic, epigenetic, and detrital mineral grains, and containing within its structure various amounts of water, oils, and gases. Each coal is unique, having been derived from different plant sources over geologic time, having experienty -45ced different thermal histories, and having been exposed to varying geologic processes. This diversity presents a challenge to constructing a coherent picture of coal geochemistry and the processes that influence the chemical composition of coal.Despite the challenge coal presents to geochemists, a thorough understanding of the chemistry and geology of this complex natural substance is essential because of its importance to our society. Coal is, and will remain for sometime, a crucial source of energy for the US and for many other countries (Figure 1). In the USA, more than half of the electricity is generated by coal-fired power plants, and almost 90% of the coal mined in the USA is sold for electricity generation (Pierce et al., 1996). It is also an important source of coke for steel production, chemicals, pharmaceuticals, and even perfumes ( Schobert, 1987). It may also, in some cases, be an economic source of various mineral commodities. The utilization of coal through mining, transport, storage, combustion, and the disposal of the combustion by-products, also presents a challenge to geochemists because of the wide range of environmental and human health problems arising from these activities. The sound and effective use of coal as a natural resource requires a better understanding of the geochemistry of coal, i.e., the chemical and mineralogical characteristics of the coal that control its

  8. Photonic water dynamically responsive to external stimuli

    NASA Astrophysics Data System (ADS)

    Sano, Koki; Kim, Youn Soo; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Aida, Takuzo

    2016-08-01

    Fluids that contain ordered nanostructures with periodic distances in the visible-wavelength range, anomalously exhibit structural colours that can be rapidly modulated by external stimuli. Indeed, some fish can dynamically change colour by modulating the periodic distance of crystalline guanine sheets cofacially oriented in their fluid cytoplasm. Here we report that a dilute aqueous colloidal dispersion of negatively charged titanate nanosheets exhibits structural colours. In this `photonic water', the nanosheets spontaneously adopt a cofacial geometry with an ultralong periodic distance of up to 675 nm due to a strong electrostatic repulsion. Consequently, the photonic water can even reflect near-infrared light up to 1,750 nm. The structural colour becomes more vivid in a magnetic flux that induces monodomain structural ordering of the colloidal dispersion. The reflective colour of the photonic water can be modulated over the entire visible region in response to appropriate physical or chemical stimuli.

  9. Photonic water dynamically responsive to external stimuli.

    PubMed

    Sano, Koki; Kim, Youn Soo; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Aida, Takuzo

    2016-01-01

    Fluids that contain ordered nanostructures with periodic distances in the visible-wavelength range, anomalously exhibit structural colours that can be rapidly modulated by external stimuli. Indeed, some fish can dynamically change colour by modulating the periodic distance of crystalline guanine sheets cofacially oriented in their fluid cytoplasm. Here we report that a dilute aqueous colloidal dispersion of negatively charged titanate nanosheets exhibits structural colours. In this 'photonic water', the nanosheets spontaneously adopt a cofacial geometry with an ultralong periodic distance of up to 675 nm due to a strong electrostatic repulsion. Consequently, the photonic water can even reflect near-infrared light up to 1,750 nm. The structural colour becomes more vivid in a magnetic flux that induces monodomain structural ordering of the colloidal dispersion. The reflective colour of the photonic water can be modulated over the entire visible region in response to appropriate physical or chemical stimuli. PMID:27572806

  10. A peptide's perspective of water dynamics.

    PubMed

    Ghosh, Ayanjeet; Hochstrasser, Robin M

    2011-11-18

    This Perspective is focused on amide groups of peptides interacting with water. The 2D IR spectroscopy has already enabled structural aspects of the peptide backbone to be determined through its ability to measure the coupling between different amide-I modes. Here we describe why nonlinear IR is emerging as the method of choice to examine the fast components of the water dynamics near peptides and how isotopically edited peptide links can be used to probe the local water at a residue level in proteins. This type of research necessarily involves an intimate mix of theory and experiment. The description of the results is underpinned by relatively well established quantum-statistical theories that describe the important manifestations of peptide vibrational frequency fluctuations. PMID:22844177

  11. Photonic water dynamically responsive to external stimuli

    PubMed Central

    Sano, Koki; Kim, Youn Soo; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Aida, Takuzo

    2016-01-01

    Fluids that contain ordered nanostructures with periodic distances in the visible-wavelength range, anomalously exhibit structural colours that can be rapidly modulated by external stimuli. Indeed, some fish can dynamically change colour by modulating the periodic distance of crystalline guanine sheets cofacially oriented in their fluid cytoplasm. Here we report that a dilute aqueous colloidal dispersion of negatively charged titanate nanosheets exhibits structural colours. In this ‘photonic water', the nanosheets spontaneously adopt a cofacial geometry with an ultralong periodic distance of up to 675 nm due to a strong electrostatic repulsion. Consequently, the photonic water can even reflect near-infrared light up to 1,750 nm. The structural colour becomes more vivid in a magnetic flux that induces monodomain structural ordering of the colloidal dispersion. The reflective colour of the photonic water can be modulated over the entire visible region in response to appropriate physical or chemical stimuli. PMID:27572806

  12. Dynamic Coupling of Iron, Manganese, and Phosphorus Behavior in Water and Sediment of Shallow Ice-Covered Eutrophic Lakes.

    PubMed

    Schroth, Andrew W; Giles, Courtney D; Isles, Peter D F; Xu, Yaoyang; Perzan, Zachary; Druschel, Gregory K

    2015-08-18

    Decreasing duration and occurrence of northern hemisphere ice cover due to recent climate warming is well-documented; however, biogeochemical dynamics underneath the ice are poorly understood. We couple time-series analyses of water column and sediment water interface (SWI) geochemistry with hydrodynamic data to develop a holistic model of iron (Fe), manganese (Mn), and phosphorus (P) behavior underneath the ice of a shallow eutrophic freshwater bay. During periods of persistent subfreezing temperatures, a highly reactive pool of dissolved and colloidal Fe, Mn, and P develops over time in surface sediments and bottom waters due to reductive dissolution of Fe/Mn(oxy)hydroxides below the SWI. Redox dynamics are driven by benthic O2 consumption, limited air-water exchange of oxygen due to ice cover, and minimal circulation. During thaw events, the concentration, distribution and size partitioning of all species changes, with the highest concentrations of P and "truly dissolved" Fe near the water column surface, and a relatively well-mixed "truly dissolved" Mn and "colloidal" Fe profile due to the influx of geochemically distinct river water and increased circulation. The partitioning and flux of trace metals and phosphorus beneath the ice is dynamic, and heavily influenced by climate-dependent physical processes that vary in both time and space.

  13. Geohydrology, Geochemistry, and Ground-Water Simulation-Optimization of the Central and West Coast Basins, Los Angeles County, California

    USGS Publications Warehouse

    Reichard, Eric G.; Land, Michael; Crawford, Steven M.; Johnson, Tyler D.; Everett, Rhett; Kulshan, Trayle V.; Ponti, Daniel J.; Halford, Keith L.; Johnson, Theodore A.; Paybins, Katherine S.; Nishikawa, Tracy

    2003-01-01

    Historical ground-water development of the Central and West Coast Basins in Los Angeles County, California through the first half of the 20th century caused large water-level declines and induced seawater intrusion. Because of this, the basins were adjudicated and numerous ground-water management activities were implemented, including increased water spreading, construction of injection barriers, increased delivery of imported water, and increased use of reclaimed water. In order to improve the scientific basis for these water management activities, an extensive data collection program was undertaken, geohydrological and geochemical analyses were conducted, and ground-water flow simulation and optimization models were developed. In this project, extensive hydraulic, geologic, and chemical data were collected from new multiple-well monitoring sites. On the basis of these data and data compiled and collected from existing wells, the regional geohydrologic framework was characterized. For the purposes of modeling, the three-dimensional aquifer system was divided into four aquifer systems?the Recent, Lakewood, Upper San Pedro, and Lower San Pedro aquifer systems. Most pumpage in the two basins is from the Upper San Pedro aquifer system. Assessment of the three-dimensional geochemical data provides insight into the sources of recharge and the movement and age of ground water in the study area. Major-ion data indicate the chemical character of water containing less than 500 mg/L dissolved solids generally grades from calcium-bicarbonate/sulfate to sodium bicarbonate. Sodium-chloride water, high in dissolved solids, is present in wells near the coast. Stable isotopes of oxygen and hydrogen provide information on sources of recharge to the basin, including imported water and water originating in the San Fernando Valley, San Gabriel Valley, and the coastal plain and surrounding hills. Tritium and carbon-14 data provide information on relative ground-water ages. Water with

  14. Geochemistry of batch-extract waters derived from spoil material collected at the Cordero coal mine, Powder River basin, Wyoming

    USGS Publications Warehouse

    Naftz, D.L.

    1990-01-01

    Batch-mixing experiments to evaluate postmining water quality at the Cordero Mine were conducted by the U.S. Geological Survey during 1984 to 1985. Contact of groundwater from the spoil aquifer with fresh spoil material caused only small changes in major-element concentrations and in pH, unless sulfide oxidation or contact with soluble salts, such as epsomite, occurred. In contrast, large changes in major-element concentration resulted when water from the coal aquifer contacted the spoil material. Only three of seven reaction models considered to explain the water quality changes during the batch-mixing experiments were consistent with the thermodynamic and mineralogical data. The three models used to account for the observed water quality changes derived potassium from potassium feldspar; magnesium from chlorite or epsomite or both; sodium from cation exchange and halite; chloride from halite; silica from potassium feldspar and chlorite; sulfate from gypsum, or epsomite or both, and carbon from carbon dioxide. In general, water quality samples obtained from the batch-mixing experiments using water from the coal aquifer had smaller major-ion concentrations than the actual water quality in the spoil aquifer. These differences can be explained by the limited amount of efflorescent salt dissolution and volume of water used in the experiments. Correction ratios calculated for these experiments may be applied to batch-mixing experiments at other mines in the area, to predict postmining water quality. (USGS)

  15. Water balance dynamics in the Nile Basin

    USGS Publications Warehouse

    Senay, G.B.; Asante, Kwasi; Artan, G.

    2009-01-01

    Understanding the temporal and spatial dynamics of key water balance components of the Nile River will provide important information for the management of its water resources. This study used satellite-derived rainfall and other key weather variables derived from the Global Data Assimilation System to estimate and map the distribution of rainfall, actual evapotranspiration (ETa), and runoff. Daily water balance components were modelled in a grid-cell environment at 0.1 degree (~10 km) spatial resolution for 7 years from 2001 through 2007. Annual maps of the key water balance components and derived variables such as runoff and ETa as a percent of rainfall were produced. Generally, the spatial patterns of rainfall and ETa indicate high values in the upstream watersheds (Uganda, southern Sudan, and southwestern Ethiopia) and low values in the downstream watersheds. However, runoff as a percent of rainfall is much higher in the Ethiopian highlands around the Blue Nile subwatershed. The analysis also showed the possible impact of land degradation in the Ethiopian highlands in reducing ETa magnitudes despite the availability of sufficient rainfall. Although the model estimates require field validation for the different subwatersheds, the runoff volume estimate for the Blue Nile subwatershed is within 7.0% of a figure reported from an earlier study. Further research is required for a thorough validation of the results and their integration with ecohydrologic models for better management of water and land resources in the various Nile Basin ecosystems. Published in 2009 by John Wiley & Sons, Ltd.

  16. Geochemistry of surface-waters in mineralized and non-mineralized areas of the Yukon-Tanana Uplands

    USGS Publications Warehouse

    Wang, B.; Wanty, R.B.; Vohden, J.

    2005-01-01

    The U.S. Geological Survey (USGS) and Alaska Department of Natural Resources (ADNR) are continuing investigations on element mobility in mineralized and non-mineralized areas of the Yukon-Tanana Upland in east-central Alaska. The chemistry of stream water is evaluated in the context of regional bedrock geology and geologic structure. Sampling sites were located in the Big Delta B2 quadrangle, which includes the mineralized areas of the Pogo claim block. The area is typified by steep, subarctic-alpine, boreal forest catchment basins. Samples were collected from catchments that either cross structural features and lithologic contacts, or are underlain by a single lithology. Waters are generally dilute (< 213 mg/L TDS), and are classified as Ca2+ and Mg2+-HCO3- to Ca2+ and Mg2+-SO42- waters. Gneissic lithologies are more SO42- dominated than the intrusive units. The major-ion chemistry of the waters reflects a rock-dominated aqueous system. Trace-element concentrations in water are generally low; however, As and Sb are detected near mineralized areas but in most cases rapidly attenuated downstream and processes other than simple dilution are controlling the concentrations of these trace elements. There is a tendency toward increasing SO42- concentrations downstream in waters both proximal and distal to mineralized areas. More work is necessary to determine what proportion of the increase in SO42- could be derived from the oxidation of sulfide minerals as opposed to water influenced by the underlying gneissic units.

  17. Geochemistry of thermal/mineral waters in the Clear Lake region, California, and implications for hot dry rock geothermal development

    SciTech Connect

    Goff, F.; Adams, A.I.; Trujillo, P.E.; Counce, D.; Mansfield, J.

    1993-02-01

    Thermal/mineral waters of the Clear Lake region are broadly classified as thermal meteoric and connote types based on chemical and isotopic criteria. Ratios of conservative components such as B/Cl are extremely different among all thermal/mineral waters of the Clear Lake region except for clusters of waters emerging from specific areas such as the Wilbur Springs district and the Agricultural Park area south of Mt. Konocti. In contrast, ratios of conservative components in large, homogeneous geothermal reservoirs are constant. Stable isotope values of Clear Lake region waters show a mixing trend between thermal meteoric and connote end-members. The latter end-member has enriched [delta]D as well as enriched d[sup l8]O, very different from typical high-temperature geothermal reservoir waters. Tritium data and modeling of ages indicate most Clear Lake region waters are 500 to > 10,000 yr., although mixing of old and young components is implied by the data. The age of end-member connate water is probably > 10,000 yr. Subsurface equilibration temperature of most thermal/mineral waters of the Clear Lake region is [le] 150[degrees]C based on chemical geothermometers but it is recognized that Clear Lake region waters are not typical geothermal fluids and that they violate rules of application of many geothermometers. The combined data indicate that no large geothermal reservoir underlies the Clear Lake region and that small localized reservoirs have equilibration temperatures [le] 150[degrees]C (except for Sulphur Bank Mine). Hot dry rock technologies are the best way to commercially exploit the known high temperatures existing beneath the Clear Lake region, particularly within the main Clear Lake volcanic field.

  18. Structure and dynamics of amorphous water ice.

    PubMed

    Laufer, D; Kochavi, E; Bar-Nun, A

    1987-12-15

    Further insight into the structure and dynamics of amorphous water ice, at low temperatures, was obtained by trapping in it Ar, Ne, H2, and D2. Ballistic water-vapor deposition results in the growth of smooth, approximately 1 x 0.2 micrometer2, ice needles. The amorphous ice seems to exist in at least two separate forms, at T < 85 K and at 85 < T < 136.8 K, and transform irreversibly from one form to the other through a series of temperature-dependent metastable states. The channels formed by the water hexagons in the ice are wide enough to allow the free penetration of H2 and D2 into the ice matrix even in the relatively compact cubic ice, resulting in H2-(D2-) to-ice ratios (by number) as high as 0.63. The larger Ar atoms can penetrate only into the wider channels of amorphous ice, and Ne is an intermediate case. Dynamic percolation behavior explains the emergence of Ar and Ne (but not H2 and D2) for the ice, upon warming, in small and big gas jets. The big jets, each containing approximately 5 x 10(10) atoms, break and propel the ice needles. Dynamic percolation also explains the collapse of the ice matrix under bombardment by Ar , at a pressure exceeding 2.6 dyn cm-2, and the burial of huge amounts of gas inside the collapsed matrix, up to an Ar-to-ice of 3.3 (by number). The experimental results could be relevant to comets, icy satellites, and icy grain mantles in dense interstellar clouds.

  19. Structure and dynamics of amorphous water ice

    NASA Technical Reports Server (NTRS)

    Laufer, D.; Kochavi, E.; Bar-Nun, A.; Owen, T. (Principal Investigator)

    1987-01-01

    Further insight into the structure and dynamics of amorphous water ice, at low temperatures, was obtained by trapping in it Ar, Ne, H2, and D2. Ballistic water-vapor deposition results in the growth of smooth, approximately 1 x 0.2 micrometer2, ice needles. The amorphous ice seems to exist in at least two separate forms, at T < 85 K and at 85 < T < 136.8 K, and transform irreversibly from one form to the other through a series of temperature-dependent metastable states. The channels formed by the water hexagons in the ice are wide enough to allow the free penetration of H2 and D2 into the ice matrix even in the relatively compact cubic ice, resulting in H2-(D2-) to-ice ratios (by number) as high as 0.63. The larger Ar atoms can penetrate only into the wider channels of amorphous ice, and Ne is an intermediate case. Dynamic percolation behavior explains the emergence of Ar and Ne (but not H2 and D2) for the ice, upon warming, in small and big gas jets. The big jets, each containing approximately 5 x 10(10) atoms, break and propel the ice needles. Dynamic percolation also explains the collapse of the ice matrix under bombardment by Ar , at a pressure exceeding 2.6 dyn cm-2, and the burial of huge amounts of gas inside the collapsed matrix, up to an Ar-to-ice of 3.3 (by number). The experimental results could be relevant to comets, icy satellites, and icy grain mantles in dense interstellar clouds.

  20. The effect of weathering in the Buyukmelen River basin on the geochemistry of suspended and bed sediments and the hyrogeochemical characteristics of river water, Duzce, Turkey

    NASA Astrophysics Data System (ADS)

    Pehlivan, Rustem

    2010-07-01

    The Buyukmelen River is expected to be a water source that can supply the drinking water needs of Istanbul until 2040. The drinking and utility water needs of Istanbul are to transport water from the Buyukmelen River to Istanbul via pipeline and pump it into the Alibeykoy and Omerli reservoirs when their water levels drop. The Buyukmelen River is located in the province of Duzce in 170 km east of Istanbul and its water basin is approximately 2250 km 2. The Buyukmelen River flows muddy in the rainy season and into the Black Sea. The chemical compositions of natural waters alter due to interaction with geological formations, physical and chemical weathering of various rocks and the effects of mining and agricultural production. A research was conducted at the Buyukmelen River basin to determine the effects of hydrological processes. Therefore, the samples of rocks, soil, stream water, suspended and bed sediment were collected from the Buyukmelen River basin. Geochemical and water chemistry analyses of samples were performed at ALS Chemex laboratories, Canada. The bed sediments contain quartz, calcite, plagioclase, amphibole and clay minerals. The clay minerals in the suspended and bed sediment samples are kaolinite, smectite and illite. The water samples collected from the Aksu, Kucukmelen, Asarsu and Ugursuyu streams and the Buyukmelen River in winter (December 2005) and summer (June 2006) periods are rich in Ca and HCO 3 ions. The ions most abundant in rainfall sample are HCO 3 and Na. The ion compositions of surface waters have increased due to the weathering of limestone, agglomerate and volcanic sandstones, light acidic rainfall, semi-arid Black Sea climate in the Buyukmelen basin. The suspended sediment amount of the Buyukmelen River in the rainy season (December 2005) is 174 mg/l. According to the water contamination regulation of Turkey, the Buyukmelen Rivers belongs to quality class 4 based on Al ion and to quality class 3 based on Fe ion in winter period

  1. Polarizable water model for Dissipative Particle Dynamics

    NASA Astrophysics Data System (ADS)

    Pivkin, Igor; Peter, Emanuel

    2015-11-01

    Dissipative Particle Dynamics (DPD) is an efficient particle-based method for modeling mesoscopic behavior of fluid systems. DPD forces conserve the momentum resulting in a correct description of hydrodynamic interactions. Polarizability has been introduced into some coarse-grained particle-based simulation methods; however it has not been done with DPD before. We developed a new polarizable coarse-grained water model for DPD, which employs long-range electrostatics and Drude oscillators. In this talk, we will present the model and its applications in simulations of membrane systems, where polarization effects play an essential role.

  2. Ground-water quality and geochemistry of aquifers associated with coal in the Allegheny and Monongahela formations, southeastern Ohio

    USGS Publications Warehouse

    Razem, A.C.; Sedam, A.C.

    1985-01-01

    Ground water from aquifers associated with coal beds in the Allegheny and Monongahela Formations in southeastern Ohio is predominantly a calcium magnesium bicarbonate type. Sodium bicarbonate type water is less common. Isolated areas of sodium chloride and calcium sulfate types also are present. The water is predominantly very hard, and has a median hardness concentration of 258 milligrams per liter as calcium carbonate and a median dissolved-solids concentration of 436 milligrams per liter. Few wells contain water with dissolved-solids concentrations in excess of 1,000 milligrams per liter. Bicarbonate concentration in ground water was found to be significantly different among coals, whereas concentrations of bicarbonate, hardness, calcium, magnesium, sodium, iron, manganese, and strontium were significantly different between ground water in the Allegheny and Monongahela Formations. Many constituents are significantly correlated, but few correlation coefficients are high. The presence of sulfate or iron is attributed to the kinetic mechanism operating during the oxidation of pyrite. The position along the sulfide or ferrous-iron oxidation pathways controls the reaction products of pyrite found in solution, and the formation of either the sulfate of iron constituents. The availability and rate of diffusion of oxygen in the formations exerts control on the water quality. Discriminant-function analysis correctly classifies 89 percent of the observations into the Allegheny or Monongahela Formations. As a verifications, 39 of 41 observations from another study were correctly classified by formation. The differences in water chemistry between the Allegheny and the Monongahela Formations are gradational and are attributed the oxidation of iron sulfide. The diffusion and availability of oxygen, which controls the chemical reaction, is regulated by the porosity and permeability of the rock with respect to oxygen and the presence or absence of carbonates, which controls the

  3. Questa Baseline and Pre-Mining Ground-Water Quality Investigation. 25. Summary of Results and Baseline and Pre-Mining Ground-Water Geochemistry, Red River Valley, Taos County, New Mexico, 2001-2005

    USGS Publications Warehouse

    Nordstrom, D. Kirk

    2008-01-01

    -sediment chemistry; geomorphology and its effect on ground-water flow; geophysical studies on depth to ground-water table and depth to bedrock; bedrock fractures and their potential influence on ground-water flow; leaching studies of scars and waste-rock piles; mineralogy and mineral chemistry and their effect on ground-water quality; debris-flow hazards; hydrology and water balance for the Red River Valley; ground-water geochemistry of selected wells undisturbed by mining in the Red River Valley; and quality assurance and quality control of water analyses. Studies aimed specifically at the Straight Creek natural-analog site include electrical surveys; high-resolution seismic survey; age-dating with tritium/helium; water budget; ground-water hydrology and geochemistry; and comparison of mineralogy and lithology to that of the mine site. The highly mineralized and hydrothermally altered volcanic rocks of the Red River Valley contain several percent pyrite in the quartz-sericite-pyrite (QSP) alteration zone, which weather naturally to acid-sulfate surface and ground waters that discharge to the Red River. Weathering of waste-rock piles containing pyrite also contributes acid water that eventually discharges into the Red River. These acid discharges are neutralized by circumneutral-pH, carbonate-buffered surface and ground waters of the Red River. The buffering capacity of the Red River, however, decreases from the town of Red River to the U.S. Geological Survey (USGS) gaging station near Questa. During short, but intense, storm events, the buffering capacity is exceeded and the river becomes acid from the rapid flushing of acidic materials from natural scar areas. The lithology, mineralogy, elevation, and hydrology of the Straight Creek proximal analog site were found to closely approximate those of the mine site with the exception of the mine site?s Sulphur Gulch catchment. Sulphur Gulch contains three subcatchments?upper Sulphur Gulch, Blind Gulch, and Spring Gulc

  4. Changes in acidity and metal geochemistry in soils, groundwater, drain and river water in the Lower Murray River after a severe drought.

    PubMed

    Mosley, Luke M; Fitzpatrick, Rob W; Palmer, David; Leyden, Emily; Shand, Paul

    2014-07-01

    Acid sulfate soils with sulfuric material (pH<4) can have significant impacts on surface water quality and aquatic ecosystems due to low pH and high soluble metal concentrations in runoff and drainage discharges. There has been limited research on the complex geochemical transformations that occur along flow pathways from the soil acidity source to receiving waters. We studied the integrated geochemistry of metals in acid sulfate soils with sulfuric material, groundwater, drain and river water in the Lower Murray River (South Australia) over a 2 year period. The oxidation of an estimated 3500 ha of acid sulfate soils with sulfidic material (pH>4) underlying this former floodplain occurred due to falling river and groundwater levels during the 2006-2010 extreme "millennium" drought. A low pH (<4.5) soil layer was found approximately 1-2.5m below ground level with substantial amounts (up to 0.2 mol H(+)/kg dry weight) of available/soluble acidity and retained acidity in the form of the Fe oxyhydroxy sulfate mineral jarosite. The jarosite appears to be dissolving over time and buffering the sub-surface soil layers at pH≈4. Metal (Fe, Al, Mn) and metalloid (As) lability was greatly increased in the acidic soil layer. Highly acidic and metal rich groundwater (median pH 4.3, Fe, Al, Mn of 0.04-0.52 mmol/L) was observed at the same depths as the acidic soil layers. Nearly all of the dissolved Fe in the groundwater was present as Fe(2+). In the drains, increases in pH and redox potential promoted formation of the Fe oxyhydroxysulfate mineral schwertmannite. This mineral precipitation transferred a portion of the dissolved acidity to the drain sediments. Upon discharge to, and dilution of, the acid drainage in the river, pH neutralisation and rapid oxidation, hydrolysis, and precipitation of solid Al and Fe phases occurred in a localised area. Acidity is persisting (>3 years) following a return to pre-drought water levels.

  5. Regional ground-water flow and geochemistry in the Midwest Basins and Arches aquifer system in parts of Indiana, Ohio, Michigan and Illinois

    USGS Publications Warehouse

    Eberts, Sandra M.; George, Lori L.

    2000-01-01

    This report synthesizes information on the regional ground-water flow and geochemistry in the Midwestern Basins and Arches aquifer system in parts of Indiana, Ohio, Michigan, and Illinois. Aquifers that compose this water-table aquifer system include glacial aquifers and an underlying, areally extensive carbonate-rock aquifer. Water within the aquifers is most commonly a Ca-Mg-HCO3 type or a Ca-Mg-SO4 type. In general, the distribution of hydrochemical facies within the aquifer system is controlled by the mineralogy of the aquifer material, rather than by a chemical evolution of water along general directions of regional ground-water flow.Some ground-water flow systems within the aquifer system provide base flow to streams in response to ground-water recharge events. Other (often deeper) ground-water flow systems respond minimally to variations in ground-water recharge from precipitation and provide a fairly constant supply of water to streams. Streamflow hydrographs and base-flow duration curves were used to estimate such components of base flow in selected streams for long-term steady-state conditions in the aquifer system. Mean sustained ground-water discharge (discharge from fairly stable ground-water flow systems) ranges from 3 to 50 percent of mean ground-water discharge (discharge from all ground-water flow systems) to the selected stream reaches. These percentages indicate that 50 to 97 percent of base flow in the streams within the study area can be attributed to transient ground-water flow systems, which typically have a major component of local-scale flow. Because ground-water flow across the external boundaries of the aquifer system is minimal, such percentages indicate that most ground-water flow in the aquifer system is associated with seasonally transient local flow systems.Results of a ground-water flow model that was calibrated by use of regression methods and that simulates regional flow systems within the aquifer system (approximately 10 percent

  6. Geochemistry of ground water in alluvial basins of Arizona and adjacent parts of Nevada, New Mexico, and California

    USGS Publications Warehouse

    Robertson, Frederick N.

    1991-01-01

    Chemical and isotope analyses of ground water from 28 basins in the Basin and Range physiographic province of Arizona and parts of adjacent States were used to evaluate ground-water quality, determine processes that control ground-water chemistry, provide independent insight into the hydrologic flow system, and develop information transfer. The area is characterized by north- to northwest-trending mountains separated by alluvial basins that form a regional topography of alternating mountains and valleys. On the basis of ground-water divides or zones of minimal basin interconnection, the area was divided into 72 basins, each representing an individual aquifer system. These systems are joined in a dendritic pattern and collectively constitute the major water resource in the region. Geochemical models were developed to identify reactions and mass transfer responsible for the chemical evolution of the ground water. On the basis of mineralogy and chemistry of the two major rock associations of the area, a felsic model and a mafic model were developed to illustrate geologic, climatic, and physiographic effects on ground-water chemistry. Two distinct hydrochemical processes were identified: (1) reactions of meteoric water with minerals and gases in recharge areas and (2) reactions of ground water as it moves down the hydraulic gradient. Reactions occurring in recharge and downgradient areas can be described by a 13-component system. Major reactions are the dissolution and precipitation of calcite and dolomite, the weathering of feldspars and ferromagnesian minerals, the formation of montmorillonite, iron oxyhydroxides, and probably silica, and, in some basins, ion exchange. The geochemical modeling demonstrated that relatively few phases are required to derive the ground-water chemistry; 14 phases-12 mineral and 2 gas-consistently account for the chemical evolution in each basin. The final phases were selected through analysis of X-ray diffraction and fluorescence data

  7. Dynamical properties of water-methanol solutions.

    PubMed

    Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Vasi, Cirino; Vasi, Sebastiano; Stanley, H Eugene

    2016-02-14

    We study the relaxation times tα in the water-methanol system. We examine new data and data from the literature in the large temperature range 163 < T < 335 K obtained using different experimental techniques and focus on how tα affects the hydrogen bond structure of the system and the hydrophobicity of the alcohol methyl group. We examine the relaxation times at a fixed temperature as a function of the water molar fraction XW and observe two opposite behaviors in their curvature when the system moves from high to low T regimes. This behavior differs from that of an ideal solution in that it has excess values located at different molar fractions (XW = 0.5 for high T and 0.75 in the deep supercooled regime). We analyze the data and find that above a crossover temperature T ∼ 223 K, hydrophobicity plays a significant role and below it the water tetrahedral network dominates. This temperature is coincident with the fragile-to-strong dynamical crossover observed in confined water and supports the liquid-liquid phase transition hypothesis. At the same time, the reported data suggest that this crossover temperature (identified as the Widom line temperature) also depends on the alcohol concentration.

  8. Monitoring water phase dynamics in winter clouds

    NASA Astrophysics Data System (ADS)

    Campos, Edwin F.; Ware, Randolph; Joe, Paul; Hudak, David

    2014-10-01

    This work presents observations of water phase dynamics that demonstrate the theoretical Wegener-Bergeron-Findeisen concepts in mixed-phase winter storms. The work analyzes vertical profiles of air vapor pressure, and equilibrium vapor pressure over liquid water and ice. Based only on the magnitude ranking of these vapor pressures, we identified conditions where liquid droplets and ice particles grow or deplete simultaneously, as well as the conditions where droplets evaporate and ice particles grow by vapor diffusion. The method is applied to ground-based remote-sensing observations during two snowstorms, using two distinct microwave profiling radiometers operating in different climatic regions (North American Central High Plains and Great Lakes). The results are compared with independent microwave radiometer retrievals of vertically integrated liquid water, cloud-base estimates from a co-located ceilometer, reflectivity factor and Doppler velocity observations by nearby vertically pointing radars, and radiometer estimates of liquid water layers aloft. This work thus makes a positive contribution toward monitoring and nowcasting the evolution of supercooled droplets in winter clouds.

  9. Hydrogeochemical evolution of inland lakes' water: A study of major element geochemistry in the Wadi El Raiyan depression, Egypt.

    PubMed

    Mohamed, Essam A; El-Kammar, Ahmed M; Yehia, Mohamed M; Abu Salem, Hend S

    2015-11-01

    Wadi El Raiyan is a great depression located southwest of Cairo in the Western Desert of Egypt. Lake Qarun, located north of the study area, is a closed basin with a high evaporation rate. The source of water in the lake is agricultural and municipal drainage from the El Faiyum province. In 1973, Wadi El Raiyan was connected with the agricultural wastewater drainage system of the Faiyum province and received water that exceeded the capacity of Lake Qarun. Two hydrogeological regimes have been established in the area: (i) higher cultivated land and (ii) lower Wadi El Raiyan depression lakes. The agricultural drainage water of the cultivated land has been collected in one main drain (El Wadi Drain) and directed toward the Wadi El Raiyan depression, forming two lakes at different elevations (upper and lower). In the summer of 2012, the major chemical components were studied using data from 36 stations distributed over both hydrogeological regimes in addition to one water sample collected from Bahr Youssef, the main source of freshwater for the Faiyum province. Chemical analyses were made collaboratively. The major ion geochemical evolution of the drainage water recharging the El Raiyan depression was examined. Geochemically, the Bahr Youssef sample is considered the starting point in the geochemical evolution of the studied surface water. In the cultivated area, major-ion chemistry is generally influenced by chemical weathering of rocks and minerals that are associated with anthropogenic inputs, as well as diffuse urban and/or agricultural drainage. In the depression lakes, the water chemistry generally exhibits an evaporation-dependent evolutionary trend that is further modified by cation exchange and precipitation of carbonate minerals. PMID:26644942

  10. Hydrogeochemical evolution of inland lakes’ water: A study of major element geochemistry in the Wadi El Raiyan depression, Egypt

    PubMed Central

    Mohamed, Essam A.; El-Kammar, Ahmed M.; Yehia, Mohamed M.; Abu Salem, Hend S.

    2015-01-01

    Wadi El Raiyan is a great depression located southwest of Cairo in the Western Desert of Egypt. Lake Qarun, located north of the study area, is a closed basin with a high evaporation rate. The source of water in the lake is agricultural and municipal drainage from the El Faiyum province. In 1973, Wadi El Raiyan was connected with the agricultural wastewater drainage system of the Faiyum province and received water that exceeded the capacity of Lake Qarun. Two hydrogeological regimes have been established in the area: (i) higher cultivated land and (ii) lower Wadi El Raiyan depression lakes. The agricultural drainage water of the cultivated land has been collected in one main drain (El Wadi Drain) and directed toward the Wadi El Raiyan depression, forming two lakes at different elevations (upper and lower). In the summer of 2012, the major chemical components were studied using data from 36 stations distributed over both hydrogeological regimes in addition to one water sample collected from Bahr Youssef, the main source of freshwater for the Faiyum province. Chemical analyses were made collaboratively. The major ion geochemical evolution of the drainage water recharging the El Raiyan depression was examined. Geochemically, the Bahr Youssef sample is considered the starting point in the geochemical evolution of the studied surface water. In the cultivated area, major-ion chemistry is generally influenced by chemical weathering of rocks and minerals that are associated with anthropogenic inputs, as well as diffuse urban and/or agricultural drainage. In the depression lakes, the water chemistry generally exhibits an evaporation-dependent evolutionary trend that is further modified by cation exchange and precipitation of carbonate minerals. PMID:26644942

  11. Geochemistry of acid mine drainage from a coal mining area and processes controlling metal attenuation in stream waters, southern Brazil.

    PubMed

    Campaner, Veridiana P; Luiz-Silva, Wanilson; Machado, Wilson

    2014-05-14

    Acid drainage influence on the water and sediment quality was investigated in a coal mining area (southern Brazil). Mine drainage showed pH between 3.2 and 4.6 and elevated concentrations of sulfate, As and metals, of which, Fe, Mn and Zn exceeded the limits for the emission of effluents stated in the Brazilian legislation. Arsenic also exceeded the limit, but only slightly. Groundwater monitoring wells from active mines and tailings piles showed pH interval and chemical concentrations similar to those of mine drainage. However, the river and ground water samples of municipal public water supplies revealed a pH range from 7.2 to 7.5 and low chemical concentrations, although Cd concentration slightly exceeded the limit adopted by Brazilian legislation for groundwater. In general, surface waters showed large pH range (6 to 10.8), and changes caused by acid drainage in the chemical composition of these waters were not very significant. Locally, acid drainage seemed to have dissolved carbonate rocks present in the local stratigraphic sequence, attenuating the dispersion of metals and As. Stream sediments presented anomalies of these elements, which were strongly dependent on the proximity of tailings piles and abandoned mines. We found that precipitation processes in sediments and the dilution of dissolved phases were responsible for the attenuation of the concentrations of the metals and As in the acid drainage and river water mixing zone. In general, a larger influence of mining activities on the chemical composition of the surface waters and sediments was observed when enrichment factors in relation to regional background levels were used.

  12. Geochemistry of surface water in alpine catchments in central Colorado, USA: Resolving host-rock effects at different spatial scales

    USGS Publications Warehouse

    Wanty, R.B.; Verplanck, P.L.; San, Juan C.A.; Church, S.E.; Schmidt, T.S.; Fey, D.L.; deWitt, E.H.; Klein, T.L.

    2009-01-01

    The US Geological Survey is conducting a study of surface-water quality in the Rocky Mountains of central Colorado, an area of approximately 55,000 km2. Using new and existing geologic maps, the more than 200 rock formations represented in the area were arranged into 17 groups based on lithologic similarity. The dominant regional geologic feature affecting water quality in central Colorado is the Colorado mineral belt (CMB), a NE-trending zone hosting many polymetallic vein or replacement deposits, and porphyry Mo deposits, many of which have been mined historically. The influence of the CMB is seen in lower surface-water pH (<5), and higher concentrations of SO42 - (>100 mg/L) and chalcophile metals such as Cu (>10 ??g/L), Zn (>100 ??g/L), and Cd (>1 ??g/L) relative to surface water outside the CMB. Not all streams within the CMB have been affected by mineralization, as there are numerous catchments within the CMB that have no mineralization or alteration exposed at the surface. At the regional-scale, and away from sites affected by mineralization, hydrothermal alteration, or mining, the effects of lithology on water quality can be distinguished using geochemical reaction modeling and principal components analysis. At local scales (100 s of km2), effects of individual rock units on water chemistry are subtle but discernible, as shown by variations in concentrations of major lithophile elements or ratios between them. These results demonstrate the usefulness of regional geochemical sampling of surface waters and process-based interpretations incorporating geologic and geochemical understanding to establish geochemical baselines.

  13. The geochemistry of water near a surficial organic-rich uranium deposit, northeastern Washington State, U.S.A.

    USGS Publications Warehouse

    Zielinski, R.A.; Otton, J.K.; Wanty, R.B.; Pierson, C.T.

    1987-01-01

    The chemistry of three stream, three spring and six near-surface waters in the vicinity of a Holocene organic-rich uranium deposit is described, with particular emphasis on the chemistry of U. Results characterize the solution behavior of uranium as U-bearing water interacts with relatively undecomposed, surficial organic matter. Of the measured major and trace chemical species, only U is consistently highly enriched (17-318 ppb) relative to reported values for regional waters, or to literature values for waters in largely granitic terrains. R-mode factor analysis of the chemical data suggests that most U is present in a soluble form, but that some U is also associated with fine suspended particulates of clay, organic matter, or hydrous oxides. Calculations that apply thermodynamic data to predict U speciation in solution indicate the relative importance of uranyl carbonate and uranyl phosphate complexes. Analysis of more finely filtered samples (0.05 ??m vs. 0.45 ??m), and direct radiographic observations using fission-track detectors suspended in the waters indicate the presence of some uraniferous particulate matter. Application of existing thermodynamic data for uranous- and uranyl-bearing minerals indicates that all waters are undersaturated with U minerals as long as ambient Eh ??? +0.1 v. If coexisting surface and near-surface waters are sufficiently oxidizing, initial fixation of U in the deposit should be by a mechanism of adsorption. Alternatively, more reducing conditions may prevail in deeper pore waters of the organic-rich host sediments, perhaps leading to direct precipitation or diagenetic formation of U4+ minerals. A 234U 238U alpha activity ratio of 1.08 ?? 0.02 in a spring issuing from a hillslope above the deposit suggests a relatively soluble source of U. In contrast, higher activity ratios of 234U 238U (??? 1.3) in waters in contact with the uraniferous valley-fill sediments suggest differences in the nature of interaction between groundwater

  14. Effects of sediment depositional environment and ground-water flow on the quality and geochemistry of water in aquifers in sediments of Cretaceous age in the coastal plain of South Carolina

    USGS Publications Warehouse

    Speiran, Gary K.; Aucott, Walter R.

    1994-01-01

    The quality and geochemistry of ground water are significantly affected by the depositional environment of aquifer sediments. Cretaceous sediments in the Coastal Plain of South Carolina have been deposited in fluvial, delta-plain, marginal-marine, and marine environments. Depositional environments of sediments within a single aquifer may grade from nonmarine, fluvial, or upper delta plain near the updip limit of the aquifer to transitional, lower delta plain and to marine toward the coast. In nonmarine sediments the major source of inorganic carbon in the water is the decomposition of organic material. The major aqueous geochemical processes are the dissolution and alteration of silicate minerals. Silica makes up a major part of the dissolved constituents in water from these sediments. In transitional and marine sediments the major aqueous geochemical processes are (1) the dissolution of calcium carbonate by hydrolysis and by carbonic acid derived from the decomposition of organic material and (2) the exchange of calcium in solution for sodium on the marine-clay minerals. The clay minerals may also serve as buffers by neutralizing the hydroxyl ion produced by hydrolysis. The effects of incompletely flushed dilute saltwater on water quality increase toward the coast and toward the northeast.

  15. Quantifying early 17th century changes in Chesapeake Bay estuarine carbon dynamics from James River, VA oyster geochemistry

    NASA Astrophysics Data System (ADS)

    Grimm, B. L.; Spero, H. J.; Harding, J. M.

    2012-12-01

    The first successful European colonization of North America occurred in 1607 following the arrival of English settlers at Jamestown, Virginia. Within a few decades, land use changes and clear-cutting farming practices dramatically altered the terrestrial landscape and removed the overlying canopy and stabilizing root network of the previously-dominant hardwood forests. The Eastern oyster, Crassostrea virginica, has inhabited the Chesapeake Bay since the end of the last deglaciation. During the start of the Jamestown Colony, an extensive drought (1606-1612) shifted James River salinity zones upriver, expanding the available oyster habitat to the vicinity of Jamestown. This allowed the colonists to collect and eat oysters from areas near the colony down to the river's entry into the bay, and later discard the shells in wells and trash pits that have recently been excavated. The oysters' calcium carbonate shells discovered in these deposits act as multi-year stationary recorders preserving the local environmental chemistry throughout their life until collection. Here we present δ13C, δ18O, and radiocarbon data from historical oyster shell hinge transects that encompass the time period between ~1609 and the early 1700s. Samples include shells from the 1609 Jamestown freshwater well and five additional sites, as well as modern shells collected in 2006. Because shell δ13C and radiocarbon (14C) reflect James River δ13CDIC, it is possible to document carbon source changes during this period of land use change. Our preliminary data suggest a decrease in ambient δ13CDIC of approximately 2‰ between just prior to 1609 conditions and the modern estuary. This is most likely due to an increase in isotopically light organic carbon loading into the river as water moves more rapidly through the terrestrial system. Radiocarbon reservoir ages will also be presented to better constrain carbon flow through the system during this period of disturbance. δ18O measurements from the

  16. The hydro- and multi-isotope geochemistry of iron-rich ground waters emerging at the southern Baltic Sea coast line

    NASA Astrophysics Data System (ADS)

    Lipka, Marko; Wu, Zijun; Escher, Peter; Struck, Ulrich; Dellwig, Olaf; Schafmeister, Maria; Böttcher*, Michael E.

    2013-04-01

    Iron-rich groundwater springs emerging at the shore zone of the southern Baltic Sea (BS; Site Meschendorf) were examined on a seasonal base for a period of about two years. Besides major, minor, and trace elements, stable isotopes of water (H-2, O-18), dissolved inorganic carbon (DIC; C-13), and sulfate (S-34) were analyzed. The stream bed sediment was extracted for the geochemistry of the newly formed precipitates and further characterized via SEM-EDAX. Subsequently, the hydrogeochemical results were subjected to a thermodynamic analysis via the PHREEQC speciation model. The springs emerge from small pits (about 60 cm diameter; up to 15cm depth). Surrounding sediments are sandy with gravels found at depth and corresponding high permeabilities. The positions of different springs on the shore zone were stable during the investigation period while the shape of the pits and the stream beds may vary due to wind- and wave-driven forces. Selected measurements of spring yield discharges close to 10 L/min. The H-2 and O-18 contents of the spring waters indicate the ground water to originate from relatively young mixed meteoric waters. The hydrochemistry of the springs was similar and showed some variability in between which indicates that the genetic processes for the ground water before reaching the surface may slightly differ. The springs are characterized by dissolved Ca, Mg, Na, DIC and sulfate, mainly reflecting the interaction with soils and bedrocks in the recharge area that is dominated by marly till. The oxygen-free ground water is rich in Fe, P, and DIC. Iron and dissolved sulfate originate from the oxidation of pyrite, as further confirmed by the 34-S signature of sulfate. The carbon isotope signature of DIC indicates a mixture of biogenic CO2 from the soil zone with some water-rock interaction with carbonate minerals. The streams flow towards the BS and, in contact with the atmosphere, outgas carbon dioxide and takes up oxygen. Upon CO2-degassing, C-12 is

  17. Geochemistry of pore waters from Shell Oil Company drill holes on the continental slope of the northern Gulf of Mexico

    USGS Publications Warehouse

    Manheim, F. T.; Bischoff, J.L.

    1969-01-01

    Pore waters were analyzed from 6 holes drilled from M.V. "Eureka" as a part of the Shell Oil Co. deeper offshore study. The holes were drilled in water depths of 600-3,000 ft. (approximately 180-550 m) and penetrated up to 1,000 ft. (300 m) of Pliocene-Recent clayey sediments. Salt and anhydrite caprock was encountered in one diapiric structure on the continental slope. Samples from holes drilled near diapiric structures showed systematic increases of pore-water salinity with depth, suggestive of salt diffusion from underlying salt plugs. Anomalous concentrations of K and Br indicate that at least one plug contains late-stage evaporite minerals. Salinities approaching halite saturation were observed. Samples from holes away from diapiric structures showed little change in pore-water chemistry, except for loss of SO4 and other variations attributable to early-stage diagenetic reactions with enclosing sediments. Thus, increased salt concentrations in even shallow sediments from this part of the Gulf appear to provide an indicator of salt masses at depth. ?? 1969.

  18. Radioactivity and geochemistry of selected mineral-spring waters in the Western United States; basic data and multivariate statistical analysis

    USGS Publications Warehouse

    Felmlee, J.K.; Cadigan, R.A.

    1982-01-01

    Multivariate statistical analyses were performed on data from 156 mineral-spring sites in nine Western States to analyze relationships among the various parameters measured in the spring waters. Correlation analysis and R-mode factor analysis indicate that three major factors affect water composition in the spring systems studied: (1) duration of water circulation, (2) depth of water circulation, and (3) partial pressure of carbon dioxide. An examination of factor scores indicates that several types of hydrogeologic systems were sampled. Most of the samples are (1) older water from deeper circulating systems having relatively high salinity, high temperature, and low Eh or (2) younger water from shallower circulating systems having relatively low salinity, low temperature, and high Eh. The rest of the samples are from more complex systems. Any of the systems can have a relatively high or low content of dissolved carbonate species, resulting in a low or high pH, respectively. Uranium concentrations are commonly higher in waters of relatively low temperature and high Eh, and radium concentrations are commonly higher in waters having a relatively high carbonate content (low pH) and, secondarily, relatively high salinity. Water samples were collected and (or) measurements were taken at 156 of the 171 mineral-spring sites visited. Various samples were analyzed for radium, uranium, radon, helium, and radium-228 as well as major ions and numerous trace elements. On-site measurements for physical properties including temperature, specific conductance, pH, Eh, and dissolved oxygen were made. All constituents and properties show a wide range of values. Radium concentrations range from less than 0.01 to 300 picocuries per liter; they average 1.48 picocuries per liter and have an anomaly threshold value of 171 picocuries per liter for the samples studied. Uranium concentrations range from less than 0.01 to 120 micrograms per liter and average 0.26 micrograms per liter; they

  19. Geochemistry of shallow ground water in coastal plain environments in the southeastern United States: Implications for aquifer susceptibility

    USGS Publications Warehouse

    Tesoriero, A.J.; Spruill, T.B.; Eimers, J.L.

    2004-01-01

    Ground-water chemistry data from coastal plain environments have been examined to determine the geochemical conditions and processes that occur in these areas and assess their implications for aquifer susceptibility. Two distinct geochemical environments were studied to represent a range of conditions: an inner coastal plain setting having more well-drained soils and lower organic carbon (C) content and an outer coastal plain environment that has more poorly drained soils and high organic C content. Higher concentrations of most major ions and dissolved inorganic and organic C in the outer coastal plain setting indicate a greater degree of mineral dissolution and organic matter oxidation. Accordingly, outer coastal plain waters are more reducing than inner coastal plain waters. Low dissolved oxygen (O2) and nitrate (NO 3-) concentrations and high iron (Fe) concentrations indicate that ferric iron (Fe (III)) is an important electron acceptor in this setting, while dissolved O2 is the most common terminal electron acceptor in the inner coastal plain setting. The presence of a wide range of redox conditions in the shallow aquifer system examined here underscores the importance of providing a detailed geochemical characterization of ground water when assessing the intrinsic susceptibility of coastal plain settings. The greater prevalence of aerobic conditions in the inner coastal plain setting makes this region more susceptible to contamination by constituents that are more stable under these conditions and is consistent with the significantly (p<0.05) higher concentrations of NO3- found in this setting. Herbicides and their transformation products were frequently detected (36% of wells sampled), however concentrations were typically low (<0.1 ??g/L). Shallow water table depths often found in coastal plain settings may result in an increased risk of the detection of pesticides (e.g., alachlor) that degrade rapidly in the unsaturated zone.

  20. Trace element geochemistry and surface water chemistry of the Bon Air coal, Franklin County, Cumberland Plateau, southeast Tennessee

    USGS Publications Warehouse

    Shaver, S.A.; Hower, J.C.; Eble, C.F.; McLamb, E.D.; Kuers, K.

    2006-01-01

    surface waters, highest levels of most trace elements occur in mine-adit or mine-dump drainage. Effluent flow rates strongly affect both acidity and trace element levels. Adit drainages where flow is only a trickle have the most acidic waters (pH 3.78-4.80) and highest trace element levels (up to two orders of magnitude higher than in non-mine site waters). Nonetheless, nearly all surface waters have low absolute concentrations of trace elements of environmental concern, and all waters sampled meet U.S. EPA primary drinking water standards and aquatic life criteria for all elements analyzed. Secondary drinking water standards are also met for all parameters except Al, pH, Fe, and Mn, but even in extreme cases (mine waters with pH as low as 3.78 and up to 1243 ppb Al, 6280 ppb Fe, and 721 ppb Mn, and non-mine dam-outflow waters with up to 18,400 ppb Fe and 1540 ppb Mn) downslope attenuation is apparently rapid, as down-drainage plateau-base streams show background levels for all these parameters. ?? 2005 Elsevier B.V. All rights reserved.

  1. Geochemistry of Mine Waste and Mill Tailings, Meadow Deposits, Streambed Sediment, and General Hydrology and Water Quality for the Frohner Meadows Area, Upper Lump Gulch, Jefferson County, Montana

    USGS Publications Warehouse

    Klein, Terry L.; Cannon, Michael R.; Fey, David L.

    2004-01-01

    Frohner Meadows, an area of low-topographic gradient subalpine ponds and wetlands in glaciated terrane near the headwaters of Lump Gulch (a tributary of Prickly Pear Creek), is located about 15 miles west of the town of Clancy, Montana, in the Helena National Forest. Mining and ore treatment of lead-zinc-silver veins in granitic rocks of the Boulder batholith over the last 120 years from two sites (Frohner mine and the Nellie Grant mine) has resulted in accumulations of mine waste and mill tailings that have been distributed downslope and downstream by anthropogenic and natural processes. This report presents the results of an investigation of the geochemistry of the wetlands, streams, and unconsolidated-sediment deposits and the hydrology, hydrogeology, and water quality of the area affected by these sources of ore-related metals. Ground water sampled from most shallow wells in the meadow system contained high concentrations of arsenic, exceeding the Montana numeric water-quality standard for human health. Transport of cadmium and zinc in ground water is indicated at one site near Nellie Grant Creek based on water-quality data from one well near the creek. Mill tailings deposited in upper Frohner Meadow contribute large arsenic loads to Frohner Meadows Creek; Nellie Grant Creek contributes large arsenic, cadmium, and zinc loads to upper Frohner Meadows. Concentrations of total-recoverable cadmium, copper, lead, and zinc in most surface-water sites downstream from the Nellie Grant mine area exceeded Montana aquatic-life standards. Nearly all samples of surface water and ground water had neutral to slightly alkaline pH values. Concentrations of arsenic, cadmium, lead, and zinc in streambed sediment in the entire meadow below the mine waste and mill tailings accumulations are highly enriched relative to regional watershed-background concentrations and exceed consensus-based, probable-effects concentrations for streambed sediment at most sites. Cadmium, copper, and

  2. Geochemistry of waters from springs, wells, and snowpack on and adjacent to Medicine Lake volcano, northern California

    USGS Publications Warehouse

    Mariner, R.H.; Lowenstern, Jacob B.

    1999-01-01

    Chemical analyses of waters from cold springs and wells of the Medicine Lake volcano and surrounding region indicate small chloride anomalies that may be due to water-rock interaction or limited mixing with high-temperature geothermal fluids. The Fall River Springs (FRS) with a combined discharge of approximately 37 m3/s, show a negative correlation between chloride (Cl) and temperature, implying that the Cl is not derived from a high-temperature geothermal fluid. The high discharge from the FRS indicates recharge over a large geographic region. Chemical and isotopic variations in the FRS show that they contain a mixture of three distinct waters. The isotopic composition of recharge on and adjacent to the volcano are estimated from the isotopic composition of snow and precipitation amounts adjusted for evapotranspiration. Enough recharge of the required isotopic composition (-100 parts per thousand ??D) is available from a combination of the Medicine Lake caldera, the Fall River basin and the Long Bell basin to support the slightly warmer components of the FRS (32 m3/s). The cold-dilute part of the FRS (approximately 5 m3/s) may recharge in the Bear Creek basin or at lower elevations in the Fall River basin.

  3. Geochemistry of the Adige River water from the Eastern Alps to the Adriatic Sea (Italy): evidences for distinct hydrological components and water-rock interactions.

    PubMed

    Natali, C; Bianchini, G; Marchina, C; Knöller, K

    2016-06-01

    The Adige River flows from the Eastern Alps to the Adriatic Sea and the understanding of its fluvial dynamics can be improved by geochemical and O-H isotopic investigation. The most negative isotopic compositions are recorded close to the source (δ(18)O between -14.1 and -13.8 ‰, δD between -100.3 and -97.0 ‰), and δD and δ(18)O values generally increase downstream through the upper part (UP, the mountainous sector), stabilizing along the lower part (LP, the alluvial plain) of the river with δ(18)O between -12.4 and -11.8 ‰, δD between -86.9 and -83.7 ‰. The isotopic variations along the stream path (δ(18)O-δD vs distance from the source) depict subparallel distributions for all the investigated periods, with less negative values recorded in winter. Total dissolved solids (TDS) concentration shows the lowest value (<100 mg/l) at the river source, jumping to 310 mg/l at the Rio Ram inflow, then decreasing down to the Isarco River confluence; from here, we observed an increase toward the river mouth, with different values in the distinct sampling periods. The lowest values (140-170 mg/l) were recorded during high discharge in spring, whereas higher TDS values (up to 250 mg/l) were recorded during winter low flow conditions. Extreme TDS values were observed in the estuarine samples (up to 450 mg/l), as result of mixing with seawater. The results allow for the identification of distinct water end-members: glacio-nival component(s) characterized by the most negative isotopic composition and extremely low TDS, a rainfall component characterized by intermediate isotopic and elemental composition and groundwater characterized by the less negative isotopic composition and comparatively higher TDS. An additional component is represented by seawater, which is recorded at the lowest reach of the river during drought periods. These contributions variously mix along the stream path in the distinct hydrological periods, and the presented data are a

  4. Geochemistry of the Adige River water from the Eastern Alps to the Adriatic Sea (Italy): evidences for distinct hydrological components and water-rock interactions.

    PubMed

    Natali, C; Bianchini, G; Marchina, C; Knöller, K

    2016-06-01

    The Adige River flows from the Eastern Alps to the Adriatic Sea and the understanding of its fluvial dynamics can be improved by geochemical and O-H isotopic investigation. The most negative isotopic compositions are recorded close to the source (δ(18)O between -14.1 and -13.8 ‰, δD between -100.3 and -97.0 ‰), and δD and δ(18)O values generally increase downstream through the upper part (UP, the mountainous sector), stabilizing along the lower part (LP, the alluvial plain) of the river with δ(18)O between -12.4 and -11.8 ‰, δD between -86.9 and -83.7 ‰. The isotopic variations along the stream path (δ(18)O-δD vs distance from the source) depict subparallel distributions for all the investigated periods, with less negative values recorded in winter. Total dissolved solids (TDS) concentration shows the lowest value (<100 mg/l) at the river source, jumping to 310 mg/l at the Rio Ram inflow, then decreasing down to the Isarco River confluence; from here, we observed an increase toward the river mouth, with different values in the distinct sampling periods. The lowest values (140-170 mg/l) were recorded during high discharge in spring, whereas higher TDS values (up to 250 mg/l) were recorded during winter low flow conditions. Extreme TDS values were observed in the estuarine samples (up to 450 mg/l), as result of mixing with seawater. The results allow for the identification of distinct water end-members: glacio-nival component(s) characterized by the most negative isotopic composition and extremely low TDS, a rainfall component characterized by intermediate isotopic and elemental composition and groundwater characterized by the less negative isotopic composition and comparatively higher TDS. An additional component is represented by seawater, which is recorded at the lowest reach of the river during drought periods. These contributions variously mix along the stream path in the distinct hydrological periods, and the presented data are a

  5. Geochemistry of carbonate cements in Cretaceous sandstones, southeast Benue Trough, Nigeria: Implications for geochemical evolution of formation waters

    NASA Astrophysics Data System (ADS)

    Odigi, Minapuye I.; Amajor, Levi C.

    2010-05-01

    Carbonate cements including calcite, siderite, dolomite/ankerite were formed throughout the diagenetic history of the Asu River Group, Eze-Aku Group and Campano-Maastrichtain proto-Niger Delta sequences were analyzed for their major and trace element (Fe, Mn, Mg, Ca and Sr) and isotopic compositions. The earliest, ferroan carbonate cement has the following mean major and trace element concentration: Fe - 0.11 wt.%; Mn - 0.43 wt.%; Mg - 2.16 wt.%; Sr - 1050 ppm. The late ferroan has the following mean compositions: Fe - 0.48 wt.%; Mn - 0.22 wt.%; Mg - 0.25 wt.%; Sr - 1010 ppm. Earliest Fe-calcites, formed prior to significant compaction of the sediments, are relatively enriched in Mg (up to 4.12 mol.%), and have δ 18O values between -4.45% and -6.898% PDB close to the ideal original Cretaceous marine pore waters. Late calcites are relatively Fe-calcites (up to 4.2 mol.%). The earliest ferroan calcite occurs in both the Albian Asu River Group and Eze-Aku Group while late ferroan occurs in the three lithostratigraphic units studied. These geochemical variations appear to have resulted principally to reflect changes in pore water chemistry during diagenesis. The high value of Sr in cements is most likely due to interaction between pore waters and Sr-rich clay and possibly feldspar in the three lithostratigraphic units studied. Pore water Fe 2+ concentration was probably controlled by diagenetic alterations involving Fe-bearing minerals (e.g. pyrite precipitation). The low δ 18O value of some calcite cements (-11.62‰, -12.66‰, -14.31‰ PDB) suggests that an influx of meteoric water may have occurred in the Turonian-Coniacian, although the low value could also result from an abnormal geothermal gradient associated with tectonic activity in the trough. The elemental and isotopic composition of these cements varies as a function of the time of precipitation.

  6. Dissociation energy and dynamics of water clusters

    NASA Astrophysics Data System (ADS)

    Ch'ng, Lee Chiat

    The state-to-state vibrational predissociation (VP) dynamics of water clusters were studied following excitation of a vibrational mode of each cluster. Velocity-map imaging (VMI) and resonance-enhanced multiphoton ionization (REMPI) were used to determine pair-correlated center-of-mass translational energy distributions. Product energy distributions and dissociation energies were determined. Following vibrational excitation of the HCl stretch fundamental of the HCl-H2O dimer, HCl fragments were detected by 2 + 1 REMPI via the f 3□2(nu' = 0) ← X 1Sigma+(nu'' = 0) and V1Sigma + (nu' = 11 and 12) ← X1Sigma+ (nu'' = 0) transitions. REMPI spectra clearly show HCl from dissociation produced in the ground vibrational state with J'' up to 11. The fragments' center-of-mass translational energy distributions were determined from images of selected rotational states of HCl and were converted to rotational state distributions of the water cofragment. All the distributions could be fit well when using a dimer dissociation energy of bond dissociation energy D0 = 1334 +/- 10 cm--1. The rotational distributions in the water cofragment pair-correlated with specific rotational states of HCl appear nonstatistical when compared to predictions of the statistical phase space theory. A detailed analysis of pair-correlated state distributions was complicated by the large number of water rotational states available, but the data show that the water rotational populations increase with decreasing translational energy. H2O fragments of this dimer were detected by 2 + 1 REMPI via the C˜1B1(000) ← X˜1A1(000) transition. REMPI clearly shows that H2O from dissociation is produced in the ground vibrational state. The fragment's center-of-mass translational energy distributions were determined from images of selected rotational states of H2O and were converted to rotational state distributions of the HCl cofragment. The distributions gave D0 = 1334 +/- 10 cm --1 and show a clear

  7. Water conditions and geochemistry in northern Adriatic anoxia-prone areas and response of benthic faunas to oxygen deficiencies

    NASA Astrophysics Data System (ADS)

    Zuschin, Martin; Riedel, Bettina; Stachowitsch, Michael; Cermelj, Branko

    2010-05-01

    One predicted effect of global climate change, specifically global warming, is the increase in the temperatures and stratification of shallow coastal and estuarine systems. This, coupled with ongoing anthropogenic eutrophication, will exacerbate hypoxia and benthic mortalities, significantly damaging these critical marine ecosystems. These phenomena are particularly severe on sublitoral soft-bottoms such as the poorly sorted silty sands at the study site in the northern Adriatic Sea. We deployed a specially developed underwater chamber to artificially induce anoxia in situ. Our Experimental Anoxia Generating Unit (EAGU) is a large plexiglass chamber that combines a digital camera with oxygen/hydrogen sulphide/pH sensors along with flashes and battery packs. The unit can be deployed for up to five days to autonomously generate oxygen crises and quantify both physico-chemical parameters and benthic responses. The system is initially positioned in an "open" configuration (open-sided aluminium frame) over the benthic fauna ("control" experiment). After 24 h the EAGU is switched to its "closed" configuration (plexiglass enclosure) and repositioned over the same assemblage. In this contribution, we focus on the natural oxygen content, temperature and pH of bottom waters during summer, the course of oxygen decrease during our experiments and the onset of H2S development. Oxygen content of the bottom water, a few centimetres above the sediment-water interface, ranges from ~3.5-8 but is mostly between 4-6 ml l-1 during July to September of the study periods (2005 and 2006) and decreases to zero within ~1-3 days after initiation of our experiments. In parallel, H2S starts to develop at the onset of anoxia. Water temperatures at the bottom were stable during experiments and ranged from 18.5°C to 21.4°C, but pH decreased from 8.3 to 8.1 at the beginning to 7.9 to 7.7 at the end of the experiments. Sediment profiling indicates that the diffusive benthic boundary layer is

  8. Appendix G: Geochemistry

    SciTech Connect

    Cantrell, Kirk J.; Serne, R. Jeffrey; Zachara, John M.; Krupka, Kenneth M.; Dresel, P. Evan; Brown, Christopher F.; Freshley, Mark D.

    2008-01-17

    This appendix discusses the geology of the Hanford Site and singe-shell tank (SST) waste management areas (WMAs). The purpose is to provide the most recent geochemical information available for the SST WMAs and the Integrated Disposal Facility. This appendix summarizes the information in the geochemistry data package for the SST WMAs.

  9. Geochemistry of some deep gold mine waters from the western portion of the Witwatersrand Basin, South Africa

    NASA Astrophysics Data System (ADS)

    Duane, M. J.; Pigozzi, G.; Harris, C.

    1997-02-01

    A suite of 12 mine water samples within the Witwatersrand Basin (South Africa) were analysed for trace element concentrations, strontium isotopic composition and stable isotopes (O and H). Chemical profiles for four Au mines (Western Deep Levels, Vaal Reefs, Freddies and President Steyn) are used to infer origin, chemical and isotopic evolution of the brines and for comparison with basement brines from other Precambrian areas. Systematic relationships are observed between {87Sr}/{86Sr} and {1}/{Sr} : two major mixing trends are required to explain the range of very radiogenic end-members. Possible end-members for the two components could be (1) {87Sr}/{86Sr} = 0.7251 , Sr concentration = 0.12 mg l -1 from a Vaal Reefs compartment and {87Sr}/{86Sr} = 0.7694 , Sr = 39.3 mg l -1 from a Freddies compartment. (2) {87Sr}/{86Sr} = 0.7251 , Sr = 0.12 mg l -1 (as above) with a {87Sr}/{86Sr} = 0.7404 , Sr = 745 mg l -1 from Western Deep Levels. Strontium isotope ratios range above those expected for present-day seawater and are even higher than some locally-derived low Rb minerals from the Precambrian basement. The brines acquired radiogenic 87Sr through interaction with granitic basement (Kaapvaal Craton), shales of the Central Rand Group (in particular Ventersdorp Contact Reef), siliclastics within the West Rand Group and particularly with dolomites from the overlying Transvaal Supergroup. In order to obtain their multielement and radiogenic isotope signatures the meteoric waters descended through fractured rocks between the main dykes and faults (example: Oberholzer and Bank Dyke at Western Deep Levels). They slowly interacted with Au bearing conglomerates and quartzites of the West Rand Group. The inverse relationship between Sr isotope composition and precious/heavy metal concentration suggests fluid/rock interaction within the shales and volcanics of the Ventersdsorp Contact Reef (high in Au and total organic carbon [TOC], less radiogenic strontium composition by

  10. Fluid flow and water-rock interaction across the active Nankai Trough subduction zone forearc revealed by boron isotope geochemistry

    NASA Astrophysics Data System (ADS)

    Hüpers, Andre; Kasemann, Simone A.; Kopf, Achim J.; Meixner, Anette; Toki, Tomohiro; Shinjo, Ryuichi; Wheat, C. Geoffrey; You, Chen-Feng

    2016-11-01

    Compositional changes, dehydration reactions and fluid flow in subducted sediments influence seismogenesis and arc magmatism in subduction zones. To identify fluid flow and water-rock interaction processes in the western Nankai Trough subduction zone (SW Japan) we analyzed boron concentration and boron isotope composition (δ11B) of pore fluids sampled across the subduction zone forearc from depths of up to ∼922 m below seafloor during four Integrated Ocean Drilling Program (IODP) Expeditions. The major structural regimes that were sampled by coring include: (1) sedimentary inputs, (2) the frontal thrust zone, (3) the megasplay fault zone, and (4) the forearc basin. From mass balance consideration we find that consumption of boron (B) by ash alteration and desorption of B from the solid phase, mediated by organic matter degradation, produces a net decrease in B concentrations with depth down to ∼120 μM and variable δ11B values in the range of ∼+20‰ and +49‰. Interstitial water in sediments on the incoming oceanic plate are influenced by more efficient mobilization of exchangeable B from the solid phase due to higher temperatures and alteration of the oceanic crust that acts as a sink for 10B. At the tip of the megasplay fault zone, elevated B concentration and B isotopic composition suggest that underthrust coarse-grained slope sediments provide a pathway for fluids out of the upper (<2 km) accretionary prism. Silt and sand layers in the underthrust section of the downgoing plate favor fluid escape in seaward direction from depths equivalent to the temperature range of 60-150 °C. At both locations the δ11B signature evolves during updip migration through re-adsorption. Mass balance considerations suggest a shallower fluid source depth compared to pore fluids sampled previously near the décollement zone along the central portion of the Nankai margin.

  11. A study on groundwater geochemistry and water quality in layered aquifers system of Pondicherry region, southeast India

    NASA Astrophysics Data System (ADS)

    Thilagavathi, R.; Chidambaram, S.; Prasanna, M. V.; Thivya, C.; Singaraja, C.

    2012-12-01

    Geochemical signatures of groundwater in the Pondicherry region, south India, were determined. The coastal aquifers are fragile and this situation becomes more intense in layered aquifer systems like that of the Pondicherry region. In this region, groundwater occurs in alluvium, Lower Cuddalore, Upper Cuddalore, Tertiary, Cretaceous and mixed aquifers. The geochemical signature of groundwater in these formations was studied by collecting 93 groundwater samples. The collected samples from specific formations were analysed for physical parameters, such as electrical conductivity (EC), pH and major ion concentrations, such as Ca, Mg, Na, K, Cl, HCO3, PO4 and SO4. The results of the analysis were interpreted with geology; the ionic concentrations in the groundwater vary spatially and temporally. The abundance of these ions are in the following order: Na > Ca > Mg > K = Cl > HCO3 > SO4. Interpretation of analytical data shows that Ca-Na and Cl-SO4-HCO3 is the dominant facies in all the formations. Groundwater in the area is generally hard and fresh-brackish in most of the formations and brackish in nature in alluvium formation. The sodium absorption ratio shows that most of the samples are grouped under excellent category to good category in all the formations. The residual sodium carbonate also are in good category in all the formations. Chloro-alkaline indices reveal that the majority of samples show negative values in all the litho units indicating the exchange of Na and K in groundwater with Mg or Ca in rock. Scholler classification of water indicates that longer residence time of water with more prominent base exchange. High EC and TDS values in certain locations of alluvial, Upper Cuddalore and Cretaceous formations prove to be unsuitable for drinking and irrigation purposes.

  12. Water in channel-like cavities: structure and dynamics.

    PubMed Central

    Sansom, M S; Kerr, I D; Breed, J; Sankararamakrishnan, R

    1996-01-01

    Ion channels contain narrow columns of water molecules. It is of interest to compare the structure and dynamics of such intrapore water with those of the bulk solvent. Molecular dynamics simulations of modified TIP3P water molecules confined within channel-like cavities have been performed and the orientation and dynamics of the water molecules analyzed. Channels were modeled as cylindrical cavities with lengths ranging from 15 to 60 A and radii from 3 to 12 A. At the end of the molecular dynamics simulations water molecules were observed to be ordered into approximately concentric cylindrical shells. The waters of the outermost shell were oriented such that their dipoles were on average perpendicular to the normal of the wall of the cavity. Water dynamics were analyzed in terms of self-diffusion coefficients and rotational reorientation rates. For cavities of radii 3 and 6 A, water mobility was reduced relative to that of simulated bulk water. For 9- and 12-A radii confined water molecules exhibited mobilities comparable with that of the bulk solvent. If water molecules were confined within an hourglass-shaped cavity (with a central radius of 3 A increasing to 12 A at either end) a gradient of water mobility was observed along the cavity axis. Thus, water within simple models of transbilayer channels exhibits perturbations of structure and dynamics relative to bulk water. In particular the reduction of rotational reorientation rate is expected to alter the local dielectric constant within a transbilayer pore. Images FIGURE 6 PMID:8789086

  13. Geochemistry of urban sediments from small urban areas and potential impact on surface waters: a case study in Northern Portugal

    NASA Astrophysics Data System (ADS)

    Reis, Anabela; Oliveira, Ana Isabel; Pinto, João; Parker, Andrew

    2015-04-01

    Urban sediments are an important source of contaminants in urban catchments with impact on river ecosystems. Surface runoff from impermeable surfaces transfers sediments and associated contaminants to water bodies affecting the quality of both water and sediment compartments. This study aims to evaluate the metal contents in urban sediments (road deposited sediments) in a small sized urban area, located in a rural mountainous region with no significant industrial units, or mining activities in the vicinity, and subsequently have an insight on the potential contribution to the metal loads transported by fluvial sediments in the streams from the surrounding drainage network. The area under investigation locates in the northeast Portugal, in the Trás-os-Montes region (NE Portugal). Vila Real is a rural city, with 52781 inhabitants, and in the urban area there are dispersed parks with forest and gardens; locally and in the surroundings of the city there are agricultural terrains. The industry is concentrated, in general, in the industry park. Major pollutant activities can be considered the agriculture (pollution by sediments, metals and use of fertilizers) and urban activities such as atmospheric deposition, vehicular traffic, residential activities, soil erosion and industrial activities. According to the aim of the study, road deposited sediment samples were collected in urban and periurban areas as well as in public playgrounds and in the industrial area. The samples were decomposed with aqua regia, and the concentrations of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn and V were obtained by ICP-AES. The total concentrations of As, Cr, Cu, Fe, Mn, Ni, Pb, Zn and V, in road-deposited sediments, indicate relative enrichments in samples collected in the main streets and roads, showing spatial variability. The association of Cu, Pb and Zn is observed in samples collected in the streets with high traffic density and industrial activity; in general, higher relative contents

  14. Statistical analysis of major ion and trace element geochemistry of water, 1986-2006, at seven wells transecting the freshwater/saline-water interface of the Edwards Aquifer, San Antonio, Texas

    USGS Publications Warehouse

    Mahler, Barbara J.

    2008-01-01

    The statistical analyses taken together indicate that the geochemistry at the freshwater-zone wells is more variable than that at the transition-zone wells. The geochemical variability at the freshwater-zone wells might result from dilution of ground water by meteoric water. This is indicated by relatively constant major ion molar ratios; a preponderance of positive correlations between SC, major ions, and trace elements; and a principal components analysis in which the major ions are strongly loaded on the first principal component. Much of the variability at three of the four transition-zone wells might result from the use of different laboratory analytical methods or reporting procedures during the period of sampling. This is reflected by a lack of correlation between SC and major ion concentrations at the transition-zone wells and by a principal components analysis in which the variability is fairly evenly distributed across several principal components. The statistical analyses further indicate that, although the transition-zone wells are less well connected to surficial hydrologic conditions than the freshwater-zone wells, there is some connection but the response time is longer. 

  15. Relation of specific conductance in ground water to intersection of flow paths by wells, and associated major ion and nitrate geochemistry, Barton Springs Segment of the Edwards Aquifer, Austin, Texas, 1978-2003

    USGS Publications Warehouse

    Garner, Bradley D.; Mahler, Barbara J.

    2007-01-01

    Understanding of karst flow systems can be complicated by the presence of solution-enlarged conduits, which can transmit large volumes of water through the aquifer rapidly. If the geochemistry at a well can be related to streamflow or spring discharge (springflow), or both, the relations can indicate the presence of recent recharge in water at the well, which in turn might indicate that the well intersects a conduit (and thus a major flow path). Increasing knowledge of the occurrence and distribution of conduits in the aquifer can contribute to better understanding of aquifer framework and function. To that end, 26 wells in the Barton Springs segment of the Edwards aquifer, Austin, Texas, were investigated for potential intersection with conduits; 26 years of arbitrarily timed specific conductance measurements in the wells were compared to streamflow in five creeks that provide recharge to the aquifer and were compared to aquifer flow conditions as indicated by Barton Springs discharge. A nonparametric statistical test (Spearman's rho) was used to divide the 26 wells into four groups on the basis of correlation of specific conductance of well water to streamflow or spring discharge, or both. Potential relations between conduit intersection by wells and ground-water geochemistry were investigated through analysis of historical major ion and nitrate geochemistry for wells in each of the four groups. Specific conductance at nine wells was negatively correlated with both streamflow and spring discharge, or streamflow only. These correlations were interpreted as evidence of an influx of surface-water recharge during periods of high streamflow and the influence at the wells of water from a large, upgradient part of the aquifer; and further interpreted as indicating that four wells intersect major aquifer flow paths and five wells intersect minor aquifer flow paths (short, tributary conduits). Specific conductance at six wells was positively correlated with spring

  16. Internal features, mineralogy and geochemistry of ferromanganese nodules from the Gulf of Cadiz: The role of the Mediterranean Outflow Water undercurrent

    NASA Astrophysics Data System (ADS)

    González, F. J.; Somoza, L.; Lunar, R.; Martínez-Frías, J.; Rubí, J. A. Martín; Torres, T.; Ortiz, J. E.; Díaz-del-Río, V.

    2010-03-01

    A large suite of Fe-Mn nodules (561 samples) were recovered during the Anastasya2001 cruise (TASYO project) along the continental margin of the Gulf of Cadiz (Eastern Central Atlantic), at the confluence of the Mediterranean Sea with the Atlantic Ocean, where extensive nodule fields were discovered. Based on wide previous studies that included swath bathymetry, multi-channel and very high-resolution seismic reflection, gravimetry, magnetism, heat flow probes and underwater photography surveys, nodules were collected at water depths ranging from 850 to 1000 m, associated with hydrocarbon-derived Mg-calcite, ankerite and dolomite chimneys and crusts. Forty-six selected samples among the various morphological types were used for the laboratory analysis of physical properties (morphology, color, surface texture, sphericity, weight and size), mineralogy (XRD, optical and electronic microscopy), geochemistry (XRF, AAS, ICP-MS, ICP-AES, EPMA, and GC-MS) and stable isotopes. The nodules show a wide range of sizes, densities, weights and morphologies. They are formed by multiple millimeter-thick layers of Fe and Mn oxyhydroxides surrounding the nucleus composed of Early-Middle Miocene plastic marl and sediment, which were derived from underlying units by fluid venting. Massive, laminated, detrital and mottled to dendritic textural features were developed by the Fe and Mn oxyhydroxide layers. The main components are Goethite, lepidocrocite, Mn oxides (7 Å manganates and 10 Å manganates), quartz, and phyllosilicates. Accessory minerals are calcite, dolomite, siderite, rhodochrosite, kutnahorite, pyrite, chalcopyrite, potassium feldspar, zircon, rutile, ilmenite and chlorite. Fe-Mn carbonates from the siderite-rhodochrosite continuous series are the principal constituent of the nuclei. Framboidal, filamentous and globular textures are observed in Fe-Mn oxides and pyrite, suggesting biogenic origin. The nodules show a high mean abundance of Fe (38.6%), moderate Mn (6.0%) and

  17. Questa baseline and pre-mining ground-water quality investigation. 14. Interpretation of ground-water geochemistry in catchments other than the Straight Creek catchment, Red River Valley, Taos County, New Mexico, 2002-2003

    USGS Publications Warehouse

    Nordstrom, D. Kirk; McCleskey, R. Blaine; Hunt, Andrew G.; Naus, Cheryl A.

    2005-01-01

    The U.S. Geological Survey, in cooperation with the New Mexico Environment Department, is investigating the pre-mining ground-water chemistry at the Molycorp molybdenum mine in the Red River Valley, New Mexico. The primary approach is to determine the processes controlling ground-water chemistry at an unmined, off-site but proximal analog. The Straight Creek catchment, chosen for this purpose, consists of the same Tertiary-age quartz-sericite-pyrite altered andesite and rhyolitic volcanics as the mine site. Straight Creek is about 5 kilometers east of the eastern boundary of the mine site. Both Straight Creek and the mine site are at approximately the same altitude, face south, and have the same climatic conditions. Thirteen wells in the proximal analog drainage catchment were sampled for ground-water chemistry. Eleven wells were installed for this study and two existing wells at the Advanced Waste-Water Treatment (AWWT) facility were included in this study. Eight wells were sampled outside the Straight Creek catchment: one each in the Hansen, Hottentot, and La Bobita debris fans, four in a well cluster in upper Capulin Canyon (three in alluvial deposits and one in bedrock), and an existing well at the U.S. Forest Service Questa Ranger Station in Red River alluvial deposits. Two surface waters from the Hansen Creek catchment and two from the Hottentot drainage catchment also were sampled for comparison to ground-water compositions. In this report, these samples are evaluated to determine if the geochemical interpretations from the Straight Creek ground-water geochemistry could be extended to other ground waters in the Red River Valley , including the mine site. Total-recoverable major cations and trace metals and dissolved major cations, selected trace metals, anions, alkalinity; and iron-redox species were determined for all surface- and ground-water samples. Rare-earth elements and low-level As, Bi, Mo, Rb, Re, Sb, Se, Te, Th, U, Tl, V, W, Y, and Zr were

  18. Molecular dynamics studies of interfacial water at the alumina surface.

    SciTech Connect

    Argyris, Dr. Dimitrios; Ho, Thomas; Cole, David

    2011-01-01

    Interfacial water properties at the alumina surface were investigated via all-atom equilibrium molecular dynamics simulations at ambient temperature. Al-terminated and OH-terminated alumina surfaces were considered to assess the structural and dynamic behavior of the first few hydration layers in contact with the substrates. Density profiles suggest water layering up to {approx}10 {angstrom} from the solid substrate. Planar density distribution data indicate that water molecules in the first interfacial layer are organized in well-defined patterns dictated by the atomic terminations of the alumina surface. Interfacial water exhibits preferential orientation and delayed dynamics compared to bulk water. Water exhibits bulk-like behavior at distances greater than {approx}10 {angstrom} from the substrate. The formation of an extended hydrogen bond network within the first few hydration layers illustrates the significance of water?water interactions on the structural properties at the interface.

  19. Geology, ground-water hydrology, geochemistry, and ground-water simulation of the Beaumont and Banning Storage Units, San Gorgonio Pass area, Riverside County, California

    USGS Publications Warehouse

    Rewis, Diane L.; Christensen, Allen H.; Matti, Jonathan; Hevesi, Joseph A.; Nishikawa, Tracy; Martin, Peter

    2006-01-01

    Ground water has been the only source of potable water supply for residential, industrial, and agricultural users in the Beaumont and Banning storage units of the San Gorgonio Pass area, Riverside County, California. Ground-water levels in the Beaumont area have declined as much as 100 feet between the early 1920s and early 2000s, and numerous natural springs have stopped flowing. In 1961, the San Gorgonio Pass Water Agency (SGPWA) entered into a contract with the California State Department of Water Resources to receive 17,300 acre-feet per year of water to be delivered by the California State Water Project (SWP) to supplement natural recharge. Currently (2005), a pipeline is delivering SWP water into the area, and the SGPWA is artificially recharging the ground-water system using recharge ponds located along Little San Gorgonio Creek in Cherry Valley with the SWP water. In addition to artificial recharge, SGPWA is considering the direct delivery of SWP water for the irrigation of local golf courses and for agricultural supply in lieu of ground-water pumpage. To better understand the potential hydrologic effects of different water-management alternatives on ground-water levels and movement in the Beaumont and Banning storage units, existing geohydrologic and geochemical data were compiled, new data from a basin-wide ground-water level and water-quality monitoring network were collected, monitoring wells were installed near the Little San Gorgonio Creek recharge ponds, geohydrologic and geochemical analyses were completed, and a ground-water flow simulation model was developed. The San Gorgonio Pass area was divided into several storage units on the basis of mapped or inferred faults. This study addresses primarily the Beaumont and Banning storage units. The geologic units in the study area were generalized into crystalline basement rocks and sedimentary deposits. The younger sedimentary deposits and the surficial deposits are the main water-bearing deposits in the

  20. Quantification of Dynamic Water-Rock-Microbe Interactions in a Travertine-Depositing Hot Spring, Mammoth Hot Springs, Yellowstone National Park, USA

    NASA Astrophysics Data System (ADS)

    DeMott, L. M.; Sivaguru, M.; Fried, G.; Sanford, R. A.; Fouke, B. W.

    2014-12-01

    Filamentous microbial mats in a travertine-depositing hot spring at Mammoth Hot Springs in Yellowstone National Park exert primary controls on the growth rate, mineralogy, and crystal fabric of calcium carbonate minerals (travertine) that precipitate in the spring. Filaments directly affect porosity and permeability of travertine by providing a structural framework consisting of "ropes" of microbial cells around which carbonate minerals precipitate, creating a uniquely biogenetic mineral fabric characterized by horizontal layers of large tubular pores. Nanometer scale microscopy reveals that these mineral fabrics may be directly tied to microbial activities, as aragonite crystals precipitating directly on filaments are smaller and more densely packed than crystals precipitating on extra-polymeric substances (EPS) between filaments. In order to more closely examine the processes which control calcium carbonate crystallization dynamics in this system, a high-resolution transect of water and travertine was sampled for geochemistry, microscopy, and microbial biomass along the primary flow path from upstream to downstream of Narrow Gauge spring at Mammoth Hot Springs. Travertine samples were analyzed for petrography using transmitted light, cathodoluminescence, and laser confocal microscopy to examine crystal morphology and associations with microbial filaments and provide insight on pore network distributions. Additionally, travertine and spring water geochemistry was also analyzed for major and trace ions, δ34S, δ13C, and δ18O, to identify any trends that may relate to crystallization rates, microbial biomass, or crystal habit. Total biomass was determined using dried weight. Water-rock-microbe interactions result in upstream-to-downstream variations in travertine crystal morphology and water chemistry that are directly related to systematic changes in microbial biomass and community respiration. Geochemical modeling lends insight into the biogeochemical reactions

  1. STABLE ISOTOPES AS INDICATORS OF SOIL WATER DYNAMICS IN WATERSHEDS

    EPA Science Inventory

    Stream water quality and quantity depend on discharge rates of water and nutrients from soils. However, soil-water storage is very dynamic and strongly influenced by plants. We analyzed stable isotopes of oxygen and hydrogen to quantify spatial and temporal changes in evaporati...

  2. Linking Weathering, Rock Moisture Dynamics, Geochemistry, Runoff, Vegetation and Atmospheric Processes through the Critical Zone: Graduate Student led Research at the Eel River Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Dietrich, W. E.

    2014-12-01

    In the Eel River Critical Zone Observatory lies Rivendell, a heavily-instrumented steep forested hillslope underlain by nearly vertically dipping argillite interbedded with sandstone. Under this convex hillslope lies "Zb", the transition to fresh bedrock, which varies from less than 6 m below the surface near the channel to 20 m at the divide. Rempe and Dietrich (2014, PNAS) show that the Zb profile can be predicted from the assumption that weathering occurs when drainage is induced in the uplifting fresh bedrock under hillslopes by lateral head gradients driven by channel incision at the hillslope boundary. Infiltrating winter precipitation is impeded at the lower conductivity boundary at Zb, generating perched groundwater that dynamically pulses water laterally to the channel, controlling stream runoff. Below the soil and above the water table lies an unsaturated zone through which all recharge to the perched groundwater (and thus all runoff to channels) occurs. It is this zone and the waters in them that profoundly affect critical zone processes. In our seasonally dry environment, the first rains penetrate past the soil and moisten the underlying weathered bedrock (Salve et al., 2012, WRR). It takes about 200 to 400 mm of cumulative rain, however, before the underlying groundwater rises significantly. Oshun et al (in review) show that by this cumulative rainfall the average of the wide-ranging isotopic signature of rain reaches a nearly constant average annual value. Consequently, the recharging perched groundwater shows only minor temporal isotopic variation. Kim et al, (2014, GCA) find that the winter high-flow groundwater chemistry is controlled by relatively fast-reacting cation exchange processes, likely occurring in transit in the unsaturated zone. Oshun also demonstrates that the Douglas fir rely on this rock moisture as a water source, while the broadleaf trees (oaks and madrone) use mostly soil moisture. Link et al (2014 WRR) show that Doug fir declines

  3. Method of analysis and quality-assurance practices by the U.S. Geological Survey Organic Geochemistry Research Group; determination of geosmin and methylisoborneol in water using solid-phase microextraction and gas chromatography/mass spectrometry

    USGS Publications Warehouse

    Zimmerman, L.R.; Ziegler, A.C.; Thurman, E.M.

    2002-01-01

    A method for the determination of two common odor-causing compounds in water, geosmin and 2-methylisoborneol, was modified and verified by the U.S. Geological Survey's Organic Geochemistry Research Group in Lawrence, Kansas. The optimized method involves the extraction of odor-causing compounds from filtered water samples using a divinylbenzene-carboxen-polydimethylsiloxane cross-link coated solid-phase microextraction (SPME) fiber. Detection of the compounds is accomplished using capillary-column gas chromatography/mass spectrometry (GC/MS). Precision and accuracy were demonstrated using reagent-water, surface-water, and ground-water samples. The mean accuracies as percentages of the true compound concentrations from water samples spiked at 10 and 35 nanograms per liter ranged from 60 to 123 percent for geosmin and from 90 to 96 percent for 2-methylisoborneol. Method detection limits were 1.9 nanograms per liter for geosmin and 2.0 nanograms per liter for 2-methylisoborneol in 45-milliliter samples. Typically, concentrations of 30 and 10 nanograms per liter of geosmin and 2-methylisoborneol, respectively, can be detected by the general public. The calibration range for the method is equivalent to concentrations from 5 to 100 nanograms per liter without dilution. The method is valuable for acquiring information about the production and fate of these odor-causing compounds in water.

  4. Global water dynamics: issues for the 21st century.

    PubMed

    Simonovic, Slobodan P

    2002-01-01

    The WorldWater system dynamics model has been developed for modeling the global world water balance and capturing the dynamic character of the main variables affecting water availability and use in the future. Despite not being a novel approach, system dynamics offers a new way of addressing complex systems. WorldWater simulations are clearly demonstrating the strong feedback relation between water availability and different aspects of world development. Results of numerous simulations are contradictory to the assumption made by many global modelers that water is not an issue on the global scale. Two major observations can be made from early simulations: (a) the use of clean water for dilution and transport of wastewater, if not dealt with in other ways, imposes a major stress on the global world water balance; and (b) water use by different sectors is demonstrating quite different dynamics than predicted by classical forecasting tools and other water-models. Inherent linkages between water quantity and quality sectors with food, industry, persistent pollution, technology, and non-renewable resources sectors of the model create shoot and collapse behavior in water use dynamics. This paper discusses a number of different water-related scenarios and their implications on the global water balance. In particular, two extreme scenarios (business as usual - named "Chaos", and unlimited desalination - named "Ocean") are presented in the paper. Based on the conclusions derived from these two extreme cases a set of more moderate and realistic scenarios (named "Conservation") is proposed and their consequences on the global water balance are evaluated.

  5. Global water dynamics: issues for the 21st century.

    PubMed

    Simonovic, Slobodan P

    2002-01-01

    The WorldWater system dynamics model has been developed for modeling the global world water balance and capturing the dynamic character of the main variables affecting water availability and use in the future. Despite not being a novel approach, system dynamics offers a new way of addressing complex systems. WorldWater simulations are clearly demonstrating the strong feedback relation between water availability and different aspects of world development. Results of numerous simulations are contradictory to the assumption made by many global modelers that water is not an issue on the global scale. Two major observations can be made from early simulations: (a) the use of clean water for dilution and transport of wastewater, if not dealt with in other ways, imposes a major stress on the global world water balance; and (b) water use by different sectors is demonstrating quite different dynamics than predicted by classical forecasting tools and other water-models. Inherent linkages between water quantity and quality sectors with food, industry, persistent pollution, technology, and non-renewable resources sectors of the model create shoot and collapse behavior in water use dynamics. This paper discusses a number of different water-related scenarios and their implications on the global water balance. In particular, two extreme scenarios (business as usual - named "Chaos", and unlimited desalination - named "Ocean") are presented in the paper. Based on the conclusions derived from these two extreme cases a set of more moderate and realistic scenarios (named "Conservation") is proposed and their consequences on the global water balance are evaluated. PMID:12019833

  6. Dynamic behavior of interfacila water at the silica surface

    SciTech Connect

    Argyris, Dr. Dimitrios; Cole, David R; Striolo, Alberto

    2009-01-01

    Molecular dynamics simulations were employed to study the dynamics properties of water at the silica-liquid interface at ambient temperature. Three different degrees of hydroxylation of a crystalline silica surface were used. To assess the water dynamic properties we calculated the residence probability and in-plane mean square displacement as a function of distance from the surface. The data indicate that water molecules at the fully hydroxylated surface remain longer, on average, in the interfacial region than in the other cases. By assessing the dynamics of molecular dipole moment and hydrogen-hydrogen vector an anisotropic reorientation was discovered for interfacial water in contact with any of the surfaces considered. However, the features of the anisotropic reorientation observed for water molecules depend strongly on the relative orientation of interfacial water molecules and their interactions with surface hydroxyl groups. On the partially hydroxylated surface, where water molecules with hydrogen-down and hydrogen-up orientation are both found, those water molecules associated with surface hydroxyl groups remain at the adsorbed locations longer and reorient slower than the other water molecules. A number of equilibrium properties, including density profiles, hydrogen bond networks, charge densities, and dipole moment densities are also reported to explain the dynamics results.

  7. From single molecules to water networks: Dynamics of water adsorption on Pt(111)

    NASA Astrophysics Data System (ADS)

    Naderian, Maryam; Groß, Axel

    2016-09-01

    The adsorption dynamics of water on Pt(111) was studied using ab initio molecular dynamics simulations based on density functional theory calculations including dispersion corrections. Sticking probabilities were derived as a function of initial kinetic energy and water coverage. In addition, the energy distribution upon adsorption was monitored in order to analyze the energy dissipation process. We find that on the water pre-covered surface the sticking probability is enhanced because of the attractive water-water interaction and the additional effective energy dissipation channels to the adsorbed water molecules. The water structures forming directly after the adsorption on the pre-covered surfaces do not necessarily correspond to energy minimum structures.

  8. Anomalously soft dynamics of water in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kolesnikov, A. I.; Loong, C.-K.; de Souza, N. R.; Burnham, C. J.; Moravsky, A. P.

    2006-11-01

    The structure and dynamics of water confined to the one-dimensional nanotube interior are found to be drastically altered with respect to bulk water. Neutron diffraction, inelastic and quasielastic neutron scattering measurements in parallel with MD simulations have clearly shown the entry of water into open-ended single-wall carbon nanotubes and identified an ice-shell plus central water-chain structure. The observed extremely soft dynamics of nanotube-water arises mainly from a qualitatively large reduction in the hydrogen-bond connectivity of the water chain. Anomalously enhanced thermal motions in the water chain, modeled by a low-barrier, flattened, highly anharmonic potential well, explain the large mean-square displacement of hydrogen and the fluid-like behavior of nanotube-water at temperatures far below the nominal freezing point.

  9. DYNAMICS OF THE CYTOSKELETON: HOW MUCH DOES WATER MATTER?

    PubMed Central

    Lenormand, Guillaume; Millet, Emil; Park, Chan Young; Hardin, C. Corey; Butler, James P.; Moldovan, Nicanor I.; Fredberg, Jeffrey J.

    2013-01-01

    The principal constituent of the living cell is water. The role of the hydration shell and bulk H2O solvent is well recognized in dynamics of isolated proteins, but the role of water in the dynamics of the integrated living cytoskeleton (CSK) remains obscure. Here we report a direct connection of dynamics of water to dynamics of the integrated CSK. The latter are known to be scale-free and to hinge upon a frequency, f0, that is roughly invariant across cell types. Although f0 is comparable in magnitude to the rotational relaxation frequency of water (gigahertz range), the physical basis of f0 remains unknown. Using the human airway smooth muscle cell as a model system, we show here that replacing water acutely with deuterium oxide impacts CSK dynamics in major ways, slowing CSK remodeling dynamics appreciably and lowering f0 by up to 4 orders of magnitude. Although these observations do not distinguish contributions of bulk solvent versus hydration shell, they suggest a novel and unifying hypothesis, namely, that dynamics of integrated CSK network are slaved in a direct fashion to fluctuations arising in intracellular water. PMID:21797414

  10. Dynamics of the cytoskeleton: How much does water matter?

    NASA Astrophysics Data System (ADS)

    Lenormand, Guillaume; Millet, Emil; Park, Chan Young; Hardin, C. Corey; Butler, James P.; Moldovan, Nicanor I.; Fredberg, Jeffrey J.

    2011-06-01

    The principal constituent of the living cell is water. The role of the hydration shell and bulk H2O solvent is well recognized in the dynamics of isolated proteins, but the role of water in the dynamics of the integrated living cytoskeleton (CSK) remains obscure. Here we report a direct connection of dynamics of water to dynamics of the integrated CSK. The latter are known to be scale-free and to hinge upon a frequency f0 that is roughly invariant across cell types. Although f0 is comparable in magnitude to the rotational relaxation frequency of water (gigahertz range), the physical basis of f0 remains unknown. Using the human airway smooth muscle cell as a model system, we show here that replacing water acutely with deuterium oxide impacts CSK dynamics in major ways, slowing CSK remodeling dynamics appreciably, and lowering f0 by up to four orders of magnitude. Although these observations do not distinguish contributions of bulk solvent versus hydration shell, they suggest a unifying hypothesis, namely, that dynamics of integrated CSK networks are slaved in a direct fashion to fluctuations arising in intracellular water.

  11. Geochemistry and the environment

    NASA Astrophysics Data System (ADS)

    Moldan, Bedřich

    Geochemistry is one of the most important environmental disciplines. Indeed, a more proper term for this scientific field is biogeochemistry. The connection between the crucial aspects of the environment appears clearly from this term. It was coined by V.I. VERNADSKY in 1923 (MOCHALOV 1982). Later he incorporated this idea into the famous concept of the biosphere (VERNADSKY 1926) adopted by UNESCO in 1968 (UNESCO 1970) and is today one of the frequently used terms not only in scientific but also in general vocabulary.

  12. Reorientation and Allied Dynamics in Water and Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Laage, Damien; Stirnemann, Guillaume; Sterpone, Fabio; Rey, Rossend; Hynes, James T.

    2011-05-01

    The reorientation of a water molecule is important for a host of phenomena, ranging over—in an only partial listing—the key dynamic hydrogen-bond network restructuring of water itself, aqueous solution chemical reaction mechanisms and rates, ion transport in aqueous solution and membranes, protein folding, and enzymatic activity. This review focuses on water reorientation and related dynamics in pure water, and for aqueous solutes with hydrophobic, hydrophilic, and amphiphilic character, ranging from tetra-methylurea to halide ions and amino acids. Attention is given to the application of theory, simulation, and experiment in the probing of these dynamics, in usefully describing them, and in assessing the description. Special emphasis is placed on a novel sudden, large-amplitude jump mechanism for water reorientation, which contrasts with the commonly assumed Debye rotational diffusion mechanism, characterized by small-amplitude angular motion. Some open questions and directions for further research are also discussed.

  13. Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. III. An anion-exchange resin technique for sampling and preservation of sulfoxyanions in natural waters

    PubMed Central

    Druschel, Greg K; Schoonen, Martin AA; Nordstrom, D Kirk; Ball, James W; Xu, Yong; Cohn, Corey A

    2003-01-01

    A sampling protocol for the retention, extraction, and analysis of sulfoxyanions in hydrothermal waters has been developed in the laboratory and tested at Yellowstone National Park and Green Lake, NY. Initial laboratory testing of the anion-exchange resin Bio-Rad™ AG1-X8 indicated that the resin was well suited for the sampling, preservation, and extraction of sulfate and thiosulfate. Synthetic solutions containing sulfate and thiosulfate were passed through AG1-X8 resin columns and eluted with 1 and 3 M KCl, respectively. Recovery ranged from 89 to 100%. Comparison of results for water samples collected from five pools in Yellowstone National Park between on-site 1C analysis (U.S. Geological Survey mobile lab) and IC analysis of resin-stored sample at SUNY-Stony Brook indicates 96 to 100% agreement for three pools (Cinder, Cistern, and an unnamed pool near Cistern) and 76 and 63% agreement for two pools (Sulfur Dust and Frying Pan). Attempts to extract polythionates from the AG1-X8 resin were made using HCl solutions, but were unsuccessful. Bio-Rad™ AG2-X8, an anion-exchange resin with weaker binding sites than the AG1-X8 resin, is better suited for polythionate extraction. Sulfate and thiosulfate extraction with this resin has been accomplished with KCl solutions of 0.1 and 0.5 M, respectively. Trithionate and tetrathionate can be extracted with 4 M KCl. Higher polythionates can be extracted with 9 M hydrochloric acid. Polythionate concentrations can then be determined directly using ion chromatographic methods, and laboratory results indicate recovery of up to 90% for synthetic polythionate solutions using AG2-X8 resin columns.

  14. Water Determines the Structure and Dynamics of Proteins.

    PubMed

    Bellissent-Funel, Marie-Claire; Hassanali, Ali; Havenith, Martina; Henchman, Richard; Pohl, Peter; Sterpone, Fabio; van der Spoel, David; Xu, Yao; Garcia, Angel E

    2016-07-13

    Water is an essential participant in the stability, structure, dynamics, and function of proteins and other biomolecules. Thermodynamically, changes in the aqueous environment affect the stability of biomolecules. Structurally, water participates chemically in the catalytic function of proteins and nucleic acids and physically in the collapse of the protein chain during folding through hydrophobic collapse and mediates binding through the hydrogen bond in complex formation. Water is a partner that slaves the dynamics of proteins, and water interaction with proteins affect their dynamics. Here we provide a review of the experimental and computational advances over the past decade in understanding the role of water in the dynamics, structure, and function of proteins. We focus on the combination of X-ray and neutron crystallography, NMR, terahertz spectroscopy, mass spectroscopy, thermodynamics, and computer simulations to reveal how water assist proteins in their function. The recent advances in computer simulations and the enhanced sensitivity of experimental tools promise major advances in the understanding of protein dynamics, and water surely will be a protagonist. PMID:27186992

  15. Water Determines the Structure and Dynamics of Proteins.

    PubMed

    Bellissent-Funel, Marie-Claire; Hassanali, Ali; Havenith, Martina; Henchman, Richard; Pohl, Peter; Sterpone, Fabio; van der Spoel, David; Xu, Yao; Garcia, Angel E

    2016-07-13

    Water is an essential participant in the stability, structure, dynamics, and function of proteins and other biomolecules. Thermodynamically, changes in the aqueous environment affect the stability of biomolecules. Structurally, water participates chemically in the catalytic function of proteins and nucleic acids and physically in the collapse of the protein chain during folding through hydrophobic collapse and mediates binding through the hydrogen bond in complex formation. Water is a partner that slaves the dynamics of proteins, and water interaction with proteins affect their dynamics. Here we provide a review of the experimental and computational advances over the past decade in understanding the role of water in the dynamics, structure, and function of proteins. We focus on the combination of X-ray and neutron crystallography, NMR, terahertz spectroscopy, mass spectroscopy, thermodynamics, and computer simulations to reveal how water assist proteins in their function. The recent advances in computer simulations and the enhanced sensitivity of experimental tools promise major advances in the understanding of protein dynamics, and water surely will be a protagonist.

  16. Evaluating Water Conservation and Reuse Policies Using a Dynamic Water Balance Model

    NASA Astrophysics Data System (ADS)

    Qaiser, Kamal; Ahmad, Sajjad; Johnson, Walter; Batista, Jacimaria R.

    2013-02-01

    A dynamic water balance model is created to examine the effects of different water conservation policies and recycled water use on water demand and supply in a region faced with water shortages and significant population growth, the Las Vegas Valley (LVV). The model, developed using system dynamics approach, includes an unusual component of the water system, return flow credits, where credits are accrued for returning treated wastewater to the water supply source. In LVV, Lake Mead serves as, both the drinking water source and the receiving body for treated wastewater. LVV has a consumptive use allocation from Lake Mead but return flow credits allow the water agency to pull out additional water equal to the amount returned as treated wastewater. This backdrop results in a scenario in which conservation may cause a decline in the available water supply. Current water use in LVV is 945 lpcd (250 gpcd), which the water agency aims to reduce to 752 lpcd (199 gpcd) by 2035, mainly through water conservation. Different conservation policies focused on indoor and outdoor water use, along with different population growth scenarios, are modeled for their effects on the water demand and supply. Major contribution of this study is in highlighting the importance of outdoor water conservation and the effectiveness of reducing population growth rate in addressing the future water shortages. The water agency target to decrease consumption, if met completely through outdoor conservation, coupled with lower population growth rate, can potentially satisfy the Valley's water demands through 2035.

  17. Hydration-dependent dynamic crossover phenomenon in protein hydration water

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Fratini, Emiliano; Li, Mingda; Le, Peisi; Mamontov, Eugene; Baglioni, Piero; Chen, Sow-Hsin

    2014-10-01

    The characteristic relaxation time τ of protein hydration water exhibits a strong hydration level h dependence. The dynamic crossover is observed when h is higher than the monolayer hydration level hc=0.2-0.25 and becomes more visible as h increases. When h is lower than hc, τ only exhibits Arrhenius behavior in the measured temperature range. The activation energy of the Arrhenius behavior is insensitive to h, indicating a local-like motion. Moreover, the h dependence of the crossover temperature shows that the protein dynamic transition is not directly or solely induced by the dynamic crossover in the hydration water.

  18. Ecohydrology of dry regions: storage versus pulse soil water dynamics

    USGS Publications Warehouse

    Lauenroth, William K.; Schlaepfer, Daniel R.; Bradford, John B.

    2014-01-01

    Although arid and semiarid regions are defined by low precipitation, the seasonal timing of temperature and precipitation can influence net primary production and plant functional type composition. The importance of precipitation seasonality is evident in semiarid areas of the western U.S., which comprise the Intermountain (IM) zone, a region that receives important winter precipitation and is dominated by woody plants and the Great Plains (GP), a region that receives primarily summer precipitation and is dominated by perennial grasses. Although these general relationships are well recognized, specific differences in water cycling between these regions have not been well characterized. We used a daily time step soil water simulation model and twenty sites from each region to analyze differences in soil water dynamics and ecosystem water balance. IM soil water patterns are characterized by storage of water during fall, winter, and spring resulting in relatively reliable available water during spring and early summer, particularly in deep soil layers. By contrast, GP soil water patterns are driven by pulse precipitation events during the warm season, resulting in fluctuating water availability in all soil layers. These contrasting patterns of soil water—storage versus pulse dynamics—explain important differences between the two regions. Notably, the storage dynamics of the IN sites increases water availability in deep soil layers, favoring the deeper rooted woody plants in that region, whereas the pulse dynamics of the Great Plains sites provide water primarily in surface layers, favoring the shallow-rooted grasses in that region. In addition, because water received when plants are either not active or only partially so is more vulnerable to evaporation and sublimation than water delivered during the growing season, IM ecosystems use a smaller fraction of precipitation for transpiration (47%) than GP ecosystems (49%). Recognizing the pulse-storage dichotomy in

  19. Structure and dynamics of supercooled water in neutral confinements

    NASA Astrophysics Data System (ADS)

    Klameth, F.; Vogel, M.

    2013-04-01

    We perform molecular dynamics simulations to study the structure and dynamics of liquid water in neutral nanopores, which are generated by pinning a suitable subset of water molecules in an equilibrium configuration of a bulk system. It is found that such neutral confinement does not disturb the structure of water, in particular, the local tetrahedral order, while it imposes a pronounced spatial inhomogeneity on the dynamics of water. Specifically, when the pore wall is approached, hopping motion sets in and water dynamics slows down. We show that the logarithm of the correlation time is an exponential function of the distance to the wall, indicating a tremendous gradient of water mobility across the confinement. Upon cooling, the length scale associated with this exponential distance dependence and, thus, the range of the wall effect increases, at least down to the critical temperature of mode coupling theory, Tc. Also, the temperature dependence of water dynamics varies across the pore, i.e., fragility is high in the pore center, while it is low near the pore wall. Due to all these effects, time-temperature superposition is violated. Our observations for a neutral confinement reveal that specific interactions at hydrophilic or hydrophobic walls are not the main cause of spatially inhomogeneous dynamics of confined water. In view of similarities with the behavior of Lennard-Jones liquids in neutral confinements, one may rather speculate that the effects observed for confined water are general and result from the existence of a static contribution to the energy landscape, which is imprinted by an immobile environment.

  20. Temperature effects on dynamic water absorption into paper.

    PubMed

    Songok, Joel; Salminen, Pekka; Toivakka, Martti

    2014-03-15

    Mechanisms controlling short time water absorption and the effect of temperature on water absorption into paper were investigated by analyzing previously published data. A dynamic contact angle effect caused by contact line friction explained the liquid uptake dynamics at short times. The water absorption rate increase with temperature is suggested to be controlled by the molecular processes occurring in front of the advancing liquid front. The increase in the non-equilibrium vapor pressure at air-liquid interface leads to higher water molecule adsorption onto fibers and associated lowering of the solid-gas interfacial tension, thereby increasing the wetting velocity and water absorption. The classical Lucas-Washburn equation was found to be inadequate for predicting water absorption into paper both at short times and as a function of temperature. PMID:24461858

  1. Dynamics and Structure of Bitumen-Water Mixtures.

    PubMed

    Lemarchand, Claire A; Greenfield, Michael L; Hansen, Jesper S

    2016-06-23

    Systems of Cooee bitumen and water up to 4% mass are studied by molecular dynamics simulations. The cohesive energy density of the system is shown to decrease with an increasing water content. This decrease is due mainly to an increase in the interaction energy which is not high enough to counterbalance the increase in volume due to the addition of water. It is not due to a decrease of interaction energy between the slightly polar asphaltene molecules. The water molecules tend to form a droplet in bitumen. The size and the distribution of sizes of the droplets are quantified, with multiple droplets being more stable at the highest temperature simulated. The droplet is mainly located close to the saturates molecules in bitumen. Finally, it is shown that the water dynamics is much slower in bitumen than in pure water because it is governed by the diffusion of the droplet and not of the single molecules.

  2. Dynamical Crossover in Hot Dense Water: The Hydrogen Bond Role.

    PubMed

    Ranieri, Umbertoluca; Giura, Paola; Gorelli, Federico A; Santoro, Mario; Klotz, Stefan; Gillet, Philippe; Paolasini, Luigi; Koza, Michael Marek; Bove, Livia E

    2016-09-01

    We investigate the terahertz dynamics of liquid H2O as a function of pressure along the 450 K isotherm, by coupled quasielastic neutron scattering and inelastic X-ray scattering experiments. The pressure dependence of the single-molecule dynamics is anomalous in terms of both microscopic translation and rotation. In particular, the Stokes-Einstein-Debye equations are shown to be violated in hot water compressed to the GPa regime. The dynamics of the hydrogen bond network is only weakly affected by the pressure variation. The time scale of the structural relaxation driving the collective dynamics increases by a mere factor of 2 along the investigated isotherm, and the structural relaxation strength turns out to be almost pressure independent. Our results point at the persistence of the hydrogen bond network in hot dense water up to ice VII crystallization, thus questioning the long-standing perception that hydrogen bonds are broken in liquid water under the effect of compression. PMID:27479235

  3. Wetting dynamics of a water nanodrop on graphene.

    PubMed

    Andrews, Joseph Eugene; Sinha, Shayandev; Chung, Peter W; Das, Siddhartha

    2016-09-14

    Water-graphene wetting interactions are central to several applications such as desalination, water filtration, electricity generation, biochemical sensing, fabrication of fuel cells, and many more. While substantial attention has been devoted to probe the wetting statics of a water drop on graphene, unraveling the possible wetting translucency nature of graphene, very little research has been done on the dynamics of wetting of water drops on graphene-coated solids or free-standing graphene layers. In this paper, we employ molecular dynamics (MD) simulations to study the contact and the spreading of a water nanodrop, quantifying its wetting dynamics, on supported and free-standing graphene. We demonstrate that nanoscale water drops establish contact with graphene by forming patches on graphene, and this patch formation is hastened for graphene layer(s) supported on hydrophilic solids. More importantly, our results demonstrate that the nanodrop spreading dynamics, regardless of the number of graphene layers or the nature of the underlying solid, obey the half-power law, i.e., r∼t(1/2) (where r is the wetting contact radius and t is the spreading time) for the entire timespan of spreading except towards the very end of the spreading lifetime when the spreading stops. Such a spreading behavior is exactly analogous to the spreading dynamics of nanodroplets for standard solids - this is in sharp contrast to the wetting statics of graphene where the wetting translucency effect makes graphene different from other standard solids.

  4. Wetting dynamics of a water nanodrop on graphene.

    PubMed

    Andrews, Joseph Eugene; Sinha, Shayandev; Chung, Peter W; Das, Siddhartha

    2016-09-14

    Water-graphene wetting interactions are central to several applications such as desalination, water filtration, electricity generation, biochemical sensing, fabrication of fuel cells, and many more. While substantial attention has been devoted to probe the wetting statics of a water drop on graphene, unraveling the possible wetting translucency nature of graphene, very little research has been done on the dynamics of wetting of water drops on graphene-coated solids or free-standing graphene layers. In this paper, we employ molecular dynamics (MD) simulations to study the contact and the spreading of a water nanodrop, quantifying its wetting dynamics, on supported and free-standing graphene. We demonstrate that nanoscale water drops establish contact with graphene by forming patches on graphene, and this patch formation is hastened for graphene layer(s) supported on hydrophilic solids. More importantly, our results demonstrate that the nanodrop spreading dynamics, regardless of the number of graphene layers or the nature of the underlying solid, obey the half-power law, i.e., r∼t(1/2) (where r is the wetting contact radius and t is the spreading time) for the entire timespan of spreading except towards the very end of the spreading lifetime when the spreading stops. Such a spreading behavior is exactly analogous to the spreading dynamics of nanodroplets for standard solids - this is in sharp contrast to the wetting statics of graphene where the wetting translucency effect makes graphene different from other standard solids. PMID:27306955

  5. Using Ethanol to Investigate Dynamic Soil Water Repellency

    NASA Astrophysics Data System (ADS)

    Smith, James E.; Beatty, Sarah M.

    2016-04-01

    Large gaps remain in our fundamental understanding of the behaviour of water in dynamically repellent soils. By investigating these systems using other miscible fluids that minimize or eliminate repellency, e.g. ethanol, we seek to better understand and quantify soil water repellency. The advantages of the enhanced wettability of water repellent soils to other miscible fluids, however, come with complications including shifts in effective pore water pressures induced through variable interfacial tensions as well as differences in fluid mobility due to variable fluid viscosities and densities. With these considerations in mind, we compare and contrast the observed behaviours of fluid infiltration and retention in dynamically hydrophobic soils and hydrophilic soils. We conducted field and laboratory studies using tension disc infiltrometers along with water and ethanol solutions to investigate dynamic repellency in post-wildfire soils from Northern Ontario, Canada. Tension infiltrometers maintain a constant negative liquid pressure at the surface which proved to be useful for isolating wettable behaviours sensitive to dynamic changes in wettability. We present the data and system conceptualised and explained through contact angle dynamics and variable fractional wettability of the soil. The limitations of extending hydrophilic concepts and hydraulic functions to hydrophobic soils are discussed along with persistent challenges to advance our ability to simulate and predict system behaviours in naturally occurring water repellent soils.

  6. DOE workshop: Sedimentary systems, aqueous and organic geochemistry

    SciTech Connect

    Not Available

    1993-07-01

    A DOE workshop on sedimentary systems, aqueous and organic geochemistry was held July 15-16, 1993 at Lawrence Berkeley Laboratory. Papers were organized into several sections: Fundamental Properties, containing papers on the thermodynamics of brines, minerals and aqueous electrolyte solutions; Geochemical Transport, covering 3-D imaging of drill core samples, hydrothermal geochemistry, chemical interactions in hydrocarbon reservoirs, fluid flow model application, among others; Rock-Water Interactions, with presentations on stable isotope systematics of fluid/rock interaction, fluid flow and petotectonic evolution, grain boundary transport, sulfur incorporation, tracers in geologic reservoirs, geothermal controls on oil-reservoir evolution, and mineral hydrolysis kinetics; Organic Geochemistry covered new methods for constraining time of hydrocarbon migration, kinetic models of petroleum formation, mudstones in burial diagenesis, compound-specific carbon isotope analysis of petroleums, stability of natural gas, sulfur in sedimentary organic matter, organic geochemistry of deep ocean sediments, direct speciation of metal by optical spectroscopies; and lastly, Sedimentary Systems, covering sequence stratigraphy, seismic reflectors and diagenetic changes in carbonates, geochemistry and origin of regional dolomites, and evidence of large comet or asteroid impacts at extinction boundaries.

  7. Nonlinear Dynamic Characteristics of Oil-in-Water Emulsions

    NASA Astrophysics Data System (ADS)

    Yin, Zhaoqi; Han, Yunfeng; Ren, Yingyu; Yang, Qiuyi; Jin, Ningde

    2016-08-01

    In this article, the nonlinear dynamic characteristics of oil-in-water emulsions under the addition of surfactant were experimentally investigated. Firstly, based on the vertical upward oil-water two-phase flow experiment in 20 mm inner diameter (ID) testing pipe, dynamic response signals of oil-in-water emulsions were recorded using vertical multiple electrode array (VMEA) sensor. Afterwards, the recurrence plot (RP) algorithm and multi-scale weighted complexity entropy causality plane (MS-WCECP) were employed to analyse the nonlinear characteristics of the signals. The results show that the certainty is decreasing and the randomness is increasing with the increment of surfactant concentration. This article provides a novel method for revealing the nonlinear dynamic characteristics, complexity, and randomness of oil-in-water emulsions with experimental measurement signals.

  8. Molecular dynamics insights into human aquaporin 2 water channel.

    PubMed

    Binesh, A R; Kamali, R

    2015-12-01

    In this study, the first molecular dynamics simulation of the human aquaporin 2 is performed and for a better understanding of the aquaporin 2 permeability performance, the characteristics of water transport in this protein channel and key biophysical parameters of AQP2 tetramer including osmotic and diffusive permeability constants and the pore radius are investigated. For this purpose, recently recovered high resolution X-ray crystal structure of` the human aquaporin 2 is used to perform twenty nanosecond molecular dynamics simulation of fully hydrated tetramer of this protein embedded in a lipid bilayer. The resulting water permeability characteristics of this protein channel showed that the water permeability of the human AQP2 is in a mean range in comparison with other human aquaporins family. Finally, the results reported in this research demonstrate that molecular dynamics simulation of human AQP2 provided useful insights into the mechanisms of water permeation and urine concentration in the human kidney. PMID:26489820

  9. Molecular dynamics insights into human aquaporin 2 water channel.

    PubMed

    Binesh, A R; Kamali, R

    2015-12-01

    In this study, the first molecular dynamics simulation of the human aquaporin 2 is performed and for a better understanding of the aquaporin 2 permeability performance, the characteristics of water transport in this protein channel and key biophysical parameters of AQP2 tetramer including osmotic and diffusive permeability constants and the pore radius are investigated. For this purpose, recently recovered high resolution X-ray crystal structure of` the human aquaporin 2 is used to perform twenty nanosecond molecular dynamics simulation of fully hydrated tetramer of this protein embedded in a lipid bilayer. The resulting water permeability characteristics of this protein channel showed that the water permeability of the human AQP2 is in a mean range in comparison with other human aquaporins family. Finally, the results reported in this research demonstrate that molecular dynamics simulation of human AQP2 provided useful insights into the mechanisms of water permeation and urine concentration in the human kidney.

  10. Structure and dynamics of water inside endohedrally functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Paul, Sanjib; Abi, T. G.; Taraphder, Srabani

    2014-05-01

    We have carried out classical molecular dynamics simulations on the formation of extended water chains inside single-walled carbon nanotubes (SWCNTs) in water in the presence of selected functional groups covalently attached to the inner wall of the tube. Analogues of polar amino acid sidechains have been chosen to carry out the endohedral functionalization of SWCNTs. Our results show a spontaneous and asymmetric filling of the nanotube with dynamical water chains in all the cases studied. The presence of Asp- and Glu-like sidechains is found to result in the formation of well-ordered water chains across the tube having the maximum number of water molecules being retained within the core with the largest residence times. The presence of methyl or methylene groups along the suspended chain is observed to disrupt the formation of water chains with higher length and/or longer residence times. The importance of hydrogen bonding in forming these water chains is assessed in terms of the relaxations of different hydrogen bond correlation functions. For a given dimension of the hydrophobic nanopore, we thus obtain a scale comparing the ability of carboxylic, alcohol, and imidazole groups in controlling the structure and dynamics of water in it. Our results also suggest that SWCNTs of varying lengths, endohedrally functionalized with Asp- and Glu-like sidechains, may be used as design templates in CNT-based water storage devices.

  11. Aqua Dynamics. Physical Conditioning through Water Exercises.

    ERIC Educational Resources Information Center

    President's Council on Physical Fitness and Sports, Washington, DC.

    Swimming is recognized as America's most popular active sport. It is one of the best physical activities for people of all ages and for people who are physically handicapped. Vigorous water exercises can increase a person's flexibility, strength, and cardio-vascular endurance. Exercises requiring flexibility are performed more easily in water…

  12. Mixing Dynamics Between Water and Biofuels

    NASA Astrophysics Data System (ADS)

    Cotel, Aline; Demond, Avery; Lei, Jiariu; Green, Erica

    2013-11-01

    Currently, ethanol-based biofuels are considered to be among the best alternatives to gasoline. However, the potential environmental impact of a spill of such fuels on aquatic environments is an area of open discussion and research. Since these fuels are a combination of a miscible fluid (ethanol) and an immiscible fluid (gasoline), models used for traditional gasoline fuels (immiscible in water) are not applicable. Preliminary experiments show that when a solution of ethanol and glycol is mixed with water, a third mixed fluid is formed. Two distinct mixing regimes are observed. A turbulent wake is created between the ethanol/glycol and water layers to cause the ethanol and glycol solution to entrain and mix into with the water phase. In the first regime, due to nonlinear mixing behavior, a dramatic overturning is possible for a certain range of parameters. The second regime begins when the turbulent wake has dissipated and the internal wave created by the plate has begun to settle, typically within the first minute. At this point, Bénard-like cells, similar to those typically seen in Rayleigh-Bénard convection, form at the interface and relatively slow mass transfer is evident. Both regimes are described quantitatively with a set of dimensionless parameters.

  13. Sulfide Mineralogy and Geochemistry

    NASA Astrophysics Data System (ADS)

    Dilles, John

    2007-02-01

    Reviews in Mineralogy and Geochemistry Series, Volume 61 David J. Vaughan, Editor Geochemical Society and Mineralogical Society of America; ISBN 0-939950-73-1 xiii + 714 pp.; 2006; $40. Sulfide minerals as a class represent important minor rock-forming minerals, but they are generally known as the chief sources of many economic metallic ores. In the past two decades, sulfide research has been extended to include important roles in environmental geology of sulfide weathering and resultant acid mine drainage, as well as in geomicrobiology in which bacteria make use of sulfides for metabolic energy sources. In the latter respect, sulfides played an important role in early evolution of life on Earth and in geochemical cycling of elements in the Earth's crust and hydrosphere.

  14. Molecular dynamics simulations of water within models of ion channels.

    PubMed Central

    Breed, J; Sankararamakrishnan, R; Kerr, I D; Sansom, M S

    1996-01-01

    The transbilayer pores formed by ion channel proteins contain extended columns of water molecules. The dynamic properties of such waters have been suggested to differ from those of water in its bulk state. Molecular dynamics simulations of ion channel models solvated within and at the mouths of their pores are used to investigate the dynamics and structure of intra-pore water. Three classes of channel model are investigated: a) parallel bundles of hydrophobic (Ala20) alpha-helices; b) eight-stranded hydrophobic (Ala10) antiparallel beta-barrels; and c) parallel bundles of amphipathic alpha-helices (namely, delta-toxin, alamethicin, and nicotinic acetylcholine receptor M2 helix). The self-diffusion coefficients of water molecules within the pores are reduced significantly relative to bulk water in all of the models. Water rotational reorientation rates are also reduced within the pores, particularly in those pores formed by alpha-helix bundles. In the narrowest pore (that of the Ala20 pentameric helix bundle) self-diffusion coefficients and reorientation rates of intra-pore waters are reduced by approximately an order of magnitude relative to bulk solvent. In Ala20 helix bundles the water dipoles orient antiparallel to the helix dipoles. Such dipole/dipole interaction between water and pore may explain how water-filled ion channels may be formed by hydrophobic helices. In the bundles of amphipathic helices the orientation of water dipoles is modulated by the presence of charged side chains. No preferential orientation of water dipoles relative to the pore axis is observed in the hydrophobic beta-barrel models. Images FIGURE 1 FIGURE 5 FIGURE 7 PMID:8785323

  15. Dynamic adhesion forces between microparticles and substrates in water.

    PubMed

    Xu, Quan; Li, Mingtao; Zhang, Lipeng; Niu, Jianbing; Xia, Zhenhai

    2014-09-23

    The interactions between micrometer-sized particles and substrates in aqueous environment are fundamental to numerous natural phenomena and industrial processes. Here we report a dynamically induced enhancement in adhesion interactions between microparticles and substrates immerged in water, air, and hexane. The dynamic adhesion force was measured by pulling microsized spheres off various substrate (hydrophilic/hydrophobic) surfaces at different retracting velocities. It was observed that when the pull-off velocity varies from 0.02 to 1500 μm/s, there is 100-200% increase in adhesion force in water while it has a 100% increase in nitrogen and hexane. The dynamic adhesion enhancement reduces with increasing effective contact angle defined by the average cosine of wetting angles of the substrates and the particles, and approaches the values measured in dry nitrogen and hexane as the effective contact angle is larger than 90(o). A dynamic model was developed to predict the adhesion forces resulting from this dynamic effect, and the predictions correlate well with the experimental results. The stronger dynamic adhesion enhancement in water is mainly attributed to electrical double layers and the restructuring of water in the contact area between particles and substrates. PMID:25162139

  16. Different aggregation dynamics of benzene-water mixtures.

    PubMed

    Fu, Cen-Feng; Tian, Shan Xi

    2014-10-28

    All-atom molecular dynamics simulations for benzene-water mixtures are performed, aiming to explore the relationship between the microscopic structures and the thermodynamic properties, in particular, the transformation dynamics from the mutually soluble state to the phase-separated state. We find that the molecular aggregation of benzene in the water-rich mixture is distinctly different from that of water in the benzene-rich mixture. This aggregation difference is attributed to the different intermolecular interactions: the clustering of benzene molecules in the water-rich mixture is primarily driven by weak short-distance π-π interactions; while the formation of water clusters in the benzene-rich solution is triggered by long-range dipole-dipole electrostatic interactions. Moreover, the molecular aggregations show double-scaled features: firstly assembling in a quasi-plane at a low concentration, then bulking in three dimensions with an increase in concentration.

  17. Orientational Dynamics of Water at an Extended Hydrophobic Interface.

    PubMed

    Xiao, Shunhao; Figge, Florian; Stirnemann, Guillaume; Laage, Damien; McGuire, John A

    2016-05-01

    We report on the orientational dynamics of water at an extended hydrophobic interface with an octadecylsilane self-assembled monolayer on fused silica. The interfacial dangling OH stretch mode is excited with a resonant pump, and its evolution followed in time by a surface-specific, vibrationally resonant, infrared-visible sum-frequency probe. High sensitivity pump-probe anisotropy measurements and isotopic dilution clearly reveal that the decay of the dangling OH stretch excitation is almost entirely due to a jump to a hydrogen-bonded configuration that occurs in 1.61 ± 0.10 ps. This is more than twice as fast as the jump time from one hydrogen-bonded configuration to another in bulk H2O but about 50% slower than the reported out-of-plane reorientation at the air/water interface. In contrast, the intrinsic population lifetime of the dangling OH stretch in the absence of such jumps is found to be >10 ps. Molecular dynamics simulations of air/water and hexane/water interfaces reproduce the fast jump dynamics of interfacial dangling OH with calculated jump times of 1.4 and 1.7 ps for the air and hydrophobic interfaces, respectively. The simulations highlight that while the air/water and hydrophobic/water surfaces exhibit great structural similarities, a small stabilization of the OH groups by the hydrophobic interface produces the pronounced difference in the dynamics of dangling bonds. PMID:27045950

  18. Structure and dynamics of water in nanoscopic spheres and tubes.

    PubMed

    van der Loop, Tibert H; Ottosson, Niklas; Lotze, Stephan; Kentzinger, Emmanuel; Vad, Thomas; Sager, Wiebke F C; Bakker, Huib J; Woutersen, Sander

    2014-11-14

    We study the reorientation dynamics of liquid water confined in nanometer-sized reverse micelles of spherical and cylindrical shape. The size and shape of the micelles are characterized in detail using small-angle x-ray scattering, and the reorientation dynamics of the water within the micelles is investigated using GHz dielectric relaxation spectroscopy and polarization-resolved infrared pump-probe spectroscopy on the OD-stretch mode of dilute HDO:H2O mixtures. We find that the GHz dielectric response of both the spherical and cylindrical reverse micelles can be well described as a sum of contributions from the surfactant, the water at the inner surface of the reversed micelles, and the water in the core of the micelles. The Debye relaxation time of the core water increases from the bulk value τ(H2O) of 8.2 ± 0.1 ps for the largest reverse micelles with a radius of 3.2 nm to 16.0 ± 0.4 ps for the smallest micelles with a radius of 0.7 nm. For the nano-spheres the dielectric response of the water is approximately ∼6 times smaller than expected from the water volume fraction and the bulk dielectric relaxation of water. We find that the dielectric response of nano-spheres is more attenuated than that of nano-tubes of identical composition (water-surfactant ratio), whereas the reorientation dynamics of the water hydroxyl groups is identical for the two geometries. We attribute the attenuation of the dielectric response compared to bulk water to a local anti-parallel ordering of the molecular dipole moments. The difference in attenuation between nano-spheres and nano-cylinders indicates that the anti-parallel ordering of the water dipoles is more pronounced upon spherical than upon cylindrical nanoconfinement. PMID:25399200

  19. Calcium carbonate production and sea surface dynamics during MIS 9 to 13 in the Southern Ocean: Evidence from calcareous nannofossils and sediment geochemistry

    NASA Astrophysics Data System (ADS)

    Flores, J.; Sierro, F. J.; Filippelli, G. M.; Latimer, J. C.

    2001-12-01

    The calcareous nannofossils (CN-present day coccolithophores) as autotrophic phytoplankton inhabitant of the photic zone, have demonstrate to be an excellent tool fort paleoceanografic reconstructions. However, this fossil group is susceptible of dissolution due to their calcium carbonate composition. Here we shown a comparative study between CN and different geochemical proxies in order to estimate, 1) degree of dissolution in the CN assemblages, and 2) the contribution the primary production of these organisms and their relationship with surface-water dynamics. We analyzed several cores along the Atlantic and Pacific sectors (Subantarctic) in the Southern Ocean, for the interval comprise between MIS 9 to 13, paying special attention to ODP Site 1089 (Cape Basin). This interval is characterized in the whole ocean by a dominance of Gephyrocapsa caribbeanica (a small but robust and well-calcified placolith). Although the record of CN is continuous, we observed important fluctuations in the degree of preservation in the CN assemblages, that during interglacial periods shown high to moderate dissolution. Conversely, glacials are characterized by moderate to good CN preservation. It is interesting to note that during Terminations IV and V, we observed maxima in CN accumulation, but with moderate preservation. This pattern allow us to propose that maxima in CN production occurs during Terminations. These data agree with the geochemical data such as P/Ti ratio and Sr concentration. These proxies, not affected by dissolution, show peaks during Terminations IV and V. Although, according with the available information, maximum production of calcium carbonate in the ocean is referred to interglacial period. In the case of MIS 11, related with the so-called Mid-Brunhes event", we discuss the possibility that the dissolution interval occurring at this time was related with high production of calcium carbonate and burial in the ocean, and a consequent rising of CCD and

  20. Dynamics of water in prussian blue analogues: Neutron scattering study

    SciTech Connect

    Sharma, V. K.; Mitra, S.; Thakur, N.; Yusuf, S. M.; Mukhopadhyay, R.; Juranyi, Fanni

    2014-07-21

    Dynamics of crystal water in Prussian blue (PB), Fe(III){sub 4}[Fe(II)(CN){sub 6}]{sub 3}.14H{sub 2}O and its analogue Prussian green (PG), ferriferricynaide, Fe(III){sub 4}[Fe(III)(CN){sub 6}]{sub 4}.16H{sub 2}O have been investigated using Quasielastic Neutron Scattering (QENS) technique. PB and its analogue compounds are important materials for their various interesting multifunctional properties. It is known that crystal water plays a crucial role towards the multifunctional properties of Prussian blue analogue compounds. Three structurally distinguishable water molecules: (i) coordinated water molecules at empty nitrogen sites, (ii) non-coordinated water molecules in the spherical cavities, and (iii) at interstitial sites exist in PB. Here spherical cavities are created due to the vacant sites of Fe(CN){sub 6} units. However, PG does not have any such vacant N or Fe(CN){sub 6} units, and only one kind of water molecules, exists only at interstitial sites. QENS experiments have been carried out on both the compounds in the temperature range of 260–360 K to elucidate the dynamical behavior of different kinds of water molecules. Dynamics is found to be much more pronounced in case of PB, compared to PG. A detailed data analysis showed that localized translational diffusion model could describe the observed data for both PB and PG systems. The average diffusion coefficient is found to be much larger in the PB than PG. The obtained domain of dynamics is found to be consistent with the geometry of the structure of the two systems. Combining the data of the two systems, a quantitative estimate of the dynamics, corresponding to the water molecules at different locations is made.

  1. Dissolution dynamics of the calcite-water interface observed in situ by glancing-incidence X-ray scattering

    SciTech Connect

    Sturchio, N.C.; Chiarello, R.P.

    1995-06-02

    Glancing-incidence X-ray scattering measurements made at the National Synchrotron Light Source were used to investigate dissolution dynamics in situ at the calcite-water interface. The relation between calcite saturation state and roughness of the calcite (1014) cleavage surface as a function of time was examined during pH titrations of an initially calcite-saturated solution. Systematic variations in roughness were observed as a function of saturation state as pH was titrated to values below that of calcite saturation. Different steady-state values of roughness were evident at fixed values of {Delta}G{sub r}, and these were correlated with the extent of undersaturation. A significant increase in roughness begins to occur with increasing undersaturation at a {Delta}G{sub r} value of approximately {minus}2.0 kcal/mol. The dissolution rate corresponding to this increase is about 1.5 x 10{sup 7} mmol/cm {center_dot} sec. This increase in roughness is attributed to a transition in the principal rate-determining dissolution mechanism, and is consistent with both powder-reaction studies of dissolution kinetics and single-crystal dissolution studies by atomic force microscopy. These data indicate some important potential applications of GIXS in the study of mineral-water interface geochemistry.

  2. Quantum effects in the dynamics of deeply supercooled water

    SciTech Connect

    Agapov, Alexander L.; Kolesnikov, Alexander I.; Novikov, Vladimir N.; Richert, Ranko; Sokolov, Alexei P

    2015-02-26

    In spite of its simple chemical structure, water remains one of the most puzzling liquids with many anomalies at low temperatures. Combining neutron scattering and dielectric relaxation spectroscopy, we show that quantum fluctuations are not negligible in deeply supercooled water. Our dielectric measurements reveal the anomalously weak temperature dependence of structural relaxation in vapor-deposited water close to the glass transition temperature Tg~136K. We demonstrate that this anomalous behavior can be explained well by quantum effects. In conclusion, these results have significant implications for our understanding of water dynamics.

  3. Quantum effects in the dynamics of deeply supercooled water

    DOE PAGES

    Agapov, Alexander L.; Kolesnikov, Alexander I.; Novikov, Vladimir N.; Richert, Ranko; Sokolov, Alexei P

    2015-02-26

    In spite of its simple chemical structure, water remains one of the most puzzling liquids with many anomalies at low temperatures. Combining neutron scattering and dielectric relaxation spectroscopy, we show that quantum fluctuations are not negligible in deeply supercooled water. Our dielectric measurements reveal the anomalously weak temperature dependence of structural relaxation in vapor-deposited water close to the glass transition temperature Tg~136K. We demonstrate that this anomalous behavior can be explained well by quantum effects. In conclusion, these results have significant implications for our understanding of water dynamics.

  4. Spatial and dynamic simulation for Miyun Reservoir waters in Beijing.

    PubMed

    Jia, H; Cheng, S

    2002-01-01

    In order to assist the water quality management in Miyun Reservoir, a spatial and dynamic simulation model system was built. In the model system, GIS was integrated with the WASP5 model. The integrated model system was then calibrated and verified in different sets of field data. The result showed that the integrated model system could characterize the Miyun Reservoir waters. Two scenarios were then designed and analyzed with the integrated model system. It was indicated that the water quality would improve if the cage fishery was banned, the algae blooms might occur in Miyun Reservoir if the low water stage ocurred but loads remained unchanged.

  5. Dynamics of water interacting with interfaces, molecules, and ions.

    PubMed

    Fayer, Michael D

    2012-01-17

    Water is a critical component of many chemical processes, in fields as diverse as biology and geology. Water in chemical, biological, and other systems frequently occurs in very crowded situations: the confined water must interact with a variety of interfaces and molecular groups, often on a characteristic length scale of nanometers. Water's behavior in diverse environments is an important contributor to the functioning of chemical systems. In biology, water is found in cells, where it hydrates membranes and large biomolecules. In geology, interfacial water molecules can control ion adsorption and mineral dissolution. Embedded water molecules can change the structure of zeolites. In chemistry, water is an important polar solvent that is often in contact with interfaces, for example, in ion-exchange resin systems. Water is a very small molecule; its unusual properties for its size are attributable to the formation of extended hydrogen bond networks. A water molecule is similar in mass and volume to methane, but methane is a gas at room temperature, with melting and boiling points of 91 and 112 K, respectively. This is in contrast to water, with melting and boiling points of 273 and 373 K, respectively. The difference is that water forms up to four hydrogen bonds with approximately tetrahedral geometry. Water's hydrogen bond network is not static. Hydrogen bonds are constantly forming and breaking. In bulk water, the time scale for hydrogen bond randomization through concerted formation and dissociation of hydrogen bonds is approximately 2 ps. Water's rapid hydrogen bond rearrangement makes possible many of the processes that occur in water, such as protein folding and ion solvation. However, many processes involving water do not take place in pure bulk water, and water's hydrogen bond structural dynamics can be substantially influenced by the presence of, for example, interfaces, ions, and large molecules. In this Account, spectroscopic studies that have been used

  6. Imaging the molecular dynamics of dissociative electron attachment to water

    SciTech Connect

    Adaniya, Hidihito; Rudek, B.; Osipov, Timur; Haxton, Dan; Weber, Thorsten; Rescigno, Thomas N.; McCurdy, C.W.; Belkacem, Ali

    2009-10-19

    Momentum imaging experiments on dissociative electron attachment to the water molecule are combined with ab initio theoretical calculations of the angular dependence of the quantum mechanical amplitude for electron attachment to provide a detailed picture of the molecular dynamics of dissociation attachment via the two lowest energy Feshbach resonances. The combination of momentum imaging experiments and theory can reveal dissociation dynamics for which the axial recoil approximation breaks down and thus provides a powerful reaction microscope for DEA to polyatomics.

  7. Water and polymer dynamics in highly crosslinked polyamide membranes

    NASA Astrophysics Data System (ADS)

    Frieberg, Bradley; Chan, Edwin; Tyagi, Madhu; Stafford, Christopher; Soles, Christopher

    Highly crosslinked polyamides for reverse osmosis are the state-of-the-art active material in membranes for desalination. The thin film composite membrane structure that is used commercially has been empirically designed to selectively allow the passage of water molecules and minimize the passage of solutes such as salt. However, due to the large roughness and variability of the polyamide layer, there is a limited understanding of the structure-property relationship for these materials as well as the transport mechanism. To better understand the water transport mechanism we measure the water and polymer dynamics of polyamide membranes using quasi-elastic neutron scattering (QENS). By hydrating the membrane with deuterated water, we are able to isolate the dynamics of the hydrogenated membrane on the pico- and nanosecond time scales. By subsequently hydrating the membranes with hydrogenated water, the QENS measurements on the same times scales reveal information about both the translational and rotational dynamics of water confined within the polyamide membrane. Further understanding of the water diffusion mechanism will establish design rules in which the performance of future membrane materials can be improved.

  8. Linking Water Table Dynamics to Carbon Cycling in Artificial Soil Column Incubations

    NASA Astrophysics Data System (ADS)

    Geertje, Pronk; Adrian, Mellage; Tatjana, Milojevic; Fereidoun, Rezanezhad; Cappellen Philippe, Van

    2016-04-01

    The biogeochemistry of wetlands soils is closely tied to their hydrology. Water table fluctuations that cause flooding and drying of these systems may lead to enhanced degradation of organic matter and release of greenhouse gasses (e.g. CO2, CH4) to the atmosphere. However, predicting the influence of water table fluctuations on the biogeochemical functioning of soils requires an understanding of the interactions of soil hydrology with biogeochemical and microbial processes. To determine the effects of water table dynamics on carbon cycling, we are carrying out state-of-the-art automated soil column experiments with fully integrated monitoring of hydro-bio-geophysical process variables under both constant and oscillating water table conditions. An artificial, homogeneous mixture consisting of minerals and organic matter is used to provide a well-defined starting material. The artificial soils are composed of quartz sand, montmorillonite, goethite and humus from a forested riparian zone, from which we also extracted the microbial inoculum added to the soil mixture. The artificial soils are packed into 60 cm high, 7.5 cm wide columns. In the currently ongoing experiment, three replicate columns are incubated while keeping the water table constant water at mid-depth, while another three columns alternate between drained and saturated conditions. Micro-sensors installed at different depths below the soil surface record time-series redox potentials (Eh) varying between oxidizing (~+700 mV) and reducing (~-200 mV) conditions. Continuous O2 levels throughout the soil columns are monitored using high-resolution, luminescence-based, Multi Fiber Optode (MuFO) microsensors. Pore waters are collected periodically with MicroRhizon samplers from different depths, and analyzed for pH, EC, dissolved inorganic and organic carbon and ion/cation compositions. These measurements allow us to track the changes in pore water geochemistry and relate them to differences in carbon cycling

  9. Molecular dynamic simulations of the water absorbency of hydrogels.

    PubMed

    Ou, Xiang; Han, Qiang; Dai, Hui-Hui; Wang, Jiong

    2015-09-01

    A polymer gel can imbibe solvent molecules through surface tension effect. When the solvent happens to be water, the gel can swell to a large extent and forms an aggregate called hydrogel. The large deformation caused by such swelling makes it difficult to study the behaviors of hydrogels. Currently, few molecular dynamic simulation works have been reported on the water absorbing mechanism of hydrogels. In this paper, we first use molecular dynamic simulation to study the water absorbing mechanism of hydrogels and propose a hydrogel-water interface model to study the water absorbency of the hydrogel surface. Also, the saturated water content and volume expansion rate of the hydrogel are investigated by building a hydrogel model with different cross-linking degree and by comparing the water absorption curves under different temperatures. The sample hydrogel model used consists of Polyethylene glycol diglycidyl ether (PEGDGE) as epoxy and the Jeffamine, poly-oxy-alkylene-amines, as curing agent. The conclusions obtained are useful for further investigation on PEGDGE/Jeffamine hydrogel. Moreover, the simulation methods, including hydrogel-water interface modeling, we first propose are also suitable to study the water absorbing mechanism of other hydrogels. PMID:26271733

  10. Arctic Pacific water dynamics from model intercomparison and observations

    NASA Astrophysics Data System (ADS)

    Aksenov, Yevgeny; Karcher, Michael; Proshutinsky, Andrey; Gerdes, Ruediger; Bacon, Sheldon; Nurser, George; Coward, Andrew; Golubeva, Elena; Kauker, Frank; Nguyen, An; Platov, Gennady; Wadley, Martin; Watanabe, Eiji

    2016-04-01

    Pacific Water imports heat and fresh water from the northern Pacific in the Arctic Ocean, impacting upper ocean mixing and dynamics, as well as Arctic sea ice. Pathways and the circulation of PW in the central Arctic Ocean are not well known due to the lack of observations. This study uses an ensemble of the sea ice-ocean models integrated with passive tracer released in the Bering Strait to simulate Pacific water spread. We investigate different branches and modes of Pacific water and analyse changes in the water mass distribution through the Arctic Ocean due to changes in the wind and ocean potential vorticity. We focus on seasonal cycle and inter-decadal variations. The first results have been published recently (Aksenov et al., 2015) as a part of Forum for Arctic Ocean Modeling and Observational Synthesis (FAMOS) project. In the present study we extend the examination further and discuss the role of the Pacific water variability in the recent changes in the Arctic heat and fresh water storage. We present insights in the projected future changes to Pacific water dynamics. Reference Aksenov, Y., et al. (2015), Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments, J. Geophys. Res. Oceans, 120, doi:10.1002/2015JC011299.

  11. Quantum tunneling and vibrational dynamics of ultra-confined water

    NASA Astrophysics Data System (ADS)

    Kolesnikov, Alexander I.; Anovitz, Lawrence M.; Ehlers, Georg; Mamontov, Eugene; Podlesnyak, Andrey; Prisk, Timothy R.; Seel, Andrew; Reiter, George F.

    2015-03-01

    Vibrational dynamics of ultra-confined water in single crystals beryl, the structure of which contains ~ 5 Å diameter channels along the c-axis was studied with inelastic (INS), quasi-elastic (QENS) and deep inelastic (DINS) neutron scattering. The results reveal significantly anisotropic dynamical behavior of confined water, and show that effective potential experienced by water perpendicular to the channels is significantly softer than along them. The observed 7 peaks in the INS spectra (at energies 0.25 to 15 meV), based on their temperature and momentum transfer dependences, are explained by transitions between the split ground states of water in beryl due to water quantum tunneling between the 6-fold equivalent positions across the channels. DINS study of beryl at T=4.3 K shows narrow, anisotropic water proton momentum distribution with corresponding kinetic energy, EK=95 meV, which is much less than was previously observed in bulk water (~150 meV). We believe that the exceptionally small EK in beryl is a result of water quantum tunneling ∖ delocalization in the nanometer size confinement and weak water-cage interaction. The neutron experiment at ORNL was sponsored by the Sci. User Facilities Div., BES, U.S. DOE. This research was sponsored by the Div. Chemical Sci, Geosciences, and Biosciences, BES, U.S. DOE. The STFC RAL is thanked for access to ISIS neutron facilities.

  12. Water exchange dynamics around H3O+ and OH- ions

    NASA Astrophysics Data System (ADS)

    Roy, Santanu; Dang, Liem X.

    2015-05-01

    In this letter, we report the first computer simulation of the dynamics of water exchanging between the first and second solvation shells of H3O+. Employing different rate theories for chemical reactions such as the transition state theory, the Grote-Hynes theory, the reactive flux method, and the Impey-Madden-McDonald method, we calculate the solvent exchange rates from molecular dynamics simulations that account for explicit polarization effects. In addition, we also study water exchanges around OH- and find that the corresponding time scale is much smaller than that for H3O+.

  13. Dynamics of lysozyme and its hydration water under electric field

    SciTech Connect

    Favi, Pelagie M; Zhang, Qiu; O'Neill, Hugh Michael; Mamontov, Eugene; Omar Diallo, Souleymane; Palmer, Jeremy

    2014-01-01

    The effects of static electric field on the dynamics of lysozyme and its hydration water have been investigated by means of incoherent quasi-elastic neutron scattering (QENS). Measurements were performed on lysozyme samples, hydrated respectively with heavy water (D2O) to capture the protein dynamics, and with light water (H2O), to probe the dynamics of the hydration shell, in the temperature range from 210 < T < 260 K. The hydration fraction in both cases was about 0.38 gram of water per gram of dry protein. The field strengths investigated were respectively 0 kV/mm and 2 kV/mm ( 2 106 V/m) for the protein hydrated with D2O and 0 kV and 1 kV/mm for the H2O-hydrated counterpart. While the overall internal protons dynamics of the protein appears to be unaffected by the application of electric field up to 2 kV/mm, likely due to the stronger intra-molecular interactions, there is also no appreciable quantitative enhancement of the diffusive dynamics of the hydration water, as would be anticipated based on our recent observations in water confined in silica pores under field values of 2.5 kV/mm. This may be due to the difference in surface interactions between water and the two adsorption hosts (silica and protein), or to the existence of a critical threshold field value Ec 2 3 kV/mm for increased molecular diffusion, for which electrical breakdown is a limitation for our sample.

  14. Dielectric spectroscopy study of water dynamics in frozen bovine milk.

    PubMed

    Agranovich, Daniel; Ben Ishai, Paul; Katz, Gil; Bezman, Dror; Feldman, Yuri

    2016-05-01

    Bovine milk is a complex colloidal liquid exhibiting a multi-scaled structure. It is of particular importance, both commercially and scientifically, to investigate both its dynamic and structural properties. In the current study we have employed the broadband dielectric spectroscopy (BDS) technique in the frequency range of 10(-1)-10(6)Hz and the temperature range of 176-230 K in order to examine the molecular structure and dynamics of quenched bovine milk. Four dielectric relaxation processes were identified. Three of them are associated with water in its different forms: water-lactose complexes, bulk hexagonal and cubic ices. The fourth process is attributed to domain wall relaxations linked to the presence of micro-cracks in the ice structures. In addition, the first process, attributed to water-lactose complexes, obeys the Meyer-Neldel compensation law and can be taken as evidence of differing interfaces of these complexes with the bulk water of the milk, mediated by the lactose concentration. Furthermore, an intriguing structural-dynamic transition around 200K was observed. Considering the mentioned above, we conclude that our results emphasize the structural and dynamical significance of water in bovine milk. PMID:26878290

  15. Water circulation and global mantle dynamics: Insight from numerical modeling

    NASA Astrophysics Data System (ADS)

    Nakagawa, Takashi; Nakakuki, Tomoeki; Iwamori, Hikaru

    2015-05-01

    We investigate water circulation and its dynamical effects on global-scale mantle dynamics in numerical thermochemical mantle convection simulations. Both dehydration-hydration processes and dehydration melting are included. We also assume the rheological properties of hydrous minerals and density reduction caused by hydrous minerals. Heat transfer due to mantle convection seems to be enhanced more effectively than water cycling in the mantle convection system when reasonable water dependence of viscosity is assumed, due to effective slab dehydration at shallow depths. Water still affects significantly the global dynamics by weakening the near-surface oceanic crust and lithosphere, enhancing the activity of surface plate motion compared to dry mantle case. As a result, including hydrous minerals, the more viscous mantle is expected with several orders of magnitude compared to the dry mantle. The average water content in the whole mantle is regulated by the dehydration-hydration process. The large-scale thermochemical anomalies, as is observed in the deep mantle, is found when a large density contrast between basaltic material and ambient mantle is assumed (4-5%), comparable to mineral physics measurements. Through this study, the effects of hydrous minerals in mantle dynamics are very important for interpreting the observational constraints on mantle convection.

  16. Deconstructing the hydrologic response: pattern and dynamics of water age

    NASA Astrophysics Data System (ADS)

    Hrachowitz, Markus; Savenije, Hubert; Soulsby, Chris; Tetzlaff, Doerthe

    2013-04-01

    The water storage and release dynamics at the catchment scale are still incompletely understood. This is in particular true when considering actual particle transport rather than only the hydraulic response. The use of environmental tracers is frequently instructive for getting insights into these transport process patterns. However, the potential of tracers is frequently underexploited. Although known since the early days of tracer hydrology that the composition of water in the runoff, i.e. the water age distribution can be highly variable as a function of flow volumes, it is often treated as being time- and thus flow-invariant. Here we use long term (< 20 years) precipitation, flow and tracer (chloride) data of three contrasting upland catchments in the Scottish Highlands to inform integrated conceptual models. Using the models as virtual laboratories, water and tracer fluxes were tracked through the system in order to get a better understanding of the patterns and temporal, wetness induced dynamics in the composition of stream water and its age distributions. Tracking fluxes through the system showed that the various components of a model, representing individual flow processes, such as preferential or groundwater flow, can be characterized by fundamentally different water age distributions. As a consequence, the wetness dependent dynamics and connectivity patterns of these distinct pools of water are responsible for potentially fast and substantial switches in water age distributions. Further, modeled flux water age distributions were found to be highly sensitive to variable catchment wetness conditions and exhibited considerable hysteresis effects, depending on the catchment wetness history. While the water age during wetting-up conditions is controlled by fast processes (e.g. preferential flow), it is controlled by slow processes (e.g. groundwater flow) under drying-up conditions. This non-linearity is caused by the fact that water age distributions are not

  17. From single molecules to water networks: Dynamics of water adsorption on Pt(111).

    PubMed

    Naderian, Maryam; Groß, Axel

    2016-09-01

    The adsorption dynamics of water on Pt(111) was studied using ab initio molecular dynamics simulations based on density functional theory calculations including dispersion corrections. Sticking probabilities were derived as a function of initial kinetic energy and water coverage. In addition, the energy distribution upon adsorption was monitored in order to analyze the energy dissipation process. We find that on the water pre-covered surface the sticking probability is enhanced because of the attractive water-water interaction and the additional effective energy dissipation channels to the adsorbed water molecules. The water structures forming directly after the adsorption on the pre-covered surfaces do not necessarily correspond to energy minimum structures. PMID:27609006

  18. Proline induced disruption of the structure and dynamics of water.

    PubMed

    Yu, Dehong; Hennig, Marcus; Mole, Richard A; Li, Ji Chen; Wheeler, Cheryl; Strässle, Thierry; Kearley, Gordon J

    2013-12-21

    We use quasi-elastic neutron scattering spectroscopy to study the diffusive motion of water molecules at ambient temperature as a function of the solute molar fraction of the amino acid, proline. We validate molecular dynamics simulations against experimental quasielastic neutron scattering data and then use the simulations to reveal, and understand, a strong dependence of the translational self-diffusion coefficient of water on the distance to the amino acid molecule. An analysis based on the juxtaposition of water molecules in the simulation shows that the rigidity of proline imposes itself on the local water structure, which disrupts the hydrogen-bond network of water leading to an increase in the mean lifetime of hydrogen bonds. The net effect is some distortion of the proline molecule and a slowing down of the water mobility. PMID:24177249

  19. Molecular dynamics simulation of liquid water confined inside graphite channels: dielectric and dynamical properties.

    PubMed

    Martí, J; Nagy, G; Guàrdia, E; Gordillo, M C

    2006-11-30

    Electric and dielectric properties and microscopic dynamics of liquid water confined between graphite slabs are analyzed by means of molecular dynamics simulations for several graphite-graphite separations at ambient conditions. The electric potential across the interface shows oscillations due to water layering, and the overall potential drop is about -0.28 V. The total dielectric constant is larger than the corresponding value for the bulklike internal region of the system. This is mainly due to the preferential orientations of water nearest the graphite walls. Estimation of the capacitance of the system is reported, indicating large variations for the different adsorption layers. The main trend observed concerning water diffusion is 2-fold: on one hand, the overall diffusion of water is markedly smaller for the closest graphite-graphite separations, and on the other hand, water molecules diffuse in interfaces slightly slower than those in the bulklike internal areas. Molecular reorientational times are generally larger than those corresponding to those of unconstrained bulk water. The analysis of spectral densities revealed significant spectral shifts, compared to the bands in unconstrained water, in different frequency regions, and associated to confinement effects. These findings are important because of the scarce information available from experimental, theoretical, and computer simulation research into the dielectric and dynamical properties of confined water.

  20. Evaluating water conservation and reuse policies using a dynamic water balance model.

    PubMed

    Qaiser, Kamal; Ahmad, Sajjad; Johnson, Walter; Batista, Jacimaria R

    2013-02-01

    A dynamic water balance model is created to examine the effects of different water conservation policies and recycled water use on water demand and supply in a region faced with water shortages and significant population growth, the Las Vegas Valley (LVV). The model, developed using system dynamics approach, includes an unusual component of the water system, return flow credits, where credits are accrued for returning treated wastewater to the water supply source. In LVV, Lake Mead serves as, both the drinking water source and the receiving body for treated wastewater. LVV has a consumptive use allocation from Lake Mead but return flow credits allow the water agency to pull out additional water equal to the amount returned as treated wastewater. This backdrop results in a scenario in which conservation may cause a decline in the available water supply. Current water use in LVV is 945 lpcd (250 gpcd), which the water agency aims to reduce to 752 lpcd (199 gpcd) by 2035, mainly through water conservation. Different conservation policies focused on indoor and outdoor water use, along with different population growth scenarios, are modeled for their effects on the water demand and supply. Major contribution of this study is in highlighting the importance of outdoor water conservation and the effectiveness of reducing population growth rate in addressing the future water shortages. The water agency target to decrease consumption, if met completely through outdoor conservation, coupled with lower population growth rate, can potentially satisfy the Valley's water demands through 2035.

  1. Dynamics of Hydration Water in Sugars and Peptides Solutions

    SciTech Connect

    Perticaroli, Stefania; Nakanishi, Masahiro; Pashkovski, Eugene; Sokolov, Alexei P

    2013-01-01

    We analyzed solute and solvent dynamics of sugars and peptides aqueous solutions using extended epolarized light scattering (EDLS) and broadband dielectric spectroscopies (BDS). Spectra measured with both techniques reveal the same mechanism of rotational diffusion of peptides molecules. In the case of sugars, this solute reorientational relaxation can be isolated by EDLS measurements, whereas its ontribution to the dielectric spectra is almost negligible. In the presented analysis, we characterize the hydration water in terms of hydration number and retardation ratio between relaxation times of hydration and bulk water. Both techniques provide similar estimates of . The retardation imposed on the hydration water by sugars is 3.3 1.3 and involves only water molecules hydrogen-bonded (HB) to solutes ( 3 water molecules per sugar OH-group). In contrast, polar peptides cause longer range erturbations beyond the first hydration shell, and between 2.8 and 8, increasing with the number of chemical groups engaged in HB formation. We demonstrate that chemical heterogeneity and specific HB interactions play a crucial role in hydration dynamics around polar solutes. The obtained results help to disentangle the role of excluded volume and enthalpic contributions in dynamics of hydration water at the interface with biological molecules.

  2. Structure and dynamics of water confined in silica nanopores

    NASA Astrophysics Data System (ADS)

    Milischuk, Anatoli A.; Ladanyi, Branka M.

    2011-11-01

    We report the results of molecular simulation of water in silica nanopores at full hydration and room temperature. The model systems are approximately cylindrical pores in amorphous silica, with diameters ranging from 20 to 40 Å. The filled pores are prepared using grand canonical Monte Carlo simulation and molecular dynamics simulation is used to calculate the water structure and dynamics. We found that water forms two distinct molecular layers at the interface and exhibits uniform, but somewhat lower than bulk liquid, density in the core region. The hydrogen bond density profile follows similar trends, with lower than bulk density in the core and enhancements at the interface, due to hydrogen bonds between water and surface non-bridging oxygens and OH groups. Our studies of water dynamics included translational mean squared displacements, orientational time correlations, survival probabilities in interfacial shells, and hydrogen bond population relaxation. We found that the radial-axial anisotropy in translational motion largely follows the predictions of a model of free diffusion in a cylinder. However, both translational and rotational water mobilities are strongly dependent on the proximity to the interface, with pronounced slowdown in layers near the interface. Within these layers, the effects of interface curvature are relatively modest, with only a small increase in mobility in going from the 20 to 40 Å diameter pore. Hydrogen bond population relaxation is nearly bulk-like in the core, but considerably slower in the interfacial region.

  3. Socioeconomic dynamics of water quality in the Egyptian Nile

    NASA Astrophysics Data System (ADS)

    Malik, Maheen; Nisar, Zainab; Karakatsanis, Georgios

    2016-04-01

    The Nile River remains the most important source of freshwater for Egypt as it accounts for nearly all of the country's drinking and irrigation water. About 95% of the total population is accounted to live along the Banks of the Nile(1). Therefore, water quality deterioration in addition to general natural scarcity of water in the region(2) is the main driver for carrying out this study. What further aggravates this issue is the water conflict in the Blue Nile region. The study evaluates different water quality parameters and their concentrations in the Egyptian Nile; further assessing the temporal dynamics of water quality in the area with (a) the Environmental Kuznets Curve (EKC)(3) and (b) the Jevons Paradox (JP)(4) in order to identify water quality improvements or degradations using selected socioeconomic variables(5). For this purpose various environmental indicators including BOD, COD, DO, Phosphorus and TDS were plotted against different economic variables including Population, Gross Domestic Product (GDP), Annual Fresh Water Withdrawal and Improved Water Source. Mathematically, this was expressed by 2nd and 3rd degree polynomial regressions generating the EKC and JP respectively. The basic goal of the regression analysis is to model and highlight the dynamic trend of water quality indicators in relation to their established permissible limits, which will allow the identification of optimal future water quality policies. The results clearly indicate that the dependency of water quality indicators on socioeconomic variables differs for every indicator; while COD was above the permissible limits in all the cases despite of its decreasing trend in each case, BOD and phosphate signified increasing concentrations for the future, if they continue to follow the present trend. This could be an indication of rebound effect explained by the Jevons Paradox i.e. water quality deterioration after its improvement, either due to increase of population or intensification

  4. Anomalously rapid hydration water diffusion dynamics near DNA surfaces

    PubMed Central

    Franck, John M.; Ding, Yuan; Stone, Katherine

    2015-01-01

    The emerging Overhauser effect Dynamic Nuclear Polarization (ODNP) technique measures the translational mobility of water within the vicinity (5-15 Å) of preselected sites. The work presented here expands the capabilities of the ODNP technique and illuminates an important, previously unseen, property of the translational diffusion dynamics of water at the surface of DNA duplexes. We attach nitroxide radicals (i.e., spin labels) to multiple phosphate backbone positions of DNA duplexes, allowing ODNP to measure the hydration dynamics at select positions along the DNA surface. With a novel approach to ODNP analysis, we isolate the contributions of water molecules at these sites that undergo free translational diffusion from water molecules that either loosely bind to or exchange protons with the DNA. The results reveal that a significant population of water in a localized volume adjacent to the DNA surface exhibits fast, bulk-like characteristics and moves unusually rapidly compared to water found in similar probe volumes near protein and membrane surfaces. Control studies show that the observation of these characteristics are upheld even when the DNA duplex is tethered to streptavidin or the mobility of the nitroxides is altered. This implies that, as compared to protein or lipid surfaces, it is an intrinsic feature of the DNA duplex surface that it interacts only weakly with a significant fraction of a network of surface hydration water. The displacement of this translationally mobile water is energetically less costly than that of more strongly bound water by up to several kBT and thus can lower the activation barrier for interactions involving the DNA surface. PMID:26256693

  5. Anomalously Rapid Hydration Water Diffusion Dynamics Near DNA Surfaces.

    PubMed

    Franck, John M; Ding, Yuan; Stone, Katherine; Qin, Peter Z; Han, Songi

    2015-09-23

    The emerging Overhauser effect dynamic nuclear polarization (ODNP) technique measures the translational mobility of water within the vicinity (5-15 Å) of preselected sites. The work presented here expands the capabilities of the ODNP technique and illuminates an important, previously unseen, property of the translational diffusion dynamics of water at the surface of DNA duplexes. We attach nitroxide radicals (i.e., spin labels) to multiple phosphate backbone positions of DNA duplexes, allowing ODNP to measure the hydration dynamics at select positions along the DNA surface. With a novel approach to ODNP analysis, we isolate the contributions of water molecules at these sites that undergo free translational diffusion from water molecules that either loosely bind to or exchange protons with the DNA. The results reveal that a significant population of water in a localized volume adjacent to the DNA surface exhibits fast, bulk-like characteristics and moves unusually rapidly compared to water found in similar probe volumes near protein and membrane surfaces. Control studies show that the observation of these characteristics are upheld even when the DNA duplex is tethered to streptavidin or the mobility of the nitroxides is altered. This implies that, as compared to protein or lipid surfaces, it is an intrinsic feature of the DNA duplex surface that it interacts only weakly with a significant fraction of the surface hydration water network. The displacement of this translationally mobile water is energetically less costly than that of more strongly bound water by up to several kBT and thus can lower the activation barrier for interactions involving the DNA surface.

  6. Dynamic water accounting in heavily committed river basins

    NASA Astrophysics Data System (ADS)

    Tilmant, Amaury; Marques, Guilherme

    2014-05-01

    Many river basins throughout the world are increasingly under pressure as water demands keep rising due to population growth, industrialization, urbanization and rising living standards. In the past, the typical answer to meet those demands focused on the supply-side and involved the construction of hydraulic infrastructures to capture more water from surface water bodies and from aquifers. As river basins were being more and more developed, downstream water users and ecosystems have become increasingly dependant on the management actions taken by upstream users. The increased interconnectedness between water users, aquatic ecosystems and the built environment is further compounded by climate change and its impact on the water cycle. Those pressures mean that it has become increasingly important to measure and account for changes in water fluxes and their corresponding economic value as they progress throughout the river system. Such basin water accounting should provide policy makers with important information regarding the relative contribution of each water user, infrastructure and management decision to the overall economic value of the river basin. This paper presents a dynamic water accounting approach whereby the entire river basin is considered as a value chain with multiple services including production and storage. Water users and reservoirs operators are considered as economic agents who can exchange water with their hydraulic neighbors at a price corresponding to the marginal value of water. Effective water accounting is made possible by keeping track of all water fluxes and their corresponding transactions using the results of a hydro-economic model. The proposed approach is illustrated with the Eastern Nile River basin in Africa.

  7. Dynamics of Biofilm Regrowth in Drinking Water Distribution Systems

    PubMed Central

    Husband, S.; Loza, V.; Boxall, J.

    2016-01-01

    ABSTRACT The majority of biomass within water distribution systems is in the form of attached biofilm. This is known to be central to drinking water quality degradation following treatment, yet little understanding of the dynamics of these highly heterogeneous communities exists. This paper presents original information on such dynamics, with findings demonstrating patterns of material accumulation, seasonality, and influential factors. Rigorous flushing operations repeated over a 1-year period on an operational chlorinated system in the United Kingdom are presented here. Intensive monitoring and sampling were undertaken, including time-series turbidity and detailed microbial analysis using 16S rRNA Illumina MiSeq sequencing. The results show that bacterial dynamics were influenced by differences in the supplied water and by the material remaining attached to the pipe wall following flushing. Turbidity, metals, and phosphate were the main factors correlated with the distribution of bacteria in the samples. Coupled with the lack of inhibition of biofilm development due to residual chlorine, this suggests that limiting inorganic nutrients, rather than organic carbon, might be a viable component in treatment strategies to manage biofilms. The research also showed that repeat flushing exerted beneficial selective pressure, giving another reason for flushing being a viable advantageous biofilm management option. This work advances our understanding of microbiological processes in drinking water distribution systems and helps inform strategies to optimize asset performance. IMPORTANCE This research provides novel information regarding the dynamics of biofilm formation in real drinking water distribution systems made of different materials. This new knowledge on microbiological process in water supply systems can be used to optimize the performance of the distribution network and to guarantee safe and good-quality drinking water to consumers. PMID:27208119

  8. Phosphorus Fluxes in the Beartooth Mountains: a Record of Detailed P Geochemistry from Island Lake

    NASA Astrophysics Data System (ADS)

    McLennan, D. A.; Latimer, J. C.; Williams, T. M.; Brown, S. R.; Stone, J.; McCune, A.

    2014-12-01

    Island Lake, situated within the Precambrian rocks of the Beartooth Mountains that run along the border of Wyoming and Montana, is a glacial lake located at the tree line with an elevation of 3048 m, a maximum water depth of 33 m, a catchment area of 11.7 km2, and a lake area of 0.61 km2. Like many alpine lakes, Island Lake is highly transparent with a deep chlorophyll maximum. Alpine settings may be more susceptible to small perturbations in climate and thus good sensors for investigating climate change. It is hypothesized that this low-nutrient alpine lake has shifted from a nitrogen-limiting system to one that is limited by phosphorus (P) availability. In summer 2013, a 1.54-m sediment core was collected for diatom and geochemical analyses, including P and metals. Detailed P geochemistry can be used to elucidate landscape evolution and P burial fluxes can provide insight into biogeochemical cycling over time. Changes in landscape due to fire, zonal shifts in vegetation, and shifts in climatological factors such as precipitation can impact the bioavailability of P entering the lake as well as burial fluxes. The sediment record will clarify the role of P in lake biogeochemical cycling at Island Lake through the Holocene. Planktonic diatom abundances have been used to reconstruct a history of Holocene lake stratification, and ongoing detailed P geochemistry using a sequential extraction technique (SEDEX) will be used to identify the role of P fluxes on productivity within the lake. SEDEX can differentiate between P associated with oxides/oxyhydroxides, mineral fractions, and organic matter, and the relative changes in these fractions provide insight into landscape dynamics. Coupled with diatom proxies, P geochemistry can also provide a better understanding of biogeochemical cycling within the lake. This multiproxy approach should provide insight into the responses within the catchment to environmental changes over the Holocene.

  9. Molecular dynamics simulations of lysozyme in water/sugar solutions

    NASA Astrophysics Data System (ADS)

    Lerbret, A.; Affouard, F.; Bordat, P.; Hédoux, A.; Guinet, Y.; Descamps, M.

    2008-04-01

    Structural and dynamical properties of the solvent at the protein/solvent interface have been investigated by molecular dynamics simulations of lysozyme in trehalose, maltose and sucrose solutions. Results are discussed in the framework of the bioprotection phenomena. The analysis of the relative concentration of water oxygen atoms around lysozyme suggests that lysozyme is preferentially hydrated. When comparing the three sugars, trehalose is seen more excluded than maltose and sucrose. The preferential exclusion of sugars from the protein surface induces some differences in the behavior of trehalose and maltose, particularly at 50 and 60 wt% concentrations, that are not observed experimentally in binary sugar/mixtures. The dynamical slowing down of the solvent is suggested to mainly arise from the homogeneity of the water/sugar matrices controlled by the percolation of the sugar hydrogen bonds networks. Furthermore, lysozyme strongly increases relaxation times of solvent molecules at the protein/solvent interface.

  10. Static and dynamic properties of supercooled water in small nanotubes.

    PubMed

    Khademi, Mahdi; Sahimi, Muhammad

    2016-07-14

    The static and dynamic properties of water in small silicon-carbide and carbon nanotubes have been studied over the temperature range 100 K-298 K, using extensive molecular dynamics simulations. The computed properties include the radial distribution function, the cage correlation function, the space-time autocorrelation function, the velocity autocorrelation function, and the self-diffusivity. They all indicate that, under the conditions that we study, water does not freeze in small nanotubes; the Stokes-Einstein relation breaks down, and the self-diffusivity exhibits a transition around 230 K, very close to 228 K, the temperature at which a fragile-to-strong dynamic crossover is supposed to happen. The cage correlation function C(t) decays according to a stretched-exponential function, C(t) ∼ exp[ - (t/τ)(β)], where τ is a relaxation time and β is a topological exponent. PMID:27421415

  11. Static and dynamic properties of supercooled water in small nanotubes

    NASA Astrophysics Data System (ADS)

    Khademi, Mahdi; Sahimi, Muhammad

    2016-07-01

    The static and dynamic properties of water in small silicon-carbide and carbon nanotubes have been studied over the temperature range 100 K-298 K, using extensive molecular dynamics simulations. The computed properties include the radial distribution function, the cage correlation function, the space-time autocorrelation function, the velocity autocorrelation function, and the self-diffusivity. They all indicate that, under the conditions that we study, water does not freeze in small nanotubes; the Stokes-Einstein relation breaks down, and the self-diffusivity exhibits a transition around 230 K, very close to 228 K, the temperature at which a fragile-to-strong dynamic crossover is supposed to happen. The cage correlation function C(t) decays according to a stretched-exponential function, C(t) ˜ exp[ - (t/τ)β], where τ is a relaxation time and β is a topological exponent.

  12. Methods of analysis by the U.S. Geological Survey Organic Geochemistry Research Group : determination of selected herbicides and their degradation products in water using solid-phase extraction and gas chromatography/mass spectrometry

    USGS Publications Warehouse

    Kish, J.L.; Thurman, E.M.; Scribner, E.A.; Zimmerman, L.R.

    2000-01-01

    A method for the extraction and analysis of eight herbicides and five degradation products using solid-phase extraction from natural water samples followed by gas chromatography/mass spectrometry is presented in this report. This method was developed for dimethenamid; flufenacet; fluometuron and its degradation products, demethylfluometuron (DMFM), 3-(trifluromethyl)phenylurea (TFMPU), 3-(trifluromethyl)-aniline (TFMA); molinate; norflurazon and its degradation product, demethylnorflurazon; pendamethalin; the degradation product of prometryn, deisopropylprometryn; propanil; and trifluralin. The eight herbicides are used primarily in the southern United States where cotton, rice, and soybeans are produced. The exceptions are dimethenamid and flufenacet, which are used on corn in the Midwest. Water samples received by the U.S. Geological Survey's Organic Geochemistry Research Group in Lawrence, Kansas, are filtered to remove suspended particulate matter and then passed through disposable solid-phase extraction columns containing octadecyl-bonded porous silica (C-18) to extract the compounds. The herbicides and their degradation products are removed from the column by ethyl acetate elution. The eluate is evaporated under nitrogen, and components then are separated, identified, and quantified by injecting an aliquot of the concentrated extract into a high-resolution, fused-silica capillary column of a gas chromatograph/mass spectrometer under selected-ion mode. Method detection limits ranged from 0.02 to 0.05 ?g/L for all compounds with the exception of TFMPU, which has a method detection limit of 0.32 ?g/L. The mean absolute recovery is 107 percent. This method for the determination of herbicides and their degradation products is valuable for acquiring information about water quality and compound fate and transport in water.

  13. Water Table Dynamics of a Rocky Mountain Riparian Area

    NASA Astrophysics Data System (ADS)

    Westbrook, C. J.

    2009-05-01

    Riparian areas in mountain valleys serve as collection points for local precipitation, hillslope runoff, deeper groundwater, and channel water. Little is known about how complex hydrological interactions among these water sources govern riparian water table dynamics, particularly on an event basis partly owing to a lack of high frequency spatial and temporal data. Herein I describe the magnitude and rate of change of groundwater storage in a 1.3 km2 Canadian Rocky Mountain peat riparian area. Weekly manual measurement of hydraulic heads in a network of 51 water table wells during the summers of 2006 and 2007 showed large temporal and spatial variations in well response. A near constant increase in the spatial heterogeneity of the water table was observed as the riparian area dried. Cluster analysis and principle components analysis were performed on these weekly data to objectively classify the riparian area into spatial response units. Results were classification of the standpipes into five distinct water table regimes. One well representing each water table regime was outfitted with a sensor in 2008 that measured hourly head, which was used to characterize temporal dynamics of water table response. In spring, snowmelt runoff combined with an ice lens 20-30 cm below the ground surface led to consistently high water tables throughout the riparian area. In summer, the water table fell throughout the riparian in response to declining hillslope inputs and increased evaporative demand, but rates of decline were highly variable among the water table regimes. Chloride concentrations suggest variability reflects differences in the degree to which the water table regimes are influenced by stream stage, hillslope inputs, and proximity to beaver dams. Water table regime responses to rain events were flashy, with dramatic rises and falls (up to 20 cm) in short periods of time (<30 h), suggesting the unsaturated soil was near saturation. The stream was considerably more

  14. Dynamics of Confined Water Molecules in Aqueous Salt Hydrates

    SciTech Connect

    Werhahn, Jasper C.; Pandelov, S.; Yoo, Soohaeng; Xantheas, Sotiris S.; Iglev, H.

    2011-04-01

    The unusual properties of water are largely dictated by the dynamics of the H bond network. A single water molecule has more H bonding sites than atoms, hence new experimental and theoretical investigations about this peculiar liquid have not ceased to appear. Confinement of water to nanodroplets or small molecular clusters drastically changes many of the liquid’s properties. Such confined water plays a major role in the solvation of macro molecules such as proteins and can even be essential to their properties. Despite the vast results available on bulk and confined water, discussions about the correlation between spectral and structural properties continue to this day. The fast relaxation of the OH stretching vibration in bulk water, and the variance of sample geometries in the experiments on confined water obfuscate definite interpretation of the spectroscopic results in terms of structural parameters. We present first time-resolved investigations on a new model system that is ideally suited to overcome many of the problems faced in spectroscopical investigation of the H bond network of water. Aqueous hydrates of inorganic salts provide water molecules in a crystal grid, that enables unambiguous correlations of spectroscopic and structural features. Furthermore, the confined water clusters are well isolated from each other in the crystal matrix, so different degrees of confinement can be achieved by selection of the appropriate salt.

  15. Understanding the dynamics of water availability and use in China

    SciTech Connect

    Thomas, R.P.; Conrad, S.H.; Jeppesen, D.M.; Engi, E.

    1997-07-01

    This report presents the preliminary results of an analysis of China`s water resources, part of an effort undertaken by the National Intelligence Council Medea scientists to improve the understanding of future food production and consumption in the People`s Republic of China. A dynamic water model was developed to simulate the hydrological budgetary processes in five river drainage basins located in northeastern, central, and southern China: the Chang Jiang (Yangtse River), Huanghe (Yellow River), Haihe, Huaihe, and Liaohe. The model was designed to assess the effects of changes in urban, industrial, and agricultural water use requirements on the availability of water in each basin and to develop estimates of the water surpluses and/or deficits in China through the year 2025. The model imposes a sustainable yield constraint, that is, groundwater extraction is not allowed to exceed the sustainable yield; if the available water does not meet the total water use requirements, a deficit results. An agronomic model was also developed to generate projections of the water required to service China`s agricultural sector and compare China`s projected grain production with projected grain consumption requirements to estimate any grain surplus and/or deficit. In future refinements, the agronomic model will interface directly with the water model to provide for the exchange of information on projected water use requirements and available water. The preliminary results indicate that the Chang Jiang basin will have a substantial surplus of water through 2025 and that the Haihe basin is in an ongoing situation. The agricultural water use requirements based on grain production indicate that an agricultural water deficit in the Haihe basin begins before the onset of the modeling period (1980) and steadily worsens through 2025. This assumption is confirmed by reports that groundwater mining is already under way in the most intensely cultivated and populated areas of northern China.

  16. Ionization dynamics of small water clusters: Proton transfer rate

    NASA Astrophysics Data System (ADS)

    Tachikawa, Hiroto; Takada, Tomoya

    2016-08-01

    The surfaces of icy planets and comets are composed of frozen water (H2O), carbon dioxide (CO2), and methane (CH4). These surfaces are irradiated by solar wind and cosmic rays from the interstellar space and they cause ionization of surface molecules. In this report, the effects of ionization of cold water clusters have been investigated using a direct ab initio molecular dynamics (AIMD) method to elucidate the rate of proton transfer (PT) in cations of small water clusters (H2O)n (n = 2-7). After ionization of the water clusters, PT occurred in all the cluster cations, and dissociation of the OH radical occurred for n = 4-7. The time of PT decreased with increasing the cluster size at n = 2-5 and reached a limiting value at n = 6 and 7. The mechanism of the PT process in ionized water clusters was discussed based on the theoretical results.

  17. Understanding water: Molecular dynamics simulations of solubilized and crystallized myoglobin

    SciTech Connect

    Wei Gu; Garcia, A.E.; Schoenborn, B.P.

    1994-12-31

    Molecular dynamics simulations were performed on CO myoglobin to evaluate the stability of the bound water molecules as determined in a neutron diffraction analysis. The myoglobin structure derived from the neutron analysis provided the starting coordinate set used in the simulations. The simulations show that only a few water molecules are tightly bound to protein atoms, while most solvent molecules are labile, breaking and reforming hydrogen bonds. Comparison between myoglobin in solution and in a single crystal highlighted some of the packing effects on the solvent structure and shows that water solvent plays an indispensable role in protein dynamics and structural stability. The described observations explain some of the differences in the experimental results of protein hydration as observed in NMR, neutron and X-ray diffraction studies.

  18. The Evolving Properties of Water in a Dynamic Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Ciesla, Fred

    2015-08-01

    Protoplanetary disks are dynamic objects, through which mass and angular momentum are transported as part of the final stages of pre-main sequence evolution of their central stars. These disks are also rich chemical factories, in which materials inherited from the interstellar medium are transformed through a series of reactions (involving, gases, solids, ions, and photons) to the eventual building blocks of the planets.The chemical and physical evolution of a protoplanetary disk are intimately connected. Both solids and gases are subjected to large-scale motions associated with disk evolution and diffusion within the gas. Solids also settle toward the disk midplane and migrate inwards due to gravity and gas drag. This dynamical evolution exposes primitive materials to a range of physical conditions (pressure, temperature, radiation environment) within the disk. It is the integrated effects of these environments that define the physical and chemical properties of a solid grain prior to its incorporation into a planetesimal or planet.Water serves as an interesting tracer of this evolution, as it would be processed in a variety of ways within a protoplanetary disk. I will discuss new methods that allow us to trace the dynamical movement of water vapor and ice throughout the lifetime of a protoplanetary disk and to determine the physical environments to which the water would be exposed. In particular, I will show how the early evolution of a protoplanetary disk impacts the D/H ratio of the water inherited by planetary materials. I will also explore how photodesorption of water by UV photons can lead to the formation of amorphous ice and thus the trapping of noble gases and other volatiles at levels that are much greater than predicted by equilibrium chemistry models. These effects combine to lead to constantly evolving properties of water during the early stages of planet formation. I will also discuss how the observed properties of Solar System bodies constrain these

  19. Does consideration of water routing affect simulated water and carbon dynamics in terrestrial ecosystems?

    NASA Astrophysics Data System (ADS)

    Tang, G.; Schneiderman, E. M.; Band, L. E.; Hwang, T.; Pierson, D. C.; Pradhanang, S. M.; Zion, M. S.

    2013-10-01

    The cycling of carbon in terrestrial ecosystems is closely coupled with the cycling of water. An important mechanism connecting ecological and hydrological processes in terrestrial ecosystems is lateral flow of water along landscapes. Few studies, however, have examined explicitly how consideration of water routing affects simulated water and carbon dynamics in terrestrial ecosystems. The objective of this study is to explore how consideration of water routing in a process-based hydroecological model affects simulated water and carbon dynamics. To achieve that end, we rasterized the regional hydroecological simulation systems (RHESSys) and employed the rasterized RHESSys (R-RHESSys) in a forested watershed. We performed and compared two contrasting simulations, one with and another without water routing. We found that R-RHESSys is able to correctly simulate major hydrological and ecological variables regardless of whether water routing is considered. When water routing was neglected, however, soil water table depth and saturation deficit were simulated to be smaller and spatially more homogeneous. As a result, evaporation, forest productivity and soil heterotrophic respiration also were simulated to be spatially more homogeneous compared to simulation with water routing. When averaged for the entire watershed, however, differences in simulated water and carbon fluxes are not significant between the two simulations. Overall, the study demonstrated that consideration of water routing enabled R-RHESSys to better capture our preconception of the spatial patterns of water table depth and saturation deficit across the watershed. Because the spatial pattern of soil moisture is fundamental to water efflux from land to the atmosphere, forest productivity and soil microbial activity, ecosystem and carbon cycle models, therefore, need to explicitly represent water routing in order to accurately quantify the magnitudes and patterns of water and carbon fluxes in terrestrial

  20. Coarse grained molecular dynamics simulation of nanoconfined water.

    PubMed

    Eslami, Hossein; Jaafari, Bahram; Mehdipour, Nargess

    2013-04-01

    A coarse-grained (CG) model for the simulation of nanoconfined water between graphene surfaces is developed. For this purpose, mixed-grained simulations are done, in which the two-site water model of Riniker and van Gunsteren [S. Riniker, W. F. van Gunsteren, J. Chem. Phys. 2011, 134, 084110] is simulated between atomistically resolved graphene surfaces. In the developed pure CG model, the two interaction sites of water and a combination of eight carbon atoms in the graphene surface are grouped together to construct water and surface CG beads. The pure CG potentials are constructed by iteratively matching the radial distribution functions and the density profiles of water beads in the pore with the corresponding mixed-grained distributions. The constructed potentials are shown to be pore-size transferable, capable of predicting structural properties of confined water over the whole range of pore sizes, ranging from extremely narrow pores to bulk water. The model is used to simulate a number of nanoconfined systems of a variety of pore sizes at constant temperature, constant parallel component of pressure, and constant surface area of the confining surfaces. The model is shown to predict the layering of water in contact with the surfaces, and the solvation force is in complete agreement with the mixed-grained model. It is shown that water molecules in the pore have smaller parallel diffusion coefficients compared to bulk water. Well-organized layers beside the surfaces are shown to have lower diffusion coefficients than diffuse layers. More information on the dynamics of water in the pore is obtained by calculating the rate of water exchange between slabs parallel to the surfaces. The time scale to achieve equilibrium for this process, depending on the pore width and on the degree of layering of water beside the surfaces, is a few nanoseconds in nanometric pores.

  1. Understanding Dynamic Soil Water Repellency and its Hydrological Implications

    NASA Astrophysics Data System (ADS)

    Beatty, S. M.; Smith, J. E.

    2009-05-01

    The adverse effects of water repellent soils on vadose zone hydrology are being increasingly identified worldwide in both rural and urban landscapes. Among the affected landscapes are agricultural fields, forests, effluent application sites, golf greens, wetlands, and wildfire sites. In spite of cross-discipline research efforts put forth in recent years, understanding of fundamental parameters controlling soil water behaviour in these systems is lacking. This is due, in part, to inherent complexities of water repellent soil systems and logistical shortcomings of methods commonly used by researchers in-situ and in the lab. As a result, modeling flow in these systems has further proven to be a difficult task. The objectives of our study were 1) to systematically measure and quantify water infiltration and distribution in dynamic water repellent systems and 2) to identify fundamental hydraulic behaviours that lead to the expression of changes in soil water repellency. To achieve this, we combined techniques to elucidate soil- water interactions at a post-wildfire site. Field tests and subsequent lab work reveal essential hydrological information on fire-affected water repellent soils at variable scales and under different burn conditions. Through the use of traditional and newer techniques, our work shows unique and previously unreported behaviour of soil water in these systems. We also address limitations of current field methods used to study repellency and associated infiltration behaviours.

  2. Temporal Geochemistry Data from Five Springs in the Cement Creek Watershed, San Juan County, Colorado

    USGS Publications Warehouse

    Johnson, Raymond H.; Wirt, Laurie; Leib, Kenneth J.

    2008-01-01

    Temporal data from five springs in the Cement Creek watershed, San Juan County, Colorado provide seasonal geochemical data for further research in the formation of ferricretes. In addition, these data can be used to help understand the ground-water flow system. The resulting data demonstrate the difficulty in gathering reliable seasonal data from springs, show the unique geochemistry of each spring due to local geology, and provide seasonal trends in geochemistry for Tiger Iron Spring.

  3. Nanosecond Relaxation Dynamics of Hydrated Proteins: Water versus protein contributions

    SciTech Connect

    Khodadadi, S; Curtis, J. E.; Sokolov, Alexei P

    2011-01-01

    We have studied picosecond to nanosecond dynamics of hydrated protein powders using dielectric spectroscopy and molecular dynamics (MD) simulations. Our analysis of hydrogen-atom single particle dynamics from MD simulations focused on main ( main tens of picoseconds) and slow ( slow nanosecond) relaxation processes that were observed in dielectric spectra of similar hydrated protein samples. Traditionally, the interpretation of these processes observed in dielectric spectra has been ascribed to the relaxation behavior of hydration water tightly bounded to a protein and not to protein atoms. Detailed analysis of the MD simulations and comparison to dielectric data indicate that the observed relaxation process in the nanosecond time range of hydrated protein spectra is mainly due to protein atoms. The relaxation processes involve the entire structure of protein including atoms in the protein backbone, side chains, and turns. Both surface and buried protein atoms contribute to the slow processes; however, surface atoms demonstrate slightly faster relaxation dynamics. Analysis of the water molecule residence and dipolar relaxation correlation behavior indicates that the hydration water relaxes at much shorter time scales.

  4. On the slowdown mechanism of water dynamics around small amphiphiles.

    PubMed

    Homsi Brandeburgo, Wagner; van der Post, Sietse Thijmen; Meijer, Evert Jan; Ensing, Bernd

    2015-10-14

    Aqueous solvation of small amphiphilic molecules exhibits a unique and complex dynamics, that is only partially understood. A recent series of studies on the hydration of small organic compounds, such as tetramethylurea (TMU), trimethylamine N-oxide (TMAO) and urea, has provided strong evidence of a slowdown of the dynamics of the hydrating water molecules. However, the mechanism of this slowdown is still a matter of debate. We analyze the slowdown mechanism by combining molecular dynamics (MD) simulations, using ab initio and classical force field methods, with mid-infrared pump-probe spectroscopy. Aqueous solutions of TMU and of urea were studied at a 0.1 solute/solvent ratio, where we decompose the contribution of different solvating groups to the orientational dynamics. Our results reveal that two competing processes govern the H-bond breaking mechanism: H-bond switching through an associative partner exchange and a dissociative breaking characterized by an unbound state. H-bond switches are shown to occur less often near hydrophobic groups, thus creating a subset of OH groups that do not switch and therefore do not significantly reorient within the lifetime of one H-bond, but will require at least a second H-bond to be formed and broken before it may switch. Our results shed new light on the role of hydrophobic solvation in the water orientational dynamics and help to conciliate the controversy regarding the timescale separation, providing a mechanistic explanation for the observed slow component. PMID:26344919

  5. Water dynamics in divalent and monovalent concentrated salt solutions.

    PubMed

    Giammanco, Chiara H; Wong, Daryl B; Fayer, Michael D

    2012-11-26

    Water hydrogen bond dynamics in concentrated salt solutions are studied using polarization-selective IR pump-probe spectroscopy and 2D IR vibrational echo spectroscopy performed on the OD hydroxyl stretching mode of dilute HOD in H(2)O/salt solutions. The OD stretch is studied to eliminate vibrational excitation transfer, which interferes with the dynamical measurements. Though previous research suggested that only the anion affected dynamics in solution, here it is shown that the cation plays a role as well. From FT-IR spectra of the OD stretch, it is seen that replacing either ion of the salt pair causes a shift in absorption frequency relative to that of the OD stretch absorption in bulk pure water. This shift becomes pronounced with larger, more polarizable anions or smaller, high charge-density cations. The vibrational lifetime of the OD hydroxyl stretch in these solutions is a local property and is primarily dependent on the nature of the anion and whether the OD is hydrogen bonded to the anion or to the oxygen of another water molecule. However, the cation still has a small effect. Time dependent anisotropy measurements show that reorientation dynamics in these concentrated solutions is a highly concerted process. While the lifetime, a local probe, displays an ion-associated and a bulk-like component in concentrated solutions, the orientational relaxation does not have two subensemble dynamics, as demonstrated by the lack of a wavelength dependence. The orientational relaxation of the single ensemble is dependent on the identity of both the cation and anion. The 2D IR vibrational echo experiments measure spectral diffusion that is caused by structural evolution of the system. The vibrational echo measurements yield the frequency-frequency correlation function (FFCF). The results also show that the structural dynamics are dependent on the cation as well as the anion. PMID:23113682

  6. Effects of Dimerization of Serratia marcescens Endonuclease on Water Dynamics.

    SciTech Connect

    Chen, Chuanying; Beck, Brian W.; Krause, Kurt; Weksberg, Tiffany E.; Pettitt, Bernard M.

    2007-02-15

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The dynamics and structure of Serratia marcescens endonuclease and its neighboring solvent are investigated by molecular dynamics (MD). Comparisons are made with structural and biochemical experiments. The dimer form is physiologic and functions more processively than the monomer. We previously found a channel formed by connected clusters of waters from the active site to the dimer interface. Here, we show that dimerization clearly changes correlations in the water structure and dynamics in the active site not seen in the monomer. Our results indicate that water at the active sites of the dimer is less affected compared with bulk solvent than in the monomer where it has much slower characteristic relaxation times. Given that water is a required participant in the reaction, this gives a clear advantage to dimerization in the absence of an apparent ability to use both active sites simultaneously.

  7. Dynamic regulation of aquaporin-4 water channels in neurological disorders

    PubMed Central

    Hsu, Ying; Tran, Minh; Linninger, Andreas A.

    2015-01-01

    Aquaporin-4 water channels play a central role in brain water regulation in neurological disorders. Aquaporin-4 is abundantly expressed at the astroglial endfeet facing the cerebral vasculature and the pial membrane, and both its expression level and subcellular localization significantly influence brain water transport. However, measurements of aquaporin-4 levels in animal models of brain injury often report opposite trends of change at the injury core and the penumbra. Furthermore, aquaporin-4 channels play a beneficial role in brain water clearance in vasogenic edema, but a detrimental role in cytotoxic edema and exacerbate cell swelling. In light of current evidence, we still do not have a complete understanding of the role of aquaporin-4 in brain water transport. In this review, we propose that the regulatory mechanisms of aquaporin-4 at the transcriptional, translational, and post-translational levels jointly regulate water permeability in the short and long time scale after injury. Furthermore, in order to understand why aquaporin-4 channels play opposing roles in cytotoxic and vasogenic edema, we discuss experimental evidence on the dynamically changing osmotic gradients between blood, extracellular space, and the cytosol during the formation of cytotoxic and vasogenic edema. We conclude with an emerging picture of the distinct osmotic environments in cytotoxic and vasogenic edema, and propose that the directions of aquaporin-4-mediated water clearance in these two types of edema are distinct. The difference in water clearance pathways may provide an explanation for the conflicting observations of the roles of aquaporin-4 in edema resolution. PMID:26526878

  8. Dynamic factor analysis for estimating ground water arsenic trends.

    PubMed

    Kuo, Yi-Ming; Chang, Fi-John

    2010-01-01

    Drinking ground water containing high arsenic (As) concentrations has been associated with blackfoot disease and the occurrence of cancer along the southwestern coast of Taiwan. As a result, 28 ground water observation wells were installed to monitor the ground water quality in this area. Dynamic factor analysis (DFA) is used to identify common trends that represent unexplained variability in ground water As concentrations of decommissioned wells and to investigate whether explanatory variables (total organic carbon [TOC], As, alkalinity, ground water elevation, and rainfall) affect the temporal variation in ground water As concentration. The results of the DFA show that rainfall dilutes As concentration in areas under aquacultural and agricultural use. Different combinations of geochemical variables (As, alkalinity, and TOC) of nearby monitoring wells affected the As concentrations of the most decommissioned wells. Model performance was acceptable for 11 wells (coefficient of efficiency >0.50), which represents 52% (11/21) of the decommissioned wells. Based on DFA results, we infer that surface water recharge may be effective for diluting the As concentration, especially in the areas that are relatively far from the coastline. We demonstrate that DFA can effectively identify the important factors and common effects representing unexplained variability common to decommissioned wells on As variation in ground water and extrapolate information from existing monitoring wells to the nearby decommissioned wells.

  9. Dynamic regulation of aquaporin-4 water channels in neurological disorders.

    PubMed

    Hsu, Ying; Tran, Minh; Linninger, Andreas A

    2015-10-01

    Aquaporin-4 water channels play a central role in brain water regulation in neurological disorders. Aquaporin-4 is abundantly expressed at the astroglial endfeet facing the cerebral vasculature and the pial membrane, and both its expression level and subcellular localization significantly influence brain water transport. However, measurements of aquaporin-4 levels in animal models of brain injury often report opposite trends of change at the injury core and the penumbra. Furthermore, aquaporin-4 channels play a beneficial role in brain water clearance in vasogenic edema, but a detrimental role in cytotoxic edema and exacerbate cell swelling. In light of current evidence, we still do not have a complete understanding of the role of aquaporin-4 in brain water transport. In this review, we propose that the regulatory mechanisms of aquaporin-4 at the transcriptional, translational, and post-translational levels jointly regulate water permeability in the short and long time scale after injury. Furthermore, in order to understand why aquaporin-4 channels play opposing roles in cytotoxic and vasogenic edema, we discuss experimental evidence on the dynamically changing osmotic gradients between blood, extracellular space, and the cytosol during the formation of cytotoxic and vasogenic edema. We conclude with an emerging picture of the distinct osmotic environments in cytotoxic and vasogenic edema, and propose that the directions of aquaporin-4-mediated water clearance in these two types of edema are distinct. The difference in water clearance pathways may provide an explanation for the conflicting observations of the roles of aquaporin-4 in edema resolution. PMID:26526878

  10. Time-dependent water dynamics in hydrated uranyl fluoride

    SciTech Connect

    Miskowiec, Andrew J.; Anderson, Brian B.; Herwig, Kenneth W.; Huq, Ashfia; Mamontov, Eugene; Rondinone, Adam; Trowbridge, Lee D.

    2015-09-15

    In this study, uranyl fluoride is a three-layer, hexagonal structure with significant stacking disorder in the c-direction. It supports a range of unsolved ‘thermodynamic’ hydrates with 0–2.5 water molecules per uranium atom, and perhaps more. However, the relationship between water, hydrate crystal structures, and thermodynamic results, collectively representing the chemical pathway through these hydrate structures, has not been sufficiently elucidated. We used high-resolution quasielastic neutron scattering to study the dynamics of water in partially hydrated uranyl fluoride powder over the course of 4 weeks under closed conditions. The spectra are composed of two quasielastic components: one is associated with translational diffusive motion of water that is approximately five to six times slower than bulk water, and the other is a slow (on the order of 2–300 ps), spatially bounded water motion. The translational component represents water diffusing between the weakly bonded layers in the crystal, while the bounded component may represent water trapped in subnanometre ‘pockets’ formed by the space between uranium-centred polymerisation units. Complementary neutron diffraction measurements do not show any significant structural changes, suggesting that a chemical conversion of the material does not occur in the thermodynamically isolated system on this timescale.

  11. Time-dependent water dynamics in hydrated uranyl fluoride

    DOE PAGES

    Miskowiec, Andrew J.; Anderson, Brian B.; Herwig, Kenneth W.; Huq, Ashfia; Mamontov, Eugene; Rondinone, Adam; Trowbridge, Lee D.

    2015-09-15

    In this study, uranyl fluoride is a three-layer, hexagonal structure with significant stacking disorder in the c-direction. It supports a range of unsolved ‘thermodynamic’ hydrates with 0–2.5 water molecules per uranium atom, and perhaps more. However, the relationship between water, hydrate crystal structures, and thermodynamic results, collectively representing the chemical pathway through these hydrate structures, has not been sufficiently elucidated. We used high-resolution quasielastic neutron scattering to study the dynamics of water in partially hydrated uranyl fluoride powder over the course of 4 weeks under closed conditions. The spectra are composed of two quasielastic components: one is associated with translationalmore » diffusive motion of water that is approximately five to six times slower than bulk water, and the other is a slow (on the order of 2–300 ps), spatially bounded water motion. The translational component represents water diffusing between the weakly bonded layers in the crystal, while the bounded component may represent water trapped in subnanometre ‘pockets’ formed by the space between uranium-centred polymerisation units. Complementary neutron diffraction measurements do not show any significant structural changes, suggesting that a chemical conversion of the material does not occur in the thermodynamically isolated system on this timescale.« less

  12. Molecular Dynamics Simulations of Carbon Nanotubes in Water

    NASA Technical Reports Server (NTRS)

    Walther, J. H.; Jaffe, R.; Halicioglu, T.; Koumoutsakos, P.

    2000-01-01

    We study the hydrophobic/hydrophilic behavior of carbon nanotubes using molecular dynamics simulations. The energetics of the carbon-water interface are mainly dispersive but in the present study augmented with a carbon quadrupole term acting on the charge sites of the water. The simulations indicate that this contribution is negligible in terms of modifying the structural properties of water at the interface. Simulations of two carbon nanotubes in water display a wetting and drying of the interface between the nanotubes depending on their initial spacing. Thus, initial tube spacings of 7 and 8 A resulted in a drying of the interface whereas spacing of > 9 A remain wet during the course of the simulation. Finally, we present a novel particle-particle-particle-mesh algorithm for long range potentials which allows for general (curvilinear) meshes and "black-box" fast solvers by adopting an influence matrix technique.

  13. Propagation Dynamics of Airy Water-Wave Pulses.

    PubMed

    Fu, Shenhe; Tsur, Yuval; Zhou, Jianying; Shemer, Lev; Arie, Ady

    2015-07-17

    We observe the propagation dynamics of surface gravity water waves, having an Airy function envelope, in both the linear and the nonlinear regimes. In the linear regime, the shape of the envelope is preserved while propagating in an 18-m water tank, despite the inherent dispersion of the wave packet. The Airy wave function can propagate at a velocity that is slower (or faster if the Airy envelope is inverted) than the group velocity. Furthermore, the introduction of the Airy wave packet as surface water waves enables the observation of its position-dependent chirp and cubic-phase offset, predicted more than 35 years ago, for the first time. When increasing the envelope of the input Airy pulse, nonlinear effects become dominant, and are manifested by the generation of water-wave solitons. PMID:26230797

  14. Dynamics in urban water quality: monitoring the Amsterdam city area

    NASA Astrophysics Data System (ADS)

    van der Vlugt, Corné; Yu, Liang; Rozemeijer, Joachim; van Breukelen, Boris; Ouboter, Maarten; Stuurman, Roelof; Broers, Hans Peter

    2014-05-01

    Urban water quality is influenced by a large number of heterogeneous sources. We aimed to identify solute pathways from different sources in the urban area of Amsterdam, The Netherlands. The city is situated in the Dutch delta, and largely below mean sea level. The water system of the centre of the city is connected to the large fresh water lake Ijsselmeer, but suburbs are mainly located within reclaimed lake and polder areas where water is pumped out in order to maintain the water levels, which are generally 1 tot 4 m. below sea level. Sources of water include: urban storm runoff, inlet water from the Ijsselmeer and surrounding areas, groundwater seepage and possibly also leaking sewage systems. The temporal dynamics and spatial patterns related to these flow routes and sources were largely unknown to date. Water quality is measured at those pumping stations systematically each month. We analysed the pumping discharge data and the concentration data to calculate daily water balances and annual load estimates for HCO3,Ca, Cl, Na, SO4, Ptot, Ntot ,NH4, NH3 and NO3. Chloride appears to be a good tracer to identify inlet water and bicarbonate and DIC were effective to estimate the groundwater contribution to the surface water outflow to the regional system. We were able to improve the solute balances by calibrating the measured temporal patterns of chloride and DIC using known concentrations from the individual sources. Subsequently the water balances where used to identify periods where one of the sources was dominant and by doing so we improved our understanding of the dynamics of N, P and S fluxes and the relations with dry and wet meteorological conditions. It appeared that N and P were largely related to groundwater outflow , whereas S was mainly related to dry periods and shallow flow routes influenced by sewage, urban storm runoff and shallow groundwater flow . The results are used to optimize urban water management which benefits from the improved insight in

  15. Molecular dynamics studies of supercooled water using a monatomic model

    NASA Astrophysics Data System (ADS)

    Moore, Emily Brooke

    There remain many unanswered questions regarding the structure and behavior of water, particularly when cooled below the melting temperature into water's supercooled region. In this region, liquid water is metastable, and rapid crystallization makes it difficult to study experimentally the liquid and the crystallization process. Computational studies are hindered by the complexity of accurately modeling water and the computational cost of simulating processes such as crystallization. In this work, the development and validation of mW, a monatomic water model, is presented. This model is able to quantitatively reproduce the structure, dynamic anomalies and phase behavior of water without hydrogen atoms or electrostatics by reproducing water's propensity to form locally tetrahedral structures. Using the mW water model in molecular dynamics simulations, we show the evolution of the local structure of water from 300--100 K. We find that the thermodynamic and structural properties studied, density, tetrahedrality and structural correlation length, change maximally or are maximum at 202 +/- 2 K, the liquid-liquid transformation temperature. Shifting to water confined within cylindrical nanopores, we present the development of a rotationally invariant method, the CHILL algorithm, to distinguish between liquid, hexagonal and cubic ice. We analyze the process of homogeneous nucleation, growth and melting within hydrophilic pores, as well as the effect of water-pore interaction strength on the melting of ice and liquid-ice coexistence within pores. Crystallization within the nanopores results in cubic ice with hexagonal stacking faults in agreement with experiments. We also investigate crystallization of bulk liquid within water's experimentally inaccessible "no man's land." Crystallization occurs through rapid development of ice nuclei that grow and consolidate, precluding the measurement of diffusion within the liquid. Analysis of how ice structure develops shows that

  16. Water transfers, agriculture, and groundwater management: a dynamic economic analysis.

    PubMed

    Knapp, Keith C; Weinberg, Marca; Howitt, Richard; Posnikoff, Judith F

    2003-04-01

    Water transfers from agricultural to urban and environmental uses will likely become increasingly common worldwide. Many agricultural areas rely heavily on underlying groundwater aquifers. Out-of-basin surface water transfers will increase aquifer withdrawals while reducing recharge, thereby altering the evolution of the agricultural production/groundwater aquifer system over time. An empirical analysis is conducted for a representative region in California. Transfers via involuntary surface water cutbacks tilt the extraction schedule and lower water table levels and net benefits over time. The effects are large for the water table but more modest for the other variables. Break-even prices are calculated for voluntary quantity contract transfers at the district level. These prices differ considerably from what might be calculated under a static analysis which ignores water table dynamics. Canal-lining implies that districts may gain in the short-run but lose over time if all the reduction in conveyance losses is transferred outside the district. Water markets imply an evolving quantity of exported flows over time and a reduction in basin net benefits under common property usage. Most aquifers underlying major agricultural regions are currently unregulated. Out-of-basin surface water transfers increase stress on the aquifer and management benefits can increase substantially in percentage terms but overall continue to remain small. Conversely, we find that economically efficient management can mitigate some of the adverse consequences of transfers, but not in many circumstances or by much. Management significantly reduced the water table impacts of cutbacks but not annual net benefit impacts. Neither the break-even prices nor the canal-lining impacts were altered by much. The most significant difference is that regional water users gain from water markets under efficient management.

  17. Entropy of Liquid Water from Ab Initio Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Spanu, Leonardo; Zhang, Cui; Galli, Giulia

    2012-02-01

    The debate on the structural properties of water has been mostly based on the calculation of pair correlation functions. However, the simulation of thermodynamic and spectroscopic quantities may be of great relevance for the characterization of liquid water properties. We have computed the entropy of liquid water using a two-phase thermodynamic model and trajectories generated by ab initio molecular dynamics simulations [1]. In an attempt to better understand the performance of several density functionals in simulating liquid water, we have performed ab initio molecular dynamics using semilocal, hybrid [2] and van der Waals density functionals [3]. We show that in all cases, at the experimental equilibrium density and at temperatures in the vicinity of 300 K, the computed entropies are underestimated, with respect to experiment, and the liquid exhibits a degree of tetrahedral order higher than in experiments. We also discuss computational strategies to simulate spectroscopic properties of water, including infrared and Raman spectra.[4pt] [1] C.Zhang, L.Spanu and G.Galli, J.Phys.Chem. B 2011 (in press)[0pt] [2] C.Zhang, D.Donadio, F.Gygi and G.Galli, J. Chem. Theory Comput. 7, 1443 (2011)[0pt] [3] C.Zhang, J.Wu, G.Galli and F.Gygi, J. Chem. Theory Comput. 7, 3061 (2011)

  18. Dynamic Ice-Water Interactions Form Europa's Chaos Terrains

    NASA Astrophysics Data System (ADS)

    Blankenship, D. D.; Schmidt, B. E.; Patterson, G. W.; Schenk, P.

    2011-12-01

    Unique to the surface of Europa, chaos terrain is diagnostic of the properties and dynamics of its icy shell. We present a new model that suggests large melt lenses form within the shell and that water-ice interactions above and within these lenses drive the production of chaos. This model is consistent with key observations of chaos, predicts observables for future missions, and indicates that the surface is likely still active today[1]. We apply lessons from ice-water interaction in the terrestrial cryosphere to hypothesize a dynamic lense-collapse model to for Europa's chaos terrain. Chaos terrain morphology, like that of Conamara chaos and Thera Macula, suggests a four-phase formation [1]: 1) Surface deflection occurs as ice melts over ascending thermal plumes, as regularly occurs on Earth as subglacial volcanoes activate. The same process can occur at Europa if thermal plumes cause pressure melt as they cross ice-impurity eutectics. 2) Resulting hydraulic gradients and driving forces produce a sealed, pressurized melt lense, akin to the hydraulic sealing of subglacial caldera lakes. On Europa, the water cannot escape the lense due to the horizontally continuous ice shell. 3) Extension of the brittle ice lid above the lense opens cracks, allowing for the ice to be hydrofractured by pressurized water. Fracture, brine injection and percolation within the ice and possible iceberg toppling produces ice-melange-like granular matrix material. 4) Refreezing of the melt lense and brine-filled pores and cracks within the matrix results in raised chaos. Brine soaking and injection concentrates the ice in brines and adds water volume to the shell. As this englacial water freezes, the now water-filled ice will expand, not unlike the process of forming pingos and other "expansion ice" phenomena on Earth. The refreezing can raise the surface and create the oft-observed matrix "domes" In this presentation, we describe how catastrophic ice-water interactions on Earth have

  19. World continental modeling for water resources using system dynamics

    NASA Astrophysics Data System (ADS)

    Kojiri, Toshiharu; Hori, Tomoharu; Nakatsuka, Junpei; Chong, Teng-Sheng

    This research assesses the severity of future water scarcity and its impact on the growth of human civilization through system dynamics modeling of the world at regional level. Six sectors of activities are modeled in each continent to represent the human society. Continental interactions such as migration and trade are also modeled to express the synergy of activities among the various continents. Results of the model simulations from 1960 to 2100 show that water scarcity, unlike other limitations such as nonrenewable resources and persistent pollution, gives severe, detrimental problems within short delays after its occurrence.

  20. Energy deposition dynamics of femtosecond pulses in water

    SciTech Connect

    Minardi, Stefano Pertsch, Thomas; Milián, Carles; Couairon, Arnaud; Majus, Donatas; Tamošauskas, Gintaras; Dubietis, Audrius; Gopal, Amrutha

    2014-12-01

    We exploit inverse Raman scattering and solvated electron absorption to perform a quantitative characterization of the energy loss and ionization dynamics in water with tightly focused near-infrared femtosecond pulses. A comparison between experimental data and numerical simulations suggests that the ionization energy of water is 8 eV, rather than the commonly used value of 6.5 eV. We also introduce an equation for the Raman gain valid for ultra-short pulses that validates our experimental procedure.

  1. Shock induced phase transition of water: Molecular dynamics investigation

    NASA Astrophysics Data System (ADS)

    Neogi, Anupam; Mitra, Nilanjan

    2016-02-01

    Molecular dynamics simulations were carried out using numerous force potentials to investigate the shock induced phenomenon of pure bulk liquid water. Partial phase transition was observed at single shock velocity of 4.0 km/s without requirement of any external nucleators. Change in thermodynamic variables along with radial distribution function plots and spectral analysis revealed for the first time in the literature, within the context of molecular dynamic simulations, the thermodynamic pathway leading to formation of ice VII from liquid water on shock loading. The study also revealed information for the first time in the literature about the statistical time-frame after passage of shock in which ice VII formation can be observed and variations in degree of crystallinity of the sample over the entire simulation time of 100 ns.

  2. Microscopic dynamics of nanoparticle monolayers at air-water interface.

    PubMed

    Bhattacharya, R; Basu, J K

    2013-04-15

    We present results of surface mechanical and particle tracking measurements of nanoparticles trapped at the air-water interface as a function of their areal density. We monitor both the surface pressure (Π) and isothermal compression modulus (ϵ) as well as the dynamics of nanoparticle clusters, using fluorescence confocal microscopy while they are compressed to very high density near the two dimensional close packing density Φ∼0.82. We observe non-monotonic variation in both ϵ and the dynamic heterogeneity, characterized by the dynamical susceptibility χ4 with Φ, in such high density monolayers. We provide insight into the underlying nature of such transitions in close packed high density nanoparticle monolayers in terms of the morphology and flexibility of these soft colloidal particles. We discuss the significance our results in the context of related studies on two dimensional granular or colloidal systems. PMID:23411354

  3. Protein-water dynamics in antifreeze protein III activity

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Bäumer, Alexander; Meister, Konrad; Bischak, Connor G.; DeVries, Arthur L.; Leitner, David M.; Havenith, Martina

    2016-03-01

    We combine Terahertz absorption spectroscopy (THz) and molecular dynamics (MD) simulations to investigate the underlying molecular mechanism for the antifreeze activity of one class of antifreeze protein, antifreeze protein type III (AFP-III) with a focus on the collective water hydrogen bond dynamics near the protein. After summarizing our previous work on AFPs, we present a new investigation of the effects of cosolutes on protein antifreeze activity by adding sodium citrate to the protein solution of AFP-III. Our results reveal that for AFP-III, unlike some other AFPs, the addition of the osmolyte sodium citrate does not affect the hydrogen bond dynamics at the protein surface significantly, as indicated by concentration dependent THz measurements. The present data, in combination with our previous THz measurements and molecular simulations, confirm that while long-range solvent perturbation is a necessary condition for the antifreeze activity of AFP-III, the local binding affinity determines the size of the hysteresis.

  4. Dynamics of Ice/Water Confined in Nanoporous Alumina.

    PubMed

    Suzuki, Yasuhito; Steinhart, Martin; Graf, Robert; Butt, Hans-Jürgen; Floudas, George

    2015-11-19

    Dielectric (DS), IR spectroscopy, and (1)H MAS NMR are employed in the study of ice/water confined in nanoporous alumina with pore diameters ranging from 400 nm down to 25 nm. Within nanoporous alumina there is a transformation from heterogeneous nucleation of hexagonal ice in the larger pores to homogeneous nucleation of cubic ice in the smaller pores. DS and IR show excellent agreement in the temperature interval and pore size dependence of the transformation. DS further revealed two dynamic processes under confinement. The "fast" and "slow" processes with an Arrhenius temperature dependence are attributed to ice and supercooled water relaxation, respectively. The main relaxation process of ice under confinement ("slow" process) has an activation energy of 44 ± 2 kJ/mol. The latter is in agreement with the reported relaxation times and activation energy of cubic ice prepared following a completely different route (by pressure). (1)H MAS NMR provided new insight in the state of ice structures as well as of supercooled water. Under confinement, a layer of liquid-like water coexists with ice structures. In addition, both ice structures under confinement appear to be more ordered than bulk hexagonal ice. Supercooled water in the smaller pores is different from bulk water. It shows a shift of the signal toward higher chemical shift values which may suggest stronger hydrogen bonding between the water molecules or increasing interactions with the AAO walls. PMID:26511073

  5. Dynamics of Ice/Water Confined in Nanoporous Alumina.

    PubMed

    Suzuki, Yasuhito; Steinhart, Martin; Graf, Robert; Butt, Hans-Jürgen; Floudas, George

    2015-11-19

    Dielectric (DS), IR spectroscopy, and (1)H MAS NMR are employed in the study of ice/water confined in nanoporous alumina with pore diameters ranging from 400 nm down to 25 nm. Within nanoporous alumina there is a transformation from heterogeneous nucleation of hexagonal ice in the larger pores to homogeneous nucleation of cubic ice in the smaller pores. DS and IR show excellent agreement in the temperature interval and pore size dependence of the transformation. DS further revealed two dynamic processes under confinement. The "fast" and "slow" processes with an Arrhenius temperature dependence are attributed to ice and supercooled water relaxation, respectively. The main relaxation process of ice under confinement ("slow" process) has an activation energy of 44 ± 2 kJ/mol. The latter is in agreement with the reported relaxation times and activation energy of cubic ice prepared following a completely different route (by pressure). (1)H MAS NMR provided new insight in the state of ice structures as well as of supercooled water. Under confinement, a layer of liquid-like water coexists with ice structures. In addition, both ice structures under confinement appear to be more ordered than bulk hexagonal ice. Supercooled water in the smaller pores is different from bulk water. It shows a shift of the signal toward higher chemical shift values which may suggest stronger hydrogen bonding between the water molecules or increasing interactions with the AAO walls.

  6. Dynamics and energetics of water permeation through the aquaporin channel.

    PubMed

    Vidossich, Pietro; Cascella, Michele; Carloni, Paolo

    2004-06-01

    Structural properties of water inside bovine aquaporin-1 are investigated by molecular simulation. The calculations, which are based on the recently determined X-ray structure at 2.2 A resolution (Sui et al., Nature 2001;414:872-878), are carried out on one monomeric subunit immersed in a water-n-octane-water bilayer. Molecular dynamics (MD) simulations suggest that His182, a fully conserved residue in the channel pore, is protonated in the delta position. Furthermore, they reveal a highly ordered water structure in the channel, induced by the electrostatic properties of the protein. Multiple-steering MD simulations are used to calculate the free-energy of water diffusion. To the best of our knowledge, this represents the first free-energy calculation based on the new, high-resolution structure of the pore. The calculated barrier is 2.5 kcal/mol, and it is associated to water permeation through the Asn-Pro-Ala (NPA) region of the pore, where water molecules are only hydrogen-bonded with themselves. These findings are fully consistent with those based on the previous MD studies on the human protein (de Groot and Grubmüller, Science 2001;294:2353-2357). PMID:15146490

  7. Utilizing Resistivity Soundings and Forensic Geochemistry to Better Understand the Groundwater Contributions and the Interaction with Surface Water in a Streambed in the Texas Gulf Coast Area

    NASA Astrophysics Data System (ADS)

    Bighash, P.

    2012-12-01

    Water quality and quantity in a reservoir can be significantly affected by interactions between surface waters and adjacent aquifers. Environments that exhibit transient hydraulic conditions, such as changes in recharge and groundwater flow rates, are not well understood. The associated impacts to coastal water resources during elevated drought conditions can be better managed with a better understanding of the groundwater-surface water interaction and the transition zone. Proper characterization of the spatial and temporal extent of groundwater discharge is important for water resource management and contaminant migration pathways. The Texas coastal area has been experiencing exceptional drought conditions over the past few years which are expected to persist or intensify in the coming years. An investigation of how the hydrologic system is impacted by these conditions can be a valuable tool regarding water resource management, sustainability and conservation of the Gulf Coast region of South Texas. This study will be using resistivity soundings to vertically and laterally characterize groundwater-surface water interaction and provide a stratigraphic characterization of the transition zone in this area. Chemical and isotope tracers will be used to compliment the resistivity data in order to trace water sources in the surface water and transition zone. This information can aid in evaluating the extent of interaction and degree of mixing between the surface water and groundwater. The ultimate goal of this research is to provide new valuable information that could help professionals and researchers understand complex processes such as groundwater-surface water interaction using new methods that would improve the speed and accuracy of existing systems or techniques. This multidisciplinary approach can be useful in investigating land use impacts on groundwater inflow and in forecasting the availability of water resources in environmentally sensitive ecosystems such as

  8. High-frequency longitudinal and transverse dynamics in water

    SciTech Connect

    Pontecorvo, E.; Ruocco, G.; Krisch, M.; Monaco, G.; Mermet, A.; Verbeni, R.; Sette, F.; Cunsolo, A.

    2005-01-01

    High-resolution, inelastic x-ray scattering measurements of the dynamic structure factor S(Q,{omega}) of liquid water have been performed for wave vectors Q between 4 and 30 nm{sup -1} in distinctly different thermodynamic conditions (T=263-420 K; at, or close to, ambient pressure and at P=2 kbar). In agreement with previous inelastic x-ray and neutron studies, the presence of two inelastic contributions (one dispersing with Q and the other almost nondispersive) is confirmed. The study of their temperature and Q dependence provides strong support for a dynamics of liquid water controlled by the structural relaxation process. A viscoelastic analysis of the Q-dispersing mode, associated with the longitudinal dynamics, reveals that the sound velocity undergoes a complete transition from the adiabatic sound velocity (c{sub 0}) (viscous limit) to the infinite-frequency sound velocity (c{sub {infinity}}) (elastic limit). On decreasing Q, as the transition regime is approached from the elastic side, we observe a decrease of the intensity of the second, weakly dispersing feature, which completely disappears when the viscous regime is reached. These findings unambiguously identify the second excitation to be a signature of the transverse dynamics with a longitudinal symmetry component, which becomes visible in S(Q,{omega}) as soon as the purely viscous regime is left.

  9. Dynamic Stackelberg game model for water rationalization in drought emergency

    NASA Astrophysics Data System (ADS)

    Kicsiny, R.; Piscopo, V.; Scarelli, A.; Varga, Z.

    2014-09-01

    In water resource management, in case of a limited resource, there is a conflict situation between different consumers. In this paper, a dynamic game-theoretical model is suggested for the solution of such conflict. Let us suppose that in a region, water supply is based on a given aquifer, from which a quantity of effective reserve can be used without damaging the aquifer, and a long drought is foreseen. The use of water is divided between the social sector represented by the local authority, and the production sector, in our case, simplified to a single agricultural producer using water for irrigation; they are the players in the game. For a fixed time period, every day, a given amount is available, from which first the authority, then the producer takes a proportion, which corresponds to the strategy choices of the players. A price function is given, which depends on the total available reserve, the payoffs of both players are quantified as their net incomes for the whole period: for the producer: profit from selling the product minus price of water and tax paid, for the authority: tax received plus the gain for the authority from selling the water bought to the social sector minus price of water purchased. A solution (equilibrium) of the game consists of such strategy choices of both players, with which each player maximizes her/his total payoff (over the whole time horizon of the game) provided that the other player also maximizes her/his own payoff. In the paper, in a mathematical model for the above conflict situation, a deterministic continuum-strategy two-player discrete-time dynamic Stackelberg game with fixed finite time duration and closed-loop information structure is proposed, where the authority is “leader” and the producer is “follower”. The algorithms for the solution of the game are based on recent theoretical results of the authors. Illustrative numerical examples are also given.

  10. Dynamics of the global virtual water trade network

    NASA Astrophysics Data System (ADS)

    Dalin, C.; Konar, M.; Hanasaki, N.; Rodriguez-Iturbe, I.

    2011-12-01

    Water resources are under increasing pressure from population growth, socio-economic development and climate change. Since agriculture is by far the most freshwater-consuming process, the international food trade may be a way of transferring water resources to water-scarce countries, and of saving water globally by encouraging trade from water-efficient countries to less water-efficient countries. We applied complex network theory to analyze the dynamics of the global virtual water trade network. Our goal was to assess how the properties of the virtual water trade network changed in time, and how these changes are related to national policies, economic and weather conditions or events. We found that, on average, the number of trade partners of each country in the network doubled from 1986 to 2007, while the volume of water associated with food trade tripled. Despite this growth of the network, we found that the shape of the network properties distributions remained similar: for all years studied, the degree distribution is well fitted by an exponential distribution and the strength distribution compares well with a stretched exponential distribution, indicating high heterogeneity of flows between nations. Other global network structure characteristics, such as the power law relationship between node strength and node degree, dissasortative behavior and weighted rich club phenomenon were also stable through the 22 year-period. However, there are significant changes at the country and link scale of analysis. The USA has remained the world's top exporter of virtual water, while, since 2001, China has been the world's largest virtual water importer, a position formerly occupied by Russia and Japan. The sharp increase in China's virtual water imports is mostly due to its increased soybean imports, following a domestic policy shift regarding the soy trade in 2000 and 2001. Importantly, the food trade has led to enhanced savings in global water resources over the last few

  11. The geochemistry of iodine - a review.

    PubMed

    Fuge, R; Johnson, C C

    1986-06-01

    Iodine has long been recognised as an important element environmentally. Despite this there are many gaps in our knowledge of its geochemistry and even where information is available much of this is based on old data which, in the light of recent data, are suspect.Iodine forms few independent minerals and is unlikely to enter most rock-forming minerals. In igneous rocks its concentration is fairly uniform and averages 0.24 mg/kg. Sedimentary rocks tend to have higher concentrations with average iodine contents of:-recent sediments 5-200 mg/kg, carbonates 2.7 mg/kg, shales 2.3 mg/kg and sandstones 0.8 mg/kg. Organic-rich sediments are particularly enriched in iodine.Soils, generally, are much richer in iodine than the parent rocks with the actual level being decided mainly by soil type and locality. Little soil iodine is water-soluble and much iodine is thought to be associated with organic matter, clays and aluminium and iron oxides. Most iodine in soils is derived from the atmosphere where, in turn, it has been derived from the oceans. Seawater has a mean iodine content of 58 μg/L, while non-saline surface waters have lower and very variable levels. Subsurface brines and mineral waters are generally strongly enriched in iodine.Marine plants are frequently enriched in iodine while terrestrial plants have generally low contents. Iodine is essential for all mammals.Consideration of the geochemical cycle of iodine reveals that its transfer from the oceans to the atmosphere is probably the most important process in its geochemistry.

  12. Questa baseline and pre-mining ground-water quality investigation. 5. Well installation, water-level data, and surface- and ground-water geochemistry in the Straight Creek drainage basin, Red River Valley, New Mexico, 2001-03

    USGS Publications Warehouse

    Naus, Cheryl A.; McCleskey, R. Blaine; Nordstrom, D. Kirk; Donohoe, Lisa C.; Hunt, Andrew G.; Paillet, Frederick L.; Morin, Roger H.; Verplanck, Philip L.

    2005-01-01

    The U.S. Geological Survey, in cooperation with the New Mexico Environment Department, is investigating the pre-mining ground-water chemistry at the Molycorp molybdenum mine in the Red River Valley, northern New Mexico. The primary approach is to determine the processes controlling ground-water chemistry at an unmined, off-site, proximal analog. The Straight Creek drainage basin, chosen for this purpose, consists of the same quartz-sericite-pyrite altered andesitic and rhyolitic volcanic rock of Tertiary age as the mine site. The weathered and rugged volcanic bedrock surface is overlain by heterogeneous debris-flow deposits that interfinger with alluvial deposits near the confluence of Straight Creek and the Red River. Pyritized rock in the upper part of the drainage basin is the source of acid rock drainage (pH 2.8-3.3) that infiltrates debris-flow deposits containing acidic ground water (pH 3.0-4.0) and bedrock containing water of circumneutral pH values (5.6-7.7). Eleven observation wells were installed in the Straight Creek drainage basin. The wells were completed in debris-flow deposits, bedrock, and interfingering debris-flow and Red River alluvial deposits. Chemical analyses of ground water from these wells, combined with chemical analyses of surface water, water-level data, and lithologic and geophysical logs, provided information used to develop an understanding of the processes contributing to the chemistry of ground water in the Straight Creek drainage basin. Surface- and ground-water samples were routinely collected for determination of total major cations and selected trace metals; dissolved major cations, selected trace metals, and rare-earth elements; anions and alkalinity; and dissolved-iron species. Rare-earth elements were determined on selected samples only. Samples were collected for determination of dissolved organic carbon, mercury, sulfur isotopic composition (34S and 18O of sulfate), and water isotopic composition (2H and 18O) during

  13. Constraints on water chemistry by chemical weathering in the Lake Qinghai catchment, northeastern Tibetan Plateau (China): clues from Sr and its isotopic geochemistry

    NASA Astrophysics Data System (ADS)

    Jin, Zhangdong; Yu, Jimin; Wang, Sumin; Zhang, Fei; Shi, Yuewei; You, Chen-Feng

    2009-12-01

    Lake water, river water, and groundwater from the Lake Qinghai catchment in the northeastern Tibetan Plateau, China have been analyzed and the results demonstrate that the chemical components and 87Sr/86Sr ratios of the waters are strictly constrained by the age and rock types of the tributaries, especially for groundwater. Dissolved ions in the Lake Qinghai catchment are derived from carbonate weathering and part from silicate sources. The chemistry of Buha River water, the largest tributary within the catchment, underlain by the late Paleozoic marine limestone and sandstones, constrains carbonate-dominated compositions of the lake water, being buffered by the waters from the other tributaries and probably by groundwater. The variation of 87Sr/86Sr ratios with cation concentrations places constraint on the Sr-isotopic compositions of the main subcatchments surrounding Lake Qinghai. The relative significance of river-water sources from different tributaries (possibly groundwater as well) in controlling the Sr distribution in Lake Qinghai provides the potential to link the influence of hydrological processes to past biological and physical parameters in the lake. The potential role of groundwater input in the water budget and chemistry of the lake emphasizes the need to further understand hydrogeological processes within the Lake Qinghai system.

  14. Dynamic simulation of water resources in an urban wetland based on coupled water quantity and water quality models.

    PubMed

    Zeng, Weibo; Xu, Youpeng; Deng, Xiaojun; Han, Longfei; Zhang, Qianyu

    2015-01-01

    Water quality in wetlands plays a huge role in maintaining the health of the wetland ecosystem. Water quality should be controlled by an appropriate water allocation policy for the protection of the wetlands. In this paper, models of rainfall/runoff, non-point source pollution load, water quantity/quality, and dynamic pollutant-carrying capacity were established to simulate the water quantity/quality of Xixi-wetland river network (in the Taihu basin, China). The simulation results showed a satisfactory agreement with field observations. Furthermore, a 'node-river-node' algorithm that adjusts to the 'Three Steps Method' was adopted to improve the dynamic pollutant-carrying capacity model and simulate the pollutant-carrying capacity in benchmark years. The simulation result shows that the water quality of the river network could reach class III stably all year round if the anthropogenic pollution is reduced to one-third of the current annual amount. Further investigation estimated the minimum amount of water diversion in benchmark years under the reasonable water quantity-regulating rule to keep water quality as class III. With comparison of the designed scale, the water diversion can be reduced by 184 million m3 for a dry year, 191 million m3 for a normal year, and 198 million m3 for a wet year.

  15. Dynamic simulation of water resources in an urban wetland based on coupled water quantity and water quality models.

    PubMed

    Zeng, Weibo; Xu, Youpeng; Deng, Xiaojun; Han, Longfei; Zhang, Qianyu

    2015-01-01

    Water quality in wetlands plays a huge role in maintaining the health of the wetland ecosystem. Water quality should be controlled by an appropriate water allocation policy for the protection of the wetlands. In this paper, models of rainfall/runoff, non-point source pollution load, water quantity/quality, and dynamic pollutant-carrying capacity were established to simulate the water quantity/quality of Xixi-wetland river network (in the Taihu basin, China). The simulation results showed a satisfactory agreement with field observations. Furthermore, a 'node-river-node' algorithm that adjusts to the 'Three Steps Method' was adopted to improve the dynamic pollutant-carrying capacity model and simulate the pollutant-carrying capacity in benchmark years. The simulation result shows that the water quality of the river network could reach class III stably all year round if the anthropogenic pollution is reduced to one-third of the current annual amount. Further investigation estimated the minimum amount of water diversion in benchmark years under the reasonable water quantity-regulating rule to keep water quality as class III. With comparison of the designed scale, the water diversion can be reduced by 184 million m3 for a dry year, 191 million m3 for a normal year, and 198 million m3 for a wet year. PMID:26540537

  16. Water dynamics in the rhizosphere - a new model of coupled water uptake and mucilage exudation

    NASA Astrophysics Data System (ADS)

    Kroener, Eva; Holz, Maire; Ahmed, Mutez; Zarebanadkouki, Mohsen; Bittelli, Marco; Carminati, Andrea

    2016-04-01

    The flow of water from soil to plant roots is affected by the narrow region of soil close to the roots, the so-called rhizosphere. The rhizosphere is influenced by mucilage, a polymeric gel exuded by roots that alters the hydraulic properties of the rhizosphere. Here we present a model that accounts for: (a) an increase in equilibrium water retention curve caused by the water holding capacity of mucilage, (b) a reduction of hydraulic conductivity at a given water content due to the higher viscosity of mucilage and (c) the swelling and shrinking dynamics by decoupling water content and water potential and introducing a non-equilibrium water retention curve. The model has been tested for mixtures of soil and mucilage and we applied it to simulate observations of previous experiments with real plants growing in soil that show evidences of altered hydraulic dynamics in the rhizosphere. Furthermore we present results about how the parameters of the model depend on soil texture and root age. Finally we couple our hydraulic model to a diffusion model of mucilage into the soil. Opposed to classical solute transport models here the water flow in the rhizosphere is affected by the concentration distribution of mucilage.

  17. Water dynamics in the rhizosphere - a new model of coupled water uptake and mucilage exudation

    NASA Astrophysics Data System (ADS)

    Kroener, E.

    2015-12-01

    The flow of water from soil to plant roots is affected by the narrow region of soil close to the roots, the so called rhizosphere. The rhizosphere is influenced by mucilage, a polymeric gel exuded by roots that alters the hydraulic properties of the rhizosphere. Here we present a model that accounts for: (a) an increase in equilibrium water retention curve caused by the water holding capacity of mucilage, (b) a reduction of hydraulic conductivity at same water content due to the higher viscosity of mucilage and (c) the swelling and shrinking dynamics by decoupling water content and water potential and introducing a non-equilibrium water retention curve. The model has been tested for mixtures of soil and mucilage and we applied it to simulate observations of previous experiments with real plants growing in soil that show evidences of altered hydraulic dynamics in the rhizosphere. Furthermore we presen results about how the parameters of the model depend on soil texture and root age. Finally we couple our hydraulic model to a diffusion model of mucilage into the soil. Opposed to classical solute transport experiments the water flow in the rhizosphere is affected by the concentration distribution of mucilage.

  18. Systems Dynamic ToolBox for Water Resource Planning

    2006-08-01

    The Fully Integrated System Dynamics Tookbox for Water Resources Planning (Toolbox) is a library of generic modules intended to assist in water management planning and decision making in watersheds around the world. The modules - built in a commercially available modeling environment called Powersim Studio Expert, represent the different sub-systems ina watershed, including population, agriculture, economics, climate, reservoirs, stream flows, and fish populations, and provides generic building blocks with which complex models of complex modelsmore » of complex watersheds can be assembled. The resulting models provide a tool for observing how research management decision made in one sector of a basin can affect other sectors. Improved water resource management contributes to improved public health, economic development, ecological sustainability, and overall security and stability.« less

  19. Dynamic criteria of plankton jumping out of water.

    PubMed

    Kim, Seong Jin; Hasanyan, Jalil; Gemmell, Brad J; Lee, Sungyon; Jung, Sunghwan

    2015-10-01

    In nature, jumping out of water is a behaviour commonly observed in aquatic species to either escape from predators or hunt prey. However, not all aquatic species are capable of jumping out, especially small organisms whose length scales are comparable to the capillary length (approx. 2.7 mm for water). Some aquatic animals smaller than the capillary length are able to jump out while others are not, as observed in some marine copepods. To understand the dynamics of jumping out of the water-air interface, we perform physical experiments by shooting a spherical particle towards the liquid-air interface from below. Experimental results show that the particle either penetrates or bounces back from the interface, depending on the particle and fluid properties, and the impact velocity. The transition from bouncing to penetration regimes, which is theoretically predicted based on a particle force balance, is in good agreement with both physical experiments and plankton behavioural data.

  20. Dynamics of charged microparticles at oil-water interfaces.

    PubMed

    Wu, Chih-Yuan; Tarimala, Sowmitri; Dai, Lenore L

    2006-02-28

    Solid-stabilized emulsions have been used as a model system to investigate the dynamics of charged microparticles with diameters of 1.1 microm at oil-water interfaces. Using confocal microscopy, we investigated the influences of interfacial curvature, cluster size, and temperature on the diffusion of solid particles. Our work suggests that a highly curved emulsion interface slows the motion of solid particles. This qualitatively supports the theoretical work by Danov et al. (Danov, K. D.; Dimova, R.; Pouligny, B. Phys. Fluids 2000, 12, 2711); however, the interfacial curvature effect decreases with increasing oil-phase viscosity. The diffusion of multiparticle clusters at oil-water interfaces is a strong function of cluster size and oil-phase viscosity and can be quantitatively related to fractal dimension. Finally, we report the influence of temperature and quantify the diffusion activation energy and friction factor of the particles at the investigated oil-water interfaces.

  1. Non-Equilibrium Water-Glassy Polymer Dynamics

    NASA Astrophysics Data System (ADS)

    Davis, Eric; Minelli, Matteo; Baschetti, Marco; Sarti, Giulio; Elabd, Yossef

    2012-02-01

    For many applications (e.g., medical implants, packaging), an accurate assessment and fundamental understanding of the dynamics of water-glassy polymer interactions is of great interest. In this study, sorption and diffusion of pure water in several glassy polymers films, such as poly(styrene) (PS), poly(methyl methacrylate) (PMMA), poly(lactide) (PLA), were measured over a wide range of vapor activities and temperatures using several experimental techniques, including quartz spring microbalance (QSM), quartz crystal microbalance (QCM), and time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian behavior (diffusion-relaxation phenomena) was observed by all three techniques, while FTIR-ATR spectroscopy also provides information about the distribution of the states of water and water transport mechanisms on a molecular-level. Specifically, the states of water are significantly different in PS compared to PMMA and PLA. Additionally, a purely predictive non-equilibrium lattice fluid (NELF) model was applied to predict the sorption isotherms of water in these glassy polymers.

  2. Molecular dynamics simulations of water droplets on polymer surfaces.

    PubMed

    Hirvi, Janne T; Pakkanen, Tapani A

    2006-10-14

    Molecular dynamics simulations were used to study the wetting of polymer surfaces with water. Contact angles of water droplets on crystalline and two amorphous polyethylene (PE) and poly(vinyl chloride) (PVC) surfaces were extracted from atomistic simulations. Crystalline surfaces were produced by duplicating the unit cell of an experimental crystal structure, and amorphous surfaces by pressing the bulk polymer step by step at elevated temperature between two repulsive grid surfaces to a target density. Different-sized water droplets on the crystalline PE surface revealed a slightly positive line tension on the order of 10(-12)-10(-11) N, whereas droplets on crystalline PVC did not yield a definite line tension. Microscopic contact angles produced by the simple point charge (SPC) water model were mostly a few degrees smaller than those produced by the extended SPC model, which, as the model with lowest bulk energy, presents an upper boundary for contact angles. The macroscopic contact angle for the SPC model was 94 degrees on crystalline PVC and 113 degrees on crystalline PE. Amorphicity of the surface increased the water contact angle on PE but decreased it on PVC, for both water models. If the simulated contact angles on crystalline and amorphous surfaces are combined in proportion to the crystallinity of the polymer in question, simulated values in relatively good agreement with measured values are obtained.

  3. What is the primary mover of water dynamics?

    PubMed

    Ben Ishai, P; Tripathi, S R; Kawase, K; Puzenko, A; Feldman, Yu

    2015-06-21

    Even today, the H-bonded cluster structure of water still stands as a major point of debate in the science of liquids. Much of this discussion is devoted to understand its dynamic nature. This has a direct impact on deciphering the many anomalies of water such as its exceptional heat capacity. Of these properties, dielectric permittivity and relaxation are of particular interest. The argument rages over whether the almost Debye-like character of the dispersion is the result of the reorientation of an apparent dipole moment of the water cluster or simply the cumulative effect of single water molecule reorientation. Furthermore, like many glass formers, it has a high frequency excess wing that does not fit into the accepted models of a single relaxation time of the main peak. Herein, we present evidence that the microscopic origins of both the excess wing and the main relaxation process of pure water are the same. The origin of these two features is explored and we suggest a new paradigm for water relaxation based on the concept of a proton cascade leading to a cluster reorientation. PMID:26008633

  4. Geochemistry and magnetic measurements of suspended sediment in urban sewage water vis-à-vis quantification of heavy metal pollution in Ganga and Yamuna Rivers, India.

    PubMed

    Chakarvorty, Munmun; Dwivedi, Akhil Kumar; Shukla, Anil Dutt; Kumar, Sujeet; Niyogi, Ambalika; Usmani, Mavera; Pati, Jayanta Kumar

    2015-09-01

    Sewage water is becoming a key source of heavy metal toxicity in large river systems worldwide and the two major Himalayan Rivers in India (Ganga and Yamuna) are severely affected. The high population density in the river banks combined with increased anthropogenic and industrial activities is contributing to the heavy metal pollution in these rivers. Geochemical data shows a significant increase in the concentration of all heavy metals (Pb, 48-86 ppm; Zn, 360-834 ppm; V, 45-101 ppm; Ni, 20-143 ppm; Cr, 79-266 ppm; Co, 8.62-22.12 ppm and Mn, 313-603 ppm) in sewage and mixed water (sewage and river water confluence site) samples due to increased effluent discharge from the catchment area. The ΣREE content of sewage water (129 ppm) is lower than the average mixed water samples (142 ppm). However, all the samples show similar REE pattern. The mass magnetic susceptibility (Xlf) values of suspended sediments (28 to 1000 × 10(-8) m(3) kg(-1)) indicate variable concentration of heavy metals. The Xlf values show faint positive correlation with their respective bulk heavy metal contents in a limited sample population. The present study comprising geochemical analysis and first magnetic measurement data of suspended sediments in water samples shows a strongly polluted nature of Ganga and Yamuna Rivers at Allahabad contrary to the previous report mainly caused by overtly polluted city sewage water. PMID:26318318

  5. Geochemistry and magnetic measurements of suspended sediment in urban sewage water vis-à-vis quantification of heavy metal pollution in Ganga and Yamuna Rivers, India.

    PubMed

    Chakarvorty, Munmun; Dwivedi, Akhil Kumar; Shukla, Anil Dutt; Kumar, Sujeet; Niyogi, Ambalika; Usmani, Mavera; Pati, Jayanta Kumar

    2015-09-01

    Sewage water is becoming a key source of heavy metal toxicity in large river systems worldwide and the two major Himalayan Rivers in India (Ganga and Yamuna) are severely affected. The high population density in the river banks combined with increased anthropogenic and industrial activities is contributing to the heavy metal pollution in these rivers. Geochemical data shows a significant increase in the concentration of all heavy metals (Pb, 48-86 ppm; Zn, 360-834 ppm; V, 45-101 ppm; Ni, 20-143 ppm; Cr, 79-266 ppm; Co, 8.62-22.12 ppm and Mn, 313-603 ppm) in sewage and mixed water (sewage and river water confluence site) samples due to increased effluent discharge from the catchment area. The ΣREE content of sewage water (129 ppm) is lower than the average mixed water samples (142 ppm). However, all the samples show similar REE pattern. The mass magnetic susceptibility (Xlf) values of suspended sediments (28 to 1000 × 10(-8) m(3) kg(-1)) indicate variable concentration of heavy metals. The Xlf values show faint positive correlation with their respective bulk heavy metal contents in a limited sample population. The present study comprising geochemical analysis and first magnetic measurement data of suspended sediments in water samples shows a strongly polluted nature of Ganga and Yamuna Rivers at Allahabad contrary to the previous report mainly caused by overtly polluted city sewage water.

  6. Dynamic mechanical analysis of supercooled water in nanoporous confinement

    NASA Astrophysics Data System (ADS)

    Soprunyuk, Viktor; Schranz, Wilfried; Huber, Patrick

    2016-08-01

    Dynamical mechanical analysis (\\text{DMA})(f=0.2\\text{--}100 \\text{Hz}) is used to study the dynamics of confined water in mesoporous Gelsil (2.6 nm and 5 nm pores) and Vycor (10 nm) in the temperature range from T=80 \\text{K} to 300 K. Confining water into nanopores partly suppresses crystallization and allows us to perform measurements of supercooled water below 235 K, i.e., in water's so-called “no man's land”, in parts of the pores. Two distinct relaxation peaks are observed in tan δ around T1 ≈ 145 \\text{K} (P1) and T2 ≈ 205 \\text{K}~(P2) for Gelsil 2.6 nm and Gelsil 5 nm at 0.2 Hz. Both peaks shift to higher T with increasing pore size d and change with f in a systematic way, typical of an Arrhenius behaviour of the corresponding relaxation times. For P 1 we obtain an average activation energy of E\\text{a} = 0.47 \\text{eV} , in good agreement with literature values, suggesting that P 1 corresponds to the glass transition of supercooled water. The observation of a pronounced softening of the Young's modulus around 165 K (for Gelsil 2.6 nm at 0.2 Hz) supports the conjecture of a glass-to-liquid transition in the vicinity of P 1. In addition we find a clear-cut (1/d)-dependence of the calculated glass transition temperatures which extrapolates to T_\\text{g}(1/d=0)=136 \\text{K} , in agreement with the traditional value of water.

  7. Analysis of the ground-water flow system, geochemistry, and underseepage in the vicinity of the Red Rock Dam near Pella, Iowa

    USGS Publications Warehouse

    Lucey, K.J.

    1991-01-01

    The increased hydraulic head imposed on the system by the impounded waters of Lake Red Rock causes recharge and flow to the deeper bedrock aquifers in the immediate vicinity of the dam. This effect is manifested in the observation wells along and downstream from the dam axis, implying flow through the grout curtain in the bedrock foundation of the dam. There is potential for dissolution of the gypsum and anhydrite in the bedrock foundation, because reservoir water and shallow ground water in the vicinity of the dam are undersaturated with respect to these evaporite minerals.

  8. Hydrology and geochemistry of a slag-affected aquifer and chemical characteristics of slag-affected ground water, northwestern Indiana and northeastern Illinois

    USGS Publications Warehouse

    Bayless, E. Randall; Greeman, T.K.; Harvey, C.C.

    1998-01-01

    Slag is a by-product of steel manufacturing and a ubiquitous fill material in northwestern Indiana. Ground water associated with slag deposits generally is characterized by high pH and elevated concentrations of many inorganic water-quality constituents. The U.S. Geological Survey, in cooperation with the Indiana Department of Environmental Management, conducted a study in northwestern Indiana from June 1995 to September 1996 to improve understanding of the effects of slag deposits on the water quality of a glacial-outwash aquifer. The Bairstow Landfill, a slag-fill deposit overlying the Calumet aquifer near Hammond, Indiana, was studied to represent conditions in slag-deposit settings that are common in northwestern Indiana. Ground water from 10 observation wells, located in four nests at the site, and surface water from the adjacent Lake George were analyzed for values of field-measured parameters and concentrations of major ions, nutrients, trace elements, and bulk properties. Solid-phase samples of slag and aquifer sediment collected during drilling were examined with X-ray diffraction and geochemical digestion and analysis. Concentrations of calcium, potassium, sodium, and sulfate were highest in wells screened partly or fully in slag. Potassium concentrations in ground water ranged from 2.9 to 120 milligrams per liter (mg/L), were highest in water from slag deposits, and decreased with depth. The highest concentrations for aluminum, barium, molybdenum, nickel, and selenium were in water from the slag. Silica concentrations were highest in wells screened directly beneath the slag?aquifer interface, and magnesium concentrations were highest in intermediate and deep aquifer wells. Silica concentrations in shallow and intermediate aquifer wells ranged from 27 to 41 mg/L and were about 10 times greater than those in water from slag deposits. The highest concentrations for chromium, lead, and zinc were in ground water from immediately below the slag

  9. Defining dynamic pelagic habitats in oceanic waters off eastern Australia

    NASA Astrophysics Data System (ADS)

    Hobday, A. J.; Young, J. W.; Moeseneder, C.; Dambacher, J. M.

    2011-03-01

    Although many species in the pelagic ocean are widespread, they are not randomly distributed. These species may have associations with particular water masses or habitats, but to best understand patterns in the ocean, these habitats must be identified. Previous efforts have produced static or seasonal climatologies, which still represent smearing over habitats. The Eastern Tuna and Billfish Longline Fishery (ETBF) targets a range of high trophic level species in oceanic waters off eastern Australia. In this study, dynamic ocean habitats in the region were identified for each month based on cluster analysis of five oceanographic variables averaged at a monthly time scale and a spatial scale of 0.5° for the period 1995-2006. A total of seven persistent habitats were identified off eastern Australia with intra and interannual variation in size and location, indicating the importance of spatial and temporal variation in the dynamics of the region. The degree to which these dynamic habitats were distinguished was tested using (i) stable isotope analysis of top fish predators caught in the region and (ii) estimates of variation in estimated abundance generated from catch data from the fishery. More precise estimates (measured as lower total CV) of isotopic values from swordfish ( Xiphias gladius), yellowfin tuna ( Thunnus albacares) and albacore ( Thunnus alalunga) were obtained for 4 of 6 isotope comparisons using the dynamic habitat groupings, which indicate that stratifying by pelagic habitat improved precision. Dynamic habitats produced more precise abundance estimates for 7 of 8 large pelagic species examined, with an average reduction in total CV of 19% compared to when abundance was estimated based on static habitat stratification. These findings could be used to guide development of effective monitoring strategies that can distinguish patterns due to environmental variation, and in the longer term, climate change.

  10. Geochemistry and health in the United Kingdom.

    PubMed

    Thornton, I; Webb, J S

    1979-12-11

    Before the 1960s, comparisons between the distribution of trace elements in the environment and health in the United Kingdom were primarily confined to ad hoc studies in areas associated with particular agricultural disorders or with unusual human mortality or morbidity records. More recently, increasing interest in the importance of trace elements in crop and animal production and in the hazards of environmental pollution have created a need for more systematic geochemical data. Geochemical reconnaissance maps for England, Wales, Northern Ireland and parts of Scotland have demonstrated the extent of many known clinical trace element problems in agriculture and have also been valuable in delineating areas within which subclinical disorders may occur. Their application to studies on the composition of soils, food crops and surface waters in relation to public health has proved encouraging. Current knowledge and present investigations into environmental geochemistry and human health in the U.K. are reviewed, together with future research requirements. PMID:43529

  11. Vibration-rotation-tunneling dynamics in small water clusters

    SciTech Connect

    Pugliano, N.

    1992-11-01

    The goal of this work is to characterize the intermolecular vibrations of small water clusters. Using tunable far infrared laser absorption spectroscopy, large amplitude vibration-rotation-tunneling (VRT) dynamics in vibrationally excited states of the water dimer and the water trimer are investigated. This study begins with the measurement of 12 VRT subbands, consisting of approximately 230 transitions, which are assigned to an 82.6 cm{sup {minus}1} intermolecular vibration of the water dimer-d{sub 4}. Each of the VRT subbands originate from K{sub a}{double_prime}=0 and terminate in either K{sub a}{prime}=0 or 1. These data provide a complete characterization of the tunneling dynamics in the vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A{prime} rotational constant is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined to exhibit large dependencies with both the K{sub a}{prime} quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method treatment which has been developed to model the tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable for this vibrational coordinate. The data are consistent with a motion possessing a{prime} symmetry, and the vibration is assigned as the {nu}{sub 12} acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry, the resultsof high level ab initio calculations, and preliminary data assigned to the analogous vibration in the D{sub 2}O-DOH isotopomer.

  12. Vibration-rotation-tunneling dynamics in small water clusters

    SciTech Connect

    Pugliano, N.

    1992-11-01

    The goal of this work is to characterize the intermolecular vibrations of small water clusters. Using tunable far infrared laser absorption spectroscopy, large amplitude vibration-rotation-tunneling (VRT) dynamics in vibrationally excited states of the water dimer and the water trimer are investigated. This study begins with the measurement of 12 VRT subbands, consisting of approximately 230 transitions, which are assigned to an 82.6 cm[sup [minus]1] intermolecular vibration of the water dimer-d[sub 4]. Each of the VRT subbands originate from K[sub a][double prime]=0 and terminate in either K[sub a][prime]=0 or 1. These data provide a complete characterization of the tunneling dynamics in the vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A[prime] rotational constant is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined to exhibit large dependencies with both the K[sub a][prime] quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method treatment which has been developed to model the tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable for this vibrational coordinate. The data are consistent with a motion possessing a[prime] symmetry, and the vibration is assigned as the [nu][sub 12] acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry, the resultsof high level ab initio calculations, and preliminary data assigned to the analogous vibration in the D[sub 2]O-DOH isotopomer.

  13. Hydro-geochemistry and application of water quality index (WQI) for groundwater quality assessment, Anna Nagar, part of Chennai City, Tamil Nadu, India

    NASA Astrophysics Data System (ADS)

    Krishna kumar, S.; Logeshkumaran, A.; Magesh, N. S.; Godson, Prince S.; Chandrasekar, N.

    2015-12-01

    In the present study, the geochemical characteristics of groundwater and drinking water quality has been studied. 24 groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids, carbonate, bicarbonate, chloride, sulphate, nitrate, calcium, magnesium, sodium, potassium and total hardness. The results were evaluated and compared with WHO and BIS water quality standards. The studied results reveal that the groundwater is fresh to brackish and moderately high to hard in nature. Na and Cl are dominant ions among cations and anions. Chloride, calcium and magnesium ions are within the allowable limit except few samples. According to Gibbs diagram, the predominant samples fall in the rock-water interaction dominance and evaporation dominance field. The piper trilinear diagram shows that groundwater samples are Na-Cl and mixed CaMgCl type. Based on the WQI results majority of the samples are falling under excellent to good category and suitable for drinking water purposes.

  14. HYDROGIOLOGIC FRAMEWORK, GROUND-WATER GEOCHEMISTRY, AND ASSESSMENT OF NITROGEN YIELD FROM BASE FLOW IN TWO AGRICULTURAL WATERSHEDS, KENT COUNTY, MARYLAND

    EPA Science Inventory

    Hydrostratigraphic and geochemical data collected in two adjacent watersheds on the Delmarva Peninsula, in Kent County, Maryland, indicate that shallow subsurface stratigraphy is an important factor that affects the concentrations of nitrogen in ground water discharging as stream...

  15. Environmental geochemistry of shale-hosted Ag-Pb-Zn massive sulfide deposits in northwest Alaska: Natural background concentrations of metals in water from mineralized areas

    USGS Publications Warehouse

    Kelley, K.D.; Taylor, C.D.

    1997-01-01

    Red Dog, Lik and Drenchwater are shale-hosted stratiform Ag-Pb-Zn massive sulfide deposits in the northwestern Brooks Range. Natural background concentrations of metals in waters from the undisturbed (unmined) Drenchwater prospect and Lik deposit were compared to pre-mining baseline studies conducted at Red Dog. The primary factors affecting water chemistry are the extent of exposure of the deposits, the grade of mineralization, the presence of carbonate reeks in the section, and the proportion of Fe-sulfide in the ore. Surface water samples from the Drenchwater prospect, which has pyrite-dominant mineralization exposed in outcrop, have pH values as low as 2.8 and high dissolved concentrations of metals including as much as 95 mg 1-1 Al, 270 mg 1-1 Fe, 8 ??1-1 Cd, 10 ??1-1 Pb, and 2600 ??1-1 Zn, with As up to 26 ??g1-1. Surface waters from the Red Dog deposit prior to mining were also acidic and metal-rich, however, dissolved metal concentrations in Red Dog waters were many times greater. The higher metal concentrations in Red Dog waters reflect the high Zn grades and the abundant sphalerite, pyrite, and galena that were present in outcrop prior to mining. In contrast, despite significant mineralization at the Lik deposit, carbonate rocks in the section buffer the system, resulting in less acidic, mostly near-neutral pH values with low concentrations of most metals except Zn.

  16. Water and rock geochemistry, geologic cross sections, geochemical modeling, and groundwater flow modeling for identifying the source of groundwater to Montezuma Well, a natural spring in central Arizona

    USGS Publications Warehouse

    Johnson, Raymond H.; DeWitt, Ed; Wirt, Laurie; Arnold, L. Rick; Horton, John D.

    2011-01-01

    The National Park Service (NPS) seeks additional information to better understand the source(s) of groundwater and associated groundwater flow paths to Montezuma Well in Montezuma Castle National Monument, central Arizona. The source of water to Montezuma Well, a flowing sinkhole in a desert setting, is poorly understood. Water emerges from the middle limestone facies of the lacustrine Verde Formation, but the precise origin of the water and its travel path are largely unknown. Some have proposed artesian flow to Montezuma Well through the Supai Formation, which is exposed along the eastern margin of the Verde Valley and underlies the Verde Formation. The groundwater recharge zone likely lies above the floor of the Verde Valley somewhere to the north or east of Montezuma Well, where precipitation is more abundant. Additional data from groundwater, surface water, and bedrock geology are required for Montezuma Well and the surrounding region to test the current conceptual ideas, to provide new details on the groundwater flow in the area, and to assist in future management decisions. The results of this research will provide information for long-term water resource management and the protection of water rights.

  17. Water quality and geochemistry evaluation of groundwater upstream and downstream of the Khirbet Al-Samra wastewater treatment plant/Jordan

    NASA Astrophysics Data System (ADS)

    Bajjali, William; Al-Hadidi, Kheir; Ismail, Ma'mmon

    2015-01-01

    Groundwater in the northeastern Amman-Zarqa basin is an important source of water for irrigation. The quality and quantity of water has deteriorated due to mismanagement and misunderstanding of the hydrogeological system. Overexploitation of groundwater resources upstream of the Khirbet Al-Samra wastewater treatment plant (KSWTP) has lowered the water table 43 m since the beginning of groundwater development in 1968. Heavy pumping of groundwater downstream of KSWTP has not dropped the water level due to constant recharge from the Zarqa river bed. The water level of groundwater is rising continuously at a rate of 20 cm per year since building the KSWTP in 1985. Groundwater salinity has also shifted the quality of the aquifer from fresh to brackish. Continual irrigation from the groundwater upstream of KSWTP dissolves accumulated salt from the soil formed by evaporation, and the contaminated water infiltrates back to the aquifer, thereby increasing both salt and nitrate concentrations. The intense irrigation from the reclaimed water downstream of KSWTP and leakage of treated wastewater from the Zarqa River to the shallow groundwater is a secondary source of salt and nitrates. The isotopic composition of groundwater varies over a wide range and is associated with the meteoric water line affected by Mediterranean Sea air moisture. The isotopic composition of groundwater is represented by evaporation line (EL) with a low slope of 3.6. The enrichment of groundwater in δ18O and δD is attributed mainly to the two processes of evaporation before infiltration of return flow and mixing of different types of water in KSWTP originating from different aquifers. The EL starts from a location more depleted than the weighted mean value of the Amman rainfall station on the Eastern Meteoric Water Line indicating that the recharge took place under the climate regime prevailing today in Jordan and the recharge of the groundwater originates from a greater elevation than that of the

  18. Hydro-dynamic damping theory in flowing water

    NASA Astrophysics Data System (ADS)

    Monette, C.; Nennemann, B.; Seeley, C.; Coutu, A.; Marmont, H.

    2014-03-01

    Fluid-structure interaction (FSI) has a major impact on the dynamic response of the structural components of hydroelectric turbines. On mid-head to high-head Francis runners, the rotor-stator interaction (RSI) phenomenon always has to be considered carefully during the design phase to avoid operational issues later on. The RSI dynamic response amplitudes are driven by three main factors: (1) pressure forcing amplitudes, (2) excitation frequencies in relation to natural frequencies and (3) damping. The prediction of the two first factors has been largely documented in the literature. However, the prediction of fluid damping has received less attention in spite of being critical when the runner is close to resonance. Experimental damping measurements in flowing water on hydrofoils were presented previously. Those results showed that the hydro-dynamic damping increased linearly with the flow. This paper presents development and validation of a mathematical model, based on momentum exchange, to predict damping due to fluid structure interaction in flowing water. The model is implemented as an analytical procedure for simple structures, such as cantilever beams, but is also implemented in more general ways using three different approaches for more complex structures such as runner blades: a finite element procedure, a CFD modal work based approach and a CFD 1DOF approach. The mathematical model and all three implementation approaches are shown to agree well with experimental results.

  19. Application of dynamic programming to control khuzestan water resources system

    USGS Publications Warehouse

    Jamshidi, M.; Heidari, M.

    1977-01-01

    An approximate optimization technique based on discrete dynamic programming called discrete differential dynamic programming (DDDP), is employed to obtain the near optimal operation policies of a water resources system in the Khuzestan Province of Iran. The technique makes use of an initial nominal state trajectory for each state variable, and forms corridors around the trajectories. These corridors represent a set of subdomains of the entire feasible domain. Starting with such a set of nominal state trajectories, improvements in objective function are sought within the corridors formed around them. This leads to a set of new nominal trajectories upon which more improvements may be sought. Since optimization is confined to a set of subdomains, considerable savings in memory and computer time are achieved over that of conventional dynamic programming. The Kuzestan water resources system considered in this study is located in southwest Iran, and consists of two rivers, three reservoirs, three hydropower plants, and three irrigable areas. Data and cost benefit functions for the analysis were obtained either from the historical records or from similar studies. ?? 1977.

  20. Cavitation in confined water: ultra-fast bubble dynamics

    NASA Astrophysics Data System (ADS)

    Vincent, Olivier; Marmottant, Philippe

    2012-02-01

    In the hydraulic vessels of trees, water can be found at negative pressure. This metastable state, corresponding to mechanical tension, is achieved by evaporation through a porous medium. It can be relaxed by cavitation, i.e. the sudden nucleation of vapor bubbles. Harmful for the tree due to the subsequent emboli of sap vessels, cavitation is on the contrary used by ferns to eject spores very swiftly. We will focus here on the dynamics of the cavitation bubble, which is of primary importance to explain the previously cited natural phenomena. We use the recently developed method of artificial tress, using transparent hydrogels as the porous medium. Our experiments, on water confined in micrometric hydrogel cavities, show an extremely fast dynamics: bubbles are nucleated at the microsecond timescale. For cavities larger than 100 microns, the bubble ``rings'' with damped oscillations at MHz frequencies, whereas for smaller cavities the oscillations become overdamped. This rich dynamics can be accounted for by a model we developed, leading to a modified Rayleigh-Plesset equation. Interestingly, this model predicts the impossibility to nucleate bubbles above a critical confinement that depends on liquid negative pressure and corresponds to approximately 100 nm for 20 MPa tensions.

  1. Ground-water flow, geochemistry, and effects of agricultural practices on nitrogen transport at study sites in the Piedmont and Coastal Plain physiographic provinces, Patuxent River basin, Maryland

    USGS Publications Warehouse

    McFarland, E. Randolph

    1997-01-01

    In an effort to improve water quality in Chesapeake Bay, agricultural practices are being promoted that are intended to reduce contaminant transport to the Bay. The effects of agricultural practices on nitrogen transport were assessed at two 10-acre study sites in the Patuxent River basin, Maryland, during 1986-92. Nitrogen load was larger in ground water than in surface runoff at both sites. At the study site in the Piedmont Province, nitrogen load in ground water decreased from 12 to 6 (lb/acre)/yr (pound per acre per year) as corn under no-till cultivation was replaced by no-till soybeans, continuous alfalfa, and contoured strip crops alternated among corn, alfalfa, and soybeans. At the study site in the Coastal Plain Province, no-till soybeans resulted in a nitrogen load in ground water of 12.55 (lb/acre)/yr, whereas conventional-till soybeans resulted in a nitrogen load in ground water of 11.51 (lb/acre)/yr.

  2. Rethinking early Earth phosphorus geochemistry

    PubMed Central

    Pasek, Matthew A.

    2008-01-01

    Phosphorus is a key biologic element, and a prebiotic pathway leading to its incorporation into biomolecules has been difficult to ascertain. Most potentially prebiotic phosphorylation reactions have relied on orthophosphate as the source of phosphorus. It is suggested here that the geochemistry of phosphorus on the early Earth was instead controlled by reduced oxidation state phosphorus compounds such as phosphite (HPO32−), which are more soluble and reactive than orthophosphates. This reduced oxidation state phosphorus originated from extraterrestrial material that fell during the heavy bombardment period or was produced during impacts, and persisted in the mildly reducing atmosphere. This alternate view of early Earth phosphorus geochemistry provides an unexplored route to the formation of pertinent prebiotic phosphorus compounds, suggests a facile reaction pathway to condensed phosphates, and is consistent with the biochemical usage of reduced oxidation state phosphorus compounds in life today. Possible studies are suggested that may detect reduced oxidation state phosphorus compounds in ancient Archean rocks. PMID:18195373

  3. Static and dynamic correlations in water at hydrophobic interfaces

    PubMed Central

    Mittal, Jeetain; Hummer, Gerhard

    2008-01-01

    We study the static and dynamic properties of the water-density fluctuations in the interface of large nonpolar solutes. With the help of extensive molecular dynamics simulations of TIP4P water near smooth spherical solutes, we show that for large solutes, the interfacial density profile is broadened by capillary waves. For purely repulsive solutes, the squared width of the interface increases linearly with the logarithm of the solute size, as predicted by capillary-wave theory. The apparent interfacial tension extracted from the slope agrees with that of a free liquid–vapor interface. The characteristic length of local density fluctuations is ≈0.5 nm, measured along the arc, again consistent with that of a free liquid–vapor interface. Probed locally, the interfacial density fluctuations exhibit large variances that exceed those expected for an ideal gas. Qualitatively consistent with theories of the free liquid–vapor interface, we find that the water interface near large and strongly nonpolar solutes is flickering, broadened by capillary-wave fluctuations. These fluctuations result in transitions between locally wet and dry regions that are slow on a molecular time scale. PMID:19074279

  4. Cavity dynamics in high-speed water entry

    NASA Astrophysics Data System (ADS)

    Lee, M.; Longoria, R. G.; Wilson, D. E.

    1997-03-01

    A method is presented for modeling the cavity formation and collapse induced by high-speed impact and penetration of a rigid projectile into water. The approach proposes that high-speed water-entry is characterized by a cavity that experiences a deep closure prior to closure at the surface. This sequence in the physical events of the induced cavity dynamics is suggested by the most recent high-speed water-entry experimental data, by results from numerical experiments using a hydrocode, and by an understanding of the fundamental physics of the processes that govern surface closure. The analytical model, which specifies the energy transfer for cavity production as equivalent to the energy dissipated by velocity-dependent drag on the projectile, provides accurate estimates for variables that are important in characterizing the cavity dynamics, and reveals useful knowledge regarding magnitudes and trends. In particular, it is found that the time of deep closure is essentially constant and independent of the impact velocity for a given projectile size, while the location of deep closure has a weak dependence on impact velocity. Comparison of these analytical results with experimental results from the literature and with results from numerical simulations verifies the analytical solutions.

  5. Ultrafast photo-excitation dynamics in isolated, neutral water clusters

    SciTech Connect

    Liu, H. T.; Mueller, J. P.; Beutler, M.; Ghotbi, M.; Noack, F.; Radloff, W.; Zhavoronkov, N.; Schulz, C. P.; Hertel, I. V.

    2011-03-07

    Using the efficient nonlinear conversion scheme which was recently developed in our group [M. Beutler, M. Ghotbi, F. Noack, and I. V. Hertel, Opt. Lett. 134, 1491 (2010); M. Ghotbi, M. Beutler, and F. Noack, ibid 35, 3492 (2010)] to provide intense sub-50 fs vacuum ultraviolet laser pulses we have performed the first real time study of ultrafast, photo-induced dynamics in the electronically excited A-tilde-state of water clusters (H{sub 2}O){sub n} and (D{sub 2}O){sub n}, n = 2-10. Three relevant time scales, 1.8-2.5, 10-30, and 50-150 fs, can be distinguished which - guided by the available theoretical results - are attributed to H (D)-ejection, OH (OD) dissociation, and a nonadiabatic transition through a conical intersection, respectively. While a direct quantitative comparison is only very preliminary, the present results provide a crucial test for future modeling of excited state dynamics in water clusters, and should help to unravel some of the many still unresolved puzzles about water.

  6. Hydrogeology, geochemistry, and quality of water of The Basin and Oak Spring areas of the Chisos Mountains, Big Bend National Park, Texas

    USGS Publications Warehouse

    Baker, E.T.; Buszka, P.M.

    1993-01-01

    Water-chemistry data, hydrochemical facies, and isotopic data also indicate that water from Oak Spring originates principally from precipitation onto the land surface of the Oak Spring area. Tritium data indicate that Oak Spring water is "modern," with an average age of recharge less than 14 years. The flow rates recorded almost continuously at Oak Spring beginning in December 1986 show a close relation between precipitation and discharge. The highest recorded spring flow of 167 gallons per minute in December 1986 is attributed to record high precipitation in the area during 1986. The lowest recorded flow of 22.4 gallons per minute, in December 1989, followed a period of 20 out of 26 months of below-normal precipitation. Flow at Oak Spring typically lags behind precipitation by about 1 month. This fairly rapid response indicates the spring is fed by a shallow aquifer having good permeability and effective recharge areas with the ability to absorb precipitation rapidly.

  7. Lagrangian water quality dynamics in the San Luis Drain, California.

    NASA Astrophysics Data System (ADS)

    Volkmar, E. C.; Dahlgren, R. A.; Stringfellow, W. T.; Henson, S. S.; Borglin, S. E.; Kendall, C.

    2007-12-01

    Integration of temporal changes in biological and water quality constituents during downstream transport is critical to understanding aquatic ecosystem and biogeochemical dynamics of rivers, estuaries, and the near- coastal waters into which rivers flow. Changes in chemical, physical, and biological water quality constituents during downstream transport can be evaluated by following a specific parcel of water, known as a Lagrangian study. The objective of this study was to differentiate changes in water quality constituents occurring within a parcel of water as it travels downstream to the changes observed at a fixed sampling location. We sampled a parcel of agricultural drainage water as it traveled downstream for 84 h in a concrete-lined channel (San Luis Drain in San Joaquin Valley) with no additional water inputs or outputs. The Lagrangian sampling occurred in August 2006 and June 2007. Data from the Lagrangian study was compared to data collected at a fixed point using an automatic pump sampler and water quality sonde. Fluorescence (a measure of algal pigments), dissolved oxygen, temperature, pH, and conductivity were measured every 30 minutes, as well as collecting grab samples every 2 h for nutrient and suspended sediment analyses. Sinusoidal diel (24 h) patterns were observed for dissolved oxygen, pH, and temperature within the parcel of water. Algal pigments, nutrients, suspended solids, and turbidity did not exhibit sinusoidal diel patterns, generally observed at a fixed sampling location. The diel patterns observed indicated changes that would occur during downstream transport. Algal pigments showed a rapid day time increase during the first 24 to 48 h followed by a plateau or decrease for the remainder of the study. Algal growth was apparent each day during the study, as measured by increasing dissolved oxygen concentrations, in spite of non-detectable phosphate concentrations (<5 ppb) and nearly complete consumption of soluble silica during the 2007

  8. Solvation structures and dynamics of alkaline earth metal halides in supercritical water: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Keshri, Sonanki; Mandal, Ratnamala; Tembe, B. L.

    2016-09-01

    Constrained molecular dynamics simulations of alkaline earth metal halides have been carried out to investigate their structural and dynamical properties in supercritical water. Potentials of mean force (PMFs) for all the alkaline earth metal halides in supercritical water have been computed. Contact ion pairs (CIPs) are found to be more stable than all other configurations of the ion pairs except for MgI2 where solvent shared ion pair (SShIP) is more stable than the CIP. There is hardly any difference in the PMFs between the M2+ (M = Mg, Ca, Sr, Ba) and the X- (X = F, Cl, Br, I) ions whether the second X- ion is present in the first coordination shell of the M2+ ion or not. The solvent molecules in the solvation shells diffuse at a much slower rate compared to the bulk. Orientational distribution functions of solvent molecules are sharper for smaller ions.

  9. Structure and dynamics in concentrated, amorphous carbohydrate--water systems by molecular dynamics simulation

    SciTech Connect

    Roberts, C.J.; Debenedetti, P.G.

    1999-08-26

    The authors report results from molecular simulations of binary aqueous solutions of the carbohydrate stereoisomers, {beta}-D-glucose, {beta}-D-mannose, and D-fructose over a concentration range from zero to 80 wt % carbohydrate at 300 and 270 K. It is found that increasing carbohydrate concentration has a number of striking effects on the microscopic structure and dynamics of these solutions, including (1) a percolation threshold for connected water clusters at ca. 60 wt % carbohydrate, (2) a maximum in the hydrogen bond network strength and degree of ordering, as a function of carbohydrate concentration, at ca. 29 wt %, and (3) activated or hopping dynamics in the translational diffusion of water due to the influence of (1) and (2). There are appreciable differences in the magnitudes of these effects as a function of sugar type for the three stereoisomers studied. The relevance of these results is discussed in the context of the efficacy of sugars in biopreservation and lyophilization applications.

  10. Hydrogeology and geochemistry of acid mine drainage in ground water in the vicinity of Penn Mine and Camanche Reservoir, Calaveras County, California; first-year summary

    USGS Publications Warehouse

    Hamlin, S.N.; Alpers, C.N.

    1995-01-01

    Acid drainage from the Penn Mine in Calaveras County, California, has caused contamination of ground water between Mine Run Dam and Camanche Reservoir. The Penn Mine was first developed in the 1860's primarily for copper and later produced lesser amounts of zinc, lead, silver, and gold from steeply dipping massive sulfide lenses in metamorphic rocks. Surface disposal of sulfidic waste rock and tailings from mine operations has produced acidic drainage with pH values between 2.3 and 2.7 and elevated concentrations of sulfate and metals, including copper, zinc, cadmium, iron, and aluminum. During the mine's operation and after its subsequent abandonment in the late 1950's, acid mine drainage flowed down Mine Run into the Mokelumne River. Construction of Camanche Dam in 1963 flooded part of the Mokelumne River adjacent to Penn Mine. Surface-water diversions and unlined impoundments were constructed at Penn Mine in 1979 to reduce runoff from the mine, collect contaminated surface water, and enhance evaporation. Some of the contaminated surface water infiltrates the ground water and flows toward Camanche Reservoir. Ground- water flow in the study area is controlled by the local hydraulic gradient and the hydraulic characteristics of two principal rock types, a Jurassic metavolcanic unit and the underlying Salt Spring slate. The hydraulic gradient is west from Mine Run impoundment toward Camanche Reservoir. The median hydraulic conductivity was about 10 to 50 times higher in the metavolcanic rock (0.1 foot per day) than in the slate (0.002 to 0.01 foot per day); most flow occurs in the metavolcanic rock where hydraulic conductivity is as high as 50 feet per day in two locations. The contact between the two rock units is a fault plane that strikes N20?W, dips 20?NE, and is a likely conduit for ground-water flow, based on down-hole measurements with a heatpulse flowmeter. Analyses of water samples collected during April 1992 provide a comprehensive characterization of

  11. The interplay between dynamic heterogeneities and structure of bulk liquid water: A molecular dynamics simulation study

    SciTech Connect

    Demontis, Pierfranco; Suffritti, Giuseppe B.; Gulín-González, Jorge; Sant, Marco

    2015-06-28

    In order to study the interplay between dynamical heterogeneities and structural properties of bulk liquid water in the temperature range 130–350 K, thus including the supercooled regime, we use the explicit trend of the distribution functions of some molecular properties, namely, the rotational relaxation constants, the atomic mean-square displacements, the relaxation of the cross correlation functions between the linear and squared displacements of H and O atoms of each molecule, the tetrahedral order parameter q and, finally, the number of nearest neighbors (NNs) and of hydrogen bonds (HBs) per molecule. Two different potentials are considered: TIP4P-Ew and a model developed in this laboratory for the study of nanoconfined water. The results are similar for the dynamical properties, but are markedly different for the structural characteristics. In particular, for temperatures higher than that of the dynamic crossover between “fragile” (at higher temperatures) and “strong” (at lower temperatures) liquid behaviors detected around 207 K, the rotational relaxation of supercooled water appears to be remarkably homogeneous. However, the structural parameters (number of NNs and of HBs, as well as q) do not show homogeneous distributions, and these distributions are different for the two water models. Another dynamic crossover between “fragile” (at lower temperatures) and “strong” (at higher temperatures) liquid behaviors, corresponding to the one found experimentally at T{sup ∗} ∼ 315 ± 5 K, was spotted at T{sup ∗} ∼ 283 K and T{sup ∗} ∼ 276 K for the TIP4P-Ew and the model developed in this laboratory, respectively. It was detected from the trend of Arrhenius plots of dynamic quantities and from the onset of a further heterogeneity in the rotational relaxation. To our best knowledge, it is the first time that this dynamical crossover is detected in computer simulations of bulk water. On the basis of the simulation results, the possible

  12. Bottom water production variability in the Ross Sea slope during the Late-Pleistocene-Holocene as revealed by benthic foraminifera and sediment geochemistry

    NASA Astrophysics Data System (ADS)

    Asioli, A.; Langone, L.; Tateo, F.; Giannossi, M. L.; Giglio, F.; Summa, V.; Piva, A.; Ridente, D.; Trincardi, F.

    2009-04-01

    The Antarctic area produces bottom waters that ventilate the vast majority of the deep basins in the rest of the world ocean. The rate of formation in the source area and the strength of these cold bottom waters affect their flow toward the equator and are key factors affecting the Global Thermohaline Circulation during modern and past climate conditions. We present the results of a multidisciplinary study carried out on a core collected in 2377m of water depth on the slope off the Drygalski Basin (Ross Sea), along the modern path of the bottom waters. The goal of this research is to detect a qualitative signal of possible changes in the rate of bottom water production during the Late Pleistocene-Holocene by integrating micropaleontological and geochemical proxies. The micropaleontological signal is represented by the quantitative and qualitative variations of the agglutinated benthic foraminifera assemblages, while the amount of TOC, nitrogen, δ13C, δ15N, biogenic silica, CaCO3 in the sediment, along with the bulk rock mineralogy, provide information on the paleoproductivity and allow reconstruction of changes in the paleocirculation. The chronology is supported by 14C AMS datings on organic matter. Although this study is still in progress, the results obtained allow the following observations: 1) the Holocene sequence includes a major turnover around 8-8.5 calib kyr BP, leading to reduced nutrient utilization, probably reflecting an increased nutrient supply induced by an enhanced Upper Circumpolar Deep Water upwelling; 2) within this general context, the total concentration of benthic foraminifera preserved in the fossil component records millennial scale cycles of variable amplitude after 8.5 calib kyr BP and to present time. This oscillatory trend is paralleled by other parameters, such as the magnetic susceptibility, the dry density, the sheet silicates and the δ15N; 3) minima in foraminifera concentration reflect relatively increased dissolution, weaker

  13. Femtosecond dynamics of a cardiotonic medicine (milrinone) in neutral water

    NASA Astrophysics Data System (ADS)

    Gil, M.; Douhal, A.

    2006-09-01

    Milrinone is a medicine used to attenuate heart attack disease. Understanding its interaction with water is of importance for the knowledge of its stability and related phenomena. This intimate information requires the unraveling of the dynamics under the physiological conditions. Here we report the first study of ultrafast processes of this medicine. We show that S 2 relaxation of the keto structure (K) occurs in ˜150 fs and the intramolecular-charge transfer reaction in less than 100 fs to produce a relaxed CT-K state. An observed ˜10 ps decay is assigned to vibrational relaxation/cooling and twisting in the formed CT-K.

  14. Preliminary report on mercury geochemistry of placer gold dredge tailings, sediments, bedrock, and waters in the Clear Creek restoration area, Shasta County, California

    USGS Publications Warehouse

    Ashley, Roger P.; Rytuba, James J.; Rogers, Ronald; Kotlyar, Boris B.; Lawler, David

    2002-01-01

    Clear Creek, one of the major tributaries of the upper Sacramento River, drains the eastern Trinity Mountains. Alluvial plain and terrace gravels of lower Clear Creek, at the northwest edge of the Sacramento Valley, contain placer gold that has been mined since the Gold Rush by various methods including dredging. In addition, from the 1950s to the 1980s aggregate-mining operations removed gravel from the lower Clear Creek flood plain. Since Clear Creek is an important stream for salmon production, a habitat restoration program is underway to repair damage from mining and improve conditions for spawning. This program includes using dredge tailings to fill in gravel pits in the flood plain, raising the concern that mercury lost to these tailings in the gold recovery process may be released and become available to biota. The purposes of our study are to determine concentrations and speciation of mercury in sediments, tailings, and water in the lower Clear Creek area, and to determine its mobility. Mercury concentrations in bedrock and unmined gravels both within and above the mined area are low, and are taken to represent background concentrations. Bulk mercury values in flood-plain sediments and dry tailings are elevated to several times these background concentrations. Mercury in sediments and tailings is associated with fine size fractions. Although methylmercury levels are generally low in sediments, shallow ponds in the flood plain may have above-normal methylation potential. Stream waters in the area show low mercury and methylmercury levels. Ponds with elevated methylmercury in sediments have more methylmercury in their waters as well. One seep in the area is highly saline, and enriched in mercury, lithium, and boron, similar to connate waters that are expelled along thrust faults to the south on the west side of the Sacramento Valley. This occurrence suggests that mercury in waters may at least in part be from sources other than placer mining.

  15. The Widom line and dynamical crossover in supercritical water: Popular water models versus experiments

    NASA Astrophysics Data System (ADS)

    Corradini, D.; Rovere, M.; Gallo, P.

    2015-09-01

    In a previous study [Gallo et al., Nat. Commun. 5, 5806 (2014)], we have shown an important connection between thermodynamic and dynamical properties of water in the supercritical region. In particular, by analyzing the experimental viscosity and the diffusion coefficient obtained in simulations performed using the TIP4P/2005 model, we have found that the line of response function maxima in the one phase region, the Widom line, is connected to a crossover from a liquid-like to a gas-like behavior of the transport coefficients. This is in agreement with recent experiments concerning the dynamics of supercritical simple fluids. We here show how different popular water models (TIP4P/2005, TIP4P, SPC/E, TIP5P, and TIP3P) perform in reproducing thermodynamic and dynamic experimental properties in the supercritical region. In particular, the comparison with experiments shows that all the analyzed models are able to qualitatively predict the dynamical crossover from a liquid-like to a gas-like behavior upon crossing the Widom line. Some of the models perform better in reproducing the pressure-temperature slope of the Widom line of supercritical water once a rigid shift of the phase diagram is applied to bring the critical points to coincide with the experimental ones.

  16. The Widom line and dynamical crossover in supercritical water: Popular water models versus experiments

    SciTech Connect

    Corradini, D.; Rovere, M.; Gallo, P.

    2015-09-21

    In a previous study [Gallo et al., Nat. Commun. 5, 5806 (2014)], we have shown an important connection between thermodynamic and dynamical properties of water in the supercritical region. In particular, by analyzing the experimental viscosity and the diffusion coefficient obtained in simulations performed using the TIP4P/2005 model, we have found that the line of response function maxima in the one phase region, the Widom line, is connected to a crossover from a liquid-like to a gas-like behavior of the transport coefficients. This is in agreement with recent experiments concerning the dynamics of supercritical simple fluids. We here show how different popular water models (TIP4P/2005, TIP4P, SPC/E, TIP5P, and TIP3P) perform in reproducing thermodynamic and dynamic experimental properties in the supercritical region. In particular, the comparison with experiments shows that all the analyzed models are able to qualitatively predict the dynamical crossover from a liquid-like to a gas-like behavior upon crossing the Widom line. Some of the models perform better in reproducing the pressure-temperature slope of the Widom line of supercritical water once a rigid shift of the phase diagram is applied to bring the critical points to coincide with the experimental ones.

  17. Native sulfur, sulfates and sulfides from the active Campi Flegrei volcano (southern Italy): Genetic environments and degassing dynamics revealed by mineralogy and isotope geochemistry

    NASA Astrophysics Data System (ADS)

    Piochi, Monica; Mormone, Angela; Balassone, Giuseppina; Strauss, Harald; Troise, Claudia; De Natale, Giuseppe

    2015-10-01

    We investigated sulfur-bearing minerals from the Campi Flegrei caldera, southern Italy, in relation to the increase of hydrothermal activity phenomena since 2006, aimed at providing insights into the volcanic system dynamics. Mineral encrustations and muds were sampled between 2013 and 2015 at the long-standing degassing crater of the Solfatara tuff cone and its recently restless north-eastern Pisciarelli slope. Deep-seated sulfides were further separated from two drill cores (AGIP's Mofete boreholes: 1500 m and 2695 m depth). The mineral assemblage and texture of sampled encrustations were determined by X-ray diffraction, optical and scanning electron microscopy and X-ray microanalysis by energy dispersive spectrometry. Native sulfur and alunite dominate among the newly formed mineral phases. Other minerals are mostly alunogen, and locally pickeringite, potassium alum, hematite and pyrite. Mereiterite and amarillite sporadically occur. The mud pools are rich in gypsum, potassium alum and pyrite. Quartz and argillic phases, locally with analcime, are dispersed in the outcropping rocks. δ34S values were determined for shallow subsurface native sulfur (- 5.5 to 0.0‰) and alunite (- 1.7 to - 0.2‰), as well as for the deep-seated pyrite (3.3 to 7.4‰ in the depth range:1500-2695 m). δ18O values were measured for shallow native alunite (4.2 to 7.0‰). Pisciarelli alunite was finally analyzed for its 87Sr/86Sr ratio and 143Nd/144Nd ratios (0.707517 ± 6 and 0.512459 ± 6, respectively). Textural and isotopic data constrain the genesis of alunite at the expense of K-feldspars through rock alteration by hydrothermal fluids. We suggest that the caldera is a low-sulfidation system hosting acid-sulfate deposits in its active degassing area. The acid-sulfate environment developed on an argillitic facies that thins outwards and is characteristic for steam-heated and magmatic-steam environments. These environments developed in relation to the fractured settings that

  18. Supply-based dynamic Ramsey pricing: Avoiding water shortages

    NASA Astrophysics Data System (ADS)

    Saǧlam, Yiǧit

    2015-01-01

    In many countries, current water-pricing policies are dictated by the sole objective of financial breaking even. This results in large withdrawals, which are not sustainable in the long run, hence not optimal. In this paper, we derive the optimal dynamic pricing policy, which targets efficient distribution while breaking even through a rebate scheme. Using data from Turkey, we estimate the demand for water by user groups. We carry out simulations to compare the effects of the current and optimal pricing policies on the frequency and severity of shortages. We find that, under the policy of break-even prices, the supplier runs into a shortage every 8 years. In contrast, if the prices were to set optimally, shortages would be practically nonexistent over the next century.

  19. Dynamic criteria of plankton jumping out of water

    PubMed Central

    Kim, Seong Jin; Hasanyan, Jalil; Gemmell, Brad J.; Lee, Sungyon; Jung, Sunghwan

    2015-01-01

    In nature, jumping out of water is a behaviour commonly observed in aquatic species to either escape from predators or hunt prey. However, not all aquatic species are capable of jumping out, especially small organisms whose length scales are comparable to the capillary length (approx. 2.7 mm for water). Some aquatic animals smaller than the capillary length are able to jump out while others are not, as observed in some marine copepods. To understand the dynamics of jumping out of the water–air interface, we perform physical experiments by shooting a spherical particle towards the liquid–air interface from below. Experimental results show that the particle either penetrates or bounces back from the interface, depending on the particle and fluid properties, and the impact velocity. The transition from bouncing to penetration regimes, which is theoretically predicted based on a particle force balance, is in good agreement with both physical experiments and plankton behavioural data. PMID:26468066

  20. An automated dynamic water vapor permeation test method

    NASA Astrophysics Data System (ADS)

    Gibson, Phillip; Kendrick, Cyrus; Rivin, Donald; Charmchii, Majid; Sicuranza, Linda

    1995-05-01

    This report describes an automated apparatus developed to measure the transport of water vapor through materials under a variety of conditions. The apparatus is more convenient to use than the traditional test methods for textiles and clothing materials, and allows one to use a wider variety of test conditions to investigate the concentration-dependent and nonlinear transport behavior of many of the semipermeable membrane laminates which are now available. The dynamic moisture permeation cell (DMPC) has been automated to permit multiple setpoint testing under computer control, and to facilitate investigation of transient phenomena. Results generated with the DMPC are in agreement with and of comparable accuracy to those from the ISO 11092 (sweating guarded hot plate) method of measuring water vapor permeability.

  1. Discovery Venera surface: Atmosphere geochemistry experiments mission concept

    NASA Technical Reports Server (NTRS)

    Surkov, Yuri A.; Head, James W.; Kremnev, Roald; Nock, K. T.

    1993-01-01

    The phenomenal increase in our understanding of Venus provided by the Magellan Mission has raised a series of focused, fundamental scientific questions about the geochemistry of the surface of Venus, the nature of the lower atmosphere, and the relationship of the lower atmosphere and surface. First, surface geochemical measurements from the Venera/Vega spacecraft showed that widely spaced regions of the venusian plains are made of basalts; thus basalts are significant and may be the only component of the venusian crust. But we lack information on the composition of several key elements of Venus geology: (1) Tessera terrain (which may be outcrops of continental-like non-basaltic crustal material) and steep-sided domes/festoons are promising candidates for non-basaltic geochemically evolved material. The composition of the lower part of the Venusian crust is unknown: however, ejecta from large venusian craters provides us with the possibility of sampling this material on the surface; (2) bulk chemistry (structure and dynamics) of the venusian atmosphere are known. The altitude profiles of water vapor content and minor admixtures relevant to redox conditions in the lower atmosphere (less than 20 km altitude) remain uncertain. Lack of that knowledge means that we do not understand the fine chemical structure of the main mass of the Venusian atmosphere; and (3) thermodynamic models predict that igneous materials on the surface of Venus should react with gases of the venusian atmosphere. But because the water vapor content and redox conditions in the lower atmosphere are not well known, we do not understand the nature of venusian weathering: oxidation, sulfatization, carbonatization, and hydration. The answers to these questions are critical to the understanding of Venus, the most Earth-like of the terrestrial planets.

  2. Water savings potentials of irrigation systems: dynamic global simulation

    NASA Astrophysics Data System (ADS)

    Jägermeyr, J.; Gerten, D.; Heinke, J.; Schaphoff, S.; Kummu, M.; Lucht, W.

    2015-04-01

    Global agricultural production is heavily sustained by irrigation, but irrigation system efficiencies are often surprisingly low. However, our knowledge of irrigation efficiencies is mostly confined to rough indicative estimates for countries or regions that do not account for spatio-temporal heterogeneity due to climate and other biophysical dependencies. To allow for refined estimates of global agricultural water use, and of water saving and water productivity potentials constrained by biophysical processes and also non-trivial downstream effects, we incorporated a dynamic representation of the three major irrigation systems (surface, sprinkler, and drip) into a process-based bio- and agrosphere model, LPJmL. Based on this enhanced model we provide a gridded worldmap of dynamically retrieved irrigation efficiencies reflecting differences in system types, crop types, climatic and hydrologic conditions, and overall crop management. We find pronounced regional patterns in beneficial irrigation efficiency (a refined irrigation efficiency indicator accounting for crop-productive water consumption only), due to differences in these features, with lowest values (< 30%) in South Asia and Sub-Saharan Africa and highest values (> 60%) in Europe and North America. We arrive at an estimate of global irrigation water withdrawal of 2396 km3 (2004-2009 average); irrigation water consumption is calculated to be 1212 km3, of which 511 km3 are non-beneficially consumed, i.e. lost through evaporation, interception, and conveyance. Replacing surface systems by sprinkler or drip systems could, on average across the world's river basins, reduce the non-beneficial consumption at river basin level by 54 and 76%, respectively, while maintaining the current level of crop yields. Accordingly, crop water productivity would increase by 9 and 15%, respectively, and by much more in specific regions such as in the Indus basin. This study significantly advances the global quantification of

  3. Dynamics of water trimer in femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Wang, Zhiping; Zhang, Fengshou; Xu, Xuefeng; Wang, Yanbiao; Qian, Chaoyi

    2016-07-01

    With the help of the time-dependent local-density approximation (TDLDA) coupled non-adiabatically to molecular dynamics (MD), we studied both the static properties and irradiation dynamics of water trimer subject to the short and intense femtosecond laser field. It is shown that the optimized geometry and the optical absorption strength of the water trimer accord well with results in literature. Three typical possible irradiated scenarios of water trimer which are “normal oscillation”, “dissociation and formation” and “pure OH dissociation” are exhibited by investigating the ionization and the level depletion related to electrons as well as the OH bonds, proton-transfer, the intermolecular distance and the kinetic energy connected with ions. In three scenarios, the behaviors of water trimer can be attributed to the sequential combination of responses of the electrons emission, the proton-transfer, OH vibration and rotation, OH dissociation and hydroxyl formation, respectively. The relevant time scales of the first proton-transfer and OH dissociation are identified as 13 fs and 10-20 fs, respectively. The study of kinetic energies of ions show that the kinetic energies of the remaining ions are all below 4.5 eV and outgoing hydrogen ions carry a kinetic energy about 5-12 eV. Furthermore, it is found that in the tunneling ionization situations the depletion is fairly shared between the various levels except the most deep occupied electronic level while in the multiphotonic ionization case the electron loss comes from all single-electron levels and the HOMO level contributes the most.

  4. Dynamic safety systems in U.S. light water reactors

    SciTech Connect

    Miller, D.W.; Adams, G.; Hajek, B.K.

    1995-12-31

    The use of dynamic rather than static logic in reactor safety function systems provides significant benefits in achieving a fail-safe design. Dynamic safety system (DSS) are based on such an approach that can be realized in hardware- and/or software-based products. AEA Technology has implemented a dynamic architecture in a number of systems licensed and used on commercial gas-cooled reactors, including those in Refs. 1, 2, and 3, where software elements are operationally verified by hardwired components. The principal software-based components in DSS are the trip algorithm computers (TACs) and vote algorithm computers (VACs). The TACs provide trip thresholds or trip requirements for individual plant variables or channels, The VACs provide voter requirements for groups of channels or plant variables as specified to initiate a trip condition. Continuous dynamic testing of instrument loops occurs by a programmed pattern of simulated trip/nontrip conditions, which exercise both software and hardware in the safety channel. The pattern recognition logic (PRL) is a hardware wired component programmed to maintain nontrip output only when this excepted time-dependent pattern is not changed. If a change occurs, as will happen if there is a plant trip condition or safety system failure - either hardware or software - then the PRL will initiate a trip condition. In summary, DSS provides for continuous dynamic testing of safety-related components and fail-safe operation. Through scenario testing of a DSS emulator on a boiling water reactor (BWR) plant training simulator it has been shown that DSS can provide a cost- effective safety system in BWR power plants. Experimental research has been completed that indicates the feasibility of extending DSS to include the plant nuclear instrumentation in the DSS test domain. This extension has the potential to decrease operating and maintenance (O&M) costs and improve fault diagnosis.

  5. Dynamics of groundwater-surface water interactions in urban streams

    NASA Astrophysics Data System (ADS)

    Musolff, A.; Schmidt, C.; Fleckenstein, J. H.

    2010-12-01

    In industrialized countries the majority of streams and rivers have been subject to changes in the hydrological regime and alteration of the channel morphology. Urban streams are typically characterized by “flashier” hydrographs as a result of more direct runoff from impervious surfaces. Channel structure and complexity are often impaired compared to pristine streams. As a consequence the potential for bedform-driven water flow in the streambed is reduced. The downward transport of oxygen by advective flow in the streambed is known to be of great ecological importance for the hyporheic macro and micro fauna and facilitates nutrient cycling and the degradation of organic pollutants. We studied the dynamics of groundwater-surface water exchange of two anthropogenically impacted streams in urban areas to examine the effects of variable hydrologic boundary conditions on water flux and redox conditions in the streambed. The first stream is fed by groundwater as well as storm-water from a large industrial area. Here, we monitored the variability of vertical hydraulic gradients, streambed temperature and redox conditions in the streambed over the course of 5 months. The second stream is frequently polluted by combined sewer overflows (CSO) from an urban watershed. Here, we measured the vertical hydraulic gradients, streambed temperature and electrical conductivity (EC) in the stream, the streambed and in the adjacent aquifer. Both streams are characterized by strong variations in hydraulic gradients due to the dynamic hydrographs as well as the variations in total head in the shallow aquifer. Therefore, magnitude and direction of water flux through the streambed changed significantly over time. At the first site long-term variations of redox conditions in the shallow streambed (0.1 m) were related to the direction of water fluxes. Downward water flow resulted in increased redox potentials. However, the high short-term variability of redox conditions could not be

  6. Mercury Geochemistry of Gold Placer Tailings, Sediments, Bedrock, and Waters in the Lower Clear Creek Area, Shasta County, California - Report of Investigations, 2001-2003

    USGS Publications Warehouse

    Ashley, Roger P.; Rytuba, James J.

    2008-01-01

    Clear Creek, one of the major tributaries of the upper Sacramento River, drains the eastern Trinity Mountains. Alluvial plain and terrace gravels of lower Clear Creek, at the northwest edge of the Sacramento Valley, contain placer gold that has been mined since the Gold Rush by various methods including hydraulic mining and dredging. In addition, from the 1950s to the 1980s aggregate-mining operations removed gravel from the lower Clear Creek flood plain. Since Clear Creek is an important stream for salmon production, a habitat restoration program is underway to repair damage from mining and improve conditions for spawning. This program includes moving dredge tailings to increase the area of spawning gravel and to fill gravel pits in the flood plain, raising the concern that mercury lost to these tailings in the gold recovery process may be released and become available to biota. The purposes of our study are to identify sources, transport, and dispersal of mercury in the lower Clear Creek area and identify environments in which bioavailable methylmercury is produced. Analytical data acquired include total mercury and methylmercury concentrations in sediments, tailings, and water. Mercury concentrations in bedrock and unmined gravels in and around the mined area are low and are taken to represent background concentrations. Bulk mercury values in placer mining tailings range from near-background in coarse dry materials to more than 40 times background in sands and silts exposed to mercury in sluices. Tailings are entrained in flood-plain sediments and active stream sediments; consequently, mercury concentrations in these materials range from background to about two to three times background. Mercury in sediments and tailings is associated with fine size fractions. The source of most of this mercury is historical gold mining in the Clear Creek watershed. Although methylmercury levels are low in most of these tailings and sediments, flood-plain sediment in shallow

  7. Charge-transfer water potential for solvated protein dynamics

    NASA Astrophysics Data System (ADS)

    Janardhanam, Vijay; Amo-Kwao, Godwin; Atlas, Susan R.

    2010-03-01

    Water plays a critical role in simulations of complex structure-function relationships such as the mechanochemistry of molecular motor proteins, wherein solvating water molecules interact with divalent cations such as Mg^+2, salt bridges, and polar or charged amino acids. Existing fixed-charge and fluctuating charge water models are inadequate in these environments, since they do not support reactive charge transfer with proper long-range dissociation behavior. The charge-transfer embedded atom method (CT-EAM) potential of Valone and Atlas was developed to address these challenges. It includes charge-polarized and ionic embedding terms that describe many-body atomistic interactions as a statistical ensemble of integer-charge excitations; background embedding densities are functions of local pseudoatom electron density distributions that integrate to non-integer charges and evolve dynamically under chemical potential equalization. Here we report first results from simulations of water using the CT-EAM potential of [1] and compare with characteristic properties of the liquid as determined via conventional force fields. [1] K. Muralidharan, S. M. Valone, and S.R. Atlas. arXiv:cond-mat/0705.0857v1, submitted.

  8. Chicago's water market: Dynamics of demand, prices and scarcity rents

    USGS Publications Warehouse

    Ipe, V.C.; Bhagwat, S.B.

    2002-01-01

    Chicago and its suburbs are experiencing an increasing demand for water from a growing population and economy and may experience water scarcity in the near future. The Chicago metropolitan area has nearly depleted its groundwater resources to a point where interstate conflicts with Wisconsin could accompany an increased reliance on those sources. Further, the withdrawals from Lake Michigan is limited by the Supreme Court decree. The growing demand and indications of possible scarcity suggest a need to reexamine the pricing policies and the dynamics of demand. The study analyses the demand for water and develops estimates of scarcity rents for water in Chicago. The price and income elasticities computed at the means are -0.002 and 0.0002 respectively. The estimated scarcity rents ranges from $0.98 to $1.17 per thousand gallons. The results indicate that the current prices do not fully account for the scarcity rents and suggest a current rate with in the range $1.53 to $1.72 per thousand gallons.

  9. OTEC Cold Water Pipe-Platform Subsystem Dynamic Interaction Validation

    SciTech Connect

    Varley, Robert; Halkyard, John; Johnson, Peter; Shi, Shan; Marinho, Thiago

    2014-05-09

    A commercial floating 100-megawatt (MW) ocean thermal energy conversion (OTEC) power plant will require a cold water pipe (CWP) with a diameter of 10-meter (m) and length of up to 1,000 m. The mass of the cold water pipe, including entrained water, can exceed the mass of the platform supporting it. The offshore industry uses software-modeling tools to develop platform and riser (pipe) designs to survive the offshore environment. These tools are typically validated by scale model tests in facilities able to replicate real at-sea meteorological and ocean (metocean) conditions to provide the understanding and confidence to proceed to final design and full-scale fabrication. However, today’s offshore platforms (similar to and usually larger than those needed for OTEC applications) incorporate risers (or pipes) with diameters well under one meter. Secondly, the preferred construction method for large diameter OTEC CWPs is the use of composite materials, primarily a form of fiber-reinforced plastic (FRP). The use of these material results in relatively low pipe stiffness and large strains compared to steel construction. These factors suggest the need for further validation of offshore industry software tools. The purpose of this project was to validate the ability to model numerically the dynamic interaction between a large cold water-filled fiberglass pipe and a floating OTEC platform excited by metocean weather conditions using measurements from a scale model tested in an ocean basin test facility.

  10. Supercooled water relaxation dynamics probed with heterodyne transient grating experiments

    NASA Astrophysics Data System (ADS)

    Taschin, Andrea; Bartolini, Paolo; Eramo, Roberto; Torre, Renato

    2006-09-01

    We report results from a heterodyne-detected transient grating experiment on liquid and supercooled water in a wide temperature range, from -17.5to90°C . The measured signal covers an extremely large time window with an excellent signal-to-noise ratio that enables the investigation in a single experiment of the sound speed and attenuation, thermal diffusivity, and temperature dependence of the dielectric constant. The experimental data clearly show the effect of the density and the temperature fluctuations on the water dielectric function. In order to describe the experimental results, we introduce a comprehensive hydrodynamic model taking into account the coupled density and temperature variables and their relevance in the definition of the spontaneous and forced dielectric variations. We use this model to describe the measured signal in transient grating experiments, including the heating and the electrostrictive sources produced by the laser excitation. The fitting procedure enables the safe extraction of several dynamic proprieties of liquid and supercooled water: the sound velocity and its damping, the thermal diffusivity, and the ratio between the dielectric thermodynamic derivatives. The measured parameters are compared to the literature data and discussed in the complex scenario of water physics.

  11. Molecular Dynamics of a Water-Lipid Bilayer Interface

    NASA Technical Reports Server (NTRS)

    Wilson, Michael A.; Pohorille, Andrew

    1994-01-01

    We present results of molecular dynamics simulations of a glycerol 1-monooleate bilayer in water. The total length of analyzed trajectories is 5ns. The calculated width of the bilayer agrees well with the experimentally measured value. The interior of the membrane is in a highly disordered fluid state. Atomic density profile, orientational and conformational distribution functions, and order parameters indicate that disorder increases toward the center of the bilayer. Analysis of out-of-plane thermal fluctuations of the bilayer surfaces occurring at the time scale of the present calculations reveals that the distribution of modes agrees with predictions of the capillary wave model. Fluctuations of both bilayer surfaces are uncorrelated, yielding Gaussian distribution of instantaneous widths of the membrane. Fluctuations of the width produce transient thinning defects in the bilayer which occasionally span almost half of the membrane. The leading mechanism of these fluctuations is the orientational and conformational motion of head groups rather than vertical motion of the whole molecules. Water considerably penetrates the head group region of the bilayer but not its hydrocarbon core. The total net excess dipole moment of the interfacial water points toward the aqueous phase, but the water polarization profile is non-monotonic. Both water and head groups significantly contribute to the surface potential across the interface. The calculated sign of the surface potential is in agreement with that from experimental measurements, but the value is markedly overestimated. The structural and electrical properties of the water-bilayer system are discussed in relation to membrane functions, in particular transport of ions and nonelectrolytes across membranes.

  12. Integrated system dynamics toolbox for water resources planning.

    SciTech Connect

    Reno, Marissa Devan; Passell, Howard David; Malczynski, Leonard A.; Peplinski, William J.; Tidwell, Vincent Carroll; Coursey, Don (University of Chicago, Chicago, IL); Hanson, Jason (University of New Mexico, Albuquerque, NM); Grimsrud, Kristine (University of New Mexico, Albuquerque, NM); Thacher, Jennifer (University of New Mexico, Albuquerque, NM); Broadbent, Craig (University of New Mexico, Albuquerque, NM); Brookshire, David; Chemak, Janie; Cockerill, Kristan; Aragon, Carlos , Socorro, NM); Hallett, Heather (New Mexico Univeristy of Technology and Mining , Socorro, NM); Vivoni, Enrique (New Mexico Univeristy of Technology and Mining , Socorro, NM); Roach, Jesse

    2006-12-01

    Public mediated resource planning is quickly becoming the norm rather than the exception. Unfortunately, supporting tools are lacking that interactively engage the public in the decision-making process and integrate over the myriad values that influence water policy. In the pages of this report we document the first steps toward developing a specialized decision framework to meet this need; specifically, a modular and generic resource-planning ''toolbox''. The technical challenge lies in the integration of the disparate systems of hydrology, ecology, climate, demographics, economics, policy and law, each of which influence the supply and demand for water. Specifically, these systems, their associated processes, and most importantly the constitutive relations that link them must be identified, abstracted, and quantified. For this reason, the toolbox forms a collection of process modules and constitutive relations that the analyst can ''swap'' in and out to model the physical and social systems unique to their problem. This toolbox with all of its modules is developed within the common computational platform of system dynamics linked to a Geographical Information System (GIS). Development of this resource-planning toolbox represents an important foundational element of the proposed interagency center for Computer Aided Dispute Resolution (CADRe). The Center's mission is to manage water conflict through the application of computer-aided collaborative decision-making methods. The Center will promote the use of decision-support technologies within collaborative stakeholder processes to help stakeholders find common ground and create mutually beneficial water management solutions. The Center will also serve to develop new methods and technologies to help federal, state and local water managers find innovative and balanced solutions to the nation's most vexing water problems. The toolbox is an important step toward achieving the technology development goals of this center.

  13. Dynamics of flood water infiltration and ground water recharge in hyperarid desert.

    PubMed

    Dahan, Ofer; Tatarsky, Boaz; Enzel, Yehouda; Kulls, Christoph; Seely, Mary; Benito, Gererdo

    2008-01-01

    A study on flood water infiltration and ground water recharge of a shallow alluvial aquifer was conducted in the hyperarid section of the Kuiseb River, Namibia. The study site was selected to represent a typical desert ephemeral river. An instrumental setup allowed, for the first time, continuous monitoring of infiltration during a flood event through the channel bed and the entire vadose zone. The monitoring system included flexible time domain reflectometry probes that were designed to measure the temporal variation in vadose zone water content and instruments to concurrently measure the levels of flood and ground water. A sequence of five individual floods was monitored during the rainy season in early summer 2006. These newly generated data served to elucidate the dynamics of flood water infiltration. Each flood initiated an infiltration event which was expressed in wetting of the vadose zone followed by a measurable rise in the water table. The data enabled a direct calculation of the infiltration fluxes by various independent methods. The floods varied in their stages, peaks, and initial water contents. However, all floods produced very similar flux rates, suggesting that the recharge rates are less affected by the flood stages but rather controlled by flow duration and available aquifer storage under it. Large floods flood the stream channel terraces and promote the larger transmission losses. These, however, make only a negligible contribution to the recharge of the ground water. It is the flood duration within the active streambed, which may increase with flood magnitude that is important to the recharge process.

  14. Ground-water quality and geochemistry of Las Vegas Valley, Clark County, Nevada, 1981-83; implementation of a monitoring network

    USGS Publications Warehouse

    Dettinger, M.D.

    1987-01-01

    As a result of rapid urban growth in Las Vegas Valley, rates of water use and wastewater disposal have grown rapidly during the last 25 years. Concern has developed over the potential water quality effects of this growth. The deep percolation of wastewater and irrigation return flow (much of which originates as imported water from Lake Mead), along with severe overdraft conditions in the principal aquifers of the valley, could combine to pose a long-term threat to groundwater quality. The quantitative investigations of groundwater quality and geochemical conditions in the valley necessary to address these concerns would include the establishment of data collection networks on a valley-wide scale that differ substantially from existing networks. The valley-wide networks would have a uniform areal distribution of sampling sites, would sample from all major depth zones, and would entail repeated sampling from each site. With these criteria in mind, 40 wells were chosen for inclusion in a demonstration monitoring network. Groundwater in the northern half of the valley generally contains 200 to 400 mg/L of dissolved solids, and is dominated by calcium, magnesium , and bicarbonate ions, reflecting a chemical equilibrium between the groundwater and the dominantly carbonate rocks in the aquifers of this area. The intermediate to deep groundwater in the southern half of the valley is of poorer quality (containing 700 to 1,500 mg/L of dissolved solids) and is dominated by calcium, magnesium, sulfate, and bicarbonate ions, reflecting the occurrence of other rock types including evaporite minerals among the still-dominant carbonate rocks in the aquifers of this part of the valley. The poorest quality groundwater in the valley is generally in the lowland parts of the valley in the first few feet beneath the water table, where dissolved solids concentrations range from 2,000 to > 7,000 mg/L , and probably reflects the effects of evaporite dissolution, secondary recharge, and

  15. Holistic irrigation water management approach based on stochastic soil water dynamics

    NASA Astrophysics Data System (ADS)

    Alizadeh, H.; Mousavi, S. J.

    2012-04-01

    Appreciating the essential gap between fundamental unsaturated zone transport processes and soil and water management due to low effectiveness of some of monitoring and modeling approaches, this study presents a mathematical programming model for irrigation management optimization based on stochastic soil water dynamics. The model is a nonlinear non-convex program with an economic objective function to address water productivity and profitability aspects in irrigation management through optimizing irrigation policy. Utilizing an optimization-simulation method, the model includes an eco-hydrological integrated simulation model consisting of an explicit stochastic module of soil moisture dynamics in the crop-root zone with shallow water table effects, a conceptual root-zone salt balance module, and the FAO crop yield module. Interdependent hydrology of soil unsaturated and saturated zones is treated in a semi-analytical approach in two steps. At first step analytical expressions are derived for the expected values of crop yield, total water requirement and soil water balance components assuming fixed level for shallow water table, while numerical Newton-Raphson procedure is employed at the second step to modify value of shallow water table level. Particle Swarm Optimization (PSO) algorithm, combined with the eco-hydrological simulation model, has been used to solve the non-convex program. Benefiting from semi-analytical framework of the simulation model, the optimization-simulation method with significantly better computational performance compared to a numerical Mote-Carlo simulation-based technique has led to an effective irrigation management tool that can contribute to bridging the gap between vadose zone theory and water management practice. In addition to precisely assessing the most influential processes at a growing season time scale, one can use the developed model in large scale systems such as irrigation districts and agricultural catchments. Accordingly

  16. Structure and Dynamics of Confined Alcohol-Water Mixtures.

    PubMed

    Bampoulis, Pantelis; Witteveen, Jorn P; Kooij, E Stefan; Lohse, Detlef; Poelsema, Bene; Zandvliet, Harold J W

    2016-07-26

    The effect of confinement between mica and graphene on the structure and dynamics of alcohol-water mixtures has been studied in situ and in real time at the molecular level by atomic force microscopy (AFM) at room temperature. AFM images reveal that the adsorbed molecules are segregated into faceted alcohol-rich islands on top of an ice layer on mica, surrounded by a pre-existing multilayer water-rich film. These faceted islands are in direct contact with the graphene surface, revealing a preferred adsorption site. Moreover, alcohol adsorption at low relative humidity (RH) reveals a strong preference of the alcohol molecules for the ordered ice interface. The growth dynamics of the alcohol islands is governed by supersaturation, temperature, the free energy of attachment of molecules to the island edge and two-dimensional (2D) diffusion. The measured diffusion coefficients display a size dependence on the molecular size of the alcohols, and are about 6 orders of magnitude smaller than the bulk diffusion coefficients, demonstrating the effect of confinement on the behavior of the alcohols. These experimental results provide new insights into the behavior of multicomponent fluids in confined geometries, which is of paramount importance in nanofluidics and biology. PMID:27337245

  17. Structure and Dynamics of Confined Alcohol-Water Mixtures.

    PubMed

    Bampoulis, Pantelis; Witteveen, Jorn P; Kooij, E Stefan; Lohse, Detlef; Poelsema, Bene; Zandvliet, Harold J W

    2016-07-26

    The effect of confinement between mica and graphene on the structure and dynamics of alcohol-water mixtures has been studied in situ and in real time at the molecular level by atomic force microscopy (AFM) at room temperature. AFM images reveal that the adsorbed molecules are segregated into faceted alcohol-rich islands on top of an ice layer on mica, surrounded by a pre-existing multilayer water-rich film. These faceted islands are in direct contact with the graphene surface, revealing a preferred adsorption site. Moreover, alcohol adsorption at low relative humidity (RH) reveals a strong preference of the alcohol molecules for the ordered ice interface. The growth dynamics of the alcohol islands is governed by supersaturation, temperature, the free energy of attachment of molecules to the island edge and two-dimensional (2D) diffusion. The measured diffusion coefficients display a size dependence on the molecular size of the alcohols, and are about 6 orders of magnitude smaller than the bulk diffusion coefficients, demonstrating the effect of confinement on the behavior of the alcohols. These experimental results provide new insights into the behavior of multicomponent fluids in confined geometries, which is of paramount importance in nanofluidics and biology.

  18. Global dynamical behaviors in a physical shallow water system

    NASA Astrophysics Data System (ADS)

    Tchakoutio Nguetcho, Aurélien Serge; Li, Jibin; Bilbault, Jean-Marie

    2016-07-01

    The theory of bifurcations of dynamical systems is used to investigate the behavior of travelling wave solutions in an entire family of shallow water wave equations. This family is obtained by a perturbative asymptotic expansion for unidirectional shallow water waves. According to the parameters of the system, this family can lead to different sets of known equations such as Camassa-Holm, Korteweg-de Vries, Degasperis and Procesi and several other dispersive equations of the third order. Looking for possible travelling wave solutions, we show that different phase orbits in some regions of parametric planes are similar to those obtained with the model of the pressure waves studied by Li and Chen. Many other exact explicit travelling waves solutions are derived as well, some of them being in perfect agreement with solutions obtained in previous works by researchers using different methods. When parameters are varied, the conditions under which the above solutions appear are also shown. The dynamics of singular nonlinear travelling system is completely determined for each of the above mentioned equations. Moreover, we define sufficient conditions leading to the existence of propagating wave solutions and demonstrate how and why travelling waves lose their smoothness and develop into solutions with compact support or breaking waves.

  19. Dynamics of Nano-Confined Water under Pressure

    SciTech Connect

    Omar Diallo, Souleymane; Jazdzewska, Monika; Palmer, Jeremy; Mamontov, Eugene; Gubbins, Dr. K. E.; Sliwinska-Bartkowiak, M

    2013-01-01

    We report a study of the effects of pressure on the diffusivity of water molecules confined in single- wall carbon nanotubes (SWNT) with average mean pore diameter of 16 A. The measurements were carried out using high-resolution neutron scattering, over the temperature range 220 T 260 K, and at two pressure conditions: ambient and elevated pressure. The high pressure data were collected at constant volume on cooling, with P varying from 1.92 kbar at temperature T = 260 K to 1.85 kbar at T = 220 K. Analysis of the observed dynamic structure factor S(Q, E) reveals the presence of two relaxation processes, a faster diffusion component (FC) associated with the motion of caged or restricted molecules, and a slower component arising from the free water molecules diffusing within the SWNT matrix. While the temperature dependence of the slow relaxation time exhibits a Vogel-Fulcher-Tammann law and is non-Arrhenius in nature, the faster component follows an Arrhenius exponential law at both pressure conditions. The application of pressure remarkably slows down the overall molecular dynamics, in agreement with previous observations, but most notably affects the slow relaxation. The faster relaxation shows marginal or no change with pressure within the experimental conditions.

  20. Geohydrology, geochemistry, and groundwater simulation (1992-2011) and analysis of potential water-supply management options, 2010-60, of the Langford Basin, California

    USGS Publications Warehouse

    Voronin, Lois M.; Densmore, Jill N.; Martin, Peter; Brush, Charles F.; Carlson, Carl S.; Miller, David M.

    2013-01-01

    Groundwater withdrawals began in 1992 from the Langford Basin within the Fort Irwin National Training Center (NTC), California. From April 1992 to December 2010, approximately 12,300 acre-feet of water (averaging about 650 acre-feet per year) has been withdrawn from the basin and transported to the adjacent Irwin Basin. Since withdrawals began, water levels in the basin have declined by as much as 40 feet, and the quality of the groundwater withdrawn from the basin has deteriorated. The U.S. Geological Survey collected geohydrologic data from Langford Basin during 1992–2011 to determine the quantity and quality of groundwater available in the basin. Geophysical surveys, including gravity, seismic refraction, and time-domain electromagnetic induction surveys, were conducted to determine the depth and shape of the basin, to delineate depths to the Quaternary-Tertiary interface, and to map the depth to the water table and changes in water quality. Data were collected from existing wells and test holes, as well as 11 monitor wells that were installed at 5 sites as part of this study. Water-quality samples collected from wells in the basin were used to determine the groundwater chemistry within the basin and to delineate potential sources of poor-quality groundwater. Analysis of stable isotopes of oxygen and hydrogen in groundwater indicates that present-day precipitation is not a major source of recharge to the basin. Tritium and carbon-14 data indicate that most of the basin was recharged prior to 1952, and the groundwater in the basin has an apparent age of 12,500 to 30,000 years. Recharge to the basin, estimated to be less than 50 acre-feet per year, has not been sufficient to replenish the water that is being withdrawn from the basin. A numerical groundwater-flow model was developed for the Langford Basin to better understand the aquifer system used by the Fort Irwin NTC as part of its water supply, and to provide a tool to help manage groundwater resources at

  1. Reservoir Characterization using geostatistical and numerical modeling in GIS with noble gas geochemistry

    NASA Astrophysics Data System (ADS)

    Vasquez, D. A.; Swift, J. N.; Tan, S.; Darrah, T. H.

    2013-12-01

    The integration of precise geochemical analyses with quantitative engineering modeling into an interactive GIS system allows for a sophisticated and efficient method of reservoir engineering and characterization. Geographic Information Systems (GIS) is utilized as an advanced technique for oil field reservoir analysis by combining field engineering and geological/geochemical spatial datasets with the available systematic modeling and mapping methods to integrate the information into a spatially correlated first-hand approach in defining surface and subsurface characteristics. Three key methods of analysis include: 1) Geostatistical modeling to create a static and volumetric 3-dimensional representation of the geological body, 2) Numerical modeling to develop a dynamic and interactive 2-dimensional model of fluid flow across the reservoir and 3) Noble gas geochemistry to further define the physical conditions, components and history of the geologic system. Results thus far include using engineering algorithms for interpolating electrical well log properties across the field (spontaneous potential, resistivity) yielding a highly accurate and high-resolution 3D model of rock properties. Results so far also include using numerical finite difference methods (crank-nicholson) to solve for equations describing the distribution of pressure across field yielding a 2D simulation model of fluid flow across reservoir. Ongoing noble gas geochemistry results will also include determination of the source, thermal maturity and the extent/style of fluid migration (connectivity, continuity and directionality). Future work will include developing an inverse engineering algorithm to model for permeability, porosity and water saturation.This combination of new and efficient technological and analytical capabilities is geared to provide a better understanding of the field geology and hydrocarbon dynamics system with applications to determine the presence of hydrocarbon pay zones (or

  2. The geochemistry of lithium-bearing geothermal water, Taupo Volcanic Zone, and shallow fluid processes in a very active silicic volcanic arc

    NASA Astrophysics Data System (ADS)

    Dean, A. S.; Hoskin, P. W.; Rudnick, R. L.; Liu, X.; Boseley, C.

    2011-12-01

    The Li abundances and isotopic systematics of Taupo Volcanic Zone (TVZ) geothermal fluids preserves a record of processes occurring within shallow portions of geothermal reservoirs as well as deeper portions of the arc crust. Understanding Li cycling and isotopic fractionation in TVZ geothermal systems contributes to a more refined understanding of physicochemical processes affecting New Zealand's geothermal resources. A comprehensive dataset of 73 samples was compiled, with samples collected from geothermal surface features (springs, spouters, geysers, etc.) and electric-power industry production wells, collectively representing18 geothermal fields across the breadth and width the TVZ. No comparable dataset of fluid analyses exists. Ion chromatography, AAS, and quadrupole ICP-MS analyses were done for Li, Cl-, SiO2, SO42- K, Na, Ca, Mg, B, Sr and Pb concentrations. Lithium abundance in geothermal fluids from the TVZ have a dataset-wide average of 5.9 mg/L and range 4 μg/L to 29 mg/L. The Li abundance and Li/Cl ratios for geothermal water and steam condensates vary systematically as a result of boiling, mixing, and water/rock reaction. Lithium abundance and Li/Cl ratios are, therefore, indicators of shallow (above 2.5 km) and locally variable reservoir processes. δ7Li analysis of 63 samples was performed at the University of Maryland, College Park. Data quality was controlled by measurement of L-SVEC as a calibration standard and by multiple analysis of selected samples. The average δ7Li value for TVZ geothermal fluids is -0.8%. Most δ7Li values for geothermal water fall within a small range of about -3% to+2% indicating similar processes are causing similar isotopic fractionation throughout the region. Considered together, Li aundances and δ7Li values, in combination with numerical models, indicate possible evolution pathways and water/rock reactions in TVZ geothermal systems. Models based on rocks and surface water analysis indicate that Li cycles and

  3. Effect of supercritical water shell on cavitation bubble dynamics

    NASA Astrophysics Data System (ADS)

    Shao, Wei-Hang; Chen, Wei-Zhong

    2015-05-01

    Based on reported experimental data, a new model for single cavitation bubble dynamics is proposed considering a supercritical water (SCW) shell surrounding the bubble. Theoretical investigations show that the SCW shell apparently slows down the oscillation of the bubble and cools the gas temperature inside the collapsing bubble. Furthermore, the model is simplified to a Rayleigh-Plesset-like equation for a thin SCW shell. The dependence of the bubble dynamics on the thickness and density of the SCW shell is studied. The results show the bubble dynamics depends on the thickness but is insensitive to the density of the SCW shell. The thicker the SCW shell is, the smaller are the wall velocity and the gas temperature in the bubble. In the authors’ opinion, the SCW shell works as a buffering agent. In collapsing, it is compressed to absorb a good deal of the work transformed into the bubble internal energy during bubble collapse so that it weakens the bubble oscillations. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174145 and 11334005).

  4. [Functionally-relevant conformational dynamics of water-soluble proteins].

    PubMed

    Novikov, G V; Sivozhelezov, V S; Shaĭtan, K V

    2013-01-01

    A study is reported of the functional-relevant dynamics of three typical water-soluble proteins: Calmodulin, Src-tyrosine kinase as well as repressor of Trp operon. Application of the state-of-art methods of structural bioinformatics allowed to identify dynamics seen in the X-ray structures of the investigated proteins associated with their specific biological functions. In addition, Normal Mode analysis technique revealed the most probable directions of the functionally-relevant motions for all that proteins were also predicted. Importantly, overall type of the motions observed on the lowest-frequency modes was very similar to the motions seen from the analysis of the X-ray data of the examined macromolecules. Thereby it was shown that the large-scale as well as local conformational motions of the proteins might be predetermined already at the level of their tertiary structures. In particular, the determining factor might be the specific fold of the alpha-helixes. Thus functionally-relevant in vivo dynamics of the investigated proteins might be evolutionally formed by means of natural selection at the level of the spatial topology. PMID:23705506

  5. Geochemistry of surface and subsurface waters in quartz-sandstones: significance for the geomorphic evolution of tepui table mountains (Gran Sabana, Venezuela)

    NASA Astrophysics Data System (ADS)

    Mecchia, Marco; Sauro, Francesco; Piccini, Leonardo; De Waele, Jo; Sanna, Laura; Tisato, Nicola; Lira, Jesus; Vergara, Freddy

    2014-04-01

    In situ measurements of discharge, pH, electric conductivity (EC), temperature, and SiO2 content have been carried out during five expeditions in the last 20 years on the summit plateaus, inside caves and along the rivers of the surrounding lowlands of three tepui massifs in Venezuela (Auyan, Roraima, and Chimanta). Additionally, detailed chemical analyses were performed on waters sampled in a newly discovered extensive quartz-sandstone cave system on the Auyan Tepui. Rock samples of the quartz-sandstone bedrock from different locations have been analysed to obtain their chemical composition with a wavelength dispersive X-ray fluorescence spectrometer. These data show that the majority of silica present in surface and subsurface water comes from dissolution of quartz and only in minor amount from hydrolysis of other silicate minerals. Probably the presence of a hardened crust of iron hydroxides limits the dissolution of silica on the top surface of tepuis. Dissolution in the subsurface, instead, is more significant and causes, in the long term, the “arenisation” of the quartz-sandstone and its subsequent removal by mechanical erosion. On the other hand, waters flowing on the arkosic rock outcropping on the lowland below the tepuis obtain their high dissolved silica content mainly from hydrolysis of silicates. The morphological evolution of these table mountains appears thus to be controlled mainly by the underground weathering of the quartz-sandstone, with the opening of deep fractures (grietas) and the collapse of large underground horizontal cave systems. Scarp retreat, instead, seems to be related to the higher weathering rate of the more arkosic formations underlying the quartz-sandstones.

  6. Multielement geochemistry of solid materials in geothermal systems and its applications. Part 1. Hot-water system at the Roosevelt Hot Springs KGRA, Utah

    SciTech Connect

    Bamford, R.W.; Christensen, O.D.; Capuano, R.M.

    1980-02-01

    Geochemical studies of the geothermal system at Roosevelt Hot Springs, Utah, have led to development of chemical criteria for recognition of major features of the system and to a three-dimensional model for chemical zoning in the system. Based on this improved level of understanding several new or modified geochemical exploration and assessment techniques have been defined and are probably broadly applicable to evaluation of hot-water geothermal systems. The main purpose of this work was the development or adaptation of solids geochemical exploration techniques for use in the geothermal environment. (MHR)

  7. Geohydrology, geochemistry, and groundwater simulation (1992-2011) and analysis of potential water-supply management options, 2010-60, of the Langford Basin, California

    USGS Publications Warehouse

    Voronin, Lois M.; Densmore, Jill N.; Martin, Peter; Brush, Charles F.; Carlson, Carl S.; Miller, David M.

    2013-01-01

    Groundwater withdrawals began in 1992 from the Langford Basin within the Fort Irwin National Training Center (NTC), California. From April 1992 to December 2010, approximately 12,300 acre-feet of water (averaging about 650 acre-feet per year) has been withdrawn from the basin and transported to the adjacent Irwin Basin. Since withdrawals began, water levels in the basin have declined by as much as 40 feet, and the quality of the groundwater withdrawn from the basin has deteriorated. The U.S. Geological Survey collected geohydrologic data from Langford Basin during 1992–2011 to determine the quantity and quality of groundwater available in the basin. Geophysical surveys, including gravity, seismic refraction, and time-domain electromagnetic induction surveys, were conducted to determine the depth and shape of the basin, to delineate depths to the Quaternary-Tertiary interface, and to map the depth to the water table and changes in water quality. Data were collected from existing wells and test holes, as well as 11 monitor wells that were installed at 5 sites as part of this study. Water-quality samples collected from wells in the basin were used to determine the groundwater chemistry within the basin and to delineate potential sources of poor-quality groundwater. Analysis of stable isotopes of oxygen and hydrogen in groundwater indicates that present-day precipitation is not a major source of recharge to the basin. Tritium and carbon-14 data indicate that most of the basin was recharged prior to 1952, and the groundwater in the basin has an apparent age of 12,500 to 30,000 years. Recharge to the basin, estimated to be less than 50 acre-feet per year, has not been sufficient to replenish the water that is being withdrawn from the basin. A numerical groundwater-flow model was developed for the Langford Basin to better understand the aquifer system used by the Fort Irwin NTC as part of its water supply, and to provide a tool to help manage groundwater resources at

  8. Single particle and pair dynamics in water-formic acid mixtures containing ionic and neutral solutes: nonideality in dynamical properties.

    PubMed

    Gupta, Rini; Chandra, Amalendu

    2008-05-14

    A series of molecular dynamics simulations of water-formic acid mixtures containing either an ionic solute or a neutral hydrophobic solute has been performed to study the extent of nonideality in the dynamics of these solutes for varying composition of the mixtures. The diffusion coefficients of the charged solutes, both cationic and anionic, are found to show nonideal behavior with variation of composition, and similar nonideality is also observed for the diffusion and orientational relaxation of solvent molecules in these mixtures. The diffusion coefficient of a neutral hydrophobic solute, however, decreases monotonically with increase in water concentration. We have also investigated some of the pair dynamical properties such as water-water and water-formic acid hydrogen bond relaxation and residence dynamics of water molecules in water and formic acid hydration shells. The lifetimes of water-water hydrogen bonds are found to be longer than those between formic acid carbonyl oxygen-water hydrogen bonds, whereas the lifetimes of formic acid hydroxyl hydrogen-water hydrogen bonds are longer than those of water-water hydrogen bonds. In general, the hydrogen bond lifetimes for both water-water and water-formic acid hydrogen bonds are found to decrease with increase in water concentration. Residence times of water molecules also show the same trend with increase in formic acid concentration. Interestingly, these pair dynamical properties show a monotonic dependence on composition without any maximum or minimum and behave almost ideally with respect to changes in the composition of the mixtures. The present calculations are performed with fixed-charge nonpolarizable models of the solvent and solute molecules without taking into account many-body polarization effects in an explicit manner. PMID:18532825

  9. Thermodynamic study on dynamic water vapor sorption in Sylgard-184.

    PubMed

    Harley, Stephen J; Glascoe, Elizabeth A; Maxwell, Robert S

    2012-12-01

    The dynamic and equilibrium water vapor sorption properties of Sylgard-184, a commercially available poly(dimethylsiloxane) elastomer (PDMS), were determined via gravimetric analysis from 30 to 70 °C. Described here is a methodology for quantitatively assessing how water vapor diffuses and ad/absorbs into polymeric materials that are traditionally considered hydrophobic. PDMS materials are frequently chosen for their moisture barrier properties; our results, however, demonstrate that moisture is able to penetrate the material over a range of temperatures and humidities. The sorption values measured here ranged from ca. 0.1 to 1.4 cm(3) (STP) H(2)O/g Sylgard. The isotherms exhibited sigmoidal character and were fit to a triple mode sorption model. Asymptotic behavior at low water activities was characterized using a Langmuir type adsorption model, linear behavior was fit to a Henry's law type dependence, and the convex portion at higher activities was fit with good agreement to Park's equation for pooling or clustering. The thermal dependence of these sorption modes was also explored and reported. The dynamics of the sorption process were fit to a Fickian model and effective diffusivities are reported along with corresponding activation energies. The diffusivity values measured here ranged from ca. 0.5 to 3.5 × 10(-5) cm(2)/s depending on the temperature and relative humidity. The concentration dependence of the diffusivity showed a direct correlation with the three modes of uptake obtained from the isotherms. Corrections to the diffusivities were calculated using existing models that take into account adsorption and pooling. PMID:23153278

  10. Observation of dynamic water microadsorption on Au surface

    SciTech Connect

    Huang, Xiaokang Gupta, Gaurav; Gao, Weixiang; Tran, Van; Nguyen, Bang; McCormick, Eric; Cui, Yongjie; Yang, Yinbao; Hall, Craig; Isom, Harold

    2014-05-15

    Experimental and theoretical research on water wettability, adsorption, and condensation on solid surfaces has been ongoing for many decades because of the availability of new materials, new detection and measurement techniques, novel applications, and different scales of dimensions. Au is a metal of special interest because it is chemically inert, has a high surface energy, is highly conductive, and has a relatively high melting point. It has wide applications in semiconductor integrated circuitry, microelectromechanical systems, microfluidics, biochips, jewelry, coinage, and even dental restoration. Therefore, its surface condition, wettability, wear resistance, lubrication, and friction attract a lot of attention from both scientists and engineers. In this paper, the authors experimentally investigated Au{sub 2}O{sub 3} growth, wettability, roughness, and adsorption utilizing atomic force microscopy, scanning electron microscopy, reflectance spectrometry, and contact angle measurement. Samples were made using a GaAs substrate. Utilizing a super-hydrophilic Au surface and the proper surface conditions of the surrounding GaAs, dynamic microadsorption of water on the Au surface was observed in a clean room environment. The Au surface area can be as small as 12 μm{sup 2}. The adsorbed water was collected by the GaAs groove structure and then redistributed around the structure. A model was developed to qualitatively describe the dynamic microadsorption process. The effective adsorption rate was estimated by modeling and experimental data. Devices for moisture collection and a liquid channel can be made by properly arranging the wettabilities or contact angles of different materials. These novel devices will be very useful in microfluid applications or biochips.

  11. Thermodynamic study on dynamic water vapor sorption in Sylgard-184.

    PubMed

    Harley, Stephen J; Glascoe, Elizabeth A; Maxwell, Robert S

    2012-12-01

    The dynamic and equilibrium water vapor sorption properties of Sylgard-184, a commercially available poly(dimethylsiloxane) elastomer (PDMS), were determined via gravimetric analysis from 30 to 70 °C. Described here is a methodology for quantitatively assessing how water vapor diffuses and ad/absorbs into polymeric materials that are traditionally considered hydrophobic. PDMS materials are frequently chosen for their moisture barrier properties; our results, however, demonstrate that moisture is able to penetrate the material over a range of temperatures and humidities. The sorption values measured here ranged from ca. 0.1 to 1.4 cm(3) (STP) H(2)O/g Sylgard. The isotherms exhibited sigmoidal character and were fit to a triple mode sorption model. Asymptotic behavior at low water activities was characterized using a Langmuir type adsorption model, linear behavior was fit to a Henry's law type dependence, and the convex portion at higher activities was fit with good agreement to Park's equation for pooling or clustering. The thermal dependence of these sorption modes was also explored and reported. The dynamics of the sorption process were fit to a Fickian model and effective diffusivities are reported along with corresponding activation energies. The diffusivity values measured here ranged from ca. 0.5 to 3.5 × 10(-5) cm(2)/s depending on the temperature and relative humidity. The concentration dependence of the diffusivity showed a direct correlation with the three modes of uptake obtained from the isotherms. Corrections to the diffusivities were calculated using existing models that take into account adsorption and pooling.

  12. Geochemistry of Inorganic Nitrogen in Waters Released from Coal-Bed Natural Gas Production Wells in the Powder River Basin, Wyoming

    USGS Publications Warehouse

    Smith, Richard L.; Repert, Deborah A.; Hart, Charles P.

    2009-01-01

    Water originating from coal-bed natural gas (CBNG) production wells typically contains ammonium and is often disposed via discharge to ephemeral channels. A study conducted in the Powder River Basin, Wyoming, documented downstream changes in CBNG water composition, emphasizing nitrogen-cycling processes and the fate of ammonium. Dissolved ammonium concentrations from 19 CBNG discharge points ranged from 95 to 527 µM. Within specific channels, ammonium concentrations decreased with transport distance, with subsequent increases in nitrite and nitrate concentrations. Removal efficiency, or uptake, of total dissolved inorganic nitrogen (DIN) varied between channel types. DIN uptake was greater in the gentle-sloped, vegetated channel as compared to the incised, steep, and sparsely vegetated channel and was highly correlated with diel patterns of incident light and dissolved oxygen concentration. In a larger main channel with multiple discharge inputs (n = 13), DIN concentrations were >300 µM, with pH > 8.5, after 5 km of transport. Ammonium represented 25-30% of the large-channel DIN, and ammonium concentrations remained relatively constant with time, with only a weak diel pattern evident. In July 2003, the average daily large-channel DIN load was 23 kg N day-1 entering the Powder River, an amount which substantially increased the total Powder River DIN load after the channel confluence. These results suggest that CBNG discharge may be an important source of DIN to western watersheds, at least at certain times of the year, and that net oxidation and/or removal is dependent upon the extent of contact with sediment and biomass, type of drainage channel, and time of day.

  13. Geochemistry of inorganic nitrogen in waters released from coal-bed natural gas production wells in the Powder River Basin, Wyoming.

    PubMed

    Smith, Richard L; Repert, Deborah A; Hart, Charles P

    2009-04-01

    Water originating from coal-bed natural gas (CBNG) production wells typically contains ammonium and is often disposed via discharge to ephemeral channels. A study conducted in the Powder River Basin, Wyoming, documented downstream changes in CBNG water composition, emphasizing nitrogen-cycling processes and the fate of ammonium. Dissolved ammonium concentrations from 19 CBNG discharge points ranged from 95 to 527 microM. Within specific channels, ammonium concentrations decreased with transport distance, with subsequent increases in nitrite and nitrate concentrations. Removal efficiency, or uptake, oftotal dissolved inorganic nitrogen (DIN) varied between channel types. DIN uptake was greater in the gentle-sloped, vegetated channel as compared to the incised, steep, and sparsely vegetated channel and was highly correlated with diel patterns of incident light and dissolved oxygen concentration. In a larger main channel with multiple discharge inputs (n=13), DIN concentrations were >300 microM, with pH > 8.5, after 5 km of transport. Ammonium represented 25-30% of the large-channel DIN, and ammonium concentrations remained relatively constant with time, with only a weak diel pattern evident. In July 2003, the average daily large-channel DIN load was 23 kg N day(-1) entering the Powder River, an amount which substantially increased the total Powder River DIN load after the channel confluence. These results suggest that CBNG discharge may be an important source of DIN to western watersheds, at least at certain times of the year, and that net oxidation and/or removal is dependent upon the extent of contact with sediment and biomass, type of drainage channel, and time of day.

  14. Geochemistry of inorganic nitrogen in waters released from coal-bed natural gas production wells in the powder river basin, wyoming

    USGS Publications Warehouse

    Smith, R.L.; Repert, D.A.; Hart, C.P.

    2009-01-01

    Water originating from coal-bed natural gas (CBNG) production wells typically contains ammonium and is often disposed via discharge to ephemeral channels. A. study conducted in the Powder River Basin, Wyoming, documented downstream changes in CBNG water composition, emphasizing nitrogen-cycling processes and the fate of ammonium. Dissolved ammonium concentrations from 19 CBNG discharge points ranged from 95 to 527 ??M. Within specific channels, ammonium concentrations decreased with transport distance, with subsequent increases in nitrite and nitrate concentrations. Removal efficiency, or uptake, of total dissolved inorganic nitrogen (DIN) varied between channel types. DIN uptake was greater in the gentle-sloped, vegetated channel as compared to the incised, steep, and sparsely vegetated channel and was highly correlated with diel patterns of incident light and dissolved oxygen concentration. In a larger main channel with multiple discharge inputs (n = 13), DIN concentrations were >300 ??M, with pH > 8.5, after 5 km of transport. Ammonium represented 25-30% of the large-channel DIN, and ammonium concentrations remained relatively constant with time, with only a weak diel pattern evident. In July 2003, the average daily large-channel DIN load was 23 kg N day-1 entering the Powder River, an amount which substantially increased the total Powder River DIN load after the channel confluence. These results suggest that CBNG discharge may be an important source of DIN to western watersheds, at least at certain times of the year, and that net oxidation and/or removal is dependent upon the extent of contact with sediment and biomass, type of drainage channel, and time of day. ?? 2009 American Chemical Society.

  15. Isotope geochemistry and fluxes of carbon and organic matter in tropical small mountainous river systems and adjacent coastal waters of the Caribbean

    USGS Publications Warehouse

    Moyer, Ryan; Bauer, James; Grottoli, Andrea

    2012-01-01

    Recent studies have shown that small mountainous rivers (SMRs) may act as sources of aged and/or refractory carbon (C) to the coastal ocean, which may increase organic C burial at sea and subsidize coastal food webs and heterotrophy. However, the characteristics and spatial and temporal variability of C and organic matter (OM) exported from tropical SMR systems remain poorly constrained. To address this, the abundance and isotopic character (δ13C and Δ14C) of the three major C pools were measured in two Puerto Rico SMRs with catchments dominated by different land uses (agricultural vs. non-agricultural recovering forest). The abundance and character of C pools in associated estuaries and adjacent coastal waters were also examined. Riverine dissolved and particulate organic C (DOC and POC, respectively) concentrations were highly variable with respect to land use and sampling month, while dissolved inorganic C (DIC) was significantly higher at all times in the agricultural catchment. In both systems, riverine DOC and POC ranged from modern to highly aged (2,340 years before present), while DIC was always modern. The agricultural river and irrigation canals contained very old DOC (1,184 and 2,340 years before present, respectively), which is consistent with findings in temperate SMRs and indicates that these tropical SMRs provide a source of aged DOC to the ocean. During months of high river discharge, OM in estuarine and coastal waters had C isotope signatures reflective of direct terrestrial input, indicating that relatively unaltered OM is transported to the coastal ocean at these times. This is also consistent with findings in temperate SMRs and indicates that C transported to the coastal ocean by SMRs may differ from that of larger rivers because it is exported from smaller catchments that have steeper terrains and fewer land-use types.

  16. Computational Fluid Dynamics Analysis of Canadian Supercritical Water Reactor (SCWR)

    NASA Astrophysics Data System (ADS)

    Movassat, Mohammad; Bailey, Joanne; Yetisir, Metin

    2015-11-01

    A Computational Fluid Dynamics (CFD) simulation was performed on the proposed design for the Canadian SuperCritical Water Reactor (SCWR). The proposed Canadian SCWR is a 1200 MW(e) supercritical light-water cooled nuclear reactor with pressurized fuel channels. The reactor concept uses an inlet plenum that all fuel channels are attached to and an outlet header nested inside the inlet plenum. The coolant enters the inlet plenum at 350 C and exits the outlet header at 625 C. The operating pressure is approximately 26 MPa. The high pressure and high temperature outlet conditions result in a higher electric conversion efficiency as compared to existing light water reactors. In this work, CFD simulations were performed to model fluid flow and heat transfer in the inlet plenum, outlet header, and various parts of the fuel assembly. The ANSYS Fluent solver was used for simulations. Results showed that mass flow rate distribution in fuel channels varies radially and the inner channels achieve higher outlet temperatures. At the outlet header, zones with rotational flow were formed as the fluid from 336 fuel channels merged. Results also suggested that insulation of the outlet header should be considered to reduce the thermal stresses caused by the large temperature gradients.

  17. (17)O NMR Investigation of Water Structure and Dynamics.

    PubMed

    Keeler, Eric G; Michaelis, Vladimir K; Griffin, Robert G

    2016-08-18

    The structure and dynamics of the bound water in barium chlorate monohydrate were studied with (17)O nuclear magnetic resonance (NMR) spectroscopy in samples that are stationary and spinning at the magic-angle in magnetic fields ranging from 14.1 to 21.1 T. (17)O NMR parameters of the water were determined, and the effects of torsional oscillations of the water molecule on the (17)O quadrupolar coupling constant (CQ) were delineated with variable temperature MAS NMR. With decreasing temperature and reduction of the librational motion, we observe an increase in the experimentally measured CQ explaining the discrepancy between experiments and predictions from density functional theory. In addition, at low temperatures and in the absence of (1)H decoupling, we observe a well-resolved (1)H-(17)O dipole splitting in the spectra, which provides information on the structure of the H2O molecule. The splitting arises because of the homogeneous nature of the coupling between the two (1)H-(17)O dipoles and the (1)H-(1)H dipole. PMID:27454747

  18. (17)O NMR Investigation of Water Structure and Dynamics.

    PubMed

    Keeler, Eric G; Michaelis, Vladimir K; Griffin, Robert G

    2016-08-18

    The structure and dynamics of the bound water in barium chlorate monohydrate were studied with (17)O nuclear magnetic resonance (NMR) spectroscopy in samples that are stationary and spinning at the magic-angle in magnetic fields ranging from 14.1 to 21.1 T. (17)O NMR parameters of the water were determined, and the effects of torsional oscillations of the water molecule on the (17)O quadrupolar coupling constant (CQ) were delineated with variable temperature MAS NMR. With decreasing temperature and reduction of the librational motion, we observe an increase in the experimentally measured CQ explaining the discrepancy between experiments and predictions from density functional theory. In addition, at low temperatures and in the absence of (1)H decoupling, we observe a well-resolved (1)H-(17)O dipole splitting in the spectra, which provides information on the structure of the H2O molecule. The splitting arises because of the homogeneous nature of the coupling between the two (1)H-(17)O dipoles and the (1)H-(1)H dipole.

  19. A review of progress in understanding the fluid geochemistry of the Cerro Prieto geothermal system

    USGS Publications Warehouse

    Truesdell, A.H.; Nehring, N.L.; Thompson, J.M.; Janik, C.J.; Coplen, T.B.

    1984-01-01

    Fluid geochemistry has played a major role in our present understanding of the Cerro Prieto geothermal system. Fluid chemical and isotopic compositions have been used to indicate the origin of water, salts and gases, original subsurface temperature and fluid flow, fluid-production mechanisms, and production-induced aquifer boiling and cold-water entry. The extensive geochemical data and interpretations for Cerro Prieto published from 1964 to 1981 are reviewed and discussed. Fluid geochemistry must continue to play an important role in the further development of the Cerro Prieto field. ?? 1984.

  20. Major Ion Geochemistry of Horseshoe Lake, Mammoth Lakes, California: Water Quality in a Region with Elevated CO2 from Sub-Surface Leakage

    NASA Astrophysics Data System (ADS)

    Santilena, R.; Szutu, D.; Ellis, A. S.; Khachikian, C. S.

    2010-12-01

    Tree-kill areas around Horseshoe Lake indicate how naturally high levels of carbon dioxide (CO2) emitted from a cooling magma chamber are affecting the ecosystem. CO2 leakage from geologically sequestered CO2 sites may have similar effects. Weathering processes and water quality changes are two other environmental impacts of high levels of CO2 leaking from subsurface CO2 reservoirs. This study’s focus was to conduct a geochemical study of Horseshoe Lake with emphasis on water chemistry to determine any quantifiable effects from the high release of volcanic CO2. We collected 22 water samples, including 5 samples from streams that drained into the lake. Two interior locations were sampled at the surface and at depths of 2-meter intervals. The interior lake samples showed increasing Mg and Ca concentrations from the surface to 12 m in depth, and increasing Sr and Si from the surface to 4 m in depth. Water samples were measured for temperature, conductivity, pH, alkalinity, and analyzed for major ions Ca2+, K+, Na+, Mg2+, Cl-, SO42-, and HCO3- (from alkalinity). Amounts of Al, Ca, K, Mg, Na, and high levels of Si from elemental data are consistent with waters in granitic environments. Temperature in the lakes and streams ranged from 3.5 to 16 °C, pH ranged from 5.9-7.2, conductivity ranged from 8.66 to 21.93 μS/cm, and alkalinity ranged from 0.137- 0.408 meq/L. A TSI Q-Trak™ measured soil and ambient CO2 concentrations in July and a Vernier LabQuest was used in August. A bottomless bottle was placed in the soil in a10cm deep hole with the probe inserted in the top. A probe about 1 m above ground measured the ambient CO2 concentrations. To determine the flux of soil CO2, concentrations were read over a 5-minute time period. CO2 gas concentrations in the tree kill area ranged from 600 to 1,700 ppm in ambient air, and over 99,000 ppm in the soil. Maximum readings were exceeded so actual values of CO2 in the soil are not known. The stream samples had a different

  1. Geochemistry of Groundwater in the Beaver and Camas Creek Drainage Basins, Idaho

    NASA Astrophysics Data System (ADS)

    Rattray, G.

    2013-12-01

    The U.S. Geological Survey, in cooperation with the U.S. Department of Energy, is studying the fate and transport of waste solutes in the eastern Snake River Plain (ESRP) aquifer at the Idaho National Laboratory (INL) in eastern Idaho. This effort requires an understanding of the natural and anthropogenic geochemistry of groundwater at the INL and of the important physical and chemical processes controlling the geochemistry. In this study, the USGS applied geochemical modeling to investigate the geochemistry of groundwater in the Beaver and Camas Creek drainage basins, which provide groundwater recharge to the ESRP aquifer underlying the northeastern part of the INL. Data used in this study include petrology and mineralogy from two sediment and three rock samples and water-quality analyses from four surface-water and 18 groundwater samples. The mineralogy of the sediment and rock samples was analyzed with X-ray diffraction and the mineralogy and petrology of the rock samples were examined in thin sections. The water samples were analyzed for field parameters, major ions, nutrients, dissolved organic carbon, trace elements, tritium, and the stable isotope ratios of hydrogen, oxygen, carbon, sulfur, and nitrogen. The groundwater geochemistry was influenced by reactions with rocks of the geologic terranes--carbonate rocks, rhyolite, basalt, evaporite deposits, and sediment comprised of all of these rocks. Agricultural practices near and south of Dubois and application of road anti-icing liquids on U.S. Interstate Highway15 were a source of nitrate, chloride, calcium, and magnesium to groundwater. Groundwater geochemistry was successfully modeled in the alluvial aquifer in Camas Meadows and the ESRP aquifer using the geochemical modeling code PHREEQC. The primary geochemical processes appear to be precipitation of calcite and dissolution of silicate minerals. Dissolution of evaporite minerals, associated with Pleistocene Lake Terreton, is an important contributor of

  2. Geochemistry of groundwater in the Beaver and Camas Creek drainage basins, eastern Idaho

    USGS Publications Warehouse

    Rattray, Gordon W.; Ginsbach, Michael L.

    2014-01-01

    The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, is studying the fate and transport of waste solutes in the eastern Snake River Plain (ESRP) aquifer at the Idaho National Laboratory (INL) in eastern Idaho. This effort requires an understanding of the natural and anthropogenic geochemistry of groundwater at the INL and of the important physical and chemical processes controlling the geochemistry. In this study, the USGS applied geochemical modeling to investigate the geochemistry of groundwater in the Beaver and Camas Creek drainage basins, which provide groundwater recharge to the ESRP aquifer underlying the northeastern part of the INL. Data used in this study include petrology and mineralogy from 2 sediment and 3 rock samples, and water-quality analyses from 4 surface-water and 18 groundwater samples. The mineralogy of the sediment and rock samples was analyzed with X-ray diffraction, and the mineralogy and petrology of the rock samples were examined in thin sections. The water samples were analyzed for field parameters, major ions, silica, nutrients, dissolved organic carbon, trace elements, tritium, and the stable isotope ratios of hydrogen, oxygen, carbon, sulfur, and nitrogen. Groundwater geochemistry was influenced by reactions with rocks of the geologic terranes—carbonate rocks, rhyolite, basalt, evaporite deposits, and sediment comprised of all of these rocks. Agricultural practices near and south of Dubois and application of road anti-icing liquids on U.S. Interstate Highway 15 were likely sources of nitrate, chloride, calcium, and magnesium to groundwater. Groundwater geochemistry was successfully modeled in the alluvial aquifer in Camas Meadows and the ESRP fractured basalt aquifer using the geochemical modeling code PHREEQC. The primary geochemical processes appear to be precipitation or dissolution of calcite and dissolution of silicate minerals. Dissolution of evaporite minerals, associated with Pleistocene Lake

  3. Water geochemistry of the Qiantangjiang River, East China: Chemical weathering and CO2 consumption in a basin affected by severe acid deposition

    NASA Astrophysics Data System (ADS)

    Liu, Wenjing; Shi, Chao; Xu, Zhifang; Zhao, Tong; Jiang, Hao; Liang, Chongshan; Zhang, Xuan; Zhou, Li; Yu, Chong

    2016-09-01

    The chemical composition of the Qiantangjiang River, the largest river in Zhejiang province in eastern China, was measured to understand the chemical weathering of rocks and the associated CO2 consumption and anthropogenic influences within a silicate-dominated river basin. The average total dissolved solids (TDS, 113 mg l-1) and total cation concentration (TZ+, 1357 μeq l-1) of the river waters are comparable with those of global major rivers. Ca2+ and HCO3- followed by Na2+ and SO42-, dominate the ionic composition of the river water. There are four major reservoirs (carbonates, silicates, atmospheric and anthropogenic inputs) contributing to the total dissolved load of the investigated rivers. The dissolved loads of the rivers are dominated by both carbonate and silicate weathering, which together account for about 76.3% of the total cationic load origin. The cationic chemical weathering rates of silicate and carbonate for the Qiantangjiang basin are estimated to be approximately 4.9 ton km-2 a-1 and 13.9 ton km-2 a-1, respectively. The calculated CO2 consumption rates with the assumption that all the protons involved in the weathering reaction are provided by carbonic acid are 369 × 103 mol km-2 a-1 and 273 × 103 mol km-2 a-1 by carbonate and silicate weathering, respectively. As one of the most severe impacted area by acid rain in China, H2SO4 from acid precipitation is also an important proton donor in weathering reactions. When H2SO4 is considered, the CO2 consumption rates for the river basin are estimated at 286 × 103 mol km-2 a-1 for carbonate weathering and 211 × 103 mol km-2 a-1 for silicate weathering, respectively. The results highlight that the drawdown effect of CO2 consumption by carbonate and silicate weathering can be largely overestimated if the role of sulfuric acid is ignored, especially in the area heavily impacted by acid deposition like Qiantangjiang basin. The actual CO2 consumption rates (after sulfuric acid weathering effect

  4. Coupling all-atom molecular dynamics simulations of ions in water with Brownian dynamics

    PubMed Central

    2016-01-01

    Molecular dynamics (MD) simulations of ions (K+, Na+, Ca2+ and Cl−) in aqueous solutions are investigated. Water is described using the SPC/E model. A stochastic coarse-grained description for ion behaviour is presented and parametrized using MD simulations. It is given as a system of coupled stochastic and ordinary differential equations, describing the ion position, velocity and acceleration. The stochastic coarse-grained model provides an intermediate description between all-atom MD simulations and Brownian dynamics (BD) models. It is used to develop a multiscale method which uses all-atom MD simulations in parts of the computational domain and (less detailed) BD simulations in the remainder of the domain. PMID:27118886

  5. Modeling water table dynamics in managed and restored peatlands

    NASA Astrophysics Data System (ADS)

    Cresto Aleina, Fabio; Rasche, Livia; Hermans, Renée; Subke, Jens-Arne; Schneider, Uwe; Brovkin, Victor

    2016-04-01

    European peatlands have been extensively managed over past centuries. Typical management activities consisted of drainage and afforestation, which lead to considerable damage to the peat and potentially significant carbon loss. Recent efforts to restore previously managed peatlands have been carried out throughout Europe. These restoration efforts have direct implications for water table depth and greenhouse gas emissions, thus impacting on the ecosystem services provided by peatland areas. In order to quantify the impact of peatland restoration on water table depth and greenhouse gas budget, We coupled the Environmental Policy Integrated Climate (EPIC) model to a process-based model for methane emissions (Walter and Heimann, 2000). The new model (EPIC-M) can potentially be applied at the European and even at the global scale, but it is yet to be tested and evaluated. We present results of this new tool from different peatlands in the Flow Country, Scotland. Large parts of the peatlands of the region have been drained and afforested during the 1980s, but since the late 1990s, programs to restore peatlands in the Flow Country have been enforced. This region offers therefore a range of peatlands, from near pristine, to afforested and drained, with different resoration ages in between, where we can apply the EPIC-M model and validate it against experimental data from all land stages of restoration Goals of this study are to evaluate the EPIC-M model and its performances against in situ measurements of methane emissions and water table changes in drained peatlands and in restored ones. Secondly, our purpose is to study the environmental impact of peatland restoration, including methane emissions, due to the rewetting of drained surfaces. To do so, we forced the EPIC-M model with local meteorological and soil data, and simulated soil temperatures, water table dynamics, and greenhouse gas emissions. This is the first step towards a European-wide application of the EPIC

  6. Water Plan 2030: A Dynamic Education Model for Teaching Water Management Issues

    NASA Astrophysics Data System (ADS)

    Rupprecht, C.; Washburne, J.; Lansey, K.; Williams, A.

    2006-12-01

    Dynamic educational tools to assist teachers and students in recognizing the impacts of water management decisions in a realistic context are not readily available. Water policy issues are often complex and difficult for students trying to make meaningful connections between system components. To fill this need, we have developed a systems modeling-based educational decision support system (DSS) with supplementary materials. This model, called Water Plan 2030, represents a general semi-arid watershed; it allows users to examine water management alternatives by changing input values for various water uses and basin conditions and immediately receive graphical outputs to compare decisions. The main goal of our DSS model is to foster students' abilities to make knowledgeable decisions with regard to water resources issues. There are two reasons we have developed this model for traditional classroom settings. First, the DSS model provides teachers with a mechanism for educating students about inter-related hydrologic concepts, complex systems and facilitates discussion of water resources issues. Second, Water Plan 2030 encourages student discovery of cause/effect relationships in a dynamic, hands-on environment and develops the ability to realize the implications of water management alternatives. The DSS model has been utilized in an undergraduate, non-major science class for 5 course hours, each of the past 4 semesters. Accompanying the PC-based model are supplementary materials to improve the effectiveness of implementation by emphasizing important concepts and guiding learners through the model components. These materials include in-class tutorials, introductory questions, role-playing activities and homework extensions that have been revised after each user session, based on student and instructor feedback. Most recently, we have developed individual lessons that teach specific model functions and concepts. These modules provide teachers the flexibility to adapt

  7. Dynamic water loss of antigorite by impact process

    NASA Astrophysics Data System (ADS)

    Sekine, Toshimori; Kimura, Tomoaki; Kobayashi, Takamichi; Mashimo, Tsutomu

    2015-04-01

    Impact-induced dehydration of serpentine in primitive meteorites is believed to be a mechanism to provide water in terrestrial planets. Primitive meteorites show a wide range of porosity and it is necessary to know the effect of porosity on the dehydration. In this work we report the dynamic dehydration reaction in powdered samples of antigorite by shock recovery experiments, in which recovered samples were investigated using techniques of X-ray diffractions, electron microscopy, and thermal analyses of shock recovered samples. The present experimental results indicate that the dehydration reaction is weakly pressure-dependent below a peak shock pressure of ∼21 GPa and becomes violent at pressures of 21-60 GPa. The kinetics was found to be dependent on not only peak shock pressure but also the initial porosity and sample amount. We discuss the heterogeneous dehydration reactions based on the phases identified in the recovered samples, more than previously thought.

  8. A Remotely Controlled Siphon System for Dynamic Water Storage Management

    NASA Astrophysics Data System (ADS)

    Alnahit, A. O.; Leon, A. S.

    2015-12-01

    This paper presents an analytical, experimental and numerical study of the initiation of flows in a siphon for rapid and gradual openings of a downstream valve. Three initial water levels in the upstream tank and four final positions for the downstream valve were investigated. Two opening times of the downstream valve were also studied. Good agreement between analytical, experimental and numerical results were obtained. The proposed siphon system was found to initiate the flow regardless the downstream valve is opened gradually or rapidly. However, small leakages may lead to air at atmospheric pressure to rush into the top of the siphon and stop the flow. Overall, the proposed siphon system can be an effective and inexpensive method to dynamically manage the storage of ponds and wetlands for flood control.

  9. Dynamics of tightly focused femtosecond laser pulses in water

    NASA Astrophysics Data System (ADS)

    Sreeja, S.; Leela, Ch; Rakesh Kumar, V.; Bagchi, Suman; Shuvan Prashant, T.; Radhakrishnan, P.; Tewari, Surya P.; Venugopal Rao, S.; Kiran, P. Prem

    2013-10-01

    The dynamics of tightly focused ultrashort (40 fs) pulses manifested in terms of supercontinuum emission (SCE) and cavitation-induced bubbles (CIB) resulting from propagation in water over a wide range of input powers (6 mW-1.8 W) are presented. The effect of linear polarization (LP) and circular polarization (CP) on SCE in different external focal geometries (f/6, f/7.5 and f/10) is investigated and the results are discussed. SCE with higher efficiency and a considerable spectral blue shift is observed under tight focusing conditions (f/6) compared to loose focusing conditions (f/10). At higher input powers, CIB along the axis of propagation are observed to be assisting deeper propagation of these short pulses and enhanced SCE.

  10. Chemical "Double Slits": dynamical interference of photodissociation pathways in water

    PubMed

    Dixon; Hwang; Yang; Harich; Lin; Yang

    1999-08-20

    Photodissociation of water at a wavelength of 121.6 nanometers has been investigated by using the H-atom Rydberg tagging technique. A striking even-odd intensity oscillation was observed in the OH(X) product rotational distribution. Model calculations attribute this oscillation to an unusual dynamical interference brought about by two dissociation pathways that pass through dissimilar conical intersections of potential energy surfaces, but result in the same products. The interference pattern and the OH product rotational distribution are sensitive to the positions and energies of the conical intersections, one with the atoms collinear as H-OH and the other as H-HO. An accurate simulation of the observations would provide a detailed test of global H(2)O potential energy surfaces for the three (&Xtilde;/A/&Btilde;) contributing states. The interference observed from the two conical intersection pathways provides a chemical analog of Young's well-known double-slit experiment.

  11. Confinement effects on collective water dynamics: Molecular dynamics study of optical Kerr response in silica nanopores

    NASA Astrophysics Data System (ADS)

    Milischuk, Anatoli; Ladanyi, Branka

    2014-03-01

    We report the results of the study of the effects of confinement on collective dynamical properties of water in model nanopores at ambient conditions. The main focus is on approximately cylindrical pores composed of amorphous silica, with diameters ranging from 20 to 40 Å, designed to represent MCM-41 materials. Results for hydrophilic and hydrophobic pores of similar dimensions, but with roughness reduced compared to silica nanopores, are also considered. The main quantity studied is the polarizability anisotropy time correlation function (TCF), which is related to the experimentally-observed optical Kerr effect (OKE) nuclear response. We investigate the effects on this TCF of the reduced molecular translational and rotational water mobility in the layers near the interface. We find that these effects lead to pore diameter dependent slowdown of polarizability anisotropy relaxation, in agreement with OKE experiments. Support from NSF grant number 1213682 is acknowledged.

  12. 78 FR 34090 - New Hampshire Water Resources Board, Hydro Dynamics Corporation; Notice of Transfer of Exemption

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-06

    ... Energy Regulatory Commission New Hampshire Water Resources Board, Hydro Dynamics Corporation; Notice of... and the New Hampshire Department of Environmental Services, as successor agency, and Hydro Dynamics Corporation as co- exemptee, Goffstown Hydro Corporation, successor in interest informed the Commission...

  13. Protein-like dynamics of polycarbonate polymers in water.

    PubMed

    Zidar, Jernej; Lim, Geraldine S; Cheong, Daniel W; Klähn, Marco

    2015-01-01

    The dynamics of amphiphilic peptide-mimicking polycarbonate polymers are investigated, considering variations in polymer length, monomer sequence, and monomer modification. The polymers are simulated in aqueous solution with atomistic molecular dynamics simulations and an empirical force field. Various structural polymer properties, interaction strengths, and solvation free energies are derived. It is found that water is a less favorable solvent for these polymers than for peptides. Moreover, polymers readily adopt irreversibly a compact state that consists of a variety of distinct compact conformations that are adopted through frequent transitions. Furthermore, the polymers exhibit a strong propensity to form large aggregates. The driving forces for these processes appear to be a hydrophobic effect and more favorable polymer-solvent interactions of aggregates that overcome the otherwise strong mutual repulsion between the positively charged polymers. Replacing hydrophobic residues with polar side chains destabilizes the compact conformations of the polymers. Our results also indicate that the monomer sequence has little effect on the overall solvation properties of the polymer molecule. However, the sequence influences flexibility and compactness of the monomer in solution. Overall, the results of this work confirm the protein-like characteristics of these polymers and elucidate the role of single residues in influencing the structure and aggregation in aqueous solution.

  14. Ionization dynamics of water dimer on ice surface

    NASA Astrophysics Data System (ADS)

    Tachikawa, Hiroto

    2016-05-01

    The solid surface provides an effective two-dimensional reaction field because the surface increases the encounter probability of bi-molecular collision reactions. Also, the solid surface stabilizes a reaction intermediate because the excess energy generated by the reaction dissipates into the bath modes of surface. The ice surface in the universe is one of the two dimensional reaction fields. However, it is still unknown how the ice surface affects to the reaction mechanism. In the present study, to elucidate the specific property of the ice surface reaction, ionization dynamics of water dimer adsorbed on the ice surface was theoretically investigated by means of direct ab-initio molecular dynamics (AIMD) method combined with ONIOM (our own n-layered integrated molecular orbital and molecular mechanics) technique, and the result was compared with that of gas phase reaction. It was found that a proton is transferred from H2O+ to H2O within the dimer and the intermediate complex H3O+(OH) is formed in both cases. However, the dynamic features were different from each other. The reaction rate of the proton transfer on the ice surface was three times faster than that in the gas phase. The intermediate complex H3O+(OH) was easily dissociated to H3O+ and OH radical on the ice surface, and the lifetime of the complex was significantly shorter than that of gas phase (100 fs vs. infinite). The reason why the ice surface accelerates the reaction was discussed in the present study.

  15. Generic reactive transport codes as flexible tools to integrate soil organic matter degradation models with water, transport and geochemistry in soils

    NASA Astrophysics Data System (ADS)

    Jacques, Diederik; Gérard, Fréderic; Mayer, Uli; Simunek, Jirka; Leterme, Bertrand

    2016-04-01

    A large number of organic matter degradation, CO2 transport and dissolved organic matter models have been developed during the last decades. However, organic matter degradation models are in many cases strictly hard-coded in terms of organic pools, degradation kinetics and dependency on environmental variables. The scientific input of the model user is typically limited to the adjustment of input parameters. In addition, the coupling with geochemical soil processes including aqueous speciation, pH-dependent sorption and colloid-facilitated transport are not incorporated in many of these models, strongly limiting the scope of their application. Furthermore, the most comprehensive organic matter degradation models are combined with simplified representations of flow and transport processes in the soil system. We illustrate the capability of generic reactive transport codes to overcome these shortcomings. The formulations of reactive transport codes include a physics-based continuum representation of flow and transport processes, while biogeochemical reactions can be described as equilibrium processes constrained by thermodynamic principles and/or kinetic reaction networks. The flexibility of these type of codes allows for straight-forward extension of reaction networks, permits the inclusion of new model components (e.g.: organic matter pools, rate equations, parameter dependency on environmental conditions) and in such a way facilitates an application-tailored implementation of organic matter degradation models and related processes. A numerical benchmark involving two reactive transport codes (HPx and MIN3P) demonstrates how the process-based simulation of transient variably saturated water flow (Richards equation), solute transport (advection-dispersion equation), heat transfer and diffusion in the gas phase can be combined with a flexible implementation of a soil organic matter degradation model. The benchmark includes the production of leachable organic matter

  16. Dynamic Change of Water Quality in Hyporheic Zone at Water Curtain Cultivation Area, Cheongju, Korea

    NASA Astrophysics Data System (ADS)

    Moon, S. H.; Kim, Y.

    2015-12-01

    There has been recently growing numbers of facilities for water curtain cultivation of strawberry and lettuce in Korea. These areas are nearly all located in the fluvial deposits near streams which can replenish water resources into exhausted groundwater aquifers during peak season. The purpose of this study is on groundwater chemistry and the change in physical and chemical properties due to stream-groundwater exchange or mixing in the representative agricultural area among the Jurassic granitic terrain of Korea. In the study area, groundwater level continuously decreased from November through March due to intensive use of groundwater, which forced stream water into aquifer. After March, groundwater level was gradually recovered to the original state. To evaluate the extent and its variations of stream water mixing into aquifer, field parameters including T, pH, EC and DO values, concentrations of major ions and oxygen and hydrogen stable isotopic ratios were used. Field measurements and water sample collections were performed several times from 2012 to 2015 mainly during peak time of groundwater use. To compare the temporal variations and areal differences, 21 wells from four cross sections perpendicular to stream line were used. While water temperature, EC values and concentrations of Ca, Mg, Si, HCO3 showed roughly gradual increase from stream line to 150 m distance, pH and DO values showed reverse phenomenon. This can be used to evaluate the extent and limit of stream water introduction into aquifer. However, individual wells showed yearly variations in those parameters and this dynamic and unstable feature indicates that mixing intensity of stream water over groundwater in this hyporheic zone varied year by year according to amounts of groundwater use and decrease of groundwater level.

  17. Isotope Geochemistry Researches in China

    NASA Astrophysics Data System (ADS)

    Chen, James H.

    The publication of Isotope Geochemistry Researches in China represents a major milestone in such research in China. Every isotope geochemist will find at least one informative article in his or her own field of interest in this large and comprehensive volume.The book is divided into 27 chapters, written by 41 authors, and the scope, content, and quality of the chapters are variable. In general, each is a review or an overview of a topic in geochemistry. Some of the chapters are very short and provide only a very general overview. Others are long and provide a detailed and more comprehensive review of a specific subject. Most are translated into English and they are generally professionally done. The quality of the figures and tables varies, but most are clear and informative. An extensive, current bibliography (some in Chinese publications) is provided at the end of the book for each chapter, but there is no index.To help readers find the localities of the areas studied, a table is appended containing names in English and Chinese with latitude and longitude, but no map is included.

  18. Solitary wave dynamics in shallow water over periodic topography.

    PubMed

    Nakoulima, Ousseynou; Zahibo, Narcisse; Pelinovsky, Efim; Talipova, Tatiana; Kurkin, Andrey

    2005-09-01

    The problem of long-wave scattering by piecewise-constant periodic topography is studied both for a linear solitary-like wave pulse, and for a weakly nonlinear solitary wave [Korteweg-de Vries (KdV) soliton]. If the characteristic length of the topographic irregularities is larger than the pulse length, the solution of the scattering problem is obtained analytically for a leading wave in the framework of linear shallow-water theory. The wave decrement in the case of the small height of the topographic irregularities is proportional to delta2, where delta is the relative height of the topographic obstacles. An analytical approximate solution is also obtained for the weakly nonlinear problem when the length of the irregularities is larger than the characteristic nonlinear length scale. In this case, the Korteweg-de Vries equation is solved for each piece of constant depth by using the inverse scattering technique; the solutions are matched at each step by using linear shallow-water theory. The weakly nonlinear solitary wave decays more significantly than the linear solitary pulse. Solitary wave dynamics above a random seabed is also discussed, and the results obtained for random topography (including experimental data) are in reasonable agreement with the calculations for piecewise topography. PMID:16253002

  19. Trout production dynamics and water quality in Minnesota streams

    USGS Publications Warehouse

    Kwak, T.J.; Waters, T.F.

    1997-01-01

    We sampled fish assemblages and quantified production dynamics of brook trout Salvelinus fontinalis, brown trout Salmo trutta, and rainbow trout Oncorhynchus mykiss in 13 southeastern Minnesota streams during 1988-1990 to examine the influence of water quality on fish populations in fertile trout streams. Fish assemblages in 15 stream reaches were abundant, but low in diversity; 13 species were collected. Parameter means (ranges) over the reaches were species richness, 4.1 (1-8); density, 29,490 (1,247-110,602) fish/ha; and biomass, 253.5 (49.6-568.6) kg/ha. Means (ranges) for salmonids were annual mean density, 2,279 (343-8,096) fish/ha; annual mean biomass, 162.0 (32.5-355.5) kg/ha; and annual production, 155.6 (36.7-279.6) kg/ha. Salmoid production and mean biomass were greater during the spring-fall interval than during fall-spring; young cohorts (ages 0-1) contributed the greatest proprotion to population biomass and production. Salmonid annual production-to-mean-biomass ratio (P/B??) averaged 1.06 (0.64-1.42), and means were significantly different among species (1.03 for brown trout, 1.54 for brook trout, and 1.92 for rainbow trout). A significant linear model was developed that describes P/B?? as an inverse function of population age structure and may be used to improve accuracy in approximations of annual productions from mean biomass. Fish density, biomass, or production were not correlated with eight water quality variables describing ionic and nutrient content in these streams, but when data from other United States streams with a wide range in alkalinity were incorporated, salmonid production was strongly, positively correlated with alkalinity. The wide range in fish population and production statistics and their lack of correlation with water quality suggest that no uniform fish carrying capacity exists among these streams and that factors other than water fertility limit fish density, biomass and productivity at this spatia scale, but the overall

  20. Geochemistry of the Cambrian-Ordovician aquifer system in the northern midwest, United States

    SciTech Connect

    Siegel, D.I.

    1989-01-01

    The geochemistry of the Cambrian-Ordovician aquifer system was modified during the Pleistocene by large-scale emplacement of glacial meltwater, as indicated by large-scale emplacement of glacial meltwater, as indicated by the investigation of stable isotopes of water, and a plume of dilute water that trends perpendicular to the direction of ground-water flow in Iowa and Missouri. Ground water in this part of the aquifer system could be hundreds of thousands of years old.

  1. Germanium geochemistry and mineralogy

    USGS Publications Warehouse

    Bernstein, L.R.

    1985-01-01

    Germanium is enriched in the following geologic environments: 1. (1) iron meteorites and terrestrial iron-nickel; 2. (2) sulfide ore deposits, particularly those hosted by sedimentary rocks; 3. (3) iron oxide deposits; 4. (4) oxidized zones of Ge-bearing sulfide deposits; 5. (5) pegmatites, greisens, and skarns; and 6. (6) coal and lignitized wood. In silicate melts, Ge is highly siderophile in the presence of native iron-nickel; otherwise, it is highly lithophile. Among silicate minerals, Ge is concentrated in those having less polymerized silicate tetrahedra such as olivine and topaz. In deposits formed from hydrothermal solutions, Ge tends to be enriched mostly in either sulfides or in fluorine-bearing phases; it is thus concentrated both in some hydrothermal sulfide deposits and in pegmatites, greisens, and skarns. In sulfide deposits that formed from solutions having low to moderate sulfur activity, Ge is concentrated in sphalerite in amounts up to 3000 ppm. Sulfide deposits that formed from solutions having higher sulfur activity allowed Ge to either form its own sulfides, particularly with Cu, or to substitute for As, Sn, or other metals in sulfosalts. The Ge in hydrothermal fluids probably derives from enrichment during the fractional crystallization of igneous fluids, or is due to the incorporation of Ge from the country rocks, particularly from those containing organic material. Germanium bonds to lignin-derivative organic compounds that are found in peat and lignite, accounting for its common concentration in coals and related organic material. Germanium is precipitated from water together with iron hydroxide, accounting for its concentration in some sedimentary and supergene iron oxide deposits. It also is able to substitute for Fe in magnetite in a variety of geologic environments. In the oxidized zone of Ge-bearing sulfide deposits, Ge is concentrated in oxides, hydroxides, and hydroxy-sulfates, sometimes forming its own minerals. It is particularly

  2. Nitrogen dynamics at the groundwater-surface water interface of a degraded urban stream (journal)

    EPA Science Inventory

    Urbanization degrades stream ecosystems by altering hydrology and nutrient dynamics, yet relatively little effort has been devoted to understanding biogeochemistry of urban streams at the ground water-surface water interface. This zone may be especially important for nitrogen re...

  3. Effects of Disaccharide Sugars on Dynamics of Water Molecules: Dynamic Light Scattering and Dielectric Loss Spectroscopy Studies

    NASA Astrophysics Data System (ADS)

    Seo, Jeong-Ah; Kwon, Hyun-Joung; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2008-02-01

    We studied the effects of disaccharide sugars (trehalose, sucrose, and maltose) on the dynamics of water molecules in sugar-water mixtures. We measured the acoustic phonons in sugar-water mixtures with different sugar contents by using a Sandercock Tandem 6-pass Febry-Petor interferometer and found that the Brillouin peak positions shifted to higher frequencies as the sugar concentration increased. We also measured the dielectric loss of hydrogen bonds in water molecules in sugar-water mixtures by using a Network analyzer with different sugar contents. The loss peak position in the dielectric loss spectra moved to lower frequencies as the sugar contents increased. The trehalose-water mixture showed the largest Brillouin peak shift and relaxation time change with increasing sugar content among three disaccharides indicating that the effect of trehalose on the dynamics of water molecules is the strongest. This unique property of trehalose sugar might be the origin of the superior bio-protection ability of trehalose.

  4. REVIEW ARTICLE: The high-frequency dynamics of liquid water

    NASA Astrophysics Data System (ADS)

    Ruocco, Giancarlo; Sette, Francesco

    1999-06-01

    This article is dedicated to reviewing the recent inelastic x-ray scattering (IXS) work on the high-frequency collective dynamics in liquid water. The results obtained with the IXS technique are directly compared with existing ones from inelastic neutron scattering (INS) and molecular dynamics simulation investigations that were carried out with the aim of achieving an understanding of the collective properties of water at the microscopic level. The IXS work has made it possible to demonstrate experimentally the existence, in the range of exchange momentum (Q) examined (1-10 nm-1), of two branches of collective modes: one linearly dispersing with Q (with the apparent sound velocity of icons/Journals/Common/approx" ALT="approx" ALIGN="TOP"/>3200 m s-1) and the other at almost constant energy (5-7 meV). It has been possible to show that the dispersing branch originates from an upwards bend of the ordinary sound branch observed in low-frequency measurements. The study of this sound velocity dispersion, marking a transition from the ordinary sound, co, to the `fast' sound, cicons/Journals/Common/infty" ALT="infty" ALIGN="MIDDLE"/>, as a function of temperature, has made it possible to relate the origin of this phenomenon to a structural relaxation process, which presents many analogies with those observed for glass-forming systems. The possibility of estimating from the IXS data the value of the relaxation time, icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/>, as a function of temperature leads to a relating of the relaxation process to the structural rearrangements induced by the making and breaking of hydrogen bonds. In this framework, it is then possible to recognize a hydrodynamical `normal' regime, i.e. one for which the density fluctuations have a period of oscillation that is on a timescale that is long with respect to icons/Journals/Common/tau" ALT="tau" ALIGN="TOP"/>, and a solid-like regime in the opposite limit. In the latter regime, the density

  5. Comparing the relationship between precipitation and river geochemistry

    NASA Astrophysics Data System (ADS)

    Epp, A.; Luymes, R.; Bennett, M.; DaSilva, J.; Marsh, S. J.; Gillies, S. L.; Peucker-Ehrenbrink, B.; Voss, B.

    2013-12-01

    The geochemistry of precipitation affects the geochemistry of river water. Ideally, studies of river biogeochemistry should therefore include collection and analyses of dry and wet deposition. The Global Rivers Observatory has studied the Fraser River near Vancouver since the summer of 2009 at roughly bi-weekly resolution. The interpretation of this temporal record of river biogeochemistry, particularly the various sources of solutes, could be improved with a better understanding of atmospheric contributions. In this study precipitation and river water will be analysed from the Fraser River basin for nutrients as well as major and select trace ion concentrations. The nutrients analyzed will include ammonium (NH4), nitrate and nitrate (NO3-NO2), phosphate (PO4) and silicate (SiO4). Major ions include sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chloride (Cl), and sulfate (SO4). Trace elements may include molybdenum, strontium, barium, uranium, rubidium, manganese and iron. Samples will be collected using the bulk method which collects both wet and dry deposition . Correlating precipitation chemistry with data on wind direction may help elucidate sources of nutrients and major ions. For instance, westerly sources may transport pollution from the City of Vancouver and agricultural lands in the Fraser delta. Such pollutants may increase the acidity of precipitation and imprint the water chemistry with a unique chemical signature . The results of this study will be helpful in correcting Fraser River water data for contributions from atmospheric deposition.

  6. Horizontal soil water potential heterogeneity: simplifying approaches for crop water dynamics models

    NASA Astrophysics Data System (ADS)

    Couvreur, V.; Vanderborght, J.; Beff, L.; Javaux, M.

    2014-05-01

    use of 1-D spatial discretisation to represent soil-plant water dynamics is a worthy choice for densely seeded crops. For wide-row crops, e.g. maize, further theoretical developments that better account for horizontal SWP heterogeneity might be needed in order to properly predict soil-plant hydrodynamics in 1-D.

  7. Horizontal soil water potential heterogeneity: simplifying approaches for crop water dynamics models

    NASA Astrophysics Data System (ADS)

    Couvreur, V.; Vanderborght, J.; Beff, L.; Javaux, M.

    2014-01-01

    use of 1-D spatial discretisation to represent soil-plant water dynamics is a worthy choice for densely seeded crops. For wide-row crops, e.g. maize, further theoretical developments that better account for horizontal SWP heterogeneity might be needed in order to properly predict soil-plant hydrodynamics in 1-D.

  8. Overview of fundamental geochemistry basic research at the Oak Ridge National Laboratory

    SciTech Connect

    Anovitz, L.M.; Benezeth, P.; Blencoe, J.G.

    1996-01-01

    Researchers in ORNL`s Geochemistry and High Temperature Aqueous Chemistry groups are conducting detailed experimental studies of physicochemical properties of the granite-melt-brine system; sorption of water on rocks from steam-dominated reservoirs; partitioning of salts and acid volatiles between brines and steam; effects of salinity on H and O isotope partitioning between brines, minerals, and steam; and aqueous geochemistry of Al. These studies contribute in many ways to cost reductions and improved efficiency in the discovery, characterization, and production of energy from geothermal resources.

  9. Simulating long-term carbon and water dynamics in northern peatlands (Invited)

    NASA Astrophysics Data System (ADS)

    Frolking, S. E.; Roulet, N. T.; Quillet, A.; Tuittila, E.; Bubier, J. L.

    2009-12-01

    We present a new model that simulates coupled carbon and water dynamics of northern peatlands at an annual time step over time scales of decades to millennia. The Holocene Peatland Model (HPM) simulates peatland carbon and water dynamics as the net consequence of several interacting processes: (1) above- and below-ground vegetation NPP and litter production for bryophytes and vascular plants; (2) aerobic and anaerobic litter/peat decomposition down the peat profile; (3) the dependence of peat physical and hydraulic properties on peat humification; and (4) peatland annual water balance, water table depth, and unsaturated zone water content. The model generates time series of vegetation, carbon and water dynamics over a 5000-10000 year simulation, and a ‘final state’ peat core that can be compared to contemporary peat core data. The sensitivities of peatland carbon and water dynamics to climate and climate variability and to succession rate are evaluated.

  10. Dynamics of Hydration Water around Native and Misfolded α-Lactalbumin.

    PubMed

    Brotzakis, Z F; Groot, C C M; Brandeburgo, W H; Bakker, H J; Bolhuis, P G

    2016-06-01

    As water is an essential ingredient in protein structure, dynamics, and functioning, knowledge of its behavior near proteins is crucial. We investigate water dynamics around bovine α-lactalbumin by combining molecular dynamics simulations with polarization-resolved femtosecond infrared (fs-IR) spectroscopy. We identify slowly reorienting surface waters and establish their hydrogen-bond lifetime and reorientation dynamics, which we compare to the experimentally measured anisotropy decay. The calculated number of slow surface waters is in reasonable agreement with the results of fs-IR experiments. While surface waters form fewer hydrogen bonds than the bulk, within the hydration layer water is slower when donating more hydrogen bonds. At concave sites the protein-water hydrogen bonds break preferably via translational diffusion rather than via a hydrogen-bond jump mechanism. Water molecules reorient slower near these sites than at convex water-exposed sites. Protein misfolding leads to an increased exposure of hydrophobic groups, inducing relatively faster surface water dynamics. Nevertheless, the larger exposed surface slows down a larger amount of water. While for native proteins hydrating water is slower near hydrophobic than near hydrophilic residues, mainly due to stronger confinement, misfolding causes hydrophobic water to reorient relatively faster because exposure of hydrophobic groups destroys concave protein cavities with a large excluded volume. PMID:27137845

  11. Quantum effects of hydrogen atoms on the dynamical rearrangement of hydrogen-bond networks in liquid water.

    PubMed

    Hyeon-Deuk, Kim; Ando, Koji

    2010-04-28

    Quantum effects such as zero-point energy and delocalization of wave packets (WPs) representing water hydrogen atoms are essential to understand anomalous energetics and dynamics in water. Since quantum calculations of many-body dynamics are highly complicated, no one has yet directly viewed the quantum WP dynamics of hydrogen atoms in liquid water. Our semiquantum molecular dynamics simulation made it possible to observe the hydrogen WP dynamics in liquid water. We demonstrate that the microscopic WP dynamics are closely correlated with and actually play key roles in the dynamical rearrangement in the hydrogen-bond network (HBN) of bulk water. We found the quantum effects of hydrogen atoms on liquid water dynamics such as the rearrangement of HBN and the concomitant fluctuation and relaxation. Our results provide new physical insights on HBN dynamics in water whose significance is not limited to pure liquid dynamics but also a greater understanding of chemical and biological reactions in liquid water.

  12. Optimization of conventional water treatment plant using dynamic programming.

    PubMed

    Mostafa, Khezri Seyed; Bahareh, Ghafari; Elahe, Dadvar; Pegah, Dadras

    2015-12-01

    In this research, the mathematical models, indicating the capability of various units, such as rapid mixing, coagulation and flocculation, sedimentation, and the rapid sand filtration are used. Moreover, cost functions were used for the formulation of conventional water and wastewater treatment plant by applying Clark's formula (Clark, 1982). Also, by applying dynamic programming algorithm, it is easy to design a conventional treatment system with minimal cost. The application of the model for a case reduced the annual cost. This reduction was approximately in the range of 4.5-9.5% considering variable limitations. Sensitivity analysis and prediction of system's feedbacks were performed for different alterations in proportion from parameters optimized amounts. The results indicated (1) that the objective function is more sensitive to design flow rate (Q), (2) the variations in the alum dosage (A), and (3) the sand filter head loss (H). Increasing the inflow by 20%, the total annual cost would increase to about 12.6%, while 20% reduction in inflow leads to 15.2% decrease in the total annual cost. Similarly, 20% increase in alum dosage causes 7.1% increase in the total annual cost, while 20% decrease results in 7.9% decrease in the total annual cost. Furthermore, the pressure decrease causes 2.95 and 3.39% increase and decrease in total annual cost of treatment plants.

  13. Dynamics of aluminum leaching from water purification sludge.

    PubMed

    Cheng, Wen-Po; Fu, Chi-Hua; Chen, Ping-Hung; Yu, Ruey-Fang

    2012-05-30

    In this investigation, the shrinking core model is used to study the rate of aluminum salt leaching from water purification sludge (WPS). This model, which describes the aluminum leaching rate, can be developed to maximize the Al(III) recovering efficiency. Laboratory results indicate that when the mixing speed exceeds 80rpm, the effect of film diffusion control on the leaching process is greatly reduced, such that any further increase in the mixing speed does not affect the Al(III) leaching rate. Additionally, increasing the temperature or acid concentration improves Al(III) leaching rate. The laboratory data were verified by using the shrinking core model to confirm that the leaching of Al(III) from WPS is consistent with the inert-layer diffusion control model. This finding reveals that large amounts of SiO(2), Al(2)O(3) and other inert constituents will form an inter diffusion layer in the WPS and thus become the major limiting factors that control the Al(III) leaching process. The dynamic equation can be expressed as 1-3(1-x)(2/3)+2(1-x)=(2707.3 exp(-3887.6/T))t, in which the apparent activation energy and pre-exponential factors are 32.32 kJ/mol and 2707.3 min(-1), respectively, as determined by solving the Arrhenius equation.

  14. High-frequency dynamics of liquid and supercritical water

    SciTech Connect

    Bencivenga, F.; Cunsolo, A.; Ruocco, G.

    2007-05-15

    The dynamic structure factor S(Q,{omega}) of water has been determined by high-resolution inelastic x-ray scattering (IXS) in a momentum (Q) and energy (E) transfer range extending from 2 to 4 nm{sup -1} and from {+-}40 meV. IXS spectra have been recorded along an isobaric path (400 bar) in a temperature (T) interval ranging from ambient up to supercritical (T>647 K) conditions. The experimental data have been described in the frame of the generalized hydrodynamic theory, utilizing a model based on the memory function approach. This model allows identifying the active relaxation processes which affect the time decay of density fluctuations, as well as a direct determination of the Q, T, and density ({rho}) dependencies of the involved transport parameters. The experimental spectra are well described by considering three different relaxation processes: the thermal, the structural, and the instantaneous one. On approaching supercritical conditions, we observe that the microscopic mechanism responsible for the structural relaxation is no longer related to the making and breaking of intermolecular bonds, but to binary intermolecular collisions.

  15. Mosaic of Water Orientation Structures at a Neutral Zwitterionic Lipid/Water Interface Revealed by Molecular Dynamics Simulations.

    PubMed

    Re, Suyong; Nishima, Wataru; Tahara, Tahei; Sugita, Yuji

    2014-12-18

    Ordering of water structures near the surface of biological membranes has been recently extensively studied using interface-selective techniques like vibrational sum frequency generation (VSFG) spectroscopy. The detailed structures of interface water have emerged for charged lipids, but those for neutral zwitterionic lipids remain obscure. We analyze an all-atom molecular dynamics (MD) trajectory of a hydrated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer to characterize the orientation of interface waters in different chemical environments. The structure and dynamics of interfacial waters strongly depend on both their vertical position along the bilayer normal as well as vicinal lipid charged groups. Water orientation in the vicinity of phosphate groups is opposite to that around choline groups. The results are consistent with observed VSFG spectra and demonstrate that a mosaic of water orientation structures exists on the surface of a neutral zwitterionic phospholipid bilayer, reflecting rapid water exchange and the influence of local chemical environments. PMID:26273985

  16. Dynamics and structure of hydration water on rutile and cassiterite nanopowders studied by quasielastic neutron scattering and molecular dynamics simulations.

    SciTech Connect

    Mamontov, Eugene; Vlcek, Lukas; Wesolowski, David J

    2007-03-01

    Quasielastic neutron scattering (QENS) experiments carried out using time-of-flight and backscattering neutron spectrometers with widely different energy resolution and dynamic range revealed the diffusion dynamics of hydration water in nanopowder rutile (TiO{sub 2}) and cassiterite (SnO{sub 2}) that possess the rutile crystal structure with the (110) crystal face predominant on the surface. These isostructural oxides differ in their bulk dielectric constants, metal atom electronegativities, and lattice spacings, which may all contribute to differences in the structure and dynamics of sorbed water. When hydrated under ambient conditions, the nanopowders had similar levels of hydration: about 3.5 (OH/H{sub 2}O) molecules per Ti{sub 2}O{sub 4} surface structural unit of TiO{sub 2} and about 4.0 (OH/H{sub 2}O) molecules per Sn{sub 2}O{sub 4} surface unit of SnO{sub 2}. Ab initio optimized classical molecular dynamics (MD) simulations of the (110) surfaces in contact with SPC/E water at these levels of hydration indicate three structurally distinct sorbed water layers L{sub 1}, L{sub 2}, and L{sub 3}, where the L{sub 1} species are either associated water molecules or dissociated hydroxyl groups in direct contact with the surface, L{sub 2} water molecules are hydrogen bonded to L{sub 1} and structural oxygen atoms at the surface, and L{sub 3} water molecules are more weakly bound. At the hydration levels studied, L{sub 3} is incomplete compared with axial oxygen density profiles of bulk SPC/E water in contact with these surfaces, but the structure and dynamics of L{sub 1}-L{sub 3} species are remarkably similar at full and reduced water coverage. Three hydration water diffusion components, on the time scale of a picosecond, tens of picoseconds, and a nanosecond could be extracted from the QENS spectra of both oxides. However, the spectral weight of the faster components was significantly lower for SnO{sub 2} compared to TiO{sub 2}. In TiO{sub 2} hydration water, the

  17. Unusual dynamic properties of water near the ice-binding plane of hyperactive antifreeze protein

    SciTech Connect

    Kuffel, Anna; Czapiewski, Dariusz; Zielkiewicz, Jan

    2015-10-07

    The dynamical properties of solvation water of hyperactive antifreeze protein from Choristoneura fumiferana (CfAFP) are analyzed and discussed in context of its antifreeze activity. The protein comprises of three well-defined planes and one of them binds to the surface of ice. The dynamical properties of solvation water around each of these planes were analyzed separately; the results are compared with the dynamical properties of solvation water of ice around its two crystallographic planes: basal and prism. Three main conclusions are inferred from our investigations. The first one is that the solvation shell of CfAFP does not seem to be particularly far-ranged, at least not beyond what is usually observed for proteins that do not interact with ice. Therefore, it does not appear to us that the antifreeze activity is enhanced by a long-ranged retardation of water mobility. Also the correlation between the collective mobility of water and the collective mobility of protein atoms highly resembles the one measured for the protein that does not interact with ice. Our second conclusion is that the dynamical properties of solvation water of CfAFP are non-uniform. The dynamics of solvation water of ice-binding plane is, in some respects, different from the dynamics of solvation water of the two remaining planes. The feature that distinguishes the dynamics of solvation water of the three planes is the activation energy of diffusion process. The third conclusion is that—from the three analyzed solvation shells of CfAFP—the dynamical properties of solvation water of the ice-binding plane resemble the most the properties of solvation water of ice; note, however, that these properties still clearly differ from the dynamic properties of solvation water of ice.

  18. Geochemistry

    ERIC Educational Resources Information Center

    Brett, Robin; Hanshaw, Bruce B.

    1978-01-01

    The past year has seen the development of certain fields of geochemical research including Nd-Sm isotope studies of meteorites and ancient terrestrial rocks; the use of the consortium approach of assembling a multidisciplined team to tackle a problem; and the handling and analysis of small quantities of materials. (Author/MA)

  19. Coupling of the hydration water dynamics and the internal dynamics of actin detected by quasielastic neutron scattering

    SciTech Connect

    Fujiwara, Satoru; Plazanet, Marie; Oda, Toshiro

    2013-02-15

    Highlights: ► Quasielastic neutron scattering spectra of F-actin and G-actin were measured. ► Analysis of the samples in D{sub 2}O and H{sub 2}O provided the spectra of hydration water. ► The first layer hydration water around F-actin is less mobile than around G-actin. ► This difference in hydration water is in concert with the internal dynamics of actin. ► Water outside the first layer behaves bulk-like but influenced by the first layer. -- Abstract: In order to characterize dynamics of water molecules around F-actin and G-actin, quasielastic neutron scattering experiments were performed on powder samples of F-actin and G-actin, hydrated either with D{sub 2}O or H{sub 2}O, at hydration ratios of 0.4 and 1.0. By combined analysis of the quasielastic neutron scattering spectra, the parameter values characterizing the dynamics of the water molecules in the first hydration layer and those of the water molecules outside of the first layer were obtained. The translational diffusion coefficients (D{sub T}) of the hydration water in the first layer were found to be 1.2 × 10{sup −5} cm{sup 2}/s and 1.7 × 10{sup −5} cm{sup 2}/s for F-actin and G-actin, respectively, while that for bulk water was 2.8 × 10{sup −5} cm{sup 2}/s. The residence times were 6.6 ps and 5.0 ps for F-actin and G-actin, respectively, while that for bulk water was 0.62 ps. These differences between F-actin and G-actin, indicating that the hydration water around G-actin is more mobile than that around F-actin, are in concert with the results of the internal dynamics of F-actin and G-actin, showing that G-actin fluctuates more rapidly than F-actin. This implies that the dynamics of the hydration water is coupled to the internal dynamics of the actin molecules. The D{sub T} values of the water molecules outside of the first hydration layer were found to be similar to that of bulk water though the residence times are strongly affected by the first hydration layer. This supports the

  20. Simulations of structural and dynamic anisotropy in nano-confined water between parallel graphite plates.

    PubMed

    Mosaddeghi, Hamid; Alavi, Saman; Kowsari, M H; Najafi, Bijan

    2012-11-14

    We use molecular dynamics simulations to study the structure, dynamics, and transport properties of nano-confined water between parallel graphite plates with separation distances (H) from 7 to 20 Å at different water densities with an emphasis on anisotropies generated by confinement. The behavior of the confined water phase is compared to non-confined bulk water under similar pressure and temperature conditions. Our simulations show anisotropic structure and dynamics of the confined water phase in directions parallel and perpendicular to the graphite plate. The magnitude of these anisotropies depends on the slit width H. Confined water shows "solid-like" structure and slow dynamics for the water layers near the plates. The mean square displacements (MSDs) and velocity autocorrelation functions (VACFs) for directions parallel and perpendicular to the graphite plates are calculated. By increasing the confinement distance from H = 7 Å to H = 20 Å, the MSD increases and the behavior of the VACF indicates that the confined water changes from solid-like to liquid-like dynamics. If the initial density of the water phase is set up using geometric criteria (i.e., distance between the graphite plates), large pressures (in the order of ~10 katm), and large pressure anisotropies are established within the water. By decreasing the density of the water between the confined plates to about 0.9 g cm(-3), bubble formation and restructuring of the water layers are observed.

  1. Simulations of structural and dynamic anisotropy in nano-confined water between parallel graphite plates

    NASA Astrophysics Data System (ADS)

    Mosaddeghi, Hamid; Alavi, Saman; Kowsari, M. H.; Najafi, Bijan

    2012-11-01

    We use molecular dynamics simulations to study the structure, dynamics, and transport properties of nano-confined water between parallel graphite plates with separation distances (H) from 7 to 20 Å at different water densities with an emphasis on anisotropies generated by confinement. The behavior of the confined water phase is compared to non-confined bulk water under similar pressure and temperature conditions. Our simulations show anisotropic structure and dynamics of the confined water phase in directions parallel and perpendicular to the graphite plate. The magnitude of these anisotropies depends on the slit width H. Confined water shows "solid-like" structure and slow dynamics for the water layers near the plates. The mean square displacements (MSDs) and velocity autocorrelation functions (VACFs) for directions parallel and perpendicular to the graphite plates are calculated. By increasing the confinement distance from H = 7 Å to H = 20 Å, the MSD increases and the behavior of the VACF indicates that the confined water changes from solid-like to liquid-like dynamics. If the initial density of the water phase is set up using geometric criteria (i.e., distance between the graphite plates), large pressures (in the order of ˜10 katm), and large pressure anisotropies are established within the water. By decreasing the density of the water between the confined plates to about 0.9 g cm-3, bubble formation and restructuring of the water layers are observed.

  2. A decision support tool for sustainable planning of urban water systems: presenting the Dynamic Urban Water Simulation Model.

    PubMed

    Willuweit, Lars; O'Sullivan, John J

    2013-12-15

    Population growth, urbanisation and climate change represent significant pressures on urban water resources, requiring water managers to consider a wider array of management options that account for economic, social and environmental factors. The Dynamic Urban Water Simulation Model (DUWSiM) developed in this study links urban water balance concepts with the land use dynamics model MOLAND and the climate model LARS-WG, providing a platform for long term planning of urban water supply and water demand by analysing the effects of urbanisation scenarios and climatic changes on the urban water cycle. Based on potential urbanisation scenarios and their effects on a city's water cycle, DUWSiM provides the functionality for assessing the feasibility of centralised and decentralised water supply and water demand management options based on forecasted water demand, stormwater and wastewater generation, whole life cost and energy and potential for water recycling. DUWSiM has been tested using data from Dublin, the capital of Ireland, and it has been shown that the model is able to satisfactorily predict water demand and stormwater runoff. PMID:24183560

  3. A decision support tool for sustainable planning of urban water systems: presenting the Dynamic Urban Water Simulation Model.

    PubMed

    Willuweit, Lars; O'Sullivan, John J

    2013-12-15

    Population growth, urbanisation and climate change represent significant pressures on urban water resources, requiring water managers to consider a wider array of management options that account for economic, social and environmental factors. The Dynamic Urban Water Simulation Model (DUWSiM) developed in this study links urban water balance concepts with the land use dynamics model MOLAND and the climate model LARS-WG, providing a platform for long term planning of urban water supply and water demand by analysing the effects of urbanisation scenarios and climatic changes on the urban water cycle. Based on potential urbanisation scenarios and their effects on a city's water cycle, DUWSiM provides the functionality for assessing the feasibility of centralised and decentralised water supply and water demand management options based on forecasted water demand, stormwater and wastewater generation, whole life cost and energy and potential for water recycling. DUWSiM has been tested using data from Dublin, the capital of Ireland, and it has been shown that the model is able to satisfactorily predict water demand and stormwater runoff.

  4. Impact of permafrost thaw on Arctic tundra pond geochemistry

    NASA Astrophysics Data System (ADS)

    Reyes, F.; Lougheed, V.

    2012-12-01

    Increasing evidence indicates the arctic tundra is changing physically, biologically, and chemically due to climate warming. With a warmer climate, permafrost is expected to thaw and influence the chemistry of arctic aquatic ecosystems. However, knowledge is limited on how geochemistry of arctic tundra pond ecosystems will respond. By re-sampling historical IBP ponds in Barrow, AK first sampled in the 1970s, previous studies have shown an increase in water temperature, nutrients and algal biomass through time. Results from this study indicate an increase of Ca, Mg, and Na in the water column, and a decrease in pH relative to the 1970s, suggesting an increased rate and magnitude of carbonate and Mg release. Seasonal trends were also examined to understand what processes, such as mineral weathering, peat decomposition and evaporation, were currently most influential in determining pond geochemistry. An increase in Ca/Na molar ratios, and carbonate and magnesium concentrations indicates that these tundra ponds are experiencing greater carbonate weathering compared to the 1970s and the rate of carbonate weathering increases in ponds as the summer progresses. However, increasing dissolved organic carbon (DOC) concentrations originating from peat decomposition are likely neutralizing additional inputs of carbonate, causing pond pH to decrease and exacerbating mineral weathering. A strong positive relationship between element concentrations and active layer pond thaw depth suggests that the origin of these additional solutes is likely from permafrost thaw. Active layer thaw depth has increased substantially over the past 40 years in the IBP ponds. Chloride/Bromide molar ratios and Deuterium/ 18-Oxygen isotope ratios will be used to determine the degree of evaporation occurring in tundra ponds. Ultimately, this study provides evidence for how geochemistry can identify the sources of chemical inputs to Arctic ponds affected by climate change and permafrost thaw.

  5. Ring-type multisoliton dynamics in shallow water.

    PubMed

    Mannan, Abdul; Fedele, Renato; Onorato, Miguel; De Nicola, Sergio; Jovanović, Dušan

    2015-01-01

    The propagation, in a shallow water, of nonlinear ring waves in the form of multisolitons is investigated theoretically. This is done by solving both analytically and numerically the cylindrical (also referred to as concentric) Korteweg-de Vries equation (cKdVE). The latter describes the propagation of weakly nonlinear and weakly dispersive ring waves in an incompressible, inviscid, and irrotational fluid. The spatiotemporal evolution is determined for a cylindrically symmetric response to the free fall of an initially given multisoliton ring. Analytically, localized solutions in the form of tilted solitons are found. They can be thought as single- or multiring solitons formed on a conic-modulated water surface, with an oblique asymptote in arbitrary radial direction (tilted boundary condition). Conversely, the ring solitons obtained from numerical solutions are localized single- or multiring structures (standard solitons), whose wings vanish along all radial directions (standard boundary conditions). It is found that the wave dynamics of these standard ring-type localized structures differs substantially from that of the tilted structures. A detailed analysis is performed to determine the main features of both multiring localized structures, particularly their break-up, multiplet formation, overlapping of pulses, overcoming of one pulse by another, "amplitude-width" complementarity, etc., that are typically ascribed to a solitonlike behavior. For all the localized structures investigated, the solitonlike character of the rings is found to be preserved during (almost) entire temporal evolution. Due to their cylindrical character, each ring belonging to one of these multiring localized structures experiences the physiological decay of the peak and the physiological increase of the width, respectively, while propagating ("amplitude-width" complementarity). As in the planar geometry, i.e., planar Korteweg-de Vries equation (pKdVE), we show that, in the case of the

  6. Molecular dynamics simulation of the behaviour of water in nano-confined ionic liquid-water mixtures

    NASA Astrophysics Data System (ADS)

    Docampo-Álvarez, B.; Gómez-González, V.; Montes-Campos, H.; Otero-Mato, J. M.; Méndez-Morales, T.; Cabeza, O.; Gallego, L. J.; Lynden-Bell, R. M.; Ivaništšev, V. B.; Fedorov, M. V.; Varela, L. M.

    2016-11-01

    This work describes the behaviour of water molecules in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid under nanoconfinement, between graphene sheets. By means of molecular dynamics simulations, the adsorption of water molecules at the graphene surface is studied. A depletion of water molecules in the vicinity of the neutral and negatively charged graphene surfaces, and their adsorption at the positively charged surface are observed in line with the preferential hydration of the ionic liquid anions. The findings are appropriately described using a two-level statistical model. The confinement effect on the structure and dynamics of