Assessing the Behavior of Typically Lithophile Elements Under Highly Reducing Conditions Relevant to the Planet Mercury

NASA Technical Reports Server (NTRS)

Rowland, Rick, II; Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Danielson, Lisa R.

2017-01-01

With the data returned from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, there are now numerous constraints on the physical and chemical properties of Mercury, including its surface composition. The high Sand low FeO contents observed from MESSENGER suggest a low oxygen fugacity of the present materials on the planet's surface. Most of our understanding of elemental partitioning behavior comes from observations made on terrestrial rocks, but Mercury's oxygen fugacity is far outside the conditions of those samples, estimated at approximately 3-7 log units below the Iron-Wtistite (lW) oxygen buffer, several orders of magnitude more reducing than other terrestrial bodies we have data from. With limited oxygen available, lithophile elements may instead exhibit chalcophile, halophile, or siderophile behaviors. Furthermore, very few natural samples of rocks that formed under reducing conditions (e.g., enstatite chondrites, achondrites, aubrites) are available in our collections for examination of this change in geochemical affinity. Our goal is to determine the elemental partitioning behavior of typically lithophile elements at lower oxygen fugacity as a function of temperature and pressure. Experiments were conducted at I GPa in a 13 mm QUICKpress piston cylinder and at 4 GPa in an 880-ton multianvil press, at temperatures up to 1850degC. The composition of starting materials for the experiments were designed so the final run products contained metal, silicate melt, and sulfide melt phases. Oxygen fugacity was controlled in the experiments by adding silicon metal to the samples, in order to utilize the Si-Si02 buffer, which is approximately 5 log units more reducing than the IW buffer at our temperatures of interest. The target silicate melt composition was diopside (CaMgSi206) because measured surface compositions indicate partial melting of a pyroxene-rich mantle. The results of our experiments will aid in our understanding of the fate of elements during the differentiation and thermal evolution of Mercury and other highly reducing planetary bodies.

OH in Rutile: an Oxygen and Water Barometer

NASA Astrophysics Data System (ADS)

Johnson, E. A.; Manning, C. E.; Antignano, A.; Tropper, P.

2005-12-01

Dehydration of the subducting lithosphere induces oxidation and partial melting in the mantle wedge above subduction zones, and storage of water in the form of hydroxyl in high-pressure mineral phases may be an important mechanism for transfer of water to the mantle. It is therefore important to quantify water content of fluids and oxygen fugacity in subduction zones, but these variables can be difficult to measure or infer in many rocks. This study investigates the possibility of determining oxygen fugacity or water activity based on OH concentration measurements in rutile. The solubility of OH in pure rutile has been determined using rutile grains from aqueous fluid solubility experiments (Tropper and Manning 2005, Am Min, 90, 502). In pure rutile, H+ is stoichiometrically incorporated into the structure via reduction of Ti4+ to Ti3+, resulting in a change in color from pale yellow to deep blue. Synthetic rutile crystals were equilibrated in pure H2O or a H2O-NaCl solution at 1-2 GPa and 600-1100°C. The runs were unbuffered with respect to oxygen fugacity but were close to the NNO buffer (Newton and Manning 2005, J Petr, 46, 701). Rutile OH concentrations were determined using FTIR spectroscopy and the calibration of Maldener (2001, Min Pet, 71, 21). At a constant pressure of 1 GPa, OH concentrations of rutile in equilibrium with pure H2O increase exponentially from 600 to 1100°C. The data are fit with the equation [OH] = 17.7exp(4.00×10-3T) (R=0.998), where [OH] is in ppm H2O wt. and T is in °C. Increasing pressure from 1 to 2 GPa at 1100°C results in an increase in OH solubility from 1540 to 2220 ppm H2O. OH solubility in rutile decreases from 2220 to 1290 ppm H2O by lowering the water activity of the fluid from 1 to 0.49 at P = 2 GPa and T = 1100°C. Using the solubility data and the exchange reaction, Ti3+O(OH) + O2 = Ti4+O2 + <

Assessing the Behavior of Typically Lithophile Elements Under Highly Reducing Conditions Relevant to the Planet Mercury

NASA Astrophysics Data System (ADS)

Rowland, R. L., II; Vander Kaaden, K. E.; McCubbin, F. M.; Danielson, L. R.

2017-12-01

With the data returned from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, there are now numerous constraints on the physical and chemical properties of Mercury, including its surface composition. The high S and low FeO contents observed from MESSENGER suggest a low oxygen fugacity of the present materials on the planet's surface. Most of our understanding of elemental partitioning behavior comes from observations made on terrestrial rocks, but Mercury's oxygen fugacity is far outside the conditions of those samples, estimated at approximately 3-7 log units below the Iron-Wüstite (IW) oxygen buffer, several orders of magnitude more reducing than other terrestrial bodies we have data from. With limited oxygen available, lithophile elements may instead exhibit chalcophile, halophile, or siderophile behaviors. Furthermore, very few natural samples of rocks that formed under reducing conditions (e.g., enstatite chondrites, achondrites, aubrites) are available in our collections for examination of this change in geochemical affinity. Our goal is to determine the elemental partitioning behavior of typically lithophile elements at lower oxygen fugacity as a function of temperature and pressure. Experiments were conducted at 1 GPa in a 13 mm QUICKpress piston cylinder and at 4 GPa in an 880-ton multi-anvil press, at temperatures up to 1850°C. The composition of starting materials for the experiments were designed so the final run products contained metal, silicate melt, and sulfide melt phases. Oxygen fugacity was controlled in the experiments by adding silicon metal to the samples, in order to utilize the Si-SiO2 buffer, which is 5 log units more reducing than the IW buffer at our temperatures of interest. The target silicate melt composition was diopside (CaMgSi2O6) because measured surface compositions indicate partial melting of a pyroxene-rich mantle. The results of our experiments will aid in our understanding of the fate of elements during the differentiation and thermal evolution of Mercury and other highly reducing planetary bodies.

Highly Reducing Partitioning Experiments Relevant to the Planet Mercury

NASA Technical Reports Server (NTRS)

Rowland, Rick, II; Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Danielson, Lisa R.

2017-01-01

With the data returned from the MErcury Surface Space ENvironment GEochemistry and Ranging (MESSENGER) mission, there are now numerous constraints on the physical and chemical properties of Mercury, including its surface composition. The high S and low FeO contents observed from MESSENGER on the planet's surface suggests a low oxygen fugacity of the present planetary materials. Estimates of the oxygen fugacity for Mercurian magmas are approximately 3-7 log units below the Iron-Wüstite (Fe-FeO) oxygen buffer, several orders of magnitude more reducing than other terrestrial bodies we have data from such as the Earth, Moon, or Mars. Most of our understanding of elemental partitioning behavior comes from observations made on terrestrial rocks, but Mercury's oxygen fugacity is far outside the conditions of those samples. With limited oxygen available, lithophile elements may instead exhibit chalcophile, halophile, or siderophile behaviors. Furthermore, very few natural samples of rocks that formed under reducing conditions are available in our collections (e.g., enstatite chondrites, achondrites, aubrites). With this limited amount of material, we must perform experiments to determine the elemental partitioning behavior of typically lithophile elements as a function of decreasing oxygen fugacity. Experiments are being conducted at 4 GPa in an 880-ton multi-anvil press, at temperatures up to 1850degC. The composition of starting materials for the experiments were selected for the final run products to contain metal, silicate melt, and sulfide melt phases. Oxygen fugacity is controlled in the experiments by adding silicon metal to the samples, using the Si-SiO2 oxygen buffer, which is approximately 5 log units more reducing than the Fe-FeO oxygen buffer at our temperatures of interest. The target silicate melt compositional is diopside (CaMgSi2O6) because measured surface compositions indicate partial melting of a pyroxene-rich mantle. Elements detected on Mercury's surface by MESSENGER (K, Na, Fe, Ti, Cl, Al, Cr, Mn, U, Th) and other geochemically relevant elements (P, F, H, N, C, Co, Ni, Mo, Ce, Nd, Sm, Eu, Gd, Dy, Yb) are added to the starting composition at trace abundances (approximately 500 ppm) so that they are close enough to infinite dilution to follow Henry's law of trace elements, and their partitioning behavior can be measured between the metal, silicate, and sulfide phases. The results of these experiments will allow us to assess the thermal and magmatic evolution of the planet Mercury from a geochemical standpoint.

Low hydrogen contents in the cores of terrestrial planets.

PubMed

Clesi, Vincent; Bouhifd, Mohamed Ali; Bolfan-Casanova, Nathalie; Manthilake, Geeth; Schiavi, Federica; Raepsaet, Caroline; Bureau, Hélène; Khodja, Hicham; Andrault, Denis

2018-03-01

Hydrogen has been thought to be an important light element in Earth's core due to possible siderophile behavior during core-mantle segregation. We reproduced planetary differentiation conditions using hydrogen contents of 450 to 1500 parts per million (ppm) in the silicate phase, pressures of 5 to 20 GPa, oxygen fugacity varying within IW-3.7 and IW-0.2 (0.2 to 3.7 log units lower than iron-wüstite buffer), and Fe alloys typical of planetary cores. We report hydrogen metal-silicate partition coefficients of ~2 × 10 -1 , up to two orders of magnitude lower than reported previously, and indicative of lithophile behavior. Our results imply H contents of ~60 ppm in the Earth and Martian cores. A simple water budget suggests that 90% of the water initially present in planetary building blocks was lost during planetary accretion. The retained water segregated preferentially into planetary mantles.

Oxygen fugacity of gases and rocks from Momotombo Volcano, Nicaragua: Application to volcanological monitoring

NASA Astrophysics Data System (ADS)

Benhamou, G.; Allard, P.; Sabroux, J. C.; Vitter, G.; Dajlevic, D.; Creusot, A.

1988-12-01

The oxygen fugacity (fO2) and the fO2 versus T°C relationship of high-temperature (600°-860°C) gas emissions from Momotombo volcano, Nicaragua, was determined from both field electrochemical measurements (electrolytic cell assembly) and thermodynamic computations on gas samples collected between 1978 and 1985. It was then compared with the intrinsic fO2 of fresh and altered lavas from the last eruption (1905), as measured between 500° and 1100°C in laboratory. The electrochemical results show that the oxygen fugacity of Momotombo fumaroles, at equivalent temperature, is much higher than that of the fresh 1905 lava (˜FMQ buffer) and closer to that of their altered wall rocks (˜FMQ buffer). The equilibrium O2 fugacities calculated from the chemistry of gas samples confirm this pattern. However, they suggest that the gas mixtures preserve the (variable) memory of a higher thermal equilibrium achieved at depth, under temperature and fO2 conditions of up to 1050°C and 10-9.0 atm, respectively, which correspond to the cross over between the fO2-T gas and lava trends. These data thus support the idea that Momotombo volcanic gases, released in a period of increasing activity, escape from a shallow magma body before suffering a variable oxidation during their ascent through both unbuffered cooling and reactions with environmental fluids and rocks. This late oxidation is weaker at central fumaroles than at peripherical ones. While between 1978 and 1985 the temperature of the hottest fumarole increased from 750° to 865°-900°C, the equilibrium fO2 of the gas decreased by nearly one order of magnitude (at comparable equilibrium temperature). Such an evolution presumably reflects an increasing connection between the surface exhalations and the magma degassing at depth along with time. This work underlines the possibility of monitoring the processes of magma ascent and gas-magma separation within a volcano before an eruption by continuously recording the changes of both oxygen fugacity and temperature in hot fumaroles.

Vegetated Ditches for the Mitigation of Pesticides Runoff in the Po Valley.

PubMed

Otto, Stefan; Pappalardo, Salvatore E; Cardinali, Alessandra; Masin, Roberta; Zanin, Giuseppe; Borin, Maurizio

2016-01-01

In intensive agricultural systems runoff is one of the major potential diffuse pollution pathways for pesticides and poses a risk to surface water. Ditches are common in the Po Valley and can potentially provide runoff mitigation for the protection of watercourses. The effectiveness depends on ditch characteristics, so there is an urgent need for site-specific field trials. The use of a fugacity model (multimedia model) can allows recognition of the mitigation main processes. A field experiment was conducted in order to evaluate the mitigation capacity of a typical vegetated ditch, and results were compared with predictions by a fugacity model. To evaluate herbicide mitigation after an extreme runoff, the ditch was flooded with water containing mesotrione, S-metolachlor and terbuthylazine. Two other subsequent floods with uncontaminated water were applied 27 and 82 days later to evaluate herbicides release. Results show that the ditch can immediately reduce runoff concentration of herbicides by at least 50% even in extreme flooding conditions. The half-distances were about 250 m. As a general rule, a runoff of 1 mm from 5 ha is mitigated by 99% in 100 m of vegetated ditch. Herbicides retention in the vegetated ditch was reversible, and the second flood mobilized 0.03-0.2% of the previous one, with a concentration below the drinking water limit of 0.1 μg L(-1). No herbicide was detected in the third flood, because the residual amount in the ditch was too low. Fugacity model results show that specific physical-chemical parameters may be used and a specific soil-sediment-plant compartment included for modelling herbicides behaviour in a vegetated ditch, and confirm that accumulation is low or negligible for herbicides with a half-life of 40 days or less. Shallow vegetated ditches can thus be included in a general agri-environment scheme for the mitigation of pesticides runoff together with wetlands and linear buffer strips. These structures are present in the landscape, and their environmental role can be exploited by proper management.

Vegetated Ditches for the Mitigation of Pesticides Runoff in the Po Valley

PubMed Central

Pappalardo, Salvatore E.; Cardinali, Alessandra; Masin, Roberta; Zanin, Giuseppe; Borin, Maurizio

2016-01-01

In intensive agricultural systems runoff is one of the major potential diffuse pollution pathways for pesticides and poses a risk to surface water. Ditches are common in the Po Valley and can potentially provide runoff mitigation for the protection of watercourses. The effectiveness depends on ditch characteristics, so there is an urgent need for site-specific field trials. The use of a fugacity model (multimedia model) can allows recognition of the mitigation main processes. A field experiment was conducted in order to evaluate the mitigation capacity of a typical vegetated ditch, and results were compared with predictions by a fugacity model. To evaluate herbicide mitigation after an extreme runoff, the ditch was flooded with water containing mesotrione, S-metolachlor and terbuthylazine. Two other subsequent floods with uncontaminated water were applied 27 and 82 days later to evaluate herbicides release. Results show that the ditch can immediately reduce runoff concentration of herbicides by at least 50% even in extreme flooding conditions. The half-distances were about 250 m. As a general rule, a runoff of 1 mm from 5 ha is mitigated by 99% in 100 m of vegetated ditch. Herbicides retention in the vegetated ditch was reversible, and the second flood mobilized 0.03-0.2% of the previous one, with a concentration below the drinking water limit of 0.1 μg L-1. No herbicide was detected in the third flood, because the residual amount in the ditch was too low. Fugacity model results show that specific physical-chemical parameters may be used and a specific soil-sediment-plant compartment included for modelling herbicides behaviour in a vegetated ditch, and confirm that accumulation is low or negligible for herbicides with a half-life of 40 days or less. Shallow vegetated ditches can thus be included in a general agri-environment scheme for the mitigation of pesticides runoff together with wetlands and linear buffer strips. These structures are present in the landscape, and their environmental role can be exploited by proper management. PMID:27070781

A modeling study of the long-term mineral trapping in deep saline marine sands aquifers (Invited)

NASA Astrophysics Data System (ADS)

Aagaard, P.; Pham, V.; Hellevang, H.

2009-12-01

Simulation of geochemical processes due to CO2 injection and storage are dependent on sediment petrography and the kinetics of mineral fluid reactions. Mineral trapping of CO2 in the Utsira sand and similar marine sand reservoirs have been revisited based on critical review of rate data and geochemical constraints on formation waters. Reaction paths calculations were done with the PHREEQC modeling software at relevant reservoir conditions covering a temperature range of 30-100 °C and corresponding reservoir pressures. Initial CO2 saturation was determined by the fluid fugacity corresponding with reservoir conditions. The mineral dissolution kinetics was expressed with a chemical affinity term (Aagaard & Helgeson,1982) while a critical super-saturation for mineral growth was included in the precipitation rate expression. The redox conditions and the H2S fugacity in the simulations were constrained by the acetic/propionic acid buffer trend and the magnetite-pyrite buffer (Aagaard et al. 2001) respectively. We used a revised mineralogical composition for the Utsira sand also performed a sensitivity analyses with respect to mineral content. The simulations were run over a period of 10000 years. The main simulation results included dissolution of glauconite, smectite, pyrite, muscovite and albite, with precipitation of the carbonates siderite, ankerite, and minor dawsonite, as well as kaolinite, silica (either chalcedony or quartz), and K-feldspar. The uncertainties in the simulations are specially connected with initial mineral abundances. The effect of critical super-saturation and reactive surface area for precipitation needs to be further evaluated and tested. Aagaard, P. and H.C. Helgeson (1982). Thermodynamic and Kinetic Constraints on Reaction Rates among Minerals and Aqueous Solutions. I. Theoretical Considerations. Am. J. Sci., v. 282, p. 257-285. P. Aagaard, J. Jahren & S.N. Ehrenberg (2001) H2S controling reactions in clastic hydrocarbon reservoirs from the Norwegian Shelf and Gulf Coast, in Cidu, R.(ed) Water-Rock Interaction, WRI-10, Balkema, p. 129-132.

The oxidation state of Fe in MORB glasses and the oxygen fugacity of the upper mantle

NASA Astrophysics Data System (ADS)

Cottrell, Elizabeth; Kelley, Katherine A.

2011-05-01

Micro-analytical determination of Fe3+/∑Fe ratios in mid-ocean ridge basalt (MORB) glasses using micro X-ray absorption near edge structure (μ-XANES) spectroscopy reveals a substantially more oxidized upper mantle than determined by previous studies. Here, we show that global MORBs yield average Fe3+/∑Fe ratios of 0.16 ± 0.01 (n = 103), which trace back to primary MORB melts equilibrated at the conditions of the quartz-fayalite-magnetite (QFM) buffer. Our results necessitate an upward revision of the Fe3+/∑Fe ratios of MORBs, mantle oxygen fugacity, and the ferric iron content of the mantle relative to previous wet chemical determinations. We show that only 0.01 (absolute, or < 10%) of the difference between Fe3+/∑Fe ratios determined by micro-colorimety and XANES can be attributed to the Mössbauer-based XANES calibration. The difference must instead derive from a bias between micro-colorimetry performed on experimental vs. natural basalts. Co-variations of Fe3+/∑Fe ratios in global MORB with indices of low-pressure fractional crystallization are consistent with Fe3+ behaving incompatibly in shallow MORB magma chambers. MORB Fe3+/∑Fe ratios do not, however, vary with indices of the extent of mantle melting (e.g., Na2O(8)) or water concentration. We offer two hypotheses to explain these observations: The bulk partition coefficient of Fe3+ may be higher during peridotite melting than previously thought, and may vary with temperature, or redox exchange between sulfide and sulfate species could buffer mantle melting at ~ QFM. Both explanations, in combination with the measured MORB Fe3+/∑Fe ratios, point to a fertile MORB source with greater than 0.3 wt.% Fe2O3.

Oxygen Fugacity at High Pressure: Equations of State of Metal-Oxide Pairs

NASA Technical Reports Server (NTRS)

Campbell A. J.; Danielson, L.; Righter, K.; Wang, Y.; Davidson, G.; Wang, Y.

2006-01-01

Oxygen fugacity (fO2) varies by orders of magnitude in nature, and can induce profound changes in the chemical state of a substance, and also in the chemical equilibrium of multicomponent systems. One prominent area in high pressure geochemistry, in which fO2 is widely recognized as a principal controlling factor, is that of metal-silicate partitioning of siderophile trace elements (e.g., [1]). Numerous experiments have shown that high pressures and temperatures can significantly affect metal/silicate partitioning of siderophile and moderately siderophile elements. Parameterization of these experimental results over P, T, X, and fO2 can allow the observed siderophile element composition of the mantle to be associated with particular thermodynamic conditions [2]. However, this is best done only if quantitative control exists over each thermodynamic variable relevant to the experiments. The fO2 values for many of these partitioning experiments were determined relative to a particular metal-oxide buffer (e.g., Fe-FeO (IW), Ni-NiO (NNO), Co-CoO, Re-ReO2 (RRO)), but the parameterization of all experimental results is weakened by the fact that the pressure-induced relative changes between these buffer systems are imprecisely known.

High temperature deformation of hot-pressed polycrystalline orthoenstatite. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Dehghan-Banadaki, A.

1983-01-01

Artificial hot pressed polycrystalline samples were prepared from purified powder of Bamble, Norway, orthoenstatite, (Mg0.86Fe0.14)SiO3. The uniaxial creep behavior of the polycrystalline orthoenstatite was studied over stress ranges of 10-180 MPa and temperatures of 1500-1700 K (0.82-0.93 T sub m) under two different oxygen fugacities, namely equilibrium (Mo-MoO2 buffer) and a reducing (graphite heating element) atmosphere, respectively. An intergranular glassy phase of different compositions with a cavitational creep deformation were observed. In the Mo-MoO2 buffer atmosphere with PO2 approx. 10 to the minus 11 power - 10 to the minus 13 power atmospheres, the results of an analytical electron microscopy analysis indicate that the glassy phases are richer in Ca and Al due to the residual impurities after hot pressing. In the reducing atmosphere with an oxygen fugacity of PO2 approx. 10 to the minus 3 power - 10 to the minus 25 power atmospheres, the results of analytical electron microscopy analysis indicate that the glassy phase is almost pure silica with the presence of free iron precipitate on grain facets and at triple junctions due to the reduction of bulk materials.

Oxygen fugacity of mare basalts and the lunar mantle application of a new microscale oxybarometer based on the valence state of vanadium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shearer, C.K.; Karner, J.; Papike, J.J.

2004-05-25

Using the valence state of vanadium on a microscale in lunar volcanic glasses we have developed another approach to estimating the oxygen fugacity of mare basalts. The ability to estimate oxygen fugacities for mare basalts and to extend these observations to the lunar mantle is limited using bulk analysis techniques based on buffering assemblages or the valence state of iron. These limitations are due to reequilibration of mineral assemblages at subsolidus conditions, deviations of mineral compositions from thermodynamic ideality, size requirements, and the limits of the iron valence at very low fO{sub 2}. Still, these approaches have been helpful andmore » indicate that mare basalts crystallized at fO{sub 2} between the iron-wuestite buffer (IW) and the ilmenite breakdown reaction (ilmenite = rutile + iron). It has also been inferred from these estimates that the lunar mantle is also highly reduced lying at conditions below IW. Generally, these data cannot be used to determine if the mare basalts become increasingly reduced during transport from their mantle source and eruption at the lunar surface and if there are differences in fO{sub 2} among mare basalts or mantle sources. One promising approach to determining the fO2 of mare basalts is using the mean valence of vanadium (2+, 3+, 4+, 5+) determined on spots of a few micrometers in diameter using synchrotron x-ray absorption fine structure (XAFS) spectroscopy. The average valence state of V in basaltic glasses is a function of fO{sub 2}, temperature, V coordination, and melt composition. Here, we report the initial results of this approach applied to lunar pyroclastic glasses.« less

Assessing the Behavior of Typically Lithophile Elements Under Highly Reducing Conditions Relevant to the Planet Mercury

NASA Technical Reports Server (NTRS)

Rowland, Rick, II; Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Danielson, Lisa R.

2017-01-01

With the data returned from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, there are now numerous constraints on the physical and chemical properties of Mercury, including its surface composition (e.g., Evans et al. 2012; Nittler et al. 201 l; Peplowski et al. 2012; Weider et al. 2012). The high Sand low FeO contents observed from MESSENGER on the planet's surface suggests a low oxygen fugacity of the present planetary materials. Estimates of the oxygen fugacity for Mercurian magmas are approximately 3- 7 log units below the Iron-Wiistite (Fe-FeO) oxygen buffer (McCubbin et al. 2012; Zolotov et al. 2013), several orders of magnitude more reducing than other terrestrial bodies we have data from such as the Earth, Moon, or Mars (Herd 2008; Sharp, McCubbin, and Shearer 2013; Wadhwa 2008). Most of our understanding of elemental partitioning behavior comes from observations made on terrestrial rocks, but Mercury's oxygen fugacity is far outside the conditions of those samples. With limited oxygen available, lithophile elements may instead exhibit chalcophile, halophile, or siderophile behaviors. Furthermore, very few natural samples of rocks that formed under reducing conditions are available in our collections (e.g., enstatite chondrites, achondrites, aubrites). The goal of this study is to conduct experiments at high pressure and temperature conditions to determine the elemental partitioning behavior of typically lithophile elements as a function of decreasing oxygen fugacity.

The effect of oxygen fugacity on the partitioning of nickel and cobalt between olivine, silicate melt, and metal

NASA Technical Reports Server (NTRS)

Ehlers, Karin; Grove, Timothy L.; Sisson, Thomas W.; Recca, Steven I.; Zervas, Deborah A.

1992-01-01

The effect of oxygen fugacity, f(O2), on the partitioning behavior of Ni and Co between olivine, silicate melt, and metal was investigated in the CaO-MgO-Al2O3-SiO2-FeO-Na2O system, an analogue of a chondrule composition from an ordinary chondrite. The conditions were 1350 C and 1 atm, with values of f(O2) varying between 10 exp -5.5 and 10 exp -12.6 atm (i.e., the f(O2) range relevant for crystal/liquid processes in terrestrial planets and meteorite parent bodies). Results of chemical analysis showed that the values of the Ni and Co partitioning coefficients begin to decrease at values of f(O2) that are about 3.9 log units below the nickel-nickel oxide and cobalt-cobalt oxide buffers, respectively, near the metal saturation for the chondrule analogue composition.

The effect of oxygen fugacity on the rheological evolution of crystallizing basaltic melts

NASA Astrophysics Data System (ADS)

Kolzenburg, S.; Di Genova, D.; Giordano, D.; Hess, K. U.; Dingwell, D. B.

2018-04-01

Storage and transport of silicate melts in the Earth's crust and their emplacement on the planet's surface occur almost exclusively at sub-liquidus temperatures. At these conditions, the melts undergo crystallization under a wide range of cooling-rates, deformation-rates, and oxygen fugacities (fO2). Oxygen fugacity is known to influence the thermodynamics and kinetics of crystallization in magmas and lavas. Yet, its influence on sub-liquidus rheology remains largely uncharted. We present the first rheological characterization of crystallizing lavas along natural cooling paths and deformation-rates and at varying fO2. Specifically, we report on apparent viscosity measurements for two crystallizing magmatic suspensions 1) at log ⁡ fO2 of -9.15 (quartz-fayalite-magnetite buffer, QFM, -2.1) and 2) in air. These fugacities span a range of reduced to oxidized conditions pertinent to magma migration and lava emplacement. We find that: 1) crystallization at constant cooling-rates results in a quasi-exponential increase in the apparent viscosity of the magmatic suspensions until they achieve their rheological cut off temperature (Tcutoff), where the melt effectively solidifies 2) the rheological departure and Tcutoff increase with increasing fO2 and 3) increasing fO2 results in decreased crystallization-rates. Based on the experimental results and by comparison with previous rheological isothermal studies we propose a generalisation of the effect of fO2 on the dynamic rheological evolution of natural magmatic and volcanic suspensions. We further discuss the implications for magmatic transport in plumbing and storage systems (e.g. conduits, dikes and magma chambers) and during lava flow emplacement.

Carbon and nitrogen speciation in nitrogen-rich C-O-H-N fluids at 5.5-7.8 GPa

NASA Astrophysics Data System (ADS)

Sokol, Alexander G.; Palyanov, Yury N.; Tomilenko, Anatoly A.; Bul'bak, Taras A.; Palyanova, Galina A.

2017-02-01

Carbon and nitrogen speciation has been studied in high-pressure experiments in the C-O-H-N and C-O-H-N-Fe3C systems at 5.5 to 7.8 GPa and 1100 to 1500 °C using a split-sphere multi-anvil apparatus. Oxygen fugacity in the samples was either buffered by the Mo-MoO2 (MMO) and Fe-FeO (IW) equilibria using a double-capsule technique or left unbuffered. fO2 varied from 2 log units below to +4 log units above the iron-wüstite oxygen buffer (IW) depending on water contents in the charges and buffering. Ultra-reduced fluids contained NH3 as the dominant species, but its concentration was slightly lower, while CH4 was higher at higher temperatures. As oxygen fugacity and temperature increased to fO2 0.7 log units above IW and T ≥ 1400 °C, N2 became the predominant nitrogen species; the dominance among carbon species changed from CH4 and C2-C5 alkanes to oxygenated hydrocarbons and higher alkanes. It has been found out for the first time that the N2-rich fluid lacks methane at fO2 4 log units above IW but may bear a few percent of C2H6, C3H8, and C15-C18 alkanes and within one percent of alcohols, aldehydes, ketones, carboxylic acids, and furans. Thus, the NH3 enrichment of fluids and the nitrogen storage capacity of silicates at depths ∼200 km are expected to be the greatest in cold (1100-1200 °C) and reduced continental lithospheric mantle. In a hotter lithosphere of ∼1400 °C, the concentrations of NH3 and N2 in fluids are similar, and the nitrogen storage capacity of silicates should be relatively low. The stability of some higher alkanes and oxygenated hydrocarbons in nitrogen-rich fluids near the enstatite-magnesite-olivine-diamond/graphite (EMOG/D) equilibrium suggest that these carbon species, together with N2, can survive at the redox barrier, where silicate or silicate-carbonate melts capture them and entrain to shallow mantle.

Copper and Gold Partitioning Between Brine and Vapor as a Function of Reduced Sulfur

NASA Astrophysics Data System (ADS)

Ehlich, J. J.; Frank, M. R.; Bodnar, R. J.

2017-12-01

This study examined Cu and Au partitioning between sulfur-rich vapors (v) and brines (b) at conditions representative of porphyry ore deposits. Experiments were conducted at 700 °C and 100 MPa, with oxygen fugacity, f(O2), buffered by either Ni-NiO or MnO-Mn3O4. Sulfur fugacity, f(S2), was buffered by pyrrhotite + chalcopyrite or bornite + pyrrhotite + chalcopyrite mineral assemblages between log -5.6 and log 0.6. The fugacities of H2S and SO2 were calculated using the known values of fO2 and fS2. In each experiment, a gold capsule was loaded with a sulfide assemblage, a quartz core to trap fluid inclusions, and a 5 wt.% NaCl-equivalent aqueous solution containing NaCl, KCl and HCl with molar NaCl:KCl and NaCl:HCl ratios of 1 and 100, respectively. Coexisting low salinity (v) and high salinity (b) inclusions were trapped in the quartz and their salinities were estimated using microthermometry, and verified against expected salinities from the NaCl-H2O system. Na, K, Fe, Cu, and Au concentrations from 73 b and 39 v fluid inclusions were determined using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Nernst-style partition coefficients between b and v for a given element (Dxb/v) were determined as a function of O2, S2, H2S, and SO2 fugacities. DCub/v ranged from 2.8 to 6.6 and increased with increasing f(O2), decreased with increasing f(S2), and decreased with increasing f(H2S). Gold partition coefficients ranged from 4.6 to 8.5, with DAub/v increasing with increasing f(O2), decreasing with increasing f(S2), and decreasing with increasing f(H2S). The absolute concentrations of Cu and Au increased in both the b and v phases with increasing f(H2S), but the increase was proportionally greater in v than b. Cu and Au partitioned into b relative to v at all conditions, but Dxb/v decreased slightly with decreasing O2 or increasing S2 fugacity. Dxb/v for Cu and Au appear most strongly linked to H2S, consistently decreasing with increasing f(H2S), but our data suggest that Cu and Au prefer chloride-complexes in porphyry systems (Dxb/v always >1). Reduced sulfur species may become increasingly important ligands in the porphyry-epithermal transition, in particularly high f(H2S) systems, or in systems dominated by a low salinity supercritical fluid or vapor.

Ferric iron partitioning between plagioclase and silicate liquid: thermodynamics and petrological applications

NASA Astrophysics Data System (ADS)

Sugawara, Toru

2001-06-01

A series of Fe and Mg partition experiments between plagioclase and silicate liquid were performed in the system SiO2-Al2O3-Fe2O3-FeO-MgO-CaO-Na2O under oxygen fugacities from below the IW buffer up to that of air. A thermodynamic model of plagioclase solid solution for the (CaAl,NaSi,KSi)(Fe3+,Al3+)Si2O8-Ca(Fe2+,Mg)Si3O8 system is proposed and is calibrated by regression analysis based on new and previously reported experimental data of Fe and Mg partitioning between plagioclase and silicate liquid, and reported thermodynamic properties of end members, ternary feldspar and silicate liquid. Using the derived thermodynamic model, FeOt, MgO content and Mg/(Fet+Mg) in plagioclase can be predicted from liquid composition with standard deviations of +/-0.34 wt% (relative error =9%) and +/-0.08 wt% (14%) and +/-0.7 (8%) respectively. Calculated Fe3+-Al exchange chemical potentials of plagioclase, $μ { Fe{ 3 + } ( {Al} ){ - 1} }{ Pl} agree with those calculated using reported thermodynamic models for multicomponent spinel, μ { Fe{ 3 + } ( {Al} ){ - 1} }{ Sp} and clinopyroxene, μ { Fe{ 3 + } ( {Al} ){ - 1} }{ Cpx} $ . The FeOt content of plagioclase coexisting with spinel or clinopyroxene is affected by Fe3+/(Fe3++Al) and Mg/(Fe+Mg) of spinel or clinopyroxene and temperature, while it is independent of the anorthite content of plagioclase. Three oxygen barometers based on the proposed model are investigated. Although the oxygen fugacities predicted by the plagioclase-liquid oxygen barometer are scattered, this study found that plagioclase-spinel-clinopyroxene-oxygen and plagioclase-olivine-oxygen equilibria can be used as practical oxygen barometers. As a petrological application, prediction of plagioclase composition and fO2 are carried out for the Upper Zone of the Skaergaard intrusion. The estimated oxygen fugacities are well below QFM buffer and consistent with the estimation of oxidization states in previous studies.

Miocene and early Pliocene epithermal gold-silver deposits in the northern Great Basin, western United States: Characteristics, distribution, and relationship to Magmatism

USGS Publications Warehouse

John, D.A.

2001-01-01

Numerous important Miocene and early Pliocene epithermal Au-Ag deposits are present in the northern Great Basin. Most deposits are spatially and temporally related to two magmatic assemblages: bimodal basalt-rhyolite and western andesite. These magmatic assemblages are petrogenetic suites that reflect variations in tectonic environment of magma generation. The bimodal assemblage is a K-rich tholeiitic series formed during continental rifting. Rocks in the bimodal assemblage consist mostly of basalt to andesite and rhyolite compositions that generally contain anhydrous and reduced mineral assemblages (e.g., quartz + fayalite rhyolites). Eruptive forms include mafic lava flows, dikes, cinder and/or spatter cones, shield volcanoes, silicic flows, domes, and ash-flow calderas. Fe-Ti oxide barometry indicates oxygen fugacities between the magnetite-wustite and fayalite-magnetite-quartz oxygen buffers for this magmatic assemblage. The western andesite assemblage is a high K calc-alkaline series that formed a continental-margin are related to subduction of oceanic crust beneath the western coast of North America. In the northern Great Basin, most of the western andesite assemblage was erupted in the Walker Lane belt, a zone of transtension and strike-slip faulting. The western andesite assemblage consists of stratovolcanoes, dome fields, and subvolcanic plutons, mostly of andesite and dacite composition. Biotite and hornblende phenocrysts are abundant in these rocks. Oxygen fugacities of the western andesite assemblage magmas were between the nickel-nickel oxide and hematite-magnetite buffers, about two to four orders of magnitude greater than magmas of the bimodal assemblage. Numerous low-sulfidation Au-Ag deposits in the bimodal assemblage include deposits in the Midas (Ken Snyder), Sleeper, DeLamar, Mule Canyon, Buckhorn, National, Hog Ranch, Ivanhoe, and Jarbidge districts; high-sulfidation gold and porphyry copper-gold deposits are absent. Both high- and low-sulfidation gold-silver and porphyry copper-gold deposits are affiliated with the western andesite assemblage and include the Comstock Lode, Tonopah, Goldfield, Aurora, Bodie, Paradise Peak, and Rawhide deposits. Low-sulfidation Au-Ag deposits in the bimodal assemblage formed under relatively low oxygen and sulfur fugacities and have generally low total base metal (Cu + Pb + Zn) contents, low Ag/Au ratios, and notably high selenide mineral contents compared to temporally equivalent low-sulfidation deposits in the western andesite assemblage. Petrologic studies suggest that these differences may reflect variations in the magmatic-tectonic settings of the associated magmatic assemblages-deposits in the western andesite assemblage formed from oxidized, water-rich, subduction-related calc-alkaline magmas, whereas deposits in the bimodal assemblage were associated with reduced, water-poor tholeiitic magmas derived from the lithospheric mantle during continental extension. The contrasting types and characteristics of epithermal deposits and their affinities with associated igneous rocks suggest that a genetic relationship is present between these Au-Ag deposits and their temporally associated magmatism, although available data do not prove this relationship for most low-sulfidation deposits.

Partitioning of Ni, Co and V between Spinel-Structured Oxides and Silicate Melts: Importance of Spinel Composition

NASA Technical Reports Server (NTRS)

Righter, K.; Leeman, W. P.; Hervig, R. L.

2006-01-01

Partitioning of Ni, Co and V between Cr-rich spinels and basaltic melt has been studied experimentally between 1150 and 1325 C, and at controlled oxygen fugacity from the Co-CoO buffer to slightly above the hematite magnetite buffer. These new results, together with new Ni, Co and V analyses of experimental run products from Leeman [Leeman, W.P., 1974. Experimental determination of the partitioning of divalent cations between olivine and basaltic liquid, Pt. II. PhD thesis, Univ. Oregon, 231 - 337.], show that experimentally determined spinel melt partition coefficients (D) are dependent upon temperature (T), oxygen fugacity (fO2) and spinel composition. In particular, partition coefficients determined on doped systems are higher than those in natural (undoped) systems, perhaps due to changing activity coefficients over the composition range defined by the experimental data. Using our new results and published runs (n =85), we obtain a multilinear regression equation that predicts experimental D(V) values as a function of T, fO2, concentration of V in melt and spinel composition. This equation allows prediction of D(V) spinel/melt values for natural mafic liquids at relevant crystallization conditions. Similarly, D(Ni) and D(Co) values can be inferred from our experiments at redox conditions approaching the QFM buffer, temperatures of 1150 to 1250 C and spinel composition (early Cr-bearing and later Ti-magnetite) appropriate for basic magma differentiation. When coupled with major element modelling of liquid lines of descent, these values (D(Ni) sp/melt=10 and D(Co) sp/melt=5) closely reproduce the compositional variation observed in komatiite, mid-ocean ridge basalt (MORB), ocean island basalt (OIB) and basalt to rhyolite suites.

Redox Evolution in Magma Oceans Due to Ferric/Ferrous Iron Partitioning

NASA Astrophysics Data System (ADS)

Schaefer, L.; Elkins-Tanton, L. T.; Pahlevan, K.

2017-12-01

A long-standing puzzle in the evolution of the Earth is that while the present day upper mantle has an oxygen fugacity close to the QFM buffer, core formation during accretion would have occurred at much lower oxygen fugacities close to IW. We present a new model based on experimental evidence that normal solidification and differentiation processes in the terrestrial magma ocean may explain both core formation and the current oxygen fugacity of the mantle without resorting to a change in source material or process. A commonly made assumption is that ferric iron (Fe3+) is negligible at such low oxygen fugacities [1]. However, recent work on Fe3+/Fe2+ ratios in molten silicates [2-4] suggests that the Fe3+ content should increase at high pressure for a given oxygen fugacity. While disproportionation was not observed in these experiments, it may nonetheless be occurring in the melt at high pressure [5]. Therefore, there may be non-negligible amounts of Fe3+ formed through metal-silicate equilibration at high pressures within the magma ocean. Homogenization of the mantle and further partitioning of Fe2+/Fe3+ as the magma ocean crystallizes may explain the oxygen fugacity of the Earth's mantle without requiring additional oxidation mechanisms. We present here models using different parameterizations for the Fe2+/Fe3+ thermodynamic relationships in silicate melts to constrain the evolution of the redox state of the magma ocean as it crystallizes. The model begins with metal-silicate partitioning at high pressure to form the core and set the initial Fe3+ abundance. Combined with previous work on oxygen absorption by magma oceans due to escape of H from H2O [6], we show that the upper layers of solidifying magma oceans should be more oxidized than the lower mantle. This model also suggests that large terrestrial planets should have more oxidized mantles than small planets. From a redox perspective, no change in the composition of the Earth's accreting material needs to be invoked to explain mantle oxygen fugacity, although implications for trace elements in the Earth's core and mantle are still being explored. [1] Ringwood, AE (1979) [2] Armstrong, K et al (2016) LPSC, 2580 [3] Armstrong, K et al (2017) ACCRETE workshop [4] Zhang, HL et al (2017) GCA, 204, 83 [5] Frost, DJ et al (2004) Nature, 428, 409 [6] Schaefer, L et al (2016) ApJ, 829, 63

Constraints on oxygen fugacity within metal capsules

NASA Astrophysics Data System (ADS)

Faul, Ulrich H.; Cline, Christopher J., II; Berry, Andrew; Jackson, Ian; Garapić, Gordana

2018-06-01

Experiments were conducted with olivine encapsulated or wrapped in five different metals (Pt, Ni, Ni_{70}Fe_{30}, Fe, and Re) to determine the oxygen fugacity in the interior of large capsules used for deformation and seismic property experiments. Temperature (1200°C), pressure (300 MPa), and duration (24 h) were chosen to represent the most common conditions in these experiments. The oxygen fugacity was determined by analysing the Fe content of initially pure Pt particles that were mixed with the olivine powder prior to the experiments. Oxygen fugacities in the more oxidizing metal containers are substantially below their respective metal-oxide buffers, with the fO_2 of sol-gel olivine in Ni about 2.5 orders of magnitude below Ni-NiO. Analysis of olivine and metal blebs reveals three different length-, and hence diffusive time scales: (1) Fe loss to the capsule over ˜ 100 μ m, (2) fO_2 gradients at the sample-capsule interface up to 2 mm into the sample, and (3) constant interior fO_2 values with an ordering corresponding to the capsule material. The inferred diffusive processes are: Fe diffusion in olivine with a diffusivity ˜ 10^{-14} m^2/s, diffusion possibly of oxygen along grain boundaries with a diffusivity ˜ 10^{-12} m^2/s, and diffusion possibly involving pre-existing defects with a diffusivity ˜ 10^{-10} m^2/s. The latter, fast adjustment to changing fO_2 may consist of a rearrangement of pre-existing defects, representing a metastable equilibrium, analogous to decoration of pre-existing defects by hydrogen. Full adjustment to the external fO_2 requires atomic diffusion.

Hydrogen-water vapor mixtures: Control of hydrothermal atmospheres by hydrogen osmosis

USGS Publications Warehouse

Shaw, H.R.

1963-01-01

Experiments at 700??C and 800 bars total pressure demonstrate positive deviations from ideality for mixtures of hydrogen and H2O gases. The deviations are greater than predicted with Stockmayer's method. The composition of the mixture and the fugacity of hydrogen are controlled by diffusing hydrogen through metallic membranes. The results give the fugacities of both H 2O and oxygen.

Fluid-absent metamorphism in the Adirondacks

NASA Technical Reports Server (NTRS)

Valley, J. W.

1986-01-01

Results on late Proterozoic metamorphism of granulite in the Adirondacks are presented. There more than 20,000 sq km of rock are at granulite facies. Low water fugacites are implied by orthopyroxene bearing assemblages and by stability of k'spar-plag-quartz assemblages. After mentioning the popular concept of infiltration of carbon dioxide into Precambrian rocks and attendent generation of granulite facies assemblages, several features of Adirondack rocks pertinent to carbon dioxide and water during their metamorphism are summarized: wollastonite occurs in the western lowlands; contact metamorphism by anorthosite preceeding granulite metamorphism is indicated by oxygen isotopes. Oxygen fugacity lies below that of the QFM buffer; total P sub water + P sub carbon dioxide determined from monticellite bearing assemblages are much less than P sub total (7 to 7.6 kb). These and other features indicate close spatial association of high- and low-P sub carbon dioxide assemblages and that a vapor phase was not present during metamorphism. Thus Adirondack rocks were not infiltrated by carbon dioxide vapor. Their metamorphism, at 625 to 775 C, occurred either when the protoliths were relatively dry or after dessication occurred by removal of a partial melt phase.

Explosive volcanism and the graphite-oxygen fugacity buffer on the parent asteroid(s) of the ureilite meteorites

NASA Technical Reports Server (NTRS)

Warren, Paul H.; Kallemeyn, Gregory W.

1992-01-01

A new model of the production of the uniformly low plagioclase and Al contents of ureilites is proposed. It is argued that those contents are consequences of widespread explosive volcanism during the evolution of the parent asteroid(s). It is noted that the great abundance of graphite on the ureilite asteroid(s) made them ideal sites for explosive volcanism driven by oxidation of graphite in partial melts ascending within the asteroid(s).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alderman, O. L. G.; Wilding, M. C.; Tamalonis, A.

Here, the local structure about Fe(II) and Fe(III) in silicate melts was investigated in-situ using iron K-edge X-ray absorption near-edge structure (XANES) spectroscopy. An aerodynamic levitation and laser heating system was used to allow access to high temperatures without contamination, and was combined with a chamber and gas mixing system to allow the iron oxidation state, Fe 3+/ΣFe, to be varied by systematic control of the atmospheric oxygen fugacity. Eleven alkali-free, mostly iron-rich and depolymerized base compositions were chosen for the experiments, including pure oxide FeO, olivines (Fe,Mg) 2SiO 4, pyroxenes (Fe,Mg)SiO 3, calcic FeO-CaSiO 3, and a calcium aluminosilicatemore » composition, where total iron content is denoted by FeO for convenience. Melt temperatures varied between 1410 and 2160 K and oxygen fugacities between FMQ – 2.3(3) to FMQ + 9.1(3) log units (uncertainties in parentheses) relative to the fayalite-magnetite-β-quartz (FMQ) buffer.« less

Gold-bearing hedenbergite skarns from the SW contact of the Andorra granite (Central Pyrenees, Spain)

NASA Astrophysics Data System (ADS)

Soler, A.; Ayora, C.; Cardellach, E.; Delgado, J.

1990-12-01

Several varieties of skarn outcrop have been found to develop along the contact between the Andorra granite and the Devonian limestones. The skarns contain variable amounts of gold ranging up to 5 g/t, always associated with sulphides. The sulphides in the skarn include arsenopyrite and pyrrhotite with lesser amounts of chalcopyrite, galena, sphalerite and Bi-minerals. Geothermometric and geobarometric data indicate the skarns formed at about 2 kbar and temperatures ranging from 500 ° to 350 °C from CO2-free polysaline brines at a slightly acidic pH and oxygen fugacity which decreases with time from the pyrite-pyrrhotite-magnetite towards the QFM buffer. Available data on gold solubility suggest that sufficient quantities of gold to form an ore deposit could have been transported as AuCl{2/-}at the high temperatures and salinities under which the skarns formed. Both gold deposition and sulphide precipitation could have occurred due to a decrease in temperature and/or oxygen fugacity.

Iron Redox Systematics of Shergottites and Martian Magmas

NASA Technical Reports Server (NTRS)

Righter, Kevin; Danielson, L. R.; Martin, A. M.; Newville, M.; Choi, Y.

2010-01-01

Martian meteorites record a range of oxygen fugacities from near the IW buffer to above FMQ buffer [1]. In terrestrial magmas, Fe(3+)/ SigmaFe for this fO2 range are between 0 and 0.25 [2]. Such variation will affect the stability of oxides, pyroxenes, and how the melt equilibrates with volatile species. An understanding of the variation of Fe(3+)/SigmaFe for martian magmas is lacking, and previous work has been on FeO-poor and Al2O3-rich terrestrial basalts. We have initiated a study of the iron redox systematics of martian magmas to better understand FeO and Fe2O3 stability, the stability of magnetite, and the low Ca/high Ca pyroxene [3] ratios observed at the surface.

Noble Metal Arsenides and Gold Inclusions in Northwest Africa 8186

NASA Technical Reports Server (NTRS)

Srinivasan, P.; McCubbin, F. M.; Rahman, Z.; Keller, L. P.; Agee, C. B.

2016-01-01

CK carbonaceous chondrites are a highly thermally altered group of carbonaceous chondrites, experiencing temperatures ranging between approximately 576-867 degrees Centigrade. Additionally, the mineralogy of the CK chondrites record the highest overall oxygen fugacity of all chondrites, above the fayalite-magnetite-quartz (FMQ) buffer. Me-tallic Fe-Ni is extremely rare in CK chondrites, but magnetite and Fe,Ni sulfides are commonly observed. Noble metal-rich inclusions have previously been found in some magnetite and sulfide grains. These arsenides, tellurides, and sulfides, which contain varying amounts of Pt, Ru, Os, Te, As, Ir, and S, are thought to form either by condensation from a solar gas, or by exsolution during metamorphism on the chondritic parent body. Northwest Africa (NWA) 8186 is a highly metamorphosed CK chondrite. This meteorite is predominately composed of NiO-rich forsteritic olivine (Fo65), with lesser amounts of plagioclase (An52), augite (Fs11Wo49), magnetite (with exsolved titanomagnetite, hercynite, and titanohematite), monosulfide solid solution (with exsolved pentlandite), and the phosphate minerals Cl-apatite and merrillite. This meteorite contains coarse-grained, homogeneous silicates, and has 120-degree triple junctions between mineral phases, which indicates a high degree of thermal metamorphism. The presence of NiO-rich olivine, oxides phases all bearing Fe3 plus, and the absence of metal, are consistent with an oxygen fugacity above the FMQ buffer. We also observed noble metal-rich phases within sulfide grains in NWA 8186, which are the primary focus of the present study.

Noble Metal Arsenides and Gold Inclusions in Northwest Africa 8186

NASA Technical Reports Server (NTRS)

Srinivasan, P.; McCubbin, F. M.; Rahman, Z.; Keller, L. P.; Agee, C. B.

2016-01-01

CK carbonaceous chondrites are a highly thermally altered group of carbonaceous chondrites, experiencing temperatures ranging between approx.576-867 C. Additionally, the mineralogy of the CK chondrites record the highest overall oxygen fugacity of all chondrites, above the fayalite-magnetite-quartz (FMQ) buffer. Metallic Fe-Ni is extremely rare in CK chondrites, but magnetite and Fe,Ni sulfides are commonly observed. Noble metal-rich inclusions have previously been found in some magnetite and sulfide grains. These arsenides, tellurides, and sulfides, which contain varying amounts of Pt, Ru, Os, Te, As, Ir, and S, are thought to form either by condensation from a solar gas, or by exsolution during metamorphism on the chondritic parent body. Northwest Africa (NWA) 8186 is a highly metamorphosed CK chondrite. This meteorite is predominately composed of NiO-rich forsteritic olivine (Fo65), with lesser amounts of plagioclase (An52), augite (Fs11Wo49), magnetite (with exsolved titanomagnetite, hercynite, and titanohematite), monosulfide solid solution (with exsolved pentlandite), and the phosphate minerals Cl-apatite and merrillite. This meteorite contains coarse-grained, homogeneous silicates, and has 120deg triple junctions between mineral phases, which indicates a high degree of thermal metamorphism. The presence of NiO-rich olivine, oxides phases all bearing Fe3+, and the absence of metal, are consistent with an oxygen fugacity above the FMQ buffer. We also observed noble metal-rich phases within sulfide grains in NWA 8186, which are the primary focus of the present study.

Oxygen Fugacity of Mare Basalts and the Lunar Mantle Application of a New Microscale Oxybarometer Based on the Valence State of Vanadium

NASA Technical Reports Server (NTRS)

Shearer, C. K.; Karner, J.; Papike, J. J.; Sutton, S. R.

2004-01-01

The ability to estimate oxygen fugacities for mare basalts and to extend these observations to the lunar mantle is limited using bulk analysis techniques based on buffering assemblages or the valence state of iron. These limitations are due to reequilibration of mineral assemblages at subsolidus conditions, deviations of mineral compositions from thermodynamic ideality, size requirements, and the limits of the iron valence at very low fO2. Still, these approaches have been helpful and indicate that mare basalts crystallized at fO2 between the iron-w stite buffer (IW) and the ilmenite breakdown reaction (ilmenite = rutile + iron). It has also been inferred from these estimates that the lunar mantle is also highly reduced lying at conditions below IW. Generally, these data cannot be used to determine if the mare basalts become increasingly reduced during transport from their mantle source and eruption at the lunar surface and if there are differences in fO2 among mare basalts or mantle sources. One promising approach to determining the fO2 of mare basalts is using the mean valence of vanadium (2+, 3+, 4+, 5+) determined on spots of a few micrometers in diameter using synchrotron x-ray absorption fine structure (XAFS) spectroscopy. The average valence state of V in basaltic glasses is a function of fO2, temperature, V coordination, and melt composition. Here, we report the initial results of this approach applied to lunar pyroclastic glasses.

Modeling the influence of climate change on the mass balance of polychlorinated biphenyls in the Adriatic Sea.

PubMed

Lamon, Lara; MacLeod, Matthew; Marcomini, Antonio; Hungerbühler, Konrad

2012-05-01

Climate forcing is forecasted to influence the Adriatic Sea region in a variety of ways, including increasing temperature, and affecting wind speeds, marine currents, precipitation and water salinity. The Adriatic Sea is intensively developed with agriculture, industry, and port activities that introduce pollutants to the environment. Here, we developed and applied a Level III fugacity model for the Adriatic Sea to estimate the current mass balance of polychlorinated biphenyls in the Sea, and to examine the effects of a climate change scenario on the distribution of these pollutants. The model's performance was evaluated for three PCB congeners against measured concentrations in the region using environmental parameters estimated from the 20th century climate scenario described in the Special Report on Emission Scenarios (SRES) by the IPCC, and using Monte Carlo uncertainty analysis. We find that modeled fugacities of PCBs in air, water and sediment of the Adriatic are in good agreement with observations. The model indicates that PCBs in the Adriatic Sea are closely coupled with the atmosphere, which acts as a net source to the water column. We used model experiments to assess the influence of changes in temperature, wind speed, precipitation, marine currents, particulate organic carbon and air inflow concentrations forecast in the IPCC A1B climate change scenario on the mass balance of PCBs in the Sea. Assuming an identical PCBs' emission profile (e.g. use pattern, treatment/disposal of stockpiles, mode of entry), modeled fugacities of PCBs in the Adriatic Sea under the A1B climate scenario are higher because higher temperatures reduce the fugacity capacity of air, water and sediments, and because diffusive sources to the air are stronger. Copyright © 2012 Elsevier Ltd. All rights reserved.

The W-W02 Oxygen Fugacity Buffer at High Pressures and Temperatures: Implications for f02 Buffering and Metal-silicate Partitioning

NASA Technical Reports Server (NTRS)

Shofner, G. A.; Campbell, A. J.; Danielson, L.; Righter, K.

2013-01-01

Oxygen fugacity (fO2) controls multivalent phase equilibria and partitioning of redox-sensitive elements, and it is important to understand this thermodynamic parameter in experimental and natural systems. The coexistence of a metal and its oxide at equilibrium constitutes an oxygen buffer which can be used to control or calculate fO2 in high pressure experiments. Application of 1-bar buffers to high pressure conditions can lead to inaccuracies in fO2 calculations because of unconstrained pressure dependencies. Extending fO2 buffers to pressures and temperatures corresponding to the Earth's deep interior requires precise determinations of the difference in volume (Delta) V) between the buffer phases. Synchrotron x-ray diffraction data were obtained using diamond anvil cells (DAC) and a multi anvil press (MAP) to measure unit cell volumes of W and WO2 at pressures and temperatures up to 70 GPa and 2300 K. These data were fitted to Birch-Murnaghan 3rd-order thermal equations of state using a thermal pressure approach; parameters for W are KT = 306 GPa, KT' = 4.06, and aKT = 0.00417 GPa K-1. Two structural phase transitions were observed for WO2 at 4 and 32 GPa with structures in P21/c, Pnma and C2/c space groups. Equations of state were fitted for these phases over their respective pressure ranges yielding the parameters KT = 190, 213, 300 GPa, KT' = 4.24, 5.17, 4 (fixed), and aKT = 0.00506, 0.00419, 0.00467 GPa K-1 for the P21/c, Pnma and C2/c phases, respectively. The W-WO2 buffer (WWO) was extended to high pressure by inverting the W and WO2 equations of state to obtain phase volumes at discrete pressures (1-bar to 100 GPa, 1 GPa increments) along isotherms (300 to 3000K, 100 K increments). The slope of the absolute fO2 of the WWO buffer is positive with increasing temperature up to approximately 70 GPa and is negative above this pressure. The slope is positive along isotherms from 1000 to 3000K with increasing pressure up to at least 100 GPa. The WWO buffer is at a higher fO2 than the IW buffer at pressures lower than 40 GPa, and the magnitude of this difference decreases at higher pressures. This qualitatively indicates an increasingly lithophile character for W at higher pressures. The WWO buffer was quantitatively applied to W metal-silicate partitioning by using the WWO-IW buffer difference in combination with literature data on W metal-silicate partitioning to model the exchange coefficient (KD) for the Fe-W exchange reaction. This approach captures the pressure dependence of W metal-silicate partitioning using the WWO-IW buffer difference and models the activities of the components in the silicate and metallic phases using an expression of the Gibbs excess energy of mixing. Calculation of KD along a peridotite liquidus predicts a decrease in W siderophility at higher pressures that supports the qualitative behavior predicted by the WWO-IW buffer difference, and agrees with findings of others. Comparing the competing effects of temperature and pressure on W metal-silicate partitioning, our results indicate that pressure exerts a greater effect.

Redox systematics of a magma ocean with variable pressure-temperature gradients and composition.

PubMed

Righter, K; Ghiorso, M S

2012-07-24

Oxygen fugacity in metal-bearing systems controls some fundamental aspects of the geochemistry of the early Earth, such as the FeO and siderophile trace element content of the mantle, volatile species that influence atmospheric composition, and conditions for organic compounds synthesis. Redox and metal-silicate equilibria in the early Earth are sensitive to oxygen fugacity (fO(2)), yet are poorly constrained in modeling and experimentation. High pressure and temperature experimentation and modeling in metal-silicate systems usually employs an approximation approach for estimating fO(2) that is based on the ratio of Fe and FeO [called "ΔIW (ratio)" hereafter]. We present a new approach that utilizes free energy and activity modeling of the equilibrium: Fe + SiO(2) + O(2) = Fe(2)SiO(4) to calculate absolute fO(2) and relative to the iron-wüstite (IW) buffer at pressure and temperature [ΔIW (P,T)]. This equilibrium is considered across a wide range of pressures and temperatures, including up to the liquidus temperature of peridotite (4,000 K at 50 GPa). Application of ΔIW (ratio) to metal-silicate experiments can be three or four orders of magnitude different from ΔIW (P,T) values calculated using free energy and activity modeling. We will also use this approach to consider the variation in oxygen fugacity in a magma ocean scenario for various thermal structures for the early Earth: hot liquidus gradient, 100 °C below the liquidus, hot and cool adiabatic gradients, and a cool subsolidus adiabat. The results are used to assess the effect of increasing P and T, changing silicate composition during accretion, and related to current models for accretion and core formation in the Earth. The fO(2) in a deep magma ocean scenario may become lower relative to the IW buffer at hotter and deeper conditions, which could include metal entrainment scenarios. Therefore, fO(2) may evolve from high to low fO(2) during Earth (and other differentiated bodies) accretion. Any modeling of core formation and metal-silicate equilibrium should take these effects into account.

Fugacity ratio estimations for high-melting rigid aromatic compounds.

PubMed

Van Noort, Paul C M

2004-07-01

Prediction of the environmental fate of organic compounds requires knowledge of their tendency to stay in the gas and water phase. Vapor pressure and aqueous solubility are commonly used descriptors for these processes. Depending on the type of distribution process, values for either the pure solid state or the (subcooled) liquid state have to be used. Values for the (subcooled) liquid state can be calculated from those for the solid state, and vice versa, using the fugacity ratio. Fugacity ratios are usually calculated from the entropy of fusion and the melting point. For polycyclic aromatic hydrocarbons, chlorobenzenes, chlorodibenzofuranes, and chlorodibenzo(p)dioxins, fugacity ratios calculated using experimental entropies of fusion were systematically less than those obtained from a thermodynamically more rigorous approach using heat capacity data. The deviation was more than 1 order of magnitude at the highest melting point. The use of a universal value for the entropy of fusion of 56 J/molK resulted in either over or underestimation by up to more than 1 order of magnitude. A simple correction factor, based on the melting point only, was derived. This correction factor allowed the fugacity ratios to be estimated from experimental entropies of fusion and melting point with an accuracy better than 0.1-0.2 log units. Copyright 2004 Elsevier Ltd.

Iron K-edge X-ray absorption near-edge structure spectroscopy of aerodynamically levitated silicate melts and glasses

DOE PAGES

Alderman, O. L. G.; Wilding, M. C.; Tamalonis, A.; ...

2017-01-26

Here, the local structure about Fe(II) and Fe(III) in silicate melts was investigated in-situ using iron K-edge X-ray absorption near-edge structure (XANES) spectroscopy. An aerodynamic levitation and laser heating system was used to allow access to high temperatures without contamination, and was combined with a chamber and gas mixing system to allow the iron oxidation state, Fe 3+/ΣFe, to be varied by systematic control of the atmospheric oxygen fugacity. Eleven alkali-free, mostly iron-rich and depolymerized base compositions were chosen for the experiments, including pure oxide FeO, olivines (Fe,Mg) 2SiO 4, pyroxenes (Fe,Mg)SiO 3, calcic FeO-CaSiO 3, and a calcium aluminosilicatemore » composition, where total iron content is denoted by FeO for convenience. Melt temperatures varied between 1410 and 2160 K and oxygen fugacities between FMQ – 2.3(3) to FMQ + 9.1(3) log units (uncertainties in parentheses) relative to the fayalite-magnetite-β-quartz (FMQ) buffer.« less

Highly oxidising fluids generated during serpentinite breakdown in subduction zones.

PubMed

Debret, B; Sverjensky, D A

2017-09-04

Subduction zones facilitate chemical exchanges between Earth's deep interior and volcanism that affects habitability of the surface environment. Lavas erupted at subduction zones are oxidized and release volatile species. These features may reflect a modification of the oxidation state of the sub-arc mantle by hydrous, oxidizing sulfate and/or carbonate-bearing fluids derived from subducting slabs. But the reason that the fluids are oxidizing has been unclear. Here we use theoretical chemical mass transfer calculations to predict the redox state of fluids generated during serpentinite dehydration. Specifically, the breakdown of antigorite to olivine, enstatite, and chlorite generates fluids with high oxygen fugacities, close to the hematite-magnetite buffer, that can contain significant amounts of sulfate. The migration of these fluids from the slab to the mantle wedge could therefore provide the oxidized source for the genesis of primary arc magmas that release gases to the atmosphere during volcanism. Our results also show that the evolution of oxygen fugacity in serpentinite during subduction is sensitive to the amount of sulfides and potentially metal alloys in bulk rock, possibly producing redox heterogeneities in subducting slabs.

The Mineralogy, Geochemistry, and Redox State of Multivalent Cations During the Crystallization of Primitive Shergottitic Liquids at Various (f)O2. Insights into the (f)O2 Fugacity of the Martian Mantle and Crustal Influences on Redox Conditions of Martian Magmas.

NASA Technical Reports Server (NTRS)

Shearer, C. K.; Bell, A. S.; Burger, P. V.; Papike, J. J.; Jones, J.; Le, L.; Muttik, N.

2016-01-01

The (f)O2 [oxygen fugacity] of crystallization for martian basalts has been estimated in various studies to range from IW-1 to QFM+4 [1-3]. A striking geochemical feature of the shergottites is the large range in initial Sr isotopic ratios and initial epsilon(sup Nd) values. Studies by observed that within the shergottite group the (f)O2 [oxygen fugacity] of crystallization is highly correlated with these chemical and isotopic characteristics with depleted shergottites generally crystallizing at reduced conditions and enriched shergottites crystallizing under more oxidizing conditions. More recent work has shown that (f)O2 [oxygen fugacity] changed during the crystallization of these magmas from one order of magnitude in Y980459 (Y98) to several orders of magnitude in Larkman Nunatak 06319. These real or apparent variations within single shergottitic magmas have been attributed to mixing of a xenocrystic olivine component, volatile loss-water disassociation, auto-oxidation during crystallization of mafic phases, and assimilation of an oxidizing crustal component (e.g. sulfate). In contrast to the shergottites, augite basalts such as NWA 8159 are highly depleted yet appear to be highly oxidized (e.g. QFM+4). As a first step in attempting to unravel petrologic complexities that influence (f)O2 [oxygen fugacity] in martian magmas, this study explores the effect of (f)O2 [oxygen fugacity] on the liquid line of descent (LLD) for a primitive shergottite liquid composition (Y98). The results of this study will provide a fundamental basis for reconstructing the record of (f)O2 [oxygen fugacity] in shergottites and other martian basalts, its effect on both mineral chemistries and valence state partitioning, and a means for examining the role of crystallization (and other more complex processes) on the petrologic linkages between olivine-phyric and pyroxene-plagioclase shergottites.

Oxygen Buffering in High Pressure Solid Media Assemblies: New Approach Enabling Study of fO2 from IW-4 to IW+4.5

NASA Technical Reports Server (NTRS)

Righter, K.; Pando, K. M.; Ross, D. K.; Butterworth, A. L.; Gainsforth, Z.; Jilly-Rehak, C. E.; Westphal, A. J.

2017-01-01

Oxygen fugacity is an intensive parameter that controls some fundamental chemical and physical properties in planetary materials. In terrestrial magmas high fO2 promotes magnetite stability and low fO2 causes Fe-enrichment due to magnetite suppression. In lunar and asteroidal basalts, low fO2 can allow metal to be stable. Experimental studies will therefore be most useful if they are done at a specific and relevant fO2 for the samples under consideration. Control of fO2 in the solid media apparatus (piston cylinder multi-anvil) has relied on either sliding sensors or graphite capsule buffering, which are of limited application to the wide range of fO2 recorded in planetary or astromaterials. Here we describe a new approach that allows fO2 to be specified across a wide range of values relevant to natural samples.

The oxidation state of the mantle and the extraction of carbon from Earth's interior.

PubMed

Stagno, Vincenzo; Ojwang, Dickson O; McCammon, Catherine A; Frost, Daniel J

2013-01-03

Determining the oxygen fugacity of Earth's silicate mantle is of prime importance because it affects the speciation and mobility of volatile elements in the interior and has controlled the character of degassing species from the Earth since the planet's formation. Oxygen fugacities recorded by garnet-bearing peridotite xenoliths from Archaean lithosphere are of particular interest, because they provide constraints on the nature of volatile-bearing metasomatic fluids and melts active in the oldest mantle samples, including those in which diamonds are found. Here we report the results of experiments to test garnet oxythermobarometry equilibria under high-pressure conditions relevant to the deepest mantle xenoliths. We present a formulation for the most successful equilibrium and use it to determine an accurate picture of the oxygen fugacity through cratonic lithosphere. The oxygen fugacity of the deepest rocks is found to be at least one order of magnitude more oxidized than previously estimated. At depths where diamonds can form, the oxygen fugacity is not compatible with the stability of either carbonate- or methane-rich liquid but is instead compatible with a metasomatic liquid poor in carbonate and dominated by either water or silicate melt. The equilibrium also indicates that the relative oxygen fugacity of garnet-bearing rocks will increase with decreasing depth during adiabatic decompression. This implies that carbon in the asthenospheric mantle will be hosted as graphite or diamond but will be oxidized to produce carbonate melt through the reduction of Fe(3+) in silicate minerals during upwelling. The depth of carbonate melt formation will depend on the ratio of Fe(3+) to total iron in the bulk rock. This 'redox melting' relationship has important implications for the onset of geophysically detectable incipient melting and for the extraction of carbon dioxide from the mantle through decompressive melting.

Electrical properties of granite with implications for the lower crust.

USGS Publications Warehouse

Olhoeft, G.R.

1981-01-01

The electrical properties of granite appear to be dominantly controlled by the amount of free water in the granite and by temperature. Minor contributions to the electrical properties are provided by hydrostatic and lithostatic pressure, structurally bound water, oxygen fugacity, and other parameters. The effect of sulphur fugacity may be important but is experimentally unconfirmed. In addition to changing the magnitude of electrical properties, the amount and chemistry of water in granite significantly changes the temperature dependence of the electrical properties. With increasing temperature, changes in water content retain large, but lessened, effects on electrical properties. Near room temperature, a monolayer of water will decrease the electrical resistivity by an order of magnitude. Several weight-percent water may decrease the electrical resistivity by as much as nine orders of magnitude and decrease the thermal activation energy by a factor of five. At elevated temperatures just below granitic melting, a few weight-percent water may still decrease the resistivity by as much as 3 orders of magnitude and the activation energy by a factor of two.-Author

The effect of water activity and oxygen fugacity on the phase relations and oxidation state of Fe in parental ferrobasaltic magma of Skaergaard

NASA Astrophysics Data System (ADS)

Botcharnikov, R.; Koepke, J.; Holtz, F.; McCammon, C.

2003-04-01

Phase relations and differentiation in the ferrobasaltic (FeO*=13wt%) system "SC1", an assumed parental liquid of the Skaergaard layered intrusion, have been investigated experimentally at dry conditions (1 atm) [1, 2]. However, the Skaergaard magma is believed to contain water. The present study investigates the role of water and fO2 on the phase relations and differentiation of the "SC1" ferrobasaltic system. The crystallization experiments have been performed in an internally heated pressure vessel equipped with a rapid quench facility and Shaw-membrane to determine the prevailing oxygen fugacity within the sample capsule [3]. To prevent the Fe-loss into the capsule material and ensure the desired conditions inside the capsule, the AuPd capsules were presaturated with iron and starting glasses were preequilibrated at the expected fO2 of the run. Water activity was varied by changing the H2O/CO2 ratio in the fluid phase. The first results of the experiments at P=200 MPa, T=1200-1000°C, various oxygen fugacities (logfO2=FMQ+4 to FMQ-1) and water activities (0 to 1) show that water influences not only the liquidus temperatures and temperature interval of mineral crystallization but also the sequence of crystallizing minerals; when compared with the dry system. Since water solubility strongly depends on pressure in the pressure range of 200-300 MPa, corresponding to the storage conditions of Skaergaard magma, the aH2O of hydrous magma may change significantly as a result of convection. Thus, convection has the potential to produce significant differences in stability and proportions of the prevailing minerals. This, in turn, may contribute to the formation of complex layering of the Skaergaard intrusion. The Moessbauer analysis of the quenched glasses shows that the Fe3+ / Sum Fe ratio of the silicate melt is a positive function of the water activity and has a linear dependence on water mole fraction in the system at 1200°C. The decrease of Fe3+ / Sum Fe ratio of the water-bearing melt with decreasing oxygen fugacity is more pronounced than that calculated for dry melts after [4]. [1] Toplis MJ &Carroll MR, J. Petrol., 36, 1137-1170, 1995. [2] Lattard D &Partsch GM, Eur. J. Mineral., 13, 467-478, 2001. [3] Berndt J et al., Am. Mineral., 87, 1717-1726, 2002. [4] Kress VC &Carmichael ISE, Contr.Min.Petrol., 108, 82-92, 1991.

Redox systematics of a magma ocean with variable pressure-temperature gradients and composition

PubMed Central

Righter, K.; Ghiorso, M. S.

2012-01-01

Oxygen fugacity in metal-bearing systems controls some fundamental aspects of the geochemistry of the early Earth, such as the FeO and siderophile trace element content of the mantle, volatile species that influence atmospheric composition, and conditions for organic compounds synthesis. Redox and metal-silicate equilibria in the early Earth are sensitive to oxygen fugacity (fO2), yet are poorly constrained in modeling and experimentation. High pressure and temperature experimentation and modeling in metal-silicate systems usually employs an approximation approach for estimating fO2 that is based on the ratio of Fe and FeO [called “ΔIW (ratio)” hereafter]. We present a new approach that utilizes free energy and activity modeling of the equilibrium: Fe + SiO2 + O2 = Fe2SiO4 to calculate absolute fO2 and relative to the iron-wüstite (IW) buffer at pressure and temperature [ΔIW (P,T)]. This equilibrium is considered across a wide range of pressures and temperatures, including up to the liquidus temperature of peridotite (4,000 K at 50 GPa). Application of ΔIW (ratio) to metal-silicate experiments can be three or four orders of magnitude different from ΔIW (P,T) values calculated using free energy and activity modeling. We will also use this approach to consider the variation in oxygen fugacity in a magma ocean scenario for various thermal structures for the early Earth: hot liquidus gradient, 100 °C below the liquidus, hot and cool adiabatic gradients, and a cool subsolidus adiabat. The results are used to assess the effect of increasing P and T, changing silicate composition during accretion, and related to current models for accretion and core formation in the Earth. The fO2 in a deep magma ocean scenario may become lower relative to the IW buffer at hotter and deeper conditions, which could include metal entrainment scenarios. Therefore, fO2 may evolve from high to low fO2 during Earth (and other differentiated bodies) accretion. Any modeling of core formation and metal-silicate equilibrium should take these effects into account. PMID:22778438

Sensing the flux of volatile chemicals through the air-water interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mackay, D.; Schroeder, W.H.; Ooijen, H. von

1997-12-31

There are several situations in which there is a need to assess the direction and magnitude of the flux across the air-water interface. Contaminants may be evaporating or absorbing in wastewater treatment systems in natural lake, river, estuarine and marine systems, and any attempt to compile a mass balance must include this process. In this study the authors review the theory underlying air-water exchange, then describe and discuss a sparging approach by which the direction and magnitude of the flux can be ascertained. The principle of the method is that a known flow rate of air is bubbled through themore » sparger and allowed to equilibrate with the water. The gas exiting the water surface is passed through a sorbent trap and later analyzed. The concentration, and hence the fugacity, of the contaminant in the sparged air can be deduced. In parallel, a similar flow of air from the atmosphere above the water is drawn through another sparger at a similar flow rate for a similar time and the trapped chemical analyzed giving the concentration and fugacity in the air. These data show the direction of air-water exchange (i.e. from high to low fugacity) and with information on the mass transfer coefficients and area, the flux. Successful tests were conducted of the system in a laboratory tank, in Lake Ontario and in Hamilton Harbour. Analyses of the traps showed a large number of peaks on the chromatogram many of which are believed to be of petroleum origin from fuels and vessel exhaust. The system will perform best under conditions where concentrations of specific contaminants are large, as occurs in waste water treatment systems. The approach has the potential to contribute to more accurate assessment of air-water fluxes. It avoids the problems of different analytical methodologies and the effect of sorption in the water column.« less

Experimental calibration of a new oxybarometer for silicic magmas based on the partitioning of vanadium between magnetite and silicate melt

NASA Astrophysics Data System (ADS)

Arató, Róbert; Audétat, Andreas

2016-04-01

Oxygen fugacity is an important parameter in magmatic systems that affects the stability of mineral phases and fluid species. However, there is no well-established method to reconstruct the oxygen fugacity of slowly cooled magmas such as granite, for example, because existing oxybarometers (e.g., magnetite-ilmenite method) are susceptible to re-equilibration processes during slow cooling and thus lead to erroneous results when applied for granitic rocks. In this study, we aim at developing an oxybarometer that is based on the partitioning of vanadium (a redox-sensitive element) between magnetite inclusions and silicate melt inclusions preserved in quartz phenocrysts, where they were protected from subsolidus alteration and can be measured as entities by LA-ICP-MS. In the first - experimental - part of this study we investigated the effects of temperature (800-950 ° C), pressure (1-2 kbar), oxygen fugacity (from ΔFMQ+0.7 to ΔFMQ+4.0), magnetite composition, and melt composition on the partition coefficient of vanadium between magnetite and melt (DVmgt-melt). The experiments were carried out in cold-seal pressure vessels and the starting material was a mixture of V-doped haplogranite glasses or natural obsidian powder with variable aluminum saturation index (ASI), and synthetic, V-free magnetite of 10-20 μm grain size. The vanadium partition coefficient was found to depend strongly on oxygen fugacity, and to lesser (but still considerable) degrees on melt composition and temperature. A more than 1.5 log unit decrease in DVmgt-melt values with increasing oxygen fugacity can be explained by a change of the dominant valence state of V in the silicate melt. For a given oxygen fugacity buffer DVmgt-melt decreases with increasing temperature, but this reflects mostly the change in absolute fO2 values while the net temperature effect is in fact positive. DVmgt-melt depends significantly on melt composition, resulting in higher D-values with increasing aluminum saturation index (ASI). This seems to reflect less favorable incorporation of V into peraluminous melts compared to depolymerized, peralkaline melts. Changing pressure from 1 to 2 kbar had an effect only at NNO, causing 0.3 log unit increase in D, whereas the Ti-content of magnetite turned out to have negligible effect on the V partitioning. In summary, the dependence of DVmgt-melt on temperature, ASI and oxygen fugacity can be described by the following regression equation: logD(V)mgt/melt=-1.22+0.31*10^5/T(° K) +1.73*ASI -0.49*ΔFMQ First tests of the equation on natural samples were carried out on rapidly cooled tuffs and vitrophyres from variable tectonic settings, for which fO2 could be constrained independently by the magnetite-ilmenite method. All calculated fO2 values fall within ± 0.75 log unit within those suggested by the Fe-Ti oxybarometer, whereas 12 out of 16 samples agree within 0.5 log units .

Modeling the effect of water on mantle rheology

NASA Technical Reports Server (NTRS)

Bounama, CH.; Franck, S.

1994-01-01

To study the thermal history of the Earth we use a parameterized model of mantle convection. This model includes a mathematical description of de- and regassing processes of water from the Earth's mantle. The rates of this processes are considered to be directly proportional to the seafloor spreading rate. The kinematic viscosity of the mantle depends on the temperature/pressure as well as on the volatile content. Dissolved volatiles such as water weaken the minerals by reducing their activation energy for solid state creep. Karato and Toriumi showed a power law dependence between creep rate and water fugacity derived from experimental results. Therefore, we use such flow parameters of diffusion creep in olivine under wet and dry conditions to calculate the mantle viscosity as a function of the water content. Because the creep rate is proportional to the concentration of water-related point deflects we assume that the water fugacity is proportional to the water weight fraction. An equation for the steady-state strain rate under wet conditions is established. To assess the unknown constant K in this equation, we use flow law parameters given by Karato and Wu as well as the results of McGovern and Schubert.

CuCl Complexation in the Vapor Phase: Insights from Ab Initio Molecular Dynamics Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, Yuan; Liu, Weihua; Migdiov, A. A.

We invesmore » tigated the hydration of the CuCl 0 complex in HCl-bearing water vapor at 350°C and a vapor-like fluid density between 0.02 and 0.09 g/cm 3 using ab initio molecular dynamics (MD) simulations. The simulations reveal that one water molecule is strongly bonded to Cu(I) (first coordination shell), forming a linear [H 2O-Cu-Cl] 0 moiety. The second hydration shell is highly dynamic in nature, and individual configurations have short life-spans in such low-density vapors, resulting in large fluctuations in instantaneous hydration numbers over a timescale of picoseconds. The average hydration number in the second shell (m) increased from ~0.5 to ~3.5 and the calculated number of hydrogen bonds per water molecule increased from 0.09 to 0.25 when fluid density (which is correlated to water activity) increased from 0.02 to 0.09 g/cm 3 ( f H 2O 1.72 to 2.05). These changes of hydration number are qualitatively consistent with previous solubility studies under similar conditions, although the absolute hydration numbers from MD were much lower than the values inferred by correlating experimental Cu fugacity with water fugacity. This could be due to the uncertainties in the MD simulations and uncertainty in the estimation of the fugacity coefficients for these highly nonideal “vapors” in the experiments. Finally, our study provides the first theoretical confirmation that beyond-first-shell hydrated metal complexes play an important role in metal transport in low-density hydrothermal fluids, even if it is highly disordered and dynamic in nature.« less

CuCl Complexation in the Vapor Phase: Insights from Ab Initio Molecular Dynamics Simulations

DOE PAGES

Mei, Yuan; Liu, Weihua; Migdiov, A. A.; ...

2018-05-02

We invesmore » tigated the hydration of the CuCl 0 complex in HCl-bearing water vapor at 350°C and a vapor-like fluid density between 0.02 and 0.09 g/cm 3 using ab initio molecular dynamics (MD) simulations. The simulations reveal that one water molecule is strongly bonded to Cu(I) (first coordination shell), forming a linear [H 2O-Cu-Cl] 0 moiety. The second hydration shell is highly dynamic in nature, and individual configurations have short life-spans in such low-density vapors, resulting in large fluctuations in instantaneous hydration numbers over a timescale of picoseconds. The average hydration number in the second shell (m) increased from ~0.5 to ~3.5 and the calculated number of hydrogen bonds per water molecule increased from 0.09 to 0.25 when fluid density (which is correlated to water activity) increased from 0.02 to 0.09 g/cm 3 ( f H 2O 1.72 to 2.05). These changes of hydration number are qualitatively consistent with previous solubility studies under similar conditions, although the absolute hydration numbers from MD were much lower than the values inferred by correlating experimental Cu fugacity with water fugacity. This could be due to the uncertainties in the MD simulations and uncertainty in the estimation of the fugacity coefficients for these highly nonideal “vapors” in the experiments. Finally, our study provides the first theoretical confirmation that beyond-first-shell hydrated metal complexes play an important role in metal transport in low-density hydrothermal fluids, even if it is highly disordered and dynamic in nature.« less

Formation of ore minerals in metamorphic rocks of the German continental deep drilling site (KTB)

NASA Astrophysics Data System (ADS)

Kontny, A.; Friedrich, G.; Behr, H. J.; de Wall, H.; Horn, E. E.; Möller, P.; Zulauf, G.

1997-08-01

The German Continental Deep Drilling Program (KTB) drilled a 9.1 km deep profile through amphibolite facies metamorphic rocks and reached in situ temperatures of 265°C. Each lithologic unit is characterized by typical ore mineral assemblages related to the regional metamorphic conditions. Paragneisses contain pyrrhotite + rutile + ilmenite ± graphite, metabasic units bear ilmenite + rutile + pyrrhotite ± pyrite, and additionally, the so-called variegated units yield pyrrhotite + titanite assemblages. In the latter unit, magnetite + ilmenite + rutile + titanite assemblages related to the lower amphibolite facies breakdown of ilmenite-hematite solid solution also occur locally. Retrograde hydrothermal mineralization which commenced during Upper Carboniferous times is characterized by the following geochemical conditions: (1) low saline Na-K-Mg-Cl fluids with sulfur and oxygen fugacities at the pyrite-pyrrhotite buffer and temperatures of 400-500°C, (2) fluids with CO2, CH4±N2, andpH, Eh, sulfur, and oxygen fugacity in the stability field of graphite + pyrite at temperatures of 280-350° and (3) moderate to high saline Ca-Na-Cl fluids with CH4+ N2; sulfur and oxygen fugacity are in the stability field of pyrrhotite at temperatures <300°C. The latter environment is confirmed by in situ conditions found at the bottom of the deep drilling. Monoclinic, ferrimagnetic pyrrhotite is the main carrier of magnetization which disappears below about 8.6 km, corresponding to in situ temperatures of about 250°C. Below this depth, hexagonal antiferromagnetic pyrrhotite with a Curie temperature of 260°C is the stable phase. Temperature-dependent transformation of pyrrhotite and the reaching of its Curie isotherm within the Earth crust are one of the striking results of the KTB deep drilling project.

The Mineralogical Record of Oxygen Fugacity Variation and Alteration in Northwest Africa 8159: Evidence for Interaction Between a Mantle Derived Martian Basalt and a Crustal Component(s)

NASA Technical Reports Server (NTRS)

Shearer, Charles K.; Burger, Paul V.; Bell, Aaron S.; McCubbin, Francis M.; Agee, Carl; Simon, Justin I.; Papike, James J.

2015-01-01

A prominent geochemical feature of basaltic magmatism on Mars is the large range in initial Sr isotopic ratios (approx. 0.702 - 0.724) and initial epsilon-Nd values (approx. -10 to greater than +50). Within this range, the shergottites fall into three discreet subgroups. These subgroups have distinct bulk rock REE patterns, mineral chemistries (i.e. phosphate REE patterns, Ni, Co, V in olivine), oxygen fugacity of crystallization, and stable isotopes, such as O. In contrast, nakhlites and chassignites have depleted epsilon-Nd values (greater than or equal to +15), have REE patterns that are light REE enriched, and appear to have crystallized near the FMQ buffer. The characteristics of these various martian basalts have been linked to different reservoirs in the martian crust and mantle, and their interactions during the petrogenesis of these magmas. These observations pose interesting interpretive challenges to our understanding of the conditions of the martian mantle (e.g. oxygen fugacity) and the interaction of mantle derived magmas with the martian crust and surface. Martian meteorite NWA 8159 is a unique fine-grained augite basalt derived from a highly depleted mantle source as reflected in its initial epsilon-Nd value, contains a pronounced light REE depleted pattern, and crystallized presumably under very oxidizing conditions. Although considerably older than both shergottites and nahklites, it has been petrogenetically linked to both styles of martian magmatism. These unique characteristics of NWA 8159 may provide an additional perspective for deciphering the petrogenesis of martian basalts and the nature of the crust of Mars.

Diffusion of Redox-Sensitive Elements in Basalt at Different Oxygen Fugacities

NASA Technical Reports Server (NTRS)

Szumila, I.; Trail, D.; Danielson, L. R.

2017-01-01

The terrestrial planets and moons of our solar system have differentiated over a range of oxygen fugacity conditions. Basalts formed from magmas on the Earth cover a range of more oxidized states (from approximately IW (iron wustite) plus 2 to approximately FMQ (fayalite-magnetite-quartz) plus 3) than crustal rocks from Mars (IW to approximately IW plus 3), and basalts from the Moon are more reduced than both, ranging from IW to IW minus 2. The small body Vesta differentiated around IW minus 4. Characterization of redox sensitive elements' diffusivities will offer insight into behavior of these elements as a function of f (fugacity of) O2 for these planetary bodies. Here, we report a systematic study of the diffusion of redox-sensitive elements in basaltic melts with varying oxygen fugacities (fO2) for trace elements, V, Nb, W, Mo, La, Ce, Pr, Sm, Eu, Gd, Ta, and W. Since fO2 is an intensive variable that is different for the reservoirs of various planets and moons in our solar system, it is important to characterize how changes in redox states will affect diffusion. We conducted experiments in a piston cylinder device at 1300 degrees Centigrade and 1 gigapascal, at the University of Rochester and NASA Johnson Space Center. We buffered some experiments at Ru-RuO2 (FMQ plus 6.00), and conducted other experiments within either a graphite or Mo capsule, which corresponds to fO2s of either FMQ minus1.2, or FMQ minus 3.00, respectively. Characterizing the diffusivities of redox sensitive elements at different fO2s is important because some elements, like Eu, have varying valence states, such as Eu (sup 2 plus) and Eu (sup 3 plus). Differences in charge and ion radii may lead to differences in diffusivities within silicate melts. This could, lead to formation of a Eu anomaly by diffusion, the magnitude of which may be controlled by the fO2. Characterization of trace element diffusion is also important in understanding trace element fractionation. We found, during the course of our investigation, that not only did the diffusivities of the redox sensitive elements change with fO2, but that the diffusivities of all other analyzed elements also changed. This indicates that not only do changes in valence influence trace elements diffusivities but that the structure of melt may have changed with varying oxygen fugacity, probably due to changes in the speciation of the major element Fe.

SNC Oxygen Fugacity Recorded in Pyroxenes and its Implications for the Oxidation State of the Martian Interior: An Experimental and Analytical Study

NASA Technical Reports Server (NTRS)

McCanta, M. C.; Rutherford, M. J.

2003-01-01

Knowledge of the oxidation state of a magma is critical as it is one of the parameters which controls the nature and composition of the resulting crystals. In terrestrial magmatic systems, oxygen fugacity (fo2) is known to vary by over nine orders of magnitude. With variations of this magnitude, understanding the compositional differences, phase changes, and crystallization sequence variations, caused by the magma fo2, is essential in deciphering the origin of all igneous rocks. Magmatic oxidation state is of great importance in that it reflects the degree of oxidation of the source region and can provide insight into magmatic processes, such as metasomatism, degassing, and assimilation, which may have changed them. Carmichael [1991] argues that most magmas are unlikely to have their redox states altered from those of their source region. This assumption allows for estimation of the oxidation state of planetary interiors. Conversely, it is known that the fo2 of the magma can be affected by other processes, which occur outside of the source region and therefore, the oxidation state may record those too. Processes which could overprint source region fugacities include melt dehydrogenation or other volatile loss, water or melt infiltration, or assimilation of oxidized or reduced wallrock. Understanding which of these processes is responsible for the redox state of a magma can provide crucial information regarding igneous processes and other forces active in the region. The composition of the SNC basalts and their widely varying proposed oxidation states raise some interesting questions. Do the SNC meteorites have an oxidized or reduced signature? What was the oxygen fugacity of the SNC source region at the time of melt generation? Is the fugacity calculated for the various SNC samples the fugacity of the magma source region or was it overprinted by later events? Are there different oxidation states in the Martian interior or a single one? This proposal seeks to address all of these questions.

Acute and chronic environmental effects of clandestine methamphetamine waste.

PubMed

Kates, Lisa N; Knapp, Charles W; Keenan, Helen E

2014-09-15

The illicit manufacture of methamphetamine (MAP) produces substantial amounts of hazardous waste that is dumped illegally. This study presents the first environmental evaluation of waste produced from illicit MAP manufacture. Chemical oxygen demand (COD) was measured to assess immediate oxygen depletion effects. A mixture of five waste components (10mg/L/chemical) was found to have a COD (130 mg/L) higher than the European Union wastewater discharge regulations (125 mg/L). Two environmental partition coefficients, K(OW) and K(OC), were measured for several chemicals identified in MAP waste. Experimental values were input into a computer fugacity model (EPI Suite™) to estimate environmental fate. Experimental log K(OW) values ranged from -0.98 to 4.91, which were in accordance with computer estimated values. Experimental K(OC) values ranged from 11 to 72, which were much lower than the default computer values. The experimental fugacity model for discharge to water estimates that waste components will remain in the water compartment for 15 to 37 days. Using a combination of laboratory experimentation and computer modelling, the environmental fate of MAP waste products was estimated. While fugacity models using experimental and computational values were very similar, default computer models should not take the place of laboratory experimentation. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of fO2 on phase relationship in basaltic andesites during magmatic differentiation: Control of fO2 and sulphur speciation in piston cylinder experiments.

NASA Astrophysics Data System (ADS)

Matjuschkin, Vladimir; Tattitch, Brian; Blundy, Jonathan D.; Skora, Susanne

2014-05-01

Within the mantle wedge above subduction zones, oxidation reaction take place by interaction of reduced mantle rocks with more oxidized, hydrous fluids, which can cause a local drop of the solidus, resulting in partial melting (2,6,7). The resultant melts are more oxidized that their ocean floor counterparts, which has implications for their subsequent differentiation paths, the speciation of multivalent elements and the solubility and transport of chemical compounds in magmatic systems (1,4,5). We present a series of sulphur-doped high-pressure experiments conducted to investigate the effect of oxygen fugacity on phase relationships and the behaviour of sulphur in silicate melts. Natural aphyric andesite (FM37) erupted from Laguna del Maule volcano, Chile (3) was selected as a starting composition. Experiments were carried out at 5kbar, 950-1150° C and variable oxygen fugacity conditions. New experiments buffered at Co-CoO and Ni-NiO buffer conditions have been performed using a new "MTB capsule design" developed in order to accurately control fO2 by means of a double capsule containing metal-oxide buffers and a pyrex sleeve to minimise H2 diffusion. This new design constrains oxygen fugacity to within ±0.1-0.2logfO2 units of the target value. Before conducting these experiments, the assemblage was tested multiple times at 10kbar, 1000° C over 24-48 hours and demonstrated consistent, accurate fO2 control. Analyses of the preliminary experimental run products, from a related Chilean basaltic andesite starting composition, demonstrate a clear effect of fO2 on phase relationships and the proportion of melt generated during experiments. Under oxidized conditions, as temperature decreased from 1150° C to 1050° C, the amount of melt decreased from 100% to ~80%, due to the formation of orthopyroxene, anhydrite and plagioclase. In contrast, in reduced runs the system remains nearly liquid (~5% crystals) down to 950° C due to the change in sulphur speciation and onset of orthopyroxene precipitation at much lower temperatures. The change in temperature from 1150 to 950° C resulted in a drop in S content from ~2500ppm to ~1000ppm in the melt for oxidized experiments, whereas S slightly increased from ~3000 to ~3500ppm in the reduced experiments. Quantitative control over fO2 will allow for more precise determination of phase relations and control of sulphur specification, offering a possibility of detailed reconstruction of metals enrichment in silicate melts. Cited references: [1] Botcharnikov et al. (2011) Nature 4:217-230, [2] Foley (2011) J Petrol 52:1363-1391, [3] Frey et al. (1984) CMP 88:133-149, [4] Jenner et al. (2010) J Petrol 51:2445-2464, [5] Jugo et al. (2010) GCA 74:5926-5938, [6] Rohrbach et al. (2007) Nature 449:456-458, [7] Taylor and Green (1988) Nature 332:349-352

Gas solubility in hydrophobic confinement.

PubMed

Luzar, Alenka; Bratko, Dusan

2005-12-01

Measured forces between apolar surfaces in water have often been found to be sensitive to exposure to atmospheric gases despite low gas solubilities in bulk water. This raises questions as to how significant gas adsorption is in hydrophobic confinement, whether it is conducive to water depletion at such surfaces, and ultimately if it can facilitate the liquid-to-gas phase transition in the confinement. Open Ensemble molecular simulations have been used here to determine saturated concentrations of atmospheric gases in water-filled apolar confinements as a function of pore width at varied gas fugacities. For paraffin-like confinements of widths barely exceeding the mechanical instability threshold (spinodal) of the liquid-to-vapor transition of confined water (aqueous film thickness between three and four molecular diameters), mean gas concentrations in the pore were found to exceed the bulk values by a factor of approximately 30 or approximately 15 in cases of N2 and CO2, respectively. At ambient conditions, this does not result in visible changes in the water density profile next to the surfaces. Whereas the barrier to capillary evaporation has been found to decrease in the presence of dissolved gas (Leung, K.; Luzar, A.; and Bratko, D. Phys. Rev. Lett. 2003, 90, 065502), gas concentrations much higher than those observed at normal atmospheric conditions would be needed to produce noticeable changes in the kinetics of capillary evaporation. In simulations, dissolved gas concentrations corresponding to fugacities above approximately 40 bar for N2, or approximately 2 bar for CO2, were required to trigger expulsion of water from a hydrocarbon slit as narrow as 1.4 nm. For nanosized pore widths corresponding to the mechanical instability threshold or above, no significant coupling between adsorption layers at opposing confinement walls was observed. This finding explains the approximately linear increase in gas solubility with inverse confinement width and the apparent validity of Henry's law in the pores over a broad fugacity range.

Evaluation of triclosan and triclocarban at river basin scale using monitoring and modeling tools: implications for controlling of urban domestic sewage discharge.

PubMed

Zhao, Jian-Liang; Zhang, Qian-Qian; Chen, Feng; Wang, Li; Ying, Guang-Guo; Liu, You-Sheng; Yang, Bin; Zhou, Li-Jun; Liu, Shan; Su, Hao-Chang; Zhang, Rui-Quan

2013-01-01

Triclosan (TCS) and triclocarban (TCC) are two commonly used personal care products. They may enter into aquatic environments after consumption and pose potential risks to aquatic organisms. We investigated the occurrence and fate of TCS and TCC in five large rivers (the Liao River, Hai River, Yellow River, Zhujiang River and Dongjiang River) in China, and compared the monitoring data with the predicted results from Level III fugacity modeling. TCS and TCC were detected in the five large rivers with the detection frequencies of 100% or close to 100% in surface water and sediments of almost every river. TCS and TCC were found at concentrations of up to 478 ng/L and 338 ng/L in surface water, and up to 1329 ng/g and 2723 ng/g in sediments. Cluster analysis indicated that the sites with higher concentrations were usually located in or near urban area. Meanwhile, principal component analysis also suggested that the mass inventories of TCS and TCC in water and sediment were significantly influenced by the factors such as the total or untreated urban domestic sewage discharge at river basin scale. The concentrations and mass inventories from the fugacity modeling were found at the same order of magnitude with the measured values, suggesting that the fugacity modeling can provide a useful tool for evaluating the fate of TCS and TCC in riverine environments. Both monitoring and modeling results indicated that the majority of mass inventories of TCS and TCC were stored into sediment, which could be a potential pollution source for river water. The wide presence of TCS and TCC in these large rivers of China implies that better controlling of urban domestic sewage discharge is needed. Copyright © 2012 Elsevier Ltd. All rights reserved.

Degassing of reduced carbon from planetary basalts.

PubMed

Wetzel, Diane T; Rutherford, Malcolm J; Jacobsen, Steven D; Hauri, Erik H; Saal, Alberto E

2013-05-14

Degassing of planetary interiors through surface volcanism plays an important role in the evolution of planetary bodies and atmospheres. On Earth, carbon dioxide and water are the primary volatile species in magmas. However, little is known about the speciation and degassing of carbon in magmas formed on other planets (i.e., Moon, Mars, Mercury), where the mantle oxidation state [oxygen fugacity (fO2)] is different from that of the Earth. Using experiments on a lunar basalt composition, we confirm that carbon dissolves as carbonate at an fO2 higher than -0.55 relative to the iron wustite oxygen buffer (IW-0.55), whereas at a lower fO2, we discover that carbon is present mainly as iron pentacarbonyl and in smaller amounts as methane in the melt. The transition of carbon speciation in mantle-derived melts at fO2 less than IW-0.55 is associated with a decrease in carbon solubility by a factor of 2. Thus, the fO2 controls carbon speciation and solubility in mantle-derived melts even more than previous data indicate, and the degassing of reduced carbon from Fe-rich basalts on planetary bodies would produce methane-bearing, CO-rich early atmospheres with a strong greenhouse potential.

Workshop on Oxygen in the Terrestrial Planets

NASA Technical Reports Server (NTRS)

2004-01-01

This volume contains abstracts that have been accepted for presentation at the Workshop on Oxygen in the Terrestrial Planets, July 20-23,2004, Santa Fe, New Mexico. The contents include: 1) Experimental Constraints on Oxygen and Other Light Element Partitioning During Planetary Core Formation; 2) In Situ Determination of Fe(3+)/SigmaFe of Spinels by Electron Microprobe: An Evaluation of the Flank Method; 3) The Effect of Oxygen Fugacity on Large-Strain Deformation and Recrystallization of Olivine; 4) Plagioclase-Liquid Trace Element Oxygen Barometry and Oxygen Behaviour in Closed and Open System Magmatic Processes; 5) Core Formation in the Earth: Constraints from Ni and Co; 6) Oxygen Isotopic Compositions of the Terrestrial Planets; 7) The Effect of Oxygen Fugacity on Electrical Conduction of Olivine and Implications for Earth s Mantle; 8) Redox Chemical Diffusion in Silicate Melts: The Impact of the Semiconductor Condition; 9) Ultra-High Temperature Effects in Earth s Magma Ocean: Pt and W Partitioning; 10) Terrestrial Oxygen and Hydrogen Isotope Variations: Primordial Values, Systematics, Subsolidus Effects, Planetary Comparisons, and the Role of Water; 11) Redox State of the Moon s Interior; 12) How did the Terrestrial Planets Acquire Their Water?; 13) Molecular Oxygen Mixing Ratio and Its Seasonal Variability in the Martian Atmosphere; 14) Exchange Between the Atmosphere and the Regolith of Mars: Discussion of Oxygen and Sulfur Isotope Evidence; 15) Oxygen and Hydrogen Isotope Systematics of Atmospheric Water Vapor and Meteoric Waters: Evidence from North Texas; 16) Implications of Isotopic and Redox Heterogeneities in Silicate Reservoirs on Mars; 17) Oxygen Isotopic Variation of the Terrestrial Planets; 18) Redox Exchanges in Hydrous Magma; 19) Hydrothermal Systems on Terrestrial Planets: Lessons from Earth; 20) Oxygen in Martian Meteorites: A Review of Results from Mineral Equilibria Oxybarometers; 21) Non-Linear Fractionation of Oxygen Isotopes Implanted in Lunar Metal Grains: Solar, Lunar or Terrestrial Origin? 22) Isotopic Zoning in the Inner Solar System; 23) Redox Conditions on Small Bodies; 24) Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update; 25) Mantle Redox Evolution and the Rise of Atmospheric O2; 26) Variation of Kd for Fe-Mg Exchange Between Olivine and Melt for Compositions Ranging from Alkaline Basalt to Rhyolite; 27) Determining the Partial Pressure of Oxygen (PO,) in Solutions on Mars; 28) The Influence of Oxygen Environment on Kinetic Properties of Silicate Rocks and Minerals; 29) Redox Evolution of Magmatic Systems; 30) The Constancy of Upper Mantlefo, Through Time Inferred from V/Sc Ratios in Basalts: Implications for the Rise in Atmospheric 0 2; 31) Nitrogen Solubility in Basaltic Melt. Effects of Oxygen Fugacity, Melt Composition and Gas Speciation; 32) Oxygen Isotope Anomalies in the Atmospheres of Earth and Mars; 33) The Effect of Oxygen Fugacity on Interdiffusion of Iron and Magnesium in Magnesiowiistite 34) The Calibration of the Pyroxene Eu-Oxybarometer for the Martian Meteorites; 35) The Europium Oxybarometer: Power and Pitfalls; 36) Oxygen Fugacity of the Martian Mantle from PigeoniteMelt Partitioning of Samarium, Europium and Gadolinium; 37) Oxidation-Reduction Processes on the Moon: Experimental Verification of Graphite Oxidation in the Apollo 17 Orange Glasses; 38) Oxygen and Core Formation in the Earth; 39) Geologic Record of the Atmospheric Sulfur Chemistry Before the Oxygenation of the Early Earth s Atmosphere; 40) Comparative Planetary Mineralogy: V/(CrCAl) Systematics in Chromite as an Indicator of Relative Oxygen Fugacity; 41) How Well do Sulfur Isotopes Constrain Oxygen Abundance in the Ancient Atmospheres? 42) Experimental Constraints on the Oxygen Isotope (O-18/ O-16) Fractionation in the Ice vapor and Adsorbant vapor Systems of CO2 at Conditions Relevant to the Surface of Mars; 43) Micro-XANES Measurements on Experimental Spinels andhe Oxidation State of Vanadium in Spinel-Melt Pairs; 44) Testing the Magma Ocean Hypothesis Using Metal-Silicate Partitioning of Te, Se and S; 45) Solubility of Oxygen in Liquid Iron at High Pressure and Consequences for the Early Differentiation of Earth and Mars Metallic Liquid Segregation in Planetesimals; 46) Oxygen Fugacity of Lunar Basalts and the Lunar Mantle. Range of fo2 and the Effectiveness of Oxybarometers; 47) Thermodynamic Study of Dissociation Processes of Molecular Oxygen in Vapor over Oxide Compounds; 48) Oxygen Profile of a Thermo-Haliophilic Community in the Badwater Salt Flat; 49) Oxygen Barometry Using Synchrotron MicroXANES of Vanadium; 50) Mass-Independent Isotopic Fractionation of Sulfur from Sulfides in the Huronian Supergroup, Canada; 51) Mass Independent Isotopes and Applications to Planetary Atmospheres; 52) Electrical Conductivity, Oxygen Fugacity, and Mantle Materials; 53) Crustal Evolution and Maturation on Earth: Oxygen Isotope Evidence; 54) The Oxygen Isotope Composition of the Moon: Implications for Planet Formation; 55) Oxygen Isotope Composition of Eucrites and Implications for the Formation of Crust on the HED Parent Body; and 56) The Role of Water in Determining the Oxygen Isotopic Composition of Planets.

Interpreting Assemblages with Titanite (Sphene): It Does not have to be Greek to You.

NASA Technical Reports Server (NTRS)

Xirouchakis, Dimitrios M.; Lindsley, Donald H.; McKay, Gordon A. (Technical Monitor)

2000-01-01

Assemblages with titanite, pyroxene(s), olivine, ilmenite, magnetite, and quartz can be used to constrain the intensive and compositional variables that operate during crystallization. Such assemblages are relatively rare in metamorphic rocks, but they are more common in igneous rocks and more frequently reported in plutonic than volcanic rocks. We used the program QUILF, enhanced with thermodynamic data for titanite, to compute stable reactions among titanite (CaTiOSiO4), Fe-Mg-Ti ilmenite and magnetite (hereafter ilmenite and magnetite), Ca-Mg-Fe pyroxenes and olivine, and quartz, and to evaluate some of the factors that control titanite stability. Calculations at 1, 3, and 6 Kbar and 650, 850, 1100 0 C, in the system CaO - MgO - FeO Fe2O3 - TiO2 - SiO2, suggest that the reactions: Augitc + Ilmenite = Titanite + Magnetite + Quartz and Augite + Ilmenite + Quartz = Titanite + Orthopyroxene, impose well defined fugacity of O2, alpha(sub SiO2), , and compositional restrictions to the assemblages: (1) Titanite + Magnetite + Quartz, (2) Titanite + Orthopyroxene, (3) Augite + Ilmenite, and consequently titanite stability. From our calculations in this system we can draw the following general conclusions: (1) The assemblage Titanite + Magnetite + Quartz is always a good indicator of relatively high fugacity of O2, and it is likely more common in relatively iron-rich bulk compositions and for decreasing temperature and pressure conditions. (2) At high temperatures (>= 650 C) titanite is not stable in quartz-saturated rocks that contain the assemblage Orthopyroxene + Augite + Ilmenite + Magnetite. (3) In quartz-saturated rocks the coexistence of titanite and magnetite with either orthopyroxene or olivine requires a confluence of conditions relating bulk composition, fugacity of O2, and slow cooling. Thus, such assemblages must be rare. (4) Regardless of T and fugacity of O2 conditions, and bulk-composition, titanite is not stable in quartz-absent rocks that contain Olivine + Orthopyroxene + Augite + Ilmenite + Magnetite. Decreasing temperature and pressure conditions appear to favor titanite crystallization, thus, it is not unsurprising that titanite is frequently observed in slowly cooled rocks, albeit, in association with amphibole. We argue that the titanite + amphibole association is likely favored by high water activity, regardless of oxygen fugacity. Because water activity increases during crystallization of a pluton, the association titanite + amphibole, and consequently titanite, is likely to be more common in plutonic rocks than in volcanic rocks.

Untangling the History of Oceanic Peridotites Using Spinel Oxybarometry

NASA Astrophysics Data System (ADS)

Birner, S.; Warren, J. M.; Cottrell, E.; Davis, F. A.

2014-12-01

Comprehensive knowledge of the oxygen fugacity of the upper mantle is critical to understanding the processes associated with melt production, interaction, and extraction. Thus, it is important to understand how fO2 changes during a peridotite's thermal and petrologic history in the asthenospheric and lithospheric mantle, as metamorphic subsolidus reequilibration can result in changes to recorded fO2. A case study of Tongan forearc peridotites highlights the heterogeneity seen in mantle peridotites. We analyzed two dredges located 250 km apart along the trench: one dredge ranges in fO2 from 0.5 to 1 log unit above the QFM buffer, similar to analyses of supra-subduction zone xenoliths (e.g. Brandon and Draper, 1996; Wood and Virgo, 1989) while the other dredge ranges from QFM-0.75 to QFM+0.25 and exhibits high spinel Cr# (ranging from 0.45 to 0.75). Systematics between fO2, Ti concentration, olivine forsterite content, and Cr# within each dredge allow us to differentiate between the effects of melt extraction, melt interaction, and cooling. Because the spinel oxybarometry equation is dependent on temperature, it is important to be able to accurately determine the temperature recorded by peridotites. Though many geothermometers are available for mantle rocks, we assert that geothermometers based on Fe-Mg exchange between olivine and spinel are the most applicable to fO2 calculations, because the oxygen fugacity recorded by a mantle assemblage is primarily controlled by this exchange. Additionally, preliminary analyses of diffusion profiles across olivine-spinel grain boundaries provide insight into the cooling of peridotite in the oceanic lithosphere and its effects on oxygen fugacity. Mg-Fe exchange between olivine and spinel is controlled by the distribution coefficient, KD, which is dependent on both temperature and the proportion of Cr to other trivalent cations in spinel. We see an increase in olivine forsterite content towards the olivine-spinel interface, consistent with an increase in KD as cooling occurs. Limited data indicate that while spinel Cr# decreases as the interface is approached, no change is seen in spinel Fe3+/ΣFe ratios. As a result, the increased Fo# in olivine dominates the oxybarometry equation, resulting in higher oxygen fugacity values near the interface as cooling occurs.

Experimental determination of activities of FeO and Fe 2O 3 components in hydrous silicic melts under oxidizing conditions

NASA Astrophysics Data System (ADS)

Gaillard, Fabrice; Pichavant, Michel; Scaillet, Bruno

2003-11-01

The critical role of iron on crystal-silicate liquid relationships and melt differentiation is mainly controlled by the redox conditions prevailing in magmas, but the presently available database merely constrains the thermodynamic properties of iron-bearing components in strongly reduced and anhydrous molten silicate where iron is in the ferrous form. This paper provides new standard states for pure ferrous (FeOliq) and ferric (Fe2O3liq) molten iron oxides and extends the experimental database towards oxidizing and water-bearing domains. Iron-iridium, iron-platinum alloys, magnetite or hematite were equilibrated with synthetic silicic liquids at high temperature and high pressure under controlled oxygen fugacity (fO2) to determine activity-composition relationships for FeOliq and Fe2O3liq. Between 1000 and 1300°C, the fO2 ranges from that in air to 3-log units below that of the nickel-nickel oxide buffer (NNO). Experiments were performed on both anhydrous and hydrous melts containing up to 6-wt.% water. Incorporation of water under reducing conditions increases the activity coefficient of FeOliq but has an opposite effect on Fe2O3liq. As calcium is added to system, the effect of water becomes weaker and is inverted for Fe2O3liq. Under oxidizing conditions, water has a negligible effect on both activities of FeOliq and Fe2O3liq. In contrast, changes in redox conditions dominate the activity coefficients of both FeOliq and Fe2O3liq, which increase significantly with increasing fO2. The present results combined with the previous work provide a specific database on the energetics of iron in silicate melts that cover most of the condition prevailing in natural magmas.

Peridotites and basalts reveal broad congruence between two independent records of mantle fO2 despite local redox heterogeneity

NASA Astrophysics Data System (ADS)

Birner, Suzanne K.; Cottrell, Elizabeth; Warren, Jessica M.; Kelley, Katherine A.; Davis, Fred A.

2018-07-01

The oxygen fugacity (fO2) of the oceanic upper mantle has fundamental implications for the production of magmas and evolution of the Earth's interior and exterior. Mid-ocean ridge basalts and peridotites sample the oceanic upper mantle, and retain a record of oxygen fugacity. While fO2 has been calculated for mid-ocean ridge basalts worldwide (>200 locations), ridge peridotites have been comparatively less well studied (33 samples from 11 locations), and never in the same geographic location as basalts. In order to determine whether peridotites and basalts from mid-ocean ridges record congruent information about the fO2 of the Earth's interior, we analyzed 31 basalts and 41 peridotites from the Oblique Segment of the Southwest Indian Ridge. By measuring basalts and peridotites from the same ridge segment, we can compare samples with maximally similar petrogenetic histories. We project the composition and oxygen fugacity of each lithology back to source conditions, and evaluate the effects of factors such as subsolidus diffusion in peridotites and fractional crystallization in basalts. We find that, on average, basalts and peridotites from the Oblique Segment both reflect a source mantle very near the quartz-fayalite-magnetite (QFM) buffer. However, peridotites record a significantly wider range of values (nearly 3 orders of magnitude in fO2), with a single dredge recording a range in fO2 greater than that previously reported for mid-ocean ridge peridotites worldwide. This suggests that mantle fO2 may be heterogeneous on relatively short length scales, and that this heterogeneity may be obscured within aggregated basalt melts. We further suggest that the global peridotite fO2 dataset may not provide a representative sample of average basalt-source mantle. Our study motivates further investigation of the fO2 recorded by ridge peridotites, as peridotites record information about the fO2 of the Earth's interior that cannot be gleaned from analysis of basalts alone.

Redox dependent behaviour of molybdenum during magmatic processes in the terrestrial and lunar mantle: Implications for the Mo/W of the bulk silicate Moon

NASA Astrophysics Data System (ADS)

Leitzke, F. P.; Fonseca, R. O. C.; Sprung, P.; Mallmann, G.; Lagos, M.; Michely, L. T.; Münker, C.

2017-09-01

We present results of high-temperature olivine-melt, pyroxene-melt and plagioclase-melt partitioning experiments aimed at investigating the redox transition of Mo in silicate systems. Data for a series of other minor and trace elements (Sc, Ba, Sr, Cr, REE, Y, HFSE, U, Th and W) were also acquired to constrain the incorporation of Mo in silicate minerals. All experiments were carried out in vertical tube furnaces at 1 bar and temperatures ranging from ca. 1220 to 1300 °C. Oxygen fugacity was controlled via CO-CO2 gas mixtures and varied systematically from 5.5 log units below to 1.9 log units above the fayalite-magnetite-quartz (FMQ) redox buffer thereby covering the range in oxygen fugacities of terrestrial and lunar basalt genesis. Molybdenum is shown to be volatile at oxygen fugacities above FMQ and that its compatibility in pyroxene and olivine increases three orders of magnitude towards the more reducing conditions covered in this study. The partitioning results show that Mo is dominantly tetravalent at redox conditions below FMQ-4 and dominantly hexavalent at redox conditions above FMQ. Given the differences in oxidation states of the terrestrial (oxidized) and lunar (reduced) mantles, molybdenum will behave significantly differently during basalt genesis in the Earth (i.e. highly incompatible; average DMoperidotite/melt ∼ 0.008) and Moon (i.e. moderately incompatible/compatible; average DMoperidotite/melt ∼ 0.6). Thus, it is expected that Mo will strongly fractionate from W during partial melting in the lunar mantle, given that W is broadly incompatible at FMQ-5. Moreover, the depletion of Mo and the Mo/W range in lunar samples can be reproduced by simply assuming a primitive Earth-like Mo/W for the bulk silicate Moon. Such a lunar composition is in striking agreement with the Moon being derived from the primitive terrestrial mantle after core formation on Earth.

Experimental petrology and origin of rocks from the Descartes Highlands

NASA Technical Reports Server (NTRS)

Walker, D.; Longhi, J.; Grove, T. L.; Stolper, E.; Hays, J. F.

1973-01-01

Petrographic studies of Apollo 16 samples indicate that rocks 62295 and 68415 are crystallization products of highly aluminous melts. 60025 is a shocked, crushed and partially annealed plagioclase cumulate. 60315 is a recrystallized noritic breccia of disputed origin. 60335 is a feldspathic basalt filled with xenoliths and xenocrysts of anorthosite, breccia, and anorthite. The Fe/(Fe+Mg) of plagioclase appears to be a relative crystallization index. Low pressure melting experiments with controlled Po2 indicate that the igneous samples crystallized at oxygen fugacities well below the Fe/FeO buffer. Crystallization experiments at various pressures suggest that the 62295 and 68415 compositions were produced by partial or complete melting of lunar crustal materials, and not by partial melting of the deep lunar interior.

Hydrogen and Ferric Iron in Mars Materials

NASA Technical Reports Server (NTRS)

Dyar, Melinda D.

2004-01-01

Knowledge of oxygen and hydrogen fugacity is of paramount importance in constraining phase equilibria and crystallization processes of melts, as well as understanding the partitioning of elements between the cope and silicate portions of terrestrial planets. H and Fe(3+) must both be analyzed in order to reconstruct hydrogen and oxygen fugacities on Mars. To date, SIMS data have elucidated D/H and H contents of hydrous phases in SNC meteorites, but until now anhydrous martian minerals have not been systematically examined for trace hydrogen. Ferric iron has been quantified using XANES in many martian phases, but integrated studies of both Fe(3+) and H on the same spots are really needed to address the H budget. Finally, the effects of shock on both Fe(3+) and H in hydrous and anhydrous phases must be quantified. Thus, the overall goal of this research was to understand the oxygen and hydrogen fugacities under which martian samples crystallized. In this research one-year project, we approached this problem by 1) characterizing Fe(3+) and H contents of SNC meteorites using both bulk (Mossbauer spectroscopy and uranium extraction, respectively) and microscale (synchrotron micro-XANES and SIMS) methods; 2) relating Fe(3+) and H contents of martian minerals to their oxygen and hydrogen fugacities through analysis of experimentally equilibrated phases (for pyroxene) and through study of volcanic rocks in which the oxygen and hydrogen fugacities can be independently constrained (for feldspar); and 3) studying the effects of shock processes on Fe(3+) and H contents of the phases of interest. Results have been used to assess quantitatively the distribution of H and Fe(3+) among phases in the martian interior, which will better constrain the geodynamic processes of the interior, as well as the overall hydrogen and water budgets on Mars. There were no inventions funded by this research.

Calculation of Oxygen Fugacity in High Pressure Metal-Silicate Experiments and Comparison to Standard Approaches

NASA Technical Reports Server (NTRS)

Righter, K.; Ghiorso, M.

2009-01-01

Calculation of oxygen fugacity in high pressure and temperature experiments in metal-silicate systems is usually approximated by the ratio of Fe in the metal and FeO in the silicate melt: (Delta)IW=2*log(X(sub Fe)/X(sub FeO)), where IW is the iron-wustite reference oxygen buffer. Although this is a quick and easy calculation to make, it has been applied to a huge variety of metallic (Fe- Ni-S-C-O-Si systems) and silicate liquids (SiO2, Al2O3, TiO2, FeO, MgO, CaO, Na2O, K2O systems). This approach has surely led to values that have little meaning, yet are applied with great confidence, for example, to a terrestrial mantle at "IW-2". Although fO2 can be circumvented in some cases by consideration of Fe-M distribution coefficient, these do not eliminate the effects of alloy or silicate liquid compositional variation, or the specific chemical effects of S in the silicate liquid, for example. In order to address the issue of what the actual value of fO2 is in any given experiment, we have calculated fO2 from the equilibria 2Fe (metal) + SiO2 (liq) + O2 = Fe2SiO4 (liq).

Fugacity of H2O from 0° to 350°C at the liquid-vapor equilibrium and at 1 atmosphere

USGS Publications Warehouse

Hass, John L.

1970-01-01

The fugacity and fugacity coefficient of H2O at the liquid-vapor equilibrium, the fugacity and the Gibbs free energy of formation of H2O at 1 atm (1.01325 bars) total pressure have been calculated from published data on the physical and thermodynamic properties of H2O and are presented at ten-degree intervals from 0° to 350°C.

Assessment of the air-soil partitioning of polycyclic aromatic hydrocarbons in a paddy field using a modified fugacity sampler.

PubMed

Wang, Yan; Luo, Chunling; Wang, Shaorui; Liu, Junwen; Pan, Suhong; Li, Jun; Ming, Lili; Zhang, Gan; Li, Xiangdong

2015-01-06

Rice, one of the most widely cultivated crops, has received great attention in contaminant uptake from soil and air, especially for the special approaches used for its cultivation. The dry-wet alternation method can influence the air-soil partitioning of semivolatile organic compounds (SVOCs) in the paddy ecosystem. Here, we modified a fugacity sampler to investigate the air-surface in situ partitioning of ubiquitous polycyclic aromatic hydrocarbons (PAHs) at different growth stages in a suburban paddy field in South China. The canopy of rice can form a closed space, which acts like a chamber that can force the air under the canopy to equilibrate with the field surface. When we compared the fugacities calculated using a fugacity model of the partition coefficients to the measured fugacities, we observed similar trends in the variation, but significantly different values between different growing stages, especially during the flooding stages. However, the measured and calculated fugacity fractions were comparable when uncertainties in our calculations were considered, with the exception of the high molecular weight (HMW) PAHs. The measured fugacity fractions suggested that the HMW PAHs were also closed to equilibrium between the paddy field and atmosphere. The modified fugacity sampler provided a novel way of accurately determining the in situ air-soil partitioning of SVOCs in a wet paddy field.

Degassing of reduced carbon from planetary basalts

PubMed Central

Wetzel, Diane T.; Rutherford, Malcolm J.; Jacobsen, Steven D.; Hauri, Erik H.; Saal, Alberto E.

2013-01-01

Degassing of planetary interiors through surface volcanism plays an important role in the evolution of planetary bodies and atmospheres. On Earth, carbon dioxide and water are the primary volatile species in magmas. However, little is known about the speciation and degassing of carbon in magmas formed on other planets (i.e., Moon, Mars, Mercury), where the mantle oxidation state [oxygen fugacity (fO2)] is different from that of the Earth. Using experiments on a lunar basalt composition, we confirm that carbon dissolves as carbonate at an fO2 higher than -0.55 relative to the iron wustite oxygen buffer (IW-0.55), whereas at a lower fO2, we discover that carbon is present mainly as iron pentacarbonyl and in smaller amounts as methane in the melt. The transition of carbon speciation in mantle-derived melts at fO2 less than IW-0.55 is associated with a decrease in carbon solubility by a factor of 2. Thus, the fO2 controls carbon speciation and solubility in mantle-derived melts even more than previous data indicate, and the degassing of reduced carbon from Fe-rich basalts on planetary bodies would produce methane-bearing, CO-rich early atmospheres with a strong greenhouse potential. PMID:23569260

Carbon isotope fractionation during diamond growth in depleted peridotite: Counterintuitive insights from modelling water-maximum CHO fluids as multi-component systems

NASA Astrophysics Data System (ADS)

Stachel, T.; Chacko, T.; Luth, R. W.

2017-09-01

Because of the inability of depleted cratonic peridotites to effectively buffer oxygen fugacities when infiltrated by CHO or carbonatitic fluids, it has been proposed recently (Luth and Stachel, 2014) that diamond formation in peridotites typically does not occur by rock-buffered redox reactions as previously thought but by an oxygen-conserving reaction in which minor coexisting CH4 and CO2 components in a water-rich fluid react to form diamond (CO2 + CH4 = 2C + 2H2O). In such fluid-buffered systems, carbon isotope fractionation during diamond precipitation occurs in the presence of two dominant fluid carbon species. Carbon isotope modelling of diamond precipitation from mixed CH4- and CO2-bearing fluids reveals unexpected fundamental differences relative to diamond crystallization from a single carbon fluid species: (1) irrespective of which carbon fluid species (CH4 or CO2) is dominant in the initial fluid, diamond formation is invariably associated with progressive minor (<1‰) enrichment of diamond in 13C as crystallization proceeds. This is in contrast to diamond precipitation by rock-buffered redox processes from a fluid containing only a single carbon species, which can result in either progressive 13C enrichment (CO2 or carbonate fluids) or 13C depletion (CH4 fluids) in the diamond. (2) Fluid speciation is the key factor controlling diamond δ13 C values; as XCO2 (XCO2 = CO2/[CO2 + CH4]) in the initial fluid increases from 0.1 to 0.9 (corresponding to an increase in fO2 of 0.8 log units), the carbon isotope composition of the first-precipitated diamond decreases by 3.7‰. The tight mode in δ13C of - 5 ± 1 ‰ for diamonds worldwide places strict constraints on the dominant range of XCO2 in water-rich fluids responsible for diamond formation. Specifically, precipitation of diamonds with δ13C values in the range -4 to -6‰ from mantle-derived fluids with an average δ13C value of -5‰ (derived from evidence not related to diamonds) requires that diamond-forming fluids were relatively reduced and had methane as the dominant carbon species (XCO2 = 0.1-0.5). Application of our model to a recently published set of in-situ carbon isotope analyses for peridotitic diamonds from Marange, Zimbabwe (Smit et al., 2016), which contain CH4 fluid inclusions, allows us to perfectly match the observed co-variations in δ13 C, δ15 N and N content and at the same time explain the previously counter-intuitive observation of progressive 13C enrichment in diamonds that appear to have grown from a fluid with methane as the dominant carbon species. Similarly, the almost complete absence in the published record of progressive 13C depletion trends within diamonds likely reflects ubiquitous precipitation from CH4- and CO2-bearing water-rich fluids, rather than diamond formation exclusively by carbonate-bearing and CH4-free oxidized fluids or melts.

Mutual interactions of redox couples via electron exchange in silicate melts - Models for geochemical melt systems

NASA Technical Reports Server (NTRS)

Schreiber, Henry D.; Merkel, Robert C., Jr.; Schreiber, V. Lea; Balazs, G. Bryan

1987-01-01

The mutual interactions via electron exchange of redox couples in glass-forming melts were investigated both theoretically and experimentally. A thermodynamic approach for considering the mutual interactions leads to conclusion that the degree of mutual interaction in the melt should be proportional in part to the difference in relative reduction potentials of the interacting redox couples. Experimental studies verify this conclusion for numerous redox couples in several composition/temperature/oxygen fugacity regimes. Geochemical systems simultaneously possess many potentially multivalent elements; the stabilized redox states in the resulting magmas can be explained in part by mutual interactions and by redox buffering through the central Fe(III)- Fe(II) couples in the melts. The significance of these results for basaltic magmas of the earth, moon, and meteorites is addressed.

Utilizing Polymer-Coated Vials to Illustrate the Fugacity and Bioavailability of Chlorinated Pesticide Residues in Contaminated Soils

ERIC Educational Resources Information Center

Andrade, Natasha A.; McConnell, Laura L.; Torrents, Alba; Hapeman, Cathleen J.

2013-01-01

Fugacity and bioavailability can be used to facilitate students' understanding of potential environmental risks associated with toxic chemicals and, therefore, should be incorporated in environmental chemistry and science laboratories. Although the concept of concentration is easy to grasp, fugacity and bioavailability can be challenging…

Effect of Water on the Rheology of Clinopyroxene at High Temperature and Pressure

NASA Astrophysics Data System (ADS)

Wang, Z.; Zhang, J.

2017-12-01

Clinopyroxene is one of the most important constituent minerals in the lower crust and the upper mantle, and its rheological properties may determine the strength and seismic properties of the lower crust. Previous studies have shown that water content in clinopyroxene of lower crust and upper mantle varies significantly by tectonic backgrounds ranging from 50-700 ppm. However quantitative experimental investigations on the effect of water on the rheological properties of clinopyroxene have been sparse and controversy. We report here experimental deformation on synthesized clinopyroxene aggregates of varying amounts of water using a 5 GPa modified Griggs-type apparatus. Clinopyroxene aggregates of different water contents are prepared by dehydration of a water-rich natural clinopyroxene aggregates at room pressure in a mixed gaseous CO/CO2 flow buffered oven. The water contents are measured by FTIR before and after each experiment. Our results show that the strength of clinopyroxene aggregates decreases exponentially with the increase of water content. The rheological strength of clinopyroxene aggregates is reduced by about 4 times when the water content increases from 84 ppm to 662 ppm (the span of major water contents reported for clinopyroxene of lower crust and upper mantle), corresponding to a water fugacity exponent (r) value of 1.77. It is between the r values previously reported for clinopyroxene (r = 3.0, Chen et al., 2006; r = 1.4±0.2, Hier-Majunder et al., 2005). This r value is less than that reported for garnet (r = 2.4, Katayama and Karato, 2008), but larger than those reported for olivine (r = 0.7-1.25, Karato and Jung, 2003, Mei and Kohlstedt, 2000; r = 1/3, Fei et al., 2013) and plagioclase (r = 1.0±0.3, Rybacki et al., 2006). The effect of water on the rheological strength of clinopyroxene might be more significant than those for olivine and plagioclase but less significant than that for garnet. These results provide important constraints on the effect of water on the rheological properties of clinopyroxene in lithosphere.

Evaluating the multimedia fate of organic chemicals: A level III fugacity model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mackay, D.; Paterson, S.

A multimedia model is developed and applied to selected organic chemicals in evaluative and real regional environments. The model employs the fugacity concept and treats four bulk compartments: air, water, soil, and bottom sediment, which consist of subcompartments of varying proportions of air, water, and mineral and organic matter. Chemical equilibrium is assumed to apply within (but not between) each bulk compartment. Expressions are included for emissions, advective flows, degrading reactions, and interphase transport by diffusive and non-diffusive processes. Input to the model consists of a description of the environment, the physical-chemical and reaction properties of the chemical, and emissionmore » rates. For steady-state conditions the solution is a simple algebraic expression. The model is applied to six chemicals in the region of southern Ontario and the calculated fate and concentrations are compared with observations. The results suggest that the model may be used to determine the processes that control the environmental fate of chemicals in a region and provide approximate estimates of relative media concentrations.« less

Fugacity analysis of polycyclic aromatic hydrocarbons between microplastics and seawater

NASA Astrophysics Data System (ADS)

Lee, Hwang; Chang, Sein; Kim, Seung-Kyu; Kwon, Jung-Hwan

2017-03-01

Recently, the accumulation of plastic debris in the marine environment has become a great concern worldwide. Although plastics are biologically and chemically inert, plastic debris has been suspected of causing adverse effects on ecosystems due to the increase in reactivity by size reduction and/or micropollutants associated with plastics. Because of the high sorption capacity of microplastics toward organic micropollutants, it is suspected that microplastics may play roles in the distribution and fate of micropollutants. In order to quantitatively evaluate the "net flow" of environmental contaminants in water-plastic-organism systems, a fugacity analysis was conducted using concentrations of polycyclic aromatic hydrocarbons (PAHs) in open oceans and in polyethylene as a representative material of plastic debris. Ratio of fugacity in polyethylene to that in seawater showed a decreasing trend with increasing partition coefficient between polyethylene and seawater (KPE/sw). This indicates that phase equilibrium between polyethylene and seawater is not attained for higher molecular weight PAHs. Disequilibrium of high molecular weight PAHs suggests that transfer from seawater to plastic debris is thermodynamically driven and the role of plastic debris as a vector to transfer them to living organisms would be minimal. However, additives may slowly migrate from plastics into the environment causing potentially serious effects on ecosystems.

Magmatic oxygen fugacity estimated using zircon-melt partitioning of cerium

NASA Astrophysics Data System (ADS)

Smythe, Duane J.; Brenan, James M.

2016-11-01

Using a newly-calibrated relation for cerium redox equilibria in silicate melts (Smythe and Brenan, 2015), and an internally-consistent model for zircon-melt partitioning of Ce, we provide a method to estimate the prevailing redox conditions during crystallization of zircon-saturated magmas. With this approach, oxygen fugacities were calculated for samples from the Bishop tuff (USA), Toba tuff (Indonesia) and the Nain plutonic suite (Canada), which typically agree with independent estimates within one log unit or better. With the success of reproducing the fO2 of well-constrained igneous systems, we have applied our Ce-in-zircon oxygen barometer to estimating the redox state of Earth's earliest magmas. Using the composition of the Jack Hills Hadean zircons, combined with estimates of their parental magma composition, we determined the fO2 during zircon crystallization to be between FMQ -1.0 to +2.5 (where FMQ is the fayalite-magnetite-quartz buffer). Of the parental magmas considered, Archean tonalite-trondhjemite-granodiorite (TTG) compositions yield zircon-melt partitioning most similar to well-constrained modern suites (e.g., Sano et al., 2002). Although broadly consistent with previous redox estimates from the Jack Hills zircons, our results provide a more precise determination of fO2, narrowing the range for Hadean parental magmas by more than 8 orders of magnitude. Results suggest that relatively oxidized magmatic source regions, similar in oxidation state to that of 3.5 Ga komatiite suites, existed by ∼4.4 Ga.

Pyrochlore-rich titanate ceramics for the immobilization of plutonium: redox effects on phase equilibria in cerium- and thorium- substituted analogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryerson, F J; Ebbinghaus, B

2000-05-25

Three compositions representing plutonium-free analogs of a proposed Ca-Ti-Gd-Hf-U-PU oxide ceramic for the immobilization of plutonium were equilibrated at 1 atm, 1350 C over a range of oxygen fugacities between air and that equivalent to the iron-wuestite buffer. The cerium analog replaces Pu on a mole-per-mole basic with Ce; the thorium analog replaces Pu with Th. A third material has 10 wt% Al{sub 2}O{sub 3} added to the cerium analog to encourage the formation of a Hf-analog of, CaHfTi{sub 2}O{sub 7}, zirconolite, which is referred to as hafnolite. The predominant phase produced in each formulation under all conditions is pyrochlore,more » A{sub 2}T{sub 2}O{sub 7}, where the T site is filled by Ti, and Ca, the lanthanides, Hf, U and Pu are accommodated on the A-site. Other lanthanide and uranium-bearing phases encountered include brannerite (UTi{sub 2}O{sub 6}), hafnolite (CaHfTi{sub 2}O{sub 7}), perovskite (CaTiO{sub 3}) and a calcium-lanthanide aluminotitanate with nominal stoichiometry (Ca,Ln)Ti{sub 2}Al{sub 9}O{sub 19}, where Ln is a lanthanide. The phase compositions show progressive shifts with decreasing oxygen fugacity. All of the phases observed have previously been identified in titanate-based high-level radioactive waste ceramics and demonstrate the flexibility of these ceramics to variations in processing parameters. The main variation is an increase in the uranium concentrations of pyrochlore and brannerite which must be accommodated by variations in modal abundance. Pyrochlore compositions are consistent with existing spectroscopic data suggesting that uranium is predominantly pentavalent in samples synthesized in air. A simple model based on ideal stoichiometry suggests the U{sup +4}/{Sigma}U varies linearly with log fO{sub 2} and that all of the uranium is quadravalent at the iron-wuestite buffer.« less

Intrinsic oxygen fugacity measurements on seven chondrites, a pallasite, and a tektite and the redox state of meteorite parent bodies

USGS Publications Warehouse

Brett, R.; Sato, M.

1984-01-01

Intrinsic oxygen-fugacity (fO2) measurements were made on five ordinary chondrites, a carbonaceous chondrite, an enstatite chondrite, a pallasite, and a tektite. Results are of the form of linear log fO2 - 1 T plots. Except for the enstatite chondrite, measured results agree well with calculated estimates by others. The tektite produced fO2 values well below the range measured for terrestrial and lunar rocks. The lowpressure atmospheric regime that is reported to follow large terrestrial explosions, coupled with a very high temperature, could produce glass with fO2 in the range measured. The meteorite Salta (pallasite) has low fO2 and lies close to Hvittis (E6). Unlike the other samples, results for Salta do not parallel the iron-wu??stite buffer, but are close to the fayalite-quartz-iron buffer in slope. Minor reduction by graphite appears to have taken place during metamorphism of ordinary chondrites. fO2 values of unequilibrated chondrites show large scatter during early heating suggesting that the constituent phases were exposed to a range of fO2 conditions. The samples equilibrated with respect to fO2 in relatively short time on heating. Equilibration with respect to fO2 in ordinary chondrites takes place between grades 3 and 4 of metamorphism. Application of P - T - fO2 relations in the system C-CO-CO2 indicates that the ordinary chondrites were metamorphosed at pressures of 3-20 bars, as it appears that they lay on the graphite surface. A steep positive thermal gradient in a meteorite parent body lying at the graphite surface will produce thin reduced exterior, an oxidized near-surface layer, and an interior that is increasingly reduced with depth; a shallow thermal gradient will produce the reverse. A body heated by accretion on the outside will have a reduced exterior and oxidized interior. Meteorites from the same parent body clearly are not required to have similar redox states. ?? 1984.

The partitioning of sulfur between multicomponent aqueous fluids and felsic melts

NASA Astrophysics Data System (ADS)

Binder, Bernd; Wenzel, Thomas; Keppler, Hans

2018-02-01

Sulfur partitioning between melt and fluid phase largely controls the environmental impact of volcanic eruptions. Fluid/melt partitioning data also provide the physical basis for interpreting changes in volcanic gas compositions that are used in eruption forecasts. To better constrain some variables that control the behavior of sulfur in felsic systems, in particular the interaction between different volatiles, we studied the partitioning of sulfur between aqueous fluids and haplogranitic melts at 200 MPa and 750-850 °C as a function of oxygen fugacity (Ni-NiO or Re-ReO2 buffer), melt composition (Al/(Na + K) ratio), and fluid composition (NaCl and CO2 content). The data confirm a first-order influence of oxygen fugacity on the partitioning of sulfur. Under "reducing conditions" (Ni-NiO buffer), D fluid/melt is nearly one order of magnitude larger (323 ± 14 for a metaluminous melt) than under "oxidizing conditions" (Re-ReO2 buffer; 74 ± 5 for a metaluminous melt). This effect is likely related to a major change in sulfur speciation in both melt and fluid. Raman spectra of the quenched fluids show the presence of H2S and HS- under reducing conditions and of SO4 2- and HSO4 - under oxidizing conditions, while SO2 is undetectable. The latter observation suggests that already at the Re-ReO2 buffer, sulfur in the fluid is almost completely in the S6+ state and, therefore, more oxidized than expected according to current models. CO2 in the fluid (up to x CO2 = 0.3) has no effect on the fluid/melt partitioning of sulfur, neither under oxidizing nor under reducing conditions. However, the effect of NaCl depends on redox state. While at oxidizing conditions, D fluid/melt is independent of x NaCl, the fluid/melt partition coefficient strongly decreases with NaCl content under reducing conditions, probably due to a change from H2S to NaSH as dominant sulfur species in the fluid. A decrease of D fluid/melt with alkali content in the melt is observed over the entire compositional range under reducing conditions, while it is prominent only between the peraluminous and metaluminous composition in oxidizing experiments. Overall, the experimental results suggest that for typical oxidized, silicic to intermediate subduction zone magmas, the degassing of sulfur is not influenced by the presence of other volatiles, while under reducing conditions, strong interactions with chlorine are observed. If the sulfur oxidation state is preserved during an explosive eruption, a large fraction of the sulfur released from oxidized magmas may be in the S6+ state and may remain undetected by conventional methods that only measure SO2. Accordingly, the sulfur yield and the possible climatic impact of some eruptions may be severely underestimated.

Solubility of C-O-H volatiles in graphite-saturated martian basalts and application to martian atmospheric evolution

NASA Astrophysics Data System (ADS)

Stanley, B. D.; Hirschmann, M. M.; Withers, A. C.

2012-12-01

The modern martian atmosphere is thin, leading to surface conditions too cold to support liquid water. Yet, there is evidence of liquid surface water early in martian history that is commonly thought to require a thick CO2 atmosphere. Our previous work follows the analysis developed by Holloway and co-workers (Holloway et al. 1992; Holloway 1998), which predicts a linear relationship between CO2 and oxygen fugacity (fO2) in graphite-saturated silicate melts. At low oxygen fugacity, the solubility of CO2 in silicate melts is therefore very low. Such low calculated solubilities under reducing conditions lead to small fluxes of CO2 associated with martian magmatism, and therefore production of a thick volcanogenic CO2 atmosphere could require a prohibitively large volume of mantle-derived magma. The key assumption in these previous calculations is that the carbonate ion is the chief soluble C-O-H species. The results of the calculations would not be affected appreciably if molecular CO2, rather than carbonate ion, were an important species, but could be entirely different if there were other appreciable C-species such as CO, carbonyl (C=O) complexes, carbide (Si-C), or CH4. Clearly, graphite-saturated experiments are required to explore how much volcanogenic C may be degassed by reduced martian lavas. A series of piston-cylinder experiments were performed on synthetic martian starting materials over a range of oxygen fugacities (IW+2.3 to IW-0.9), and at pressures of 1-3 GPa and temperatures of 1340-1600 °C in Pt-graphite double capsules. CO2 contents in experimental glasses were determined using Fourier transform infrared spectroscopy (FTIR) and range from 0.0026-0.50 wt%. CO2 solubilities change by one order of magnitude with an order of magnitude change in oxygen fugacity, as predicted by previous work. Secondary ion mass spectrometry (SIMS) determinations of C contents in glasses range from 0.0131-0.2626 wt%. C contents determined by SIMS are consistently higher than CO2 contents determined by FTIR. This difference, termed excess C, is attributed to the presence of other reduced C-species, such as carbonyls and amides (which have C=O and N-H bonds), detected using FTIR in reduced graphite-saturated martian basalts. An atmosphere produced by degassing of magmas similar to this study would be richer in C-O-H species than previously modeled using only CO2 and could create a much warmer climate that stabilizes liquid water on the ancient martian surface.

Phase equilibria constraints on the chemical and physical evolution of the campanian ignimbrite

USGS Publications Warehouse

Fowler, S.J.; Spera, F.J.; Bohrson, W.A.; Belkin, H.E.; de Vivo, B.

2007-01-01

The Campanian Ignimbrite is a > 200 km3 trachyte-phonolite pyroclastic deposit that erupted at 39.3 ?? 0.1 ka within the Campi Flegrei west of Naples, Italy. Here we test the hypothesis that Campanian Ignimbrite magma was derived by isobaric crystal fractionation of a parental basaltic trachyandesitic melt that reacted and came into local equilibrium with small amounts (5-10 wt%) of crustal rock (skarns and foid-syenites) during crystallization. Comparison of observed crystal and magma compositions with results of phase equilibria assimilation-fractionation simulations (MELTS) is generally very good. Oxygen fugacity was approximately buffered along QFM+1 (where QFM is the quartz-fayalite-magnetite buffer) during isobaric fractionation at 0.15 GPa (???6 km depth). The parental melt, reconstructed from melt inclusion and host clinopyroxene compositions, is found to be basaltic trachyandesite liquid (51.1 wt% SiO2, 9.3 wt% MgO, 3 wt% H2O). A significant feature of phase equilibria simulations is the existence of a pseudo-invariant temperature, ???883??C, at which the fraction of melt remaining in the system decreases abruptly from ???0.5 to < 0.1. Crystallization at the pseudo-invariant point leads to abrupt changes in the composition, properties (density, dissolved water content), and physical state (viscosity, volume fraction fluid) of melt and magma. A dramatic decrease in melt viscosity (from 1700 Pa s to ???200 Pa s), coupled with a change in the volume fraction of water in magma (from ??? 0.1 to 0.8) and a dramatic decrease in melt and magma density acted as a destabilizing eruption trigger. Thermal models suggest a timescale of ??? 200 kyr from the beginning of fractionation until eruption, leading to an apparent rate of evolved magma generation of about 10-3 km3/year. In situ crystallization and crystal settling in density-stratified regions, as well as in convectively mixed, less evolved subjacent magma, operate rapidly enough to match this apparent volumetric rate of evolved magma production. ?? Copyright 2007 Oxford University Press.

The Effects of Redox Reactions on Sulfur Isotopes in Sulfide Melts at 1200 °C: Implications for 34S Enrichment in Magmas

NASA Astrophysics Data System (ADS)

Sanderson, A. M.; Frank, M. R.; Dodd, J. P.; Walker, J. A.

2017-12-01

δ34S values of mantle derived melts in subduction zones can differ from mantle values. This is often attributed to assimilation of country rock or interaction with another S-bearing reservoir. We hypothesized that variations in oxygen fugacity, f(O2), and in sulfur's valence state, may impact a change in the measured δ34S value of sulfide melts. Two synthetic sulfide melts (SM5 & SM7) with a composition of the mono-sulfide solution (MSS; Fe51S37Ni5Cu7) were homogenized for 30, 60 and 90 minutes at an oxygen fugacity between the quartz-fayalite-magnetite (QFM) and iron-wüstite (IW) buffers. Samples were separated into aliquots and subjected to varying fO2 (atmospheric O2, nickel-nickel oxide (NNO), QFM, and IW) at 1200 °C. Equilibrium was established through reversals and as a function of time. The δ34S value of the starting material was measured to be +7.3 to 7.9 ‰ (VCDT). δ34S values from experiments are displayed here relative to the starting material used for that experiment (δ34Ssample - δ34Sstarting). Experiments conducted at log f(O2) of -11.74 (IW), -10.02, -8.3 (QFM), and -7.6 (NNO) were found to be +0.1, +0.6, +1.7, and +1.8 ‰, respectively. The measured average δ34S values were found to vary directly with the imposed oxygen fugacity. The enrichment in 34S relative to 32S is most likely related to changes in the sulfur redox state (from S2-) or sulfur volatilization. Our results suggest that volatilization or variations in a magma's oxidation state can produce measurable changes in δ34S and that those changes must be considered when using δ34S to evaluate possible external sulfur contributions. These results will likely inform discussions on the source of metals and sulfur in layered mafic intrusions (e.g. Bushveld Complex).

An experimental study of ^{{{{Fe}}^{2 + } {-}{{Mg}}}} K_{{D}} between orthopyroxene and rhyolite: a strong dependence on H2O in the melt

NASA Astrophysics Data System (ADS)

Waters, Laura E.; Lange, Rebecca A.

2017-06-01

The effect of temperature, pressure, and dissolved H2O in the melt on the Fe2+-Mg exchange coefficient between orthopyroxene and rhyolite melt was investigated with a series of H2O fluid-saturated phase-equilibrium experiments. Experiments were conducted in a rapid-quench cold-seal pressure vessel over a temperature and pressure range of 785-850 °C and 80-185 MPa, respectively. Oxygen fugacity was buffered with the solid Ni-NiO assemblage in a double-capsule assembly. These experiments, when combined with H2O-undersaturated experiments in the literature, show that ^{{{{Fe}}^{2 + } {-}{{Mg}}}} K_{{D}} between orthopyroxene and rhyolite liquid increases strongly (from 0.23 to 0.54) as a function of dissolved water in the melt (from 2.7 to 5.6 wt%). There is no detectable effect of temperature or pressure over an interval of 65 °C and 100 MPa, respectively, on the Fe2+-Mg exchange coefficient values. The data show that Fe-rich orthopyroxene is favored at high water contents, whereas Mg-rich orthopyroxene crystallizes at low water contents. It is proposed that the effect of dissolved water in the melt on the composition of orthopyroxene is analogous to its effect on the composition of plagioclase. In the latter case, dissolved hydroxyl groups preferentially complex with Na+ relative to Ca2+, which reduces the activity of the albite component, leading to a more anorthite-rich (calcic) plagioclase. Similarly, it is proposed that dissolved hydroxyl groups preferentially complex with Mg2+ relative to Fe2+, thus lowering the activity of the enstatite component, leading to a more Fe-rich orthopyroxene at high water contents in the melt. The experimental results presented in this study show that reversely zoned pyroxene (i.e., Mg-rich rims) in silicic magmas may be a result of H2O degassing and not necessarily the result of mixing with a more mafic magma.

Electrochemical measurements and thermodynamic calculations of redox equilibria in pallasite meteorites - Implications for the eucrite parent body

NASA Technical Reports Server (NTRS)

Righter, Kevin; Arculus, Richard J.; Paslick, Cassi; Delano, John W.

1990-01-01

The intrinsic oxygen fugacity (IOF) of olivine separates from the Salta, Springwater, and Eagle Station pallasites was measured between 850 and 1150 C using oxygen-specific solid zirconia electrolytes at 100,000 Pa. Thermodynamic calculations of redox equilibria involving equalibrium pallasite assemblages are in good agreement with the experimental results and provide a lower limit to pallasite redox stability; others involving disequilibrium assemblages, suggest that pallasites experienced localized, late-stage oxidation and reduction effects. Consideration of the redox buffer metal-olivine-orthopyroxene utilizing calculated Eucrite Parent Body (EPB) mantle phase compositions indicates that small redox gradients may have existed in the EPB. Such gradients may have produced strong compositional variation within the EPB. In addition, there is apparently significant redox heterogeneity in the source area of Eagle Station Trio pallasites and Bocaiuva iron meteorites.

Fate of polycyclic aromatic hydrocarbons from the North Pacific to the Arctic: Field measurements and fugacity model simulation.

PubMed

Ke, Hongwei; Chen, Mian; Liu, Mengyang; Chen, Meng; Duan, Mengshan; Huang, Peng; Hong, Jiajun; Lin, Yan; Cheng, Shayen; Wang, Xuran; Huang, Mengxue; Cai, Minggang

2017-10-01

Polycyclic aromatic hydrocarbons (PAHs) have accumulated ubiquitously inArctic environments, where re-volatilization of certain organic pollutants as a result of climate change has been observed. To investigate the fate of semivolatile organic compounds in the Arctic, dissolved PAHs in the surface seawaters from the temperate Pacific Ocean to the Arctic Ocean, as well as a water column in the Arctic Ocean, were collected during the 4th Chinese National Arctic Research Expedition in summer 2010. The total concentrations of seven dissolved PAHs in surface water ranged from 1.0 to 5.1 ng L -1 , decreasing with increasing latitude. The vertical profile of PAHs in the Arctic Ocean was generally characteristic of surface enrichment and depth depletion, which emphasized the role of vertical water stratification and particle settling processes. A level III fugacity model was developed in the Bering Sea under steady state assumption. Model results quantitatively simulated the transfer processes and fate of PAHs in the air and water compartments, and highlighted a summer air-to-sea flux of PAHs in the Bering Sea, which meant that the ocean served as a sink for PAHs, at least in summer. Acenaphthylene and acenaphthene reached equilibrium in air-water diffusive exchange, and any perturbation, such as a rise in temperature, might lead to disequilibrium and remobilize these compounds from their Arctic reservoirs. Copyright © 2017 Elsevier Ltd. All rights reserved.

The influence of water and redox conditions on the seismic properties of olivine

NASA Astrophysics Data System (ADS)

Cline, C. J., II; Jackson, I.; Faul, U.; David, E. C.; Berry, A.

2017-12-01

Eight polycrystalline olivine specimens of both synthetic (solution-gelation derived) and natural (San Carlos) origins were fabricated by hot-pressing at 1200°C and 300 MPa. Amongst these specimens, six contained varying concentrations of Ti, allowing control of hydroxyl (or `water') content through the creation of the energetically favored Ti-clinohumite-like defect (doubly protonated Si vacancy associated with a Ti/Mg substitution). Along with a Ti-free Fo90 specimen, these materials have Ti contents ranging between 0 and 802 atom ppm Ti/Si and associated chemically bound `water' contents between 0 and 1150 atom ppm H/Si, along with molecular water concentrations between 0 and 245 atom ppm H/Si. Each hot-pressed specimen was then subsequently wrapped in Pt, Ni or NiFe foil to control oxygen fugacity (fO2), and interrogated under water-undersaturated conditions via forced torsional oscillation. Testing was conducted at seismic periods of 1 - 1000 s and 200 MPa confining pressure during slow staged cooling from 1200 to 25°C. All specimens, regardless of water content or metal sleeving, exhibit high temperature background behavior, involving monotonically increasing levels of dissipation and concomitantly decreasing shear modulus with increasing oscillation period and increasing temperature. Our experimental results demonstrate unambiguously that water content (and water fugacity) has a negligible effect on the measured seismic properties olivine. Rather, a relationship between the prevailing redox conditions set by the metal sleeving and the magnitude of anelastic relaxation was observed. These results suggest that low velocity and high attenuation anomalies in the upper mantle are not due to elevated water contents. Instead, in oxidized and hydrous regions above subducting slabs and perhaps in the oceanic asthenosphere, high attenuation may reflect elevated fO2 conditions.

Workshop on Parent-Body and Nebular Modification of Chondritic Materials

NASA Technical Reports Server (NTRS)

Zolensky, M. E. (Editor); Krot, A. N. (Editor); Scott, E. R. D. (Editor)

1997-01-01

Topics considered include: thermal Metamorphosed Antarctic CM and CI Carbonaceous Chondrites in Japanese Collections, and Transformation Processes of Phyllosilicates; use of Oxygen Isotopes to Constrain the Nebular and Asteroidal Modification of Chondritic Materials; effect of Revised Nebular Water Distribution on Enstatite Chondrite Formation; interstellar Hydroxyls in Meteoritic Chondrules: Implications for the Origin of Water in the Inner Solar System; theoretical Models and Experimental Studies of Gas-Grain Chemistry in the Solar Nebula; chemical Alteration of Chondrules on Parent Bodies; thermal Quenching of Silicate Grains in Protostellar Sources; an Experimental Study of Magnetite Formation in the Solar Nebula; the Kaidun Meteorite: Evidence for Pre- and Postaccretionary Aqueous Alteration; a Transmission Electron Microscope Study of the Matrix Mineralogy of the Leoville CV3 (Reduced-Group) Carbonaceous Chondrite: Nebular and Parent-Body Features; rubidium-Strontium Isotopic Systematic of Chondrules from the Antarctic CV Chondrites Yamato 86751 and Yamato 86009: Additional Evidence for Late Parent-Body Modification; oxygen-Fugacity Indicators in Carbonaceous Chondrites: Parent-Body Alteration or High-Temperature Nebular Oxidation; thermodynamic Modeling of Aqueous Alteration in CV Chondrites; asteroidal Modification of C and O Chondrites: Myths and Models; oxygen Fugacity in the Solar Nebular; and the History of Metal and Sulfides in Chondrites.

The Abandoned E-Waste Recycling Site Continued to Act As a Significant Source of Polychlorinated Biphenyls: An in Situ Assessment Using Fugacity Samplers.

PubMed

Wang, Yan; Luo, Chunling; Wang, Shaorui; Cheng, Zhineng; Li, Jun; Zhang, Gan

2016-08-16

The recycling of e-waste has attracted significant attention due to emissions of polychlorinated biphenyls (PCBs) and other contaminants into the environment. We measured PCB concentrations in surface soils, air equilibrated with the soil, and air at 1.5-m height using a fugacity sampler in an abandoned electronic waste (e-waste) recycling site in South China. The total concentrations of PCBs in the soils were 39.8-940 ng/g, whereas the concentrations in air equilibrated with the soil and air at 1.5 m height were 487-8280 pg/m(3) and 287-7380 pg/m(3), respectively. The PCB concentrations displayed seasonal variation; they were higher in winter in the soils and higher in summer in the air, indicating that the emission of PCBs from the soil was enhanced during hot seasons for the relatively high temperature or additional sources, especially for low-chlorinated PCBs. We compared two methods (traditional fugacity model and fugacity sampler) for assessing the soil-air partition coefficients (Ksa) and the fugacity fractions of PCBs. The results suggested that the fugacity sampler provided more instructive and practical estimation on Ksa values and trends in air-soil exchange, especially for low-chlorinated PCBs. The abandoned e-waste burning site still acted as a significant source of PCBs many years after the prohibition on open burning.

Semi-empirical estimation of organic compound fugacity ratios at environmentally relevant system temperatures.

PubMed

van Noort, Paul C M

2009-06-01

Fugacity ratios of organic compounds are used to calculate (subcooled) liquid properties, such as solubility or vapour pressure, from solid properties and vice versa. They can be calculated from the entropy of fusion, the melting temperature, and heat capacity data for the solid and the liquid. For many organic compounds, values for the fusion entropy are lacking. Heat capacity data are even scarcer. In the present study, semi-empirical compound class specific equations were derived to estimate fugacity ratios from molecular weight and melting temperature for polycyclic aromatic hydrocarbons and polychlorinated benzenes, biphenyls, dibenzo[p]dioxins and dibenzofurans. These equations estimate fugacity ratios with an average standard error of about 0.05 log units. In addition, for compounds with known fusion entropy values, a general semi-empirical correction equation based on molecular weight and melting temperature was derived for estimation of the contribution of heat capacity differences to the fugacity ratio. This equation estimates the heat capacity contribution correction factor with an average standard error of 0.02 log units for polycyclic aromatic hydrocarbons, polychlorinated benzenes, biphenyls, dibenzo[p]dioxins and dibenzofurans.

RESTORED RIPARIAN BUFFERS AS TOOLS FOR ECOSYSTEM RESTORATION IN THE MAIA PROCESSES, ENDPOINTS, AND MEASURES OF SUCCESS FOR WATER, SOIL, FLORA AND FAUNA

EPA Science Inventory

Riparian buffer restorations are used as management tools to produce favorable water quality impacts, moreover the basis for riparian buffers as an instrument of water quality restoration rests on a relatively firm foundation. However, the extent to which buffers can restore rip...

The impact of degassing on the oxidation state of basaltic magmas: A case study of Kīlauea volcano

NASA Astrophysics Data System (ADS)

Moussallam, Yves; Edmonds, Marie; Scaillet, Bruno; Peters, Nial; Gennaro, Emanuela; Sides, Issy; Oppenheimer, Clive

2016-09-01

Volcanic emissions link the oxidation state of the Earth's mantle to the composition of the atmosphere. Whether the oxidation state of an ascending magma follows a redox buffer - hence preserving mantle conditions - or deviates as a consequence of degassing remains under debate. Thus, further progress is required before erupted basalts can be used to infer the redox state of the upper mantle or the composition of their co-emitted gases to the atmosphere. Here we present the results of X-ray absorption near-edge structure (XANES) spectroscopy at the iron K-edge carried out for a series of melt inclusions and matrix glasses from ejecta associated with three eruptions of Kīlauea volcano (Hawai'i). We show that the oxidation state of these melts is strongly correlated with their volatile content, particularly in respect of water and sulfur contents. We argue that sulfur degassing has played a major role in the observed reduction of iron in the melt, while the degassing of H2O and CO2 appears to have had a negligible effect on the melt oxidation state under the conditions investigated. Using gas-melt equilibrium degassing models, we relate the oxidation state of the melt to the composition of the gases emitted at Kīlauea. Our measurements and modelling yield a lower constraint on the oxygen fugacity of the mantle source beneath Kīlauea volcano, which we infer to be near the nickel nickel-oxide (NNO) buffer. Our findings should be widely applicable to other basaltic systems and we predict that the oxidation state of the mantle underneath most hotspot volcanoes is more oxidised than that of the associated lavas. We also suggest that whether the oxidation states of a basalt (in particular MORB) reflects that of its source, is primarily determined by the extent of sulfur degassing.

The solubility of gold in silicate melts: First results

NASA Technical Reports Server (NTRS)

Borisov, A.; Palme, H.; Spettel, B.

1993-01-01

The effects of oxygen fugacity and temperature on the solubility of Au in silicate melts were determined. Pd-Au alloys were equilibrated with silicate of anorthite-diopside eutectic composition at different T-fO2 conditions. The behavior of Au was found to be similar to that of Pd reported recently. Au solubilities for alloys with 30 to 40 at. percent Au decrease at 1400 C from 12 ppm in air to 160 ppb at a log fO2 = -8.7. The slope of the log(Me-solubility) vs. log(fO2) curve is close to 1/4 for Au and the simultaneously determined Pd suggesting a formal valence of Au and Pd of 1+. Near the IW buffer Pd and Au solubilities become even less dependent on fO2 perhaps reflecting the presence of some metallic Au and Pd.

Microscopic iron metal on glass and minerals - A tool for studying regolith maturity

NASA Technical Reports Server (NTRS)

Allen, C. C.; Morris, R. V.; Lauer, H. V., Jr.; Mckay, D. S.

1993-01-01

A novel method of producing mixtures of glass or minerals with iron metal is presented. A portion of the Fe(2+) in basaltic glass and minerals can be reduced to metal in a few hours at 1100 C and an oxygen fugacity well below the iron-wustite buffer. Part of the iron metals forms rounded submicrometer blebs on the surfaces and in some cases within the grains. A concentration of such blebs equivalent to 20-30 percent of a grain's surface area can totally dominate the reflectance spectra of basaltic glass, pyroxene, and olivine. The production of optically opaque iron metal blebs, combined with the decline in Fe(2+), affects the glass and mineral reflectance spectra in three ways: by lowering the overall reflectivity, reducing the spectral contrast of absorption features, and producing a continuum with a general rise in reflectivity toward longer wavelengths.

Thermal reduction of MoO3 in sub- and supercritical water: Insights on redox conditions in Hydrothermal Diamond Anvil Cell (HDAC) experiments

NASA Astrophysics Data System (ADS)

Solferino, G.; Anderson, A. J.

2011-12-01

The Hydrothermal Diamond Anvil Cell (HDAC) is a key tool used in the study of volatile bearing melts and solute-rich fluids at the pressure and temperatures existent in the crust and shallow upper mantle (100-1500 MPa). Oxygen fugacity is among the key parameters that must be constrained in phase equilibrium and speciation studies of melt and aqueous fluid systems. It is however difficult to assess fO2 during HDAC experiments due to decomposition of water, interaction of fluid with gasket materials and the diamond themselves. In this study the temperature at which molybdenum trioxide was thermally reduced to molybdenum dioxide in the presence of deoxygenated water was measured in order to constrain the oxygen fugacity in the HDAC experiment. The sample was contained within either a rhenium gasket between two diamond anvils or within a laser-milled recess in the culet face of one of the diamond anvils (i.e. no gasket). Experiments consisted of loading a MoO3 crystal and deoxygenated water into the sample chamber and then holding the system at a temperature for the desired amount of time. MoO3 dissolved in large part or completely after 30-60 minutes at high temperature. In most experiments tugarinovite (MoO2) precipitated directly from solution once the temperature of thermal reduction was attained. MicroRaman spectroscopy was used to characterize run products. The temperature at which tugarinovite appeared varied depending on the experimental setup, and was 315 ± 2.0 °C in experiments where a gasket was used and 344 ± 2.5 °C in the experiments without a gasket. This implies that the presences of a Re gasket resulted in more reducing conditions of log(fO2) = -20.6 ± 0.5, compared to log(fO2) = -19.5 ± 0.2 for the series without gasket. Moreover, in some of the experiments performed below the transition temperature to tugarinovite, and when MoO3 crystals were not dissolved completely, an additional Raman peak at 854 cm-1 was observed that is not present in pure orthorhombic molybdite (α-MoO3). This feature, which is attributed to the presence of metastable monoclinic MoO3, is absent or poorly developed in runs where no gasket was used but was very intense in experiments where a gasket was used. According to previous studies, monoclinic MoO3 is formed in reducing conditions. The results indicate that for very simple systems, where water is the only or the dominating fluid medium, a Re gasket has a significant reducing effect on the fO2 at relatively low temperatures (200-400 °C). Furthermore, the fO2 conditions appear to be imposed (mainly) by the fluid and not by the noble metal gasket. Despite the reducing effect of the rhenium metal on the fluid, fO2 values for the Re-ReO2 buffer are much smaller than those extrapolated for our runs (i.e. log (fO2) = -27 to -29).

RESEARCH NEEDS IN RIPARIAN BUFFER RESTORATION

EPA Science Inventory

Riparian buffer restorations are used as management tools to produce favorable water quality impacts; moreover, the basis for riparian buffers as an instrument of water quality restoration rests on a relatively firm foundation. However, the extent to which buffers can restore rip...

On the habitability of a stagnant-lid Earth

NASA Astrophysics Data System (ADS)

Tosi, Nicola; Stracke, Barbara; Godolt, Mareike; Ruedas, Thomas; Grenfell, John Lee; Höning, Dennis; Nikolaou, Athanasia; Plesa, Ana-Catalina; Breuer, Doris; Spohn, Tilman

2016-04-01

Whether plate tectonics is a recurrent feature of terrestrial bodies orbiting other stars or is unique to the Earth is unknown. The stagnant-lid may rather be the most common tectonic mode through which terrestrial bodies operate. Here we model the thermal history of the mantle, the outgassing evolution of H2O and CO2, and the resulting climate of a hypothetical planet with the same mass, radius, and composition as the Earth, but lacking plate tectonics. We employ a 1-D model of parameterized stagnant-lid convection to simulate the evolution of melt generation, crust production, and volatile extraction over a timespan of 4.5 Gyr, focusing on the effects of three key mantle parameters: the initial temperature, which controls the overall volume of partial melt produced; the initial water content, which affects the mantle rheology and solidus temperature; and the oxygen fugacity, which is employed in a model of redox melting to determine the amount of carbon stored in partial melts. We assume that the planet lost its primordial atmosphere and use the H2O and CO2 outgassed from the interior to build up a secondary atmosphere over time. Furthermore, we assume that the planet may possess an Earth-like ocean. We calculate the atmospheric pressure based on the solubility of H2O and CO2 in basaltic magmas at the evolving surface pressure conditions. We then employ a 1-D radiative-convective, cloud-free stationary atmospheric model to calculate the resulting atmospheric temperature, pressure and water content, and the corresponding boundaries of the habitable zone (HZ) accounting for the evolution of the Sun's luminosity with time but neglecting escape processes. The interior evolution is characterized by a large initial production of partial melt accompanied by the formation of crust that rapidly grows until its thickness matches that of the stagnant lid so that the convecting sublithospheric mantle prevents further crustal growth. Even for initial water concentrations in excess of thousands of ppm, the high solubility of water in surface magmas limits the maximal partial pressure of atmospheric H2O to a few tens of bars, which places de facto an upper bound on the amount of water that can be delivered to the surface and atmosphere from the interior. The relatively low solubility of CO2 causes instead most of the carbon contained in surface melts to be outgassed. As a consequence, the partial pressure of atmospheric CO2 is largely controlled by the redox state of the mantle, with values that range from a few up to tens of bars for oxygen fugacities between the iron-wüstite buffer and one log-unit above it. At 1 AU and for most cases, liquid water on the surface is possible, hence the planets considered would be regarded as habitable although the atmospheric temperature may be well above the temperature limits for terrestrial life. The inner edge of the HZ depends on the amount of outgassed H2O and is located further away from the star if no initial water ocean is assumed. The outer edge of the HZ is controlled by the amount of outgassed CO2, hence by the assumed redox state of the mantle and its initial temperature.

Water sensitivity of the seismic properties of upper-mantle olivine

NASA Astrophysics Data System (ADS)

Cline, Christopher; David, Emmanuel; Faul, Ulrich; Berry, Andrew; Jackson, Ian

2017-04-01

The wave speeds and attenuation of seismic waves in the upper mantle are expected to be strongly influenced by the defect chemistry of olivine grain interiors and the associated chemical complexity of grain-boundary regions. Changes in chemical environment (oxygen fugacity and/or water fugacity) can impose different defect chemistries, including the creation and retention of hydrous defects, and therefore can directly influence anelastic relaxation involving stress-induced migration of lattice defects and/or grain-boundary sliding. Here we report the first low-frequency experimental study of the seismic properties of olivine under water-undersaturated conditions. Three synthetic sol-gel derived olivine (Fo90) specimens were fabricated by hot-pressing in welded Pt capsules with various concentrations of hydroxyl, chemically bound as doubly protonated Si vacancies, charge balanced by substitution of Ti on a neighboring M-site (i.e., the Ti-clinohumite-like defect). Hydroxyl contents, determined following the subsequent mechanical testing within Pt sleeves, increased systematically with the amount of added Ti-dopant. Added Ti concentrations ranged between 176 and 802 atom ppm Ti/Si, resulting in concentrations of bound hydrogen in the three samples ranging between 330 and 1150 atom ppm H/Si. Each hot-pressed specimen was precision ground and then sleeved in Pt for mechanical testing in forced torsional oscillation under water-undersaturated conditions. Forced-oscillation tests were conducted at seismic periods of 1 - 1000 s and 200 MPa confining pressure during slow staged cooling from 1200 to 25°C. Each Ti-doped specimen showed mechanical behavior of the high-temperature background type involving monotonically increasing dissipation and decreasing shear modulus with increasing oscillation period and increasing temperature. Comparison of the mechanical data acquired in these water-undersaturated conditions with a similarly tested, but dry, Ti-bearing specimen (enclosed within an Ni-Fe sleeve under more reducing conditions) shows a marked contrast. The OH-bearing specimens exhibit much lower shear moduli (by as much as 80%) and higher levels of dissipation (by as much as 0.5 log units in Q-1), but also limited sensitivity of the seismic properties to the total water content among the hydrated specimens in the series. These results indicate that the higher oxygen and water fugacities prevailing within Pt-sleeved specimens result in lower shear moduli and higher dissipation under water-undersaturated conditions - presumably attributable to contrasting defect populations and/or grain boundary chemistries. Clarification of the relative roles of grain-boundary sliding and any additional intragranular relaxation under increased fH2O and fO2 thus offers the prospect of an improved understanding of the seismological signature of more oxidized/hydrous portions of the Earth's upper mantle, such as subduction zone environments.

Water quality in relation to vegetative buffers around sinkholes in karst terrain

USGS Publications Warehouse

Petersen, A.; Vondracek, B.

2006-01-01

There are approximately 8,340 mapped sinkholes in karst terrain of southeast Minnesota. Most sinkholes are adjacent to row crops that likely contribute pollutants to surface waters and aquifers. Vegetated buffers can improve water quality by reducing sediment, fertilizers, pesticides, and other potential contaminants from runoff, and may benefit water quality when placed around sinkholes. We evaluated sediment, nitrogen, phosphorus, and runoff for buffers from 2.5 to 30 m (8.3 to 98 ft) wide with a spreadsheet model. We found buffers 30 m (98 ft) wide may reduce pollution by 80 percent, although buffers 15 m (49 ft) wide may be most cost effective. Buffers could contribute to goals of reducing sediment, nitrogen, and phosphorus loads in Minnesota waters. Buffers 15 m (49 ft) wide around all sinkholes would retire approximately 436 ha (1,077 ac) of land from production and cost approximately $260,000 yr-1 based on Conservation Reserve Program payments, while requiring <14 percent of the budget of the program for groundwater protection in southeast Minnesota.

Platinum catalytic effect on oxygen fugacity of CO 2H 2 gas mixtures measured with ZrO 2 oxygen sensor at 105 Pa from 1300 to 700°C

NASA Astrophysics Data System (ADS)

Miyamoto, M.; Mikouchi, T.

1996-08-01

The oxygen fugacity of CO 2H 2 gas mixtures were measured with a ZrO 2 oxygen sensor at high temperatures in a furnace. We confirmed that the oxygen fugacity values measured by the ZrO 2 cell are more reducing than those of the CO 2H 2 gas mixtures calculated by using JANAF data at temperatures below 1150°C as was previously reported by Huebner (1975). We successfully decreased the deviation of the measured oxygen-fugacity value from the calculated one down to temperature of 800°C by using a Pt catalyst. Our results suggest that the deviation is probably due to incomplete equilibration of the gases.

Anionic Pt in Silicate Melts at Low Oxygen Fugacity: Speciation, Partitioning and Implications for Core Formation Processes on Asteroids

NASA Technical Reports Server (NTRS)

Medard, E.; Martin, A. M.; Righter, K.; Malouta, A.; Lee, C.-T.

2017-01-01

Most siderophile element concentrations in planetary mantles can be explained by metal/ silicate equilibration at high temperature and pressure during core formation. Highly siderophile elements (HSE = Au, Re, and the Pt-group elements), however, usually have higher mantle abundances than predicted by partitioning models, suggesting that their concentrations have been set by late accretion of material that did not equilibrate with the core. The partitioning of HSE at the low oxygen fugacities relevant for core formation is however poorly constrained due to the lack of sufficient experimental constraints to describe the variations of partitioning with key variables like temperature, pressure, and oxygen fugacity. To better understand the relative roles of metal/silicate partitioning and late accretion, we performed a self-consistent set of experiments that parameterizes the influence of oxygen fugacity, temperature and melt composition on the partitioning of Pt, one of the HSE, between metal and silicate melts. The major outcome of this project is the fact that Pt dissolves in an anionic form in silicate melts, causing a dependence of partitioning on oxygen fugacity opposite to that reported in previous studies.

Redox States of Initial Atmospheres Outgassed on Rocky Planets and Planetesimals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaefer, Laura; Fegley, Bruce Jr., E-mail: lschaefer@asu.edu

2017-07-10

The Earth and other rocky planets and planetesimals in the solar system formed through the mixing of materials from various radial locations in the solar nebula. This primordial material likely had a range of oxidation states as well as bulk compositions and volatile abundances. We investigate the oxygen fugacity produced by the outgassing of mixtures of solid meteoritic material, which approximate the primitive nebular materials. We find that the gas composition and oxygen fugacity of binary and ternary mixtures of meteoritic materials vary depending on the proportion of reduced versus oxidized material, and also find that mixtures using differentiated materialsmore » do not show the same oxygen fugacity trends as those using similarly reduced but undifferentiated materials. We also find that simply mixing the gases produced by individual meteoritic materials together does not correctly reproduce the gas composition or oxygen fugacity of the binary and ternary mixtures. We provide tabulated fits for the oxygen fugacities of all of the individual materials and binary mixtures that we investigate. These values may be useful in planetary formation models, models of volatile transport on planetesimals or meteorite parent bodies, or models of trace element partitioning during metal-silicate fractionation.« less

Water and the oxidation state of subduction zone magmas.

PubMed

Kelley, Katherine A; Cottrell, Elizabeth

2009-07-31

Mantle oxygen fugacity exerts a primary control on mass exchange between Earth's surface and interior at subduction zones, but the major factors controlling mantle oxygen fugacity (such as volatiles and phase assemblages) and how tectonic cycles drive its secular evolution are still debated. We present integrated measurements of redox-sensitive ratios of oxidized iron to total iron (Fe3+/SigmaFe), determined with Fe K-edge micro-x-ray absorption near-edge structure spectroscopy, and pre-eruptive magmatic H2O contents of a global sampling of primitive undegassed basaltic glasses and melt inclusions covering a range of plate tectonic settings. Magmatic Fe3+/SigmaFe ratios increase toward subduction zones (at ridges, 0.13 to 0.17; at back arcs, 0.15 to 0.19; and at arcs, 0.18 to 0.32) and correlate linearly with H2O content and element tracers of slab-derived fluids. These observations indicate a direct link between mass transfer from the subducted plate and oxidation of the mantle wedge.

Mineral chemistry of Pangidi basalt flows from Andhra Pradesh

NASA Astrophysics Data System (ADS)

Nageswara Rao, P. V.; Swaroop, P. C.; Karimulla, Syed

2012-04-01

This paper elucidates the compositional studies on clinopyroxene, plagioclase, titaniferous magnetite and ilmenite of basalts of Pangidi area to understand the geothermometry and oxybarometry conditions. Petrographic evidence and anorthite content (up to 85%) of plagioclase and temperature estimates of clinopyroxene indicate that the clinopyroxene is crystallized later than or together with plagioclase. The higher An content indicates that the parent magma is tholeiitic composition. The equilibration temperatures of clinopyroxene (1110-1190°C) and titaniferous magnetite and ilmenite coexisting mineral phases (1063-1103°C) are almost similar in lower basalt flow and it is higher for clinopyroxene (900-1110°C) when compared to titaniferous magnetite and ilmenite coexisting mineral phases (748-898°C) in middle and upper basalt flows. From this it can be inferred that the clinopyroxene is crystallized earlier than Fe-Ti oxide phases reequilibration, which indicates that the clinopyroxene temperature is the approximate eruption temperature of the present lava flows. The wide range of temperatures (900-1190°C) attained by clinopyroxene may point out that the equilibration of clinopyroxene crystals initiated from depth till closer to the surface before the melt erupted. Pangidi basalts follow the QFM buffer curve which indicates the more evolved tholeiitic composition. This suggests the parent tholeiitic magma suffered limited fractionation at high temperature under increasing oxygen fugacity in lower basalt flow and more fractionation at medium to lower temperatures under decreasing oxygen fugacity conditions during cooling of middle and upper basalt flows. The variation of oxygen fugacity indicates the oxidizing conditions for lower basalt flow (9.48-10.3) and extremely reducing conditions for middle (12.1-15.5) and upper basalt (12.4-15.54) flows prevailed at the time of cooling. Temperature vs. (FeO+Fe2O3)/(FeO+Fe2O3 +MgO) data plots for present basalts suggested the lower basaltic flow is formed at higher temperatures while the middle and upper basalt flows at medium to lower temperatures. The lower basalt flow is represented by higher temperatures which shows high modal values of opaques and glass whereas the medium to lower temperatures of middle and upper flow are caused by vesicular nature which contain larger content of gases and humid to semi-arid conditions during cooling.

No effect of H2O degassing on the oxidation state of hydrous rhyolite magmas: a comparison of pre- and post-eruptive Fe2+ concentrations in six obsidian samples from the Mexican and Cascade arcs

NASA Astrophysics Data System (ADS)

Waters, L.; Lange, R. A.

2011-12-01

The extent to which degassing affects the oxidation state of arc magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of magmas, and it has been proposed that degassing may induce either oxidation or reduction depending on the initial oxidation state. A commonly proposed oxidation reaction is related to H2O degassing: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt). Another mechanism by which H2O degassing can affect the iron redox state is if dissolved water affects the activity of ferrous and/or ferric iron in the melt. Although Moore et al. (1995) presented experiments showing no evidence of an affect of dissolved water on the activity of the ferric-ferrous ratio in silicate melts, other experimental results (e.g., Baker and Rutherford, 1996; Gaillard et al., 2001; 2003) indicate that there may be such an effect in rhyolite liquids. It has long been understood that rhyolites, owing to their low total iron concentrations, are more sensitive than other magma types to degassing-induced change in redox state. Therefore, a rigorous test of whether H2O degassing affects the redox state of arc magmas is best evaluated on rhyolites. In this study, a comparison is made between the pre-eruptive (pre-degassing) Fe2+ concentrations in six, phenocryst-poor (<5%), fresh, glassy obsidian samples with their post-eruptive (post-degassing) Fe2+ concentrations. Near-liquidus co-precipitation of two Fe-Ti oxides allows the pre-eruptive oxygen fugacity and temperature to be calculated in each rhyolite using the oxygen barometer and thermometer of Ghiorso and Evans (2008). Temperatures range from 793 (± 19) to 939 (± 15) °C, and ΔNNO values (log10fO2 of sample - log10fO2 of Ni-NiO buffer) range from -0.4 to +1.4. These ΔNNO values allow the ferric-ferrous ratio in the liquid to be calculated, using the experimental calibration of Kress and Carmichael (1991), which relates melt composition (not including dissolved water), oxygen fugacity and temperature to melt ferric-ferrous ratios. With temperature known, the plagioclase-liquid hygrometer of Lange et al. (2009) was applied and maximum melt water concentrations range from 4.2 to 7.5 wt%. Both the oxidation state and water concentration are known prior to eruption, at the time of phenocryst growth. After eruption, the rhyolites lost nearly all of their volatiles, as indicated by the low loss on ignition values (LOI ≤ 0.7 wt%). In order to test how much oxidation of ferrous iron occurred as a consequence of that degassing, we measured the ferrous iron concentration in the bulk samples by titration, using the Wilson (1960) method, which was successfully tested again three USGS and one Canadian Geological Survey standards. Our results indicate no detectable change within analytical error between pre- and post-eruptive FeO concentrations, with an average deviation of 0.09 wt% and a maximum deviation of 0.15 wt%. Our results show that H2O degassing has no effect on the redox state of rhyolite magmas, which requires that dissolved water has no resolvable affect on the activity ratio of the iron oxide components in melt.

Redox state of the Archean mantle: Evidence from V partitioning in 3.5-2.4 Ga komatiites

NASA Astrophysics Data System (ADS)

Nicklas, Robert W.; Puchtel, Igor S.; Ash, Richard D.

2018-02-01

Oxygen fugacity of the mantle is a crucial thermodynamic parameter that controls such fundamental processes as planetary differentiation, mantle melting, and possible core-mantle exchange. Constraining the evolution of the redox state of the mantle is of paramount importance for understanding the chemical evolution of major terrestrial reservoirs, including the core, mantle, and atmosphere. In order to evaluate the secular evolution of the redox state of the mantle, oxygen fugacities of six komatiite systems, ranging in age from 3.48 to 2.41 Ga, were determined using high-precision partitioning data of the redox-sensitive element vanadium between liquidus olivine, chromite and komatiitic melt. The calculated oxygen fugacities range from -0.11 ± 0.30 ΔFMQ log units in the 3.48 Ga Komati system to +0.43 ± 0.26 ΔFMQ log units in the 2.41 Ga Vetreny system. Although there is a slight hint in the data for an increase in the oxygen fugacity of the mantle between 3.48 and 2.41 Ga, these values generally overlap within their respective uncertainties; they are also largely within the range of oxygen fugacity estimates for modern MORB lavas of +0.60 ± 0.30 ΔFMQ log units that we obtained using the same technique. Our results are consistent with the previous findings that argued for little change in the mantle oxygen fugacity since the early Archean and indicate that the mantle had reached its nearly-present day redox state by at least 3.48 Ga.

Mass balance modelling of contaminants in river basins: a flexible matrix approach.

PubMed

Warren, Christopher; Mackay, Don; Whelan, Mick; Fox, Kay

2005-12-01

A novel and flexible approach is described for simulating the behaviour of chemicals in river basins. A number (n) of river reaches are defined and their connectivity is described by entries in an n x n matrix. Changes in segmentation can be readily accommodated by altering the matrix entries, without the need for model revision. Two models are described. The simpler QMX-R model only considers advection and an overall loss due to the combined processes of volatilization, net transfer to sediment and degradation. The rate constant for the overall loss is derived from fugacity calculations for a single segment system. The more rigorous QMX-F model performs fugacity calculations for each segment and explicitly includes the processes of advection, evaporation, water-sediment exchange and degradation in both water and sediment. In this way chemical exposure in all compartments (including equilibrium concentrations in biota) can be estimated. Both models are designed to serve as intermediate-complexity exposure assessment tools for river basins with relatively low data requirements. By considering the spatially explicit nature of emission sources and the changes in concentration which occur with transport in the channel system, the approach offers significant advantages over simple one-segment simulations while being more readily applicable than more sophisticated, highly segmented, GIS-based models.

Long-term geochemical surveillance of fumaroles at Showa-Shinzan dome, Usu volcano, Japan

USGS Publications Warehouse

Symonds, R.B.; Mizutani, Y.; Briggs, P.H.

1996-01-01

This study investigates 31 years of fumarole gas and condensate (trace elements) data from Showa-Shinzan, a dacitic dome-cryptodome complex that formed during the 1943-1945 eruption of Usu volcano. Forty-two gas samples were collected from the highest-temperature fumarole, named A-1, from 1954 (800??C) to 1985 (336??C), and from lower-temperature vents. Condensates were collected contemporaneously with the gas samples, and we reanalyzed ten of these samples, mostly from the A-1 vent, for 32 cations and three anions. Modeling using the thermochemical equilibrium program, SOLVGAS, shows that the gas samples are mild disequilibrium mixtures because they: (a) contain unequilibrated sedimentary CH4 and NH3; (b) have unequilibrated meteoric water; or (c) lost CO, either by air oxidation or by absorption by the sodium hydroxide sampling solution. SOLVGAS also enabled us to restore the samples by removing these disequilibrium effects, and to estimate their equilibrium oxygen fugacities and amounts of S2 and CH4. The restored compositions contain > 98% H2O with minor to trace amounts of CO2, H2, HCl, SO2, HF, H2S, CO, S2 and CH4. We used the restored gas and condensate data to test the hypotheses that these time-series compositional data from the dome's fumaroles provide: (1) sufficient major-gas data to analyze long-term degassing trends of the dome's magma-hydrothermal system without the influence of sampling or contamination effects; (2) independent oxygen fugacity-versus-temperature estimates of the Showa-Shinzan dacite; (3) the order of release of trace elements, especially metals, from magma; and (4) useful information for assessing volcanic hazards. The 1954-1985 restored A-1 gas compositions confirm the first hypothesis because they are sufficient to reveal three long-term degassing trends: (1) they became increasingly H2O-rich with time due to the progressive influx of meteoric water into the dome; (2) their C/S and S/Cl ratios decreased dramatically while their Cl/F ratios stayed roughly constant, indicating the progressive outgassing of less soluble components (F ??? Cl > S > C) from the magma reservoir; and (3) their H2O/H2, CO2/CO and H2S/SO2 ratios increased significantly in concert with equilibrium changes expected for the ??? 500??C temperature drop. When plotted against reciprocal temperature, the restored-gas log oxygen fugacities follow a tight linear trend from 800??C to NNO + 2.5 at ??? 400??C. This trend largely disproves the second hypothesis because the oxygen fugacities for the < 800??C restored gases can only be explained by mixing of hot magmatic gases with ??? 350??C steam from superheated meteoric water. But above 800??C this trend intersects the opposing linear trend for other Usu eruptive products, implying a log oxygen fugacity of -11.45 at 902??C for the Showa-Shinzan magma. The time-series trace-element data also disprove the third hypothesis because rock- and incrustation-particle contaminants in the condensates account for most of the trace-element variation. Nonetheless, highly volatile elements like B and As are relatively unaffected by this particle contamination, and they show similar time-series trends as Cl and F. Finally, except for infrequent sampling around the 1977 Usu eruption, the results generally confirm the fourth hypothesis, since the time-series trends for the major gases and selected trace elements indicate that, with time, the system cooled, degassed and was infiltrated by meteoric water, all of which are positive signs that volcanic activity declined over the 31-year history. This study also suggests that second boiling of shallow magma within and possibly beneath the cryptodome sustained magmatic degassing for at least 20 years after emplacement.

Stream water responses to timber harvest: Riparian buffer width effectiveness

Treesearch

Barton D. Clinton

2011-01-01

Vegetated riparian buffers are critical for protecting aquatic and terrestrial processes and habitats in southern Appalachian ecosystems. In this case study, we examined the effect of riparian buffer width on stream water quality following upland forest management activities in four headwater catchments. Three riparian buffer widths were delineated prior to cutting; 0m...

Multimedia fate modeling and risk assessment of a commonly used azole fungicide climbazole at the river basin scale in China.

PubMed

Zhang, Qian-Qian; Ying, Guang-Guo; Chen, Zhi-Feng; Liu, You-Sheng; Liu, Wang-Rong; Zhao, Jian-Liang

2015-07-01

Climbazole is an antidandruff active ingredient commonly used in personal care products, but little is known about its environmental fate. The aim of this study was to evaluate the fate of climbazole in water, sediment, soil and air compartments of the whole China by using a level III multimedia fugacity model. The usage of climbazole was calculated to be 345 t in the whole China according to the market research data, and after wastewater treatment a total emission of 245 t was discharged into the receiving environment with approximately 93% into the water compartment and 7% into the soil compartment. The developed fugacity model was successfully applied to estimate the contamination levels and mass inventories of climbazole in various environmental compartments of the river basins in China. The predicted environmental concentration ranges of climbazole were: 0.20-367 ng/L in water, and 0.009-25.2 ng/g dry weight in sediment. The highest concentration was mainly found in Haihe River basin and the lowest was in basins of Tibet and Xinjiang regions. The mass inventory of climbazole in the whole China was estimated to be 294 t, with 6.79% in water, 83.7% in sediment, 9.49% in soil, and 0.002% in air. Preliminary risk assessment showed high risks in sediment posed by climbazole in 2 out of 58 basins in China. The medium risks in water and sediment were mostly concentrated in north China. To the best of our knowledge, it is the first report on the emissions and multimedia fate of climbazole in the river basins of the whole China. Copyright © 2015 Elsevier B.V. All rights reserved.

Experimental Constraints on the Stability of Clinopyroxene (+) Magnesite in Iron Bearing Planetary Mantles: Implications for Nakhlite Formation

NASA Technical Reports Server (NTRS)

Martin, Audrey M.; Righter, Kevin

2010-01-01

Carbon is present in various forms in the Earth s upper mantle (carbonate- or diamond-bearing mantle xenoliths, carbonatite magmas, CO2 emissions from volcanoes...). Moreover, there is enough carbon in chondritic material to stabilize carbonates into the mantles of Mars or Venus as well as in the Earth. However, the interactions with iron have to be constrained, because Fe is commonly thought to buffer oxygen fugacity into planetary mantles. [1] and [2] show evidences of the stability of clinopyroxene Ca(Mg,Fe)Si2O6 + magnesite (Mg,Fe)CO3 in the Earth s mantle around 6GPa (about 180km). The stability of oxidized forms of carbon (like magnesite) depends on the oxygen fugacity of the system. In the Earth s mantle, the maximum carbon content is 10000 ppm [3]. The fO2 parameter varies vertically as a function of pressure, but also laterally because of geodynamic processes like subduction. Thus, carbonates, graphite, diamond, C-rich gases and melts are all stable forms of carbon in the Earth s mantle. [4] show that the fO2 variations observed in SNC meteorites can be explained by polybaric graphite-CO-CO2 equilibria in the Martian mantle. [5] inferred from thermodynamic calculations that the stable form of carbon in the source regions of the Martian basalts should be graphite (and/or diamond). After [6], a metasomatizing agent like a CO2-rich melt may infiltrate the mantle source of nakhlites. However, according to [7] and [8], the FeO wt% value in the Martian bulk mantle is more than twice that of the Earth s mantle (KLB-1 composition by [9]). As iron and carbon are two elements with various oxidation states, Fe/C interaction mechanisms must be considered.

Graphite solubility and co-vesiculation in basalt-like melts at one-ATM

NASA Technical Reports Server (NTRS)

Colson, R. O.

1993-01-01

The identity and source of the vapor phase that caused lunar lava-fountaining and vesiculation in lunar basalts continues to be of interest because of its implications for the composition and state of the lunar interior and because of its implications for lunar resources. In light of the apparent near-absence of H2O on the Moon, it has been suggested that the vapor phase may be CO2-CO. This premise is supported by the presence of carbon on the surface of volcanic glass beads. However, although the rapid exsolution of CO2 from a melt during decompression may be consistent with firefountaining, it fails to provide a satisfying explanation for vesiculation in mare basalt where exsolution of the gas phase would more reasonably be related to cooling/crystallization at low pressure rather than decompression from high pressure. Also, geochemical trends in lunar volcanic glasses suggest that their source has an oxygen fugacity more reducing than the iron-wustite buffer, an oxygen fugacity that is inconsistent with presence of dissolved CO2-CO at depth. The results of experiments in which a vesicular 'basalt' is produced from a melt equilibrated with graphite and pure CO gas at one atmosphere pressure are reported. The vesiculation is apparently related to exsolution of CO or a CO species during cooling of the melt or growth of quench crystals. Additionally, particulate carbon dispersed through the quenched sample suggests that elemental carbon is either in solution in the melt prior to quenching or tends to go into suspension perhaps as colloid-like particles. These two observations may provide insight into the nature of fire-fountaining and vesiculation on the Moon.

Buffer strip design for protecting water quality and fish habitat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belt, G.H.; O'Laughlin, J.

1994-04-01

Buffer strips are protective areas adjacent to streams or lakes. Among other functions, they protect water quality and fish habitat. A typical buffer strip is found in western Oregon, where they are called Riparian Management Areas (RMAs). The authors use the term buffer strip to include functional descriptions such as filter, stabilization, or leave strips, and administrative designations such as Idaho's Stream Protection Zone (SPZ), Washington's Riparian Management Zone (RMZ), and the USDA Forest Service's Streamside Management Zone (SMZ). They address water quality and fishery protective functions of buffer strips on forestlands, pointing out improvements in buffer strip design possiblemore » through research or administrative changes. Buffer strip design requirements found in some western Forest Practices Act (FPA) regulations are also compared and related to findings in the scientific literature.« less

Riparian buffer design guidelines for water quality and wildlife habitat functions on agricultural landscapes in the Intermountain West

Treesearch

Craig W. Johnson; Susan Buffler

2008-01-01

Intermountain West planners, designers, and resource managers are looking for science-based procedures for determining buffer widths and management techniques that will optimize the benefits riparian ecosystems provide. This study reviewed the riparian buffer literature, including protocols used to determine optimum buffer widths for water quality and wildlife habitat...

Experimental Constraints on the Cr Content, Oxygen Fugacity, and Petrogenesis of EETA79001 Lithology A

NASA Technical Reports Server (NTRS)

Herd, C. D. K.; Jones, J. H.; Papike, J. J.

2000-01-01

Experiments involving the composition of the groundmass of EETA79001 Lithology A constrain the Cr content of the melt and the oxygen fugacity, and suggest that overgrowth of olivine and pyroxene from the groundmass onto xenocrysts has occurred.

Stream Community Structure: An Analysis of Riparian Forest Buffer Restoration in the Chesapeake Bay Watershed

NASA Astrophysics Data System (ADS)

Orzetti, L. L.; Jones, R. C.

2005-05-01

Forested riparian buffer zones have been proposed as an important aid in curtailing upland sources of pollution before they reach stream surface waters, and enhancing habitat for stream organisms. Our objective was to test the efficacy of restored forest riparian buffers along streams in the Chesapeake Bay watershed by examining the stream macrobenthic community structure. To test our hypothesis, we collected riffle benthic and water samples, and performed habitat evaluations at 30 stream sites in the mid-Atlantic Piedmont, ranging in buffer age from 0 to greater than 50 years of age. Results showed that habitat, water quality, and benthic macroinvertebrate metrics improved with age of restored buffer. Habitat scores were driven mostly by instream substrate availability and width and age of riparian buffer zones. Water quality parameters varied within buffer age groups depending age of surrounding forest vegetation. Benthic invertebrate taxa richness, % EPT, % Plecoptera, % Ephemeroptera, and the FBI all improved with age of buffer zone. Instream habitat quality was the greatest driver of benthic macroinvertebrate community diversity and health, and appeared to plateau within 10-15 years of restoration with noticeable improvements occurring within 5-10 years post restoration.

Precipitation of Excess Hydrogen in Olivine During Cooling Under Pressures: An Experimental Study

NASA Astrophysics Data System (ADS)

Borinski, S.; Karato, S.

2007-12-01

Water (hydrogen) content in olivine transported from the upper mantle is used to infer the water content in the upper mantle (e.g., Bell and Rossman 1992). However, since hydrogen diffusion is known to be fast, processes of hydrogen loss need to be examined. In many literature, diffusion loss (or gain) of hydrogen is usually considered, but in addition to diffusion loss, hydrogen could also precipitate inside of olivine as small inclusions. Consider an upward transport of olivine-bearing rock that originally contained a large amount of hydrogen in the deep interior. As this rock is transported to the shallow region, the solubility limit of hydrogen will decrease because of the reduction of pressure (and temperature) (Kohlstedt et al. 1996, Zhao et al 2004). Consequently, excess hydrogen will precipitate to form water bubbles and/or hydrous minerals as inclusions. Frequently observed submicron-scale inclusions of hydrous minerals (Khisina and Wirth 2002, Kitamura et al. 1987) may correspond to these precipitation products. If that is the case, hydrogen content corresponding to these minerals should not be excluded when estimating the hydrogen content of a sample in the Earth's upper mantle. However, kinetics of precipitation of hydrogen from olivine have not been investigated in the laboratory. We have conducted a series of experimental study in which we annealed hydrogen-saturated olivine single crystals in two different P- T conditions. The starting material was an olivine crystal in which ~1,135 H/106Si (70 wt ppm H2O) was dissolved at P= 3.5 GPa and T=1,573 K. A small piece of this crystal (0.5 mm3) was placed in a multianvil at P=3.5 GPa and either at T= 873K or 1,173K with oxygen fugacity, fO2, buffered by the Ni-NiO solid-state reaction and silica activity, aSiO2, buffered by the presence of orthopyroxene powder in contact with the crystal. Annealing experiments were conducted up to 72 hours. Hydroxyl concentrations were determined from infrared spectra obtained from polished thin sections from crack-free regions of 100 x 100 μm. The hydroxyl concentration at the OH-stretching region around 3678 cm-1 increases systematically with increasing time at 873 K, whereas this band is not detected in samples annealed at 1,173 K. The peak(s) at 3678 cm-1 corresponds to the OH-stretching vibration in hydrous minerals such as serpentine (Mellini et al. 2002, Hofmeister and Bowey 2006). We conclude that the water in the upper mantle not only diffuse out and disappear during the ascent (cooling and depressurization), but also is bounded in hydrous minerals (e.g. serpentine).

Buffer substitution in malaria rapid diagnostic tests causes false-positive results

PubMed Central

2010-01-01

Background Malaria rapid diagnostic tests (RDTs) are kits that generally include 20 to 25 test strips or cassettes, but only a single buffer vial. In field settings, laboratory staff occasionally uses saline, distilled water (liquids for parenteral drugs dilution) or tap water as substitutes for the RDT kit's buffer to compensate for the loss of a diluent bottle. The present study assessed the effect of buffer substitution on the RDT results. Methods Twenty-seven RDT brands were run with EDTA-blood samples of five malaria-free subjects, who were negative for rheumatoid factor and antinuclear antibodies. Saline, distilled water and tap water were used as substitute liquids. RDTs were also run with distilled water, without adding blood. Results were compared to those obtained with the RDT kit's buffer and Plasmodium positive samples. Results Only eight cassettes (in four RDT brands) showed no control line and were considered invalid. Visible test lines occurred for at least one malaria-free sample and one of the substitutes in 20/27 (74%) RDT brands (saline: n = 16; distilled water: n = 17; and tap water: n = 20), and in 15 RDTs which were run with distilled water only. They occurred for all Plasmodium antigens and RDT formats (two-, three- and four-band RDTs). Clearance of the background of the strip was excellent except for saline. The aspects (colour, intensity and crispness) of the control and the false-positive test lines were similar to those obtained with the RDT kits' buffer and Plasmodium positive samples. Conclusion Replacement of the RDT kit's dedicated buffer by saline, distilled water and tap water can cause false-positive test results. PMID:20650003

UNDERSTANDING, DERIVING, AND COMPUTING BUFFER CAPACITY

EPA Science Inventory

Derivation and systematic calculation of buffer capacity is a topic that seems often to be neglected in chemistry courses and given minimal treatment in most texts. However, buffer capacity is very important in the chemistry of natural waters and potable water. It affects corro...

Technical Update: Johnson Space Center system using a solid electrolytic cell in a remote location to measure oxygen fugacities in CO/CO2 controlled-atmosphere furnaces

NASA Technical Reports Server (NTRS)

Jurewicz, A. J. G.; Williams, R. J.; Le, L.; Wagstaff, J.; Lofgren, G.; Lanier, A.; Carter, W.; Roshko, A.

1993-01-01

Details are given for the design and application of a (one atmosphere) redox-control system. This system differs from that given in NASA Technical Memorandum 58234 in that it uses a single solid-electrolytic cell in a remote location to measure the oxygen fugacities of multiple CO/CO2 controlled-atmosphere furnaces. This remote measurement extends the range of sample-furnace conditions that can be measured using a solid-electrolytic cell, and cuts costs by extending the life of the sensors and by minimizing the number of sensors in use. The system consists of a reference furnace and an exhaust-gas manifold. The reference furnace is designed according to the redox control system of NASA Technical Memorandum 58234, and any number of CO/CO2 controlled-atmosphere furnaces can be attached to the exhaust-gas manifold. Using the manifold, the exhaust gas from individual CO/CO2 controlled atmosphere furnaces can be diverted through the reference furnace, where a solid-electrolyte cell is used to read the ambient oxygen fugacity. The oxygen fugacity measured in the reference furnace can then be used to calculate the oxygen fugacity in the individual CO/CO2 controlled-atmosphere furnace. A BASIC computer program was developed to expedite this calculation.

Synchrotron Micro-XANES Measurements of Vanadium Oxidation State in Glasses as a Function of Oxygen Fugacity: Experimental Calibration of Data Relevant to Partition Coefficient Determination

NASA Technical Reports Server (NTRS)

Delaney, J. S.; Sutton, S. R.; Newville, M.; Jones, J. H.; Hanson, B.; Dyar, M. D.; Schreiber, H.

2000-01-01

Oxidation state microanalyses for V in glass have been made by calibrating XANES spectral features with optical spectroscopic measurements. The oxidation state change with fugacity of O2 will strongly influence partitioning results.

Utilizing polymer-coated vials to illustrate the fugacity and bioavailability of chlorinated pesticide residues in contaminated soils

USDA-ARS?s Scientific Manuscript database

Fugacity and bioavailability concepts can be challenging topics to communicate effectively in the timeframe of an academic laboratory course setting. In this experiment, students observe partitioning of the residues over time into an artificial biological matrix. The three compounds utilized are o...

Improving Water Quality With Conservation Buffers

NASA Astrophysics Data System (ADS)

Lowrance, R.; Dabney, S.; Schultz, R.

2003-12-01

Conservation buffer technologies are new approaches that need wider application. In-field buffer practices work best when used in combination with other buffer types and other conservation practices. Vegetative barriers may be used in combination with edge-of-field buffers to protect and improve their function and longevity by dispersing runoff and encouraging sediment deposition upslope of the buffer. It's important to understand how buffers can be managed to help reduce nutrient transport potential for high loading of nutrients from manure land application sites, A restored riparian wetland buffer retained or removed at least 59 percent of the nitrogen and 66 percent of the phosphorus that entered from an adjacent manure land application site. The Bear Creek National Restoration Demonstration Watershed project in Iowa has been the site of riparian forest buffers and filter strips creation; constructed wetlands to capture tile flow; stream-bank bioengineering; in-stream structures; and controlling livestock grazing. We need field studies that test various widths of buffers of different plant community compositions for their efficacy in trapping surface runoff, reducing nonpoint source pollutants in subsurface waters, and enhancing the aquatic ecosystem. Research is needed to evaluate the impact of different riparian grazing strategies on channel morphology, water quality, and the fate of livestock-associated pathogens and antibiotics. Integrating riparian buffers and other conservation buffers into these models is a key objective in future model development.

Reports of investigations on: Derivation of an infinite-dilution activity coefficient model and application to two-component vapor/liquid equilibria data: Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roper, V.P.; Kobayashi, R.

1988-02-01

Infinite-dilution fugacity coefficients were obtained for the system fluorene/phenanthrene at thirteen temperatures by fitting total pressure across the entire mole fraction range by a computer routine. A thermodynamically consistent routine, that allowed for both positive and negative pressure deviations from the ideal values, was used to correlate data over the full mole fraction range from 0 to 1. The four-suffix Margules activity coefficient model without modification essentially served this purpose since total pressures and total pressure derivatives with respect to mole fraction were negligible compared to pressure measurement precision. The water/ethanol system and binary systems comprised of aniline, chlorobenzene, acetonitrilemore » and other polar compounds were fit for total pressure across the entire mole fraction range for binary Vapor-Liquid-Equilbria (VLE) using the rigorous, thermodynamically consistent Gibbs-Duhem Relation derived by Ibl and Dodge. Data correlation was performed using a computer least squares procedure. Infinite-dilution fugacity coefficients were obtained using a modified Margules activity coefficient model.« less

Petrology of Igneous Clasts in Regolithic Howardite EET 87503

NASA Technical Reports Server (NTRS)

Hodges, Z. V.; Mittlefehldt, D. W.

2017-01-01

The howardite, eucrite and diogenite (HED) clan of meteorites is widely considered to originate from asteroid 4 Vesta, as a result of a global magma ocean style of differentiation. A global magmatic stage would allow silicate material to be well mixed, destroying any initial heterogeneity that may have been present resulting in the uniformity of eucrite and diogenite delta(exp 17)O, for example. The Fe/Mn ratio of mafic phases in planetary basalts can be diagnostic of different source bodies as this ratio is little-affected by igneous processes, so long as the oxygen and sulphur fugacities are buffered. Here, pyroxene Fe/Mn ratios in mafic clasts in howardite EET 87503 have been determined to further evaluate whether the HED parent asteroid is uniform. Uniformity would suggest that the parent asteroid was subject to homogenization prior to the formation of HED lithologies, likely through an extensive melting phase. Whereas, distinct differences may point towards heterogeneity of the parent body.

Free Available Chlorine Disinfection Criteria for Fixed Army Installation Primary Drinking Water

DTIC Science & Technology

1981-12-01

Buffered Water with Fuivic Acid (5 C.U.) at pH 9 and 60C ............................................ 6. FAC Disinfection of f 2 Coliphage in Buffered Water ...with and without 250 mg/L -Ca+ at pH 5, 7, and 9 and 6°C ............... 31 10. FAC Disinfection of f 2 Coliphage in Water Containing 5 NTU Bentonite2...rngi L Ca+ 2 at pH- 5, 7, and q and 60C ...... ........................ 34 13. FAC Disinfection of f 2 Coliphage in Borate-Buffered Water with 250 mg

Riparian buffer design guidelines for water quality and wildlife habitat functions on agricultural landscapes in the Intermountain West: Case Study

Treesearch

Craig W. Johnson; Susan Buffler

2008-01-01

This hypothetical case study illustrates how the riparian buffer planning protocol described in the RB handbook is used to plan a buffer for both water quality and wildlife conservation on a specific project site. The case study site includes riparian buffer characteristics typical of the study area-variable topography and soils, flood plain wetlands, seeps, springs,...

BETR North America: A regionally segmented multimedia contaminant fate model for North America

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacLeod, M.; Woodfine, D.G.; Mackay, D.

We present the Berkeley-Trent North American contaminant fate model (BETR North America), a regionally segmented multimedia contaminant fate model based on the fugacity concept. The model is built on a framework that links contaminant fate models of individual regions, and is generally applicable to large, spatially heterogeneous areas. The North American environment is modeled as 24 ecological regions, within each region contaminant fate is described using a 7 compartment multimedia fugacity model including a vertically segmented atmosphere, freshwater, freshwater sediment, soil, coastal water and vegetation compartments. Inter-regional transport of contaminants in the atmosphere, freshwater and coastal water is described usingmore » a database of hydrological and meteorological data compiled with Geographical Information Systems (GIS) techniques. Steady-state and dynamic solutions to the 168 mass balance equations that make up the linked model for North America are discussed, and an illustrative case study of toxaphene transport from the southern United States to the Great Lakes Basin is presented. Regionally segmented models such as BETR North America can provide a critical link between evaluative models of long-range transport potential and contaminant concentrations observed in remote regions. The continent-scale mass balance calculated by the model provides a sound basis for evaluating long-range transport potential of organic pollutants, and formulation of continent scale management and regulatory strategies for chemicals.« less

Placement of riparian forest buffers to improve water quality

Treesearch

Mark D. Tomer; Michael G. Dosskey; Michael R. Burkart; David E. James; Matthew J. Helmers; Dean E. Eisenhauer

2005-01-01

Riparian forest buffers can improve stream water quality, provided they intercept and remove contaminants from surface runoff and/or shallow groundwater. Soils, topography, hydrology, and surficial geology detemine the capability of forest buffers to intercept and treat these flows. This paper describes landscape analysis techniques for identifying and mapping...

Deformation of Olivine at Subduction Zone Conditions Determined from In situ Measurements with Synchrotron Radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

H Long; D Weidner; L Li

2011-12-31

We report measurements of the deformation stress for San Carlos olivine at pressures of 3-5 GPa, temperatures of 25-1150 C, and strain rates of 10{sup -7}-10{sup -5} s{sup -1}. We determine a deformation stress of approximately 2.5 GPa that is relatively temperature and strain rate independent in the temperature range of 400-900 C. The deformation experiments have been carried out on a deformation DIA (D-DIA) apparatus, Sam85, at X17B2, NSLS. Powder samples are used in these experiments. Enstatite (MgSiO{sub 3}) (3-5% total quality of sample) is used as the buffer to control the activity of silica. Ni foil is usedmore » in some experiments to buffer the oxygen fugacity. Water content is confirmed by IR spectra of the recovered samples. Samples are compressed at room temperature and are then annealed at 1200 C for at least 2 h before deformation. The total (plastic and elastic) strains (macroscopic) are derived from the direct measurements of the images taken by X-ray radiograph technique. The differential stresses are derived from the diffraction determined elastic strains. In the regime of 25-400 C, there is a small decrease of stress at steady state as temperature increases; in the regime of 400 C to the 'transition temperature', the differential stress at steady state ({approx}2.5 GPa) is relatively insensitive to the changes of temperature and strain rate; however, it drastically decreases to about 1 GPa and becomes temperature-dependent above the transition temperature and thereafter. The transition temperature is near 900 C. Above the transition temperature, the flow agrees with power law creep measurements of previous investigations. The anisotropy of differential stress in individual planes indicates that the deformation of olivine at low temperature is dominated by [0 0 1](1 0 0). Accounting to a slower strain rate in the natural system, the transition temperature for the olivine in the slab is most likely in the range of 570-660 C.« less

Immunogenicity of a live-attenuated human rotavirus RIX4414 vaccine with or without buffering agent.

PubMed

Kerdpanich, Angkool; Chokephaibulkit, Kulkanya; Watanaveeradej, Veerachai; Vanprapar, Nirun; Simasathien, Sriluck; Phavichitr, Nopaorn; Bock, Hans L; Damaso, Silvia; Hutagalung, Yanee; Han, Htay-Htay

2010-03-26

The lyophilized form of the human rotavirus RIX4414 vaccine (Rotarix()) is usually reconstituted with a liquid calcium carbonate (CaCO(3)) buffer and administered orally. However, errors in the reconstitution could occur (e.g. reconstituted with water instead of CaCO(3) buffer) or the buffer might be temporarily unavailable in few instances. This study was conducted to evaluate the immunogenicity of the RIX4414 vaccine if the vaccine was reconstituted with other agents (e.g., water) instead of CaCO(3) buffer. There was no statistical difference detected between RIX4414 vaccine reconstituted with buffer or water in vaccine take or in seroconversion rate. The anti-rotavirus Immunoglobulin A (IgA) seroconversion rate 2 months post-Dose 2 was 84.7% (95% CI: 78.1-90.0) for the group with buffer and 78.6% (95% CI: 71.2-84.8) for the group with water. Solicited and unsolicited symptoms reported were similar across groups. No vaccine related serious adverse events (SAEs) were reported. Healthy infants aged 6-12 weeks, received two oral doses of the RIX4414 vaccine/placebo, reconstituted either with injectable water or CaCO(3) buffer according to a 0, 2 month schedule. Seroconversion rates in terms of anti-RV IgA antibody levels (cut off: >/=20 U/ml by ELISA) and vaccine take were calculated 2 months post-Dose 2. Solicited and unsolicited symptoms reported during the 15- and 31-day follow-up period after each dose and SAE s reported during the entire study period were recorded. Administration of RIX4414 vaccine in the absence of CaCO(3) buffer was shown to be well tolerated and immunogenic in Thai infants.

Methods to prioritize placement of riparian buffers for improved water quality

Treesearch

Mark D. Tomer; Michael G. Dosskey; Michael R. Burkart; David E. James; Matthew J. Helmers; Dean E. Eisenhauer

2008-01-01

Agroforestry buffers in riparian zones can improve stream water quality, provided they intercept and remove contaminants from surface runoff and/or shallow groundwater. Soils, topography, surficial geology, and hydrology determine the capability of forest buffers to intercept and treat these flows. This paper describes two landscape analysis techniques for identifying...

Nonthermal inactivation of Escherichia coli K12 in buffered peptone water using a pilot-plant scale supercritical carbon dioxide system with gas-liquid porous metal contractor

USDA-ARS?s Scientific Manuscript database

This study evaluated the effectiveness of a supercritical carbon dioxide (SCCO2) system, with a gas-liquid CO2 contactor, for reducing Escherichia coli K12 in diluted buffered peptone water. 0.1% (w/v) buffered peptone water inoculated with E. coli K12 was processed using the SCCO2 system at CO2 con...

The P-T-fO 2 stability of deerite, Fe{12/2+}Fe{6/3+}[Si12O40](OH)10

NASA Astrophysics Data System (ADS)

Lattard, Dominique; Le Breton, Nicole

1994-02-01

New equilibrium experiments have been performed in the 20 27 kbar range to determine the upper thermal stability limit of endmember deerite, Fe{12/2+}Fe{6/3+}[Si12O40](OH)10. In this pressure range, the maximum thermal stability limit is represented by the oxygen-conserving reaction: deerite(De)=9 ferrosilite(Fs)+3 magnetite(Mag)+3 quartz(Qtz)+5 H2O(W) (1). Under the oxygen fugacities of the Ni-NiO buffer the breakdown-reduction reaction: De=12 Fs+2 Mag+5 W+1/2 O2 (10) takes place at lower temperatures (e.g. ΔT=63° at 27 kbar). The experimental brackets can be fitted using thermodynamic data for ferrosilite, magnetite and quartz from Berman (1988) and the following 1 bar, 298 K data for deerite (per gfw): Vo=55.74 J.bar-1, So=1670 J.K-1, ΔH{f/o}=-18334 kJ, α=2.5x10-5K-1, β=-0.18x10-5 bar-1. Using these data in conjunction with literature data on coesite, grunerite, minnesotaite, and greenalite, the P-T stability field of endmember deerite has been calculated for P s= P H 2O. This field is limited by 6 univariant oxygenconserving dehydration curves, from which three have positive d P/d T slopes, the other three negative slopes. The lower pressure end of the stability field of endmember deerite is thus located at an invariant point at 250±70°C and 10+-1.5 kbar. Deerite rich in the endmember can thus appear only in environments with geothermal gradients lower than 10°C/km and at pressures higher than about 10 kbar, which is in agreement with 4 out of 5 independent P-T estimates for known occurrences. The presence of such deerite places good constraints on minimum pressure and maximum temperature conditions. From log f O 2- T diagrams constructed with the same data base at different pressures, it appears that endmember deerite is, at temperatures near those of its upper stability limit, stable only over a narrow range of oxygen fugacities within the magnetite field. With decreasing temperatures, deerite becomes stable towards slightly higher oxygen fugacities but reaches the hematite field only at temperatures more than 200°C lower than the upper stability limit. This practically precludes the coexistence deerite-hematite with near-endmember deerite in natural environments.

Use of Physicochemical Parameters to Assess the Environmental Fate of Organic Pollutants: The Fugacity Model

ERIC Educational Resources Information Center

Domenech, Xavier; Ayllon, Jose Antonio; Peral, Jose

2006-01-01

The environmental fate and behavior of different organic pollutants based on the qualitative analysis of thermodynamic and kinetic data is presented. The Fugacity model allows the use of different partition constants in an easy way, to determine the distribution of chemical between different phases in equilibrium of an environmental system.

A Graphical Representation for the Fugacity of a Pure Substance

ERIC Educational Resources Information Center

Book, Neil L.; Sitton, Oliver C.

2010-01-01

The thermodynamic equations used to define and compute the fugacity of a pure substance are depicted as processes on a semi-logarithmic plot of pressure vs. molar Gibbs energy (PG diagram) with isotherms for the substance behaving as an ideal gas superimposed. The PG diagram clearly demonstrates the physical basis for the definitions and the…

Fugacity and concentration gradients in a gravity field

NASA Technical Reports Server (NTRS)

May, C. E.

1986-01-01

Equations are reviewed which show that at equilibrium fugacity and concentration gradients can exist in gravitational fields. At equilibrium, the logarithm of the ratio of the fugacities of a species at two different locations in a gravitational field is proportional to the difference in the heights of the two locations and the molecular weight of the species. An analogous relation holds for the concentration ratios in a multicomponent system. The ratio is calculated for a variety of examples. The kinetics for the general process are derived, and the time required to approach equilibrium is calculated for several systems. The following special topics are discussed: ionic solutions, polymers, multiphase systems, hydrostatic pressure, osmotic pressure, and solubility gradients in a gravity field.

[Quantification study on the runoff and seepage distribution and N, P pollutants removal of the vegetated buffer strips].

PubMed

Wang, Min; Huang, Yu-Chi; Wu, Jian-Qiang

2010-11-01

By using the constructed buffer strips test base and the runoff hydrometric devices, a research on stagnant runoff and nitrogen (N), phosphorous (P) pollutants removal capacity of the vegetated buffer strips was conducted. The results show that the vegetated buffer strips might reduce the speed of runoff significantly and improve the hydraulic permeability of soil. The runoff water output time of 19 m buffer strips planted with Cynodon dactylon, Festuca arundinacea and Trifolium repens are 2.46, 1.72 and 2.03 times higher than the control (no vegetation) respectively; The seepage water quantity of three vegetation buffer strips are 3.01, 2.16 and 2.45 times higher than the control respectively as well. Total removal efficiency of the three buffer strips increase about 237%, 268% and 274% comparing with the control respectively. The N, P removal capacity of seepage is significantly higher than that of the runoff, the larger seepage water quantity will cause higher N, P total removal efficiency and removal loads of unit area. With different vegetated buffer strips, the TN, NH4(+) -N, TP removal ratio of seepage and runoff are 2.79, 2.02 and 2.83 respectively.

Water body and riparian buffer strip characteristics in a vineyard area to support aquatic pesticide exposure assessment.

PubMed

Ohliger, Renja; Schulz, Ralf

2010-10-15

The implementation of a geodata-based probabilistic pesticide exposure assessment for surface waters in Germany offers the opportunity to base the exposure estimation on more differentiated assumptions including detailed landscape characteristics. Since these characteristics can only be estimated using field surveys, water body width and depth, hydrology, riparian buffer strip width, ground vegetation cover, existence of concentrated flow paths, and riparian vegetation were characterised at 104 water body segments in the vineyard region Palatinate (south-west Germany). Water body segments classified as permanent (n=43) had median values of water body width and depth of 0.9m and 0.06m, respectively, and the determined median width:depth ratio was 15. Thus, the deterministic water body model (width=1m; depth=0.3m) assumed in regulatory exposure assessment seems unsuitable for small water bodies in the study area. Only 25% of investigated buffer strips had a dense vegetation cover (>70%) and allow a laminar sheet flow as required to include them as an effective pesticide runoff reduction landscape characteristic. At 77 buffer strips, bordering field paths and erosion rills leading into the water body were present, concentrating pesticide runoff and consequently decreasing buffer strip efficiency. The vegetation type shrubbery (height>1.5m) was present at 57 (29%) investigated riparian buffer strips. According to their median optical vegetation density of 75%, shrubberies may provide a spray drift reduction of 72±29%. Implementing detailed knowledge in an overall assessment revealed that exposure via drift might be 2.4 and via runoff up to 1.6 fold higher than assumed by the deterministic approach. Furthermore, considering vegetated buffer strips only by their width leads to an underestimation of exposure by a factor of as much as four. Our data highlight that the deterministic model assumptions neither represent worst-case nor median values and therefore cannot simply be adopted in a probabilistic approach. Copyright © 2010 Elsevier B.V. All rights reserved.

Hydrochemical buffer assessment in agricultural landscapes: from local to catchment scale.

PubMed

Viaud, Valérie; Merot, Philippe; Baudry, Jacques

2004-10-01

Non-point-source pollution of surface and groundwater is a prominent environmental issue in rural catchments, with major consequences on water supply and aquatic ecosystem quality. Among surface-water protection measures, environmental or landscape management policies support the implementation and the management of buffer zones. Although a great number of studies have focused on buffer zones, quantification of the buffer effect is still a recurring question. The purpose of this article is a critical review of the assessment of buffer-zone functioning. Our objective is to provide land planners and managers with a set of variables to assess the limits and possibilities for quantifying buffer impact at the catchment scale. We first consider the scale of the local landscape feature. The most commonly used empirical method for assessing buffers is to calculate water/nutrient budgets from inflow-outflow monitoring at the level of landscape structures. We show that several other parameters apart from mean depletion of flux can be used to describe buffer functions. Such parameters include variability, with major implication for water management. We develop a theoretical framework to clarify the assessment of the buffer effect and propose a systematic analysis taking account of temporal variability. Second, we review the current assessment of buffer effects at the catchment scale according to the theoretical framework established at the local scale. Finally, we stress the limits of direct empirical assessment at the catchment scale and, in particular, we emphasize the hierarchy in hydrological processes involved at the catchment scale: The landscape feature function is constrained by other factors (climate and geology) that are of importance at a broader spatial and temporal scale.

Erosion rills offset the efficacy of vegetated buffer strips to mitigate pesticide exposure in surface waters.

PubMed

Stehle, Sebastian; Dabrowski, James Michael; Bangert, Uli; Schulz, Ralf

2016-03-01

Regulatory risk assessment considers vegetated buffer strips as effective risk mitigation measures for the reduction of runoff-related pesticide exposure of surface waters. However, apart from buffer strip widths, further characteristics such as vegetation density or the presence of erosion rills are generally neglected in the determination of buffer strip mitigation efficacies. This study conducted a field survey of fruit orchards (average slope 3.1-12.2%) of the Lourens River catchment, South Africa, which specifically focused on the characteristics and attributes of buffer strips separating orchard areas from tributary streams. In addition, in-stream and erosion rill water samples were collected during three runoff events and GIS-based modeling was employed to predict losses of pesticides associated with runoff. The results show that erosion rills are common in buffer strips (on average 13 to 24 m wide) of the tributaries (up to 6.5 erosion rills per km flow length) and that erosion rills represent concentrated entry pathways of pesticide runoff into the tributaries during rainfall events. Exposure modeling shows that measured pesticide surface water concentrations correlated significantly (R(2)=0.626; p<0.001) with runoff losses predicted by the modeling approach in which buffer strip width was set to zero at sites with erosion rills; in contrast, no relationship between predicted runoff losses and in-stream pesticide concentrations were detected in the modeling approach that neglected erosion rills and thus assumed efficient buffer strips. Overall, the results of our study show that erosion rills may substantially reduce buffer strip pesticide retention efficacies during runoff events and suggest that the capability of buffer strips as a risk mitigation tool for runoff is largely overestimated in current regulatory risk assessment procedures conducted for pesticide authorization. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of a nucleic Acid extraction procedure for simultaneous recovery of DNA and RNA from diverse microbes in water.

PubMed

Hill, Vincent R; Narayanan, Jothikumar; Gallen, Rachel R; Ferdinand, Karen L; Cromeans, Theresa; Vinjé, Jan

2015-05-26

Drinking and environmental water samples contain a diverse array of constituents that can interfere with molecular testing techniques, especially when large volumes of water are concentrated to the small volumes needed for effective molecular analysis. In this study, a suite of enteric viruses, bacteria, and protozoan parasites were seeded into concentrated source water and finished drinking water samples, in order to investigate the relative performance of nucleic acid extraction techniques for molecular testing. Real-time PCR and reverse transcription-PCR crossing threshold (CT) values were used as the metrics for evaluating relative performance. Experimental results were used to develop a guanidinium isothiocyanate-based lysis buffer (UNEX buffer) that enabled effective simultaneous extraction and recovery of DNA and RNA from the suite of study microbes. Procedures for bead beating, nucleic acid purification, and PCR facilitation were also developed and integrated in the protocol. The final lysis buffer and sample preparation procedure was found to be effective for a panel of drinking water and source water concentrates when compared to commercial nucleic acid extraction kits. The UNEX buffer-based extraction protocol enabled PCR detection of six study microbes, in 100 L finished water samples from four drinking water treatment facilities, within three CT values (i.e., within 90% difference) of the reagent-grade water control. The results from this study indicate that this newly formulated lysis buffer and sample preparation procedure can be useful for standardized molecular testing of drinking and environmental waters.

Development of a Nucleic Acid Extraction Procedure for Simultaneous Recovery of DNA and RNA from Diverse Microbes in Water

PubMed Central

Hill, Vincent R.; Narayanan, Jothikumar; Gallen, Rachel R.; Ferdinand, Karen L.; Cromeans, Theresa; Vinjé, Jan

2015-01-01

Drinking and environmental water samples contain a diverse array of constituents that can interfere with molecular testing techniques, especially when large volumes of water are concentrated to the small volumes needed for effective molecular analysis. In this study, a suite of enteric viruses, bacteria, and protozoan parasites were seeded into concentrated source water and finished drinking water samples, in order to investigate the relative performance of nucleic acid extraction techniques for molecular testing. Real-time PCR and reverse transcription-PCR crossing threshold (CT) values were used as the metrics for evaluating relative performance. Experimental results were used to develop a guanidinium isothiocyanate-based lysis buffer (UNEX buffer) that enabled effective simultaneous extraction and recovery of DNA and RNA from the suite of study microbes. Procedures for bead beating, nucleic acid purification, and PCR facilitation were also developed and integrated in the protocol. The final lysis buffer and sample preparation procedure was found to be effective for a panel of drinking water and source water concentrates when compared to commercial nucleic acid extraction kits. The UNEX buffer-based extraction protocol enabled PCR detection of six study microbes, in 100 L finished water samples from four drinking water treatment facilities, within three CT values (i.e., within 90% difference) of the reagent-grade water control. The results from this study indicate that this newly formulated lysis buffer and sample preparation procedure can be useful for standardized molecular testing of drinking and environmental waters. PMID:26016775

The atmosphere of Mars - Resources for the exploration and settlement of Mars

NASA Technical Reports Server (NTRS)

Meyer, T. R.; Mckay, C. P.

1984-01-01

This paper describes methods of processing the Mars atmosphere to supply water, oxygen and buffer gas for a Mars base. Existing life support system technology is combined with innovative methods of water extraction, and buffer gas processing. The design may also be extended to incorporate an integrated greenhouse to supply food, oxygen and water recycling. It is found that the work required to supply one kilogram of an argon/nitrogen buffer gas is 9.4 kW-hr. To extract water from the dry Martian atmosphere can require up to 102.8 kW-hr per kilogram of water depending on the relative humidity of the air.

TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: phase diagrams and molecular dynamic simulations.

PubMed

Taha, Mohamed; Lee, Ming-Jer

2013-06-28

Water and the organic solvents tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone are completely miscible in all proportions at room temperature. Here, we present new buffering-out phase separation systems that the above mentioned organic aqueous solutions can be induced to form two liquid phases in the presence of a biological buffer 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid (TES). The lower liquid phase is rich in water and buffer, and the upper phase is organic rich. This observation has both practical and mechanistic interests. The phase diagrams of these systems were constructed by experimental measurements at ambient conditions. Molecular dynamic (MD) simulations were performed for TES + water + THF system to understand the interactions between TES, water, and organic solvent at molecular level. Several composition-sets for this system, beyond and inside the liquid-liquid phase-splitting region, have been simulated. Interestingly, the MD simulation for compositions inside the phase separation region showed that THF molecules are forced out from the water network to start forming a new liquid phase. The hydrogen-bonds, hydrogen-bonds lifetimes, hydrogen-bond energies, radial distribution functions, coordination numbers, the electrostatic interactions, and the van der Waals interactions between the different pairs have been calculated. Additionally, MD simulations for TES + water + tert-butanol∕acetonitrile∕acetone phase separation systems were simulated. The results from MD simulations provide an explanation for the buffering-out phenomena observed in [TES + water + organic solvent] systems by a mechanism controlled by the competitive interactions of the buffer and the organic solvent with water. The molecular mechanism reported here is helpful for designing new benign separation materials.

Establishing conservation buffers using precision information

Treesearch

Mike G. Dosskey; Dean E. Eisenhauer; Matthew J. Helmers

2005-01-01

Conservation buffers, such as filter strips and riparian forest buffers, are widely prescribed to improve and protect water quality in agricultural landscapes. These buffers intercept field runoff and retain some of its pollutant load before it reaches a waterway. A buffer typically is designed to have uniform width along a field margin and to intercept runoff that...

Ocean Surface Carbon Dioxide Fugacity Observed from Space

NASA Technical Reports Server (NTRS)

Liu, W. Timothy; Xie, Xiaosu

2014-01-01

We have developed and validated a statistical model to estimate the fugacity (or partial pressure) of carbon dioxide (CO2) at sea surface (pCO2sea) from space-based observations of sea surface temperature (SST), chlorophyll, and salinity. More than a quarter million in situ measurements coincident with satellite data were compiled to train and validate the model. We have produced and made accessible 9 years (2002-2010) of the pCO2sea at 0.5 degree resolutions daily over the global ocean. The results help to identify uncertainties in current JPL Carbon Monitoring System (CMS) model-based and bottom-up estimates over the ocean. The utility of the data to reveal multi-year and regional variability of the fugacity in relation to prevalent oceanic parameters is demonstrated.

Solubility of copper in silicate melts as function of oxygen and sulfur fugacities, temperature, and silicate composition

NASA Astrophysics Data System (ADS)

Holzheid, A.; Lodders, K.

2001-06-01

The solubility of Cu in silicate melts coexisting with liquid Cu(Fe) metal and liquid Cu(Fe) sulfide was determined experimentally at oxygen fugacities ranging from 10 -9.1 to 10 -13.6 bar and sulfur fugacities ranging from 10 -2.5 to 10 -6.3 bar at 1300°C. An iron oxide-free silicate of anorthite-diopside eutectic composition and a synthetic MgO-rich basaltic silicate (FeO-bearing) were used in the partitioning experiments. In S-containing systems, some of the metal reacted to metal sulfide. The silicates in the four systems investigated (Fe-free and S-free; Fe-containing and S-free; Fe-free and S-containing; Fe-containing and S-containing) had different colors depending on the dissolved Cu species and the presence of iron and/or sulfur. Irrespective of the presence of sulfur, the solubility of Cu in the silicate increases with increasing oxygen fugacity and metal/silicate partition coefficients for Cu decrease. Increasing the temperature from 1300°C to 1514°C increases the Cu solubility (decreases the metal/silicate partition coefficient) at an oxygen fugacity 0.5 log units below the iron-wüstite (IW) equilibrium in the Fe-free, S-free and Fe-containing, S-free systems. We infer the presence of monovalent Cu + ("CuO 0.5") in the silicate melt on the basis of the solubility of Cu as function of oxygen fugacity. Experiments containing iron yield a formal valence of ˜0.5 for Cu at very low oxygen fugacities, which is not observed in Fe-free systems. The low formal valence is explained by redox reactions between iron and copper in the silicate melts. There is no evidence for sulfidic dissolution of Cu in the silicates but sulfur has indirect effects on Cu partitioning. Iron metal/silicate partition coefficients depend on oxygen fugacity and on sulfur fugacity. Sulfidic dissolution of iron and oxide-sulfide exchange reactions with Cu cause a small increase in Cu metal/silicate partition coefficients. We derive an activity coefficient (γ CuO 0.5) of 10 ± 1 for liquid CuO 0.5 at 1300°C for the silicate melts used here. A comparison with literature data shows that log γ CuO 0.5 increases in proportion to the mass percentages [CaO +(Al 2O 3)/2] in silicate melts. We recommend the following equations for Cu metal/silicate and sulfide/silicate partitioning for geochemical and cosmochemical modeling if silicate composition and the activity of Cu in the metal or sulfide is known: log D met/sil = -0.48 - 0.25 · log fO 2 - log γ Cu metal + 0.02 · [CaO + (Al 2O 3)/2; wt%] silicate logD sul/sil=+0.76-0.25 · logfO 2+0.25logfS 2-logγ CS 0.5,sulfide +0.02 · [CaO+Al 2O 3/2;wt%] silicate. The derived Cu metal/silicate and metal/sulfide partition coefficients are applied to core formation in the Earth and Mars. The observed Cu abundances in the Earth cannot be easily explained by simple core-mantle equilibrium, but the observed Cu abundances for Mars are consistent with core-mantle equilibrium at low pressure and temperatures.

Evaluating the potential of 'on-line' constructed wetlands for mitigating pesticide transfers from agricultural land to surface waters

NASA Astrophysics Data System (ADS)

Whelan, Michael; Ramos, Andre; Guymer, Ian; Villa, Raffaella; Jefferson, Bruce

2016-04-01

Pesticides make important contributions to modern agriculture but losses from land to water can present problems for environmental management, particularly in catchments where surface waters are abstracted for drinking water. Where artificial field drains represent a dominant pathway for pesticide transfers, buffer zones provide little mitigation potential. Instead, "on-line" constructed wetlands have been proposed as a potential means of reducing pesticide fluxes in drainage ditches and headwater streams. Here, we evaluate the potential of small free-surface wetlands to reduce pesticide concentrations in surface waters using a combination of field monitoring and numerical modelling. Two small constructed wetland systems in a first order catchment in Cambridgeshire, UK, were monitored over the 2014-2015 winter season. Discharge was measured at several flow control structures and samples were collected every eight hours and analysed for metaldehyde, a commonly-used molluscicide. Metaldehyde is moderately mobile and, like many other compounds, it has been regularly detected at high concentrations in surface water samples in a number of drinking water supply catchments in the UK over the past few years. However, it is unusually difficult to remove via conventional drinking water treatment which makes it particularly problematical for water companies. Metaldehyde losses from the upstream catchment were significant with peak concentrations occurring in the first storm events in early autumn, soon after application. Concentrations and loads appeared to be unaffected by transit through the wetland over a range of flow conditions - probably due to short solute residence times (quantified via several tracing experiments employing rhodamine WT - a fluorescent dye). A dynamic model, based on fugacity concepts, was constructed to describe chemical fate in the wetland system. The model was used to evaluate mitigation potential and management options under field conditions and for a range of different pesticides under alternative flow and wetland dimension scenarios. In agreement with observations, model predictions for metaldehyde losses in the monitored system were negligible. The scenario analysis suggested that, even for pesticides with a relatively short aquatic half life, wetland systems would need to be much larger than those studied here in order to get any appreciable attenuation. Shallow systems have highest potential for promoting losses due to biodegradation, if we assume that most degrading organisms reside in fixed biofilms in the sediment. Sorption is not predicted to represent a significant net sink, except over short time scales in the first runoff event after application.

Dynamics and mitigation of six pesticides in a "Wet" forest buffer zone.

PubMed

Passeport, Elodie; Richard, Benjamin; Chaumont, Cédric; Margoum, Christelle; Liger, Lucie; Gril, Jean-Joël; Tournebize, Julien

2014-04-01

Pesticide pollution is one of the main current threats on water quality. This paper presents the potential and functioning principles of a "Wet" forest buffer zone for reducing concentrations and loads of glyphosate, isoproturon, metazachlor, azoxystrobin, epoxiconazole, and cyproconazole. A tracer injection experiment was conducted in the field in a forest buffer zone at Bray (France). A fine time-scale sampling enabled to illustrate that interactions between pesticides and forest buffer substrates (soil and organic-rich litter layer), had a retarding effect on molecule transfer. Low concentrations were observed for all pesticides at the forest buffer outlet thus demonstrating the efficiency of "Wet" forest buffer zone for pesticide dissipation. Pesticide masses injected in the forest buffer inlet directly determined concentration peaks observed at the outlet. Rapid and partially reversible adsorption was likely the major process affecting pesticide transfer for short retention times (a few hours to a few days). Remobilization of metazachlor, isoproturon, desmethylisoproturon, and AMPA was observed when non-contaminated water flows passed through the forest buffer. Our data suggest that pesticide sorption properties alone could not explain the complex reaction mechanisms that affected pesticide transfer in the forest buffer. Nevertheless, the thick layer of organic matter litter on the top of the forest soil was a key parameter, which enhanced partially reversible sorption of pesticide, thus retarded their transfer, decreased concentration peaks, and likely increased degradation of the pesticides. Consequently, to limit pesticide pollution transported by surface water, the use of already existing forest areas as buffer zones should be equally considered as the most commonly implemented grass buffer strips.

Using soil surveys to target riparian buffers in the Chesapeake Bay watershed

Treesearch

Michael G. Dosskey

2008-01-01

The efficacy of vegetative buffers for improving water quality could be enhanced by distinguishing differences in buffer capability across watersheds and accounting for them in buffer planning. A soil survey-based method was applied to riparian areas in the Chesapeake Bay watershed. The method is based on soil attributes that are important in determining buffer...

Riparian buffer design guidelines for water quality and wildlife habitat functions on agricultural landscapes in the Intermountain West: Appendix C

Treesearch

Susan Buffler

2008-01-01

Currently, there is no scientific literature examining appropriate riparian buffer widths for water quality for streams on private agriculturally dominated lands in arid regions of the Intermountain West. The initial step in this research effort was a review of buffer research as documented in the literature in other physiographic regions of the United States. Research...

Oxygen Fugacity of Abyssal Peridotites Along the Gakkel Ridge

NASA Astrophysics Data System (ADS)

Said, M.; Birner, S.; Cottrell, E.

2015-12-01

The oxygen budget of the Earth's mantle is important in understanding how our planet evolves chemically over time. The Gakkel Ridge is the world's slowest spreading ridge [1], and exposes peridotites along its axis that record the activity of oxygen in the upper mantle. Our samples comprise relatively fertile lherzolites and harzburgites (Cr#=0.13-0.17, 3.1-8.3% modal cpx [2]) as well as refractory harzburgites (Cr#=0.43-0.55, 0.2-1.0% modal cpx [2]). Using spinel peridotite oxygen barometry [3], we calculated the oxygen fugacity (fO2) of a suite of 10 peridotites from the Gakkel Ridge in order to investigate how melt processes affect the oxygen budget of the Earth's interior. We show that the low-Cr# lherzolites and harzburgites range from -0.1 to +0.6 log units relative to the QFM buffer, consistent with the global abyssal peridotite array, whereas high-Cr# refractory harzburgites have low fO2 values, ranging from -0.7 to -2.7 log units below QFM, with the most refractory samples falling significantly lower than the global array. Because D'Errico et al. (submitted) interprets the refractory samples as recording ancient melt extraction, the low fO2 recorded by these samples may originate in the geologic past, perhaps even in a different tectonic setting. While LREE enrichment in the refractory harzburgites [2] provides evidence for refertilization by an infiltrating melt that could have recently imprinted reducing conditions, we see no corresponding increase in TiO2 content in the spinels, which weakens this hypothesis. Further research on additional refractory harzburgites is needed to constrain whether the reduced nature of these samples is telling us something about the effect of extreme melt extraction on fO2 at ridges, or whether these samples record a unique history that obscures processes operating at ridges today. [1] Coakley and Cochran, EPSL (1998), [2] D'Errico et al., submitted, [3] Bryndzia and Wood, American Journal of Science (1990)

Experimental determination of Pb partitioning between sulfide melt and basalt melt as a function of P, T and X

NASA Astrophysics Data System (ADS)

Hart, Stanley R.; Gaetani, Glenn A.

2016-07-01

We have measured the partition coefficient of Pb (KdPb) between FeS melt and basalt melt at temperatures of 1250-1523 °C, pressures of 1.0-3.5 GPa and oxygen fugacities at iron-wustite and wustite-magnetite. The total observed range of KdPb is 4.0-66.6, with a strong negative dependence on pressure and a strong negative dependence on FeO of the silicate melt (Fe+2 only). The FeO control was constrained over a wide range of FeO (4.2-39.5%). We found that the effect of oxygen fugacity can be subsumed under the FeO control parameter. Prior work has established the lack of a significant effect of temperature (Kiseeva and Wood, 2015; Li and Audétat, 2015). Our data are parameterized as: KdPb = 4.8 + (512 - 119*P in GPa)*(1/FeO - 0.021). We also measured a single value of KdPb between clinopyroxene and basalt melt at 2.0 GPa of 0.020 ± 0.001. This experimental data supports the ;natural; partitioning of Pb measured on sulfide globules in MORB (Patten et al., 2013), but not the low KdPb of ∼3 inferred from sulfides in abyssal peridotites by Warren and Shirey (2012). It also quantitatively affirms the modeling of Hart and Gaetani (2006) with respect to using sulfide to buffer the canonical Nd/Pb ratio for MORB and OIB (Hofmann, 2003). For the low FeO and pressure of segregation typical of MORB, KdPb ∼ 45, and the Nd/Pb ratio of erupted basalts will be the same as the Nd/Pb ratio of the mantle source. The remaining puzzle is why MORB and OIB have the same Nd/Pb when they clearly have different FeO and pressure of melt segregation.

Electrochemically-Induced Redox Reactions in Basalt at High Pressure and Temperature: An Iron and Vanadium K-edge XANES Study

NASA Astrophysics Data System (ADS)

Kavner, A.; Walker, D.; Newville, M.; Sutton, S. R.

2005-12-01

An applied electric field across a silicate sample at high pressures and temperatures in a piston cylinder apparatus can generate a wide range of oxidation states of polyvalent cations within a single experiment. If two or more polyvalent cations are included, this technique can be used to cross-calibrate oxybarometers within a single experiment. The redox state of Fe and V within a partially melted basaltic silicate was manipulated in situ in a piston-cylinder experiment with a DC power supply providing a source and sink of electrons to the sample. A 1V electrical potential differential was applied across vanadium-doped and Fe-bearing synthetic basalt samples for 24 hrs. at 20 kbar and 1400°C in a specially-designed piston cylinder sample assembly. Three experiments were performed: a control sample with no applied voltage, one with bottom cathode and top anode, and a third with top cathode and bottom anode. Synchrotron-based x-ray absorption near edge structure (XANES) spectroscopy was used to provide spot analysis of iron and vanadium oxidation states with 5μm x 5μm spatial resolution throughout the recovered samples. Systematic spatial changes of increasing oxidation states of V and Fe were observed approaching the anode. The differences in oxidation states were mapped to a corresponding local effective oxygen fugacity by comparison and extension of a calibration of vanadium oxidation states as a function of controlled oxygen fugacity from a previous study (Sutton et al., 2005, GCA, vol. 69, pp. 2333-2348). The vanadium mapping indicates that a 1V potential drop across the sample induces effective oxygen fugacity perturbations in excess of ten orders of magnitude. The presence of both Fe and V within the same sample provides a wide range of oxygen fugacity cross-calibration in these recovered samples. A relationship between oxygen fugacity and electrochemical driving force is derived. The experimental results are in good agreement with the derived relationship between applied electrochemical potential difference (the 1V in this experiment), and corresponding calculated oxygen fugacity.

Factors controlling sulfur concentrations in volcanic apatite

USGS Publications Warehouse

Peng, G.; Luhr, J.F.; McGee, J.J.

1997-01-01

Apatite crystals from two types of samples were analyzed by electron microprobe for 15 major and trace elements: (1) apatite in H2O- and S-saturated experimental charges of the 1982 El Chicho??n trachyandesite and (2) apatite in volcanic rocks erupted from 20 volcanoes. The SO3 contents of the experimental apatite increase with increasing oxygen fugacity (fo2), from ???0.04 wt% in reduced charges buffered by fayalite-magnetite-quartz (FMQ), to 1.0-2.6 wt% in oxidized charges buffered by manganosite-hausmanite (MNH) or magnetite-hematite (MTH). The SO3 contents of MNH- and MTH-buffered apatite also generally increase with increasing pressure from 2 to 4 kbar and decreasing temperature from 950 to 800??C. The partition coefficient for SO3 between apatite and oxidized melt increases with decreasing temperature but appears to be independent of pressure. Apatites in volcanic rocks show a wide range of SO3 contents (<0.04 to 0.63 wt%). Our sample set includes one group known to contain primary anhydrite and a second group inferred to have been free of primary anhydrite. No systematic differences in apatite S contents are observed between these two groups. Our study was initiated to define the factors controlling S contents in apatite and to evaluate the hypothesis that high S contents in apatite could be characteristic of S-rich anhydrite-bearing magmas such as those erupted from El Chicho??n in 1982 and Pinatubo in 1991. This hypothesis is shown to be invalid, probably chiefly a consequence of the slow intra-crystaline diffusion that limits re-equilibration between early formed apatite and the evolving silicate melt. Contributing factors include early crystallization of most apatite over a relatively small temperature interval, common late-stage magmatic enrichment of S, progressive oxidation during magmatic evolution, and strong controls on S contents in apatite exerted fo2, temperature, and pressure.

Enhanced transpiration by riparian buffer trees in response to advection in a humid temperate agricultural landscape

USGS Publications Warehouse

Hernandez-Santana, V.; Asbjornsen, H.; Sauer, T.; Isenhart, T.; Schilling, K.; Schultz, Ronald

2011-01-01

Riparian buffers are designed as management practices to increase infiltration and reduce surface runoff and transport of sediment and nonpoint source pollutants from crop fields to adjacent streams. Achieving these ecosystem service goals depends, in part, on their ability to remove water from the soil via transpiration. In these systems, edges between crop fields and trees of the buffer systems can create advection processes, which could influence water use by trees. We conducted a field study in a riparian buffer system established in 1994 under a humid temperate climate, located in the Corn Belt region of the Midwestern U.S. (Iowa). The goals were to estimate stand level transpiration by the riparian buffer, quantify the controls on water use by the buffer system, and determine to what extent advective energy and tree position within the buffer system influence individual tree transpiration rates. We primarily focused on the water use response (determined with the Heat Ratio Method) of one of the dominant species (Acer saccharinum) and a subdominant (Juglans nigra). A few individuals of three additional species (Quercus bicolor, Betula nigra, Platanus occidentalis) were monitored over a shorter time period to assess the generality of responses. Meteorological stations were installed along a transect across the riparian buffer to determine the microclimate conditions. The differences found among individuals were attributed to differences in species sap velocities and sapwood depths, location relative to the forest edge and prevailing winds and canopy exposure and dominance. Sapflow rates for A. saccharinum trees growing at the SE edge (prevailing winds) were 39% greater than SE interior trees and 30% and 69% greater than NW interior and edge trees, respectively. No transpiration enhancement due to edge effect was detected in the subdominant J. nigra. The results were interpreted as indicative of advection effects from the surrounding crops. Further, significant differences were document in sapflow rates between the five study species, suggesting that selection of species is important for enhancing specific riparian buffer functions. However, more information is needed on water use patterns among diverse species growing under different climatic and biophysical conditions to assist policy and management decisions regarding effective buffer design. ?? 2011.

Effects of groundwater-flow paths on nitrate concentrations across two riparian forest corridors

USGS Publications Warehouse

Speiran, Gary K.

2010-01-01

Groundwater levels, apparent age, and chemistry from field sites and groundwater-flow modeling of hypothetical aquifers collectively indicate that groundwater-flow paths contribute to differences in nitrate concentrations across riparian corridors. At sites in Virginia (one coastal and one Piedmont), lowland forested wetlands separate upland fields from nearby surface waters (an estuary and a stream). At the coastal site, nitrate concentrations near the water table decreased from more than 10 mg/L beneath fields to 2 mg/L beneath a riparian forest buffer because recharge through the buffer forced water with concentrations greater than 5 mg/L to flow deeper beneath the buffer. Diurnal changes in groundwater levels up to 0.25 meters at the coastal site reflect flow from the water table into unsaturated soil where roots remove water and nitrate dissolved in it. Decreases in aquifer thickness caused by declines in the water table and decreases in horizontal hydraulic gradients from the uplands to the wetlands indicate that more than 95% of the groundwater discharged to the wetlands. Such discharge through organic soil can reduce nitrate concentrations by denitrification. Model simulations are consistent with field results, showing downward flow approaching toe slopes and surface waters to which groundwater discharges. These effects show the importance of buffer placement over use of fixed-width, streamside buffers to control nitrate concentrations.

Study to optimize gellant polymer-water systems for the control of hypergolic spills and fires

NASA Technical Reports Server (NTRS)

Jennings, R. R.; Macwilliams, D. C.; Foshee, W. C.; Katzer, M. F.

1973-01-01

A system of buffered gelled water was developed to prevent and control fires from small spills of nitrogen tetroxide-(N2O4)-Aerozine 50-hypergolic fuel. Laboratory studies on various alkalis, buffers, and seavengers for the fuel components are described. Chilling and sodium acetate-acetic acid buffer was found to be the best additives to the gelled water. Field tests and a delivery system (airborne) for the extinguishant are described. A short movie showing the field testing is available upon request.

Precipitation-mediated responses of soil acid buffering capacity to long-term nitrogen addition in a semi-arid grassland

NASA Astrophysics Data System (ADS)

Cai, Jiangping; Luo, Wentao; Liu, Heyong; Feng, Xue; Zhang, Yongyong; Wang, Ruzhen; Xu, Zhuwen; Zhang, Yuge; Jiang, Yong

2017-12-01

Atmospheric nitrogen (N) deposition can result in soil acidification and reduce soil acid buffering capacity. However, it remains poorly understood how changes in precipitation regimes with elevated atmospheric N deposition affect soil acidification processes in a water-limited grassland. Here, we conducted a 9-year split-plot experiment with water addition as the main factor and N addition as the second factor. Results showed that soil acid buffering capacity significantly decreased with increased N inputs, mainly due to the decline of soil effective cation exchange capacity (ECEC) and exchangeable basic cations (especially Ca2+), indicating an acceleration of soil acidification status in this steppes. Significant interactive N and water effects were detected on the soil acid buffering capacity. Water addition enhanced the soil ECEC and exchangeable base cations and thus alleviated the decrease of soil acid buffering capacity under N addition. Our findings suggested that precipitation can mitigate the impact of increased N deposition on soil acidification in semi-arid grasslands. This knowledge should be used to improve models predicting soil acidification processes in terrestrial ecosystems under changing environmental conditions.

Improved indexes for targeting placement of buffers of Hortonian runoff

Treesearch

M.G. Dosskey; Z. Qiu; M.J. Helmers; D.E. Eisenhauer

2011-01-01

Targeting specific locations within agricultural watersheds for installing vegetative buffers has been advocated as a way to enhance the impact of buffers and buffer programs on stream water quality. Existing models for targeting buffers of Hortonian, or infiltration-excess, runoff are not well developed. The objective was to improve on an existing soil survey–based...

Platinum Partitioning at Low Oxygen Fugacity: Implications for Core Formation Processes

NASA Technical Reports Server (NTRS)

Medard, E.; Martin, A. M.; Righter, K.; Lanziroti, A.; Newville, M.

2016-01-01

Highly siderophile elements (HSE = Au, Re, and the Pt-group elements) are tracers of silicate / metal interactions during planetary processes. Since most core-formation models involve some state of equilibrium between liquid silicate and liquid metal, understanding the partioning of highly siderophile elements (HSE) between silicate and metallic melts is a key issue for models of core / mantle equilibria and for core formation scenarios. However, partitioning models for HSE are still inaccurate due to the lack of sufficient experimental constraints to describe the variations of partitioning with key variable like temperature, pressure, and oxygen fugacity. In this abstract, we describe a self-consistent set of experiments aimed at determining the valence of platinum, one of the HSE, in silicate melts. This is a key information required to parameterize the evolution of platinum partitioning with oxygen fugacity.

Retention of ionisable compounds on high-performance liquid chromatography XVII. Estimation of the pH variation of aqueous buffers with the change of the methanol fraction of the mobile phase.

PubMed

Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

2007-01-05

The use of methanol-aqueous buffer mobile phases in HPLC is a common election when performing chromatographic separations of ionisable analytes. The addition of methanol to the aqueous buffer to prepare such a mobile phase changes the buffer capacity and the pH of the solution. In the present work, the variation of these buffer properties is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-hydrogencitrate-citrate, and ammonium-ammonia buffers. It is well established that the pH change of the buffers depends on the initial concentration and aqueous pH of the buffer, on the percentage of methanol added, and on the particular buffer used. The proposed equations allow the pH estimation of methanol-water buffered mobile phases up to 80% in volume of organic modifier from initial aqueous buffer pH and buffer concentration (before adding methanol) between 0.001 and 0.01 mol L(-1). From both the estimated pH values of the mobile phase and the estimated pKa of the ionisable analytes, it is possible to predict the degree of ionisation of the analytes and therefore, the interpretation of acid-base analytes behaviour in a particular methanol-water buffered mobile phase.

How did fixed-width buffers become standard practice for protecting freshwaters and their riparian areas from forest harvest practices?

Treesearch

John S. Richardson; Robert J. Naiman; Peter A. Bisson

2012-01-01

Riparian buffers provide improved protection for water quality and biota, and narrow, fixed-width buffers of native vegetation along streams have been used to mitigate the effects of forest harvest at least since the 1960s. The practice of leaving unmanaged strips of vegetation along water courses in agricultural lands had been used before the 1960s in southern Europe...

Programmable pH buffers

DOEpatents

Gough, Dara Van; Huber, Dale L.; Bunker, Bruce C.; Roberts, Mark E.

2017-01-24

A programmable pH buffer comprises a copolymer that changes pK.sub.a at a lower critical solution temperature (LCST) in water. The copolymer comprises a thermally programmable polymer that undergoes a hydrophobic-to-hydrophilic phase change at the LCST and an electrolytic polymer that exhibits acid-base properties that are responsive to the phase change. The programmable pH buffer can be used to sequester CO.sub.2 into water.

Green-ampt infiltration parameters in riparian buffers

Treesearch

L.M. Stahr; D.E. Eisenhauer; M.J. Helmers; Mike G. Dosskey; T.G. Franti

2004-01-01

Riparian buffers can improve surface water quality by filtering contaminants from runoff before they enter streams. Infiltration is an important process in riparian buffers. Computer models are often used to assess the performance of riparian buffers. Accurate prediction of infiltration by these models is dependent upon accurate estimates of infiltration parameters....

Mapping out the QCD phase transition in multiparticle production

NASA Astrophysics Data System (ADS)

Kabana, Sonja; Minkowski, Peter

2001-04-01

We analyse multiparticle production in a thermal framework for seven central nucleus + nucleus collisions, e+ + e- annihilation into hadrons on the Z resonance and four hadronic reactions p + p and p + pbar with partial centrality selection), with centre of mass energies ranging from √(s) = 2.6 GeV (per nucleon pair) to 1.8 TeV. Thermodynamic parameters at chemical freeze-out (temperature and baryon and strangeness fugacities) are obtained from appropriate fits, generally improving in quality for reactions subjected to centrality cuts. All systems with non-vanishing fugacities are extrapolated along trajectories of equal energy density, density and entropy density to zero fugacities. The so-obtained temperatures extrapolated to zero fugacities as a function of initial energy density ɛin universally show a strong rise followed by a saturating limit of Tlim = 155 +/- 6 +/- 20 MeV. We interpret this behaviour as mapping out the boundary between quark gluon plasma and hadronic phases. The ratio of strange antiquarks to light ones as a function of the initial energy density ɛin shows the same behaviour as the temperature, saturating at a value of 0.365 +/- 0.033 +/- 0.07. No distinctive feature of `strangeness enhancement' is seen for heavy ion collisions relative to hadronic and leptonic reactions, when compared at the same initial energy density.

The Role of Carbon in Exotic Crust Formation on Mercury

NASA Technical Reports Server (NTRS)

Vander Kaaden, Kathleen E.; McCubbin, Francis M.

2018-01-01

The terrestrial planets that comprise our inner Solar System, including the Moon, are all rocky bodies that have differentiated into a crust, mantle, and core. Furthermore, all of these bodies have undergone various igneous processes since their time of primary crust formation. These processes have resurfaced each of these bodies, at least in part, resulting in the production of a secondary crust, to which Mercury is no exception. From its first flyby encounter with Mercury on January 14, 2008, the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) spacecraft collected data on the structure, chemical makeup, and density of the planet among other important characteristics. The X-Ray Spectrometer on board MESSENGER measured elevated abundances of sulfur and low abundances of iron, suggesting the planets oxygen fugacity (fO2) is several log10 units below the Iron-Wustite buffer. Similar to the role of other volatiles (e.g. sulfur) on highly reducing planetary bodies, carbon is expected to behave differently in an oxygen starved environment than it does in an oxygen enriched environment (e.g., Earth).

Analysis of Natural Buffer Systems and the Impact of Acid Rain

ERIC Educational Resources Information Center

Powers, David C.; Yoder, Claude H.; Higgs, Andrew T.; Obley, Matt L.; Hess, Kenneth R.; Leber, Phyllis A.

2005-01-01

The environmental significance of acid rain on water systems of different buffer capacities is discussed. The most prevalent natural buffer system is created by the equilibrium between carbonate ions and carbon dioxide.

Analysis of microbial populations, denitrification, and nitrous oxide production in riparian buffers

USDA-ARS?s Scientific Manuscript database

Riparian buffers are used extensively to protect water bodies from nonpoint source nitrogen pollution. However there is relatively little information on the impact of these buffers on production of nitrous oxide (N2O). In this study, we assessed nitrous oxide production in riparian buffers of the so...

BACTERIAL INHIBITORS IN LAKE WATER

EPA Science Inventory

The populations of six bacterial genera fell rapidly after their addition to sterile lake water but not after their addition to buffer. The decline in numbers of two species that were studied further, Klebsiella pneumoniae and Micrococcus flavus, occurred even when the buffer was...

Dominant oceanic bacteria secure phosphate using a large extracellular buffer

PubMed Central

Zubkov, Mikhail V.; Martin, Adrian P.; Hartmann, Manuela; Grob, Carolina; Scanlan, David J.

2015-01-01

The ubiquitous SAR11 and Prochlorococcus bacteria manage to maintain a sufficient supply of phosphate in phosphate-poor surface waters of the North Atlantic subtropical gyre. Furthermore, it seems that their phosphate uptake may counter-intuitively be lower in more productive tropical waters, as if their cellular demand for phosphate decreases there. By flow sorting 33P-phosphate-pulsed 32P-phosphate-chased cells, we demonstrate that both Prochlorococcus and SAR11 cells exploit an extracellular buffer of labile phosphate up to 5–40 times larger than the amount of phosphate required to replicate their chromosomes. Mathematical modelling is shown to support this conclusion. The fuller the buffer the slower the cellular uptake of phosphate, to the point that in phosphate-replete tropical waters, cells can saturate their buffer and their phosphate uptake becomes marginal. Hence, buffer stocking is a generic, growth-securing adaptation for SAR11 and Prochlorococcus bacteria, which lack internal reserves to reduce their dependency on bioavailable ambient phosphate. PMID:26198420

Hydrogeological constraints on riparian buffers for reduction of diffuse pollution: examples from the Bear Creek watershed in Iowa, USA.

PubMed

Simpkins, W W; Wineland, T R; Andress, R J; Johnston, D A; Caron, G C; Isenhart, T M; Schultz, R C

2002-01-01

Riparian Management Systems (RiMS) have been proposed to minimize the impacts of agricultural production and improve water quality in Iowa in the Midwestern USA. As part of RiMS, multispecies riparian buffers have been shown to decrease nutrient, pesticide, and sediment concentrations in runoff from adjacent crop fields. However, their effect on nutrients and pesticides moving in groundwater beneath buffers has been discussed only in limited and idealized hydrogeologic settings. Studies in the Bear Creek watershed of central Iowa show the variability inherent in hydrogeologic systems at the watershed scale, some of which may be favorable or unfavorable to future implementation of buffers. Buffers may be optimized by choosing hydrogeologic systems where a shallow groundwater flow system channels water directly through the riparian buffer at velocities that allow for processes such as denitrification to occur.

Oxygen fugacities directly measured in magmatic gases.

PubMed

Sato, M; Wright, T L

1966-09-02

An electrochemical device was used to measure the fugacity of oxygen (fo(o2)) in holes drilled through the crust of Makaopuhi lava lake, Kilauea Volcano, Hawaii. Results obtained within 6 months of the lake formation show that log fo(o2) normally varies linearly with the reciprocal of the absolute temperature, and that chemical changes occurring in the cooling tholeiitic basalt are reflected in the fo(o2) values measured in the holes.

A fugacity-based indoor residential pesticide fate model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennett, Deborah H.; Furtaw, Edward J.; McKone, Thomas E.

Dermal and non-dietary pathways are potentially significant exposure pathways to pesticides used in residences. Exposure pathways include dermal contact with residues on surfaces, ingestion from hand- and object-to-mouth activities, and absorption of pesticides into food. A limited amount of data has been collected on pesticide concentrations in various residential compartments following an application. But models are needed to interpret this data and make predictions about other pesticides based on chemical properties. In this paper, we propose a mass-balance compartment model based on fugacity principles. We include air (both gas phase and aerosols), carpet, smooth flooring, and walls as model compartments.more » Pesticide concentrations on furniture and toys, and in food, are being added to the model as data becomes available. We determine the compartmental fugacity capacity and mass transfer-rate coefficient for wallboard as an example. We also present the framework and equations needed for a dynamic mass-balance model.« less

Reconnecting tile drainage to riparian buffer hydrology for enhanced nitrate removal.

PubMed

Jaynes, D B; Isenhart, T M

2014-03-01

Riparian buffers are a proven practice for removing NO from overland flow and shallow groundwater. However, in landscapes with artificial subsurface (tile) drainage, most of the subsurface flow leaving fields is passed through the buffers in drainage pipes, leaving little opportunity for NO removal. We investigated the feasibility of re-routing a fraction of field tile drainage as subsurface flow through a riparian buffer for increasing NO removal. We intercepted an existing field tile outlet draining a 10.1-ha area of a row-cropped field in central Iowa and re-routed a fraction of the discharge as subsurface flow along 335 m of an existing riparian buffer. Tile drainage from the field was infiltrated through a perforated pipe installed 75 cm below the surface by maintaining a constant head in the pipe at a control box installed in-line with the existing field outlet. During 2 yr, >18,000 m (55%) of the total flow from the tile outlet was redirected as infiltration within the riparian buffer. The redirected water seeped through the 60-m-wide buffer, raising the water table approximately 35 cm. The redirected tile flow contained 228 kg of NO. On the basis of the strong decrease in NO concentrations within the shallow groundwater across the buffer, we hypothesize that the NO did not enter the stream but was removed within the buffer by plant uptake, microbial immobilization, or denitrification. Redirecting tile drainage as subsurface flow through a riparian buffer increased its NO removal benefit and is a promising management practice to improve surface water quality within tile-drained landscapes. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Use of water-external micellar dispersions in oil recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, S.C.

1970-04-14

A water-external micellar dispersion followed by a mobility buffer and a water drive were used for enhanced oil recovery. Field Berea sandstone cores (19.6 percent porosity, 387 md permeability) were saturated with brine (16,500 ppM sodium chloride), flooded with crude oil from the Henry lease in Illinois (viscosity of 5.9 cp at 72/sup 0/F, specific gravity of 0.833), and waterflooded with water from Henry lease (17,210 ppM TDS). The micellar dispersion followed by the mobility buffer produced 99.6 percent of the oil in the core. The micellar slug contained ammonium petroleum sulfonate (MW 450), Henry crude oil, isopropanol, nonyl phenol,more » sodium hydroxide, and water from the Palestine water reservoir in Palestine, Illinois (412 ppM TDS). No. 530 Pusher, ammonium thiocyanate, isopropanol, and Palestine water were in the mobility buffer.« less

Effect of buffer at nanoscale molecular recognition interfaces - electrostatic binding of biological polyanions.

PubMed

Rodrigo, Ana C; Laurini, Erik; Vieira, Vânia M P; Pricl, Sabrina; Smith, David K

2017-10-19

We investigate the impact of an over-looked component on molecular recognition in water-buffer. The binding of a cationic dye to biological polyanion heparin is shown by isothermal calorimetry to depend on buffer (Tris-HCl > HEPES > PBS). The heparin binding of self-assembled multivalent (SAMul) cationic micelles is even more buffer dependent. Multivalent electrostatic molecular recognition is buffer dependent as a result of competitive interactions between the cationic binding interface and anions present in the buffer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, H. L.; Hirschmann, M. M.; Cottrell, E.

Experiments establishing the effect of pressure on the Fe 3+/ΣFe ratio of andesitic silicate melts buffered by coexisting Ru and RuO 2 were performed from 100 kPa to 7 GPa and 1400–1750 °C. Fe 3+/ΣFe ratios were determined by room temperature Mössbauer spectroscopy, but corrected for the effects of recoilless fraction. Fe 3+/ΣFe ratios in quenched glasses decrease with increasing pressure consistent with previous results between 100 kPa and 3 GPa (O’Neill et al., 2006), but show only small pressure effects above 5 GPa. Ratios also decrease with increasing temperature. Mössbauer hyperfine parameters indicate mean coordination of Fe 3+ ionsmore » of ~5 in glasses, with no dependence on the pressure from which the glasses were quenched, but show an increase with pressure in mean coordination of Fe 2+ ions, from ~5 to ~6. XANES spectra on these glasses show variations in pre-edge intensities and centroid positions that are systematic with Fe 3+/ΣFe, but are displaced from those established from otherwise identical andesitic glasses quenched at 100 kPa (Zhang et al., 2016). These systematics permit construction of a new XANES calibration curve relating pre-edge sub-peak intensities to Fe 3+/ΣFe applicable to high pressure glasses. Consistent with interpretations of the Mössbauer hyperfine parameters, XANES pre-edge peak features in high pressure glasses are owing chiefly to the effects of pressure on the coordination of Fe 2+ ions from ~5.5 to ~6, with negligible effects evident for Fe 3+ ions. We use the new data to construct a thermodynamic model relating the effects of oxygen fugacity and pressure on Fe 3+/ΣFe. We apply this model to calculate variations in oxygen fugacity in isochemical (constant Fe 3+/ΣFe) columns of magma representative of magma oceans, in which fO2 is fixed at the base by equilibration with molten Fe. These calculations indicate that oxygen fugacities at the surface of shallow magma oceans are more reduced than at depth. For magma oceans in which the pressure at the base is near 5 GPa, as may be appropriate for Mercury and the Moon, conditions at the surface are ~1.5 log unit more reduced at the surface than at their base. If the results calibrated up to pressures of 7 GPa can be extrapolated to higher pressures appropriate for magma oceans on larger terrestrial planets such as Mars or Earth, then conditions at the surface are ~2 or 2.5 log units more reduced at the surface than at the base, respectively. Thus, atmospheres overlying shallow magma oceans should be highly reduced and rich in H 2 and CO.« less

Experimental Study into the Partitioning Behavior of Fluorine, Chlorine, Hydroxyl, and Sulfur (S2-) Between Apatite and a Synthetic Kreep Basalt Melt

NASA Technical Reports Server (NTRS)

Turner, Amber; Vander Kaaden, Kathleen; McCubbin, Francis; Danielson, Lisa R.

2017-01-01

The mineral apatite (Ca5 (PO4)3(F, Cl, OH)) is known for its ability to constrain the petrogenesis of the rock in which it is hosted and for its ubiquity throughout the Solar System, as it is found in lunar, martian, and terrestrial rocks alike (McCubbin et. al, 2015). The abundance of volatile elements, and for this particular study, the elevated abundance of sulfur (S2-) in high-Al basalt samples bearing apatite, could provide more insight for inquiries posed about the behavior of volatiles in lunar and martian magmatic systems (Boyce et. al, 2010). Oxygen fugacity will be an important parameter for these experiments, as the Moon, Mars, and Earth have different redox states (Herd, 2008). The objective of this experimental endeavor is to determine apatite-melt partition coefficients for the volatile elements (F-, Cl-, OH-, S2-) that make up the X-site (i.e., the typically monovalent anion site) in the mineral apatite in a lunar melt composition under lunar oxygen fugacity conditions approx.1-2 log units below the iron-wüstite buffer). All experiments will be conducted at NASA, Johnson Space Center in the High Pressure Experimental Petrology Laboratory. In order to conduct apatite-melt partition experiments with oxygen fugacity as an additional parameter, we will create a synthetic mix of the lunar KREEP basalt 15386, a sample retrieved during Apollo 15 that is believed to represent an indigenous volcanic melt derived from the lunar interior (Rhodes, J.M et. al, 2006). Other geochemically significant elements including C, Co, Ni, Mo, and rare earth elements will be included in the mix at trace abundances in order to assess their partitioning behavior without effecting the overall behavior of the system. The synthetic mix will then be loaded into a piston cylinder, an apparatus used to simulate high-pressure/high-temperature conditions of planetary interiors, and exposed to 0.5 GPa of pressure, the pressure observed in the upper mantle of the Moon, and heated to the melting temperature of the materials. To make sure crystals grow large enough for the necessary analyses, the sample will be kept at the crystallization temperature for 8 hours. This extended run time should also allow the sample to achieve a steady state which is necessary to accurately assess the partitioning of these elements between apatite and melt. The results from this experimental study will allow us to determine the fate of F-, Cl-, OH-, and S2- during the magmatic evolution of the Moon.

Effect of buffer strips and soil texture on runoff losses of flufenacet and isoxaflutole from maize fields.

PubMed

Milan, Marco; Ferrero, Aldo; Letey, Marilisa; De Palo, Fernando; Vidotto, Francesco

2013-01-01

The influence of buffer strips and soil texture on runoff of flufenacet and isoxaflutole was studied for two years in Northern Italy. The efficacy of buffer strips was evaluated on six plots characterized by different soil textures; two plots had Riva soil (18.6% sand, 63.1% silt, 18.3% clay) while the remaining four plots had Tetto Frati (TF) soil (37.1% sand, 57% silt, 5.9% clay). Additionally, the width of the buffer strips, constituted of spontaneous vegetation grown after crop sowing, was also compared for their ability to abate runoff waters. Chemical residues in water following runoff events were investigated, as well as their dissipation in the soil. After the first runoff events, concentrations of herbicides in water samples collected from Riva plots were as much as four times lower in waters from TF plots. On average of two growing seasons, the field half-life of flufenacet in the upper soil layer (5 cm) ranged between 8.1 and 12.8 days in Riva soil, 8.5 and 9.3 days in TF soil. Isoxaflutole field half-life was less than 1 day. The buffer strip was very affective by the uniformity of the vegetative cover, particularly, at the beginning of the season. In TF plots, concentration differences were generally due to the presence or absence of the buffer strip, regardless of its width.

Extending the applicability of pressurized hot water extraction to compounds exhibiting limited water solubility by pH control: curcumin from the turmeric rhizome.

PubMed

Euterpio, Maria Anna; Cavaliere, Chiara; Capriotti, Anna Laura; Crescenzi, Carlo

2011-11-01

Pressurized hot water extraction (PHWE, also known as subcritical water extraction) is commonly considered to be an environmentally friendly extraction technique that could potentially replace traditional methods that use organic solvents. Unfortunately, the applicability of this technique is often limited by the very low water solubility of the target compounds, even at high temperatures. In this paper, the scope for broadening the applicability of PHWE by adjusting the pH of the water used in the extraction is demonstrated in the extraction of curcumin (which exhibits very limited water solubility) from untreated turmeric (Curcuma longa L.) rhizomes. Although poor extraction yields were obtained, even at high temperatures when using degassed water or neutral phosphate buffer as the extraction medium, yields exceeding those obtained by Soxhlet extraction were achieved using highly acidic pH buffers due to curcumin protonation. The influence of the temperature, pH, and buffer concentration on the extraction yield were investigated in detail by means of a series of designed experiments. Optimized conditions for the extraction of curcumin from turmeric by PHWE were estimated at 197 °C using 62 g/L buffer concentration at pH 1.6. The relationships between these variables were subjected to statistical analysis using response surface methodology.

META-ANALYSIS OF NITROGEN REMOVAL IN RIPARIAN BUFFERS

EPA Science Inventory

Riparian buffer zones, the vegetated region adjacent to streams and wetlands, are thought to be effective at intercepting and controlling nitrogen loads entering water bodies. Riparian buffer width may be positively related to nitrogen removal effectiveness by influencing nitrog...

Application of a level IV fugacity model to simulate the long-term fate of hexachlorocyclohexane isomers in the lower reach of Yellow River basin, China.

PubMed

Ao, Jiangting; Chen, Jingwen; Tian, Fulin; Cai, Xiyun

2009-01-01

A level IV multimedia fugacity model was established to simulate the fate and transfer of hexachlorocyclohexane (HCH) isomers in the lower reach of the Yellow River basin, China, during 1952-2010. The predicted concentrations of HCHs are in good agreement with the observed ones, as indicated by the residual errors being generally lower than 0.5 logarithmic units. The effects of extensive agricultural application and subsequent prohibition of HCHs are reflected by the temporal variation of HCHs predicted by the model. It is predicted that only 1.8 tons of HCHs will be left in 2010, less than 0.06% of the highest contents (in 1983) in the study area, and about 99% of HCHs remain in soil. The proportions of HCH isomers in the environment also changed with time due to their different physicochemical properties. Although beta-HCH is not the main component of the technical HCHs, it has become the most abundant isomer in the environment because of its persistence. The dominant transfer processes between the adjacent compartments were deposition from air to soil, air diffusion through the air-water interface and runoff from soil to water. Sensitivity analysis showed that degradation rate in soil, parameters related to major sources, and thickness of soils had the strongest influence on the model result. Results of Monte Carlo simulation indicated the overall uncertainty of model predictions, and the coefficients of variation of the estimated concentrations of HCHs in all the compartments ranged from 0.5 to 5.8.

Riparian buffer zones on selected rivers in Lower Silesia - an important conservation practice and the management strategy in urban planning

NASA Astrophysics Data System (ADS)

Adamska, Maryna

2013-09-01

Buffer zones are narrow strips of land lying along the surface water, covered with appropriately selected vegetation. They separate aquatic ecosystems from the direct impact of agricultural land and reduce the movement of nutrients in the environment. In 2008 the European Commission established requirements for the implementation of buffer strips along water courses. Poland committed to the enforcement of these requirements until 1 January 2012. This was one of the reasons of this study. The subject of the analysis included the following rivers in Lower Silesia: Smortawa, Krynka, Czarna Woda and the selected transects of Ślęza and Nysa Łużycka. Detailed studies were designed to estimate the buffer zones occurring on these watercourses and assess these zones’ structure. This will be used to develop clear criteria for the selection of the width of these zones based on land use land management. It can be used in the implementation of executive acts at different levels of space management. Field research consisted of inventory the extent of riparian buffer strips on selected water courses and photographic documentation. Species composition of the vegetation forming a buffer zone was identified by using Braun-Blanquet method. There was lack of continuity of the riparian buffer zones on investigated rivers. Buffer zones should have carefully formulated definition and width because they are element of the significant ecological value, they perform important environmental protective functions and they are also the subject of Community law.

IPE 7

NASA Technical Reports Server (NTRS)

1983-01-01

A description is given of the collection and treatment of samples of Prochloron cells. The cells of Prochloron were obtained and prepared in the following way. Colonies of the symbiotic host, the giant didemnid ascidian Lissoclinum patella, were collected at low-tide level on reef-flat sand between Kamori Island and Koror, Palau, Western Caroline Islands. The animal colonies were taken, immersed in sea water, to an 8,000-litre holding tank and kept with constantly running sea water at 30 deg. Individual colonies were picked clean of contaminants, rinsed in sea water buffered with 40 nM or 100 mM Tris buffer at pH 8.4, and squeezed by hand to express the algal cells from the cloacal atria. The algae were received in about an equal volume of the same buffered sea water; this neutralized the acids liberated by the bruised ascidians and thereby maintained the Ph high enough to keep the algal cells green. The Prochloron cells were washed twice with buffered sea water and concentrated by centrifugation at about 50 g for 90 seconds. Microscopic examination revealed that contamination by animal host cells or bacteria was negligible (much less than 1%).

Scale effects on spatially varying relationships between urban landscape patterns and water quality.

PubMed

Sun, Yanwei; Guo, Qinghai; Liu, Jian; Wang, Run

2014-08-01

Scientific interpretation of the relationships between urban landscape patterns and water quality is important for sustainable urban planning and watershed environmental protection. This study applied the ordinary least squares regression model and the geographically weighted regression model to examine the spatially varying relationships between 12 explanatory variables (including three topographical factors, four land use parameters, and five landscape metrics) and 15 water quality indicators in watersheds of Yundang Lake, Maluan Bay, and Xinglin Bay with varying levels of urbanization in Xiamen City, China. A local and global investigation was carried out at the watershed-level, with 50 and 200 m riparian buffer scales. This study found that topographical features and landscape metrics are the dominant factors of water quality, while land uses are too weak to be considered as a strong influential factor on water quality. Such statistical results may be related with the characteristics of land use compositions in our study area. Water quality variations in the 50 m buffer were dominated by topographical variables. The impact of landscape metrics on water quality gradually strengthen with expanding buffer zones. The strongest relationships are obtained in entire watersheds, rather than in 50 and 200 m buffer zones. Spatially varying relationships and effective buffer zones were verified in this study. Spatially varying relationships between explanatory variables and water quality parameters are more diversified and complex in less urbanized areas than in highly urbanized areas. This study hypothesizes that all these varying relationships may be attributed to the heterogeneity of landscape patterns in different urban regions. Adjustment of landscape patterns in an entire watershed should be the key measure to successfully improving urban lake water quality.

Equations for calculating hydrogeochemical reactions of minerals and gases such as CO2 at high pressures and temperatures

USGS Publications Warehouse

Appelo, C.A.J.; Parkhurst, David L.; Post, V.E.A.

2014-01-01

Calculating the solubility of gases and minerals at the high pressures of carbon capture and storage in geological reservoirs requires an accurate description of the molar volumes of aqueous species and the fugacity coefficients of gases. Existing methods for calculating the molar volumes of aqueous species are limited to a specific concentration matrix (often seawater), have been fit for a limited temperature (below 60 °C) or pressure range, apply only at infinite dilution, or are defined for salts instead of individual ions. A more general and reliable calculation of apparent molar volumes of single ions is presented, based on a modified Redlich–Rosenfeld equation. The modifications consist of (1) using the Born equation to calculate the temperature dependence of the intrinsic volumes, following Helgeson–Kirkham–Flowers (HKF), but with Bradley and Pitzer’s expression for the dielectric permittivity of water, (2) using the pressure dependence of the extended Debye–Hückel equation to constrain the limiting slope of the molar volume with ionic strength, and (3) adopting the convention that the proton has zero volume at all ionic strengths, temperatures and pressures. The modifications substantially reduce the number of fitting parameters, while maintaining or even extending the range of temperature and pressure over which molar volumes can be accurately estimated. The coefficients in the HKF-modified-Redlich–Rosenfeld equation were fitted by least-squares on measured solution densities.The limiting volume and attraction factor in the Van der Waals equation of state can be estimated with the Peng–Robinson approach from the critical temperature, pressure, and acentric factor of a gas. The Van der Waals equation can then be used to determine the fugacity coefficients for pure gases and gases in a mixture, and the solubility of the gas can be calculated from the fugacity, the molar volume in aqueous solution, and the equilibrium constant. The coefficients for the Peng–Robinson equations are readily available in the literature.The required equations have been implemented in PHREEQC, version 3, and the parameters for calculating the partial molar volumes and fugacity coefficients have been added to the databases that are distributed with PHREEQC. The ease of use and power of the formulation are illustrated by calculating the solubility of CO2 at high pressures and temperatures, and comparing with well-known examples from the geochemical literature. The equations and parameterizations are suitable for wide application in hydrogeochemical systems, especially in the field of carbon capture and storage.

Equations for calculating hydrogeochemical reactions of minerals and gases such as CO2 at high pressures and temperatures

NASA Astrophysics Data System (ADS)

Appelo, C. A. J.; Parkhurst, D. L.; Post, V. E. A.

2014-01-01

Calculating the solubility of gases and minerals at the high pressures of carbon capture and storage in geological reservoirs requires an accurate description of the molar volumes of aqueous species and the fugacity coefficients of gases. Existing methods for calculating the molar volumes of aqueous species are limited to a specific concentration matrix (often seawater), have been fit for a limited temperature (below 60 °C) or pressure range, apply only at infinite dilution, or are defined for salts instead of individual ions. A more general and reliable calculation of apparent molar volumes of single ions is presented, based on a modified Redlich-Rosenfeld equation. The modifications consist of (1) using the Born equation to calculate the temperature dependence of the intrinsic volumes, following Helgeson-Kirkham-Flowers (HKF), but with Bradley and Pitzer’s expression for the dielectric permittivity of water, (2) using the pressure dependence of the extended Debye-Hückel equation to constrain the limiting slope of the molar volume with ionic strength, and (3) adopting the convention that the proton has zero volume at all ionic strengths, temperatures and pressures. The modifications substantially reduce the number of fitting parameters, while maintaining or even extending the range of temperature and pressure over which molar volumes can be accurately estimated. The coefficients in the HKF-modified-Redlich-Rosenfeld equation were fitted by least-squares on measured solution densities. The limiting volume and attraction factor in the Van der Waals equation of state can be estimated with the Peng-Robinson approach from the critical temperature, pressure, and acentric factor of a gas. The Van der Waals equation can then be used to determine the fugacity coefficients for pure gases and gases in a mixture, and the solubility of the gas can be calculated from the fugacity, the molar volume in aqueous solution, and the equilibrium constant. The coefficients for the Peng-Robinson equations are readily available in the literature. The required equations have been implemented in PHREEQC, version 3, and the parameters for calculating the partial molar volumes and fugacity coefficients have been added to the databases that are distributed with PHREEQC. The ease of use and power of the formulation are illustrated by calculating the solubility of CO2 at high pressures and temperatures, and comparing with well-known examples from the geochemical literature. The equations and parameterizations are suitable for wide application in hydrogeochemical systems, especially in the field of carbon capture and storage.

Developing V-Xanes Oxybarometry for Probing Materials Formed in Reducing Environments in the Early Solar Disk

NASA Technical Reports Server (NTRS)

Butterworth, A. L.; Gainsforth, Z.; Jilly-Rehak, C. E.; Righter, K.; Westphal, A. J.

2017-01-01

Vanadium exhibits four oxidation states (V(sup 2+), V(sup 3+), V(sup 4+) and V(sup 5+)) that have been shown to preferentially partition between melt phases dependent on redox conditions, spanning oxygen fugacity across more than 10 log units. We are developing synchrotron-based x-ray absorption spectroscopy of low-fugacity standards for the determination of V oxidation state in highly reducing conditions relevant to the early solar nebula.

Micro-XANES Measurements on Experimental Spinels and the Oxidation State of Vanadium in Spinel-Melt Pairs

NASA Technical Reports Server (NTRS)

Righter, K.; Sutton, S.R.; Newville, M.

2004-01-01

Spinel can be a significant host phase for V as well as other transition metals such as Ni and Co. However, vanadium has multiple oxidation states V(2+), V(3+), V(4+) or V(5+) at oxygen fugacities relevant to natural systems. We do know that D(V) spinel/melt is correlated with V and TiO2 content and fO2, but the uncertainty of the oxidation state under the range of natural conditions has made elusive a thorough understanding of D(V) spinel/melt. For example, V(3+) is likely to be stable in spinels, based on exchange with Al in experiments in the CaO-MgO-Al2O3-SiO2 system. On the other hand, it has been argued that V(4+) will be stable across the range of natural oxygen fugacities in nature. In order to gain a better understanding of D(V) spinel/melt we have equilibrated spinel-melt pairs at controlled oxygen fugacities, between HM to NNO, where V is present in the spinel at natural levels (approx. 300 ppm V). These spinel-melt pairs were analyzed using micro-XANES at the Advanced Photon Source at Argonne National Laboratory. The new results will be used together with spinel compositional data (Ti, V content) and oxygen fugacity, to unravel the effects of these variables on D(V) spinel/melt.

Prototype repository: A full scale experiment at Äspö HRL

NASA Astrophysics Data System (ADS)

Johannesson, Lars-Erik; Börgesson, Lennart; Goudarzi, Reza; Sandén, Torbjörn; Gunnarsson, David; Svemar, Christer

At Äspö Hard Rock Laboratory a full scale test of the Swedish concept for disposal of nuclear waste (KBS-3V) is in progress. The Prototype Repository project consists of two sections. The installation of the first section was made during summer and autumn 2001 and the second section during spring and summer 2003. Section 1 consists of four full-scale deposition holes, copper canisters equipped with electrical heaters, bentonite buffer consisting of blocks and pellets and a deposition tunnel backfilled with a mixture of bentonite and crushed rock, ending with a concrete plug. Section 2 consists of two full-scale deposition holes with a backfilled tunnel section and ends also with a concrete plug. Altogether 84 large bentonite blocks, with a total weight of about 130 tons, were installed and more than 2000 tons of backfill material were mixed and compacted in situ. Earlier developed techniques for both manufacturing and installing the buffer and the backfill were used in the project. Measurements and data from the installation allow calculations of the expected density in the buffer and in different parts of the backfill. The bentonite buffer in deposition holes 1, 3, 5 and 6, the backfill and the surrounding rock are instrumented with gauges for measuring temperature, water pressure, total pressure, relative humidity, resistivity, canister displacement and rock stresses. The instruments are connected to data acquisition systems by cables protected by tubes. These tubes are led through the rock in watertight lead-throughs to a nearby tunnel where the data acquisition systems are situated. More than 1100 transducers have been installed in the rock, buffer and the backfill. The technique for protecting the transducers from high water and swelling pressure was developed in this and preceding projects and furthermore different designs of transducers are used for the same type of measurement in order to compare their behaviour. The deposition holes have different water inflow rates (from 0.0007 to 0.08 l/min), resulting in different water uptake rates of the buffer. The water ratio as a function of time for different parts of the buffer can be estimated from measurement of the relative humidity in the pore system of the buffer. Deposition hole 1 with a relatively high water inflow (0.08 l/min), shows in some parts of the buffer very high degree of saturation while the drier holes 2, 3, 4, 5 and 6 (0.0007-0.003 l/min) show a very slow saturation rate in most parts of the buffer. The temperature in the buffer and on the surface of the canisters is carefully studied. The temperature measurements indicate a rather large drop in temperature (approx. 10 °C) over the 10 mm gap between the canister and the buffer. In deposition hole 1 the gap has vanished due to high degree of saturation, resulting in a lower temperature on the surface of the canister. The displacement of the canisters in deposition holes 3 and 6 has been measured continuously with six transducers in each deposition hole. The measurement allows calculation of the displacement of the canisters in all three directions. The maximum measured vertical displacement so far is about 8 mm upwards. The water uptake in the backfill is measured continuously with soil psychrometers. The results indicate a high degree of saturation close to the rock wall and on top of the buffer in the deposition holes, while the backfill in the more central part of tunnel shows slow increase in water ratio over the time. Transducers for measuring suction in the rock (soil psychrometers) have been installed very close to the surface of one of the deposition holes. The transducers are measuring rather high suctions close to the rock surface, indicating a not fully saturated pore system of the rock. The paper describes the following items: the test design, the installation phase, example of measurements made during the water uptake and some preliminary evaluations of water uptake of both the buffer and backfill up to November 1, 2004. The paper is mainly focused on the engineered barriers.

Stability of the Stevia-Derived Sweetener Rebaudioside A in Solution as Affected by Ultraviolet Light Exposure.

PubMed

Zhang, Jiewen; Bell, Leonard N

2017-04-01

Rebaudioside A is a natural noncaloric high-potency sweetener extracted from the leaves of Stevia rebaudiana. With rebaudioside A use increasing in foods, understanding the factors affecting its stability is necessary. This project evaluated the degradation rate constants of rebaudioside A in water, 0.1 M phosphate buffer, and 0.1 M citrate buffer at pH 3 and 7 as a function of ultraviolet (UV) light intensity (365 nm, 0 μW/cm 2 for dark conditions, 27 μW/cm 2 for low intensity, and 190 μW/cm 2 for high intensity) at 32.5 °C. Rebaudioside A stability was adversely affected by light exposure. The pseudo-1st-order degradation rate constants increased significantly (P < 0.05) with increasing light intensity in all solutions. Under dark conditions, rebaudioside A in phosphate buffers was more susceptible to breakdown than in water and citrate buffers at both pH levels. However, exposure to UV light resulted in rebaudioside A degradation occurring approximately 10 times faster in citrate than in phosphate buffers at both pH levels. The sensitivity of rebaudioside A to UV light was greater in citrate buffers than in water or phosphate buffers. The use of light-protective packaging for beverages containing rebaudioside A will improve its stability. © 2017 Institute of Food Technologists®.

Storage of Explosive versus Effusive Rhyolite Magma at the Yellowstone Volcanic Center

NASA Astrophysics Data System (ADS)

Gardner, J. E.

2007-12-01

The Yellowstone volcanic center has erupted more than 900 km3 of rhyolitic magma in the last 600,000 years (1). Most of that magma extruded as large lava flows, with only a few known explosive eruptions. Why have explosive eruptions been so rare in the recent history of the Yellowstone volcanic system? To explore that question, we focus on the Tuff of Bluff Point (TBP), about 50 km3 of magma that explosively erupted 173 ka, forming the West Thumb caldera (1). Like most other recent eruptions of Yellowstone, TBP is high silica rhyolite, with phenocrysts of quartz, sanidine, and minor ferro-pyroxenes and Fe-Ti oxides. Fe-Ti oxide and pyroxene compositions indicate that the magma had equilibrated at an oxygen fugacity equal to the QFM buffer. Rehomogenized glass inclusions (n=7) in quartz contain 2.2-3.1 wt.% water and between 400-650 ppm CO2. Those volatile contents indicate storage pressures of 90-160 MPa. Ubiquitous pyrrhotite shows that the magma was sulfur saturated, and most likely volatile saturated. The co-existing fluid would be only 42-47% water. Cathodoluminescence (CL) images of quartz phenocrysts reveal mainly concentric growth zones, with occasional dissolution boundaries present. Ti contents in quartz generally decrease from core to rim, indicating cooling of the magma, although the relative temperature changes recorded are only 10-15°, with only minor changes across dissolution boundaries. To put our observations in perspective of the recent Yellowstone magma system, we have begun examining some of the recent rhyolitic lavas, including the Pitchstone Plateau (PP), a single homogeneous lava flow of 70 km3 that erupted 79 ka (1). CL images also reveal mainly concentric quartz growth, with few dissolution boundaries obvious. Ti contents in quartz also generally decrease from core to rim, but are uniformly lower than in those in TBP, suggesting that PP magma was colder than TBP magma. Glass inclusions (n=20) in PP are generally water poor and rarely contain CO2. A few do have more than 2 wt.% water, but only100-200 ppm CO2, indicating storage pressure of 80-100 MPa. (1) Christiansen et al., USGS Open-file Report 2007-1071, 2007, 94 p.

Potential benefits of pH 8.8 alkaline drinking water as an adjunct in the treatment of reflux disease.

PubMed

Koufman, Jamie A; Johnston, Nikki

2012-07-01

At the cellular level, tissue-bound pepsin is fundamental to the pathophysiologic mechanism of reflux disease, and although the thresholds for laryngeal damage in laryngopharyngeal reflux and for esophageal damage in gastroesophageal reflux disease differ, both forms of damage are due to pepsin, which requires acid for its activation. In addition, human pepsin remains stable at pH 7.4 and may be reactivated by hydrogen ions from any source. Thus, most tap and bottled waters (typically pH 6.7 to 7.4) would not be expected to affect pepsin stability. The purposes of these in vitro studies were to investigate whether artesian well water containing natural bicarbonate (pH 8.8) might irreversibly denature (inactivate) human pepsin, and to establish its potential acid-buffering capacity. Laboratory studies were performed to determine whether human pepsin was inactivated by pH 8.8 alkaline water. In addition, the buffering capacity of the alkaline water was measured and compared to that of the two most popular commercially available bottled waters. The pH 8.8 alkaline water irreversibly inactivated human pepsin (in vitro), and its hydrochloric acid-buffering capacity far exceeded that of the conventional-pH waters. Unlike conventional drinking water, pH 8.8 alkaline water instantly denatures pepsin, rendering it permanently inactive. In addition, it has good acid-buffering capacity. Thus, the consumption of alkaline water may have therapeutic benefits for patients with reflux disease.

Watershed scale impacts of buffers and upland conservation practices on agrochemical delivery to streams

Treesearch

T.G. Franti; D.E. Eisenhauer; M.C. McCullough; L.M. Stahr; Mike G. Dosskey; D.D. Snow; R.F. Spalding; A.L. Boldt

2004-01-01

Conservation buffers are designed to reduce sediment and agrichemical runoff to surface water. Much is known about plot and field scale effectiveness of buffers; but little is known about their - watershed scale impact. Our objective was to estimate the watershed scale impact of grass buffers by comparing sediment and agrichemical losses from two adjacent 141 - 165...

Carbon contents in reduced basalts at graphite saturation: Implications for the degassing of Mars, Mercury, and the Moon

NASA Astrophysics Data System (ADS)

Li, Yuan; Dasgupta, Rajdeep; Tsuno, Kyusei

2017-06-01

Carbon contents in reduced Martian basalts at graphite saturation were experimentally studied at 1400-1550°C, 1-2 GPa, and logfO2 of IW - 0.4 to IW + 1.5 (IW denotes the Fe-FeO buffer). The results show that carbon solubility in Martian basalts, determined by secondary ion mass spectrometry, is 20 to 1400 ppm, increasing with increasing fO2. Raman and Fourier transform infrared spectroscopic measurements on the quenched silicate glasses show that the dominant carbon species in Martian basalts is carbonate (CO32-). The experimental data generated here were combined with literature data on similar graphite-saturated carbon solubility for mafic-ultramafic compositions to develop an empirical model that can be used to predict carbon content of graphite-saturated reduced basalts at vapor-absent conditions: At IW+1.7 ≥logfO2 ≥ IW-1: (Cppm)=-3702(±534)/T-194(±49)P/T-0.0034(±0.043) logXH2O +0.61(±0.07)NBO/T+0.55(±0.02) ΔIW +3.5(±0.3)R2=0.89 At IW-5.3 ≤ logfO2 ≤ IW-1: (Cppm)=0.96(±0.19) logXH2O-0.25(±0.04)ΔIW+2.83(±0.34)R2=0.6) in which T is temperature in K, P is pressure in GPa, XH2O is mole fraction of water in basalts, ΔIW is the oxygen fugacity relative to the IW buffer, and NBO/T = 2 total O/T - 4 (T = Si + Ti + Al + Cr + P). This model was applied to predict carbon content in graphite-saturated mantle melts of the Mercury, Mars, and the Moon. The results show that graphite may be consumed during the production and extraction of some Martian basalts, and CO2 released by volcanism on Mars cannot be an efficient greenhouse gas in the early Mars. The lunar mantle carbon may be one of the main propellant driving the fire-fountain eruption on the Moon; however, the Mercurian mantle carbon may not be an important propellant for the explosive eruption on Mercury.

Soil water nitrate concentrations in giant cane and forest riparian buffer zones

Treesearch

Jon E. Schoonover; Karl W. J. Williard; James J. Zaczek; Jean C. Mangun; Andrew D. Carver

2003-01-01

Soil water nitrate concentrations in giant cane and forest riparian buffer zones along Cypress Creek in southern Illinois were compared to determine if the riparian zones were sources or sinks for nitrogen in the rooting zone. Suction lysimeters were used to collect soil water samples from the lower rooting zone in each of the two vegetation types. The cane riparian...

Identifying riparian zones appropriate for installation of saturated buffers: A multi-watershed assessment

USDA-ARS?s Scientific Manuscript database

Saturated riparian buffers are a new type of conservation practice that divert a portion of subsurface tile drainage from discharge to surface water into distribution pipes that discharge tile water into riparian soils. This enables natural processes of biological uptake and denitrification to decre...

Defining Steamside Management Zones or Riparian Buffers

Treesearch

Thomas M. Williams; Donald J. Lipscomb; Christopher J. Post

2004-01-01

Forestry Best Management Practices (BMPs) have been highly successful in protecting water quality throughout the Southeast. Numerous studies have found them to be effective in protecting water quality. Despite being mostly voluntary, compliance is generally about 90 percent across the region. Streamside Management Zones (SMZs) or riparian buffers are specified for...

Water and the Interior Structure of Terrestrial Planets and Icy Bodies

NASA Astrophysics Data System (ADS)

Monteux, J.; Golabek, G. J.; Rubie, D. C.; Tobie, G.; Young, E. D.

2018-02-01

Water content and the internal evolution of terrestrial planets and icy bodies are closely linked. The distribution of water in planetary systems is controlled by the temperature structure in the protoplanetary disk and dynamics and migration of planetesimals and planetary embryos. This results in the formation of planetesimals and planetary embryos with a great variety of compositions, water contents and degrees of oxidation. The internal evolution and especially the formation time of planetesimals relative to the timescale of radiogenic heating by short-lived 26Al decay may govern the amount of hydrous silicates and leftover rock-ice mixtures available in the late stages of their evolution. In turn, water content may affect the early internal evolution of the planetesimals and in particular metal-silicate separation processes. Moreover, water content may contribute to an increase of oxygen fugacity and thus affect the concentrations of siderophile elements within the silicate reservoirs of Solar System objects. Finally, the water content strongly influences the differentiation rate of the icy moons, controls their internal evolution and governs the alteration processes occurring in their deep interiors.

A Review of Effectiveness of Vegetative Buffers on Sediment Trapping in Agricultural Areas

EPA Science Inventory

In recent years, there has been growing recognition of the importance of riparian buffers between agricultural fields and waterbodies. Riparian buffers play an important role in mitigating the impacts of land use activities on water quality and aquatic ecosystems. However, eval...

The effect of oxygen fugacity on the solubility of carbon-oxygen fluids in basaltic melt

NASA Technical Reports Server (NTRS)

Pawley, Alison R.; Holloway, John R.; Mcmillan, Paul F.

1992-01-01

The solubility of CO2-CO fluids in a midocean ridge basalt have been measured at 1200 C, 500-1500 bar, and oxygen fugacities between NNO and NNO-4. In agreement with results of previous studies, the results reported here imply that, at least at low pressures, CO2 dissolves in basaltic melt only in the form of carbonate groups. The dissolution reaction is heterogeneous, with CO2 molecules in the fluid reacting directly with reactive oxygens in the melt to produce CO3(2-). CO, on the other hand, is insoluble, dissolving neither as carbon, molecular CO, nor CO3(2-). It is shown that, for a given pressure and temperature, the concentration of dissolved carbon-bearing species in basaltic melt in equilibrium with a carbon-oxygen fluid is proportional to the mole fraction of CO2 in the fluid, which is a function of fO2. At low pressures CO2 solubility is a linear function of CO2 fugacity at constant temperatures.

Effects of rehydration and food consumption on salivary flow, pH and buffering capacity in young adult volunteers during ergometer exercise.

PubMed

Tanabe, Mai; Takahashi, Toshiyuki; Shimoyama, Kazuhiro; Toyoshima, Yukako; Ueno, Toshiaki

2013-10-28

The aim of this study was to investigate the influences of rehydration and food consumption on salivary flow, pH, and buffering capacity during bicycle ergometer exercise in participants. Ten healthy volunteers exercised on a bicycle ergometer at 80% of their maximal heart rate. These sessions lasted for two periods of 20 min separated by 5-min rest intervals. Volunteers were subjected to one of the following conditions: (1) no water (mineral water) or food consumption, (2) only water for rehydration, (3) water and food consumption, (4) a sports drink only for rehydration, and (5) rehydration with a sports drink and food. Statistical significance was assessed using one-way analysis of variance and Dunnett's test (p < 0.05). The salivary pH decreased significantly during and after exercise in conditions 4 and 5. The salivary buffering capacity decreased significantly during exercise and/or after the exercise in conditions 1, 3, 4, and 5. The results showed that salivary pH and buffering capacity decreased greatly depending on the combination of a sports drink and food.

Third Bose fugacity coefficient in one dimension, as a function of asymptotic quantities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amaya-Tapia, A., E-mail: jano@fis.unam.mx; Larsen, S.Y.; Lassaut, M.

2011-02-15

In one of the very few exact quantum mechanical calculations of fugacity coefficients, [L.R. Dodd, A.M. Gibbs. J. Math. Phys. 15 (1974) 41] obtained b{sub 2} and b{sub 3} for a one dimensional Bose gas, subject to repulsive delta-function interactions, by direct integration of the wave functions. For b{sub 2}, we have shown [A. Amaya-Tapia, S.Y. Larsen, M. Lassaut. Mol. Phys. 103 (2005) 1301-1306. < (arXiv:physics/0405150)>] that Dodd and Gibbs' result can be obtained from a phase shift formalism, if one also includes the contribution of oscillating terms, usually contributing only in one dimension. Now, we develop an exact expressionmore » for b{sub 3}-b{sub 3}{sup 0} (where b{sub 3}{sup 0} is the free particle fugacity coefficient) in terms of sums and differences of three-body eigenphase shifts. Further, we show that if we obtain these eigenphase shifts in a Distorted-Born approximation, then, to first order, we reproduce the leading low temperature behaviour, obtained from an expansion of the twofold integral of Dodd and Gibbs. The contributions of the oscillating terms cancel. The formalism that we propose is not limited to one dimension, but seeks to provide a general method to obtain virial coefficients, fugacity coefficients, in terms of asymptotic quantities. The exact one dimensional results allow us to confirm the validity of our approach in this domain.« less

Role of riparian areas in atmospheric pesticide deposition and its potential effect on water quality

USDA-ARS?s Scientific Manuscript database

Riparian buffers are known to mitigate hydrologic losses of nutrients and other contaminants as they exit agricultural fields. The vegetation of riparian buffers can also trap atmospheric contaminants, but these pollutants can subsequently be delivered via rain to the riparian buffer floor. These ...

Riparian ecosystems and buffers - multiscale structure, function, and management: introduction

Treesearch

Kathleen A. Dwire; Richard R. Lowrance

2006-01-01

Given the importance of issues related to improved understanding and management of riparian ecosystems and buffers, the American Water Resources Association (AWRA) sponsored a Summer Specialty Conference in June 2004 at Olympic Valley, California, entitled 'Riparian Ecosystems and Buffers: Multiscale Structure, Function, and Management.' The primary objective...

A comparison of alternative strategies for cost-effective water quality management in lakes.

PubMed

Kramer, Daniel Boyd; Polasky, Stephen; Starfield, Anthony; Palik, Brian; Westphal, Lynne; Snyder, Stephanie; Jakes, Pamela; Hudson, Rachel; Gustafson, Eric

2006-09-01

Roughly 45% of the assessed lakes in the United States are impaired for one or more reasons. Eutrophication due to excess phosphorus loading is common in many impaired lakes. Various strategies are available to lake residents for addressing declining lake water quality, including septic system upgrades and establishing riparian buffers. This study examines 25 lakes to determine whether septic upgrades or riparian buffers are a more cost-effective strategy to meet a phosphorus reduction target. We find that riparian buffers are the more cost-effective strategy in every case but one. Large transaction costs associated with the negotiation and monitoring of riparian buffers, however, may be prohibiting lake residents from implementing the most cost-effective strategy.

Thermodynamic study of the transfer of acetanilide and phenacetin from water to different organic solvents.

PubMed

Baena, Yolima; Pinzón, Jorge A; Barbosa, Helber J; Martínez, Fleming

2005-06-01

The molar (K(C)(o/w)) and rational (K(X)(o/w)) partition coefficients in the octanol/buffer, i-propyl myristate/buffer, chloroform/buffer, and cyclohexane/buffer systems were determined for acetanilide and phenacetin at 25.0, 30.0, 35.0, and 40.0 degrees C. In all cases except for cyclohexane, the K(C)(o/w) and K(X)(o/w) values were greater than unity. This demonstrates that these two drugs have predominantly lipophilic behavior. Gibbs and van't Hoff thermodynamic analyses have revealed that the transfer of these drugs from water to organic solvents is spontaneous and that it is mainly driven enthalpically for i-propyl myristate and chloroform, and entropy-driven for octanol and cyclohexane.

A Comparison of Alternative Strategies for Cost-Effective Water Quality Management in Lakes

NASA Astrophysics Data System (ADS)

Kramer, Daniel Boyd; Polasky, Stephen; Starfield, Anthony; Palik, Brian; Westphal, Lynne; Snyder, Stephanie; Jakes, Pamela; Hudson, Rachel; Gustafson, Eric

2006-09-01

Roughly 45% of the assessed lakes in the United States are impaired for one or more reasons. Eutrophication due to excess phosphorus loading is common in many impaired lakes. Various strategies are available to lake residents for addressing declining lake water quality, including septic system upgrades and establishing riparian buffers. This study examines 25 lakes to determine whether septic upgrades or riparian buffers are a more cost-effective strategy to meet a phosphorus reduction target. We find that riparian buffers are the more cost-effective strategy in every case but one. Large transaction costs associated with the negotiation and monitoring of riparian buffers, however, may be prohibiting lake residents from implementing the most cost-effective strategy.

Relating rheology to geometry in large-scale natural shear zones

NASA Astrophysics Data System (ADS)

Platt, John

2016-04-01

The geometry and width of the ductile roots of plate boundary scale faults are very poorly understood. Some field and geophysical data suggests widths of tens of km in the lower crust, possibly more in the upper mantle. Other observations suggest they are much narrower. Dip slip shear zones may flatten out and merge into zones of subhorizontal lower crustal or asthenospheric flow. The width of a ductile shear zone is simply related to relative velocity and strain rate. Strain rate is related to stress through the constitutive relationship. Can we constrain the stress, and do we understand the rheology of materials in ductile shear zones? A lot depends on how shear zones are initiated. If they are localized by pre-existing structures, width and/or rheology may be inherited, and we have too many variables. If shear zones are localized primarily by shear heating, initial shear stress has to be very high (> 1 GPa) to overcome conductive heat loss, and very large feedbacks (both positive and negative) make the system highly unstable. Microstructural weakening requires a minimum level of stress to cause deformation and damage in surrounding rock, thereby buffering the stress. Microstructural weakening leads to grain-size sensitive creep, for which we have constitutive laws, but these are complicated by phase mixing in polyphase materials, by viscous anisotropy, by hydration, and by changes in mineral assemblage. Here are some questions that need to be addressed. (1) If grain-size reduction by dynamic recrystallization results in a switch to grain-size sensitive creep (GSSC) in a stress-buffered shear zone, does dynamic recrystallization stop? Does grain growth set in? If grain-size is still controlled by dislocation processes, then the effective stress exponent for GSSC is 4-5, even though the dominant mechanism may be diffusion and/or grain-boundary sliding (GBS). (2) Is phase mixing in ultramylonites primarily a result of GBS + neighbour switching, creep cavitation and diffusion, or metamorphic reactions? (3) In two-phase / polyphase mixtures, does the strong phase generally form a load-bearing framework, favoring constant strain-rate (Voigt) bound behavior, or does the weak phase form through-going strain pathways, favoring constant stress (Reuss) bound behavior, or do the phases remain well mixed, favoring an intermediate behavior (e.g., Tullis et al model)? (4) How do we deal with the rheological effect of water? Is it simply an unconstrained variable in nature? Is the water fugacity model in flow laws adequate? (5) How can we better relate experimental results (often carried out at constant strain-rate, and not reaching microstructural steady state) to deformation in natural shear zones? Rheological observations on well-constrained natural shear zones are helping us answer some of these questions.

Synthesis of Ti Oxides at Reducing Conditions: Implications for Beamline Standards and Cosmochemistry

NASA Technical Reports Server (NTRS)

Righter, K.; Pando, K. A.; Butterworth, A. L.; Gainsforth, Z.; Jilly-Rehak, C. E.; Westphal, A. J.

2017-01-01

These initial experiments demonstrate the great potential for synthesizing customized compounds for use as standards, or in buffering experiments at reducing conditions. We are also investigating Cr and V oxides, as well as compounds containing these elements such as FeV2O4 and FeCr2O4. Oxygen fugacity exerts a major control on mineral major element chemistry and elemental valence of minerals in any plane-tary compositional system [1]. For Earth, Fe is multivalent ranging from nearly Fe0 at low fO2 in the deep mantle to Fe2+ to Fe3+ at high low fO2. For solar nebular and meteoritic materials fO2 ranges from near IW to 10 log fO2 units below the IW buffer [1]. Phases in CAIs, for example, contain no Fe2+, but may contain Ti4+, Ti3+, or Ti2+, and Cr3+ or Cr2+, and V3+ or V2+ [1,2,3]. De-tailed study of inclusions may reveal important differences in fO2 thus reflecting different environments in the solar nebula [4]. XANES, FEG-SEM, and TEM can reveal such variations in micro and nano samples such as Stardust and cosmic dust particles [5], but successful application to reduced conditions depends upon the availability of well characterized standards. Acquiring appropriate standards for reduced phases that contain Ti3+ or Ti2+, Cr3+ or Cr2+, and V3+ or V2+ can be a challenge. Here we report our preliminary results at synthesizing reduced Ti bearing standards, and focus on the preliminary characterization.

Variability of CO2 fugacity at the western edge of the tropical Atlantic Ocean from the 8°N to 38°W PIRATA buoy

NASA Astrophysics Data System (ADS)

Bruto, Leonardo; Araujo, Moacyr; Noriega, Carlos; Veleda, Dóris; Lefèvre, Nathalie

2017-06-01

Hourly data of CO2 fugacity (fCO2) at 8°N-38°W were analyzed from 2008 to 2011. Analyses of wind, rainfall, temperature and salinity data from the buoy indicated two distinct seasonal periods. The first period (January to July) had a mean fCO2 of 378.9 μatm (n = 7512). During this period, in which the study area was characterized by small salinity variations, the fCO2 is mainly controlled by sea surface temperature (SST) variations (fCO2 = 24.4*SST-281.1, r2 = 0.8). During the second period (August-December), the mean fCO2 was 421.9 μatm (n = 11571). During these months, the region is subjected to the simultaneous action of (a) rainfall induced by the presence of the Intertropical Convergence Zone (ITCZ); (b) arrival of fresh water from the Amazon River plume that is transported to the east by the North Equatorial Countercurrent (NECC) after the retroflection of the North Brazil Current (NBC); and (c) vertical input of CO2-rich water due to Ekman pumping. The data indicated the existence of high-frequency fCO2 variability (periods less than 24 h). This high variability is related to two different mechanisms. In the first mechanism, fCO2 increases are associated to rapid increases in SST and are attributed to the diurnal cycle of solar radiation. In addition, low wind speed contributes to SST rising by inhibiting vertical mixing. In the second mechanism, fCO2 decreases are associated to SSS decreases caused by heavy rainfall.

Nitrate-nitrogen reduction by established tree and pasture buffer strips associated with a cattle feedlot effluent disposal area near Armidale, NSW Australia.

PubMed

Wang, Liangmin; Duggin, John A; Nie, Daoping

2012-05-30

Vegetated buffer strips have been recognized as an important element in overall agro-ecosystem management to reduce the delivery of non-point source pollutants from agricultural land to inland water systems. A buffer strip experiment consisting of two tree species (Eucalyptus camaldulensis and Casuarina cunninghamiana) with two planting densities and a pasture treatment was conducted to determine the effectiveness of NO(3)-N removal from a cattle feedlot effluent disposal area at Tullimba near Armidale, NSW Australia. Different management methods were applied for the buffers where grass and weeds were mowed 2-3 times during the second and third years and were not managed during the rest experimental years for the tree buffer, while grass was harvested 1-3 times per year for the pasture buffer. The differences between tree species and planting density significantly affected tree growth, but the growth difference did not significantly affect their capacities to reduce NO(3)-N in soil surface runoff and groundwater. On average for all the tree and pasture treatments, the buffer strips reduced NO(3)-N concentration by 8.5%, 14.7% and 14.4% for the surface runoff, shallow and deep groundwater respectively. The tree and pasture buffer strips were not significantly different in NO(3)-N reduction for both shallow and deep groundwater while the pasture buffer strips reduced significantly more NO(3)-N concentration in surface runoff than the tree buffer strips. Both buffer strips reduced more than 50% of surface runoff volume indicating that both the tree and pasture buffer strips were efficient at removing water and nutrients, mostly through a significant reduction in soil surface runoff volume. Copyright © 2012 Elsevier Ltd. All rights reserved.

Simulating and evaluating best management practices for integrated landscape management scenarios in biofuel feedstock production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ha, Miae; Wu, May

Sound crop and land management strategies can maintain land productivity and improve the environmental sustainability of agricultural crop and feedstock production. With this study, it evaluates a strategy of incorporating landscape design and management concepts into bioenergy feedstock production. It examines the effect of land conversion and agricultural best management practices (BMPs) on water quality (nutrients and suspended sediments) and hydrology. The strategy was applied to the watershed of the South Fork Iowa River in Iowa, where the focus was on converting low-productivity land to provide cellulosic biomass and implementing riparian buffers. The Soil and Water Assessment Tool (SWAT) wasmore » employed to simulate the impact at watershed and sub-basin scales. The study compared the representation of buffers by using trapping efficiency and area ratio methods in SWAT. Landscape design and management scenarios were developed to quantify water quality under (i) current land use, (ii) partial land conversion to switchgrass, and (iii) riparian buffer implementation. Results show that implementation of vegetative barriers and riparian buffer can trap the loss of total nitrogen, total phosphorus, and sediment significantly. The effect increases with the increase of buffer area coverage. Implementing riparian buffer at 30 m width is able to produce 4 million liters of biofuels. When low-productivity land (15.2% of total watershed land area) is converted to grow switchgrass, suspended sediment, total nitrogen, total phosphorus, and nitrate loadings are reduced by 69.3%, 55.5%, 46.1%, and 13.4%, respectively. The results highlight the significant role of lower-productivity land and buffers in cellulosic biomass and provide insights into the design of an integrated landscape with a conservation buffer for future bioenergy feedstock production.« less

Simulating and evaluating best management practices for integrated landscape management scenarios in biofuel feedstock production

DOE PAGES

Ha, Miae; Wu, May

2015-09-08

Sound crop and land management strategies can maintain land productivity and improve the environmental sustainability of agricultural crop and feedstock production. With this study, it evaluates a strategy of incorporating landscape design and management concepts into bioenergy feedstock production. It examines the effect of land conversion and agricultural best management practices (BMPs) on water quality (nutrients and suspended sediments) and hydrology. The strategy was applied to the watershed of the South Fork Iowa River in Iowa, where the focus was on converting low-productivity land to provide cellulosic biomass and implementing riparian buffers. The Soil and Water Assessment Tool (SWAT) wasmore » employed to simulate the impact at watershed and sub-basin scales. The study compared the representation of buffers by using trapping efficiency and area ratio methods in SWAT. Landscape design and management scenarios were developed to quantify water quality under (i) current land use, (ii) partial land conversion to switchgrass, and (iii) riparian buffer implementation. Results show that implementation of vegetative barriers and riparian buffer can trap the loss of total nitrogen, total phosphorus, and sediment significantly. The effect increases with the increase of buffer area coverage. Implementing riparian buffer at 30 m width is able to produce 4 million liters of biofuels. When low-productivity land (15.2% of total watershed land area) is converted to grow switchgrass, suspended sediment, total nitrogen, total phosphorus, and nitrate loadings are reduced by 69.3%, 55.5%, 46.1%, and 13.4%, respectively. The results highlight the significant role of lower-productivity land and buffers in cellulosic biomass and provide insights into the design of an integrated landscape with a conservation buffer for future bioenergy feedstock production.« less

Exsolution of Iron-Titanium Oxides in Magnetite in Miller Range (MIL) 03346 Nakhlite: Evidence for Post Crystallization Reduction in the Nakhlite Cumulate Pile

NASA Technical Reports Server (NTRS)

Righter, Kevin; Keller, L. P.; Rahman, Z.; Christoffersen, R.

2012-01-01

MIL 03346 is one of the most mesostasis-rich nakhlites [1] and thought to have equilibrated at oxygen fugacities near the fayalite-magnetite-quartz oxygen (FMQ) buffer ([2,3]). Studies of FeTi oxides in nakhlites have led to additional constraints on their equilibration temperatures and fO2s [4,5,6,7]. Comparison of these results to fO2s calculated for shergottites indicates that nakhlites are among the most oxidized samples from the martian meteorite suite [2]. The mesostasis of MIL 03346 contains skeletal titanomagnetite. Several scientists noticed several years ago (e.g. [8]) that this titanomagnetite contains very fine oxidation-driven exsolution lamellae (Figure 1). However, the lamellae are so small that they cannot be characterized by electron microprobe analysis (EMPA). Here we select several areas for focused ion beam (FIB) extraction, prepare transmission electron microscopy (TEM) foils, and identify and analyze the lamellae using TEM at the Johnson Space Center (JSC). The resulting analyses are combined with previous work on nakhlites to interpret the thermal and oxidation history of this meteorite group.

Conservation Buffers—Design guidelines for buffers, corridors, and greenways

Treesearch

G. Bentrup

2008-01-01

Over 80 illustrated design guidelines for conservation buffers are synthesized and developed from a review of over 1,400 research publications. Each guideline describes a specific way that a vegetative buffer can be applied to protect soil, improve air and water quality, enhance fish and wildlife habitat, produce economic products, provide recreation opportunities, or...

Where should buffers go? modeling riparian habitat connectivity in northeast Kansas

Treesearch

Gary Bentrup; Todd Kellerman

2004-01-01

Through many funding programs, riparian buffers are being created on agricultural lands to address significant water quality problems. Society and landowners are demanding many other environmental and social services (e.g., wildlife habitat and income diversification) from this practice. Resource planners therefore need to design riparian buffer systems in the right...

Regulating riparian forests for aquatic productivity in the Pacific Northwest, USA: addressing a paradox.

PubMed

Newton, Michael; Ice, George

2016-01-01

Forested riparian buffers isolate streams from the influence of harvesting operations that can lead to water temperature increases. Only forest cover between the sun and stream limits stream warming, but that cover also reduces in-stream photosynthesis, aquatic insect production, and fish productivity. Water temperature increases that occur as streams flow through canopy openings decrease rapidly downstream, in as little as 150 m. Limiting management options in riparian forests restricts maintenance and optimization of various buffer contributions to beneficial uses, including forest products, fish, and their food supply. Some riparian disturbance, especially along cold streams, appears to benefit fish productivity. Options for enhancing environmental investments in buffers should include flexibility in application of water quality standards to address the general biological needs of fish and temporary nature of clearing induced warming. Local prescriptions for optimizing riparian buffers and practices that address long-term habitat needs deserve attention. Options and incentives are needed to entice landowners to actively manage for desirable riparian forest conditions.

Buffers and vegetative filter strips

Treesearch

Matthew J. Helmers; Thomas M. Isenhart; Michael G. Dosskey; Seth M. Dabney

2008-01-01

This chapter describes the use of buffers and vegetative filter strips relative to water quality. In particular, we primarily discuss the herbaceous components of the following NRCS Conservation Practice Standards.

The solubility of gold in hydrogen sulfide gas: An experimental study

NASA Astrophysics Data System (ADS)

Zezin, Denis Yu.; Migdisov, Artashes A.; Williams-Jones, Anthony E.

2007-06-01

The solubility of gold in H 2S gas has been investigated at temperatures of 300, 350 and 400 °C and pressures up to 230 bars. Experimentally determined values of the solubility of Au are 0.4-1.4 ppb at 300 °C, 1-8 ppb at 350 °C and 8.6-95 ppb at 400 °C. Owing to a positive dependence of the logarithm of the fugacity of gold on the logarithm of the fugacity of H 2S, it is proposed that the solubility of Au can be attributed to formation of a solvated gaseous sulfide or bisulfide complex through reactions of the type: Au(s)+(n+1)·HS(g)=AuS·(HS)n(g)+H(g) or Au(g)+(n+1)·HS(g)=AuHS·(HS)n(g)+{1}/{2}H(g) which are f-dependent; n is a statistical solvation number. If the redox potential is buffered by S/H 2S (the case in our study), the corresponding reactions are: Au(s)+n·HS(g)+S(l)=AuS·(HS)n(g) or Au(s)+(n+{1}/{2})·HS(g)+{1}/{2}S(l)=AuHS·(HS)n(g) Values of n for these latter reactions were calculated to be 1.8 and 1.2 at 300 °C, 1.7 and 1.0 at 350 °C, 2.2 and 1.7 at 400 °C, respectively. The equilibrium constants for reactions 3 and D increase with temperature and have values of log K = -11.1 ± 0.2 at 300 °C (both reactions), -10.7 ± 0.3 and -10.5 ± 0.3 at 350 °C, and -10.6 ± 0.2 and -10.4 ± 0.2 at 400 °C, respectively. At the conditions of this study, the solubility of gold in H 2S gas is relatively high, and the results obtained provide strong evidence that H 2S can play an important role in the vapor transport of gold and the formation of hydrothermal gold deposits.

Solubility of Anhydrite (CaSO4) in NaCl-H2O Fluids at High T and P

NASA Astrophysics Data System (ADS)

Newton, R. C.; Manning, C. E.

2003-12-01

Weight losses of single crystals of a very pure natural anhydrite exposed to NaCl solutions of 0-0.3 mol fraction were measured at 600-800 \\deg C and 6-14 kbar. Experimental charges were contained in welded Pt capsules in 1.91 cm-diameter piston-cylinder apparatus with NaCl pressure medium for 5-72 hr. Measurements in initially pure H2O were made with HM, NNO, and MnO2 buffers, as well as without buffering. At 800 \\deg C and 10 kbar, CaSO4 molalities are: MnO2, 0.014 mol/kg H2O; HM, 0.017; NNO, 0.148; and unbuffered, 0.026. Variation in oxygen fugacity thus has a large effect on CaSO4 solubility, increasing with H2S/SO2 in the fluid. Unbuffered (self-buffered) charges gave solubilities much closer to HM than NNO. Melting occurred in the NNO experiment at this P and T. NaCl increases CaSO4 solubility enormously, with m(CaSO4) reaching 5.4, or 23.5 wt. %, at 800 \\deg C, 10 kbar and X(NaCl)=0.3. There is also a very large increase with temperature. Regression of all the data give: log(m-mo) = -1.533 + 0.00291T + (1.441 + 0.00016T)logX(NaCl) + 0.0413(P-10) where mo is molality in pure H2O, P is in kbar, and T is in Kelvins. The very large carrying capacity for sulfate in even mildly saline fluids at high P and T, together with the high oxygen potential generated when these solutions react with FeO in rocks to yield pyrrhotite, indicates that such fluids should be considered as principal agents in S-rich, highly oxidizing processes such as Pinatubo-type volcanic eruptions, certain deep-crustal granulite facies metamorphism, as in Bamble, Norway and Shevaroy Hills, S. India, and the anhydrite-related, oxidized Au ore deposits like Abitibi, Ontario, and Kalgoorlie, Australia.

Dual character of Sundarban estuary as a source and sink of CO2 during summer: an investigation of spatial dynamics.

PubMed

Akhand, Anirban; Chanda, Abhra; Dutta, Sachinandan; Manna, Sudip; Sanyal, Pranabes; Hazra, Sugata; Rao, K H; Dadhwal, V K

2013-08-01

A comprehensive attempt has been made to evaluate the diurnal and spatial pattern of CO2 exchange between the atmosphere and water along the estuarine track of Indian Sundarbans during the two summer months, April and May, 2011. Rigorous field observations were carried out which included the hourly measurements of total alkalinity, pH, fugacity of CO2 in ambient air and water surface, dissolved oxygen, and chlorophyll a. The estuarine water was found rich in total alkalinity and was oversaturated with CO2 throughout the diurnal cycle in the two stations situated at the inner and middle estuary, respectively, whereas an entirely reverse situation was observed in the outer fringes. The fugacity of CO2 in water ranged from 152 to 657 μatm during the study period. The percentage of over-saturation in inner and middle estuary varied from 103 to 168 and 103 to 176 %, respectively, whereas the degree of under-saturation in the outer estuary lied between 40 and 99 %. Chlorophyll a concentrations were found higher in the outer estuary (12.3 ± 2.2 mg m(-3)) compared to the middle (6.4 ± 0.6 mg m(-3)) and inner parts (1.6 ± 0.2 mg m(-3)), followed by a similar decreasing pattern in nutrient availability from the outer to inner estuary. The sampling stations situated at the inner and middle estuary acted as a net source of 29.69 and 23.62 mg CO2 m(-2) day(-1), respectively, whereas the outer station behaved as a net sink of -33.37 mg CO2 m(-2) day(-1). The study of primary production and community respiration further supports the heterotrophic nature of the estuary in the inner region while the outer periphery was marked by dominant autotrophic character. These contrasting results are in parity with the source characters of many inner estuaries and sinking characters of the outer estuaries situated at the distal continental shelf areas.

Detoxification of Chemical Warfare Agents Using a Zr6 -Based Metal-Organic Framework/Polymer Mixture.

PubMed

Moon, Su-Young; Proussaloglou, Emmanuel; Peterson, Gregory W; DeCoste, Jared B; Hall, Morgan G; Howarth, Ashlee J; Hupp, Joseph T; Farha, Omar K

2016-10-10

Owing to their high surface area, periodic distribution of metal sites, and water stability, zirconium-based metal-organic frameworks (Zr 6 -MOFs) have shown promising activity for the hydrolysis of nerve agents GD and VX, as well as the simulant, dimethyl 4-nitrophenylphosphate (DMNP), in buffered solutions. A hurdle to using MOFs for this application is the current need for a buffer solution. Here the destruction of the simulant DMNP, as well as the chemical warfare agents (GD and VX) through hydrolysis using a MOF catalyst mixed with a non-volatile, water-insoluble, heterogeneous buffer is reported. The hydrolysis of the simulant and nerve agents in the presence of the heterogeneous buffer was fast and effective. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NMR measurement system including two synchronized ring buffers, with 128 rf coils for in situ water monitoring in a polymer electrolyte fuel cell

NASA Astrophysics Data System (ADS)

Ogawa, Kuniyasu; Haishi, Tomoyuki; Aoki, Masaru; Hasegawa, Hiroshi; Morisaka, Shinichi; Hashimoto, Seitaro

2017-01-01

A small radio-frequency (rf) coil inserted into a polymer electrolyte fuel cell (PEFC) can be used to acquire nuclear magnetic resonance (NMR) signals from the water in a membrane electrode assembly (MEA) or in oxygen gas channels in the PEFC. Measuring the spatial distribution of the water in a large PEFC requires using many rf probes, so an NMR measurement system which acquires NMR signals from 128 rf probes at intervals of 0.5 s was manufactured. The system has eight rf transceiver units with a field-programmable gate array (FPGA) for modulation of the excitation pulse and quadrature phase detection of the NMR signal, and one control unit with two ring buffers for data control. The sequence data required for the NMR measurement were written into one ring buffer. The acquired NMR signal data were then written temporarily into the other ring buffer and then were transmitted to a personal computer (PC). A total of 98 rf probes were inserted into the PEFC that had an electrical generation area of 16 cm × 14 cm, and the water generated in the PEFC was measured when the PEFC operated at 100 A. As a result, time-dependent changes in the spatial distribution of the water content in the MEA and the water in the oxygen gas channels were obtained.

Erratum: Probabilistic application of a fugacity model to predict triclosan fate during wastewater treatment.

PubMed

Bock, Michael; Lyndall, Jennifer; Barber, Timothy; Fuchsman, Phyllis; Perruchon, Elyse; Capdevielle, Marie

2010-10-01

The fate and partitioning of the antimicrobial compound, triclosan, in wastewater treatment plants (WWTPs) is evaluated using a probabilistic fugacity model to predict the range of triclosan concentrations in effluent and secondary biosolids. The WWTP model predicts 84% to 92% triclosan removal, which is within the range of measured removal efficiencies (typically 70% to 98%). Triclosan is predominantly removed by sorption and subsequent settling of organic particulates during primary treatment and by aerobic biodegradation during secondary treatment. Median modeled removal efficiency due to sorption is 40% for all treatment phases and 31% in the primary treatment phase. Median modeled removal efficiency due to biodegradation is 48% for all treatment phases and 44% in the secondary treatment phase. Important factors contributing to variation in predicted triclosan concentrations in effluent and biosolids include influent concentrations, solids concentrations in settling tanks, and factors related to solids retention time. Measured triclosan concentrations in biosolids and non-United States (US) effluent are consistent with model predictions. However, median concentrations in US effluent are over-predicted with this model, suggesting that differences in some aspect of treatment practices not incorporated in the model (e.g., disinfection methods) may affect triclosan removal from effluent. Model applications include predicting changes in environmental loadings associated with new triclosan applications and supporting risk analyses for biosolids-amended land and effluent receiving waters. © 2010 SETAC.

Probabilistic application of a fugacity model to predict triclosan fate during wastewater treatment.

PubMed

Bock, Michael; Lyndall, Jennifer; Barber, Timothy; Fuchsman, Phyllis; Perruchon, Elyse; Capdevielle, Marie

2010-07-01

The fate and partitioning of the antimicrobial compound, triclosan, in wastewater treatment plants (WWTPs) is evaluated using a probabilistic fugacity model to predict the range of triclosan concentrations in effluent and secondary biosolids. The WWTP model predicts 84% to 92% triclosan removal, which is within the range of measured removal efficiencies (typically 70% to 98%). Triclosan is predominantly removed by sorption and subsequent settling of organic particulates during primary treatment and by aerobic biodegradation during secondary treatment. Median modeled removal efficiency due to sorption is 40% for all treatment phases and 31% in the primary treatment phase. Median modeled removal efficiency due to biodegradation is 48% for all treatment phases and 44% in the secondary treatment phase. Important factors contributing to variation in predicted triclosan concentrations in effluent and biosolids include influent concentrations, solids concentrations in settling tanks, and factors related to solids retention time. Measured triclosan concentrations in biosolids and non-United States (US) effluent are consistent with model predictions. However, median concentrations in US effluent are over-predicted with this model, suggesting that differences in some aspect of treatment practices not incorporated in the model (e.g., disinfection methods) may affect triclosan removal from effluent. Model applications include predicting changes in environmental loadings associated with new triclosan applications and supporting risk analyses for biosolids-amended land and effluent receiving waters. (c) 2010 SETAC.

Protein-Water and Protein-Buffer Interactions in the Aqueous Solution of an Intrinsically Unstructured Plant Dehydrin: NMR Intensity and DSC Aspects

PubMed Central

Tompa, P.; Bánki, P.; Bokor, M.; Kamasa, P.; Kovács, D.; Lasanda, G.; Tompa, K.

2006-01-01

Proton NMR intensity and differential scanning calorimetry measurements were carried out on an intrinsically unstructured late embryogenesis abundant protein, ERD10, the globular BSA, and various buffer solutions to characterize water and ion binding of proteins by this novel combination of experimental approaches. By quantifying the number of hydration water molecules, the results demonstrate the interaction between the protein and NaCl and between buffer and NaCl on a microscopic level. The findings overall provide direct evidence that the intrinsically unstructured ERD10 not only has a high hydration capacity but can also bind a large amount of charged solute ions. In accord, the dehydration stress function of this protein probably results from its simultaneous action of retaining water in the drying cells and preventing an adverse increase in ionic strength, thus countering deleterious effects such as protein denaturation. PMID:16798808

EQ3NR, a computer program for geochemical aqueous speciation-solubility calculations: Theoretical manual, user`s guide, and related documentation (Version 7.0); Part 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolery, T.J.

1992-09-14

EQ3NR is an aqueous solution speciation-solubility modeling code. It is part of the EQ3/6 software package for geochemical modeling. It computes the thermodynamic state of an aqueous solution by determining the distribution of chemical species, including simple ions, ion pairs, and complexes, using standard state thermodynamic data and various equations which describe the thermodynamic activity coefficients of these species. The input to the code describes the aqueous solution in terms of analytical data, including total (analytical) concentrations of dissolved components and such other parameters as the pH, pHCl, Eh, pe, and oxygen fugacity. The input may also include a desiredmore » electrical balancing adjustment and various constraints which impose equilibrium with special pure minerals, solid solution end-member components (of specified mole fractions), and gases (of specified fugacities). The code evaluates the degree of disequilibrium in terms of the saturation index (SI = 1og Q/K) and the thermodynamic affinity (A = {minus}2.303 RT log Q/K) for various reactions, such as mineral dissolution or oxidation-reduction in the aqueous solution itself. Individual values of Eh, pe, oxygen fugacity, and Ah (redox affinity) are computed for aqueous redox couples. Equilibrium fugacities are computed for gas species. The code is highly flexible in dealing with various parameters as either model inputs or outputs. The user can specify modification or substitution of equilibrium constants at run time by using options on the input file.« less

Success of riparian restoration projects in the mountains, piedmont, and coastal plain of Virginia

Treesearch

Benjamin N. Bradburn; W. Michael Aust; Matthew B. Carroll; Dean Cumbia; Jerre Creighton

2010-01-01

Forested riparian buffers are a Best Management Practice (BMP) for protection of water quality and for habitat. Since the 1990s, conservation agencies in Virginia have been involved in establishment of riparian buffers under the auspices of programs such as the Conservation Reserve Enhancement Program (CREP). Although CREP was established for protection of water...

Emission reduction by multipurpose buffer strips on arable fields.

PubMed

Sloots, K; van der Vlies, A W

2007-01-01

In the area managed by Hollandse Delta, agriculture is under great pressure and the social awareness of the agricultural sector is increasing steadily. In recent years, a stand-still has been observed in water quality, in terms of agrochemicals, and concentrations even exceed the standard. To improve the waterquality a multi-purpose Field Margin Regulation was drafted for the Hoeksche Waard island in 2005. The regulation prescribes a crop-free strip, 3.5 m wide, alongside wet drainage ditches. The strip must be sown with mixtures of grasses, flowers or herbs. No crop protection chemicals or fertilizer may be used on the strips. A total length of approximately 200 km of buffer strip has now been laid. Besides reducing emissions, the buffer strips also stimulate natural pest control methods and encourage local tourism. Finally, the strips should lead to an improvement in the farmers' image. The regulation has proved to be successful. The buffer strips boosted both local tourism and the image of the agricultural sector. Above all, the strips provided a natural shield for emission to surface water, which will lead to an improvement of the water quality and raise the farmers' awareness of water quality and the environment.

Effects of rehydration and food consumption on salivary flow, pH and buffering capacity in young adult volunteers during ergometer exercise

PubMed Central

2013-01-01

Background The aim of this study was to investigate the influences of rehydration and food consumption on salivary flow, pH, and buffering capacity during bicycle ergometer exercise in participants. Methods Ten healthy volunteers exercised on a bicycle ergometer at 80% of their maximal heart rate. These sessions lasted for two periods of 20 min separated by 5-min rest intervals. Volunteers were subjected to one of the following conditions: (1) no water (mineral water) or food consumption, (2) only water for rehydration, (3) water and food consumption, (4) a sports drink only for rehydration, and (5) rehydration with a sports drink and food. Statistical significance was assessed using one-way analysis of variance and Dunnett’s test (p < 0.05). Results The salivary pH decreased significantly during and after exercise in conditions 4 and 5. The salivary buffering capacity decreased significantly during exercise and/or after the exercise in conditions 1, 3, 4, and 5. Conclusions The results showed that salivary pH and buffering capacity decreased greatly depending on the combination of a sports drink and food. PMID:24160307

33 CFR 100.35T07-0297 - Special Local Regulation, 50 Aniversario Balneario de Boqueron, Bahia de Boqueron; Boqueron, PR.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) Buffer Zone. All waters of the Bahia de Boqueron, Boqueron, Puerto Rico encompassed within an imaginary... west back to origin. All persons and vessels except those persons and vessels enforcing the buffer zone are prohibited from entering, transiting through, anchoring in, or remaining within the buffer zone...

33 CFR 100.35T07-0297 - Special Local Regulation, 50 Aniversario Balneario de Boqueron, Bahia de Boqueron; Boqueron, PR.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) Buffer Zone. All waters of the Bahia de Boqueron, Boqueron, Puerto Rico encompassed within an imaginary... west back to origin. All persons and vessels except those persons and vessels enforcing the buffer zone are prohibited from entering, transiting through, anchoring in, or remaining within the buffer zone...

Strong Dependence of Hydration State of F-Actin on the Bound Mg(2+)/Ca(2+) Ions.

PubMed

Suzuki, Makoto; Imao, Asato; Mogami, George; Chishima, Ryotaro; Watanabe, Takahiro; Yamaguchi, Takaya; Morimoto, Nobuyuki; Wazawa, Tetsuichi

2016-07-21

Understanding of the hydration state is an important issue in the chemomechanical energetics of versatile biological functions of polymerized actin (F-actin). In this study, hydration-state differences of F-actin by the bound divalent cations are revealed through precision microwave dielectric relaxation (DR) spectroscopy. G- and F-actin in Ca- and Mg-containing buffer solutions exhibit dual hydration components comprising restrained water with DR frequency f2 (fw). The hydration state of F-actin is strongly dependent on the ionic composition. In every buffer tested, the HMW signal Dhyme (≡ (f1 - fw)δ1/(fwδw)) of F-actin is stronger than that of G-actin, where δw is DR-amplitude of bulk solvent and δ1 is that of HMW in a fixed-volume ellipsoid containing an F-actin and surrounding water in solution. Dhyme value of F-actin in Ca2.0-buffer (containing 2 mM Ca(2+)) is markedly higher than in Mg2.0-buffer (containing 2 mM Mg(2+)). Moreover, in the presence of 2 mM Mg(2+), the hydration state of F-actin is changed by adding a small fraction of Ca(2+) (∼0.1 mM) and becomes closer to that of the Ca-bound form in Ca2.0-buffer. This is consistent with the results of the partial specific volume and the Cotton effect around 290 nm in the CD spectra, indicating a change in the tertiary structure and less apparent change in the secondary structure of actin. The number of restrained water molecules per actin (N2) is estimated to be 1600-2100 for Ca2.0- and F-buffer and ∼2500 for Mg2.0-buffer at 10-15 °C. These numbers are comparable to those estimated from the available F-actin atomic structures as in the first water layer. The number of HMW molecules is roughly explained by the volume between the equipotential surface of -kT/2e and the first water layer of the actin surface by solving the Poisson-Boltzmann equation using UCSF Chimera.

Simulating and evaluating best management practices for integrated landscape management scenarios in biofuel feedstock production: Evaluating Best Management Practices for Biofuel Feedstock Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ha, Miae; Wu, May

Sound crop and land management strategies can maintain land productivity and improve the environmental sustainability of agricultural crop and feedstock production. This study evaluates the improvement of water sustainability through an integrated landscaping management strategy, where landscaping design, land management operations, crop systems, and agricultural best management practices (BMPs) play equal roles. The strategy was applied to the watershed of the South Fork Iowa River in Iowa, with a focus on implementing riparian buffers and converting low productivity land to provide cellulosic biomass while benefiting soil and water quality. The Soil and Water Assessment Tool (SWAT) was employed to simulatemore » the impact of integrated landscape design on nutrients, suspended sediments, and flow on the watershed and subbasin scales. First, the study evaluated the representation of buffer strip as a vegetative barrier and as a riparian buffer using trapping efficiency and area ratio methods in SWAT. For the riparian buffer, the area ratio method tends to be more conservative, especially in nitrate loadings, while the trapping efficiency method generates more optimistic results. The differences between the two methods increase with buffer width. The two methods may not be comparable for the field-scale vegetative barrier simulation because of limitations in model spatial resolution. Landscape scenarios were developed to quantify water quality under (1) current land use, (2) partial land conversion to switchgrass, and (3) riparian buffer implementation. Results show that when low productivity land (15.2% of total watershed land area) is converted to grow switchgrass, suspended sediment, total nitrogen, total phosphorus, and nitrate loadings are reduced by 69.3%, 55.5%, 46.1%, and 13.4%, respectively, in the watershed surface streams. The reduction was less extensive when riparian buffer strips (30 m or 50 m) were applied to the stream network at 1.4% of total land area in the watershed. At the subbasin level, the degree of nutrient and suspended sediment reduction varies extensively, ranging from a few percent up to 55%. Results indicate that effective landscape design on current agricultural land can potentially bring marked improvements in water quality and soil erosion control while producing food and fuel feedstock in the South Fork Iowa River watershed. The concept can be integrated with other watershed management programs to improve sustainability of land, water, and the ecosystem.« less

Decompression Induced Crystallization of Basaltic Andesite Magma: Constraints on the Eruption of Arenal Volcano, Costa Rica.

NASA Astrophysics Data System (ADS)

Szramek, L. A.; Gardner, J. E.; Larsen, J. F.

2004-12-01

Arenal Volcano is a small stratovolcano located 90 km NW of San Jose, Costa Rica. In 1968 current activity began with a Plinian phase, and has continued to erupt lava flows and pyroclastic flows intermittently since. Samples from the Plinian, pyroclastic flow, strombolian, and effusive phases have been studied texturally. Little variation in crystallinity occurs amongst the different phases. Number density of crystals, both 2D and 3D are 50-70 mm-2 and 30,000-50,000 mm-3 in the Plinian sample, compared to the lesser values in other eruptive types. Characteristic crystal size also increases as explosivity decreases. Two samples, both lava flows collected while warm, overlap with the Plinian sample. This suggests that the variations seen may be a result of cooling history. Plagioclase differs between the Plinian sample, in which they are only tabular in shape, and the other eruptive types, which contain both tabular and equant crystals. To link decompression paths of the Arenal magma to possible pre-eruptive conditions, we have carried out hydrothermal experiments. The experiments were preformed in TZM pressure vessels buffered at a fugacity of Ni-NiO and water saturation. Phase equilibria results in conjunction with mineral compositions and temperature estimates by previous workers from active lava flows and two-pyroxene geothermometry, constrain the likely pre-eruptive conditions for the Arenal magma to 950-1040° C with a water pressure of 50-80 MPa. Samples that started from conditions that bracket our estimated pre-eruptive conditions were decompressed in steps of 5-30 MPa and held for various times at each step until 20 MPa was reached, approximating average decompression rates of 0.25, 0.025, 0.0013 MPa/s. Comparison of textures found in the natural samples to the experimentally produced textures suggest that the Plinian eruption likely was fed by magma ascending at 0.05-1 m/s, whereas the less explosive phases were fed by magma ascending at 0.05 m/s or less.

Characteristics of trophic transfer of polychlorinated biphenyls in marine organisms in Incheon North Harbor, Korea.

PubMed

Kim, Seung Kyu; Lee, Dong Soo; Oh, Jae Ryong

2002-04-01

The trophic transfer of polychlorinated biphenyls (PCBs) was characterized for zooplankton (primarily Paracalanus spp. and Acartia spp.), pacific oyster (Crassostrea gigas), shore crab (Hemigrapsus penicillatus), and goby (Acanthogobius hasta) in the aquatic system of Incheon North Harbor, Korea. The congener pattern in the species was clearly divided by the main PCB uptake route. Compared with zooplankton and oyster, the fraction of heavier homologues increased in crab and goby that take PCBs from food. Linear relationships were observed between log (fugacity in lipid/fugacity in seawater) and log Kow for all the species. For zooplankton and oyster, such an observation should not be regarded as a true absence of superhydrophobicity, because establishment of equilibrium with seawater was not evident. For crab and goby, the absence of superhydrophobicity was evidenced by the trophic transfer factor that continuously increased with Kow up to 10(7.8). These results suggest that superhydrophobicity might be species specific. The trophic transfer factors and the fugacity levels in the lipid phase indicated that bioaccumulation in crab and goby advanced beyond the level in equilibrium with seawater in the harbor basin.

Integrated fate modeling for exposure assessment of produced water on the Sable Island Bank (Scotian shelf, Canada).

PubMed

Berry, Jody A; Wells, Peter G

2004-10-01

Produced water is the largest waste discharge from the production phase of oil and gas wells. Produced water is a mixture of reservoir formation water and production chemicals from the separation process. This creates a chemical mixture that has several components of toxic concern, ranging from heavy metals to soluble hydrocarbons. Analysis of potential environmental effects from produced water in the Sable Island Bank region (NS, Canada) was conducted using an integrated modeling approach according to the ecological risk assessment framework. A hydrodynamic dispersion model was used to describe the wastewater plume. A second fugacity-based model was used to describe the likely plume partitioning in the local environmental media of water, suspended sediment, biota, and sediment. Results from the integrated modeling showed that the soluble benzene and naphthalene components reach chronic no-effect concentration levels at a distance of 1.0 m from the discharge point. The partition modeling indicated that low persistence was expected because of advection forces caused by tidal currents for the Sable Island Bank system. The exposure assessment for the two soluble hydrocarbon components suggests that the risks of adverse environmental effects from produced water on Sable Island Bank are low.

Exposure to buffer solution alters tendon hydration and mechanics.

PubMed

Safa, Babak N; Meadows, Kyle D; Szczesny, Spencer E; Elliott, Dawn M

2017-08-16

A buffer solution is often used to maintain tissue hydration during mechanical testing. The most commonly used buffer solution is a physiological concentration of phosphate buffered saline (PBS); however, PBS increases the tissue's water content and decreases its tensile stiffness. In addition, solutes from the buffer can diffuse into the tissue and interact with its structure and mechanics. These bathing solution effects can confound the outcome and interpretation of mechanical tests. Potential bathing solution artifacts, including solute diffusion, and their effect on mechanical properties, are not well understood. The objective of this study was to measure the effects of long-term exposure of rat tail tendon fascicles to several concentrations (0.9-25%) of NaCl, sucrose, polyethylene glycol (PEG), and SPEG (NaCl+PEG) solutions on water content, solute diffusion, and mechanical properties. We found that with an increase in solute concentration the apparent water content decreased for all solution types. Solutes diffused into the tissue for NaCl and sucrose, however, no solute diffusion was observed for PEG or SPEG. The mechanical properties changed for both NaCl solutions, in particular after long-term (8h) incubation the modulus and equilibrium stress decreased compared to short-term (15min) for 25% NaCl, and the cross sectional area increased for 0.9% NaCl. However, the mechanical properties were unchanged for both PEG and SPEG except for minor alterations in stress relaxation parameters. This study shows that NaCl and sucrose buffer solutions are not suitable for long-term mechanical tests. We therefore propose using PEG or SPEG as alternative buffer solutions that after long-term incubation can maintain tissue hydration without solute diffusion and produce a consistent mechanical response. Copyright © 2017 Elsevier Ltd. All rights reserved.

Integrating economic and biophysical data in assessing cost-effectiveness of buffer strip placement.

PubMed

Balana, Bedru Babulo; Lago, Manuel; Baggaley, Nikki; Castellazzi, Marie; Sample, James; Stutter, Marc; Slee, Bill; Vinten, Andy

2012-01-01

The European Union Water Framework Directive (WFD) requires Member States to set water quality objectives and identify cost-effective mitigation measures to achieve "good status" in all waters. However, costs and effectiveness of measures vary both within and between catchments, depending on factors such as land use and topography. The aim of this study was to develop a cost-effectiveness analysis framework for integrating estimates of phosphorus (P) losses from land-based sources, potential abatement using riparian buffers, and the economic implications of buffers. Estimates of field-by-field P exports and routing were based on crop risk and field slope classes. Buffer P trapping efficiencies were based on literature metadata analysis. Costs of placing buffers were based on foregone farm gross margins. An integrated optimization model of cost minimization was developed and solved for different P reduction targets to the Rescobie Loch catchment in eastern Scotland. A target mean annual P load reduction of 376 kg to the loch to achieve good status was identified. Assuming all the riparian fields initially have the 2-m buffer strip required by the General Binding Rules (part of the WFD in Scotland), the model gave good predictions of P loads (345-481 kg P). The modeling results show that riparian buffers alone cannot achieve the required P load reduction (up to 54% P can be removed). In the medium P input scenario, average costs vary from £38 to £176 kg P at 10% and 54% P reduction, respectively. The framework demonstrates a useful tool for exploring cost-effective targeting of environmental measures. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

In-situ resource utilization technologies for Mars life support systems.

PubMed

Sridhar, K R; Finn, J E; Kliss, M H

2000-01-01

The atmosphere of Mars has many of the ingredients that can be used to support human exploration missions. It can be "mined" and processed to produce oxygen, buffer gas, and water, resulting in significant savings on mission costs. The use of local materials, called ISRU (for in-situ resource utilization), is clearly an essential strategy for a long-term human presence on Mars from the standpoints of self-sufficiency, safety, and cost. Currently a substantial effort is underway by NASA to develop technologies and designs of chemical plants to make propellants from the Martian atmosphere. Consumables for life support, such as oxygen and water, will probably benefit greatly from this ISRU technology development for propellant production. However, the buffer gas needed to dilute oxygen for breathing is not a product of a propellant production plant. The buffer gas needs on each human Mars mission will probably be in the order of metric tons, primarily due to losses during airlock activity. Buffer gas can be separated, compressed, and purified from the Mars atmosphere. This paper discusses the buffer gas needs for a human mission to Mars and consider architectures for the generation of buffer gas including an option that integrates it to the propellant production plant.

Reducing sedimentation of depressional wetlands in agricultural landscapes

USGS Publications Warehouse

Skagen, S.K.; Melcher, Cynthia; Haukos, D.A.

2008-01-01

Depressional wetlands in agricultural landscapes are easily degraded by sediments and contaminants accumulated from their watersheds. Several best management practices can reduce transport of sediments into wetlands, including the establishment of vegetative buffers. We summarize the sources, transport dynamics, and effect of sediments, nutrients, and contaminants that threaten wetlands and the current knowledge of design and usefulness of grass buffers for protecting isolated wetlands. Buffer effectiveness is dependent on several factors, including vegetation structure, buffer width, attributes of the surrounding watershed (i.e., area, vegetative cover, slope and topography, soil type and structure, soil moisture, amount of herbicides and pesticides applied), and intensity and duration of rain events. To reduce dissolved contaminants from runoff, the water must infiltrate the soil where microbes or other processes can break down or sequester contaminants. But increasing infiltration also diminishes total water volume entering a wetland, which presents threats to wetland hydrology in semi-arid regions. Buffer effectiveness may be enhanced significantly by implementing other best management practices (e.g., conservation tillage, balancing input with nutrient requirements for livestock and crops, precision application of chemicals) in the surrounding watershed to diminish soil erosion and associated contaminant runoff. Buffers require regular maintenance to remove sediment build-up and replace damaged or over-mature vegetation. Further research is needed to establish guidelines for effective buffer width and structure, and such efforts should entail a coordinated, regional, multi-scale, multidisciplinary approach to evaluate buffer effectiveness and impacts. Direct measures in "real-world" systems and field validations of buffer-effectiveness models are crucial next steps in evaluating how grass buffers will impact the abiotic and biotic variables attributes that characterize small, isolated wetlands. ?? 2008 The Society of Wetland Scientists.

Fe-SAPONITE and Chlorite Growth on Stainless Steel in Hydrothermal Engineered Barrier Experiments

NASA Astrophysics Data System (ADS)

Cheshire, M. C.; Caporuscio, F. A.; McCarney, M.

2012-12-01

The United States recently has initiated the Used Fuel Disposition campaign to evaluate various generic geological repositories for the disposal of high-level, spent nuclear fuel within environments ranging from hard-rock, salt/clay, to deep borehole settings. Previous work describing Engineered Barrier Systems (EBS) for repositories focused on low temperature and pressure conditions. The focus of this experimental work is to characterize the stability and alteration of a bentonite-based EBS with different waste container materials in brine at higher heat loads and pressures. All experiments were run at ~150 bar and 125 to 300 C for ~1 month. Unprocessed bentonite from Colony, Wyoming was used in the experiments as the clay buffer material. The redox conditions for each system were buffered along the magnetite-iron oxygen fugacity univariant curve using Fe3O4 and Feo filings. A K-Na-Ca-Cl-based salt solution was chosen to replicate deep groundwater compositions. The experimental mixtures were 1) salt solution-clay; 2) salt solution -clay-304 stainless steel; and 3) salt solution -clay-316 stainless steel with a water/bentonite ratio of ~9. Mineralogy and aqueous geochemistry of each experiment was evaluated to monitor the reactions that took place. No smectite illitization was observed in these reactions. However, it appears that K-smectite was produced, possibly providing a precursor to illitization. It is unclear whether reaction times were sufficient for bentonite illitization at 212 and 300 C or whether conditions conducive to illite formation were obtained. The more notable clay mineral reactions occurred at the stainless steel surfaces. Authigenic chlorite and Fe-saponite grew with their basal planes near perpendicular to the steel plate, forming a 10 - 40 μm thick 'corrosion' layer. Partial dissolution of the steel plates was the likely iron source for chlorite/saponite formation; however, dissolution of the Feo/Fe3O4 may also have acted as an iron source, with the steel plates acting as a substrate for chlorite/saponite growth. Trace amounts of pyrite in the bentonite appeared to have reacted to form H2S gas and pentlandite ((Ni,Fe)8S9). Mineral growth on the waste containers was influenced by the container, buffer, and fluid compositions, in addition to pressure and temperature conditions. No significant mineralogical changes were apparent away from the steel-smectite interface. Results of this research show that the waste container may act as a substrate for mineral growth in response to corrosion. However, it is presently unknown whether chlorite and Fe-saponite will act as passivating agents or whether their presence will facilitate further corrosion of the waste containers. The role of these Fe-rich minerals on the stability of steel canisters at elevated heat loads is currently under investigation. LA-UR-12-23845

The role of water in generating Fe-depletion and the calc-alkaline trend

NASA Astrophysics Data System (ADS)

Zimmer, M. M.; Plank, T.

2006-12-01

Describing a magmatic suite as calc-alkaline (CA) or tholeiitic (TH) is a first order characterization, but existing classification schemes (AFM ternary plots and FeO*/MgO vs. SiO2) may convolute magmatic processes and can result in contradictory classification. The salient feature of TH vs. CA evolution is the extent of Fe enrichment or depletion in the magma. A plot of FeO* vs. MgO provides the most straightforward way to quantify Fe enrichment and to develop models for its origin. We present a new quantitative classification utilizing the FeO*-MgO plot, the tholeiitic index (THI) = Fe3-5/Fe8 (Fe3-5=average FeO* at 3-5 wt% MgO; Fe8=FeO* at 8 wt% MgO). THI of 1.2 indicates 20% FeO* enrichment from a magma's starting composition at Fe8, while THI of 0.8 indicates 20% depletion in FeO*. A magmatic suite is CA if THI is <1, and TH if THI is >1. Arcs range from 0.6 to 1.1, back arc basins from 1.1-1.3, and MORBs are \\ge1.6. This classification allows comparison of magmatic evolution on a global basis, regardless of starting composition, and is useful for quantitative comparison to liquid line of descent models. Hypotheses for generating CA magmas include high water contents, high pressure of crystallization, high oxygen fugacity, and high Mg# andesitic starting compositions. In order to test the control of H2O, we compare the THI to average magmatic water contents from undegassed melt inclusions and glasses (S>1000 ppm or CO2>50 ppm) from twenty-eight arc volcanoes and back arc basins, including new water contents from seven Aleutian volcanoes. The resulting negative correlation (R2=0.8) between water concentration and THI (with end-members at 0.8 wt% H2O, THI =1.3 and 6.1 wt% H2O, THI = 0.6) suggests water plays a fundamental role in generating the CA fractionation trend. MORB data plot off the trend at a higher THI, possibly related to lower oxygen fugacity during melting and/or crystallization. Models using the pMelts program are consistent with experimentally- and observationally-demonstrated effects of water on suppression of plagioclase and early formation of oxides relative to silicates during magma fractionation, and the resulting FeO* depletion with respect to decreasing MgO.

A critical review of measurements of water vapor absorption in the 840 to 1100 cm(-1) spectral region

NASA Technical Reports Server (NTRS)

Grant, William B.

1987-01-01

A set of eleven measurements of the water vapor continuum absorption in the 840 to 1100 sq cm spectral region is reviewed and compared with spectral models maintained by the Air Force Geophysics Laboratory. The measurements were made in four different ways: spectrometer with a White cell, CO2 laser with a White cell, CO2 laser with a spectrophone, and broadband radiation source over a long atmospheric path. Where possible, the data were selected at a water vapor partial pressure of ten torr buffered to 760 torr with N2 or synthetic air and a temperature of between 296 and 300 K. The intercomparison of the data leads to several observations and conclusions. First, there are four sets of laboratory data taken with nitrogen as the buffer gas which generally agree well mutually and with AFGL's HITRAN code. Second, there is one set of laboratory data that shows that using air as the buffer gas gives a few percent decrease in the water vapor continuum compared with using nitrogen as the buffer gas. Third, the atmospheric long-path measurements for water vapor partial pressure below about 12 torr are roughly grouped within 20 percent of the HITRAN values. Fourth, there are three sets of spectrophone data for water vapor in synthetic air which are significantly higher than any of the other measurements. This discrepancy is attributed to the effects of impurity gases in the cell.

Rapid and sensitive analytical method for monitoring of 12 organotin compounds in natural waters.

PubMed

Vahčič, Mitja; Milačič, Radmila; Sčančar, Janez

2011-03-01

A rapid analytical method for the simultaneous determination of 12 different organotin compounds (OTC): methyl-, butyl-, phenyl- and octyl-tins in natural water samples was developed. It comprises of in situ derivatisation (by using NaBEt4) of OTC in salty or fresh water sample matrix adjusted to pH 6 with Tris-citrate buffer, extraction of ethylated OTC into hexane, separation of OTC in organic phase on 15 m GC column and subsequent quantitative determination of separated OTC by ICP-MS. To optimise the pH of ethylation, phosphate, carbonate and Tris-citrate buffer were investigated alternatively to commonly applied sodium acetate - acetic acid buffer. The ethylation yields in Tris-citrate buffer were found to be better for TBT, MOcT and DOcT in comparison to commonly used acetate buffer. Iso-octane and hexane were examined as organic phase for extraction of ethylated OTC. The advantage of hexane was in its ability for quantitative determination of TMeT. GC column of 15 m in length was used for separation of studied OTC under the optimised separation conditions and its performances compared to 30 m column. The analytical method developed enables sensitive simultaneous determination of 12 different OTC and appreciably shortened analysis time in larger series of water samples. LOD's obtained for the newly developed method ranged from 0.05-0.06 ng Sn L-1 for methyl-, 0.11-0.45 ng Sn L-1 for butyl-, 0.11-0.16 ng Sn L-1 for phenyl-, and 0.07-0.10 ng Sn L-1 for octyl-tins. By applying the developed analytical method, marine water samples from the Northern Adriatic Sea containing mainly butyl- and methyl-tin species were analysed to confirm the proposed method's applicability.

Differential effect of buffering agents on the crystallization of gemcitabine hydrochloride in frozen solutions.

PubMed

Patel, Mehulkumar; Munjal, Bhushan; Bansal, Arvind K

2014-08-25

The purpose of this study was to evaluate the differential effect of buffering agents on the crystallization of gemcitabine hydrochloride (GHCl) in frozen solutions. Four buffering agents, viz. citric acid (CA), malic acid (MA), succinic acid (SA) and tartaric acid (TA) were selected and their effect on GHCl crystallization was monitored using standard DSC and low temperature XRD. Onset of GHCl crystallization during heating run in DSC was measured to compare the differential effect of buffering agents. Glass transition temperature (Tg'), unfrozen water content in the freeze concentrate and crystallization propensity of the buffering agents was also determined for mechanistic understanding of the underlying effects. CA and MA inhibited while SA facilitated crystallization of GHCl even at 25 mM concentration. Increasing the concentration enhanced their effect. However, TA inhibited GHCl crystallization at concentrations <100mM and facilitated it at concentrations ≥100 mM. Lyophilization of GHCl with either SA or TA yielded elegant cakes, while CA and MA caused collapse. Tg' failed to explain the inhibitory effects of CA, MA and TA as all buffering agents lowered the Tg' of the system. Differential effect of buffering agents on GHCl crystallization could be explained by consideration of two opposing factors: (i) their own crystallization tendency and (ii) unfrozen water content in the freeze concentrate. In conclusion, it was established that API crystallization in frozen solution is affected by the type and concentration of the buffering agents. Copyright © 2014 Elsevier B.V. All rights reserved.

Assessing the utility of bipolar membranes for use in photoelectrochemical water-splitting cells.

PubMed

Vargas-Barbosa, Nella M; Geise, Geoffrey M; Hickner, Michael A; Mallouk, Thomas E

2014-11-01

Membranes are important in water-splitting solar cells because they prevent crossover of hydrogen and oxygen. Here, bipolar membranes (BPMs) were tested as separators in water electrolysis cells. Steady-state membrane and solution resistances, electrode overpotentials, and pH gradients were measured at current densities relevant to solar photoelectrolysis. Under forward bias conditions, electrodialysis of phosphate buffer ions creates a pH gradient across a BPM. Under reverse bias, the BPM can maintain a constant buffer pH on both sides of the cell, but a large membrane potential develops. Thus, the BPM does not present a viable solution for electrolysis in buffered electrolytes. However, the membrane potential is minimized when the anode and cathode compartments of the cell contain strongly basic and acidic electrolytes, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental Determination of Fe-Mg Interdiffusion Coefficients in Orthopyroxene Using Pulsed Laser Ablation and Nanoscale Thin Films

NASA Astrophysics Data System (ADS)

Ter Heege, J. H.; Dohmen, R.; Becker, H.; Chakraborty, S.

2006-12-01

Fe-Mg interdiffusion in silicate minerals is of interest in petrological studies for determining the closure temperature of geothermometers and for determining cooling rates from compositional profiles. It is also relevant for studies of the physical properties of silicates, such as rheology or electrical conductivity, because knowledge of its dependence on oxygen fugacity can aid in the understanding of point defect chemistry. Compositionally zoned orthopyroxenes are common in meteorites, mantle rocks, lower crustal rocks and a variety of plutonic and volcanic igneous rocks. However, experimental difficulties have precluded direct determination of Fe-Mg diffusion rates in orthopyroxenes so far and the available information comes from (1) Mg tracer diffusion coefficients obtained from isotope tracer studies using enriched ^{25}MgO films [1], (2) calculations of interdiffusion rates based on the (diffusion-controlled) order-disorder kinetics measured in orthopyroxene [2], and (3) indirect estimates from the comparison of diffusion widths in coexisting garnets and olivines, in which Fe-Mg diffusion rates are relatively well known [e.g., 3]. We have directly measured Fe-Mg interdiffusion coefficients parallel to the [001] direction in two natural orthopyroxene single crystals (approximately En95Fs5 and En90Fs10) using diffusion couples consisting of an olivine thin film (Fo30Fa70, typically 20 - 50 nm thick) deposited under vacuum on pre-heated, polished and oriented pyroxene single crystals using a pulsed laser ablation deposition technique. Samples were annealed for 4 - 337 hours at 800 - 1100 °C under atmospheric pressure in a continuous flow of CO + CO2 to control the oxygen fugacity between 10-16 and 10^{-12} bar within the stability field of pyroxene. Film thickness and compositional profiles were measured using Rutherford backscattering Spectroscopy (RBS) on reference and annealed samples, and Fe concentration depth profiles were extracted from the RBS spectra and fitted numerically. At an oxygen fugacity of 10-16 bar, Fe-Mg interdiffusion coefficients in the Fs richer orthopyroxene vary between 4.10^{-22} m2/s and 2.10^{-20} m2/s for temperatures between 800 and 1000°C. Diffusion coefficients decrease by a factor of ~ 4 with decreasing oxygen fugacity between 10^{-12} and 10-16 bar at 1000 °C. Comparison of our data with other Fe-Mg diffusion data shows that these diffusion coefficients are (1) similar to Mg tracer diffusion coefficients measured in orthopyroxene at somewhat more reducing (e.g. fO2 = 10-16 to 10^{-19} bar) conditions at the same temperatures [1], (2) similar to Mg tracer diffusion in garnets measured at higher pressures of 10 kbar at an oxygen fugacity corresponding to the C-O equilibrium in graphite present systems [4], and (3) slower than Fe-Mg diffusion rates in olivine by a factor of ~10 at the same oxygen fugacities [5]. Further experiments to quantify the dependence on composition, temperature and oxygen fugacity are in progress. References: [1] Schwandt et al. (1998), Contr. Mineral. Petrol. 130: 390-396; [2] Ganguly and Tazzoli (1994), Am. Mineral. 79: 930-937; [3] Smith and Barron (1991), Am. Mineral. 76: 1950-1963; [4] Ganguly et al. (1998), Contr. Mineral. Petrol. 131: 171-180; [5] Chakraborty (1997), J. Geoph. Res. 102: 12317-12331.

Experimental crystallization of chrome spinel in FAMOUS basalt 527-1-1

NASA Astrophysics Data System (ADS)

Fisk, Martin R.; Bence, A. E.

1980-06-01

FAMOUS basalt 527-1-1 (a high-Mg oceanic pillow basalt) has three generations of spinel which can be distinguished petrographically and chemically. The first generation (Group I) have reaction coronas and are high in Al 2O 3. The second generation (Group II) have no reaction coronas and are high in Cr 2O 3 and the third generation (Group III) are small, late-stage spinels with intermediate Al 2O 3 and Cr 2O 3. Experimental synthesis of spinels from fused rock powder of this basalt was carried out at temperatures of 1175-1270°C and oxygen fugacities of 10 -5.5 to 10 -10 atm at 1 atm pressure. Spinel is the liquidus phase at oxygen fugacities of 10 -8.5 atm and higher but it does not crystallize at any temperature at oxygen fugacities less than 10 -9.5. The composition of our spinels synthesized at 1230-1250°C and 10 -9 atm f O 2 are most similar to the high-Cr spinels (Group II) found in the rock. Spinels synthesized at 1200°C and 10 -8.5 atm O 2 are chemically similar to the Group III spinels in 527-1-1. We did not synthesize spinel at any temperature or oxygen fugacity that are similar to the high-Al (Group I) spinel found in 527-1-1. These results indicate that the high-Cr (Group II) spinel is the liquidus phase in 527-1-1 at low pressure and Group III spinel crystallize below the liquidus (˜1200°C) after eruption of the basalt on the sea floor. The high-Al spinel (Group I) could have crystallized at high pressure or from a magma enriched in Al and perhaps Mg compared to 527-1-1.

Defining relative humidity in terms of water activity. Part 1: definition

NASA Astrophysics Data System (ADS)

Feistel, Rainer; Lovell-Smith, Jeremy W.

2017-08-01

Relative humidity (RH) is a quantity widely used in various fields such as metrology, meteorology, climatology or engineering. However, RH is neither uniformly defined, nor do some definitions properly account for deviations from ideal-gas properties, nor is the application range of interest fully covered. In this paper, a new full-range definition of RH is proposed that is based on the thermodynamics of activities in order to include deviations from ideal-gas behaviour. Below the critical point of pure water, at pressures p  <  22.064 MPa and temperatures T  <  647.096 K, RH is rigorously defined as the relative activity (or relative fugacity) of water in humid air. For this purpose, reference states of the relative activity are specified appropriately. Asymptotically, the ideal-gas limit of the new definition is consistent with de-facto standard RH definitions published previously and recommended internationally. Virial approximations are reported for estimating small corrections to the ideal-gas equations.

Comparison of adhesive properties of water- and phosphate-buffer-washed cottonseed meals with cottonseed protein isolate on maple and poplar veneers

USDA-ARS?s Scientific Manuscript database

Water- and phosphate buffer (35 mM Na2HPO4/NaH2PO4, pH 7.5)-washed cottonseed meals (abbreviated as WCM and BCM, respectively) could be low-cost and environmentally friendly protein-based adhesives as their preparation does not involve corrosive alkali and acid solutions that are needed for cottonse...

Soil Water Holding Capacity Mitigates Downside Risk and Volatility in US Rainfed Maize: Time to Invest in Soil Organic Matter?

PubMed Central

Williams, Alwyn; Hunter, Mitchell C.; Kammerer, Melanie; Kane, Daniel A.; Jordan, Nicholas R.; Mortensen, David A.; Smith, Richard G.; Snapp, Sieglinde

2016-01-01

Yield stability is fundamental to global food security in the face of climate change, and better strategies are needed for buffering crop yields against increased weather variability. Regional- scale analyses of yield stability can support robust inferences about buffering strategies for widely-grown staple crops, but have not been accomplished. We present a novel analytical approach, synthesizing 2000–2014 data on weather and soil factors to quantify their impact on county-level maize yield stability in four US states that vary widely in these factors (Illinois, Michigan, Minnesota and Pennsylvania). Yield stability is quantified as both ‘downside risk’ (minimum yield potential, MYP) and ‘volatility’ (temporal yield variability). We show that excessive heat and drought decreased mean yields and yield stability, while higher precipitation increased stability. Soil water holding capacity strongly affected yield volatility in all four states, either directly (Minnesota and Pennsylvania) or indirectly, via its effects on MYP (Illinois and Michigan). We infer that factors contributing to soil water holding capacity can help buffer maize yields against variable weather. Given that soil water holding capacity responds (within limits) to agronomic management, our analysis highlights broadly relevant management strategies for buffering crop yields against climate variability, and informs region-specific strategies. PMID:27560666

An approach for using soil surveys to guide the placement of water quality buffers

Treesearch

M.G. Dosskey; M.J. Helmers; D.E. Eisenhauer

2006-01-01

Vegetative buffers may function better for filtering agricultural runoff in some locations than in others because of intrinsic characteristics of the land on which they are placed. The objective of this study was to develop a method based on soil survey attributes that can be used to compare soil map units for how effectively a buffer installed in them could remove...

Significant Reduction in the Incidence of Phlebitis with Buffered Versus Unbuffered Cephalothin

PubMed Central

Bergeron, Michel G.; Brusch, John L.; Barza, Michael; Weinstein, Louis

1976-01-01

Cephalothin (1 g every 2 h), buffered cephalothin, and diluent alone (5% dextrose in water) were each administered for 4 days intravenously to 12 volunteers in a double-blind crossover study. The incidence of phlebitis with buffered cephalothin was significantly lower than that with unbuffered drug (P < 0.01) and almost identical to the incidence with diluent alone. PMID:1267438

Phosphorus sorption and buffering mechanisms in suspended sediments from the Yangtze Estuary and Hangzhou Bay, China

NASA Astrophysics Data System (ADS)

Li, M.; Whelan, M. J.; Wang, G.; White, S. M.

2012-12-01

The adsorption isotherm and the mechanism of the buffering effect are important controls on phosphorus behaviors in estuaries and are important for estimating phosphate concentrations in aquatic environments. In this paper, we derive phosphate adsorption isotherms in order to investigate sediment adsorption and buffering capacity for phosphorus discharged from sewage outfalls in the Yangtze Estuary and Hangzhou Bay near Shanghai, China. Experiments were also carried out at different temperatures in order to explore the buffering effects for phosphate. The results show that P sorption in sediments with low fine particle fractions was best described using exponential equations. Some P interactions between water and sediment may be caused by the precipitation of CaHPO4 from Ca2+ and HPO42- when the phosphate concentration in the liquid phase is high. Results from the buffering experiments suggest that the Zero Equilibrium Phosphate Concentrations (EPC0) vary from 0.014 mg l-1 to 0.061 mg l-1, which are consistent with measured phosphate concentrations in water samples collected at the same time as sediment sampling. Values of EPC0 and linear sorption coefficients (K) in sediments with high fine particle and organic matter contents are relatively high, which implies that they have high buffering capacity. Both EPC0 and K increase with increasing temperature, indicating a higher P buffering capacity at high temperatures.

Phosphorus sorption and buffering mechanisms in suspended sediments from the Yangtze Estuary and Hangzhou Bay, China

NASA Astrophysics Data System (ADS)

Li, M.; Whelan, M. J.; Wang, G. Q.; White, S. M.

2013-05-01

The adsorption isotherm and the mechanism of the buffering effect are important controls on phosphorus (P) behaviors in estuaries and are important for estimating phosphate concentrations in aquatic environments. In this paper, we derive phosphate adsorption isotherms in order to investigate sediment adsorption and buffering capacity for phosphorus discharged from sewage outfalls in the Yangtze Estuary and Hangzhou Bay near Shanghai, China. Experiments were also carried out at different temperatures in order to explore the buffering effects for phosphate. The results show that P sorption in sediments with low fine particle fractions was best described using exponential equations. Some P interactions between water and sediment may be caused by the precipitation of CaHPO4 from Ca2+ and HPO42- when the phosphate concentration in the liquid phase is high. Results from the buffering experiments suggest that the Zero Equilibrium Phosphate Concentrations (EPC0) vary from 0.014 mg L-1 to 0.061 mg L-1, which are consistent with measured phosphate concentrations in water samples collected at the same time as sediment sampling. Values of EPC0 and linear sorption coefficients (K) in sediments with high fine particle and organic matter contents are relatively high, which implies that they have high buffering capacity. Both EPC0 and K increase with increasing temperature, indicating a higher P buffering capacity at high temperatures.

Iodine susceptibility of pseudomonads grown attached to stainless steel surfaces

NASA Technical Reports Server (NTRS)

Pyle, B. H.; McFeters, G. A.

1990-01-01

Pseudomonads were adapted to grow in phosphate-buffered water and on stainless steel surfaces to study the iodine sensitivity of attached and planktonic cells. Cultures adapted to low nutrient growth were incubated at room temperature in a circulating reactor system with stainless steel coupons to allow biofilm formation on the metal surfaces. In some experiments, the reactor was partially emptied and refilled with buffer at each sampling time to simulate a "fill-and-draw" water system. Biofilms of attached bacteria, resuspended biofilm bacteria, and reactor suspension, were exposed to 1 mg l-1 iodine for 2 min. Attached bacterial populations which established on coupons within 3 to 5 days displayed a significant increase in resistance to iodine. Increased resistance was also observed for resuspended cells from the biofilm and planktonic bacteria in the system suspension. Generally, intact biofilms and resuspended biofilm cells were most resistant, followed by planktonic bacteria and phosphate buffer cultures. Thus, biofilm formation on stainless steel surfaces within water systems can result in significantly increased disinfection resistance of commonly-occurring water-borne bacteria that may enhance their ability to colonise water treatment and distribution systems.

EnviroAtlas - Paterson, NJ - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. EnviroAtlas defines tree buffer for this community as only trees and forest. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Paterson, NJ - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. EnviroAtlas defines vegetated buffer for this community as trees and forest and grass and herbaceous. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

Tested Demonstrations.

ERIC Educational Resources Information Center

Gilbert, George L., Ed.

1983-01-01

Discusses a supplement to the "water to rose" demonstration in which a pink color is produced. Also discusses blood buffer demonstrations, including hydrolysis of sodium bicarbonate, simulated blood buffer, metabolic acidosis, natural compensation of metabolic acidosis, metabolic alkalosis, acidosis treatment, and alkalosis treatment. Procedures…

Riparian buffer strips as a multifunctional management tool in agricultural landscapes: introduction.

PubMed

Stutter, Marc I; Chardon, Wim J; Kronvang, Brian

2012-01-01

Catchment riparian areas are considered key zones to target mitigation measures aimed at interrupting the movement of diffuse substances from agricultural land to surface waters. Hence, unfertilized buffer strips have become a widely studied and implemented "edge of field" mitigation measure assumed to provide an effective physical barrier against nitrogen (N), phosphorus (P), and sediment transfer. To ease the legislative process, these buffers are often narrow mandatory strips along streams and rivers, across different riparian soil water conditions, between bordering land uses of differing pollution burdens, and without prescribed buffer management. It would be easy to criticize such regulation for not providing the opportunity for riparian ecosystems to maximize their provision for a wider range of ecosystem goods and services. The scientific basis for judging the best course of action in designing and placing buffers to enhance their multifunctionality has slowly increased over the last five years. This collection of papers aims to add to this body of knowledge by giving examples of studies related to riparian buffer management and assessment throughout Europe. This introductory paper summarizes discussion sessions and 13 selected papers from a workshop held in Ballater, UK, highlighting research on riparian buffers brought together under the EU COST Action 869 knowledge exchange program. The themes addressed are (i) evidence of catchment- to national-scale effectiveness, (ii) ecological functioning linking terrestrial and aquatic habitats, (iii) modeling tools for assessment of effectiveness and costs, and (iv) process understanding enabling management and manipulation to enhance pollutant retention in buffers. The combined understanding led us to consider four principle key questions to challenge buffer strip research and policy. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Theoretical estimation of Photons flow rate Production in quark gluon interaction at high energies

NASA Astrophysics Data System (ADS)

Al-Agealy, Hadi J. M.; Hamza Hussein, Hyder; Mustafa Hussein, Saba

2018-05-01

photons emitted from higher energetic collisions in quark-gluon system have been theoretical studied depending on color quantum theory. A simple model for photons emission at quark-gluon system have been investigated. In this model, we use a quantum consideration which enhances to describing the quark system. The photons current rate are estimation for two system at different fugacity coefficient. We discussion the behavior of photons rate and quark gluon system properties in different photons energies with Boltzmann model. The photons rate depending on anisotropic coefficient : strong constant, photons energy, color number, fugacity parameter, thermal energy and critical energy of system are also discussed.

The electrum-tarnish method for the determination of the fugacity of sulfur in laboratory sulfide systems

USGS Publications Warehouse

Barton, P.B.; Toulmin, P.

1964-01-01

A new method for the determination of the fugacity of sulfur in laboratory systems consists of visual observation of the development and decomposition of a sulfide tarnish phase on silver-gold alloy (electrum) of precisely known composition. The alloy system is calibrated against pure sulfur. The method has the following advantages: simple apparatus; ability to cover a large range of fugacity of S2; ability to cover a large temperature range by permitting runs of long duration; ability to tolerate other components in the gas phase; and ease of recovery of the quenched charges for determinations of phases and compositions. Results obtained by the electrum-tarnish method are in satisfactory agreement with those obtained by other workers for the fs2 vs. T curves for the assemblage Ni(1-x)S + NiS2. The electrum-tarnish method shows promise for investigating many other reactions. Univariant reactions studied by this method can be represented as lines forming a genetic grid in terms of the environmental parameters fs2 and T, The slopes of such lines can yield valuable thermodynamic data for the phases involved, but activity coefficients must be known for phases of variable composition. ?? 1964.

A rapidly equilibrating, thin film, passive water sampler for organic contaminants; characterization and field testing.

PubMed

St George, Tiffany; Vlahos, Penny; Harner, Tom; Helm, Paul; Wilford, Bryony

2011-02-01

Improving methods for assessing the spatial and temporal resolution of organic compound concentrations in marine environments is important to the sustainable management of our coastal systems. Here we evaluate the use of ethylene vinyl acetate (EVA) as a candidate polymer for thin-film passive sampling in waters of marine environments. Log K(EVA-W) partition coefficients correlate well (r(2) = 0.87) with Log K(OW) values for selected pesticides and polychlorinated biphenyls (PCBs) where Log K(EVA-W) = 1.04 Log K(OW) + 0.22. EVA is a suitable polymer for passive sampling due to both its high affinity for organic compounds and its ease of coating at sub-micron film thicknesses on various substrates. Twelve-day field deployments were effective in detecting target compounds with good precision making EVA a potential multi-media fugacity meter. Published by Elsevier Ltd.

[Fast separation and analysis of water-soluble vitamins in spinach by capillary electrophoresis with high voltage].

PubMed

Hu, Xiaoqin; You, Huiyan

2009-11-01

In capillary electrophoresis, 0-40 kV (even higher) voltage can be reached by a connecting double-model high voltage power supply. In the article, water-soluble vitamins, VB1, VB2, VB6, VC, calcium D-pantothenate, D-biotin, nicotinic acid and folic acid in vegetable, were separated by using the high voltage power supply under the condition of electrolyte water solution as running buffer. The separation conditions, such as voltage, the concentration of buffer and pH value etc. , were optimized during the experiments. The results showed that eight water-soluble vitamins could be baseline separated in 2.2 min at 40 kV applied voltage, 25 mmol/L sodium tetraborate buffer solution (pH 8.8). The water-soluble vitamins in spinach were quantified and the results were satisfied. The linear correlation coefficients of the water-soluble vitamins ranged from 0.9981 to 0.9999. The detection limits ranged from 0.2 to 0.3 mg/L. The average recoveries ranged from 88.0% to 100.6% with the relative standard deviations (RSD) range of 1.15%-4.13% for the spinach samples.

Water relations of baobab trees (Adansonia spp. L.) during the rainy season: does stem water buffer daily water deficits?

PubMed

Chapotin, Saharah Moon; Razanameharizaka, Juvet H; Holbrook, N Michele

2006-06-01

Baobab trees are often cited in the literature as water-storing trees, yet few studies have examined this assumption. We assessed the role of stored water in buffering daily water deficits in two species of baobabs (Adansonia rubrostipa Jum. and H. Perrier and Adansonia za Baill.) in a tropical dry forest in Madagascar. We found no lag in the daily onset of sap flow between the base and the crown of the tree. Some night-time sap flow occurred, but this was more consistent with a pattern of seasonal stem water replenishment than with diurnal usage. Intrinsic capacitance of both leaf and stem tissue (0.07-0.08 and 1.1-1.43 MPa(-1), respectively) was high, yet the amount of water that could be withdrawn before turgor loss was small because midday leaf and stem water potentials (WPs) were near the turgor-loss points. Stomatal conductance was high in the daytime but then declined rapidly, suggesting an embolism-avoidance strategy. Although the xylem of distal branches was relatively vulnerable to cavitation (P50: 1.1-1.7 MPa), tight stomatal control and minimum WPs near--1.0 MPa maintained native embolism levels at 30-65%. Stem morphology and anatomy restrict water movement between storage tissues and the conductive pathway, making stored-water usage more appropriate to longer-term water deficits than as a buffer against daily water deficits.

The quantitation of buffering action II. Applications of the formal & general approach.

PubMed

Schmitt, Bernhard M

2005-03-16

The paradigm of "buffering" originated in acid-base physiology, but was subsequently extended to other fields and is now used for a wide and diverse set of phenomena. In the preceding article, we have presented a formal and general approach to the quantitation of buffering action. Here, we use that buffering concept for a systematic treatment of selected classical and other buffering phenomena. H+ buffering by weak acids and "self-buffering" in pure water represent "conservative buffered systems" whose analysis reveals buffering properties that contrast in important aspects from classical textbook descriptions. The buffering of organ perfusion in the face of variable perfusion pressure (also termed "autoregulation") can be treated in terms of "non-conservative buffered systems", the general form of the concept. For the analysis of cytoplasmic Ca++ concentration transients (also termed "muffling"), we develop a related unit that is able to faithfully reflect the time-dependent quantitative aspect of buffering during the pre-steady state period. Steady-state buffering is shown to represent the limiting case of time-dependent muffling, namely for infinitely long time intervals and infinitely small perturbations. Finally, our buffering concept provides a stringent definition of "buffering" on the level of systems and control theory, resulting in four absolute ratio scales for control performance that are suited to measure disturbance rejection and setpoint tracking, and both their static and dynamic aspects. Our concept of buffering provides a powerful mathematical tool for the quantitation of buffering action in all its appearances.

[Indirect and repeated electromagnetic irradiation of extremely high freguency of bacteria Escherichia coli].

PubMed

Isakhanian, V; Trchunian, A

2005-01-01

It has been shown that separate irradiation of distilled water and tris-phosphate buffer containing some inorganic ions, with Escherichia coli K12 grown in anaerobic conditions upon fermentation of sugar (glucose) with "noise" electromagnetic radiation of extremely high frequencies (53.5-68 gHz) or millimeter waves (wavelength of 3 to 8 mm) with low flux capacity (0.01 mW) for 10, 30 and 60 min caused opposite effects, changing the growth of these bacteria. The irradiation of water has a bactericide effect, whereas the irradiation of the buffer stimulates bacterial growth although the buffer itself inhibits the growth. These results point out the role of water in the bactericide action of "noise" electromagnetic radiation of extremely high frequencies, and confirm the significance of membranotropic effects. The bactericide action disappeared after repeated irradiation for 10 and 30 min with 2-h intervals. This indicates the operation of some compensatory mechanisms in bacteria.

Modeling the impact of biota on polychlorinated biphenyls (PCBs) fate and transport in Lake Ontario using a population-based multi-compartment fugacity approach.

PubMed

Sun, Xiangfei; Ng, Carla A; Small, Mitchell J

2018-06-12

Organisms have long been treated as receptors in exposure studies of polychlorinated biphenyls (PCBs) and other persistent organic pollutants (POPs). The influences of environmental pollution on organisms are well recognized. However, the impact of biota on PCB transport in an environmental system has not been considered in sufficient detail. In this study, a population-based multi-compartment fugacity model is developed by reconfiguring the organisms as populated compartments and reconstructing all the exchange processes between the organism compartments and environmental compartments, especially the previously ignored feedback routes from biota to the environment. We evaluate the model performance by simulating the PCB concentration distribution in Lake Ontario using published loading records. The lake system is divided into three environment compartments (air, water, and sediment) and several organism groups according to the dominant local biotic species. The comparison indicates that the simulated results are well-matched by a list of published field measurements from different years. We identify a new process, called Facilitated Biotic Intermedia Transport (FBIT), to describe the enhanced pollution transport that occurs between environmental media and organisms. As the hydrophobicity of PCB congener increases, the organism population exerts greater influence on PCB mass flows. In a high biomass scenario, the model simulation indicates significant FBIT effects and biotic storage effects with hydrophobic PCB congeners, which also lead to significant shifts in systemic contaminant exchange rates between organisms and the environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Does tree harvesting in riparian areas increase stream sedimentation and turbidity - world-wide experience relative to Australia.

NASA Astrophysics Data System (ADS)

Neary, D.; Smethurst, P.; Petrone, K.

2009-04-01

A typical improved-pasture property in the high-rainfall zone of Australia contains 0.5-2.0 km of waterways per 100 ha. Nationwide, some 25-30 million ha of improved pasture contains about 100,000 km of streams, of which about 75% are currently un-buffered and contributing to soil and water degradation. Farmers and natural resource managers are considering ways to enhance environmental outcomes at farm and catchment scales using stream-side buffers of trees and other perennial vegetation. Benefits of buffers include improved water quality, biodiversity, carbon sequestration and aesthetics. Lack of sound information and funding for establishing and managing buffer zones is hindering wide-scale adoption of this practice. Stream-side areas of farms are generally highly productive (wet and nutrient-rich) and contain a high biodiversity, but they are also high-risk zones for soil and water values and stock safety. Development of options based on a balance between environmental and economic outcomes would potentially promote wider adoption. Australian codes of forest practice currently discourage or prevent harvesting of trees in streamside buffers. These codes were developed exclusively for large-scale native forests and industrial-scale plantations, and were applicable to farm forestry as now required. In countries including USA and Germany trees in stream-side buffers are harvested using Best Management Practices. Trees may grow at a faster rate in riparian zones and provide a commercial return, but the impacts of tree establishment and harvesting on water yield and quality must be evaluated. However, there have been few designed experiments investigating this problem. Australia has recently initiated studies to explore the use of high-value timber species and associated vegetation in riparian zones to improve water quality, particularly suspended sediment. Preliminary information from the Yan Yan Gurt Catchment in Victoria indicate that forested riparian strips can retain 98% of the sediment entrained in runoff from agricultural sections of the catchment. This paper examines the science background from North American and European experiences relative to Australia, with particular emphasis on sediment relationships after tree harvesting using Best Management Practices.

Model analysis of riparian buffer effectiveness for reducing nutrient inputs to streams in agricultural landscapes

NASA Astrophysics Data System (ADS)

McKane, R. B.; M, S.; F, P.; Kwiatkowski, B. L.; Rastetter, E. B.

2006-12-01

Federal and state agencies responsible for protecting water quality rely mainly on statistically-based methods to assess and manage risks to the nation's streams, lakes and estuaries. Although statistical approaches provide valuable information on current trends in water quality, process-based simulation models are essential for understanding and forecasting how changes in human activities across complex landscapes impact the transport of nutrients and contaminants to surface waters. To address this need, we developed a broadly applicable, process-based watershed simulator that links a spatially-explicit hydrologic model and a terrestrial biogeochemistry model (MEL). See Stieglitz et al. and Pan et al., this meeting, for details on the design and verification of this simulator. Here we apply the watershed simulator to a generalized agricultural setting to demonstrate its potential for informing policy and management decisions concerning water quality. This demonstration specifically explores the effectiveness of riparian buffers for reducing the transport of nitrogenous fertilizers from agricultural fields to streams. The interaction of hydrologic and biogeochemical processes represented in our simulator allows several important questions to be addressed. (1) For a range of upland fertilization rates, to what extent do riparian buffers reduce nitrogen inputs to streams? (2) How does buffer effectiveness change over time as the plant-soil system approaches N-saturation? (3) How can buffers be managed to increase their effectiveness, e.g., through periodic harvest and replanting? The model results illustrate that, while the answers to these questions depend to some extent on site factors (climatic regime, soil properties and vegetation type), in all cases riparian buffers have a limited capacity to reduce nitrogen inputs to streams where fertilization rates approach those typically used for intensive agriculture (e.g., 200 kg N per ha per year for corn in the U.S.A. Midwestern states). We also discuss how the insights gained from our approach cannot be achieved with modeling tools that are not both spatially explicit and process-based.

30 CFR 816.57 - Hydrologic balance: Activities in or adjacent to perennial or intermittent streams.

Code of Federal Regulations, 2012 CFR

2012-07-01

... or adjacent to perennial or intermittent streams. (a)(1) Buffer requirement. Except as provided in... section 402 or 404 of the Clean Water Act. (b) Exception. The buffer requirement of paragraph (a) of this...

30 CFR 816.57 - Hydrologic balance: Activities in or adjacent to perennial or intermittent streams.

Code of Federal Regulations, 2014 CFR

2014-07-01

... or adjacent to perennial or intermittent streams. (a)(1) Buffer requirement. Except as provided in... section 402 or 404 of the Clean Water Act. (b) Exception. The buffer requirement of paragraph (a) of this...

Effects on radionuclide concentrations by cement/ground-water interactions in support of performance assessment of low-level radioactive waste disposal facilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krupka, K.M.; Serne, R.J.

The US Nuclear Regulatory Commission is developing a technical position document that provides guidance regarding the performance assessment of low-level radioactive waste disposal facilities. This guidance considers the effects that the chemistry of the vault disposal system may have on radionuclide release. The geochemistry of pore waters buffered by cementitious materials in the disposal system will be different from the local ground water. Therefore, the cement-buffered environment needs to be considered within the source term calculations if credit is taken for solubility limits and/or sorption of dissolved radionuclides within disposal units. A literature review was conducted on methods to modelmore » pore-water compositions resulting from reactions with cement, experimental studies of cement/water systems, natural analogue studies of cement and concrete, and radionuclide solubilities experimentally determined in cement pore waters. Based on this review, geochemical modeling was used to calculate maximum concentrations for americium, neptunium, nickel, plutonium, radium, strontium, thorium, and uranium for pore-water compositions buffered by cement and local ground-water. Another literature review was completed on radionuclide sorption behavior onto fresh cement/concrete where the pore water pH will be greater than or equal 10. Based on this review, a database was developed of preferred minimum distribution coefficient values for these radionuclides in cement/concrete environments.« less

30 CFR 817.57 - Hydrologic balance: Surface activities in or adjacent to perennial or intermittent streams.

Code of Federal Regulations, 2014 CFR

2014-07-01

... activities in or adjacent to perennial or intermittent streams. (a)(1) Buffer requirement. Except as provided... section 402 or 404 of the Clean Water Act. (b) Exception. The buffer requirement of paragraph (a) of this...

30 CFR 817.57 - Hydrologic balance: Surface activities in or adjacent to perennial or intermittent streams.

Code of Federal Regulations, 2012 CFR

2012-07-01

... activities in or adjacent to perennial or intermittent streams. (a)(1) Buffer requirement. Except as provided... section 402 or 404 of the Clean Water Act. (b) Exception. The buffer requirement of paragraph (a) of this...

Proton Transfer Dynamics at the Membrane/Water Interface: Dependence on the Fixed and Mobile pH Buffers, on the Size and Form of Membrane Particles, and on the Interfacial Potential Barrier

PubMed Central

Cherepanov, Dmitry A.; Junge, Wolfgang; Mulkidjanian, Armen Y.

2004-01-01

Crossing the membrane/water interface is an indispensable step in the transmembrane proton transfer. Elsewhere we have shown that the low dielectric permittivity of the surface water gives rise to a potential barrier for ions, so that the surface pH can deviate from that in the bulk water at steady operation of proton pumps. Here we addressed the retardation in the pulsed proton transfer across the interface as observed when light-triggered membrane proton pumps ejected or captured protons. By solving the system of diffusion equations we analyzed how the proton relaxation depends on the concentration of mobile pH buffers, on the surface buffer capacity, on the form and size of membrane particles, and on the height of the potential barrier. The fit of experimental data on proton relaxation in chromatophore vesicles from phototropic bacteria and in bacteriorhodopsin-containing membranes yielded estimates for the interfacial potential barrier for H+/OH− ions of ∼120 meV. We analyzed published data on the acceleration of proton equilibration by anionic pH buffers and found that the height of the interfacial barrier correlated with their electric charge ranging from 90 to 120 meV for the singly charged species to >360 meV for the tetra-charged pyranine. PMID:14747306

Photo-degradation behaviour of roseoflavin in some aqueous solutions

NASA Astrophysics Data System (ADS)

Tyagi, A.; Penzkofer, A.; Mathes, T.; Hegemann, P.

2010-03-01

An absorption and emission spectroscopic characterization of roseoflavin (8-dimethylamino-8-demethyl-riboflavin, RoF) in aqueous solutions was carried out. The studies were concentrated on roseoflavin in pH 8 phosphate buffer. Absorption cross-section spectra, fluorescence excitation spectra, fluorescence quantum distributions, fluorescence quantum yields and fluorescence lifetimes were determined. The fluorescence of RoF is quenched by photo-induced intra-molecular charge-transfer at room temperature. The photo-degradation of RoF in un-buffered water, in Tris-HCl buffer, and in phosphate buffer was studied. Phosphate buffer and to a smaller extent Tris buffer catalyse the RoF photo-degradation. Photo-excitation of the primary photoproduct, 8-methylamino-riboflavin (8-MNH-RF), enhanced the RoF degradation by triplet 8-MNH-RF - singlet RoF excitation transfer with subsequent triplet-state RoF degradation.

A VSA-based strategy for placing conservation buffers in agricultural watersheds.

PubMed

Qiu, Zeyuan

2003-09-01

Conservation buffers have the potential to reduce agricultural nonpoint source pollution and improve terrestrial wildlife habitat, landscape biodiversity, flood control, recreation, and aesthetics. Conservation buffers, streamside areas and riparian wetlands are being used or have been proposed to control agricultural nonpoint source pollution. This paper proposes an innovative strategy for placing conservation buffers based on the able source area (VSA) hydrology. VSAs are small, variable but predictable portion of a watershed that regularly contributes to runoff generation. The VSA-based strategy involves the following three steps: first, identifying VSAs in landscapes based on natural characteristics such as hydrology, land use/cover, topography and soils; second, targeting areas within VSAs for conservation buffers; third, refining the size and location of conservation buffers based on other factors such as weather, environmental objectives, available funding and other best management practices. Building conservation buffers in VSAs allows agricultural runoff to more uniformly enter buffers and stay there longer, which increases the buffer's capacity to remove sediments and nutrients. A field-scale example is presented to demonstrate the effectiveness and cost-effectiveness of the within-VSA conservation buffer scenario relative to a typical edge-of-field buffer scenario. The results enhance the understanding of hydrological processes and interactions between agricultural lands and conservation buffers in agricultural landscapes, and provide practical guidance for land resource managers and conservationists who use conservation buffers to improve water quality and amenity values of agricultural landscape.

Testing the Success Rate of Establishing Multitrophic Vegetation for Stream Buffer Mitigation According to Georgia DOT Specifications on Different Slope Ratios

DOT National Transportation Integrated Search

2017-02-01

Multitrophic vegetative mitigation is required for stream buffers, wetlands, and retention basins within state waters. Downslopes adjacent to linear road construction are typically steep, which creates challenges for establishment and erosion control...

EnviroAtlas - Tampa, FL - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Portland, OR - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area.This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (http:/www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Woodbine, Iowa - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area.This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Milwaukee, WI - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Fresno, CA - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Pittsburgh, PA - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Portland, OR - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (http:/www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Tampa, FL - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - New Bedford, MA - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Green Bay, WI - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets ).

EnviroAtlas - Durham, NC - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas ) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets ).

EnviroAtlas - Phoenix, AZ - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Green Bay, WI - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area.This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets ).

EnviroAtlas - New Bedford, MA - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Woodbine, IA - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Fresno, CA - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area.This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Phoenix, AZ - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Portland, ME - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Portland, Maine - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Pittsburgh, PA - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Durham, NC - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas ) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets ).

EnviroAtlas - Milwaukee, WI - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the Atlas Area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

Rhizophoraceae Mangrove Saplings Use Hypocotyl and Leaf Water Storage Capacity to Cope with Soil Water Salinity Changes

PubMed Central

Lechthaler, Silvia; Robert, Elisabeth M. R.; Tonné, Nathalie; Prusova, Alena; Gerkema, Edo; Van As, Henk; Koedam, Nico; Windt, Carel W.

2016-01-01

Some of the most striking features of Rhizophoraceae mangrove saplings are their voluminous cylinder-shaped hypocotyls and thickened leaves. The hypocotyls are known to serve as floats during seed dispersal (hydrochory) and store nutrients that allow the seedling to root and settle. In this study we investigate to what degree the hypocotyls and leaves can serve as water reservoirs once seedlings have settled, helping the plant to buffer the rapid water potential changes that are typical for the mangrove environment. We exposed saplings of two Rhizophoraceae species to three levels of salinity (15, 30, and 0–5‰, in that sequence) while non-invasively monitoring changes in hypocotyl and leaf water content by means of mobile NMR sensors. As a proxy for water content, changes in hypocotyl diameter and leaf thickness were monitored by means of dendrometers. Hypocotyl diameter variations were also monitored in the field on a Rhizophora species. The saplings were able to buffer rapid rhizosphere salinity changes using water stored in hypocotyls and leaves, but the largest water storage capacity was found in the leaves. We conclude that in Rhizophora and Bruguiera the hypocotyl offers the bulk of water buffering capacity during the dispersal phase and directly after settlement when only few leaves are present. As saplings develop more leaves, the significance of the leaves as a water storage organ becomes larger than that of the hypocotyl. PMID:27446125

Evaluating the role of river-floodplain connectivity in providing beneficial hydrologic services in mountain landscapes

NASA Astrophysics Data System (ADS)

Covino, T. P.; Wegener, P.; Weiss, T.; Wohl, E.; Rhoades, C.

2017-12-01

River networks of mountain landscapes tend to be dominated by steep, valley-confined channels that have limited floodplain area and low hydrologic buffering capacity. Interspersed between the narrow segments are wide, low-gradient segments where extensive floodplains, wetlands, and riparian areas can develop. Although they tend to be limited in their frequency relative to the narrow valley segments, the low-gradient, wide portions of mountain channel networks can be particularly important to hydrologic buffering and can be sites of high nutrient retention and ecosystem productivity. Hydrologic buffering along the wide valley segments is dependent on lateral hydrologic connectivity between the river and floodplain, however these connections have been increasingly severed as a result of various land and water management practices. We evaluated the role of river-floodplain connectivity in influencing water, dissolved organic carbon (DOC), and nutrient flux in river networks of the Colorado Rockies. We found that disconnected segments with limited floodplain/riparian area had limited buffering capacity, while connected segments exhibited variable source-sink dynamics as a function of flow. Specifically, connected segments were typically a sink for water, DOC, and nutrients during high flows, and subsequently became a source as flows decreased. Shifts in river-floodplain hydrologic connectivity across flows related to higher and more variable aquatic ecosystem metabolism rates along connected relative to disconnected segments. Our data suggest that lateral hydrologic connectivity in wide valleys can enhance hydrologic and biogeochemical buffering, and promote high rates of aquatic ecosystem metabolism. While hydrologic disconnection in one river-floodplain system is unlikely to influence water resources at larger scales, the cumulative effects of widespread disconnection may be substantial. Because intact river-floodplain (i.e., connected) systems provide numerous hydrologic and ecologic benefits, understanding the dynamics and cumulative effects of disconnection is an important step toward improved water resource and ecosystem management.

A system using solid ceramic oxygen electrolyte cells to measure oxygen fugacities in gas-mixing systems

NASA Technical Reports Server (NTRS)

Williams, R. J.; Mullins, O.

1976-01-01

Details are given for the construction and operation of a 101.3 kN/sq m (1 atmosphere) redox control system. A solid ceramic oxygen electrolyte cell is used to monitor the oxygen fugacity in the furnace. The system consists of a vertical quench, gas mixing furnace with heads designed for mounting the electrolyte cell and with facilities for inserting and removing the samples. The system also contains the high input impedance electronics necessary for measurements, a simplified version of a gas mixing apparatus, and devices for experiments under controlled rates of change relative to temperature and redox state. The calibration and maintenance of the system are discussed.

Experimental Constraints on the Partitioning and Valence of V and Cr in Garnet and Coexisting Glass

NASA Technical Reports Server (NTRS)

Righter, K.; Sutton, S.; Berthet, S.; Newville, M.

2008-01-01

A series of experiments with garnet and coexisting melt have been carried out across a range of oxygen fugacities (near hematite-magnetite (HM) to below the iron-wustite (IW) buffers) at 1.7 GPa to study the partitioning and valence of Cr and V in both phases. Experiments were carried out in a non end loaded piston cylinder apparatus, and the run products were analyzed with electron microprobe and xray absorption near edge structure (XANES) analysis at beamline 13-ID at the Advanced Photon Source of Argonne National Lab. The valence of vanadium and chromium were determined using the position and intensity of the Ka pre-edge peaks, calibrated on a series of Cr and Vbearing standard glasses. This technique has been applied to V and Cr in glasses and V in spinels previously, and in these isotropic phases there are no orientational effects on the XANES spectra (Righter et al., 2006, Amer. Mineral. 91, 1643-1656). We also now demonstrate this to be true for V and Cr in garnet. Also, previous work has shown that V has a higher valence in the glass (or melt) than in the coexisting spinel. This is also true for V in garnet-glass pairs in this study. Vanadium valence in garnets varies from 2.7 below the IW buffer to 3.7 near HM, and for coexisting glass it varies from 3.2 to 4.3. Vanadium valence measured in some natural garnets from mantle localities indicates V in the more reduced range at 2.5. Comparisons will be made between fO2 estimated from V valence and other methods for garnet-bearing mantle samples. In contrast, Cr valence measured in garnet and coexisting glass for all experimental and natural samples is 2.9- 3.0, suggesting that the valence of Cr does not vary within either phase across a large fO2 range. These results demonstrate that while V varies from 2+ to 3+ to 4+ in garnet-melt systems, Cr does not, and this will ultimately affect the partitioning behavior of these two elements in natural systems. Garnet/melt D(Cr) are between 12 and 17 across this range of fO2, whereas D(V) has the highest partition coefficient approx.3, near the IW buffer where the valence of V is almost entirely 3+.

Solubility of gold in oxidized, sulfur-bearing fluids at 500-850 °C and 200-230 MPa: A synthetic fluid inclusion study

NASA Astrophysics Data System (ADS)

Guo, Haihao; Audétat, Andreas; Dolejš, David

2018-02-01

Although Au solubility in magmatic-hydrothermal fluids has been investigated by numerous previous studies, there is a dearth of data on oxidized (log fO2 > FMQ+2.5; FMQ - fayalite-magnetite-quartz buffer), sulfur-bearing fluids such as those that formed porphyry Cu-Au (-Mo) deposits. We performed experiments to constrain the effects of fluid salinity, HCl content, sulfur content, fO2 and temperature on Au solubility in such oxidized, sulfur-bearing fluids. For this purpose, small aliquots of fluids equilibrated with Au metal were trapped at high pressure and temperature in the form of synthetic fluid inclusions in quartz and were subsequently analyzed by LA-ICP-MS. Additionally, Raman spectra were collected from quartz-hosted fluid inclusions at up to 600 °C to help to identify the nature of dissolved gold and sulfur species. Gold solubility was found to be affected most strongly by the HCl content of the fluid, followed by fO2, fluid salinity and temperature. Compared to these factors the sulfur content of the fluid has relatively little influence. At 600 °C and 100 MPa, fluids with geologically realistic HCl contents (∼1.1 wt%) and salinities (7-50 wt% NaClequiv) dissolve ∼1000-3000 ppm Au at oxygen fugacities controlled by the magnetite-hematite buffer. At even more oxidized conditions (three log units above the hematite-magnetite fO2 buffer), HCl-, NaCl- and H2SO4-rich fluids can dissolve up to 5 wt% Au at 800 °C and 200 MPa. The observed Au solubility trends are controlled by HCl0 species in the Na-H-Cl-SO4 fluid and are quantitatively reproduced by existing thermodynamic data for Au-Cl complexes. In all experiments, AuCl0 and AuCl2- species are predicted to occur in comparable although variable concentrations, and account for more than 95% of Au solutes. Natural, high-temperature (>500 °C) brine inclusions from porphyry Cu-Au (-Mo) deposits contain significantly less Au than gold-saturated brines that were synthesized experimentally, implying that the natural brines were Au-undersaturated. Consequently, gold grades in Au-rich porphyries were not controlled by the precipitation of native Au, but rather by factors that caused the precipitation of Au-bearing hydrothermal sulfides such as bornite.

Cullin 5 Expression in the Rat: Cellular and Tissue Distribution, and Changes in Response to Water Deprivation and Hemorrhagic Shock

DTIC Science & Technology

2003-02-28

of Health p53 tumor suppressor PBS phosphate buffered saline PCO2 partial pressure of carbon dioxide PO2 partial pressure of oxygen PCR...buffered saline TTBS tween-20 tris buffered saline TonEBP tonicity-response enhancer binding protein TSNRP TriService Nursing Research Program...growth and metabolism (Hochstrasser, 1995; Deshaies, 1999). Although traditionally seen as no more than a means of eliminating no longer needed

Aqueous solution dispersement of carbon nanotubes

NASA Technical Reports Server (NTRS)

Kim, Jae-Woo (Inventor); Park, Cheol (Inventor); Choi, Sang H. (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

2011-01-01

Carbon nanotubes (CNTs) are dispersed in an aqueous buffer solution consisting of at least 50 weight percent water and a remainder weight percent that includes a buffer material. The buffer material has a molecular structure defined by a first end, a second end, and a middle disposed between the first and second ends. The first end is a cyclic ring with nitrogen and oxygen heteroatomes, the middle is a hydrophobic alkyl chain, and the second end is a charged group.

Method to prevent/mitigate steam explosions in casting pits

DOEpatents

Taleyarkhan, Rusi P.

1996-01-01

Steam explosions can be prevented or mitigated during a metal casting process by the placement of a perforated flooring system in the casting pit. An upward flow of compressed gas through this perforated flooring system is introduced during the casting process to produce a buffer layer between any spilled molten metal and the cooling water in the reservoir. This buffer layer provides a hydrodynamic layer which acts to prevent or mitigate steam explosions resulting from hot, molten metal being spilled into or onto the cooling water.

Pink manganian phengite in a high P/ T meta-conglomerate from northern Syros (Cyclades, Greece)

NASA Astrophysics Data System (ADS)

Altherr, Rainer; Soder, Christian; Panienka, Sandra; Peters, Daniel; Meyer, Hans-Peter

2013-11-01

A new occurrence of Mn-rich rocks was discovered within the high-pressure/low-temperature metamorphic rocks on the Palos peninsula of Syros (Greece). Near the summit of Mount Príonas, a meta-conglomerate consists of calcite (~63 wt%), pink manganian phengite, blue-purple manganian aegirine-jadeite, microcline, albite and quartz. In addition, it contains abundant braunite-rich aggregates (up to ~1.5 cm in diameter) that include hollandite [(Ba0.98-1.02K<0.01Na<0.02Ca<0.03) (Mn{1.02-1.52/3+}Fe{0.38-0.88/3+}Ti0.29-0.92Mn{5.11-5.76/4+})O16], barite and manganian hematite. Due to metamorphic recrystallization and deformation, the contacts between clasts and matrix are blurred and most clasts have lost their identity. In back-scattered electron images, many aegirine-jadeite grains appear patchy and show variable jadeite contents (Jd10-67). These pyroxenes occur in contact with either quartz or albite. Manganian phengite (3.41-3.49 Si per 11 oxygen anions) is of the 3T type and contains 1.4-2.2 wt% of Mn2O3. At the known P- T conditions of high-pressure metamorphism on Syros (~1.4 GPa/ 470 °C), the mineral sub-assemblage braunite + quartz + calcite (former aragonite) suggests high oxygen fugacities relative to the HM buffer (+7 ≤ ΔfO2 ≤ + 17) and relatively high CO2 fugacities. The exact origin of the conglomerate is not known, but it is assumed that the Fe-Mn-rich and the calcite-rich particles originated from different sources. Braunite has rather low contents of Cu (~0.19 wt%) and the concentrations of Co, Ni and Zn are less than 0.09 wt%. Hollandite shows even lower concentrations of these elements. Furthermore, the bulk-rock compositions of two samples are characterized by low contents of Cu, Co and Ni, suggesting a hydrothermal origin of the manganese ore. Most likely, these Fe-Mn-Si oxyhydroxide deposits consisted of ferrihydrite, todorokite, birnessite, amorphous silica (opal-A) and nontronite. Al/(Al + Fe + Mn) ratios of 0.355 and 0.600 suggest the presence of an aluminosilicate detrital component.

Monazite, iron oxide and barite exsolutions in apatite aggregates from CCSD drillhole eclogites and their geological implications

NASA Astrophysics Data System (ADS)

Sun, Xiaoming; Tang, Qian; Sun, Weidong; Xu, Li; Zhai, Wei; Liang, Jinlong; Liang, Yeheng; Shen, Kun; Zhang, Zeming; Zhou, Bing; Wang, Fangyue

2007-06-01

We have identified abundant exsolutions in apatite aggregates from eclogitic drillhole samples of the Chinese Continental Scientific Drilling (CCSD) project. Electron microscope and laser Raman spectroscopy analyses show that the apatite is fluorapatite, whereas exsolutions that can be classified into four types: (A) platy to rhombic monazite exsolutions; (B) needle-like hematite exsolutions; (C) irregular magnetite and hematite intergrowths; and (D) needle-like strontian barite exsolutions. The widths and lengths of type A monazite exsolutions range from about 6-10 μm (mostly 6 μm) and about 50-75 μm, respectively. Type B exsolutions are parallel with the C axis of apatite, with widths ranging from 0.5 to 2 μm, with most around 1.5 μm, and lengths that vary dramatically from 6 to 50 μm. Type C exsolutions are also parallel with the C axis of apatite, with lengths of ˜30-150 μm and widths of ˜10 to 50 μm. Type D strontian barite exsolutions coexist mostly with type B hematite exsolutions, with widths of about 9 μm and lengths of about 60-70 μm. Exsolutions of types B, C and D have never been reported in apatites before. Most of the exsolutions are parallel with the C axis of apatite, implying that they were probably exsolved at roughly the same time. Dating by the chemical Th-U-total Pb isochron method (CHIME) yields an U-Pb isochron age of 202 ± 28 Ma for monazite exsolutions, suggesting that these exsolutions were formed during recrystallization and retrograde metamorphism of the exhumed ultrahigh pressure (UHP) rocks. Quartz veins hosting apatite aggregates were probably formed slightly earlier than 202 Ma. Abundant hematite exsolutions, as well as coexistence of magnetite/hematite and barite/hematite in the apatite, suggest that the oxygen fugacity of apatite aggregates is well above the sulfide-sulfur oxide buffer (SSO). Given that quartz veins host these apatite aggregates, they were probably deposited from SiO 2-rich hydrous fluids formed during retrogression of the subducted slab. Such SiO 2-rich hydrous fluids may act as an oxidizing agent, a feasible explanation for the high oxygen fugacity in convergent margin systems.

Macrophyte and pH buffering updates to the Klamath River water-quality model upstream of Keno Dam, Oregon

USGS Publications Warehouse

Sullivan, Annett B.; Rounds, Stewart A.; Asbill-Case, Jessica R.; Deas, Michael L.

2013-01-01

A hydrodynamic, water temperature, and water-quality model of the Link River to Keno Dam reach of the upper Klamath River was updated to account for macrophytes and enhanced pH buffering from dissolved organic matter, ammonia, and orthophosphorus. Macrophytes had been observed in this reach by field personnel, so macrophyte field data were collected in summer and fall (June-October) 2011 to provide a dataset to guide the inclusion of macrophytes in the model. Three types of macrophytes were most common: pondweed (Potamogeton species), coontail (Ceratophyllum demersum), and common waterweed (Elodea canadensis). Pondweed was found throughout the Link River to Keno Dam reach in early summer with densities declining by mid-summer and fall. Coontail and common waterweed were more common in the lower reach near Keno Dam and were at highest density in summer. All species were most dense in shallow water (less than 2 meters deep) near shore. The highest estimated dry weight biomass for any sample during the study was 202 grams per square meter for coontail in August. Guided by field results, three macrophyte groups were incorporated into the CE-QUAL-W2 model for calendar years 2006-09. The CE-QUAL-W2 model code was adjusted to allow the user to initialize macrophyte populations spatially across the model grid. The default CE-QUAL-W2 model includes pH buffering by carbonates, but does not include pH buffering by organic matter, ammonia, or orthophosphorus. These three constituents, especially dissolved organic matter, are present in the upper Klamath River at concentrations that provide substantial pH buffering capacity. In this study, CE-QUAL-W2 was updated to include this enhanced buffering capacity in the simulation of pH. Acid dissociation constants for ammonium and phosphoric acid were taken from the literature. For dissolved organic matter, the number of organic acid groups and each group's acid dissociation constant (Ka) and site density (moles of sites per mole of carbon) were derived by fitting a theoretical buffering response to measured upper Klamath River alkalinity titration curves. The organic matter buffering in the Klamath River was modeled with two monoprotic organic acids: carboxylic acids with a mean pKa of 5.584 and site density of 0.1925, and phenolic organic acids with a mean pKa of 9.594 and site density of 0.6466. Total inorganic carbon concentrations in the model boundary inputs were recalculated based on the new buffering equations. CE-QUAL-W2 was also adjusted to allow the simulation of nonconservative alkalinity caused by nitrification, denitrification, photosynthesis, and respiration. The Klamath River model was recalibrated after the macrophyte and pH buffering updates producing improved predictions for pH, dissolved oxygen, and particulate carbon.

RIPARIAN BUFFER WIDTH, VEGETATIVE COVER, AND NITROGEN REMOVAL EFFECTIVENESS: A REVIEW OF CURRENT SCIENCE AND REGULATIONS

EPA Science Inventory

Riparian zones, the vegetated region adjacent to streams and wetlands, are thought to be effective at intercepting and controlling nitrogen loads entering water bodies. Buffer width may be positively related to nitrogen removal efficiency by influencing nitrogen retention throug...

Soil quality indicator responses to row crop, grazed pasture, and agroforestry buffer management

USDA-ARS?s Scientific Manuscript database

Incorporation of trees and establishment of grass buffers within agroecosystems are management practices shown to enhance soil quality. Soil enzyme activities and water stable aggregates (WSA) have been identified as sensitive soil quality indicators to evaluate early responses to soil management. ...

Identifying Riparian Buffer Effects on Stream 1 Nitrogen in Southeastern Coastal Plain Watersheds

EPA Science Inventory

Riparian areas have long demonstrated their ability to attenuate nutrients and sediments from agricultural runoff at the field scale; however, to inform effective nutrient management choices, the impact of riparian buffers on water quality services must be assessed at watershed s...

Connecting Seasonal Riparian Buffer Metrics and Nitrogen Concentrations in a Pulse-Driven Agricultural System

EPA Science Inventory

Riparian buffers have been well studied as best management practices for nutrient reduction at field scales yet their effectiveness for bettering water quality at watershed scales has been difficult to determine. Seasonal dynamics of the stream network are often overlooked when ...

APEX Model Simulation for Row Crop Watersheds with Agroforestry and Grass Buffers

USDA-ARS?s Scientific Manuscript database

Watershed model simulation has become an important tool in studying ways and means to reduce transport of agricultural pollutants. Conducting field experiments to assess buffer influences on water quality are constrained by the large-scale nature of watersheds, high experimental costs, private owner...

Diffusivities of Redox-Sensitive Elements in Basalt vs. Oxygen Fugacity Determined by LA-ICP-MS

NASA Technical Reports Server (NTRS)

Szumila, Ian; Danielson, Lisa; Trail, Dustin

2017-01-01

Several diffusion experiments were conducted in a piston cylinder device across a range of oxygen fugacities (FMQ-3 FMQ-1.2, FMQ+6) at 1 GPa and 1300 C. This was done to explore the effects of oxygen fugacity (fO2) on diffusivity of redox sensitive trace elements. This allows investigation of how these elements diffuse across the fO2 range encountered in different reservoirs on planets and moons in our solar system. The University of Rochester LA-ICP-MS system was used for analysis of samples. Analyses were conducted using an Agilent 7900 quadrupole mass spectrometer connected to a Photon Machines 193 nm G2 laser ablation (LA) system equipped with a HelEx 2-volume sample chamber. Spots used were 35 micrometers circles spaced at 65 micrometers intervals. Laser fluence was 7.81 J/cm^2 with a rep rate of 10 Hz. The iolite software package was used to reduce data collected from laser ablation analysis of experiments with Si-29 used as the internal standard isotope. Iolite's global fit module was used to simultaneously fit elements' diffusivities in each experiment while keeping the Matano interface constant. Elements analysed include V, Nb, W, Mo, La, Ce, Pr, Sm, Eu, Gd, Ta, and W. Figures

Pressure effect on Fe3+/FeT in silicate melts and applications to magma redox, particularly in magma oceans

NASA Astrophysics Data System (ADS)

Zhang, H.; Hirschmann, M. M.

2014-12-01

The proportions of Fe3+ and Fe2+ in magmas reflect the redox conditions of their origin and influence the chemical and physical properties of natural silicate liquids, but the relationship between Fe3+/FeT and oxygen fugacity depends on pressure owing to different molar volumes and compressibilities of Fe3+ and Fe2+ in silicates. An important case where the effect of pressure effect may be important is in magma oceans, where well mixed (and therefore potentially uniform Fe3+/FeT) experiencses a wide range of pressures, and therefore can impart different ƒO2 at different depths, influencing magma ocean degassing and early atmospheres, as well as chemical gradients within magma oceans. To investigate the effect of pressure on magmatic Fe3+/FeT we conducted high pressure expeirments on ƒO2-buffered andestic liquids. Quenched glasses were analyzed by Mössbauer spectroscopy. To verify the accuracy of Mössbauer determinations of Fe3+/FeT in glasses, we also conducted low temperature Mössbauer studies to determine differences in the recoilless fraction (ƒ) of Fe2+ and Fe3. These indicate that room temperature Mössbauer determinations of on Fe3+/FeT glasses are systematically high by 4% compared to recoilless-fraction corrected ratios. Up to 7 GPa, pressure decreases Fe3+/FeT, at fixed ƒO2 relative to metal-oxide buffers, meaning that an isochemical magma will become more reduced with decreasing pressure. Consequently, for small planetary bodies such as the Moon or Mercury, atmospheres overlying their MO will be highly reducing, consisting chiefly of H2 and CO. The same may also be true for Mars. The trend may reverse at higher pressure, as is the case for solid peridotite, and so for Earth, Venus, and possibly Mars, more oxidized atmospheres above MO are possible. Diamond anvil experiments are underway to examine this hypothesis.

Nuclear Repository steel canister: experimental corrosion rates

NASA Astrophysics Data System (ADS)

Caporuscio, F.; Norskog, K.

2017-12-01

The U.S. Spent Fuel & Waste Science & Technology campaign evaluates various generic geological repositories for the disposal of spent nuclear fuel. This experimental work analyzed and characterized the canister corrosion and steel interface mineralogy of bentonite-based EBS 304 stainless steel (SS), 316 SS, and low-carbon steel coupons in brine at higher heat loads and pressures. Experiments contrasted EBS with and without an argillite wall rock. Unprocessed bentonite from Colony, Wyoming simulated the clay buffer and Opalinus Clay represented the wall rock. Redox conditions were buffered at the magnetite-iron oxygen fugacity univariant curve. A K-Na-Ca-Cl-based brine was chosen to replicate generic granitic groundwater compositions, while Opalinous Clay groundwater was used in the wall rock series of experiments. Most experiments were run at 150 bar and 300°C for 4 to 6 weeks and one was held at elevated conditions for 6 months. The two major experimental mixtures were 1) brine-bentonite clay- steel, and 2) brine-bentonite clay-Opalinus Clay-steel. Both systems were equilibrated at a high liquid/clay ratio. Mineralogy and aqueous geochemistry of each experiment were evaluated to monitor the reactions that took place. In total 4291 measurements were obtained: 2500 measured steel corrosion depths and 1791 were of phyllosilicate mineral reactions/growths at the interface. The low carbon steel corrosion mechanism was via pit corrosion, while 304 SS and 316 SS were by general corrosion. The low carbon steel corrosion rate (1.95 μm/day) was most rapid. The 304 SS corrosion rate (0.37 μm/day) was slightly accelerated versus the 316 SS corrosion rate (0.26 μm/day). Note that the six month 316 SS experiment shows inhibited corrosion rates (0.07 μm/day). This may be in part due to mantling by the Fe-saponite/chlorite authigenic minerals. All phyllosilicate growth rates at the interface exhibit similar growth rate patterns to the steels (i.e. LCS>304>316> 316 six month).

Solubility of water in lunar basalt at low pH2O

NASA Astrophysics Data System (ADS)

Newcombe, M. E.; Brett, A.; Beckett, J. R.; Baker, M. B.; Newman, S.; Guan, Y.; Eiler, J. M.; Stolper, E. M.

2017-03-01

We report the solubility of water in Apollo 15 basaltic "Yellow Glass" and an iron-free basaltic analog composition at 1 atm and 1350 °C. We equilibrated melts in a 1-atm furnace with flowing H2/CO2 gas mixtures that spanned ∼8 orders of magnitude in fO2 (from three orders of magnitude more reducing than the iron-wüstite buffer, IW-3.0, to IW+4.8) and ∼4 orders of magnitude in pH2/pH2O (from 0.003 to 24). Based on Fourier transform infrared spectroscopy (FTIR), our quenched experimental glasses contain 69-425 ppm total water (by weight). Our results demonstrate that under the conditions of our experiments: (1) hydroxyl is the only H-bearing species detected by FTIR; (2) the solubility of water is proportional to the square root of pH2O in the furnace atmosphere and is independent of fO2 and pH2/pH2O; (3) the solubility of water is very similar in both melt compositions; (4) the concentration of H2 in our iron-free experiments is <∼4 ppm, even at oxygen fugacities as low as IW-2.3 and pH2/pH2O as high as 11; (5) Secondary ion mass spectrometry (SIMS) analyses of water in iron-rich glasses equilibrated under variable fO2 conditions may be strongly influenced by matrix effects, even when the concentration of water in the glasses is low; and (6) Our results can be used to constrain the entrapment pressure of lunar melt inclusions and the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads. We find that the most water-rich melt inclusion of Hauri et al. (2011) would be in equilibrium with a vapor with pH2O ∼ 3 bar and pH2 ∼ 8 bar. We constrain the partial pressures of water and molecular hydrogen in the carrier gas of the lunar pyroclastic glass beads to be 0.0005 bar and 0.0011 bar respectively. We calculate that batch degassing of lunar magmas containing initial volatile contents of 1200 ppm H2O (dissolved primarily as hydroxyl) and 4-64 ppm C would produce enough vapor to reach the critical vapor volume fraction thought to be required for magma fragmentation (∼65-75 vol.%) at a total pressure of ∼5 bar (corresponding to a depth beneath the lunar surface of ∼120 m). At a fragmentation pressure of ∼5 bar, the calculated vapor composition is dominated by H2, supporting the hypothesis that H2, rather than CO, was the primary propellant of the lunar fire fountain eruptions. The results of our batch degassing model suggest that initial melt compositions with >∼200 ppm C would be required for the vapor composition to be dominated by CO rather than H2 at 65-75% vesicularity.

Fit-for-purpose phosphorus management: do riparian buffers qualify in catchments with sandy soils?

PubMed

Weaver, David; Summers, Robert

2014-05-01

Hillslope runoff and leaching studies, catchment-scale water quality measurements and P retention and release characteristics of stream bank and catchment soils were used to better understand reasons behind the reported ineffectiveness of riparian buffers for phosphorus (P) management in catchments with sandy soils from south-west Western Australia (WA). Catchment-scale water quality measurements of 60 % particulate P (PP) suggest that riparian buffers should improve water quality; however, runoff and leaching studies show 20 times more water and 2 to 3 orders of magnitude more P are transported through leaching than runoff processes. The ratio of filterable reactive P (FRP) to total P (TP) in surface runoff from the plots was 60 %, and when combined with leachate, 96 to 99 % of P lost from hillslopes was FRP, in contrast with 40 % measured as FRP at the large catchment scale. Measurements of the P retention and release characteristics of catchment soils (<2 mm) compared with stream bank soil (<2 mm) and the <75-μm fraction of stream bank soils suggest that catchment soils contain more P, are more P saturated and are significantly more likely to deliver FRP and TP in excess of water quality targets than stream bank soils. Stream bank soils are much more likely to retain P than contribute P to streams, and the in-stream mixing of FRP from the landscape with particulates from stream banks or stream beds is a potential mechanism to explain the change in P form from hillslopes (96 to 99 % FRP) to large catchments (40 % FRP). When considered in the context of previous work reporting that riparian buffers were ineffective for P management in this environment, these studies reinforce the notion that (1) riparian buffers are unlikely to provide fit-for-purpose P management in catchments with sandy soils, (2) most P delivered to streams in sandy soil catchments is FRP and travels via subsurface and leaching pathways and (3) large catchment-scale water quality measurements are not good indicators of hillslope P mobilisation and transport processes.

Evaluation of sequential extraction procedures for soluble and insoluble hexavalent chromium compounds in workplace air samples.

PubMed

Ashley, Kevin; Applegate, Gregory T; Marcy, A Dale; Drake, Pamela L; Pierce, Paul A; Carabin, Nathalie; Demange, Martine

2009-02-01

Because toxicities may differ for Cr(VI) compounds of varying solubility, some countries and organizations have promulgated different occupational exposure limits (OELs) for soluble and insoluble hexavalent chromium (Cr(VI)) compounds, and analytical methods are needed to determine these species in workplace air samples. To address this need, international standard methods ASTM D6832 and ISO 16740 have been published that describe sequential extraction techniques for soluble and insoluble Cr(VI) in samples collected from occupational settings. However, no published performance data were previously available for these Cr(VI) sequential extraction procedures. In this work, the sequential extraction methods outlined in the relevant international standards were investigated. The procedures tested involved the use of either deionized water or an ammonium sulfate/ammonium hydroxide buffer solution to target soluble Cr(VI) species. This was followed by extraction in a sodium carbonate/sodium hydroxide buffer solution to dissolve insoluble Cr(VI) compounds. Three-step sequential extraction with (1) water, (2) sulfate buffer and (3) carbonate buffer was also investigated. Sequential extractions were carried out on spiked samples of soluble, sparingly soluble and insoluble Cr(VI) compounds, and analyses were then generally carried out by using the diphenylcarbazide method. Similar experiments were performed on paint pigment samples and on airborne particulate filter samples collected from stainless steel welding. Potential interferences from soluble and insoluble Cr(III) compounds, as well as from Fe(II), were investigated. Interferences from Cr(III) species were generally absent, while the presence of Fe(II) resulted in low Cr(VI) recoveries. Two-step sequential extraction of spiked samples with (first) either water or sulfate buffer, and then carbonate buffer, yielded quantitative recoveries of soluble Cr(VI) and insoluble Cr(VI), respectively. Three-step sequential extraction gave excessively high recoveries of soluble Cr(VI), low recoveries of sparingly soluble Cr(VI), and quantitative recoveries of insoluble Cr(VI). Experiments on paint pigment samples using two-step extraction with water and carbonate buffer yielded varying percentages of relative fractions of soluble and insoluble Cr(VI). Sequential extractions of stainless steel welding fume air filter samples demonstrated the predominance of soluble Cr(VI) compounds in such samples. The performance data obtained in this work support the Cr(VI) sequential extraction procedures described in the international standards.

Approaching Mars-like geochemical conditions in the laboratory: omission of artificial buffers and reductants in a study of biogenic methane production on a smectite clay.

PubMed

Chastain, Brendon K; Kral, Timothy A

2010-11-01

Methanogens have not been shown to metabolize in conditions exactly analogous to those present in Mars' subsurface. In typical studies of methanogenic metabolism, nutrient-rich buffered media and reducing agents are added to the cultures in an attempt to optimize the environment for methanogen survival and growth. To study methanogens in more Mars-relevant laboratory conditions, efforts should be made to eliminate artificial media, buffers, and reducing agents from investigations of methanogenic metabolism. After preliminary work to compare methanogen viability on montmorillonite clay and JSC Mars-1 regolith simulant, a study was conducted to determine whether biological methanogenesis could occur in non-reduced, non-buffered environments containing only H(2), CO(2), montmorillonite, and the liquid fraction extracted from a montmorillonite/deionized water suspension. Biogenic methane was observed in the microenvironments despite the omission of traditional media, buffers, and reducing agents. Mean headspace methane concentration after 96 days of observation was 10.23% ± 0.64% (% vol ± SEM, n = 4). However, methane production was severely decreased with respect to reduced, buffered microenvironments (Day 28: 31.98% ± 0.19%, n = 3). Analysis of results and comparison to previous work indicate that montmorillonite clay has a strong ability to supply micronutrients necessary for methanogenic metabolism, and the liquid fraction from a montmorillonite/deionized water slurry can successfully be used as an alternative to reduced and buffered nutritive media in Mars-relevant studies of methanogenic metabolism.

Solubility of tungsten in a haplobasaltic melt as a function of temperature and oxygen fugacity

NASA Astrophysics Data System (ADS)

Ertel, W.; O'Neill, H. St. C.; Dingwell, D. B.; Spettel, B.

1996-04-01

The solubility of tungsten (W) in a haplobasaltic melt has been determined as a function of oxygen fugacity in the temperature range 1300-1500°C using the mechanically assisted equilibrium technique of Dingwell et al. (1994), and at 1600-1700°C by the wire loop method. Quenched samples were analysed for W by using ICP-AES as well as INAA, and sample major element compositions were checked by electron microprobe. W concentrations ranged from 20 ppm to 17 wt%, and the solution of WO 2 in the melt may be described by Henry's Law up to remarkably high concentrations (e.g., 14 wt% at 1500°C). W dissolves in the melt with a quadrivalent (4+) formal oxidation state over the entire range of oxygen fugacity and temperature investigated. The solubility of W decreases strongly with increasing temperature at constant oxygen fugacity. The solubility data have been used to calculate trace distribution coefficients for W between Fe-rich metal and silicate melt, using literature values for the activity coefficient of W in liquid Fe. Comparison of our data with the distribution coefficients for Mo calculated from the analogous Mo solubility data of Holzheid et al. (1994) shows that the ratio of the metal-silicate distribution coefficient DMomet/sil/ DWmet/sil remains very high (~10 3) at all T-fO 2 conditions. However, in the Earth's mantle, Mo is relatively more depleted than W only by a factor of three. The relative abundances of W and Mo in the Earth's mantle cannot, therefore, be explained by core formation from a homogeneously accreted Earth whatever the temperature at which metal/silicate equilibrium may have ocurred might have been. Their abundances may be quantitatively accounted for by a heterogeneous accretion model such as that of O'Neill (1991).

Alteration of Al-rich inclusions inside amoeboid olivine aggregates in the Allende meteorite

NASA Technical Reports Server (NTRS)

Hashimoto, Akihiko; Grossman, Lawrence

1987-01-01

The primary phases of Al-rich inclusions in amoeboid olivine aggregates have undergone alteration reactions with the solar nebular gas. The simplest interpretation of the present observations is that melilite was the first primary phase to disappear with falling temperature, and was replaced by grossular + anorthite + feldspathoids, followed by fassaite; spinel was the last phase to be altered. Thermodynamic calculations suggest that Na-rich phlogopite could have formed at about 470 K and chlorite at about 328 K at a water fugacity of 0.000001, which is that of a gas of solar composition in this temperature range. The olivine around Al-rich inclusions is not serpentized, indicating the cessation of gas-solid equilibrium above 274 K.

Biomagnification of organochlorines in Lake Erie white bass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, R.W.; Lazar, R.; Haffner, G.D.

1995-04-01

Biomagnification of HCB and PCBs was measured in a natural fish population of white bass (Morone chrysops) and their prey, emerald shiner (Notropis atherinoides). It was observed that biomagnification occurred only for chemicals with an octanol/water partition coefficient (log K{sub ow}) greater than 6.1. Hexachlorobenzene and PCB 52 did not biomagnify while PCBs 87, 138, and 180 showed significant biomagnification in Lake Erie white bass. Biomagnification factors increased proportionately with K{sub ow}, and it was concluded that high K{sub ow} chemicals were more important in the biomagnification process. Lipid proportions and chemical concentrations in prey fish (emerald shiner) and whitemore » bass intestinal contents were consistent with a fugacity model of chemical assimilation from food.« less

APEX model simulation of edge-of-field water quality benefits from upland buffers

USDA-ARS?s Scientific Manuscript database

For maximum usefulness, simulation models must be able to estimate the effectiveness of management practices not represented in the dataset used for model calibration. This study focuses on the ability of the Agricultural Policy Environmental eXtender (APEX) to simulate upland buffer effectiveness f...

Effects of thinning on transpiration by riparian buffer trees in response to advection and solar radiation

USDA-ARS?s Scientific Manuscript database

Advective energy occurring in edge environments may increase tree water use. In humid agricultural landscapes, advection-enhanced transpiration in riparian buffers may provide hydrologic regulation; however, research in humid environments is lacking. The objectives of this study were to determine ho...

Effects of thinning on transpiration by riparian buffer trees in response to advection and solar radiation

USDA-ARS?s Scientific Manuscript database

Advective energy occurring in edge environments may increase tree water use (e.g., latent heat loss, LE > net radiation, Rn). In humid agricultural landscapes, advection-enhanced transpiration in riparian buffers may provide hydrologic regulation and flood control benefits; however, research in humi...

Soil quality parameters for row-crop and grazed pasture systems with agroforestry buffers

USDA-ARS?s Scientific Manuscript database

Incorporation of trees and establishment of buffers are practices that can improve soil quality. Soil enzyme activities and water stable aggregates are sensitive indices for assessing soil quality by detecting early changes in soil management. However, studies comparing grazed pasture and row crop...

RIPARIAN BUFFER WIDTH, VEGETATIVE COVER, AND NITROGEN REMOVAL EFFECTIVENESS: A REVIEW OF CURRENT SCIENCE AND REGULATIONS

EPA Science Inventory

Riparian zones, the vegetated region adjacent to streams and wetlands, are thought to be effective at intercepting and controlling nitrogen loads entering water bodies. Buffer width may be related to nitrogen removal efficiency by influencing nitrogen retention through plant seq...

Nitrous Oxide Emissions from Riparian Forest Buffers, Warm-Season and Cool-Season Grass Filters, and Crop Fields

USDA-ARS?s Scientific Manuscript database

Increasing denitrification rates in riparian buffers may be trading the problem of nonpoint source (NPS) pollution of surface waters for atmospheric deterioration and increased global warming potential because denitrification produces nitrous oxide (N2O), a greenhouse gas also involved in stratosphe...

Storage and recycling of water and carbon dioxide in the earth

NASA Technical Reports Server (NTRS)

Wood, Bernard J.

1994-01-01

The stabilities and properties of water- and carbon-bearing phases in the earth have been determined from phase equilibrium measurements, combined with new data on the equations of state of water, carbon dioxide, carbonates and hydrates. The data have then been used to predict the fate of calcite and hydrous phases in subducting oceanic lithosphere. From the compositions of MORB's one can estimate concentrations of water and carbon of around 200 ppm and 80 ppm respectively in the upper mantle. Lower mantle estimates are very uncertain, but 1900 ppm water and 2000 ppm C are plausible concentrations. Measurements of the density of supercritical water to 3 GPa demonstrate that this phase is less compressible than anticipated from the equations of state of Haar et al. or Saul and Wagner and is closer to predictions based on molecular dynamics simulations. Conversely, fugacity measurements on carbon dioxide to 7 GPa show that this fluid is more compressible than predicted from the MRK equation of state. The results imply that hydrates are relatively more stable and carbonates less stable at pressures greater than 5 GPa than would be predicted from simple extrapolation of the low pressure data. Nevertheless, carbonates remain extremely refractory phases within both the upper and lower mantle.

A Polygenetic Origin for some Oceanic Lithosphere: Evidence from Forearc, Continental Margin and Ophiolite Mantle Sequences

NASA Astrophysics Data System (ADS)

Pearce, J. A.; Parkinson, I. J.

2003-12-01

It is a common assumption that ophiolites and oceanic lithosphere attain their structures and compositions through partial melting of mantle in a single tectonic setting and with a simple petrogenetic relationship between all the units. There is, however, growing evidence that some oceanic lithosphere and ophiolite complexes contain a record of a polygenetic history of formation. This may be apparent in crustal units (complex lava stratigraphies or cross-cutting dykes and gabbros) but the best evidence is recorded in the chrome spinel compositions of residual mantle. Among the most effective plots is that of oxygen fugacity, calculated from accurately-determined ferric iron concentrations, against Cr-number. In the ocean basins, forearc peridotites from the Izu-Bonin Mariana, Tonga and South Sandwich systems may be of two types. In the first, both peridotites and dunites have similar oxygen fugacities and a small range in Cr-number. We interpret these as mongenetic. In the second, the peridotites have low oxygen fugacities and moderate Cr-number and trend towards dunites with high oxygen fugacities and high Cr-number. We interpret these as representing mid-ocean ridge mantle lithosphere, which existed prior to a subduction event and was subsequently invaded by subduction-related melts. The time-gap between the ridge and subduction events may be millions of years or, in the case of subduction initiation, represent a continuum. At passive continental margins, such as the Galicia margin, the origin may again be monogenetic or polygenetic. In the latter case, the mantle peridotites may exhibit a trend from low Cr-number to moderate Cr-number and decreasing oxygen fugacity. We interpret these as representing orogenic peridotite uplifted during an amagmatic extensional event and invaded by MORB magma during subsequent spreading. As with forearc peridotites, the time gap between these two events may be large or there be a continuum. A surprising number of ophiolites exhibit this polygenetic character, especially those which may be linked to subduction initiation (such as the northern Semail ophiolite, Pindos, Zambales) or to ocean opening (e.g. Western Mediterranean ophiolites, Othris, Lizard). And even in essentially monogenetic ophiolites, such as the Troodos Massif, there are subtle variations that may be related to ridge jumps or other local processes. These observations raise questions over the extent to which oceanic lithosphere really is the product of 100% extension or whether it may sometimes contain relics of a more complex history.

Guide to Managing Pasture Water: Streamside Buffers

USDA-ARS?s Scientific Manuscript database

Properly managed pasture water not only provides high-quality water which promotes healthy and productive livestock, but also contributes to maintaining water quality downstream. Riparian (streamside) areas serve as a transition between upland pastures and waterways. In other words, they link pastur...

Bentonite Clay Evolution at Elevated Pressures and Temperatures: An experimental study for generic nuclear repositories

NASA Astrophysics Data System (ADS)

Caporuscio, F. A.; Cheshire, M.; McCarney, M.

2012-12-01

The Used Fuel Disposition Campaign is presently engaged in looking at various generic repository options for disposal of used fuel. Of interest are the disposal of high heat load canisters ,which may allow for a reduced repository footprint. The focus of this experimental work is to characterize Engineered Barrier Systems (EBS) conditions in repositories. Clay minerals - as backfill or buffer materials - are critical to the performance of the EBS. Experiments were performed in Dickson cells at 150 bar and sequentially stepped from 125 oC to 300 oC over a period of ~1 month. An unprocessed bentonite from Colony, Wyoming was used as the buffer material in each experiment. An K-Ca-Na-Cl-rich brine (replicating deep Stripa groundwater) was used at a 9:1 water:rock ratio. The baseline experiment contained brine + clay, while three other experiments contained metals that could be used as waste form canisters (brine +clay+304SS, brine+clay+316SS, brine+clay+Cu). All experiments were buffered at the Mt-Fe oxygen fugacity univarient line. As experiment temperature increased and time progressed, pH, K and Ca ion concentrations dropped, while Si, Na, and SO4 concentrations increased. Silicon was liberated into the fluid phase (>1000 ppm) and precipitated during the quenching of the experiment. The precipitated silica transformed to cristobalite as cooling progressed. Potassium was mobilized and exchanged with interlayer Na, transitioning the clay from Na-montmorillonite to K-smectite. Though illitization was not observed in these experiments, its formation may be kinetically limited and longer-term experiments are underway to evaluate the equilibrium point in this reaction. Clinoptilolite present in the starting bentonite mixture is unstable above 150 oC. Hence, the zeolite broke down at high temperatures but recrystallized as the quench event occurred. This was borne out in SEM images that showed clinoptilolite as a very late stage growth mineral. Both experimental runs containing steel exhibit the generation of a chlorite / Fe-saponite layer at the clay-metal boundary. The formation of minor amounts of pentlandite [(Fe,Ni)9S8] also occurs on both steel plates. Chalcocite (Cu2S) formed as a corrosion product on the Cu plates. The two sulfide phases have been produced by the generation of H2S gas during the experimental runs. The H2S is formed by the breakdown of pyrite framboids at high temperature in the bentonite. Such experiments on representative EBS materials at elevated P,T repository conditions are providing useful information for generic repository studies. Lack of illite formation is common in clay experiments and may be related to kinetics or K concentration. Precipitated SiO2 may potentially seal heating cracks in the clay backfill. The chlorite layer generated on steel may act as a passivation material and prevent corrosion of the steel canister wall. Finally, even if zeolites break down during the high temperature thermal pulse of a repository, zeolites may form again as the repository inventory cools off and perform as radionuclide sorbing phases.

Kinetics and equilibria of redox systems at temperatures as low as 300°C

NASA Astrophysics Data System (ADS)

Burkhard, Dorothee J. M.; Ulmer, Gene C.

1995-05-01

ZrO 2 oxygen sensors, gas mixtures, and conventional solid buffers have been used for decades to either control or measure oxygen fugacity (ƒ O 2) at high temperatures. In dry systems below ca. 700°C these techniques were used cautiously, if at all, due to doubt that there was any equilibration at lower temperatures. We have re-investigated these three types of redox systems in a study where each system (two different Y 2O 3ZrO 2 cells, four different gas mixtures, and four different dry solid buffers) was simultaneously cross-checked with the other to temperatures below 300°C and compared to JANAF data, extrapolated down to low temperatures. Steady and reproducible readings were observed down to T ≤ 300°C, from which we infer fast kinetics for all three systems. Specifically, we find equilibration of various CO 2H 2 gas mixtures over the entire temperature range and to much lower temperature than previously predicted. We assign the reactivity (decomposition) of CO 2 at low T to the catalytic action of Pt, whereby chemisorption of H 2 on the platinum surface enhances the reactivity with CO 2. This catalytic reactivity is diminished over time due to a long-term irreversible reaction of Pt with H 2. Subsequent embrittling and aging after prolonged exposure to H 2 explains erroneously high emf readings. Oxygen sensing of ZrO 2 cells is linear in 1/ T-log ƒ O 2 space and Nernstian at high temperatures. However, for cells with a specific and complex trace element chemistry, one may observe a non-Nernstian behavior in the low T range, i.e., below 470° or lower, probably caused by partially blocked O 2- migration, dependent on the H 2 content in the gas mixture. Linearity and reproducibility of this deviation still allows, however, a useable calibration. Solid buffers of the metal-metal oxide type are known to alloy with noble metals and we therefore used AgPd electrodes, for consistency in all studies, including (IW), (IM), (FMQ), and (NNO). Whereas (IW) and (IM) can be used in the temperature range of consideration, (FMQ) and (NNO) react sluggishly. Complex defect structure of (FMQ) and age alteration of Ni surfaces by chemisorption of oxygen and/or AgNi alloying of (NNO) may be the reason. Fast kinetics and successful redox sensing of CO 2H 2 gas mixtures, of ZrO 2 cells and of at least some solid buffers are therefore promising for future research on low- T redox equilibria.

A comparison of CO2 dynamics and air-water fluxes in a river-dominated estuary and a mangrove-dominated marine estuary

NASA Astrophysics Data System (ADS)

Akhand, Anirban; Chanda, Abhra; Manna, Sudip; Das, Sourav; Hazra, Sugata; Roy, Rajdeep; Choudhury, S. B.; Rao, K. H.; Dadhwal, V. K.; Chakraborty, Kunal; Mostofa, K. M. G.; Tokoro, T.; Kuwae, Tomohiro; Wanninkhof, Rik

2016-11-01

The fugacity of CO2 (fCO2 (water)) and air-water CO2 flux were compared between a river-dominated anthropogenically disturbed open estuary, the Hugli, and a comparatively pristine mangrove-dominated semiclosed marine estuary, the Matla, on the east coast of India. Annual mean salinity of the Hugli Estuary (≈7.1) was much less compared to the Matla Estuary (≈20.0). All the stations of the Hugli Estuary were highly supersaturated with CO2 (annual mean 2200 µatm), whereas the Matla was marginally oversaturated (annual mean 530 µatm). During the postmonsoon season, the outer station of the Matla Estuary was under saturated with respect to CO2 and acted as a sink. The annual mean CO2 emission from the Hugli Estuary (32.4 mol C m-2 yr-1) was 14 times higher than the Matla Estuary (2.3 mol C m-2 yr-1). CO2 efflux rate from the Hugli Estuary has increased drastically in the last decade, which is attributed to increased runoff from the river-dominated estuary.

Levels and distribution of dissolved hydrophobic organic contaminants in the Morava river in Zlín district, Czech Republic as derived from their accumulation in silicone rubber passive samplers.

PubMed

Prokeš, Roman; Vrana, Branislav; Klánová, Jana

2012-07-01

Dissolved waterborne polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were assessed over a period of one year at five sampling sites in a model industrial region in the Czech Republic using silicone rubber passive samplers. The spatial variability of POPs in the studied region in water was small and diffusive pollution sources predominate. Concentrations of the most volatile PAHs decreased with increasing water temperature in the whole region, which reflects the seasonality in atmospheric deposition. The dissolved concentrations of more hydrophobic PAHs, PCBs and OCPs in and downstream the industrial zone are related to desorption from suspended particles. Upstream the industrial area, a positive correlation of dissolved and particle-bound contamination was observed only for DDT metabolites and hexachlorobenzene. Calculated fugacities in water and bottom sediment indicated a fair degree of equilibrium between these compartments for OCPs and PCBs, whereas sediment represented a potential source of PAHs. Copyright © 2012 Elsevier Ltd. All rights reserved.

Melting Himalayan glaciers contaminated by legacy atmospheric depositions are important sources of PCBs and high-molecular-weight PAHs for the Ganges floodplain during dry periods.

PubMed

Sharma, Brij Mohan; Nizzetto, Luca; Bharat, Girija K; Tayal, Shresth; Melymuk, Lisa; Sáňka, Ondřej; Přibylová, Petra; Audy, Ondřej; Larssen, Thorjørn

2015-11-01

Melting glaciers are natural redistributors of legacy airborne pollutants, affecting exposure of pristine proglacial environments. Our data shows that melting Himalayan glaciers can be major contributors of polychlorinated biphenyls (PCBs) and high-molecular-weight polycyclic aromatic hydrocarbons (PAHs) for surface water in the Gangetic Plain during the dry season. Glacial emissions can exceed in some cases inputs from diffuse sources within the catchment. We analyzed air, deposition and river water in several sections along the Ganges River and its major headwaters. The predominant glacial origin of these contaminants in the Himalayan reach was demonstrated using air-water fugacity ratios and mass balance analysis. The proportion of meltwater emissions compared to pollutant discharge at downstream sections in the central part of the Gangetic Plain was between 2 and 200%. By remobilizing legacy pollutants from melting glaciers, climate change can enhance exposure levels over large and already heavily impacted regions of Northern India. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electrical conductivity structure of the mantle derived from inversion of geomagnetic observatory data: implications for lateral variations in temperature, composition and water content.

NASA Astrophysics Data System (ADS)

Munch, Federico; Grayver, Alexander; Khan, Amir; Kuvshinov, Alexey

2017-04-01

As most of Earth's interior remains geochemically unsampled, geophysical techniques based on seismology, geodesy, gravimetry, and electromagnetic studies play prominent roles because of their ability to sense structure at depth. Although seismic tomography maps show a variety of structures, separating thermal and compositional contributions from seismic velocities alone still remains a challenging task. Alternatively, as electrical conductivity is sensitive to temperature, chemical composition, oxygen fugacity, water content, and the presence of melt, it can serve for determining chemistry, mineralogy, and physical structure of the deep mantle. In this work we estimate and invert local C-responses (period range 3-100 days) for a number of worldwide geomagnetic observatories to map lateral variations of electrical conductivity in Earth's mantle (400-1600 km depth). The obtained conductivity profiles are interpreted in terms of basalt fraction in a basalt-harzburgite mixture, temperature structure, and water content variations. Interpretation is based on a self-consistent thermodynamic calculation of mineral phase equilibria, electrical conductivity databases, and probabilistic inverse methods.

Evaluating the environmental fate of pharmaceuticals using a level III model based on poly-parameter linear free energy relationships.

PubMed

Zukowska, Barbara; Breivik, Knut; Wania, Frank

2006-04-15

We recently proposed how to expand the applicability of multimedia models towards polar organic chemicals by expressing environmental phase partitioning with the help of poly-parameter linear free energy relationships (PP-LFERs). Here we elaborate on this approach by applying it to three pharmaceutical substances. A PP-LFER-based version of a Level III fugacity model calculates overall persistence, concentrations and intermedia fluxes of polar and non-polar organic chemicals between air, water, soil and sediments at steady-state. Illustrative modeling results for the pharmaceuticals within a defined coastal region are presented and discussed. The model results are highly sensitive to the degradation rate in water and the equilibrium partitioning between organic carbon and water, suggesting that an accurate description of this particular partitioning equilibrium is essential in order to obtain reliable predictions of environmental fate. The PP-LFER based modeling approach furthermore illustrates that the greatest mobility in aqueous phases may be experienced by pharmaceuticals that combines a small molecular size with strong H-acceptor properties.

Designing bioenergy crop buffers to mitigate nitrous oxide emissions and water quality impacts from agriculture

NASA Astrophysics Data System (ADS)

Gopalakrishnan, G.; Negri, C. M.

2010-12-01

There is a strong societal need to evaluate and understand the environmental aspects of bioenergy production, especially due to the significant increases in production mandated by many countries, including the United States. Bioenergy is a land-based renewable resource and increases in production are likely to result in large-scale conversion of land from current uses to bioenergy crop production; potentially causing increases in the prices of food, land and agricultural commodities as well as disruption of ecosystems. Current research on the environmental sustainability of bioenergy has largely focused on the potential of bioenergy crops to sequester carbon and mitigate greenhouse gas (GHG) emissions and possible impacts on water quality and quantity. A key assumption in these studies is that bioenergy crops will be grown in a manner similar to current agricultural crops such as corn and hence would affect the environment similarly. This study presents a systems approach where the agricultural, energy and environmental sectors are considered as components of a single system, and bioenergy crops are used to design multi-functional agricultural landscapes that meet society’s requirements for food, energy and environmental protection. We evaluate the production of bioenergy crop buffers on marginal land and using degraded water and discuss the potential for growing cellulosic bioenergy crops such as miscanthus and switchgrass in optimized systems such that (1) marginal land is brought into productive use; (2) impaired water is used to boost yields (3); clean freshwater is left for other uses that require higher water quality; and (4) feedstock diversification is achieved that helps ecological sustainability, biodiversity, and economic opportunities for farmers. The process-based biogeochemical model DNDC was used to simulate crop yield, nitrous oxide production and nitrate concentrations in groundwater when bioenergy crops were grown in buffer strips adjacent to corn fields. The bioenergy crops used in this study were miscanthus, switchgrass and native prairie grasses. Results indicated that growing bioenergy crops in buffer strips mitigated nutrient runoff and reduced nitrate concentrations in groundwater to below EPA’s mandated drinking water limit (10 mg/l). Additionally, nitrous oxide emissions in these systems were reduced by 50-90% when compared to corn fields without the bioenergy buffer strips. While all the bioenergy crop buffers had significant positive environmental benefits, switchgrass performed the best with respect to minimizing nutrient runoff and nitrous oxide emissions. The findings of this research have important implications with respect to land management for agriculture and bioenergy.

Deriving a sea surface climatology of CO2 fugacity in support of air-sea gas flux studies

NASA Astrophysics Data System (ADS)

Goddijn-Murphy, L. M.; Woolf, D. K.; Land, P. E.; Shutler, J. D.; Donlon, C.

2014-07-01

Climatologies, or long-term averages, of essential climate variables are useful for evaluating models and providing a baseline for studying anomalies. The Surface Ocean Carbon Dioxide (CO2) Atlas (SOCAT) has made millions of global underway sea surface measurements of CO2 publicly available, all in a uniform format and presented as fugacity, fCO2. fCO2 is highly sensitive to temperature and the measurements are only valid for the instantaneous sea surface temperature (SST) that is measured concurrent with the in-water CO2 measurement. To create a climatology of fCO2 data suitable for calculating air-sea CO2 fluxes it is therefore desirable to calculate fCO2 valid for climate quality SST. This paper presents a method for creating such a climatology. We recomputed SOCAT's fCO2 values for their respective measurement month and year using climate quality SST data from satellite Earth observation and then extrapolated the resulting fCO2 values to reference year 2010. The data were then spatially interpolated onto a 1° × 1° grid of the global oceans to produce 12 monthly fCO2 distributions for 2010. The partial pressure of CO2 (pCO2) is also provided for those who prefer to use pCO2. The CO2 concentration difference between ocean and atmosphere is the thermodynamic driving force of the air-sea CO2 flux, and hence the presented fCO2 distributions can be used in air-sea gas flux calculations together with climatologies of other climate variables.

The Derivation Of A CO2 Fugacity Climatology From SOCAT's Global In SITU Data

NASA Astrophysics Data System (ADS)

Goddijn-Murphy, L. M.; Woolf, D. K.; Land, P. E.; Shutler, J. D.

2013-12-01

The Surface Ocean CO2 Atlas (SOCAT) has made millions of global underway sea surface measurements of CO2 publicly available, all in a uniform format and presented as fugacity, fCO2. However, these fCO2 values are valid strictly only for the instantaneous temperature at measurement and are not ideal for climatology. We recomputed these fCO2 values for the measurement month to be applicable to climatological sea surface temperatures, extrapolated to reference year 2010. The data were then spatially interpolated on a 1°×1° grid of the global oceans to produce 12 monthly fCO2 distributions. Our climatology data will be shared with the science community.

Measured oxygen fugacities of the Angra dos Reis achondrite as a function of temperature

USGS Publications Warehouse

Brett, R.; Stephen, Huebner J.; Sato, M.

1977-01-01

Measurements of the oxygen fugacity (f{hook}O2) as a function of temperature (T) were made on an interior bulk sample of the cumulate achondrite, Angra dos Reis. Data clustered between the f{hook}O2-T relationship of the iron-wu??stite assemblage and 1.2 log atm units above iron-wu??stite. Interpretation of the data indicates that, throughout most of the cooling history of the meteorite, f{hook}O2 values were defined by equilibria involving iron-bearing species at values close to the f{hook}O2 of the assemblage iron-wu??stite. Measured f{hook}O2 data are compatible with crystallization and cooling at pressures greater than 50 bars. ?? 1977.

Escherichia coli growth changes by the mediated effects after low-intensity electromagnetic irradiation of extremely high frequencies.

PubMed

Torgomyan, Heghine; Hovnanyan, Karlen; Trchounian, Armen

2013-04-01

Water is the major constituent of environmental medium and biological systems. The effects occurring in water as a result of low-intensity electromagnetic irradiation (EMI) in extremely high frequencies are supposed to be the primary mechanism to create conditions for biological responses. The EMI effects on Escherichia coli, after irradiation of their suspension, are most probably water-mediated. Indirect effects of EMI at 51.8, 53, 70.6, and 73 GHz frequencies on bacteria, through water, assay buffer (Tris-phosphate buffer with inorganic salts at low or moderate concentrations), or peptone growth medium were studied. The mediated effects of 70.6 and 73 GHz irradiated water, assay buffer, and growth medium on E. coli growth characteristics were insignificant. But the results were different for 51.8 and 53 GHz. EMI mediated effects on bacterial growth were clearly demonstrated. The effects were more strongly expressed with 53 GHz. Moreover, it was shown that 70.6 and 73 GHz similarly suppressed the cell growth after direct irradiation of E. coli in water or on solid medium. Interestingly, for 51.8 and 53 GHz the bacterial growth decreases after suspension irradiation was less, compared to the direct irradiation of bacteria on solid medium. Especially, it was also more expressed in case of 53 GHz. Also with electron microscopy, EMI-induced bacterial cell sizes and structure different changes were detected. In addition, the distinguished changes in surface tension, oxidation-reduction potential and pH of water, assay buffer, growth medium, and bacterial suspension were determined. They depended on EMI frequency used. The differences could be associated with the partial absorbance of EMI energy by the surrounding medium, which depends on a specific frequency. The results are crucial to understand biophysical mechanisms of EMI effects on bacteria.

The potential effects of pH and buffering capacity on dental erosion.

PubMed

Owens, Barry M

2007-01-01

Soft drink pH (initial pH) has been shown to be a causative factor--but not necessarily the primary initiating factor--of dental erosion. The titratable acidity or buffering capacity has been acknowledged as playing a significant role in the etiology of these lesions. This in vitro study sought to evaluate five different soft drinks (Coca-Cola Classic, Diet Coke, Gatorade sports drink, Red Bull high-energy drink, Starbucks Frappucino coffee drink) and tap water (control) in terms of initial pH and buffering capacity. Initial pH was measured in triplicate for the six beverages. The buffering capacity of each beverage was assessed by measuring the weight (in grams) of 0.10 M sodium hydroxide necessary for titration to pH levels of 5.0, 6.0, 7.0, and 8.3. Coca-Cola Classic produced the lowest mean pH, while Starbucks Frappucino produced the highest pH of any of the drinks except for tap water. Based on statistical analysis using ANOVA and Fisher's post hoc tests at a P < 0.05 level of significance, Red Bull had the highest mean buffering capacity (indicating the strongest potential for erosion of enamel), followed by Gatorade, Coca-Cola Classic, Diet Coke, and Starbucks Frappucino.

Cost of riparian buffer zones: A comparison of hydrologically adapted site-specific riparian buffers with traditional fixed widths

NASA Astrophysics Data System (ADS)

Tiwari, T.; Lundström, J.; Kuglerová, L.; Laudon, H.; Öhman, K.; Ågren, A. M.

2016-02-01

Traditional approaches aiming at protecting surface waters from the negative impacts of forestry often focus on retaining fixed width buffer zones around waterways. While this method is relatively simple to design and implement, it has been criticized for ignoring the spatial heterogeneity of biogeochemical processes and biodiversity in the riparian zone. Alternatively, a variable width buffer zone adapted to site-specific hydrological conditions has been suggested to improve the protection of biogeochemical and ecological functions of the riparian zone. However, little is known about the monetary value of maintaining hydrologically adapted buffer zones compared to the traditionally used fixed width ones. In this study, we created a hydrologically adapted buffer zone by identifying wet areas and groundwater discharge hotspots in the riparian zone. The opportunity cost of the hydrologically adapted riparian buffer zones was then compared to that of the fixed width zones in a meso-scale boreal catchment to determine the most economical option of designing riparian buffers. The results show that hydrologically adapted buffer zones were cheaper per hectare than the fixed width ones when comparing the total cost. This was because the hydrologically adapted buffers included more wetlands and low productive forest areas than the fixed widths. As such, the hydrologically adapted buffer zones allows more effective protection of the parts of the riparian zones that are ecologically and biogeochemically important and more sensitive to disturbances without forest landowners incurring any additional cost than fixed width buffers.

Rapid determination of water- and fat-soluble vitamins with microemulsion electrokinetic chromatography.

PubMed

Yin, Changna; Cao, Yuhua; Ding, Shaodong; Wang, Yun

2008-06-06

A rapid, reliable and reproducible method based on microemulsion electrokinetic chromatography (MEEKC) for simultaneous determination of 13 kinds of water- and fat-soluble vitamins has been developed in this work. A novel microemulsion system consisting of 1.2% (w/w) sodium lauryl sulphate (SDS), 21% (v/v) 1-butanol, 18% (v/v) acetonitrile, 0.8% (w/w) n-hexane, 20mM borax buffer (pH 8.7) was applied to improve selectivity and efficiency, as well as shorten analysis time. The composition of microemulsion used as the MEEKC running buffer was investigated thoroughly to obtain stable separation medium, as well as the optimum determination conditions. Acetonitrile as the organic solvent modifier, pH of the running buffer and 1-butanol as the co-surfactant played the most important roles for the separation of the fat-soluble vitamins, water-soluble vitamins and stabilization of system, respectively. The 13 water- and fat-soluble vitamins were baseline separated within 30 min. The system was applied to determine water- and fat-soluble vitamins in commercial multivitamin pharmaceutical formulation, good accuracy and precision were obtained with recoveries between 97% and 105%, relative standard derivations (RSDs) less than 1.8% except vitamin C, and acceptable quantitative results corresponding to label claim.

Method to prevent/mitigate steam explosions in casting pits

DOEpatents

Taleyarkhan, R.P.

1996-12-24

Steam explosions can be prevented or mitigated during a metal casting process by the placement of a perforated flooring system in the casting pit. An upward flow of compressed gas through this perforated flooring system is introduced during the casting process to produce a buffer layer between any spilled molten metal and the cooling water in the reservoir. This buffer layer provides a hydrodynamic layer which acts to prevent or mitigate steam explosions resulting from hot, molten metal being spilled into or onto the cooling water. 3 figs.

Calc-Alkaline Liquid Lines of Descent Produced Under Oxidizing Conditions: An Experimental and Petrologic Study of Basaltic Tephras from the Western Aleutians, AK

NASA Astrophysics Data System (ADS)

Waters, L. E.; Cottrell, E.; Kelley, K. A.; Coombs, M. L.

2017-12-01

Buldir, a volcano in the western Aleutian Arc, features eruptive products that form one of the most strongly calc-alkaline compositional trends observed in modern island arcs. Previous studies of Buldir and nearby submarine dredge samples suggest that Buldir's mineral phases and isotopic signatures may be introduced through mixing of two distinct magmas and/or melts, as no experimental study has been able to create a liquid line of descent (LLD) as calc-alkaline as Buldir's whole rock trend. To further test this hypothesis, we present new experimental results and petrographic analysis of tephras from the 2015 field season of the GeoPRISMS shared platform. Tephras (51.4-54.8 wt% SiO2) have a phenocryst assemblage of olivine + plagioclase + cpx + spinel ± hornblende (hbl). In natural samples, plagioclase comprises most of the crystal volume, followed by either olivine or hornblende. In samples that contain abundant hbl (Hbl Mg#=65-80), olivine and plagioclase span a range of compositions from Fo72-86 and An60-93, respectively. In samples without hbl, olivines are more forsteritic (Fo79-90), and plagioclase is less calcic (An65-83). Spinel is ubiquitous; with Cr- rich spinel inclusions in olivine and hbl, and magnetite in the groundmass. Our petrologic observations do not require magma mixing. To determine whether these observations could be consistent with the LLD of a single parental liquid, we conducted a series of phase equilibrium experiments at 100 MPa in a rapid-quench cold-seal (MHC) apparatus on the most primitive natural lava from Buldir (9.34 wt% MgO). Experiments were equilibrated in noble metal capsules pre-saturated with Fe, and buffered at Re-ReO2 under water-saturated conditions. Spinel [(Mg80, Fe2+20)(Fe3+52, Cr83, Al66)O4] is the liquidus phase, followed by olivine, then plagioclase, then cpx, and lastly, hbl. Once cpx and hbl saturate, spinel composition shifts to magnetite. Experimental run products demonstrate that all mineral phases observed in the tephras are plausible phenocrysts. Experimental glass compositions demonstrate that the strongly calc-alkaline trend observed at Buldir can be produced through crystallization of a parental liquid under water-saturated conditions at relatively high oxygen fugacity, where the effect of high fO2 is to stabilize spinel as a liquidus phase.

Using GIS Models to Identify Relative Nitrogen Attenuation by Riparian Buffers in the Coastal Plain of North Carolina

EPA Science Inventory

Riparian areas have demonstrated the ability to attenuate nutrients and provide water quality services at the field scale, but services of riparian buffers for downstream users should be assessed at watershed scales. GIS-based riparian models have been developed to connect ripari...

EnviroAtlas - Austin, TX - 15m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 15-m riparian buffer that is vegetated. Vegetated cover is defined as Trees & Forest and Grass & Herbaceous. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Austin, TX - 15m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 15-m riparian buffer that is forested. Forest is defined as Trees & Forest. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Des Moines, IA - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. Vegetated cover is defined as Trees & Forest and Grass & Herbaceous. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://enviroatlas.epa.gov/EnviroAtlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets)

EnviroAtlas - New York, NY - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. In this community, vegetated cover is defined as Trees & Forest and Grass & Herbaceous. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets)

EnviroAtlas - Austin, TX - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. Vegetated cover is defined as Trees & Forest and Grass & Herbaceous. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Minneapolis/St. Paul, MN - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. In this community, forest is defined as Trees and Forest and Woody Wetlands. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Cleveland, OH - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. In this community, forest is defined as Trees & Forest and Woody Wetlands. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas ) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets)

EnviroAtlas - New York, NY - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. In this community, forest is defined as Trees & Forest. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets)

EnviroAtlas - Memphis, TN - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. Vegetated cover is defined as Trees & Forest, Grass & Herbaceous, Woody Wetlands, and Emergent Wetlands. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Cleveland, OH - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. In this community, vegetated cover is defined as Trees & Forest, Grass & Herbaceous, Woody Wetlands, and Emergent Wetlands. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas ) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets)

EnviroAtlas - Austin, TX - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. Forest is defined as Trees & Forest. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Memphis, TN - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. Forest is defined as Trees & Forest and Woody Wetlands. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

EnviroAtlas - Des Moines, IA - 51m Riparian Buffer Forest Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is forested. Forest is defined as Trees & Forest. There is a potential for decreased water quality in areas where the riparian buffer is less forested. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://enviroatlas.epa.gov/EnviroAtlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets)

Nogo goes in the pure water: solution structure of Nogo-60 and design of the structured and buffer-soluble Nogo-54 for enhancing CNS regeneration.

PubMed

Li, Minfen; Liu, Jingxian; Song, Jianxing

2006-08-01

The inability to determine the structure of the buffer-insoluble Nogo extracellular domain retarded further design of Nogo receptor (NgR) antagonists to treat CNS axonal injuries. Very surprisingly, we recently discovered that Nogo-60 was soluble and structured in salt-free water, thus allowing the determination of the first Nogo structure by heteronuclear NMR spectroscopy. Nogo-60 adopts an unusual helical structure with the N- and C-terminal helices connected by a long middle helix. While the N-helix has no contact with the rest of the molecule, the C-helix flips back to pack against the 20-residue middle helix. This packing appears to trigger the formation of the stable Nogo-60 structure because Nogo-40 with the last helix truncated is unstructured. The Nogo-60 structure offered us rationales for further design of the structured and buffer-soluble Nogo-54, which may be used as a novel NgR antagonist. Furthermore, our discovery may imply a general solution to solubilizing a category of buffer-insoluble proteins for urgent structural investigations.

Agroforestry buffers for nonpoint source pollution reductions from agricultural watersheds.

PubMed

Udawatta, Ranjith P; Garrett, Harold E; Kallenbach, Robert

2011-01-01

Despite increased attention and demand for the adoption of agroforestry practices throughout the world, rigorous long-term scientific studies confirming environmental benefits from the use of agroforestry practices are limited. The objective was to examine nonpoint-source pollution (NPSP) reduction as influenced by agroforestry buffers in watersheds under grazing and row crop management. The grazing study consists of six watersheds in the Central Mississippi Valley wooded slopes and the row crop study site consists of three watersheds in a paired watershed design in Central Claypan areas. Runoff water samples were analyzed for sediment, total nitrogen (TN), and total phosphorus (TP) for the 2004 to 2008 period. Results indicate that agroforestry and grass buffers on grazed and row crop management sites significantly reduce runoff, sediment, TN, and TP losses to streams. Buffers in association with grazing and row crop management reduced runoff by 49 and 19%, respectively, during the study period as compared with respective control treatments. Average sediment loss for grazing and row crop management systems was 13.8 and 17.9 kg ha yr, respectively. On average, grass and agroforestry buffers reduced sediment, TN, and TP losses by 32, 42, and 46% compared with the control treatments. Buffers were more effective in the grazing management practice than row crop management practice. These differences could in part be attributed to the differences in soils, management, and landscape features. Results from this study strongly indicate that agroforestry and grass buffers can be designed to improve water quality while minimizing the amount of land taken out of production. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Comparison of riparian plant communities under four land management systems in southwestern Wisconsin

USGS Publications Warehouse

Paine, L.K.; Ribic, C.A.

2002-01-01

Riparian plant community composition is influenced by moisture, erosion, original native plant communities, and current and past land use. This study compared riparian plant communities under four types of management: woody buffer strip, grassy buffer strip, rotational grazing, and continuous grazing. Study sites were located along spring-fed streams in the unglaciated region of southwestern Wisconsin, USA. At each site, plant community surveys were conducted using a point transect method. Among the treatments, woody buffer strips, rotationally grazed and continuously grazed riparian areas had greater plant species richness than grassy buffer strips, and woody buffer strips had the greatest native plant species richness. Reed canary grass (Phalaris arundinacea L.) was prevalent in grassy buffer strips (44% of all observations), common in woody buffer strips (15%), and rare in sites that were rotationally or continuously grazed (3 and 5%, respectively). Pasture sites had greater proportions of native grasses and grass relatives and moderate levels of overall native species richness. Considered a water quality best management practice, well-managed rotational grazing may be a reasonable alternative to buffer strips which can contribute to protection and enhancement of native vegetation biodiversity. ?? 2002 Elsevier Science B.V. All rights reserved.

ssDNA degradation along capillary electrophoresis process using a Tris buffer.

PubMed

Ric, Audrey; Ong-Meang, Varravaddheay; Poinsot, Verena; Martins-Froment, Nathalie; Chauvet, Fabien; Boutonnet, Audrey; Ginot, Frédéric; Ecochard, Vincent; Paquereau, Laurent; Couderc, François

2017-06-01

Tris-Acetate buffer is currently used in the selection and the characterization of ssDNA by capillary electrophoresis (CE). By applying high voltage, the migration of ionic species into the capillary generates a current that induces water electrolysis. This phenomenon is followed by the modification of the pH and the production of Tris derivatives. By injecting ten times by capillary electrophoresis ssDNA (50 nM), the whole oligonucleotide was degraded. In this paper, we will show that the Tris buffer in the running vials is modified along the electrophoretic process by electrochemical reactions. We also observed that the composition of the metal ions changes in the running buffer vials. This phenomenon, never described in CE, is important for fluorescent ssDNA analysis using Tris buffer. The oligonucleotides are degraded by electrochemically synthesized species (present in the running Tris vials) until it disappears, even if the separation buffer in the capillary is clean. To address these issues, we propose to use a sodium phosphate buffer that we demonstrate to be electrochemically inactive. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modeling of a complex, polar system with a modified Soave-Redlich-Kwong equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sturnfield, E.A.; Matherne, J.L.

1988-01-01

It is computationally feasible to use a simple equation of state (like a Redlich-Kwong) to calculate liquid fugacity but the simpler equations work well only for moderately non-ideal systems. More complex equations (like Ghemling-Lui-Prausnitz) predict system behavior more accurately but are much more complicated to use and can require fitting many parameters to data. This paper illustrates success in using a modified Redlich-Kwong to model a complex system including water, hydrogen, sub and supercritical ammonia, and amines. The binary interaction parameter ({Kappa}/sub ij/) of the Soave-Redlich-Kwong equation has been modified to be both asymmetric and temperature dependent. Further, the aimore » constant was determined by fitting vapor pressure data. Predicted model results are compared to literature (example 1) or plant data (examples 2-4) for four systems: 1. The ammonia-water binary over a wide range of pressure and temperature including ammonia above its critical. 2. A multicomponent Vapor-Liquid equilibrium flash tank and condenser containg hydrogen, amonia, water, and other heavier compounds. 3. A multicomponent vapor-liquid equilibrium flash tank containing water, heavier mines, and the amine salts. 4. A Liquid-Liquid-Vapor equilibrium decanter system containing water, ammonia, and an organic chloride.« less

The buffer value of groundwater when well yield is limited

NASA Astrophysics Data System (ADS)

Foster, T.; Brozović, N.; Speir, C.

2017-04-01

A large proportion of the total value of groundwater in conjunctive use systems is associated with the ability to smooth out shortfalls in surface water supply during droughts. Previous research has argued that aquifer depletion in these regions will impact farmers negatively by reducing the available stock of groundwater to buffer production in future periods, and also by increasing the costs of groundwater extraction. However, existing studies have not considered how depletion may impact the productivity of groundwater stocks in conjunctive use systems through reductions in well yields. In this work, we develop a hydro-economic modeling framework to quantify the effects of changes in well yields on the buffer value of groundwater, and apply this model to an illustrative case study of tomato production in California's Central Valley. Our findings demonstrate that farmers with low well yields are forced to forgo significant production and profits because instantaneous groundwater supply is insufficient to buffer surface water shortfalls in drought years. Negative economic impacts of low well yields are an increasing function of surface water variability, and are also greatest for farmers operating less efficient irrigation systems. These results indicate that impacts of well yield reductions on the productivity of groundwater are an important economic impact of aquifer depletion, and that failure to consider this feedback may lead to significant errors in estimates of the value of groundwater management in conjunctive use systems.

Determination of cytokinins in coconut (Cocos nucifera L.) water using capillary zone electrophoresis-tandem mass spectrometry.

PubMed

Ge, Liya; Yong, Jean Wan Hong; Tan, Swee Ngin; Ong, Eng Shi

2006-06-01

The applicability of CZE in combination with MS and MS/MS methods for the simultaneous separation and determination of 12 cytokinins was investigated for the first time. Cytokinins were first completely separated by CZE within less than 20 min using a volatile buffer and then detected directly by MS or MS/MS. Satisfactory separation of the 12 cytokinin standards was achieved using a 25 mM ammonium formate/formic acid buffer (pH 3.4) and 3% ACN v/v with a separation voltage of 25 kV. On the basis of the resolution of the neighboring peaks, the various parameters for CZE-MS optimization, such as buffer pH value, concentration of buffer and organic modifier, applied voltage and sheath liquid, were evaluated systematically. MS/MS with multiple reaction monitoring detection was carried out to obtain sufficient selectivity and sensitivity. The combination of on-line sample stacking and CZE-MS/MS achieved a detection limit in the range of 0.05-0.18 microM for the 12 cytokinins at an S/N of 3. The optimized CZE-MS/MS method was simple, rapid, low cost, robust and highly selective. Furthermore, the developed method was successfully applied to screen for endogenous cytokinins in purified coconut water extract sample. Nine cytokinins were detected and quantified in coconut water after SPE.

Drought effects on evapotransiration and subsurface water storage in the southern Sierra Nevada

NASA Astrophysics Data System (ADS)

Bales, R. C.; Goulden, M.; Hunsaker, C. T.; Conklin, M. H.; Hartsough, P. C.; O'Geen, T. T.; Hopmans, J. W.; Safeeq, M.

2015-12-01

Multi-year measurements of evapotranspiration (ET) at three elevations in the southern Sierra Nevada show the extent to which subsurface water storage in the regolith provides a buffer against multi-year dry periods. ET in a 2000-m elevation mixed-conifer forest showed a 24% decrease in ET in water-year 2014, the third dry year, as compared to the wet year of 2011. This decrease reflected reduced transpiration for the July to September period. Over half of the annual ET in both wet and dry years came from below the 1-m depth mapped soil, and with come coming from below the 2.5 m depth of our soil-moisture measurements. The ability of trees to access water from these depths does provide a 2-3 year buffer for ET, which also depends on forest density and the balance between perennial overstory and annual understory vegetation. An equally dense lower-elevation pine-oak forest (1160 m) showed nearly a 50% decrease in ET during the third year of drought, with significant visible effects on vegetation. While this lower elevation forest may have as much or more subsurface storage as does that at 2000-m elevation, the combination of lower precipitation as one goes down in elevation and very high forest density provides only a one-year buffer for ET in dry years. Regaining resiliency in this forest will only occur with significant reductions in biomass and commensurate lowering of ET. In a 400-m elevation oak savannah ET responds to annual precipitation, with essentially no multi-year buffer provided by subsurface storage.

Simple, sensitive, selective and validated spectrophotometric methods for the estimation of a biomarker trigonelline from polyherbal gels

NASA Astrophysics Data System (ADS)

Chopra, Shruti; Motwani, Sanjay K.; Ahmad, Farhan J.; Khar, Roop K.

2007-11-01

Simple, accurate, reproducible, selective, sensitive and cost effective UV-spectrophotometric methods were developed and validated for the estimation of trigonelline in bulk and pharmaceutical formulations. Trigonelline was estimated at 265 nm in deionised water and at 264 nm in phosphate buffer (pH 4.5). Beer's law was obeyed in the concentration ranges of 1-20 μg mL -1 ( r2 = 0.9999) in deionised water and 1-24 μg mL -1 ( r2 = 0.9999) in the phosphate buffer medium. The apparent molar absorptivity and Sandell's sensitivity coefficient were found to be 4.04 × 10 3 L mol -1 cm -1 and 0.0422 μg cm -2/0.001A in deionised water; and 3.05 × 10 3 L mol -1 cm -1 and 0.0567 μg cm -2/0.001A in phosphate buffer media, respectively. These methods were tested and validated for various parameters according to ICH guidelines. The detection and quantitation limits were found to be 0.12 and 0.37 μg mL -1 in deionised water and 0.13 and 0.40 μg mL -1 in phosphate buffer medium, respectively. The proposed methods were successfully applied for the determination of trigonelline in pharmaceutical formulations (vaginal tablets and bioadhesive vaginal gels). The results demonstrated that the procedure is accurate, precise, specific and reproducible (percent relative standard deviation <2%), while being simple and less time consuming and hence can be suitably applied for the estimation of trigonelline in different dosage forms and dissolution studies.

A view inside the nature of protein crystals

NASA Astrophysics Data System (ADS)

Oswald, R.; Pietzsch, M.; Ulrich, J.

2017-07-01

In this work a fundamental analysis of protein crystal modifications was presented to compare and confirm the components of protein crystal modifications. The result is that a protein crystal contains besides the protein, the precipitant and water. A mass spectrometer coupled to a thermogravimetry device was used to confirm the different waters (free water -the chosen buffer- and bound water) inside the crystals. Here the biggest amount of water is the free water (the buffer) with an amount of approximately 35%. The bound water (in the sense of a hydrate) has only an amount of about 1-1.5%. Furthermore, an x-ray analysis to confirm the influence range of pH value on the stability of one crystal modification for the understanding of effects on dissolution mechanism of protein crystals was investigated. The crystals of the tetragonal modification crystallized at pH 4.7, 4.85, 5.0, 5.15 and 5.3 maintain according to the x-ray measurements the same lattice parameters. The measured data are discussed.

Denitrification and N2O emissions in annual croplands, perennial grass buffers, and restored perennial grasslands

USDA-ARS?s Scientific Manuscript database

Inclusion of perennial vegetation filter strips (PFS) in the toeslope of annual cropland watersheds can decrease nitrate (NO3) losses to ground and surface waters. Although PFS are similar to riparian buffers, PFS are a relatively new conservation tool and the processes responsible for NO3 removal f...

Streambank Erosion from Grazed Pastures, Grass Filters and Forest Buffers Over a Six-Year Period

USDA-ARS?s Scientific Manuscript database

In agricultural landscapes, streambank erosion, as a source of non-point water pollution, is one of the major contributors to stream habitat degradation. Streambank erosion rates from riparian forest buffers, grass filters and grazed pastures (stocking rates ranged from 0.23 to 1.15 cow-days ha-1 m-...

Investigations on the Crystal Structure and the Stability Field of FCAM-I (Ca3MgAl6Fe10O28), an Iso-structure to SFCA-I

NASA Astrophysics Data System (ADS)

Zöll, Klaus; Manninger, Tanja; Kahlenberg, Volker; Krüger, Hannes; Tropper, Peter

2017-08-01

In a study on parts of the system Fe2O3-CaO-Al2O3-MgO, the previously unknown compound Ca3MgAl6Fe10O28 or FCAM-I (iso-structural with SFCA-I) has been synthesized. The two principal aims of our investigations have been (i) analysis of the stability field of the new phase as a function of T and fO2 and (ii) determination of its crystal structure. Two experimental series in air and under controlled oxygen fugacity via the hematite-magnetite buffer were conducted. Pure polycrystalline FCAM-I has been obtained at 1463.15 K (1190 °C) in air. While increasing the temperature from 1573.15 K to 1673.15 K (1300 °C to 1400 °C), the FCAM-I phase breaks down forming a variety of new compounds depending on T and fO2. Ca3MgAl6Fe10O28 has a triclinic crystal structure (space group P \\overline{1} ). Basic crystallographic data are as follows: a = 10.2980(4) Å, b = 10.4677(4) Å, c = 11.6399(4) Å, α = 94.363(3)°, β = 111.498(3)°, γ = 109.744(3)°, V = 1069.81(7) Å3, Z = 2.

Determining the Oxygen Fugacity of Lunar Pyroclastic Glasses Using Vanadium Valence - An Update

NASA Technical Reports Server (NTRS)

Karner, J. M.; Sutton, S. R.; Papike, J. J.; Shearer, C. K.; Jones, J. H.; Newville, M.

2004-01-01

We have been developing an oxygen barometer based on the valence state of V (V(2+), V(3+), V(4+), and V(5+)) in solar system basaltic glasses. The V valence is determined by synchrotron micro x-ray absorption near edge structure (XANES), which uses x-ray absorption associated with core-electronic transitions (absorption edges) to reveal a pre-edge peak whose intensity is directly proportional to the valence state of an element. XANES has advantages over other techniques that determine elemental valence because measurements can be made non-destructively in air and in situ on conventional thin sections at a micrometer spatial resolution with elemental sensitivities of approx. 100 ppm. Recent results show that fO2 values derived from the V valence technique are consistent with fO2 estimates determined by other techniques for materials that crystallized above the IW buffer. The fO2's determined by V valence (IW-3.8 to IW-2) for the lunar pyroclastic glasses, however, are on the order of 1 to 2.8 log units below previous estimates. Furthermore, the calculated fO2's decrease with increasing TiO2 contents from the A17 VLT to the A17 Orange glasses. In order to investigate these results further, we have synthesized lunar green and orange glasses and examined them by XANES.

Economic analysis of best management practices to reduce watershed phosphorus losses.

PubMed

Rao, Nalini S; Easton, Zachary M; Lee, David R; Steenhuis, Tammo S

2012-01-01

In phosphorus-limited freshwater systems, small increases in phosphorus (P) concentrations can lead to eutrophication. To reduce P inputs to these systems, various environmental and agricultural agencies provide producers with incentives to implement best management practices (BMPs). In this study, we examine both the water quality and economic consequences of systematically protecting saturated, runoff-generating areas from active agriculture with selected BMPs. We also examine the joint water quality/economic impacts of these BMPs-specifically BMPs focusing on barnyards and buffer areas. Using the Variable Source Loading Function model (a modified Generalized Watershed Loading Function model) and net present value analysis (NPV), the results indicate that converting runoff-prone agricultural land to buffers and installing barnyard BMPs are both highly effective in decreasing dissolved P loss from a single-farm watershed, but are also costly for the producer. On average, including barnyard BMPs decreases the nutrient loading by about 5.5% compared with only implementing buffers. The annualized NPV for installing both buffers on only the wettest areas of the landscape and implementing barnyard BMPs becomes positive only if the BMPs lifetime exceeds 15 yr. The spatial location of the BMPs in relation to runoff producing areas, the time frame over which the BMPs are implemented, and the marginal costs of increasing buffer size were found to be the most critical considerations for water quality and profitability. The framework presented here incorporates estimations of nutrient loading reductions in the economic analysis, and is applicable to farms facing BMP adoption decisions. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Chemical composition and the potential for proteomic transformation in cancer, hypoxia, and hyperosmotic stress

PubMed Central

2017-01-01

The changes of protein expression that are monitored in proteomic experiments are a type of biological transformation that also involves changes in chemical composition. Accompanying the myriad molecular-level interactions that underlie any proteomic transformation, there is an overall thermodynamic potential that is sensitive to microenvironmental conditions, including local oxidation and hydration potential. Here, up- and down-expressed proteins identified in 71 comparative proteomics studies were analyzed using the average oxidation state of carbon (ZC) and water demand per residue (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}${\\overline{n}}_{{\\mathrm{H}}_{2}\\mathrm{O}}$\\end{document}n¯H2O), calculated using elemental abundances and stoichiometric reactions to form proteins from basis species. Experimental lowering of oxygen availability (hypoxia) or water activity (hyperosmotic stress) generally results in decreased ZC or \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}${\\overline{n}}_{{\\mathrm{H}}_{2}\\mathrm{O}}$\\end{document}n¯H2O of up-expressed compared to down-expressed proteins. This correspondence of chemical composition with experimental conditions provides evidence for attraction of the proteomes to a low-energy state. An opposite compositional change, toward higher average oxidation or hydration state, is found for proteomic transformations in colorectal and pancreatic cancer, and in two experiments for adipose-derived stem cells. Calculations of chemical affinity were used to estimate the thermodynamic potentials for proteomic transformations as a function of fugacity of O2 and activity of H2O, which serve as scales of oxidation and hydration potential. Diagrams summarizing the relative potential for formation of up- and down-expressed proteins have predicted equipotential lines that cluster around particular values of oxygen fugacity and water activity for similar datasets. The changes in chemical composition of proteomes are likely linked with reactions among other cellular molecules. A redox balance calculation indicates that an increase in the lipid to protein ratio in cancer cells by 20% over hypoxic cells would generate a large enough electron sink for oxidation of the cancer proteomes. The datasets and computer code used here are made available in a new R package, canprot. PMID:28603672

The effects of a CO2-bearing fluid on the rheology of quartz-bearing rocks in subduction zones

NASA Astrophysics Data System (ADS)

Ashley, K. T.; Behr, W. M.

2017-12-01

The weakening effect of water on quartz rheology has been a well-recognized phenomenon for several decades. In many tectonic environments, however, the fluid phase is not pure H2O, but commonly includes other species such as CO2, dissolved silicates, and/or salts. CO2 is especially prevalent in subduction zone fluids due to subduction of carbonates and/or graphitic sediments. Some deformation experiments as well as natural observations suggest that CO2 can affect rheology and development of anisotropy in quartz-rich rocks, but the precise effects of CO2 are poorly understood. Here we take a petrologic approach to assess the role of a mixed H2O-CO2 fluid phase for deforming quartzite in the viscous regime. For quartz dislocation creep, CO2 in the fluid acts as a non-wetting phase, resulting in the reduction of water fugacity. However, for most rocks, the activity-composition (a-X) relationship of a H2O-CO2 fluid phase requires very high CO2 mole fractions to have a significant effect on strain rate. For XCO2 = 0.5 at 500°C, with a differential stress of 10 MPa, the water fugacity is only reduced by 30% and resultant strain rates are slowed by less than a factor of 3 — much less than the inherent uncertainty of the flow law. In contrast, because silica does not form complexes with CO2, its solubility greatly decreases at high carbonic fractions and pressure solution is greatly slowed. For most diagenetic conditions, a 50:50 H2O-CO2 fluid phase compared to a pure-H2O fluid phase results in a strain rate that is an order of magnitude slower. Higher carbonic fractions has dramatic effects on the rate of pressure solution (decreased by >3 orders of magnitude at XCO2 = 0.8). The difference in the response of quartz deformation mechanisms to changes in the fluid composition suggests CO2-rich fluids could result in the suppression of pressure solution and the activation of dislocation creep (or brittle failure) at lower temperatures than expected for a pure H2O fluid.

Sediment yield along an actively managed riparian buffer

Treesearch

Ferhat Kara; Edward F. Loewenstein; Latif Kalin

2012-01-01

High quality water is generally associated with forested watersheds. However, intensive forestry activities within these watersheds can negatively affect water quality. In order to mitigate negative effects of forestry operations on water quality, best management practices (BMPs) are recommended. In this study, effects of silvicultural treatments on water quality are...

The effect of the type of HA on the degradation of PLGA/HA composites.

PubMed

Naik, Ashutosh; Shepherd, David V; Shepherd, Jennifer H; Best, Serena M; Cameron, Ruth E

2017-01-01

The aim of this study is to explore the importance of the potentially competing effects of buffering effects of the calcium phosphate filler and particle-mediated water sorption on the degradation products of poly(d,l lactide-co-glycolide (50:50))(PLGA)/hydroxyapatite(HA) composites. Further the influence of type of HA on the mechanical properties of the composites was investigated. Phase pure HA was synthesised via a reaction between aqueous solutions of calcium hydroxide and orthophosphoric acid. The powder produced was either used as produced (uncalcined) or calcined in air or calcined in a humidified argon atmosphere. An in-vitro degradation study was carried out in phosphate buffered saline (PBS). The results obtained indicated that the degradation rate of the composite might be better understood if both the buffering effects and the rate of water sorption by the composites are considered. Copyright © 2016 Elsevier B.V. All rights reserved.

[Role of the blood bicarbonate buffer system in the mechanism of fish adaptation to different levels of carbonic acid in an aqueous medium].

PubMed

Romanenko, V D; Kotsar', N I

1976-01-01

The role of a bicarbonate buffer system of fish (Cyprinidae family) blood was studied in their organism addaptive reactions to different levels of CO2 in the aqueous medium. The fish is established to prossess rather effective for maintaining blood acid-base balance. It permits the fish to endure for a long time essential fluctuations of carbonic acid concentration in water. In prevention of possible development of carbonic acid acidosis an essential role belongs to formation of bicarbonates as a blood buffer system stablizing pH is shown to be significant for preventing possible development of acidosis. The adaptation potentialities of Cyprinidae family permit them to endure an increase of CO2 in water and are determined by the ability of their organism to formations of bicarbonate and their retaining in blood.

Lunar and Planetary Science XXXV: Special Session: Oxygen in the Solar System, II

NASA Technical Reports Server (NTRS)

2004-01-01

The Special Session: Oxygen in the Solar System, II, included the following reports:Evolution of Oxygen Isotopes in the Solar Nebula; Disequilibrium Melting of Refractory Inclusions: A Mechanism for High-Temperature Oxygen; Isotope Exchange in the Solar Nebula; Oxygen Isotopic Compositions of the Al-rich Chondrules in the CR Carbonaceous Chondrites: Evidence for a Genetic Link to Ca-Al-rich Inclusions and for Oxygen Isotope Exchange During Chondrule Melting; Nebular Formation of Fayalitic Olivine: Ineffectiveness of Dust Enrichment; Water in Terrestrial Planets: Always an Oxidant?; Oxygen Barometry of Basaltic Glasses Based on Vanadium Valence Determination Using Synchrotron MicroXANES; A New Oxygen Barometer for Solar System Basaltic Glasses Based on Vanadium Valence; The Relationship Between Clinopyroxene Fe3+ Content and Oxygen Fugacity ; and Olivine-Silicate Melt Partitioning of Iridium.

An electrochemical series of redox couples in silicate melts - A review and applications to geochemistry

NASA Technical Reports Server (NTRS)

Schreiber, Henry D.

1987-01-01

An electrochemical series for redox couples in a glass-forming oxide melt is developed. This series is a quantitative numerical scale of reference reduction potentials of the redox couples in a silicate melt that is a model for basaltic magmas. The redox couples are ordered in terms of their reference reduction potentials; the order appears to be relatively independent of the exact melt composition and temperature. Thus, upon calibration to a desired composition, oxygen fugacity, and temperature, this electrochemical series can provide estimates of redox state proportions in basaltic magmas on different planetary bodies. The geochemical electrochemical series can also be used to understand the interrelationship of the redox state of the magma and the presence of volatile species such as oxygen, water, sulfur gases, and carbon gases.

Study on the reduction and hysteresis effect of soil nitrogen pollution by Alfalfa in channel buffer bank

NASA Astrophysics Data System (ADS)

Chi, Yixia; Xue, Lianqing; Zhang, Zhanyu; Li, Dongying

2018-01-01

Based on the simulation experiments of solute transport in channel buffer bank and pot experiments, this study analyzed the transport of nitrogen pollution from farmland drains along the South-North Water Transfer east route project; and compared the nitrogen transport rule and purification effect of alfalfa in channel buffer bank soil under situations of bare land and alfalfa mulching. The results showed that: (1) soil nitrogen content decreased gradually with the width increase of channel buffer bank by the soil adsorption and decomposition; (2) the migration rates of nitrogen were 0.06 g·kg-1 by the alfalfa mulching; (3) the removed rates of nitrogen from the soil were 0.088 g·kg-1 by cutting alfalfa; (4) the residual nitrogen of soil with alfalfa was 10% of the bare land. Alfalfa in channel buffer bank had obvious reduction and hysteresis effect to soil nitrogen pollution.

Determination of Oxygen Fugacity using Olivine-Melt Equilibrium: Implications for the Redox States of Mid-Ocean Ridge Basalt, Ocean Island Basalt, and Island Arc Basalt Mantle Source Regions

NASA Astrophysics Data System (ADS)

Peterman, K. J.; Bryson, S.; Rilling-Hall, S.; Barton, M.

2017-12-01

In order to connect volcanic rocks to their mantle sources, it is essential to consider redox equilibria and their dependence on temperature, pressure, chemical composition, and oxygen fugacity. Oxygen fugacity (fO2) is an intensive variable that strongly affects the behavior of those elements in magmas that are sensitive to changes in redox state, such as Fe, and therefore Mg-Fe silicates, such as olivine. Since fO2 plays an important role in fractional crystallization, in principle it is possible to estimate fO2 from analyses of olivine in equilibrium with the melt. This research describes a new method based on this principle called the Olivine-Melt Equilibrium Method. The Fe3+ and Fe2+ contents of melt in equilibrium with olivine are calculated from the relationship of Gee and Sack (1988) that describes the partitioning of Mg and Fe2+ between olivine and melt. The Fe3+ and Fe2+ contents of the melt are then used to calculate the fO2 at which olivine and melt are in equilibrium using the model of Kress and Carmichael (1991) for the relationship between Fe3+/Fe2+ , fO2, T, P, and melt composition. We have calculated oxygen fugacities from published analyses of coexisting glass and olivine pairs in 1020 samples from three different tectonic settings. The results (expressed as ΔFMQ) for Mid-Ocean Ridge Basalts from the Mid-Atlantic Ridge (-1.55 ± 0.75), the East Pacific Rise (-0.65 ± 0.51), the Juan de Fuca Ridge (-0.77 ± 0.42), and the Galápagos Spreading Center (+0.08 ± 0.48) agree with results obtained using other methods and average -1.09 ± 0.89. Ocean Island Basalts from Iceland and the Galápagos Islands (ΔFMQ = -0.43 ± 0.71 and -0.33 ± 0.35 respectively) also yield values consistent with those obtained by other methods and fall in the same range as MORB. However, lavas from the Canary Islands are more oxidized than typical MORB and OIB, with values (average = +0.68 ± 0.52) approaching those for island arc magmas. We obtain ΔFMQ = +1.03 ± 0.52 for olivine-melt pairs from Sunda arc basalts. The results for MORB and OIB potentially provide evidence for redox heterogeneity in the mantle, possibly as the result of crustal recycling. However it is necessary to evaluate the possibility that fO2 changes during magma ascent before concluding that the oxygen fugacities of erupted magmas directly reflect those of the mantle source regions.

Si and O partitioning between core metal and lower mantle minerals during core formation

NASA Astrophysics Data System (ADS)

Nakajima, Y.; Frost, D. J.; Rubie, D. C.

2010-12-01

In addition to Fe and Ni, the Earth’s core contains light alloying elements (e.g., H, C, O, Si, and/or S) in order to explain the 10% core density deficit (e.g., Birch, 1964, JGR). Experimental data on the partitioning behavior of siderophile elements such as Ni and Co between liquid Fe and mantle minerals indicate that equilibration between core-forming metal and a silicate magma ocean likely occurred at lower-mantle pressures (e.g., Li and Agee, 1996 Nature). If core-mantle differentiation has occurred under such conditions, significant quantities of O or Si could have entered the core. At these conditions the nature of the dominant light element in the core will depend strongly on the oxygen fugacity at which equilibration occurred. High pressure experiments were carried out at 25 GPa and 2400-2950 K using a Kawai-type multi-anvil apparatus in order to investigate the partitioning of Si and O between liquid Fe and (Mg,Fe)SiO3 perovskite (Pv), silicate melt, and (Mg,Fe)O ferropericlace (Fp). Starting materials consisting of metallic Fe (+-Si) and olivine (Fo70-95) were contained in single-crystal MgO capsules. Over the oxygen fugacity range IW-0.5 to -3, the Si molar partition coefficient D* (= [Si]metal /[Si]silicate) between metal and Pv increases linearly with decreasing oxygen fugacity at a fixed given temperature. The partition coefficient between metal and silicate melt is of a similar magnitude but is less dependent on the oxygen fugacity. The obtained oxygen distribution coefficient Kd (= [Fe]metal[O]metal /[FeO]Fp) is in agreement with that determined in the Fe-Fp binary system (Asahara et al., 2007 EPSL) below the silicate liquidus temperature. In contrast, a correlation between the O partitioning and Si concentration in Fe is observed above 2700 K where liquid metal coexists with silicate melt + Fp. With an increasing concentration of Si in the liquid metal, O partitioning into Fp is strongly enhanced. Five atomic% Si in the metal reduces the metal-silicate O partition coefficient by about 1 order magnitude. Near the base of a deep magma ocean where pressures exceed 20 GPa, liquid metal could have coexisted with silicate melt, Pv, and Fp. Our results show that Si would readily partitioned into core-forming metal from both perovskite and silicate liquid at a relevant oxygen fugacity (e.g., IW-2). Simultaneously, the Si solubility would hinder the dissolution of O in the liquid metal. This implies that the presence of Si in liquid metal must be included in models of O partitioning.

Micro solid-phase derivatization analysis of low-molecular mass aldehydes in treated water by micellar electrokinetic chromatography.

PubMed

Fernández-Molina, José María; Silva, Manuel

2014-03-01

A MEKC method was developed for the determination of aliphatic and aromatic low-molecular mass aldehydes (LMMAs) in treated water samples. The method involves the precapillary derivatization and extraction of the aldehydes on a Telos™ENV μ-SPE column impregnated with 2,4-dinitrophenylhydrazine . After elution of the hydrazones with ACN, the derivatives were analyzed using MEKC-DAD. Resolution of the MEKC procedure was studied by changing the pH and the concentration of the buffer, the type, and the concentration of surfactant, and the organic modifier content in the BGE. A running buffer consisting of a phosphate buffer (pH 7.2, 75 mM) with CTAB (50 mM) and ACN (30%) gave the best results. Linearity was established over the concentration range 0.5-500 μg/L and LODs from 65 to 775 ng/L; the interday precision was expressed as the RSD of the aldehydes ranging from 6.6 to 8.4%. Matrix effects were shown to be negligible by comparing the response factors obtained in ultrapure and treated waters. Aldehydes were readily determined at 1.1-8.4 μg/L levels in ozonated and chlorinated water samples, the method proposed being the first CE contribution developed for the systematic analysis of both aliphatic and aromatic LMMAs in water samples. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Factors affecting the recovery of Legionella pneumophila serogroup 1 from cooling tower water systems.

PubMed

Lu, H F; Tsou, M F; Huang, S Y; Tsai, W C; Chung, J G; Cheng, K S

2001-09-01

A total of 20 water samples collected from the cooling towers at 20 different sites were analyzed under various conditions for the presence of Legionella pneumophila serogroup 1. A comparative assessment was performed to evaluate methods of sample collection (spray drops, beneath water at 20- to 40-cm depth, and water outlet), concentration (filtration and centrifugation), acid buffer treatment (no treatment, treatment for 3, 5, and 15 min), and CO2 incubation or candle jar incubation. The reduction in viable colonies and false negative rate were compared for the different factors. No quantitative differences in isolation of L. pneumophila serogroup 1 was found among samples collected from water at a depth of 20 to 40 cm, from water outlet, and from spray drops. Treatment in an acid buffer for 15 min significantly reduced the recovery rate, with a reduction in bacterial counts of about 40%, compared with a 3-min (12%) or a 5-min (25%) treatment. Acid buffer treatment for 3 or 5 min reduced the overgrowth of commensal flora. This treatment improved the selectivity but not the sensitivity for L. pneumophila serogroup 1. Colonies on plates incubated at 37 degrees C in a candle jar with a humidified atmosphere grew better than those incubated at 35 degrees C with 5% CO2. These results demonstrate that methods of sample collection, concentration, and incubation, but not collection site, can affect the isolation rate for L. pneumophila serogroup 1.

Redox-influenced seismic properties of upper-mantle olivine

NASA Astrophysics Data System (ADS)

Cline, C. J., II; Faul, U. H.; David, E. C.; Berry, A. J.; Jackson, I.

2018-03-01

Lateral variations of seismic wave speeds and attenuation (dissipation of strain energy) in the Earth’s upper mantle have the potential to map key characteristics such as temperature, major-element composition, melt fraction and water content. The inversion of these data into meaningful representations of physical properties requires a robust understanding of the micromechanical processes that affect the propagation of seismic waves. Structurally bound water (hydroxyl) is believed to affect seismic properties but this has yet to be experimentally quantified. Here we present a comprehensive low-frequency forced-oscillation assessment of the seismic properties of olivine as a function of water content within the under-saturated regime that is relevant to the Earth’s interior. Our results demonstrate that wave speeds and attenuation are in fact strikingly insensitive to water content. Rather, the redox conditions imposed by the choice of metal sleeving, and the associated defect chemistry, appear to have a substantial influence on the seismic properties. These findings suggest that elevated water contents are not responsible for low-velocity or high-attenuation structures in the upper mantle. Instead, the high attenuation observed in hydrous and oxidized regions of the upper mantle (such as above subduction zones) may reflect the prevailing oxygen fugacity. In addition, these data provide no support for the hypothesis whereby a sharp lithosphere–asthenosphere boundary is explained by enhanced grain boundary sliding in the presence of water.

Control of electrochemical reactions at the capillary electrophoresis outlet/electrospray emitter electrode under CE/ESI-MS through the application of redox buffers.

PubMed

Smith, A D; Moini, M

2001-01-15

It was found that combining capillary electrophoresis (CE) and electrospray ionization mass spectrometry (ESI-MS) overlays two controlled current techniques to form a three-electrode system (CE inlet, CE outlet/ES emitter, and MS inlet electrodes) in which the CE outlet electrode and the ES emitter electrode were shared between the CE and the ESI-MS circuits. Depending on the polarities and magnitudes of the voltages at the CE inlet, CE outlet/ES emitter, and MS inlet electrodes, the nature of the two redox reactions at the shared electrode was the same or different (both reduction, both oxidation, or one oxidation and the other reduction). Several redox buffers were introduced for controlling electrochemical reactions at the shared electrode. By reacting at this electrode, redox buffers were able to maintain electrode potentials below the onset of water electrolysis, thereby eliminating gas bubble formation and/or pH drift. The volume of the gas generated due to water electrolysis was used to quantitate water oxidation or reduction at this electrode. Two types of redox buffers were used. A reactive electrode with an oxidation potential below that of water was used as the electrode under anodic conditions. Also, a reactive compound with a redox potential below that of water was added to the CE and/or ESI running buffer. When the shared electrode was the anode of both CE and ESI-MS circuits, the use of iron or etched and sanded stainless steel (ss) wire, instead of platinum wire, suppressed bubble formation at the shared electrode. Under these conditions, corrosion of the Fe wire and formation of Fe2+ replaced oxidation of water, eliminating O2 gas bubble and H+ formation. When mixtures of peptides were analyzed, iron adducts of peptides were observed. For a fresh wire, however, the intensities of adduct ions were less than 3% of the protonated molecules. After a few days of operation, the intensities of the adduct ions increased to approximately 50%, due to rust formation on the Fe wire. On-column rinsing with a 40% solution of citric acid rejuvenated the Fe wire and reduced the adduct peak intensities to less than 3%. Unmodified ss wire did not quench bubble formation, which was attributed to its passivated surface. When Fe, ss, and Pt wires were used as the shared electrode under forward polarity CE and positive ESI mode, where the shared electrode acted as a cathode with respect to CE inlet and as an anode with respect to MS inlet, reduction of water at the cathodic end of the electrode and, in the case of ss and Pt wires, oxidation of water at the anodic end of the shared electrode produced a significant amount of bubbles. Under these conditions, however, a buffer containing 50 mM p-benzoquinone completely suppressed both cathodic reduction and anodic oxidation of water for CE currents up to 4 microA. Reduction of p-benzoquinone at the cathodic end of the shared electrode to hydroquinone, and oxidation of this hydroquinone at the anodic end of the electrode, replaced reduction and oxidation of water, eliminating bubble formation. A 0.1% acetic acid solution saturated with I2 was also found to suppress bubble formation at the cathode for CE currents up to 3 microA; however, strong iodine adduct ions were observed under CE/ESI-MS when a mixture of peptides was analyzed. The application of iron as an in-capillary electrode for the analysis of a peptide mixture and a protein digest demonstrated a high separation efficiency similar to when hydroquinone was used as a redox buffer.

Effects of AN Alfalfa (medicago Sativa) Buffer Strip on Leached δ15NNITRATE Values: Implications for Management of Hydrologic N Losses

NASA Astrophysics Data System (ADS)

Kelley, C. J.; Keller, C. K.; Smith, J. L.; Evans, R. D.; Harlow, B.

2011-12-01

Buffer strips are commonly used to decrease agricultural runoff with the objective of limiting sediment and agrochemicals fluxes to surface waters. The objective of this study was to determine the effects of an alfalfa buffer strip on the magnitude and source(s) of leached nitrate from a dryland agricultural field. Previous research at the Cook Agronomy Farm has inferred two sources of nitrate in tile drain discharge, a high-discharge-season (January through May) synthetic fertilizer source, and a low-discharge-season (June through December) soil organic nitrogen source. This study examines how a change in management strategy and crop species alters the low discharge season nitrate source. In the spring of 2006 an alfalfa buffer strip approximately 20 m wide was planted running approximately north-south in the lowland portion of a 12 ha tile-drained field bordering a ditch that drains into Missouri Flat Creek. Three-year (2003 through 2005) average NO3--N flux prior to the planting of the alfalfa buffer strip was ~0.40 kg ha-1 year-1. After planting, the three-year (2006 through 2008) average NO3--N flux was ~0.38 kg ha-1 year-1. The lack of evident buffer-strip influence on the fluxes may be due in part to the large variation in precipitation amounts and timing that control water flows through the system. Three-year average δ15Nnitrate values for the tile drain pre and post planting of the alfalfa buffer strip were 6.9 ± 1.1 % and 4.2 ± 0.9 % respectively. We hypothesize that the significant difference indicates that the alfalfa strip affects the source of leached nitrate. Before planting the alfalfa buffer strip, the interpreted source of nitrate was mineralization of soil organic nitrogen from non-N2 fixing crops (spring and summer wheat varieties). After planting the alfalfa buffer strip, the source of nitrate was interpreted to be a mixture of mineralized soil organic nitrogen from N2 fixing alfalfa and non-N2 fixing crops. Further work is needed to test alternative explanations for the observed isotopic shift. This study suggests that the effects of leguminous buffer strips on nutrient fluxes are not simple, and may depend on combinations of hydrologic and pedo-geologic factors.

Gilliam County Riparian Buffers; 2003-2004 Annual Reports.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coiner, Josh

Interest appears to be at an all-time high for riparian conservation programs in Gilliam County. With the recently added Herbaceous Buffer and the already established CREP program interest is booming. However, more and more people are turning towards the herbaceous buffer because of expense. The riparian forest buffer is becoming too expensive. Even with the excellent cost share and incentives landowners are having trouble with Farm Service Agency's payment limitation. Because of this payment limitation landowners are not receiving their full rental and incentive payments, usually in year one. This has cooled the installation of riparian forest buffers and peakedmore » interest in the CP-29 (Herbaceous Buffer for Wildlife). Either way, riparian lands are being enhanced and water quality is being improved. Year three should be very similar to the accomplishments of year 2. There has already been several projects proposed that may or may not be approved during year 3. I am currently working on three projects that are all over 2.5 miles long on each side and total anywhere from 60 to 250 acres in size. Along with these three projects there at least seven small projects being proposed. Four of those projects are riparian forest buffers and the remaining are herbaceous buffers.« less

Co-solvent enhanced zinc oxysulfide buffer layers in Kesterite copper zinc tin selenide solar cells.

PubMed

Steirer, K Xerxes; Garris, Rebekah L; Li, Jian V; Dzara, Michael J; Ndione, Paul F; Ramanathan, Kannan; Repins, Ingrid; Teeter, Glenn; Perkins, Craig L

2015-06-21

A co-solvent, dimethylsulfoxide (DMSO), is added to the aqueous chemical "bath" deposition (CBD) process used to grow ZnOS buffer layers for thin film Cu2ZnSnSe4 (CZTSe) solar cells. Device performance improves markedly as fill factors increase from 0.17 to 0.51 upon the co-solvent addition. X-ray photoelectron spectroscopy (XPS) analyses are presented for quasi-in situ CZTSe/CBD-ZnOS interfaces prepared under an inert atmosphere and yield valence band offsets equal to -1.0 eV for both ZnOS preparations. When combined with optical band gap data, conduction band offsets exceed 1 eV for the water and the water/DMSO solutions. XPS measurements show increased downward band bending in the CZTSe absorber layer when the ZnOS buffer layer is deposited from water only. Admittance spectroscopy data shows that the ZnOS deposited from water increases the built-in potential (Vbi) yet these solar cells perform poorly compared to those made with DMSO added. The band energy offsets imply an alternate form of transport through this junction. Possible mechanisms are discussed, which circumvent the otherwise large conduction band spike between CZTSe and ZnOS, and improve functionality with the low-band gap absorber, CZTSe (Eg = 0.96 eV).

WATER LEVEL AND OXYGEN DELIVERY/UTILIZATION IN POROUS SALT MARSH SEDIMENTS

EPA Science Inventory

Increasing terrestrial nutrient inputs to coastal waters is a global water quality issue worldwide, and salt marshes may provide a valuable nutrient buffer, either by direct removal or by smoothing out pulse inputs between sources and sensitive estuarine habitats. A major challen...

Using physical parameters and geographic information system analyses to predict potential riparian restoration sites for giant cane in southern Illinois

Treesearch

Amanda M. Nelson; Timothy J. Stoebner; Jon E. Schoonover; Karl W.J. Williard

2014-01-01

Riparian buffers have been widely advocated as a best management practice for improving stream and lake water quality. Giant cane (Arundinaria gigantean) is a good candidate to include in multispecies riparian buffers designs, as it promotes infiltration of surface runoff and deposition of sediment and associated nutrients. To examine the potential...

Toward quantifying water pollution abatement in response to installing buffers on crop land

Treesearch

Michael G. Dosskey

2001-01-01

The scientific research literature is reviewed (i) for evidence of how much reduction in nonpoint source pollution can be achieved by installing buffers on crop land, (ii) to summarize important factors that can affect this response, and (iii) to identify remaining major information gaps that limit our ability to make probable estimates. This review is intended to...

Water Splitting via Decoupled Photocatalytic Water Oxidation and Electrochemical Proton Reduction Mediated by Electron-Coupled-Proton Buffer.

PubMed

Li, Fei; Yu, Fengshou; Du, Jian; Wang, Yong; Zhu, Yong; Li, Xiaona; Sun, Licheng

2017-10-18

Water splitting mediated by electron-coupled-proton buffer (ECPB) provides an efficient way to avoid gas mixing by separating oxygen evolution from hydrogen evolution in space and time. Though electrochemical and photoelectrochemcial water oxidation have been incorporated in such a two-step water splitting system, alternative ways to reduce the cost and energy input for decoupling two half-reactions are desired. Herein, we show the feasibility of photocatalytic oxygen evolution in a powder system with BiVO 4 as a photocatalyst and polyoxometalate H 3 PMo 12 O 40 as an electron and proton acceptor. The resulting reaction mixture was allowed to be directly used for the subsequent hydrogen evolution with the reduced H 3 PMo 12 O 40 as electron and proton donors. Our system exhibits excellent stability in repeated oxygen and hydrogen evolution, which brings considerable convenience to decoupled water splitting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stability of a secondary-type recovery process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, S.C.

1970-04-21

To provide good mobility control and to protect the components of the micellar dispersion displacing fluid from ''leaching'' into the drive fluid (water), the front portion of the drive fluid contained a mobility reducing agent, an electrolyte, and a semipolar organic compound. Berea sandstone cores (20.2 percent porosity, 336 md permeability) were saturated with water from Henry lease in Illinois (18,000 ppM TDS), flooded with sweet black crude oil (7 cp at 72/sup 0/F) from the Henry lease, and waterflooded with Henry lease water. A recovery of 93.9 percent of original oil in place was obtained by a micellar dispersionmore » followed by the mobility buffer. The micellar dispersion contained ammonium petroleum sulfonate, crude column overhead (a heavy naptha), isopropanol, p-nonyl phenol, water and sodium hydroxide. No. 530 Pusher, water from the Palestine water reservoir in Palestine, Illinois (450 ppM TDS), 50 ppM ammonium thiocyanate, n-butanol, and isopropyl alcohol (to facilitate the solubilization of the polymer) were in the mobility buffer.« less

Stability of a secondary-type recovery process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, S.C.

1970-07-14

To provide good mobility control and to protect the components of the micellar dispersion displacing fluid from ''leaching'' into the drive fluid (water), the front portion of the drive fluid contained a mobility reducing agent, an electrolyte, and a semipolar organic compound. Berea sandstone cores (20.2 percent porosity, 336 md permeability) were saturated with water from Henry lease in Illinois (18,000 ppM TDS), flooded with sweet black crude oil (7 cp at 72/sup 0/F) from the Henry lease, and waterflooded with Henry lease water. A recovery of 93.9 percent of original oil in place was obtained by a micellar dispersionmore » followed by the mobility buffer. The micellar dispersion contained ammonium petroleum sulfonate, crude column overhead (a heavy naptha), isopropanol, p-nonyl phenol, water and sodium hydroxide. No. 530 Pusher, water from the Palestine water reservoir in Palestine, Illinois (450 ppM TDS), 50 ppM ammonium thiocyanate, n-butanol, and isopropyl alcohol (to facilitate the solubilization of the polymer) were in the mobility buffer.« less

EnviroAtlas - Minneapolis/St. Paul, MN - 51m Riparian Buffer Vegetated Cover

EPA Pesticide Factsheets

This EnviroAtlas dataset describes the percentage of a 51-m riparian buffer that is vegetated. In this community, vegetated cover is defined as Trees and Forest, Grass and Herbaceous, Woody Wetlands, and Emergent Wetlands. There is a potential for decreased water quality in areas where the riparian buffer is less vegetated. The displayed line represents the center of the analyzed riparian buffer. The water bodies analyzed include hydrologically connected streams, rivers, connectors, reservoirs, lakes/ponds, ice masses, washes, locks, and rapids within the EnviroAtlas community area. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).

Understanding the fate and transport of petroleum hydrocarbons from coal tar within gasholders.

PubMed

Coulon, Frédéric; Orsi, Roberto; Turner, Claire; Walton, Chris; Daly, Paddy; Pollard, Simon J T

2009-02-01

Coal tars have been identified as posing a threat to human health due to their toxic, mutagenic and carcinogenic characteristics. Workers involved in former gasholders decommissioning are potentially exposed to relevant concentrations of volatile and semi-volatile hydrocarbons upon opening up derelict tanks and during tar excavation/removal. While information on contaminated sites air-quality and its implications on medium-long term exposure is available, acute exposure issues associated with the execution of critical tasks are less understood. Calculations indicated that the concentration of a given contaminant in the gasholder vapour phase only depends on the coal tar composition, being only barely affected by the presence of water in the gasholder and the tar volume/void space ratio. Fugacity modelling suggested that risk-critical compounds such as benzene, naphthalene and other monocyclic and polycyclic aromatic hydrocarbons may gather in the gasholder air phase at significant concentrations. Gasholder emissions were measured on-site and compared with the workplace exposure limits (WELs) currently in use in UK. While levels for most of the toxic compounds were far lower than WELs, benzene air-concentrations where found to be above the accepted threshold. In addition due to the long exposure periods involved in gasholder decommissioning and the significant contribution given by naphthalene to the total coal tar vapour concentration, the adoption of a WEL for naphthalene may need to be considered to support operators in preventing human health risk at the workplace. The Level I fugacity approach used in this study demonstrated its suitability for applications to sealed environments such as gasholders and its further refining could provide a useful tool for land remediation risk assessors.

Mineralogical and geochemical consequences of the long-term presence of CO2 in natural reservoirs: An example from the Springerville-St. Johns Field, Arizona, and New Mexico, U.S.A

USGS Publications Warehouse

Moore, J.; Adams, M.; Allis, R.; Lutz, S.; Rauzi, S.

2005-01-01

The Springerville-St. Johns CO2 field in eastern Arizona and western New Mexico is one of more than a dozen gas fields developed within the Colorado Plateau and Southern Rocky Mountain region. Extensive travertine (CaCO3) deposits record a long history of CO2 migration and leakage to the atmosphere. The oldest travertine deposits may have formed during the initial filling of the CO2 reservoir when groundwaters exsolved CO2 upon reaching the surface. The youngest travertine deposits are associated with springs on the floor of the Little Colorado River valley, but travertine deposition appears to be insignificant today. Older deposits occur up to 325 m above the valley floor. Geologic relationships suggest travertine deposition began in the late Pleistocene after volcanic activity ended at ???0.3 Ma. Most of the CaCO3 could have been derived from dissolution of the underlying limestones and dolomites. Interactions between the reservoir fluids and rocks were observed in core samples from one of the intervals that produced dry gas. These reactions resulted in the dissolution of carbonate cements and detrital feldspars and the formation of dawsonite and kaolinite. Geochemical simulations suggest that the dawsonite could have been deposited when the CO2 fugacity reached 20 bars and that the kaolinite formed as the CO2 fugacity decreased. Corrosion of drill pipe by acidic waters and a pronounced HCO3 anomaly above the CO2 reservoir provide evidence of a continuing flux of CO2 from depth. CO2 storage occurs primarily as dissolved carbonate species and as gas accumulations. Only a small percentage of the CO2 was sequestered in secondary minerals. ?? 2005 Elsevier B.V. All rights reserved.

The OceanFlux Greenhouse Gases methodology for deriving a sea surface climatology of CO2 fugacity in support of air-sea gas flux studies

NASA Astrophysics Data System (ADS)

Goddijn-Murphy, L. M.; Woolf, D. K.; Land, P. E.; Shutler, J. D.; Donlon, C.

2015-07-01

Climatologies, or long-term averages, of essential climate variables are useful for evaluating models and providing a baseline for studying anomalies. The Surface Ocean CO2 Atlas (SOCAT) has made millions of global underway sea surface measurements of CO2 publicly available, all in a uniform format and presented as fugacity, fCO2. As fCO2 is highly sensitive to temperature, the measurements are only valid for the instantaneous sea surface temperature (SST) that is measured concurrently with the in-water CO2 measurement. To create a climatology of fCO2 data suitable for calculating air-sea CO2 fluxes, it is therefore desirable to calculate fCO2 valid for a more consistent and averaged SST. This paper presents the OceanFlux Greenhouse Gases methodology for creating such a climatology. We recomputed SOCAT's fCO2 values for their respective measurement month and year using monthly composite SST data on a 1° × 1° grid from satellite Earth observation and then extrapolated the resulting fCO2 values to reference year 2010. The data were then spatially interpolated onto a 1° × 1° grid of the global oceans to produce 12 monthly fCO2 distributions for 2010, including the prediction errors of fCO2 produced by the spatial interpolation technique. The partial pressure of CO2 (pCO2) is also provided for those who prefer to use pCO2. The CO2 concentration difference between ocean and atmosphere is the thermodynamic driving force of the air-sea CO2 flux, and hence the presented fCO2 distributions can be used in air-sea gas flux calculations together with climatologies of other climate variables.

Nuclear Waste Package Mockups: A Study of In-situ Redox State

NASA Astrophysics Data System (ADS)

Helean, K.; Anderson, B.; Brady, P. V.

2006-05-01

The Yucca Mountain Repository (YMR), located in southern Nevada, is to be the first facility in the U.S. for the permanent disposal of high-level radioactive waste and spent nuclear fuels. Total system performance assessment(TSPA) has indicated that among the major radionuclides contributing to dose are Np, Tc, and I. These three radionuclides are mobile in most geochemical settings, and therefore sequestering them within the repository horizon is a priority for the Yucca Mountain Project (YMP). Corroding steel may offset radionuclide transport processes within the proposed waste packages at YMR by retaining radionuclides, creating locally reducing conditions, and reducing porosity. Ferrous iron has been shown to reduce UO22+ to UO2s, and some ferrous iron-bearing ion-exchange materials have been shown to adsorb radionuclides and heavy metals. Locally reducing conditions may lead to the reduction and subsequent immobilization of problematic dissolved species such as TcO4-, NpO2+, and UO22+ and can also inhibit corrosion of spent nuclear fuel. Water occluded during corrosion produces bulky corrosion products, and consequently less porosity is available for water and radionuclide transport. The focus of this study is on the nature of Yucca Mountain waste package corrosion products and their effects on local redox conditions, radionuclide transport, and porosity. In order to measure in-situ redox, six small-scale (1:40) waste package mockups were constructed using A516 and 316 stainless steel, the same materials as the proposed Yucca Mountain waste packages. The mockups are periodically injected with a simulated groundwater and the accumulated effluent and corrosion products are evaluated for their Fe(II)/Fe(III) content and mineralogy. Oxygen fugacities are then calculated and, thus, in-situ redox conditions are determined. Early results indicate that corrosion products are largely amorphous Fe-oxyhydroxides, goethite and magnetite. That information together with the measured Fe(II)/Fe(III) ratios in the mockup effluent constrain the oxygen fugacity to approximately 10-38 atm, many orders of magnitude below ambient. These results and their impact on radionuclide migration from YMR will be discussed.

Effects of vehicles and prodrug properties and their interactions on the delivery of 6-mercaptopurine through skin: bisacyloxymethyl-6-mercaptopurine prodrugs.

PubMed

Waranis, R P; Sloan, K B

1987-08-01

A series of S6,9-bisacyloxymethyl-6-mercaptopurine (6,9-bis-6-MP) prodrug derivatives was synthesized and characterized. The solubilities of the derivatives in solvents (vehicles), which exhibited a wide range of polarities from water to oleic acid, were measured. The abilities of the prodrugs to deliver 6-mercaptopurine (6-MP) from the vehicles have also been determined, and experimental fluxes and permeability coefficients (Kp) have been calculated for a large number of prodrug: vehicle combinations. Generally the best prodrugs of the series in terms of delivering 6-MP, regardless of the vehicle, were the first two members--the bisacetyl- and the bispropionyloxymethyl-6-mercaptopurine prodrugs. This result has been attributed mainly to the increased water solubility of these two prodrugs compared with that of 6-MP and the other prodrugs, since all of the prodrugs are much more lipid soluble than 6-MP. For three vehicles--isopropyl myristate, propylene glycol, and water--there was a good correlation between log experimental Kp for the delivery of 6-MP by the prodrugs from those vehicles and the theoretical solubility parameters of the prodrugs. The stabilities of the bisacetyl-(2), bisproprionyl-(3), and bisbutyryloxymethyl-6-mercaptopurine (4) derivatives were determined in buffer and in buffer containing enzymes leached from the dermis. Prodrug 2 was more stable than 3 or 4 in the buffer containing the enzymes, while 4 was more stable than 2 or 3 in the plain buffer.

Effect of hydrogen on the device performance and stability characteristics of amorphous InGaZnO thin-film transistors with a SiO2/SiNx/SiO2 buffer

NASA Astrophysics Data System (ADS)

Han, Ki-Lim; Ok, Kyung-Chul; Cho, Hyeon-Su; Oh, Saeroonter; Park, Jin-Seong

2017-08-01

We investigate the influence of the multi-layered buffer consisting of SiO2/SiNx/SiO2 on amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs). The multi-layered buffer inhibits permeation of water from flexible plastic substrates and prevents degradation of overlying organic layers. The a-IGZO TFTs with a multi-layered buffer suffer less positive bias temperature stress instability compared to the device with a single SiO2 buffer layer after annealing at 250 °C. Hydrogen from the SiNx layer diffuses into the active layer and reduces electron trapping at loosely bound oxygen defects near the SiO2/a-IGZO interface. Quantitative analysis shows that a hydrogen density of 1.85 × 1021 cm-3 is beneficial to reliability. However, the multi-layered buffer device annealed at 350 °C resulted in conductive characteristics due to the excess carrier concentration from the higher hydrogen density of 2.12 × 1021 cm-3.

USE OF MEMBRANE BIOREACTOR FOR BIODEGRADATION OF MTBE IN CONTAMINATED WATER1

EPA Science Inventory

An ultrafiltration membrane bioreactor was evaluated for biodegradation of methyl tert-butyl ether (MTBE) in contaminated water. The system was fed 5 mg/L MTBE in granular activated carbon (GAC) treated Cincinnati tap water containing ample buffer and nutrients. Within 120...

Spectral chemistry of green glass-bearing 15426 regolith

NASA Technical Reports Server (NTRS)

Burns, R. G.; Dyar, M. D.

1983-01-01

The detection of appreciable concentrations of ferric iron in a synthetic green glass equilibrated at an oxygen fugacity of 10 to the -11th atm prompted a Moessbauer spectral study of pristine emerald-green glass spherules carefully handpicked from regolith sample 15426. No Fe(3+) ions were detected in this lunar sample or in a synthetic green glass simulant equilibrated at fO2 = 10 to the -14th atm, suggesting that the green glass clods in rock 15426 formed under conditions of correspondingly low oxygen fugacities. The Moessbauer spectra indicated the presence of olivine crystallites in the lunar emerald green glass spherules. Measurements of homogeneous and partially devitrified synthetic silicate glasses revealed that significant changes of coordination environment about Fe(2+) ions in the glass structure occur during crystallization of olivine crystals from the melt.

Magma Ocean Depth and Oxygen Fugacity in the Early Earth--Implications for Biochemistry.

PubMed

Righter, Kevin

2015-09-01

A large class of elements, referred to as the siderophile (iron-loving) elements, in the Earth's mantle can be explained by an early deep magma ocean on the early Earth in which the mantle equilibrated with metallic liquid (core liquid). This stage would have affected the distribution of some of the classic volatile elements that are also essential ingredients for life and biochemistry - H, C, S, and N. Estimates are made of the H, C, S, and N contents of Earth's early mantle after core formation, considering the effects of variable temperature, pressure, oxygen fugacity, and composition on their partitioning. Assessment is made of whether additional, exogenous, sources are required to explain the observed mantle concentrations, and areas are identified where additional data and experimentation would lead to an improved understanding of this phase of Earth's history.

PCB and organochlorine pesticides in northern fulmars (Fulmarus glacialis) from a High Arctic colony: chemical exposure, fate, and transfer to predators.

PubMed

Foster, Karen L; Mallory, Mark L; Hill, Laura; Blais, Jules M

2011-09-01

Organochlorine contaminant concentrations, associated fugacities, and stable isotopes of nitrogen (δ(15) N) are reported for liver, whole body homogenate, and opportunistically collected samples of prey (amphipods), stomach oils, digestive tract contents, and guano for northern fulmars (Fulmarus glacialis) collected at Cape Vera, Devon Island in the Canadian High Arctic. Liver concentrations of polychlorinated biphenyls (ΣPCB) and ΣDDT were on average 49.9 ± 35.4 ng g(-1) and 29.9 ± 25.2 ng g(-1) wet weight, respectively. Whole body homogenate concentrations of ΣPCB and ΣDDT were 637 ± 293 ng g(-1) and 365 ± 212 ng g(-1) wet weight, respectively. A mass and energy balance showed that whole body contaminant concentrations, which are seldom reported for Arctic seabirds, are critical in determining contaminant exposure and associated risk to predators such as the Arctic fox (Alopex lagopus). Biomagnification in the fulmars is evident, because concentrations and fugacities of contaminants were generally one to three orders of magnitude higher than those of likely prey items. The fate of diet-derived contaminants along the digestive tract is discussed, in particular with respect to stomach oils, which are used to feed chicks and for defensive purposes. The benefits of considering both concentrations and fugacities are demonstrated and provide information on the absorption and distribution of chemicals within the fulmars and contaminant transfer to offspring and predators. Copyright © 2011 SETAC.

Developing and applying a site-specific multimedia fate model to address ecological risk of oxytetracycline discharged with aquaculture effluent in coastal waters off Jangheung, Korea.

PubMed

Kim, Woojung; Lee, Yunho; Kim, Sang Don

2017-11-01

The overuse of oxytetracycline (OTC) in aquaculture has become a problem because of its chronic toxic effects on marine ecosystems. The present study assessed the ecological risk of OTC in the coastal waters near the Jangheung Flatfish Farm using a site-specific multimedia fate model to analyze exposure. Before the model was applied, its performance was validated by comparing it with field data. The coastal waters in the testbed were sampled and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) followed by solid-phase extraction (SPE). The concentrations of OTC measured varied from 7.05 to 95.39ng/L. The results of validating the models showed that the site-specific multimedia fate model performed better (root mean square error (RMSE): 24.217, index of agreement (IOA): 0.739) than conventional fugacity approaches. This result demonstrated the utility of this model in supporting effective future management of aquaculture effluent. The results of probabilistic risk assessment indicated that OTC from aquaculture effluent did not cause adverse effects, even in a maximum-use scenario. Copyright © 2017 Elsevier Inc. All rights reserved.

Synthesis and characterization of oxytetracycline imprinted magnetic polymer for application in food

NASA Astrophysics Data System (ADS)

Aggarwal, Sneha; Rajput, Yudhishthir Singh; Singh, Gulab; Sharma, Rajan

2016-02-01

Magnetic imprinted polymer was prepared by polymerization of methacrylate and ethyleneglycoldimethacrylate in the presence of oxytetracycline on the surface of iron magnetite. Selectivity of prepared polymer was calculated from ratio of partition coefficient of oxytetracycline for imprinted and non- imprinted polymer in water, acetonitrile, methanol and at different pH in aqueous buffer. pH of solvent exhibited pronounced effect on selectivity. Selectivity at pH 7.0, 6.0 and 5.0 was 36.0, 2.25 and 1.61 fold higher than at pH 4.0. Imprinted polymer was not selective for oxytetracycline in methanol. However, selectivity in water and acetonitrile was 19.42 and 2.86, respectively. Oxytetracycline did bind to imprinted polymer in water or aqueous buffer (pH 7.0) and could be eluted with methanol. Prepared polymer extracted 75-80 % oxytetracycline from water, honey and egg white.

Optimizing buffering chemistry to maintain near neutral pH of broiler feed during pre-enrichment for Salmonella.

PubMed

Berrang, M E; Cosby, D E; Cox, N A; Cason, J A; Richardson, K E

2015-12-01

Salmonella is a human pathogen that can accompany live broilers to the slaughter plant, contaminating fully processed carcasses. Feed is one potential source of Salmonella to growing broilers. Monitoring feed for the presence of Salmonella is part of good agricultural practice. The first step in culturing feed for Salmonella (which may be at low numbers and sub-lethally stressed) is to add it to a pre-enrichment broth which is incubated for 24 h. During the course of pre-enrichment, extraneous bacteria metabolize carbohydrates in some feed and excrete acidic byproducts, causing the pH to drop dramatically. An acidic pre-enrichment pH can injure or kill Salmonella resulting in a failure to detect, even if it is present and available to infect chickens. The objective of this study was to test an array of buffering chemistries to prevent formation of an injurious acidic environment during pre-enrichment of feed in peptone water. Five grams of feed were added to 45 mL of peptone water buffered with carbonate, Tris pH 8, and phosphate buffering ingredients individually and in combination. Feed was subjected to a pre-enrichment at 35°C for 24 h; pH was measured at 0, 18, and 24 h. Standard phosphate buffering ingredients at concentrations up to 4 times the normal formulation were unable to fully prevent acidic conditions. Likewise, carbonate and Tris pH 8 were not fully effective. The combination of phosphate, carbonate, and Tris pH 8 was the most effective buffer tested. It is recommended that a highly buffered pre-enrichment broth be used to examine feed for the presence of Salmonella. Published by Oxford University Press on behalf of Poultry Science Association 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Solubility of oxygen in liquid Fe at high pressure and consequences for the early differentiation of Earth and Mars

NASA Astrophysics Data System (ADS)

Rubie, D. C.; Gessmann, C. K.; Frost, D. J.

2003-04-01

Knowledge of the solubility of oxygen in liquid iron enables the partitioning of oxygen between metal and silicates and the oxidation state of residual silicates to be constrained during core formation in planetary bodies. We have determined oxygen solubility experimentally at 5--23 GPa, 2100--2700 K and oxygen fugacities 1--4 log units below the iron-wüstite buffer in samples of liquid Ni-Fe alloy contained in magnesiowüstite capsules using a multianvil apparatus. Results show that oxygen solubility increases with increasing temperature but decreases slightly with increasing pressure over the range of experimental conditions, at constant oxygen fugacity. Using an extrapolation of the results to higher pressures and temperatures, we have modeled the geochemical consequences of metal-silicate separation in magma oceans in order to explain the contrasting FeO contents of the mantles of Earth and Mars. We assume that both Earth and Mars accreted originally from material with a chondritic composition; because the initial oxidation state is uncertain, we vary this parameter by defining the initial oxygen content. Two metal-silicate fractionation models are considered: (1) Metal and silicate are allowed to equilibrate at fictive conditions that approximate the pressure and temperature at the base of a magma ocean. (2) The effect of settling Fe droplets in a magma ocean is determined using a simple polybaric metal-silicate fractionation model. We assume that the temperature at the base of a magma ocean is close to the peridotite liquidus. In the case of Earth, high temperatures in a magma ocean with a depth >1200 km would have resulted in significant quantities of oxygen dissolving in the liquid metal with the consequent extraction of FeO from the residual silicate. In contrast, on Mars, even if the magma ocean extended to the depth of the current core-mantle boundary, temperatures would not have been sufficiently high for oxygen solubility in liquid metal to be significant. The results show that Earth and Mars could have accreted from similar material, with an initial FeO content around 18 wt%. On Earth, oxygen was extracted from silicates by the segregating metal during core formation, leaving the mantle with its present FeO content of ˜8 wt%. On Mars, in contrast, the segregating metal extracted little or no oxygen and left the FeO content unaltered at ˜18 wt%. A consequence of this model is that oxygen should be an important light element in the Earth's core but not in the Martian core.

The solubility of Pd and Au in hydrous intermediate silicate melts: The effect of oxygen fugacity and the addition of Cl and S

NASA Astrophysics Data System (ADS)

Sullivan, Neal A.; Zajacz, Zoltan; Brenan, James M.

2018-06-01

The solubilities of Pd and Au in a hydrous trachyandesitic melt were experimentally determined at 1000 °C and 200 MPa at oxygen fugacity (ƒO2) from 0.45 log units below to 6.55 log units above the Ni-NiO buffer (NNO). The effect of adding metal-binding ligands (i.e. Cl and S) to the silicate melt was also studied. The solubility of Au increases from 0.15 ± 0.1 to 3.85 ± 1.48 ppm in Cl- and S-free melts with ƒO2 increasing from NNO-0.45 to NNO+6.55 with a slope that suggests that it is present in 1+ oxidation state over the entire studied ƒO2 range. On the other hand, Pd solubility, shows a more moderate increase with ƒO2, especially in the lower half of the studied range, increasing from 2.66 ± 0.25 ppm at NNO-0.45 to only 3.62 ± 0.38 ppm at NNO+1.72 in Cl- and S-free melts. Overall, the variation in Pd solubility as a function of ƒO2 indicates Pd being dissolved in the silicate melt in both zero and 1+ oxidation state, with the former being dominant below NNO+4.5. At NNO-0.45 to +3.48, the addition of 3170-4060 ppm Cl to the silicate melt increased the solubility of Au by an average factor of 1.5, in comparison to Cl-free melts. However, at NNO+6.55, Au solubility increased by a factor of 2.5. The addition of Cl had a negligible effect on the solubility of Pd except for a large increase (factor of 2.4) at NNO+6.55. At reducing conditions (NNO-0.45), the addition of 170 ppm S to the silicate melt increased the solubility of Au by a factor of ∼4 but did not change the solubility of Pd in comparison to S-free melts. The observation that Pd is dominantly present as Pd0 at NNO < +4.5 may explain the lack of complexation with potential reduced sulfur-bearing and chloride ligands. As one may expect similar behavior in fluids degassing from magmas at depth, the lack of oxidized Pd species could be an important factor behind the scarcity of economically viable Pd-rich magmatic-hydrothermal deposits observed in nature.

The effect of residual water on antacid properties of sucralfate gel dried by microwaves.

PubMed

Gainotti, Alessandro; Losi, Elena; Colombo, Paolo; Santi, Patrizia; Sonvico, Fabio; Baroni, Daniela; Massimo, Gina; Colombo, Gaia; Del Gaudio, Pasquale

2006-01-20

The aim of this work was to study the acid neutralization characteristics of microwave-dried sucralfate gel in relation to the water content and physical structure of the substance. Several dried sucralfate gels were compared with humid sucralfate gel and sucralfate nongel powder in terms of neutralization rate and buffering capacity. Humid sucralfate gel and microwave-dried gel exhibited antacid effectiveness. In particular, the neutralization rate of dried gel powders was inversely related to the water content: as the water content of dried powders decreased, the acid reaction rate linearly increased. The relationship was due to the different morphology of dried sucralfate gels. In fact, the porosity of the dried samples increased with the water reduction. However, the acid neutralization equivalent revealed that the dried sucralfate gel became more resistant to acid attack in the case of water content below 42%. Then, the microwave drying procedure had the opposite effect on the reactivity of the aluminum hydroxide component of dried sucralfate gel powders, since the rate of the reaction increased whereas the buffering capacity decreased as the amount of water was reduced.

The effect of residual water on antacid properties of sucralfate gel dried by microwaves.

PubMed

Gainotti, Alessandro; Losi, Elena; Colombo, Paolo; Santi, Patrizia; Sonvico, Fabio; Baroni, Daniela; Massimo, Gina; Colombo, Gaia; Del Gaudio, Pasquale

2006-03-01

The aim of this work was to study the acid neutralization characteristics of microwave-dried sucralfate gel in relation to the water content and physical structure of the substance. Several dried sucralfate gels were compared with humid sucralfate gel and sucralfate nongel powder in terms of neutralization rate and buffering capacity. Humid sucralfate gel and microwave-dried gel exhibited antacid effectiveness. In particular, the neutralization rate of dried gel powders was inversely related to the water content: as the water content of dried powders decreased, the acid reaction rate linearly increased. The relationship was due to the different morphology of dried sucralfate gels. In fact, the porosity of the dried samples increased with the water reduction. However, the acid neutralization equivalent revealed that the dried sucralfate gel became more resistant to acid attack in the case of water content below 42%. Then, the microwave drying procedure had the opposite effect on the reactivity of the aluminum hydroxide component of dried sucralfate gel powders, since the rate of the reaction increased whereas the buffering capacity decreased as the amount of water was reduced.

Application of a Homogenous Assay for the Detection of 2,4,6-Trinitrotoluene to Environmental Water Samples

PubMed Central

Goldman, Ellen R.; Egge, Adrienne L.; Medintz, Igor L.; Lassman, Michael E.; Anderson, George P.

2005-01-01

A homogeneous assay was used to detect 2,4,6-trinitrotoluene (TNT) spiked into environmental water samples. This assay is based on changes in fluorescence emission intensity when TNT competitively displaces a fluorescently labeled, TNT analog bound to an anti-TNT antibody. The effectiveness of the assay was highly dependent on the source of the sample being tested. As no correlation between pH and assay performance was observed, ionic strength was assumed to be the reason for variation in assay results. Addition of 10x phosphate-buffered saline to samples to increase their ionic strength to that of our standard laboratory buffer (about 0.17 M) significantly improved the range over which the assay functioned in several river water samples. PMID:15915298

CONSTRUCTED WETLANDS IN SUPPORT OF RIPARIAN RESTORATION: WATER QUALITY BENEFITS AND HABITAT RESTORATION IN DELAWARE AGRICULTURAL AREAS

EPA Science Inventory

Surface water runoff from agricultural landscapes is one of the major sources of water quality impairment in the United States. With the advent of buffer strips and conservation minded tilling practices the agricultural community has made significant reductions in overland runof...

DENITRIFICATION ENZYME ACTIVITY OF FRINGE SALT MARSHES IN NEW ENGLAND (USA)

EPA Science Inventory

Coastal salt marshes are a buffer between the uplands and adjacent coastal waters in New England (USA). With increasing N loads from developed watersheds, salt marshes could play an important role in the water quality maintenance of coastal waters. In this study we examined seaso...

Influence of Dissolution Media and Presence of Alcohol on the In Vitro Performance of Pharmaceutical Products Containing an Insoluble Drug.

PubMed

Friuli, Valeria; Bruni, Giovanna; Musitelli, Giorgio; Conte, Ubaldo; Maggi, Lauretta

2018-01-01

The purpose of this investigation is to determine how the dissolution media may influence the release rate of an insoluble drug in in vitro conditions. Some oral dosage forms containing ibuprofen, a molecule that shows pH-dependent solubility, are tested. They are evaluated in different media to simulate the gastrointestinal transit at paddle rotation speeds of 50 and 100 rpm. Moreover, the potential effect of different ethanol concentrations on drug release is tested. The dissolution profiles of the tablets show a similar behavior in water (pH 1.0) and phosphate buffer (pH 4.5) where the 2 doses are not completely dissolved. The soft capsules show a different behavior: a certain amount of ibuprofen, which is in solution inside the capsule, reprecipitates in water and in the pH 4.5 buffer. Instead, ibuprofen dissolves rapidly in the pH 6.8 buffer from all the formulations. In the water-ethanol solutions, the dissolution curves show a valuable increase in the drug dissolved at higher ethanol concentrations. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Application of low frequency pulsed ohmic heating for inactivation of foodborne pathogens and MS-2 phage in buffered peptone water and tomato juice.

PubMed

Kim, Sang-Soon; Choi, Won; Kang, Dong-Hyun

2017-05-01

The purpose of this study was to inactivate foodborne pathogens effectively by ohmic heating in buffered peptone water and tomato juice without causing electrode corrosion and quality degradation. Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes were used as representative foodborne pathogens and MS-2 phage was used as a norovirus surrogate. Buffered peptone water and tomato juice inoculated with pathogens were treated with pulsed ohmic heating at different frequencies (0.06-1 kHz). Propidium iodide uptake values of bacterial pathogens were significantly (p < 0.05) larger at 0.06-0.5 kHz than at 1 kHz, and sub-lethal injury of pathogenic bacteria was reduced by decreasing frequency. MS-2 phage was inactivated more effectively at low frequency, and was more sensitive to acidic conditions than pathogenic bacteria. Electrode corrosion and quality degradation of tomato juice were not observed regardless of frequency. This study suggests that low frequency pulsed ohmic heating is applicable to inactivate foodborne pathogens effectively without causing electrode corrosion and quality degradation in tomato juice. Copyright © 2016. Published by Elsevier Ltd.

Climate regulation, energy provisioning and water purification: Quantifying ecosystem service delivery of bioenergy willow grown on riparian buffer zones using life cycle assessment.

PubMed

Styles, David; Börjesson, Pål; D'Hertefeldt, Tina; Birkhofer, Klaus; Dauber, Jens; Adams, Paul; Patil, Sopan; Pagella, Tim; Pettersson, Lars B; Peck, Philip; Vaneeckhaute, Céline; Rosenqvist, Håkan

2016-12-01

Whilst life cycle assessment (LCA) boundaries are expanded to account for negative indirect consequences of bioenergy such as indirect land use change (ILUC), ecosystem services such as water purification sometimes delivered by perennial bioenergy crops are typically neglected in LCA studies. Consequential LCA was applied to evaluate the significance of nutrient interception and retention on the environmental balance of unfertilised energy willow planted on 50-m riparian buffer strips and drainage filtration zones in the Skåne region of Sweden. Excluding possible ILUC effects and considering oil heat substitution, strategically planted filter willow can achieve net global warming potential (GWP) and eutrophication potential (EP) savings of up to 11.9 Mg CO 2 e and 47 kg PO 4 e ha -1 year -1 , respectively, compared with a GWP saving of 14.8 Mg CO 2 e ha -1 year -1 and an EP increase of 7 kg PO 4 e ha -1 year -1 for fertilised willow. Planting willow on appropriate buffer and filter zones throughout Skåne could avoid 626 Mg year -1 PO 4 e nutrient loading to waters.

Intertidal salt marshes as an important source of inorganic carbon to the coastal ocean

USGS Publications Warehouse

Wang, Zhaohui Aleck; Kroeger, Kevin D.; Ganju, Neil K.; Gonneea, Meagan; Chu, Sophie N.

2016-01-01

Dynamic tidal export of dissolved inorganic carbon (DIC) to the coastal ocean from highly productive intertidal marshes and its effects on seawater carbonate chemistry are thoroughly evaluated. The study uses a comprehensive approach by combining tidal water sampling of CO2parameters across seasons, continuous in situ measurements of biogeochemically-relevant parameters and water fluxes, with high-resolution modeling in an intertidal salt marsh of the U.S. northeast region. Salt marshes can acidify and alkalize tidal water by injecting CO2 (DIC) and total alkalinity (TA). DIC and TA generation may also be decoupled due to differential effects of marsh aerobic and anaerobic respiration on DIC and TA. As marsh DIC is added to tidal water, the buffering capacity first decreases to a minimum and then increases quickly. Large additions of marsh DIC can result in higher buffering capacity in ebbing tide than incoming tide. Alkalization of tidal water, which mostly occurs in the summer due to anaerobic respiration, can further modify buffering capacity. Marsh exports of DIC and alkalinity may have complex implications for the future, more acidified ocean. Marsh DIC export exhibits high variability over tidal and seasonal cycles, which is modulated by both marsh DIC generation and by water fluxes. The marsh DIC export of 414 g C m−2 yr−1, based on high-resolution measurements and modeling, is more than twice the previous estimates. It is a major term in the marsh carbon budget and translates to one of the largest carbon fluxes along the U.S. East Coast.

Buffer salt effects in off-line coupling of capillary electrophoresis and mass spectrometry.

PubMed

Marák, Jozef; Stanová, Andrea

2014-05-01

In this work, the impact of buffer salts/matrix effects on the signal in direct injection MS with an electrospray interface (DI-ESI-MS) following pITP fractionation of the sample was studied. A range of buffers frequently used in CE analyses (pH 3-10) was prepared containing 10, 50, and 90% v/v of ACN, respectively. The sets of calibration solutions of cetirizine (an antihistaminic drug with an amphiprotic character) within a 0.05-2.0 mg/L concentration range were prepared in different buffers. The greatest enhancements in the MS signal (in terms of change in the slope of the calibration line) were obtained for the beta-alanine buffer (pH 3.5) in positive ionization and for the borate buffer (pH 9.2) in negative ionization, respectively. The procedure was successfully applied to the analysis of buserelin (a peptidic drug). The slope of the calibration line for solutions containing the beta-alanine buffer with 50% of ACN was 4 times higher than for water or urine, respectively. This study clearly demonstrates that the buffer salt/matrix effects in an offline combination of pITP and DI-ESI-MS can also play a positive role, as they can enhance the signal in MS. A similar influence of the above effects can also be presumed in the CE techniques combined on-line with ESI-MS.

Flow Injection Analysis with Electrochemical Detection for Rapid Identification of Platinum-Based Cytostatics and Platinum Chlorides in Water

PubMed Central

Kominkova, Marketa; Heger, Zbynek; Zitka, Ondrej; Kynicky, Jindrich; Pohanka, Miroslav; Beklova, Miroslava; Adam, Vojtech; Kizek, Rene

2014-01-01

Platinum-based cytostatics, such as cisplatin, carboplatin or oxaliplatin are widely used agents in the treatment of various types of tumors. Large amounts of these drugs are excreted through the urine of patients into wastewaters in unmetabolised forms. This phenomenon leads to increased amounts of platinum ions in the water environment. The impacts of these pollutants on the water ecosystem are not sufficiently investigated as well as their content in water sources. In order to facilitate the detection of various types of platinum, we have developed a new, rapid, screening flow injection analysis method with electrochemical detection (FIA-ED). Our method, based on monitoring of the changes in electrochemical behavior of analytes, maintained by various pH buffers (Britton-Robinson and phosphate buffer) and potential changes (1,000, 1,100 and 1,200 mV) offers rapid and cheap selective determination of platinum-based cytostatics and platinum chlorides, which can also be present as contaminants in water environments. PMID:24499878

[Determination of equilibrium solubility and n-octanol/water partition coefficient of pulchinenosiden D by HPLC].

PubMed

Rao, Xiao-Yong; Yin, Shan; Zhang, Guo-Song; Luo, Xiao-Jian; Jian, Hui; Feng, Yu-Lin; Yang, Shi-Lin

2014-05-01

To determine the equilibrium solubility of pulchinenosiden D in different solvents and its n-octanol/water partition coefficients. Combining shaking flask method and high performance liquid chromatography (HPLC) to detect the n-octanol/water partition coefficients of pulchinenosiden D, the equilibrium solubility of pulchinenosiden D in six organic solvents and different pH buffer solution were determined by HPLC analysis. n-Octanol/water partition coefficients of pulchinenosiden D in different pH were greater than zero, the equilibrium solubility of pulchinenosiden D was increased with increase the pH of the buffer solution. The maximum equilibrium solubility of pulchinenosiden D was 255.89 g x L(-1) in methanol, and minimum equilibrium solubility of pulchinenosiden D was 0.20 g x L(-1) in acetonitrile. Under gastrointestinal physiological conditions, pulchinenosiden D exists in molecular state and it has good absorption but poor water-solubility, so increasing the dissolution rate of pulchinenosiden D may enhance its bioavailability.

Formation of hydrothermal tin deposits: Raman spectroscopic evidence for an important role of aqueous Sn(IV) species

NASA Astrophysics Data System (ADS)

Schmidt, Christian

2018-01-01

The speciation of tin and the solubility of cassiterite in H2O + HCl were determined at temperatures to 600 °C using in situ Raman spectroscopy. In addition, information on the fluid-melt partition of Sn was obtained at 700 °C and indicated a preference of the fluid only at HCl concentrations that are much higher than in fluids exsolved from natural felsic melts. Dissolution of cassiterite generally resulted in formation of Sn(IV) species unless reduced conditions were generated by hydrogen permeation or carbohydrates in the starting material. The prevalent aqueous Sn(IV) species was [SnCl4(H2O)2]0, with additional [SnCl3(H2O)3]+ and [SnCl5(H2O)]-. The only detectable Sn(II) species was very likely [Sn(II)Cl3]-. Cassiterite solubility increased with HCl concentration and was generally high in H2O+HCl fluids, with no strong dependencies on temperature, pressure, or the oxidation state of tin in the fluid. The Sn(IV) concentrations at 500 and 600 °C determined from the integrated ν1[Sn(IV)sbnd Cl] band intensity are in good agreement with literature data on the cassiterite solubility in H2O + HCl at oxygen fugacities along the hematite-magnetite buffer. The combined results from previous experimental studies and this study demonstrate that HCl molality is a crucial parameter for hydrothermal mobilization and transport of tin and for cassiterite precipitation, and that pH, pressure and temperature are less important. Current models on hydrothermal tin deposit formation need to be augmented to include Sn(IV)sbnd Cl complexes as significant tin-transporting species. Irrespective of the oxidation state of tin in the fluid, cassiterite precipitates due to reaction of the hydrothermal fluid with the wall rock (greisen or skarn formation), dilution (mixing with meteoric water) or a decrease in the HCl activity in the aqueous liquid by boiling. A redox reaction is only required for tin transported as Sn(II) to be converted to Sn(IV).

Water quality impact assessment of agricultural Beneficial Management Practices (BMPs) simulated for a regional catchment in Quebec, Eastern Canada

NASA Astrophysics Data System (ADS)

Rousseau, Alain N.; Hallema, Dennis W.; Gumiere, Silvio J.; Savary, Stéphane; Hould Gosselin, Gabriel

2014-05-01

Water quality has become a matter of increasing concern over the past four decades as a result of the intensification of agriculture, and more particularly so in Canada where agriculture has evolved into the largest non-point source of surface water pollution. The Canadian WEBs project (Watershed Evaluation of Beneficial Management Practices, BMPs) was initiated in order to determine the efficiency of BMPs in improving the surface water quality of rural catchments, and the economic aspects related to their implementation on the same scale. In this contribution we use the integrated watershed modelling platform GIBSI (Gestion Intégrée des Bassins versants à l'aide d'un Système Informatisé) to evaluate the effects of various BMPs on sediment and nutrient yields and, in close relation to this, the surface water quality for the Beaurivage River catchment (718 km2) in Quebec, eastern Canada. A base scenario of the catchment is developed by calibrating the different models of the GIBSI platform, namely HYDROTEL for hydrology, the Revised Universal Soil Loss Equation (RUSLE) for soil erosion, the Erosion-Productivity Impact Calculator (EPIC) of the Soil and Water Assessment Tool (SWAT) for contaminant transport and fate, and QUAL2E for stream water quality. Four BMPs were analysed: (1) vegetated riparian buffer strips, (2) precision slurry application, (3) transition of all cereal and corn fields to grassland (grassland conversion), and (4) no-tillage on corn fields. Simulations suggest that riparian buffer strips and grassland conversion are more effective in terms of phosphorus, nitrogen and sediment load reduction than precision slurry application and no-tillage on corn fields. The results furthermore indicate the need for a more profound understanding of sediment dynamics in streams and on riparian buffer strips.

Upland-wetland connectivity provides a significant nexus between isolated wetlands and downstream water bodies

NASA Astrophysics Data System (ADS)

Mclaughlin, D. L.; Kaplan, D. A.; Cohen, M. J.

2013-12-01

Recent rulings by the U.S. Supreme Court have limited federal protection over isolated wetlands, requiring documentation of a 'significant nexus' to a navigable water body to ensure federal jurisdiction. Despite geographic isolation, isolated wetlands influence the surficial aquifer dynamics that regulate baseflow to surface water systems. Due to differences in specific yield (Sy) between upland soils and inundated wetlands, responses of the upland water table to atmospheric fluxes (precipitation, P, and evapotranspiration, ET) are amplified relative to wetland water levels, leading to reversals in the hydraulic gradient between the two systems. As such, wetlands act as a water sink during wet cycles (via wetland exfiltration) and a source (via infiltration) during drier times, regulating both the surficial aquifer and its baseflow to downstream systems. To explore the importance of this wetland function at the landscape scale, we integrated models of soil moisture, upland water table, and wetland stage to simulate the hydrology of a low-relief, depressional landscape. We quantified the hydrologic buffering effect of wetlands by calculating the relative change in the standard deviation (SD) of water table elevation between model runs with and without wetlands. Using this model we explored the effects wetland area and spatial distribution over a range of climatic drivers (P and ET) and soil types. Increasing wetland cumulative area and/or density reduced water table variability relative to landscapes without wetlands, supporting the idea that wetlands stabilize regional hydrologic variation, but also increased mean water table depth because of sustained high ET rates in wetlands during dry periods. Maintaining high cumulative wetland area, but with fewer wetlands, markedly reduced the effect of wetland area, highlighting the importance of small, distributed wetlands on water table regulation. Simulating a range of climate scenarios suggested that the capacity of wetlands to buffer water table variation is most pronounced along a 'sweet spot' where P and ET are relatively balanced. High P and low ET yielded consistently high water tables with wetlands acting predominantly as sinks (i.e., little switching behavior), while low P and high ET scenarios limited wetland inundation. On the other hand, when both P and ET were moderate, the SD of the regional water table was reduced by nearly 50% for landscapes with 30% wetland area distributed over ~1 ha watersheds. Additionally, we found these buffering effects to be stronger in coarser soils compared with finer soils. Considering the strong influence of regional water table on downstream surface water systems, loss of isolated wetland area or mitigation of this loss at the expense of wetland density (i.e., large mitigation banks to replace small distributed systems) has the potential to significantly impact downstream water bodies. Isolated wetlands buffer surficial aquifer dynamics by providing water storage capacitance at the landscape scale and ultimately exert hydraulic regulation of regional surface waters through an indirect, but significant nexus.

Biomass production in the Lower Mississippi River Basin: Mitigating associated nutrient and sediment discharge to the Gulf of Mexico.

PubMed

Ha, Miae; Zhang, Zhonglong; Wu, May

2018-04-24

A watershed model was developed using the Soil and Water Assessment Tool (SWAT) that simulates nitrogen, phosphorus, and sediment loadings in the Lower Mississippi River Basin (LMRB). The LMRB SWAT model was calibrated and validated using 21 years of observed flow, sediment, and water-quality data. The baseline model results indicate that agricultural lands within the Lower Mississippi River Basin (LMRB) are the dominant sources of nitrogen and phosphorus discharging into the Gulf of Mexico. The model was further used to evaluate the impact of biomass production, in the presence of riparian buffers in the LMRB, on suspended-sediment and nutrient loading discharge from the Mississippi River into the Gulf of Mexico. The interplay among land use, riparian buffers, crop type, land slope, water quality, and hydrology were anlyzed at various scales. Implementing a riparian buffer in the dominant agricultural region within the LMRB could reduce suspended sediment, nitrogen, and phosphorus loadings at the regional scale by up to 65%, 38%, and 39%, respectively. Implementation of this land management practice can reduce the suspended-sediment content and improve the water quality of the discharge from the LMRB into the Gulf of Mexico and support the potential production of bioenergy and bio-products within the Mississippi River Basin. Copyright © 2017 Elsevier B.V. All rights reserved.

On the pH of Aqueous Attoliter-Volume Droplets

NASA Astrophysics Data System (ADS)

Ramos, Kieran P.; Velpula, Samson S.; Demille, Trevor B.; Pajela, Ryan; Goldner, Lori S.

Droplets of water dispersed in perfluorinated liquids have widespread use including microfluidics, drug delivery and single-molecule measurements. Perfluorinated liquids are distinctly biocompatible due to their stability, low surface tension, lipophobicity, and hydrophobicity. For this reason, the effect of the perfluorinated surface on droplet contents is usually ignored. However, as the droplet diameter is reduced, we expect that any effect of the water/oil interface on droplet contents will become more obvious. We studied the pH of attoliter-volume aqueous droplets in perfluorinated liquids using pH-sensing fluorescent dyes. Droplets were prepared either by sonication or extrusion from buffer and perfluorinated liquids (FC40 or FC77). A non-ionic surfactant was used to stabilize the droplets. Buffer strength, ionic strength, and pH of the aqueous phase were varied and resulting droplet pH compared to the pH of the buffer from which they were formed. Preliminary data are consistent with a pH in droplets that depends on the concentration of non-ionic surfactant. At low surfactant concentrations, the pH in droplets is distinctly lower than the stock buffer. However, as the concentration of non-ionic surfactant is increased the change in pH decreases. This work was funded by NSF/DBI-1152386.

Defect prevention in silica thin films synthesized using AP-PECVD for flexible electronic encapsulation

NASA Astrophysics Data System (ADS)

Elam, Fiona M.; Starostin, Sergey A.; Meshkova, Anna S.; van der Velden-Schuermans, Bernadette C. A. M.; van de Sanden, Mauritius C. M.; de Vries, Hindrik W.

2017-06-01

Industrially and commercially relevant roll-to-roll atmospheric pressure-plasma enhanced chemical vapour deposition was used to synthesize smooth, 80 nm silica-like bilayer thin films comprising a dense ‘barrier layer’ and comparatively porous ‘buffer layer’ onto a flexible polyethylene 2,6 naphthalate substrate. For both layers, tetraethyl orthosilicate was used as the precursor gas, together with a mixture of nitrogen, oxygen and argon. The bilayer films demonstrated exceptionally low effective water vapour transmission rates in the region of 6.1  ×  10-4 g m-2 d-1 (at 40 °C, 90% relative humidity), thus capable of protecting flexible photovoltaics and thin film transistors from degradation caused by oxygen and water. The presence of the buffer layer within the bilayer architecture was mandatory in order to achieve the excellent encapsulation performance. Atomic force microscopy in addition to solvent permeation measurements, confirmed that the buffer layer prevented the formation of performance-limiting defects in the bilayer thin films, which likely occur as a result of excessive plasma-surface interactions during the deposition process. It emerged that the primary function of the buffer layer was therefore to act as a protective coating for the flexible polymer substrate material.

THE INDOOR FUGACITY MODEL

EPA Science Inventory

Dermal and non-dietary pathways are potentially significant exposure pathways to pesticides used in the home. The exposure pathways include dermal contact through the hands and skin, ingestion from hand to mouth activities, ingestion through contact with toys and other items, ...

Hydrothermal stability of adenine under controlled fugacities of N2, CO2 and H2.

PubMed

Franiatte, Michael; Richard, Laurent; Elie, Marcel; Nguyen-Trung, Chinh; Perfetti, Erwan; LaRowe, Douglas E

2008-04-01

An experimental study has been carried out on the stability of adenine (one of the five nucleic acid bases) under hydrothermal conditions. The experiments were performed in sealed autoclaves at 300 degrees C under fugacities of CO(2), N(2) and H(2) supposedly representative of those in marine hydrothermal systems on the early Earth. The composition of the gas phase was obtained from the degradation of oxalic acid, sodium nitrite and ammonium chloride, and the oxidation of metallic iron. The results of the experiments indicate that after 200 h, adenine is still present in detectable concentration in the aqueous phase. In fact, the concentration of adenine does not seem to be decreasing after approximately 24 h, which suggests that an equilibrium state may have been established with the inorganic constituents of the hydrothermal fluid. Such a conclusion is corroborated by independent thermodynamic calculations.

57Fe Mössbauer spectroscopy of mineral assemblages in mantle spinel lherzolites from Cenozoic alkali basalt, eastern China: Petrological applications

NASA Astrophysics Data System (ADS)

Hao, Xi-Luo; Li, Yi-Liang

2013-01-01

Mineral assemblages in spinel lherzolite xenoliths from the Cenozoic alkali basalt of eastern China were analyzed by 57Fe Mössbauer spectroscopy for Fe3+/ΣFe and distribution of Fe2+/Fe3+ in non-equivalent crystal cites. Orthopyroxene, clinopyroxene and spinel have 0.08-0.13, 0.19-0.31 and 0.13-0.23 Fe3+/ΣFe, respectively. The cation-exchange equilibrium temperatures, Fe3+ partition coefficient and oxygen fugacity of the upper mantle peridotites were calculated. The equilibrium temperatures are between 1103 K and 1405 K consistent with those reported elsewhere. The oxygen fugacities of spinel lherzolites calculated with olivine-orthopyroxene-spinel (ΔlogƒO2 from - 1.1 to 0) and clinopyroxene-olivine-orthopyroxene oxybarometers (ΔlogƒO2 from - 2.0 to 0.7) are consistent with previously reported upper mantle values.

The Fe-C-O-H-N system at 6.3-7.8 GPa and 1200-1400 °C: implications for deep carbon and nitrogen cycles

NASA Astrophysics Data System (ADS)

Sokol, Alexander G.; Tomilenko, Anatoly A.; Bul'bak, Taras A.; Kruk, Alexey N.; Zaikin, Pavel A.; Sokol, Ivan A.; Seryotkin, Yurii V.; Palyanov, Yury N.

2018-06-01

Interactions in a Fe-C-O-H-N system that controls the mobility of siderophile nitrogen and carbon in the Fe0-saturated upper mantle are investigated in experiments at 6.3-7.8 GPa and 1200-1400 °C. The results show that the γ-Fe and metal melt phases equilibrated with the fluid in a system unsaturated with carbon and nitrogen are stable at 1300 °C. The interactions of Fe3C with an N-rich fluid in a graphite-saturated system produce the ɛ-Fe3N phase (space group P63/ mmc or P6322) at subsolidus conditions of 1200-1300 °C, while N-rich melts form at 1400 °C. At IW- and MMO-buffered hydrogen fugacity ( fH2), fluids vary from NH3- to H2O-rich compositions (NH3/N2 > 1 in all cases) with relatively high contents of alkanes. The fluid derived from N-poor samples contains less H2O and more carbon which mainly reside in oxygenated hydrocarbons, i.e., alcohols and esters at MMO-buffered fH2 and carboxylic acids at unbuffered fH2 conditions. In unbuffered conditions, N2 is the principal nitrogen host (NH3/N2 ≤ 0.1) in the fluid equilibrated with the metal phase. Relatively C- and N-rich fluids in equilibrium with the metal phase (γ-Fe, melt, or Fe3N) are stable at the upper mantle pressures and temperatures. According to our estimates, the metal/fluid partition coefficient of nitrogen is higher than that of carbon. Thus, nitrogen has a greater affinity for iron than carbon. The general inference is that reduced fluids can successfully transport volatiles from the metal-saturated mantle to metal-free shallow mantle domains. However, nitrogen has a higher affinity for iron and selectively accumulates in the metal phase, while highly mobile carbon resides in the fluid phase. This may be a controlling mechanism of the deep carbon and nitrogen cycles.

Contaminant fate and transport in the Venice Lagoon: results from a multi-segment multimedia model.

PubMed

Sommerfreund, J K; Gandhi, N; Diamond, M L; Mugnai, C; Frignani, M; Capodaglio, G; Gerino, M; Bellucci, L G; Giuliani, S

2010-03-01

Contaminant loadings to the Venice Lagoon peaked from 1950s-1980s and although they have since declined, contaminant concentrations remain elevated in sediment and seafood. In order to identify the relative importance of contaminant sources, inter-media exchange and removal pathways, a modified 10-segment fugacity/aquivalence-based model was developed for octachlorodibenzodioxin/furan (OCDD/F), PCB-180, Pb and Cu in the Venice Lagoon. Results showed that in-place pollution nearby the industrial area, current industrial discharges, and tributary loadings were the main sources of contaminants to the lagoon, with negligible contributions from the atmosphere. The fate of these contaminants was governed by sediment-water exchange with simultaneous advective transport by water circulation. Contaminants circulated amongst the northern and central basins with a small fraction reaching the far southern basin and the Chioggia inlet. As a consequence, we estimated limited contaminant transfer to the Adriatic Sea, trapping the majority of contaminants in the sediment in this "average" circulation scenario which does not account for periodic flooding events. (c) 2009 Elsevier Inc. All rights reserved.

Ocean and Coastal Acidification off New England and Nova Scotia

EPA Science Inventory

New England coastal and adjacent Nova Scotia shelf waters have a reduced buffering capacity because of significant freshwater input, making the region’s waters potentially more vulnerable to coastal acidification. Nutrient loading and heavy precipitation events further acid...

Design of Phosphonium-Type Zwitterion as an Additive to Improve Saturated Water Content of Phase-Separated Ionic Liquid from Aqueous Phase toward Reversible Extraction of Proteins

PubMed Central

Ito, Yoritsugu; Kohno, Yuki; Nakamura, Nobuhumi; Ohno, Hiroyuki

2013-01-01

We designed phosphonium-type zwitterion (ZI) to control the saturated water content of separated ionic liquid (IL) phase in the hydrophobic IL/water biphasic systems. The saturated water content of separated IL phase, 1-butyl-3-methyimidazolium bis(trifluoromethanesulfonyl)imide, was considerably improved from 0.4 wt% to 62.8 wt% by adding N,N,N-tripentyl-4-sulfonyl-1-butanephosphonium-type ZI (P555C4S). In addition, the maximum water content decreased from 62.8 wt% to 34.1 wt% by increasing KH2PO4/K2HPO4 salt content in upper aqueous phosphate buffer phase. Horse heart cytochrome c (cyt.c) was dissolved selectively in IL phase by improving the water content of IL phase, and spectroscopic analysis revealed that the dissolved cyt.c retained its higher ordered structure. Furthermore, cyt. c dissolved in IL phase was re-extracted again from IL phase to aqueous phase by increasing the concentration of inorganic salts of the buffer solution. PMID:24013379

Purification effect of two typical water source vegetation buffer zones on land-sourced pollutants

NASA Astrophysics Data System (ADS)

Li, Gang

2017-03-01

Two vegetation buffer zones (tree-shrub-grass pattern and tree-grass pattern) were selected as test objects around Siming reservoir in Yuyao City of China. The effect of the storm runoff intensity (low and high intensity) and the buffer zone width (1 m, 3 m, 5 m, 7 m, 9 m, 12 m, 16 m) on pollutants (suspended solids, ammonium nitrogen and total phosphorus) was studied by the artificial simulation runoff. The results showed that with the increase of the width of buffer zone, the pollutant concentration was decreased. The purification effect of the two buffer zones on suspended solids and total phosphorus was basically stable at 52-55% and 34-37%, respectively. But the purification effect on ammonium nitrogen was the tree-shrub-grass pattern (69.7%) significantly better than that of tree-grass pattern (52.1%). The purification rate at the low runoff intensity was 1.8-2.0 times that at the high runoff intensity. The relationship between the purification rate and buffer zone width can be expressed by the natural logarithm equation, and the model adjustment coefficient was greater than 0.92.

TRIS buffer in simulated body fluid distorts the assessment of glass-ceramic scaffold bioactivity.

PubMed

Rohanová, Dana; Boccaccini, Aldo Roberto; Yunos, Darmawati Mohamad; Horkavcová, Diana; Březovská, Iva; Helebrant, Aleš

2011-06-01

The paper deals with the characterisation of the bioactive phenomena of glass-ceramic scaffold derived from Bioglass® (containing 77 wt.% of crystalline phases Na(2)O·2CaO·3SiO(2) and CaO·SiO(2) and 23 wt.% of residual glass phase) using simulated body fluid (SBF) buffered with tris-(hydroxymethyl) aminomethane (TRIS). A significant effect of the TRIS buffer on glass-ceramic scaffold dissolution in SBF was detected. To better understand the influence of the buffer, the glass-ceramic scaffold was exposed to a series of in vitro tests using different media as follows: (i) a fresh liquid flow of SBF containing tris (hydroxymethyl) aminomethane; (ii) SBF solution without TRIS buffer; (iii) TRIS buffer alone; and (iv) demineralised water. The in vitro tests were provided under static and dynamic arrangements. SBF buffered with TRIS dissolved both the crystalline and residual glass phases of the scaffold and a crystalline form of hydroxyapatite (HAp) developed on the scaffold surface. In contrast, when TRIS buffer was not present in the solutions only the residual glassy phase dissolved and an amorphous calcium phosphate (Ca-P) phase formed on the scaffold surface. It was confirmed that the TRIS buffer primarily dissolved the crystalline phase of the glass-ceramic, doubled the dissolving rate of the scaffold and moreover supported the formation of crystalline HAp. This significant effect of the buffer TRIS on bioactive glass-ceramic scaffold degradation in SBF has not been demonstrated previously and should be considered when analysing the results of SBF immersion bioactivity tests of such systems. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Interactions of TRIS [tris(hydroxymethyl)aminomethane] and related buffers with peptide backbone: thermodynamic characterization.

PubMed

Taha, Mohamed; Lee, Ming-Jer

2010-10-21

In a situation which is far from ideal, many buffers have been found to be quite reactive, besides maintaining their stable pH values. On the basis of apparent transfer free energies (ΔG(tr)'), through solubility measurements the interactions of zwitterionic glycine peptides: glycine (Gly), diglycine (Gly(2)), triglycine (Gly(3)), and tetraglycine (Gly(4)), with several common neutral pH, amine-based buffers have been studied. The biological buffers studied in this work, including TRIS, TES, TAPS, TAPSO, and TABS are structurally related and all contain TRIS groups. These buffers have pK(a) values ranging from 7.5-9.0, which allow them to be used in biological, biochemical or environmental studies. We observed negative values of ΔG(tr)' for Gly(3) and Gly(4) from water to buffer, indicating that the interactions are favorable. However, the ΔG(tr)' values are positive for Gly and Gly(2), revealing unfavorable interactions, which except for the latter in TRIS buffer are negative. The surprising result in our data is the unexpected extraordinarily high favorable interactions between TRIS buffer and peptides (in comparison with the effect of the most common denaturants, urea and guanidine hydrochloride). The transfer free energies (ΔG(tr)') of the peptide backbone unit (-CH(2)C=O-NH-) contributions have been estimated from ΔG(tr)' values. We have also investigated the interactions of TRIS buffer with Bovine Serum Albumin (BSA), as a globular protein, using dynamic light scattering (DLS), zeta potential, UV-Visible absorption, fluorescence and Raman spectroscopy measurements. The results indicated that TRIS buffer stabilized the BSA molecules.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Esswein, AJ; Surendranath, Y; Reece, SY

A high surface area electrode is functionalized with cobalt-based oxygen evolving catalysts (Co-OEC = electrodeposited from pH 7 phosphate, Pi, pH 8.5 methylphosphonate, MePi, and pH 9.2 borate electrolyte, Bi). Co-OEC prepared from MePi and operated in Pi and Bi achieves a current density of 100 mA cm(-2) for water oxidation at 442 and 363 mV overpotential, respectively. The catalyst retains activity in near-neutral pH buffered electrolyte in natural waters such as those from the Charles River (Cambridge, MA) and seawater (Woods Hole, MA). The efficacy and ease of operation of anodes functionalized with Co-OEC at appreciable current density togethermore » with its ability to operate in near neutral pH buffered natural water sources bodes well for the translation of this catalyst to a viable renewable energy storage technology.« less

Dynamic coupled metal transport-speciation model: application to assess a zinc-contaminated lake.

PubMed

Bhavsar, Satyendra P; Diamond, Miriam L; Gandhi, Nilima; Nilsen, Joel

2004-10-01

A coupled metal transport and speciation/complexation model (TRANSPEC) has been developed to estimate the speciation and fate of multiple interconverting species in surface aquatic systems. Dynamic-TRANSPEC loosely, sequentially couples the speciation/complexation and fate modules that, for the unsteady state formulation, run alternatively at every time step. The speciation module first estimates species abundance using, in this version, MINEQL+ considering time-dependent changes in water and pore-water chemistry. The fate module is based on the quantitative water air sediment interaction (QWASI) model and fugacity/aquivalence formulation, with the option of using a pseudo-steady state solution to account for past discharges. Similarly to the QWASI model for organic contaminants, TRANSPEC assumes the instantaneous equilibrium distribution of metal species among dissolved, colloidal, and particulate phases based on ambient chemistry parameters that can be collected through conventional field methods. The model is illustrated with its application to Ross Lake (Manitoba, Canada) that has elevated Zn concentrations due to discharges over 70 years from a mining operation. Using measurements from field studies, the model reproduces year-round variations in Zn water concentrations. A 10-year projection for current conditions suggests decreasing Zn remobilization and export from the lake. Decreasing Zn loadings increases sediment-to-water transport but decreases water concentrations, and vice versa. Species distribution is affected by pH such that a decrease in pH increases metal export from the lake and vice versa.

Crystal-liquid Fugacity Ratio as a Surrogate Parameter for Intestinal Permeability.

PubMed

Zakeri-Milani, Parvin; Fasihi, Zohreh; Akbari, Jafar; Jannatabadi, Ensieh; Barzegar-Jalali, Mohammad; Loebenberg, Raimar; Valizadeh, Hadi

We assessed the feasibility of using crystal-liquid fugacity ratio (CLFR) as an alternative parameter for intestinal permeability in the biopharmaceutical classification (BCS) of passively absorbed drugs. Dose number, fraction of dose absorbed, intestinal permeability, and intrinsic dissolution rate were used as the input parameters. CLFR was determined using thermodynamic parameters i.e., melting point, molar fusion enthalpy, and entropy of drug molecules obtained using differential scanning calorimetry. The CLFR values were in the range of 0.06-41.76 mole percent. There was a close relationship between CLFR and in vivo intestinal permeability (r > 0.8). CLFR values of greater than 2 mole percent corresponded to complete intestinal absorption. Applying CLFR versus dose number or intrinsic dissolution rate, more than 92% of tested drugs were correctly classified with respect to the reported classification system on the basis of human intestinal permeability and solubility. This investigation revealed that the CLFR might be an appropriate parameter for quantitative biopharmaceutical classification. This could be attributed to the fact that CLFR could be a measure of solubility of compounds in lipid bilayer which was found in this study to be directly proportional to the intestinal permeability of compounds. This classification enables researchers to define characteristics for intestinal absorption of all four BCS drug classes using suitable cutoff points for both intrinsic dissolution rate and crystal-liquid fugacity ratio. Therefore, it may be used as a surrogate for permeability studies. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Thermodynamic controls on element partitioning between titanomagnetite and andesitic-dacitic silicate melts

NASA Astrophysics Data System (ADS)

Sievwright, R. H.; Wilkinson, J. J.; O'Neill, H. St. C.; Berry, A. J.

2017-08-01

Titanomagnetite-melt partitioning of Mg, Mn, Al, Ti, Sc, V, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Hf and Ta was investigated experimentally as a function of oxygen fugacity ( fO2) and temperature ( T) in an andesitic-dacitic bulk-chemical compositional range. In these bulk systems, at constant T, there are strong increases in the titanomagnetite-melt partitioning of the divalent cations (Mg2+, Mn2+, Co2+, Ni2+, Zn2+) and Cu2+/Cu+ with increasing fO2 between 0.2 and 3.7 log units above the fayalite-magnetite-quartz buffer. This is attributed to a coupling between magnetite crystallisation and melt composition. Although melt structure has been invoked to explain the patterns of mineral-melt partitioning of divalent cations, a more rigorous justification of magnetite-melt partitioning can be derived from thermodynamic principles, which accounts for much of the supposed influence ascribed to melt structure. The presence of magnetite-rich spinel in equilibrium with melt over a range of fO2 implies a reciprocal relationship between a(Fe2+O) and a(Fe3+O1.5) in the melt. We show that this relationship accounts for the observed dependence of titanomagnetite-melt partitioning of divalent cations with fO2 in magnetite-rich spinel. As a result of this, titanomagnetite-melt partitioning of divalent cations is indirectly sensitive to changes in fO2 in silicic, but less so in mafic bulk systems.

A re-assessment of the oxidation state of iron in MORB glasses

NASA Astrophysics Data System (ADS)

Berry, Andrew J.; Stewart, Glen A.; O'Neill, Hugh St. C.; Mallmann, Guilherme; Mosselmans, J. Fred W.

2018-02-01

The oxidation state of Fe, Fe/+3 ΣFe (where ΣFe =Fe2+ +Fe3+), in glass samples of mid-ocean ridge basalt (MORB), from a wide range of localities, was determined by XANES spectroscopy to be 0.10(2) (n = 42). This value is lower than that reported previously by XANES, 0.16 (1) (n = 103), but consistent with the most recent value determined by redox titrations, 0.11 (2) (n = 104), all for similar sets of samples. We attribute the anomalously high XANES value of 0.16 to a calibration error resulting from the interpretation of Mössbauer spectra and the resulting Fe/+3 ΣFe values of the standards. Our alternative interpretation removes the problem of resolving Fe/+3 ΣFe values <∼0.1 in basaltic glasses, produces isomer shift and quadrupole splitting values for Fe3+ that are independent of Fe3+/ΣFe (as is the case for Fe2+), and gives Fe/+3 ΣFe values that are consistent with the thermodynamically expected dependence on oxygen fugacity (fO2). Fe/+3Fe2+ is related to fO2 for our synthetic MORB composition by the temperature independent expression ΔQFM = 4 log ⁡ (Fe3+ /Fe2+) + 4.23 (5), where ΔQFM is the fO2 in log units relative to the quartz-fayalite-magnetite buffer. The average fO2 of natural MORB was estimated to be QFM+0.1.

A review of the compositional variation of amphiboles in alkaline plutonic complexes

NASA Astrophysics Data System (ADS)

Mitchell, Roger H.

1990-12-01

Compositional data for amphiboles occurring in alkaline plutonic complexes are reviewed and a standard procedure for plotting these data in an isometric prism is proposed. The main compositional trend found in both oversaturated and undersaturated complexes of either miascitic or peralkaline affinity is referred to as the primary magmatic trend. Amphiboles range in composition from magnesian hastingsitic hornblende and ferro-edenitic hornblende through katophorite to ferro-richterite and arfvedsonite. Individual complexes differ with respect to the amphibole {Mg}/{Fe} and {Si}/{Al} ratio and the extent of Na-enrichment. Extensive or limited ranges in the composition of amphiboles may occur in a given complex. A subtrend found only in oversaturated complexes is from ferro-edenitic hornblende to ferro-actinolite. This trend termed the ferro-actinolitic subtrend is found only in low temperature non-peralkaline residua. Some aluminous nepheline syenites and associated alkali gabbros contain amphiboles which range in composition from kaersutite through ferroan pargasitic hornblende to hastingsite. This trend termed the primary miascitic magmatic trend is is one of decreasing {Mg}/{Fe}, at essentially constant {Si}/{Al} and Ca content. Na-enrichment does not occur. Amphiboles formed by reactions of preexisting phases with hydrothermal or deuteric fluids are termed the late stage reaction assemblage. Amphibole compositional trends from calcic through sodic-calcic to sodic amphiboles reflect decreasing temperature and oxygen fugacity at or below the QFM oxygen buffer. The compositional trends are of use in determining petrogenetic relationships between apparently consanguineous syenites.

Dielectric properties and the monoclinictriclinic inversion in albite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, P.; Duba, A.; Piwinskii, A.J.

1976-12-01

Dielectric properties (epsilon', real part of complex permittivity; epsilon'', imaginary part of complex permittivity; tan delta, loss tangent = epsilon''/epsilon') of single crystal Amelia albite have been measured parallel to the b-axis under controlled oxygen fugacity near the QFM buffer in the temperature range 1000 to 1373/sup 0/K at frequencies (..nu..) of 0.2 to 10 kHz. Plots of epsilon' and epsilon'' as a function of temperature exhibit minima which depend on time and ..nu.. in this albite. In addition, plots of tan delta as a function of temperature develop maxima which are also time-dependent. When epsilon', epsilon'', and tan deltamore » were investigated between 1220 and 1320/sup 0/K as a function of time, a break in these dielectric parameters with temperature was found. Epsilon' and epsilon'' increased with time above this break, while they decreased with time below the break. Values of loss tangent were also non-linear functions of temperature. Epsilon' and epsilon'' minima, tan delta maxima, and the temperature break in these dielectric properties were found to converge at approximately 1283/sup 0/K as time increases. Assuming that the epsilon' and epsilon'' increase and the tan delta decrease are the result of increasing disorder in this albite, these experimental data suggest that 1283 +- 20/sup 0/K is the temperature of the monoclinic-triclinic transition in this albite. This agrees well with electrical conductivity results which indicate 1253 +- 30/sup 0/K.« less

Ferric Iron Production in Magma Oceans and Evolution of Mantle Oxidation State

NASA Astrophysics Data System (ADS)

Schaefer, L.; Elkins-Tanton, L. T.; Pahlevan, K.

2018-05-01

Self-oxidation of the magma ocean by ferric iron production at high pressure may explain the mantle oxidation state of the Earth. Partitioning during fractional crystallization can further increase the mantle oxygen fugacity during solidification.

Volatile Element Behavior During Melting and Vaporisation on Earth and Protoplanets.

NASA Astrophysics Data System (ADS)

Wood, B. J.; Norris, C. A.

2017-12-01

During accretion the Earth and many of the smaller bodies which were added to it, underwent periods of partial melting, vaporisation and re-condensation. This resulted in patterns of volatile element depletion relative to CI chondrite which are difficult to interpret. The behavior of moderately volatile elements (Pb, Cd, Zn,Cu, In,Tl etc) during these melting, vaporisation and condensation processes is usually approximated by the temperature of condensation from a gas of solar composition. Thus, Tl and In have low condensation temperatures and are regarded as the most volatile of this group. In order to test this volatility approximation we have studied the vaporisation behavior of 13 elements (Ag,Bi,Cd,Cr,Cu,Ga,Ge,In,Pb,Sb,Sn,Tl,Zn) from molten basalt at 1 atm pressure and oxygen fugacities between Ni-NiO and 2 log units below Fe-FeO. The relative volatilities of the elements turn out to be only weakly correlated with condensation temperature, indicating that the latter is a poor proxy for volatility on molten bodies. Cu, Zn and In for example all have similar volatility in the oxygen fugacity range of concern, despite the condensation temperature of Cu (1037K at 10-4bar) being 500K greater than that of In. The oxygen fugacity dependence of volatility indicates that the volatile species are, for all elements more reduced than the melt species. We addressed the differences between condensation temperature and relative volatility in 2 steps. Firstly we used metal-silicate partitioning experiments to estimate the activity coefficients of the trace element oxides in silicate melts. We then used available thermodynamic data to compute the vapor pressures of the stable species of these 13 elements over the silicate melt at oxygen fugacities ranging from Ni-NiO to about 6 log units below Fe-FeO, which approximates the solar gas. Thus we find that presence of Cl and S in the solar gas and the stable Cl and S species of In,Tl Ga Ge Cd and Sn are important contributing factors to volatility in the solar nebula. Our measured volatilities from silicate melt under reducing (S and Cl-absent) conditions are consistent with abundances in the silicate Earth, indicating that these moderately volatile elements were added to Earth in bodies which had undergone episodes of melting and vaporisation.

Complications in Determining Oxygen Fugacities From Olivine-Melt Equilibrium Illustrated by the Pu'u'O'o Lavas, Hawaii

NASA Astrophysics Data System (ADS)

McCann, V. E.; Barton, M.; Thornber, C. R.

2005-12-01

We have shown previously that oxygen fugacities calculated from olivine-melt equilibrium using rim compositions agree well with those calculated from analyzed Fe3+/σFe for MORB and for Icelandic OIB (MORB - average ΔFMQ -0.72 versus -0.70, Iceland average ΔFMQ -0.49 versus -0.58). The agreement between oxygen fugacities calculated from Ol-melt equilibrium and those calculated from analyzed Fe3+/σFe is excellent for individual samples of MORB from the FAMOUS region and Blanco Trough ( difference in calculated ΔFMQ < 0.30). Published analyses of Fe3+/σFe yield oxygen fugacilties of ΔFMQ= -0.72±0.43 for lavas from Kilauea and Mauna Loa, and ΔFMQ=0.91±0.72 for Loihi, very close to those for MORB. Oxygen fugacities determined using carefully selected Ol-melt analyses (ΔFMQ= -0.43±0.32) are in reasonable agreement with those determined from Fe3+/σFe for Kilauea and Mauna Loa, and agreement between fO2 calculated from Ol-melt equilibrium (ΔFMQ= -0.26) and that calculated from Fe3+/σFe (ΔFMQ= -0.64) is excellent for one sample from Kilauea. However, olivine-melt pairs from some samples, including those from the Pu'u'O'o lavas, yield anomalously high or low estimates of fO2 (average ΔFMQ =-0.6907, range -4.07 to +0.34). We suggest that these anomalous values reflect the complex history of olivines in these lavas, in particular the effects of magma mixing. Some olivines in the Pu'u'O'o lavas clearly have rims that are anomalously rich in Fa, whereas others have rims that are anomalously rich in Fo and do not appear to have equilibrium compositions. Given the dependence of olivine composition on melt Fe3+/σFe, there is no simple method to determine the equilibrium composition of olivine for a particular melt. However, detailed zoning profiles and analyses of microphenocrysts allow probable equilibrium compositions to be identified. We suggest that the average fO2 of Hawaiian lavas lies close to (ΔFMQ= -1) based on published results using spinel-melt equilibrium and Fe-Ni exchange between olivine and sulfide liquid. Olivine-glass inclusion data for Koolau samples also suggest (ΔFMQ= ~-1).

Spatial-Temporal Variations of Water Quality and Its Relationship to Land Use and Land Cover in Beijing, China

PubMed Central

Chen, Xiang; Zhou, Weiqi; Pickett, Steward T. A.; Li, Weifeng; Han, Lijian

2016-01-01

Rapid urbanization with intense land use and land cover (LULC) change and explosive population growth has a great impact on water quality. The relationship between LULC characteristics and water quality provides important information for non-point sources (NPS) pollution management. In this study, we first quantified the spatial-temporal patterns of five water quality variables in four watersheds with different levels of urbanization in Beijing, China. We then examined the effects of LULC on water quality across different scales, using Pearson correlation analysis, redundancy analysis, and multiple regressions. The results showed that water quality was improved over the sampled years but with no significant difference (p > 0.05). However, water quality was significantly different among nonurban and both exurban and urban sites (p < 0.05). Forest land was positively correlated with water quality and affected water quality significantly (p < 0.05) within a 200 m buffer zone. Impervious surfaces, water, and crop land were negatively correlated with water quality. Crop land and impervious surfaces, however, affected water quality significantly (p < 0.05) for buffer sizes greater than 800 m. Grass land had different effects on water quality with the scales. The results provide important insights into the relationship between LULC and water quality, and thus for controlling NPS pollution in urban areas. PMID:27128934

Use of Fuzzy rainfall-runoff predictions for claypan watersheds with conservation buffers in Northeast Missouri

NASA Astrophysics Data System (ADS)

Anomaa Senaviratne, G. M. M. M.; Udawatta, Ranjith P.; Anderson, Stephen H.; Baffaut, Claire; Thompson, Allen

2014-09-01

Fuzzy rainfall-runoff models are often used to forecast flood or water supply in large catchments and applications at small/field scale agricultural watersheds are limited. The study objectives were to develop, calibrate, and validate a fuzzy rainfall-runoff model using long-term data of three adjacent field scale row crop watersheds (1.65-4.44 ha) with intermittent discharge in the claypan soils of Northeast Missouri. The watersheds were monitored for a six-year calibration period starting 1991 (pre-buffer period). Thereafter, two of them were treated with upland contour grass and agroforestry (tree + grass) buffers (4.5 m wide, 36.5 m apart) to study water quality benefits. The fuzzy system was based on Mamdani method using MATLAB 7.10.0. The model predicted event-based runoff with model performance coefficients of r2 and Nash-Sutcliffe Coefficient (NSC) values greater than 0.65 for calibration and validation. The pre-buffer fuzzy system predicted event-based runoff for 30-50 times larger corn/soybean watersheds with r2 values of 0.82 and 0.68 and NSC values of 0.77 and 0.53, respectively. The runoff predicted by the fuzzy system closely agreed with values predicted by physically-based Agricultural Policy Environmental eXtender model (APEX) for the pre-buffer watersheds. The fuzzy rainfall-runoff model has the potential for runoff predictions at field-scale watersheds with minimum input. It also could up-scale the predictions for large-scale watersheds to evaluate the benefits of conservation practices.

Thermal - Hydraulic Behavior of Unsaturated Bentonite and Sand-Bentonite Material as Seal for Nuclear Waste Repository: Numerical Simulation of Column Experiments

NASA Astrophysics Data System (ADS)

Ballarini, E.; Graupner, B.; Bauer, S.

2015-12-01

For deep geological repositories of high-level radioactive waste (HLRW), bentonite and sand bentonite mixtures are investigated as buffer materials to form a a sealing layer. This sealing layer surrounds the canisters and experiences an initial drying due to the heat produced by HLRW and a successive re-saturation with fluid from the host rock. These complex thermal, hydraulic and mechanical processes interact and were investigated in laboratory column experiments using MX-80 clay pellets as well as a mixture of 35% sand and 65% bentonite. The aim of this study is to both understand the individual processes taking place in the buffer materials and to identify the key physical parameters that determine the material behavior under heating and hydrating conditions. For this end, detailed and process-oriented numerical modelling was applied to the experiments, simulating heat transport, multiphase flow and mechanical effects from swelling. For both columns, the same set of parameters was assigned to the experimental set-up (i.e. insulation, heater and hydration system), while the parameters of the buffer material were adapted during model calibration. A good fit between model results and data was achieved for temperature, relative humidity, water intake and swelling pressure, thus explaining the material behavior. The key variables identified by the model are the permeability and relative permeability, the water retention curve and the thermal conductivity of the buffer material. The different hydraulic and thermal behavior of the two buffer materials observed in the laboratory observations was well reproduced by the numerical model.

Causes of acidification of four streams on Laurel Hilld in southwestern Pennsylvania

USGS Publications Warehouse

Sharpe, William E.; DeWalle, David R.; Leibfried, Robert T.; Dinicola, Richard S.; Kimmel, William G.; Sherwin, Lysle S.

1984-01-01

Atmospheric deposition, soils developed from bedrock, a natural bog, gas wells, and a ski area were all investigated as possible sources of water quality degradation for four streams on Laurel Hill in southwestern Pennsylvania where fish kills have been reported since 1960. An intensive study of the chemistry of atmospheric deposition, soil leachate, and stream water and fish populations was conducted on these basins during 1980–1981 with emphasis on dormant season periods with runoff from snowmelt and rain. Although bedrock geology was found to control the natural buffering capacity of these streams, only acid precipitation could be linked to sharp drops in pH and increases in total Al concentrations observed during stormflows in the poorly buffered streams. Three poorly buffered streams exhibited drops to pH 4.4 to 4.5 and increases in total Al concentrations up to 1.5 mg/L during observed peak flows. Mineral soil leachate from the three major soil series on the basins during this time exhibited a low pH of 4.3 and mean total Al concentrations of 3.6 mg/L, indicating stream response during storms was closely linked to chemistry of soil leachate. Poorly buffered streams did not support reproducing populations of trout (Salmonidae sp.) or other fishes. In contrast, one well-buffered stream (20 mg/L CaCO3) exhibited drops to pH 5.5 during peak flow and supported reproducing trout and sculpin (Cottus bairdi) populations. The acidification of the four streams studied was attributed to atmospheric deposition.

Contributions of separate reactions to the acid-base buffering of soils in brook floodplains (Central Forest State Reserve)

NASA Astrophysics Data System (ADS)

Sokolova, T. A.; Tolpeshta, I. I.; Rusakova, E. S.

2016-04-01

The acid-base buffering of gleyic gray-humus soils developed in brook floodplains and undisturbed southern-taiga landscapes has been characterized by the continuous potentiometric titration of soil water suspensions. During the interaction with an acid, the major amount of protons (>80%) is consumed for the displacement of exchangeable bases and the dissolution of Ca oxalates. In the O and AY horizons, Mn compounds make the major contribution (2-15%) to the acid buffering. The buffer reactions with the participation of Al compounds make up from 0.5 to 1-2% of the total buffering capacity, and the protonation of the surface OH groups of kaolinite consumes 2-3% of the total buffering capacity. The deprotonation of OH groups on the surface of Fe hydroxides (9-43%), the deprotonation of OH groups on the surface of illite crystals (3-19%), and the dissolution of unidentified aluminosilicates (9-14%) are the most significant buffer reactions whose contributions have been quantified during the interaction with a base. The contribution of the deprotonation of OH groups on the surface of kaolinite particles is lower (1-5%) because of the small specific surface area of this mineral, and that of the dissolution of Fe compounds is insignificant. In the AY horizon, the acid and base buffering of soil in the rhizosphere is higher than beyond the rhizosphere because of the higher contents of organic matter and nonsilicate Fe and Al compounds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ok, Kyung-Chul; Park, Jin-Seong, E-mail: hkim-2@naver.com, E-mail: jsparklime@hanyang.ac.kr; Ko Park, Sang-Hee

We demonstrated the fabrication of flexible amorphous indium gallium zinc oxide thin-film transistors (TFTs) on high-temperature polyimide (PI) substrates, which were debonded from the carrier glass after TFT fabrication. The application of appropriate buffer layers on the PI substrates affected the TFT performance and stability. The adoption of the SiN{sub x}/AlO{sub x} buffer layers as water and hydrogen diffusion barriers significantly improved the device performance and stability against the thermal annealing and negative bias stress, compared to single SiN{sub x} or SiO{sub x} buffer layers. The substrates could be bent down to a radius of curvature of 15 mm and themore » devices remained normally functional.« less

Deforestation and benthic indicators: how much vegetation cover is needed to sustain healthy Andean streams?

PubMed

Iñiguez-Armijos, Carlos; Leiva, Adrián; Frede, Hans-Georg; Hampel, Henrietta; Breuer, Lutz

2014-01-01

Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices) and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS), we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%). Our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. This research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments.

Deforestation and Benthic Indicators: How Much Vegetation Cover Is Needed to Sustain Healthy Andean Streams?

PubMed Central

Iñiguez–Armijos, Carlos; Leiva, Adrián; Frede, Hans–Georg; Hampel, Henrietta; Breuer, Lutz

2014-01-01

Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices) and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS), we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%). Our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. This research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments. PMID:25147941

The potential water buffering capacity of urban green infrastructure in an arid environment

NASA Astrophysics Data System (ADS)

Wang, Z.; Yang, J.

2017-12-01

Urban green infrastructure offers arid cities an attractive means of mitigation/adaptation to environmental challenges of elevated thermal stress, but imposes the requirement of outdoor irrigation that aggravates the stress of water resource management. Future development of cities is inevitably constrained by the limited availability of water resources, under challenges of emergent climate change and continuous population growth. This study used the Weather Research and Forecasting model with urban dynamics to assess the potential water buffering capacity of urban green infrastructure in arid environments and its implications for sustainable urban planning. The Phoenix metropolitan area, Arizona, United States, is adopted as a testbed with two hypothetical cases, viz. the water-saving and the fully-greening scenarios investigated. Modifications of the existing green infrastructure and irrigation practices are found to significantly influence the thermal environment of Phoenix. In addition, water saving by xeriscaping (0.77 ± 0.05 × 10^8 m^3) allows the region to support 19.8% of the annual water consumption by the projected 2.62 million population growth by 2050, at a cost of an increase in urban ambient temperature of about 1 o^C.

Importance of water quality in container plant production

Treesearch

John M. Ruter

2013-01-01

High substrate pH is a major problem for producers of container-grown plants and seedlings. The primary cause of high substrate pH is irrigation water with high alkalinity. Alkalinity is defined as the capacity of water to neutralize acids. Some alkalinity in irrigation water is beneficial as it serves as a buffer to large swings in pH levels, but high alkalinity in...

Hydrology and water quality of a field and riparian buffer adjacent to a mangrove wetland in Jobos Bay Watershed, Puerto Rico

USDA-ARS?s Scientific Manuscript database

Models that estimate the effects of agricultural conservation practices on water quantity and quality have become increasingly important tools for short- and long-term assessments. In this study, we simulated the water quality and hydrology of a portion of the Jobos Bay watershed, Puerto Rico using...

Hydrology in a peaty high marsh: hysteretic flow and biogeochemical implications

EPA Science Inventory

Terrestrial nutrient input to coastal waters is a critical water quality problem worldwide, and salt marshes may provide a valuable nutrient buffer (either by removal or by smoothing out pulse inputs) between terrestrial sources and sensitive estuarine habitats. One of the major...

Behavior of soluble and immobilized acid phosphatase in hydro-organic media.

PubMed

Wan, H; Horvath, C

1975-11-20

The hydrolysis of p-nitrophenyl phosphate by wheat germ acid phosphatase (orthophosphoric monoester phosphohydrolase, EC 3.1.3.2) has been investigated in mixtures of aqueous buffers with acetone, dioxane and acetonitrile. The enzyme was either in free solution or immobilized on a pellicular support which consisted of a porous carbonaceous layer on solid glass beads. The highest enzyme activity was obtained in acetone and acetonitrile mixed with citrate buffer over a wide range of organic solvent concentration. In 50% (v/v) acetone both V and Km of the immobilized enzyme were about half of the values in the neat aqueous buffer, but the Ki for inorganic phosphate was unchanged. In 50% (v/v) mixtures of various solvents and citrate buffers of different pH, the enzymic activity was found to depend on the pH of the aqueous buffer component rather than the pH of the hydro-organic mixture as measured with the glass-calomel electrode. The relatively high rates of p-nitrophenol liberation in the presence of glucose even at high organic solvent concentrations suggest that transphosphorylation is facilitated at low water activity.

Fundamental and Applied Studies of Polymer Membranes

NASA Astrophysics Data System (ADS)

Imbrogno, Joseph

Four major areas have been studied in this research: 1) synthesizing novel monomers, e.g. chiral monomers, to produce new types of functionalized membranes for the biotechnology and pharmaceutical industries, 2) hydrophobic brush membranes for desalinating brackish water, sea water, and separating organics, 3) fundamental studies of water interactions at surfaces using sum frequency generation (SFG), and 4) discovering new surface chemistries that will control the growth and differentiation of stem cells. We have developed a novel synthesis method in order to increase the breadth of our high throughput screening library. This library was generated using maleimide chemistry to react a common methacrylate linker with a variety of different functions groups (R groups) in order to form new monomers that were grafted from the surface of PES ultrafiltration membranes. From this work, we discovered that the chirality of a membrane can affect performance when separating chiral feed streams. This effect was observed when filtering bovine serum albumin (BSA) and ovalbumin in a high salt phosphate buffered saline (PBS, 150 mM salt). The Phe grafted membranes showed a large difference in performance when filtering BSA with selectivity of 1.13 and 1.00 for (S) and (R) Phe, respectively. However, when filtering ovalbumin, the (S) and (R) modified surfaces showed selectivity of 2.06 and 2.31, respectively. The higher selectivity enantiomer switched for the two different proteins. Permeability when filtering BSA was 3.06 LMH kPa-1 and 4.31 LMH kPa -1 for (S)- and (R)- Phe, respectively, and 2.65 LMH kPa -1 and 2.10 LMH kPa-1 when filtering ovalbumin for (S)- and (R)- Phe, respectively. Additionally, these effects were no longer present when using a low salt phosphate buffer (PB, 10 mM salt). Since, to our knowledge, membrane chirality is not considered in current industrial systems, this discovery could have a large impact on the pharmaceutical and biotechnology industries. We have developed hydrophobic brush membranes that were able to selectively separate valuable organics (isobutanol) from water, while rejecting other undesirable species, such as enzymes, using pervaporation (PV). These membranes (grafted from nanofiltration (NF) support membranes) had a selectivity ˜1.5x higher than the current industrial standard, polydimethylsiloxane (PDMS), with alpha = 10.1 +/- 0.9 for our brush membranes and alpha = 6.7 +/- 0.1 for PDMS membranes. Since the mechanism of pervaporation is based on the solution diffusion (SD) model, these membranes may be used to desalinate water or fractionate gases since they are also based on the SD mechanism. We have discovered that hydrophobic brush membranes are able to reject monovalent salt ions. This type of membrane is analogous to carbon nanotubes (CNTs), which are believed to have extremely high water fluxes through them due to near frictionless flow caused by a lack of hydrogen bonding. Using these brush membranes we were able to achieve 42% monovalent (NaCl) salt rejection of simulated seawater (32,000 ppm salt). These membranes are easier to scale-up than current composite membranes produced using interfacial polymerization. We have been using SFG to study interfacial water on membrane surfaces. We believe that water interactions with the membrane surface and with the feed species, e.g. proteins, play a critical role during the fouling process. Relevant buffers, such as phosphate buffered saline (PBS) and phosphate buffer, contain ions that are known to restructure water at interfaces. Sum frequency generation spectroscopy (SFG) was used to characterize interfacial water structure at poly(ether sulfone) (PES) thin films in the presence of 0.01 M phosphate buffer (low salt) and 0.01 M phosphate buffered saline (high salt). Three model surfaces were studied: unmodified PES, hydrophobic alkane (C18) modified PES, and poly(ethylene glycol) (PEG) modified PES. In the presence of the low salt phosphate buffer (10 mM salt), phosphate anions were excluded from the PEG-modified PES film. This led to a charge separation between the phosphate anions and sodium cations, creating a surface potential which strongly ordered water molecules into the bulk. When using high salt PBS (138 mM salt) the sodium chloride ions screened this charge and reduced water ordering. Interestingly, this effect was the greatest for the PEG modified surface, with minor or no effects observed for the C18 modified PES and unmodified PES, respectively. Using our high throughput screening platform, we were able to determine that (N-[3-(dimethylamino)propyl] methacrylamide), DMAPMA, supported strong attachment and long-term self-renewal of mouse embryonic stem (ES) cells while preventing differentiation (maintaining pluripotency). After developing this platform, it was used to screen for a surface that could instead induce differentiation of bovine and human retinal pigment epithelium (RPE) cells while promoting cell growth. Several PEG based surfaces were able to induce cobblestone morphology of the RPE cells, which is indicative of differentiation. (Abstract shortened by UMI.).

FUGACITY-BASED INDOOR RESIDENTIAL PESTICIDE FATE MODEL

EPA Science Inventory

Dermal and non-dietary pathways are possibly important for exposure to pesticides used in residences. Limited data have been collected on pesticide concentrations in residential air and surfaces following application. Models may be useful for interpreting these data and to make...

A FUGACITY-BASED INDOOR RESIDENTIAL PESTICIDE FATE MODEL

EPA Science Inventory

Dermal and non-dietary pathways are potentially significant exposure pathways to pesticides used in the home. Exposure pathways include dermal contact of pesticide residues with the hands and skin, ingestion from hand-to-mouth activities, ingestion through contact with toys an...

A THREE-DIMENSIONAL MODEL ASSESSMENT OF THE GLOBAL DISTRIBUTION OF HEXACHLOROBENZENE

EPA Science Inventory

The distributions of persistent organic pollutants (POPs) in the global environment have been studied typically with box/fugacity models with simplified treatments of atmospheric transport processes1. Such models are incapable of simulating the complex three-dimensional mechanis...