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Sample records for conductivity ph dissolved

  1. Comparison of temperature, specific conductance, pH, and dissolved oxygen at selected basic fixed sites in south-central Texas, 1996-98

    USGS Publications Warehouse

    Ging, Patricia B.; Otero, Cassi L.

    2003-01-01

    One component of the surface-water part of the U.S. Geological Survey National Water-Quality Assessment Program is the use of continuous water-quality monitors to help characterize the spatial and temporal distribution of general water quality in relation to hydrologic conditions. During 1996?98, six continuous water-quality monitors in the South-Central Texas study unit collected water temperature, specific conductance, pH, and dissolved oxygen data. The data were compared among the six sites using boxplots of monthly mean values, summary statistics of monthly values, and hydrographs of daily mean values.

  2. Water Temperature, Specific Conductance, pH, and Dissolved-Oxygen Concentrations in the Lower White River and the Puyallup River Estuary, Washington, August-October 2002

    USGS Publications Warehouse

    Ebbert, James C.

    2003-01-01

    The U.S. Geological Survey, Washington State Department of Ecology, and Puyallup Tribe of Indians monitored water temperature, specific conductance, pH, and dissolved-oxygen concentrations in the White River at river miles 4.9 and 1.8 from August until mid-October 2002. Water diverted from the White River upstream from the monitoring sites into Lake Tapps is returned to the river at river mile 3.6 between the two sites. The same characteristics were measured in a cross section of the Puyallup River estuary at river mile 1.5 during high and low tides in September 2002. In late August, maximum daily water temperatures in the White River of 21.1oC (degrees Celsius) at river mile 4.9 and 19.6oC at river mile 1.8 exceeded the water-quality standard of 18oC at both monitoring sites. In mid-September, maximum daily water temperatures at river mile 4.9 exceeded the standard on 5 days. From August 2-25, water temperatures at both monitoring sites were similar and little or no water was discharged from Lake Tapps to the White River. Increases in water temperature at river mile 1.8 in late September and early October were caused by the mixing of warmer water discharged from Lake Tapps with cooler water in the White River. Specific conductance in the White River usually was lower at river mile 1.8 than at river mile 4.9 because of mixing with water from Lake Tapps, which has a lower specific conductance. Maximum values of pH in the White River at river mile 4.9 often exceeded the upper limit of the water-quality standard, 8.5 pH units, from early September until mid-October, when turbidity decreased. The pH standard was not exceeded at river mile 1.8. Dissolved-oxygen concentrations in the White River were often lower at river mile 1.8 than at river mile 4.9 because of mixing with water discharged from Lake Tapps, which has lower dissolved-oxygen concentrations. The lowest concentration of dissolved oxygen observed was 7.9 mg/L (milligrams per liter) at river mile 1.8. The lower limit allowed by the water-quality standard is 8 mg/L. Concentrations of dissolved oxygen measured in a cross section of the Puyallup River estuary at high tide on September 12, 2002, ranged from 9.9 to 10.2 mg/L in fresh water at the surface and from 8.1 to 8.4 mg/L in salt water near the riverbed. These values were within limits set by Washington State water-quality standards for dissolved oxygen of 8 mg/L in fresh water and 6 mg/L in marine water.

  3. Daily and seasonal variability of pH, dissolved oxygen, temperature, and specific conductance in the Colorado River between the forebay of Glen Canyon, Dam and Lees Ferry, northeastern Arizona, 1998-99

    USGS Publications Warehouse

    Flynn, Marilyn E.; Hart, Robert J.; Marzolf, G. Richard; Bowser, Carl J.

    2001-01-01

    The productivity of the trout fishery in the tailwater reach of the Colorado River downstream from Glen Canyon Dam depends on the productivity of lower trophic levels. Photosynthesis and respiration are basic biological processes that control productivity and alter pH and oxygen concentration. During 1998?99, data were collected to aid in the documentation of short- and long-term trends in these basic ecosystem processes in the Glen Canyon reach. Dissolved-oxygen, temperature, and specific-conductance profile data were collected monthly in the forebay of Glen Canyon Dam to document the status of water chemistry in the reservoir. In addition, pH, dissolved-oxygen, temperature, and specific-conductance data were collected at five sites in the Colorado River tailwater of Glen Canyon Dam to document the daily, seasonal, and longitudinal range of variation in water chemistry that could occur annually within the Glen Canyon reach.

  4. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

  5. [Effects of dissolved oxygen and pH on Candida utilis batch fermentation of glutathione].

    PubMed

    Wei, Gong-Yuan; Li, Yin; Du, Guo-Cheng; Chen, Jian

    2003-11-01

    The effects of dissolved oxygen (DO) and pH on glutathione batch fermentation by Candida utilis WSH-02-08 in a 7 liters stirred fermentor were investigated. It was shown that DO concentration is an important factor in glutathione production. With the initial glucose concentration of 30 g/L and a 5 L/min air flow rate, and the agitation rate less than 250 r/min, the DO concentration was not sufficient to satisfy the oxygen requirement during the fermentation. With an agitation rate of more than 300 r/min, the cell growth and glutathione production were enhanced significantly, with the dry cell mass and glutathione production were 20% and 25% higher than that at 200 r/min. When C. utilis WSH 02-08 was cultivated in a batch process without pH control, cell growth and glutathione production were inhibited, likely due to a dramatic decrease in the pH. Intracellular glutathione leakages were observed when the pH was 1.5 or less. To assess the effect of pH on glutathione production, six batch processes controlled at pH 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5 were conducted. The yield was highest at pH 5.5, when the dry cell mass and yield were 27% and 95% respectively higher than fermentation without pH control. The maximal intracellular glutathione content (2.15 %) was also achieved at the pH. To improve our understandings on the effect of pH on the batch glutathione production, a modified Logistic equation and Luedeking-Piret equation were used to simulate cell growth and glutathione production, respectively, under different pH. Based on the parameters obtained by the nonlinear estimation, kinetic analysis was performed to elucidate the effect of pH on the batch glutathione production. The process controlled at pH 5.5 was proven to be the best due to the higher value of K(I) (substrate inhibitory constant in the Logistic equation), lower value of a and higher value of beta (slope and intercept in the Luedeking-Piret equation, respectively). PMID:15971589

  6. Dissolved oxygen and pH relationships in northern Australian mangrove waterways

    SciTech Connect

    Boto, K.G.; Bunt, J.S.

    1981-01-01

    Consistent, highly significant linear correlations (R2 greater than or equal to 0.8) between pH and dissolved oxygen levels have been found in northern Australian mangrove waterways. These properties seem to be influenced by dissolved organic matter, mainly polyphenolic compounds, present in the creeks and tidal channel waters.

  7. Relative effect of temperature and pH on diel cycling of dissolved trace elements in prickly pear creek, Montana

    USGS Publications Warehouse

    Jones, C.A.; Nimick, D.A.; McCleskey, R.B.

    2004-01-01

    Diel (24 hr) cycles in dissolved metal and As concentrations have been documented in many northern Rocky Mountain streams in the U.S.A. The cause(s) of the cycles are unknown, although temperature- and pH-dependent sorption reactions have been cited as likely causes. A light/dark experiment was conducted to isolate temperature and pH as variables affecting diel metal cycles in Prickly Pear Creek, Montana. Light and dark chambers containing sediment and a strand of macrophyte were placed in the stream to simulate instream temperature oscillations. Photosynthesis-induced pH changes were allowed to proceed in the light chambers while photosynthesis was prevented in the dark chambers. Water samples were collected periodically for 22 hr in late July 2001 from all chambers and the stream. In the stream, dissolved Zn concentrations increased by 300% from late afternoon to early morning, while dissolved As concentrations exhibited the opposite pattern, increasing 33% between early morning and late afternoon. Zn and As concentrations in the light chambers showed similar, though less pronounced, diel variations. Conversely, Zn and As concentrations in the dark chambers had no obvious diel variation, indicating that light, or light-induced reactions, caused the variation. Temperature oscillations were nearly identical between light and dark chambers, strongly suggesting that temperature was not controlling the diel variations. As expected, pH was negatively correlated (P < 0.01) with dissolved Zn concentrations and positively correlated with dissolved As concentrations in both the light and dark chambers. From these experiments, photosynthesis-induced pH changes were determined to be the major cause of the diel dissolved Zn and As cycles in Prickly Pear Creek. Further research is necessary in other streams to verify that this finding is consistent among streams having large differences in trace-element concentrations and mineralogy of channel substrate. ?? 2004 Kluwer Academic Publishers.

  8. THE EFFECT OF PH AND DISSOLVED INORGANIC CARBON ON THE PROPERTIES OF IRON COLLOIDAL SUSPENSIONS

    EPA Science Inventory

    Discolored water resulting from suspended iron particles is a relatively common drinking water consumer complaint. These particles result from the oxygenation of Fe(II), and this study shows that pH and dissolved inorganic carbon (DIC) have important effects on their properties....

  9. The influence of dissolved organic carbon on pH measurements of low solute content waters

    NASA Astrophysics Data System (ADS)

    Metcalf, Richard C.; Peck, David V.; Lori, Arent J.

    1989-04-01

    This study has thoroughly examined the concern that dissolved organic carbon (DOC) interferes with pH electrode measurements of low solute content waters. Using Ross pH combination electrodes according to protocols of the U.S. Environmental Protection Agency's National Surface Water Survey (NSWS), our laboratory pH measurements of 10 -4 N H 2SO 4 standards (spiked from 0 to 100 mg L -1 DOC with potassium hydrogen ortho-phthalate, humic acid, or the surfactant Tergitol 15-S-9) showed little or no evidence of DOC interference, within the 0.05 (2s) pH unit measurement precision. Concern with DOC-induced pH measurement errors prompted previous researchers to advocate using a calculated pH value, based on measurements of dissolved inorganic carbon (DIC), P co 2, water temperature, and the appropriate carbonate equilibria. CO 2-equilibrated pH measurements from the Eastern Lake Survey Phase-I showed no significant difference with calculated pH values based on the above model. A limited sensitivity analysis of the errors associated with direct pH electrode measurements compared to calculated pH values indicates that, for a regional survey taking place over weeks or months, potentiometric determinations are more precise at present. All of this evidence suggests that the pH measurements for the NSWS (as well as a long series of prior regional studies) are unaffected by DOC-induced pH measurement errors, although reference electrode junction errors still deserve greater attention in many studies.

  10. pH measurement of low-conductivity waters

    USGS Publications Warehouse

    Busenberg, Eurybiades; Plummer, L.N.

    1987-01-01

    pH is an important and commonly measured parameter of precipitation and other natural waters. The various sources of errors in pH measurement were analyzed and procedures for improving the accuracy and precision of pH measurements in natural waters with conductivities of < 100 uS/cm at 25 C are suggested. Detailed procedures are given for the preparation of dilute sulfuric acid standards to evaluate the performance of pH electrodes in low conductivity waters. A daily check of the pH of dilute sulfuric acid standards and deionized water saturated with a gas mixture of low carbon dioxide at partial pressure (air) prior to the measurement of the pH of low conductivity waters is suggested. (Author 's abstract)

  11. Salivary pH while dissolving vitamin C-containing tablets.

    PubMed

    Hays, G L; Bullock, Q; Lazzari, E P; Puente, E S

    1992-10-01

    Vitamin C is packaged in numerous forms which allow protracted exposure of the teeth to ascorbic acid. The repeated use of chewable mega dose tablets of vitamin C as a mint can damage the teeth by dissolving the enamel. In the time it takes to dissolve a chewable vitamin C tablet, a salivary pH drop takes place; salivary calcium and phosphorus ion concentration drops, and enamel dissolution may begin. Although sodium ascorbate, a buffering agent, is present in many vitamin C products, it may be added in insufficient quantity to be effective. With no apparent therapeutic value from topical vitamin C, vitamin C-containing products should be swallowed. PMID:1299255

  12. INFLUENCE OF PH, DISSOLVED OXYGEN, SUSPENDED SOLIDS OR DISSOLVED SOLIDS UPON VENTILATORY AND COUGH FREQUENCIES IN THE BLUEGILL 'LEPOMIS MACROCHIRUS' AND BROOK TROUT 'SALVELINUS FONTINALIS'

    EPA Science Inventory

    Conservative no-effect concentration ranges were estimated for ventilatory and coughing responses of bluegill sunfish Lepomis macrochirus and brook trout Salvelinus fontinalis exposed to altered pH, or to changes in dissolved oxygen (DO), suspended solids, or dissolved solids con...

  13. Influence of pH on fluorescent dissolved organic matter photo-degradation.

    PubMed

    Timko, Stephen A; Gonsior, Michael; Cooper, William J

    2015-11-15

    A novel semi-continuous excitation emission matrix (EEM) fluorescence and absorbance monitoring system has been developed. Full EEMs were collected simultaneously with absorbance spectra every 20 min during 24 h solar-simulated irradiation experiments, and the kinetic change of fluorescence of Suwannee River natural organic matter IHSS standard material (SRNOM) at various pH values was investigated. Parallel factor analysis (PARAFAC) was then used to isolate the photo-labile and pH-influenced fluorescent components of SRNOM. Kinetic analysis showed increasing rates of fluorescence loss with increasing pH. This has significant implications for the photo-degradation of dissolved natural organic matter during estuarine mixing, when large increases of pH are common. The influence of pH on fluorescence and photo-degradation kinetics emphasizes the need for pH to be monitored and accurately controlled during laboratory experiments. It is also highly recommended that when constructing PARAFAC models or monitoring changes in fluorescence data between samples of different origins, that the pH be held constant to remove any potential artifacts or misinterpretation of data. PMID:26342180

  14. Effect of pH on dynamic and equilibrium surface tension of dissolve organic matter

    NASA Astrophysics Data System (ADS)

    Arye, Gilboa; Trifonov, Pavel; Ilani, Talli

    2014-05-01

    Dissolved organic matter (DOM) in the terrestrial environment may originate from the decomposition of soil organic matter accumulated from the degradation of vegetative residues, the release of root exudates, the lysis of microorganisms and addition of organic wastes, such as livestock manure, biosolids, and different composted organic residues, or from irrigation with wastewater. The structure of DOM macromolecules is known to vary with the following aqueous solution properties: ionic strength, the nature of the inorganic ions, pH and dissolved organic carbon (DOC) concentration. In aqueous solution, the DOM molecules are amphiphilic, that is, it possesses both hydrophilic and hydrophobic functional groups in the same molecule. This simultaneous presence, gave rise to the conceptual surfactant like model for DOM which has been studies in conjunction with the equilibrium surface tension at the liquid-air interface (STeq, mN/m). Measurements of STeq of DOM solution were reported in a relatively small number of studies for the conditions of the aqueous solution (e.g., temperature, pH, ionic strength, the valence of the metal ions, and DOC concentration). All studies demonstrate the decrease in STeq with increase aqueous concentration of the DOC. The effect of pH, however, exhibit contradictory results. Specifically, for a given DOC concentration, the patterns reported for STeq versus pH were different. With increasing pH values, STeq has been reported to decrease, increase or exhibit a minimum. These contradictory results have been attributed to the different DOC concentration examined in each of the studies. In current study we hypothesized that the inconsistent results of STeq vs. pH may also stem from the adsorption kinetics of the DOM amphiphilic molecules at the liquid air interface, which can be evaluated form dynamic surface tension measurements (STt). The STt is approaching STeq values and commonly exhibiting an exponential decay pattern. If for different pH values STt is not reaching STeq, different apparent STeq vs. pH patterns can be obtain. In this study measurement of STt and STeq as a function of pH will be presented for DOM solutions from different origins. The analysis of the STt curves will be demonstrated based on a short and long term diffusion model.

  15. Scales and sources of pH and dissolved oxygen variability in a shallow, upwelling-driven ecosystem

    NASA Astrophysics Data System (ADS)

    Tanner, C. A.; Martz, T.; Levin, L. A.

    2011-12-01

    In the coastal zone extreme variability in carbonate chemistry and oxygen is driven by fluctuations in temperature, salinity, air-sea gas exchange, mixing processes, and biology. This variability appears to be magnified in upwelling-driven ecosystems where low oxygen and low pH waters intrude into shallow depths. The oxygen and carbon chemistry signal can be further confounded by highly productive ecosystems such as kelp beds where photosynthesis and respiration consume and release significant amounts of dissolved inorganic carbon and oxygen. This variability poses a challenge for scientists assessing the impacts of climate change on nearshore ecosystems. We deployed physical & biogeochemical sensors in order to observe these processes in situ. The "SeapHOx" instruments used in this study consist of a modified Honeywell Durafet° ISFET pH sensor, an Aanderra Optode Oxygen sensor, and a SBE-37 conductivity, temperature, pressure sensor. The instruments were deployed on and around the La Jolla Kelp Forest at a variety of depths. Our goals were to (a) characterize the link between pH and oxygen and identify the magnitude of pH and oxygen variability over a range of intra-annual time scales and (b) investigate spatial patterns of pH and oxygen variability associated with depth, proximity to shore, and presence of kelp. Results thus far reveal a strong relationship between oxygen and pH. Temporal variability is greatest at the semidiurnal frequency where pH (at 7 m) can range up to 0.3 units and oxygen can change 50% over 6 h. Diurnal variability is a combination of the diurnal tidal component and diel cycles of production and respiration. Event-scale dynamics associated with upwelling can maintain pH and oxygen below 7.8 units and 200 μmol kg-1, respectively, for multiple days. Frequent current reversals drive changes in the observed oxygen and pH variability. When alongshore currents are flowing southward, driven by upwelling-favorable winds, the magnitude of semidiurnal pH variability increases 5-fold relative to the magnitude of change during northward alongshore. Applying an empirically-determined alkalinity relationship, we conclude that changes in the carbonate chemistry parameters are largely driven by changes in total carbon. On small spatial scales, cross-shore differences exist in mean oxygen and pH but differences in alongshore mean oxygen and pH at a given depth appears to be negligible. Cross-shore differences can equate to a 0.05 pH unit decrease and 25 μmol kg-1 oxygen decrease over 1 km at a given depth. Strong spatial variability in pH and oxygen conditions exist over vertical gradients in the kelp forest, with mean pH at the surface (7m) being 0.2 pH units greater than at the bottom (17m) and mean oxygen being 104 μmol kg-1 greater. The observed range of pH (7.55-8.22) observed in this shallow environment during the course of a year is greater than open ocean predictions for a global mean pH reduction of 0.2-0.3 units predicted by the year 2100. These results suggest that organisms on exposed upwelling coasts may be adapted to a range of pH conditions and highlight the need for scientists to consider biological response to varying scales of pH change in order to develop more realistic predictions of the impacts of climate change for the coastal zone.

  16. Versatile common instrumentation for optical detection of pH and dissolved oxygen

    NASA Astrophysics Data System (ADS)

    Sardesai, Neha; Rao, Govind; Kostov, Yordan

    2015-07-01

    The recent trend toward use of disposable and miniature bioreactors requires the use of appropriate sensors. pH and dissolved oxygen (DO) are often measured using optical chemical sensors due to their small form factor and convenience in use. These sensors are often interrogated using a specialized opto-electronic transducer that is designed around the optical sensor. In this contribution, we are presenting a new class of opto-electronic transducers that are usable with several different chemical sensors without the need to switch the optics or hardware when changing the type of the chemical sensor. This allows flexibility closer to the lab-grade devices while the size is closer to a dedicated sensor. This versatile instrumentation is capable of seamlessly switching between the pH and DO measurement modes and is capable of auto recognition of the sensor type. The principle of ratiometric fluorescence is used for pH measurements, and that of fluorescence lifetime for DO measurements. An approach to obtain identical calibrations between several devices is also presented. The described hardware constitutes common instrumentation for measuring either pH or DO and has been tested in actual bioprocesses. It has been found adequate for continuous bioprocess monitoring.

  17. Versatile common instrumentation for optical detection of pH and dissolved oxygen.

    PubMed

    Sardesai, Neha; Rao, Govind; Kostov, Yordan

    2015-07-01

    The recent trend toward use of disposable and miniature bioreactors requires the use of appropriate sensors. pH and dissolved oxygen (DO) are often measured using optical chemical sensors due to their small form factor and convenience in use. These sensors are often interrogated using a specialized opto-electronic transducer that is designed around the optical sensor. In this contribution, we are presenting a new class of opto-electronic transducers that are usable with several different chemical sensors without the need to switch the optics or hardware when changing the type of the chemical sensor. This allows flexibility closer to the lab-grade devices while the size is closer to a dedicated sensor. This versatile instrumentation is capable of seamlessly switching between the pH and DO measurement modes and is capable of auto recognition of the sensor type. The principle of ratiometric fluorescence is used for pH measurements, and that of fluorescence lifetime for DO measurements. An approach to obtain identical calibrations between several devices is also presented. The described hardware constitutes common instrumentation for measuring either pH or DO and has been tested in actual bioprocesses. It has been found adequate for continuous bioprocess monitoring. PMID:26233397

  18. Versatile common instrumentation for optical detection of pH and dissolved oxygen

    SciTech Connect

    Sardesai, Neha; Rao, Govind; Kostov, Yordan

    2015-07-15

    The recent trend toward use of disposable and miniature bioreactors requires the use of appropriate sensors. pH and dissolved oxygen (DO) are often measured using optical chemical sensors due to their small form factor and convenience in use. These sensors are often interrogated using a specialized opto-electronic transducer that is designed around the optical sensor. In this contribution, we are presenting a new class of opto-electronic transducers that are usable with several different chemical sensors without the need to switch the optics or hardware when changing the type of the chemical sensor. This allows flexibility closer to the lab-grade devices while the size is closer to a dedicated sensor. This versatile instrumentation is capable of seamlessly switching between the pH and DO measurement modes and is capable of auto recognition of the sensor type. The principle of ratiometric fluorescence is used for pH measurements, and that of fluorescence lifetime for DO measurements. An approach to obtain identical calibrations between several devices is also presented. The described hardware constitutes common instrumentation for measuring either pH or DO and has been tested in actual bioprocesses. It has been found adequate for continuous bioprocess monitoring.

  19. Bulk Dissolution Rates of Cadmium and Bismuth Tellurides As a Function of pH, Temperature and Dissolved Oxygen.

    PubMed

    Biver, Marc; Filella, Montserrat

    2016-05-01

    The toxicity of Cd being well established and that of Te suspected, the bulk, surface-normalized steady-state dissolution rates of two industrially important binary tellurides-polycrystalline cadmium and bismuth tellurides- were studied over the pH range 3-11, at various temperatures (25-70 °C) and dissolved oxygen concentrations (0-100% O2 in the gas phase). The behavior of both tellurides is strikingly different. The dissolution rates of CdTe monotonically decreased with increasing pH, the trend becoming more pronounced with increasing temperature. Activation energies were of the order of magnitude associated with surface controlled processes; they decreased with decreasing acidity. At pH 7, the CdTe dissolution rate increased linearly with dissolved oxygen. In anoxic solution, CdTe dissolved at a finite rate. In contrast, the dissolution rate of Bi2Te3 passed through a minimum at pH 5.3. The activation energy had a maximum in the rate minimum at pH 5.3 and fell below the threshold for diffusion control at pH 11. No oxygen dependence was detected. Bi2Te3 dissolves much more slowly than CdTe; from one to more than 3.5 orders of magnitude in the Bi2Te3 rate minimum. Both will readily dissolve under long-term landfill deposition conditions but comparatively slowly. PMID:27043466

  20. Fertilization and pH effects on processes and mechanisms controlling dissolved inorganic phosphorus in soils

    NASA Astrophysics Data System (ADS)

    Devau, Nicolas; Hinsinger, Philippe; Le Cadre, Edith; Colomb, Bruno; Gérard, Frédéric

    2011-05-01

    We used of a set of mechanistic adsorption models (1-pK TPM, ion exchange and Nica-Donnan) within the framework of the component additive (CA) approach in an attempt to determine the effect of repeated massive application of inorganic P fertilizer on the processes and mechanisms controlling the concentration of dissolved inorganic phosphorus (DIP) in soils. We studied the surface layer of a Luvisol with markedly different total concentrations of inorganic P as the result of different P fertilizer history (i.e. massive or no application for 40 years). Soil pH was made to vary from acid to alkaline. Soil solutions were extracted with water and CaCl 2 (0.01 M). The occurrence of montmorillonite led us to determine the binding properties of P and Ca ions for this clay mineral. Satisfactory results were obtained using generic values for model parameters and soil-specific ones, which were either determined directly by measurements or estimated from the literature. We showed that adsorption largely controlled the variations of DIP concentration and that, because of kinetic constrains, only little Ca-phosphates may be precipitated under alkaline conditions, particularly in the P fertilized treatment. The mineral-P pool initially present in both P treatments did not dissolve significantly during the course of the experiments. The adsorption of Ca ions onto soil minerals also promoted adsorption of P ions through electrostatic interactions. The intensity of the mechanism was high under neutral to alkaline conditions. Changes in DIP concentration as a function of these environmental variables can be related to changes in the contribution of the various soil minerals to P adsorption. The extra P adsorbed in the fertilized treatment compared with the control treatment was mainly adsorbed onto illite. This clay mineral was the major P-fixing constituent from neutral to alkaline pH conditions, because the repulsion interactions between deprotonated hydroxyl surface sites and P ions were sufficiently counterbalanced by Ca ions. The drastic increase of DIP observed at acid pH was due to the effect of the lower concentration of surface sites of Fe oxides and kaolinite. In addition to confirming the validity of our approach to model DIP concentrations in soils, the present investigation showed that adsorption was the predominant geochemical process even in the P fertilized soil, and that Ca ions can have an important promoting effect on P adsorption. However the influence of the dissolution of the mineral-P pool under field conditions remained questionable.

  1. The capacity of biochar made from common reeds to neutralise pH and remove dissolved metals in acid drainage.

    PubMed

    Mosley, Luke M; Willson, Philip; Hamilton, Benjamin; Butler, Greg; Seaman, Russell

    2015-10-01

    We tested the capacity of biochar (made at 450 °C from a common reed species) to neutralise pH and remove metals in two acid drainage waters (pH 2.6 and 4.6) using column leaching and batch mixing experiments. In the column experiments, the acid drainage water was neutralised upon passage through the biochar with substantial increases (4-5 pH units) in the leachate pH. In the batch experiments, the leachate pH remained above 6.5 when the drainage:biochar ratio was less than approximately 700:1 (L acid drainage:kg biochar) and 20:1 for the pH 4.6 and pH 2.6 drainage waters, respectively. Dissolved metal concentrations were reduced by 89-98 % (Fe ≈ Al > Ni ≈ Zn > Mn) in the leachate from the biochar. A key mechanism of pH neutralisation appears to be solid carbonate dissolution as calcite (CaCO3) was identified (via X-ray diffraction) in the biochar prior to contact with acid drainage, and dissolved alkalinity and Ca was observed in the leachate. Proton and metal removal by cation exchange, direct binding to oxygen-containing functional groups, and metal oxide precipitation also appears important. Further evaluation of the treatment capacity of other biochars and field trials are warranted. PMID:26004563

  2. DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING NATURAL ORGANIC MATTER IN SOILS AND WATER

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

  3. pH, dissolved oxygen, and adsorption effects on metal removal in anaerobic bioreactors.

    PubMed

    Willow, Mark A; Cohen, Ronald R H

    2003-01-01

    Anaerobic bioreactors were used to test the effect of the pH of influent on the removal efficiency of heavy metals from acid-rock drainage. Two studies used a near-neutral-pH, metal-laden influent to examine the heavy metal removal efficiency and hydraulic residence time requirements of the reactors. Another study used the more typical low-pH mine drainage influent. Experiments also were done to (i) test the effects of oxygen content of feed water on metal removal and (ii) the adsorptive capacity of the reactor organic substrate. Analysis of the results indicates that bacterial sulfate reduction may be a zero-order kinetic reaction relative to sulfate concentrations used in the experiments, and may be the factor that controls the metal mass removal efficiency in the anaerobic treatment systems. The sorptive capacities of the organic substrate used in the experiments had not been exhausted during the experiments as indicated by the loading rates of removal of metals exceeding the mass production rates of sulfide. Microbial sulfate reduction was less in the reactors receiving low-pH influent during experiments with short residence times. Sulfate-reducing bacteria may have been inhibited by high flows of low-pH water. Dissolved oxygen content of the feed waters had little effect on sulfate reduction and metal removal capacity. PMID:12931874

  4. Processes controlling dissolved oxygen and pH in the upper Willamette River basin, Oregon, 1994

    USGS Publications Warehouse

    Pogue, Ted R., Jr.; Anderson, Chauncey W.

    1995-01-01

    In July and August of 1994, the U. S. Geological Survey in cooperation with the Oregon Department of Environmental Quality (ODEQ) collected data to document the spatial extent and diel variability of dissolved oxygen (DO) concentrations and pH levels in selected reaches of streams in the upper Willamette River Basin. These data were also collected to identify primary factors that control DO concentrations downstream from major point sources as well as to provide ODEQ with data to refine calibration of their steady-state DO and nutrient models for the upper Willamette River Basin. All of the reaches studied had diel variations in DO and pH. The magnitude of the diel variations in DO ranged from 0.2 to 3.9 milligrams per liter (7 to 50 percent-saturation units based on ambient water temperature and barometric pressure) and in pH from 0.3 to 1.4 units. However, of the reaches studied, only the Coast Fork Willamette River from river mile (RM) 21.7 to 12.5 and the Willamette River from RM 151 to 141.6 had field measured violations of State standards for DO and pH. DO concentration and pH in water depend on many factors. Data were collected to examine several major factors, including BOD (biochemical oxygen demand), carbonaceous BOD, nitrogenous BOD, and measures of photosynthetic activity. Of the four study reaches, only a short stretch of the Coast Fork Willamette River has potential for important levels of oxygen consumption from BOD or nitrification. Additionally, water-column primary-productivity measurements indicated that respiration and photosynthesis by free-floating algae did not explain the observed diel variations in DO in the study reaches. Results from a simple mathematical model incorporating measures of community respiration and net primary productivities indicated that periphyton are capable of producing a diel variation of the order of magnitude observed during the August study period. In the Willamette River near Peoria, the combined periphyton DO consumption and production estimate at RM 151 (2.4 mg/L) and RM 144.6 (1.7 mg/L) would account for 90 and 63 percent, respectively, of the observed diel fluctuation. The estimates for the Corvallis reach at RM 132.6 (0.4 mg/L) and RM 130.7 (2.9 mg/L) had a considerably larger range of 36 to 264 percent of DO saturation, respectively. Therefore, because BOD and phytoplankton do not appear to be important contributors to diel DO fluctuations, periphyton are likely the primary contributor to diel fluctuations in the upper Willamette River Basin during July and August.

  5. Effects of pH and dissolved oxygen on the photodegradation of 17α-ethynylestradiol in dissolved humic acid solution.

    PubMed

    Ren, Dong; Huang, Bin; Bi, Tingting; Xiong, Dan; Pan, Xuejun

    2016-01-01

    To probe the mechanisms responsible for pH and dissolved oxygen (DO) affecting the photodegradation of 17α-ethynylestradiol (EE2) in dissolved humic acid (HA) solution, EE2 aqueous solutions with pH values ranging from 3.0 to 11.0 and different DO conditions were irradiated by using a 300 W mercury lamp equipped with 290 nm light cutoff filters. In 5.0 mg L(-1) HA solutions (pH 8.0), EE2 was degraded at a rate of 0.0739 h(-1) which was about 4-fold faster than that in Milli-Q water. The degradation of EE2 was mainly caused by the oxidation of photogenerated reactive species (RS), and the contribution of direct photodegradation to EE2 degradation was always lower than 27%. Both the direct and indirect photodegradation of EE2 were closely dependent on the EE2 initial concentration, pH value and DO concentration. The photodegradation rate of EE2 decreased with increased initial concentration of EE2 due to the limitation of photon flux. With pH and DO increasing, the degradation rate of EE2 increased significantly due to the increase in the yields of excited EE2 and RS. Among the photogenerated RS, HO˙ and (3)HA* were determined to be the key contributors, and their global contribution to EE2 photodegradation was about 50%. Although HA could generate more (1)O2 than HO˙, the contribution of (1)O2 to EE2 degradation was lower than 13% due to its low reactivity towards EE2. This study could enlarge our knowledge on the photochemical behaviors of steroid estrogens in natural sunlit waters. PMID:26611276

  6. Sulfamethazine sorption to soil: vegetative management, pH, and dissolved organic matter effects

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Elucidating veterinary antibiotic (VA) interactions with soil is important for assessing and mitigating possible environmental hazards. Objectives of this study were to investigate the effects of vegetative management, soil physical and chemical properties, and manure-derived dissolved organic matte...

  7. The Molecular Composition of Dissolved Organic Matter in Forest Soils as a Function of pH and Temperature

    PubMed Central

    Roth, Vanessa-Nina; Dittmar, Thorsten; Gaupp, Reinhard; Gleixner, Gerd

    2015-01-01

    We examined the molecular composition of forest soil water during three different seasons at three different sites, using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS). We examined oxic soils and tested the hypothesis that pH and season correlate with the molecular composition of dissolved organic matter (DOM). We used molecular formulae and their relative intensity from ESI-FT-ICR-MS for statistical analysis. Applying unconstrained and constrained ordination methods, we observed that pH, dissolved organic carbon (DOC) concentration and season were the main factors correlating with DOM molecular composition. This result is consistent with a previous study where pH was a main driver of the molecular differences between DOM from oxic rivers and anoxic bog systems in the Yenisei River catchment. At a higher pH, the molecular formulae had a lower degree of unsaturation and oxygenation, lower molecular size and a higher abundance of nitrogen-containing compounds. These characteristics suggest a higher abundance of tannin connected to lower pH that possibly inhibited biological decomposition. Higher biological activity at a higher pH might also be related to the higher abundance of nitrogen-containing compounds. Comparing the seasons, we observed a decrease in unsaturation, molecular diversity and the number of nitrogen-containing compounds in the course of the year from March to November. Temperature possibly inhibited biological degradation during winter, which could cause the accumulation of a more diverse compound spectrum until the temperature increased again. Our findings suggest that the molecular composition of DOM in soil pore waters is dynamic and a function of ecosystem activity, pH and temperature. PMID:25793306

  8. B/Ca in coccoliths and relationship to calcification vesicle pH and dissolved inorganic carbon concentrations

    NASA Astrophysics Data System (ADS)

    Stoll, Heather; Langer, Gerald; Shimizu, Nobumichi; Kanamaru, Kinuyo

    2012-03-01

    Coccolithophorid algae are microscopic but prolific calcifiers in modern and ancient oceans. When the pH of seawater is modified, as may occur in the future due to ocean acidification, different species and strains of coccolithophorids have exhibited diverse calcification responses in laboratory culture. Since their biomineralization is a completely intracellular process, it is unclear why their response should be affected by extracellular seawater pH. Variations in the B/Ca in coccoliths are potential indicators of pH shifts in the intracellular coccolith vesicle where calcification occurs, because B/Ca in abiogenic calcites increases at higher pH due to the greater abundance of borate ions, the only B species incorporated into calcite. We used a SIMS ion probe to measure B/Ca of coccoliths from three different strains of Emiliania huxleyi and one strain of Coccolithus braarudii braarudii cultured under different seawater pH conditions to ascertain if the B/Ca can be used to elucidate how coccolithophorids respond to changing ocean pH. These data are interpreted with the aid of a conceptual model of cellular boron acquisition by coccolithophorids. Based on uptake in other plants, we infer that boron uptake by coccolithophorid cells is dominated by passive uptake of boric acid across the lipid bilayer. Subsequently, in the alkaline coccolith vesicle (C.V.), boron speciates according to the C.V. pH, and borate is incorporated into the coccolith. At increasing seawater pH, the relative abundance of the neutral boric acid in seawater decreases, lowering the potential B flux into the cell. Homeostasis or constant pH of the coccolith vesicle results in a decrease of the B/Ca in the coccolith with increasing seawater pH. In contrast, if coccolith vesicle pH increases with increasing seawater pH, then the B/Ca will increase as the fraction of borate in the coccolith vesicle increases. The coccolith B/Ca is also expected to depend inversely on the dissolved inorganic carbon (DIC) concentration in the coccolith vesicle. The B/Ca in cultured coccoliths is much lower than that of foraminifera or corals and limits precision in the analysis. Modest variations in DIC or pH of the coccolith vesicle can account for the observed trends in B/Ca in cultured coccoliths. The model shows that paired measurements of B/Ca and B isotopic composition of the calcite could distinguish between regulation of pH or DIC in the coccolith vesicle.

  9. Limestone drains to increase pH and remove dissolved metals from an acidic coal-mine discharge in Pennsylvania

    SciTech Connect

    Cravotta, C.A. III; Trahan, M.K.

    1996-12-31

    Limestone drains are used to increase pH and remove dissolved metals from acidic mine drainage. However, the chemistry of mine drainage is variable and geochemical processes within these treatment systems are poorly understood. To resolve uncertainties about some of the factors affecting chemical reactions within limestone drains, three identical drains were constructed in parallel to treat acidic drainage from an abandoned coal mine in east-central Pennsylvania. A static mixer was installed to enable aeration of the inflow to one or all three drains. Samples of water were collected at the inflow to the drains, at points within the drains, and at the outflow from the drains. The samples were analyzed to evaluate the rate of dissolution of limestone and the extent of hydrolysis and precipitation of iron, aluminum, manganese, and other dissolved metals. The inflow rate was varied to determine any effects on the rates of dissolution and precipitation reactions and the transport of reaction products through the drains.

  10. Influence of increasing dissolved inorganic carbon concentrations and decreasing pH on chemolithoautrophic bacteria from oxic-sulfidic interfaces

    NASA Astrophysics Data System (ADS)

    Mammitzsch, K.; Jost, G.; Jürgens, K.

    2012-12-01

    Increases in the dissolved inorganic carbon (DIC) concentration are expected to cause a decrease in the pH of ocean waters, a process known as ocean acidification. In oxygen-deficient zones this will add to already increased DIC and decreased pH values. It is not known how this might affect microbial communities and microbially mediated processes. In this study, the potential effects of ocean acidification on chemolithoautotrophic prokaryotes of marine oxic-anoxic transition zones were investigated, using the chemoautotrophic denitrifying ɛ-proteobacterium "Sulfurimonas gotlandica" strain GD1 as a model organism. This and related taxa use reduced sulfur compounds, e.g. sulfide and thiosulfate, as electron donors and were previously shown to be responsible for nitrate removal and sulfide detoxification in redox zones of the Baltic Sea water column but occur also in other oxygen-deficient marine systems. Bacterial cell growth within a broad range of DIC concentrations and pH values was monitored and substrate utilization was determined. The results showed that the DIC saturation concentration for growth was already reached at 800 μM, which is well below in situ DIC levels. The pH optimum was between 6.6 and 8.0. Within a pH range of 6.6-7.1 there was no significant difference in substrate utilization; however, at lower pH values cell growth decreased sharply and cell-specific substrate consumption increased. These findings suggest that a direct effect of ocean acidification, with the predicted changes in pH and DIC, on chemolithoautotrophic bacteria such as "S. gotlandica" str. GD1 is generally not very probable.

  11. Influence of pH, hardness, dissolved organic carbon concentration, and dissolved organic matter source on the acute toxicity of copper to Daphnia magna in soft waters: implications for the biotic ligand model.

    PubMed

    Ryan, Adam C; Tomasso, Joseph R; Klaine, Stephen J

    2009-08-01

    The influence of pH, dissolved organic carbon (DOC) concentration, water hardness, and dissolved organic matter (DOM) source on the acute toxicity of copper were investigated with standardized 48-h Daphnia magna toxicity tests. Toxicity tests were conducted according to a four-factor complete factorial design. Nominal factor levels were as follows: pH 6 and 8; DOC, 2.5 and 10 mg/L; hardness, 10, 20, and 40 mg/L as CaCO3; and two DOM sources (collected from the Black River and Edisto River, SC, USA). The experimental design resulted in 24 different factor level combinations. Results indicated that all factors had significant effects on copper toxicity. Furthermore, a strong interactive effect of DOC concentration and pH was detected. Because the biotic ligand model (BLM) has become a widely used tool for predicting toxicity and interpreting toxicity test results, its performance with these data was evaluated. Seventy percent of BLM predictions were within twofold of the observed median lethal concentrations. However, BLM parameters could be adjusted to improve model performance with this data set. This analysis suggested that in soft waters, the CuOH+ complex binds more strongly with the biotic ligand and that the competitive effect of hardness cations should be increased. The results of the present study may have implications for application of the BLM to some types of surface waters. Furthermore, a comprehensive analysis of BLM performance with all available data should be performed, and necessary updates to model parameters should be made to produce the most robust and widely applicable model. PMID:19265455

  12. Aqueous stability of leuprolide acetate: effect of temperature, dissolved oxygen, pH and complexation with β-cyclodextrin.

    PubMed

    Rahimi, Mehdi; Mobedi, Hamid; Behnamghader, Aliasghar

    2016-02-01

    In the present research, the aqueous stability of leuprolide acetate (LA) in phosphate buffered saline (PBS) medium was studied (pH = 2.0-7.4). For this purpose, the effect of temperature, dissolved oxygen and pH on the stability of LA during 35 days was investigated. Results showed that the aqueous stability of LA was higher at low temperatures. Degassing of the PBS medium partially increased the stability of LA at 4 °C, while did not change at 37 °C. The degradation of LA was accelerated at lower pH values. In addition, complexes of LA with different portions of β-cyclodextrin (β-CD) were prepared through freeze-drying procedure and characterized by Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) analyses. Studying their aqueous stability at various pH values (2.0-7.4) showed LA/β-CD complexes exhibited higher stability when compared with LA at all pH values. The stability of complexes was also improved by increasing the portion of LA/β-CD up to 1/10. PMID:25331295

  13. Novel probes for pH and dissolved oxygen measurements in cultivations from millilitre to benchtop scale.

    PubMed

    Demuth, Caspar; Varonier, Joel; Jossen, Valentin; Eibl, Regine; Eibl, Dieter

    2016-05-01

    pH value and the concentration of dissolved oxygen (DO) are key parameters to monitor and control cell growth in cultivation studies. Reliable, robust and accurate methods to measure these parameters in cultivation systems in real time guarantee high product yield and quality. This mini-review summarises the current state of the art of pH and DO sensors that are applied to bioprocesses from millilitre to benchtop scale by means of a short introduction on measuring principles and selected applications. Special emphasis is placed on single-use bioreactors, which have been increasingly employed in bioprocess development and production in recent years. Working principles, applications and the particular requirements of sensors in these cultivation systems are given. In such processes, optical sensors for pH and DO are often preferred to electrochemical probes, as they allow semi-invasive measurements and can be miniaturised to micrometre scale or lower. In addition, selected measuring principles of novel sensing technologies for pH and DO are discussed. These include solid-state sensors and miniaturised devices that are not yet commercially available, but show promising characteristics for possible use in bioprocesses in the near future. PMID:26995606

  14. Impact of shear stress and pH changes on floc size and removal of dissolved organic matter (DOM).

    PubMed

    Slavik, Irene; Müller, Susanne; Mokosch, Regina; Azongbilla, Joseph Abanga; Uhl, Wolfgang

    2012-12-01

    The impact of shear stress and increases in pH on the release of natural dissolved organic matter (DOM) from Fe-DOM and Al-DOM flocs was investigated for a high organic matter, low turbidity raw water by application of a dynamic extinction probe (DEP) and liquid chromatography organic carbon detection (LC-OCD). It was shown that high shear forces resulted in a breakage of Fe-DOM flocs. Re-growth took place during subsequent low shear phases. However, re-growth was limited. The flocs regained a size of about 50% of the size after initial coagulation. Cyclic shearing resulted in slower re-growth rates. A new insight was that when enough time was given, similar sizes of the re-grown flocs were regained. As shown by bulk DOC, only an insignificant release of DOM took place when flocs were exposed to shear. Increase in shear stress resulted in smaller flocs with higher specific outer surface area. However, DOM removal did not change. Thus, there was no increase in adsorption capacity due to floc breakage. Consequently, DOM must be adsorbed inside the amorphous flocs rather than on the outer surface. Also, as shear results in more compact flocs, compaction does not have an effect on DOM removal. A pH increase of 0.5, as it can happen during water treatment after coagulation, resulted in a release of DOM. Humic substances accounted for the largest proportion of total DOM released. The increase in pH did not affect floc size. Consequently, DOM removal is mainly governed by the dependence of DOM properties on pH with the final pH determining the degree of DOM removal and not the path on which this pH is reached. The physical properties of the flocs have no impact on DOM removal. PMID:23047054

  15. High temporal and spatial variability of dissolved oxygen and pH in a nearshore California kelp forest

    NASA Astrophysics Data System (ADS)

    Frieder, C. A.; Nam, S. H.; Martz, T. R.; Levin, L. A.

    2012-10-01

    Predicting consequences of ocean deoxygenation and ocean acidification for nearshore marine ecosystems requires baseline dissolved oxygen (DO) and carbonate chemistry data that are both high-frequency and high-quality. Such data allow accurate assessment of environmental variability and present-day organism exposure regimes. In this study, scales of DO and pH variability were characterized over one year in a nearshore kelp forest ecosystem in the Southern California Bight. DO and pH were strongly, positively correlated, revealing that organisms on this upwelling shelf are not only exposed to low pH but also to low DO. The dominant scale of temporal DO and pH variability occurred on semidiurnal, diurnal and event (days-weeks) time scales. Daily ranges in DO and pH at 7 m water depth (13 mab) could be as large as 220 μmol kg-1 and 0.36 units, respectively. Sources of pH and DO variation include photosynthesis within the kelp forest ecosystem, which can elevate DO and pH by up to 60 μmol kg-1 and 0.1 units over one week following the intrusion of high-density, nutrient-rich water. Accordingly, highly productive macrophyte-based ecosystems could serve as deoxygenation and acidification refugia by acting to elevate DO and pH relative to surrounding waters. DO and pH exhibited greater spatial variation over a 10 m increase in water depth (from 7 to 17 m) than along a 5 km stretch of shelf in a cross-shore or alongshore direction. Over a three-month time period, mean DO and pH at 17 m water depth were 168 μmol kg-1 and 7.87, respectively. These values represent a 35% decrease in mean DO and 37% increase in [H+] relative to near-surface waters. High-frequency variation was also reduced at depth. The mean daily range in DO and pH was 39% and 37% less, respectively, at 17 m water depth relative to 7 m. As a consequence, the exposure history of an organism is largely a function of its depth of occurrence within the kelp forest. With knowledge of local alkalinity conditions and high-frequency temperature, salinity, and pH data, we estimated pCO2 and calcium carbonate saturation states with respect to calcite and aragonite (Ωcalc and Ωarag) for the La Jolla kelp forest at 7 m and 17 m water depth. pCO2 ranged from 246 to 1016 μatm, Ωcalc was always supersaturated, and Ωarag was undersaturated at the beginning of March for five days when pH was less than 7.75 and DO was less than 115 μmol kg-1. These findings raise the possibility that the benthic communities along eastern boundary current systems are currently acclimatized and adapted to natural, variable, and low DO and pH. Still, future exposure of coastal California populations to even lower DO and pH may increase as upwelling intensifies and hypoxic boundaries shoal, compressing habitats and challenging the physiological capacity of intolerant species.

  16. High temporal and spatial variability of dissolved oxygen and pH in a nearshore California kelp forest

    NASA Astrophysics Data System (ADS)

    Frieder, C. A.; Nam, S. H.; Martz, T. R.; Levin, L. A.

    2012-03-01

    Predicting consequences of ocean deoxygenation and ocean acidification for nearshore marine ecosystems requires baseline dissolved oxygen (DO) and carbonate chemistry data that are both high-frequency and high-quality. Such data allow accurate assessment of environmental variability and present-day organism exposure regimes. In this study, scales of DO and pH variability were characterized over one year in a nearshore, kelp forest ecosystem in the Southern California Bight. DO and pH were strongly, positively correlated revealing that organisms on this upwelling shelf are not only exposed to low pH but also low DO. The dominant temporal scale of DO and pH variability occurred on semidiurnal, diurnal and event (days-weeks) time scales. Daily ranges in DO and pH at 7 m water depth (13 mab) could be as large as 220 μmol kg-1 and 0.36 units, respectively. This range is much greater than the expected decreases in pH in the open ocean by the year 2100. Sources of pH and DO variation include photosynthesis within the kelp forest ecosystem, which can elevate DO and pH by up to 60 μmol kg-1 and 0.1 units over one week following the intrusion of high-density, nutrient-rich water. Accordingly, highly productive macrophyte-based ecosystems could serve as deoxygenation and acidification refugia by acting to elevate DO and pH relative to surrounding waters. DO and pH exhibited greater spatial variation over a 10 m increase in water depth (from 7 to 17 m) than along a 5-km stretch of shelf in a cross-shore or alongshore direction. Over a three-month time period mean DO and pH at 17-m water depth were 168 μmol kg-1 and 7.87, respectively. These values represent a 35% decrease in mean DO and 37% increase in [H+] relative to surface waters. High-frequency variation was also reduced at depth. The mean daily range in DO and pH was 39% and 37% less, respectively, at 17-m water depth relative to the surface. As a consequence, the exposure history of an organism is largely a function of its depth of occurrence within the kelp forest. These findings raise the possibility that the benthic communities along eastern boundary current systems are currently acclimatized and adapted to natural, variable, and low DO and pH. Future exposure of coastal California populations to low DO and pH may increase as upwelling intensifies and hypoxic boundaries shoal, compressing habitats and challenging the physiological capacity of intolerant species.

  17. Marine microbial production of dimethylsulfide from dissolved dimethylsulfoniopropionate. Ph. D. Thesis

    SciTech Connect

    Ledyard, K.M.

    1993-02-01

    Dimethylsulfide (DMS) plays a central role in the transfer of sulfur from the ocean to the atmosphere and ultimately to land. The most abundant volatile organosulfur compound in seawater, DMS is believed to account for the bulk of the sea-to-air biogenic sulfur flux. DMS has also been implicated as the major precursor of submicron-sized sulfate aerosol over the ocean. This aerosol acts as an effective site for cloud droplet condensation suggesting a possibly important role for DMS in marine cloud formation. In the ocean, the precursor of DMS is presumed to be the zwitterionic sulfonium compound dimethylsulfoniopropionate (DMSP), a common osmoticum in certain classes of marine algae. While some algae can cleave DMSP intracellularly to form DMS, correlation of DMS concentrations with indicators of algal productivity on a local scale is poor. This thesis focuses on an alternative pathway of DMS formation: microbial cleavage of dissolved (extracellular) DMSP. In laboratory studies, bacteria able to cleave DMSP to form DMS were isolated from seawater by a DMSP enrichment technique, and the kinetics of DMSP uptake and DMS production were examined closely in pure cultures of a bacterial isolate from the Sargasso Sea. The isolate could grow with both DMSP and acrylic acid, one of the products of DMSP cleavage, as the sole source of carbon and energy, and the enzyme catalyzing DMSP cleavage appeared to be induced by both of these compounds. Kinetic parameters were estimated for DMSP uptake and cleavage by whole cells. Comparison of the 16S rRNA sequence of this isolate with that of known eubacteria showed that it was most closely related to Erythrobacter longus, an aerobic, bacteriochlorophyll-containing member of the alpha proteobacteria.

  18. Effects of pH, Temperature, Dissolved Oxygen, and Flow Rate on Phosphorus Release Processes at the Sediment and Water Interface in Storm Sewer

    PubMed Central

    Li, Haiyan; Li, Mingyi; Zhang, Xiaoran

    2013-01-01

    The effects of pH, temperature, dissolved oxygen (DO), and flow rate on the phosphorus (P) release processes at the sediment and water interface in rainwater pipes were investigated. The sampling was conducted in a residential storm sewer of North Li Shi Road in Xi Cheng District of Beijing on August 3, 2011. The release rate of P increased with the increase of pH from 8 to 10. High temperature is favorable for the release of P. The concentration of total phosphorus (TP) in the overlying water increased as the concentration of DO decreased. With the increase of flow rate from 0.7 m s−1 to 1.1 m s−1, the concentration of TP in the overlying water increased and then tends to be stable. Among all the factors examined in the present study, the flow rate is the primary influence factor on P release. The cumulative amount of P release increased with the process of pipeline runoff in the rainfall events with high intensities and shorter durations. Feasible measures such as best management practices and low-impact development can be conducted to control the P release on urban sediments by slowing down the flow rate. PMID:24349823

  19. Rates of zinc and trace metal release from dissolving sphalerite at pH 2.0-4.0

    USGS Publications Warehouse

    Stanton, M.R.; Gemery-Hill, P. A.; Shanks, Wayne C., III; Taylor, C.D.

    2008-01-01

    High-Fe and low-Fe sphalerite samples were reacted under controlled pH conditions to determine nonoxidative rates of release of Zn and trace metals from the solid-phase. The release (solubilization) of trace metals from dissolving sphalerite to the aqueous phase can be characterized by a kinetic distribution coefficient, (Dtr), which is defined as [(Rtr/X(tr)Sph)/(RZn/X(Zn) Sph)], where R is the trace metal or Zn release rate, and X is the mole fraction of the trace metal or Zn in sphalerite. This coefficient describes the relationship of the sphalerite dissolution rate to the trace metal mole fraction in the solid and its aqueous concentration. The distribution was used to determine some controls on metal release during the dissolution of sphalerite. Departures from the ideal Dtr of 1.0 suggest that some trace metals may be released via different pathways or that other processes (e.g., adsorption, solubility of trace minerals such as galena) affect the observed concentration of metals. Nonoxidative sphalerite dissolution (mediated by H+) is characterized by a "fast" stage in the first 24-30 h, followed by a "slow" stage for the remainder of the reaction. Over the pH range 2.0-4.0, and for similar extent of reaction (reaction time), sphalerite composition, and surface area, the rates of release of Zn, Fe, Cd, Cu, Mn and Pb from sphalerite generally increase with lower pH. Zinc and Fe exhibit the fastest rates of release, Mn and Pb have intermediate rates of release, and Cd and Cu show the slowest rates of release. The largest variations in metal release rates occur at pH 2.0. At pH 3.0 and 4.0, release rates show less variation and appear less dependent on the metal abundance in the solid. For the same extent of reaction (100 h), rates of Zn release range from 1.53 ?? 10-11 to 5.72 ?? 10-10 mol/m2/s; for Fe, the range is from 4.59 ?? 10-13 to 1.99 ?? 10-10 mol/m2/s. Trace metal release rates are generally 1-5 orders of magnitude slower than the Zn or Fe rates. Results indicate that the distributions of Fe and Cd are directly related to the rate of sphalerite dissolution throughout the reaction at pH 3.0 and 4.0 because these two elements substitute readily into sphalerite. These two metals are likely to be more amenable to usage in predictive acid dissolution models because of this behavior. The Pb distribution shows no strong relation to sphalerite dissolution and appears to be controlled by pH-dependent solubility, most likely related to trace amounts of galena. The distribution of Cu is similar to that of Fe but is the most-dependent of all metals on its mole fraction ratio (Zn:Cu) in sphalerite. The Mn distributions suggest an increase in the rate of Mn release relative to sphalerite dissolution occurs in low Mn samples as pH increases. The Mn distribution in high Mn samples is nearly independent of pH and sphalerite dissolution at pH 2.0 but shows a dependence on these two parameters at higher pH (3.0-4.0).

  20. Geochemistry of dissolved aluminum at low pH: Extent and significance of Al-Fe(III) coprecipitation below pH 4.0

    NASA Astrophysics Data System (ADS)

    Sánchez-España, Javier; Yusta, Iñaki; Gray, Jennifer; Burgos, William D.

    2016-02-01

    This work examines the geochemical behavior of dissolved aluminum in sulfate-rich acidic waters. Our observations were obtained during several years of geochemical and mineralogical research in the San Telmo acidic pit lake and other pit lakes of SW Spain. The work includes scanning and transmission electron microscopy (SEM, TEM) of suspended mineral colloids found in deep lake waters. Energy dispersive spectroscopy (EDS) coupled to scanning and high resolution transmission electron microscopy (STEM, HRTEM) revealed not only the presence and formation of discrete, sub-micron Al solids like alunite, but also the abundance and distribution of Al into Fe(III) phases typical of acid mine drainage, such as schwertmannite and jarosite, at a nanometric resolution. The main conclusion emerging from our work is that the fate and transport of Al at low pH (<4.0) can be largely influenced by adsorption on and/or coprecipitation with both schwertmannite and jarosite. Under the geochemical conditions studied (SO42- = 10-2 M, Fe(III) ∼ Al = 10-3 M), alunite formation may occur at pH > 3.3, as suggested by mineralogical observations and geochemical modelling. Below this pH, and contrary to the extended assumption, Al is not truly conservative, and in the presence of ferric iron, both metals may co-precipitate at a substantial extent to form either particles of Al-rich schwertmannite (containing up to ca. 8 at.% Al with [Fe/(Fe + Al)] = 0.77) and/or crystals of H3O+- to K+-jarosite (containing up to ca. 10 at.% Al with [Fe/(Fe + Al)] = 0.54). This Al incorporation seems to take place by adsorption on particle surfaces in schwertmannite and by atomic substitution for Fe3+ in jarosite. Alunite is also unstable at this low pH range with respect to jarosite, which may lead either to isomorphic transformation and/or to chemically zoned crystals with jarositic rims around previously formed alunite cores. As a whole, the compositional spectrum of the analyzed jarosites and alunites describes a discontinuous, coupled (Al3+-Fe3+, H3O+-K+) solid solution series with an apparent gap at intermediate compositions. However, this gap seems to follow geochemical aspects more than crystallographic factors (i.e., immiscibility). The combination of this macroscopically invisible Al incorporated into Fe(III) solids along with subordinate alunite formation may cause significant Al removal even at very low pH (e.g., 20% decrease in Al concentration in San Telmo at pH < 3.1). Furthermore, this Fe(III)-Al co-precipitation may also affect the fate of toxic trace elements like As and Pb.

  1. pH : a key control of the nature and distribution of dissolved organic matter and associated trace metals in soil

    NASA Astrophysics Data System (ADS)

    Pédrot, M.; Dia, A.; Davranche, M.

    2009-04-01

    Dissolved organic matter is ubiquitous at the Earth's surface and plays a prominent role in controlling metal speciation and mobility from soils to hydrosystems. Humic substances (HS) are usually considered to be the most reactive fraction of organic matter. Humic substances are relatively small and formed by chemically diverse organic molecules, bearing different functional groups that act as binding sites for cations and mineral surfaces. Among the different environmental physicochemical parameters controlling the metal speciation, pH is likely to be the most important one. Indeed, pH affect the dissociation of functional groups, and thus can influence the HS structure, their ability to complex metals, their solubility degree allowing the formation of aggregates at the mineral surface. In this context, soil/water interactions conducted through batch system experiments, were carried out with a wetland organic-rich soil to investigate the effect of pH on the release of dissolved organic carbon (DOC) and associated trace elements. The pH was regulated between 4 and 7.5 using an automatic pH stat titrator. Ultrafiltration experiments were performed to separate the dissolved organic pool following decreasing pore sizes (30 kDa, 5 kDa and 2 kDa with 1 Da = 1 g.mol-1). The pH increase induced a significant DOC release, especially in heavy organic molecules (size >5 kDa) with a high aromaticity (>30 %). These were probably humic acids (HA). This HA release influenced (i) directly the trace element concentrations in soil solution since HA were enriched in several trace elements such as Th, REE, Y, U, Cr and Cu; and (ii) indirectly by the breaking of clay-humic complexes releasing Fe- and Al-rich nanoparticles associated with V, Pb and Ti. By contrast, at acid pH, most HS were complexed onto mineral surfaces. They also sequestered iron nanoparticles. Therefore, at low pH, most part of DOC molecules had a size < 5 kDa and lower aromaticity. Thus, the DOC was mostly composed of simple organic compounds little complexing. Consequently, the soil solution was depleted in trace elements such as Th, REE, Y, U, Cr, Cu, Al, Fe, V, Pb and Ti, but also enriched in Ca, Sr, Ba, Mn, Mg, Co, Zn and in a lesser proportion in Rb, Li and Ni. The aromaticity in the fractions <5 kDa was higher than in the fractions <30 kDa or <0.2 µm. Complementary experiments were performed to understand the HS size distribution and aromaticity according to pH and ionic strength .The molecular size and shape of HS is usually explained by two concepts: (i) the macropolymeric structure with heavy organic molecules considered to be flexible linear polyelectrolytes and (ii) the supramolecular structure with an association of a complex mixture of different molecules held together by dispersive weak forces. Ours results supported the HA supramolecular structure at neutral or basic pH conditions. But, at acid pH, a disruption of the humic supramolecular associations involved the release of small organic molecules with a high aromaticity. Moreover, this aromaticity variation can be due also to the presence of fulvic acids in the fractions <5 kDa and a mixture of heavy organic molecules little complexing in the fractions >5 kDa. These latter molecules displayed a low aromaticity decreasing the global aromaticity of the fractions <30 kDa and <0.2 µm. To summarize, these new data demonstrated that the DOC and trace element concentrations of the soil solutions were strongly controlled by pH. This parameter influenced the nature and the size of the DOC as well as, the trace element concentrations in the soil solutions, with a decreasing contribution of HA when pH decreased. This pH dependence is a key issue of concern since local (human pressure) and/or global (climatic) warning result in pH water changes.

  2. Binding interactions of dissolved organic matter with iron and copper: Effects of source and pH

    NASA Astrophysics Data System (ADS)

    Du, Y.; Jaffe, R.

    2014-12-01

    Dissolved organic matter(DOM) fluxes from terrestrial to marine environments have increased as a result of anthropogenic activities and climate change, and DOM is known to facilitate the transport of both metals and trace organics. The nature and composition of DOM may influence its binding properties to metals and thus affect their mobility and fate in aquatic environments. Humic substances make up the majority of DOM in many aquatic ecosystems. Metals such as Fe and Cu are not only important as nutrients in aquatic systems, but also in controlling biogeochemical and ecotoxicological processes respectively. Thus, gaining a better understanding on the interaction of humic substances with Fe or Cu is important in the assessment of the bioavailability of such metals in aquatic systems. In this study, the binding processes of two different DOM samples (Suwanee River humic acid, SRHA and Nordic Lake fulvic acid, NLFA)with Fe(III) and Cu(II) were examined. With the assistance of excitation-emission matrix fluorescence (EEM) and parallel factor analysis (PARAFAC), three humic-like components (C1, C2 and C4), and one microbial humic-like component (C3), were identified in the characterization of the samples. The quenching rates of C2 and C4 fluorescence in the presence of Cu were similar, which were slightly faster than that forC1. In contrast, the C3 fluorescence was significantly less affected by the addition of metals. In the presence of Fe, the most significant quenching was also observed for C2, and the behavior of C4 fluorescence was dependent on the pH value. Some differences in the fluorescence quenching were also observed between the two humic acid standards (one more higher-plant/terrestrially derived vs. the other more microbial/aquatic derived). In addition, pH had a significant effect on the metal binding with significantly lower quenching at lower pH values. Some variations where observed for the higher pH conditions particularly for Cu(II). A modified version of the Ryan-Weber model was used to calculate conditional stability constants (KM) and the complex capacity (CL). Effects of metal type, DOM type and pH on the fluorescence quenching are discussed.

  3. [Characteristics of precipitation pH and conductivity at Mt. Huang].

    PubMed

    Shi, Chun-e; Deng, Xue-liang; Wu, Bi-wen; Hong, Jie; Zhang, Su; Yang, Yuan-jian

    2013-05-01

    To understand the general characteristics of pH distribution and pollution in precipitation at Mt. Huang, statistical analyses were conducted for the routine measurements of pH and conductivity (K) at Mt. Huang during 2006-2011. The results showed that: (1) Over the period of study, the annual volume weighted mean (VWM) precipitation pH varied from 4.81 to 5.57, with precipitation acidity strengthening before 2009 and weakening thereafter. The precipitation acidity showed evident seasonal variations, with the VWM pH lowest in winter (4.78), and highest in summer (5.33). The occurrence frequency of acid rain was 46% , accounting for 45% of total rainfalls and with the most frequent pH falling into weak acid to neutral rain. (2) The annual VWM K varied from 16.91 to 27.84 microS x cm(-1), with no evident trend. As for ions pollution, the precipitation was relatively clean at Mt. Huang, with the most frequent K range being below 15 microS x cm(-1), followed by 15-25 microS x cm(-1). From February 2010 to December 2011, precipitation samples were collected on daily basis for ions analysis, as well as pH and K measurement in lab. Detailed comparisons were conducted between the two sets of pH and K, one set from field measurement and the other from lab measurement. The results indicated: (1) The lab measured pH (K) was highly correlated with the field pH (K); however, the lab pH tended to move towards neutral comparing with the corresponding field pH, and the shift range was closely correlated with the field pH and rainfall. The shift range of K from field to lab was highly correlated with the total ion concentration of precipitation. The field K showed evident negative correlation with the field pH with a correlation coefficient of -0.51. (2) When sampling with nylon-polyethylene bags, the statistics showed smaller bias between two sets of pH, with higher correlation coefficient between two sets of K. Furthermore, the lab K also showed evident negative correlation with the lab pH. Comparing with the observations at other alpine sites in central to eastern China, the natural precipitation at Mt. Huang was weaker in acidity and contains lower ion concentration. PMID:23914555

  4. Evaluation of Total Dissolved Solids and Specific Conductance Water Quality Targets with Paired Single-Species and Mesocosm Community Exposures

    EPA Science Inventory

    Isolated single-species exposures were conducted in parallel with 42 d mesocosm dosing studies that measured in-situ and whole community responses to different recipes of excess total dissolved solids (TDS). The studies were conducted with cultured species and native taxa from mo...

  5. Impact of pH, dissolved inorganic carbon, and polyphosphates for the initial stages of water corrosion of copper surfaces investigated by AFM and NEXAFS

    EPA Science Inventory

    Nanoscale studies at the early stages of the exposure of copper surfaces after systematic treatments in synthesized water solutions can provide useful information about corrosion processes. The corrosion and passivation of copper surfaces as influenced by pH, dissolved inorganic ...

  6. Microbioreactor arrays with integrated mixers and fluid injectors for high-throughput experimentation with pH and dissolved oxygen control.

    PubMed

    Lee, Harry L T; Boccazzi, Paolo; Ram, Rajeev J; Sinskey, Anthony J

    2006-09-01

    We have developed an integrated array of microbioreactors, with 100 microL working volume, comprising a peristaltic oxygenating mixer and microfluidic injectors. These integrated devices were fabricated in a single chip and can provide a high oxygen transfer rate (k(L)a approximately 0.1 s(-1)) without introducing bubbles, and closed loop control over dissolved oxygen and pH (+/-0.1). The system was capable of supporting eight simultaneous Escherichia coli fermentations to cell densities greater than 13 g-dcw L(-1) (1 cm OD(650 nm) > 40). This cell density was comparable to that achieved in a 4 litre reference fermentation, conducted with the same strain, in a bench scale stirred tank bioreactor and is more than four times higher than cell densities previously achieved in microbioreactors. Bubble free oxygenation permitted near real time optical density measurements which could be used to observe subtle changes in the growth rate and infer changes in the state of microbial genetic networks. Our system provides a platform for the study of the interaction of microbial populations with different environmental conditions, which has applications in basic science and industrial bioprocess development. We leverage the advantages of microfluidic integration to deliver a disposable, parallel bioreactor in a single chip, rather than robotically multiplexing independent bioreactors, which opens a new avenue for scaling small scale bioreactor arrays with the capabilities of bench scale stirred tank reactors. PMID:16929403

  7. Improved curdlan fermentation process based on optimization of dissolved oxygen combined with pH control and metabolic characterization of Agrobacterium sp. ATCC 31749.

    PubMed

    Zhang, Hong-Tao; Zhan, Xiao-Bei; Zheng, Zhi-Yong; Wu, Jian-Rong; English, Nike; Yu, Xiao-Bin; Lin, Chi-Chung

    2012-01-01

    A significant problem in scale-down cultures, rarely studied for metabolic characterization and curdlan-producing Agrobacterium sp. ATCC 31749, is the presence of dissolved oxygen (DO) gradients combined with pH control. Constant DO, between 5% and 75%, was maintained during batch fermentations by manipulating the agitation with PID system. Fermentation, metabolic and kinetic characterization studies were conducted in a scale-down system. The curdlan yield, intracellular nucleotide levels and glucose conversion efficiency into curdlan were significantly affected by DO concentrations. The optimum DO concentrations for curdlan production were 45-60%. The average curdlan yield, curdlan productivity and glucose conversion efficiency into curdlan were enhanced by 80%, 66% and 32%, respectively, compared to that at 15% DO. No apparent difference in the gel strength of the resulting curdlan was detected. The comparison of curdlan biosynthesis and cellular nucleotide levels showed that curdlan production had positive relationship with intracellular levels of UTP, ADP, AMP, NAD(+), NADH and UDP-glucose. The curdlan productivity under 45% DO and 60% DO was different during 20-50 h. However, after 60 h curdlan productivity of both conditions was similar. On that basis, a simple and reproducible two-stage DO control process for curdlan production was developed. Curdlan production yield reached 42.8 g/l, an increase of 30% compared to that of the single agitation speed control process. PMID:21739265

  8. Biochar-induced changes in soil hydraulic conductivity and dissolved nutrient fluxes constrained by laboratory experiments.

    PubMed

    Barnes, Rebecca T; Gallagher, Morgan E; Masiello, Caroline A; Liu, Zuolin; Dugan, Brandon

    2014-01-01

    The addition of charcoal (or biochar) to soil has significant carbon sequestration and agronomic potential, making it important to determine how this potentially large anthropogenic carbon influx will alter ecosystem functions. We used column experiments to quantify how hydrologic and nutrient-retention characteristics of three soil materials differed with biochar amendment. We compared three homogeneous soil materials (sand, organic-rich topsoil, and clay-rich Hapludert) to provide a basic understanding of biochar-soil-water interactions. On average, biochar amendment decreased saturated hydraulic conductivity (K) by 92% in sand and 67% in organic soil, but increased K by 328% in clay-rich soil. The change in K for sand was not predicted by the accompanying physical changes to the soil mixture; the sand-biochar mixture was less dense and more porous than sand without biochar. We propose two hydrologic pathways that are potential drivers for this behavior: one through the interstitial biochar-sand space and a second through pores within the biochar grains themselves. This second pathway adds to the porosity of the soil mixture; however, it likely does not add to the effective soil K due to its tortuosity and smaller pore size. Therefore, the addition of biochar can increase or decrease soil drainage, and suggests that any potential improvement of water delivery to plants is dependent on soil type, biochar amendment rate, and biochar properties. Changes in dissolved carbon (C) and nitrogen (N) fluxes also differed; with biochar increasing the C flux from organic-poor sand, decreasing it from organic-rich soils, and retaining small amounts of soil-derived N. The aromaticity of C lost from sand and clay increased, suggesting lost C was biochar-derived; though the loss accounts for only 0.05% of added biochar-C. Thus, the direction and magnitude of hydraulic, C, and N changes associated with biochar amendments are soil type (composition and particle size) dependent. PMID:25251677

  9. Biochar-Induced Changes in Soil Hydraulic Conductivity and Dissolved Nutrient Fluxes Constrained by Laboratory Experiments

    PubMed Central

    Barnes, Rebecca T.; Gallagher, Morgan E.; Masiello, Caroline A.; Liu, Zuolin; Dugan, Brandon

    2014-01-01

    The addition of charcoal (or biochar) to soil has significant carbon sequestration and agronomic potential, making it important to determine how this potentially large anthropogenic carbon influx will alter ecosystem functions. We used column experiments to quantify how hydrologic and nutrient-retention characteristics of three soil materials differed with biochar amendment. We compared three homogeneous soil materials (sand, organic-rich topsoil, and clay-rich Hapludert) to provide a basic understanding of biochar-soil-water interactions. On average, biochar amendment decreased saturated hydraulic conductivity (K) by 92% in sand and 67% in organic soil, but increased K by 328% in clay-rich soil. The change in K for sand was not predicted by the accompanying physical changes to the soil mixture; the sand-biochar mixture was less dense and more porous than sand without biochar. We propose two hydrologic pathways that are potential drivers for this behavior: one through the interstitial biochar-sand space and a second through pores within the biochar grains themselves. This second pathway adds to the porosity of the soil mixture; however, it likely does not add to the effective soil K due to its tortuosity and smaller pore size. Therefore, the addition of biochar can increase or decrease soil drainage, and suggests that any potential improvement of water delivery to plants is dependent on soil type, biochar amendment rate, and biochar properties. Changes in dissolved carbon (C) and nitrogen (N) fluxes also differed; with biochar increasing the C flux from organic-poor sand, decreasing it from organic-rich soils, and retaining small amounts of soil-derived N. The aromaticity of C lost from sand and clay increased, suggesting lost C was biochar-derived; though the loss accounts for only 0.05% of added biochar-C. Thus, the direction and magnitude of hydraulic, C, and N changes associated with biochar amendments are soil type (composition and particle size) dependent. PMID:25251677

  10. Ensuring PhD development of responsible conduct of research behaviors: who's responsible?

    PubMed

    Titus, Sandra L; Ballou, Janice M

    2014-03-01

    The importance of public confidence in scientific findings and trust in scientists cannot be overstated. Thus, it becomes critical for the scientific community to focus on enhancing the strategies used to educate future scientists on ethical research behaviors. What we are lacking is knowledge on how faculty members shape and develop ethical research standards with their students. We are presenting the results of a survey with 3,500 research faculty members. We believe this is the first report on how faculty work with and educate their PhD students on basic research standards. Specifically, we wanted to determine whether individual faculty members, who are advisors or mentors, differ in how they implemented components of responsible conduct of research (RCR) with their PhD students. Mentors were more likely than advisors or supervisors to report working with all of their PhDs, who graduated in the last 5 years, on the 17 recognized critical components of RCR training and research skill development. We also found about half of the faculty members believe RCR is an institutional responsibility versus a faculty responsibility. Less than a quarter have had opportunities to participate in faculty training to be a better mentor, advisor, or research teacher, and about one third of faculty did not or could not remember whether they had guidelines related to their responsibilities to PhD students. We discuss the implications of our findings and focus on ways that PhD research mentoring can be enhanced. PMID:23686393

  11. Continuous-flow electrophoresis: Membrane-associated deviations of buffer pH and conductivity

    NASA Technical Reports Server (NTRS)

    Smolka, A. J. K.; Mcguire, J. K.

    1978-01-01

    The deviations in buffer pH and conductivity which occur near the electrode membranes in continuous-flow electrophoresis were studied in the Beckman charged particle electrophoresis system and the Hanning FF-5 preparative electrophoresis instrument. The nature of the membranes separating the electrode compartments from the electrophoresis chamber, the electric field strength, and the flow rate of electrophoresis buffer were all found to influence the formation of the pH and conductivity gradients. Variations in electrode buffer flow rate and the time of electrophoresis were less important. The results obtained supported the hypothesis that a combination of Donnan membrane effects and the differing ionic mobilities in the electrophoresis buffer was responsible for the formation of the gradients. The significance of the results for the design and stable operation of continuous-flow electrophoresis apparatus was discussed.

  12. An empirical method for estimating instream pre-mining pH and dissolved Cu concentration in catchments with acidic drainage and ferricrete

    USGS Publications Warehouse

    Nimick, D.A.; Gurrieri, J.T.; Furniss, G.

    2009-01-01

    Methods for assessing natural background water quality of streams affected by historical mining are vigorously debated. An empirical method is proposed in which stream-specific estimation equations are generated from relationships between either pH or dissolved Cu concentration in stream water and the Fe/Cu concentration ratio in Fe-precipitates presently forming in the stream. The equations and Fe/Cu ratios for pre-mining deposits of alluvial ferricrete then were used to reconstruct estimated pre-mining longitudinal profiles for pH and dissolved Cu in three acidic streams in Montana, USA. Primary assumptions underlying the proposed method are that alluvial ferricretes and modern Fe-precipitates share a common origin, that the Cu content of Fe-precipitates remains constant during and after conversion to ferricrete, and that geochemical factors other than pH and dissolved Cu concentration play a lesser role in determining Fe/Cu ratios in Fe-precipitates. The method was evaluated by applying it in a fourth, naturally acidic stream unaffected by mining, where estimated pre-mining pH and Cu concentrations were similar to present-day values, and by demonstrating that inflows, particularly from unmined areas, had consistent effects on both the pre-mining and measured profiles of pH and Cu concentration. Using this method, it was estimated that mining has affected about 480 m of Daisy Creek, 1.8 km of Fisher Creek, and at least 1 km of Swift Gulch. Mean values of pH decreased by about 0.6 pH units to about 3.2 in Daisy Creek and by 1-1.5 pH units to about 3.5 in Fisher Creek. In Swift Gulch, mining appears to have decreased pH from about 5.5 to as low as 3.6. Dissolved Cu concentrations increased due to mining almost 40% in Daisy Creek to a mean of 11.7 mg/L and as much as 230% in Fisher Creek to 0.690 mg/L. Uncertainty in the fate of Cu during the conversion of Fe-precipitates to ferricrete translates to potential errors in pre-mining estimates of as much as 0.25 units for pH and 22% for dissolved Cu concentration. The method warrants further testing in other mined and unmined watersheds. Comparison of pre-mining water-quality estimates derived from the ferricrete and other methods in single watersheds would be particularly valuable. The method has potential for use in monitoring remedial efforts at mine sites with ferricrete deposits. A reasonable remediation objective might be realized when the downstream pattern of Fe/Cu ratios in modern streambed Fe-precipitates corresponds to the pattern in pre-mining alluvial ferricrete deposits along a stream valley.

  13. Lab-scale fermentation tests of microchip with integrated electrochemical sensors for pH, temperature, dissolved oxygen and viable biomass concentration.

    PubMed

    Krommenhoek, Erik E; van Leeuwen, Michiel; Gardeniers, Han; van Gulik, Walter M; van den Berg, Albert; Li, Xiaonan; Ottens, Marcel; van der Wielen, Luuk A M; Heijnen, Joseph J

    2008-03-01

    This article shows the development and testing of a microchip with integrated electrochemical sensors for measurement of pH, temperature, dissolved oxygen and viable biomass concentration under yeast cultivation conditions. Measurements were done both under dynamic batch conditions as well as under prolonged continuous cultivation conditions. The response of the sensors compared well with conventional measurement techniques. The biomass sensor was based on impedance spectroscopy. The results of the biomass sensor matched very well with dry weight measurements and showed a limit of detection of approximately 1 g/L. The dissolved oxygen concentration was monitored amperometrically using an ultra-microelectrode array, which showed an accuracy of approximately 0.2 mg/L and negligible drift. pH was monitored using an ISFET with an accuracy well below 0.1 pH unit. The platinum thin-film temperature resistor followed temperature changes with approximately 0.1 degrees C accuracy. The dimensions of the multi sensor chip are chosen as such that it is compatible with the 96-well plate format. PMID:17929319

  14. The synergistic effects of dissolved oxygen and pH on N2O production in biological domestic wastewater treatment under nitrifying conditions.

    PubMed

    Li, Pengzhang; Wang, Shuying; Peng, Yongzhen; Liu, Yue; He, Janzhong

    2015-01-01

    Nitrous oxide (N2O) is a potent greenhouse gas, which is produced during nitrifying and denitrifying processes. Some factors and mechanisms affecting N2O emission have been reported in previous literature, but wastewater biological nitrification is accompanied by a dynamic process of dissolved oxygen (DO) consumption and pH reduction, it is more meaningful to study the synergistic effects between DO and pH on N2O production. In this study, the synergistic effects between DO and pH on N2O production were investigated with real domestic wastewater. The results showed that high DO levels and a high pH could improve the oxidation ratio of NH4+-N and the production ratio of NO2--N, while effectively reducing the accumulation ratio of N2O. The NH4+-N was a prerequisite for nitrifier denitrification; when NH4+-N was oxidized completely, there would be no N2O production and an even higher concentration of NO2- The pH factor is shown to directly affect N2O emission, although free ammonia and free nitrous acid which changed with pH had no correlation with N2O emission. There were two reasons: (1) pH can influence the flow direction of electrons afforded by NH2OH oxidation; at high pH, electrons were mainly used for combining H+ and O2 (O2+4H++4e-=2H2O), the accumulation of NO2- cannot be a result of denitrification, and a higher DO can get more electrons to prefer NO2- and (2) NH4+ was the prerequisite for NH2OH oxidation, since NH2OH oxidation process was the way to provide electrons for nitrifier denitrification. PMID:25619120

  15. Spatial models to predict ash pH and Electrical Conductivity distribution after a grassland fire in Lithuania

    NASA Astrophysics Data System (ADS)

    Pereira, Paulo; Cerda, Artemi; Misiūnė, Ieva

    2015-04-01

    Fire mineralizes the organic matter, increasing the pH level and the amount of dissolved ions (Pereira et al., 2014). The degree of mineralization depends among other factors on fire temperature, burned specie, moisture content, and contact time. The impact of wildland fires it is assessed using the fire severity, an index used in the absence of direct measures (e.g temperature), important to estimate the fire effects in the ecosystems. This impact is observed through the loss of soil organic matter, crown volume, twig diameter, ash colour, among others (Keeley et al., 2009). The effects of fire are highly variable, especially at short spatial scales (Pereira et al., in press), due the different fuel conditions (e.g. moisture, specie distribution, flammability, connectivity, arrangement, etc). This variability poses important challenges to identify the best spatial predictor and have the most accurate spatial visualization of the data. Considering this, the test of several interpolation methods it is assumed to be relevant to have the most reliable map. The aims of this work are I) study the ash pH and Electrical Conductivity (EC) after a grassland fire according to ash colour and II) test several interpolation methods in order to identify the best spatial predictor of pH and EC distribution. The study area is located near Vilnius at 54.42° N and 25.26°E and 154 ma.s.l. After the fire it was designed a plot with a 27 x 9 m space grid. Samples were taken every 3 meters for a total of 40 (Pereira et al., 2013). Ash color was classified according to Úbeda et al. (2009). Ash pH and EC laboratory analysis were carried out according to Pereira et al. (2014). Previous to data comparison and modelling, normality and homogeneity were assessed with the Shapiro-wilk and Levene test. pH data respected the normality and homogeneity, while EC only followed the Gaussian distribution and the homogeneity criteria after a logarithmic transformation. Data spatial correlation was calculated with the Global Moran's I Index. In order to identify the best interpolator, we tested several well known techniques as inverse distance to a power (IDP), with the power of 1, 2, 3, 4 and 5, local polynomial (LP) with the power of 1 (LP1), 2 (LP2) and 3 (LP3), spline with tension (SPT), completely regularized spline (CRS), multiquadratic (MTQ), inverse multiquadratic (IMTQ) thin plate spline (TPS) and ordinary kriging. The best interpolator was the one with the lowest Root mean square error (RMSE). The results shown that on average ash pH was 8.01 (±0.20) and EC (1408± 513.51µm cm3). The coefficient of correlation between both variables was 0.34, p<0.05. Black ash had a significantly higher pH (F=6.29, p<0.05) and EC (F=5.25, p<0.05) than dark grey ash. According to Moran's I index, pH data was significantly (p<0.05) dispersed, while EC had a random pattern. The best spatial predictor for pH was IDW1 (RMSE=0.210), and for EC IMTQ (RMSE=0.141). In both cases the least accurate technique was TPS. pH data did not showed a specific spatial pattern and some high values are very close to high values which shows a great local spatial variability, mainly observed in the northern part of the plot. In relation to EC, the high values were identified in the central part of the plot. In conclusion it was observed that ash pH and EC were different according to fire severity (ash color) and data distribution has a different spatial pattern, despite the significant correlation. pH and EC had different spatial impacts on soil properties in the immediate period after the fire. Acknowledgments POSTFIRE (Soil quality, erosion control and plant cover recovery under different post-fire management scenarios, CGL2013-47862-C2-1-R), funded by the Spanish Ministry of Economy and Competitiveness; Fuegored; RECARE (Preventing and Remediating Degradation of Soils in Europe Through Land Care, FP7-ENV-2013-TWO STAGE), funded by the European Commission; and for the COST action ES1306 (Connecting European connectivity research). References Keeley, J.E. (2009) Fire intensity, fire severity and burn severity: a brief review and suggested usage. International Journal of Wildland Fire. 18, 116-126. Pereira, P., Úbeda, X., Martin, D., Mataix-Solera, J., Cerdà, A., Burguet, M. (2014) Wildfire effects on extractable elements in ash from a Pinus pinaster forest in Portugal. Hydrological Processes, 28, 3681-3690. Pereira, P., Cerdà, A., Úbeda, X., Mataix-Solera, J. Arcenegui, V., Zavala, L. Modelling the impacts of wildfire on ash thickness in a short-term period. Land Degradation and Development, (In Press), DOI: 10.1002/ldr.2195 Pereira, P., Cerdà, A., Úbeda, X., Mataix-Solera, J., Jordan, A. Burguet, M. (2013) Spatial models for monitoring the spatio-temporal evolution of ashes after fire - a case study of a burnt grassland in Lithuania, Solid Earth, 4, 153-165. Úbeda, X., Pereira, P., Outeiro, L., Martin, D. (2009) Effects of fire temperature on the physical and chemical characteristics of the ash from two plots of cork oak (Quercus suber). Land Degradation and Development, 20(6), 589-608.

  16. Coupling effect of pH and dissolved oxygen in water column on nitrogen release at water-sediment interface of Erhai Lake, China

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Wang, Shengrui; Wu, Zhihao

    2014-08-01

    Nitrogen (N), in the form of ammonia or nitrate, is a key limiting nutrient in many aquatic systems. Under certain environmental conditions it can be released from sediments into overlying water, which may have significant impact on water quality and result in continuous eutrophication. However, few studies have examined the long-term (nearly two months) coupling effect of environmental parameters on N dynamics at the sediment-water interface. This is particularly pertinent to improve the understanding of lake eutrophication processes. This study examines the coupling effects of pH and dissolved oxygen (DO) on N release at the sediment-water interface for the shallow Erhai Lake in China, and analyzes recent changes in environmental conditions and water quality to predict the risk of nitrogen release from sediment in the near future. Experimental results indicated that under anaerobic condition (DO?1 mg/L) and lower pH (pH = 6), ammonium was easily released into overlying water, potentially triggering algal blooms. Conversely aerobic conditions (DO = 8-10 mg/L) and higher pH (pH = 10) promoted nitrate release from sediment. The study also discusses possible mechanisms about the nitrogen dynamics at the sediment-water interface. Considering the overall effects of ammonium and nitrate on the trophic status of the water column, the recommended environmental condition in overlying water should be pH of around 8 under aerobic conditions. Based on the study findings, the nitrogen balance at the water-sediment interface was evaluated for different environmental conditions. Analysis of environmental conditions and water quality during 1992-2010 shows that present environmental conditions are not conducive to the release of nutrients from sediment, thereby protecting the water quality from serious endogenous pollution. However, the risk of nitrogen release from sediment sources might increase if environmental conditions change.

  17. Variation in Hydraulic Conductivity with Decreasing pH in a Biologically-Clogged Porous Medium

    NASA Astrophysics Data System (ADS)

    Kirk, M. F.; Santillan, E.; McGrath, L. K.; Altman, S. J.

    2011-12-01

    Biological clogging can significantly lower the hydraulic conductivity of porous media, potentially helping to limit CO2 transport from geological carbon storage reservoirs. How clogging is affected by CO2 injection, however, is unclear. We used column experiments to examine how decreasing pH, a geochemical change associated with CO2 injection, will affect the hydraulic conductivity (K) of biologically clogged porous medium. Four biologically-active experiments and two control experiments were performed. Columns consisted of 1 mm2 capillary tubes filled with 105-150 μm diameter glass beads. Artificial groundwater medium containing 1 mM glucose was pumped through the columns at a rate of 0.015 mL/min (q = 21.6 m/day; Re = 0.045). Each column was inoculated with 10^8 CFU of Pseudomonas fluorescens tagged with a green fluorescent protein; cells introduced to control columns were heat sterilized. Biomass distribution and transport was monitored using scanning laser confocal microscopy and effluent plating. Growth was allowed to occur for 5 days in medium with pH 7 in the biologically active columns. During that time, K decreased to values ranging from 10 to 27% of the average control K and effluent cell levels increased to about 10^8 CFU/mL. Next, the pH of the inflowing medium was lowered to 4 in three experiments and 5.5 in one experiment. After pH 4 medium was introduced, K increased to values ranging from 21 to 64% of the average control K and culturable cell levels in the effluent fell by about 4 log units. Confocal images show that clogging persisted in the columns at pH 4 because most of the microbial biomass remained attached to bead surfaces. In the experiment where pH was lowered to 5.5, K changed little because biological clogging remained entirely intact. The concentration of culturable cells in the effluent was also invariant. These results suggest that biomass in porous medium will largely remain in place following exposure to acidic water in a CO2 storage reservoir, particularly where buffering is able to limit the extent of acidification. This material is based upon work supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  18. Carbon dioxide addition to microbial fuel cell cathodes maintains sustainable catholyte pH and improves anolyte pH, alkalinity, and conductivity.

    PubMed

    Fornero, Jeffrey J; Rosenbaum, Miriam; Cotta, Michael A; Angenent, Largus T

    2010-04-01

    Bioelectrochemical system (BES) pH imbalances develop due to anodic proton-generating oxidation reactions and cathodic hydroxide-ion-generating reduction reactions. Until now, workers added unsustainable buffers to reduce the pH difference between the anode and cathode because the pH imbalance contributes to BES potential losses and, therefore, power losses. Here, we report that adding carbon dioxide (CO(2)) gas to the cathode, which creates a CO(2)/bicarbonate buffered catholyte system, can diminish microbial fuel cell (MFC) pH imbalances in contrast to the CO(2)/carbonate buffered catholyte system by Torres, Lee, and Rittmann [Environ. Sci. Technol. 2008, 42, 8773]. We operated an air-cathode and liquid-cathode MFC side-by-side. For the air-cathode MFC, CO(2) addition resulted in a stable catholyte film pH of 6.61 +/- 0.12 and a 152% increase in steady-state power density. By adding CO(2) to the liquid-cathode system, we sustained a steady catholyte pH (pH = 5.94 +/- 0.02) and a low pH imbalance (DeltapH = 0.65 +/- 0.18) over a 2-week period without external salt buffer addition. By migrating bicarbonate ions from the cathode to the anode (with an anion-exchange membrane), we increased the anolyte pH (DeltapH = 0.39 +/- 0.31), total alkalinity (494 +/- 6 to 582 +/- 6 as mg CaCO(3)/L), and conductivity (1.53 +/- 0.49 to 2.16 +/- 0.03 mS/cm) relative to the feed properties. We also verified with a phosphate-buffered MFC that our reaction rates were limited mainly by the reactor configuration rather than limitations due to the bicarbonate buffer. PMID:20178380

  19. Effects of Dissolved Sulfide, pH, and Temperature on Growth and Survival of Marine Hyperthermophilic Archaea

    PubMed Central

    Lloyd, Karen G.; Edgcomb, Virginia P.; Molyneaux, Stephen J.; Böer, Simone; Wirsen, Carl O.; Atkins, Michael S.; Teske, Andreas

    2005-01-01

    The ability of metabolically diverse hyperthermophilic archaea to withstand high temperatures, low pHs, high sulfide concentrations, and the absence of carbon and energy sources was investigated. Close relatives of our study organisms, Methanocaldococcus jannaschii, Archaeoglobus profundus, Thermococcus fumicolans, and Pyrococcus sp. strain GB-D, are commonly found in hydrothermal vent chimney walls and hot sediments and possibly deeper in the subsurface, where highly dynamic hydrothermal flow patterns and steep chemical and temperature gradients provide an ever-changing mosaic of microhabitats. These organisms (with the possible exception of Pyrococcus strain GB-D) tolerated greater extremes of low pH, high sulfide concentration, and high temperature when actively growing and metabolizing than when starved of carbon sources and electron donors/acceptors. Therefore these organisms must be actively metabolizing in the hydrothermal vent chimneys, sediments, and subsurface in order to withstand at least 24 h of exposure to extremes of pH, sulfide, and temperature that occur in these environments. PMID:16204562

  20. Effects of pH, dissolved oxygen, and ionic strength on the survival of Escherichia coli O157:H7 in organic acid solutions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability of Escherichia coli O157:H7 to survive in acidified vegetable products is of concern because of previously documented outbreaks associated with fruit juices. A study was conducted to determine the survival of E. coli O157:H7 in organic acids at pH values typical of acidified vegetable pr...

  1. Profiles for pH, temperature, and dissolved O2 levels in enzyme production: monitoring in small-scale fermentors.

    PubMed

    Peterson, R E; Nelson, G E

    1975-12-01

    The profiles thus established may be utilized for investigations of an organism's relationship to its microenvironment including metabolic shifts and pathways. Areas of maximum respiratory activity, enzyme production, enzyme degradation, and attainment of the stationary phase are quite evident; however, duration and magnitude of the various phenomena may change with nutrient, temperature, and aeration efficiency. Practical application of this simplified method would include: a) determination of environmental conditions existing during maximum growth or enzyme synthesis and application of these conditions to feedback control; b) estimation of requirements for pH, oxygen, and heat removal capacities needed for scale-up; c) specific points during the fermentation at which samples should be analyzed to yield maximum information on depletion of nutrients and its effects on microbial activity. PMID:1123

  2. An automated procedure for the simultaneous determination of specific conductance and pH in natural water samples

    USGS Publications Warehouse

    Eradmann, D.E.; Taylor, H.E.

    1978-01-01

    An automated, continuous-flow system is utilized to determine specific conductance and pH simultaneously in natural waters. A direct electrometric procedure is used to determine values in the range pH 4-9. The specific conductance measurements are made with an electronically modified, commercially available conductivity meter interfaced to a separate module containing the readout control devices and printer. The system is designed to switch ranges automatically to accommodate optimum analysis of widely varying conductances ranging from a few ??mhos cm-1 to 15,000 ??mho cm-1. Thirty samples per hour can be analyzed. Comparison of manual and automated procedures for 40 samples showed that the average differences were 1.3% for specific conductance and 0.07 units for pH. The relative standard deviation for 25 replicate values for each of five samples was significantly less than 1% for the specific conductance determination; the standard deviation for the pH determination was ??? 0.06 pH units. ?? 1978.

  3. Dissolved organic carbon from the upper Rio Negro protects zebrafish (Danio rerio) against ionoregulatory disturbances caused by low pH exposure.

    PubMed

    Duarte, Rafael M; Smith, D Scott; Val, Adalberto L; Wood, Chris M

    2016-01-01

    The so-called "blackwaters" of the Amazonian Rio Negro are rich in highly coloured dissolved organic carbon (DOC), but ion-poor and very acidic, conditions that would cause fatal ionoregulatory failure in most fish. However these blackwaters support 8% of the world's ichthyofauna. We tested the hypothesis that native DOC provides protection against ionoregulatory dysfunction in this extreme environment. DOCs were isolated by reverse-osmosis from two Rio Negro sites. Physico-chemical characterization clearly indicated a terrigenous origin, with a high proportion of hydroxyl and phenolic sites, high chemical reactivity to protons, and unusual proteinaceous fluorescence. When tested using zebrafish (a model organism), Rio Negro DOC provided almost perfect protection against ionoregulatory disturbances associated with acute exposure to pH 4.0 in ion-poor water. DOC reduced diffusive losses of Na(+) and Cl(-), and promoted a remarkable stimulation of Na(+) uptake that otherwise would have been completely inhibited. Additionally, prior acclimation to DOC at neutral pH reduced rates of branchial Na(+) turnover, and provided similar protection against acid-induced ionoregulatory disturbances, even if the DOC was no longer present. These results reinforce the important roles that DOC molecules can play in the regulation of gill functions in freshwater fish, particularly in ion-poor, acidic blackwaters. PMID:26853589

  4. Substrate-immobilized electrospun TiO2 nanofibers for photocatalytic degradation of pharmaceuticals: The effects of pH and dissolved organic matter characteristics.

    PubMed

    Maeng, Sung Kyu; Cho, Kangwoo; Jeong, Boyoung; Lee, Jaesang; Lee, Yunho; Lee, Changha; Choi, Kyoung Jin; Hong, Seok Won

    2015-12-01

    A substrate-immobilized (SI) TiO2 nanofiber (NF) photocatalyst for multiple uses was prepared through electrospinning and hot pressing. The rate of furfuryl alcohol degradation under UV irradiation was found to be the highest when the anatase to rutile ratio was 70:30; the rate did not linearly increase as a function of the NF film thickness, mainly due to diffusion limitation. Even after eight repeated cycles, it showed only a marginal reduction in the photocatalytic activity for the degradation of cimetidine. The effects of pH and different organic matter characteristics on the photodegradation of cimetidine (CMT), propranolol (PRP), and carbamazepine (CBZ) were investigated. The pH-dependence of the photocatalytic degradation rates of PRP was explained by electrostatic interactions between the selected compounds and the surface of TiO2 NFs. The degradation rates of CMT showed the following order: deionized water > l-tyrosine > secondary wastewater effluent (effluent organic matter) > Suwannee River natural organic matter, demonstrating that the characteristics of the dissolved organic matter (DOM) can affect the photodegradation of CMT. Photodegradation of CBZ was affected by the presence of DOM, and no significant change was observed between different DOM characteristics. These findings suggest that the removal of CMT, PRP, and CBZ during photocatalytic oxidation using SI TiO2 NFs is affected by the presence of DOM and/or pH, which should be importantly considered for practical applications. PMID:26025601

  5. Dissolved organic carbon from the upper Rio Negro protects zebrafish (Danio rerio) against ionoregulatory disturbances caused by low pH exposure

    PubMed Central

    Duarte, Rafael M.; Smith, D. Scott; Val, Adalberto L.; Wood, Chris M.

    2016-01-01

    The so-called “blackwaters” of the Amazonian Rio Negro are rich in highly coloured dissolved organic carbon (DOC), but ion-poor and very acidic, conditions that would cause fatal ionoregulatory failure in most fish. However these blackwaters support 8% of the world’s ichthyofauna. We tested the hypothesis that native DOC provides protection against ionoregulatory dysfunction in this extreme environment. DOCs were isolated by reverse-osmosis from two Rio Negro sites. Physico-chemical characterization clearly indicated a terrigenous origin, with a high proportion of hydroxyl and phenolic sites, high chemical reactivity to protons, and unusual proteinaceous fluorescence. When tested using zebrafish (a model organism), Rio Negro DOC provided almost perfect protection against ionoregulatory disturbances associated with acute exposure to pH 4.0 in ion-poor water. DOC reduced diffusive losses of Na+ and Cl−, and promoted a remarkable stimulation of Na+ uptake that otherwise would have been completely inhibited. Additionally, prior acclimation to DOC at neutral pH reduced rates of branchial Na+ turnover, and provided similar protection against acid-induced ionoregulatory disturbances, even if the DOC was no longer present. These results reinforce the important roles that DOC molecules can play in the regulation of gill functions in freshwater fish, particularly in ion-poor, acidic blackwaters. PMID:26853589

  6. Influence of aeration-homogenization system in stirred tank bioreactors, dissolved oxygen concentration and pH control mode on BHK-21 cell growth and metabolism.

    PubMed

    Nez, Eutimio Gustavo Fernndez; Leme, Jaci; de Almeida Parizotto, Letcia; Chagas, Wagner Antonio; de Rezende, Alexandre Gonalves; da Costa, Bruno Labate Vale; Monteiro, Daniela Cristina Ventini; Boldorini, Vera Lucia Lopes; Jorge, Soraia Attie Calil; Astray, Renato Mancini; Pereira, Carlos Augusto; Caricati, Celso Pereira; Tonso, Aldo

    2014-08-01

    This work focused on determining the effect of dissolved oxygen concentration (DO) on growth and metabolism of BHK-21 cell line (host cell for recombinant proteins manufacturing and viral vaccines) cultured in two stirred tank bioreactors with different aeration-homogenization systems, as well as pH control mode. BHK-21 cell line adapted to single-cell suspension was cultured in Celligen without aeration cage (rotating gas-sparger) and Bioflo 110, at 10, 30 and 50% air saturation (impeller for gas dispersion from sparger-ring). The pH was controlled at 7.2 as far as it was possible with gas mixtures. In other runs, at 30 and 50% (DO) in Bioflo 110, the cells grew at pH controlled with CO2 and NaHCO3 solution. Glucose, lactate, glutamine, and ammonium were quantified by enzymatic methods. Cell concentration, size and specific oxygen consumption were also determined. When NaHCO3 solution was not used, the optimal DOs were 10 and 50% air saturation for Celligen and Bioflo 110, respectively. In this condition maximum cell concentrations were higher than 4נ10(6) cell/mL. An increase in maximum cell concentration of 36% was observed in batch carried out at 30% air saturation in a classical stirred tank bioreactor (Bioflo 110) with base solution addition. The optimal parameters defined in this work allow for bioprocess developing of viral vaccines, transient protein expression and viral vector for gene therapy based on BHK-21 cell line in two stirred tank bioreactors with different agitation-aeration systems. PMID:23846480

  7. [Effect of pH on the Ultraviolet Spectra and Fluorescence Characteristics of Dissolved Organic Matter in the Process of Straw Humification].

    PubMed

    Fan, Chun-hui; Zhang, Ying-chao; Wang, Jia-hong

    2015-07-01

    Crop straw is the dominant by-product from agriculture and is regarded as the new source of non-point contamination. Straw incorporation is possible to solve the issues of straw reduction and reutilization, which is clearly required in the twelfth five-year-plan for national economic and social development of the People's Republic of China. At present, it is of noticeable lack of the investigation on straw incorporation behavior and detail humification product analysis in the representative regions under different environmental conditions. The ultraviolet and fluorescence spectrometry were used to reveal the characteristics of dissolved organic matter (DOM), affected by pH values, in the straw humification process in loess region. The results showed: the ultraviolet absorbance of DOM samples increased firstly and then decreased with the increasing wavelength from 200 to 700 nm, and the maximum absorbance peaks appeared around the wavelength of 240 nm. The maximum absorbance peaks (λmax) were greater at pH values of 6, 8 and 9 than that of 7, and the low degree of humification was indicated from the values of SUVA254, E3/E4 and A253/A203, caused by the short period of humification. The fluorescence peaks of extracted DOM from loess appeared around the regions of λ(dx/em) = 250/330 and λ(ex/em) = 325/450, referred as UV fulvic-like fluorescence, and visible fulvic-like and humic-like fluorescence, respectively. The increasing pH values resulted in the greater wavelength of absorbance peak, suggesting the increased aromaticity and conjugated degree, and the novel fluorescence peak was found in λ(ex/em) = 250/450. The pH values were more effective to change the UV fulvic-like fluorescence peaks intensity (increased firstly and then decreased) than that of visible fulvic-like and humic-like fluorescence, which might be related to buffer effect, fluorescence quenching (side effects) and component structure. The ultraviolet and fluorescence spectrometry were acceptable to illustrate the characteristics variation of DOM affected by pH values in the straw humification process. PMID:26717755

  8. Differences in conductance of M2 proton channels of two influenza viruses at low and high pH

    PubMed Central

    Chizhmakov, I V; Ogden, D C; Geraghty, F M; Hayhurst, A; Skinner, A; Betakova, T; Hay, A J

    2003-01-01

    The M2 protein of influenza A viruses forms a proton channel involved in modifying virion and trans Golgi pH during infection. Previous studies of the proton current using whole-cell patch clamp of mouse erythroleukaemia (MEL) cells expressing the M2 protein of the Weybridge strain provided evidence for two protonation sites, one involved in permeation, the other in activation by acid pH. The present report compares the M2 channels of two different strains of influenza virus, Weybridge (WM2) and Rostock (RM2). Whereas with external acid pH the current-voltage relations showed similar small degrees of inward rectification, a similar apparent Kd of approximately 10 ?m for proton permeation and a high selectivity for protons over Na+, the two M2 proteins differed in whole-cell conductance at low and high pH. The proton conductance of unit membrane area was on average 7-fold greater in RM2- than WM2-expressing MEL cells. At high external pH WM2 was shown previously to have small conductance for outward current at positive driving potential. In contrast, RM2 shows high conductance for outward current with high external pH, but shows small conductance for inward current with high internal pH, conditions in which WM2 shows high conductance for inward current. The different properties of the conductances due to the two channels at high pH were determined by three amino acids in their transmembrane domains. All intermediate mutants possessed one or other property and transformation of the WM2 phenotype into that of RM2 required substitution in all three residues V27I, F38L and D44N; single substitutions in RM2 effected the opposite phenotypic change. The significance of this difference for virus replication is not clear and it may be that the higher proton flux associated with RM2 is the main factor determining its increased ability to dissipate pH gradients. It is apparent, however, from the specific differences in the sidedness of the pH-induced changes in voltage dependence of the whole-cell current that this is an intrinsic property of the virus proton channel which may have parallels with regulation of other proton channels. PMID:12527729

  9. Nanoceria facilitates the synthesis of poly(o-phenylene diamine) with pH tunable morphology conductivity and photoluminiscent properties

    PubMed Central

    Asati, Atul; Lehmkuhl, David; Diaz, Diego; Perez, J. Manuel

    2012-01-01

    Poly(ortho-phenylene diamine) synthesis enabled by the catalytic oxidase-like activity of nanoceria was accomplished for applications in electronics, medicine and biotechnology. The polymer shows unique morphology, conductivity and photoluminescence based on pH of the solution during synthesis. The various poly(ortho-phenylene diamine) preparations were characterized by UV-visible spectroscopy, scanning electron microscopy, fluorescence spectroscopy, fluorescence microscopy, high pressure liquid chromatography and cyclic voltammetry. Poly(ortho-phenylene diamine) synthesized at pH 1.0 by nanoceria was selected to be extensively studied based on the fast synthetic kinetics and the resulting conductive and photoluminiscent properties for various applications. PMID:22920917

  10. Selective recovery of dissolved Fe, Al, Cu, and Zn in acid mine drainage based on modeling to predict precipitation pH.

    PubMed

    Park, Sang-Min; Yoo, Jong-Chan; Ji, Sang-Woo; Yang, Jung-Seok; Baek, Kitae

    2015-02-01

    Mining activities have caused serious environmental problems including acid mine drainage (AMD), the dispersion of mine tailings and dust, and extensive mine waste. In particular, AMD contaminates soil and water downstream of mines and generally contains mainly valuable metals such as Cu, Zn, and Ni as well as Fe and Al. In this study, we investigated the selective recovery of Fe, Al, Cu, Zn, and Ni from AMD. First, the speciation of Fe, Al, Cu, Zn, and Ni as a function of the equilibrium solution pH was simulated by Visual MINTEQ. Based on the simulation results, the predicted pHs for the selective precipitation of Fe, Al, Cu, and Zn/Ni were determined. And recovery yield of metals using simulation is over 99 %. Experiments using artificial AMD based on the simulation results confirmed the selective recovery of Fe, Al, Cu, and Zn/Ni, and the recovery yields of Fe/Al/Cu/Zn and Fe/Al/Cu/Ni mixtures using Na2CO3 were 99.6/86.8/71.9/77.0 % and 99.2/85.7/73.3/86.1 %, respectively. After then, the simulation results were applied to an actual AMD for the selective recovery of metals, and the recovery yields of Fe, Al, Cu, and Zn using NaOH were 97.2, 74.9, 66.9, and 89.7 %, respectively. Based on the results, it was concluded that selective recovery of dissolved metals from AMD is possible by adjusting the solution pH using NaOH or Na2CO3 as neutralizing agents. PMID:25231736

  11. METHODS FOR CONDUCTING SNAIL (APLEXA HYPNORUM) EMBRYO THROUGH ADULT EXPOSURES: EFFECTS OF CADMIUM AND REDUCED PH LEVELS

    EPA Science Inventory

    Two separate embryo through adult exposures were conducted with cadmium and with reduced pH levels to validate various test methodologies and to determine the feasibility of testing and ease of handling the freshwater snail (Aplexa hypnorum) in a test system designed for fish bio...

  12. An on-line optimisation of a SBR cycle for carbon and nitrogen removal based on on-line pH and Our: the role of dissolved oxygen control.

    PubMed

    Puig, S; Corominas, Ll; Traore, A; Colomer, J; Balaguer, M D; Colprim, J

    2006-01-01

    A pilot plant sequencing batch reactor (SBR) was applied in a wastewater treatment plant treating urban wastewater focused on carbon and nitrogen removal. From an initial predefined step-feed cycle definition, the evolution of the on-line monitored pH and calculated oxygen uptake rate (OUR) were analysed in terms of knowledge extraction. First, the aerobic phases of the SBR cycle were operated using an On/Off dissolved oxygen (DO) control strategy that concluded with a sinusoidal pH profile that made detecting the "ammonia valley" difficult. After changing to fuzzy logic control of the dissolved oxygen and by adding an air flow meter to the pilot plant, the pH evolution and on-line calculated OUR showed a clearer trend during the aerobic phases. Finally, a proposed algorithm for adjusting the aerobic phases of the SBR for carbon and ammonia removal is presented and discussed. PMID:16722067

  13. Systems Characterization of Temperature, Ph and Electrical Conductivity in Aerobic Biodegradation of Wheat Biomass at Differing Mixing Rates

    NASA Technical Reports Server (NTRS)

    Calhoun, M.; Trotman, A.; Aglan, H.

    1998-01-01

    The purpose of this preliminary study is to observe and relate the rate of mixing to pH and electrical conductivity in an aerobic, continuously stirred bioreactor. The objective is to use data collected from successive experiments as a means of a system characterization. Tests were conducted to obtain these data using a continuously stirred 20 L Cytostir glass reaction vessel as a bioreactor operated without built-in temperature or pH control. The tests were conducted on the lab bench at ambient temperatures. The substrate in the bioreactor was ground wheat biomass obtained from the Biomass Production Chamber at NASA Kennedy Space Center. In this study, the data reflect characteristics of the native (uninoculated) systems as well as inoculated systems. In the native systems, it was found that pi levels became stable after approximately 2 to 3 days. The electrical conductivity levels for the native systems tended to decrease over time. In contrast, ion activity was increased after the introduction of bacteria into the system. This could be correlated with the release of nutrients, due to the activity of the bacteria. Also, there were slight increases in pH in the inoculated system, a result which is expected for a system with no active pr controls. The data will be used to test a mathematical model in an automated system.

  14. Effect of pH, ionic strength, dissolved organic carbon, time, and particle size on metals release from mine drainage impacted streambed sediments.

    PubMed

    Butler, Barbara A

    2009-03-01

    Acid-mine drainage (AMD) input to a stream typically results in the stream having a reduced pH, increased concentrations of metals and salts, and decreased biological productivity. Removal and/or treatment of these AMD sources is desired to return the impacted stream(s) to initial conditions, or at least to conditions suitable for restoration of the aquatic ecosystem. Some expected changes in the water chemistry of the stream following removal of AMD input include an increase in pH, a decrease in ionic strength, and an increase in dissolved organic carbon (DOC) concentrations from increased biological activity in the absence of toxic metals concentrations. These changes in water chemistry may cause the existing contaminated bed sediments to become a source of metals to the stream water. Streambed sediments, collected from North Fork Clear Creek (NFCC), Colorado, currently impacted by AMD, were assessed for the effects of pH, ionic strength, DOC concentration, time, and particle size on metals release using a factorial design. The design included two levels for each chemical parameter (ionic strength = 40 and 80% lower than ambient; pH = 6 and 8; and DOC = 1 and 3 mg/l higher than ambient), ten sampling times (from zero to 48 h), and two size fractions of sediments (63 microm < or = x < 2 mm and < 63 microm). Greater concentrations of metals were released from the smaller sized sediments compared with the larger, with the exception of Cu. A mild acid digestion (0.6M HCl) evaluated the amount of each metal that could be removed easily from each of the sediment size fractions. Release of all metals over all time points, treatments, and from both sediment sizes was less than 1% of the extractable concentrations, with the exception of Mn, which ranged from 4 to 7% from the smaller sized sediment. Greater percentages of the 0.6M HCl-extractable concentrations of Cu, Fe, and Zn were released from the larger sized sediment, while this was true for release of Cd and Mn from the smaller sized sediment. Thus, at least for Cd and Mn, the observed higher concentrations released from the smaller sized sediment with each treatment solution is not simply a function of these particles having higher concentrations available for release, but that these metals also are more readily released from the smaller sediment particles versus the larger. DOC concentration strongly influenced the release of Cu; ionic strength strongly influenced the release of Cd, Mn, and Zn; and interaction effects were observed with the release of Cu, Mn, and Zn from the larger size fraction and with the release of Zn from the smaller size fraction. Overall, results suggest that the expected changes in water chemistry following removal/treatment of the AMD sources would result in a release of metals from the existing sediments, with a greater effect on the release of Cu and Fe, than on the release of Cd, Mn, and Zn. PMID:19110291

  15. Sorption-desorption and transport of trimethoprim and sulfonamide antibiotics in agricultural soil: effect of soil type, dissolved organic matter, and pH.

    PubMed

    Zhang, Ya-Lei; Lin, Shuang-Shuang; Dai, Chao-Meng; Shi, Lu; Zhou, Xue-Fei

    2014-05-01

    Use of animal manure is a main source of veterinary pharmaceuticals (VPs) in soil and groundwater through a series of migration processes. The sorption-desorption and transport of four commonly used VPs including trimethoprim (TMP), sulfapyridine, sulfameter, and sulfadimethoxine were investigated in three soil layers taken from an agricultural field in Chongming Island China and two types of aqueous solution (0.01 M CaCl2 solution and wastewater treatment plant effluent). Results from sorption-desorption experiments showed that the sorption behavior of selected VPs conformed to the Freundlich isotherm equation. TMP exhibited higher distribution coefficients (K d = 6.73-9.21) than other sulfonamides (K d = 0.03-0.47), indicating a much stronger adsorption capacity of TMP. The percentage of desorption for TMP in a range of 8-12 % is not so high to be considered significant. Low pH (dissolved organic matter might affect their sorption behavior. Column studies indicated that the transport of VPs in the soil column was mainly influenced by sorption capacity. The weakly adsorbed sulfonamides had a high recovery rate (63.6-98.0 %) in the leachate, while the recovery rate of TMP was only 4.2-10.4 %. The sulfonamides and TMP exhibited stronger retaining capacity in 20-80 cm and 0-20 cm soil samples, respectively. The transport of VPs was slightly higher in the columns leached by WWTP effluent than by CaCl2 solution (0.01 M) due to their sorption interactions. PMID:24443047

  16. Variation in hydraulic conductivity with decreasing pH in a biologically-clogged porous medium (Invited)

    NASA Astrophysics Data System (ADS)

    Altman, S. J.; Kirk, M. F.; Santillan, E. U.; McGrath, L. K.

    2013-12-01

    Microbial biomass can clog porous media and ultimately affect both structural and mineral trapping of CO2 in geological carbon storage reservoirs. Whether biomass can remain intact following a sudden decrease in groundwater pH, a geochemical change associated with CO2 injection, is unclear. We examined this question using twelve biologically-active and three control column-reactor experiments. Cell abundance and distribution was monitored using confocal microscopy, plating, and direct counting. Hydraulic conductivity (K) was monitored using pressure sensors. Growth occurred for four days at neutral pH. During that time, K within the clogged portion of the reactors decreased from 0.013 to 0.0006 cm s-1 on average, a 1.47 log reduction. Next, the pH of the inflowing aqueous medium was lowered to pH 4 in six experiments and pH 5.7 in six experiments. As a result, K increased in five of the pH 4 experiments and two of the pH 5.7 experiments. Despite this increase, however, the columns remained largely clogged. Compared to pre-inoculation K values, log reductions averaged 1.13 and 1.44 in pH 4 and pH 5.7 experiments, respectively. Our findings show that biomass can largely remain intact following acidification and continue to reduce K, even when considerable cell stress and death occurs. This material is based upon work supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  17. Carbon Dioxide Addition to Microbial Fuel Cell Cathodes Maintains Sustainable Catholyte pH and Improves Anolyte pH, Alkalinity, and Conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bioelectrochemical system (BES) pH imbalances develop due to anodic proton-generating oxidation reactions and cathodic hydroxide-ion-generating reduction reactions. Until now, workers added unsustainable buffers to reduce the pH difference between the anode and cathode because the pH imbalance cont...

  18. Summary statistics and graphical comparisons of specific conductance, temperature, and dissolved oxygen data, Buffalo Bayou, Houston, Texas, April 1986-March 1991

    USGS Publications Warehouse

    Brown, D.W.; Paul, E.M.

    1995-01-01

    Buffalo Bayou is the major stream that drains the Houston, Texas, metropolitan area. The U.S. Geological Survey has provided specific conductance, temperature, and dissolved oxygen data to the City of Houston for three sites along a 7.7-mile reach of Buffalo Bayou since 1986. Summary statistics and graphical comparisons of the data show substantial variability in the properties during 1986-91. Specific conductance ranged from about 100 microsiemens per centimeter at 25 degrees Celsius at each of the three sites to 17,100 microsiemens per centimeter at 25 degrees Celsius at the most downstream site, at the headwaters of the Houston Ship Channel. Water temperatures ranged from 5 to 33 degrees Celsius. Temperatures were very similar at the two upstream sites and slightly warmer at the most downstream site. Dissolved oxygen ranged from zero at the most downstream site to 11.7 milligrams per liter at the most upstream site.

  19. Rapid solidification of high-conductivity copper alloys. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Bloom, Theodore Atlas

    1989-01-01

    The main objective was to develop improved copper alloys of high strength and high thermal and electric conductivity. Chill block melt spinning was used to produce binary alloys of Cu-Cr and Cu-Zr, and ternary alloys of Cu-Cr-Ag. By quenching from the liquid state, up to 5 atomic percent of Cr and Zr were retained in metastable extended solid solution during the rapid solidification process. Eutectic solidification was avoided and the full strengthening benefits of the large volume fraction of precipitates were realized by subsequent aging treatment. The very low solid solubility of Cr and Zr in Cu result in a high conductivity Cu matrix strengthened by second phase precipitates. Tensile properties on as-cast and aged ribbons were measured at room and elevated temperatures. Precipitate coarsening of Cr in Cu was studied by changes in electrical resistance during aging. X-ray diffraction was used to measure the lattice parameter and the degree of supersaturation of the matrix. The microstructures were characterized by optical and electron microscopy.

  20. New Secondary Batteries Utilizing Electronically Conductive Polypyrrole Cathode. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Yeu, Taewhan

    1991-01-01

    To gain a better understanding of the dynamic behavior in electronically conducting polypyrroles and to provide guidance toward designs of new secondary batteries based on these polymers, two mathematical models are developed; one for the potentiostatically controlled switching behavior of polypyrrole film, and one for the galvanostatically controlled charge/discharge behavior of lithium/polypyrrole secondary battery cell. The first model is used to predict the profiles of electrolyte concentrations, charge states, and electrochemical potentials within the thin polypyrrole film during switching process as functions of applied potential and position. Thus, the detailed mechanisms of charge transport and electrochemical reaction can be understood. Sensitivity analysis is performed for independent parameters, describing the physical and electrochemical characteristic of polypyrrole film, to verify their influences on the model performance. The values of independent parameters are estimated by comparing model predictions with experimental data obtained from identical conditions. The second model is used to predict the profiles of electrolyte concentrations, charge state, and electrochemical potentials within the battery system during charge and discharge processes as functions of time and position. Energy and power densities are estimated from model predictions and compared with existing battery systems. The independent design criteria on the charge and discharge performance of the cell are provided by studying the effects of design parameters.

  1. Fluctuation of dissolved heavy metal concentrations in the leachate from anaerobic digestion of municipal solid waste in commercial scale landfill bioreactors: The effect of pH and associated mechanisms.

    PubMed

    Xie, S; Ma, Y; Strong, P J; Clarke, W P

    2015-12-15

    Heavy metals present in landfill leachate have infrequently been related to complete anaerobic degradation municipal solid waste (MSW) due to discrete ages of deposited MSW layers and leachate channelling in landfills. In this study, anaerobic digestion of MSW was performed in two enclosed 1000 tonne bioreactors using a unique flood and drain process. Leachates were characterised in terms of pH, soluble chemical oxygen demand, volatile fatty acids (VFAs), ammonium nitrogen and heavy metals over the entire course of digestion. All parameters, including pH, fluctuated during acidogenesis, acetogenesis and methanogenesis, which strongly impacted on the dynamics of dissolved heavy metal concentrations. The simulation of dissolution and precipitation processes indicated that metal sulphide precipitation was not a factor as metal concentrations exceeded solubility limits. The correlation of pH and dissolved heavy metal concentrations indicated that other, mechanisms were involved in the homogenised conditions within the bioreactors. Beside dissolution and precipitation, the main processes most likely involved in metal distributions were adsorption (Zn, Cu, Ni, Pb and Cd), complexation (Cr) or combinations of both process (As and Co). PMID:26259097

  2. An evaluation of in-situ measurements of water temperature, specific conductance, and pH in low ionic strength streams

    USGS Publications Warehouse

    Ranalli, A.J.

    1998-01-01

    Survey for continuous measurement of water temperature, specific conductance, and pH in four low ionic strength streams in the Catskill Mountains of New York was evaluated through a calculation of their bias, precision, and accuracy and by comparison with laboratory measurements of specific conductance and pH on samples collected concurrently. Results indicate that the mini-monitor measurements of specific conductance and pH in an acidic stream (acid-neutralizing capacity always less than 0) agreed with laboratory measurements well enough that the minimonitors can be used to supplement laboratory measurements (mean difference in pH was 0.02 pH unit and mean difference in specific conductance was 0.72 ??S cm-1. This mean difference was 0.32 ??S cm-1 if the minimonitor data were adjusted by the bias). In less acidic streams (two streams in which the acid-neutralizing capacity was always greater than 0 and one in which the acid-neutralizing capacity was greater than 0 except during high flows), there was poor agreement between laboratory and minimonitor measurements of specific conductance at high flows and pH at all flows. The water-temperature probes measured with sufficiently small bias (-0.1 ??C) and adequate precision (??0.70 ??C) for use with most applications.

  3. EFFECT OF pH, IONIC STRENGTH, DISSOLVED ORGANIC CARBON, TIME, AND PARTICLE SIZE ON METALS RELEASE FROM MINE DRAINAGE IMPACTED STREAMBED SEDIMENTS

    EPA Science Inventory

    Acid-mine drainage (AMD) input to a stream typically results in the stream having a reduced pH, increased concentrations of metals and salts, and decreased biological productivity. Removal and/or treatment of these AMD sources is desired to return the impacted stream(s) to initi...

  4. A mathematical model of pH, based on the total stoichiometric concentration of acids, bases and ampholytes dissolved in water.

    PubMed

    Mioni, Roberto; Mioni, Giuseppe

    2015-10-01

    In chemistry and in acid-base physiology, the Henderson-Hasselbalch equation plays a pivotal role in studying the behaviour of the buffer solutions. However, it seems that the general function to calculate the valence of acids, bases and ampholytes, N = f(pH), at any pH, has only been provided by Kildeberg. This equation can be applied to strong acids and bases, pluriprotic weak acids, bases and ampholytes, with an arbitrary number of acid strength constants, pKA, including water. By differentiating this function with respect to pH, we obtain the general equation for the buffer value. In addition, by integrating the titration curve, TA, proposed by Kildeberg, and calculating its Legendre transform, we obtain the Gibbs free energy of pH (or pOH)-dependent titratable acid. Starting from the law of electroneutrality and applying suitable simplifications, it is possible to calculate the pH of the buffer solutions by numerical methods, available in software packages such as Excel. The concept of buffer capacity has also been clarified by Urbansky, but, at variance with our approach, not in an organic manner. In fact, for each set of monobasic, dibasic, tribasic acids, etc., various equations are presented which independently fit each individual acid-base category. Consequently, with the increase in acid groups (pKA), the equations become more and more difficult, both in practice and in theory. Some examples are proposed to highlight the boundary that exists between acid-base physiology and the thermodynamic concepts of energy, chemical potential, amount of substance and acid resistance. PMID:26059505

  5. Soil pH effects on the interactions between dissolved zinc, non-nano- and nano-ZnO with soil bacterial communities.

    PubMed

    Read, Daniel S; Matzke, Marianne; Gweon, Hyun S; Newbold, Lindsay K; Heggelund, Laura; Ortiz, Maria Diez; Lahive, Elma; Spurgeon, David; Svendsen, Claus

    2016-03-01

    Zinc oxide nanoparticles (ZnO NPs) are used in an array of products and processes, ranging from personal care products to antifouling paints, textiles, food additives, antibacterial agents and environmental remediation processes. Soils are an environment likely to be exposed to manmade nanoparticles due to the practice of applying sewage sludge as a fertiliser or as an organic soil improver. However, understanding on the interactions between soil properties, nanoparticles and the organisms that live within soil is lacking, especially with regards to soil bacterial communities. We studied the effects of nanoparticulate, non-nanoparticulate and ionic zinc (in the form of zinc chloride) on the composition of bacterial communities in soil with a modified pH range (from pH 4.5 to pH 7.2). We observed strong pH-dependent effects on the interaction between bacterial communities and all forms of zinc, with the largest changes in bacterial community composition occurring in soils with low and medium pH levels (pH 4.8 and 5.9). The high pH soil (pH 7.2) was less susceptible to the effects of zinc exposure. At the highest doses of zinc (2500 mg/kg dw soil), both nano and non-nano particulate zinc applications elicited a similar response in the soil bacterial community, and this differed significantly to the ionic zinc salt treatment. The results highlight the importance of considering soil pH in nanotoxicology studies, although further work is needed to determine the exact mechanisms controlling the toxicity and fate and interactions of nanoparticles with soil microbial communities. PMID:25903189

  6. Design and start-up of a high rate anaerobic membrane bioreactor for the treatment of a low pH, high strength, dissolved organic waste water.

    PubMed

    Van Zyl, P J; Wentzel, M C; Ekama, G A; Riedel, K J

    2008-01-01

    A Submerged Membrane Anaerobic Reactor (SMAR) is being developed for the treatment of waste water originating in Sasol's coal to fuel synthesis process. The laboratory-scale SMAR uses A4-size submerged flat panel ultrafiltration membranes to induce a 100% solids-liquid separation. Biogas gets extracted from the headspace above the anaerobic mixed liquor and reintroduced through a coarse bubble diffuser below the membranes. This induces a gas scour on the membranes that avoids biomass immobilization and membrane fouling. The substrate is a high strength (18 gCOD/l) petrochemical effluent consisting mostly of C2 to C6 short chain fatty acids with a low pH. Because of this, the pH of the reactor has to be controlled to a pH of 7.1. Organic Loading Rates of up to 25 kgCOD/m3 reactor volume/d has been observed with effluent COD normally <500 mgCOD/l and FSA <50 mgN/l with no particulates >0.45 microm at hydraulic retention times of 17 hours. 98% of the COD is converted to methane and the remainder to biomass. Mixed Liquor (MLSS) concentrations >30 gTSS/l can be maintained without deterioration of membrane fluxes, even though the Diluted Sludge Volume Index (DSVI) indicates that the sludge cannot be settled. No noteworthy deterioration in membrane performance has been observed over the 320 day operational period. PMID:18235185

  7. A monitor for continuous measurement of temperature, pH, and conductance of wet precipitation: Preliminary results from the Adirondack Mountains, New York

    USGS Publications Warehouse

    Johnsson, P.A.; Reddy, M.M.

    1990-01-01

    This report describes a continuous wet-only precipitation monitor designed by the U.S. Geological Survey to record variations in rainfall temperature, pH, and specific conductance at 1-min intervals over the course of storms. Initial sampling in the Adirondack Mountains showed that rainfall acidity varied over the course of summer storms, with low initial pH values increasing as storm intensity increased.This report describes a continuous wet-only precipitation monitor designed by the U.S. Geological Survey to record variations in rainfall temperature, pH, and specific conductance at 1-min intervals over the course of storms. Initial sampling in the Adirondack Mountains showed that rainfall acidity varied over the course of summer storms, with low initial pH values increasing as storm intensity increased.

  8. Influence of pH, inorganic anions, and dissolved organic matter on the photolysis of antimicrobial triclocarban in aqueous systems under simulated sunlight irradiation.

    PubMed

    Ding, Shi-Ling; Wang, Xi-Kui; Jiang, Wen-Qiang; Zhao, Ru-Song; Shen, Ting-Ting; Wang, Chen; Wang, Xia

    2015-04-01

    The photolysis of the antimicrobial triclocarban (TCC) in aqueous systems under simulated sunlight irradiation was studied. The effects of several abiotic parameters, including solution pH, initial TCC concentration, presence of natural organic matter, and most common inorganic anions in surface waters, were investigated. The results show that the photolysis of TCC followed pseudo-first-order kinetics. The TCC photolysis rate constant increased with increasing solution pH and decreasing the initial TCC concentration. Compared with the TCC photolysis in pure water, the presence of aqueous bicarbonate, nitrate, humic acids, and its sodium salt decreased the TCC photolysis rate, but fulvic acid increased the TCC photolysis rate. The electron spin resonance and reactive oxygen species scavenging experiments indicated that TCC may undergo two different types of phototransformation reactions: direct photolysis and energy transfer to generate (1)O2. The main degradation products were tentatively identified by gas chromatography interfaced with mass spectrometry (GC-MS), and a possible degradation pathway was also proposed. PMID:25354431

  9. Linkage of iron elution and dissolved oxygen consumption with removal of organic pollutants by nanoscale zero-valent iron: Effects of pH on iron dissolution and formation of iron oxide/hydroxide layer.

    PubMed

    Fujioka, Nanae; Suzuki, Moe; Kurosu, Shunji; Kawase, Yoshinori

    2016-02-01

    The iron elution and dissolved oxygen (DO) consumption in organic pollutant removal by nanoscale zero-valent iron (nZVI) was examined in the range of solution pH from 3.0 to 9.0. Their behaviors were linked with the removal of organic pollutant through the dissolution of iron and the formation of iron oxide/hydroxide layer affected strongly by solution pH and DO. As an example of organic pollutants, azo-dye Orange II was chosen in this study. The chemical composition analyses before and after reaction confirmed the corrosion of nZVI into ions, the formation of iron oxide/hydroxide layer on nZVI surface and the adsorption of the pollutant and its intermediates. The complete decolorization of Orange II with nZVI was accomplished very quickly. On the other hand, the total organic carbon (TOC) removal was considerably slow and the maximum TOC removal was around 40% obtained at pH 9.0. The reductive cleavage of azo-bond by emitted electrons more readily took place as compared with the cleavage of aromatic rings of Orange II leading to the degradation to smaller molecules and subsequently the mineralization. A reaction kinetic model based on the Langmuir-Hinshelwood/Eley-Rideal approach was developed to elucidate mechanisms for organic pollutant removal controlled by the formation of iron oxide/hydroxide layer, the progress of which could be characterized by considering the dynamic concentration changes in Fe(2+) and DO. The dynamic profiles of Orange II removal linked with Fe(2+) and DO could be reasonably simulated in the range of pH from 3.0 to 9.0. PMID:26519806

  10. Electrolytic dissolver

    DOEpatents

    Wheelwright, E.J.; Fox, R.D.

    1975-08-26

    This patent related to an electrolytic dissolver wherein dissolution occurs by solution contact including a vessel of electrically insulative material, a fixed first electrode, a movable second electrode, means for insulating the electrodes from the material to be dissolved while permitting a free flow of electrolyte therebetween, means for passing a direct current between the electrodes and means for circulating electrolyte through the dissolver. (auth)

  11. K[subscript a] and K[subscript b] from pH and Conductivity Measurements: A General Chemistry Laboratory Exercise

    ERIC Educational Resources Information Center

    Nyasulu, Frazier; Moehring, Michael; Arthasery, Phyllis; Barlag, Rebecca

    2011-01-01

    The acid ionization constant, K[subscript a], of acetic acid and the base ionization constant, K[subscript b], of ammonia are determined easily and rapidly using a datalogger, a pH sensor, and a conductivity sensor. To decrease sample preparation time and to minimize waste, sequential aliquots of a concentrated standard are added to a known volume…

  12. DEVELOPMENT AND EVALUATION OF AN ACID PRECIPITATION MONITOR FOR FRACTIONAL EVENT SAMPLING WITH CAPABILITY FOR REAL-TIME PH AND CONDUCTIVITY MEASUREMENT

    EPA Science Inventory

    An acid precipitation monitor has been developed that collects fractions of rain events, measures the pH and conductivity in real-time, and stores the remaining samples under refrigerated conditions. -80 microprocessor controls all operations of the monitor including sample colle...

  13. K[subscript a] and K[subscript b] from pH and Conductivity Measurements: A General Chemistry Laboratory Exercise

    ERIC Educational Resources Information Center

    Nyasulu, Frazier; Moehring, Michael; Arthasery, Phyllis; Barlag, Rebecca

    2011-01-01

    The acid ionization constant, K[subscript a], of acetic acid and the base ionization constant, K[subscript b], of ammonia are determined easily and rapidly using a datalogger, a pH sensor, and a conductivity sensor. To decrease sample preparation time and to minimize waste, sequential aliquots of a concentrated standard are added to a known volume

  14. Revisiting the Role of Cystic Fibrosis Transmembrane Conductance Regulator and Counterion Permeability in the pH Regulation of Endocytic Organelles

    PubMed Central

    Barriere, Herve; Bagdany, Miklos; Bossard, Florian; Okiyoneda, Tsukasa; Wojewodka, Gabriella; Gruenert, Dieter; Radzioch, Danuta

    2009-01-01

    Organellar acidification by the electrogenic vacuolar proton-ATPase is coupled to anion uptake and cation efflux to preserve electroneutrality. The defective organellar pH regulation, caused by impaired counterion conductance of the mutant cystic fibrosis transmembrane conductance regulator (CFTR), remains highly controversial in epithelia and macrophages. Restricting the pH-sensitive probe to CFTR-containing vesicles, the counterion and proton permeability, and the luminal pH of endosomes were measured in various cells, including genetically matched CF and non-CF human respiratory epithelia, as well as cftr+/+ and cftr−/− mouse alveolar macrophages. Passive proton and relative counterion permeabilities, determinants of endosomal, lysosomal, and phagosomal pH-regulation, were probed with FITC-conjugated transferrin, dextran, and Pseudomonas aeruginosa, respectively. Although CFTR function could be documented in recycling endosomes and immature phagosomes, neither channel activation nor inhibition influenced the pH in any of these organelles. CFTR heterologous overexpression also failed to alter endocytic organellar pH. We propose that the relatively large CFTR-independent counterion and small passive proton permeability ensure efficient shunting of the proton-ATPase–generated membrane potential. These results have implications in the regulation of organelle acidification in general and demonstrate that perturbations of the endolysosomal organelles pH homeostasis cannot be linked to the etiology of the CF lung disease. PMID:19420138

  15. Revisiting the role of cystic fibrosis transmembrane conductance regulator and counterion permeability in the pH regulation of endocytic organelles.

    PubMed

    Barriere, Herve; Bagdany, Miklos; Bossard, Florian; Okiyoneda, Tsukasa; Wojewodka, Gabriella; Gruenert, Dieter; Radzioch, Danuta; Lukacs, Gergely L

    2009-07-01

    Organellar acidification by the electrogenic vacuolar proton-ATPase is coupled to anion uptake and cation efflux to preserve electroneutrality. The defective organellar pH regulation, caused by impaired counterion conductance of the mutant cystic fibrosis transmembrane conductance regulator (CFTR), remains highly controversial in epithelia and macrophages. Restricting the pH-sensitive probe to CFTR-containing vesicles, the counterion and proton permeability, and the luminal pH of endosomes were measured in various cells, including genetically matched CF and non-CF human respiratory epithelia, as well as cftr(+/+) and cftr(-/-) mouse alveolar macrophages. Passive proton and relative counterion permeabilities, determinants of endosomal, lysosomal, and phagosomal pH-regulation, were probed with FITC-conjugated transferrin, dextran, and Pseudomonas aeruginosa, respectively. Although CFTR function could be documented in recycling endosomes and immature phagosomes, neither channel activation nor inhibition influenced the pH in any of these organelles. CFTR heterologous overexpression also failed to alter endocytic organellar pH. We propose that the relatively large CFTR-independent counterion and small passive proton permeability ensure efficient shunting of the proton-ATPase-generated membrane potential. These results have implications in the regulation of organelle acidification in general and demonstrate that perturbations of the endolysosomal organelles pH homeostasis cannot be linked to the etiology of the CF lung disease. PMID:19420138

  16. The electrical conductivity of the Earth's upper mantle as estimated from satellite measured magnetic field variations. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Didwall, E. M.

    1981-01-01

    Low latitude magnetic field variations (magnetic storms) caused by large fluctuations in the equatorial ring current were derived from magnetic field magnitude data obtained by OGO 2, 4, and 6 satellites over an almost 5 year period. Analysis procedures consisted of (1) separating the disturbance field into internal and external parts relative to the surface of the Earth; (2) estimating the response function which related to the internally generated magnetic field variations to the external variations due to the ring current; and (3) interpreting the estimated response function using theoretical response functions for known conductivity profiles. Special consideration is given to possible ocean effects. A temperature profile is proposed using conductivity temperature data for single crystal olivine. The resulting temperature profile is reasonable for depths below 150-200 km, but is too high for shallower depths. Apparently, conductivity is not controlled solely by olivine at shallow depths.

  17. The Bulk Lunar Electrical Conductivity. Ph.D. Thesis. Final Report; [from Explorer 35 satellite and the Apollo 12 flight

    NASA Technical Reports Server (NTRS)

    Leavy, Donald Lucien

    1975-01-01

    The electrical conductivity structure was studied of a spherically layered moon consistent with the very low frequency magnetic data collected on the lunar surface and by Explorer 35. In order to obtain good agreement with the lunar surface magnetometer observations, the inclusion of a void cavity behind the moon requires a conductivity at shallow depths higher than that of models having the solar wind impinging on all sides. By varying only the source parameters, a conductivity model can be found that yields a good fit to both the tangential response upstream and the radial response downstream. This model also satisfies the dark side tangential response in the frequency range above 0.006 Hz, but the few data points presently available below this range do not seem to agree with the theory.

  18. Statistical summary of daily values data and trend analysis of dissolved-solids data at National Stream Quality Accounting Network (NASQAN) stations

    USGS Publications Warehouse

    Wells, F.C.; Schertz, T.L.

    1983-01-01

    A statistical summary is provided of the available continuous and once-daily discharge, specific-conductance, dissolved oxygen , water temperature, and pH data collected at NASQAN stations during the 1973-81 water years and documents the period of record on which the statistical calculations were based. In addition, dissolved-solids data are examined by regression analyses to determine the relation between dissolved solids and specific conductance and to determine if long-term trends can be detected in dissolved-solids concentrations. Statistical summaries, regression equations expressing the relation between dissolved solids and specific conductance, and graphical presentations of trend analyses of dissolved solids are presented for 515 NASQAN stations in the United States, Canada, Guam, and Puerto Rico. (USGS)

  19. Feasible metabolisms in high pH springs of the Philippines

    PubMed Central

    Cardace, Dawn; Meyer-Dombard, D'Arcy R.; Woycheese, Kristin M.; Arcilla, Carlo A.

    2015-01-01

    A field campaign targeting high pH, H2-, and CH4-emitting serpentinite-associated springs in the Zambales and Palawan Ophiolites of the Philippines was conducted in 2012-2013, and enabled description of several springs sourced in altered pillow basalts, gabbros, and peridotites. We combine field observations of pH, temperature, conductivity, dissolved oxygen, and oxidation-reduction potential with analyses of major ions, dissolved inorganic carbon, dissolved organic carbon, and dissolved gas phases in order to model the activities of selected phases important to microbial metabolism, and to rank feasible metabolic reactions based on energy yield. We document changing geochemical inventories in these springs between sampling years, and examine how the environment supports or prevents the function of certain microbial metabolisms. In all, this geochemistry-based assessment of feasible metabolisms indicates methane cycling, hydrogen oxidation, some iron and sulfur metabolisms, and ammonia oxidation are feasible reactions in this continental site of serpentinization. PMID:25713561

  20. Combining pH and electrical conductivity measurements to improve titrimetric methods to determine ammonia nitrogen, volatile fatty acids and inorganic carbon concentrations.

    PubMed

    Charnier, C; Latrille, E; Lardon, L; Miroux, J; Steyer, J P

    2016-05-15

    Volatile fatty acids (VFA), inorganic carbon (IC) and total ammonia nitrogen (TAN) are key variables in the current context of anaerobic digestion (AD). Accurate measurements like gas chromatography and infrared spectrometry have been developed to follow the concentration of these compounds but none of these methods are affordable for small AD units. Only titration methods answer the need for small plant monitoring. The existing methods accuracy was assessed in this study and reveals a lack of accuracy and robustness to control AD plants. To solve these issues, a new titrimetric device to estimate the VFA, IC and TAN concentrations with an improved accuracy was developed. This device named SNAC (System of titration for total ammonia Nitrogen, volatile fatty Acids and inorganic Carbon) has been developed combining the measurement of electrical conductivity and pH. SNAC were tested on 24 different plant samples in a range of 0-0.16 mol.L(-1) TAN, 0.01-0.21 mol.L(-1) IC and 0-0.04 mol.L(-1) VFA. The standard error was about 0.012 mol.L(-1) TAN, 0.015 mol.L(-1) IC and 0.003 mol.L(-1) VFA. The coefficient of determination R(2) between the estimated and reference data was 0.95, 0.94 and 0.95 for TAN, IC and VFA respectively. Using the same data, current methods based on key pH points lead to standard error more than 14.5 times higher on VFA and more than 1.2 times higher on IC. These results show that SNAC is an accurate tool to improve the management of AD plant. PMID:27010787

  1. DISSOLVED OXYGEN PROFILES AND WATER QUALITY ANALYSIS IN THE MILNER RESERVOIR NEAR BURLEY IDAHO, IDAHO, OCTOBER 1975

    EPA Science Inventory

    On August 29, 1975, Parametrix, Inc. conducted a water sampling program in the Milner Reservoir. This program was designed to determine the effects of the Ore-Ida and Simplot Companies discharges upon the dissolved oxygen, pH, alkalinity, and BOD of the receiving waters. 7 samp...

  2. Investigation of a fiber optic surface plasmon spectroscopy in conjunction with conductivity as an in situ method for simultaneously monitoring changes in dissolved organic carbon and salinity in coastal waters.

    PubMed

    Kim, Yoon-Chang; Cramer, Jeffrey A; Booksh, Karl S

    2011-10-21

    A combination surface plasmon resonance (SPR) and conductivity sensor array was developed and implemented to demonstrate the ability to differentiate among changes in dissolved organic carbon (DOC) and salinity in coastal water. The array is capable of achieving sufficient spatial and temporal data density to better understand the cycling and fate of terrestrial DOC in coastal areas. DOC is the second largest source of bioreactive carbon in the environment and plays a key role in mediating microbial activity and generation of atmospheric CO(2). In the coastal areas, the salinity is also an important property in many applications, such as leak detection for landfill liners, saltwater intrusion to drinking water, marine environment monitoring, and seasonal climate prediction. Conductivity sensors are the industry standard for determining salinity in ocean systems. However, both conductivity and refractive index sensors, such as SPR spectroscopy based sensors, respond to salinity and DOC levels. To demonstrate the capability of the SPR sensor and a conductivity sensor to collect complimentary data useful in discrimination of salinity and DOC in coastal zone water, conductivity, SPR, and temperature data were collected during passage from the Juan de Fuca ridge area returning to the University of Washington docks. PMID:21881638

  3. Effects of Method and Level of Nitrogen Fertilizer Application on Soil pH, Electrical Conductivity, and Availability of Ammonium and Nitrate in Blueberry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Blueberries (Vaccinium spp.) require low soil pH and prefer N primarily as ammonium for optimum production. Nitrogen fertilizer methods and rates were evaluated in a new field of ‘Bluecrop’ blueberry (Vaccinium corymbosum L.) to determine their effects on soil pH and availability of ammonium and nit...

  4. Sensitized photooxidation of dissolved sulfides in water

    SciTech Connect

    Brewer, T.F.; Curtis, J.G.; Marchand, E.A.; Adams, V.D.; Middlebrooks, E.J.

    1994-12-31

    A byproduct of the enhanced recovery of petroleum is flood water that is often contaminated with soluble sulfides. The ability of methylene blue (MB) and riboflavin (RF) to sensitize dissolved sulfides for photooxidation was investigated. Both MB and RF were found to be effective sensitizers for the oxidation of sulfide in water. MB-dosed batch reactors consistently reduced initial sulfide concentrations of 100 mg/l to less than 10--15 mg/l in less than one hour under artificial lighting (91% sunlight corrected fluorescent tubes) at a pH = 10 and MB = 1mg/l. Preliminary experiments have shown approximately 80--85% of the removed sulfide is accounted for as accumulated sulfate. RF is also effective at enhancing the removal of sulfide, but experiments similar to those conducted for NM revealed that RF-dosed reactors required approximately 2--3 times longer to achieve sulfide removal comparable to MB (1mg/l), even with an RF concentration of 20 mg/l. The primary product in RF-sensitized photooxidation of dissolved sulfides is also sulfate, with approximately 75-80% of removed sulfide recovered as sulfate. First order plots of experimental data yield reaction rate constants of k = 0.0097 min{sup {minus}1} for RF, and k = 0.0273 min{sup {minus}1} for MB.

  5. Isotope fractionation during oxidation of tetravalent uranium by dissolved oxygen

    NASA Astrophysics Data System (ADS)

    Wang, Xiangli; Johnson, Thomas M.; Lundstrom, Craig C.

    2015-02-01

    We conducted laboratory experiments to investigate isotopic fractionations during oxidation of tetravalent uranium, U(IV), by dissolved oxygen. In hydrochloric acid media with the U(IV) dissolved, the ?238U value of the remaining U(IV) increased as the extent of oxidation increased. The ?238U value of the product U(VI) paralleled, but was offset to 1.1 0.2 lower than the remaining U(IV). In contrast, oxidation of solid U(IV) by dissolved oxygen in 20 mM NaHCO3 solution at pH = 9.4 caused only a weak fractionation (?0.1 to 0.3), with ?238U being higher in the dissolved U(VI) relative to the solid U(IV). We suggest that isotope fractionation during oxidation of solid U(IV) is inhibited by a "rind effect", where the surface layer of the solid U(IV) must be completely oxidized before the next layer is exposed to oxidant. The necessity of complete conversion of each layer results in minimal isotopic effect. The weak shift in ?238U of U(VI) is attributed to adsorption of part of the product U(VI) to the solid U(IV) surfaces.

  6. Disposable all-solid-state pH and glucose sensors based on conductive polymer covered hierarchical AuZn oxide.

    PubMed

    Kim, Dong-Min; Cho, Seong Je; Cho, Chul-Ho; Kim, Kwang Bok; Kim, Min-Yeong; Shim, Yoon-Bo

    2016-05-15

    Poly(terthiophene benzoic acid) (pTBA) layered-AuZn alloy oxide (AuZnOx) deposited on the screen printed carbon electrode (pTBA/AuZnOx/SPCE) was prepared to create a disposable all-solid-state pH sensor at first. Further, FAD-glucose oxidase (GOx) was immobilized onto the pTBA/AuZnOx/SPCE to fabricate a glucose sensor. The characterizations of the sensor probe reveal that AuZnOx forms a homogeneous hierarchical structure, and that the polymerized pTBA layer on the alloy oxide surface captures GOx covalently. The benzoic acid group of pTBA coated on the probe layer synergetically improved the pH response of the alloy oxide and provide chemical binding sites to enzyme, which resulted in a Nernstian behavior (59.2±0.5mV/pH) in the pH range of 2-13. The experimental parameters affecting the glucose analysis were studied in terms of pH, temperature, humidity, and interferences. The sensor exhibited a fast response time <1s and a dynamic range between 30 and 500mg/dL glucose with a detection limit of 17.23±0.32mg/dL. The reliabilities of the disposable pH and glucose sensors were examined for biological samples. PMID:26703994

  7. Quality-assurance results for field pH and specific-conductance measurements, and for laboratory analysis, National Atmospheric Deposition Program and National Trends Network; January 1980-September 1984

    USGS Publications Warehouse

    Schroder, L.J.; Brooks, M.H.; Malo, B.A.; Willoughby, T.C.

    1986-01-01

    Five intersite comparison studies for the field determination of pH and specific conductance, using simulated-precipitation samples, were conducted by the U.S.G.S. for the National Atmospheric Deposition Program and National Trends Network. These comparisons were performed to estimate the precision of pH and specific conductance determinations made by sampling-site operators. Simulated-precipitation samples were prepared from nitric acid and deionized water. The estimated standard deviation for site-operator determination of pH was 0.25 for pH values ranging from 3.79 to 4.64; the estimated standard deviation for specific conductance was 4.6 microsiemens/cm at 25 C for specific-conductance values ranging from 10.4 to 59.0 microsiemens/cm at 25 C. Performance-audit samples with known analyte concentrations were prepared by the U.S.G.S.and distributed to the National Atmospheric Deposition Program 's Central Analytical Laboratory. The differences between the National Atmospheric Deposition Program and national Trends Network-reported analyte concentrations and known analyte concentrations were calculated, and the bias and precision were determined. For 1983, concentrations of calcium, magnesium, sodium, and chloride were biased at the 99% confidence limit; concentrations of potassium and sulfate were unbiased at the 99% confidence limit. Four analytical laboratories routinely analyzing precipitation were evaluated in their analysis of identical natural- and simulated precipitation samples. Analyte bias for each laboratory was examined using analysis of variance coupled with Duncan 's multiple-range test on data produced by these laboratories, from the analysis of identical simulated-precipitation samples. Analyte precision for each laboratory has been estimated by calculating a pooled variance for each analyte. Interlaboratory comparability results may be used to normalize natural-precipitation chemistry data obtained from two or more of these laboratories. (Author 's abstract)

  8. Dissolver vessel bottom assembly

    DOEpatents

    Kilian, Douglas C.

    1976-01-01

    An improved bottom assembly is provided for a nuclear reactor fuel reprocessing dissolver vessel wherein fuel elements are dissolved as the initial step in recovering fissile material from spent fuel rods. A shock-absorbing crash plate with a convex upper surface is disposed at the bottom of the dissolver vessel so as to provide an annular space between the crash plate and the dissolver vessel wall. A sparging ring is disposed within the annular space to enable a fluid discharged from the sparging ring to agitate the solids which deposit on the bottom of the dissolver vessel and accumulate in the annular space. An inlet tangential to the annular space permits a fluid pumped into the annular space through the inlet to flush these solids from the dissolver vessel through tangential outlets oppositely facing the inlet. The sparging ring is protected against damage from the impact of fuel elements being charged to the dissolver vessel by making the crash plate of such a diameter that the width of the annular space between the crash plate and the vessel wall is less than the diameter of the fuel elements.

  9. Human radiation studies: Remembering the early years: Oral history of cell biologist Don Francis Petersen, Ph.D., conducted November 29, 1994

    SciTech Connect

    1995-08-01

    This report is a transcript of an interview of Dr. Don Francis Petersen by representatives of the US DOE Office of Human Radiation Experiments. Dr. Petersen was selected for this interview because of his long research career at Los Alamos and his knowledge of the Atomic Energy Commission`s biomedical program. Dr. Petersen did not personally conduct research on human subjects. After a brief biographical sketch Dr. Petersen discusses his remembrances of the early use of radionuclides as biological tracers, aspects of nuclear weapons testing in the 1940`s and 1950`s including fallout studies, the means by which research projects were approved, use of humans in the whole-body counter, and the Health Division Biomedical responsibilities.

  10. Dissolving Bubbles in Glass

    NASA Technical Reports Server (NTRS)

    Weinberg, M. C.; Oronato, P. I.; Uhlmann, D. R.

    1984-01-01

    Analytical expression used to calculate time it takes for stationary bubbles of oxygen and carbon dioxide to dissolve from glass melt. Technique based on analytical expression for bubble radius as function time, with consequences of surface tension included.

  11. A finite element model of conduction, convection, and phase change near a solid/melt interface. Ph.D. Thesis - Michigan Univ.

    NASA Technical Reports Server (NTRS)

    Viterna, Larry A.

    1991-01-01

    Detailed understanding of heat transfer and fluid flow is required for many aerospace thermal systems. These systems often include phase change and operate over a range of accelerations or effective gravitational fields. An approach to analyzing such systems is presented which requires the simultaneous solution of the conservation laws of energy, momentum, and mass, as well as an equation of state. The variable property form of the governing equations are developed in two-dimensional Cartesian coordinates for a Newtonian fluid. A numerical procedure for solving the governing equations is presented and implemented in a computer program. The Galerkin form of the finite element method is used to solve the spatial variation of the field variables, along with the implicit Crank-Nicolson time marching algorithm. Quadratic Langrangian elements are used for the internal energy and the two components of velocity. Linear Lagrangian elements are used for the pressure. The location of the solid/liquid interface as well as the temperatures are determined form the calculated internal energy and pressure. This approach is quite general in that it can describe heat transfer without phase change, phase change with a sharp interface, and phase change without an interface. Analytical results from this model are compared to those of other researchers studying transient conduction, convection, and phase change and are found to be in good agreement. The numerical procedure presented requires significant computer resources, but this is not unusual when compared to similar studies by other researchers. Several methods are suggested to reduce the computational times.

  12. Precipitation strengthened high strength, high conductivity Cu-Cr-Nb alloys produced by chill block melt spinning. Final Report Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Michal, Gary M.

    1989-01-01

    A series of Cu-based alloys containing 2 to 10 a/o Cr and 1 to 5 a/o Nb were produced by chill block melt spinning (CBMS). The melt spun ribbons were consolidated and hot rolled to sheet to produce a supersaturated Cu-Cr-Nb solid solution from which the high melting point intermetallic compound Cr2Nb could be precipitated to strengthen the Cu matrix. The results show that the materials possess electrical conductivities in excess of 90 percent that of pure Cu at 200 C and above. The strengths of the Cu-Cr-Nb alloys were much greater than Cu, Cu-0.6 Cr, NARloy-A, and NARloy-Z in the as-melt spun condition. The strengths of the consolidated materials were less than Cu-Cr and Cu-Cr-Zr below 500 C and 600 C respectively, but were significantly better above these temperatures. The strengths of the consolidated materials were greater than NARloy-Z, at all temperatures. The GLIDCOP possessed similar strength levels up to 750 C when the strength of the Cu-Cr-Nb alloys begins to degrade. The long term stability of the Cu-Cr-Nb alloys was measured by the microhardness of aged samples and the growth of precipitates. The microhardness measurements indicate that the alloys overage rapidly, but do not suffer much loss in strength between 10 and 100 hours which confirms the results of the electrical resistivity measurements taken during the aging of the alloys at 500 C. The loss in strength from peak strength levels is significant, but the strength remains exceptionally good. Transmission electron microscopy (TEM) of the as-melt spun samples revealed that Cr2Nb precipitates formed in the liquid Cu during the chill block melt spinning, indicating a very strong driving force for the formation of the precipitates. The TEM of the aged and consolidated materials indicates that the precipitates coarsen considerably, but remain in the submicron range.

  13. Does Dissolved Inorganic Carbon Play a Role in Arsenic Mobilization?

    NASA Astrophysics Data System (ADS)

    Ford, R. G.; Wilkin, R. T.

    2001-05-01

    Recent experimental results provide evidence that dissolved inorganic carbon plays a direct role in mobilizing arsenic in anoxic aquatic environments. This hypothesis is partially supported by observed correlations between elevated levels of arsenic and alkalinity in a ground water aquifer containing buried arsenic-rich sulfidic waste materials. However, the influence of dissolved inorganic carbon is difficult to decouple from the effects of elevated pH and/or microbial processes. Laboratory experiments are being conducted to explore the effect of inorganic carbon on arsenic sulfide solubility. These experimental results along with a site-specific review of ground water geochemistry within an arsenic plume will be reviewed in order to explore the validity of the proposed correlation. Notice: The U.S. Environmental Protection Agency through its Office of Research and Development funded and managed the research described here through in-house efforts. It has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency, and no official endorsement should be inferred.

  14. Lap-Dissolve Slides

    ERIC Educational Resources Information Center

    Fine, Leonard W.; And Others

    1977-01-01

    Discusses the use of lap-dissolve projection to give students pre-laboratory instruction on an upcoming experiment. In this technique, two slide projectors are operated alternately so that one visual image fades away while the next appears on the same screen area. (MLH)

  15. Optimal Soil Eh, pH, and Water Management for Simultaneously Minimizing Arsenic and Cadmium Concentrations in Rice Grains.

    PubMed

    Honma, Toshimitsu; Ohba, Hirotomo; Kaneko-Kadokura, Ayako; Makino, Tomoyuki; Nakamura, Ken; Katou, Hidetaka

    2016-04-19

    Arsenic (As) and cadmium (Cd) concentrations in rice grains are a human health concern. We conducted field experiments to investigate optimal conditions of Eh and pH in soil for simultaneously decreasing As and Cd accumulation in rice. Water managements in the experiments, which included continuous flooding and intermittent irrigation with different intervals after midseason drainage, exerted striking effects on the dissolved As and Cd concentrations in soil through changes in Eh, pH, and dissolved Fe(II) concentrations in the soil. Intermittent irrigation with three-day flooding and five-day drainage was found to be effective for simultaneously decreasing the accumulation of As and Cd in grain. The grain As and Cd concentrations were, respectively, linearly related to the average dissolved As and Cd concentrations during the 3 weeks after heading. We propose a new indicator for expressing the degree to which a decrease in the dissolved As or Cd concentration is compromised by the increase in the other. For minimizing the trade-off relationship between As and Cd in rice grains in the field investigated, water management strategies should target the realization of optimal soil Eh of -73 mV and pH of 6.2 during the 3 weeks after heading. PMID:26999020

  16. Dissolved Oxygen Levels in Lake Chabot

    NASA Astrophysics Data System (ADS)

    Sharma, D.; Pica, R.

    2014-12-01

    Dissolved oxygen levels are crucial in every aquatic ecosystem; it allows for the fish to breathe and it is the best indicator of water quality. Lake Chabot is the main backup water source for Castro Valley, making it crucial that the lake stays in good health. Last year, research determined that the water in Lake Chabot was of good quality and not eutrophic. This year, an experiment was conducted using Lake Chabot's dissolved oxygen levels to ensure the quality of the water and to support the findings of the previous team. After testing three specifically chosen sites at the lake using a dissolved oxygen meter, results showed that the oxygen levels in the lake were within the healthy range. It was then determined that Lake Chabot is a suitable backup water source and it continues to remain a healthy habitat.

  17. RESPONSE OF LEAD SOLUBILITY TO DISSOLVED CARBONATE IN DRINKING WATER

    EPA Science Inventory

    A model is presented showing the detailed response of the theoretical solubility curves for lead to changes in dissolved inorganic carbonate concentration (TIC) and pH at 25 C. Aqueous Pb(II) ion, lead carbonate complexes, lead hydroxide monomers and polymers, and the solids lead...

  18. Prediction of dissolved oxygen in the Mediterranean Sea along Gaza, Palestine - an artificial neural network approach.

    PubMed

    Zaqoot, Hossam Adel; Ansari, Abdul Khalique; Unar, Mukhtiar Ali; Khan, Shaukat Hyat

    2009-01-01

    Artificial Neural Networks (ANNs) are flexible tools which are being used increasingly to predict and forecast water resources variables. The human activities in areas surrounding enclosed and semi-enclosed seas such as the Mediterranean Sea always produce in the long term a strong environmental impact in the form of coastal and marine degradation. The presence of dissolved oxygen is essential for the survival of most organisms in the water bodies. This paper is concerned with the use of ANNs - Multilayer Perceptron (MLP) and Radial Basis Function neural networks for predicting the next fortnight's dissolved oxygen concentrations in the Mediterranean Sea water along Gaza. MLP and Radial Basis Function (RBF) neural networks are trained and developed with reference to five important oceanographic variables including water temperature, wind velocity, turbidity, pH and conductivity. These variables are considered as inputs of the network. The data sets used in this study consist of four years and collected from nine locations along Gaza coast. The network performance has been tested with different data sets and the results show satisfactory performance. Prediction results prove that neural network approach has good adaptability and extensive applicability for modelling the dissolved oxygen in the Mediterranean Sea along Gaza. We hope that the established model will help in assisting the local authorities in developing plans and policies to reduce the pollution along Gaza coastal waters to acceptable levels. PMID:19955628

  19. Enhanced dissolution of cinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades

    SciTech Connect

    Ravichandran, M.; Ryan, J.N.; Aiken, G.R.; Reddy, M.M.

    1998-11-01

    Organic matter isolated from the Florida Everglades caused a dramatic increase in mercury release from cinnabar (HgS), a solid with limited solubility. Hydrophobic (a mixture of both humic and fulvic) acids dissolved more mercury than hydrophilic acids and other nonacid fractions of dissolved organic matter (DOM). Cinnabar dissolution by isolated organic matter and natural water samples was inhibited by cations such as Ca{sup 2+}. Dissolution was independent of oxygen content in experimental solutions. Dissolution experiments conducted in Dl water had no detectable dissolved mercury. The presence of various inorganic (chloride, sulfate, or sulfide) and organic ligands (salicylic acid, acetic acid, EDTA, or cysteine) did not enhance the dissolution of mercury from the mineral. Aromatic carbon content in the isolates correlated positively with enhanced cinnabar dissolution. {zeta}-potential measurements indicated sorption of negatively charged organic matter to the negatively charged cinnabar at pH 6.0. Possible mechanisms of dissolution include surface complexation of mercury and oxidation of surface sulfur species by the organic matter.

  20. The Effects of Acid Rock Drainage (ARD) on Fluorescent Dissolved Organic Matter (DOM)

    NASA Astrophysics Data System (ADS)

    Lee, R. H.; Gabor, R. S.; SanClements, M.; McKnight, D. M.

    2011-12-01

    Located in the Rocky Mountains of central Colorado, the catchments drained by the headwaters of the Snake River are dominated by metal- and sulfide-rich bedrock. The breakdown of these minerals results in acidic metal-rich waters in the Snake (pH ~3) that persist until the confluence with Deer Creek (pH ~7). Previous research has been conducted examining the interactions of acid-rock drainage (ARD) and dissolved organic matter (DOM), but the effects of ARD on DOM production is not as well understood. In a synoptic study, samples of creek water were collected at evenly spaced intervals along the length of a tributary to the Snake River which drains an area with ARD. At each sampling location, water samples were collected and pH, conductivity, and temperature were measured. Water samples were analyzed for metal chemistry, and the DOM was analyzed with UV-Vis and fluorescence spectroscopy. The character of the DOM was described using PARAFAC and index calculations. This work demonstrates that the introduction of acid and dissolved metal species has notable effects on DOM composition. Preliminary data suggests that the introduction of acid drainage is responsible for the formation of a fluorophore not accounted for in the Cory and McKnight PARAFAC model. Both high concentrations of heavy metals (e.g. zinc) and the novel fluorophore are present downstream from a mining site, which indicates it as a possible source of both species. The data suggest a link between the introduction of fluorophores in acidic waters and acidophile populations at the source of the acid rock drainage.

  1. Effect of Leaf Litter Diversity on Dissolved Organic Matter Export in a Deciduous Forest Soil

    NASA Astrophysics Data System (ADS)

    Scheibe*, A.; Eißfeller, V.; Langenbruch, C.; Seven, J.; Gleixner, G.

    2012-04-01

    We investigated sources and fate of dissolved organic matter (DOM) in soils in order to understand the effect of tree diversity on below ground processes. We established a leaf litter exchange experiment in the National Park Hainich (Thuringia, Germany) in December 2008. Labeled (13C) and unlabeled leaf litter of beach (Fagus sylvatica) and ash (Fraxinus excelsior) were exposed to study the decomposition process. Soil water was collected biweekly with glass suction plates (1 μm pore size, UMS, Munich, Germany) in 5 cm soil depth and pH, conductivity, DOC and anions (Cl-, NO3-, NO2-, PO43-, SO42-, F-) were determined. The 13DOC values were measured using high performance liquid chromatography - isotope ratio mass spectrometry (HPLC-IRMS). The values of conductivity and pH in the soil water indicate slower decomposition processes for leaf litter of beech in comparison to ash leaf litter. The conductivity was correlated with the Cl- ion during the first spring, which suggests the export of carbon due to leaching processes. However during the summer the conductivity correlated with the NO3- ions, which indicates mineralization as driving process. Surprisingly, the contribution of litter 13C into the dissolved carbon pool was very low. The highest contribution with up to 8.6% DOC labeled by ash litter derived carbon was found in the first 3 month of application. However, in the mean only 1.2% and 2.6% of DOC was labeled by carbon of the beech and ash litter, respectively. This represents in total only up to 0.41% of labeled litter carbon that was added. The higher percentages of ash litter derived 13C in DOM of soil water compared to beech indicates a positive effect of litter quality on decomposition. However, we did not find a faster decomposition or higher ash litter derived carbon export in mixed (ash and beech litter) treatments, which would indicate food selection or biodiversity effects.

  2. Method for dissolving plutonium dioxide

    DOEpatents

    Tallent, Othar K.

    1978-01-01

    The fluoride-catalyzed, non-oxidative dissolution of plutonium dioxide in HNO.sub.3 is significantly enhanced in rate by oxidizing dissolved plutonium ions. It is believed that the oxidation of dissolved plutonium releases fluoride ions from a soluble plutonium-fluoride complex for further catalytic action.

  3. Effect of Greenhouse Gases Dissolved in Seawater

    PubMed Central

    Matsunaga, Shigeki

    2015-01-01

    A molecular dynamics simulation has been performed on the greenhouse gases carbon dioxide and methane dissolved in a sodium chloride aqueous solution, as a simple model of seawater. A carbon dioxide molecule is also treated as a hydrogen carbonate ion. The structure, coordination number, diffusion coefficient, shear viscosity, specific heat, and thermal conductivity of the solutions have been discussed. The anomalous behaviors of these properties, especially the negative pressure dependence of thermal conductivity, have been observed in the higher-pressure region. PMID:26729101

  4. Effect of Greenhouse Gases Dissolved in Seawater.

    PubMed

    Matsunaga, Shigeki

    2016-01-01

    A molecular dynamics simulation has been performed on the greenhouse gases carbon dioxide and methane dissolved in a sodium chloride aqueous solution, as a simple model of seawater. A carbon dioxide molecule is also treated as a hydrogen carbonate ion. The structure, coordination number, diffusion coefficient, shear viscosity, specific heat, and thermal conductivity of the solutions have been discussed. The anomalous behaviors of these properties, especially the negative pressure dependence of thermal conductivity, have been observed in the higher-pressure region. PMID:26729101

  5. Method of synthesis of proton conducting materials

    DOEpatents

    Garzon, Fernando Henry; Einsla, Melinda Lou; Mukundan, Rangachary

    2010-06-15

    A method of producing a proton conducting material, comprising adding a pyrophosphate salt to a solvent to produce a dissolved pyrophosphate salt; adding an inorganic acid salt to a solvent to produce a dissolved inorganic acid salt; adding the dissolved inorganic acid salt to the dissolved pyrophosphate salt to produce a mixture; substantially evaporating the solvent from the mixture to produce a precipitate; and calcining the precipitate at a temperature of from about 400.degree. C. to about 1200.degree. C.

  6. Dissolved Oxygen and Sulfide Define the Boundaries of Thermophilic Microbial Iron Mats

    NASA Astrophysics Data System (ADS)

    St Clair, B.; Shock, E.

    2014-12-01

    Microbial iron cycling can be found in hot springs throughout Yellowstone National Park, where the process is often visibly apparent as red iron oxyhydroxide staining. We measured rates of microbial and abiotic iron oxidation and reduction in systems ranging from pH 2 to 6 and 40° to 90°C. Measurements of numerous solutes, including oxygen, sulfide, and iron, were also made on outflow channels of springs containing apparent iron metabolism. In all cases, > 16 μM dissolved oxygen was required for visible iron oxidation products to occur. Oxygen concentrations below this level do not necessarily preclude microbial iron oxidation coupled to oxygen, only the accumulation of oxidation products. Kinetics experiments conducted at these iron mats suggest that the rate of microbial iron oxidation falls below the rate of microbial reduction when dissolved oxygen falls below this concentration. In outflow channels, this is often visibly apparent as a sharp boundary between the presence and lack of red iron oxidation products. Locations with changing temperature, pH, flow rate and other factors experience changing oxygen concentrations, which causes the boundary to shift from year to year. The boundaries of iron mats are also influenced in several locations by the concentration of total dissolved sulfide. Experiments with enrichment cultures and field observations show that sulfide is not toxic to iron oxidizers, but rather inhibits the accumulation of dissolved oxygen. Microbial and abiotic sulfide oxidation, leading to visible sulfur precipitation, together with degassing of hydrogen sulfide, contribute to keeping oxygen levels low. Typically, only where sulfide concentrations fall below 20 μM are iron mats able to form. Enrichment cultures of iron oxidizers, however, grow easily at levels exceeding 100 μM sulfide. Only a handful of field locations appear to have simultaneous sulfur and iron precipitation zones. Formation of iron oxidation mats occurs at highly consistent concentrations of dissolved oxygen and sulfide in Yellowstone hot springs, and can even serve as visible indicators of the abundance of these geochemical constituents.

  7. Fast dissolving films: a review.

    PubMed

    Chaturvedi, Ankita; Srivastava, Pranati; Yadav, Sunita; Bansal, Mayank; Garg, Garima; Sharma, Pramod Kumar

    2011-07-01

    Fast-dissolving drug delivery systems have been developed as an alternative to conventional dosage form as an oral means of drug delivery in case of chronic conditions. Now a day's fast dissolving films are preferred over conventional tablets and capsules for masking the taste of bitter drugs to increase the patient compliance. Fast dissolving films consist of a very thin oral strip which dissolves in less than one minute when placed on the tongue. Dissolvable oral thin films are in the market since past few years in the form of breath strips and are widely accepted by consumers for delivering vitamins, vaccines and other drug products. The various manufacturing techniques for the preparation of films have also been detailed in the review. The present review details most of the patents on such fast dissolving films in recent years. A brief study has been made on various parameters which are used to evaluate such films. In case of chronic disorders these fast dissolving films are better for delivering drugs and obtaining faster therapeutic blood levels and superior in comparison to other oral conventional dosage forms. PMID:21453260

  8. Influence of pH and natural organic matter on zinc biosorption in a model lignocellulosic biofuel biorefinery effluent.

    PubMed

    Palumbo, Amanda J; Daughney, Christopher J; Slade, Alison H; Glover, Chris N

    2013-10-01

    The effect of dissolved natural organic matter (NOM) and pH on microbial biosorption of Zn was evaluated in a model lignocellulosic biofuel refinery effluent rich in NOM. Batch culture experiments conducted with two model microorganisms (yeast, Candida tropicalis; bacteria Novosphingobium nitrogenifigens Y88(T)), showed an inhibitory effect of NOM, and an optimum pH for Zn removal at 7.5-8.0. Membrane bioreactors with mixed autochthonous organisms were operated at pH 6.5 and pH 8.0 to better simulate real-world remediation scenarios. More Zn was removed at the high (91%) than at the low (26%) pH, presumably because the higher pH freed negatively-charged functional groups on the cellular biomass for passive Zn binding. Manipulating the pH of bioreactors can significantly improve metal removal in NOM rich wastewater. Such reactors could maintain water quality for closed-cycle biorefineries, leading to reduced water consumption, and a more sustainable biofuel. PMID:23933024

  9. Evaluation of natural and anthropogenic influences on the Guadalquivir River (Spain) by dissolved heavy metals and nutrients.

    PubMed

    Mendigucha, Carolina; Moreno, Carlos; Garca-Vargas, Manuel

    2007-11-01

    To evaluate both the natural and anthropogenic influences on surface waters of Guadalquivir River (SW-Spain), concentrations of dissolved trace metals (Mn, Co, Ni, Cu, Cd, Zn, and Pb), inorganic nutrients (N-NH(4)(+), N-NO(3)(-), N-NO(2)(-), and P-PO(4)(3-)) and other variables as conductivity, pH, dissolved oxygen (DO) and suspended solids (SS) were measured during a three-years period (2001-2003). Samples were taken at 26 stations twice a year, during rain and dry periods. The analysis of variance (ANOVA) suggested that temporal variations within the period of study were statistically negligible. Spatial distributions identified three different zones, mainly influenced by sewage (Eastern Zone), agriculture runoffs (Central Zone), and estuarine processes (Western Zone), respectively. Principal Component and Cluster Analysis allowed to identify the variables controlling the water quality of each zone as: N-NH(4)(+), N-NO(2)(-), Mn, and Co, (Eastern Zone), SS, and P-PO(4)(3-) (Central Zone), and Cd, pH and conductivity (Western Zone). Other variables such as Ni, Cu, Zn or N-NO(3)(-), influenced two different zones, while Pb presented a singular behavior. PMID:17631380

  10. Factors regulating nitrification in aquatic sediments: Effects of organic carbon, nitrogen availability, and pH

    USGS Publications Warehouse

    Strauss, E.A.; Mitchell, N.L.; Lamberti, G.A.

    2002-01-01

    We investigated the response in nitrification to organic carbon (C) availability, the interactive effects of the C: nitrogen (N) ratio and organic N availability, and differing pH in sediments from several streams in the upper midwestern United States. In addition, we surveyed 36 streams to assess variability in sediment nitrification rates. Labile dissolved organic carbon (DOC) additions of 30 mg C??L-1 (as acetate) to stream sediments reduced nitrification rates (P < 0.003), but lower concentration additions or dilution of ambient DOC concentration had no effect on nitrification. C:N and organic N availability strongly interacted to affect nitrification (P < 0.0001), with N availability increasing nitrification most at lower C:N. Nitrification was also strongly influenced by pH (P < 0.002), with maximum rates occurring at pH 7.5. A multiple regression model developed from the stream survey consisted of five variables (stream temperature, pH, conductivity, DOC concentration, and total extractable NH4+) and explained 60% of the variation observed in nitrification. Our results suggest that nitrification is regulated by several variables, with NH4+ availability and pH being the most important. Organic C is likely important at regulating nitrification only under high environmental C:N conditions and if most available C is relatively labile.

  11. METHOD OF DISSOLVING URANIUM METAL

    DOEpatents

    Slotin, L.A.

    1958-02-18

    This patent relates to an economicai means of dissolving metallic uranium. It has been found that the addition of a small amount of perchloric acid to the concentrated nitric acid in which the uranium is being dissolved greatly shortens the time necessary for dissolution of the metal. Thus the use of about 1 or 2 percent of perchioric acid based on the weight of the nitric acid used, reduces the time of dissolution of uranium by a factor of about 100.

  12. Removal of dissolved metals by plant tissue

    SciTech Connect

    Scott, C.D. )

    1992-04-25

    Various types of microbial biomass have been shown to adsorb metals dissolved in aqueous media. It has now been demonstrated that certain plant tissues are also effective for this type of adsorption process. In particular, tomato and tobacco roots harvested from field-grown plants were shown to adsorb Sr from an aqueous solution of SrCl[sub 2]. Distribution coefficients in excess of 550 were measured and the adsorption isotherms at 25 C could be fitted to Langmuir-type expressions. The bioadsorbent could be regenerated and metals recovered by either a reduction in the pH to less than 2.0 or by use of a concentrated chloride salt solution.

  13. Formulation Development and Evaluation of Fast Dissolving Film of Telmisartan

    PubMed Central

    Londhe, Vaishali Y.; Umalkar, Kashmira B.

    2012-01-01

    Hypertension is a major cause of concern not just in the elderly but also in the youngsters. An effort was made to formulate a fast dissolving film containing telmisartan which is used in the treatment of hypertension with a view to improve the onset of action, therapeutic efficacy, patient compliance and convenience. The major challenge in formulation of oral films of telmisatran is that it shows very less solubility in the pH range of 3–9. Various film forming agents and polyhydric alcohols were evaluated for optimizing composition of fast dissolving films. Fast dissolving films using hydroxypropyl methylcellulose, polyvinyl alcohol, glycerol, sorbitol, menthol and an alkalizer were formulated using solvent casting method. Optimized formulations were evaluated for their weight, thickness, folding endurance, appearance, tensile strength, disintegration time and dissolution profile. PMID:23325992

  14. Formulation development and evaluation of fast dissolving film of telmisartan.

    PubMed

    Londhe, Vaishali Y; Umalkar, Kashmira B

    2012-03-01

    Hypertension is a major cause of concern not just in the elderly but also in the youngsters. An effort was made to formulate a fast dissolving film containing telmisartan which is used in the treatment of hypertension with a view to improve the onset of action, therapeutic efficacy, patient compliance and convenience. The major challenge in formulation of oral films of telmisatran is that it shows very less solubility in the pH range of 3-9. Various film forming agents and polyhydric alcohols were evaluated for optimizing composition of fast dissolving films. Fast dissolving films using hydroxypropyl methylcellulose, polyvinyl alcohol, glycerol, sorbitol, menthol and an alkalizer were formulated using solvent casting method. Optimized formulations were evaluated for their weight, thickness, folding endurance, appearance, tensile strength, disintegration time and dissolution profile. PMID:23325992

  15. DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS

    SciTech Connect

    NA

    2004-11-22

    The purpose of this study is to evaluate dissolved concentration limits (also referred to as solubility limits) of elements with radioactive isotopes under probable repository conditions, based on geochemical modeling calculations using geochemical modeling tools, thermodynamic databases, field measurements, and laboratory experiments. The scope of this modeling activity is to predict dissolved concentrations or solubility limits for 14 elements with radioactive isotopes (actinium, americium, carbon, cesium, iodine, lead, neptunium, plutonium, protactinium, radium, strontium, technetium, thorium, and uranium) important to calculated dose. Model outputs for uranium, plutonium, neptunium, thorium, americium, and protactinium are in the form of tabulated functions with pH and log (line integral) CO{sub 2} as independent variables, plus one or more uncertainty terms. The solubility limits for the remaining elements are either in the form of distributions or single values. The output data from this report are fundamental inputs for Total System Performance Assessment for the License Application (TSPA-LA) to determine the estimated release of these elements from waste packages and the engineered barrier system. Consistent modeling approaches and environmental conditions were used to develop solubility models for all of the actinides. These models cover broad ranges of environmental conditions so that they are applicable to both waste packages and the invert. Uncertainties from thermodynamic data, water chemistry, temperature variation, and activity coefficients have been quantified or otherwise addressed.

  16. Removal properties of dissolved boron by glucomannan gel.

    PubMed

    Oishi, Kyoko; Maehata, Yugo

    2013-04-01

    Boron ions have long been known to form complexes with the cis-diol group of a polysaccharide. Konjac glucomannan (KGM) which is one of polysaccharides was used to remove dissolved boron in this study. KGM forms a complex with boron, but does not remove boron from contaminated waters as well as other polysaccharides because of its high water solubility. Therefore, the removal efficiencies of dissolved boron were examined using both an insoluble KGM gel and KGM semi-gel. The former did not remove dissolved boron, but the latter did. The difference in the ability of boron removal was due to the presence of diol group inside. KGM loses free diol group during the process of gelation. On the other hand, the semi-gel gelated only surface layer in water has diol group inside. The boron removal capacity of the semi-gel was highest at pHs⩾11, when the boron species is present as B(OH)4(-). The capacity was slightly increased by the addition of Al, Ca and Mg under high pH conditions. This was due to co-precipitation of boron with Ca dissolved from the semi-gel. The boron adsorbed to the semi-gel easily was desorbed under low pH conditions and the hysteresis was not found. PMID:23260255

  17. Small changes in pH have direct effects on marine bacterial community composition: a microcosm approach.

    PubMed

    Krause, Evamaria; Wichels, Antje; Giménez, Luis; Lunau, Mirko; Schilhabel, Markus B; Gerdts, Gunnar

    2012-01-01

    As the atmospheric CO(2) concentration rises, more CO(2) will dissolve in the oceans, leading to a reduction in pH. Effects of ocean acidification on bacterial communities have mainly been studied in biologically complex systems, in which indirect effects, mediated through food web interactions, come into play. These approaches come close to nature but suffer from low replication and neglect seasonality. To comprehensively investigate direct pH effects, we conducted highly-replicated laboratory acidification experiments with the natural bacterial community from Helgoland Roads (North Sea). Seasonal variability was accounted for by repeating the experiment four times (spring, summer, autumn, winter). Three dilution approaches were used to select for different ecological strategies, i.e. fast-growing or low-nutrient adapted bacteria. The pH levels investigated were in situ seawater pH (8.15-8.22), pH 7.82 and pH 7.67, representing the present-day situation and two acidification scenarios projected for the North Sea for the year 2100. In all seasons, both automated ribosomal intergenic spacer analysis and 16S ribosomal amplicon pyrosequencing revealed pH-dependent community shifts for two of the dilution approaches. Bacteria susceptible to changes in pH were different members of Gammaproteobacteria, Flavobacteriaceae, Rhodobacteraceae, Campylobacteraceae and further less abundant groups. Their specific response to reduced pH was often context-dependent. Bacterial abundance was not influenced by pH. Our findings suggest that already moderate changes in pH have the potential to cause compositional shifts, depending on the community assembly and environmental factors. By identifying pH-susceptible groups, this study provides insights for more directed, in-depth community analyses in large-scale and long-term experiments. PMID:23071704

  18. Small Changes in pH Have Direct Effects on Marine Bacterial Community Composition: A Microcosm Approach

    PubMed Central

    Krause, Evamaria; Wichels, Antje; Giménez, Luis; Lunau, Mirko; Schilhabel, Markus B.; Gerdts, Gunnar

    2012-01-01

    As the atmospheric CO2 concentration rises, more CO2 will dissolve in the oceans, leading to a reduction in pH. Effects of ocean acidification on bacterial communities have mainly been studied in biologically complex systems, in which indirect effects, mediated through food web interactions, come into play. These approaches come close to nature but suffer from low replication and neglect seasonality. To comprehensively investigate direct pH effects, we conducted highly-replicated laboratory acidification experiments with the natural bacterial community from Helgoland Roads (North Sea). Seasonal variability was accounted for by repeating the experiment four times (spring, summer, autumn, winter). Three dilution approaches were used to select for different ecological strategies, i.e. fast-growing or low-nutrient adapted bacteria. The pH levels investigated were in situ seawater pH (8.15–8.22), pH 7.82 and pH 7.67, representing the present-day situation and two acidification scenarios projected for the North Sea for the year 2100. In all seasons, both automated ribosomal intergenic spacer analysis and 16S ribosomal amplicon pyrosequencing revealed pH-dependent community shifts for two of the dilution approaches. Bacteria susceptible to changes in pH were different members of Gammaproteobacteria, Flavobacteriaceae, Rhodobacteraceae, Campylobacteraceae and further less abundant groups. Their specific response to reduced pH was often context-dependent. Bacterial abundance was not influenced by pH. Our findings suggest that already moderate changes in pH have the potential to cause compositional shifts, depending on the community assembly and environmental factors. By identifying pH-susceptible groups, this study provides insights for more directed, in-depth community analyses in large-scale and long-term experiments. PMID:23071704

  19. The Added Value of a PhD in Medicine--PhD Students' Perceptions of Acquired Competences

    ERIC Educational Resources Information Center

    Anttila, Henrika; Lindblom-Ylänne, Sari; Lonka, Kristi; Pyhältö, Kirsi

    2015-01-01

    PhD in the field of medicine is more common than in any other domain. Many medical doctors are driven towards PhD, but also students with other backgrounds (usually MSc) are conducting a PhD in medical schools. Higher education has invested a lot in developing generic and research competences. Still little is known about how PhD students…

  20. pH. Agricultural Lesson Plans.

    ERIC Educational Resources Information Center

    Southern Illinois Univ., Carbondale. Dept. of Agricultural Education and Mechanization.

    This lesson plan is intended for use in conducting classes on the effect of pH on plant growth. Presented first are an attention step/problem statement and a series of questions and answers designed to convey general information about soil pH and its effect on plants. The following topics are among those discussed: acidity and alkalinity; the…

  1. The seasonal influence on the spatial distribution of dissolved selected metals in Lake Naivasha, Kenya

    NASA Astrophysics Data System (ADS)

    Kamau, Joseph Nyingi; Gachanja, Anthony; Ngila, Catherine; Kazungu, Johnson Michael; Zhai, Mingzhe

    Lake Naivasha is the only freshwater Lake in Rift Valley, in Kenya. It lies in a fertile semi-arid basin. The Lake has no surface water outlet and is presumed to be under stress. Dissolved metals are directly taken up by bacteria, algae, plants, and planktonic and benthic organisms. Dissolved metals can also adsorb to particulate matter in water column and enter aquatic organisms through various routes. Cadmium, copper, lead and zinc may bioaccumulate within lower organisms, yet they do not biomagnify up the food chain as do mercury and selenium. This study reports on the levels and distribution of dissolved heavy metals and investigates the influence of physicochemical parameters on metal mobilization. The bioavailability of selected metals was investigated by relating the levels of dissolved metals to that in fish. Water abstraction for irrigation and domestic use, compounded with organic matter inflow will affect physicochemical parameters and hence influences the mobilization of heavy metals. Dissolved Zn correlated highly with sediment pH (r = 0.67) indicating that dissolution increases with increase in pH. In addition, the fact that the pH also correlated positively with organic matter r = 0.50, Eh r = 0.63, temperature r = 0.56 and dissolved oxygen r = 56, would suggest that organic bound Zn contributed significantly to the concentration of dissolved Zn. In situ flux experiments indicated that the fringing papyrus reeds located along the shores of Lake Naivasha provided sites for metal immobilization due to their coprecipitation on redox sensitive.

  2. Online dissolved methane and total dissolved sulfide measurement in sewers.

    PubMed

    Liu, Yiwen; Sharma, Keshab R; Fluggen, Markus; O'Halloran, Kelly; Murthy, Sudhir; Yuan, Zhiguo

    2015-01-01

    Recent studies using short-term manual sampling of sewage followed by off-line laboratory gas chromatography (GC) measurement have shown that a substantial amount of dissolved methane is produced in sewer systems. However, only limited data has been acquired to date due to the low frequency and short span of this method, which cannot capture the dynamic variations of in-sewer dissolved methane concentrations. In this study, a newly developed online measuring device was used to monitor dissolved methane concentrations at the end of a rising main sewer network, over two periods of three weeks each, in summer and early winter, respectively. This device uses an online gas-phase methane sensor to measure methane under equilibrium conditions after being stripped from the sewage. The data are then converted to liquid-phase methane concentrations according to Henry's Law. The detection limit and range are suitable for sewer application and can be adjusted by varying the ratio of liquid-to-gas phase volume settings. The measurement presented good linearity (R² > 0.95) during field application, when compared to off-line measurements. The overall data set showed a wide variation in dissolved methane concentration of 5-15 mg/L in summer and 3.5-12 mg/L in winter, resulting in a significant average daily production of 24.6 and 19.0 kg-CH₄/d, respectively, from the network with a daily average sewage flow of 2840 m³/day. The dissolved methane concentration demonstrated a clear diurnal pattern coinciding with flow and sulfide fluctuation, implying a relationship with the wastewater hydraulic retention time (HRT). The total dissolved sulfide (TDS) concentration in sewers can be determined simultaneously with the same principle. PMID:25462721

  3. Reducing emissions from uranium dissolving

    SciTech Connect

    Griffith, W.L.; Compere, A.L.; Huxtable, W.P.; Googin, J.M.

    1992-10-01

    This study was designed to assess the feasibility of decreasing NO{sub x} emissions from the current uranium alloy scrap tray dissolving facility. In the current process, uranium scrap is dissolved in boiling nitric acid in shallow stainless-steel trays. As scrap dissolves, more metal and more nitric acid are added to the tray by operating personnel. Safe geometry is assured by keeping liquid level at or below 5 cm, the depth of a safe infinite slab. The accountability batch control system provides additional protection against criticality. Both uranium and uranium alloys are dissolved. Nitric acid is recovered from the vapors for reuse. Metal nitrates are sent to uranium recovery. Brown NO{sub x} fumes evolved during dissolving have occasionally resulted in a visible plume from the trays. The fuming is most noticeable during startup and after addition of fresh acid to a tray. Present environmental regulations are expected to require control of brown NO{sub x} emissions. A detailed review of the literature, indicated the feasibility of slightly altering process chemistry to favor the production of NO{sub 2} which can be scrubbed and recycled as nitric acid. Methods for controlling the process to manage offgas product distribution and to minimize chemical reaction hazards were also considered.

  4. Reducing emissions from uranium dissolving

    SciTech Connect

    Griffith, W.L.; Compere, A.L.; Huxtable, W.P.; Googin, J.M.

    1992-10-01

    This study was designed to assess the feasibility of decreasing NO[sub x] emissions from the current uranium alloy scrap tray dissolving facility. In the current process, uranium scrap is dissolved in boiling nitric acid in shallow stainless-steel trays. As scrap dissolves, more metal and more nitric acid are added to the tray by operating personnel. Safe geometry is assured by keeping liquid level at or below 5 cm, the depth of a safe infinite slab. The accountability batch control system provides additional protection against criticality. Both uranium and uranium alloys are dissolved. Nitric acid is recovered from the vapors for reuse. Metal nitrates are sent to uranium recovery. Brown NO[sub x] fumes evolved during dissolving have occasionally resulted in a visible plume from the trays. The fuming is most noticeable during startup and after addition of fresh acid to a tray. Present environmental regulations are expected to require control of brown NO[sub x] emissions. A detailed review of the literature, indicated the feasibility of slightly altering process chemistry to favor the production of NO[sub 2] which can be scrubbed and recycled as nitric acid. Methods for controlling the process to manage offgas product distribution and to minimize chemical reaction hazards were also considered.

  5. Dynamics of Planktonic Prokaryotes and Dissolved Carbon in a Subtropical Coastal Lake

    PubMed Central

    Fontes, Maria Luiza S.; Tonetta, Denise; Dalpaz, Larissa; Antnio, Regina V.; Petrucio, Maurcio M.

    2013-01-01

    To understand the dynamics of planktonic prokaryotes in a subtropical lake and its relationship with carbon, we conducted water sampling through four 48-h periods in Peri Lake for 1?year. Planktonic prokaryotes were characterized by the abundance and biomass of heterotrophic bacteria (HB) and of cyanobacteria (coccoid and filamentous cells). During all samplings, we measured wind speed, water temperature (WT), pH, dissolved oxygen (DO), precipitation, dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and carbon dioxide (CO2). DOC was higher in the summer (average?=?465??M WT?=?27C) and lower in the winter (average?=?235??M WT?=?17C), with no significant variability throughout the daily cycles. CO2 concentrations presented a different pattern, with a minimum in the warm waters of the summer period (8.31??M) and a maximum in the spring (37.13??M). Daily trends were observed for pH, DO, WT, and CO2. At an annual scale, both biological and physical-chemical controls were important regulators of CO2. HB abundance and biomass were higher in the winter sampling (5.60??109?cells?L?1 and 20.83??mol?C?L?1) and lower in the summer (1.87??109?cells?L?1 and 3.95??mol?C?L?1). Filamentous cyanobacteria (0.23??1080.68??108?filaments?L?1) produced up to 167.16??mol?C?L?1 as biomass (during the warmer period), whereas coccoid cyanobacteria contributed only 0.38??mol?C?L?1. Precipitation, temperature, and the biomass of HB were the main regulators of CO2 concentrations. Temperature had a negative effect on the concentration of CO2, which may be indirectly attributed to high heterotroph activity in the autumn and winter periods. DOC was positively correlated with the abundance of total cyanobacteria and negatively with HB. Thus, planktonic prokaryotes have played an important role in the dynamics of both dissolved inorganic and organic carbon in the lake. PMID:23579926

  6. Reducing Emissions from Uranium Dissolving

    SciTech Connect

    Griffith, W.L.

    1992-01-01

    This study was designed to assess the feasibility of decreasing NO{sub x} emissions from the current uranium alloy scrap tray dissolving facility. In the current process, uranium scrap is dissolved in boiling nitric acid in shallow stainless-steel trays. As scrap dissolves, more metal and more nitric acid are added to the tray by operating personnel. Safe geometry is assured by keeping liquid level at or below 5 cm, the depth of a safe infinite slab. The accountability batch control system provides additional protection against criticality. The trays are steam coil heated. The process has operated satisfactorily, with few difficulties, for decades. Both uranium and uranium alloys are dissolved. Nitric acid is recovered from the vapors for reuse. Metal nitrates are sent to uranium recovery. Brown NO{sub x} fumes evolved during dissolving have occasionally resulted in a visible plume from the trays. The fuming is most noticeable during startup and after addition of fresh acid to a tray. Present environmental regulations are expected to require control of brown NO{sub x} emissions. Because NO{sub x} is hazardous, fumes should be suppressed whenever the electric blower system is inoperable. Because the tray dissolving process has worked well for decades, as much of the current capital equipment and operating procedures as possible were preserved. A detailed review of the literature, indicated the feasibility of slightly altering process chemistry to favor the production of NO{sub 2}, which can be scrubbed and recycled as nitric acid. Methods for controlling the process to manage offgas product distribution and to minimize chemical reaction hazards were also considered.

  7. Spatial Variability of Dissolved Organic Carbon in Headwater Wetlands in Central Pennsylvania

    NASA Astrophysics Data System (ADS)

    Reichert-Eberhardt, A. J.; Wardrop, D.; Boyer, E. W.

    2011-12-01

    Dissolved organic carbon (DOC) is known to be of an important factor in many microbially mediated biochemical processes, such as denitrification, that occur in wetlands. The spatial variability of DOC within a wetland could impact the microbes that fuel these processes, which in turn can affect the ecosystem services provided by wetlands. However, the amount of spatial variability of DOC in wetlands is generally unknown. Furthermore, it is unknown how disturbance to wetlands can affect spatial variability of DOC. Previous research in central Pennsylvania headwater wetland soils has shown that wetlands with increased human disturbance had decreased heterogeneity in soil biochemistry. To address groundwater chemical variability 20 monitoring wells were installed in a random pattern in a 400 meter squared plot in a low-disturbance headwater wetland and a high-disturbance headwater wetland in central Pennsylvania. Water samples from these wells will be analyzed for DOC, dissolved inorganic carbon, nitrate, ammonia, and sulfate concentrations, as well as pH, conductivity, and temperature on a seasonal basis. It is hypothesized that there will be greater spatial variability of groundwater chemistry in the low disturbance wetland than the high disturbance wetland. This poster will present the initial data concerning DOC spatial variability in both the low and high impact headwater wetlands.

  8. Dissolved heavy metal determination and ecotoxicological assessment: a case study of the corumbataí river (são paulo, Brazil).

    PubMed

    Aparecida Maranho, Lucineide; Teresinha Maranho, Leila; Grossi Botelho, Rafael; Luiz Tornisielo, Valdemar

    2014-09-01

    The aim of this one-year study (August 2009 to July 2010) was to evaluate the Corumbataí River water polluted by anthropogenic sources and see how it affects the reproduction of the microcrustacean Ceriodaphnia dubia (Richard, 1984) in laboratory conditions over seven days of exposure to water samples collected monthly at six different locations. We determined the concentrations of zinc (Zn), copper (Cu), nickel (Ni), lead (Pb), and cadmium (Cd), as well as physicochemical parameters such as dissolved oxygen, conductivity, water temperature, and pH. Dissolved oxygen and conductivity demonstrated anthropogenic influence, as dissolved oxygen concentration decreased and conductivity increased from the upstream to the downstream stretch of the river. The effects on C. dubia were observed in the months with high precipitation, but the toxicity cannot be associated with any particular contaminant. Heavy metal levels kept well below the limit values. Zn and Pb had the highest concentrations in the water during the sampling period, probably due to the industrial and agricultural influence. However, these levels do not seem to be associated with precipitation, which suggests that their primary source was industry. Physicochemical parameters, the ecotoxicological assay, and determination of heavy metals proved to be efficient tools to evaluate aquatic environments. PMID:25274936

  9. Dissolving pulp from jute stick.

    PubMed

    Matin, Mhafuza; Rahaman, M Mostafizur; Nayeem, Jannatun; Sarkar, Mamon; Jahan, M Sarwar

    2015-01-22

    Jute stick is woody portion of jute plant, which remain as leftover after extracting bast fibre. Presently, it is being used for fencing in the rural area. In this investigation, biorefinery concept was initiated in producing dissolving pulp from jute stick by pre-hydrolysis kraft process. At 170°C for 1h of pre-hydrolysis, 70% of hemicelluloses was dissolved with negligible loss of α-cellulose. At this condition, 75% of dissolved sugars in the pre-hydrolysis liquor were in the oligomeric form. The pre-hydrolysed jute stick was subsequently pulped by kraft process with the variation of active alkali. The pulp yield was 36.2% with kappa number 18.5 at the conditions of 16% active alkali for 2h of cooking at 170°C. Final pulp was produced with 92% α-cellulose and 89% brightness after D0EpD1EpD1 bleaching. The produced dissolving pulp can be used in rayon production. PMID:25439866

  10. METHOD OF DISSOLVING METALLIC URANIUM

    DOEpatents

    Schulz, W.W.

    1959-07-28

    A process is presented for more rapidly dissolving metallic uranium which comprises contacting the uranium with a mixture of nitric and phosphoric acids. The preferred concentration is a mixture which is about 10 M in nitric acid and between 0.1 to 0.15 M in phosphoric acid.

  11. Dissolved gas - the hidden saboteur

    SciTech Connect

    Magorien, V.G.

    1993-12-31

    Almost all hydraulic power components, to properly perform their tasks, rely on one basic, physical property, i.e., the incompressibility of the working fluid. Unfortunately, a frequently overlooked fluid property which frustrates this requirement is its ability to absorb, i.e., dissolve, store and give off gas. The gas is, most often but not always, air. This property is a complex one because it is a function not only of the fluid`s chemical make-up but temperature, pressure, exposed area, depth and time. In its relationshiop to aircraft landing-gear, where energy is absorbed hydraulically, this multi-faceted fluid property can be detrimental in two ways: dynamically, i.e., loss of energy absorption ability and statically, i.e., improper aircraft attitude on the ground. The pupose of this paper is to bring an awareness to this property by presenting: (1) examples of these manifestations with some empirical and practical solutions to them, (2) illustrations of this normally `hidden saboteur` at work, (3) Henry`s Dissolved Gas Law, (4) room-temperature, saturated values of dissolved gas for a number of different working fluids, (5) a description of the instrument used to obtain them, (6) some `missing elements` of the Dissolved Gas Law pertaining to absoption, (7) how static and dynamic conditions effect gas absorption and (8) some recommended solutions to prevent becoming a victim of this `hidden saboteur`

  12. Use of iron salts to control dissolved sulfide in trunk sewers

    SciTech Connect

    Padival, N.A.; Kimbell, W.A.; Redner, J.A.

    1995-11-01

    Sewer headspace H{sub 2}S reduction by precipitating dissolved sulfide in wastewater was investigated using iron salt (FeCl{sub 3} and FeCl{sub 2}). Full-scale experiments were conducted in a 40-km (25 mi) sewer with an average flow of 8.7 m{sup 3}/s (200 mgd). Results were sensitive to total Fe dosages and Fe(III)/Fe(II) blend ratios injected. A concentration of 16 mg/L total Fe and a blend ratio of 1.9:1 [Fe(III):Fe(II)] reduced dissolved sulfide levels by 97%. Total sulfide and headspace H{sub 2}S were reduced by 63% and 79%, respectively. Liquid and gas-phase sulfide reductions were largely due to the effective precipitation of sulfide with Fe(III) and Fe(II) and the limited volatilization of H{sub 2}S, respectively. Oxidation of sulfide in the presence of Fe(II) and minute amounts of O{sub 2} may have occurred. A combination of Fe(III) and Fe(II) proved more effective than either salt alone. By using excess Fe(III), dissolved sulfide can be reduced to undetectable levels. No specific relation between the concentration of Fe or Fe(III)/Fe(II) blend ratio and sewer crown pH was inferred. Iron salts may retard crown corrosion rates by precipitating free sulfide and reducing its release to the sewer headspace as H{sub 2}S. A mechanism to inhibit certain responsible bacteria was not established in the 40-km (25 mi) sewer.

  13. Fiber-optic dissolved oxygen and dissolved carbon dioxide sensors using fluorophores encapsulated in sol gel matrices

    NASA Astrophysics Data System (ADS)

    Kwon, Hyeog-Chan

    Fiber optic chemical sensors (FOCS) for oxygen, dissolved oxygen (DO), and dissolved CO2 sensing using thin films of fluorophores encapsulated in sol-gel matrices were made and tested. The DO/O2 sensor used ruthenium(II) tris(4,7-diphenyl-1,10-phenanthroline) perchlorate (Ru(Ph 2Phen)Cl2) as the oxygen sensitive fluorophore and methyltrimethoxysilane (MTMS) sol-gel as the encapsulating matrix material. For the DCO2 sensor, 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS) co-doped with sodium bicarbonate was used as the DCO2 sensitive fluorophore-chemical system and diisobutoxy-alumino triethoxysilane (ASE) sol-gel was used as the encapsulating matrix material. It was found that oxygen quenches the excited state Ru(Ph2Phen)Cl 2 by diffusing through the MTMS matrix. Continuous excitation of Ru(Ph 2Phen)Cl2 during MTMS drying resulted in long, single exponential lifetimes of the metal complex and increased sensor sensitivity. When the sensor was field tested, it was found to have an excellent match compared to conventional titration method for determining dissolved oxygen concentrations and had fast response times. It was determined that this sensor measured the vapor pressure of oxygen rather than the absolute concentration of dissolved oxygen. For DCO2 sensing, it was found that the dynamic response of the senor could be tuned by varying the HPTS to NaHCO3 ratios. The sensor had fast response times compared to other fiber optic DCO 2 sensors reported which typically have response times of minutes.

  14. DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS

    SciTech Connect

    P. Bernot

    2005-07-13

    The purpose of this study is to evaluate dissolved concentration limits (also referred to as solubility limits) of elements with radioactive isotopes under probable repository conditions, based on geochemical modeling calculations using geochemical modeling tools, thermodynamic databases, field measurements, and laboratory experiments. The scope of this activity is to predict dissolved concentrations or solubility limits for elements with radioactive isotopes (actinium, americium, carbon, cesium, iodine, lead, neptunium, plutonium, protactinium, radium, strontium, technetium, thorium, and uranium) relevant to calculated dose. Model outputs for uranium, plutonium, neptunium, thorium, americium, and protactinium are provided in the form of tabulated functions with pH and log fCO{sub 2} as independent variables, plus one or more uncertainty terms. The solubility limits for the remaining elements are either in the form of distributions or single values. Even though selection of an appropriate set of radionuclides documented in Radionuclide Screening (BSC 2002 [DIRS 160059]) includes actinium, transport of Ac is not modeled in the total system performance assessment for the license application (TSPA-LA) model because of its extremely short half-life. Actinium dose is calculated in the TSPA-LA by assuming secular equilibrium with {sup 231}Pa (Section 6.10); therefore, Ac is not analyzed in this report. The output data from this report are fundamental inputs for TSPA-LA used to determine the estimated release of these elements from waste packages and the engineered barrier system. Consistent modeling approaches and environmental conditions were used to develop solubility models for the actinides discussed in this report. These models cover broad ranges of environmental conditions so they are applicable to both waste packages and the invert. Uncertainties from thermodynamic data, water chemistry, temperature variation, and activity coefficients have been quantified or otherwise addressed.

  15. Rapidly dissolving repaglinide powders produced by the ultra-rapid freezing process.

    PubMed

    Purvis, Troy; Mattucci, Michal E; Crisp, M Todd; Johnston, Keith P; Williams, Robert O

    2007-01-01

    The objective of the study was to produce rapidly dissolving formulations of the poorly water-soluble drug repaglinide using an innovative new technology, ultra-rapid freezing (URF), and to investigate the influence of excipient type on repaglinide stability. Repaglinide compositions containing different types and levels of excipients and different drug potencies (50%-86%) were produced by the URF technology. Repaglinide/excipient solutions were frozen on a cryogenic substrate, collected, and lyophilized to form a dry powder. Surfactants, including sodium dodecyl sulfate, and alkalizing agents such as diethanolamine (DEA) and tromethamine (TRIS) were incorporated into the compositions. Forced degradation of repaglinide was conducted under stressed conditions (eg, elevated temperature, exposure to peroxide) to determine the stability of the drug in such environments. The solubility of repaglinide increased as a function of increasing pH; therefore, incorporation of an alkalizing agent into the URF formulations increased the drug's solubility. Drug instability resulted when the drug was exposed to pH values above 9.0. URF formulations containing alkalizing agents showed no degradation or spontaneous recrystallization in the formulation, indicating that increased stability was afforded by processing. URF processing created nanostructured drug/excipient particles with higher dissolution rates than were achieved for unprocessed drug. Alkalizing agents such as TRIS and DEA, present at levels of 25% to 33% wt/wt in the formulations, did not cause degradation of the drug when processed using URF. URF processing, therefore, yielded fast-dissolving formulations that were physically and chemically stable, resistant to alkali degradation or spontaneous recrystallization in the formulation. PMID:17915808

  16. Exercise and Pulmonary Hypertension (PH)

    MedlinePlus

    ... Coping as a Teenager with PH Coping with High School Speaking of PH... with Teachers Friends, Family and ... Coping as a Teenager with PH Coping with High School Speaking of PH... with Teachers Friends, Family and ...

  17. Carbon uptake in low dissolved inorganic carbon environments: the effect of limited carbon availability on photosynthetic organisms in thermal waters

    NASA Astrophysics Data System (ADS)

    Myers, K. D.; Omelon, C. R.; Bennett, P.

    2010-12-01

    Photosynthesis is the primary carbon fixation process in thermal waters below 70°C, but some hydrothermal waters have extremely low dissolved inorganic carbon (DIC), potentially limiting the growth of inorganic carbon fixing organisms such as algae and cyanobacteria. To address the issue of how carbon is assimilated by phototrophs in these environments, we conducted experiments to compare inorganic carbon uptake mechanisms by two phylogenetically distinct organisms collected from geographically distinct carbon limited systems: the neutral pH geothermal waters of El Tatio, Chile, and the acidic geothermal waters of Tantalus Creek in Norris Geyser Basin, Yellowstone National Park. Discharge waters at El Tatio have low total DIC concentrations (2 to 6 ppm) found mainly as HCO3-; this is in contrast to even lower measured DIC values in Tantalus Creek (as low as 0.13 ppm) that, due to a measured pH of 2.5, exists primarily as CO2. Cyanobacteria and algae are innately physiologically plastic, and we are looking to explore the possibility that carbon limitation in these environments is extreme enough to challenge that plasticity and lead to a suite of carbon uptake adaptations. We hypothesize that these microorganisms utilize adaptive modes of Ci uptake that allow them to survive under these limiting conditions. Cyanobacteria (primarily Synechococcus spp.) isolated from El Tatio can utilize either passive CO2 uptake or active HCO3- uptake mechanisms, in contrast to the eukaryotic alga Cyanidium spp. from Tantalus Creek, which is restricted to an energy-dependent CO2 uptake mechanism. To test this hypothesis, we conducted pH drift experiments (Omelon et al., 2008) to examine changes in pH and [DIC] under a range of pH and [DIC] culture conditions. This work provides baseline information upon which we will begin to investigate the effects of low [DIC] on the growth of phototrophs collected from these and other less carbon limited systems.

  18. Dissolved oxygen concentration affects hybrid striped bass growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Management of dissolved oxygen (DO) concentration in ponds at night during the growing season is important because fish growth and yield are greater in ponds with higher nightly DO concentrations. Three studies were conducted to quantify performance traits and metabolic responses of hybrid striped b...

  19. On Calibration of pH Meters

    PubMed Central

    Cheng, K. L.; Zhu, Da-Ming

    2005-01-01

    The calibration of pH meters including the pH glass electrode, ISE electrodes, buffers, and the general background for calibration are reviewed. Understanding of basic concepts of pH, pOH, and electrode mechanism is emphasized. New concepts of pH, pOH, as well as critical examination of activity, and activity coefficients are given. The emergence of new solid state pH electrodes and replacement of the salt bridge with a conducting wire have opened up a new horizon for pH measurements. A pH buffer solution with a conducting wire may be used as a stable reference electrode. The misleading unlimited linear Nernstian slope should be discarded. Calibration curves with 3 nonlinear portions for the entire 0—14 pH range due to the isoelectric point change effect are explained. The potential measurement with stirring or unstirring and effects by double layer (DL) and triple layer (TL) will be discussed.

  20. Photochemical flocculation of terrestrial dissolved organic matter and iron

    NASA Astrophysics Data System (ADS)

    Helms, John R.; Mao, Jingdong; Schmidt-Rohr, Klaus; Abdulla, Hussain; Mopper, Kenneth

    2013-11-01

    Dissolved organic matter (DOM) rich water samples (Great Dismal Swamp, Virginia) were 0.1-μm filtered and UV-irradiated in a solar simulator for 30 days. During the irradiation, pH increased, particulate organic matter (POM) and particulate iron formed. After 30 days, 7% of the dissolved organic carbon (DOC) was converted to POC while 75% was remineralized. Approximately 87% of the iron was removed from the dissolved phase after 30 days, but iron did not flocculate until a major fraction of DOM was removed by photochemical degradation and flocculation (>10 days); thus, during the initial 10 days, there were sufficient organic ligands present or the pH was low enough to keep iron in solution. Nuclear magnetic resonance and Fourier transform infrared spectroscopies indicated that photochemically flocculated POM was more aliphatic than the residual non-flocculated DOM. Photochemically flocculated POM was also enriched in amide functionality, while carbohydrate-like material was resistant to both photochemical degradation and flocculation. Abiotic photochemical flocculation likely removes a significant fraction of terrestrial DOM from the upper water column between headwaters and the ocean, but has previously been ignored. Preliminary evidence suggests that this process may significantly impact the transport of DOM and POM in ocean margin environments including estuaries.

  1. Solubility and Diffusivity of Water in Basic Silicate Melts at Low pH2O

    NASA Astrophysics Data System (ADS)

    Newcombe, M.; Brett, A.; Beckett, J.; Baker, M. B.; Newman, S.; Stolper, E. M.

    2012-12-01

    Solubility experiments were conducted at 1 atm by equilibrating melts corresponding to a synthetic Apollo 15 yellow glass (AY) [1] and the 1 atm eutectic composition on the anorthite-diopside join (AD) with H2O-CO2 gas mixtures at 1350°C. Each melt composition was equilibrated at a range of pH2O, pH2, and pO2 (by varying the H2/CO2 ratio of the gas); concentrations of hydroxyl (OH) in the quenched glasses were measured by FTIR and ranged from 10s to 100s of ppm. Our results confirm that the concentrations of OH dissolved in both the AY and AD melts are proportional to pH2O0.5 under these conditions. Moreover, the amount of dissolved OH depends only on pH2O and is independent of pH2 and pO2 across the significant experimental range (6 orders of magnitude in pO2 and 3 orders of magnitude in pH2/pH2O). Apparent diffusivities of total water (D*water [2, 3]) were determined in AD melt at 1350°C and 1 atm over significant ranges of pH2/pH2O (~0.013-1.4) and pO2 (IW-0.5 to IW+3.5). AD melts were fused in a Pt crucible at 1350°C and IW+1 for ~70 hr under a CO-CO2 gas mixture. Samples equilibrated in this way contain < 50 ppm water as OH (as measured by FTIR). With the dehydrated sample still hanging in the furnace, the gas mixture was changed to a H2-CO2 mixture, fixing pH2O and pH2 and maintaining the same pO2 as in the CO-CO2 gas mixture. After exposure to the H2-CO2 gas mixture for 5-10 min (which generated a ~103 μm diffusion profile in OH inward from the sample edge), the sample was quenched in deionized H2O. The diffusively generated concentration profiles in four experimental AD charges were measured by FTIR and SIMS. The four diffusion experiments on AD melt yield best-fit values for D*water of 1-3 × 10-10 m2s-1. Our results demonstrate that D*water is approximately constant over two orders of magnitude in pH2/pH2O, implying that diffusion of H2 does not make a significant contribution to the transport of total water in AD melt under these conditions. D*water determined in this study is ~10-100 times greater than D*water predicted by extrapolations of the speciation model [2, 3] that assumes mobile H2O molecules (with constant DH2Omol) and immobile OH groups (DOH=0). However, our preliminary results are well described by a modified speciation model in which hydroxyl groups are allowed to diffuse. This is consistent with the findings of [4] for haploandesite melt. Extension of these measurements of the diffusivity of OH to closer analogues of lunar basaltic melts will improve understanding of the mobility of H-bearing species in nature and will be directly applicable to modeling degassing of lunar magmas [e.g., 5, 6]. [1] Delano (1986) JGR, 91(B4), D201-D213. [2] Zhang et al. (1991) GCA, 55, 441-456. [3] Zhang & Stolper (1991) Nature, 351, 306-309. [4] Ni et al. (2012) submitted. [5] Saal et al. (2008) Nature, 454, 192-195. [6] Hauri et al. (2011) Science, 333, 213-215.

  2. Phosphorus and nitrogen sorption to soils in the presence of poultry litter-derived dissolved organic matter.

    PubMed

    Goyne, Keith W; Jun, Hee-Joong; Anderson, Stephen H; Motavalli, Peter P

    2008-01-01

    Two environmental aspects associated with land application of poultry litter that have not been comprehensively evaluated are (i) the competition of dissolved organic matter (DOM) and P for soil sorption sites, and (ii) the sorption of dissolved organic nitrogen (DON) relative to inorganic nitrogen species (e.g., NO(3)(-) and NH(4)(+)) and dissolved organic carbon (DOC). The competition between DOM and P for sorption sites has often been assumed to increase the amount of P available for plant growth; however, elevating DOM concentrations may also increase P available for transport to water resources. Batch sorption experiments were conducted to (i) evaluate soil properties governing P sorption to benchmark soils of Southwestern Missouri, (ii) elucidate the impact of poultry litter-derived DOM on P sorption, and (iii) investigate DON retention relative to inorganic N species and DOC. Soils were reacted for 24 h with inorganic P (0-60 mg L(-1)) in the presence and absence of DOM (145 mg C L(-1)) using a background electrolyte solution comparable to DOM extracts (I = 10.8 mmol L(-1); pH 7.7). Soil P sorption was positively correlated with metal oxide (r(2) = 0.70) and clay content (r(2) = 0.79) and negatively correlated with Bray-1 extractable P (r(2) = 0.79). Poultry litter-derived DOM had no significant negative impact on P sorption. Dissolved organic nitrogen was preferentially removed from solution relative to (NO(3)(-)-N + NO(2)(-)-N), NH(4)(+)-N, and DOC. This research indicates that poultry litter-derived DOM is not likely to enhance inorganic P transport which contradicts the assumption that DOM released from organic wastes increases plant-available P when organic amendments and fertilizer P are co-applied. Additionally, this work demonstrates the need to further evaluate the fate and transport of DON in agroecosystem soils receiving poultry litter applications. PMID:18178888

  3. Dissolving mechanism of strain P17 on insoluble phosphorus of yellow-brown soil.

    PubMed

    Zhong, Chuan-qing; Cao, Guang-xiang; Huang, Wei-yi; Luan, Xing-she; Yang, Yi-fei

    2014-01-01

    Strain P17 was a bacterial strain identified as Bacillus megaterium isolated from ground accumulating phosphate rock powder. The fermentation broth of strain P17 and the yellow-brown soil from Nanjing Agricultural University garden were collected to conduct this study. The simulation of fixed insoluble phosphorous forms after applying calcium superphosphate into yellow-brown soil was performed in pots, while available P and total P of soil were extremely positive correlative with those of groundwater. Then the dissolving effect of strain P17 on insoluble P of yellow-brown soil was studied. Results showed that Bacillus megaterium strain P17 had notable solubilizing effect on insoluble phosphates formed when too much water-soluble phosphorous fertilizer used. During 100 days after inoculation, strain P17 was dominant. Until the 120th day, compared with water addition, available P of strain P17 inoculation treated soil increased by 3 times with calcium superphosphate addition. Besides available P, pH, activity of acid and alkaline phosphatase and population of P-solubilizing microbes were detected respectively. P-solubilizing mechanism of P-solubilizing bacteria strain P17 seems to be a synergetic effect of pH decrease, organic acids, phosphatase, etc. PMID:25477929

  4. Dissolving mechanism of strain P17 on insoluble phosphorus of yellow-brown soil

    PubMed Central

    Chuan-qing, Zhong; Guang-xiang, Cao; Wei-yi, Huang; Xing-she, Luan; Yi-fei, Yang

    2014-01-01

    Strain P17 was a bacterial strain identified as Bacillus megaterium isolated from ground accumulating phosphate rock powder. The fermentation broth of strain P17 and the yellow-brown soil from Nanjing Agricultural University garden were collected to conduct this study. The simulation of fixed insoluble phosphorous forms after applying calcium superphosphate into yellow-brown soil was performed in pots, while available P and total P of soil were extremely positive correlative with those of groundwater. Then the dissolving effect of strain P17 on insoluble P of yellow-brown soil was studied. Results showed that Bacillus megaterium strain P17 had notable solubilizing effect on insoluble phosphates formed when too much water-soluble phosphorous fertilizer used. During 100 days after inoculation, strain P17 was dominant. Until the 120th day, compared with water addition, available P of strain P17 inoculation treated soil increased by 3 times with calcium superphosphate addition. Besides available P, pH, activity of acid and alkaline phosphatase and population of P-solubilizing microbes were detected respectively. P-solubilizing mechanism of P-solubilizing bacteria strain P17 seems to be a synergetic effect of pH decrease, organic acids, phosphatase, etc. PMID:25477929

  5. Adsorption and desorption of dissolved organic matter by carbon nanotubes: Effects of solution chemistry.

    PubMed

    Engel, Maya; Chefetz, Benny

    2016-06-01

    Increasing use of carbon nanotubes (CNTs) has led to their introduction into the environment where they can interact with dissolved organic matter (DOM). This study focuses on solution chemistry effects on DOM adsorption/desorption processes by single-walled CNTs (SWCNTs). Our data show that DOM adsorption is controlled by the attachment of DOM molecules to the SWCNTs, and that the initial adsorption rate is dependent on solution parameters. Adsorbed amount of DOM at high ionic strength was limited, possibly due to alterations in SWCNT bundling. Desorption of DOM performed at low pH resulted in additional DOM adsorption, whereas at high pH, adsorbed DOM amount decreased. The extent of desorption conducted at increased ionic strength was dependent on pre-adsorbed DOM concentration: low DOM loading stimulated additional adsorption of DOM, whereas high DOM loading facilitated release of adsorbed DOM. Elevated ionic strength and increased adsorbed amount of DOM reduced the oxidation temperature of the SWCNTs, suggesting that changes in the assembly of the SWCNTs had occurred. Moreover, DOM-coated SWCNTs at increased ionic strength provided fewer sites for atrazine adsorption. This study enhances our understanding of DOM-SWCNT interactions in aqueous systems influenced by rapid changes in salinity, and facilitates potential use of SWCNTs in water-purification technologies. PMID:26878603

  6. EFFECTS OF LOW DISSOLVED OXYGEN ON SURVIVAL AND REPRODUCTION OF DAPHNIA, HYALELLA, AND GAMMARUS

    EPA Science Inventory

    Daphnia magna, Daphnia pulex, Hyalella azteca, and Gammarus lacustris were exposed to low dissolved oxygen concentrations in the laboratory. Acute and chronic exposures were conducted to develop data for use in the EPA Water Quality Criteria document for dissolved oxygen. . magna...

  7. Azomethine H colorimetric method for determining dissolved boron in water

    USGS Publications Warehouse

    Spencer, R.R.; Erdmann, D.E.

    1979-01-01

    An automated colorimetric method for determining dissolved boron in water is described. The boron is complexed with azomethine H, which is readily available as the condensation product of H acid (8-amino-1-naphthol-3,6-disulfonic acid) and salicylaldehyde. The absorbance of the yellow complex formed is then measured colorimetrically at 410 nm. Interference effects from other dissolved species are minimized by the addition of diethylenetriaminepentaacetic acid (DTPA); however, iron, zinc, and bicarbonate interfere at concentrations above 400 ??g/L, 2000 ??g/L, and 200 mg/L, respectively. The bicarbonate interference can be eliminated by careful acidification of the sample with concentrated HCl to a pH between 5 and 6. Thirty samples per hour can be routinely analyzed over the range of from 10 to 400 ??g/L, boron.

  8. Determination of dissolved aluminum in water samples

    USGS Publications Warehouse

    Afifi, A.A.

    1983-01-01

    A technique has been modified for determination of a wide range of concentrations of dissolved aluminum (Al) in water and has been tested. In this technique, aluminum is complexed with 8-hydroxyquinoline at pH 8.3 to minimize interferences, then extracted with methyl isobutyl ketone (MIBK). The extract is analyzed colorimetrically at 395 nm. This technique is used to analyze two forms of monomeric Al, nonlabile (organic complexes) and labile (free, Al, Al sulfate, fluoride and hydroxide complexes). A detection limit 2 ug/L is possible with 25-ml samples and 10-ml extracts. The detection limit can be decreased by increasing the volume of the sample and (or) decreasing the volume of the methyl isobutyl ketone extract. The analytical uncertainty of this method is approximately + or - 5 percent. The standard addition technique provides a recovery test for this technique and ensures precision in samples of low Al concentrations. The average percentage recovery of the added Al plus the amount originally present was 99 percent. Data obtained from analyses of filtered standard solutions indicated that Al is adsorbed on various types of filters. However, the relationship between Al concentrations and adsorption remains linear. A test on standard solutions also indicated that Al is not adsorbed on nitric acid-washed polyethylene and polypropylene bottle wells. (USGS)

  9. Adsorption of Dissolved Metals in the Berkeley Pit using Thiol-Functionalized Self-Assembled Monolayers on Mesoporous Supports (Thiol-SAMMS)

    SciTech Connect

    Betancourt, Amaury P.; Mattigod, Shas V.; Wellman, Dawn M.

    2010-03-07

    The Berkeley Pit in Butte, Montana, is heavily contaminated with dissolved metals. Adsorption and extraction of these metals can be accomplished through the use of a selective adsorbent. For this research, the adsorbent used was thiol-functionalized Self-Assembled Monolayers on Mesoporous Supports (thiol-SAMMS), which was developed at Pacific Northwest National Laboratory (PNNL). Thiol-SAMMS selectively binds to numerous types of dissolved metals. The objective of this research was to evaluate the loading and kinetics of aluminum, beryllium, copper, and zinc on thiol-SAMMS. For the loading tests, a series of Berkeley Pit water to thiol-SAMMS ratios (mL:g) were tested. These ratios were 1000:1, 500:1, 100:1, and 50:1. Berkeley Pit water is acidic (pH {approx} 2.5). This can affect the performance of SAMMS materials. Therefore, the effect of pH was evaluated by conducting parallel series of loading tests wherein the Berkeley Pit water was neutralized before or after addition of thiol-SAMMS, and a series of kinetics tests wherein the Berkeley Pit water was neutralized before addition of thiol-SAMMS for the first test and was not neutralized for the second test. For the kinetics tests, one Berkeley Pit water to thiol-SAMMS ratio was tested, which was 2000:1. The results of the loading and kinetics tests suggest that a significant decrease in dissolved metal concentration at Berkeley Pit could be realized through neutralization of Berkeley Pit water. Thiol-SAMMS technology has a limited application under the highly acidic conditions posed by the Berkeley Pit. However, thiol-SAMMS could provide a secondary remedial technique which would complete the remedial system and remove dissolved metals from the Berkeley Pit to below drinking water standards.

  10. Yucca Mountain Area Saturated Zone Dissolved Organic Carbon Isotopic Data

    SciTech Connect

    Thomas, James; Decker, David; Patterson, Gary; Peterman, Zell; Mihevc, Todd; Larsen, Jessica; Hershey, Ronald

    2007-06-25

    Groundwater samples in the Yucca Mountain area were collected for chemical and isotopic analyses and measurements of water temperature, pH, specific conductivity, and alkalinity were obtained at the well or spring at the time of sampling. For this project, groundwater samples were analyzed for major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). The U.S. Geological Survey (USGS) performed all the fieldwork on this project including measurement of water chemistry field parameters and sample collection. The major ions dissolved in the groundwater, deuterium, oxygen-18, and carbon isotopes of dissolved inorganic carbon (DIC) were analyzed by the USGS. All preparation and processing of samples for DOC carbon isotopic analyses and geochemical modeling were performed by the Desert Research Institute (DRI). Analysis of the DOC carbon dioxide gas produced at DRI to obtain carbon-13 and carbon-14 values was conducted at the University of Arizona Accelerator Facility (a NSHE Yucca Mountain project QA qualified contract facility). The major-ion chemistry, deuterium, oxygen-18, and carbon isotopes of DIC were used in geochemical modeling (NETPATH) to determine groundwater sources, flow paths, mixing, and ages. The carbon isotopes of DOC were used to calculate groundwater ages that are independent of DIC model corrected carbon-14 ages. The DIC model corrected carbon-14 calculated ages were used to evaluate groundwater travel times for mixtures of water including water beneath Yucca Mountain. When possible, groundwater travel times were calculated for groundwater flow from beneath Yucca Mountain to down gradient sample sites. DOC carbon-14 groundwater ages were also calculated for groundwaters in the Yucca Mountain area. When possible, groundwater travel times were estimated for groundwater flow from beneath Yucca Mountain to down gradient groundwater sample sites using the DOC calculated groundwater ages. The DIC calculated groundwater ages were compared with DOC calculated groundwater ages and both of these ages were compared to travel times developed in ground-water flow and transport models. If nuclear waste is stored in Yucca Mountain, the saturated zone is the final barrier against the release of radionuclides to the environment. The most recent rendition of the TSPA takes little credit for the presence of the saturated zone and is a testament to the inadequate understanding of this important barrier. If radionuclides reach the saturated zone beneath Yucca Mountain, then there is a travel time before they would leave the Yucca Mountain area and flow down gradient to the Amargosa Valley area. Knowing how long it takes groundwater in the saturated zone to flow from beneath Yucca Mountain to down gradient areas is critical information for potential radionuclide transport. Radionuclide transport in groundwater may be the quickest pathway for radionuclides in the proposed Yucca Mountain repository to reach land surface by way of groundwater pumped in Amargosa Valley. An alternative approach to ground-water flow and transport models to determine the travel time of radionuclides from beneath Yucca Mountain to down gradient areas in the saturated zone is by carbon-14 dating of both inorganic and organic carbon dissolved in the groundwater. A standard method of determining ground-water ages is to measure the carbon-13 and carbon-14 of DIC in the groundwater and then correct the measured carbon-14 along a flow path for geochemical reactions that involve carbon containing phases. These geochemical reactions are constrained by carbon-13 and isotopic fractionations. Without correcting for geochemical reactions, the ground-water ages calculated from only the differences in carbon-14 measured along a flow path (assuming the decrease in carbon-14 is due strictly to radioactive decay) could be tens of thousands of years too old. The computer program NETPATH, developed by the USGS, is the best geochemical program for correcting carbon-14 activities for geochemical reactions. The DIC carbon-14 corrected ages can be further constrained by measuring the carbon isotopes of DOC. Because the only source of organic carbon in aquifers is almost always greater than 40,000 years old, any organic carbon that may be added to the groundwater would contain no carbon-14. Thus, ground-water ages determined by carbon isotopes of DOC should be maximum ages that can be used to constrain DIC corrected ages.

  11. PROCESS OF DISSOLVING ZIRCONIUM ALLOYS

    DOEpatents

    Shor, R.S.; Vogler, S.

    1958-01-21

    A process is described for dissolving binary zirconium-uranium alloys where the uranium content is about 2%. In prior dissolution procedures for these alloys, an oxidizing agent was added to prevent the precipitation of uranium tetrafluoride. In the present method complete dissolution is accomplished without the use of the oxidizing agent by using only the stoichiometric amount or slight excess of HF required by the zirconium. The concentration of the acid may range from 2M to 10M and the dissolution is advatageously carried out at a temperature of 80 deg C.

  12. Bromide, Chloride, and Sulfate Concentrations, and Specific Conductance, Lake Texoma, Texas and Oklahoma, 2007-08

    USGS Publications Warehouse

    Baldys, Stanley

    2009-01-01

    The U.S. Geological Survey, in cooperation with the City of Dallas Water Utilities Division, collected water-quality data from 11 sites on Lake Texoma, a reservoir on the Texas-Oklahoma border, during April 2007-September 2008. At 10 of the sites, physical properties (depth, specific conductance, pH, temperature, dissolved oxygen, and alkalinity) were measured and samples were collected for analysis of selected dissolved constituents (bromide, calcium, magnesium, potassium, sodium, carbonate, bicarbonate, chloride, and sulfate); at one site, only physical properties were measured. The primary constituent of interest was bromide. Bromate can form when ozone is used to disinfect raw water containing bromide, and bromate is a suspected human carcinogen. Chloride and sulfate were of secondary interest. Only the analytical results for bromide, chloride, sulfate, and measured specific conductance are discussed in this report. Median dissolved bromide concentrations ranged from 0.28 to 0.60 milligrams per liter. The largest median dissolved bromide concentration (0.60 milligram per liter at site 11) was from the Red River arm of Lake Texoma. Dissolved bromide concentrations generally were larger in the Red River arm of Lake Texoma than in the Washita arm of the lake. Median dissolved chloride concentrations were largest in the Red River arm of Lake Texoma at site 11 (431 milligrams per liter) and smallest at site 8 (122 milligrams per liter) in the Washita arm. At site 11 in the Red River arm, the mean and median chloride concentrations exceeded the secondary maximum contaminant level of 300 milligrams per liter for chloride established by the 'Texas Surface Water Quality Standards' for surface-water bodies designated for the public water supply use. Median dissolved sulfate concentrations ranged from 182 milligrams per liter at site 4 in the Big Mineral arm to 246 milligrams per liter at site 11 in the Red River arm. None of the mean or median sulfate concentrations exceeded the secondary maximum contaminant level of 300 milligrams per liter. Median specific conductance measurements at sites ranged from 1,120 microsiemens per centimeter at site 8 in the Washita arm to 2,100 microsiemens per centimeter in the Red River arm. The spatial distribution of specific conductance in Lake Texoma was similar to that of bromide and chloride, with larger specific conductance values in the Red River arm compared to those in the Washita arm.

  13. The influences of dissolved organic matter and surfactant on the desorption of Cu and Zn from road-deposited sediment.

    PubMed

    Zhang, Jin; Hua, Pei; Krebs, Peter

    2016-05-01

    This study showcases the desorption behaviours of copper (Cu) and zinc (Zn) in road-deposited sediment (RDS). Batch tests were conducted to investigate the influences of rainwater, major wastewater constituents of dissolved organic matter (DOM) and surfactant on the metals leaching from RDS. Results show that the rainwater solutions considerably enhanced the total amounts of Cu (319 ± 46% of the total leaching amount by blank solutions) and Zn (617 ± 130%) released from RDS compared with blank solutions. DOM enhanced the leaching of Cu from RDS at a neutral pH. By contrast, DOM had an adverse effect on the mobilization of Zn. In the absence of DOM, a higher concentration of sodium dodecyl sulfonate (SDS) slightly increased the release of Cu from RDS than a lower concentration of SDS. However, the existence of SDS suppressed the release of Zn from RDS. PMID:26891358

  14. The pH of Enceladus' ocean

    NASA Astrophysics Data System (ADS)

    Glein, Christopher R.; Baross, John A.; Waite, J. Hunter

    2015-08-01

    Saturn's moon, Enceladus, is a geologically active waterworld. The prevailing paradigm is that there is a subsurface ocean that erupts to the surface, which leads to the formation of a plume of vapor and ice above the south polar region. The chemistry of the ocean is just beginning to be understood, but is of profound geochemical and astrobiological interest. Here, we determine the pH of the ocean using a thermodynamic model of carbonate speciation. Observational data from the Cassini spacecraft are used to make a chemical model of ocean water on Enceladus. The model suggests that Enceladus' ocean is a Na-Cl-CO3 solution with an alkaline pH of ∼11-12. The dominance of aqueous NaCl is a feature that Enceladus' ocean shares with terrestrial seawater, but the ubiquity of dissolved Na2CO3 suggests that soda lakes are more analogous to the Enceladus ocean. The high pH implies that the hydroxide ion should be relatively abundant, while divalent metals should be present at low concentrations owing to buffering by carbonates and phyllosilicates on the ocean floor. Carboxyl groups in dissolved organic species would be negatively charged, while amino groups would exist predominately in the neutral form. Knowledge of the pH improves our understanding of geochemical processes in Enceladus' ocean. The high pH is interpreted to be a key consequence of serpentinization of chondritic rock, as predicted by prior geochemical reaction path models; although degassing of CO2 from the ocean may also play a role depending on the efficiency of mixing processes in the ocean. Serpentinization leads to the generation of H2, a geochemical fuel that can support both abiotic and biological synthesis of organic molecules such as those that have been detected in Enceladus' plume. Serpentinization and H2 generation should have occurred on Enceladus, like on the parent bodies of aqueously altered meteorites; but it is unknown whether these critical processes are still taking place, or if Enceladus' rocky core has been completely altered by past hydrothermal activity. The presence of native H2 in the plume would provide strong evidence for contemporary aqueous alteration that replenishes this source of energy for possible life. The high pH also suggests that the delivery of strong oxidants from the surface to the ocean has not been significant (otherwise, sulfuric acid would be produced), which would be consistent with geophysical models of episodic resurfacing activity on Enceladus. This paper represents an expansion of chemical oceanography to an "ocean planet" beyond Earth.

  15. Bench-scale evaluation of ferrous iron oxidation kinetics in drinking water: effect of corrosion control and dissolved organic matter.

    PubMed

    Rahman, Safiur; Gagnon, Graham A

    2014-01-01

    Corrosion control strategies are important for many utilities in maintaining water quality from the water treatment plant to the customers' tap. In drinking water with low alkalinity, water quality can become significantly degraded in iron-based pipes if water utilities are not diligent in maintaining proper corrosion control. This article reports on experiments conducted in bicarbonate buffered (5 mg-C/L) synthetic water to determine the effects of corrosion control (pH and phosphate) and dissolved organic matter (DOM) on the rate constants of the Fe(II) oxidation process. A factorial design approach elucidated that pH (P = 0.007, contribution: 42.5%) and phosphate (P = 0.025, contribution: 22.7%) were the statistically significant factors in the Fe(II) oxidation process at a 95% confidence level. The comprehensive study revealed a significant dependency relationship between the Fe(II) oxidation rate constants (k) and phosphate-to- Fe(II) mole ratio. At pH 6.5, the optimum mole ratio was found to be 0.3 to reduce the k values. Conversely, the k values were observed to increase for the phosphate-to- Fe(II) mole ratio > 1. The factorial design approach revealed that chlorine and DOM for the designated dosages did not cause a statistically significant (? = 0.05, P > 0.05)change in rate constants. However, an increment of the chlorine to ferrous iron mole ratio by a factor of ? 2.5 resulted in an increase k values by a factor of ? 10. This study conclusively demonstrated that the lowest Fe(II) oxidation rate constant was obtained under low pH conditions (pH ? 6.5), with chlorine doses less than 2.2 mg/L and with a phosphate-to-Fe(II) mole ratio ? 0.3 in the iron water systems. PMID:24117078

  16. The toxicity of zinc oxide nanoparticles to Lemna minor (L.) is predominantly caused by dissolved Zn.

    PubMed

    Chen, Xiaolin; O'Halloran, John; Jansen, Marcel A K

    2016-05-01

    Nano-ZnO particles have been reported to be toxic to many aquatic organisms, although it is debated whether this is caused by nanoparticles per sé, or rather dissolved Zn. This study investigated the role of dissolved Zn in nano-ZnO toxicity to Lemna minor. The technical approach was based on modulating nano-ZnO dissolution by either modifying the pH of the growth medium and/or surface coating of nano-ZnO, and measuring resulting impacts on L. minor growth and physiology. Results show rapid and total dissolution of nano-ZnO in the medium (pH 4.5). Quantitatively similar toxic effects were found when L. minor was exposed to nano-ZnO or the "dissolved Zn equivalent of dissolved nano-ZnO". The conclusion that nano-ZnO toxicity is primarily caused by dissolved Zn was further supported by the observation that phytotoxicity was absent on medium with higher pH-values (>7), where dissolution of nano-ZnO almost ceased. Similarly, the reduced toxicity of coated nano-ZnO, which displays a slower Zn dissolution, is also consistent with a major role for dissolved Zn in nano-ZnO toxicity. PMID:26918949

  17. PhD Students' Work Conditions and Study Environment in University- and Industry-Based PhD Programmes

    ERIC Educational Resources Information Center

    Kolmos, A.; Kofoed, L. B.; Du, X. Y.

    2008-01-01

    During the last 10 years, new models of funding and training PhD students have been established in Denmark in order to integrate industry into the entire PhD education. Several programmes have been conducted where it is possible to co-finance PhD scholarships or to become an employee as an industrial PhD in a company. An important question is what

  18. PhD Students' Work Conditions and Study Environment in University- and Industry-Based PhD Programmes

    ERIC Educational Resources Information Center

    Kolmos, A.; Kofoed, L. B.; Du, X. Y.

    2008-01-01

    During the last 10 years, new models of funding and training PhD students have been established in Denmark in order to integrate industry into the entire PhD education. Several programmes have been conducted where it is possible to co-finance PhD scholarships or to become an employee as an industrial PhD in a company. An important question is what…

  19. Erosion Patterns on Dissolving Surfaces

    NASA Astrophysics Data System (ADS)

    Cohen, Caroline; Polizzi, Stefano; Berhanu, Michael; Derr, Julien; Courrech Du Pont, Sylvain

    2015-11-01

    The shaping of landscapes results from water or wind erosional processes. Here we focus on dissolution processes. We perform laboratory experiments on hard caramel bodies, which dissolve on a short timescale, compared to geological material such as limestone. We highlight the spontaneous appearance of a dissolution pattern with no external flow. When a tilted hard caramel block dissolves, the syrup (denser than water) sinks in the bath and induces a flow, which results in a pattern on the bottom of the block. First parallel stripes appear, which evolve to transversal scallops in about one hour. The whole pattern moves upstream at a slow velocity. The stripes appearance is due to a buoyancy-driven instability. By varying the density and the viscosity of the bath, we show that the initial wavelengths of the pattern are in agreement with those given by the solutal Rayleigh-Benard number. Later pattern evolution to scallops results from complex interactions between the flow and the topography. Finally we emphasize that similar mechanism of patterns formation can occur in the dissolution of minerals like salt, but also in the shaping of the bottom face of melting icebergs in the cold seas.

  20. Determination of total dissolved inorganic carbon in freshwaters by reagent-free ion chromatography.

    PubMed

    Polesello, Stefano; Tartari, Gabriele; Giacomotti, Paola; Mosello, Rosario; Cavalli, Silvano

    2006-06-16

    Studies of inorganic carbon cycle in natural waters provide important information on the biological productivity and buffer capacity. Determination of total inorganic carbon, alkalinity and dissolved carbon dioxide gives an indication of the balance between photosynthesis and respiration by biota, both within the water column and sediments, and carbon dioxide transfers from the water column to the atmosphere. There are few methods to measure and distinguish the different forms of inorganic carbon, but all require a measure or an indirect quantification of total inorganic carbon. A direct measurement of TIC in water is made possible by the introduction of electrolytic generated hydroxide eluent in ion chromatography which allows to detect a chromatographic peak for carbonate. The advantage of this method is that all the inorganic forms of carbon are converted in carbonate at eluent pH and can be detected as a single peak by conductivity detection. Repeatability of carbonate peak was evaluated at different levels from 0.02 to 6 mequiv.l(-1) both in high purity water and in real samples and ranged from 1 to 9%. The calibration curve was not linear and has to be fitted by a quadratic curve. Limit of detection was estimated to be 0.02 mequiv.l(-1). Accuracy has been estimated by comparing ion chromatography method with total inorganic carbon calculated from alkalinity and pH. The correlation between the two methods was good (R(2)=0.978, n=141). The IC method has been applied to different typologies of surface waters (alpine and subalpine lakes and rivers) characterised by different chemical characteristics (alkalinity from 0.05 to 2 mequiv.l(-1) and pH from 6.7 to 8.5) and low total organic carbon concentrations. This analytical method allowed to describe the distribution of TIC along the water column of two Italian deep lakes. PMID:16620857

  1. Impact of solids retention time on dissolved organic nitrogen and its biodegradability in treated wastewater

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dissolved organic nitrogen (DON) and its biodegradability in treated wastewater have recently gained attention because DON potentially causes oxygen depletion and/or eutrophication in receiving waters. Laboratory scale chemostat experiments were conducted at 9 different solids retention times (SRTs)...

  2. Corals concentrate dissolved inorganic carbon to facilitate calcification.

    PubMed

    Allison, Nicola; Cohen, Itay; Finch, Adrian A; Erez, Jonathan; Tudhope, Alexander W

    2014-01-01

    The sources of dissolved inorganic carbon (DIC) used to produce scleractinian coral skeletons are not understood. Yet this knowledge is essential for understanding coral biomineralization and assessing the potential impacts of ocean acidification on coral reefs. Here we use skeletal boron geochemistry to reconstruct the DIC chemistry of the fluid used for coral calcification. We show that corals concentrate DIC at the calcification site substantially above seawater values and that bicarbonate contributes a significant amount of the DIC pool used to build the skeleton. Corals actively increase the pH of the calcification fluid, decreasing the proportion of DIC present as CO2 and creating a diffusion gradient favouring the transport of molecular CO2 from the overlying coral tissue into the calcification site. Coupling the increases in calcification fluid pH and [DIC] yields high calcification fluid [CO3(2-)] and induces high aragonite saturation states, favourable to the precipitation of the skeleton. PMID:25531981

  3. Method of dissolving metal oxides with di- or polyphosphonic acid and a redundant

    DOEpatents

    Horwitz, Earl P.; Chiarizia, Renato

    1996-01-01

    A method of dissolving metal oxides using a mixture of a di- or polyphosphonic acid and a reductant wherein each is present in a sufficient amount to provide a synergistic effect with respect to the dissolution of metal oxides and optionally containing corrosion inhibitors and pH adjusting agents.

  4. Ph.D. shortage

    NASA Astrophysics Data System (ADS)

    The late 1990s will see a shortage of Ph.D. graduates, according to the Association of American Universities, Washington, D.C. AAU's new comprehensive study, The Ph.D. Shortage: The Federal Role, reports that competition for new Ph.D.s is already intense and can only intensify because demand is greater than supply in both academic and nonacademic markets.Doctoral education plays an increasingly important role in U.S. research and development programs. Students have a pivotal part in doing research and enriching it with new ideas. The AAU report says that graduate students are major determinants of the creativity and productivity of U.S. academic research, the source of more than 50% of the nation's basic research. The market for doctoral education extends beyond the university. In 1985, about 43% of all Ph.D.s employed in this country were working outside higher education; the demand for doctorate recipients in nonacademic sectors continues to grow.

  5. pH optrode

    DOEpatents

    Northrup, M. Allen; Langry, Kevin C.

    1993-01-01

    A process is provided for forming a long-lasting, stable, pH-sensitive dye-acrylamide copolymer useful as a pH-sensitive material for use in an optrode or other device sensitive to pH. An optrode may be made by mechanically attaching the copolymer to a sensing device such as an optical fiber.

  6. pH Basics

    ERIC Educational Resources Information Center

    Lunelli, Bruno; Scagnolari, Francesco

    2009-01-01

    The exposition of the pervasive concept of pH, of its foundations and implementation as a meaningful quantitative measurement, in nonspecialist university texts is often not easy to follow because too many of its theoretical and operative underpinnings are neglected. To help the inquiring student we provide a concise introduction to the depth just…

  7. Seasonality of Diel Cycles of Dissolved Trace-Metal Concentrations in a Rocky Mountain Stream

    NASA Astrophysics Data System (ADS)

    Nimick, D. A.; Cleasby, T. E.; McCleskey, R. B.

    2004-12-01

    Substantial diel (24-hour) cycles in dissolved (0.1-μ m filtration) metal concentrations were observed during summer low flow, winter low flow, and snowmelt runoff in Prickly Pear Creek in southwestern Montana. The stream was alkaline (pH of 7.65-9.06), and dissolved metal concentrations were relatively low (1.8-7.1 μ g/L for As, 18-57 μ g/L for Mn, and 12-123 μ g/L for Zn). The metals are derived from abandoned mine lands in the stream's headwaters; As also is derived from geothermal sources. During seven diel sampling episodes, each lasting 34-61.5 hours, concentrations of dissolved Mn and Zn increased from minimum values in the afternoon to maximum values shortly after sunrise. The timing of diel cycles of dissolved As concentrations exhibited the inverse pattern. The magnitude of concentration increases during individual 24-hour periods ranged from 17-152% for Mn and 70-500% for Zn, and correlated positively with the magnitude of diel increases of pH and temperature, indicating that geochemical processes involving reactive inorganic and organic surfaces on and in the streambed probably control these diel metal cycles. Diel increases of As concentrations (17-55%) were proportionally smaller and less variable among the seasonal sampling episodes than for Mn and Zn, and they correlated poorly with diel increases of pH and temperature. Streamflow among the seven sampling episodes ranged from 0.35-3.3 m3/s. The timing of minimum and maximum values of diel streamflow cycles was inconsistent among sampling episodes and had little relation to the timing of metal concentration cycles, indicating that hydrological processes are not a primary control of diel metal cycles. Diel cycles of dissolved metal concentrations may occur at any time of year and during various hydrologic conditions in all streams with dissolved metals and neutral to alkaline pH.

  8. Relation between pH in the Trunk and Face: Truncal pH Can Be Easily Predicted from Facial pH

    PubMed Central

    Kim, Sung Ae; Kim, Bo Ri; Chun, Mi Young

    2016-01-01

    Background The clinical symptoms of facial and truncal acne differ. Skin surface acidity (pH), which is affected by sebum secretions, reflects the different clinical characteristics of the face and trunk. However, no studies have been conducted on truncal sebum production and skin pH. Objective We evaluated the differences and relationship between pH values of the face and trunk. We also evaluated the relationship between pH and the quantity of sebum produced in the trunk. Methods A total of 35 female patients clinically diagnosed with truncal acne were included. We measured pH on the face and truncal area using the Skin-pH-Meter PH 905®. We measured truncal sebum secretions using the Sebumeter SM 815®. Statistical analysis was performed to evaluate the correlations and differences between pH and sebum. Results Facial pH was significantly higher than chest and back pH values. The correlation between pH on the trunk and the face was significant. We used linear regression equations to estimate truncal pH using only measured pH from the chin. There was no significant relationship between truncal sebum secretion and pH. Conclusion This was the first study that evaluated the differences and correlations between facial and truncal pH. We found that facial pH can predict truncal pH. In addition, we conclude that differences in pH and sebum secretion between the face and trunk are one of the reasons for differences in acne symptom at those sites. PMID:27081270

  9. METHOD OF DISSOLVING REFRACTORY ALLOYS

    DOEpatents

    Helton, D.M.; Savolainen, J.K.

    1963-04-23

    This patent relates to the dissolution of alloys of uranium with zirconium, thorium, molybdenum, or niobium. The alloy is contacted with an anhydrous solution of mercuric chloride in a low-molecular-weight monohydric alcohol to produce a mercury-containing alcohol slurry. The slurry is then converted to an aqueous system by adding water and driving off the alcohol. The resulting aqueous slurry is electrolyzed in the presence of a mercury cathode to remove the mercury and produce a uranium-bearing aqueous solution. This process is useful for dissolving irradiated nuclear reactor fuels for radiochemical reprocessing by solvent extraction. In addition, zirconium-alloy cladding is selectively removed from uranium dioxide fuel compacts by this means. (AEC)

  10. Progress in dissolving modified LEU Cintichem targets

    SciTech Connect

    Leonard, R.A.; Chen, L.; Mertz, C.J.; Vandegrift, G.F.

    1996-12-31

    A process is under development to use low-enriched uranium (LEU) metal targets for production of {sup 99}Mo. The first step is to dissolve the irradiated foil. In past work, this has been done by heating a closed (sealed) vessel containing the foil and a solution of nitric and sulfuric acids. In this work, the authors have demonstrated that (1) the dissolver solution can contain nitric acid alone, (2) uranium dioxide is also dissolved by nitric acid alone, and (3) barrier metals of Cu, Fe, or Ni on the U foil are also dissolved by nitric acid. Changes to the dissolver design and operation needed to accommodate the uranium foil are discussed, including (1) simple operations that are easy to do in a remote-maintenance facility, (2) heat removal from the irradiated LEU foil, and (3) cold trap operation with high dissolver pressures.

  11. Carbon isotope fractionation by marine phytoplankton in culture: The effects of CO2 concentration, pH, temperature, and species

    NASA Astrophysics Data System (ADS)

    Hinga, Kenneth R.; Arthur, Michael A.; Pilson, Michael E. Q.; Whitaker, Dania

    1994-03-01

    Closed cultures of marine phytoplankton were established under variable conditions of CO2 concentration, temperature, growth rate (by light limitation), and pH (but with nearly identical [CO2aq]) in order to assess the relative influence of these variables on the extent of carbon isotope fractionation relative to dissolved inorganic carbon sources. Culture biomass was not allowed to increase beyond levels that would significantly affect the dissolved carbon system in the closed cultures. In experiments with Skeletonema costatum and Emiliania huxleyi, increasing CO2 concentrations led to increased carbon isotope discrimination (resulting in organic matter progressively depleted in δ13C, i.e., a greater, more negative ɛp). ɛp values for E. huxleyi were 8-10‰ less than for S. costatum under identical conditions. For the S. costatum cultures, there was nearly a 20 ‰ range in [CO2aq]-dependent ɛp. The effect was nonlinear with a leveling off at high [CO2aq]. Over a pH range of 7.5-8.3 but at a constant [CO2aq] there was a variation in carbon isotope fractionation by S. costatum of about 9 ‰ with a minimum at pH 7.8-7.9. There was a temperature effect of ˜8‰ on fractionation even after equilibrium temperature dependency of δ13C of CO2aq was taken into account. No growth rate effect was found for S. costatum over a modest range of growth rates. Culture experiments used to determine the carbon isotope fractionation by phytoplankton species must be conducted under well-defined conditions of temperature, pH, and CO2 concentrations. Hindcasts of ancient atmospheric pCO2 from measurements of δ13C of organic carbon in marine sediments will require careful calibration because of the variety of possible factors that influence δ13Corg.

  12. Fractionation of residual Al in natural water treatment from reservoir with poly-aluminum-silicate-chloride (PASiC): effect of OH/Al, Si/Al molar ratios and initial pH.

    PubMed

    Yang, Zhonglian; Gao, Baoyu; Wang, Yan; Zhao, Yaqin; Yue, Qinyan

    2012-01-01

    An aluminum fractionation study was conducted for a surface reservoir water treatment to understand the performance of poly-aluminum-silicate-chloride (PASiC) in terms of the residual Al fractions as a function of initial pH. The coagulation performance expressed as turbidity and organic matter removal was established as supporting data. Some extra data were evaluated in terms of the residual Al ratio of the composite PASiC coagulant. The main residual Al sources were the Al fractions derived from the use of PASiC. The turbidity and organic matter removal ability was optimal at initial pH 6.00-7.00, while the concentrations of various residual Al species and the residual Al ratio of PASiC were minimal at an initial pH range of 7.00-8.00. Under the conditions of OH/Al molar ratio = 2.00 and Si/Al molar ratio = 0.05, PASiC had superior coagulation performance and comparatively low residual Al concentrations. The Al fraction in the composite PASiC coagulant seldom remained under such conditions. Experimental data also indicated that the suspended (filterable) Al fraction was the dominant species, and organic-bound or organo-Al complex Al was considered to be the major species of dissolved Al in water treated by PASiC coagulation. Additionally, the dissolved inorganic monomeric Al species dominated the dissolved monomeric Al fraction. PMID:23534222

  13. Variation of ocean pH in the Indonesia waters

    NASA Astrophysics Data System (ADS)

    Putri, Mutiara Rachmat; Setiawan, Agus; Safitri, Mediana

    2015-09-01

    The variation of ocean acidity (pH) in the Indonesia waters is strongly influenced by monsoon. Since the climate change tends to potentially change monsoonal variation over the Indonesian region, it will give also implication to the ocean pH variation. Moreover, changes of ocean pH will give effects to the marine lifes and their environment. In order to investigate this issue, we tried to calculate monthly variation of sea surface pH in the Indonesia waters based on monthly average temperature and salinity over past 18 years data. Temperature and salinity data used in this study were taken from the hydrodynamic model of Hamburg Shelf Ocean Model (HAMSOM), while alkalinity and dissolved inorganic carbon (DIC) were from World Ocean Atlas 2009 (WOA 2009). Algorithm from Ocean Carbon Model Intercomparison Project-version.3 (OCMIP-3) was used to calculate the pH. The estimation results indicate that pH variation in the Indonesia waters changes insignificantly over 18 years. El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) contribute to physical changes of seawater, but did not affect the pH significantly. The average pH of seawater is higher during northwest monsoon than during southeast monsoon.

  14. Suspended sediments in river ecosystems: Photochemical sources of dissolved organic carbon, dissolved organic nitrogen, and adsorptive removal of dissolved iron

    NASA Astrophysics Data System (ADS)

    Riggsbee, J. Adam; Orr, Cailin H.; Leech, Dina M.; Doyle, Martin W.; Wetzel, Robert G.

    2008-09-01

    We generated suspended sediment solutions using river sediments and river water at concentrations similar to those observed during 1.5 year floods (Q1.5) and a dam removal (˜325 mg L-1) on the Deep River, North Carolina. Suspended sediment solutions were exposed to simulated solar radiation, equivalent to one clear, summer day at the study site (35°N). Concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), total dissolved nitrogen (TDN), dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON), soluble reactive phosphorus (SRP) and total dissolved iron (Fed) were measured before and after exposure. Total dissolved carbon (TDC) budgets for each experiment were produced using DOC and DIC data. Sediment suspensions in the presence of simulated solar radiation were significant sources of dissolved C (119 ± 11 μmol C L-1 d-1; ± values indicate 1 standard error) and DON (1.7 ± 0.5 μmol N L-1 d-1) but not DIN or SRP. Extrapolations through the Deep River water column suggest that suspended sediments in the presence of light represent dissolved organic matter fluxes of 3.92 mmol C m-2 d-1 and 40 μmol N m-2 d-1. Additionally, sediment suspensions lowered river water Fed concentrations immediately (˜24%) and progressively (˜40-90%) in both light and dark treatments. Our research suggests suspended sediments in river ecosystems are potential sources of dissolved organic C and dissolved organic N while effectively removing Fed from the water column.

  15. Seasonal changes of rock magnetic parameters and dissolved iron in the Hiroshima Bay

    NASA Astrophysics Data System (ADS)

    Kawamura, N.; Amano, Y.; Ishikawa, N.

    2013-12-01

    Frequent outbreaks of red tide caused by dinoflagellate blooms have been reported since 1970 in the Hiroshima bay. Iron is an essential element for dinoflagellates, and is supplied as bivalent or trivalent ions and iron compounds from lands to sea. For damage predictions of red tide, it is important to research the distribution of iron in the bay. In order to investigate the distribution and mode of iron in sediments, suspended solids (SS), and bottom water in the Hiroshima Bay, rock magnetic and geochemical analyses are performed. Sediments of 5 cm in depth and overlying bottom water were taken at three sites in the bay every month. The sediment samples were composed of clayey silt. We measured dissolved iron concentration in bottom waters filtered above 0.45 um grains. The contents of carbon, nitrogen, and sulfur in the sediments are measured. The rock magnetic measurements (magnetic susceptibility, NRM, ARM, IRM, HIRM, S-0.3T, magnetic hysteresis, and high temperature magnetometry) of the sediments and SS are conducted. Concentration dependent rock magnetic parameters of the sediments and SS show relatively high values during spring at the near estuary site. It indicates that relatively larger amount of terrigenous materials are supplied in this season. Magnetic grain size decreases during summer, while iron concentration increases in the bottom waters. Data of oceanographic observations at these sites showed that the temperature of the bottom water increased, whereas DO and pH values decreased during summer. The presence of magnetite (Fe3O4) and hematite (Fe2O3) were recognized in all analyzed samples, whereas greigite (Fe3S4) appeared during summer. The contents of sulfur in the sediments also increase in this period. It is implied that magnetite and hematite were dissolved, and greigite was formed associated with the proceeding of the anoxic condition during summer. It is suggested that irons moves between sediments and bottom water corresponding to seasonal redox conditions in the Hiroshima Bay.

  16. Experimental determination of UO 2(cr) dissolution kinetics: Effects of solution saturation state and pH

    NASA Astrophysics Data System (ADS)

    Pierce, E. M.; Icenhower, J. P.; Serne, R. J.; Catalano, J. G.

    2005-10-01

    To evaluate the release of uranium from natural ore deposits, spent nuclear fuel repositories, and REDOX permeable reactive barriers (PRB), knowledge of the fundamental reaction kinetics associated with the dissolution of uranium dioxide is necessary. Dissolution of crystalline uranium (IV) dioxide under environmental conditions has been studied for four decades but a cardinal gap in the published literature is the effect of pH and solution saturation state on UO2(cr) dissolution. To resolve inconsistencies, UO2 dissolution experiments have been conducted under oxic conditions using the single-pass flow-through system. Experiments were conducted as a function of total dissolved carbonate ([CO3-3 ]T) from 0.001 to 0.1 M; pH from 7.5 to 11.1; ratio of flow-through rate (q) to specific surface area (S), constant ionic strength (I) = 0.1 M, and temperatures (T) from 23 to 60 °C utilizing both powder and monolithic specimens. The results show that UO2 dissolution varies as a function of the ratio q/S and temperature. At values of log10 q/S > -7.0, UO2 dissolution becomes invariant with respect to q/S, which can be interpreted as evidence for dissolution at the forward rate of reaction. The data collected in these experiments show the rate of UO2 dissolution increased by an order of magnitude with a 30 °C increase in temperature. The results also show the overall dissolution rate increases with an increase in pH and decreases as the dissolved uranium concentration approaches saturation with respect to secondary reaction products. Thus, as the value of the reaction quotient, Q, approaches equilibrium, K, (with respect to a potential secondary phase) the dissolution rate decreases. This decrease in dissolution rate (r) was also observed when comparing measured UO2 dissolution rates from static tests where r = 1.7 ± 0.14 × 10-8 mol m-2 s-1 to the rate for flow-through reactors where r = 3.1 ± 1.2 × 10-7 mol m-2 s-1. Thus, using traditional static test methods can result in an underestimation of the true forward rate of UO2(cr) dissolution. These results illustrate the importance of pH, solution saturation state, and the concentration of dissolved carbonate on the release of uranium from UO2 in the natural environment.

  17. 17-4 PH and 15-5 PH

    NASA Technical Reports Server (NTRS)

    Johnson, Howard T.

    1995-01-01

    17-4 PH and 15-5 PH are extremely useful and versatile precipitation-hardening stainless steels. Armco 17-4 PH is well suited for the magnetic particle inspection requirements of Aerospace Material Specification. Armco 15-5 PH and 17-4 PH are produced in billet, plate, bar, and wire. Also, 15-5 PH is able to meet the stringent mechanical properties required in the aerospace and nuclear industries. Both products are easy to heat treat and machine, making them very useful in many applications.

  18. Dissolved Oxygen Data for Coos Estuary (Oregon)

    EPA Science Inventory

    The purpose of this product is the transmittal of dissolved oxygen data collected in the Coos Estuary, Oregon to Ms. Molly O'Neill (University of Oregon), for use in her studies on the factors influencing spatial and temporal patterns in dissolved oxygen in this estuary. These d...

  19. Investigating Students' Understanding of the Dissolving Process

    ERIC Educational Resources Information Center

    Naah, Basil M.; Sanger, Michael J.

    2013-01-01

    In a previous study, the authors identified several student misconceptions regarding the process of dissolving ionic compounds in water. The present study used multiple-choice questions whose distractors were derived from these misconceptions to assess students' understanding of the dissolving process at the symbolic and particulate levels. The…

  20. Nitrate and dissolved nitrous oxide in groundwater within cropped fields and riparian buffers

    NASA Astrophysics Data System (ADS)

    Kim, D.-G.; Isenhart, T. M.; Parkin, T. B.; Schultz, R. C.; Loynachan, T. E.

    2009-01-01

    Transport and fate of dissolved nitrous oxide (N2O) in groundwater and its significance to nitrogen dynamics within agro-ecosystems are poorly known in spite of significant potential of N2O to global warming and ozone depletion. Increasing denitrification in riparian buffers may trade a reduction in nitrate (NO3-) transport to surface waters for increased N2O emissions resulting from denitrification-produced N2O dissolved in groundwater being emitted into the air when groundwater flows into a stream or a river. This study quantifies the transport and fate of NO3- and dissolved N2O moving from crop fields through riparian buffers, assesses whether groundwater exported from crop fields and riparian buffers is a significant source of dissolved N2O emissions, and evaluates the Intergovernmental Panel on Climate Change (IPCC) methodology to estimate dissolved N2O emission. We measured concentrations of NO3-; chloride (Cl-); pH; dissolved N2O, dissolved oxygen (DO), and organic carbon (DOC) in groundwater under a multi-species riparian buffer, a cool-season grass filter, and adjacent crop fields located in the Bear Creek watershed in central Iowa, USA. In both the multi-species riparian buffer and the cool-season grass filter, concentrations of dissolved N2O in the groundwater did not change as it passed through the sites, even when the concentrations of groundwater NO3- were decreased by 50% and 59%, respectively, over the same periods. The fraction of N lost to leaching and runoff (0.05) and the modified N2O emission factor, [ratio of dissolved N2O flux to N input (0.00002)] determined for the cropped fields indicate that the current IPCC methodology overestimates dissolved N2O flux in the sites. A low ratio between dissolved N2O flux and soil N2O emission (0.0003) was estimated in the cropped fields. These results suggest that the riparian buffers established adjacent to crop fields for water quality functions (enhanced denitrification) decreased NO3- and were not a source of dissolved N2O. Also, the flux of dissolved N2O from the cropped field was negligible in comparison to soil N2O emission in the crop fields.

  1. [Impact of Rocky Desertification Treatment on Underground Water Chemistry and Dissolved Inorganic Carbon Isotope in Karst Areas].

    PubMed

    Xiao, Shi-zhen; Xiong, Kang-ning; Lan, Jia-cheng; Zhang, Hui; Yang, Long

    2015-05-01

    Five springs representing different land-use types and different karst rocky desertification treatment models were chosen at the Huajiang Karst Rocky Desertification Treatment Demonstration Site in Guanling-Zhenfeng Counties in Guizhou, to analyze the features of underground water chemistry and dissolved inorganic carbon isotopes (δ13C(DIC)) and reveal the effect of rocky desertification treatment on karstification and water quality. It was found that, the underground water type of the research area was HCO3-Ca; the water quality of the springs which were relatively less affected by human activities including Shuijingwan Spring (SJW) , Gebei Spring (GB), and Maojiawan Spring (MJW) was better than those relatively more affected by human activities including Diaojing Spring (DJ) and Tanjiazhai Spring (TJZ) , the main ion concentrations and electrical conductivity of which were higher; pH, SIc and pCO2 were sensitive to land-use types and rocky desertification treatment, which could be shown by the higher pH and SIc and lower pCO2 in MJW than those in the other four springs; (Ca(2+) + Mg2+)/HCO(3-) of SJW, MJW and GB were nearly 1:1, dominated by carbonate rock weathering by carbon acid, while the (Ca(2+) + Mg2+) of DJ and TJZ was much higher than HCO3-, suggesting that sulfate and nitrate might also dissolve carbonate rock because of the agricultural activities; δ13C(DIC) was lighter in wet season because of the higher biological activities; the average δ13C(DIC) was in the order of DJ (-12.79 per thousand) < SJW (-12.48 per thousand) < GB (-10.76 per thousand)) < MJW (-10.30 per thousand) < TJZ (-6.70 per thousand), which demonstrated that δ13C(DIC) would be heavier after rocky desertification and lighter after the rocky desertification are treated and controlled. PMID:26314104

  2. Dissolved:total metals concentrations in marine acute toxicity test simulations

    SciTech Connect

    Lussier, S.M.; Boothman, W.S.; Champlin, D.; Poucher, S.; Helmstetter, A.

    1995-12-31

    Use of water quality criteria expressed as dissolved metal is recommended by the US EPA, Office of Water, because ``dissolved metal more closely approximates the bioavailable fraction of metal in the water column than does total recoverable metal.`` Water quality criteria (WQC) are expressed in terms of total recoverable or acid-soluble metals concentrations; in part because few toxicity tests with aquatic organisms include measurement of dissolved metals. Therefore, if WQC are to be expressed as dissolved, complete retesting or derivation of dissolved:total (D:T) metals relationships to adjust existing criteria were required. To derive D:T ratios, simulated tests were conducted using concentrations and species similar to those used to derive original criteria. Dissolved (<0.45/{micro}) and total recoverable metals were measured to determine the partitioning relationship under these experimental conditions and convert criteria to reflect dissolved metals concentrations. Simulations were conducted with arsenic (III), cadmium, chromium (VI), lead, nickel, selenium, and zinc. In all simulations, average dissolved metals comprised 93--100% of total metals measured. Dissolved:total ratios did not significantly differ for a given metal throughout each test among test type or treatment concentration. Biological results, while insufficient to derive criteria directly, were generally consistent with results of historical biological response data. These results demonstrate that, under the conditions employed, i.e, short exposure periods (2--4 days) and low particulate load typical of these tests, metals are essentially not removed from solution onto particles. This does not imply that such partitioning is representative of conditions in natural waters, but rather that in the historical acute toxicity tests used to establish water quality criteria, metals were primarily dissolved.

  3. Aeration with carbon dioxide-supplemented air as a method to control pH drift in toxicity tests with effluents from wastewater treatment plants.

    PubMed

    Elphick, James R; Bailey, Howard C; Hindle, Amanda; Bertold, Stanley E

    2005-09-01

    Environment Canada methods for acute toxicity tests with rainbow trout require continuous aeration of test solutions during exposure. Depending on the sample, this procedure can result in an increase in pH as dissolved carbon dioxide (CO2) is stripped from solution as a result of aeration. In samples that contain ammonia, the pH may increase to the point where the unionized fraction results in artifactual toxicity. Consequently, aeration with air supplemented with different CO2 concentrations was investigated as a method for maintaining pH at the level found in the original sample without adversely affecting other water quality parameters. Aeration with CO2 was an effective method for maintaining pH during exposure, depending both on the concentration of CO2 and the alkalinity of the sample. A multiple regression conducted on the data determined an equation that was effective at calculating the CO2 concentration necessary in an aeration mixture to maintain a target pH value as a function of sample alkalinity. PMID:16193749

  4. Water quality and processes affecting dissolved oxygen concentrations in the Blackwater River, Canaan Valley, West Virginia

    USGS Publications Warehouse

    Waldron, M.C.; Wiley, J.B.

    1996-01-01

    The water quality and environmental processes affecting dissolved oxygen were determined for the Blackwater River in Canaan Valley, West Virginia. Canaan Valley is oval-shaped (14 miles by 5 miles) and is located in the Allegheny Mountains at an average elevation of 3,200 feet above sea level. Tourism, population, and real estate development have increased in the past two decades. Most streams in Canaan Valley are a dilute calcium magnesium bicarbonate-type water. Streamwater typicaly was soft and low in alkalinity and dissolved solids. Maximum values for specific conductance, hardness, alkalinity, and dissolved solids occurred during low-flow periods when streamflow was at or near baseflow. Dissolved oxygen concentrations are most sensitive to processes affecting the rate of reaeration. The reaeration is affected by solubility (atmospheric pressure, water temperature, humidity, and cloud cover) and processes that determine stream turbulence (stream depth, width, velocity, and roughness). In the headwaters, photosynthetic dissolved oxygen production by benthic algae can result in supersaturated dissolved oxygen concentrations. In beaver pools, dissolved oxygen consumption from sediment oxygen demand and carbonaceous biochemical oxygen demand can result in dissolved oxygen deficits.

  5. Reactive solute transport in streams. 2. Simulation of a pH modification experiment

    USGS Publications Warehouse

    Runkel, R.L.; McKnight, Diane M.; Bencala, K.E.; Chapra, S.C.

    1996-01-01

    We present an application of an equilibrium-based solute transport model to a pH-modification experiment conducted on the Snake River, an acidic, metal-rich stream located in the Rocky Mountains of Colorado. During the experiment, instream pH decreased from 4.2 to 3.2, causing a marked increase in dissolved iron concentrations. Model application requires specification of several parameters that are estimated using tracer techniques, mass balance calculations, and geochemical data. Two basic questions are addressed through model application: (1) What are the processes responsible for the observed increase in dissolved iron concentrations? (2) Can the identified processes be represented within the equilibrium-based transport model? Simulation results indicate that the increase in iron was due to the dissolution of hydrous iron oxides and the photoreduction of ferric iron. Dissolution from the streambed is represented by considering a trace compartment consisting of freshly precipitated hydrous iron oxide and an abundant compartment consisting of aged precipitates that are less soluble. Spatial variability in the solubility of hydrous iron oxide is attributed to heterogeneity in the streambed sediments, temperature effects, and/or variability in the effects of photoreduction. Solubility products estimated via simulation fall within a narrow range (pK(sp) from 40.2 to 40.8) relative to the 6 order of magnitude variation reported for laboratory experiments (pK(sp) from 37.3 to 43.3). Results also support the use of an equilibrium-based transport model as the predominate features of the iron and p H profiles are reproduced. The model provides a valuable tool for quantifying the nature and extent of pH- dependent processes within the context of hydrologic transport.

  6. An improved method for fluorescence analysis of dissolved organic matter in cave drip water

    NASA Astrophysics Data System (ADS)

    Li, Xiuli; Hu, Chaoyong; Liao, Jin; Bao, Liangliang; Mao, Qixi

    2014-12-01

    An improved synchronous fluorimetric method for the determination of dissolved organic matter in cave drip water, by adding ascorbic acid, is described. The method is based on the redox reaction between ascorbic acid and the electron-withdrawing constituents in dissolved organic matter. The results show that adding ascorbic acid can quench the minor peaks, at 200-300 nm, but does not affect the intensity of the main peaks at 300-500 nm. In addition, adding ascorbic acid can maintain relatively high and constant fluorescence intensity over a wide pH range (9-4).

  7. Dynamics and Biodegradability of Chromophoric Dissolved Organic Matter in a Severely Polluted River

    NASA Astrophysics Data System (ADS)

    Borisover, Mikhail; Laor, Yael; Saadi, Ibrahim; Lado, Marcos; Bukhanovsky, Nadezhda

    2010-05-01

    The 70-kilometer long Kishon River is one of Israel's largest rivers. Its annual discharge may vary substantially, e.g. between 47 and 10 million m3. The lower section of the river has been severely polluted for dozens of years, by industrial effluents containing heavy metals, radionuclides, nutrients, and diverse organic contaminants. The total volume of effluents discharged from the plants into the river stream may contribute as much as 30% of the total water volume. Dissolved organic matter (DOM) and specifically its chromophoric components (CDOM) including humic-like and proteinous substances may form water-soluble complexes with multiple organic and inorganic pollutants and, thus, enhance their release from the sediments and their mobility. The volatility of pollutants, their bioavailability, toxicity and potential to undergo bio-, abiotic and photodegradation may be affected by interactions with CDOM. Therefore, the dynamics of CDOM is important for understanding the fate of pollutants in aquatic environments. In this study, we intended (i) to characterize the seasonal and spatial variability of CDOM at the most contaminated lower section of the Kishon River and (ii) to assess the impact of biodegradation, dilution by seawater and contribution of discharged effluents on the overall dynamics of DOM and CDOM. For this purpose, water was sampled during 11 months at 8 locations distributed along Lower Kishon River. Samples were characterized for concentrations of dissolved organic carbon (DOC), UV- absorbance at 254 nm, electrical-conductivity, pH, concentration of dissolved oxygen and excitation emission matrices (EEM) of fluorescence. Parallel factor analysis of EEM enabled quantifying two major groups of riverine fluorescent CDOM: humic-like substances and components spectrally similar to those associated with phytoplankton productivity. CDOM (including fluorescent matter and components absorbing light at 254 nm) was found resistant to biodegradation by riverine microorganisms. The fraction of easily degradable riverine DOM that was not included in the CDOM was estimated to be between 8 and 26% of the overall DOC. The variability in DOM and CDOM composition was strongly affected by dilution with seawater. Approaching the estuary, the DOM in the Kishon River becomes depleted in CDOM. At the same time, the UV-active components become relatively enriched in fluorescent matter. It was hypothesized that the concentration of humic-like substances may increase in the river due to DOM transformation. Effluent discharge from multiple industrial sites along the river did not result in a distinct increase in concentrations of CDOM components absorbing light at 254 nm or fluorescent humic-like substances. However, an increase in the fluorescent CDOM associated with phytoplankton productivity was observed in the central section of Lower Kishon River, probably linked to an increase of nutrients supply originating from discharged effluents, which enhanced biological activity. Thus, different processes appear to influence the concentrations of two major groups of fluorescent riverine CDOM. The collected data showed significant correlations between concentration of dissolved oxygen, pH and UV- absorbance at 254 nm which may suggest that as the content of aromatic components increases, the oxygen demand for DOM biodegradation decreases, since DOM is enriched in biodegradation-resistant substances. The different dynamics of DOC and CDOM as observed in this study needs to be considered when modeling the impact of DOM on the fate of pollutants in riverine ecosystems.

  8. Effect of pH values on surface modification and solubility of phosphate bioglass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system

    NASA Astrophysics Data System (ADS)

    Li, Xudong; Cai, Shu; Zhang, Wenjuang; Xu, Guohua; Zhou, Wei

    2009-08-01

    The bioactive glass-ceramics in the CaO-P 2O 5-Na 2O-SrO-ZnO system were synthesized by the sol-gel technique, and then chemically treated at different pH values to study the solubility and surface modification. Samples sintered at 650 °C for 4 h consisted of the crystalline phase β-Ca 2P 2O 7 and the glass matrix. After soaking in the solution at pH 1.0, the residual glass matrix on the surface appeared entirely dissolved and no new phase could be detected. Whereas at pH 3.0, web-like layer exhibiting peaks corresponding to CaP 2O 6 was formed and covered the entire surface of the sample. When conducted at pH 10.0, only part of the glass matrix was dissolved and a new phase Ca 4P 6O 19 was precipitated, forming the petaline layer. The chemical treatment can easily change the surface morphologies and phase composition of this bioactive glass-ceramics. The higher level of surface roughness resulting from the new-formed layer would improve the interface bonding and benefit for cell adhesion.

  9. [Porewater Dissolved Methane in Cyperus malaccensis Marshes Along Salinity Gradient in the Minjiang River Estuary].

    PubMed

    Yang, Ping; Zhang, Zi-chuan; Du, Wei-ning; Huang, Jia-fang; Tong, Chuan

    2015-10-01

    Physicochemical properties of soil and dissolved methane concentrations of porewater in the sediments of the Cyperus malaccensis marshes along a salinity gradient in the Minjiang River estuary were evaluated, and the spatial-temporal characteristics and main impact factors were discussed. The average concentrations of dissolved methane in porewater were 331.18, 299.94 and 638.58 μmol x L(-1), respectively in the Shanyutan, Bianfuzhou and Xiayangzhou wetlands in summer. In the winter, they were 9.04, 266.67 and 322.68 μmol x L(-1), respectively. The dissolved methane concentration in porewater was higher in summer than those in winter (P < 0.05). Overall, the concentrations of dissolved methane in porewatdr showed an increasing trend from brackish to freshwater marshes. Multivariate statistics analysis showed that the concentrations of dissolved methane in porewater was positively correlated with soils temperature and DOC (P < 0.05), but negatively correlated with soils pH, salinity, and the concentrations of porewater SO4(2-) and Cl-. Spatial-temporal distribution of porewater dissolved methane in estuarine marshes represents a final result of multiple factors, including soil physicochemical properties and hydrodynamic condition. PMID:26841594

  10. Urine pH test

    MedlinePlus

    pH - urine ... meat products or cranberries can decrease your urine pH. ... provider may order this test to check for changes in your body's ... stones can form, depending on the acidity level of your urine.

  11. Influence of dissolved hydrogen on aluminum-lithium alloy fracture behavior

    NASA Technical Reports Server (NTRS)

    Rivet, F. C.; Swanson, R. E.

    1989-01-01

    The objective of this work is to study the effects of dissolved hydrogen on the mechanical properties of 2090 and 2219 alloys. Prior to mechanical testing, potentiostatic and potentiodynamic tests were performed using NaCl/HCl solutions varying in pH from 1.5 to 7.5 (3.5 pct NaCl in deionized water). After analysis of the potentiodynamic curve for each solution, several potentiostatic experiments were conducted for various times (from 10 minutes to several hours) with a cathodic overpotential of 300 mV. These experiments were performed to select charging conditions. It is shown that the fracture of L-S and T-S orientations proceeds via slipping of layers in the S-T direction. The T-S and L-S orientations fractured with substantially higher propagation energy that the L-T and T-L orientations, due in large part to the extensive delamination propagation of the fracture.

  12. Monitoring diel dissolved oxygen dynamics through integrating wavelet denoising and temporal neural networks.

    PubMed

    Evrendilek, Fatih; Karakaya, Nusret

    2014-03-01

    Diel dissolved oxygen (DO) time series measured continuously using proximal sensors in situ for a temperate lake were denoised using discrete wavelet transform (DWT) with the orthogonal wavelet families of coiflet, daubechies, and symmlet with order of 10. Diel DO time series denoised were modeled using nine temporal artificial neural networks (ANNs) as a function of water level, water temperature, electrical conductivity, pH, day of year, and hour. Our results showed that time-lag recurrent network (TLRN) using denoised data emulated diel DO dynamics better than the best-performing TLRN using the original data, time-delay neural network (TDNN), and recurrent network (RNN). Daubechies basis dealt with diel DO data slightly better than the other bases given its coefficient of determination (r (2) = 87.1 %), while symmlet performed slightly better than the other bases in terms of root mean square error (RMSE = 1.2 ppm) and mean absolute error (MAE = 0.9 ppm). PMID:24100799

  13. Laboratory and marine study of photoluminescent sensors of oxygen dissolved in seawater

    NASA Astrophysics Data System (ADS)

    Vlasov, V. L.; Konovalov, B. V.; Mosharov, V. E.; Radchenko, V. N.; Khanaev, S. A.; Khlebnikov, D. V.

    2010-02-01

    The laboratory and marine study of photoluminescent sensors developed at the TsAGI has been conducted to create a highly sensitivity gauge of the oxygen dissolved in seawater. The advantages of the photoluminescent gauge over the electrochemical ones are the following: zero sensitivity to electromagnetic fields, the pH of the water, and the hydrogen sulphide and ions of heavy metals in the water; zero oxygen consumption; and no need for the water to be pumped through the device. A breadboard model of the photoluminescent gauge with LED excitation of the luminescence has been built. The laboratory tests of the model demonstrated the accuracy of the gauge to be as high as 0.05 ml/1 in air at a response time of 0.3 s for 63% relaxation. Comparative field tests of the breadboard model and the SBE 43 electrochemical oxygen gauge (Sea-Bird Electronics Corp.) have shown good agreement of the estimates of the oxygen content in the water and clarified the prospects of model’s performance improvement.

  14. Artificial neural network modeling of dissolved oxygen in the Heihe River, Northwestern China.

    PubMed

    Wen, Xiaohu; Fang, Jing; Diao, Meina; Zhang, Chuanqi

    2013-05-01

    Identification and quantification of dissolved oxygen (DO) profiles of river is one of the primary concerns for water resources managers. In this research, an artificial neural network (ANN) was developed to simulate the DO concentrations in the Heihe River, Northwestern China. A three-layer back-propagation ANN was used with the Bayesian regularization training algorithm. The input variables of the neural network were pH, electrical conductivity, chloride (Cl(-)), calcium (Ca(2+)), total alkalinity, total hardness, nitrate nitrogen (NO3-N), and ammonical nitrogen (NH4-N). The ANN structure with 14 hidden neurons obtained the best selection. By making comparison between the results of the ANN model and the measured data on the basis of correlation coefficient (r) and root mean square error (RMSE), a good model-fitting DO values indicated the effectiveness of neural network model. It is found that the coefficient of correlation (r) values for the training, validation, and test sets were 0.9654, 0.9841, and 0.9680, respectively, and the respective values of RMSE for the training, validation, and test sets were 0.4272, 0.3667, and 0.4570, respectively. Sensitivity analysis was used to determine the influence of input variables on the dependent variable. The most effective inputs were determined as pH, NO3-N, NH4-N, and Ca(2+). Cl(-) was found to be least effective variables on the proposed model. The identified ANN model can be used to simulate the water quality parameters. PMID:23001527

  15. Tracing solid waste leachate in groundwater using δ13 C from dissolved inorganic carbon.

    PubMed

    Haarstad, Ketil; Mæhlum, Trond

    2013-01-01

    Tracers can be used to monitor emissions of leachate from landfills in order to detect hydrological pathways and to evaluate environmental pollution. We investigated the stable carbon isotope ratio (δ(13)C-Σ CO (2)) in dissolved inorganic carbon and tritium ((3)H) in water, in addition to the tracers of pollution commonly found in relatively high concentrations in leachate, such as chloride (Cl), organic matter (COD), nitrogen (total and NH(4)-N), iron (Fe), electrical conductivity (EC) and pH. The sampling was performed at seven landfills in the south-eastern part of Norway during a period of 5 years. The objective was to evaluate the potential for tracing leachate in the environment with emphasis on groundwater pollution. By measuring the δ(13)C-Σ CO (2) in leachates, groundwaters and surface waters, the influence of leachate can be identified. The value of δ(13)C-Σ CO (2) varied from-5.5 to 25.9 ‰ in leachate, from-25.4 to 14.7 ‰ in groundwater and from-19.7 to-13.1 ‰ in creeks. A comparison of the carbon isotope ratio with COD, EC and the concentrations of total and NH (4)-N, Cl and Fe showed that δ(13)C-Σ CO (2) is a good tracer for leachate due to higher sensitivity compared to other parameters. The mean concentrations of all the studied parameters were higher in the leachate samples; however, only the carbon isotope ratio showed significant differences between all the groups with strong and middle pollution and samples with low pollution, showing that it can be used as a convenient tracer for leachate in groundwater and surface water. The carbon isotope ratio showed strong correlation between nitrogen, EC and bicarbonate, but not with pH. Tritium was only sporadically found in measureable concentrations and is not considered as a suitable tracer at the sampled locations. PMID:22462764

  16. Fast Dissolving Sublingual Films of Ondansetron Hydrochloride: Effect of Additives on in vitro Drug Release and Mucosal Permeation.

    PubMed

    Koland, M; Sandeep, Vp; Charyulu, Nr

    2010-07-01

    Ondansetron hydrochloride, a 5 HT3 antagonist is a powerful antiemetic drug which has oral bioavailability of 60% due to hepatic first pass metabolism and has a short half-life of 5 h. To overcome the above draw back, the present study was carried out to formulate and evaluate fast dissolving films of ondansetron hydrochloride for sublingual administration. The films were prepared from polymers such as polyvinylalcohol, polyvinyl pyrrolidone, Carbopol 934P in different ratios by solvent casting method. Propylene glycol or PEG 400 as plasticizers and mannitol or sodium saccharin as sweeteners were also included. The IR spectral studies showed no interaction between drug and polymer or with other additives. Satisfactory results were obtained when subjected to physico-chemical tests such as uniformity of weight, thickness, surface pH, folding endurance, uniformity of drug content, swelling index, bioadhesive strength, and tensile strength. Films were also subjected to in vitro drug release studies by using USP dissolution apparatus. Ex vivo drug permeation studies were carried out using porcine membrane model. In vitro release studies indicated 81-96% release within 7 min and 66-80% within 7 min during ex vivo studies. Drug permeation of 66-77% was observed through porcine mucosa within 40 min. Higher percentage of drug release was observed from films containing the sweeteners. The stability studies conducted for a period of 8 weeks showed no appreciable change in drug content, surface pH, and in vitro drug release. PMID:21042474

  17. Use of a Ferrous Sulfate - Sodium Dithionite Blend to Treat a Dissolved Phase Cr(VI) Plume

    EPA Science Inventory

    A field study was conducted to evaluate the use of a combination of sodium dithionite and ferrous sulfate in creating an in situ redox zone for treatment of a dissolved phase Cr(VI) plume at a former industrial site. The reductant blend was injected into the path of a dissolved ...

  18. Predicting Computer Science Ph.D. Completion: A Case Study

    ERIC Educational Resources Information Center

    Cox, G. W.; Hughes, W. E., Jr.; Etzkorn, L. H.; Weisskopf, M. E.

    2009-01-01

    This paper presents the results of an analysis of indicators that can be used to predict whether a student will succeed in a Computer Science Ph.D. program. The analysis was conducted by studying the records of 75 students who have been in the Computer Science Ph.D. program of the University of Alabama in Huntsville. Seventy-seven variables were…

  19. Earth & Space Science PhDs, Class of 2001.

    ERIC Educational Resources Information Center

    Claudy, Nicholas; Henly, Megan; Migdalski, Chet

    This study documents the employment patterns and demographic characteristics of recent PhDs in earth and space science. It summarizes the latest annual survey of recent earth and space science PhDs conducted by the American Geological Institute, the American Geophysical Union, and the Statistical Research Center of the American Institute of…

  20. Predicting Computer Science Ph.D. Completion: A Case Study

    ERIC Educational Resources Information Center

    Cox, G. W.; Hughes, W. E., Jr.; Etzkorn, L. H.; Weisskopf, M. E.

    2009-01-01

    This paper presents the results of an analysis of indicators that can be used to predict whether a student will succeed in a Computer Science Ph.D. program. The analysis was conducted by studying the records of 75 students who have been in the Computer Science Ph.D. program of the University of Alabama in Huntsville. Seventy-seven variables were

  1. The Importance of Having a Ph.D., Career Advice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A presentation on the importance of having a PhD to motivate Initiative to Maximize Student Diversity Program (IMSD) undergrads towards conducting research, pursuing careers in the biomedical field, applying to grad school, and getting a Ph.D., based upon ARS scientist's experiences as a student, a ...

  2. Geochemical Data for Upper Mineral Creek, Colorado, Under Existing Ambient Conditions and During an Experimental pH Modification, August 2005

    USGS Publications Warehouse

    Runkel, Robert L.; Kimball, Briant A.; Steiger, Judy I.; Walton-Day, Katherine

    2009-01-01

    Mineral Creek, an acid mine drainage stream in south-western Colorado, was the subject of a water-quality study that employed a paired synoptic approach. Under the paired synoptic approach, two synoptic sampling campaigns were conducted on the same study reach. The initial synoptic campaign, conducted August 22, 2005, documented stream-water quality under existing ambient conditions. A second synoptic campaign, conducted August 24, 2005, documented stream-water quality during a pH-modification experiment that elevated the pH of Mineral Creek. The experimental pH modification was designed to determine the potential reductions in dissolved constituent concentrations that would result from the implementation of an active treatment system for acid mine drainage. During both synoptic sampling campaigns, a solution containing lithium bromide was injected continuously to allow for the calculation of streamflow using the tracer-dilution method. Synoptic water-quality samples were collected from 30 stream sites and 11 inflow locations along the 2-kilometer study reach. Data from the study provide spatial profiles of pH, concentration, and streamflow under both existing and experimentally-altered conditions. This report presents the data obtained August 21-24, 2005, as well as the methods used for sample collection and data analysis.

  3. A unit for collection of dissolved oxygen and water column temperature at multiple depths

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A 2004 field study conducted during actual channel catfish Ictalurus punctatus harvests, and a small-scale research study conducted in 2005, required continuous collection of dissolved oxygen concentration and temperature at two depths in the water column. The on-farm study required data collection...

  4. COMMUNITY SCALE STREAM TAXA SENSITIVITIES TO DIFFERENT COMPOSITIONS OF EXCESS TOTAL DISSOLVED SOLIDS

    EPA Science Inventory

    Model stream chronic dosing studies (42 d) were conducted with three total dissolved solids (TDS) recipes. The recipes differed in composition of major ions. Community scale emergence was compared with single-species responses conducted simultaneously using the whole effluent tox...

  5. 7 CFR 760.908 - Deceased individuals or dissolved entities.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... suffered by an eligible participant who is now a deceased individual or is a dissolved entity if a... dissolved entity must be provided. (c) If a participant is now a dissolved general partnership or...

  6. 7 CFR 760.908 - Deceased individuals or dissolved entities.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... suffered by an eligible participant who is now a deceased individual or is a dissolved entity if a... dissolved entity must be provided. (c) If a participant is now a dissolved general partnership or...

  7. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Allen, Philip B.

    1979-01-01

    Examines Drude's classical (1900) theory of electrical conduction, details the objections to and successes of the 1900 theory, and investigates the Quantum (1928) theory of conduction, reviewing its successes and limitations. (BT)

  8. Feasibility Study for Evaluating Cumulative Exposure of Downstream Migrant Juvenile Salmonids to Total Dissolved Gas. Final Report 1996.

    SciTech Connect

    Abernethy, C.Scott; Dauble, Dennis D.; Johnson, Robert L.

    1997-11-01

    A feasibility study was initiated to determine if downstream migrant salmonids could be monitored to determine potential relationships between total dissolved gas (TDG) exposure and signs of gas bubble trauma (GBT). The primary objectives were to: (1) establish logistical requirements for in-river monitoring of TDG exposure, including net pen design, deployment, and navigation constraints; (2) resolve uncertainties associated with effects of the net pen on fish behavior; (3) test the accuracy and precision of in-river monitoring equipment used to measure fish distribution and water quality; and (4) determine the application of hydrologic/flow models to predictions of TDG exposure. In-river measurements included water velocity, boat position, and selected water quality parameters (temperature, dissolved oxygen, pH, depth, conductivity). Fish distribution within the net pen was monitored using scanning sonar, and a split-beam echo sounder was used to evaluate vertical distribution of fish m in the river adjacent to the net pen. Three test drifts were conducted from late July through late August. The studies demonstrated that it was feasible to assemble and deploy a large net pen for mobile monitoring of TDG exposure. Accurate monitoring of vertical and lateral distribution of smolts was performed, and diel differences in behavior were documented. Further, the fish sounded in response to researcher activity on the perimeter platform. Thus, in-transit monitoring for GBT or mortality would affect fish depth distribution and exposure to TDG. Principal recommendations for future studies are directed at improving maneuverability of the net pen in adverse weather conditions and applying new acoustics technology to simultaneously collect fish distribution data from within and outside of the pen. 6 refs., 17 figs., 2 tabs.

  9. Photoirradiation of dissolved humic acid induces arsenic(III) oxidation.

    PubMed

    Buschmann, Johanna; Canonica, Silvio; Lindauer, Ursula; Hug, Stephan J; Sigg, Laura

    2005-12-15

    The fate of arsenic in aquatic systems is influenced by dissolved natural organic matter (DOM). Using UV-A and visible light from a medium-pressure mercury lamp, the photosensitized oxidation of As(III) to As(V) in the presence of Suwannee River humic acid was investigated. Pseudo-first-order kinetics was observed. For 5 mg L(-1) of dissolved organic carbon (DOC) and 1.85 mEinstein m(-2) s(-1) UV-A fluence rate, the rate coefficient k degrees exp was 21.2 +/- 3.2 10(-5) s(-1), corresponding to a half-life <1 h. Rates increased linearly with DOC and they increased by a factor of 10 from pH 4 to 8. Based on experiments with radical scavengers, heavy water, and surrogates for DOM, excited triplet states and/or phenoxyl radicals seem to be important photooxidants in this system (rather than singlet oxygen, hydrogen peroxide, hydroxyl radicals, and superoxide). Photoirradiation of natural samples from freshwater lakes, rivers, and rice field water (Bangladesh) showed similar photoinduced oxidation rates based on DOC. Fe(III) (as polynuclear Fe(III)-(hydr)oxo complexes or Fe(III)-DOC complexes) accelerates the rate of photoinduced As(III) oxidation in the presence of DOC by a factor of 1.5-2. PMID:16475334

  10. Simultaneous E. coli inactivation and NOM degradation in river water via photo-Fenton process at natural pH in solar CPC reactor. A new way for enhancing solar disinfection of natural water.

    PubMed

    Moncayo-Lasso, Alejandro; Sanabria, Janeth; Pulgarin, César; Benítez, Norberto

    2009-09-01

    Bacteria inactivation and natural organic matter oxidation in river water was simultaneously conducted via photo-Fenton reaction at "natural" pH ( approximately 6.5) containing 0.6 mg L(-1) of Fe(3+) and 10 mg L(-1) of H(2)O(2). The experiments were carried out by using a solar compound parabolic collector on river water previously filtered by a slow sand filtration system and voluntarily spiked with Escherichia coli. Fifty five percent of 5.3 mg L(-1) of dissolved organic carbon was mineralized whereas total disinfection was observed without re-growth after 24h in the dark. PMID:19716153

  11. Photodegradation of dissolved organic matter in ice under solar irradiation.

    PubMed

    Xue, Shuang; Wang, Chao; Zhang, Zhaohong; Song, Youtao; Liu, Qiang

    2016-02-01

    The photodegradation behavior of dissolved organic matter (DOM) with different origins in ice under solar irradiation was investigated. Exposure to sunlight at 2.7 × 10(5) J m(-2) resulted in dissolved organic carbon (DOC) reductions of 22.1-36.5% in ice. The naturally occurring DOM had higher photodegradation potentials than the wastewater-derived DOM in ice. Ultraviolet (UV)-absorbing compounds in DOM, regardless of DOM origin, had much higher photodegradation potentials than gross DOC in ice. The susceptibility of UV-absorbing compounds with natural origin to sunlight exposure in ice was higher than those derived from wastewater. Trihalomethane (THM) precursors were more susceptible to photochemical reactions than gross DOC and haloacetic acid (HAA) precursors in ice. THM precursors in naturally occurring DOM were more photoreactive than those in wastewater-derived DOM in ice, while the photoreactivity of HAA precursors in ice was independent of DOM origin. In ice, the photoreactivity of humic-like fluorescent materials, regardless of DOM origin, was higher than that of gross DOC and protein-like fluorescent materials. DOC reductions caused by sunlight irradiation were found to be negatively correlated to DOC levels, and positively correlated to the aromaticity of DOM. The photodegradation of both wastewater-derived and naturally occurring DOM in ice was significantly facilitated at both acid and alkaline pH, as compared to neutral pH. The photodegradation of DOM in ice, regardless of the origin, was facilitated by nitrate ion [Formula: see text] , nitrite ion [Formula: see text] , ferric ion (Fe(3+)) and ferrous ion (Fe(2+)), and on the other hand, was inhibited by chloridion ion (Cl(-)) and copper ion (Cu(2+)). PMID:26414742

  12. Optimizing dissolved air flotation design and saturation.

    PubMed

    Féris, L A; Gallina, C W; Rodrigues, R T; Rubio, J

    2001-01-01

    Dissolved air flotation (DAF) of iron hydroxide precipitates at working pressures lower than 3 atm, using modified flotation units to improve the collection of fragile coagula, was studied. Conventional DAF flotation was studied as a function of saturation pressure in the absence and presence of surfactants in the saturator. Without surfactants, the minimum saturation pressure required for DAF to occur was found to be 3 atm. But, by lowering the air/water surface tension in the saturator, DAF was possible at a saturation pressure of 2 atm. This behavior was found to occur in both batch and pilot DAF operation tests and almost complete recovery of the precipitates was attained. Results are explained in terms of the minimum "energy" which has to be transferred to the liquid phase to form bubbles by a cavity phenomenon. Further, studies were conducted changing equipment design and feed bubbles size distribution (mixing micro and "mid-sized" bubbles). Thus, bubbles entrance position in the collision-adhesion zone ("capture" zone) was compared to bubble entrance position in the water flow inlet below the floating bed. A "mushroom" type diffuser was used for the "capture zone" experiment and better performance was obtained. Results are explained in terms of different mass transfer phenomena in the collection zone and in the separation zone. Finally, results obtained with the use of a column flotation cell working as normal DAF and with a wide bubble size range are presented. Results indicate good performance and some gains in process kinetics with middle size bubbles. PMID:11394267

  13. New technology for the detection of pH.

    PubMed

    Yuqing, Miao; Jianrong, Chen; Keming, Fang

    2005-04-29

    The measurement of pH is the most widely employed test for (bio-)chemical lab. Since the first use of glass electrode to detect pH, new techniques and methods have broaden the scope of pH detection. Metal/metal oxide, ion sensitive field-effect transistors (ISFET), fibre-optical techniques, nanotechniques, and conducting polymer techniques have been extensively developed. This review covers the various methods for pH detection. New development trends were discussed. PMID:15892973

  14. Dissolved Free Amino Acids in Hydrothermal Springs at Yellowstone National Park, U.S.A.

    NASA Astrophysics Data System (ADS)

    Cox, J. S.; Holland, M. E.; Shock, E. L.

    2004-12-01

    Insights into the organic geochemistry of hydrothermal systems, as well as the dynamics of biotic processes in hot spring ecosystems, can be gained by identifying and quantifying dissolved free amino acids (DFAA). Hydrothermal systems form a unique environmental subset relative to other aqueous settings due to their higher temperatures, largely uncharacterized and exotic microbiology, wider pH range, and elevated levels of rare metals, sulfur, and dissolved gases. Previous studies of hot spring and geothermal systems (e.g. Mukhin et al., 1979; Svensson et al., 2004) indicated the presence of micromolar quantities of various amino acids, but the underlying mechanisms controlling amino acid production and disappearance/consumption have continued to remain elusive. DFAA were identified and quantified in five hot springs at Yellowstone National Park that span a range of pH (2 to 8) and temperature (75 to 93° C/boiling). Biotic uptake experiments and enantiomeric analyses on samples from one location were also performed to elucidate biotic pathways. Analyses were performed using high pressure anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), which is able to resolve amino acids as well as certain carbohydrates, oligopeptides, and a variety of related biological molecules. Preliminary data indicate that total DFAA concentrations are quite low (sub-micromolar range) and that amino acids with aliphatic and nitrogen-containing R-groups are predominant in the DFAA fraction. The types and concentrations of amino acids were variable across the sites. Obsidian Pool (pH 5.1, 77.5° C), where multiple microbiological studies have been conducted, was found to have a DFAA fraction consisting primarily of glycine with trace amounts of arginine, lysine, and histidine. In comparison, an acidic spring in the Sylvan Springs area (pH 1.9, 79.7° C) had higher total DFAA concentrations and was found to contain primarily arginine, lysine, and leucine, together with trace amounts of alanine, proline, and histidine. At least six other unknown compounds were also observed, one of them possibly at near-micromolar levels, and there was evidence for higher levels of organic compounds in general. The generally low concentrations observed in this study suggest that amino acids participate in highly dynamic biotic pathways in Yellowstone hot springs. Our observations of lower concentrations of amino acids and less diversity differ from literature results, but are consistent with suggestions of a positive correlation between acidic conditions and higher levels of DFAA (Svensson et al., 2004). References: Mukhin L.M., Bondarev V.B., Vakin E.A., Il'yukhina N.I., Kalinichenko V.I., Milekhina E.I., Safonova E.N. (1979) Doklady Akademii Nauk SSSR 244(4), 974-7. Svensson E., Skoog A., and Amend J.P. (2004) Organic Geochemistry 35, 1001-1014.

  15. Understanding Non-Traditional PhD Students Habitus--Implications for PhD Programmes

    ERIC Educational Resources Information Center

    Naidoo, Devika

    2015-01-01

    Against the background of vast changes in doctoral education and the emergence of non-traditional doctoral programmes, this paper investigates the habitus of non-traditional PhD students at a South African university. Bourdieu's conceptual tool of habitus informed the study. In-depth and open-ended interviews were conducted with 10 non-traditional…

  16. Understanding Non-Traditional PhD Students Habitus--Implications for PhD Programmes

    ERIC Educational Resources Information Center

    Naidoo, Devika

    2015-01-01

    Against the background of vast changes in doctoral education and the emergence of non-traditional doctoral programmes, this paper investigates the habitus of non-traditional PhD students at a South African university. Bourdieu's conceptual tool of habitus informed the study. In-depth and open-ended interviews were conducted with 10 non-traditional

  17. Sequestration of Dissolved CO2 in the Oriskany Formation

    SciTech Connect

    Dilmore, R.M.; Allen, D.E.; McCarthy-Jones, J.R.; Hedges, S.W.; Soong, Yee

    2008-04-15

    Experiments were conducted to determine the solubility of CO2 in a natural brine solution of the Oriskany formation under elevated temperature and pressure conditions. These data were collected at temperatures of 22 and 75 °C and pressures between 100 and 450 bar. Experimentally determined data were compared with CO2 solubility predictions using a model developed by Duan and Sun (Chem. Geol. 2003, 193, 257-271). Model results compare well with Oriskany brine CO2 solubility data collected experimentally, suggesting that the Duan and Sun model is a reliable tool for estimating solution CO2 capacity in high salinity aquifers in the temperature and pressure range evaluated. The capacity for the Oriskany formation to sequester dissolved CO2 was calculated using results of the solubility models, estimation of the density of CO2 saturated brine, and available geographic information system (GIS) information on the formation depth and thickness. Results indicate that the Oriskany formation can hold approximately 0.36 gigatonnes of dissolved CO2 if the full basin is considered. When only the region where supercritical CO2 can exist (temperatures greater than 31° C and pressures greater than 74 bar) is considered, the capacity of the Oriskany formation to sequester dissolved CO2 is 0.31 gigatonnes. The capacity estimate considering the potential to sequester free-phase supercritical CO2 if brine were displaced from formation pore space is 8.8 gigatonnes in the Oriskany formation.

  18. Influence of dissolved organic substances in groundwater on sorption behavior of americium and neptunium

    SciTech Connect

    Boggs, S. Jr.; Seitz, M.G.

    1984-01-01

    Groundwaters typically contain dissolved organic carbon consisting largely of high molecular weight compounds of humic and fulvic acids. To evaluate whether these dissolved organic substances can enhance the tranport of radionuclides through the groundwater system, experiments were conducted to examine the sorption of americium and neptunium onto crushed basalt in the presence of dissolved humic- and fulvic-acid organic carbon introduced into synthetic groundwater. The partitioning experiments with synthetic groundwater show that increasing the concentration of either humic or fulvic acid in the water has a significant inhibiting effect on sorption of both americium and neptunium. At 22/sup 0/C, adsorption of these radionuclides, as measured by distribution ratios (the ratio of nuclide sorbed onto the solid to nuclide in solution at the end of the experiment), decreased by 25% to 50% by addition of as little as 1 mg/L dissolved organic carbon and by one to two orders of magnitude by addition of 100 to 200 mg/L dissolved organic carbon. Distribution ratios measured in solutions reacted at 90/sup 0/C similarly decreased with the addition of dissolved organic carbon but generally ranged from one to two orders of magnitude higher than those determined in the 22/sup 0/C experiment. These results suggest that organic carbon dissolved in deep groundwaters may significantly enhance the mobility of radionuclides of americium and neptunium. 23 references, 5 figures, 11 tables.

  19. Effects of dissolved oxygen concentration on biodegradation of 2,4-dichlorophenoxyacetic acid.

    PubMed Central

    Shaler, T A; Klecka, G M

    1986-01-01

    Batch experiments were conducted to examine the effects of dissolved oxygen concentration on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by an enrichment culture of 2,4-D-utilizing bacteria. A modified Monod equation was found to describe the relationship between the specific growth rate and the concentrations of both the organic substrate and dissolved oxygen. Values for the maximum specific growth rate, yield, and Monod coefficient for growth on 2,4-D were 0.09 h-1, 0.14 g/g, and 0.6 mg/liter, respectively. The half-saturation constant for dissolved oxygen was estimated to be 1.2 mg/liter. These results suggest that dissolved oxygen concentrations below 1 mg/liter may be rate limiting for the biodegradation of chlorinated aromatic compounds such as 2,4-D, which have a requirement for molecular oxygen as a cosubstrate for metabolism. PMID:3729394

  20. Macroscopic observations of the effects of varying fresh water pH on bone.

    PubMed

    Christensen, Angi M; Myers, Sarah W

    2011-03-01

    Little is known about the decomposition of remains in aquatic environments of varying pH, and even less is known about the specific effects of these environments on bone. Bovine bones were placed in solutions of pH 1, 4, 7, 10, and 14 and observed over a period of 1 year. All solutions eventually removed or dissolved the soft tissues from the external surface of the bone. The pH 7 and pH 10 solutions had little effect on the bone, but the other solutions affected the bone to varying degrees. Extreme pH levels were the most destructive, while more moderate pH levels had lesser but significant and interesting effects. Empirical data on postmortem aquatic changes may be extremely useful in forensic contexts for both improving time since death estimates and also for providing better information to underwater recovery experts thereby potentially increasing the quantity and quality of remains recovery. PMID:21342189

  1. Effect of coal mine waters of variable pH on springwater quality: A case study

    NASA Astrophysics Data System (ADS)

    Liu, Zaihua; Yuan, Daoxian; Shen, Zhaoli

    1991-05-01

    Disruption of coal strata during mining accelerates pyrite oxidation by exposing greater surface areas of the reactive mineral to weathering. Acidic water in a coal mine in the Niangziguan spring watershed is related to this process and is characterized by low pH (min. 2.52) and high sulfate (max. 4100 mg/I), iron (max. 257 mg/I), and hardness (max. 2274.45 mg/I). However, it is possible that the kind of acidic coal mine water is subsequently neutralized because of the dissolution of calcite present in the coal strata. The hydrochemical characters of the alkaline coal mine water produced are high pH (max. 8.18), sulfate (max. 542 mg/I), and hardness (max. 1183.56 mg/I) and lower iron (min. 0.12 mg/I). Experiments were conducted to further understand the mechanism of the formation of both acidic and alkaline waters in the spring watershed coal mines by modeling natural conditions with simplification, and the results of the experiments have shown that they are basically successful. The high sulfate (max. 223.82 mg/I) and hardness (max. 435.53 mg/I) of the Niangziguan springs are related to the influence of the neutralized acid coal mine water as demonstrated by analysis of water temperature, total dissolved solid, Q-mode cluster analysis, and sulfur isotopes. The influence of the neutralized acid coal mine water on the pH and iron in the springs is not obvious because of the neutralization effect of calcite in aquifer, the buffer effect of groundwater, and the precipitation of iron. Some measures to prevent the formation of acid and alkaline coal mine water are presented.

  2. Seasonality of diel cycles of dissolved trace-metal concentrations in a Rocky Mountain stream

    USGS Publications Warehouse

    Nimick, D.A.; Cleasby, T.E.; McCleskey, R.B.

    2005-01-01

    Substantial diel (24-h) cycles in dissolved (0.1-??m filtration) metal concentrations were observed during summer low flow, winter low flow, and snowmelt runoff in Prickly Pear Creek, Montana. During seven diel sampling episodes lasting 34-61.5 h, dissolved Mn and Zn concentrations increased from afternoon minimum values to maximum values shortly after sunrise. Dissolved As concentrations exhibited the inverse timing. The magnitude of diel concentration increases varied in the range 17-152% for Mn and 70-500% for Zn. Diel increases of As concentrations (17-55%) were less variable. The timing of minimum and maximum values of diel streamflow cycles was inconsistent among sampling episodes and had little relation to the timing of metal concentration cycles, suggesting that geochemical rather than hydrological processes are the primary control of diel metal cycles. Diel cycles of dissolved metal concentrations should be assumed to occur at any time of year in any stream with dissolved metals and neutral to alkaline pH. ?? Springer-Verlag 2005.

  3. ADDING REALISM TO NUCLEAR MATERIAL DISSOLVING ANALYSIS

    SciTech Connect

    Williamson, B.

    2011-08-15

    Two new criticality modeling approaches have greatly increased the efficiency of dissolver operations in H-Canyon. The first new approach takes credit for the linear, physical distribution of the mass throughout the entire length of the fuel assembly. This distribution of mass is referred to as the linear density. Crediting the linear density of the fuel bundles results in using lower fissile concentrations, which allows higher masses to be charged to the dissolver. Also, this approach takes credit for the fact that only part of the fissile mass is wetted at a time. There are multiple assemblies stacked on top of each other in a bundle. On average, only 50-75% of the mass (the bottom two or three assemblies) is wetted at a time. This means that only 50-75% (depending on operating level) of the mass is moderated and is contributing to the reactivity of the system. The second new approach takes credit for the progression of the dissolving process. Previously, dissolving analysis looked at a snapshot in time where the same fissile material existed both in the wells and in the bulk solution at the same time. The second new approach models multiple consecutive phases that simulate the fissile material moving from a high concentration in the wells to a low concentration in the bulk solution. This approach is more realistic and allows higher fissile masses to be charged to the dissolver.

  4. Spectral studies of pH dye films for detection of toxic chemicals

    NASA Astrophysics Data System (ADS)

    Wojcik, Wieslaw; Potyrailo, Radislav A.; Golubkov, Sergei P.; Borsuk, Pavel S.

    1993-09-01

    The molecular absorption spectra of pH dyes, employed for ammonia sensing are investigated. Differences of absorption spectra of Bromothymol Blue and Bromocresol Purple dyes, dissolved in water and entrapped in Polymethylphenylsiloxane film are discussed. Correspondence of dye-films absorption bands shape to the Gauss distribution shape in the spectral region of light source emission band was determined.

  5. In situ spectrophotometric measurement of dissolved inorganic carbon in seawater.

    PubMed

    Liu, Xuewu; Byrne, Robert H; Adornato, Lori; Yates, Kimberly K; Kaltenbacher, Eric; Ding, Xiaoling; Yang, Bo

    2013-10-01

    Autonomous in situ sensors are needed to document the effects of today's rapid ocean uptake of atmospheric carbon dioxide (e.g., ocean acidification). General environmental conditions (e.g., biofouling, turbidity) and carbon-specific conditions (e.g., wide diel variations) present significant challenges to acquiring long-term measurements of dissolved inorganic carbon (DIC) with satisfactory accuracy and resolution. SEAS-DIC is a new in situ instrument designed to provide calibrated, high-frequency, long-term measurements of DIC in marine and fresh waters. Sample water is first acidified to convert all DIC to carbon dioxide (CO2). The sample and a known reagent solution are then equilibrated across a gas-permeable membrane. Spectrophotometric measurement of reagent pH can thereby determine the sample DIC over a wide dynamic range, with inherent calibration provided by the pH indicator's molecular characteristics. Field trials indicate that SEAS-DIC performs well in biofouling and turbid waters, with a DIC accuracy and precision of ∼2 μmol kg(-1) and a measurement rate of approximately once per minute. The acidic reagent protects the sensor cell from biofouling, and the gas-permeable membrane excludes particulates from the optical path. This instrument, the first spectrophotometric system capable of automated in situ DIC measurements, positions DIC to become a key parameter for in situ CO2-system characterizations. PMID:23991621

  6. In situ spectrophotometric measurement of dissolved inorganic carbon in seawater

    USGS Publications Warehouse

    Liua, Xuewu; Byrne, Robert H.; Adornato, Lori; Yates, Kimberly K.; Kaltenbacher, Eric; Ding, Xiaoling; Yang, Bo

    2013-01-01

    Autonomous in situ sensors are needed to document the effects of today’s rapid ocean uptake of atmospheric carbon dioxide (e.g., ocean acidification). General environmental conditions (e.g., biofouling, turbidity) and carbon-specific conditions (e.g., wide diel variations) present significant challenges to acquiring long-term measurements of dissolved inorganic carbon (DIC) with satisfactory accuracy and resolution. SEAS-DIC is a new in situ instrument designed to provide calibrated, high-frequency, long-term measurements of DIC in marine and fresh waters. Sample water is first acidified to convert all DIC to carbon dioxide (CO2). The sample and a known reagent solution are then equilibrated across a gas-permeable membrane. Spectrophotometric measurement of reagent pH can thereby determine the sample DIC over a wide dynamic range, with inherent calibration provided by the pH indicator’s molecular characteristics. Field trials indicate that SEAS-DIC performs well in biofouling and turbid waters, with a DIC accuracy and precision of ∼2 μmol kg–1 and a measurement rate of approximately once per minute. The acidic reagent protects the sensor cell from biofouling, and the gas-permeable membrane excludes particulates from the optical path. This instrument, the first spectrophotometric system capable of automated in situ DIC measurements, positions DIC to become a key parameter for in situ CO2-system characterizations.

  7. Design and evaluation of fast dissolving tablets of clonazepam.

    PubMed

    Shirsand, S B; Suresh, Sarasija; Swamy, P V; Kumar, D Nagendra; Rampure, M V

    2008-11-01

    In the present work, fast dissolving tablets of clonazepam were prepared by direct compression method with a view to enhance patient compliance. Three super-disintegrants, viz., crospovidone, croscarmellose sodium and sodium starch glycolate in different ratios with microcrystalline cellulose (Avicel PH-102) along with directly compressible mannitol (Pearlitol SD 200) to enhance mouth feel. The prepared batches of tablets were evaluated for hardness, friability, drug content uniformity, wetting time, water absorption ratio and in vitro dispersion time. Based on in vitro dispersion time (approximately 13 s), three formulations were tested for the in vitro drug release pattern (in pH 6.8 phosphate buffer), short-term stability (at 40°/75% relative humidity for 6 mo) and drug-excipient interaction (IR spectroscopy). Among the three promising formulations, the formulation prepared by using 10% w/w of crospovidone and 35% w/w of microcrystalline cellulose emerged as the overall best formulation (t(50%) 1.8 min) based on the in vitro drug release characteristics compared to conventional commercial tablet formulation (t(50%) 16.4 min). Short-term stability studies on the formulations indicated that there were no significant changes in drug content and in vitro dispersion time (P<0.05). PMID:21369444

  8. Acid characteristics of dissolved organic matter in wastewater

    SciTech Connect

    Wang, J.; Huang, C.P.; Allen, H.E.; Takiyama, L.R.; Poesponegoro, I.; Poesponegoro, H.; Pirestani, D.

    1998-07-01

    The presence of dissolved organic matter (DOM) in a wastewater treatment system can significantly affect the uptake of heavy metals by sludge particulates. The characteristics of DOM, its concentration, and the solution pH are important parameters governing the heavy metals uptake reaction. The characteristics of DOM of various wastewater and sludge (primary, secondary, and tertiary) samples collected from four municipal wastewater treatment plants were investigated. Results showed that the dissolution of DOM from sludge is significantly affected by pH and suspended solids concentration. Results also showed that DOM contains two discrete acid groups that are available for metals complexation. The site concentration and acidity constants were determined by an alkalimetric titration method. For all DOM samples studied, the acidity constants, pK{sub aA} and pK{sub aB}, were 5.3 and 9.5, respectively. Based on the acidity constants and the Fourier transform infrared spectra, it is believed that the acid sites consist of carboxylic and amino functional groups. The density of the first acid site was approximately 10{sup {minus}5} mol/mg chemical oxygen demand for all samples studied. However, the density of the second acid site varied significantly among the DOM samples investigated.

  9. Toxicity identification evaluation of metal-contaminated sediments using an artificial pore water containing dissolved organic carbons

    SciTech Connect

    Boucher, A.M.; Watzin, M.C.

    1999-03-01

    Recent investigations of sediment-associated pollutants in Lake Champlain indicated significant contamination with As, Mn, and Ni in Outer Malletts Bay, Vermont, US. Ceriodaphnia dubia exposed to sediment pore water from several sites in Outer Malletts Bay showed repeatable, acute mortality at only one site. A toxicity identification evaluation (TIE) was conducted on pore water to determine the contaminants causing mortality at this site. Unlike most TIE applications, the dilution water used in these tests was formulated to match the hardness, alkalinity, pH, conductivity, and dissolved organic carbon content of the pore water. Results from phase 1 of the TIE indicated that divalent metals may be responsible for toxicity. Phase 2 results revealed levels of Mn above LC50 values. Spiking experiments employed in phase 3 confirmed Mn as the principal toxicant in sediment pore water. The formulated pore water worked well and helped ensure that toxicant behavior was influenced primarily by each TIE manipulation and not by physical and chemical differences between the dilution and site water. Although the Mn toxicity at this site may be the result of its unique geomorphology, this situation underscores the need to look broadly for potential toxicants when evaluating contaminated sites.

  10. Characterization of hydraulic conductivity of the alluvium and basin fill, Pinal Creek Basin near Globe, Arizona

    USGS Publications Warehouse

    Angeroth, Cory E.

    2002-01-01

    Acidic waters containing elevated concentrations of dissolved metals have contaminated the regional aquifer in the Pinal Creek Basin, which is in Gila County, Arizona, about 100 kilometers east of Phoenix. The aquifer is made up of two geologic units: unconsolidated stream alluvium and consolidated basin fill. To better understand how contaminants are transported through these units, a better understanding of the distribution of hydraulic conductivity and processes that affect it within the aquifer is needed. Slug tests were done in September 1997 and October 1998 on 9 wells finished in the basin fill and 14 wells finished in the stream alluvium. Data from the tests were analyzed by using either the Bouwer and Rice (1976) method, or by using an extension to the method developed by Springer and Gellhar (1991). Both methods are applicable for unconfined aquifers and partially penetrating wells. The results of the analyses show wide variability within and between the two geologic units. Hydraulic conductivity estimates ranged from 0.5 to 250 meters per day for the basin fill and from 3 to 200 meters per day for the stream alluvium. Results of the slug tests also show a correlation coefficient of 0.83 between the hydraulic conductivity and the pH of the ground water. The areas of highest hydraulic conductivity coincide with the areas of lowest pH, and the areas of lowest hydraulic conductivity coincide with the areas of highest pH, suggesting that the acidic water is increasing the hydraulic conductivity of the aquifer by dissolution of carbonate minerals.

  11. Lithium ion conducting electrolytes

    DOEpatents

    Angell, C. Austen; Liu, Changle

    1996-01-01

    A liquid, predominantly lithium-conducting, ionic electrolyte having exceptionally high conductivity at temperatures of 100.degree. C. or lower, including room temperature, and comprising the lithium salts selected from the group consisting of the thiocyanate, iodide, bromide, chloride, perchlorate, acetate, tetrafluoroborate, perfluoromethane sulfonate, perfluoromethane sulfonamide, tetrahaloaluminate, and heptahaloaluminate salts of lithium, with or without a magnesium-salt selected from the group consisting of the perchlorate and acetate salts of magnesium. Certain of the latter embodiments may also contain molecular additives from the group of acetonitrile (CH.sub.3 CN) succinnonitrile (CH.sub.2 CN).sub.2, and tetraglyme (CH.sub.3 --O--CH.sub.2 --CH.sub.2 --O--).sub.2 (or like solvents) solvated to a Mg.sup.+2 cation to lower the freezing point of the electrolyte below room temperature. Other particularly useful embodiments contain up to about 40, but preferably not more than about 25, mol percent of a long chain polyether polymer dissolved in the lithium salts to provide an elastic or rubbery solid electrolyte of high ambient temperature conductivity and exceptional 100.degree. C. conductivity. Another embodiment contains up to about but not more than 10 mol percent of a molecular solvent such as acetone.

  12. Lithium ion conducting electrolytes

    DOEpatents

    Angell, C.A.; Liu, C.

    1996-04-09

    A liquid, predominantly lithium-conducting, ionic electrolyte is described having exceptionally high conductivity at temperatures of 100 C or lower, including room temperature, and comprising the lithium salts selected from the group consisting of the thiocyanate, iodide, bromide, chloride, perchlorate, acetate, tetrafluoroborate, perfluoromethane sulfonate, perfluoromethane sulfonamide, tetrahaloaluminate, and heptahaloaluminate salts of lithium, with or without a magnesium-salt selected from the group consisting of the perchlorate and acetate salts of magnesium. Certain of the latter embodiments may also contain molecular additives from the group of acetonitrile (CH{sub 3}CN), succinnonitrile (CH{sub 2}CN){sub 2}, and tetraglyme (CH{sub 3}--O--CH{sub 2}--CH{sub 2}--O--){sub 2} (or like solvents) solvated to a Mg{sup +2} cation to lower the freezing point of the electrolyte below room temperature. Other particularly useful embodiments contain up to about 40, but preferably not more than about 25, mol percent of a long chain polyether polymer dissolved in the lithium salts to provide an elastic or rubbery solid electrolyte of high ambient temperature conductivity and exceptional 100 C conductivity. Another embodiment contains up to about but not more than 10 mol percent of a molecular solvent such as acetone. 2 figs.

  13. Summary of Dissolved Concentration Limits

    SciTech Connect

    Yueting Chen

    2001-06-11

    According to the Technical Work Plan titled Technical Work Plan for Waste Form Degradation Process Model Report for SR (CRWMS M&O 2000a), the purpose of this study is to perform abstractions on solubility limits of radioactive elements based on the process-level information and thermodynamic databases provided by Natural Environment Program Operations (NEPO) and Waste Package Operations (WPO). The scope of this analysis is to produce solubility limits as functions, distributions, or constants for all transported radioactive elements identified by the Performance Assessment Operations (PAO) radioisotope screening. Results from an expert elicitation for solubility limits of most radioactive elements were used in the previous Total System Performance Assessments (TSPAs). However, the elicitation conducted in 1993 does not meet the criteria set forth by the U.S. Nuclear Regulatory Commission (NRC) due to lack of documentation and traceability (Kotra et al. 1996, Section 3). Therefore, at the Waste Form Abstraction Workshop held on February 2-4, 1999, at Albuquerque, New Mexico, the Yucca Mountain Site Characterization Project (YMP) decided to develop geochemical models to study solubility for the proposed Monitored Geologic Repository. WPO/NEPO is to develop process-level solubility models, including review and compilation of relevant thermodynamic data. PAO's responsibility is to perform abstractions based on the process models and chemical conditions and to produce solubility distributions or response surfaces applicable to the proposed repository. The results of this analysis and conceptual model will feed the performance assessment for Total System Performance Assessment--Site Recommendation (TSPA-SR) and Total System Performance Assessment--License Application (TSPA-LA), and to the Waste Form Degradation Process Model Report section on concentration limits.

  14. Process for coal liquefaction in staged dissolvers

    DOEpatents

    Roberts, George W.; Givens, Edwin N.; Skinner, Ronald W.

    1983-01-01

    There is described an improved liquefaction process by which coal is converted to a low ash and low sulfur carbonaceous material that can be used as a fuel in an environmentally acceptable manner without costly gas scrubbing equipment. In the process, coal is slurried with a pasting oil, passed through a preheater and at least two dissolvers in series in the presence of hydrogen-rich gases at elevated temperatures and pressures. Solids, including mineral ash and unconverted coal macerals, are separated from the condensed reactor effluent. In accordance with the improved process, the first dissolver is operated at a higher temperature than the second dissolver. This temperature sequence produces improved product selectivity and permits the incorporation of sufficient hydrogen in the solvent for adequate recycle operations.

  15. A Quantitative Evaluation of Dissolved Oxygen Instrumentation

    NASA Technical Reports Server (NTRS)

    Pijanowski, Barbara S.

    1971-01-01

    The implications of the presence of dissolved oxygen in water are discussed in terms of its deleterious or beneficial effects, depending on the functional consequences to those affected, e.g., the industrialist, the oceanographer, and the ecologist. The paper is devoted primarily to an examination of the performance of five commercially available dissolved oxygen meters. The design of each is briefly reviewed and ease or difficulty of use in the field described. Specifically, the evaluation program treated a number of parameters and user considerations including an initial check and trial calibration for each instrument and a discussion of the measurement methodology employed. Detailed test results are given relating to the effects of primary power variation, water-flow sensitivity, response time, relative accuracy of dissolved-oxygen readout, temperature accuracy (for those instruments which included this feature), error and repeatability, stability, pressure and other environmental effects, and test results obtained in the field. Overall instrument performance is summarized comparatively by chart.

  16. Wastewater treatment with zero dissolved oxygen

    SciTech Connect

    Hirl, P.J.

    1998-07-01

    Many wastewater treatment plants operate their biological reactors inefficiently because the aeration is not adjusted so that the oxygen supply rate equals the microbial oxygen demand in real times. Tapered aeration systems vary aeration based on the oxygen demand profile but these systems are static. Dynamic oxygen control systems have been successful but do not operate at low dissolved oxygen concentrations. The purpose of the research described is to develop a control system and reactor operating strategies to dynamically change the aeration rate to match the oxygen uptake rate while maintaining the dissolve oxygen concentration less than 0.5 mg/L. Though, low dissolved oxygen operation can reduce the rate of carbon degradation and/or promote filamentous bulking, it also maximizes the oxygen transfer rate and can promote simultaneous nitrification and denitrification. Development and testing of a control system and operating strategies at the bench scale is in progress.

  17. The pH Game.

    ERIC Educational Resources Information Center

    Chemecology, 1996

    1996-01-01

    Describes a game that can be used to teach students about the acidity of liquids and substances around their school and enable them to understand what pH levels tell us about the environment. Students collect samples and measure the pH of water, soil, plants, and other natural material. (DDR)

  18. Understanding and modelling the variability in Dissolved Organic Carbon concentrations in catchment drainage

    NASA Astrophysics Data System (ADS)

    Coleman, Martin; Waldron, Susan; Scott, Marian; Drew, Simon

    2013-04-01

    Our knowledge of dynamic natural habitats could be improved through the deployment of automated sensor technology. Dissolved organic carbon concentrations, [DOC], are of interest to water companies as purification removes this pool and currently in environmental science, due in part to rising DOC levels and also as respiration of this C pool can lead to an increased CO2 efflux. Manual sampling of catchment drainage systems has revealed seasonal patterns in DOC (Williams, P.J.L., 1995) and that hydrological events export most DOC(Raymond, P.A. and J.E. Saiers, 2010). However, manual sampling precludes detailed characterisation of the dynamic fluctuation of DOC over shorter but important time periods e.g. immediately prior to an event; the transition from base flow to a surface run-off dominated system as surface flow pathways defrost. Such insight is only gained through deployment of continuous-monitoring equipment. Since autumn 2010 we have deployed an S::CAN Spectrolyser (which from absorbance gives a measurement of [DOC]) in a 7.5 kilometre squared peaty catchment draining Europe's largest windfarm, Whitelee. Since autumn 2011, we have an almost complete time series of [DOC] every 30. Here [DOC] has ranged from 12.2 to 58.4 mg/l C and during event flow DOC had a maximum variation of 23.5 mg/l within a single day. Simultaneously with the Spectrolyser, we have logged stage height, pH and conductivity using an In-Situ Inc MD Troll 9000. Generally there is an inverse relationship between [DOC] and both pH and conductivity, but a positive relationship (albeit with seasonal differences) with [DOC] and stage height, from which we can infer hydrological changes in the source of the DOC. Here, in addition to presenting the time series of the data, and a more accurate export budget estimate, I will explore statistical methods for the handling of large datasets. Trends in the data of such large and dynamic data sets are challenging to model. Simple relationships with stage height or conductivity generally are not maintained over extended time periods and thus more complex statistical approaches are needed to understand trend and detail. For example wavelet analysis is being used to assess if periodicity in [DOC] occurs other than seasonally. Raymond, P.A. and J.E. Saiers (2010), Event controlled DOC export from forested watersheds. Biogeochemistry, 100,1-3, 197-209. Williams, P.J.L. (1995), Evidence for the seasonal accumulation of carbon-rich dissolved organic material, its scale in comparison with changes in particulate material and the consequential effect on net C/N assimilation ratios. Marine Chemistry, 51,1, 17-29.

  19. Influence of dissolved organic matter on dissolved vanadium speciation in the Churchill River estuary (Manitoba, Canada).

    PubMed

    Shi, Yong Xiang; Mangal, Vaughn; Guéguen, Céline

    2016-07-01

    Diffusive gradients in thin films (DGT) devices were used to investigate the temporal and spatial changes in vanadium (V) speciation in the Churchill estuary system (Manitoba). Thirty-six DGT sets and 95 discrete water samples were collected at 8 river and 3 estuary sites during spring freshet and summer base flow. Dissolved V concentration in the Churchill River at summer base flow was approximately 5 times higher than those during the spring high flow (27.3 ± 18.9 nM vs 4.8 ± 3.5 nM). DGT-labile V showed an opposite trend with greater values found during the spring high flow (2.6 ± 1.8 nM vs 1.4 ± 0.3 nM). Parallel factor analysis (PARAFAC) conducted on 95 excitation-emission matrix spectra validated four humic-like (C1C4) and one protein-like (C5) fluorescent components. Significant positive relationship was found between protein-like DOM and DGT-labile V (r = 0.53, p < 0.05), indicating that protein-like DOM possibly affected the DGT-labile V concentration in Churchill River. Sediment leachates were enriched in DGT-labile V and protein-like DOM, which can be readily released when river sediment began to thaw during spring freshet. PMID:27065459

  20. Coping with PH over the Long Term

    MedlinePlus

    ... Coping as a Teenager with PH Coping with High School Speaking of PH... with Teachers Friends, Family and ... Coping as a Teenager with PH Coping with High School Speaking of PH... with Teachers Friends, Family and ...

  1. Humic Acid Complexation of Th, Hf and Zr in Ligand Competition Experiments: Metal Loading and Ph Effects

    NASA Technical Reports Server (NTRS)

    Stern, Jennifer C.; Foustoukos, Dionysis I.; Sonke, Jeroen E.; Salters, Vincent J. M.

    2014-01-01

    The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories. Here, we present conditional equilibrium binding constants (Kc, MHA) of thorium, hafnium, and zirconium-humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE- ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000 Damembrane were also performed to validate the CE-ICP-MS analysis. Experiments were performed at pH 3.5-7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE-ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal- humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc, MHA several orders of magnitude above REE-humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc, MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc, MHA values attained at very low metal loading conditions are compared to existing literature data. Overall, experimental data suggest that the tetravalent transition metal/-actinide-humic acid complexation is important over a wide range of pH values, including mildly acidic conditions, and thus, these complexes should be included in speciation models.

  2. Export of dissolved organic carbon and nitrogen from drained and re-wetted bog sites in Lower Saxony (Germany)

    NASA Astrophysics Data System (ADS)

    Frank, Stefan; Tiemeyer, Bärbel; Freibauer, Annette

    2014-05-01

    Today, nearly all peatlands in Germany are drained for agriculture, forestry and peat cutting. The export of dissolved organic carbon (C) and nitrogen (N) may be important for the overall C and N balances and affects downstream ecosystems. While drainage generally increases solute losses, there is nearly no C and N export data of raised bogs in Germany which can be used to evaluate both the impact of drainage associated with intensive land use and the re-wetting of peat cutting sites. In the "Ahlenmoor" (North-Western Germany), four sampling points were chosen. Three sampling points represent a deeply drained intensively used grassland at various scales ranging from a drainage pipe (DP, 0.08 ha) and a drainage ditch (DD, 6.8 ha) to a collector ditch (CD, 20 ha). The fourth sampling point (RW) is a former peat cutting site (23 ha) re-wetted 10 years ago. At this site, polder technique was used to establish water tables at the soil surface. Sampling and discharge measurements were conducted bi-weekly from June 2011 to June 2013. Water table levels were recorded with automatic pressure sensors, and rating curves between discharge and water levels were used to calculate continuous discharge values. Samples were analyzed for dissolved organic carbon (DOC), particulate organic carbon (POC), dissolved organic nitrogen (DON), ammonium (NH4+), nitrate (NO3-), sulphate (SO42-), pH, electric conductivity (EC) and specific UV absorbance (SUVA). The discharge did not vary strongly between the sampling points and was slightly lower in the second year. Concentrations of all measured solutes were higher at the intensive grassland (DP, DD and CD) than at the re-wetted site. Surprisingly, SUVA showed no difference between all sites, while the DOC to DON ratio was narrower at DP, DD and CD than at RW. This indicates an export of more degraded dissolved organic matter (DOM) from the drained area. At the grassland sites, no statistical differences were found between the three scales except for SO42-, NO3- and pH. Thus, the grassland shows rather homogenous export patterns over various spatial scales, and there seem to be no fast mineralization or degradation of the exported DOM during the initial stage of export. In total, average losses of DOC (457 kg ha-1 a-1) and POC (40 kg ha-1 a-1) from the drained area were nearly thrice as high as from the re-wetted site (124 and 73 kg ha-1 a-1). The total nitrogen losses were even more reduced by re-wetting and dominated at all sites by DON (19.1 kg ha-1 a-1 at the grassland sites, 3.9 kg ha-1 a-1 at the re-wetted site). NH4+ (drained: 5.2 kg ha-1 a-1, re-wetted: 0.8 kg ha-1 a-1) and NO3- (drained: 1.6 kg ha-1 a-1, re-wetted: not detectable) played a minor role. Overall, differences in the export could rather be explained by differences in solute concentration than in discharge.

  3. Dissolved metals and associated constituents in abandoned coal-mine discharges, Pennsylvania, USA. Part 2: Geochemical controls on constituent concentrations

    USGS Publications Warehouse

    Cravotta, C.A., III

    2008-01-01

    Water-quality data for discharges from 140 abandoned mines in the Anthracite and Bituminous Coalfields of Pennsylvania reveal complex relations among the pH and dissolved solute concentrations that can be explained with geochemical equilibrium models. Observed values of pH ranged from 2.7 to 7.3 in the coal-mine discharges (CMD). Generally, flow rates were smaller and solute concentrations were greater for low-pH CMD samples; pH typically increased with flow rate. Although the frequency distribution of pH was similar for the anthracite and bituminous discharges, the bituminous discharges had smaller median flow rates; greater concentrations of SO4, Fe, Al, As, Cd, Cu, Ni and Sr; comparable concentrations of Mn, Cd, Zn and Se; and smaller concentrations of Ba and Pb than anthracite discharges with the same pH values. The observed relations between the pH and constituent concentrations can be attributed to (1) dilution of acidic water by near-neutral or alkaline ground water; (2) solubility control of Al, Fe, Mn, Ba and Sr by hydroxide, sulfate, and/or carbonate minerals; and (3) aqueous SO4-complexation and surface-complexation (adsorption) reactions. The formation of AlSO4+ and AlHSO42 + complexes adds to the total dissolved Al concentration at equilibrium with Al(OH)3 and/or Al hydroxysulfate phases and can account for 10-20 times greater concentrations of dissolved Al in SO4-laden bituminous discharges compared to anthracite discharges at pH of 5. Sulfate complexation can also account for 10-30 times greater concentrations of dissolved FeIII concentrations at equilibrium with Fe(OH)3 and/or schwertmannite (Fe8O8(OH)4.5(SO4)1.75) at pH of 3-5. In contrast, lower Ba concentrations in bituminous discharges indicate that elevated SO4 concentrations in these CMD sources could limit Ba concentrations by the precipitation of barite (BaSO4). Coprecipitation of Sr with barite could limit concentrations of this element. However, concentrations of dissolved Pb, Cu, Cd, Zn, and most other trace cations in CMD samples were orders of magnitude less than equilibrium with sulfate, carbonate, and/or hydroxide minerals. Surface complexation (adsorption) by hydrous ferric oxides (HFO) could account for the decreased concentrations of these divalent cations with increased pH. In contrast, increased concentrations of As and, to a lesser extent, Se with increased pH could result from the adsorption of these oxyanions by HFO at low pH and desorption at near-neutral pH. Hence, the solute concentrations in CMD and the purity of associated "ochres" formed in CMD settings are expected to vary with pH and aqueous SO4 concentration, with potential for elevated SO4, As and Se in ochres formed at low pH and elevated Cu, Cd, Pb and Zn in ochres formed at near-neutral pH. Elevated SO4 content of ochres could enhance the adsorption of cations at low pH, but decrease the adsorption of anions such as As. Such information on environmental processes that control element concentrations in aqueous samples and associated precipitates could be useful in the design of systems to reduce dissolved contaminant concentrations and/or to recover potentially valuable constituents in mine effluents.

  4. Lithium ion conducting ionic electrolytes

    DOEpatents

    Angell, C.A.; Xu, K.; Liu, C.

    1996-01-16

    A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100 C or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors. 4 figs.

  5. Lithium ion conducting ionic electrolytes

    DOEpatents

    Angell, C. Austen; Xu, Kang; Liu, Changle

    1996-01-01

    A liquid, predominantly lithium-conducting, ionic electrolyte is described which has exceptionally high conductivity at temperatures of 100.degree. C. or lower, including room temperature. It comprises molten lithium salts or salt mixtures in which a small amount of an anionic polymer lithium salt is dissolved to stabilize the liquid against recrystallization. Further, a liquid ionic electrolyte which has been rubberized by addition of an extra proportion of anionic polymer, and which has good chemical and electrochemical stability, is described. This presents an attractive alternative to conventional salt-in-polymer electrolytes which are not cationic conductors.

  6. A simple headspace equilibration method for measuring dissolved methane

    USGS Publications Warehouse

    Magen, C; Lapham, L.L.; Pohlman, John W.; Marshall, Kristin N.; Bosman, S.; Casso, Michael; Chanton, J.P.

    2014-01-01

    Dissolved methane concentrations in the ocean are close to equilibrium with the atmosphere. Because methane is only sparingly soluble in seawater, measuring it without contamination is challenging for samples collected and processed in the presence of air. Several methods for analyzing dissolved methane are described in the literature, yet none has conducted a thorough assessment of the method yield, contamination issues during collection, transport and storage, and the effect of temperature changes and preservative. Previous extraction methods transfer methane from water to gas by either a "sparge and trap" or a "headspace equilibration" technique. The gas is then analyzed for methane by gas chromatography. Here, we revisit the headspace equilibration technique and describe a simple, inexpensive, and reliable method to measure methane in fresh and seawater, regardless of concentration. Within the range of concentrations typically found in surface seawaters (2-1000 nmol L-1), the yield of the method nears 100% of what is expected from solubility calculation following the addition of known amount of methane. In addition to being sensitive (detection limit of 0.1 ppmv, or 0.74 nmol L-1), this method requires less than 10 min per sample, and does not use highly toxic chemicals. It can be conducted with minimum materials and does not require the use of a gas chromatograph at the collection site. It can therefore be used in various remote working environments and conditions.

  7. Production of Dissolved Organic Matter During Fungal Wood Rot Decay

    NASA Astrophysics Data System (ADS)

    Filley, T. R.; Jellison, J.; Goodell, B.; Kelley, S.; Davis, M.

    2002-12-01

    Dissolved organic matter mediates numerous biogeochemical processes in soil systems impacting subsurface microbial activity, redox chemistry, soil structure, and carbon and nitrogen sequestration. The structure and chemistry of DOM is a function of the inherited chemistry of the source material, the type of microbial action that has occurred, and selective interaction with mineral substrates. The type of fungal decomposition imparted to woody tissue is a major factor in determining the nature of DOM in forest soils. In order to investigate the relationship between fungal decomposition and the nature of DOM in coniferous forest soils we conducted 32-week inoculation studies on spruce sapwood with basidiomycete brown-rot wood decay fungi where leachable dissolved and colloidal organic matter was separated from decayed residue. A detailed examination of the organic fractions was conducted using 13C-labeled tetramethylammonium hydroxide thermochemolysis, solid-state 13C-NMR, and electrospray mass spectrometry. The progressive stages of microbial decay (cellulolytic and ligninolytic) were manifested in the chemical composition of the DOM which showed an evolution from a composition initially polysaccharide rich to one dominated by mildly oxidized and demethylated lignin. Upon removal of all polysaccharides at 16 weeks the DOM (up to 10% by weight of the original tissue) looked chemically distinct from the degraded residue

  8. Seasonal and regional variability in dissolved and particulate iron fluxes via glacial runoff along the West Greenland coast

    NASA Astrophysics Data System (ADS)

    Choquette, K.; Hagedorn, B.; Sletten, R. S.; Harrold, Z.; Liu, L.; Dieser, M.; Cameron, K. A.; Christner, B. C.; Junge, K.

    2012-12-01

    Subglacial weathering, due to biogeochemical and physical weathering processes, can affect the chemical evolution of subglacial waters and release dissolved and particulate iron via glacial runoff. Iron is a growth limiting nutrient and plays a critical role in the biogeochemical cycles of coastal and marine waters. More recently, dissolved and colloidal iron derived from subglacial sources have been considered an important contributor of Fe fluxes to the ocean; however, their dependency on lithology, grain size, and microbial activity is not well understood. This study characterizes the solute chemistry, in particular iron mineralogy and dissolved iron concentrations, released from beneath the Greenland Ice Sheet (GrIS), from two locations along the West Greenland coast, Thule (76°N, 68°W) and Kangerlussuaq (67°N, 50°W). We hypothesize that the subglacial lithology has a control on Fe fluxes from the GrIS to coastal and marine systems. The underlying bedrock in Thule is the Precambrian Dundas and Narssarssuk sedimentary formations which include sandstone, siltstone, and shale. The bedrock in Kangerlussuaq is dominated by Archean granodioritic gneiss and amphibolite within the Nagssugtoqidian Orogen. Supra and subglacial meltwater samples were collected directly in front of the Ice Sheet over an entire melt season in 2011 (North River, Thule) and 2012 (Akuliarusiarsuup Kuua River, Kangerlussuaq). In situ parameters such as temperature, pH, dissolved oxygen, and electrical conductivity were recorded in order to interpret meltwater chemistry. Dissolved Fe(II) and Fe(III) species were fixed immediately and analyzed within 24 hours after sampling in the field laboratory using a spectrophotometer and 10 cm cell. Total dissolved iron (FeT) of different size fractions (<0.22 and <0.05 μm) of iron were determined back in the home laboratory using reaction cell ICP MS. Preliminary results demonstrate that subglacial meltwater of North River has average FeT concentrations of 200 nM and 10 nM in the <0.22 and <0.05 μm size fraction, respectively, indicating that FeT in the <0.22 μm fraction is mostly (95%) in form of colloidal iron. In comparison, data from Kangerlussuaq show an average FeT of 580 nM in the <0.22 μm size fraction and 150 nM in the <0.05 μm fraction. Suspended load in North River increased throughout the ablation period in concurrence with variation in discharge, from an average of 0.08 g/L in the early melt stages (June), 0.21 g/L during the high melt (July-August), and 0.15 g/L during the late melt (end of August-September). Initial estimates for the suspended load for subglacial flow in Kangerlussuaq are 0.30 g/L on average. The suspended load will be analyzed for iron by sequential extraction in order to characterize how iron partitions between oxide and (oxyhydr)oxide minerals in the sediment. This comprehensive study will allow us to identify biogeochemical processes involved in the mobilization of iron and to evaluate how increased melting of GrIS will affect Fe fluxes to coastal and marine environments.

  9. Kaolinite dissolution and precipitation kinetics at 22oC and pH 4

    SciTech Connect

    Steefel, Carl; Yang, L.; Steefel, C.I.

    2008-04-01

    Dissolution and precipitation rates of low defect Georgia kaolinite (KGa-1b) as a function of Gibbs free energy of reaction (or reaction affinity) were measured at 22 C and pH 4 in continuously stirred flowthrough reactors. Steady state dissolution experiments showed slightly incongruent dissolution, with a Si/Al ratio of about 1.12 that is attributed to the re-adsorption of Al on to the kaolinite surface. No inhibition of the kaolinite dissolution rate was apparent when dissolved aluminum was varied from 0 and 60 {micro}M. The relationship between dissolution rates and the reaction affinity can be described well by a Transition State Theory (TST) rate formulation with a Temkin coefficient of 2 R{sub diss} (mol/m{sup 2}s) = 1.15 x 10{sup -13} [1-exp(-{Delta}G/2RT)]. Stopping of flow in a close to equilibrium dissolution experiment yielded a solubility constant for kaolinite at 22 C of 10{sup 7.57}. Experiments on the precipitation kinetics of kaolinite showed a more complex behavior. One conducted using kaolinite seed that had previously undergone extensive dissolution under far from equilibrium conditions for 5 months showed a quasi-steady state precipitation rate for 105 hours that was compatible with the TST expression above. After this initial period, however, precipitation rates decreased by an order of magnitude, and like other precipitation experiments conducted at higher supersaturation and without kaolinite seed subjected to extensive prior dissolution, could not be described with the TST law. The initial quasi-steady state rate is interpreted as growth on activated sites created by the dissolution process, but this reversible growth mechanism could not be maintained once these sites were filled. Long-term precipitation rates showed a linear dependence on solution saturation state that is generally consistent with a two dimensional nucleation growth mechanism following the equation R{sub ppt}(mol/m{sup 2}s) = 3.38 x 10{sup -14} exp[- 181776/T{sup 2} 1n{Omega}]. Further analysis using Synchrotron Scanning Transmission X-ray Microscopy (STXM) in Total Electron Yield (TEY) mode of the material from the precipitation experiments showed spectra for newly precipitated material compatible with kaolinite. An idealized set of reactive transport simulations of the chemical weathering of albite to kaolinite using rate laws from HELLMANN and TISSERAND (2006) and this study respectively indicate that while pore waters are likely to be close to equilibrium with respect to kaolinite at pH 4, significant kaolinite supersaturation may occur at higher pH if its precipitation rate is pH dependent.

  10. The Effective Diffusion Coefficient of Dissolved Oxygen and Oxidation Rate of Pyrite by Dissolved Oxygen in Compacted Purified and Crude Sodium Bentonites in Carbonate Buffered Solution

    SciTech Connect

    Manaka, Mitsuo

    2003-09-15

    Immediately after the geological disposal of high-level radioactive waste, the oxygen initially existing in the repository is expected to strongly affect the redox condition of the near field. The oxygen dissolves in the groundwater, is transported by diffusion through it, and is consumed by the oxidation of pyrite as an impurity in bentonite. To assess the influence of the oxygen, this study was conducted to estimate the diffusion of dissolved oxygen (DO) and the rate of pyrite oxidation by DO in compacted purified and crude sodium bentonites (SBs) in more detail than the Manaka et al. study. The effective diffusion coefficient (De) of DO in the compacted purified SB was measured in low ionic strength solution (carbonate buffered solution with pH {approx} 9) using the electrochemical method. The empirical equation between De value of DO and dry density (0.5 x 10{sup 3}-1.8 x 10{sup 3} kg m{sup -3}) of purified SB was obtained as follows:De{sub DO}{sup Kunipia-F} = 8.2 {+-} 1.5 x 10{sup -10}x exp(-2.6 {+-} 0.2 x10{sup -3}{rho},where De{sub DO}{sup Kunipia-F} is the De of DO in compacted purified SB (Kunipia F) (m{sup 2} s{sup -1}) and {rho} is the dry density of the SB (kg m{sup -3}).On the other hand, the De value of DO in the compacted crude SB was estimated using the relationship between De values of tritiated water in compacted purified and crude SBs. The empirical equation between the De value of DO and dry density (0.5 x 10{sup 3}-1.8 x 10{sup 3} kg m{sup -3}) of crude SB was derived as follows:De{sub DO}{sup Kunigel-V1} = 2.04 x 10{sup -9} exp(-2.6 x 10{sup -3}{rho}),where De{sub DO}{sup Kunigel-V1} is the De of DO in compacted crude SB (Kunigel V1) (m{sup 2} s{sup -1}) and {rho} is the dry density of the SB (kg m{sup -3}).The rates of pyrite oxidation by DO were estimated from the experimental data in pyrite-purified SB systems using the obtained De values of DO. The relation between rate constant (k') of pyrite oxidation by DO and dry density ({rho}) of the SB was derived as follows:k' = 3.9 {+-} 1.1 x 10{sup -8} exp(-1.3 {+-} 0.3 x 10{sup -3}{rho}),where k' is the rate constant at pH {approx} 9 in compacted purified SB of dry density ranging from 0.8 x 10{sup 3} to 1.2 x 10{sup 3} kg m{sup -3}.The rate constants of pyrite oxidation by DO in the compacted crude SB (0.8 x 10{sup 3} to 1.2 x 10{sup 3} kg m{sup -3}) were also calculated using the estimated De values of DO. In general, the values of rate constants in the crude SB are 1.5 times as large as that in the purified SB.

  11. Conduct disorder

    MedlinePlus

    Disruptive behavior - child; Impulse control problem - child ... Conduct disorder has been linked to: Child abuse Drug or alcohol abuse in the parents Family conflicts Genetic defects Poverty The diagnosis is more common among boys. It is ...

  12. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Hershey, David R.; Sand, Susan

    1993-01-01

    Explains how electrical conductivity (EC) can be used to measure ion concentration in solutions. Describes instrumentation for the measurement, temperature dependence and EC, and the EC of common substances. (PR)

  13. Experimental study of igneous and sedimentary apatite dissolution - Control of pH, distance from equilibrium, and temperature on dissolution rates

    NASA Astrophysics Data System (ADS)

    Guidry, Michael W.; Mackenzie, Fred T.

    2003-08-01

    Apatite dissolution experiments were conducted using both a fluidized bed and stirred tank reactor over a range of pH, temperature, solution saturation state, and on non-carbonated and carbonated apatite compositions: igneous fluorapatite (FAP) and sedimentary carbonate fluorapatite (CFA), respectively. From 2 <pH <6, the rate of release from dissolution of all apatite components [calcium (Ca), phosphorus (P), and fluoride (F)] increased with decreasing pH for FAP. From 6 < pH < 8.5, the FAP dissolution rate is pH independent. Measuring apatite dissolution rates at pH > 8.5 were not possible due to detection limits of the analytical techniques used in this study and the high insolubility of FAP. For the CFA compositions studied, the dissolution rate decreased with increasing pH from 4 < pH < 7. During early stages of the dissolution reaction for both FAP and CFA, mineral components were released in non-stoichiometric ratios with reacted solution ratios of dissolved Ca:P and Ca:F being greater than mineral stoichiometric ratios, suggesting that Ca was preferentially released compared to P and F from the mineral structure during the early stages of dissolution. An increase in reacted solution pH accompanies this early elevated release of Ca. As the dissolution reaction proceeded to steady state, dissolution became congruent. When normalized to BET measured surface area, FAP dissolved faster from 4 < pH < 7 compared to CFA. The apparent Arrhenius activation energy (E a) of FAP dissolution over the temperature range of 25-55°C at pH = 3.0, I = 0.1, and pCO 2 = 0 is 8.3 ± 0.2 kcal mol -1. Both the apparent exchange of solution H + for solid-bound Ca at low pH in the early stage of dissolution and the E a of dissolution suggest a surface and not a diffusion controlled dissolution reaction for FAP and CFA. The degree of undersaturation of the solution, ΔG R, with respect to FAP was important in determining the dissolution rate. At pH = 3.0, I = 0.1, and pCO 2 = 0, the dissolution rate of FAP was ˜ 5× greater in the far-from-equilibrium region compared to the near-equilibrium slope region. A simple apatite weathering model incorporating the experimental results from this study was constructed, and numerical calculations suggest that during the Phanerozoic both the surface area of igneous rock available for weathering and the average global temperature were important factors in determining the P weathering flux from apatite dissolution. It is possible that elevated global temperatures coupled with relatively high surface area of igneous rock during the early- to mid-Paleozoic resulted in elevated P weathering fluxes, which along with climatic evolutionary pressures of the Neoproterozoic, facilitated the radiation of multicellular organisms, large-scale phosphorite deposition, and abundance of calcium phosphate shelled organisms during the early Cambrian.

  14. The effect of pH on the in-vitro dissolution of three second-generation sulphonylurea preparations: mechanism of antacid-sulphonylurea interaction.

    PubMed

    Lehto, P; Laine, K; Kivistö, K T; Neuvonen, P J

    1996-09-01

    Simultaneously administered magnesium hydroxide or sodium bicarbonate can increase the rate and extent of absorption of non-micronized glibenclamide and glipizide. To clarify the mechanism of this interaction we have studied the effect of pH on the dissolution of two different formulations of glibenclamide (micronized and non-micronized) and one formulation of glipizide. One tablet of each sulphonylurea preparation was placed in a dissolution chamber containing continuously mixed dissolution medium at pH 2, pH 6 or pH 9; 5 mL of the medium was replaced every 2 min. The amount of glibenclamide dissolved from the non-micronized formulation within 2 h, was 1.2, 4.5 and 76% at pH 2, pH 6 and pH 9, respectively (P < 0.01), whereas 21, 29 and 100% was dissolved from the micronized formulation (P < 0.01). The amount of glipizide dissolved within 2 h at pH 2, pH 6 and pH 9 was 3.9, 24 and 92%, respectively (P < 0.01). We conclude that the elevated pH of the gastric contents is the most likely explanation for the interactions previously demonstrated between antacids and sulphonylureas after their concomitant ingestion. PMID:8910849

  15. An in-situ Mobile pH Calibrator for application with HOV and ROV platform in deep sea environments

    NASA Astrophysics Data System (ADS)

    Tan, C.; Ding, K.; Seyfried, W. E., Jr.

    2014-12-01

    Recently, a novel in-situ sensor calibration instrument, Mobile pH Calibrator (MpHC), was developed for application with HOV Alvin. It was specifically designed to conduct in-situ pH measurement in deep sea hydrothermal diffuse fluids with in-situ calibration function. In general, the sensor calibrator involves three integrated electrodes (pH, dissolved H2 and H2S) and a temperature sensor, all of which are installed in a cell with a volume of ~ 1 ml. A PEEK check valve cartridge is installed at the inlet end of the cell to guide the flow path during the measurement and calibration processes. Two PEEK tubes are connected at outlet end of the cell for drawing out hydrothermal fluid and delivering pH buffer fluids. During its measurement operation, the pump draws in hydrothermal fluid, which then passes through the check valve directly into the sensing cell. When in calibration mode, the pump delivers pH buffers into the cell, while automatically closing the check valve to the outside environment. This probe has two advantages compared to our previous unit used during KNOX18RR MAR cruise in 2008 and MARS cabled observatory deployment in 2012. First, in the former design, a 5 cm solenoid valve was equipped with the probe. This enlarged size prevented its application in specific point or small area. In this version, the probe has only a dimension of 1.6 cm for an easy access to hydrothermal biological environments. Secondly, the maximum temperature condition of the earlier system was limited by the solenoid valve precluding operation in excess of 50 ºC. The new design avoids this problem, which improves its temperature tolerance. The upper limit of temperature condition is now up to 100oC, therefore enabling broader application in hydrothermal diffuse flow system on the seafloor. During SVC cruise (AT26-12) in the Gulf of Mexico this year, the MpHC was successfully tested with Alvin dives at the depth up to 2600 m for measuring pH with in-situ calibration in seafloor cold seep environment. The measurement and calibration were also conducted in hydrothermal diffuse flow at temperature condition exceeding 70 ºC with Alvin dives during a recent cruise AT26-17 in ASHES vent field and Main Endeavour Field on Juan de Fuca Ridge. Data from these seagoing deployments will be presented, with emphasis on both technical and scientific aplications.

  16. Dissolving Microneedles for Transdermal Drug Delivery

    PubMed Central

    Lee, Jeong Woo; Park, Jung-Hwan; Prausnitz, Mark R.

    2008-01-01

    Microfabrication technology has been adapted to produce micron-scale needles as a safer and painless alternative to hypodermic needle injection, especially for protein biotherapeutics and vaccines. This study presents a design that encapsulates molecules within microneedles that dissolve within the skin for bolus or sustained delivery and leave behind no biohazardous sharp medical waste. A fabrication process was developed based on casting a viscous aqueous solution during centrifugation to fill a micro-fabricated mold with biocompatible carboxymethylcellulose or amylopectin formulations. This process encapsulated sulforhodamine B, bovine serum albumin, and lysozyme; lysozyme was shown to retain full enzymatic activity after encapsulation and to remain 96% active after storage for two months at room temperature. Microneedles were also shown to be strong enough to insert into cadaver skin and then to dissolve within minutes. Bolus delivery was achieved by encapsulating molecules just within microneedle shafts. For the first time, sustained delivery over hours to days was achieved by encapsulating molecules within the microneedle backing, which served as a controlled release reservoir that delivered molecules by a combination of swelling the backing with interstitial fluid drawn out of the skin and molecule diffusion into the skin via channels formed by dissolved microneedles. We conclude that dissolving microneedles can be designed to gently encapsulate molecules, insert into skin, and enable bolus or sustained release delivery. PMID:18261792

  17. REMOVING DISSOLVED INORGANIC CONTAMINANTS FROM WATER

    EPA Science Inventory

    Dissolved inorganic contaminants in water can be cationic, anionic, or neutral forms of ions, atoms, or molecules of any element in the periodic table. The article describes the physicochemical treatment processes typically used to remove the more common inorganic contaminants fr...

  18. Modeling Fish Growth in Low Dissolved Oxygen

    ERIC Educational Resources Information Center

    Neilan, Rachael Miller

    2013-01-01

    This article describes a computational project designed for undergraduate students as an introduction to mathematical modeling. Students use an ordinary differential equation to describe fish weight and assume the instantaneous growth rate depends on the concentration of dissolved oxygen. Published laboratory experiments suggest that continuous

  19. DISSOLVED OXYGEN IMPACT FROM URBAN STORM RUNOFF

    EPA Science Inventory

    The primary objective of the research reported here is to determine if on a national basis a correlation exists between strength of dissolved oxygen (DO) deficits and the presence of rainfall and/or storm runoff downstream of urban areas. A secondary objective is to estimate the ...

  20. Modeling Fish Growth in Low Dissolved Oxygen

    ERIC Educational Resources Information Center

    Neilan, Rachael Miller

    2013-01-01

    This article describes a computational project designed for undergraduate students as an introduction to mathematical modeling. Students use an ordinary differential equation to describe fish weight and assume the instantaneous growth rate depends on the concentration of dissolved oxygen. Published laboratory experiments suggest that continuous…

  1. The influence of pH on biotite dissolution and alteration kinetics at low temperature

    USGS Publications Warehouse

    Acker, James G.; Bricker, O.P.

    1992-01-01

    Biotite dissolution rates in acidic solutions were determined in fluidized-bed reactors and flowthrough columns. Biotite dissolution rates increased inversely as a linear function of pH in the pH range 3-7, where the rate order n = -0.34. Biotite dissolved incongruently over this pH range, with preferential release of magnesium and iron from the octahedral layer. Release of tetrahedral silicon was much greater at pH 3 than at higher pH. Iron release was significantly enhanced by low pH conditions. Solution compositions from a continuous exposure flow-through column of biotite indicated biotite dissolves incongruently at pH 4, consistent with alteration to a vermiculite-type product. Solution compositions from a second intermittent-flow column exhibited elevated cation release rates upon the initiation of each exposure to solution. The presence of strong oxidizing agents, the mineral surface area, and sample preparation methodology also influenced the dissolution or alteration kinetics of biotite. ?? 1992.

  2. Steady-state dissolved oxygen model of the Willamette River, Oregon

    USGS Publications Warehouse

    McKenzie, Stuart W.; Hines, W.G.; Rickert, D.A.; Rinella, F.A.

    1979-01-01

    For nearly half a century the Willamette River in Oregon experienced severe dissolved-oxygen problems related to large loads of organically rich waste waters from industries and municipalities. Since the mid-1950 's dissolved oxygen quality has gradually improved owing to low-flow augmentation, the achievement of basinwide secondary treatment, and the use of other waste-management practices. As a result, summer dissolved-oxygen levels have increased, salmon runs have returned, and the overall effort is widely regarded as a singular water-quality success. To document the improved dissolved-oxygen regimen, the U.S. Geological Survey conducted intensive studies of the Willamette during the summer low-flow seasons of 1973 and 1974. During each summer the mean daily dissolved-oxygen levels were found to be higher than 5 milligrams per liter throughout the river. Because of the basinwide secondary treatment, carbonaceous deoxygenation rates were low. In addition, almost half of the biochemical oxygen demand entering the Willamette was from diffuse (nonpoint) sources rather than outfalls. These results indicated that point-source biochemical oxygen demand was no longer the primary cause of dissolved-oxygen depletion. Instead, the major causes of deoxygenation were nitrification in a shallow ' surface active ' reach below Salem and an anomalous oxygen demand (believed to be primarily of benthal origin) in Portland Harbor. (Woodard-USGS)

  3. Dissolved-oxygen regimen of the Willamette River, Oregon, under conditions of basinwide secondary treatment

    USGS Publications Warehouse

    Hines, Walter G.; McKenzie, S.W.; Rickert, D.A.; Rinella, F.A.

    1977-01-01

    For nearly half a century the Willamette River in Oregon experienced severe dissolved-oxygen problems related to large loads of organically rich waste waters from industries and municipalities. Since the mid-1950 's dissolved oxygen quality has gradually improved owing to low-flow augmentation, the achievement of basinwide secondary treatment, and the use of other waste-management practices. As a result, summer dissolved-oxygen levels have increased, salmon runs have returned, and the overall effort is widely regarded as a singular water-quality success. To document the improved dissolved-oxygen regimen, the U.S. Geological Survey conducted intensive studies of the Willamette during the summer low-flow seasons of 1973 and 1974. During each summer the mean daily dissolved-oxygen levels were found to be higher than 5 milligrams per liter throughout the river. Because of the basinwide secondary treatment, carbonaceous deoxygenation rates were low. In addition, almost half of the biochemical oxygen demand entering the Willamette was from diffuse (nonpoint) sources rather than outfalls. These results indicated that point-source biochemical oxygen demand was no longer the primary cause of dissolved-oxygen depletion. Instead, the major causes of deoxygenation were nitrification in a shallow ' surface active ' reach below Salem and an anomalous oxygen demand (believed to be primarily of benthal origin) in Portland Harbor. (Woodard-USGS)

  4. Probiotic and lactulose: influence on gastrointestinal flora and pH value in minimal hepatic encephalopathy rats

    PubMed Central

    Jiang, Shu-Man; Jia, Lin; Zhang, Mei-Hua

    2015-01-01

    Aim: The present study was conducted to investigate the influence on gastrointestinal flora, counts of bifidobacteria and Enterobacterceae in colon and pH value of gastrointestinal after lactulose and probiotic treatment on rat experimental minimal hepatic encephalopathy (MHE) induced by thioactamide (TAA). Methods: MHE was induced by intraperitoneal injection of TAA. 48 male MHE models were then randomly divided into 4 groups: control group (n = 12); MHE group (n = 12) received tap water ad libitum only; lactulose group (n = 12) and probiotics group (n = 12) gavaged respectively with 8 ml/kg of lactulose and 1.5 g/kg of probiotic preparation Golden Bifid (highly concentrated combination probiotic) dissolved in 2 ml of normal saline, once a day for 8 days. The latency of Brainstem auditory evoked potentials (BAEP) I was used as objective index of MHE. Counts of gastrointestinal flora, counts of bifidobacteria and Enterobacterceae in colon and pH value of gastrointestinal were examined respectively. Results: Compared to MHE group, counts of gastrointestinal flora has greatly decreased, ratio of bifidobacteria and Enterobacterceae has greatly increased, pH value of colon has greatly descended (P < 0.05). However, there was no significant difference between lactulose group and probiotic group (P > 0.05). Both lactulose and probiotics can effectively prevent bacteria translocation and overgrowth, intensify CR, improved value of B/E, and acidify intestinal, decreased pH value of colon. Conclusion: Probiotic compound Golden Bifid is as useful as lactulose for the prevention and treatment of MHE. Probiotic therapy may be a safe, natural, well-tolerated therapy appropriate for the long-term treatment of MHE. PMID:26309689

  5. Carbon System Measurements and Potential Climatic Drivers at a Site of Rapidly Declining Ocean pH

    PubMed Central

    Wootton, J. Timothy; Pfister, Catherine A.

    2012-01-01

    We explored changes in ocean pH in coastal Washington state, USA, by extending a decadal-scale pH data series, by reporting independent measures of dissolved inorganic carbon (DIC), spectrophotometric pH, and total alkalinity (TA), by exploring pH patterns over larger spatial scales, and by probing for long-term trends in environmental variables reflecting potentially important drivers of pH. We found that pH continued to decline in this area at a rapid rate, that pH exhibited high natural variability within years, that our measurements of pH corresponded well to spectrophotometric pH measures and expected pH calculated from DIC/TA, and that TA estimates based on salinity predicted well actual alkalinity. Multiple datasets reflecting upwelling, including water temperature, nutrient levels, phytoplankton abundance, the NOAA upwelling index, and data on local wind patterns showed no consistent trends over the period of our study. Multiple datasets reflecting precipitation change and freshwater runoff, including precipitation records, local and regional river discharge, salinity, nitrate and sulfate in rainwater, and dissolved organic carbon (DOC) in rivers also showed no consistent trends over time. Dissolved oxygen did not decline over time, indicating that long-term changes did not result from shifts in contributions of respiration to pH levels. These tests of multiple potential drivers of the observed rapid rate of pH decline indicate a primary role for inorganic carbon and suggest that geochemical models of coastal ocean carbon fluxes need increased investigation. PMID:23285290

  6. Characterisation and deployment of an immobilised pH sensor spot towards surface ocean pH measurements.

    PubMed

    Clarke, Jennifer S; Achterberg, Eric P; Rérolle, Victoire M C; Abi Kaed Bey, Samer; Floquet, Cedric F A; Mowlem, Matthew C

    2015-10-15

    The oceans are a major sink for anthropogenic atmospheric carbon dioxide, and the uptake causes changes to the marine carbonate system and has wide ranging effects on flora and fauna. It is crucial to develop analytical systems that allow us to follow the increase in oceanic pCO2 and corresponding reduction in pH. Miniaturised sensor systems using immobilised fluorescence indicator spots are attractive for this purpose because of their simple design and low power requirements. The technology is increasingly used for oceanic dissolved oxygen measurements. We present a detailed method on the use of immobilised fluorescence indicator spots to determine pH in ocean waters across the pH range 7.6-8.2. We characterised temperature (-0.046 pH/°C from 5 to 25 °C) and salinity dependences (-0.01 pH/psu over 5-35), and performed a preliminary investigation into the influence of chlorophyll on the pH measurement. The apparent pKa of the sensor spots was 6.93 at 20 °C. A drift of 0.00014 R (ca. 0.0004 pH, at 25 °C, salinity 35) was observed over a 3 day period in a laboratory based drift experiment. We achieved a precision of 0.0074 pH units, and observed a drift of 0.06 pH units during a test deployment of 5 week duration in the Southern Ocean as an underway surface ocean sensor, which was corrected for using certified reference materials. The temperature and salinity dependences were accounted for with the algorithm, R=0.00034-0.17·pH+0.15·S(2)+0.0067·T-0.0084·S·1.075. This study provides a first step towards a pH optode system suitable for autonomous deployment. The use of a short duration low power illumination (LED current 0.2 mA, 5 μs illumination time) improved the lifetime and precision of the spot. Further improvements to the pH indicator spot operations include regular application of certified reference materials for drift correction and cross-calibration against a spectrophotometric pH system. Desirable future developments should involve novel fluorescence spots with improved response time and apparent pKa values closer to the pH of surface ocean waters. PMID:26515007

  7. Updated determination of particulate and dissolved thorium-234

    NASA Astrophysics Data System (ADS)

    Fleer, Alan P.

    The determination of particulate and dissolved 234Th is similar to the procedure of Anderson and Fleer [1982]. Samples are collected using 30 L Niskin bottles with Teflon- or epoxy-coated internal springs. On deck, the sample is pumped with a delrin impeller pump through a 0.45 μm pore size 147-mm diameter Millipore filter and into a pre-rinsed 6 gallon plastic cubitainer held in a plastic milk crate. An in-line plastic water meter records volumes in gallons. The particulate sample filter is folded twice and stored in a polyethylene sample bag. To the ˜20 L filtered sample is added: 30 mL reagent grade 16 N HNO3; 500 mL 230Th tracer of ˜30 dpm mL-l and 5 mL 50 mg mL-l iron carrier previously cleaned by extraction into isopropyl ether from an 8 M HCl solution and back-extracted into 0.1 M HCl. The acidified sample is allowed to equilibrate for from one day to a maximum of several days. The sample is weighed on a Heathkit digital scale and the pH is adjusted to approximately 8 with about 40 mL 10 M NH4OH to precipitate iron hydroxide, which carries the thorium and uranium from the solution. The precipitate is allowed to settle for 12 to 24 hours. The supernate is drawn off, and the precipitate is spun down in a centrifuge tube to about an 8 mL volume. The precipitate is resuspended in distilled water and spun down again, then dissolved in three times its volume with 12 N HCl to make a 9 N HCl solution. A 1.5 cm×12 cm ion exchange column is filled with AG1×8 100-200 mesh resin and conditioned with 9 N HCl. The sample solution is run slowly through.

  8. Possible method for dissolved organic carbon speciation in forest soils

    NASA Astrophysics Data System (ADS)

    Drabek, O.; Tejnecký, V.; Ash, C.; Hubova, P.; Boruvka, L.

    2013-12-01

    Dissolved organic carbon (DOC) is a natural part of dissolved organic matter and it plays an important role in the biogeochemistry of soil processes. Low Molecular Mass Organic Acids (LMMOA) are an essential part of DOC. These acids play a key role in chemical processes that affect the entire soil environment. Knowing the amount of DOC and the speciation of LMMOA is required for realistic equilibrium modelling of soil chemical processes and transport mechanisms. There have been a number of proposed methods for the quantitative analysis of DOC and for speciation of LMMOA. The first aim of this contribution is to introduce and test a modified spectroscopic method for the determination of water-extractable organic carbon (WEOC) from forest soils. In general this method is based on the oxidization of WEOC by chromium-sulphuric acid. The presented method can be used as an economical alternative to the classical, more financially demanding elemental analysis. However, the main aim is to test the reliability of the method for LMMOA speciation. Ion exchange chromatography (IC) with hydroxide elution has proven to be a useful tool for the determination of LMMOA in many different water-based samples. However, the influence of multivalent cations (often present in environmental samples) on IC results has not yet been sufficiently studied. In order to assess the influence of Al, Fe, Mn, Mg and Ca on the amount of LMMOA determined by IC, an extensive set of model solutions was prepared and immediately analysed by means of IC. Moreover, the influence of pH on determined amounts of LMMOA in model solutions and representative soil aqueous extracts was investigated. These experimental results were compared to expected values and also to results provided by the chemical equilibrium model - PHREEQC. Based on the above listed research, some modifications to the common IC method for LMMOA speciation are presented.

  9. PhEDEx Data Service

    NASA Astrophysics Data System (ADS)

    Egeland, Ricky; Wildish, Tony; Huang, Chih-Hao

    2010-04-01

    The PhEDEx Data Service provides access to information from the central PhEDEx database, as well as certificate-authenticated managerial operations such as requesting the transfer or deletion of data. The Data Service is integrated with the "SiteDB" service for fine-grained access control, providing a safe and secure environment for operations. A plug-in architecture allows server-side modules to be developed rapidly and easily by anyone familiar with the schema, and can automatically return the data in a variety of formats for use by different client technologies. Using HTTP access via the Data Service instead of direct database connections makes it possible to build monitoring web-pages with complex drill-down operations, suitable for debugging or presentation from many aspects. This will form the basis of the new PhEDEx website in the near future, as well as providing access to PhEDEx information and certificate-authenticated services for other CMS dataflow and workflow management tools such as CRAB, WMCore, DBS and the dashboard. A PhEDEx command-line client tool provides one-stop access to all the functions of the PhEDEx Data Service interactively, for use in simple scripts that do not access the service directly. The client tool provides certificate-authenticated access to managerial functions, so all the functions of the PhEDEx Data Service are available to it. The tool can be expanded by plug-ins which can combine or extend the client-side manipulation of data from the Data Service, providing a powerful environment for manipulating data within PhEDEx.

  10. Observations of changes in the dissolved CO2 system in the North Sea, in four summers of the 2001-2011 decade

    NASA Astrophysics Data System (ADS)

    Clargo, Nicola; Salt, Lesley; Thomas, Helmuth; de Baar, Hein

    2015-04-01

    Since the industrial revolution, atmospheric concentrations of carbon dioxide (CO2) have risen dramatically, largely due to the combustion of fossil fuels, changes in land-use patterns and the production of cement. The oceans have absorbed a large amount of this CO2, with resulting impacts on ocean chemistry. Coastal seas play a significant role in the mitigation of anthropogenic atmospheric CO2 as they contribute approximately 10-30% of global primary productivity despite accounting for only 7% of the surface area. The North Sea is a perfect natural laboratory in which to study the CO2 system as it consists of two biogeochemically distinct regions displaying both oceanic and relatively coastal behaviour. It has also been identified as a continental shelf pump with respect to CO2, transporting it to the deeper waters of the North Atlantic. Large scale forcing has been shown to have a significant impact on the CO2 system over varying time scales, often masking the effects of anthropogenic influence. Here, we present data from the North Sea spanning the 2001-2011 decade. In order to investigate the dynamics of the dissolved CO2 system in this region in the face of climate change, four basin-wide cruises were conducted during the summers of 2001, 2005, 2008 and 2011. The acquired Dissolved Inorganic Carbon (DIC) and alkalinity data were then used to fully resolve the carbon system in order to assess trends over the 2001-2011 decade. We find significant interannual variability, but with a consistent, notable trend in decreasing pH. We found that surface alkalinity remained relatively constant over the decade, whereas DIC increased, indicating that the pH decline is DIC-driven. We also found that the partial pressure of CO2 (pCO2) increased faster than concurrent atmospheric CO2 concentrations, and that the CO2 buffering capacity of the North Sea decreased over the decade, with implications for future CO2 uptake.

  11. Fertigation with micronized sulfur rapidly reduces soil pH in highbush blueberry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Blueberry is adapted to low soil pH in the range of 4-5.5. At higher pH, soil is often modified with elemental sulfur (S) prior to planting. A 2-year study was conducted to determine the potential of applying micronized wettable S by fertigation through the drip system to reduce soil pH in highbush ...

  12. Negative pH and extremely acidic mine waters from Iron Mountain, California

    USGS Publications Warehouse

    Nordstrom, D.K.; Alpers, C.N.; Ptacek, C.J.; Blowes, D.W.

    2000-01-01

    Extremely acidic mine waters with pH values as low as -3.6, total dissolved metal concentrations as high as 200 g/L, and sulfate concentrations as high as 760 g/L, have been encountered underground in the Richmond Mine at Iron Mountain, CA. These are the most acidic waters known. The pH measurements were obtained by using the Pitzer method to define pH for calibration of glass membrane electrodes. The calibration of pH below 0.5 with glass membrane electrodes becomes strongly nonlinear but is reproducible to a pH as low as -4. Numerous efflorescent minerals were found forming from these acid waters. These extreme acid waters were formed primarily by pyrite oxidation and concentration by evaporation with minor effects from aqueous ferrous iron oxidation and efflorescent mineral formation.

  13. Voltammetric pH Nanosensor.

    PubMed

    Michalak, Magdalena; Kurel, Malgorzata; Jedraszko, Justyna; Toczydlowska, Diana; Wittstock, Gunther; Opallo, Marcin; Nogala, Wojciech

    2015-12-01

    Nanoscale pH evaluation is a prerequisite for understanding the processes and phenomena occurring at solid-liquid, liquid-liquid, and liquid-gas interfaces, e.g., heterogeneous catalysis, extraction, partitioning, and corrosion. Research on the homogeneous processes within small volumes such as intracellular fluids, microdroplets, and microfluidic chips also requires nanometer scale pH assessment. Due to the opacity of numerous systems, optical methods are useless and, if applicable, require addition of a pH-sensitive dye. Potentiometric probes suffer from many drawbacks such as potential drift and lack of selectivity. Here, we present a voltammetric nanosensor for reliable pH assessment between pH 2 and 12 with high spatial resolution. It consists of a pyrolytic carbon nanoelectrode obtained by chemical vapor deposition (CVD) inside a quartz nanopipette. The carbon is modified by adsorption of syringaldazine from its ethanolic solution. It exhibits a stable quasi-reversible cyclic voltammogram with nearly Nernstian dependency of midpeak potentials (-54 mV/pH). This sensor was applied as a probe for scanning electrochemical microscopy (SECM) in order to map pH over a platinum ultramicroelectrode (UME), generating hydroxide ions (OH(-)) by the oxygen reduction reaction (ORR) at a diffusion-controlled rate in aerated phosphate buffered saline (PBS). The results reveal the alkalization of the electrolyte close to the oxygen reducing electrode, showing the insufficient buffer capacity of PBS to maintain a stable pH at the given conditions. PMID:26516786

  14. [Geochemical distribution of dissolved bismuth in the Yellow Sea and East China Sea].

    PubMed

    Wu, Xiao-Dan; Song, Jin-Ming; Wu, Bin; Li, Xue-Gang

    2014-01-01

    Occurrence level, geochemical distribution of dissolved bismuth and its coupling relationship to eco-environment were investigated in the Yellow Sea and East China Sea to explore the source and influencing factors. The results showed that the concentration of dissolved bismuth was within the range of 0-0. 029 microg x L(-1) at the surface and 0.001-0.189 microg x L(-1) at the bottom, with the averages of 0.008 and 0.016 microg x L(-1), respectively. Horizontally, low value of dissolved bismuth exhibited the bidirectional extension feature, indicating that it could trace the path of Changjiang Diluted Water. High value of dissolved bismuth was observed where the Subei Costal Current and Yellow Sea Warm Current flowed and the Changjiang Diluted Water and Zhejiang-Fujian Coastal Current met, suggesting that it was controlled by the cycle of current system. Vertically, the coastal water was fully mixed by water convection and eddy mixing, and was divided from the stratified water by strong tidal front, which blocked the transport of dissolved bismuth to the open sea. Thus, the concentration in front area was significantly higher than that in the open sea. Diurnal variation of dissolved bismuth was related to the hydrodynamic conditions (tide, suspension and thermocline) instead of the environmental factors (temperature and salinity). Positive relationship to SPM (suspended particulate matter) clarified that bismuth was prone to release from solid phase to liquid phase. Furthermore, conditions with temperature ranging 22-27 degrees C, salinity ranging 28-31 and pH ranging 7.9-8.1 were shown to be optimal for the release process. PMID:24720192

  15. Geochemical behaviour of dissolved trace elements in a monsoon-dominated tropical river basin, Southwestern India.

    PubMed

    Gurumurthy, G P; Balakrishna, K; Tripti, M; Audry, Stéphane; Riotte, Jean; Braun, J J; Udaya Shankar, H N

    2014-04-01

    The study presents a 3-year time series data on dissolved trace elements and rare earth elements (REEs) in a monsoon-dominated river basin, the Nethravati River in tropical Southwestern India. The river basin lies on the metamorphic transition boundary which separates the Peninsular Gneiss and Southern Granulitic province belonging to Archean and Tertiary-Quaternary period (Western Dharwar Craton). The basin lithology is mainly composed of granite gneiss, charnockite and metasediment. This study highlights the importance of time series data for better estimation of metal fluxes and to understand the geochemical behaviour of metals in a river basin. The dissolved trace elements show seasonality in the river water metal concentrations forming two distinct groups of metals. First group is composed of heavy metals and minor elements that show higher concentrations during dry season and lesser concentrations during the monsoon season. Second group is composed of metals belonging to lanthanides and actinides with higher concentration in the monsoon and lower concentrations during the dry season. Although the metal concentration of both the groups appears to be controlled by the discharge, there are important biogeochemical processes affecting their concentration. This includes redox reactions (for Fe, Mn, As, Mo, Ba and Ce) and pH-mediated adsorption/desorption reactions (for Ni, Co, Cr, Cu and REEs). The abundance of Fe and Mn oxyhydroxides as a result of redox processes could be driving the geochemical redistribution of metals in the river water. There is a Ce anomaly (Ce/Ce*) at different time periods, both negative and positive, in case of dissolved phase, whereas there is positive anomaly in the particulate and bed sediments. The Ce anomaly correlates with the variations in the dissolved oxygen indicating the redistribution of Ce between particulate and dissolved phase under acidic to neutral pH and lower concentrations of dissolved organic carbon. Unlike other tropical and major world rivers, the effect of organic complexation on metal variability is negligible in the Nethravati River water. PMID:24374620

  16. Interactive Effects of Soil ph, Halosulfuron Rate, and Application Method on Carryover to Turnip Green and Cabbage.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field studies were conducted in 2006 and 2007 to evaluate the tolerance of autumn-planted cabbage and turnip green to halosulfuron applied the previous spring to cantaloupe. Main plots were three levels of soil pH; maintained at a natural pH level, pH raised with Ca(OH)2, and pH lowered with Al2(SO...

  17. Evaluation of a vertical continuous centrifuge for clarification of HTGR dissolver slurries

    SciTech Connect

    Olguin, L.J.

    1980-03-01

    A series of statistically designed centrifuge performance tests was conducted to evaluate the solid-liquid separation efficiency of a vertical continuous centrifuge. Test results show that 100% of the particles greater than 4 microns in diameter were removed from simulated HTGR fuel reprocessing dissolver solutions. Centrifugal force and liquid density are the principal variables affecting separation efficiency.

  18. EFFECTS OF LOW DISSOLVED OXYGEN ON SURVIVAL, GROWTH AND REPRODUCTION OF DAPHNIA, HYALELLA, AND GAMMARUS

    EPA Science Inventory

    Daphnia magna, Daphnia pulex, Hyalella azteca, and Gammarus lacustris were exposed to low dissolved oxygen concentrations in the laboratory. cute and chronic exposures were conducted to develop data for use in the U.S. Environmental Protection Agency's (EPA's) water quality crite...

  19. Community-Level Effects of Excess Total Dissolved Solids Doses Using Model Streams

    EPA Science Inventory

    Model stream chronic dosing studies (42 days) were conducted with four different total dissolved solids (TDS) recipes. The recipes differed in their relative dominance of major ions. One was made from sodium and calcium chloride salts only. Another was similar to the first, but a...

  20. EVALUATION OF QUICK TESTS FOR DISSOLVED PHOSPHORUS DETERMINATION IN DAIRY MANURES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to evaluate the suitability of a hand-held reflectometer, hydrometers, and measurements of electrical conductivity (EC) and manure total solids (TS) concentrations for determining dissolved phosphorus (DP) in dairy manure suspensions, and to compare the estimated DP c...

  1. DIEL DISSOLVED OXYGEN MONITORING OF THE SPOKANE RIVER DURING EXTREME LOW FLOW. KOOTENAI COUNTY, IDAHO, 1992

    EPA Science Inventory

    Diel monitoring of dissolved oxygen and temperature was conducted on an impounded and free-flowing reach of the Spokane River, in north Idaho (17010303) on 2 occasions during an extreme low flow event in water year 1992. The objective was to document excursions from water qualit...

  2. Importance of Dissolved Organic Nitrogen to Water Quality in Narragansett Bay

    EPA Science Inventory

    This preliminary analysis of the importance of the dissolved organic nitrogen (DON) pool in Narragansett Bay is being conducted as part of a five-year study of Narragansett Bay and its watershed. This larger study includes water quality and ecological modeling components that foc...

  3. Complexation of trace organic contaminants with fractionated dissolved organic matter: implications for mass spectrometric quantification.

    PubMed

    Ruiz, Selene Hernandez; Wickramasekara, Samanthi; Abrell, Leif; Gao, Xiaodong; Chefetz, Benny; Chorover, Jon

    2013-04-01

    Interaction with aqueous phase dissolved organic matter (DOM) can alter the fate of trace organic contaminants of emerging concern once they enter the water cycle. In order to probe possible DOM binding mechanisms and their consequences for contaminant detection and quantification in natural waters, a set of laboratory experiments was conducted with aqueous solutions containing various operationally-defined "hydrophilic" and "hydrophobic" freshwater DOM fractions isolated by resin adsorption techniques from reference Suwannee River natural organic matter (SROM). Per unit mass of SROM carbon, hydrophobic acids (HoA) comprised the largest C fraction (0.63±0.029), followed by hydrophilic-neutrals (HiN, 0.11±0.01) and acids (HiA, 0.09±0.017). Aqueous solutions comprising 8mgL(-1) DOC of each SROM fraction were spiked with a concentration range (10-1000μgL(-1)) of bisphenol A (BPA), carbamazepine (CBZ), or ibuprofen (IBU) as model target compounds in 24mM NH4HCO3 background electrolyte at pH 7.4. Contaminant interaction with the SROM fractions was probed using fluorescence spectroscopy, and effects on quantitative analysis of the target compounds were measured using direct aqueous-injection liquid chromatography tandem mass spectrometry (LC-MS/MS). Total quenching was greater for the hydrophilic fractions of SROM and associations were principally with protein-like and fulvic acid-like constituents. Whereas LC-MS/MS recoveries indicated relatively weak interactions with most SROM factions, an important exception was the HiA fraction, which diminished recovery of CBZ and IBU by ca. 30% and 70%, respectively, indicating relatively strong molecular interactions. PMID:23276460

  4. The impact of blocking natural peat pipes on dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Holden, Joseph; Baird, Andy; Parry, Lauren; Chapman, Pippa; Palmer, Sheila; Wallage, Zoe; Wynne, Hannah

    2014-05-01

    Natural pipes transport water and aquatic carbon through peatlands. In 2010 pipes were blocked on Keighley Moor in northern England as part of a peatland restoration programme aimed at reducing water discolouration and dissolved organic carbon (DOC) release into stream waters used for potable water supply. Blocked and open pipes were monitored for water quality between June 2012 and October 2013. The DOC, water colour, conductivity and pH were not significantly different between open pipes and water flowing from areas where pipe blocking had occurred. A before-after control-treatment experiment was devised at another peatland site - Moor House World Biosphere Reserve in northern England. Here, the areas around six pipes were monitored for water quality, discharge, water tables, and overland flow. Four of the pipes were then blocked while monitoring continued on all six pipes. The Moor House investigation suggests that the overall effects of blocking on water colour and DOC in the following summer were small (5 % decrease in absorbance at 254 nm but 7 % increase in absorbance at 400 nm, and 2 % decrease in DOC relative to open pipe controls). There were large (40-117 %) local increases in colour and DOC in overland flow but decreases in soil water (7-10 %) relative to the areas around open pipes. Water tables rose by a few cm upslope of the pipe dams. However, downslope, water tables fell by a similar amount, thereby potentially counteracting any water quality benefits resulting from shallower water tables upslope. Pipe blocking is expensive, and our results to date suggest that any water quality benefits are outweighed by the cost of blocking. However, in highly-degraded sites where pipes are rapidly expanding to form gullies, pipe blocking may be useful as part of a larger suite of measures to help reduce peat erosion.

  5. Appropriate Conduct

    ERIC Educational Resources Information Center

    Di Lullo, Louis

    2004-01-01

    Many years ago when the author assumed the role of assistant principal for school climate, discipline, and attendance, he inherited many school policies and guidelines that were outdated, unfair, and without merit in the current school climate. Because the school conduct code had not been revised since the school opened in 1960, many of the…

  6. Dissolved Zinc Measurements Using Shipboard FIA During the 2008 GEOTRACES Cruise

    NASA Astrophysics Data System (ADS)

    Gosnell, K. J.; Landing, W. M.; Milne, A.

    2008-12-01

    Zinc concentrations in the open ocean have been measured accurately by only a few investigators due to the extreme difficulties of collecting and processing seawater samples without introducing Zn contamination. Accurate measurements of dissolved Zn are important for understanding the biogeochemical behavior of this important biochemically required element in the open ocean. Historically, reliable samples for dissolved Zn were collected using Teflon-coated GO-FLO bottles individually hung on Kevlar line. To speed up sample collection, two "Trace Metal" rosette systems were tested during Leg 1 of the GEOTRACES 2008 intercalibration cruise: a large GEOTRACES 24-bottle rosette and the smaller Measures and Landing "CLIVAR" 12-bottle rosette. Both rosettes use 12-liter, Teflon-coated GO- FLO bottles equipped with Teflon spigots and modified air-relief fittings, allowing for pressure filtration. Contamination for dissolved Zn was eliminated in the 12-liter Teflon-lined GO-FLO bottles by repeated deployments ("flushing") on both rosette systems. A Flow Injection (FIA) technique for shipboard determination of total dissolved Zn was utilized to test rosette sampling methods for Zn contamination. Samples were acidified to 0.024M HCl (pH 2) for 16 hours. Samples were buffered to pH 5.5 using ammonium acetate buffer. Dissolved Zn was pre-concentrated using a small- volume column of 8-HQ cation exchange resin. After column rinsing, Zn was eluted into the flowing stream of organic reagent p-Tosyl-8-aminoquinoline (pTAQ), which forms fluorescent complexes with Zn. A flow- through fluorometer was used to record peak heights. Calibration was performed via standard additions. Accuracy of this method was established by measuring standard SAFe D2 and S1 samples, as well as multiple samples collected and analyzed throughout Leg 1 of the GEOTRACES 2008 cruise. Dissolved Cadmium (Cd) can additionally form fluorescent complexes with pTAQ. Thus, when necessary, a small, positive, Cd interference can be corrected for using established Cd-PO4 relationships. Dissolved Zn profiles from both rosette systems agree extremely well with previously published Zn data from this region.

  7. Adsorption of dissolved aluminum on sapphire-c and kaolinite: implications for points of zero charge of clay minerals

    PubMed Central

    2014-01-01

    We have studied the impact of dissolved aluminum on interfacial properties of two aluminum bearing minerals, corundum and kaolinite. The effect of intentionally adding dissolved aluminum on electrokinetic potential of basal plane surfaces of sapphire was studied by streaming potential measurements as a function of pH and was complemented by a second harmonic generation (SHG) study at pH 6. The electrokinetic data show a similar trend as the SHG data, suggesting that the SHG electric field correlates to zeta-potential. A comparable study was carried out on kaolinite particles. In this case electrophoretic mobility was measured as a function of pH. In both systems the addition of dissolved aluminum caused significant changes in the charging behavior. The isoelectric point consistently shifted to higher pH values, the extent of the shift depending on the amount of aluminum present or added. The experimental results imply that published isoelectric points of clay minerals may have been affected by this phenomenon. The presence of dissolved aluminum in experimental studies may be caused by particular pre-treatment methods (such as washing in acids and subsequent adsorption of dissolved aluminum) or even simply by starting a series of measurements from extreme pH (causing dissolution), and subsequently varying the pH in the very same batch. This results in interactions of dissolved aluminum with the target surface. A possible interpretation of the experimental results could be that at low aluminum concentrations adatoms of aluminum (we will refer to adsorbed mineral constituents as adatoms) can form at the sapphire basal plane, which can be rather easily removed. Simultaneously, once the surface has been exposed to sufficiently high aluminum concentration, a visible change of the surface is seen by AFM which is attributed to a surface precipitate that cannot be removed under the conditions employed in the current study. In conclusion, whenever pre-treatment or the starting point of an experiment favor the dissolution of aluminum, dissolved Al may remain in the experimental system and interact with the target surfaces. The systems are then no longer pristine and points of zero charge or sorption data are those of aluminum-bearing systems. PMID:25045321

  8. Fast dissolving strips: A novel approach for the delivery of verapamil

    PubMed Central

    Kunte, S.; Tandale, P.

    2010-01-01

    Objective: Fast dissolving drug delivery system offers a solution for those patients having difficulty in swallowing tablets/capsules etc. Verapamil is a calcium channel blocker used as an antianginal, antiarrhythmic, and antihypertensive agent with extensive first pass metabolism which results in less bioavailability. This work investigated the possibility of developing verapamil fast dissolving strips allowing fast, reproducible drug dissolution in the oral cavity; thus bypassing first pass metabolism. Materials and methods: The fast dissolving strips were prepared by solvent casting technique with the help of HPMC E6 and maltodextrin. The strips were evaluated for drug content uniformity, film thickness, folding endurance, in vitro disintegration time, in vitro dissolution studies, surface pH study, and palatability study. Results: Official criteria for evaluation parameters were fulfilled by all formulations. Disintegration time showed by formulations was found to be in range of 20.4–28.6 sec. Based on the evaluation parameters, the formulation containing 2% HPMC E6 and 3.5% maltodextrin showed optimum performance against other formulations. Conclusion: It was concluded that the fast dissolving strips of verapamil can be made by solvent casting technique with enhanced dissolution rate, taste masking, and hence better patient compliance and effective therapy PMID:21180465

  9. Dissolving polymer microneedle patches for influenza vaccination.

    PubMed

    Sullivan, Sean P; Koutsonanos, Dimitrios G; Del Pilar Martin, Maria; Lee, Jeong Woo; Zarnitsyn, Vladimir; Choi, Seong-O; Murthy, Niren; Compans, Richard W; Skountzou, Ioanna; Prausnitz, Mark R

    2010-08-01

    Influenza prophylaxis would benefit from a vaccination method enabling simplified logistics and improved immunogenicity without the dangers posed by hypodermic needles. Here we introduce dissolving microneedle patches for influenza vaccination using a simple patch-based system that targets delivery to skin's antigen-presenting cells. Microneedles were fabricated using a biocompatible polymer encapsulating inactivated influenza virus vaccine for insertion and dissolution in the skin within minutes. Microneedle vaccination generated robust antibody and cellular immune responses in mice that provided complete protection against lethal challenge. Compared to conventional intramuscular injection, microneedle vaccination resulted in more efficient lung virus clearance and enhanced cellular recall responses after challenge. These results suggest that dissolving microneedle patches can provide a new technology for simpler and safer vaccination with improved immunogenicity that could facilitate increased vaccination coverage. PMID:20639891

  10. Dissolving Polymer Microneedle Patches for Influenza Vaccination

    PubMed Central

    Sullivan, Sean P.; Koutsonanos, Dimitrios G.; Martin, Maria del Pilar; Lee, Jeong-Woo; Zarnitsyn, Vladimir; Murthy, Niren; Compans, Richard W.; Skountzou, Ioanna; Prausnitz, Mark R.

    2010-01-01

    Influenza prophylaxis would benefit from a vaccination method enabling simplified logistics and improved immunogenicity without the dangers posed by hypodermic needles. Here, we introduce dissolving microneedle patches for influenza vaccination using a simple patch-based system that targets delivery to skins antigen-presenting cells. Microneedles were fabricated using a biocompatible polymer encapsulating inactivated influenza virus vaccine for insertion and dissolution in the skin within minutes. Microneedle vaccination generated robust antibody and cellular immune responses in mice that provided complete protection against lethal challenge. Compared to conventional intramuscular injection, microneedle vaccination resulted in more efficient lung virus clearance and enhanced cellular recall responses after challenge. These results suggest that dissolving microneedle patches can provide a novel technology for simpler and safer vaccination with improved immunogenicity that could facilitate increased vaccination coverage. PMID:20639891

  11. Heat conduction

    SciTech Connect

    Lilley, D.G.

    1987-01-01

    Analytical and numerical methods, including both finite difference and finite element techniques, are presented with applications to heat conduction problems. Numerical and analytical methods are integrated throughout the text and a variety of complexities are thoroughly treated with many problems, solutions and computer programs. This book is presented as a fundamental course suitable for senior undergraduate and first year graduate students, with end-of-chapter problems and answers included. Sample case studies and suggested projects are included.

  12. Dissolved organic nitrogen in precipitation: Collection, analysis and atmospheric flux

    SciTech Connect

    Scudlark, J.R.; Church, T.M.; Russell, K.M.; Montag, J.A.; Maben, J.R.; Keene, W.C.; Galloway, J.N.

    1995-12-31

    Recent studies have documented the importance of atmosphere inorganic nitrogen deposition to coastal waters. However, due to the limited number of field measurements and concerns about the reliability of measurement techniques, the aeolian flux of organic N is very uncertain. Coordinated studies have been initiated at Lewes, DE and Charlottesville, VA to evaluate collection and analysis techniques for dissolved organic nitrogen (DON) in precipitation and to provide preliminary estimate of DON wet fluxes. Sampling was conducted both manually and employing an automated wet-only collector (ACM) on a daily basis. A total of 37 events were analyzed from October 1993 through December 1994. Side-by-side comparisons of standard white HDPE buckets and stainless steel and glass collection vessels indicate sampling artifacts associate with plastic buckets. DON in precipitation appears to be highly labile, with significant losses observed in some samples within 12 hours. Analytical methods evaluated include persulfate wet chemical oxidation, UV photo-oxidation and a modified high temperature instrumental (ANTEK 7000) technique. Based on preliminary results, the volume-weighted average concentration of DON in precipitation at the mid-Atlantic coast is 9.1 {micro}moles/1. On an annual basis, DON compromises 23% of the total dissolved nitrogen in precipitation, varying from 0--64% on an event basis. From an ecological perspective, DON wet flux represents a quantitatively important exogenous source of N to coastal waters such as Chesapeake Bay.

  13. Screening for Dissolved Methane in Groundwater Across Texas Shale Plays

    NASA Astrophysics Data System (ADS)

    Nicot, J. P.; Mickler, P. J.; Hildenbrand, Z.; Larson, T.; Darvari, R.; Uhlman, K.; Smyth, R. C.; Scanlon, B. R.

    2014-12-01

    There is considerable interest in methane concentrations in groundwater, particularly as they relate to hydraulic fracturing in shale plays. Recent studies of aquifers in the footprint of several gas plays across the US have shown that (1) dissolved thermogenic methane may or may not be present in the shallow groundwater and (2) shallow thermogenic methane may be naturally occurring and emplaced through mostly vertical migration over geologic time and not necessarily a consequence of recent unconventional gas production. We are currently conducting a large sampling campaign across the state of Texas to characterize shallow methane in fresh-water aquifers overlying shale plays and other tight formations. We collected a total of ~800 water samples, ~500 in the Barnett, ~150 in the Eagle Ford, ~80 in the Haynesville shale plays as well as ~50 in the Delaware Basin of West Texas. Preliminary analytical results suggest that dissolved methane is not widespread in shallow groundwater and that, when present at concentrations exceeding 10 mg/L, it is often of thermogenic origin according to the isotopic signature and to the presence of other light hydrocarbons. The Barnett Shale contains a large methane hotspot (~ 2 miles wide) along the Hood-Parker county line which is likely of natural origin whereas the Eagle Ford and Haynesville shales, neglecting microbial methane, show more distributed methane occurrences. Samples from the Delaware Basin show no methane except close to blowouts.

  14. Diel behavior of iron and other heavy metals in a mountain stream with acidic to neutral pH: Fisher Creek, Montana, USA

    NASA Astrophysics Data System (ADS)

    Gammons, Christopher H.; Nimick, David A.; Parker, Stephen R.; Cleasby, Thomas E.; McCleskey, R. Blaine

    2005-05-01

    Three simultaneous 24-h samplings at three sites over a downstream pH gradient were conducted to examine diel fluctuations in heavy metal concentrations in Fisher Creek, a small mountain stream draining abandoned mine lands in Montana. Average pH values at the upstream (F1), middle (F2), and downstream (F3) monitoring stations were 3.31, 5.46, and 6.80, respectively. The downstream increase in pH resulted in precipitation of hydrous ferric oxide (HFO) and hydrous aluminum oxide (HAO) on the streambed. At F1 and F2, Fe showed strong diel cycles in dissolved concentration and Fe(II)/Fe(III) ratio; these cycles were attributed to daytime photoreduction of Fe(III) to Fe(II), reoxidation of Fe(II) to Fe(III), and temperature-dependent hydrolysis and precipitation of HFO. At the near-neutral downstream station, no evidence of Fe(III) photoreduction was observed, and suspended particles of HFO dominated the total Fe load. HFO precipitation rates between F2 and F3 were highest in the afternoon, due in part to reoxidation of a midday pulse of Fe 2+ formed by photoreduction in the upper, acidic portions of the stream. Dissolved concentrations of Fe(II) and Cu decreased tenfold and 2.4-fold, respectively, during the day at F3. These changes were attributed to sorption onto fresh HFO surfaces. Results of surface complexation modeling showed good agreement between observed and predicted Cu concentrations at F3, but only when adsorption enthalpies were added to the thermodynamic database to take into account diel temperature variations. The field and modeling results illustrate that the degree to which trace metals adsorb onto actively forming HFO is strongly temperature dependent. This study is an example of how diel Fe cycles caused by redox and hydrolysis reactions can induce a diel cycle in a trace metal of toxicological importance in downstream waters.

  15. Diel behavior of iron and other heavy metals in a mountain stream with acidic to neutral pH: Fisher Creek, Montana, USA

    USGS Publications Warehouse

    Gammons, C.H.; Nimick, D.A.; Parker, S.R.; Cleasby, T.E.; McCleskey, R.B.

    2005-01-01

    Three simultaneous 24-h samplings at three sites over a downstream pH gradient were conducted to examine diel fluctuations in heavy metal concentrations in Fisher Creek, a small mountain stream draining abandoned mine lands in Montana. Average pH values at the upstream (F1), middle (F2), and downstream (F3) monitoring stations were 3.31, 5.46, and 6.80, respectively. The downstream increase in pH resulted in precipitation of hydrous ferric oxide (HFO) and hydrous aluminum oxide (HAO) on the streambed. At F1 and F2, Fe showed strong diel cycles in dissolved concentration and Fe(II)/Fe(III) ratio; these cycles were attributed to daytime photoreduction of Fe(III) to Fe(II), reoxidation of Fe(II) to Fe(III), and temperature-dependent hydrolysis and precipitation of HFO. At the near-neutral downstream station, no evidence of Fe(III) photoreduction was observed, and suspended particles of HFO dominated the total Fe load. HFO precipitation rates between F2 and F3 were highest in the afternoon, due in part to reoxidation of a midday pulse of Fe2+ formed by photoreduction in the upper, acidic portions of the stream. Dissolved concentrations of Fe(II) and Cu decreased tenfold and 2.4-fold, respectively, during the day at F3. These changes were attributed to sorption onto fresh HFO surfaces. Results of surface complexation modeling showed good agreement between observed and predicted Cu concentrations at F3, but only when adsorption enthalpies were added to the thermodynamic database to take into account diel temperature variations. The field and modeling results illustrate that the degree to which trace metals adsorb onto actively forming HFO is strongly temperature dependent. This study is an example of how diel Fe cycles caused by redox and hydrolysis reactions can induce a diel cycle in a trace metal of toxicological importance in downstream waters. Copyright ?? 2005 Elsevier Ltd.

  16. Oxidative dissolution of 4C- and NC-pyrrhotite: Intrinsic reactivity differences, pH dependence, and the effect of anisotropy

    NASA Astrophysics Data System (ADS)

    Harries, Dennis; Pollok, Kilian; Langenhorst, Falko

    2013-02-01

    The crystallographic diversity of pyrrhotite (Fe1-xS), one of the most common iron sulfide minerals, offers insights into how mineral-fluid interactions are controlled by crystal structures. We have conducted oxidative dissolution experiments on monoclinic 4C-pyrrhotite and 'hexagonal' NC-pyrrhotite in aqueous H2O2/H2SO4 and FeCl3/HCl media at pH between 1.8 and 2.9 using polished surfaces of single crystals. Quantification and detailed characterization of the reaction interfaces has been accomplished by confocal 3D topometry and transmission electron microscopy (TEM) in conjunction with focused ion beam (FIB) preparation. Crystallographically coherent intergrowths of 4C- and NC-pyrrhotite in a single sample allowed unambiguous identification of strong intrinsic reactivity differences between the two closely related phases. On {1 1 0} faces in the H2O2 medium at 35 °C and pH below 2.70, NC-pyrrhotite (N ˜ 4.85) reacts about 50-80% faster than 4C-pyrrhotite. Above pH 2.70, the behavior inverts and 4C-pyrrhotite dissolves faster, while overall reaction rates drop drastically by up to two orders of magnitude. Because the two pyrrhotite phases show only marginally different Fe/S ratios but substantial differences in structural complexity with regards to vacancy ordering, we attribute the reactivity differences to structurally controlled processes at the mineral-water interface. The transition at pH 2.70 is close to the reported isoelectric point of pyrrhotite. We attribute the pH dependent changes in reaction rates and behaviors to protonation/deprotonation of surface sulfhydryl groups and related changes in speciation and bonding mode of reactive oxygen species at the mineral interface. At pH <2.70, we find elemental sulfur as a frequent reaction product in H2O2 and FeCl3 media, indicating incomplete sulfur oxidation. Above pH 2.70, elemental sulfur was not found in H2O2 experiments (no data for FeCl3). Our results show that the effects of crystal anisotropy are strong and directional preference of dissolution changes at the pH 2.70 transition point as well, leading to complex sub-μm-scale textural development at the reaction interfaces throughout the pH range studied. High resolution TEM imaging of cross sections through reacted mineral surfaces show crystalline pyrrhotite up to the reaction interface and the absence of significant non-equilibrium layers or S-enriched (poly)sulfides.

  17. Investigation of organic carbon transformation in soils of dominant dissolved organic carbon source zones

    NASA Astrophysics Data System (ADS)

    Pissarello, Anna; Miltner, Anja; Oosterwoud, Marieke; Fleckenstein, Jan; Kästner, Matthias

    2014-05-01

    Over the past 20 years both a decrease in soil organic matter (SOM) and an increase in the dissolved organic carbon (DOC) concentrations in surface water bodies, including drinking water reservoirs, have been recorded in the northern hemisphere. This development has severe consequences for soil fertility and for drinking water purification. As both processes occur simultaneously, we assume that microbial SOM degradation, which transforms SOM into CO2 and DOC, is a possible source of the additional DOC in the surface water. In addition we speculate that both processes are initially triggered by physical mechanisms, resulting in a modification of the organic matter solubility equilibria and thus in higher SOM availability and DOC mobilization. The general hypothesis of the study is therefore that SOM loss and DOC increase are combined consequences of enhanced microbial degradation of SOM and that this is a result of climate variations and global change, e.g. the increase of the temperature, the alteration of the water regime (i.e. increase of the frequency of drying and rewetting cycles and a higher number of heavy rain events), but also the decrease of the atmospheric acid deposition resulting in an increase of soil pH values. The general goal of the study is the identification of the dominant processes and controlling factors involved in soil microbial carbon turnover and mobilization of DOC in soils from catchment areas that contribute DOC to the receiving waters and the downstream Rappbode reservoir, which showed a pronounced increase in DOC concentration in recent years. This reservoir is the source of drinking water for about one million people in northern Germany. Preliminary screening experiments, consisting of 65-day soil batch incubation experiments, have been conducted in order to select the parameters (and the parameter ranges) of relevance for further in-depth experiments. During the experiments, different soil systems were exposed to different temperatures, pH, and water contents. The extractable DOC and the mineralization products (CO2) were monitored in order to obtain the mass balances of SOM turnover for the different systems. In addition, for each system the aromatic character of the DOC extracted was evaluated by analyzing the specific UV absorbance (SUVA) at 254 nm. Results from the preliminary experiments will be presented. All the environmental drivers which were studied influenced both organic matter degradation and DOC mobilization, which suggests a positive correlation between the two processes. The results of the screening experiments will be the basis for the experimental design of further experiments studying the mechanisms of these observed changes in detail.

  18. Dissolvable microneedle fabrication using piezoelectric dispensing technology.

    PubMed

    Allen, Evin A; O'Mahony, Conor; Cronin, Michael; O'Mahony, Thomas; Moore, Anne C; Crean, Abina M

    2016-03-16

    Dissolvable microneedle (DMN) patches are novel dosage forms for the percutaneous delivery of vaccines. DMN are routinely fabricated by dispensing liquid formulations into microneedle-shaped moulds. The liquid formulation within the mould is then dried to create dissolvable vaccine-loaded microneedles. The precision of the dispensing process is critical to the control of formulation volume loaded into each dissolvable microneedle structure. The dispensing process employed must maintain vaccine integrity. Wetting of mould surfaces by the dispensed formulation is also an important consideration for the fabrication of sharp-tipped DMN. Sharp-tipped DMN are essential for ease of percutaneous administration. In this paper, we demonstrate the ability of a piezoelectric dispensing system to dispense picolitre formulation volumes into PDMS moulds enabling the fabrication of bilayer DMN. The influence of formulation components (trehalose and polyvinyl alcohol (PVA) content) and piezoelectric actuation parameters (voltage, frequency and back pressure) on drop formation is described. The biological integrity of a seasonal influenza vaccine following dispensing was investigated and maintained voltage settings of 30V but undermined at higher settings, 50 and 80V. The results demonstrate the capability of piezoelectric dispensing technology to precisely fabricate bilayer DMN. They also highlight the importance of identifying formulation and actuation parameters to ensure controlled droplet formulation and vaccine stabilisation. PMID:26721722

  19. Superhydrophobic porous surfaces: dissolved oxygen sensing.

    PubMed

    Gao, Yu; Chen, Tao; Yamamoto, Shunsuke; Miyashita, Tokuji; Mitsuishi, Masaya

    2015-02-18

    Porous polymer films are necessary for dissolved gas sensor applications that combine high sensitivity with selectivity. This report describes a greatly enhanced dissolved oxygen sensor system consisting of amphiphilic acrylamide-based polymers: poly(N-(1H, 1H-pentadecafluorooctyl)-methacrylamide) (pC7F15MAA) and poly(N-dodecylacrylamide-co-5- [4-(2-methacryloyloxyethoxy-carbonyl)phenyl]-10,15,20-triphenylporphinato platinum(II)) (p(DDA/PtTPP)). The nanoparticle formation capability ensures both superhydrophobicity with a water contact angle greater than 160° and gas permeability so that molecular oxygen enters the film from water. The film was prepared by casting a mixed solution of pC7F15MAA and p(DDA/PtTPP) with AK-225 and acetic acid onto a solid substrate. The film has a porous structure comprising nanoparticle assemblies with diameters of several hundred nanometers. The film shows exceptional performance as the oxygen sensitivity reaches 126: the intensity ratio at two oxygen concentrations (I0/I40) respectively corresponding to dissolved oxygen concentration 0 and 40 (mg L(-1)). Understanding and controlling porous nanostructures are expected to provide opportunities for making selective penetration/separation of molecules occurring at the superhydrophobic surface. PMID:25659178

  20. Measurements of the dissolved inorganic carbon system and associated biogeochemical parameters in the Canadian Arctic, 1974-2009

    NASA Astrophysics Data System (ADS)

    Giesbrecht, K. E.; Miller, L. A.; Zimmermann, S.; Carmack, E.; Johnson, W. K.; Macdonald, R. W.; McLaughlin, F.; Mucci, A.; Williams, W. J.; Wong, C. S.; Yamamoto-Kawai, M.

    2013-06-01

    We have assembled and conducted primary quality control on previously publically-unavailable water column measurements of the dissolved inorganic carbon system and associated biogeochemical parameters (oxygen, nutrients, etc.) made on 25 cruises in the subarctic and Arctic regions dating from as far back as 1974. The measurements are primarily from the western side of the Canadian Arctic, but also include data ranging from the North Pacific to the Gulf of St. Lawrence. The data were subjected to primary quality control (QC) to identify outliers and obvious errors. This dataset incorporates over four thousand individual measurements of total inorganic carbon (TIC), alkalinity, and pH from the Canadian Arctic over a period of more than 30 yr and provides an opportunity to increase our understanding of temporal changes in the inorganic carbon system in northern waters and the Arctic Ocean. The dataset is available for download on the CDIAC website: http://cdiac.ornl.gov/ftp/oceans/IOS_Arctic_Database/ (doi:10.3334/CDIAC/OTG.IOS_ARCT_CARBN).

  1. Measurements of the dissolved inorganic carbon system and associated biogeochemical parameters in the Canadian Arctic, 1974-2009

    NASA Astrophysics Data System (ADS)

    Giesbrecht, K. E.; Miller, L. A.; Davelaar, M.; Zimmermann, S.; Carmack, E.; Johnson, W. K.; Macdonald, R. W.; McLaughlin, F.; Mucci, A.; Williams, W. J.; Wong, C. S.; Yamamoto-Kawai, M.

    2014-03-01

    We have assembled and conducted primary quality control on previously publicly unavailable water column measurements of the dissolved inorganic carbon system and associated biogeochemical parameters (oxygen, nutrients, etc.) made on 26 cruises in the subarctic and Arctic regions dating back to 1974. The measurements are primarily from the western side of the Canadian Arctic, but also include data that cover an area ranging from the North Pacific to the Gulf of St. Lawrence. The data were subjected to primary quality control (QC) to identify outliers and obvious errors. This data set incorporates over four thousand individual measurements of total inorganic carbon (TIC), alkalinity, and pH from the Canadian Arctic over a period of more than 30 years and provides an opportunity to increase our understanding of temporal changes in the inorganic carbon system in northern waters and the Arctic Ocean. The data set is available for download on the CDIAC (Carbon Dioxide Information Analysis Center) website: http://cdiac.ornl.gov/ftp/oceans/IOS_Arctic_Database/ (doi:10.3334/CDIAC/OTG.IOS_ARCT_CARBN).

  2. [Vermicomposting of different organic materials and three-dimensional excitation emission matrix fluorescence spectroscopic characterization of their dissolved organic matter].

    PubMed

    Yang, Wei; Wang, Dong-sheng; Liu, Man-qiang; Hu, Feng; Li, Hui-xin; Huang, Zhong-yang; Chang, Yi-jun; Jiao, Jia-guo

    2015-10-01

    In this experiment, different proportions of the cattle manure, tea-leaf, herb and mushroom residues, were used as food for earthworm (Eisenia fetida) to study the growth of the earth-worm. Then the characteristics and transformation of nutrient content and three-dimensional excitation emission matrix fluorescence (3DEEM) of dissolved organic matter (DOM) during vermistabilization were investigated by means of chemical and spectroscopic methods. The result showed that the mixture of different ratios of cattle manure with herb residue, and cattle manure with tea-leaf were conducive to the growth of earthworm, while the materials compounded with mushroom residue inhibited the growth of earthworm. With the increasing time of verimcomposting, the pH in vermicompost tended to be circumneutral and weakly acidic, and there were increases in electrical conductivity, and the contents of total nitrogen, total phosphorus, available nitrogen, and available phosphorus, while the total potassium and available potassium increased first and then decreased, and the organic matter content decreased. 3DEEM and fluorescence regional integration results indicated that, the fluorescence of protein-like fluorescence peaks declined significantly, while the intensity of humic-like fluorescence peak increased significantly in DOM. Vermicomposting process might change the compositions of DOM with elevated concentrations of humic acid and fulvic acid in the organics. In all, this study suggested the suitability of 3DEEM for monitoring the organics transformation and assessing the maturity in the vermicomposting. PMID:26995929

  3. Modelling of dissolved oxygen in the Danube River using artificial neural networks and Monte Carlo Simulation uncertainty analysis

    NASA Astrophysics Data System (ADS)

    Antanasijević, Davor; Pocajt, Viktor; Perić-Grujić, Aleksandra; Ristić, Mirjana

    2014-11-01

    This paper describes the training, validation, testing and uncertainty analysis of general regression neural network (GRNN) models for the forecasting of dissolved oxygen (DO) in the Danube River. The main objectives of this work were to determine the optimum data normalization and input selection techniques, the determination of the relative importance of uncertainty in different input variables, as well as the uncertainty analysis of model results using the Monte Carlo Simulation (MCS) technique. Min-max, median, z-score, sigmoid and tanh were validated as normalization techniques, whilst the variance inflation factor, correlation analysis and genetic algorithm were tested as input selection techniques. As inputs, the GRNN models used 19 water quality variables, measured in the river water each month at 17 different sites over a period of 9 years. The best results were obtained using min-max normalized data and the input selection based on the correlation between DO and dependent variables, which provided the most accurate GRNN model, and in combination the smallest number of inputs: Temperature, pH, HCO3-, SO42-, NO3-N, Hardness, Na, Cl-, Conductivity and Alkalinity. The results show that the correlation coefficient between measured and predicted DO values is 0.85. The inputs with the greatest effect on the GRNN model (arranged in descending order) were T, pH, HCO3-, SO42- and NO3-N. Of all inputs, variability of temperature had the greatest influence on the variability of DO content in river body, with the DO decreasing at a rate similar to the theoretical DO decreasing rate relating to temperature. The uncertainty analysis of the model results demonstrate that the GRNN can effectively forecast the DO content, since the distribution of model results are very similar to the corresponding distribution of real data.

  4. Influence of pH on transungual passive and iontophoretic transport.

    PubMed

    Smith, Kelly A; Hao, Jinsong; Li, S Kevin

    2010-04-01

    The present study investigated the effects of pH on nail permeability and the transport of ions such as sodium (Na) and chloride (Cl) ions endogenous to nail and hydronium and hydroxide ions present at low and high pH, which might compete with drug transport across hydrated nail plate during iontophoresis. Nail hydration and passive transport of water across the nail at pH 1-13 were assessed. Subsequently, passive and iontophoretic transport experiments were conducted using (22)Na and (36)Cl ions under various pH conditions. Nail hydration was independent of pH under moderate pH conditions and increased significantly under extreme pH conditions (pH >11). Likewise, nail permeability for water was pH independent at pH 1-10 and an order of magnitude higher at pH 13. The results of passive and iontophoretic transport of Na and Cl ions are consistent with the permselective property of nail. Interestingly, extremely acidic conditions (e.g., pH 1) altered nail permselectivity with the effect lasting several days at the higher pH conditions. Hydronium and hydroxide ion competition in iontophoretic transport was generally negligible at pH 3-11 was significant at the extreme pH conditions studied. PMID:19904826

  5. Mechanistic Analysis of Cocrystal Dissolution as a Function of pH and Micellar Solubilization

    PubMed Central

    2016-01-01

    The purpose of this work is to provide a mechanistic understanding of the dissolution behavior of cocrystals under the influence of ionization and micellar solubilization. Mass transport models were developed by applying Fick’s law of diffusion to dissolution with simultaneous chemical reactions in the hydrodynamic boundary layer adjacent to the dissolving cocrystal surface to predict the pH at the dissolving solid–liquid interface (i.e., interfacial pH) and the flux of cocrystals. To evaluate the predictive power of these models, dissolution studies of carbamazepine–saccharin (CBZ-SAC) and carbamazepine–salicylic acid (CBZ-SLC) cocrystals were performed at varied pH and surfactant concentrations above the critical stabilization concentration (CSC), where the cocrystals were thermodynamically stable. The findings in this work demonstrate that the pH dependent dissolution behavior of cocrystals with ionizable components is dependent on interfacial pH. This mass transport analysis demonstrates the importance of pH, cocrystal solubility, diffusivity, and micellar solubilization on the dissolution rates of cocrystals. PMID:26877267

  6. Mechanistic Analysis of Cocrystal Dissolution as a Function of pH and Micellar Solubilization.

    PubMed

    Cao, Fengjuan; Amidon, Gordon L; Rodriguez-Hornedo, Nair; Amidon, Gregory E

    2016-03-01

    The purpose of this work is to provide a mechanistic understanding of the dissolution behavior of cocrystals under the influence of ionization and micellar solubilization. Mass transport models were developed by applying Fick's law of diffusion to dissolution with simultaneous chemical reactions in the hydrodynamic boundary layer adjacent to the dissolving cocrystal surface to predict the pH at the dissolving solid-liquid interface (i.e., interfacial pH) and the flux of cocrystals. To evaluate the predictive power of these models, dissolution studies of carbamazepine-saccharin (CBZ-SAC) and carbamazepine-salicylic acid (CBZ-SLC) cocrystals were performed at varied pH and surfactant concentrations above the critical stabilization concentration (CSC), where the cocrystals were thermodynamically stable. The findings in this work demonstrate that the pH dependent dissolution behavior of cocrystals with ionizable components is dependent on interfacial pH. This mass transport analysis demonstrates the importance of pH, cocrystal solubility, diffusivity, and micellar solubilization on the dissolution rates of cocrystals. PMID:26877267

  7. Dissolved Organic Matter Concentration and Composition in Hot Spring Ecosystems

    NASA Astrophysics Data System (ADS)

    Hartnett, H.; Alexander, K.; Shock, E.; Klonowski, S.; Windman, T.

    2006-12-01

    Hot springs host dynamic ecosystems with wide ranges in temperature, pH, major and minor element content, as well as diverse microbial communities. As temperatures decrease from boiling, chemolithotrophic communities give way to phototrophic communities that include heterotrophs. As a consequence, the cycling of carbon is likely to undergo dramatic changes over fairly narrow spatial and temporal ranges. It may, therefore, not be surprising that hot springs exhibit broad ranges in dissolved organic carbon (DOC) concentrations. As an example, water samples collected in July 2005 from Yellowstone National Park hot spring ecosystems have DOC concentrations that range from less than 0.5 mg C/kg to greater than 75 mg C/kg. There are no obvious relationships between pH and DOC concentration, or temperature and DOC concentration for these systems. DOC concentrations generally decrease by 10 to 90% from the source hot spring down outflow channels, presumably due to heterotrophic activity. New results using electrospray ionization mass spectrometry (ESI-MS) indicate that hot spring DOC compounds range in molecular weight from 30 up to 1500 amu, with the most abundant peaks occurring at <400 amu. The DOC in hot springs exhibits predominantly positive-mode detected (basic-type) compounds and negative-mode detected (acidic- type) compounds. ESI-MS provides a molecular-level fingerprint of the DOC from hot springs, outflow channels and surface water sources that suggest the composition of the hot spring DOC is the result of multiple organic matter sources and a variety of biogeochemical processes. ESI-MS results allow us to begin to assess which fraction (molecular weight and general chemical character) of the DOC pool is bioavailable to heterotrophs, and how the bioavailable pool of DOC varies among hot spring systems.

  8. pH sensors based on hydrogenated diamond surfaces

    NASA Astrophysics Data System (ADS)

    Garrido, Jose A.; Härtl, Andreas; Kuch, Stefan; Stutzmann, Martin; Williams, Oliver A.; Jackmann, R. B.

    2005-02-01

    We report on the operation of ungated surface conductive diamond devices in electrolytic solutions. The effect of electrolyte pH on the channel conductivity is studied in detail. It is shown that fully hydrogen terminated diamond surfaces are not pH sensitive. However, a pronounced pH sensitivity arises after a mild surface oxidation by ozone. We propose that charged ions from the electrolyte adsorbed on the oxidized surface regions induce a lateral electrostatic modulation of the conductive hole accumulation layer on the surface. In contrast, charged ions are not expected to be adsorbed on the hydrogen terminated surface, either due to the screening induced by a dense layer of strongly adsorbed counter-ions or by the absence of the proper reactive surface groups. Therefore, the modulation of the surface conductivity is generated by the oxidized regions, which are described as microscopic chemical in-plane gates. The pH sensitivity mechanism proposed here differs qualitatively from the one used to explain the behavior of conventional ion sensitive field effect transistors, resulting in a pH sensitivity higher than the Nernstian limit.

  9. SUSPENDED AND DISSOLVED SOLIDS EFFECTS ON FRESHWATER BIOTA: A REVIEW

    EPA Science Inventory

    It is widely recognized that suspended and dissolved solids in lakes, rivers, streams, and reservoirs affect water quality. In this report the research needs appropriate to setting freshwater quality criteria or standards for suspended solids (not including bedload) and dissolved...

  10. 7 CFR 760.908 - Deceased individuals or dissolved entities.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... dissolved entity must be provided. (c) If a participant is now a dissolved general partnership or joint venture, all members of the general partnership or joint venture at the time of dissolution or their...

  11. Effect of dissolved oxygen content on stress corrosion cracking of a cold worked 316L stainless steel in simulated pressurized water reactor primary water environment

    NASA Astrophysics Data System (ADS)

    Zhang, Litao; Wang, Jianqiu

    2014-03-01

    Stress corrosion crack growth tests of a cold worked nuclear grade 316L stainless steel were conducted in simulated pressurized water reactor (PWR) primary water environment containing various dissolved oxygen (DO) contents but no dissolved hydrogen. The crack growth rate (CGR) increased with increasing DO content in the simulated PWR primary water. The fracture surface exhibited typical intergranular stress corrosion cracking (IGSCC) characteristics.

  12. Role of structural Fe in nontronite NAu-1 and dissolved Fe(II) in redox transformations of arsenic and antimony

    NASA Astrophysics Data System (ADS)

    Ilgen, Anastasia G.; Foster, Andrea L.; Trainor, Thomas P.

    2012-10-01

    Oxidation state is a major factor affecting the mobility of arsenic (As) and antimony (Sb) in soil and aquatic systems. Metal (hydr)oxides and clay minerals are effective sorbents, and may also promote redox reactions on their surfaces via direct or indirect facilitation of electron transfer. Iron substituted for Al in the octahedral sites of aluminosilicate clay minerals has the potential to be in variable oxidation states and is a key constituent of electron transfer reactions in clay minerals. This experimental work was conducted to determine whether structural Fe in clays can affect the oxidation state of As and Sb adsorbed at the clay surface. Another goal of our study was to compare the reactivity of clay structural Fe(II) with systems containing Fe(II) present in dissolved/adsorbed forms. The experimental systems included batch reactors with various concentrations of As(III), Sb(III), As(V), or Sb(V) equilibrated with oxidized (NAu-1) or partially reduced (NAu-1-Red) nontronite, hydrous aluminum oxide (HAO) and kaolinite (KGa-1b) suspensions under oxic and anoxic conditions. The reaction times ranged from 0.5 to 720 h, and pH was constrained at 5.5 (for As) and at 5.5 or 8.0 (for Sb). The oxidation state of As and Sb in the liquid phase was determined by liquid chromatography in line with an inductively coupled plasma mass spectrometer, and in the solid phase by X-ray absorption spectroscopy. Our findings show that structural Fe(II) in NAu-1-Red was not able to reduce As(V)/Sb(V) under the conditions examined, but reduction was seen when aqueous Fe(II) was present in the systems with kaolinite (KGa-1b) and nontronite (NAu-1). The ability of the structural Fe in nontronite clay NAu-1 to promote oxidation of As(III)/Sb(III) was greatly affected by its oxidation state: if all structural Fe was in the oxidized Fe(III) form, no oxidation was observed; however, when the clay was partially reduced (˜20% of structural Fe was reduced to Fe(II)), NAu-1-Red promoted the most extensive oxidation under both oxic and anoxic conditions. Electron balance considerations suggest that structural Fe(III) in the NAu-1-Red was the sole oxidant in the anoxic setup, while dissolved O2 also contributes in oxic conditions. Long-term batch experiments revealed the complex dynamics of As aqueous speciation in anoxic and oxic systems when reduced arsenic was initially added: rapid disappearance of As(III) was observed due to oxidation to As(V) followed by a slow increase of aqueous As(III). This behavior is explained by two reactions: fast initial oxidation of As(III) by structural Fe(III) (anoxic) or Fe(III) and dissolved O2 (oxic) followed by the slow reduction of As(V) by dissolved Fe(II). The resulting re-mobilization of As due to As(V) reduction by aqueous Fe(II) occurs on time scales on the order of days. These reactions are likely significant in a natural soil or aquifer environment with seasonal cycling or slightly reducing conditions with an abundance of clay minerals and dissolved Fe(II).

  13. Role of structural Fe in nontronite NAu-1 and dissolved Fe(II) in redox transformations of arsenic and antimony

    SciTech Connect

    Ilgen, Anastasia G.; Foster, Andrea L.; Trainor, Thomas P.

    2012-11-01

    Oxidation state is a major factor affecting the mobility of arsenic (As) and antimony (Sb) in soil and aquatic systems. Metal (hydr)oxides and clay minerals are effective sorbents, and may also promote redox reactions on their surfaces via direct or indirect facilitation of electron transfer. Iron substituted for Al in the octahedral sites of aluminosilicate clay minerals has the potential to be in variable oxidation states and is a key constituent of electron transfer reactions in clay minerals. This experimental work was conducted to determine whether structural Fe in clays can affect the oxidation state of As and Sb adsorbed at the clay surface. Another goal of our study was to compare the reactivity of clay structural Fe(II) with systems containing Fe(II) present in dissolved/adsorbed forms. The experimental systems included batch reactors with various concentrations of As(III), Sb(III), As(V), or Sb(V) equilibrated with oxidized (NAu-1) or partially reduced (NAu-1-Red) nontronite, hydrous aluminum oxide (HAO) and kaolinite (KGa-1b) suspensions under oxic and anoxic conditions. The reaction times ranged from 0.5 to 720 h, and pH was constrained at 5.5 (for As) and at 5.5 or 8.0 (for Sb). The oxidation state of As and Sb in the liquid phase was determined by liquid chromatography in line with an inductively coupled plasma mass spectrometer, and in the solid phase by X-ray absorption spectroscopy. Our findings show that structural Fe(II) in NAu-1-Red was not able to reduce As(V)/Sb(V) under the conditions examined, but reduction was seen when aqueous Fe(II) was present in the systems with kaolinite (KGa-1b) and nontronite (NAu-1). The ability of the structural Fe in nontronite clay NAu-1 to promote oxidation of As(III)/Sb(III) was greatly affected by its oxidation state: if all structural Fe was in the oxidized Fe(III) form, no oxidation was observed; however, when the clay was partially reduced ({approx}20% of structural Fe was reduced to Fe(II)), NAu-1-Red promoted the most extensive oxidation under both oxic and anoxic conditions. Electron balance considerations suggest that structural Fe(III) in the NAu-1-Red was the sole oxidant in the anoxic setup, while dissolved O{sub 2} also contributes in oxic conditions. Long-term batch experiments revealed the complex dynamics of As aqueous speciation in anoxic and oxic systems when reduced arsenic was initially added: rapid disappearance of As(III) was observed due to oxidation to As(V) followed by a slow increase of aqueous As(III). This behavior is explained by two reactions: fast initial oxidation of As(III) by structural Fe(III) (anoxic) or Fe(III) and dissolved O2 (oxic) followed by the slow reduction of As(V) by dissolved Fe(II). The resulting re-mobilization of As due to As(V) reduction by aqueous Fe(II) occurs on time scales on the order of days. These reactions are likely significant in a natural soil or aquifer environment with seasonal cycling or slightly reducing conditions with an abundance of clay minerals and dissolved Fe(II).

  14. Effect of pH on the concentrations of lead and trace contaminants in drinking water: a combined batch, pipe loop and sentinel home study.

    PubMed

    Kim, Eun Jung; Herrera, Jose E; Huggins, Dan; Braam, John; Koshowski, Scott

    2011-04-01

    High lead levels in drinking water are still a concern for households serviced by lead pipes in many parts of North America and Europe. This contribution focuses on the effect of pH on lead concentrations in drinking water delivered through lead pipes. Though this has been addressed in the past, we have conducted a combined batch, pipe loop and sentinel study aiming at filling some of the gaps present in the literature. Exhumed lead pipes and water quality data from the City of London's water distribution system were used in this study. As expected, the lead solubility of corrosion scale generally decreased as pH increased; whereas dissolution of other accumulated metals present in the corrosion scale followed a variety of trends. Moreover, dissolved arsenic and aluminum concentrations showed a strong correlation, indicating that the aluminosilicate phase present in the scale accumulates arsenic. A significant fraction of the total lead concentration in water was traced to particulate lead. Our results indicate that particulate lead is the primary contributor to total lead concentration in flowing systems, whereas particulate lead contribution to total lead concentrations for stagnated systems becomes significant only at high water pH values. PMID:21458838

  15. pH Optrode Instrumentation

    NASA Technical Reports Server (NTRS)

    Tabacco, Mary Beth; Zhou, Quan

    1995-01-01

    pH-sensitive chromophoric reagents immobilized in porous optical fibers. Optoelectronic instrumentation system measures acidity or alkalinity of aqueous nutrient solution. Includes one or more optrodes, which are optical-fiber chemical sensors, in sense, analogous to electrodes but not subject to some of spurious effects distorting readings taken by pH electrodes. Concept of optrodes also described in "Ethylene-Vapor Optrodes" (KSC-11579). pH optrode sensor head, with lead-in and lead-out optical fibers, convenient for monitoring solutions located away from supporting electronic equipment.

  16. Benthic flux of dissolved nickel into the water column of south San Francisco Bay

    USGS Publications Warehouse

    Topping, B.R.; Kuwabara, J.S.; Parcheso, Francis; Hager, S.W.; Arnsberg, A.J.; Murphy, Fred

    2001-01-01

    Field and laboratory studies were conducted between April, 1998 and May, 1999 to provide the first direct measurements of the benthic flux of dissolved (0.2-micron filtered) nickel between the bottom sediment and water column at three sites in the southern component of San Francisco Bay (South Bay), California. Dissolved nickel and predominant ligands (represented by dissolved organic carbon, and sulfides) were the solutes of primary interest, although a variety of ancillary measurements were also performed to provide a framework for interpretation. Results described herein integrate information needs identified by the State Water Resources Control Board and local stakeholders with fundamental research associated with the U.S. Geological Survey Toxic Substances Hydrology Program. Dissolved-Ni concentrations in the bottom water over the three sampling dates ranged from 34 to 43 nanomoles per liter. Dissolved-macronutrient concentrations in the bottom water were consistently higher (frequently by orders of magnitude) than surface-water determinations reported for similar times and locations (Regional Monitoring Program, 2001). This is consistent with measured positive benthic fluxes for the macronutrients. Benthic-flux estimates for dissolved nickel from core-incubations, when areally averaged over the South Bay, were significant (that is, of equivalent or greater order of magnitude) relative to previously reported freshwater point and non-point sources. This observation is consistent with previous determinations for other metals, and with the potential remobilization of sediment-associated metals that have been ubiquitously distributed in the South Bay. Similar to dissolved-nickel results, benthic flux of macronutrients was also consistently significant relative to surface-water inputs. These results add to a growing body of knowledge that strongly suggests a need to consider contaminant transport across the sediment-water interface when establishing future management strategies for the watershed.

  17. Dissolved sulfide-catalyzed precipitation of disordered dolomite: Implications for the formation mechanism of sedimentary dolomite

    NASA Astrophysics Data System (ADS)

    Zhang, Fangfu; Xu, Huifang; Konishi, Hiromi; Kemp, Joshua M.; Roden, Eric E.; Shen, Zhizhang

    2012-11-01

    Dolomite is a common mineral in the rock record. However, the rarity of modern dolomite and the notorious difficulty in synthesizing dolomite abiotically under normal Earth-surface conditions result in the long-standing “dolomite problem” in sedimentary geology. Some modern dolomites are associated with sediments where microbial sulfate reduction is active; however, the role of sulfate-reducing bacteria in dolomite formation is still under debate. In this study, we tested the effect of dissolved sulfide on the precipitation of Ca-Mg carbonates, which has been never explored before although dissolved sulfide is one of the major products of microbial sulfate reduction. Our results demonstrated that dissolved sulfide with a concentration of as low as several millimoles can enhance the Mg2+ incorporation into the calcitic structure, and promote the crystallization of high magnesian calcite and disordered dolomite. We also conducted seeded precipitation in experimental solutions containing dissolved sulfide, which showed that calcite seeds can inhibit the precipitation of aragonite and monohydrocalcite (CaCO3·H2O), and induce more Mg2+ incorporation. We propose that accumulated dissolved sulfide in pore waters in organic-rich sediments may trigger the precipitation of disordered dolomite which can be considered as a precursor of some sedimentary dolomite. Our adsorption experiments revealed a strong adsorption of dissolved sulfide onto calcite faces. We suggest that adsorbed dissolved sulfide can lower the energy barrier to the dehydration of Mg2+-water complexes on the growing carbonate surfaces. This study sheds new light on understanding the role of sulfate-reducing bacteria in dolomite formation and the formation mechanism of sedimentary dolomite.

  18. 7 CFR 1413.113 - Deceased individuals or dissolved entities.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Deceased individuals or dissolved entities. 1413.113... PROGRAMS Durum Wheat Quality Program § 1413.113 Deceased individuals or dissolved entities. (a) Payment may... individual or is a dissolved entity if a representative who currently has authority to enter into a...

  19. 7 CFR 760.908 - Deceased individuals or dissolved entities.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 7 2013-01-01 2013-01-01 false Deceased individuals or dissolved entities. 760.908... § 760.908 Deceased individuals or dissolved entities. (a) Payments may be made for eligible losses suffered by an eligible participant who is now a deceased individual or is a dissolved entity if...

  20. 7 CFR 1413.113 - Deceased individuals or dissolved entities.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Deceased individuals or dissolved entities. 1413.113... PROGRAMS Durum Wheat Quality Program § 1413.113 Deceased individuals or dissolved entities. (a) Payment may... individual or is a dissolved entity if a representative who currently has authority to enter into a...

  1. 7 CFR 760.908 - Deceased individuals or dissolved entities.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 7 2012-01-01 2012-01-01 false Deceased individuals or dissolved entities. 760.908... § 760.908 Deceased individuals or dissolved entities. (a) Payments may be made for eligible losses suffered by an eligible participant who is now a deceased individual or is a dissolved entity if...

  2. 27 CFR 19.455 - Dissolving of denaturants.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... denatured spirits manufactured does not fall below the proof prescribed for the applicable formula in 27 CFR... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Dissolving of denaturants... Denaturation § 19.455 Dissolving of denaturants. Denaturants which are difficult to dissolve in spirits...

  3. 7 CFR 760.115 - Deceased individuals or dissolved entities.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 7 2013-01-01 2013-01-01 false Deceased individuals or dissolved entities. 760.115... Agricultural Disaster Assistance Programs § 760.115 Deceased individuals or dissolved entities. (a) Payments... or is a dissolved entity if a representative, who currently has authority to enter into a...

  4. 7 CFR 760.115 - Deceased individuals or dissolved entities.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 7 2012-01-01 2012-01-01 false Deceased individuals or dissolved entities. 760.115... Agricultural Disaster Assistance Programs § 760.115 Deceased individuals or dissolved entities. (a) Payments... or is a dissolved entity if a representative, who currently has authority to enter into a...

  5. Remote Sensing of Dissolved Oxygen and Nitrogen in Water Using Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Ganoe, Rene; DeYoung, Russell J.

    2013-01-01

    The health of an estuarine ecosystem is largely driven by the abundance of dissolved oxygen and nitrogen available for maintenance of plant and animal life. An investigation was conducted to quantify the concentration of dissolved molecular oxygen and nitrogen in water by means of Raman spectroscopy. This technique is proposed for the remote sensing of dissolved oxygen in the Chesapeake Bay, which will be utilized by aircraft in order to survey large areas in real-time. A proof of principle system has been developed and the specifications are being honed to maximize efficiency for the final application. The theoretical criteria of the research, components of the experimental system, and key findings are presented in this report

  6. Seeded growth of hydroxyapatite in the presence of dissolved albumin.

    PubMed

    Gilman, H; Hukins, D W

    1994-07-01

    Hydroxyapatite (HAP) crystals were grown from a supersaturated solution by the addition of a suspension of seed crystals at a controlled pH value of 7.4 and a temperature of 37 degrees C. The degree of supersaturation was comparable to that in biological fluids and was such that all HAP precipitated would be expected to deposit on the seeds. Albumin was added to some of the solutions to give a concentration in the range 75-250 micrograms cm-3. Samples of solution were removed at known times after the addition of seed crystals and their calcium ion concentrations were determined by atomic absorption spectroscopy. The decrease in the dissolved calcium concentration was taken to be a measure of crystal growth. In the absence of seeds, no decrease in calcium concentration occurred. The initial rate of HAP growth decreased linearly with albumin concentration, i.e., albumin was found to inhibit crystal growth. Inhibition kinetics were consistent with a Langmuir model in which a single albumin molecule was capable of binding to more than one growth site on the crystal surface. Comparison with published results indicated that albumin was a less potent inhibitor of HAP growth than phosphoproteins but was a more potent inhibitor than magnesium or citrate ions. PMID:8046435

  7. Beyond temperature: Clumped isotope signatures in dissolved inorganic carbon species and the influence of solution chemistry on carbonate mineral composition

    NASA Astrophysics Data System (ADS)

    Tripati, Aradhna K.; Hill, Pamela S.; Eagle, Robert A.; Mosenfelder, Jed L.; Tang, Jianwu; Schauble, Edwin A.; Eiler, John M.; Zeebe, Richard E.; Uchikawa, Joji; Coplen, Tyler B.; Ries, Justin B.; Henry, Drew

    2015-10-01

    "Clumped-isotope" thermometry is an emerging tool to probe the temperature history of surface and subsurface environments based on measurements of the proportion of 13C and 18O isotopes bound to each other within carbonate minerals in 13C18O16O22- groups (heavy isotope "clumps"). Although most clumped isotope geothermometry implicitly presumes carbonate crystals have attained lattice equilibrium (i.e., thermodynamic equilibrium for a mineral, which is independent of solution chemistry), several factors other than temperature, including dissolved inorganic carbon (DIC) speciation may influence mineral isotopic signatures. Therefore we used a combination of approaches to understand the potential influence of different variables on the clumped isotope (and oxygen isotope) composition of minerals. We conducted witherite precipitation experiments at a single temperature and at varied pH to empirically determine 13C-18O bond ordering (Δ47) and δ18O of CO32- and HCO3- molecules at a 25 °C equilibrium. Ab initio cluster models based on density functional theory were used to predict equilibrium 13C-18O bond abundances and δ18O of different DIC species and minerals as a function of temperature. Experiments and theory indicate Δ47 and δ18O compositions of CO32- and HCO3- ions are significantly different from each other. Experiments constrain the Δ47-δ18O slope for a pH effect (0.011 ± 0.001; 12 ⩾ pH ⩾ 7). Rapidly-growing temperate corals exhibit disequilibrium mineral isotopic signatures with a Δ47-δ18O slope of 0.011 ± 0.003, consistent with a pH effect. Our theoretical calculations for carbonate minerals indicate equilibrium lattice calcite values for Δ47 and δ18O are intermediate between HCO3- and CO32-. We analyzed synthetic calcites grown at temperatures ranging from 0.5 to 50 °C with and without the enzyme carbonic anhydrase present. This enzyme catalyzes oxygen isotopic exchange between DIC species and is present in many natural systems. The two types of experiments yielded statistically indistinguishable results, and these measurements yield a calibration that overlaps with our theoretical predictions for calcite at equilibrium. The slow-growing Devils Hole calcite exhibits Δ47 and δ18O values consistent with lattice equilibrium. Factors influencing DIC speciation (pH, salinity) and the timescale for DIC equilibration, as well as reactions at the mineral-solution interface, have the potential to influence clumped-isotope signatures and the δ18O of carbonate minerals. In fast-growing carbonate minerals, solution chemistry may be an important factor, particularly over extremes of pH and salinity. If a crystal grows too rapidly to reach an internal equilibrium (i.e., achieve the value for the temperature-dependent mineral lattice equilibrium), it may record the clumped-isotope signature of a DIC species (e.g., the temperature-dependent equilibrium of HCO3-) or a mixture of DIC species, and hence record a disequilibrium mineral composition. For extremely slow-growing crystals, and for rapidly-grown samples grown at a pH where HCO3- dominates the DIC pool at equilibrium, effects of solution chemistry are likely to be relatively small or negligible. In summary, growth environment, solution chemistry, surface equilibria, and precipitation rate may all play a role in dictating whether a crystal achieves equilibrium or disequilibrium clumped-isotope signatures.

  8. Remote Sensing of Dissolved Oxygen and Nitrogen in Water using Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    De Young, R.; Ganoe, R.

    2013-12-01

    The health of an estuarine ecosystem is largely driven by the abundance of dissolved oxygen and nitrogen available for maintenance of plant and animal life. An investigation was conducted to quantify the concentration of dissolved molecular oxygen and nitrogen in water by means of Raman spectroscopy. This technique is proposed for the remote sensing of dissolved oxygen in the Chesapeake Bay, which will be utilized by aircraft in order to survey large areas in real-time. A proof of principle experiment has demonstrated the ability to remotely detect dissolved oxygen and nitrogen in pure water (also Chesapeake Bay water) using a 355nm Nd:YAG laser and a simple monochromater to detect the shifted Raman oxygen and nitrogen backscattered signals at 376.2 and 387.5 nm respectively. The theoretical basis for the research, components of the experimental system, and key findings are presented. A 1.3-m water cell had an attached vertical column to house a Troll 9500 dissolved oxygen in-situ monitor (In-Situ Inc Troll 9500). The Raman oxygen signal could be calibrated with this devise. While Raman backscattered water signals are low a potential aircraft remote system was designed and will be presented.

  9. Making pH Tangible.

    ERIC Educational Resources Information Center

    McIntosh, Elizabeth; Moss, Robert

    1995-01-01

    Presents a laboratory exercise in which students test the pH of different substances, study the effect of a buffer on acidic solutions by comparing the behavior of buffered and unbuffered solutions upon the addition of acid, and compare common over-the-counter antacid remedies. (MKR)

  10. Chapter A6. Section 6.3. Specific Electrical Conductance

    USGS Publications Warehouse

    Radtke, Dean B.; Davis, Jerri V.; Wilde, Franceska D.

    2005-01-01

    Electrical conductance is a measure of the capacity of a substance to conduct an electrical current. The specific electrical conductance (conductivity) of water is a function of the types and quantities of dissolved substances it contains, normalized to a unit length and unit cross section at a specified temperature. This section of the National Field Manual (NFM) describes U.S. Geological Survey (USGS) guidance and protocols for measurement of conductivity in ground and surface waters.

  11. Modeling CO2 degassing and pH in a stream-aquifer system

    USGS Publications Warehouse

    Choi, J.; Hulseapple, S.M.; Conklin, M.H.; Harvey, J.W.

    1998-01-01

    Pinal Creek, Arizona receives an inflow of ground water with high dissolved inorganic carbon (57-75 mg/l) and low pH (5.8-6.3). There is an observed increase of in-stream pH from approximately 6.0-7.8 over the 3 km downstream of the point of groundwater inflow. We hypothesized that CO2 gas-exchange was the most important factor causing the pH increase in this stream-aquifer system. An existing transport model, for coupled ground water-surface water systems (OTIS), was modified to include carbonate equilibria and CO2 degassing, used to simulate alkalinity, total dissolved inorganic carbon (C(T)), and pH in Pinal Creek. Because of the non-linear relation between pH and C(T), the modified transport model used the numerical iteration method to solve the non-linearity. The transport model parameters were determined by the injection of two tracers, bromide and propane. The resulting simulations of alkalinity, C(T) and pH reproduced, without fitting, the overall trends in downstream concentrations. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that C(T) and pH in stream water were controlled by the mixing of ground water with stream water and CO2 degassing. The relative importance of these two processes varied spatially depending on the hydrologic conditions, such as stream flow velocity and whether a reach gained or lost stream water caused by the interaction with the ground water. The coupled transport model with CO2 degassing and generalized sensitivity analysis presented in this study can be applied to evaluate carbon transport and pH in other coupled stream-ground water systems.An existing transport model for coupled groundwater-surface water systems was modified to include carbonate equilibria and CO2 degassing. The modified model was used to simulate alkalinity, total dissolved inorganic carbon (CT) and pH in Pinal Creek. The model used the numerical iteration method to solve the nonlinear relation between pH and CT. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that CT and pH in the stream water were controlled by the mixing of groundwater with stream water and CO2 degassing.

  12. Alteration of Tephra Conductivity Resulting From Secondary Pyroclast Disaggregation

    NASA Astrophysics Data System (ADS)

    Genareau, K. D.; Farley, A. W.

    2014-12-01

    In addition to influencing the electrical conductivity of volcanic ash, leachates bound to ash grain surfaces may pose significant hazards to water quality through the contribution of sulfates, fluoride, metals, and acidic compounds to local water supplies by either direct ash fallout or incorporation into precipitation runoff. In regions of active volcanism, remobilization of pyroclastic units may be a regular occurrence due to landslides or lahars, but the resultant effects of secondary disaggregation of pyroclasts have not been examined. Laboratory analyses of tephras from several eruptive centers have revealed variations in the pH, conductivity, and total dissolved solid (TDS) concentration of water-soluble compounds as a result of pyroclast disaggregation. Analyses were conducted using the standardized protocols for ash leachate analysis. TDS, conductivity, and pH were then measured and the tephra samples were allowed to air dry before being retested using identical methods. When pyroclast disaggregation was not performed, results show a progressive decrease in water conductivity, acidity, and TDS concentration following each stage of sonication. However, when an additional step of clast disaggregation (through crushing and grinding of samples) preceded the sonication step, water samples showed increases in measured properties. Mass spectroscopic analyses of water samples are in progress and results will be presented. These results indicate that secondary comminution of pyroclastic deposits will release water-soluble components from the pyroclast interior that may result in a renewed series of environmental hazards many years after the initial eruptive event. Break up of pyroclasts during transport in landslides or lahars (or even during cleanup efforts) will not only alter the size distribution of the deposit, but will also release metals, sulfates, and fluoride from the tephra interiors, altering the chemical and electrical properties of the tephra. This poses important implications for evaluating the hazards to water supplies and electrical infrastructure resulting from volcanic activity, and the need to consider how the physical modification of volcanic deposits due to surface processes may spark a renewed set of hazards in volcanically active regions.

  13. Oxidation process of dissolvable sulfide by synthesized todorokite in aqueous systems.

    PubMed

    Gao, Tianyu; Shi, Ying; Liu, Fan; Zhang, Yashan; Feng, Xionghan; Tan, Wenfeng; Qiu, Guohong

    2015-06-15

    Todorokite, formed from Mn(II) in supergene environments, can affect the transformation and migration of dissolvable sulfides in soils and water. In this work, todorokite was synthesized with different degrees of crystallinity, and the redox mechanism of dissolvable sulfide and todorokite was studied in both closed and open aqueous systems. The influences of pH, temperature, crystallinity, the amount of manganese oxides, and oxygen gas on S(2-) oxidation process were investigated. It is found that S(2-) was oxidized to S(0), SO3(2-), S2O3(2-) and SO4(2-), and about 90% of S(2-) was converted into S(0) in closed systems. The participation of oxygen facilitated the further oxidation of S(0) to S2O3(2-). S(0) and S2O3(2-) were formed with the conversion rates of S(2-) about 45.3% and 38.4% after 1h of reaction, respectively, and the conversion rate for S2O3(2-) increased as reaction prolonged for a longer period. In addition, todorokite was reduced to Mn(OH)2 in the presence of nitrogen gas, and its chemical stability increased when oxygen gas was admitted into the reaction system during the process. The oxidation rate of dissolvable sulfide followed a pseudo-first-order kinetic law in the initial stage (within 10 min), and the initial oxidation rate constant of S(2-) increased with elevating temperature, increasing the quantity and decreasing crystallinity of todorokite. The initial oxidation rate of dissolvable sulfide decreased with continuous feeding of O2 into the test solution, possibly due to a decrease in active Mn(III) content in todorokite. The present work demonstrates the redox behaviors and kinetics of dissolvable sulfide and todorokite in aquatic environments. PMID:25746570

  14. Improved Arterial Blood Oxygenation Following Intravenous Infusion of Cold Supersaturated Dissolved Oxygen Solution

    PubMed Central

    Grady, Daniel J; Gentile, Michael A; Riggs, John H; Cheifetz, Ira M

    2014-01-01

    BACKGROUND One of the primary goals of critical care medicine is to support adequate gas exchange without iatrogenic sequelae. An emerging method of delivering supplemental oxygen is intravenously rather than via the traditional inhalation route. The objective of this study was to evaluate the gas-exchange effects of infusing cold intravenous (IV) fluids containing very high partial pressures of dissolved oxygen (>760 mm Hg) in a porcine model. METHODS Juvenile swines were anesthetized and mechanically ventilated. Each animal received an infusion of cold (13 °C) Ringer’s lactate solution (30 mL/kg/hour), which had been supersaturated with dissolved oxygen gas (39.7 mg/L dissolved oxygen, 992 mm Hg, 30.5 mL/L). Arterial blood gases and physiologic measurements were repeated at 15-minute intervals during a 60-minute IV infusion of the supersaturated dissolved oxygen solution. Each animal served as its own control. RESULTS Five swines (12.9 ± 0.9 kg) were studied. Following the 60-minute infusion, there were significant increases in PaO2 and SaO2 (P < 0.05) and a significant decrease in PaCO2 (P < 0.05), with a corresponding normalization in arterial blood pH. Additionally, there was a significant decrease in core body temperature (P < 0.05) when compared to the baseline preinfusion state. CONCLUSIONS A cold, supersaturated dissolved oxygen solution may be intravenously administered to improve arterial blood oxygenation and ventilation parameters and induce a mild therapeutic hypothermia in a porcine model. PMID:25249764

  15. Studies of TPB dissolved in Toluene

    NASA Astrophysics Data System (ADS)

    Jerry, Ruel; Winslow, Lindley; Conrad, Janet

    2010-02-01

    Scintillation light in liquid argon calorimeters is produced at 128 nm. This must be shifted to the visible so that the light can be observed by phototubes. A traditional method for accomplishing this is to dissolve Tetraphenyl butadiene and plastic into toluene, and then use this mixture to coat surfaces. After the toluene evaporates, the TPB in the thin plastic skin will shift the light. In both the WARP and MicroBooNE experiments, it has been observed that impure TPB will react with Toluene when exposed to light turning the mixture green. We report on this effect in this talk. )

  16. Dissolving variables in connectionist combinatory logic

    NASA Technical Reports Server (NTRS)

    Barnden, John; Srinivas, Kankanahalli

    1990-01-01

    A connectionist system which can represent and execute combinator expressions to elegantly solve the variable binding problem in connectionist networks is presented. This system is a graph reduction machine utilizing graph representations and traversal mechanisms similar to ones described in the BoltzCONS system of Touretzky (1986). It is shown that, as combinators eliminate variables by introducing special functions, these functions can be connectionistically implemented without reintroducing variable binding. This approach 'dissolves' an important part of the variable binding problem, in that a connectionist system still has to manipulate complex data structures, but those structures and their manipulations are rendered more uniform.

  17. Atomic Layer Deposition from Dissolved Precursors.

    PubMed

    Wu, Yanlin; Döhler, Dirk; Barr, Maïssa; Oks, Elina; Wolf, Marc; Santinacci, Lionel; Bachmann, Julien

    2015-10-14

    We establish a novel thin film deposition technique by transferring the principles of atomic layer deposition (ALD) known with gaseous precursors toward precursors dissolved in a liquid. An established ALD reaction behaves similarly when performed from solutions. "Solution ALD" (sALD) can coat deep pores in a conformal manner. sALD offers novel opportunities by overcoming the need for volatile and thermally robust precursors. We establish a MgO sALD procedure based on the hydrolysis of a Grignard reagent. PMID:26418724

  18. Total dissolvable and dissolved iron isotopes in the water column of the Peru upwelling regime

    NASA Astrophysics Data System (ADS)

    Chever, Fanny; Rouxel, Olivier J.; Croot, Peter L.; Ponzevera, Emmanuel; Wuttig, Kathrin; Auro, Maureen

    2015-08-01

    Vertical distributions of iron (Fe) concentrations and isotopes were determined in the total dissolvable and dissolved pools in the water column at three coastal stations located along the Peruvian margin, in the core of the Oxygen Minimum Zone (OMZ). The shallowest station 121 (161 m total water depth) was characterized by lithogenic input from the continental plateau, yielding concentrations as high as 456 nM in the total dissolvable pool. At the 2 other stations (stations 122 and 123), Fe concentrations of dissolved and total dissolvable pools exhibited maxima in both surface and deep layers. Fe isotopic composition (δ56Fe) showed a fractionation toward lighter values for both physical pools throughout the water column for all stations with minimum values observed for the surface layer (between -0.64 and -0.97‰ at 10-20 m depth) and deep layer (between -0.03 and -1.25‰ at 160-300 m depth). An Fe isotope budget was established to determine the isotopic composition of the particulate pool. We observed a range of δ56Fe values for particulate Fe from +0.02 to -0.87‰, with lightest values obtained at water depth above 50 m. Such light values in the both particulate and dissolved pools suggest sources other than atmospheric dust deposition in the surface ocean, including lateral transport of isotopically light Fe. Samples collected at station 122 closest to the sediment show the lightest isotope composition in the dissolved and the particulate pools (-1.25 and -0.53‰ respectively) and high Fe(II) concentrations (14.2 ± 2.1 nM) consistent with a major reductive benthic Fe sources that is transferred to the ocean water column. A simple isotopic model is proposed to link the extent of Fe(II) oxidation and the Fe isotope composition of both particulate and dissolved Fe pools. This study demonstrates that Fe isotopic composition in OMZ regions is not only affected by the relative contribution of reductive and non-reductive shelf sediment input but also by seawater-column processes during the transport and oxidation of Fe from the source region to open seawater.

  19. Effect of Pattern Layout and Dissolved Oxygen in CO2 Rinse Water on Cu Corrosion during Post-Etch Cleaning

    NASA Astrophysics Data System (ADS)

    Kentaro Tokuri,; Yukinari Yamashita,; Morio Shiohara,; Noriaki Oda,; Seiichi Kondo,; Shuichi Saito,

    2010-05-01

    When post-etch cleaning was carried out in Cu dual-damascene process, Cu at the bottom of isolated via was etched out especially in the wafer edge, and this would become a critical issue as device scale is shrunk. The corrosion was caused in the rinse step rather than chemical cleaning step because dissolved oxygen in rinse water from the air increased oxidation-reduction potential (ORP) and CO2 included in the rinse water for preventing wafer electrification decreased pH. The corrosion was found to be suppressed by increasing dummy pattern density and by controlling atmosphere and pH of the rinse water.

  20. [Conduct disorders].

    PubMed

    Stadler, Christina

    2014-05-01

    The diagnosis conduct disorder (CD) is characterized by aggressive (e.g., physical aggression) as well as nonaggressive symptoms (e.g., violation of rules, truancy). Conclusions regarding the course and prognosis, or recommendations for effective interventions, seem not to be equally valid for the whole patient group. DSM-IV-TR included subtyping age-of-onset as a prognostic criterion, even though the evidence base for subtyping from age of onset was rather sparse. The relevant literature on CD has grown substantially since the publication of DSM-IV-TR in 1994. For the new DSM-5 edition, some important issues were discussed, for example, consideration of personality traits, female-specific or dimensional criteria, and adding a childhood-limited subtype (Moffitt et al., 2008). Nevertheless, the diagnostic protocol for CD was not changed in the most parts in the new edition of the DSM-5; the addition of a CD specifier with limited emotions is the most relevant change. On the basis of the existing evidence base, this review discusses whether the modifications in DSM-5 are helpful for fulfilling the requirements of a reliable and valid psychiatric classification. PMID:24846866

  1. Conduct disorders.

    PubMed

    Buitelaar, Jan K; Smeets, Kirsten C; Herpers, Pierre; Scheepers, Floor; Glennon, Jeffrey; Rommelse, Nanda N J

    2013-02-01

    Conduct disorder (CD) is a frequently occurring psychiatric disorder characterized by a persistent pattern of aggressive and non-aggressive rule breaking antisocial behaviours that lead to considerable burden for the patients themselves, their family and society. This review paper updates diagnostic and therapeutic approaches to CD in the light of the forthcoming DSM-5 definition. The diagnostic criteria for CD will remain unchanged in DSM-5, but the introduction of a specifier of CD with a callous-unemotional (CU) presentation is new. Linked to this, we discuss the pros and cons of various other ways to subtype aggression/CD symptoms. Existing guidelines for CD are, with few exceptions, already of a relatively older date and emphasize that clinical assessment should be systematic and comprehensive and based on a multi-informant approach. Non-medical psychosocial interventions are recommended as the first option for the treatment of CD. There is a role for medication in the treatment of comorbid syndromes and/or in case of insufficient response to psychosocial interventions and severe and dangerous aggressive and violent behaviours. PMID:23224151

  2. Conducting a thermal conductivity survey

    NASA Technical Reports Server (NTRS)

    Allen, P. B.

    1985-01-01

    A physically transparent approximate theory of phonon decay rates is presented starting from a pair potential model of the interatomic forces in an insulator or semiconductor. The theory applies in the classical regime and relates the 3-phonon decay rate to the third derivative of the pair potential. Phonon dispersion relations do not need to be calculated, as sum rules relate all the needed quantities directly to the pair potential. The Brillouin zone averaged phonon lifetime turns out to involve a dimensionless measure of the anharmonicity multiplied by an effective density of states for 3-phonon decay. Results are given for rare gas and alkali halide crystals. For rare gases, the results are in good agreement with more elaborate perturbation calculations. Comparison to experimental data on phonon linewidths and thermal conductivity are made.

  3. Towards an understanding of feedbacks between plant productivity, acidity and dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Rowe, Ed; Tipping, Ed; Davies, Jessica; Monteith, Don; Evans, Chris

    2014-05-01

    The recent origin of much dissolved organic carbon (DOC) (Tipping et al., 2010) implies that plant productivity is a major control on DOC fluxes. However, the flocculation, sorption and release of potentially-dissolved organic matter are governed by pH, and widespread increases in DOC concentrations observed in northern temperate freshwater systems seem to be primarily related to recovery from acidification (Monteith et al., 2007). We explore the relative importance of changes in productivity and pH using a model, MADOC, that incorporates both these effects (Rowe et al., 2014). The feedback whereby DOC affects pH is included. The model uses an annual timestep and relatively simple flow-routing, yet reproduces observed changes in DOC flux and pH in experimental (Evans et al., 2012) and survey data. However, the first version of the model probably over-estimated responses of plant productivity to nitrogen (N) deposition in upland semi-natural ecosystems. There is a strong case that plant productivity is an important regulator of DOC fluxes, and theoretical reasons for suspecting widespread productivity increases in recent years due not only to N deposition but to temperature and increased atmospheric CO2 concentrations. However, evidence that productivity has increased in upland semi-natural ecosystems is sparse, and few studies have assessed the major limitations to productivity in these habitats. In systems where phosphorus (P) limitation prevails, or which are co-limited, productivity responses to anthropogenic drivers will be limited. We present a revised version of the model that incorporates P cycling and appears to represent productivity responses to atmospheric N pollution more realistically. Over the long term, relatively small fluxes of nutrient elements into and out of ecosystems can profoundly affect productivity and the accumulation of organic matter. Dissolved organic N (DON) is less easily intercepted by plants and microbes than mineral N, and DON leaching rates may thus control soil formation (Vitousek et al., 2010). Large observed DON concentrations that were observed in an experimental study are difficult to reconcile with the amount of N retention necessary to have accumulated observed organic matter stocks. We examine potential reasons for this discrepancy. - Evans CD, Jones TG, Burden A et al. (2012) Acidity controls on dissolved organic carbon mobility in organic soils. Global Change Biology 18, 3317-3331. - Monteith DT, Stoddard JL, Evans CD et al. (2007) Rising freshwater dissolved organic carbon driven by changes in atmospheric deposition. Nature 450, 537-540. - Rowe EC, Tipping E, Posch M et al. (2014) Predicting nitrogen and acidity effects on long-term dynamics of dissolved organic matter. Environmental Pollution 184, 271-282. - Tipping E, Billett MF, Bryant CL et al. (2010) Sources and ages of dissolved organic matter in peatland streams: evidence from chemistry mixture modelling and radiocarbon data. Biogeochemistry 100, 121-137. - Vitousek PM, Porder S, Houlton BZ et al. (2010) Terrestrial phosphorus limitation: mechanisms, implications, and nitrogen-phosphorus interactions. Ecological Applications 20, 5-15.

  4. Effect of pH alkaline salts of fatty acids on the inhibition of bacteria associated with poultry processing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The agar diffusion assay was used to examine the effect of pH on the ability of alkaline salts of three fatty acids (FA) to inhibit growth of bacteria associated with poultry processing. FA solutions were prepared by dissolving 0.5 M concentrations of caprylic, capric, or lauric acid in separate ali...

  5. Novel approach of aceclofenac fast dissolving tablet.

    PubMed

    Dave, Vivek; Yadav, Sachdev; Sharma, Swapnil; Vishwakarma, Pushpendra; Ali, Nasir

    2015-01-01

    Fast disintegrating tablets (FDTs) have received ever increasing demand during the last decade, and the field has become a hastily growing area in the pharmaceutical industry. Upon introduction into the mouth, these tablets dissolve or disintegrate in the mouth in the absence of additional water for easy administration of active pharmaceutical ingredients. Aceclofenac, an NSAID, has been recommended orally for the treatment of bone and connective tissue disorder and thus the formulation of the same resulted in development of several FDT technologies. The present aim is to formulate a tablet which disintegrate and dissolve rapidly and give its rapid onset of action: analgesic, antipyretic and anti-inflammatory action. Besides, the conventional tablets also show poor patient compliance an attempt had been made to formulate for FDT of aceclofenac by using various super disintegrants like sodium starch glycolate, croscarmellose sodium and crosspovidone (polyplasdone XL) and PEG 6000 followed by novel technique. The tablets were evaluated for friability, hardness, weight variation, disintegration time, wetting time, in vitro dissolution studies and drug content studies. It was concluded that the batch which was prepared by using combination of crosspovidone and sodium starch glycolate as a super disintegrant shows excellent disintegration time, enhance dissolution rate, taste masking and hence lead to improve efficacy and bioavailability of drug. PMID:25553683

  6. Photoluminescent detection of dissolved underwater trace explosives.

    PubMed

    Langston, Tye

    2010-01-01

    A portable, rapid, and economical method for in situ trace explosive detection in aqueous solutions was demonstrated using photoluminescence. Using europium/ thenoyltrifluoroacetone as the reagent, dissolved nitroglycerin was fluorescently tagged and detected in seawater solutions without sample preparation, drying, or preconcentration. The chemical method was developed in a laboratory setting and demonstrated in a flow-through configuration using lightweight, inexpensive, commercial components by directly injecting the reagents into a continually flowing seawater stream using a small amount of organic solvent (approximately 8% of the total solution). Europium's vulnerability to vibrational fluorescence quenching by water provided the mode of detection. Without nitroglycerin in the seawater solution, the reagent's fluorescence was quenched, but when dissolved nitroglycerin was present, it displaced the water molecules from the europium/thenoyltrifluoroacetone compound and restored fluorescence. This effort focused on developing a seawater sensor, but performance comparisons were made to freshwater. The method was found to perform better in freshwater and it was shown that certain seawater constituents (such as calcium) have an adverse impact. However, the concentrations of these constituents are not expected to vary significantly from the natural seawater used herein. PMID:20364240

  7. Diel behavior of rare earth elements in a mountain stream with acidic to neutral pH

    NASA Astrophysics Data System (ADS)

    Gammons, Christopher H.; Wood, Scott A.; Nimick, David A.

    2005-08-01

    Diel (24-h) changes in concentrations of rare earth elements (REE) were investigated in Fisher Creek, a mountain stream in Montana that receives acid mine drainage in its headwaters. Three simultaneous 24-h samplings were conducted at an upstream station (pH = 3.3), an intermediate station (pH = 5.5), and a downstream station (pH = 6.8). The REE were found to behave conservatively at the two upstream stations. At the downstream station, REE partitioned into suspended particles to a degree that varied with the time of day, and concentrations of dissolved REE were 2.9- to 9.4-fold (190% to 830%) higher in the early morning vs. the late afternoon. The decrease in dissolved REE concentrations during the day coincided with a corresponding increase in the concentration of REE in suspended particles, such that diel changes in the total REE concentrations were relatively minor (27% to 55% increase at night). Across the lanthanide series, the heavy REE partitioned into the suspended solid phase to a greater extent than the light REE. Filtered samples from the downstream station showed a decrease in shale-normalized REE concentration across the lanthanide series, with positive anomalies at La and Gd, and a negative Eu anomaly. As the temperature of the creek increased in the afternoon, the slope of the REE profile steepened and the magnitude of the anomalies increased. The above observations are explained by cyclic adsorption of REE onto suspended particles of hydrous ferric and aluminum oxides (HFO, HAO). Conditional partition coefficients for each REE between the suspended solids and the aqueous phase reached a maximum at 1700 hours and a minimum at 0700 hours. This pattern is attributed to diel variations in stream temperature, possibly reinforced by kinetic factors (i.e., slower rates of reaction at night than during the day). Estimates of the enthalpy of adsorption of each REE onto suspended particles based on the field results averaged +82 kJ/mol and are similar in magnitude to estimates in the literature for adsorption of divalent metal cations onto clays and hydrous metal oxides. The results of this study have important implications to the use of REE as hydrogeochemical tracers in streams.

  8. Diel behavior of rare earth elements in a mountain stream with acidic to neutral pH

    USGS Publications Warehouse

    Gammons, C.H.; Wood, S.A.; Nimick, D.A.

    2005-01-01

    Diel (24-h) changes in concentrations of rare earth elements (REE) were investigated in Fisher Creek, a mountain stream in Montana that receives acid mine drainage in its headwaters. Three simultaneous 24-h samplings were conducted at an upstream station (pH = 3.3), an intermediate station (pH = 5.5), and a downstream station (pH = 6.8). The REE were found to behave conservatively at the two upstream stations. At the downstream station, REE partitioned into suspended particles to a degree that varied with the time of day, and concentrations of dissolved REE were 2.9- to 9.4-fold (190% to 830%) higher in the early morning vs. the late afternoon. The decrease in dissolved REE concentrations during the day coincided with a corresponding increase in the concentration of REE in suspended particles, such that diel changes in the total REE concentrations were relatively minor (27% to 55% increase at night). Across the lanthanide series, the heavy REE partitioned into the suspended solid phase to a greater extent than the light REE. Filtered samples from the downstream station showed a decrease in shale-normalized REE concentration across the lanthanide series, with positive anomalies at La and Gd, and a negative Eu anomaly. As the temperature of the creek increased in the afternoon, the slope of the REE profile steepened and the magnitude of the anomalies increased. The above observations are explained by cyclic adsorption of REE onto suspended particles of hydrous ferric and aluminum oxides (HFO, HAO). Conditional partition coefficients for each REE between the suspended solids and the aqueous phase reached a maximum at 1700 hours and a minimum at 0700 hours. This pattern is attributed to diel variations in stream temperature, possibly reinforced by kinetic factors (i.e., slower rates of reaction at night than during the day). Estimates of the enthalpy of adsorption of each REE onto suspended particles based on the field results averaged +82 kJ/mol and are similar in magnitude to estimates in the literature for adsorption of divalent metal cations onto clays and hydrous metal oxides. The results of this study have important implications to the use of REE as hydrogeochemical tracers in streams. Copyright ?? 2005 Elsevier Ltd.

  9. [Dissolved aluminum and organic carbon in soil solution under six tree stands in Lushan forest ecosystems].

    PubMed

    Wang, Lianfeng; Pan, Genxing; Shi, Shengli; Zhang, Lehua; Huang, Mingxing

    2003-10-01

    Different depths of soils under 6 tree stands in Lushan Botany Garden were sampled and water-digested at room temperature. The dissolved aluminum and organic carbon were then determined by colorimetry, using 8-hydroxylquilin and TOC Analyzer, respectively. The results indicated that even derived from a naturally identical soil type, the test soils exhibited a diverse solution chemistry, regarding with the Al speciation. The soil solutions under Japanese cedar, giant arborvitae and tea had lower pH values and higher contents of soluble aluminum than those under Giant dogwood, azalea and bamboo. Under giant arborvitae, the lowest pH and the highest content of total soluble aluminum and monomeric aluminum were found in soil solution. There was a significant correlation between soluble aluminum and DOC, which tended to depress the accumulation of toxic monomeric aluminum. The 6 tree stands could be grouped into 2 categories of solution chemistry, according to aluminum mobilization. PMID:14986348

  10. CORRELATION OF THE PARTITIONING OF DISSOLVED ORGANIC MATTER FRACTIONS WITH THE DESORPTION OF CD, CU, NI, PB AND ZN FROM 18 DUTCH SOILS

    EPA Science Inventory

    Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was also concentrated onto a macroreticular resin and fractionation into three operationally defined fract...

  11. Dissolved Mn Speciation and Ligand Characteristics in a Coastal Waterway

    NASA Astrophysics Data System (ADS)

    Oldham, V.; Jensen, L.; Luther, G. W., III

    2014-12-01

    Soluble manganese speciation (Mn(II) and Mn(III); 0.2 μm filtered) was measured along a salinity gradient in the Broadkill River, a coastal waterway bordered by wetlands and salt marshes in Delaware. We modified an established method of porphyrin (T-4(CP)P) addition, by incorporating a heating step and coupling a 100-cm cell to a UV/Vis detector, to achieve a 4.0 nM sample DL. Surface waters were collected from June to August, 2014 and total dissolved Mn (0.23 - 1.92 μM) first increased then decreased along the salinity gradient (31 ppt to freshwater). However, Mn speciation was highly variable; Mn(III) made up 0-49 % of the total dissolved Mn, where the highest Mn(III) values occurred at sites with high salt-marsh runoff. Mn(III) was not recoverable without the addition of a strong reducing agent, indicating that little or no weak ligand was present, and that a strong ligand was responsible for complexing Mn(III). An assessment of potential strong ligand character was made by precipitating humic matter, by acidifying subsamples to pH<1.5, then 100 μM Mn(III)-pyrophosphate was added to acidified supernatant samples and non-acidified samples. In non-acidified samples, the Mn(III)-pyrophosphate peak at 484 nm rapidly disappeared and was replaced by a broad peak at 400 nm and the resulting sample had a yellow color. Upon the addition of 500 μM desferrioxamine-B (DFOB) to the same sample, a peak at 310 nm appeared, indicating the formation of Mn(III)-DFOB. In acidified samples, the Mn(III)-pyrophosphate peak did not change. Humic matter, therefore, may be acting as an Mn(III) binding ligand, outcompeting pyrophosphate for Mn(III), however this natural ligand is outcompeted by a large excess of DFOB. The humic matter and increased Mn likely come from the salt marsh runoff during tidal exchange, and we observed that as salinity increased, the amount of humic binding decreased. These results present the first Mn speciation measurements along a salinity gradient in oxygenated waters.

  12. Photolytic processing of secondary organic aerosols dissolved in cloud droplets.

    PubMed

    Bateman, Adam P; Nizkorodov, Sergey A; Laskin, Julia; Laskin, Alexander

    2011-07-14

    The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05-1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300-400 nm radiation for up to 24 h. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly decreased by photolysis relative to the monomeric compounds. Direct pH measurements showed that acidic compounds increased in abundance upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and the formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonyls was further confirmed by the UV/Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n→π* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ∼0.03. The total concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content. Photolysis of dry limonene SOA deposited on substrates was investigated in a separate set of experiments. The observed effects on the average O/C and DBE were similar to the aqueous photolysis, but the extent of chemical change was smaller in dry SOA. Our results suggest that biogenic SOA dissolved in cloud and fog droplets will undergo significant photolytic processing on a time scale of hours to days. This type of photolytic processing may account for the discrepancy between the higher values of O/C measured in the field experiments relative to the laboratory measurements on SOA in smog chambers. In addition, the direct photolysis of oligomeric compounds may be responsible for the scarcity of their observation in the field. PMID:21617794

  13. Asad Umar, DVM, PhD | Division of Cancer Prevention

    Cancer.gov

    Dr. Asad Umarreceived his PhD in Biochemistry and Immunology at the Johns Hopkins University in Baltimore, MD, in 1993. He conducted his postdoctoral training in the laboratories of Patricia Gearhart in Baltimore, MD and Thomas Kunkel at the National Institutes of Environmental Health Sciences in Research Triangle Park, NC. Dr. |

  14. Asad Umar, DVM, PhD | Division of Cancer Prevention

    Cancer.gov

    Dr. Asad Umar received his PhD in Biochemistry and Immunology at the Johns Hopkins University in Baltimore, MD, in 1993. He conducted his postdoctoral training in the laboratories of Patricia Gearhart in Baltimore, MD and Thomas Kunkel at the National Institutes of Environmental Health Sciences in Research Triangle Park, NC. Dr. |

  15. PhDs by Publications: An "Easy Way Out"?

    ERIC Educational Resources Information Center

    Niven, Penelope; Grant, Carolyn

    2012-01-01

    PhDs by publications are a relatively new model for doctoral research, especially in the context of the Humanities or Education. This paper describes two writers' experiences of conducting doctoral studies in this genre and in these faculties. Each discover alternative ways of employing a body of published research papers in development of an…

  16. The Methods Behind PH WINS

    PubMed Central

    Leider, Jonathon P.; Bharthapudi, Kiran; Pineau, Vicki; Liu, Lin; Harper, Elizabeth

    2015-01-01

    The Public Health Workforce Interests and Needs Survey (PH WINS) has yielded the first-ever nationally representative sample of state health agency central office employees. The survey represents a step forward in rigorous, systematic data collection to inform the public health workforce development agenda in the United States. PH WINS is a Web-based survey and was developed with guidance from a panel of public health workforce experts including practitioners and researchers. It draws heavily from existing and validated items and focuses on 4 main areas: workforce perceptions about training needs, workplace environment and job satisfaction, perceptions about national trends, and demographics. This article outlines the conceptualization, development, and implementation of PH WINS, as well as considerations and limitations. It also describes the creation of 2 new data sets that will be available in public use for public health officials and researchers—a nationally representative data set for permanently employed state health agency central office employees comprising over 10 000 responses, and a pilot data set with approximately 12 000 local and regional health department staff responses. PMID:26422490

  17. The Methods Behind PH WINS.

    PubMed

    Leider, Jonathon P; Bharthapudi, Kiran; Pineau, Vicki; Liu, Lin; Harper, Elizabeth

    2015-01-01

    The Public Health Workforce Interests and Needs Survey (PH WINS) has yielded the first-ever nationally representative sample of state health agency central office employees. The survey represents a step forward in rigorous, systematic data collection to inform the public health workforce development agenda in the United States. PH WINS is a Web-based survey and was developed with guidance from a panel of public health workforce experts including practitioners and researchers. It draws heavily from existing and validated items and focuses on 4 main areas: workforce perceptions about training needs, workplace environment and job satisfaction, perceptions about national trends, and demographics. This article outlines the conceptualization, development, and implementation of PH WINS, as well as considerations and limitations. It also describes the creation of 2 new data sets that will be available in public use for public health officials and researchers--a nationally representative data set for permanently employed state health agency central office employees comprising over 10,000 responses, and a pilot data set with approximately 12,000 local and regional health department staff responses. PMID:26422490

  18. Sampling and analytical methods of stable isotopes and dissolved inorganic carbon from CO2 injection sites

    NASA Astrophysics Data System (ADS)

    van Geldern, Robert; Myrttinen, Anssi; Becker, Veith; Barth, Johannes A. C.

    2010-05-01

    The isotopic composition (δ13C) of dissolved inorganic carbon (DIC), in combination with DIC concentration measurements, can be used to quantify geochemical trapping of CO2 in water. This is of great importance in monitoring the fate of CO2 in the subsurface in CO2 injection projects. When CO2 mixes with water, a shift in the δ13C values, as well as an increase in DIC concentrations is observed in the CO2-H2O system. However, when using standard on-site titration methods, it is often challenging to determining accurate in-situ DIC concentrations. This may be due to CO2 degassing and CO2-exchange between the sample and the atmosphere during titration, causing a change in the pH value or due to other unfavourable conditions such as turbid water samples or limited availability of fluid samples. A way to resolve this problem is by simultaneously determining the DIC concentration and carbon isotopic composition using a standard continuous flow Isotope Ratio Mass Spectrometry (CF-IRMS) setup with a Gasbench II coupled to Delta plusXP mass spectrometer. During sampling, in order to avoid atmospheric contact, water samples taken from the borehole-fluid-sampler should be directly transferred into a suitable container, such as a gasbag. Also, to avoid isotope fractionation due to biological activity in the sample, it is recommended to stabilize the gasbags prior to sampling with HgCl2 for the subsequent stable isotope analysis. The DIC concentration of the samples can be determined from the area of the sample peaks in a chromatogram from a CF-IRMS analysis, since it is directly proportional to the CO2 generated by the reaction of the water with H3PO4. A set of standards with known DIC concentrations should be prepared by mixing NaHCO3 with DIC free water. Since the DIC concentrations of samples taken from CO2 injection sites are expected to be exceptionally high due to the additional high amounts of added CO2, the DIC concentration range of the standards should be set high enough to cover the sample concentrations. In order to assure methodological reproducibility, this 'calibration set' should be included in every sequence analysed with the Gasbench CF-IRMS system. The standards, therefore, should also be treated in the same way as the samples. For accurate determination, it is essential to know the exact amount of water in the vial and the density of the sample. This requires weighing of each vial before and after injection of the water sample. For stable isotope analysis, the required signal height can be adjusted by the sample amount. Therefore this method is suitable for analysing samples with highly differing DIC concentrations. Reproducibility and accuracy of the quantitative analysis of the dissolved inorganic carbon need to be verified by independent control standards, treated as samples. This study was conducted as a part of the R&D programme CLEAN, which is funded by the German Federal Ministry of Education in the framework of the programme GEOTECHNOLOGIEN. We would like to thank GDF SUEZ for permitting us to conduct sampling campaigns at their site.

  19. 40 CFR 430.40 - Applicability; description of the dissolving sulfite subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... dissolving sulfite subcategory. 430.40 Section 430.40 Protection of Environment ENVIRONMENTAL PROTECTION... SOURCE CATEGORY Dissolving Sulfite Subcategory § 430.40 Applicability; description of the dissolving... production of pulp at dissolving sulfite mills....

  20. 40 CFR 430.40 - Applicability; description of the dissolving sulfite subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... dissolving sulfite subcategory. 430.40 Section 430.40 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Dissolving Sulfite Subcategory § 430.40 Applicability; description of the dissolving sulfite... at dissolving sulfite mills....

  1. 40 CFR 430.40 - Applicability; description of the dissolving sulfite subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... dissolving sulfite subcategory. 430.40 Section 430.40 Protection of Environment ENVIRONMENTAL PROTECTION... SOURCE CATEGORY Dissolving Sulfite Subcategory § 430.40 Applicability; description of the dissolving... production of pulp at dissolving sulfite mills....

  2. 40 CFR 430.40 - Applicability; description of the dissolving sulfite subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... dissolving sulfite subcategory. 430.40 Section 430.40 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Dissolving Sulfite Subcategory § 430.40 Applicability; description of the dissolving sulfite... at dissolving sulfite mills....

  3. 40 CFR 430.40 - Applicability; description of the dissolving sulfite subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... dissolving sulfite subcategory. 430.40 Section 430.40 Protection of Environment ENVIRONMENTAL PROTECTION... SOURCE CATEGORY Dissolving Sulfite Subcategory § 430.40 Applicability; description of the dissolving... production of pulp at dissolving sulfite mills....

  4. Analysis of Tradeoffs between Optimal Source and Dissolved Plume Remediation

    NASA Astrophysics Data System (ADS)

    Endres, K. L.; Mayer, A. S.; Enfield, C.

    2001-12-01

    Subsurface remediation usually consists of separate schemes for source and dissolved plume cleanup. A typical approach in subsurface remediation optimization is the assumption of complete removal of the source prior to dissolved plume remediation. In reality, the source often cannot be completely removed due to technical or cost constraints. The importance of the source-plume interaction is investigated with the use of multiple simulation processes linked within an optimization framework. This paper explores the optimal tradeoff between source remediation and conventional plume pump and treat including natural aquifer biodegradation. In our remediation design optimization framework, the objective function consists of a minimizing a cost function. The design variables are the pumping rates at fixed-location extraction wells and the degree of the source remediation, measured as percent mass removal. The state variables are aquifer concentrations and hydraulic heads. The state variables are predicted by a groundwater flow and transport simulator using a variable contaminant input from the source model. A bundled tube model of the contaminant source accounts for uncertainty in the aquifer properties with the use of an inverse log-normal probability distribution of source cleanup times. The aquifer cleanup goal is incorporated as a constraint on the groundwater concentration at selected monitoring locations. The optimal allocation of costs for the remediation is produced using a niched genetic algorithm. The optimization scheme is applied to a hypothetical aquifer containing source and plume contamination. The chronological development of the contamination and remediation consists of 1) source emplacement 2) plume development 3) source remediation 4) plume remediation. Investigation of the sensitivity of the system to distribution of the source and the time of plume development is conducted.

  5. Effects of pH on aquatic biodegradation processes

    NASA Astrophysics Data System (ADS)

    Krachler, R. F.; Krachler, R.; Stojanovic, A.; Wielander, B.; Herzig, A.

    2009-01-01

    To date, little is known about the pH-stimulated mineralization of organic matter in aquatic environments. In this study, we investigated biodegradation processes in alkaline waters. Study site is a large shallow soda lake in Central Europe (Neusiedler See/Ferto). The decomposition rate of plant litter was measured as a function of pH by incubating air-saturated lake-water samples in contact with Phragmites litter (leaves) from the littoral vegetation. All samples showed high decomposition rates (up to 32% mass loss within 35 days) and a characteristic two-step degradation mechanism. During the degradation process, the solid plant litter was dissolved forming humic colloids. Subsequently, the humic colloids were mineralized to CO2 in the water column. The decomposition rate was linearly related to pH. Increasing pH values accelerated significantly the leaching of humic colloids as well as the final degradation process. The observed two-step mechanism controls the wetland/lake/air carbon fluxes, since large quantities of humic colloids are currently produced in the reed belt, exported through wind-driven circulations and incorporated into the open lake foodweb. At present, the lake is rapidly shrinking due to peat deposition in the littoral zone, whereas it has been resistant to silting-up processes for thousands of years. In order to investigate the cause of this abrupt change, the chemical composition of the lake-water was measured during 1995-2007. A thorough analysis of these data revealed that major lake-water discharges through the lake's artificial outlet channel led to a decline in salinity and alkalinity. According to our estimates, the lake's original salinity and alkalinity was 70-90% higher compared to the present conditions, with the consequence of substantially lower pH values in the present lake. The observed pH dependence of reed litter biodegradation rates points to a causal connection between low pH values and accumulation of peat in the lake basin. Our results suggest that the pH stimulated remineralisation of organic matter plays a major role in maintaining the long-term integrity of saline lake/wetland systems.

  6. Total Dissolved Gas Monitoring in Chum Salmon Spawning Gravels Below Bonneville Dam

    SciTech Connect

    Arntzen, Evan V.; Geist, David R.; Panther, Jennifer L.; Dawley, Earl

    2007-01-30

    At the request of the U.S. Army Corps of Engineers (Portland District), Pacific Northwest National Laboratory (PNNL) conducted research to determine whether total dissolved gas concentrations are elevated in chum salmon redds during spring spill operations at Bonneville Dam. The study involved monitoring the total dissolved gas levels at egg pocket depth and in the river at two chum salmon spawning locations downstream from Bonneville Dam. Dissolved atmospheric gas supersaturation generated by spill from Bonneville Dam may diminish survival of chum (Oncorhynchus keta) salmon when sac fry are still present in the gravel downstream from Bonneville Dam. However, no previous work has been conducted to determine whether total dissolved gas (TDG) levels are elevated during spring spill operations within incubation habitats. The guidance used by hydropower system managers to provide protection for pre-emergent chum salmon fry has been to limit TDG to 105% after allowing for depth compensation. A previous literature review completed in early 2006 shows that TDG levels as low as 103% have been documented to cause mortality in sac fry. Our study measured TDG in the incubation environment to evaluate whether these levels were exceeded during spring spill operations. Total dissolved gas levels were measured within chum salmon spawning areas near Ives Island and Multnomah Falls on the Columbia River. Water quality sensors screened at egg pocket depth and to the river were installed at both sites. At each location, we also measured dissolved oxygen, temperature, specific conductance, and water depth to assist with the interpretation of TDG results. Total dissolved gas was depth-compensated to determine when levels were high enough to potentially affect sac fry. This report provides detailed descriptions of the two study sites downstream of Bonneville Dam, as well as the equipment and procedures employed to monitor the TDG levels at the study sites. Results of the monitoring at both sites are then presented in both text and graphics. The findings and recommendations for further research are discussed, followed by a listing of the references cited in the report.

  7. Method for dissolving delta-phase plutonium

    DOEpatents

    Karraker, David G.

    1992-01-01

    A process for dissolving plutonium, and in particular, delta-phase plutonium. The process includes heating a mixture of nitric acid, hydroxylammonium nitrate (HAN) and potassium fluoride to a temperature between 40.degree. and 70.degree. C., then immersing the metal in the mixture. Preferably, the nitric acid has a concentration of not more than 2M, the HAN approximately 0.66M, and the potassium fluoride 0.1M. Additionally, a small amount of sulfamic acid, such as 0.1M can be added to assure stability of the HAN in the presence of nitric acid. The oxide layer that forms on plutonium metal may be removed with a non-oxidizing acid as a pre-treatment step.

  8. Production and characterization of rapidly dissolving cryopellets.

    PubMed

    Erber, Matthias; Lee, Geoffrey

    2015-05-01

    The procedure described in this study provides a platform technology for rapidly dissolving, single-dosed cryopellets. The different steps during cryopellet production were investigated, covering droplet generation, droplet freezing in liquid nitrogen (LN₂) as well as cryopellet properties. With the setup developed, uniform droplets between 4 and 14 μL were produced. The freezing behavior was similar to approaches reported in the literature. A weight loss reported for droplets frozen in LN₂ could not be confirmed. Mechanical stability as observed with texture analysis as well as dissolution time increased with increasing solid content. All cryopellets immediately disintegrated when in contact with the dissolution medium. The dissolution times of amorphous sucrose and trehalose-based cryopellets at different solid content levels were comparable. Crystalline mannitol cryopellets showed in general a higher dissolution time. The formation of δ-mannitol potentially makes the cryopellets suitable as an intermediate product for tableting. PMID:25631983

  9. Dissolved Concentration Limits of Radioactive Elements

    SciTech Connect

    Y. Chen; E.R. Thomas; F.J. Pearson; P.L. Cloke; T.L. Steinborn; P.V. Brady

    2003-06-20

    The purpose of this study is to evaluate dissolved concentration limits (also referred to as solubility limits) of radioactive elements under possible repository conditions, based on geochemical modeling calculations using geochemical modeling tools, thermodynamic databases, and measurements made in laboratory experiments and field work. The scope of this modeling activity is to predict dissolved concentrations or solubility limits for 14 radioactive elements (actinium, americium, carbon, cesium, iodine, lead, neptunium, plutonium, protactinium, radium, strontium, technetium, thorium, and uranium), which are important to calculated dose. Model outputs are mainly in the form of look-up tables plus one or more uncertainty terms. The rest are either in the form of distributions or single values. The results of this analysis are fundamental inputs for total system performance assessment to constrain the release of these elements from waste packages and the engineered barrier system. Solubilities of plutonium, neptunium, uranium, americium, actinium, thorium, protactinium, lead, and radium have been re-evaluated using the newly updated thermodynamic database (Data0.ymp.R2). For all of the actinides, identical modeling approaches and consistent environmental conditions were used to develop solubility models in this revision. These models cover broad ranges of environmental conditions so that they are applicable to both waste packages and the invert. Uncertainties from thermodynamic data, water chemistry, temperature variation, activity coefficients, and selection of solubility controlling phase have been quantified or otherwise addressed. Moreover, a new blended plutonium solubility model has been developed in this revision, which gives a mean solubility that is three orders of magnitude lower than the plutonium solubility model used for the Total System Performance Assessment for the Site Recommendation. Two alternative neptunium solubility models have also been developed in this revision. The base-case models have been validated to the level of confidence required by their relative importance to the potential performance of the repository system. The plutonium and neptunium solubility models have been validated to a higher level of confidence than the rest.

  10. Centrifugo-pneumatic valving utilizing dissolvable films.

    PubMed

    Gorkin, Robert; Nwankire, Charles E; Gaughran, Jennifer; Zhang, Xin; Donohoe, Gerard G; Rook, Martha; O'Kennedy, Richard; Ducrée, Jens

    2012-08-21

    In this article we introduce a novel technology that utilizes specialized water dissolvable thin films for valving in centrifugal microfluidic systems. In previous work (William Meathrel and Cathy Moritz, IVD Technologies, 2007), dissolvable films (DFs) have been assembled in laminar flow devices to form efficient sacrificial valves where DFs simply open by direct contact with liquid. Here, we build on the original DF valving scheme to leverage sophisticated, merely rotationally actuated vapour barriers and flow control for enabling comprehensive assay integration with low-complexity instrumentation on "lab-on-a-disc" platforms. The advanced sacrificial valving function is achieved by creating an inverted gas-liquid stack upstream of the DF during priming of the system. At low rotational speeds, a pocket of trapped air prevents a surface-tension stabilized liquid plug from wetting the DF membrane. However, high-speed rotation disrupts the metastable gas/liquid interface to wet the DF and thus opens the valve. By judicious choice of the radial position and geometry of the valve, the burst frequency can be tuned over a wide range of rotational speeds nearly 10 times greater than those attained by common capillary burst valves based on hydrophobic constrictions. The broad range of reproducible burst frequencies of the DF valves bears the potential for full integration and automation of comprehensive, multi-step biochemical assay protocols. In this report we demonstrate DF valving, discuss the biocompatibility of using the films, and show a potential sequential valving system including the on-demand release of on-board stored liquid reagents, fast centrifugal sedimentation and vigorous mixing; thus providing a viable basis for use in lab-on-a-disc platforms for point-of-care diagnostics and other life science applications. PMID:22692574

  11. Oxidation of dissolved elemental mercury by thiol compounds under anoxic conditions

    SciTech Connect

    Zheng, Wang; Lin, Hui; Mann, Benjamin F; Liang, Liyuan; Gu, Baohua

    2013-01-01

    Mercuric mercury, Hg(II), forms strong complexes with thiol compounds that commonly dominate Hg(II) speciation in natural freshwater. However, reactions between dissolved elemental Hg(0) and thiols are not well understood although these processes are likely to be important in determining Hg speciation and geochemical cycling in the environment. In this study, reaction rates and mechanisms between dissolved Hg(0) and a number of selected organic ligands with varying molecular structures and sulfur (S) oxidation states were determined to assess the role of these ligands in Hg(0) redox transformation. We found that all thiols caused oxidation of Hg(0) under anoxic conditions but, contrary to expectation, compounds with higher S-oxidation states (e.g., disulfide) than thiols exhibited little or no reactivity with Hg(0) at pH 7. The rate and extent of Hg(0) oxidation varied widely, with smaller aliphatic thiols showing the greatest degree of oxidation. The mechanism of the oxidation is attributed to a two-step process involving adsorption of Hg(0) to thiols followed by the charge transfer from Hg(0) to electron acceptors. These observations demonstrate a unique thiol-induced oxidation pathway of dissolved Hg(0), with important implications for the redox transformation, speciation, and bioavailability of Hg for microbial methylation in anoxic environments.

  12. Temperature and Hydrological Controls on Dissolved Organic Matter Mobilization and Transport within forest soils

    NASA Astrophysics Data System (ADS)

    Xu, N.; Saiers, J. E.

    2009-12-01

    Natural dissolved organic matter (DOM) influences nutrients cycling and contaminants mobility, provides an energy source for heterotrophic production, and regulates soil and water pH. The objectives of this laboratory study were (i) to investigate the relative influence of temperature and rainfall characteristics on the mobilization and transport of DOM (quantity and composition) in forest soils; (ii) to evaluate the possible difference between dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) dynamics; and (iii) to elucidate the importance of biotic and physico-chemical mechanisms that govern DOM mobilization and transport during rainfall events. We applied intermittent rainfalls to unsaturated topsoil columns. The experimental treatments were distinguished on the basis of rainfall intensity, rainfall frequency, temperature, soil biotic activity (i.e., sterile vs unsterile soil), and soil storage time before rainfall initiation. A mathematical model incorporating reversible linear kinetics expressions for DOC release at soil-water interfaces closely describes the DOC breakthrough-curve data. Our results show that temperature significantly affects the release rate and composition of leached DOM, while changes in rainfall intensity and frequency only affect the quantity of mobilized DOM. Effluent concentrations of DON showed broadly similar temporal patterns with DOC during rainfall events. Differences between the quantity of DOC and DON were reflected in the C:N ratios of effluent DOM. Our results also indicate the relative importance of physico-chemical mechanisms for the DOM export process.

  13. Formulation of rizatriptan benzoate fast dissolving buccal films by emulsion evaporation technique

    PubMed Central

    Vidyadhara, Suryadevara; Sasidhar, Reddyvallam Lankapalli; Balakrishna, Thalamanchi; Vardhan, Malapolu Santha

    2015-01-01

    Aim: The present study deals with the formulation of fast dissolving films of Rizatriptan benzoate that is used for the treatment of Migraine. The concept of fast-dissolving drug delivery emerged from the desire to provide patient with more conventional means of taking their medication. Materials and Methods: In the present research work, various trials were carried out using film forming agents such as maltodextrin, gum karaya and xanthan gum to prepare an ideal film. Emulsion evaporation method was used for the preparation of films. The prepared films were evaluated for weight uniformity, drug content, film thickness, folding endurance, dispersion test and curling. The in vitro dissolution studies were carried out using simulated salivary fluid (pH 6.8 phosphate buffer). Results: About 97% of the drug was found to be released from the film within 10 min that is a desirable character for fast absorption. The drug excipient interaction studies carried out by differential scanning calorimetry analysis and Fourier transform infrared studies revealed that there were no major interactions between the drugs and excipients used for the preparation of films. Conclusion: Fast dissolving films of Rizatriptan benzoate prepared by emulsion evaporation technique were found to be suitable for eliciting better therapeutic effect in the treatment of migraine. PMID:25838995

  14. Development of polymer-bound fast-dissolving metformin buccal film with disintegrants.

    PubMed

    Haque, Shaikh Ershadul; Sheela, Angappan

    2015-01-01

    Fast-dissolving drug-delivery systems are considered advantageous over the existing conventional oral dosage forms like tablets, capsules, and syrups for being patient friendly. Buccal films are one such system responsible for systemic drug delivery at the desired site of action by avoiding hepatic first-pass metabolism. Metformin hydrochloride (Met), an antidiabetic drug, has poor bioavailability due to its high solubility and low permeability. The purpose of the study reported here was to develop a polymer-bound fast-dissolving buccal film of metformin to exploit these unique properties. In the study, metformin fast-dissolving films were prepared by the solvent-casting method using chitosan, a bioadhesive polymer. Further, starch, sodium starch glycolate, and microcrystalline cellulose were the disintegrants added to different ratios, forming various formulations (F1 to F7). The buccal films were evaluated for various parameters like weight variation, thickness, folding endurance, surface pH, content uniformity, tensile strength, and percentage of elongation. The films were also subjected to in vitro dissolution study, and the disintegration time was found to be less than 30 minutes for all formulations, which was attributed to the effect of disintegrants. Formulation F6 showed 92.2% drug release within 6 minutes due to the combined effect of sodium starch glycolate and microcrystalline cellulose. PMID:26491321

  15. Development of polymer-bound fast-dissolving metformin buccal film with disintegrants

    PubMed Central

    Haque, Shaikh Ershadul; Sheela, Angappan

    2015-01-01

    Fast-dissolving drug-delivery systems are considered advantageous over the existing conventional oral dosage forms like tablets, capsules, and syrups for being patient friendly. Buccal films are one such system responsible for systemic drug delivery at the desired site of action by avoiding hepatic first-pass metabolism. Metformin hydrochloride (Met), an antidiabetic drug, has poor bioavailability due to its high solubility and low permeability. The purpose of the study reported here was to develop a polymer-bound fast-dissolving buccal film of metformin to exploit these unique properties. In the study, metformin fast-dissolving films were prepared by the solvent-casting method using chitosan, a bioadhesive polymer. Further, starch, sodium starch glycolate, and microcrystalline cellulose were the disintegrants added to different ratios, forming various formulations (F1 to F7). The buccal films were evaluated for various parameters like weight variation, thickness, folding endurance, surface pH, content uniformity, tensile strength, and percentage of elongation. The films were also subjected to in vitro dissolution study, and the disintegration time was found to be less than 30 minutes for all formulations, which was attributed to the effect of disintegrants. Formulation F6 showed 92.2% drug release within 6 minutes due to the combined effect of sodium starch glycolate and microcrystalline cellulose. PMID:26491321

  16. The role of fossil fuel combustion on the stability of dissolved iron in rainwater

    NASA Astrophysics Data System (ADS)

    Willey, Joan D.; Kieber, Robert J.; Humphreys, Joshua J.; Rice, Briana C.; Hopwood, Mark J.; Avery, G. Brooks; Mead, Ralph N.

    2015-04-01

    The concentration of dissolved Fe(II) has decreased in coastal NC rainwater because of less complexation and stabilization of Fe(II) (aq) by automobile and coal combustion emissions. Better emission control has removed stabilizing organic ligands hence dissolved Fe(II) currently occurs more as inorganic iron, which is not protected against oxidation. Increasing rainwater pH allows oxidation by molecular O2 in addition to H2O2 and also increases the ratio of the ion pair Fe(OH)+ to Fe(II) free ion, which increases the oxidation rates by both H2O2 and molecular oxygen. The concentration of H2O2 in rain has increased; hydrogen peroxide is the primary oxidant of inorganic Fe(II) in precipitation. The East Coast of the USA is also receiving less rain of terrestrial origin, which tends to be higher in dissolved iron and organic compounds. All these factors operate in the same direction and contribute to the lower concentrations and lack of stability of Fe(II) in rainwater currently observed. Results of this study suggest that wet deposition of soluble Fe(II) is an episodic, temporally variable factor in the iron cycle in oceanic regions adjacent to developed or developing coastal regions.

  17. Numerical simulation of dissolved oxygen in Jakarta Bay

    NASA Astrophysics Data System (ADS)

    Nurdjaman, Susanna; Radjawane, Ivonne M.; Jamelina, Sripardi

    2014-03-01

    In this paper, an ecosystem model is proposed to study interaction between ecosystem compartment such as nutrient, phytoplankton, zooplankton and detritus on dissolved oxygen (DO) in Jakarta Bay. Three-Dimensional NPZD model with adding DO compartment is applied in this region. The average of current circulation in west and east season is used as input in the model. It is assumed that the nutrients are discharged into water body with constant rates. The analysis of the model shows that the concentration of dissolved oxygen was distributed with range value 3 - 4 ppm in the bay. The air-sea interaction plays important role in decrease of dissolved oxygen than the nutrient discharge from the river. Over all the decrease of dissolved oxygen mainly due to decrease of saturated dissolved oxygen which is caused by high water temperature. There is no significant variation of dissolved oxygen concentration in west and east seasons.

  18. Characterizing natural dissolved organic matter in a freshly submerged catchment (Three Gorges Dam, China) using UV absorption, fluorescence spectroscopy and PARAFAC.

    PubMed

    Chen, Hao; Zheng, Binghui

    2012-01-01

    This study applied parallel factor analysis (PARAFAC) to fluorescence excitation-emission matrices (EEMs) of natural water samples in a freshly submerged catchment in the upper reach of Three Gorges Dam (China). Two fluorescent natural dissolved organic matter (NDOM) components (humic/fulvic-like) were uncovered and were positively correlated with selected water quality parameters, i.e. dissolved oxygen concentration, dissolved organic carbon concentration, dissolved Kjeldahl nitrogen concentration and total (dissolved plus particulate) phosphorus concentration, respectively. To other water quality parameters (i.e. total nitrogen, particulate nitrogen, particulate phosphorus, dissolved phosphorus, dissolved nitrate, pH, and chemical oxygen demand), either the two components did not show any correlation or only one component showed correlation. In particular, particulate N correlated significantly to the fulvic acid, but not to the humic acid. Meanwhile, two conventional spectroscopic indices i.e. specific UV absorbance at 254 nm (SUVA254) and fluorescence index (FI) indicated that the whole NDOM in the waters were low in aromaticity and predominantly derived from aquatic microbial processes. Given together, it concludes that N and P did not function equally in the NDOM production, and the two components were not derived from the same microbial processes. The EEMs-PARAFAC has proven to be of potential as an effective tool in investigation of the interlink between NDOM and nutrients which may be utilized as an indicator of water environment. PMID:22339034

  19. Experimental investigation and modeling of dissolved organic carbon removal by coagulation from seawater.

    PubMed

    Jeong, Sanghyun; Sathasivan, Arumugam; Kastl, George; Shim, Wang Geun; Vigneswaran, Saravanamuthu

    2014-01-01

    Coagulation removes colloidal matters and dissolved organic carbon (DOC) which can cause irreversible membrane fouling. However, how DOC is removed by coagulant is not well-known. Jar test was used to study the removal of hydrophobic and hydrophilic DOC fractions at various doses (0.5-8.0 mg-Fe(+3) L(-1)) of ferric chloride (FeCl3) and pH (5.0-9.0). Natural organic matter (NOM) in seawater and treated seawater were fractionated by liquid chromatography-organic carbon detector (LC-OCD). Compared to surface water, the removal of DOC in seawater by coagulation was remarkably different. Majority of DOC could be easily removed with very low coagulant dose (<5.0 mg-Fe(+3) L(-1)) and the removal efficiency did not vary with pH, but the DOC composition in treated water had significantly changed. Hydrophobic fraction (HB) was better removed at high pH while hydrophilic fraction (HF) was better removed at low pH. A modified model of Kastl et al. (2004) which assumed that the removal occurred by adsorption of un-dissociated compounds onto ferric hydroxide was formulated and successfully validated against the jar test data. PMID:24095612

  20. Removal of dissolved heavy metals from acid rock drainage using iron metal

    SciTech Connect

    Shokes, T.E.; Moeller, G.

    1999-01-15

    The chemical and microbial activity of corroding iron metal is examined in the acid rock drainage (ARD) resulting from pyrite oxidation to determine the effectiveness in neutralizing the ARD and reducing the load of dissolved heavy metals. ARD from Berkeley Pit, MT, is treated with iron in batch reactors and columns containing iron granules. Iron, in acidic solution, hydrolyzes water producing hydride and hydroxide ion resulting in a concomitant increase in pH and decrease in redox potential. The dissolved metals in ARD are removed by several mechanisms. Copper and cadmium cement onto the surface of the iron as zerovalent metals. Hydroxide forming metals such as aluminum, zinc, and nickel form complexes with iron and other metals precipitating from solution as the pH rises. Metalloids such as arsenic and antimony coprecipitate with iron. As metals precipitate from solution, various other mechanisms including coprecipitation, sorption, and ion exchange also enhance removal of metals from solution. Corroding iron also creates a reducing environment supportive for sulfate reducing bacteria (SRB) growth. Increases in SRB populations of 5,000-fold are observed in iron metal treated ARD solutions. Although the biological process is slow, sulfidogenesis is an additional pathway to further stabilize heavy metal precipitates.

  1. Enhanced Indirect Photochemical Transformation of Histidine and Histamine through Association with Chromophoric Dissolved Organic Matter.

    PubMed

    Chu, Chiheng; Lundeen, Rachel A; Remucal, Christina K; Sander, Michael; McNeill, Kristopher

    2015-05-01

    Photochemical transformations greatly affect the stability and fate of amino acids (AAs) in sunlit aquatic ecosystems. Whereas the direct phototransformation of dissolved AAs is well investigated, their indirect photolysis in the presence of chromophoric dissolved organic matter (CDOM) is poorly understood. In aquatic systems, CDOM may act both as sorbent for AAs and as photosensitizer, creating microenvironments with high concentrations of photochemically produced reactive intermediates, such as singlet oxygen (1O2). This study provides a systematic investigation of the indirect photochemical transformation of histidine (His) and histamine by 1O2 in solutions containing CDOM as a function of solution pH. Both His and histamine showed pH-dependent enhanced phototransformation in the CDOM systems as compared to systems in which model, low-molecular-weight 1O2 sensitizers were used. Enhanced reactivity resulted from sorption of His and histamine to CDOM and thus exposure to elevated 1O2 concentrations in the CDOM microenvironment. The extent of reactivity enhancement depended on solution pH via its effects on the protonation state of His, histamine, and CDOM. Sorption-enhanced reactivity was independently supported by depressed rate enhancements in the presence of a cosorbate that competitively displaced His and histamine from CDOM. Incorporating sorption and photochemical transformation processes into a reaction rate prediction model improved the description of the abiotic photochemical transformation rates of His in the presence of CDOM. PMID:25827214

  2. Compost impacts on dissolved organic carbon and available nitrogen and phosphorus in turfgrass soil.

    PubMed

    Wright, Alan L; Provin, Tony L; Hons, Frank M; Zuberer, David A; White, Richard H

    2008-01-01

    Compost application to turfgrass soils may increase dissolved organic C (DOC) levels which affects nutrient dynamics in soil. The objectives of this study were to investigate the influence of compost source and application rate on soil organic C (SOC), DOC, NO(3), and available P during 29 months after a one-time application to St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] turf. Compost sources had variable composition, yet resulted in few differences in SOC, DOC, and NO(3) after applied to soil. Available NO(3) rapidly decreased after compost application and was unaffected by compost source and application rate. Available P increased after compost application and exhibited cyclical seasonal patterns related to DOC. Compost application decreased soil pH relative to unamended soil, but pH increased during the course of the study due to irrigation with sodic water. Increasing the compost application rate increased SOC by 3 months, and levels remained fairly stable to 29 months. In contrast, DOC continued to increase from 3 to 29 months after application, suggesting that compost mineralization and growth of St. Augustinegrass contributed to seasonal dynamics. Dissolved organic C was 75%, 78%, and 101% greater 29 months after application of 0, 80, and 160 Mg compostha(-1), respectively, than before application. Impacts of composts on soil properties indicated that most significant effects occurred within a few months of application. Seasonal variability of SOC, DOC, and available P was likely related to St. Augustinegrass growth stages as well as precipitation, as declines occurred after precipitation events. PMID:17544640

  3. Method for dissolving plutonium oxide with HI and separating plutonium

    DOEpatents

    Vondra, Benedict L.; Tallent, Othar K.; Mailen, James C.

    1979-01-01

    PuO.sub.2 -containing solids, particularly residues from incomplete HNO.sub.3 dissolution of irradiated nuclear fuels, are dissolved in aqueous HI. The resulting solution is evaporated to dryness and the solids are dissolved in HNO.sub.3 for further chemical reprocessing. Alternatively, the HI solution containing dissolved Pu values, can be contacted with a cation exchange resin causing the Pu values to load the resin. The Pu values are selectively eluted from the resin with more concentrated HI.

  4. METHOD FOR DISSOLVING LANTHANUM FLUORIDE CARRIER FOR PLUTONIUM

    DOEpatents

    Koshland, D.E. Jr.; Willard, J.E.

    1961-08-01

    A method is described for dissolving lanthanum fluoride precipitates which is applicable to lanthanum fluoride carrier precipitation processes for recovery of plutonium values from aqueous solutions. The lanthanum fluoride precipitate is contacted with an aqueous acidic solution containing dissolved zirconium in the tetravalent oxidation state. The presence of the zirconium increases the lanthanum fluoride dissolved and makes any tetravalent plutonium present more readily oxidizable to the hexavalent state. (AEC)

  5. Method to Estimate the Dissolved Air Content in Hydraulic Fluid

    NASA Technical Reports Server (NTRS)

    Hauser, Daniel M.

    2011-01-01

    In order to verify the air content in hydraulic fluid, an instrument was needed to measure the dissolved air content before the fluid was loaded into the system. The instrument also needed to measure the dissolved air content in situ and in real time during the de-aeration process. The current methods used to measure the dissolved air content require the fluid to be drawn from the hydraulic system, and additional offline laboratory processing time is involved. During laboratory processing, there is a potential for contamination to occur, especially when subsaturated fluid is to be analyzed. A new method measures the amount of dissolved air in hydraulic fluid through the use of a dissolved oxygen meter. The device measures the dissolved air content through an in situ, real-time process that requires no additional offline laboratory processing time. The method utilizes an instrument that measures the partial pressure of oxygen in the hydraulic fluid. By using a standardized calculation procedure that relates the oxygen partial pressure to the volume of dissolved air in solution, the dissolved air content is estimated. The technique employs luminescent quenching technology to determine the partial pressure of oxygen in the hydraulic fluid. An estimated Henry s law coefficient for oxygen and nitrogen in hydraulic fluid is calculated using a standard method to estimate the solubility of gases in lubricants. The amount of dissolved oxygen in the hydraulic fluid is estimated using the Henry s solubility coefficient and the measured partial pressure of oxygen in solution. The amount of dissolved nitrogen that is in solution is estimated by assuming that the ratio of dissolved nitrogen to dissolved oxygen is equal to the ratio of the gas solubility of nitrogen to oxygen at atmospheric pressure and temperature. The technique was performed at atmospheric pressure and room temperature. The technique could be theoretically carried out at higher pressures and elevated temperatures.

  6. Photolytic processing of secondary organic aerosols dissolved in cloud droplets

    SciTech Connect

    Bateman, Adam P; Nizkorodov, Serguei; Laskin, Julia; Laskin, Alexander

    2011-05-26

    The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05 - 1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300 - 400 nm radiation for up to 24 hours. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly reduced by photolysis relative to the monomeric compounds. Direct pH measurements showed that compounds containing carboxylic acids increased upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonylswas confirmed by the UV-Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n→π* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ~ 0.03. The concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content.

  7. Analysis of RFSA Campaign No.2 Dissolver Solution for Hg(I) and Hg(II)

    SciTech Connect

    Holcomb, H.P.

    2001-05-17

    TA 2-1083, under which RFSA processing is conducted, calls for a nominal mercuric ion concentration in the dissolver solution of 0.006M with a maximum of 0.01 M. The second RFSA campaign operated according to these guidelines with the initial Hg(II) concentration being 0.0068 M. Part of this study is to ascertain optimum excess Hg(I) for chloride removal.

  8. Nanostructured conductive polymeric materials

    NASA Astrophysics Data System (ADS)

    Al-Saleh, Mohammed H.

    Conductive polymer composites (CPCs) are a suitable alternative to metals in many applications due to their light-weight, corrosion resistance, low cost, ease of processing and design flexibility. CPCs have been formulated using different types of conductive fillers. In this PhD thesis, the focus is on CPCs for electrostatic discharge (ESD) protection and electromagnetic interference (EMI) attenuation. Despite the versatility of conductive fillers, carbon black (CB) has been the dominant filler to make CPCs for ESD protection applications because CB/polymer composites have a cost advantage over all other CPCs. For EMI shielding, stainless steel fibres and metal coated fibers are the preferred fillers, however CPCs made of those fibers are not the dominant EMI shielding materials. Metal coated and polymer plated polymers are the most widely used EMI shielding options. The limited use of CPCs in the EMI shielding market is because the high filler loading required to formulate a composite with an adequate level of shielding remarkably increases the composite price. In order to increase the competitiveness of CPCs, percolation threshold should be minimized as much as possible and composites with high EMI shielding capabilities at low filler loading should be formulated because all conductive fillers are expensive compared to polymers. In this thesis, two different methodologies to reduce percolation threshold in CPCs have been successfully developed and a CPC with exceptional EMI shielding capability has been formulated using copper nanowires as conductive filler. The first percolation threshold reduction technique is based on the selective localization of CB at the interface of immiscible polymer blend. The technique requires adding a copolymer that prefers the blend's interface and for which CB nanoparticles has the highest affinity. The second method is based on producing a CPC powder and then using this powder as a conductive filler to produce composite by dry mixing with pure polymer powder followed by compression molding. The EMI shielding material was developed using copper nanowires. CuNW/Polystyrene composites exhibit EMI shielding effectiveness exceeding that of metal microfillers and carbon nanotube/polymer composites and approaching that of coating techniques have been formulated by solution processing and dry mixing.

  9. Electrochemical Stability of Polyaniline Beyond pH 9

    NASA Astrophysics Data System (ADS)

    Tarver, Jacob; Yoo, Joung Eun; Loo, Yueh-Lin

    2009-03-01

    Conductive polymer films are promising candidates for solution-based biosensor and organic electrochemical transistor devices. For many conducting polymers, however, stable electrochemical activity often demands restrictively acidic solutions. This need has in turn limited the use of conductive polymers in near-neutral and physiological conditions. Using spectroelectrochemical methods, we studied the stability of polyaniline that is template synthesized on poly(2-acrylamido-2-methyl-1-propanesulfonic acid) as a function of pH. Transitions between the different oxidation states of polyaniline are stable and reversible in solutions as high as pH 10. This range of sustained electroactivity far exceeds that of previously reported polyaniline systems. In comparison, polyaniline that is doped with small-molecule acids loses its electroactivity in solutions beyond pH 4. Immobilization of polyaniline within a polymer acid matrix retards dopant diffusivity and reduces proton mobility. The preservation of local acidic conditions within the film greatly extends the pH range of stable electroactivity.

  10. Adsorption of dissolved organics in lake water by aluminum oxide. Effect of molecular weight

    USGS Publications Warehouse

    Davis, J.A.; Gloor, R.

    1981-01-01

    Dissolved organic compounds in a Swiss lake were fractionated into three molecular size classes by gel exclusion chromatography, and adsorption of each fraction on colloidal alumina was studied as a function of pH. Organic compounds with molecular weight (Mr) greater than 1000 formed strong complexes with the alumina surface, but low molecular weight compounds were weakly adsorbed. Electrophoretic mobility measurements indicated that alumina particles suspended in the original lake water were highly negatively charged because of adsorbed organic matter. Most of the adsorbed organic compounds were in the Mr range 1000 < Mr < 3000. Adsorption of these compounds during the treatment of drinking water by alum coagulation may be responsible for the preferential removal of trihalomethane precursors. Adsorption may also influence the molecular-weight distribution of dissolved organic material in lakes. surface, the present work will focus on the influence of molecular size and pH on the adsorption behavior of dissolved organic material of a Swiss lake. From a geochemical point of view, it is important to know the molecular-weight distribution of adsorbed organic matter so that we may better assess its reactivity with trace elements. The study also serves as a first step in quantifying the role of adsorption in the geochemical cycle of organic carbon in lacustrine environments. For water-treatment practice, we need to determine whether molecular weight fractionation occurs during adsorption by aluminum oxide. Such a fractionation could be significant in the light of recent reports that chloroform and other organochlorine compounds are preferentially produced by particular molecular-weight fractions (25-27). ?? 1981 American Chemical Society.

  11. Temporal and spatial variations in dissolved trace metal species in the Chesapeake Bay

    NASA Astrophysics Data System (ADS)

    Sako, A.; Hannigan, R.; Jones, C.

    2002-12-01

    Behavior of dissolved major (e.g., Mg2+, Ca2+ and K+) and trace elements (e.g., Sr2+, Pb2+, Ba2+, Br-, etc.) in estuarine environments is a function of several factors such as salinity, pH, suspended particles and organic material contents. The fate of these metals and their distribution will differ from one estuary to another and within a given estuary. To investigate the fate and source (anthropogenic versus resuspended input) of selected major and trace elements in Chesapeake Bay (CB), water and sediment samples were collected eastern, western shores and island areas of the Bay from July to September. Water samples were filtered (0.45\\x8Dm) and acidified (pH<2) with ultrapure nitric acid prior to their analysis for trace elements by ICP-MS. A computer code (MINTEQA) was used to study metal speciation in water samples. It was assumed that water was in equilibrium with atmospheric oxygen, and therefore Fe3+ form was input in the model instead of Fe2+. As a result, MINTEQA did not have to perform redox calculations. The ratio of dissolved species to total dissolved metal indicates nonconservative behavior of major elements such Mg, Ca and K and Pb, while trace elements Sr and Ba were more conservative, in time and space. Variations in ionic strengths in different sites suggest effects of salinity and turbidity on complex formation, as ionic strength normally increases with low salinity and vice versa. Variations in spatial and temporal distribution of elements, shown in this study, are likely due to nonuniformity of the water flow regime in different zones, seasonal biological regeneration of metals from sediment and salinity gradients.

  12. Temperature Dependence of Photodegradation of Dissolved Organic Matter to Dissolved Inorganic Carbon and Particulate Organic Carbon

    PubMed Central

    Porcal, Petr; Dillon, Peter J.; Molot, Lewis A.

    2015-01-01

    Photochemical transformation of dissolved organic matter (DOM) has been studied for more than two decades. Usually, laboratory or “in-situ” experiments are used to determine photodegradation variables. A common problem with these experiments is that the photodegradation experiments are done at higher than ambient temperature. Five laboratory experiments were done to determine the effect of temperature on photochemical degradation of DOM. Experimental results showed strong dependence of photodegradation on temperature. Mathematical modeling of processes revealed that two different pathways engaged in photochemical transformation of DOM to dissolved inorganic carbon (DIC) strongly depend on temperature. Direct oxidation of DOM to DIC dominated at low temperatures while conversion of DOM to intermediate particulate organic carbon (POC) prior to oxidation to DIC dominated at high temperatures. It is necessary to consider this strong dependence when the results of laboratory experiments are interpreted in regard to natural processes. Photodegradation experiments done at higher than ambient temperature will necessitate correction of rate constants. PMID:26106898

  13. [Sources, Migration and Conversion of Dissolved Alkanes, Dissolved Fatty Acids in a Karst Underground River Water, in Chongqing Area].

    PubMed

    Liang, Zuo-bing; Sun, Yu-chuan; Wang, Zun-bo; Shi, Yang; Jiang, Ze-li; Zhang, Mei; Xie, Zheng-Lan; Liao, Yu

    2015-09-01

    Dissolved alkanes and dissolved fatty acids were collected from Qingmuguan underground river in July, October 2013. By gas chromatography-mass spectrometer (GC-MS), alkanes and fatty acids were quantitatively analyzed. The results showed that average contents of alkanes and fatty acids were 1 354 ng.L-1, 24203 ng.L-1 in July, and 667 ng.L-1, 2526 ng.L-1 in October respectively. With the increasing migration distance of dissolved alkanes and dissolved fatty acids in underground river, their contents decreased. Based on the molecular characteristic indices of alkanes, like CPI, OEP, Paq and R, dissolved alkanes were mainly originated from microorganisms in July, and aquatic plants in October. Saturated straight-chain fatty acid had the highest contents in all samples with the dominant peak in C16:0, combined with the characteristics of carbon peak, algae or bacteria might be the dominant source of dissolved fatty acids. PMID:26717680

  14. Removal of actinides from dissolved ORNL MVST sludge using the TRUEX process

    SciTech Connect

    Spencer, B.B.; Egan, B.Z.; Chase, C.W.

    1997-07-01

    Experiments were conducted to evaluate the transuranium extraction process for partitioning actinides from actual dissolved high-level radioactive waste sludge. All tests were performed at ambient temperature. Time and budget constraints permitted only two experimental campaigns. Samples of sludge from Melton Valley Storage Tank W-25 were rinsed with mild caustic (0.2 M NaOH) to reduce the concentrations of nitrates and fission products associated with the interstitial liquid. In one campaign, the rinsed sludge was dissolved in nitric acid to produce a solution containing total metal concentrations of ca. 1.8 M with a nitric acid concentration of ca. 2.9 M. About 50% of the dry mass of the sludge was dissolved. In the other campaign, the sludge was neutralized with nitric acid to destroy the carbonates, then leached with ca. 2.6 M NaOH for ca. 6 h before rinsing with the mild caustic. The sludge was then dissolved in nitric acid to produce a solution containing total metal concentrations of ca. 0.6 M with a nitric acid concentration of ca. 1.7 M. About 80% of the sludge dissolved. The dissolved sludge solution form the first campaign began gelling immediately, and a visible gel layer was observed after 8 days. In the second campaign, the solution became hazy after ca. 8 days, indicating gel formation, but did not display separated gel layers after aging for 20 days. Batch liquid-liquid equilibrium tests of both the extraction and stripping operations were conducted. Chemical analyses of both phases were used to evaluate the process. Evaluation was based on two metrics: the fraction of TRU elements removed from the dissolved sludge and comparison of the results with predictions made with the Generic TRUEX Model (GTM). The fractions of Eu, Pu, Cm, Th, and U species removed from aqueous solution in only one extraction stage were > 95% and were close to the values predicted by the GTM. Mercury was also found to be strongly extracted, with a one-stage removal of > 92%.

  15. Experimental study of dissolved oxygen transport by regular waves through a perforated breakwater

    NASA Astrophysics Data System (ADS)

    Yin, Zegao; Yu, Ning; Liang, Bingchen; Zeng, Jixiong; Xie, Shaohua

    2016-02-01

    The perforated breakwater is an environmentally friendly coastal structure, and dissolved oxygen concentration levels are an important index to denote water quality. In this paper, oxygen transport experiments with regular waves through a vertical perforated breakwater were conducted. The oxygen scavenger method was used to reduce the dissolved oxygen concentration of inner water body with the chemicals Na2SO3 and CoCl2. The dissolved oxygen concentration and wave parameters of 36 experimental scenarios were measured with different perforated arrangements and wave conditions. It was found that the oxygen transfer coefficient through wave surface, K1 a 1, is much lower than the oxygen transport coefficient through the perforated breakwater, K2 a 2. If the effect of K1 a 1 is not considered, the dissolved oxygen concentration computation for inner water body will not be greatly affected. Considering the effect of a permeable area ratio a, relative location parameter of perforations δ and wave period T, the aforementioned data of 30 experimental scenarios, the dimensional analysis and the least squares method were used to derive an equation of K2 a 2 (K2 a 2=0.0042 a 0.5 δ 0.2 T -1). It was validated with 6 other experimental scenarios data, which indicates an approximate agreement. Therefore, this equation can be used to compute the DO concentration caused by the water transport through perforated breakwater.

  16. Regulation of arsenic mobility on basaltic glass surfaces by speciation and pH.

    PubMed

    Sigfusson, Bergur; Meharg, Andrew A; Gislason, Sigurdur R

    2008-12-01

    The importance of geothermal energy as a source for electricity generation and district heating has increased over recent decades. Arsenic can be a significant constituent of the geothermal fluids pumped to the surface during power generation. Dissolved As exists in different oxidation states, mainly as As(III) and As(V), and the charge of individual species varies with pH. Basaltic glass is one of the most important rock types in many high-temperature geothermal fields. Static batch and dynamic column experiments were combined to generate and validate sorption coefficients for As(III) and As(V) in contact with basaltic glass at pH 3-10. Validation was carried out by two empirical kinetic models and a surface complexation model (SCM). The SCM provided a better fit to the experimental column data than kinetic models at high pH values. However, in certain circumstances, an adequate estimation of As transport in the column could not be attained without incorporation of kinetic reactions. The varying mobility with pH was due to the combined effects of the variable charge of the basaltic glass with the pH point of zero charge at 6.8 and the individual As species as pH shifted, respectively. The mobility of As(III) decreased with increasing pH. The opposite was true for As(V), being nearly immobile at pH 3 to being highly mobile at pH 10. Incorporation of appropriate sorption constants, based on the measured pH and Eh of geothermal fluids, into regional groundwater-flow models should allow prediction of the As(III) and As(V) transport from geothermal systems to adjacent drinking water sources and ecosystems. PMID:19192803

  17. Arsenic release from iron rich mineral processing waste: Influence of pH and redox potential.

    PubMed

    Al-Abed, Souhail R; Jegadeesan, G; Purandare, J; Allen, D

    2007-01-01

    This paper presents the effect of pH and redox potential on the potential mobility of arsenic (As) from a contaminated mineral processing waste. The selected waste contained about 0.47 g kg(-1) of As and 66.2 g kg(-1) of iron (Fe). The characteristic of the waste was identified by acid digestion, X-ray diffraction and sequential extraction procedures. Less than 2% of the total As was acid extractable with the remaining 98% associated with Fe-oxyhydroxides and oxides. Batch leaching tests at different pH conditions showed a strong pH dependence on arsenic and iron leaching. Arsenic leaching followed a "V" shaped profiles with significant leaching in the acidic and alkaline pH region. Acid extractable phases dissolved at acidic pH, while desorption of arsenic due to increase in pH resulted in high arsenic concentration at alkaline pH. Under aerobic conditions and pH 7, As solubility was low, probably due to its precipitation on Fe-oxyhydroxides. Maximum As solubilization occurred at pH 11 (3.59 mg l(-1)). Similarity in the As and Fe leaching profiles suggested that the release of As was related to the dissolution of Fe in the low pH region. In general, redox potential did not play a significant role in arsenic or iron solubilization. It was thus concluded that for this solid waste, desorption was the predominant mechanism in arsenic leaching. A simple thermodynamic model based on arsenic and iron redox reactions was developed to identify the more sensitive redox couple. PMID:16949129

  18. Dissolved organic carbon reduces the toxicity of aluminum to three tropical freshwater organisms.

    PubMed

    Trenfield, Melanie A; Markich, Scott J; Ng, Jack C; Noller, Barry; van Dam, Rick A

    2012-02-01

    The influence of dissolved organic carbon (DOC) on the toxicity of aluminum (Al) at pH 5 (relevant to acid mine drainage conditions), to the tropical green hydra (Hydra viridissima), green alga (Chlorella sp.), and cladoceran (Moinodaphnia macleayi) was assessed. Two DOC sources, a natural in situ DOC in soft billabong water (SBW) and Suwannee River fulvic acid (SRFA) standard, were compared. The order of sensitivity of the test organisms to dissolved Al (0.1 µm fraction) was Hydra viridissima > Moinodaphnia macleayi > Chlorella sp. with DOC reducing dissolved Al toxicity most for Hydra viridissima. However, colloidal or precipitated Al may contribute indirectly to the toxicity for M. macleayi and Chlorella sp. The toxicity of dissolved Al was up to six times lower in test waters containing 10 mg L(-1) DOC (in the form of SRFA), relative to toxicity observed at 1 mg L(-1) DOC. In contrast, the toxicity of Al was up to two times lower in SBW containing 10 mg L(-1) DOC, relative to water containing 1 mg L(-1) DOC. The increased ability of SRFA in reducing Al toxicity was linked to its greater affinity for complexing Al compared with the in situ DOC. This has important implications for studies that use commercial standards of humic substances to predict Al toxicity in local environments. Speciation modeling demonstrated that Al(3+) and AlOH(2+) provided a strong relationship with toxicity. An empirical relationship is provided for each organism that can be used to predict Al toxicity at a given Al and DOC concentration. PMID:22105345

  19. Abundance and Characterization of Dissolved Organic Carbon in Suburban Streams of Baltimore, Maryland, USA

    NASA Astrophysics Data System (ADS)

    Mora, G.; Fazekas, M.

    2014-12-01

    The contribution of streams and rivers to the carbon cycle is significant, transporting to the oceans ~1.4 Pg C/yr, with dissolved carbon corresponding to as much as 0.7 Pg C/yr. Changes in land use have the potential effect of modifying this flux, particularly in urban areas where impervious areas are common. To investigate the effect of urbanization on riverine carbon transport, we studied four first-order streams in Towson, a suburb of Baltimore, Maryland, USA. The watersheds from the studied streams exhibit different levels of urbanization as measured by the percentage of impervious areas. Samples from these four streams were taken weekly, and several chemical constituents were measured either in the field or in the laboratory. These constituents included nitrate, dissolved organic nitrogen, pH, dissolved organic carbon (DOC), total carbon, dissolved inorganic carbon (DIC), phosphate, the carbon isotopic compositions of DOC and DIC, and fluorescence intensity of the DOC. Results show that DOC concentrations were consistently below 5 mg C/L regardless of the level of imperviousness of the watershed. Similarly, carbon isotope ratios were consistent across the studied streams, with values centered around -26.4 per mil, thus suggesting a significant influx of soil-derived organic carbon originated from C3 plants that are common in the watersheds. Confirming this interpretation, fluorescence spectroscopy data suggest a humic-like origin for the DOC of the streams, thus pointing to the heterotrophic nature of the streams. The combined results suggest that the studied streams exhibit similar DOC concentrations, carbon isotopic values, and fluorescence spectra, despite their level of impervious surfaces in their watersheds.

  20. Effect of pH on the properties of chemical bath deposited polyaniline thin film

    NASA Astrophysics Data System (ADS)

    Patil, Rahul B.; Jatratkar, Aviraj A.; Devan, Rupesh S.; Ma, Yuan-Ron; Puri, R. K.; Puri, Vijaya; Yadav, J. B.

    2015-02-01

    This paper reports the effect of pH on chemical bath deposited polyaniline (PANI) thin film properties. Various analytical techniques have been used to study morphological, structural and optical properties. The smooth surface morphology observed in PANI film prepared at lower pH has become rough with increase in pH value. In UV-vis spectra, two peaks are observed at 400 nm and 800 nm and the peak observed at 800 nm is shifted toward higher wavelength with increase in pH value. The Cl is introduced in the B ring of the PANI that makes PANI more oxidized with decrease in pH value. In XPS N1s core level spectra also, PANI is observed in more oxidized state with decrease in pH value. This indicates that the pH of monomer solution varies the morphology, structure, oxidation state as well as the conductivity of the film.

  1. Transient Dissolved Organic Carbon Through Soils

    NASA Astrophysics Data System (ADS)

    Mei, Y.; Hornberger, G. M.; Kaplan, L. A.; Newbold, J. D.; Aufdenkampe, A. K.; Tsang, Y.

    2009-12-01

    Dissolved organic carbon (DOC) is an important constituent of soil solution that plays a role in many chemical and biological processes in soils; it is also an important energy source for bacteria in the soil ecosystem. Hydrology has a significant control on the transport and fate of dissolved organic carbon in the soil but mechanisms that affect said transport are not well understood. In particular, dynamic information on DOC transport through forest soils on short time scales (one or two precipitation event) is lacking at present. DOC is a very complex mix of organic compounds. A key to quantifying DOC dynamics is to establish useful approximations for behavior of this complex mixture. Biodegradable dissolved organic carbon (BDOC) is an important part of DOC. It is reported that between 12 and 44% of DOC released from the forest floor can be decomposed in solutions by indigenous microbes. In our study, we considered how DOC, BDOC, and flow interact in soil columns. In-situ soil cores with two different lengths were installed under a mixed deciduous canopy. The effects of artificial rain on DOC and BDOC transport were examined by dripping nano pure water amended with bromide on the top of soil cores and sampling the water collected at the bottom of the cores for DOC and BDOC. We used plug-flow biofilm reactors to measure the BDOC concentration. It is likely that reduced rates of decomposition in dry soils will cause microbial products of DOC to accumulate; hence DOC concentration should be high at the first flush of rain and decline as the event proceeds. The experimental results show the expected pattern, that is, the first samples we collected always had the highest DOC and BDOC concentrations. The concentrations tend to decline through the simulated precipitation event. Application of a second “storm” forty minutes after the cessation of the first application of water resulted in effluent DOC concentration increasing a small amount initially and then declining with time. A model based on a one-dimensional Richards’ equation coupled with reactive convection-dispersion equations and a heat transport model to characterize the temperature pattern along the core was developed to explore the experimental results mechanistically. Parameters for both the flow and transport models were selected using trial and error calibration first, and then refined using UCODE (USGS). The results show that the model can match the main features of the observed DOC and BDOC patterns under transient soil water flux conditions. These results indicate that future work to extend the model to two and three dimensions to describe hillslope and catchment processes is a reasonable goal, although additional processes (e.g. bacterial growth) will have to be incorporated to achieve an appropriate degree of realism.

  2. Dissolved aluminium in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Middag, R.; van Slooten, C.; de Baar, H. J. W.; Laan, P.

    2011-12-01

    Dissolved aluminium (Al) occurs in a wide range of concentrations in the world oceans. The concentrations of Al in the Southern Ocean are among the lowest ever observed. An all-titanium CTD sampling system makes it possible to study complete deep ocean sections of Al and other trace elements with the same high vertical resolution of 24 depths as normal for traditional CTD/Rosette sampling. Overall, 470 new data points of Al are reported for 22 full depth stations and 24 surface sampling positions along one transect. This transect consisted of 18 stations on the zero meridian proper from 51°57' S until 69°24'S, and 4 stations somewhat to the northeast towards Cape Town from 42°20'S, 09°E to 50°17'S, 01°27'E. The actual concentrations of Al in the Southern Ocean were lower than previously reported. The concentration of Al in the upper 25 m was relatively elevated with an average concentration of 0.71 nM ( n=22; S.D.=0.43 nM), most likely due to atmospheric input by a suggested combination of direct atmospheric (wet and dry) input and indirect atmospheric input via melting sea ice. Below the surface waters there was a distinct Al minimum with an average concentration of 0.33 nM ( n=22; S.D.=0.13 nM) at an average depth of 120 m. In the deep southernmost Weddell Basin the concentration of Al increased with depth to ˜0.8 nM at 4000 m, and a higher concentration of ˜1.5 nM in the ˜4500-5200 m deep Weddell Sea Bottom Water. Over the Bouvet triple junction region, where three deep ocean ridges meet, the concentration of Al increased to ˜1.4 nM at about 2000 m depth over the ridge crest. In the deep basin north of the Bouvet region the concentration of Al increased to higher deep values of 4-6 nM due to influence of North Atlantic Deep Water. In general the intermediate and deep distribution of Al results from the mixing of water masses with different origins, the formation of deep water and additional input from sedimentary sources at sea floor elevations. No significant correlation between Al and silicate (Si) was observed. This is in contrast to some other ocean regions. In the Southern Ocean the supply of Al is extremely low and any signal from Al uptake and dissolution with biogenic silica is undetectable against the high dissolved Si and low dissolved Al concentrations. Here the Al-Si relation in the deep ocean is uncoupled. This is due to the scavenging and subsequent loss of the water column of Al, whereas the concentration of Si increases in the deep ocean due to its input from deep dissolution of biogenic diatom frustules settling from the surface layer.

  3. Concentrations of dissolved oxygen in the lower Puyallup and White rivers, Washington, August and September 2000 and 2001

    USGS Publications Warehouse

    Ebbert, J.C.

    2002-01-01

    The U.S. Geological Survey, Washington State Department of Ecology, and Puyallup Tribe of Indians conducted a study in August and September 2001 to assess factors affecting concentrations of dissolved oxygen in the lower Puyallup and White Rivers, Washington. The study was initiated because observed concentrations of dissolved oxygen in the lower Puyallup River fell to levels ranging from less than 1 milligram per liter (mg/L) to about 6 mg/L on several occasions in September 2000. The water quality standard for the concentration of dissolved oxygen in the Puyallup River is 8 mg/L.This study concluded that inundation of the sensors with sediment was the most likely cause of the low concentrations of dissolved oxygen observed in September 2000. The conclusion was based on (1) knowledge gained when a dissolved-oxygen sensor became covered with sediment in August 2001, (2) the fact that, with few exceptions, concentrations of dissolved oxygen in the lower Puyallup and White Rivers did not fall below 8 mg/L in August and September 2001, and (3) an analysis of other mechanisms affecting concentrations of dissolved oxygen.The analysis of other mechanisms indicated that they are unlikely to cause steep declines in concentrations of dissolved oxygen like those observed in September 2000. Five-day biochemical oxygen demand ranged from 0.22 to 1.78 mg/L (mean of 0.55 mg/L), and river water takes only about 24 hours to flow through the study reach. Photosynthesis and respiration cause concentrations of dissolved oxygen in the lower Puyallup River to fluctuate as much as about 1 mg/L over a 24-hour period in August and September. Release of water from Lake Tapps for the purpose of hydropower generation often lowered concentrations of dissolved oxygen downstream in the White River by about 1 mg/L. The effect was smaller farther downstream in the Puyallup River at river mile 5.8, but was still observable as a slight decrease in concentrations of dissolved oxygen caused by photosynthesis and respiration. The upper limit on oxygen demand caused by the scour of anoxic bed sediment and subsequent oxidation of reduced iron and manganese is less than 1 mg/L. The actual demand, if any, is probably negligible.In August and September 2001, concentrations of dissolved oxygen in the lower Puyallup River did not fall below the water-quality standard of 8 mg/L, except at high tide when the saline water from Commencement Bay reached the monitor at river mile 2.9. The minimum concentration of dissolved oxygen (7.6 mg/L) observed at river mile 2.9 coincided with the maximum value of specific conductance. Because the dissolved-oxygen standard for marine water is 6.0 mg/L, the standard was not violated at river mile 2.9. The concentration of dissolved oxygen at river mile 1.8 in the White River dropped below the water-quality standard on two occasions in August 2001. The minimum concentration of 7.8 mg/L occurred on August 23, and a concentration of 7.9 mg/L was recorded on August 13. Because there was some uncertainty in the monitoring record for those days, it cannot be stated with certainty that the actual concentration of dissolved oxygen in the river dropped below 8 mg/L. However, at other times when the quality of the monitoring record was good, concentrations as low as 8.2 mg/L were observed at river mile 1.8 in the White River.

  4. Dissolved organic C export is highly dynamic - capturing this variability and challenges in modelling

    NASA Astrophysics Data System (ADS)

    Waldron, S.; Coleman, M.; Scott, E. M.; Drew, S.

    2013-12-01

    High resolution, field-deployable sensors offer opportunities to deepen our understanding of natural environmental systems, and measure the ';riverine pulse'. Studies utilising high-resolution equipment have demonstrated that sampling hydrological variables on traditional low frequency rates (such as once a week) creates a simplified picture of conditions that does not capture a true reflection of how fluvial systems operate. Dissolved organic carbon (DOC) represents a large and diverse mixture of compounds (including sugars, amino acids and humic substances) and concentration and composition of this pool varies globally. Understanding transport of this C pool in fluvial systems is important as it 1) represents the lateral export of C no longer sequestered in the terrestrial system, 2) surface water concentrations have been observed to have increased globally and we need to know if this trend is continuing and 3) when water is abstracted the purification processes removing DOC from the water, can create harmful by-products and so prior knowledge of inflow loading is valuable. Traditionally [DOC] has been measured using manual sampling methods, where a water sample would be collected in the field and returned to the lab. This approach can provide reliable data but the resource required to sustain this make it nearly impossible to measure the ';riverine pulse' through the information in long and detailed time series. In recent years new technology designed to estimate [DOC] in-situ has been developed. We have used one of these devices, which measures absorption in both the visible and UV wavelength regions of the electromagnetic spectrum and from this absorbance profile an algorithm estimates [DOC]. We have deployed this system in the field environment and after overcoming initial challenges have an almost continuous time series of [DOC], measured at 30 minute intervals, since May 2012. The logger has been functioning over a temperature range of 0.5 - 23 C and a [DOC] range of 8 - 55.6 mg/l C, with the greatest shift in a single day being 23.5 mg/l C. We will present this highly dynamic [DOC] time series and also contemporaneous data from an in-situ water chemistry sonde profiling other measures of the ';riverine circulation system': pH, conductivity, temperature and stage height. The challenge now is how to allow data series of ~17,500 measurements per annum to interact to better understand and model drivers of carbon export. We are exploring the application of wavelet analysis to identify periods of coherence between [DOC] and these other variables. Our initial results indicate show that coherence with [DOC] can be intermittent and irregular, and so the challenge sensor technology presents continues.

  5. Aggregation of nanoscale iron oxyhydroxides and corresponding effects on metal uptake, retention, and speciation: I. Ionic-strength and pH

    NASA Astrophysics Data System (ADS)

    Dale, J. G.; Stegemeier, J. P.; Kim, C. S.

    2015-01-01

    The capacity of nanosized particles to adsorb and sequester dissolved metals can be significantly impacted by the mechanism and extent of aggregation the particles have undergone, which in turn can affect the long-term fate and transport of potentially toxic metals in natural aqueous systems. Suspensions of monodisperse nanoscale iron oxyhydroxides were synthesized and subjected to increased pH (pH 8.0, 10.0) or ionic strength (0.1, 1.0 M NaNO3) conditions to induce various states of aggregation prior to conducting macroscopic adsorption/desorption experiments with dissolved Cu(II) or Zn(II). The metal adsorption and retention capacities of the nanoparticle aggregates were compared to one another and to non-aggregated control nanoparticles, while the mode(s) of metal sorption to the nanoparticle surfaces were characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy analysis. With increasing aggregation by both pH and ionic strength, the proportion of introduced zinc adsorbed to the iron oxyhydroxide nanoparticles progressively decreased from 45% on the monodispersed control particles to as low as 16% on the aggregates, while the proportion of introduced zinc retained upon desorption (obtained by lowering the suspension pH) increased from 7% on the control particles to as much as 17% on the aggregated particles. Copper exhibited a subtler trend of only slightly declining uptake (from 43% to 36%) and retention (from 35% to 30%) with increasing aggregation state. EXAFS analysis was consistent with the macroscopic results, showing relatively little change in Cu speciation between samples analyzed before and after the desorption step but significant increases in Zn-Fe interatomic distances and coordination numbers after desorption. This suggests the presence of both strongly- and weakly-bound zinc ions; the latter are likely affiliated with less stable, more distorted surface sorption sites and are thus more readily desorbed, resulting in the retention of zinc that is bound to more stable, less-distorted sorption sites. For both metals, inner-sphere bidentate sorption appears to dominate the sorption process to the nanoparticle aggregates, with potential structural incorporation into the aggregates themselves.

  6. Inexpensive and Disposable pH Electrodes

    ERIC Educational Resources Information Center

    Goldcamp, Michael J.; Conklin, Alfred; Nelson, Kimberly; Marchetti, Jessica; Brashear, Ryan; Epure, Emily

    2010-01-01

    Inexpensive electrodes for the measurement of pH have been constructed using the ionophore tribenzylamine for sensing H[superscript +] concentrations. Both traditional liquid-membrane electrodes and coated-wire electrodes have been constructed and studied, and both exhibit linear, nearly Nernstian responses to changes in pH. Measurements of pH

  7. Defining and Teaching pH

    NASA Astrophysics Data System (ADS)

    Burton, Richard F.

    2007-07-01

    The 1909 definition of pH given in most general chemistry textbooks conflicts with the modern, operationally-defined pH scale that underlies laboratory measurement and relates to activities. At an elementary level, pH and the algebra of equilibria can be simply and correctly taught, without logarithms, in terms of the latter scale.

  8. IMPACT OF WATER PH ON ZEBRA MUSSEL MORTALITY

    SciTech Connect

    Daniel P. Molloy

    2002-10-15

    The experiments conducted this past quarter have suggested that the bacterium Pseudomonas fluorescens strain CL0145A is effective at killing zebra mussels throughout the entire range of pH values tested (7.2 to 8.6). Highest mortality was achieved at pH values characteristic of preferred zebra mussel waterbodies, i.e., hard waters with a range of 7.8 to 8.6. In all water types tested, however, ranging from very soft to very hard, considerable mussel kill was achieved (83 to 99% mean mortality), suggesting that regardless of the pH or hardness of the treated water, significant mussel kill can be achieved upon treatment with P. fluorescens strain CL0145A. These results further support the concept that this bacterium has significant potential for use as a zebra mussel control agent in power plant pipes receiving waters with a wide range of physical and chemical characteristics.

  9. Formation of Hg(II) Tetrathiolate Complexes with Cysteine at Neutral pH

    PubMed Central

    Warner, Thomas; Jalilehvand, Farideh

    2015-01-01

    Mercury(II) ions precipitate from aqueous cysteine (H2Cys) solutions containing H2Cys/Hg(II) mole ratio ≥ 2.0 as Hg(S-HCys)2. In absence of additional cysteine, the precipitate dissolves at pH ~12 with the [Hg(S,N-Cys)2]2− complex dominating. With excess cysteine (H2Cys/Hg(II) mole ratio ≥ 4.0), higher complexes form and the precipitate dissolves at lower pH values. Previously, we found that tetrathiolate [Hg(S-Cys)4]6− complexes form at pH = 11.0; in this work we extend the investigation to pH values of physiological interest. We examined two series of Hg(II)-cysteine solutions in which CHg(II) varied between 8 – 9 mM and 80 – 100 mM, respectively, with H2Cys/Hg(II) mole ratios from 4 to ~20. The solutions were prepared in the pH range 7.1 – 8.8, at the pH at which the initial Hg(S-HCys)2 precipitate dissolved. The variations in the Hg(II) speciation were followed by 199Hg NMR, X-ray absorption and Raman spectroscopic techniques. Our results show that in the dilute solutions (CHg(II) = 8 – 9 mM), mixtures of di-, tri- (major) and tetrathiolate complexes exist at moderate cysteine excess (CH2Cys ~ 0.16 M) at pH 7.1. In the more concentrated solutions (CHg(II) = 80 – 100 mM) with high cysteine excess (CH2Cys > 0.9 M), tetrathiolate [Hg(S-cysteinate)4]m-6 (m = 0 – 4) complexes dominate in the pH range 7.3 – 7.8, with lower charge than for the [Hg(S-Cys)4]6− complex due to protonation of some (m) of the amino groups of the coordinated cysteine ligands. The results of this investigation could provide a key to the mechanism of biosorption and accumulation of Hg(II) ions in biological / environmental systems. PMID:27064521

  10. Exhaled breath condensate pH is influenced by respiratory droplet dilution.

    PubMed

    Bikov, Andras; Galffy, Gabriella; Tamasi, Lilla; Lazar, Zsofia; Losonczy, Gyorgy; Horvath, Ildiko

    2012-12-01

    Several studies support that airway acid stress plays a role in the pathophysiology of asthma. Exhaled breath condensate pH (EBC pH) was suggested as a surrogate marker of airway acidification. The dilution of airway lining fluid (ALF) acids and bases by alveolar water may influence condensate pH, but it has not been studied yet. The aim of our study was to investigate the relationship between EBC pH and ALF dilution in EBC samples obtained from asthmatic and healthy subjects. EBC was collected from 55 asthmatic and 57 healthy subjects for pH and conductivity measurements. Fractional exhaled nitric oxide (FE(NO)) and lung function tests were also performed in asthmatic patients. EBC pH was determined after 10 min of argon deareation and the dilution was estimated by the measurement of conductivity in vacuum-treated samples. There was no difference either in EBC pH or dilution between the two groups. However, a significant relationship was found between EBC pH and dilution in both groups (p < 0.05, r = -0.35 and r = -0.29, asthmatic and healthy groups, respectively). Our results suggest important methodological aspect indicating that EBC pH is affected by respiratory droplet dilution, and this effect should be taken into consideration when interpreting EBC pH data. PMID:22990071

  11. A Fluorescence Based Dissolved Oxygen Sensor

    NASA Astrophysics Data System (ADS)

    McFarlane, Ronald; Hamilton, M. Coreen

    1987-10-01

    A sensor based on fluorescence quenching has been built to detect oxygen activity in gas and water. The sensor consists of a xenon flash bulb as a light source; an excitation wavelength band pass filter; a dichroic beam splitter; collimating and focussing lenses; a plastic clad silica (PCS) rod with the fluorophore immobilized at the tip of it; an emission wavelength band pass filter; a photomultiplier tube (PMT); a monitor PIN photodiode detector; and interface electronics to couple a computer to the rest of the sensor. The device demonstrates a reversible change in fluorescence quenching for changes in oxygen activity. The fluorescence signal seen by the PMT varies over a factor of 3, being highest at 0 oxygen activity and lowest at atmospheric oxygen activity. The device exhibits a 63 % response time of less than 1 second for gases and less than 10 seconds for oxygen dissolved in water. The noise floor of the sensor is approximately 1%. The present embodiment of the device was designed to allow the sensor to operate in the marine environment. The optical components, computer, batteries, and power supply circuitry are mounted on a rack that is enclosed in a pressure housing. The immobilized fluorophore is exposed to sea water. The light travels along the PCS rod, through a pressure seal, to the rest of the system. Present investigations are centered around long term stability of the fluorophore and constituents of the real ocean that will interfere with the quenching mechanism.

  12. Methanex, Hoechst Celanese dissolve methanol partnership

    SciTech Connect

    Morris, G.D.L.

    1993-03-31

    One of the many joint venture alliances recently announced in the petrochemical sector is ending in divorce. Hoechst Celanese Chemical (Dallas) and Methanex Corp. (Vancouver) are in the process of dissolving the partnership they had formed to restart Hoechst Celanese's methanol plant at Clear Lake, TX. Hoechst Celanese says it is actively seeking replacement partners and has several likely prospects, while Methanex is concentrating on its other ventures. Those include its just-completed acquisition of Fletcher Challenge's (Auckland, NZ) methanol business and a joint venture with American Cyanamid to convert an ammonia plant at Fortier, LA to methanol. Methanex will still be the world's largest producer of methanol. Officially, the negotiations between Methanex and Hoechst Celanese just broke down over the last month or so,' says Steve Yurich, operations manager for the Clear Lake plant. Market sources, however, say that Methanex found itself with too many irons in the fire' and pulled out before it ran into financial or perhaps even antitrust difficulties.

  13. Composition of dissolved organic matter in groundwater

    NASA Astrophysics Data System (ADS)

    Longnecker, Krista; Kujawinski, Elizabeth B.

    2011-05-01

    Groundwater constitutes a globally important source of freshwater for drinking water and other agricultural and industrial purposes, and is a prominent source of freshwater flowing into the coastal ocean. Therefore, understanding the chemical components of groundwater is relevant to both coastal and inland communities. We used electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to examine dissolved organic compounds in groundwater prior to and after passage through a sediment-filled column containing microorganisms. The data revealed that an unexpectedly high proportion of organic compounds contained nitrogen and sulfur, possibly due to transport of surface waters from septic systems and rain events. We matched 292 chemical features, based on measured mass:charge ( m/z) values, to compounds stored in the Kyoto Encyclopedia of Genes and Genomes (KEGG). A subset of these compounds (88) had only one structural isomer in KEGG, thus supporting tentative identification. Most identified elemental formulas were linked with metabolic pathways that produce polyketides or with secondary metabolites produced by plants. The presence of polyketides in groundwater is notable because of their anti-bacterial and anti-cancer properties. However, their relative abundance must be quantified with appropriate analyses to assess any implications for public health.

  14. Dissolved methane in Indian freshwater reservoirs.

    PubMed

    Narvenkar, G; Naqvi, S W A; Kurian, S; Shenoy, D M; Pratihary, A K; Naik, H; Patil, S; Sarkar, A; Gauns, M

    2013-08-01

    Emission of methane (CH4), a potent greenhouse gas, from tropical reservoirs is of interest because such reservoirs experience conducive conditions for CH4 production through anaerobic microbial activities. It has been suggested that Indian reservoirs have the potential to emit as much as 33.5 MT of CH4 per annum to the atmosphere. However, this estimate is based on assumptions rather than actual measurements. We present here the first data on dissolved CH4 concentrations from eight freshwater reservoirs in India, most of which experience seasonal anaerobic conditions and CH4 buildup in the hypolimnia. However, strong stratification prevents the CH4-rich subsurface layers to ventilate CH4 directly to the atmosphere, and surface water CH4 concentrations in these reservoirs are generally quite low (0.0028-0.305 μM). Moreover, only in two small reservoirs substantial CH4 accumulation occurred at depths shallower than the level where water is used for power generation and irrigation, and in the only case where measurements were made in the outflowing water, CH4 concentrations were quite low. In conjunction with short periods of CH4 accumulation and generally lower concentrations than previously assumed, our study implies that CH4 emission from Indian reservoirs has been greatly overestimated. PMID:23397538

  15. Salicylhydroxamic acid (SHAM) inhibition of the dissolved inorganic carbon concentrating process in unicellular green algae

    SciTech Connect

    Goyal, A.; Tolbert, N.E. )

    1990-03-01

    Rates of photosynthetic O{sub 2} evolution, for measuring K{sub 0.5}(CO{sub 2} + HCO{sub 3}{sup {minus}}) at pH 7, upon addition of 50 micromolar HCO{sub 3}{sup {minus}} to air-adapted Chlamydomonas, Dunaliella, or Scenedesmus cells, were inhibited up to 90% by the addition of 1.5 to 4.0 millimolar salicylhydroxamic acid (SHAM) to the aqueous medium. The apparent K{sub i}(SHAM) for Chlamydomonas cells was about 2.5 millimolar, but due to low solubility in water effective concentrations would be lower. Salicylhydroxamic acid did not inhibit oxygen evolution or accumulation of bicarbonate by Scenedesmus cells between pH 8 to 11 or by isolated intact chloroplasts from Dunaliella. Thus, salicylhydroxamic acid appears to inhibit CO{sub 2} uptake, whereas previous results indicate that vanadate inhibits bicarbonate uptake. These conclusions were confirmed by three test procedures with three air-adapted algae at pH 7. Salicylhydroxamic acid inhibited the cellular accumulation of dissolved inorganic carbon, the rate of photosynthetic O{sub 2} evolution dependent on low levels of dissolved inorganic carbon (50 micromolar NaHCO{sub 3}), and the rate of {sup 14}CO{sub 2} fixation with 100 micromolar ({sup 14}C)HCO{sub 3}{sup {minus}}. Salicylhydroxamic acid inhibition of O{sub 2} evolution and {sup 14}CO{sub 2}-fixation was reversed by higher levels of NaHCO{sub 3}. Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO{sub 2} accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

  16. Dissolved P in streams in dry years and wet years

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dissolved phosphorus (P) has often been identified as the nutrient of concern in lakes, reservoirs, and streams especially where there is evidence of eutrophication. We analyzed contiguous-spatial and temporal variability of dissolved P [soluble reactive P (SRP)] stream concentrations during times ...

  17. Black Carbon in Estuarine and Coastal Ocean Dissolved Organic Matter

    NASA Technical Reports Server (NTRS)

    Mannino, Antonio; Harvey, H. Rodger

    2003-01-01

    Analysis of high-molecular-weight dissolved organic matter (DOM) from two estuaries in the northwest Atlantic Ocean reveals that black carbon (BC) is a significant component of previously uncharacterized DOM, suggesting that river-estuary systems are important exporters of recalcitrant dissolved organic carbon to the ocean.

  18. Effects of ph, carbonate, orthophosphate, and redox potential on cuprosolvency

    SciTech Connect

    Schock, M.R.; Lytle, D.A.; Clement, J.A.

    1995-12-01

    A comprehensive solubility model for copper in drinking water has been developed, that is consistent with available data for copper dissolution and passivation in drinking water systems. Copper solubility (cuprosolvency) is greatly affected by the redox conditions of the systems. The concentration of Cu(I) is dominated by Cu{sub 2}O(s) or CuOH(s) solid phases, plus soluble aqueous ammonia and chloride complexes. In new piping, the concentration of Cu(II) is mainly governed by Cu(OH){sub 2}(s) (cupric hydroxide), rather than CuO(s) (tenorite) or Cu{sub 2}(OH){sub 2}CO{sub 3}(s)(malachite). Complexation of Cu(II) by DIC and hydroxide ion is extremely important. Increases in DIC are predicted to cause significant increases in copper solubility in the pH range of 7.5--10. Utilities may trade off increasing cuprosolvency by DIC addition for ensuring adequate buffering intensity in the finished water. Sufficient dosages of orthophosphate in the pH range of 6.5 to 7.5 may reduce cuprosolvency under oxidizing conditions. Sulfate may decrease cuprosolvency under some conditions, or may interfere with the formation of cupric hydroxide films under mildly alkaline conditions. Dissolved oxygen and chlorine residual play complicated roles in determining copper concentrations after various standing times. Frequently, 48--72 hours are necessary to reach equilibrium levels of copper in disinfected systems.

  19. Which Firms Want PhDs? An Analysis of the Determinants of the Demand

    ERIC Educational Resources Information Center

    Garcia-Quevedo, Jose; Mas-Verdu, Francisco; Polo-Otero, Jose

    2012-01-01

    PhD graduates hold the highest education degree, are trained to conduct research and can be considered a key element in the creation, commercialization and diffusion of innovations. The impact of PhDs on innovation and economic development takes place through several channels such as the accumulation of scientific capital stock, the enhancement of…

  20. Career Outcomes in a Matched Sample of Men and Women Ph.Ds. An Analytical Report.

    ERIC Educational Resources Information Center

    Ahren, Nancy C.; Scott, Elizabeth L.

    A study analyzed the career outcomes of men and women Ph.D.s Based on a sample survey of approximately 50,000 Ph.D scientists, engineers, and humanists, conducted in 1979 by the National Research Council, the study examined 5164 triads consisting of one woman and two men who were matched as nearly as possible according to selected background…

  1. SOIL REDOX AND PH EFFECTS ON METHANE PRODUCTION IN A FLOODED RICE SOIL

    EPA Science Inventory

    Methane formation in soil is a microbiological process controlled by many factors. f them soil redox potential (Eh) and soil pH are considered as critical controls. aboratory incubation experiment was conducted to study the critical initiation soil Eh, the optimum soil pH and the...

  2. Egg quality in fish: pH of stripped eggs can predict catfish hatching success

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was conducted to determine the feasibility of measuring the pH of stripped unfertilized channel catfish eggs to predict the hatching success of channel x blue hybrid catfish eggs. A significant correlation was established between the ovarian fluid pH of stripped eggs and subsequent hatch...

  3. Nutrient Availability from Douglas Fir Bark in Response to Substrate pH

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two studies were conducted to determine the influence of substrate pH on nutrient availability in douglas fir bark (DFB). Douglas fir bark was amended with either calcium carbonate (CaCO3) or calcium hydroxide [Ca(OH)2] at 13 rates to generate substrates with low to high pH. A non-amended control ...

  4. Which Firms Want PhDs? An Analysis of the Determinants of the Demand

    ERIC Educational Resources Information Center

    Garcia-Quevedo, Jose; Mas-Verdu, Francisco; Polo-Otero, Jose

    2012-01-01

    PhD graduates hold the highest education degree, are trained to conduct research and can be considered a key element in the creation, commercialization and diffusion of innovations. The impact of PhDs on innovation and economic development takes place through several channels such as the accumulation of scientific capital stock, the enhancement of

  5. DIGESTION PRODUCTS OF THE PH20 HYALURONIDASE INHIBIT REMYELINATION

    PubMed Central

    Preston, Marnie; Gong, Xi; Su, Weiping; Matsumoto, Steven G.; Banine, Fatima; Winkler, Clayton; Foster, Scott; Xing, Rubing; Struve, Jaime; Dean, Justin; Baggenstoss, Bruce; Weigel, Paul H.; Montine, Thomas J.; Back, Stephen A.; Sherman, Larry S.

    2012-01-01

    OBJECTIVE Oligodendrocyte progenitor cells (OPCs) recruited to demyelinating lesions often fail to mature into oligodendrocytes (OLs) that remyelinate spared axons. The glycosaminoglycan hyaluronan (HA) accumulates in demyelinating lesions and has been implicated in the failure of OPC maturation and remyelination. We tested the hypothesis that OPCs in demyelinating lesions express a specific hyaluronidase, and that digestion products of this enzyme inhibit OPC maturation. METHODS Mouse OPCs grown in vitro were analyzed for hyaluronidase expression and activity. Gain of function studies were used to define the hyaluronidases that blocked OPC maturation. Mouse and human demyelinating lesions were assessed for hyaluronidase expression. Digestion products from different hyaluronidases and a hyaluronidase inhibitor were tested for their effects on OPC maturation and functional remyelination in vivo. RESULTS OPCs demonstrated hyaluronidase activity in vitro and expressed multiple hyaluronidases including HYAL1, HYAL2, and PH20. HA digestion by PH20 but not other hyaluronidases inhibited OPC maturation into OLs. In contrast, inhibiting HA synthesis did not influence OPC maturation. PH20 expression was elevated in OPCs and reactive astrocytes in both rodent and human demyelinating lesions. HA-digestion products generated by the PH20 hyaluronidase but not another hyaluronidase inhibited remyelination following lysolecithin-induced demyelination. Inhibition of hyaluronidase activity lead to increased OPC maturation and promoted increased conduction velocities through lesions. INTERPRETATION We determined that PH20 is elevated in demyelinating lesions and that increased PH20 expression is sufficient to inhibit OPC maturation and remyelination. Pharmacological inhibition of PH20 may therefore be an effective way to promote remyelination in multiple sclerosis and related conditions. PMID:23463525

  6. A multi-scale comparison of dissolved Al, Fe and S in a boreal acid sulphate soil.

    PubMed

    Virtanen, Seija; Simojoki, Asko; Rita, Hannu; Toivonen, Janne; Hartikainen, Helinä; Yli-Halla, Markku

    2014-11-15

    Acid sulphate (AS) soils are most prevalent in the tropics, but the acidic discharge from cultivated AS soils also threatens water bodies under boreal conditions. Feasible options to reduce the acid load are needed. In this study, the groundwater of an AS field was monitored for 3.5 years, and the efficiency of waterlogging in mitigating the environmental risks caused by acidic discharge was investigated in a 2.5-year experiment with 10 monolithic lysimeters taken from the same field. In order to unravel the transferability of the results from lysimeters to the field scale, the Al, Fe and S concentrations in discharge water from the lysimeters were compared with those in the groundwater of the AS field (pedon and field scale), and in pore water (pedon and horizon scale). In the waterlogged bare lysimeters (HWB), the Al, Fe and S concentrations in discharge waters were broadly similar to those measured in the groundwater and followed the changes in the pore water. In the waterlogged cropped (reed canary grass, Phalaris arundinacea) lysimeters (HWC), in contrast, the discharge waters were markedly higher in Fe and lower in Al than the groundwater in the field. This outcome was attributable to the reduction of Fe(3+) to the more soluble Fe(2+) and the reduction-induced increase in pH, which enhanced the formation of Al(3+) hydroxy species. Lowering of the water table (LWC) caused soil ripening, which resulted in increased saturated hydraulic conductivity and porosity and enhanced the oxidation of sulphidic materials and acid formation. The responses of Al, Fe and S in drainage waters from HWC and LWC lysimeters resembled previous findings in AS soils. Based on this and the similarity between dissolved element concentrations in the discharge water of HWB lysimeters and groundwater in the field, we conclude that our monolithic lysimeters yielded realistic results concerning the efficiency of various methods in mitigating environmental risks related to cultivated AS soils. PMID:25203826

  7. Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

    USGS Publications Warehouse

    Shellenbarger, Gregory; Schoellhamer, David H.; Morgan, Tara L.; Takekawa, John Y.; Athearn, Nicole D.; Henderson, Kathleen D.

    2008-01-01

    Initial restoration of former salt evaporation ponds under the South Bay Salt Pond Restoration Project in San Francisco Bay included the changing of water-flow patterns and the monitoring of water quality of discharge waters from the ponds. Low dissolved oxygen (DO) concentrations became evident in discharge waters when the ponds first were opened in 2004. This was a concern, because of the potential for low-DO pond discharge to decrease the DO concentrations in the sloughs that receive water from the ponds. However, as of summer 2007, only limited point-measurements of DO concentrations had been made in the receiving sloughs adjacent to the discharge ponds. In this report, we describe two short studies aimed at understanding the natural variability of slough DO and the effect of pond discharge on the DO concentrations in the sloughs. Pond A3W (a discharge pond) and the adjacent Guadalupe Slough were instrumented in August and September 2007 to measure DO, temperature, conductivity, and pH. In addition, Mowry and Newark Sloughs were instrumented during the August study to document DO variability in nearby sloughs that were unaffected by pond discharge. The results showed that natural tidal variability in the slough appeared to dominate and control the slough DO concentrations. Water-quality parameters between Guadalupe Slough and Mowry and Newark Sloughs could not be directly compared because deployment locations were different distances from the bay. Pond-discharge water was identified in Guadalupe Slough using the deployed instruments, but, counter to the previous assumption, the pond discharge, at times, increased DO concentrations in the slough. The effects of altering the volume of pond discharge were overwhelmed by natural spring-neap tidal variability in the slough. This work represents a preliminary investigation by the U.S. Geological Survey of the effects of pond discharge on adjacent sloughs, and the results will be used in designing a comprehensive DO study to determine normal variability for this region.

  8. Electrostatic Spraying With Conductive Liquids

    NASA Technical Reports Server (NTRS)

    Kosmo, Joseph J.; Dawn, Frederic S.; Erlandson, Robert E.; Atkins, Loren E.

    1989-01-01

    Thin, uniform polymer coatings applied in water base normally impossible to charge. Electrostatic sprayer modified so applies coatings suspended or dissolved in electrically conductive liquids. Nozzle and gun constructed of nonconductive molded plastic. Liquid passageway made long enough electrical leakage through it low. Coaxial hose for liquid built of polytetrafluoroethylene tube, insulating sleeve, and polyurethane jacket. Sprayer provided with insulated seal at gun-to-hose connection, nonconductive airhose, pressure tank electrically isolated from ground, and special nozzle electrode. Supply of atomizing air reduced so particle momentum controlled by electrostatic field more effectively. Developed to apply water-base polyurethane coating to woven, shaped polyester fabric. Coating provides pressure seal for fabric, which is part of spacesuit. Also useful for applying waterproof, decorative, or protective coatings to fabrics for use on Earth.

  9. [Regulation effects of tourmaline on seawater pH value].

    PubMed

    Xia, Meisheng; Zhang, Hongmei; Hu, Caihong; Xu, Zirong

    2005-10-01

    In this paper, chemical analysis, X-ray diffraction and atomic force microscopy were employed to examine the characteristics of tourmaline produced in east Inner Mongolia Autonomous Region, and batch experiments were conducted to study its regulation effects on seawater pH value. The factors affecting the regulation, such as the dosage of tourmaline and the salinity and initial pH value of seawater, were also studied. The results showed that tourmaline could regulate the seawater pH value from its initial 3 and 10 to 7.1 and 8.9, respectively, and the regulation effect was greater in the seawater with lower salinity, e.g., after 120 minutes treatment, the initial pH value (5.0) of the seawater with a salinity of 5, 10, 15, 20 and 35 was increased by 3.24, 3.16, 3.06, 2.99 and 2.85 unit, respectively. Tourmaline had little effect on seawater conductivity. This study would provide an experimental base for the application of tourmaline in aquaculture. PMID:16422525

  10. pH dependence of iron photoreduction in a rocky mountain stream affected by acid mine drainage

    USGS Publications Warehouse

    McKnight, Diane M.; Kimball, B.A.; Runkel, R.L.

    2001-01-01

    The redox speciation of dissolved iron and the transport of iron in acidic, metal-enriched streams is controlled by precipitation and dissolution of iron hydroxides, by photoreduction of dissolved ferric iron and hydrous iron oxides, and by oxidation of the resulting dissolved ferrous iron. We examined the pH dependence of these processes in an acidic mine-drainage stream, St Kevin Gulch, Colorado, by experimentally increasing the pH of the stream from about 4.0 to 6.5 and following the downstream changes in iron species. We used a solute transport model with variable flow to evaluate biogeochemical processes controlling downstream transport. We found that at pH 6.4 there was a rapid and large initial loss of ferrous iron concurrent with the precipitation of aluminium hydroxide. Below this reach, ferrous iron was conservative during the morning but there was a net downstream loss of ferrous iron around noon and in the afternoon. Calculation of net oxidation rates shows that the noontime loss rate was generally much faster than rates for the ferrous iron oxidation at pH 6 predicted by Singer and Stumm (1970. Science 167: 1121). The maintenance of ferrous iron concentrations in the morning is explained by the photoreduction of photoreactive ferric species, which are then depleted by noon. Copyright ?? 2001 John Wiley & Sons, Ltd.

  11. pH dependence of iron photoreduction in a rocky mountain stream affected by acid mine drainage

    NASA Astrophysics Data System (ADS)

    McKnight, Diane M.; Kimball, Briant A.; Runkel, Robert L.

    2001-07-01

    The redox speciation of dissolved iron and the transport of iron in acidic, metal-enriched streams is controlled by precipitation and dissolution of iron hydroxides, by photoreduction of dissolved ferric iron and hydrous iron oxides, and by oxidation of the resulting dissolved ferrous iron. We examined the pH dependence of these processes in an acidic mine-drainage stream, St Kevin Gulch, Colorado, by experimentally increasing the pH of the stream from about 4·0 to 6·5 and following the downstream changes in iron species. We used a solute transport model with variable flow to evaluate biogeochemical processes controlling downstream transport. We found that at pH 6·4 there was a rapid and large initial loss of ferrous iron concurrent with the precipitation of aluminium hydroxide. Below this reach, ferrous iron was conservative during the morning but there was a net downstream loss of ferrous iron around noon and in the afternoon. Calculation of net oxidation rates shows that the noontime loss rate was generally much faster than rates for the ferrous iron oxidation at pH 6 predicted by Singer and Stumm (1970. Science 167: 1121). The maintenance of ferrous iron concentrations in the morning is explained by the photoreduction of photoreactive ferric species, which are then depleted by noon.

  12. Macroalgae contribute to nested mosaics of pH variability in a subarctic fjord

    NASA Astrophysics Data System (ADS)

    Krause-Jensen, D.; Duarte, C. M.; Hendriks, I. E.; Meire, L.; Blicher, M. E.; Marbà, N.; Sejr, M. K.

    2015-08-01

    The Arctic Ocean is considered the most vulnerable ecosystem to ocean acidification, and large-scale assessments of pH and the saturation state for aragonite (Ωarag) have led to the notion that the Arctic Ocean is already close to a corrosive state. In high-latitude coastal waters the regulation of pH and Ωarag is, however, far more complex than offshore because increased biological activity and input of glacial meltwater affect pH. Effects of ocean acidification on calcifiers and non-calcifying phototrophs occupying coastal habitats cannot be derived from extrapolation of current and forecasted offshore conditions, but they require an understanding of the regimes of pH and Ωarag in their coastal habitats. To increase knowledge of the natural variability in pH in the Arctic coastal zone and specifically to test the influence of benthic vegetated habitats, we quantified pH variability in a Greenland fjord in a nested-scale approach. A sensor array logging pH, O2, PAR, temperature and salinity was applied on spatial scales ranging from kilometre scale across the horizontal extension of the fjord; to 100 m scale vertically in the fjord, 10-100 m scale between subtidal habitats with and without kelp forests and between vegetated tidal pools and adjacent vegetated shores; and to centimetre to metre scale within kelp forests and millimetre scale across diffusive boundary layers of macrophyte tissue. In addition, we assessed the temporal variability in pH on diurnal and seasonal scales. Based on pH measurements combined with point samples of total alkalinity, dissolved inorganic carbon and relationships to salinity, we also estimated variability in Ωarag. Results show variability in pH and Ωarag of up to 0.2-0.3 units at several scales, i.e. along the horizontal and vertical extension of the fjord, between seasons and on a diel basis in benthic habitats and within 1 m3 of kelp forest. Vegetated intertidal pools exhibited extreme diel pH variability of > 1.5 units and macrophyte diffusive boundary layers a pH range of up to 0.8 units. Overall, pelagic and benthic metabolism was an important driver of pH and Ωarag producing mosaics of variability from low levels in the dark to peak levels at high irradiance generally appearing favourable for calcification. We suggest that productive coastal environments may form niches of high pH in a future acidified Arctic Ocean.

  13. Complexation of Arsenite with Dissolved Organic Matter: Conditional Distribution Coefficients and Apparent Stability Constants

    PubMed Central

    Liu, Guangliang; Cai, Yong

    2010-01-01

    The complexation of arsenic (As) with dissolved organic matter (DOM), although playing an important role in regulating As mobility and transformation, is poorly characterized, as evidenced by scarce reporting of fundamental parameters of As-DOM complexes. The complexation of arsenite (AsIII) with Aldrich humic acid (HA) at different pHs was characterized using a recently developed analytical technique to measure both free and DOM-bound As. Conditional distribution coefficient (KD), describing capacity of DOM in binding AsIII from the mass perspective, and apparent stability constant (Ks), describing stability of resulting AsIII-DOM complexes, were calculated to characterize AsIII-DOM complexation. Log KD of AsIII ranged from 3.7 to 2.2 (decreasing with increase of As/DOM ratio) at pH 5.2, from 3.6 to 2.6 at pH 7, and from 4.3 to 3.2 at pH = 9.3, respectively. Two-site ligand binding models can capture the heterogeneity of binding sites and be used to calculate Ks by classifying the binding sites into strong (S1) and weak (S2) groups. Log Ks for S1 sites are 7.0, 6.5, and 5.9 for pH 5.2, 7, and 9.3, respectively, which are approximately 1–2 orders of magnitude higher than for weak S2 sites. The results suggest that AsIII complexation with DOM increases with pH, as evidenced by significant spikes in concentrations of DOM-bound AsIII and in KD values at pH 9.3. In contrary to KD, log Ks decreased with pH, in particular for S1 sites, probably due to the presence of negatively charged H2AsO3− and the involvement of metal-bridged AsIII-DOM complexation at pH 9.3. PMID:20801484

  14. Bioavailability and characterization of dissolved organic nitrogen and dissolved organic phosphorus in wastewater effluents.

    PubMed

    Qin, Chao; Liu, Haizhou; Liu, Lei; Smith, Scott; Sedlak, David L; Gu, April Z

    2015-04-01

    There is still a great knowledge gap in the understanding of characteristics and bioavailability of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) in wastewater effluents, which surmise implications related to both discharge regulation and treatment practice. In this study, we simultaneously investigated the characteristics and bioavailability of both DON and DOP, with separated hydrophilic versus hydrophobic fractions, in highly-treated wastewater effluents for the first time. The tertiary effluents from two wastewater treatment plants were separated into two fractions by XAD-8 resin coupled with anion exchange resin based on the hydrophobicity. Results showed that the majority of DON was present in hydrophilic forms while more DOP existed in hydrophobic forms. Hydrophilic DON contributed to 64.0%-72.2% of whole DON, while hydrophobic DOP accounted for 61.4%-80.7% of total DOP for the two plants evaluated. The effluents and their fractions were then subject to bioavailability assay based on 14-day algae growth. The results indicated that majority (~73-75%) of the effluent DOP, particularly the hydrophobic fraction with lower C/P ratio was more likely to be bioavailable for algal growth. The bioavailable fraction of DON varied widely (28%-61%) for the two plants studied and the hydrophilic fraction with lower C/N ratio seemed to exhibit higher bioavailability than the hydrophobic portion. The differences in bioavailable DON and DOP distributions of effluents from those two plants could be attributed to different receiving effluent compositions and wastewater treatment processes. In addition, fluorescence excitation-emission matrices (EEMs) combined with parallel factor analysis (PARAFAC) were used to characterize the dissolved organic matter (DOM) in wastewater effluent, which provided insights into the nature of organic matter in wastewater samples with different characteristics and originating sources. PMID:25527968

  15. Dissolved organic carbon and chromophoric dissolved organic matter properties of rivers in the USA

    USGS Publications Warehouse

    Spencer, Robert G.M.; Butler, Kenna D.; Aiken, George R.

    2012-01-01

    Dissolved organic carbon (DOC) concentration and chromophoric dissolved organic matter (CDOM) parameters were measured over a range of discharge in 30 U.S. rivers, covering a diverse assortment of fluvial ecosystems in terms of watershed size and landscape drained. Relationships between CDOM absorption at a range of wavelengths (a254, a350, a440) and DOC in the 30 watersheds were found to correlate strongly and positively for the majority of U.S. rivers. However, four rivers (Colorado, Colombia, Rio Grande and St. Lawrence) exhibited statistically weak relationships between CDOM absorption and DOC. These four rivers are atypical, as they either drain from the Great Lakes or experience significant impoundment of water within their watersheds, and they exhibited values for dissolved organic matter (DOM) parameters indicative of autochthonous or anthropogenic sources or photochemically degraded allochthonous DOM and thus a decoupling between CDOM and DOC. CDOM quality parameters in the 30 rivers were found to be strongly correlated to DOM compositional metrics derived via XAD fractionation, highlighting the potential for examining DOM biochemical quality from CDOM measurements. This study establishes the ability to derive DOC concentration from CDOM absorption for the majority of U.S. rivers, describes characteristics of riverine systems where such an approach is not valid, and emphasizes the possibility of examining DOM composition and thus biogeochemical function via CDOM parameters. Therefore, the usefulness of CDOM measurements, both laboratory-based analyses and in situ instrumentation, for improving spatial and temporal resolution of DOC fluxes and DOM dynamics in future studies is considerable in a range of biogeochemical studies.

  16. Effects of Dissolved Carbonate on Arsenate Adsorption and Surface Speciation at the Hematite-Water Interface

    USGS Publications Warehouse

    Arai, Y.; Sparks, D.L.; Davis, J.A.

    2004-01-01

    Effects of dissolved carbonate on arsenate [As(V)] reactivity and surface speciation at the hematite-water interface were studied as a function of pH and two different partial pressures of carbon dioxide gas [PCO2 = 10 -3.5 atm and ???0; CO2-free argon (Ar)] using adsorption kinetics, pseudo-equilibrium adsorption/titration experiments, extended X-ray absorption fine structure spectroscopic (EXAFS) analyses, and surface complexation modeling. Different adsorbed carbonate concentrations, due to the two different atmospheric systems, resulted in an enhanced and/or suppressed extent of As(V) adsorption. As(V) adsorption kinetics [4 g L -1, [As(V)]0 = 1.5 mM and / = 0.01 M NaCl] showed carbonate-enhanced As(V) uptake in the air-equilibrated systems at pH 4 and 6 and at pH 8 after 3 h of reaction. Suppressed As(V) adsorption was observed in the air-equilibrated system in the early stages of the reaction at pH 8. In the pseudo-equilibrium adsorption experiments [1 g L-1, [As(V)] 0 = 0.5 mM and / = 0.01 M NaCl], in which each pH value was held constant by a pH-stat apparatus, effects of dissolved carbonate on As(V) uptake were almost negligible at equilibrium, but titrant (0.1 M HCl) consumption was greater in the air-equilibrated systems (PCO2 = 10-3.5 atm)than in the CO2-free argon system at pH 4-7.75. The EXAFS analyses indicated that As(V) tetrahedral molecules were coordinated on iron octahedral via bidentate mononuclear (???2.8 A??) and bidentate binuclear (???3.3 A??) bonding at pH 4.5-8 and loading levels of 0.46-3.10 ??M m-2. Using the results of the pseudoequilibrium adsorption data and the XAS analyses, the pH-dependent As(V) adsorption under the PCO2 = 10-3.5 atm and the CO2-free argon system was modeled using surface complexation modeling, and the results are consistent with the formation of nonprotonated bidentate surface species at the hematite surfaces. The results also suggest that the acid titrant consumption was strongly affected by changes to electrical double-layer potentials caused by the adsorption of carbonate in the air-equilibrated system. Overall results suggest that the effects of dissolved carbonate on As(V) adsorption were influenced by the reaction conditions [e.g., available surface sites, initial As(V) concentrations, and reaction times]. Quantifying the effects of adsorbed carbonate may be important in predicting As(V) transport processes in groundwater, where iron oxide-coated aquifer materials are exposed to seasonally fluctuating partial pressures of CO2(g).

  17. Distribution of dissolved pesticides and other water quality constituents in small streams, and their relation to land use, in the Willamette River Basin, Oregon, 1996

    USGS Publications Warehouse

    Anderson, Chauncey W.; Wood, Tamara M.; Morace, Jennifer L.

    1997-01-01

    Water quality samples were collected at sites in 16 randomly selected agricultural and 4 urban subbasins as part of Phase III of the Willamette River Basin Water Quality Study in Oregon during 1996. Ninety-five samples were collected and analyzed for suspended sediment, conventional constituents (temperature, dissolved oxygen, pH, specific conductance, nutrients, biochemical oxygen demand, and bacteria) and a suite of 86 dissolved pesticides. The data were collected to characterize the distribution of dissolved pesticide concentrations in small streams (drainage areas 2.6? 13 square miles) throughout the basin, to document exceedances of water quality standards and guidelines, and to identify the relative importance of several upstream land use categories (urban, agricultural, percent agricultural land, percent of land in grass seed crops, crop diversity) and seasonality in affecting these distributions. A total of 36 pesticides (29 herbicides and 7 insecticides) were detected basinwide. The five most frequently detected compounds were the herbicides atrazine (99% of samples), desethylatrazine (93%), simazine (85%), metolachlor (85%), and diuron (73%). Fifteen compounds were detected in 12?35% of samples, and 16 compounds were detected in 1?9% of samples. Water quality standards or criteria were exceeded more frequently for conventional constituents than for pesticides. State of Oregon water quality standards were exceeded at all but one site for the indicator bacteria E. coli, 3 sites for nitrate, 10 sites for water temperature, 4 sites for dissolved oxygen, and 1 site for pH. Pesticide concentrations, which were usually less than 1 part per billion, exceeded State of Oregon or U.S. Environmental Protection Agency aquatic life toxicity criteria only for chlorpyrifos, in three samples from one site; such criteria have been established for only two other detected pesticides. However, a large number of unusually high concentrations (1?90 parts per billion) were detected, indicating that pesticides in the runoff sampled in these small streams were more highly concentrated than in the larger streams sampled in previous studies. These pulses could have had short term toxicological implications for the affected streams; however, additional toxicological assessment of the detected pesticides was limited because of a lack of available information on the response of aquatic life to the observed pesticide concentrations. Six pesticides, including atrazine, diuron, and metolachlor, had significantly higher (p<0.08 for metolachlor, p<0.05 for the other five) median concentrations at agricultural sites than at urban sites. Five other compounds ?carbaryl, diazinon, dichlobenil, prometon, and tebuthiuron?had significantly higher (p<0.05) concentrations at the urban sites than at the agricultural sites. Atrazine, metolachlor, and diuron also had significantly higher median concentrations at southern agricultural sites (dominated by grass seed crops) than northern agricultural sites. Other compounds that had higher median concentrations in the south included 2,4-D and metribuzin, which are both used on grass seed crops, and triclopyr, bromacil, and pronamide. A cluster analysis of the data grouped sites according to their pesticide detections in a manner that was almost identical to a grouping made solely on the basis of their upstream land use patterns (urban, agricultural, crop diversity, percentage of basin in agricultural production). In this way inferences about pesticide associations with different land uses could be drawn, illustrating the strength of these broad land use categories in determining the types of pesticides that can be expected to occur. Among the associations observed were pesticides that occurred at a group of agricultural sites, but which have primarily noncropland uses such as vegetation control along rights-of-way. Also, the amount of forested land in a basin was negatively associated with pesticide occurrence, sugges

  18. Dissolved organic carbon fluxes under bare soil.

    PubMed

    Mertens, Jan; Vanderborght, Jan; Kasteel, Roy; Pütz, Thomas; Merckx, Roel; Feyen, Jan; Smolders, Erik

    2007-01-01

    The flux of dissolved organic carbon (DOC) in soil facilitates transport of nutrients and contaminants in soil. There is little information on DOC fluxes and the relationship between DOC concentration and water flux in agricultural soils. The DOC fluxes and concentrations were measured during 2.5 yr using 30 automatic equilibrium tension plate lysimeters (AETPLs) at 0.4 m and 30 AETPLs at 1.20-m depth in a bare luvisol, previously used as an arable soil. Average annual DOC fluxes of the 30 AETPLS were 4.9 g C m(-2) y(-1) at 0.4 m and 2.4 g C m(-2) y(-1) at 1.2 m depth. The average leachate DOC concentrations were 17 mg C L(-1) (0.4 m) and 9 mg C L(-1) (1.2 m). The DOC concentrations were unrelated to soil moisture content or average temperature and rarely dropped below 9 mg C L(-1) (0.4 m) and 5 mg C L(-1) (1.2 m). The variability in cumulative DOC fluxes among the plates was positively related to leachate volume and not to average DOC concentrations at both depths. This suggests that water fluxes are the main determinants of spatial variability in DOC fluxes. However, the largest DOC concentrations were inversely proportional to the mean water velocity between succeeding sampling periods, suggesting that the maximal net DOC mobilization rate in the topsoil is limited. Elevated DOC concentrations, up to 90 mg C L(-1), were only observed at low water velocities, reducing the risks of DOC-facilitated transport of contaminants to groundwater. The study emphasizes that water flux and velocity are important parameters for DOC fluxes and concentrations. PMID:17332264

  19. Scavenging dissolved oxygen via acoustic droplet vaporization.

    PubMed

    Radhakrishnan, Kirthi; Holland, Christy K; Haworth, Kevin J

    2016-07-01

    Acoustic droplet vaporization (ADV) of perfluorocarbon emulsions has been explored for diagnostic and therapeutic applications. Previous studies have demonstrated that vaporization of a liquid droplet results in a gas microbubble with a diameter 5-6 times larger than the initial droplet diameter. The expansion factor can increase to a factor of 10 in gassy fluids as a result of air diffusing from the surrounding fluid into the microbubble. This study investigates the potential of this process to serve as an ultrasound-mediated gas scavenging technology. Perfluoropentane droplets diluted in phosphate-buffered saline (PBS) were insonified by a 2MHz transducer at peak rarefactional pressures lower than and greater than the ADV pressure amplitude threshold in an in vitro flow phantom. The change in dissolved oxygen (DO) of the PBS before and after ADV was measured. A numerical model of gas scavenging, based on conservation of mass and equal partial pressures of gases at equilibrium, was developed. At insonation pressures exceeding the ADV threshold, the DO of air-saturated PBS decreased with increasing insonation pressures, dropping as low as 25% of air saturation within 20s. The decrease in DO of the PBS during ADV was dependent on the volumetric size distribution of the droplets and the fraction of droplets transitioned during ultrasound exposure. Numerically predicted changes in DO from the model agreed with the experimentally measured DO, indicating that concentration gradients can explain this phenomenon. Using computationally modified droplet size distributions that would be suitable for in vivo applications, the DO of the PBS was found to decrease with increasing concentrations. This study demonstrates that ADV can significantly decrease the DO in an aqueous fluid, which may have direct therapeutic applications and should be considered for ADV-based diagnostic or therapeutic applications. PMID:26964964

  20. High dissolved methane concentrations in the deep-water Ulleung Basin, East Sea of Korea

    NASA Astrophysics Data System (ADS)

    Ryu, Byong-Jae; Chun, Jong-Hwa

    2014-05-01

    As a part of the Korean National Gas Hydrate Program, a production test in the Ulleung Basin is planned to be performed in 2015. The targets are the gas hydrate-bearing sand reservoirs, which were found during the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) in 2010. To ensure a safe production test, an environmental program has been conducted by the Korea Institute of Geoscience and Mineral Resources (KIGAM) since 2012. This program includes a baseline survey using a KIGAM Seafloor Observation System (KISOS) and R/V TAMHAE II of KIGAM, development of a KIGAM Seafloor Monitoring System (KIMOS), and seafloor monitoring on various potential hazards associated with the dissociated gas from gas hydrates using the KIMOS during the production test. A survey for measuring the dissolved methane concentrations in the area at and nearby the gas hydrate production testing site was performed using R/V TAMHAE II and the KISOS. The water samples were also collected and analyzed to measure the dissolved methane concentrations by the SBE carousel water sampler installed in the KISOS and gas chromatography (GC) at KIGAM. The dissolved methane concentrations were also measured using a Frantech METS methane sensor installed in the KISOS. No dissolved methane anomaly was detected at the site where any evidence of gas hydrate presence has not been observed. On the other hand, the water analysis showed high dissolved methane concentrations at the water depth above and within the gas hydrate stability zone (GHSZ) at the site where gas hydrates were identified by drilling. However, these dissolved methane anomalies within the GHSZ were not detected by methane sensor. To examine these uncertain dissolved methane anomalies within the GHSZ, the water samples will be collected and analyzed once again, and the analytical result will be also carefully compared with the data collected using the methane sensor and deep ocean mass spectrometer (DOMS) developed by the University of Hawaii. The results of baseline surveys will be used to set up the KIMOS efficiently.

  1. Selective Sorption of Dissolved Organic Carbon Compounds by Temperate Soils

    PubMed Central

    Jagadamma, Sindhu; Mayes, Melanie A.; Phillips, Jana R.

    2012-01-01

    Background Physico-chemical sorption onto soil minerals is one of the major processes of dissolved organic carbon (OC) stabilization in deeper soils. The interaction of DOC on soil solids is related to the reactivity of soil minerals, the chemistry of sorbate functional groups, and the stability of sorbate to microbial degradation. This study was conducted to examine the sorption of diverse OC compounds (D-glucose, L-alanine, oxalic acid, salicylic acid, and sinapyl alcohol) on temperate climate soil orders (Mollisols, Ultisols and Alfisols). Methodology Equilibrium batch experiments were conducted using 0–100 mg C L−1 at a solid-solution ratio of 1∶60 for 48 hrs on natural soils and on soils sterilized by γ-irradiation. The maximum sorption capacity, Qmax and binding coefficient, k were calculated by fitting to the Langmuir model. Results Ultisols appeared to sorb more glucose, alanine, and salicylic acid than did Alfisols or Mollisols and the isotherms followed a non-linear pattern (higher k). Sterile experiments revealed that glucose and alanine were both readily degraded and/or incorporated into microbial biomass because the observed Qmax under sterile conditions decreased by 22–46% for glucose and 17–77% for alanine as compared to non-sterile conditions. Mollisols, in contrast, more readily reacted with oxalic acid (Qmax of 886 mg kg−1) and sinapyl alcohol (Qmax of 2031 mg kg−1), and no degradation was observed. The reactivity of Alfisols to DOC was intermediate to that of Ultisols and Mollisols, and degradation followed similar patterns as for Ultisols. Conclusion This study demonstrated that three common temperate soil orders experienced differential sorption and degradation of simple OC compounds, indicating that sorbate chemistry plays a significant role in the sorptive stabilization of DOC. PMID:23209742

  2. Response of Dissolved Organic Matter to Warming and Nitrogen Addition

    NASA Astrophysics Data System (ADS)

    Choi, J. H.; Nguyen, H.

    2014-12-01

    Dissolved Organic Matter (DOM) is a ubiquitous mixture of soluble organic components. Since DOM is produced from the terrestrial leachate of various soil types, soil may influence the chemistry and biology of freshwater through the input of leachate and run-off. The increased temperature by climate change could dramatically change the DOM characteristics of soils through enhanced decomposition rate and losses of carbon from soil organic matter. In addition, the increase in the N-deposition affects DOM leaching from soils by changing the carbon cycling and decomposition rate of soil decay. In this study, we conducted growth chamber experiments using two types of soil (wetland and forest) under the conditions of temperature increase and N-deposition in order to investigate how warming and nitrogen addition influence the characteristics of the DOM leaching from different soil types. This leachate controls the quantity and quality of DOM in surface water systems. After 10 months of incubation, the dissolved organic carbon (DOC) concentrations decreased for almost samples in the range of 7.6 to 87.3% (ANOVA, p<0.05). The specific UV absorption (SUVA) values also decreased for almost samples after the first 3 months and then increased gradually afterward in range of 3.3 to 108.4%. Both time and the interaction between time and the temperature had the statistically significant effects on the SUVA values (MANOVA, p<0.05). Humification index (HIX) showed the significant increase trends during the duration of incubation and temperature for almost the samples (ANOVA, p<0.05). Higher decreases in the DOC values and increases in HIX were observed at higher temperatures, whereas the opposite trend was observed for samples with N-addition. The PARAFAC results showed that three fluorescence components: terrestrial humic (C1), microbial humic-like (C2), and protein-like (C3), constituted the fluorescence matrices of soil samples. During the experiment, labile DOM from the soils was consumed and transformed into resistant aromatic carbon structures and less biodegradable components via microbial processes. Both time and the temperature presented the statistically significant effects on DOM characteristics of soil samples while the N-addition exhibited the insignificant difference among the samples.

  3. Hydrogeologic and landscape controls of dissolved inorganic nitrogen (DIN) and dissolved silica (DSi) fluxes in heterogeneous catchments

    NASA Astrophysics Data System (ADS)

    Onderka, Milan; Wrede, Sebastian; Rodn, Marek; Pfister, Laurent; Hoffmann, Lucien; Krein, Andreas

    2012-07-01

    SummaryThis paper examines the combined effects of catchment complexity in terms of physiography, land use patterns, and lithology on the export of dissolved inorganic nitrogen and dissolved silica from heterogeneous nested catchments in the Grand-Duchy of Luxembourg. Using results from water quality monitoring at 24 sampling sites, we determined the first-order controls on these fluxes. Land cover with four classes (forest, agriculture, grassland and urban), dominant lithology (schist, marls, sandstone, limestone, alluvial sediments), physiographic indices (elevation, flow path length, ratio of flow path length to flow path gradient, topographic wetness index, and other), and a suite of hydrological indices (baseflow, flashiness index and runoff coefficient), were calculated and used as potential controls. Given the high co-dependence of the predictors, Partial Least Square Regression was used to shed light on the linkages between export fluxes and the metrics composed of the 19 selected catchment characteristics. The first-order controls were determined by calculating the Variable Influence on Projection (VIP). These values revealed that the overall dissolved inorganic nitrogen fluxes are controlled primarily by lithology, land cover, topographic wetness index and flow path length. The first-order controls of dissolved silica fluxes are runoff coefficient, average topographic slope and land cover. Fluxes of dissolved inorganic nitrogen and dissolved silica did not show any strong relation to catchment scale. Apart from the widely accepted effect of land cover, our results indicate that catchment topography has an essential impact on the fluxes of dissolved inorganic nitrogen. The ratio of flow path length and flow path gradient, previously suggested as a proxy of mean water transit time, exerted a relatively strong control on dissolved inorganic nitrogen fluxes (VIP > 1) with a negative relation to dissolved inorganic nitrogen fluxes, suggesting that dissolved inorganic nitrogen fluxes decrease with an increasing flow path gradient.

  4. ELECTROKINETIC PHENOMENA : XIII. A COMPARISON OF THE ISOELECTRIC POINTS OF DISSOLVED AND CRYSTALLINE AMINO ACIDS.

    PubMed

    Abramson, H A; Moyer, L S

    1938-07-20

    1. Although the isoelectric points of dissolved cystine, tyrosine, and aspartic acid molecules lie at widely differing pH values, the isoelectric points of the surfaces of these substances in the crystalline state are all near pH 2.3. This was found to be true in solutions of hydrochloric acid and in acetate buffers of approximately constant ionic strength. 2. When suspended in gelatin, tyrosine and cystine crystals adsorb the protein and attain a surface identical in behavior with gelatin-coated quartz or collodion particles. 3. Aluminum ions at low concentrations reduce the electric mobilities of tyrosine crystals to zero in a manner analogous to their effect on other surfaces. 4. Alkyl benzene droplets also have their electric mobility reduced to zero at low pH values but, unlike the amino acids, a change in sign was never noticed. 5. The mobility of tyrosine crystals is independent of crystal length between 2-100micro. Below this size the mobilities are decreased. 6. These results are discussed in connection with the concept of the general definition of the isoelectric point and the behavior of certain insoluble proteins such as wool and silk fibroin. PMID:19873079

  5. Fluorescence Characterization of Dissolved Organic Matter (DOC) from Marine and Terrestrial Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Hartnett, H. E.; Coe, J. D.; Smith, Z. P.

    2013-12-01

    Hydrothermal ecosystems exhibit a wide range in temperature, pH, and solute concentrations, including dissolved organic carbon (DOC). Here we compare DOC concentrations among marine (Iheya North Field, East China Sea) and terrestrial (Yunnan Province, China and Yellowstone National Park, USA) hydrothermal systems. We further characterize DOC fluorescence in these three systems using 3D excitation-emission matrix spectroscopy (EEMs) and PARAFAC modeling. DOC concentrations in pore waters from the Iheya North hydrothermal field are always extremely low (<1 mg/L) and EEMs analysis suggests the DOC is of microbial origin. DOC concentrations in terrestrial springs from both China and Yellowstone have somewhat consistent variations with pH; generally, there are lower DOC concentrations in alkaline springs and higher, but more variable, DOC concentrations in acidic springs. DOC concentrations in alkaline springs are generally <2 mg/L, but in acidic hot springs DOC can be >100 mg/L. Fluorescence analysis of DOC from terrestrial hot springs reveals that some, but by no means all, of the fluorophores exhibit relationships with pH similar to those of the bulk DOC. In contrast, other fluorophores vary independently of the bulk DOC concentration. The DOC in hot springs from both China and Yellowstone appears to be predominantly of microbial origin but there are as yet unidentified fluorophores in both regions that could be unique tracers for DOC in hydrothermal systems.

  6. Evaluation of filter media for clarification of partially dissolved residues containing plutonium

    SciTech Connect

    Foley, E.S.

    1989-10-09

    A common process in the chemical industry employs the leaching of a desirable component from an insoluble substrate, followed by filtration to produce a clarified solution of the desirable component and a discardable residue. The work described here involved evaluating sintered metal filter media for separating dissolved plutonium from undissolved residues generated at various locations owned by the Department of Energy throughout the United States. The work was performed during a six-week assignment at the Savannah River Laboratory as part of a high school science enrichment program conducted in the summer of 1989. The leach step used included dissolving the plutonium-containing solids in a solution of nitric-hydrofluoric acid. To simulate the partial solubility of the actual plutonium-containing residues, a non-radioactive power plant flyash was used. 6 refs., 14 figs., 1 tab.

  7. Accuracy of different sensors for the estimation of pollutant concentrations (total suspended solids, total and dissolved chemical oxygen demand) in wastewater and stormwater.

    PubMed

    Lepot, Mathieu; Aubin, Jean-Baptiste; Bertrand-Krajewski, Jean-Luc

    2013-01-01

    Many field investigations have used continuous sensors (turbidimeters and/or ultraviolet (UV)-visible spectrophotometers) to estimate with a short time step pollutant concentrations in sewer systems. Few, if any, publications compare the performance of various sensors for the same set of samples. Different surrogate sensors (turbidity sensors, UV-visible spectrophotometer, pH meter, conductivity meter and microwave sensor) were tested to link concentrations of total suspended solids (TSS), total and dissolved chemical oxygen demand (COD), and sensors' outputs. In the combined sewer at the inlet of a wastewater treatment plant, 94 samples were collected during dry weather, 44 samples were collected during wet weather, and 165 samples were collected under both dry and wet weather conditions. From these samples, triplicate standard laboratory analyses were performed and corresponding sensors outputs were recorded. Two outlier detection methods were developed, based, respectively, on the Mahalanobis and Euclidean distances. Several hundred regression models were tested, and the best ones (according to the root mean square error criterion) are presented in order of decreasing performance. No sensor appears as the best one for all three investigated pollutants. PMID:23863442

  8. How much does fluvial dissolved organic carbon export from blanket bogs vary at the regional scale? An example from the Pennine region of Yorkshire, UK

    NASA Astrophysics Data System (ADS)

    Grayson, Richard; Blundell, Antony; Holden, Joseph

    2014-05-01

    Often only one or a very small number of stream sampling points are used to infer wider regional export of fluvial carbon from peatlands. However, we suggest that the amount of fluvial carbon being exported varies enormously within regions even when blanket peat is the dominant land cover type. Here we present results from an extensive and comprehensive monitoring project covering blanket peat dominated catchments across the Pennine region of the UK using data from 2006 onwards. Up to the start of January 2014 the dataset contained dissolved organic carbon (DOC) data for approximately 11500 stream water samples (both routine spot samples and storm event samples). The majority of these DOC measurements also have associated UV-Vis absorbance data allowing an insight into the composition of the DOC present, specifically the dominance of humic versus fulvic acids and the degree of aromaticity (SUVA254). Additional data to support interpretation of the regional variability of DOC includes particulate organic carbon, discharge, pH, conductivity and turbidity, water table depth, soil water chemistry and meteorological data. We provide an unparalleled insight into the spatial and temporal variability of DOC in a region of blanket bogs showing how catchment attributes influence fluvial DOC, how there are hotspots of DOC production and how high flow events regulating DOC export and its composition.

  9. Fish embryos are damaged by dissolved PAHs, not oil particles.

    PubMed

    Carls, Mark G; Holland, Larry; Larsen, Marie; Collier, Tracy K; Scholz, Nathaniel L; Incardona, John P

    2008-06-23

    To distinguish the toxicity of whole oil droplets from compounds dissolved in water, responses of zebrafish embryos exposed to particulate-laden, mechanically dispersed Alaska North Slope crude oil (mechanically dispersed oil (MDO)) were compared to those of embryos protected from direct oil droplet contact by an agarose matrix. Most polycyclic aromatic hydrocarbons (PAHs) in MDO were contained in oil droplets; about 16% were dissolved. The agarose precluded embryo contact with particulate oil but allowed diffusive passage of dissolved PAHs. The incidence of edema, hemorrhaging, and cardiac abnormalities in embryos was dose-dependent in both MDO and agarose and the biological effects in these compartments were identical in character. Although mean total PAH (TPAH) concentrations in MDO were about 5-9 times greater than in agarose, dissolved PAH concentrations were similar in the two compartments. Furthermore, mean differences in paired embryo responses between compartments were relatively small (14-23%, grand mean 17%), typically with a larger response in embryos exposed to MDO. Therefore, the embryos reacted only to dissolved PAHs and the response difference between compartments is explained by diffusion. Averaged over 48 h, the estimated mean TPAH concentration in agarose was about 16% less than the dissolved TPAH concentration in MDO. Thus, PAHs dissolved from oil are toxic and physical contact with oil droplets is not necessary for embryotoxicity. PMID:18479765

  10. Functional photoacoustic microscopy of pH

    NASA Astrophysics Data System (ADS)

    Chatni, M. Rameez; Yao, Junjie; Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin I.; Wang, Lihong V.

    2012-02-01

    pH is a tightly regulated indicator of metabolic activity. In mammalian systems, imbalance of pH regulation may result from or result in serious illness. Even though the regulation system of pH is very robust, tissue pH can be altered in many diseases such as cancer, osteoporosis and diabetes mellitus. Traditional high-resolution optical imaging techniques, such as confocal microscopy, routinely image pH in cells and tissues using pH sensitive fluorescent dyes, which change their fluorescence properties with the surrounding pH. Since strong optical scattering in biological tissue blurs images at greater depths, high-resolution pH imaging is limited to penetration depths of 1mm. Here, we report photoacoustic microscopy (PAM) of commercially available pH-sensitive fluorescent dye in tissue phantoms. Using both opticalresolution photoacoustic microscopy (OR-PAM), and acoustic resolution photoacoustic microscopy (AR-PAM), we explored the possibility of recovering the pH values in tissue phantoms. In this paper, we demonstrate that PAM was capable of recovering pH values up to a depth of 2 mm, greater than possible with other forms of optical microscopy.

  11. Dissolved carbon dioxide in basaltic glasses: concentrations and speciation

    NASA Astrophysics Data System (ADS)

    Fine, Gerald; Stolper, Edward

    1986-01-01

    Carbon dioxide dissolved in both synthetic Ca±Mg-bearing silicate glasses and natural basaltic glasses has been characterized using infrared spectroscopy. CO 2 is inferred to be dissolved in these glasses as distorted Ca or Mg carbonate ionic complexes that result in unique infrared absorption bands at 1515 cm -1 and 1435 cm -1. This speciation contrasts with the case of CO 2-bearing sodium aluminosilicate glasses, which contain both dissolved molecular CO 2 and dissolved Na-carbonate ionic-complexes. The difference in speciation in Ca±Mg-bearing melts may result in part from a higher activity of oxygens that react with CO 2 molecules to produce carbonate. Dissolved CO 2 contents of natural basaltic glasses can be determined from the intensities of the carbonate absorption bands at 1515 cm -1 and 1435 cm -1. The uncertainty of the method is estimated to be ± 15% of the amount present. The infrared technique is a powerful tool for the measurement of dissolved CO 2 contents in natural basaltic glasses since it is non-destructive, can be aimed at regions of glass a few tens of microns in size, and can discriminate between dissolved carbonate and carbon present as carbonate alteration, contained in fluid inclusions, or adsorbed on the glass. A set of submarine basaltic glasses dredged from a variety of locations contain 0-400 ppm dissolved CO 2, measured using the infrared technique. These concentrations are lower than most previous reports for similar basaltic glasses. No general relationship is observed between dissolved CO 2 content and depth of magmatic eruption, although some correlation might be present in restricted geographic locales.

  12. Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater

    USGS Publications Warehouse

    Chapelle, Francis H.; Bradley, Paul M.; McMahon, Peter B.; Kaiser, Karl; Benner, Ron

    2012-01-01

    Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in the bioavailability of naturally occurring DOC might contribute to these observations. This hypothesis was examined by comparing nine different biochemical indicators of DOC bioavailability in groundwater sampled from these two systems. Concentrations of DOC, total hydrolysable neutral sugars (THNS), total hydrolysable amino acids (THAA), mole% glycine of THAA, initial bacterial cell counts, bacterial growth rates, and carbon dioxide production/consumption were greater in SC samples relative to CA samples. In contrast, the mole% glucose of THNS and the aromaticity (SUVA254) of DOC was greater in CA samples. Each of these indicator parameters were observed to change with depth in the SC system in a manner consistent with active biodegradation. These results are uniformly consistent with the hypothesis that the bioavailability of DOC is greater in SC relative to CA groundwater samples. This, in turn, suggests that the presence/absence of a hyperbolic DO-DOC relationship may be a qualitative indicator of relative DOC bioavailability in groundwater systems.

  13. Dissolved and particulate metals dynamics in a human impacted estuary from the SW Atlantic

    NASA Astrophysics Data System (ADS)

    La Colla, Noelia S.; Negrin, Vanesa L.; Marcovecchio, Jorge E.; Botté, Sandra E.

    2015-12-01

    In order to evaluate metal behavior in urban stressed estuaries, the distribution of major elements (Fe and Mn) and trace elements (Cd and Cu) between suspended particulate matter (SPM) and subsuperficial seawater in the Bahía Blanca Estuary, Argentina, was studied. Four different impacted areas were selected to study the spatial and temporal distribution of these metals in an estuary in continuous industrial development and where an environmental law was implemented to supervise industrial discharges in waters. Sampling was performed within intertidal areas. Physicochemical conditions usually influence the partitioning of metals between the dissolved and particulate fraction thus, salinity, pH, turbidity, temperature and dissolved oxygen were also measured. Dissolved metals were analyzed with atomic absorption spectrophotometry (AAS) and the particulate fraction with inductively coupled plasma optical emission spectrometry (ICP OES). Metals concentration ranges, within the dissolved fraction (μg/L), were from below the method detection limit for all the elements to 4.7 in the case of Cd, 6.0 for Cu and 62 for Fe. Minimum and maximum values in the particulate fraction (μg/g, d.w.) were from below the method detection limit to 11 for Cd; from 24 to 220 for Cu and from 630 to 1500 for Mn. For Fe, concentrations ranged from 2.2 to 9.6 (%). The general order of the dissolved/particulate partition coefficients (Log10Kds) for the studied metals, considering mean values, were: Fe (7.0) > Cu (4.2) > Cd (3.3). The metals values as well as the physicochemical parameters showed temporal variations and many correlations were found among them. Log10Kd Fe values were the highest, highlighting its strong affinity for particles. Metals concentrations were sometimes higher than those from other polluted areas as well as from previous studies from the same estuary, which highlights the potential impact of these elements in the study area. The concentrations of particulate metals achieved in the present work were in some cases of higher ranges than the previous from the same estuary and/or from other polluted estuarine environments. Thus, the environmental law that regulates the discharge of industrial waters appeared not to have a specific impact on the metals concentrations found. Moreover, human activities that surround the estuary and are in continue development should be considered as they might constitute a source of metals for the estuarine system.

  14. Isolation and chemical characterization of dissolved and colloidal organic matter

    USGS Publications Warehouse

    Aiken, G.; Leenheer, J.

    1993-01-01

    Commonly used techniques for the concentration and isolation of organic matter from water, such as preparative chromatography, ultrafiltration and reverse osmosis, and the methods used to analyze the organic matter obtained by these methods are reviewed. The development of methods to obtain organic matter that is associated with fractions of the dissolved organic carbon other than humic substances, such as organic bases, hydrophilic organic acids and colloidal organic matter are discussed. Methods specifically used to study dissolved organic nitrogen and dissolved organic phosphorous are also discussed. -from Authors

  15. Chemical and optical phototransformation of dissolved organic matter.

    PubMed

    Loiselle, Steven; Vione, Davide; Minero, Claudio; Maurino, Valter; Tognazzi, Antonio; Dattilo, Arduino M; Rossi, Claudio; Bracchini, Luca

    2012-06-15

    Dissolved organic matter represents the main reservoir of organic carbon in most aquatic ecosystems. In the present study, we determined the optical changes and the quantum yields of transient species formation for chromophoric dissolved organic matter (CDOM) samples undergoing photodegradation. The results show that the triplet states (3)CDOM* are potentially key players in CDOM photodegradation and that such transformations are strongly influenced by small differences in CDOM sources and sinks. In contrast, ·OH radicals are very unlikely to play a key role in phototransformation. These results represent an important first step in combining optical and transient species analyses to understand photodegradation processes of dissolved organic matter. PMID:22503589

  16. Chapter A6. Section 6.2. Dissolved Oxygen

    USGS Publications Warehouse

    Revised by Lewis, Michael Edward

    2006-01-01

    Accurate data for the concentration of dissolved oxygen in surface and ground waters are essential for documenting changes in environmental water resources that result from natural phenomena and human activities. Dissolved oxygen is necessary in aquatic systems for the survival and growth of many aquatic organisms and is used as an indicator of the health of surface-water bodies. This section of the National Field Manual (NFM) includes U.S. Geological Survey (USGS) guidance and protocols for four methods to determine dissolved-oxygen concentrations: the amperometric, luminescent-sensor, spectrophotometric, and iodometric (Winkler) methods.

  17. Influence of dissolved hydrogen on the fatigue crack growth behaviour of AISI 4140 steel

    NASA Astrophysics Data System (ADS)

    Ramasagara Nagarajan, Varun

    Many metallic structural components come into contact with hydrogen during manufacturing processes or forming operations such as hot stamping of auto body frames and while in service. This interaction of metallic parts with hydrogen can occur due to various reasons such as water molecule dissociation during plating operations, interaction with atmospheric hydrogen due to the moisture present in air during stamping operations or due to prevailing conditions in service (e.g.: acidic or marine environments). Hydrogen, being much smaller in size compared to other metallic elements such as Iron in steels, can enter the material and become dissolved in the matrix. It can lodge itself in interstitials locations of the metal atoms, at vacancies or dislocations in the metallic matrix or at grain boundaries or inclusions (impurities) in the alloy. This dissolved hydrogen can affect the functional life of these structural components leading to catastrophic failures in mission critical applications resulting in loss of lives and structural component. Therefore, it is very important to understand the influence of the dissolved hydrogen on the failure of these structural materials due to cyclic loading (fatigue). For the next generation of hydrogen based fuel cell vehicles and energy systems, it is very crucial to develop structural materials for hydrogen storage and containment which are highly resistant to hydrogen embrittlement. These materials should also be able to provide good long term life in cyclic loading, without undergoing degradation, even when exposed to hydrogen rich environments for extended periods of time. The primary focus of this investigation was to examine the influence of dissolved hydrogen on the fatigue crack growth behaviour of a commercially available high strength medium carbon low alloy (AISI 4140) steel. The secondary objective was to examine the influence of microstructure on the fatigue crack growth behaviour of this material and to determine the hydrogen induced failure mechanism in this material during cyclic loading. The secondary objective of this investigation was to determine the role of inclusions and their influence in affecting the fatigue crack growth rate of this material. Compact tension and tensile specimens were prepared as per ASTM E-647, E-399 and E-8 standards. The specimens were tested in three different heat treated conditions i.e. annealed (as received) as well as two austempered conditions. These specimens were precharged with hydrogen (ex situ) using cathodic charging method at a constant current density at three different time periods ranging from 150 to 250 hours before conducting fatigue crack growth tests. Mode 1 type fatigue tests were then performed in ambient atmosphere at constant amplitude using load ratio R of 0.1. The near threshold fatigue crack growth rate, fatigue threshold and the fatigue crack growth rate in the linear region were determined. Fatigue crack growth behaviour of specimens without any dissolve hydrogen were then compared with the specimens with different concentration of dissolved hydrogen. The test results show that the dissolved hydrogen concentration increases with the increase in charging time in all three heat treated conditions and the hydrogen uptake shows a strong dependence on the microstructure of the alloy. It was also observed that the microstructure has a significant influence of on the fatigue crack growth and SCC behaviour of the alloy with dissolved hydrogen. As the dissolved hydrogen concentration increases, the fatigue threshold was found to decrease and the near threshold crack growth rate increases in all three heat treated conditions showing the deleterious effect of hydrogen, but to a different extent in each condition. Current test results also indicate that the fatigue crack growth rates in the linear region increases as the dissolved hydrogen content increases in all three heat treated conditions. It is also observed that increasing the austempering temperature decreases the resistance to hydrogen embrittlement. An interesting phenomenon was also observed in annealed specimen charged with hydrogen for 250 h which had an unusually high fatigue threshold (DeltaKth).

  18. Dissolved gas and isotopic tracers of denitrification

    SciTech Connect

    Singleton, M J; Moran, J E; Esser, B K; McNab, W W; Carle, S F; Cey, B D

    2008-02-28

    We present results from field studies in California (USA) where tritium-helium age dating is used in conjunction with major gases (N{sub 2}, O{sub 2}, CH{sub 4}, CO{sub 2}), noble gases (He, Ne, Ar, Kr, Xe), and stable isotopes ({sup 15}N/{sup 14}N, {sup 18}O/{sup 16}O) in order to document nitrate loading and denitrification associated with confined animal agricultural operations and septic systems. Preliminary results show that in-field extraction of the full suite of dissolved gases will be possible using a new Gas Extraction System under development to augment the current Noble Gas Mass Spectrometry and Membrane Inlet Mass Spectrometry techniques. Ascribing observed groundwater nitrate levels to specific current and past land use practices is often complicated by uncertainty in groundwater age and the degree and locus of dentrification. Groundwater age dating at dairy field sites using the {sup 3}H-{sup 3}He method indicates that the highest nitrate concentrations (150-260 mg/L-NO3) occur in waters with apparent ages of <5 yrs, whereas older waters contain excess N{sub 2} from saturated zone denitrification [1]. At a residential septic system site in Livermore, CA, waters with young apparent ages (<1 yr) proximal to leach line drainage have lower nitrate concentrations and elevated nitrate {delta}{sup 15}N and {delta}{sup 18}O values consistent with denitrification, but little evidence for excess N{sub 2}, indicating that denitrification is occurring in the unsaturated zone. Degassing of groundwater can complicate efforts to calculate travel times [2] and to quantify denitrification. Degassed groundwater underlying dairy operations is formed by two distinct mechanisms: (1) recharge of manure lagoon water affected by biogenic gas ebullition [3] and (2) saturated zone denitrification producing N{sub 2} gas above solubility in groundwater. Gas loss due to both mechanisms is evident in the concentrations of noble gases and major gases in dairy groundwater samples.

  19. Evaluation of specific ultraviolet absorbance as an indicator of the chemical composition and reactivity of dissolved organic carbon

    USGS Publications Warehouse

    Weishaar, J.L.; Aiken, G.R.; Bergamaschi, B.A.; Fram, M.S.; Fujii, R.; Mopper, K.

    2003-01-01

    Specific UV absorbance (SUVA) is defined as the UV absorbance of a water sample at a given wavelength normalized for dissolved organic carbon (DOC) concentration. Our data indicate that SUVA, determined at 254 nm, is strongly correlated with percent aromaticity as determined by 13C NMR for 13 organic matter isolates obtained from a variety of aquatic environments. SUVA, therefore, is shown to be a useful parameter for estimating the dissolved aromatic carbon content in aquatic systems. Experiments involving the reactivity of DOC with chlorine and tetramethylammonium hydroxide (TMAH), however, show a wide range of reactivity for samples with similar SUVA values. These results indicate that, while SUVA measurements are good predictors of general chemical characteristics of DOC, they do not provide information about reactivity of DOC derived from different types of source materials. Sample pH, nitrate, and iron were found to influence SUVA measurements.

  20. Effect of bacteria and dissolved organics on mineral dissolution kinetics:

    NASA Astrophysics Data System (ADS)

    Pokrovsky, Oleg; Shirokova, Liudmila; Benezeth, Pascale; Zabelina, Svet