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Sample records for freely dissolved concentration

  1. Effects of dissolved organic matter from a eutrophic lake on the freely dissolved concentrations of emerging organic contaminants.

    PubMed

    Xiao, Yi-Hua; Huang, Qing-Hui; Vähätalo, Anssi V; Li, Fei-Peng; Chen, Ling

    2014-08-01

    The authors studied the effects of dissolved organic matter (DOM) on the bioavailability of bisphenol A (BPA) and chloramphenicol by measuring the freely dissolved concentrations of the contaminants in solutions containing DOM that had been isolated from a mesocosm in a eutrophic lake. The abundance and aromaticity of the chromophoric DOM increased over the 25-d mesocosm experiment. The BPA freely dissolved concentration was 72.3% lower and the chloramphenicol freely dissolved concentration was 56.2% lower using DOM collected on day 25 than using DOM collected on day 1 of the mesocosm experiment. The freely dissolved concentrations negatively correlated with the ultraviolent absorption coefficient at 254 nm and positively correlated with the spectral slope of chromophoric DOM, suggesting that the bioavailability of these emerging organic contaminants depends on the characteristics of the DOM present. The DOM-water partition coefficients (log KOC ) for the emerging organic contaminants positively correlated with the aromaticity of the DOM, measured as humic acid-like fluorescent components C1 (excitation/emission=250[313]/412 nm) and C2 (excitation/emission=268[379]/456 nm). The authors conclude that the bioavailability of emerging organic contaminants in eutrophic lakes can be affected by changes in the DOM. PMID:24839192

  2. Passive sampling methods for contaminated sediments: scientific rationale supporting use of freely dissolved concentrations.

    PubMed

    Mayer, Philipp; Parkerton, Thomas F; Adams, Rachel G; Cargill, John G; Gan, Jay; Gouin, Todd; Gschwend, Philip M; Hawthorne, Steven B; Helm, Paul; Witt, Gesine; You, Jing; Escher, Beate I

    2014-04-01

    Passive sampling methods (PSMs) allow the quantification of the freely dissolved concentration (Cfree ) of an organic contaminant even in complex matrices such as sediments. Cfree is directly related to a contaminant's chemical activity, which drives spontaneous processes including diffusive uptake into benthic organisms and exchange with the overlying water column. Consequently, Cfree provides a more relevant dose metric than total sediment concentration. Recent developments in PSMs have significantly improved our ability to reliably measure even very low levels of Cfree . Application of PSMs in sediments is preferably conducted in the equilibrium regime, where freely dissolved concentrations in the sediment are well-linked to the measured concentration in the sampler via analyte-specific partition ratios. The equilibrium condition can then be assured by measuring a time series or a single time point using passive samplers with different surface to volume ratios. Sampling in the kinetic regime is also possible and generally involves the application of performance reference compounds for the calibration. Based on previous research on hydrophobic organic contaminants, it is concluded that Cfree allows a direct assessment of 1) contaminant exchange and equilibrium status between sediment and overlying water, 2) benthic bioaccumulation, and 3) potential toxicity to benthic organisms. Thus, the use of PSMs to measure Cfree provides an improved basis for the mechanistic understanding of fate and transport processes in sediments and has the potential to significantly improve risk assessment and management of contaminated sediments. PMID:24288295

  3. Review of polyoxymethylene passive sampling methods for quantifying freely dissolved porewater concentrations of hydrophobic organic contaminants.

    PubMed

    Arp, Hans Peter H; Hale, Sarah E; Elmquist Kruså, Marie; Cornelissen, Gerard; Grabanski, Carol B; Miller, David J; Hawthorne, Steven B

    2015-04-01

    Meth ods involving polyoxymethylene (POM) as a passive sampler are increasing in popularity to assess contaminant freely dissolved porewater concentrations in soils and sediments. These methods require contaminant-specific POM-water partition coefficients, KPOM . Certain methods for determining KPOM perform reproducibly (within 0.2 log units). However, other methods can give highly varying KPOM values (up to 2 log units), especially for polycyclic aromatic hydrocarbons (PAHs). To account for this variation, the authors tested the influence of key methodological components in KPOM determinations, including POM thickness, extraction procedures, and environmental temperature and salinity, as well as uptake kinetics in mixed and static systems. All inconsistencies in the peer-reviewed literature can be accounted for by the likelihood that thick POM materials (500??m or thicker) do not achieve equilibrium (causing negative biases up to 1 log unit), or that certain POM extraction procedures do not ensure quantitative extraction (causing negative biases up to 2 log units). Temperature can also influence KPOM , although all previous literature studies were carried out at room temperature. The present study found that KPOM values at room temperature are independent (within 0.2 log units) of POM manufacture method, of thickness between 17??m and 80??m, and of salinity between 0% and 10%. Regarding kinetics, monochloro- to hexachloro-polychlorinated biphenyls (PCBs) were within 0.2 log units of equilibrium after 28?d in the mixed system, but only dichloro-PCBs achieved near equilibrium after 126?d in the static system. Based on these insights, recommended methods and KPOM values to facilitate interlaboratory reproducibility are presented. PMID:25702935

  4. Equilibrium sampling through membranes of freely dissolved copper concentrations with selective hollow fiber membranes and the spectrophotometric detection of a metal stripping agent.

    PubMed

    Romero, Roberto; Liu, Jing-Fu; Mayer, Philipp; Jönsson, Jan Ake

    2005-12-01

    A sensitive spectrophotometric method for the determination of freely dissolved copper concentrations in aqueous samples after preconcentration with hollow fiber membrane extraction has been developed. The method is based on the equilibrium sampling through a selective membrane into an acceptor solution containing 4-(pyridyl-2-azo)resorcinol (PAR), which serves as stripping agent and metal indicator. Negligible extraction of interferences and equilibrium enrichment of copper allowed for selective spectrophotometric determination of the Cu-PAR complex. Some important extraction parameters such as acceptor composition, shaking, equilibrium time, and sample volume were studied. The optimized methodology showed good linearity in the range of 5-100 microg/L, an enrichment factor of 93, good repeatability and reproducibility (RSDs < 6%, n = 6), and a detection limit of 4 microg/L. The cationic metals Ni2+, C(2+, Cd2+, Fe3+, Pb2+, Zn2+, and Mn2+ were shown not to interfere with the measurement of Cu2+. Measurements on samples containing mixtures of various ligands and cations were in good agreement with theoretically calculated concentrations, and the method was also applied to environmental samples. The developed technique requires less labor and less sophisticated equipment than conventional methods typically based on atomic absorption spectrometry or ICP. PMID:16316167

  5. A passive sampler based on solid phase microextraction (SPME) for sediment-associated organic pollutants: Comparing freely-dissolved concentration with bioaccumulation.

    PubMed

    Maruya, Keith A; Lao, Wenjian; Tsukada, David; Diehl, Dario W

    2015-10-01

    The elevated occurrence of hydrophobic organic chemicals (HOCs) such as polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCBs) and legacy organchlorine pesticides (e.g. chlordane and DDT) in estuarine sediments continues to poses challenges for maintaining the health of aquatic ecosystems. Current efforts to develop and apply protective, science-based sediment quality regulations for impaired waterbodies are hampered by non-concordance between model predictions and measured bioaccumulation and toxicity. A passive sampler incorporating commercially available solid phase microextraction (SPME) fibers was employed in lab and field studies to measure the freely dissolved concentration of target HOCs (Cfree) and determine its suitability as a proxy for bioaccumulation. SPME deduced Cfree for organochlorines was highly correlated with tissue concentrations (Cb) of Macoma and Nereis spp. co-exposed in laboratory microcosms containing both spiked and naturally contaminated sediments. This positive association was also observed in situ for endemic bivalves, where SPME samplers were deployed for up to 1 month at an estuarine field site. The concordance between Cb and Cfree for PAH was more variable, in part due to likely biotransformation by model invertebrates. These results indicate that SPME passive samplers can serve as a proxy for bioaccumulation of sediment-associated organochlorines in both lab and field studies, reducing the uncertainty associated with model predictions that do not adequately account for differential bioavailability. PMID:26246043

  6. Evaluation of passive samplers with neutral or ion-exchange polymer coatings to determine freely dissolved concentrations of the basic surfactant lauryl diethanolamine: Measurements of acid dissociation constant and organic carbon-water sorption coefficient.

    PubMed

    Wang, Fang; Chen, Yi; Hermens, Joop L M; Droge, Steven T J

    2013-11-01

    A passive sampler tool (solid-phase microextraction, SPME) was optimized to measure freely dissolved concentrations (Cw,free) of lauryl diethanolamine (C12-DEA). C12-DEA can be protonated and act as a cationic surfactant. From the pH-dependent sorption to neutral SPME coatings (polyacrylate and PDMS), a pKa of 8.7 was calculated, which differs more than two units from the value of 6.4 reported elsewhere. Polyacrylate coated SPME could not adequately sample largely protonated C12-DEA in humic acid solutions of pH 6. A new hydrophobic SPME coating with cation-exchange properties (C18/SCX) sorbed C12-DEA 100 fold stronger than polyacrylate, because it specifically sorbs protonated C12-DEA species. The C18/SCX-SPME fiber showed linear calibration isotherms in a concentration range of <1 nM-1 ?M (well below the CMC). Using the C18/SCX-SPME fibers, linear sorption isotherms to Aldrich humic acid at pH 6 (ionic strength 0.015 M) were measured over a broad concentration range with a sorption coefficient of 10(5.3). PMID:24094752

  7. Equilibrium Partitioning Sediment Benchmarks (ESBs) for the Protection of Benthic Organisms: Procedures for the Determination of the Freely Dissolved Interstitial Water Concentrations of Nonionic Organics

    EPA Science Inventory

    This document describes procedures to determine the concentrations of nonionic organic chemicals in sediment interstitial waters. In previous ESB documents, the general equilibrium partitioning (EqP) approach was chosen for the derivation of sediment benchmarks because it account...

  8. Monitoring the freely dissolved concentrations of polycyclic aromatic hydrocarbons (PAH) and alkylphenols (AP) around a Norwegian oil platform by holistic passive sampling.

    PubMed

    Harman, Christopher; Thomas, Kevin V; Tollefsen, Knut Erik; Meier, Sonnich; Bøyum, Olav; Grung, Merete

    2009-11-01

    In order to assess the environmental impact of aquatic discharges from the offshore oil industry, polar organic chemical integrative samplers (POCIS) and semipermeable membrane devices (SPMDs) were deployed around an oil platform and at reference locations in the North Sea. Exposure to polycyclic aromatic hydrocarbons (PAH) and alkylated phenols (AP) was determined from passive sampler accumulations using an empirical uptake model, the dissipation of performance reference compounds and adjusted laboratory derived sampling rates. Exposure was relatively similar within 1-2 km of the discharge point, with levels dominated by short chained C1-C3 AP isomers (19-51 ngL(-1)) and alkylated naphthalenes, phenanthrenes and dibenzothiophenes (NPD, 29-45 ngL(-1)). Exposure stations showed significant differences to reference sites for NPD, but not always for more hydrophobic PAH. These concentrations are several orders of magnitude lower than those reported to give both acute and sub-lethal effects, although their long term consequences are unknown. PMID:19682711

  9. The total and freely dissolved polycyclic aromatic hydrocarbons content in residues from biogas production.

    PubMed

    Stefaniuk, Magdalena; Oleszczuk, Patryk

    2016-01-01

    In the situation of increasing agricultural utilization of residues from biogas production (RBP) it is important to determine the concentration of contaminants, which could occur in these materials. The group of contaminants that requires special attention are polycyclic aromatic hydrocarbons (PAH). The objective of the study was to determine the total and freely dissolved (Cfree) of PAHs in RBP from 6 different biogas plants operating under various temperature conditions and without or with the separation into the solid and liquid fractions. The freely dissolved PAHs were determined using polyoxymethylene (POM method). The total content of the ?16 PAHs in RBP varied from 449 to 6147 ?g/kgdw, while that of Cfree PAHs was at the level from 57 to 653 ng/L. No significant differences were noted in the content of the ?16 PAHs (total) between the solid and the liquid fractions. This indicates that in the course of the separation, the PAHs are distributed proportionally between the fractions. However in the case of Cfree, PAHs content in the solid fraction was over twice as high as in the liquid fraction. This was probably due to the greater affinity of the particles present in the liquid fraction to the analysed PAHs than to the particles of the solid fraction. Higher affinity to liquid fraction was also confirmed by the distribution coefficients KTOC determined on the basis of Cfree. PMID:26586628

  10. Application of passive sampling for measuring dissolved concentrations of organic contaminants in the water column at three marine superfund sites

    EPA Science Inventory

    At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column concentrations of freely dissolved contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). However, historically a...

  11. 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.

  12. Spatial and temporal variation of freely dissolved polycyclic aromatic hydrocarbons in an urban river undergoing Superfund remediation

    SciTech Connect

    Aregory James Sower; Kim A. Anderson

    2008-12-15

    Urban rivers with a history of industrial use can exhibit spatial and temporal variations in contaminant concentrations that may significantly affect risk evaluations and even the assessment of remediation efforts. Concentrations of 15 biologically available priority pollutant polycyclic aromatic hydrocarbons (PAHs) were measured over five years along 18.5 miles of the lower Willamette River using passive sampling devices and HPLC. The study area includes the Portland Harbor Superfund megasite with several PAH sources including remediation operations for coal tar at RM 6.3 west and an additional Superfund site, McCormick and Baxter, at RM 7 east consisting largely of creosote contamination. Study results show that organoclay capping at the McCormick and Baxter Superfund Site reduced PAHs from a precap average of 440 {+-} 422 ng/L to 8 {+-} 3 ng/L postcapping. Results also reveal that dredging of submerged coal tar nearly tripled nearby freely dissolved PAH concentrations. For apportioning sources, fluoranthene/pyrene and phenanthrene/anthracene diagnostic ratios from passive sampling devices were established for creosote and coal tar contamination and compared to published sediment values. 29 refs., 3 figs., 3 tabs.

  13. Application of Passive Sampling for Measuring Dissolved Concentrations of Organic Contaminants in the Water Column at Three U.S. EPA Marine Superfund Sites

    EPA Science Inventory

    At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column concentrations of freely dissolved contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). Historically acquiring ...

  14. Application of Passive Sampling for Measuring Dissolved Concentrations of Organic Contaminants in the Water Column at Three U.S. EPA Marine Superfund Sites.

    EPA Science Inventory

    At contaminated sediment sites, including U.S. EPA Superfund sites, it is critical to measure water column concentrations of freely dissolved contaminants to understand the complete exposure of aquatic organisms to hydrophobic organic contaminants (HOCs). Historically, acquiring...

  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. 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.

  17. 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.

  18. Estimation of Freely-Dissolved Concentrations of Polychlorinated Biphenyls, 2,3,7,8-Substituted Congeners and Homologs of Polychlorinated dibenzo-p-dioxins and Dibenzofurans in Water for Development of Total Maximum Daily Loadings for the Bluestone River Watershed, Virginia and West Virginia

    USGS Publications Warehouse

    Gale, Robert W.

    2007-01-01

    The Commonwealth of Virginia Department of Environmental Quality, working closely with the State of West Virginia Department of Environmental Protection and the U.S. Environmental Protection Agency is undertaking a polychlorinated biphenyl source assessment study for the Bluestone River watershed. The study area extends from the Bluefield area of Virginia and West Virginia, targets the Bluestone River and tributaries suspected of contributing to polychlorinated biphenyl, polychlorinated dibenzo-p-dioxin and dibenzofuran contamination, and includes sites near confluences of Big Branch, Brush Fork, and Beaver Pond Creek. The objectives of this study were to gather information about the concentrations, patterns, and distribution of these contaminants at specific study sites to expand current knowledge about polychlorinated biphenyl impacts and to identify potential new sources of contamination. Semipermeable membrane devices were used to integratively accumulate the dissolved fraction of the contaminants at each site. Performance reference compounds were added prior to deployment and used to determine site-specific sampling rates, enabling estimations of time-weighted average water concentrations during the deployed period. Minimum estimated concentrations of polychlorinated biphenyl congeners in water were about 1 picogram per liter per congener, and total concentrations at study sites ranged from 130 to 18,000 picograms per liter. The lowest concentration was 130 picograms per liter, about threefold greater than total hypothetical concentrations from background levels in field blanks. Polychlorinated biphenyl concentrations in water fell into three groups of sites: low (130-350 picogram per liter); medium (640-3,500 picogram per liter; and high (11,000-18,000 picogram per liter). Concentrations at the high sites, Beacon Cave and Beaverpond Branch at the Resurgence, were about four- to sixfold higher than concentrations estimated for the medium group of sites. Minimum estimated concentrations of polychlorinated dibenzo-p-dioxin and dibenzofuran congeners in water were about 0.2 to 1 femtograms per liter. Estimated total concentrations of 2,3,7,8-substituted congeners in water at study sites ranged from less than 1 to 22,000 femtograms per liter and less than 1 to 2,300 femtograms per liter for polychlorinated dibenzo-p-dioxin and dibenzofuran congeners, respectively. Total concentrations of 2,3,7,8-substituted congeners in water were comprised largely of octachlorodibenzo-p-dioxin and dibenzofuran, with less than 10 percent of the total contributed by concentrations of other congeners, mainly 2,3,7,8-heptachlorodibenzo-p-dioxin and dibenzofuran. Of special interest for this study was 2,3,7,8-tetrachlorodibenzo-p-dioxin with a regulatory surface water-quality criterion of 1,200 femtograms per liter. Estimated concentrations in water ranged from 0.5 to 41 femtograms per liter. Concentrations in water were less than 5 femtograms per liter at all study sites, except the Bluefield Westside Sewage Treatment Plan, with an estimated concentration of 41 femtograms per liter. Estimated total concentrations of homologs of polychlorinated dibenzo-p-dioxins and dibenzofurans in water at the study sites ranged from 3,200 to 36,000 femtograms per liter and 210-4,800 femtograms per liter, respectively. Again, homologs of polychlorinated dibenzo-p-dioxins and dibenzofurans in water were comprised largely of octachlorodibenzo-p-dioxin and dibenzofuran.

  19. The effect of membrane filtration on dissolved trace element concentrations

    USGS Publications Warehouse

    Horowitz, A.J.; Lum, K.R.; Garbarino, J.R.; Hall, G.E.M.; Lemieux, C.; Demas, C.R.

    1996-01-01

    The almost universally accepted operational definition for dissolved constituents is based on processing whole-water samples through a 0.45-??m membrane filter. Results from field and laboratory experiments indicate that a number of factors associated with filtration, other than just pore size (e.g., diameter, manufacturer, volume of sample processed, amount of suspended sediment in the sample), can produce substantial variations in the 'dissolved' concentrations of such elements as Fe, Al, Cu, Zn, Pb, Co, and Ni. These variations result from the inclusion/exclusion of colloidally- associated trace elements. Thus, 'dissolved' concentrations quantitated by analyzing filtrates generated by processing whole-water through similar pore- sized membrane filters may not be equal/comparable. As such, simple filtration through a 0.45-??m membrane filter may no longer represent an acceptable operational definition for dissolved chemical constituents. This conclusion may have important implications for environmental studies and regulatory agencies.

  20. Effect of membrane filtration artifacts on dissolved trace element concentrations

    USGS Publications Warehouse

    Horowitz, Arthur J.; Elrick, Kent A.; Colberg, Mark R.

    1992-01-01

    Among environment scientists, the current and almost universally accepted definition of dissolved constituents is an operational one; only those materials which pass through a 0.45-??m membrane filter are considered to be dissolved. Detailed laboratory and field studies on Fe and Al indicate that a number of factors associated with filtration, other than just pore size, can substantially alter 'dissolved' trace element concentrations; these include: filter type, filter diameter, filtration method, volume of sample processed, suspended sediment concentration, suspended sediment grain-size distribution, concentration of colloids and colloidally associated trace elements and concentration of organic matter. As such, reported filtered-water concentrations employing the same pore size filter may not be equal. Filtration artifacts may lead to the production of chemical data that indicate seasonal or annual 'dissolved' chemical trends which do not reflect actual environmental conditions. Further, the development of worldwide averages for various dissolved chemical constituents, the quantification of geochemical cycles, and the determination of short- or long-term environmental chemical trends may be subject to substantial errors, due to filtration artifacts, when data from the same or multiple sources are combined. Finally, filtration effects could have a substantial impact on various regulatory requirements.

  1. Investigating Factors that Affect Dissolved Oxygen Concentration in Water

    ERIC Educational Resources Information Center

    Jantzen, Paul G.

    1978-01-01

    Describes activities that demonstrate the effects of factors such as wind velocity, water temperature, convection currents, intensity of light, rate of photosynthesis, atmospheric pressure, humidity, numbers of decomposers, presence of oxidizable ions, and respiration by plants and animals on the dissolved oxygen concentration in water. (MA)

  2. Variations in dissolved organic carbon concentrations across peatland hillslopes

    NASA Astrophysics Data System (ADS)

    Boothroyd, I. M.; Worrall, F.; Allott, T. E. H.

    2015-11-01

    Peatlands are important terrestrial carbon stores and dissolved organic carbon (DOC) is one of the most important contributors to carbon budgets in peatland systems. Many studies have investigated factors affecting DOC concentration in peatland systems, yet hillslope position has been thus far overlooked as a variable that could influence DOC cycling. This study investigates the importance of hillslope position with regard to DOC cycling. Two upland peat hillslopes were studied in the Peak District, UK, to determine what impact, if any, hillslope position had upon DOC concentration. Hillslope position was found to be a significant factor affecting variation in soil pore water DOC concentration, with bottom-slope positions having significantly lower DOC concentrations than up-slope because of dilution of DOC as water moves down-slope and is flushed out of the system via lateral throughflow. Water table drawdown on steeper mid-slopes increased DOC concentrations through increased DOC production and extended residence times allowing a build-up of humic-rich DOC compounds. Hillslope position did not significantly affect DOC concentrations in surface runoff water because of the dilution of near-surface soil pore water by precipitation inputs, while stream water had similar water chemistry properties to soil pore water under low-flow conditions.

  3. Using Performance Reference Compounds (PRCs) to measure dissolved water concentrations (Cfree) in the water column: Assessing equilibrium models

    EPA Science Inventory

    Equilibrium-based passive sampling methods are often used in aquatic environmental monitoring to measure hydrophobic organic contaminants (HOCs) and in the subsequent evaluation of their effects on ecological and human health. HOCs freely dissolved in water (Cfree) will partition...

  4. 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

  5. Dissolved-solids concentrations of ground water in the Sacramento Valley, California

    USGS Publications Warehouse

    Fogelman, Ronald P.

    1982-01-01

    The general quality of the ground water in the Sacramento Valley , Calif., in terms of dissolved-solids concentration is considered good for irrigation, domestic, and most other uses. This map shows the distribution of dissolved-solids concentrations and is based on about 1,330 chemical analyses collected from about 900 wells between 1974 and 1978. On the west side of the valley some of the smaller streams contribute water of higher dissolved-solids concentrations to the ground water. The sources of these waters are thought to be the upper Cretaceous Chico Formation or marine deposits of Early Cretaceous age that are exposed in the Coast Ranges. (USGS)

  6. Quantitative concentration measurements of creatinine dissolved in water and urine using Raman

    E-print Network

    Berger, Andrew J.

    Quantitative concentration measurements of creatinine dissolved in water and urine using Raman (LCOF) geometry to enhance the collection of Raman scattering from the biochemical creatinine, dissolved in water and in urine. At short integration times, where shot noise is most troublesome, the enhanced

  7. [Concentrations and Speciation of Dissolved Heavy Metal in Rainwater in Guiyang, China].

    PubMed

    Zhu, Zhao-zhou; Li, Jun; Wang, Zhi-ru

    2015-06-01

    In order to understand the pollution situation, as well as seasonal changes in characteristics and speciation of dissolved heavy metals in acid rain control zone, the concentrations of dissolved heavy metals in rainwater collected at Guiyang were measured using inductively coupled plasma mass spectrometry (ICP-MS). And the speciation of dissolved heavy metals was further simulated by PHREEQC model. The results showed that the dissolved Co, Ni, Cu, Zn and Cd concentrations were low and not higher than the national standards for drinking water quality in China. The dissolved Pd concentrations were high in fall and winter and higher than the national standards for drinking water quality in China. The Co and Ni in rainwater mainly came from the crust and there was almost no human impact. The Cu, Zn, Cd and Pd pollutions in rainwater were affected by human activity with different levels. The degrees of contamination in autumn and winter were more serious than those in spring and summer. The free metal ion species was the dominant form of dissolved heavy metal, accounting for 47.27%-95.28% of the dissolved metal in rainwater from Guiyang city. The free metal ion species was followed in abundance by Metal-Oxalate and Metal-sulfate complexes that accounted for 0.72% -51.87% and 0.50%-7.66%, respectively. The acidity of rainwater, acid type as well as content of ligand more likely controlled the distribution of dissolved heavy metal in precipitation. PMID:26387294

  8. COEUR D'ALENE LAKE, IDAHO. HYPOLIMNETIC CONCENTRATIONS OF DISSOLVED OXYGEN, NUTRIENTS, AND TRACE ELEMENTS, 1987

    EPA Science Inventory

    A reconnaissance study of Coeur dAlene Lake, Idaho (17010303) done from May through November 1987 assessed water quality throughout the lake. Particular emphasis was on hypolimnetic concentrations of dissolved oxygen, nutrients, and trace elements. Study results enabled refinem...

  9. 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.

  10. Production Responses of Channel Catfish to Minimum Daily Dissolved Oxygen Concentrations in Earthen Ponds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The purpose of this study was to determine the effects of the minimum daily dissolved oxygen (DO) concentration on production parameters of channel catfish Ictalurus punctatus in earthen ponds. Fifteen one-acre ponds (5 ponds per treatment) were managed as High Oxygen (minimum DO concentrations aver...

  11. The effect of membrane filtration artifacts on dissolved trace element concentrations

    USGS Publications Warehouse

    Horowitz, A.J.; Elrick, K.A.; Colberg, M.R.

    1992-01-01

    Among environment scientists, the current and almost universally accepted definition of dissolved constituents is an operational one only those materials which pass through a 0.45-??m membrane filter are considered to be dissolved. Detailed laboratory and field studies on Fe and Al indicate that a number of factors associated with filtration, other than just pore size, can substantially alter 'dissolved' trace element concentrations; these include: filter type, filter diameter, filtration method, volume of sample processed, suspended sediment concentration, suspended sediment grain-size distribution, concentration of colloids and colloidally-associated trace elements and concentration of organic matter. As such, reported filtered-water concentrations employing the same pore size filter may not be equal. Filtration artifacts may lead to the production of chemical data that indicate seasonal or annual 'dissolved' chemical trends which do not reflect actual environmental conditions. Further, the development of worldwide averages for various dissolved chemical constituents, the quantification of geochemical cycles, and the determination of short- or long-term environmental chemical trends may be subject to substantial errors, due to filtration artifacts, when data from the same or multiple sources are combined. Finally, filtration effects could have a substantial impact on various regulatory requirements.

  12. Dissolved volatile concentrations in an ore-forming magma

    USGS Publications Warehouse

    Lowenstern, J. B.

    1994-01-01

    Infrared spectroscopic measurements of glass inclusions within quartz phenocrysts from the Plinian fallout of the 22 Ma tuff of Pine Grove show that the trapped silicate melt contained high concentrations of H2O and CO2. Intrusive porphyries from the Pine Grove system are nearly identical in age, composition, and mineralogy to the tephra, and some contain high-grade Mo mineralization. Assuming that the porphyry magmas originally contained similar abundances of volatile components as the erupted rocks, they would have been saturated with fluid at pressures far greater than those at which the porphyries were emplaced and mineralized. The data are consistent with formation of Climax-type Mo porphyry deposits by prolonged fluid flux from a large volume of relatively Mo-poor (1-5 ppm) magma. -from Author

  13. Application of passive sampling for measuring dissolved concentrations of organic contaminants in the water column at three marine superfund sites.

    PubMed

    Burgess, Robert M; Lohmann, Rainer; Schubauer-Berigan, Joseph P; Reitsma, Pamela; Perron, Monique M; Lefkovitz, Lisa; Cantwell, Mark G

    2015-08-01

    Currently, there is an effort under way to encourage remedial project managers at contaminated sites to use passive sampling to collect freely dissolved concentrations (Cfree ) of hydrophobic organic contaminants to improve site assessments. The objective of the present study was to evaluate the use of passive sampling for measuring water column Cfree for several hydrophobic organic contaminants at 3 US Environmental Protection Agency Superfund sites. Sites investigated included New Bedford Harbor (New Bedford, MA, USA), Palos Verdes Shelf (Los Angeles, CA, USA), and Naval Station Newport (Newport, RI, USA); and the passive samplers evaluated were polyethylene, polydimethylsiloxane-coated solid-phase microextraction fibers, semipermeable membrane devices, and polyoxymethylene. In general, the different passive samplers demonstrated good agreement, with Cfree values varying by a factor of 2 to 3. Further, at New Bedford Harbor, where conventional water sample concentrations were also measured (i.e., grab samples), passive sampler-based Cfree values agreed within a factor of 2. These findings suggest that all of the samplers were experiencing and measuring similar Cfree during their respective deployments. Also, at New Bedford Harbor, a strong log-linear, correlative, and predictive relationship was found between polyethylene passive sampler accumulation and lipid-normalized blue mussel bioaccumulation of polychlorinated biphenyls (r(2) ?=?0.92, p?

  14. Diel Variation in Dissolved Trace-Element Concentrations in Streams Draining Abandoned Mine Lands

    NASA Astrophysics Data System (ADS)

    Nimick, D. A.

    2001-12-01

    Substantial diel (24-hour) variations in dissolved trace-element concentrations have been measured during 20 different hourly sampling episodes at 14 sites on 9 streams draining historical mining areas in Montana. At all sites, concentrations of dissolved (0.1-um filtration) Cd, Mn, and Zn increased during the night, reaching maximum values shortly after sunrise; concentrations then decreased to minimum values during mid to late afternoon. Dissolved As concentrations exhibited the opposite temporal pattern, while variations in dissolved Cu concentrations were small and displayed no consistent pattern. Most sites were sampled during low-flow conditions, but two sampling episodes during snowmelt runoff at one site showed that similar diel variations occur during high flow. All sites had near neutral to slightly alkaline pH. Diel variations did not occur in two other acidic (pH of 4.0-5.5) streams. The magnitude of change during diel concentration cycles varied for each trace element. Zn and Mn concentrations exhibited the largest variation, with maximum concentrations ranging from 120 to 590 percent higher than minimum concentrations. Cd maximum concentrations were about 200 percent higher than minimum concentrations, whereas As maximum concentrations were 115 to 155 percent higher. Diel trace-element cycles appear to be independent of concentration magnitude, occurring over a wide range of concentrations: 5-44 ug/L As; 1-7 ug/L Cd, 18-609 ug/L Mn, and 2-4,940 ug/L Zn. Several chemical, physical, and biological processes potentially can explain diel dissolved-trace-element cycles. Temperature- and pH-dependent sorption reactions occurring on streambed material in the channel and hyporheic zone are considered the most likely mechanisms because of the strong similarity in the symmetry and magnitude of temporal plots of concentration, temperature, and pH. In addition, sorption processes can explain the simultaneous decrease in divalent metal concentrations during the day (when pH and temperature increase) and increase in anion concentrations such as arsenate. Many sorption studies have documented the importance of pH, but the role of temperature has been largely overlooked. Diel cycles are robust and reproducible and are sufficiently widespread and of sufficient magnitude that our understanding of trace-element mobility needs reconsideration. Consequently, diel cycles are a very important consideration when developing or interpreting trace-element studies designed to identify trace-element sources, long-term trends, or effectiveness of remediation activities.

  15. Titrimetric determination of silicon dissolved in concentrated HF-HNO3-etching solutions.

    PubMed

    Henssge, Antje; Acker, Jörg; Müller, Constanze

    2006-01-15

    The wet chemical etching of silicon by concentrated HF-HNO(3) mixtures in solar and semiconductor wafer fabrication requires the strict control of the etching conditions. Surface morphology and etch rates are mainly affected by the amount of dissolved silicon, that is continuously enriched in the etching solution with each etching run. A fast and robust method for the titrimetric determination of the total dissolved silicon content out of the concentrated etching solution is presented. This method is based on the difference between the two equivalence points of the total amount of acid and the hydrolysis of the hexafluorosilicic anion. This approach allows a silicon determination directly from the etching process in spite of the presence of dissolved nitric oxides in the etching solution. The influences of different acid mixing ratios and of the etching solution density depending on the silicon content is considered and discussed in detail. PMID:18970360

  16. Problems associated with using filtration to define dissolved trace element concentrations in natural water samples

    USGS Publications Warehouse

    Horowitz, A.J.; Lum, K.R.; Garbarino, J.R.; Hall, G.E.M.; Lemieux, C.; Demas, C.R.

    1996-01-01

    Field and laboratory experiments indicate that a number of factors associated with filtration other than just pore size (e.g., diameter, manufacturer, volume of sample processed, amount of suspended sediment in the sample) can produce significant variations in the 'dissolved' concentrations of such elements as Fe, Al, Cu, Zn, Pb, Co, and Ni. The bulk of these variations result from the inclusion/exclusion of colloidally associated trace elements in the filtrate, although dilution and sorption/desorption from filters also may be factors. Thus, dissolved trace element concentrations quantitated by analyzing filtrates generated by processing whole water through similar pore-sized filters may not be equal or comparable. As such, simple filtration of unspecified volumes of natural water through unspecified 0.45-??m membrane filters may no longer represent an acceptable operational definition for a number of dissolved chemical constituents.

  17. Declines in Dissolved Silica Concentrations in Western Virginia Streams (1988- 2003)

    NASA Astrophysics Data System (ADS)

    Grady, A. E.; Scanlon, T. M.; Galloway, J. N.

    2006-12-01

    Dissolved silica concentrations in western Virginia streams showed a significant bias toward declines (p<0.0001) over the time period from 1988-2003. Streams with the greatest declines were those that had the highest mean dissolved silica concentrations, specific to watersheds underlain by basaltic and granitic bedrock. We examined potential geochemical, hydrological, and biological factors that could account for the observed widespread declines, focusing on six core watersheds where weekly stream chemistry data were available. No relationships were evident between stream water dissolved silica concentrations and pH, a finding supported by the results from a geochemical model applied to the dominant bedrock mineralogy. Along with changes in watershed acidity, changes in precipitation and discharge were also discounted since no significant trends were observed over the study period. Analyses of two longer-term datasets that extend back to 1979 revealed that the initiation of the dissolved silica declines coincided with the timing of a gypsy moth (Lymantria dispar) defoliation event. We develop a conceptual model centered on benthic diatoms, which are found within each of the six core watersheds but in greater abundance in the more silica-rich streams. Gypsy moth defoliation lead to greater sunlight penetration and enhanced nitrate concentrations in the streams, which could have spurred population growth and silica uptake. The model can explain why the observed declines are primarily driven by decreased concentrations during low-flow conditions. This study illustrates lasting effects of disturbance on watershed biogeochemistry, in this case causing decadal-scale variability in stream water dissolved silica concentrations.

  18. Novel Apparatus for the Real-Time Quantification of Dissolved Gas Concentrations and Isotope Ratios

    NASA Astrophysics Data System (ADS)

    Gupta, M.; Leen, J.; Baer, D. S.; Owano, T. G.; Liem, J.

    2013-12-01

    Measurements of dissolved gases and their isotopic composition are critical in studying a variety of phenomena, including underwater greenhouse gas generation, air-surface exchange, and pollution migration. These studies typically involve obtaining water samples from streams, lakes, or ocean water and transporting them to a laboratory, where they are degased. The gases obtained are then generally measured using gas chromatography and isotope ratio mass spectrometry for concentrations and isotope ratios, respectively. This conventional, off-line methodology is time consuming, significantly limits the number of the samples that can be measured and thus severely inhibits detailed spatial and temporal mapping of gas concentrations and isotope ratios. In this work, we describe the development of a new membrane-based degassing device that interfaces directly to Los Gatos Research (cavity enhanced laser absorption or Off-Axis ICOS) gas analyzers (cavity enhanced laser absorption or Off-Axis ICOS analyzers) to create an autonomous system that can continuously and quickly measure concentrations and isotope ratios of dissolved gases in real time in the field. By accurately controlling the water flow rate through the membrane degasser, gas pressure on the outside of the membrane, and water pressure on the inside of the membrane, the system is able to generate precise and highly reproducible results. Moreover, by accurately measuring the gas flow rates in and out of the degasser, the gas-phase concentrations (ppm) could be converted into dissolved gas concentrations (nM). We will present detailed laboratory test data that quantifies the linearity, precision, and dynamic range of the system for the concentrations and isotope ratios of dissolved methane, carbon dioxide, and nitrous oxide. By interfacing the degassing device to a novel cavity-enhanced spectrometer (developed by LGR), preliminary data will also be presented for dissolved volatile organics (VOC) and other pollutants. Finally, the system was deployed shipboard, and field deployment data will also be presented.

  19. Declines in dissolved silica concentrations in western Virginia streams (19882003): Gypsy moth defoliation stimulates diatoms?

    E-print Network

    Scanlon, Todd

    Declines in dissolved silica concentrations in western Virginia streams (1988­2003): Gypsy moth with the timing of a gypsy moth (Lymantria dispar) defoliation event. We develop a conceptual model centered in the more silica-rich streams. Gypsy moth defoliation led to greater sunlight penetration and enhanced

  20. ACUTE SENSITIVITY OF JUVENILE SHORTNOSE STURGEON TO LOW DISSOLVED OXYGEN CONCENTRATIONS

    EPA Science Inventory

    Campbell, Jed G. and Larry R. Goodman. 2004. Acute Sensitivity of Juvenile Shortnose Sturgeon to Low Dissolved Oxygen Concentrations. EPA/600/J-04/175. Trans. Am. Fish. Soc. 133(3):772-776. (ERL,GB 1155).

    There is considerable concern that factors such as eutrophication, ...

  1. Naturally dissolved arsenic concentrations in the Alpine/Mediterranean Var River watershed (France).

    PubMed

    Barats, Aurélie; Féraud, Gilbert; Potot, Cécile; Philippini, Violaine; Travi, Yves; Durrieu, Gaël; Dubar, Michel; Simler, Roland

    2014-03-01

    A detailed study on arsenic (As) in rocks and water from the Var River watershed was undertaken aiming at identifying (i) the origin and the distribution of As in this typical Alpine/Mediterranean basin, and (ii) As input into the Mediterranean Sea. Dissolved As concentrations in the Var River range from 0.1 to 4.5 ?g?L(-1), due to high hydrological variability and the draining through different geological formations. In the upper part of the Var drainage basin, in the Tinée and the Vésubie valleys, high levels of dissolved As concentrations occur (up to 263 ?g?L(-1)). The two main sources of As in rocks are the Hercynian metamorphic rocks and the Permian argilites. Highly heterogeneous distribution of As in waters draining through metamorphic rocks is probably related to ore deposits containing arsenopyrite. As, U, W and Mo concentrations in water and rocks correspond to the formation of As-rich ore deposits around Argentera granite by hydrothermal fluids deposited at the end of the Hercynian chain formation, which occurred about 300 My ago. In 2009, weekly monitoring was performed on the Var River (15 km upstream of the mouth), highlighting an average dissolved As concentration (<0.45 ?m) of 2.7 ± 0.9 ?g?L(-1), which is significantly higher than the world-average baseline for river water (0.83 ?g?L(-1)). Taking the average annual discharge (49.4 m(3)?s(-1)) into account and the As levels in the dissolved phase and in deposits of the Var River, dissolved As input into the Mediterranean Sea would be 4. 2± 1.4 tons?year(-1) which represents 59% of the total As flux. This study also reveals a probable non-conservative As behaviour, i.e., possible transfer between aqueous and solid phases, during the mixing of the Var River with a tributary. PMID:24388820

  2. Fluoride, Nitrate, and Dissolved-Solids Concentrations in Ground Waters of Washington

    USGS Publications Warehouse

    Lum, W. E., II; Turney, Gary L.

    1984-01-01

    This study provides basic data on ground-water quality throughout the State. It is intended for uses in planning and management by agencies and individuals who have responsibility for or interest in, public health and welfare. It also provides a basis for directing future studies of ground-water quality toward areas where ground-water quality problems may already exist. The information presented is a compilation of existing data from numerous sources including: the Washington Departments of Ecology and Social and Health Services, the Environmental Protection Agency, as well as many other local, county, state and federal agencies and private corporations. Only data on fluoride, nitrate, and dissolved-solids concentrations in ground water are presented, as these constituents are among those commonly used to determine the suitability of water for drinking or other purposes. They also reflect both natural and man-imposed effects on water quality and are the most readily available water-quality data for the State of Washington. The percentage of wells with fluoride, nitrate, or dissolved-solids concentrations exceeding U.S. Environmental Protection Agency Primary and Secondary Drinking Water Regulations were about 1, about 3, and about 3, respectively. Most high concentrations occurred in widely separated wells. Two exceptions were: high concentrations of nitrate and dissolved solids in wells on the Hanford Department of Energy Facility and high concentrations of nitrate in the lower Yakima River basin. (USGS)

  3. 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.

  4. The "dead zone" is a large area of decreased dissolved oxygen concentration in bottom waters that forms

    E-print Network

    Dodds, Walter

    The "dead zone" is a large area of decreased dissolved oxygen concentration in bottom waters.frontiersinecology.org REVIEWS REVIEWS REVIEWS Nutrients and the "dead zone": the link between nutrient ratios and dissolved oxygen in the northern Gulf of Mexico Walter K Dodds The "dead zone", an area with reduced concentrations

  5. Impact of solute concentration on the electrocatalytic conversion of dissolved gases in buffered solutions

    NASA Astrophysics Data System (ADS)

    Shinagawa, Tatsuya; Takanabe, Kazuhiro

    2015-08-01

    To maintain local pH levels near the electrode during electrochemical reactions, the use of buffer solutions is effective. Nevertheless, the critical effects of the buffer concentration on electrocatalytic performances have not been discussed in detail. In this study, two fundamental electrochemical reactions, oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR), on a platinum rotating disk electrode are chosen as model gas-related aqueous electrochemical reactions at various phosphate concentrations. Our detailed investigations revealed that the kinetic and limiting diffusion current densities for both the ORR and HOR logarithmically decrease with increasing solute concentration (log |jORR | = - 0.39 c + 0.92 , log |jHOR | = - 0.35 c + 0.73) . To clarify the physical aspects of this phenomenon, the electrolyte characteristics are addressed: with increasing phosphate concentration, the gas solubility decrease, the kinematic viscosity of the solution increase and the diffusion coefficient of the dissolved gases decrease. The simulated limiting diffusion currents using the aforementioned parameters match the measured ones very well (log |jORR | = - 0.43 c + 0.99 , log |jHOR | = - 0.40 c + 0.54) , accurately describing the consequences of the electrolyte concentration. These alterations of the electrolyte properties associated with the solute concentration are universally applicable to other aqueous gas-related electrochemical reactions because the currents are purely determined by mass transfer of the dissolved gases.

  6. Diel cycles in dissolved metal concentrations in streams: Occurrence and possible causes

    USGS Publications Warehouse

    Nimick, D.A.; Gammons, C.H.; Cleasby, T.E.; Madison, J.P.; Skaar, D.; Brick, C.M.

    2003-01-01

    Substantial diel (24-hour) cycles in dissolved (0.1-??m filtration) metal concentrations were observed during low flow for 18 sampling episodes at 14 sites on 12 neutral and alkaline streams draining historical mining areas in Montana and Idaho. At some sites, concentrations of Cd, Mn, Ni, and Zn increased as much as 119, 306, 167, and 500%, respectively, from afternoon minimum values to maximum values shortly after sunrise. Arsenic concentrations exhibited the inverse temporal pattern with increases of up to 54%. Variations in Cu concentrations were small and inconsistent. Diel metal cycles are widespread and persistent, occur over a wide range of metal concentrations, and likely are caused primarily by instream geochemical processes. Adsorption is the only process that can explain the inverse temporal patterns of As and the divalent metals. Diel metal cycles have important implications for many types of water-quality studies and for understanding trace-metal mobility.

  7. Dissolved sulfide in groundwater with elevated arsenic concentrations at Winthrop, Maine

    NASA Astrophysics Data System (ADS)

    He, Y.; Zheng, Y.; Zheng, Y.; Locke, D. C.; Simpson, J. H.; Stute, M.

    2001-12-01

    Although sulfur is a biogeochemically significant element because of its strong influence on and response to redox conditions, there are relatively few reliable data sets of trace levels of dissolved sulfide \\(less than1 uM \\) in groundwaters This circumstance results from the relatively high detection limit \\(˜ 1uM \\) of methylene blue colorimetry and the general lack of sensitive methods for field analysis. We were motivated to investigate trace levels of dissolved sulfide because highly insoluble sulfide precipitates of many elements such as As and Fe represent important removal pathways for these metals in reducing groundwaters. Using differential pulse cathodic stripping voltammetry \\(DPCSV\\) capable of detecting 4 nM of dissolved sulfide, we observed that at a site in Winthrop, Maine, groundwater sulfide concentrations ranged from less than 4 nM to ˜ 2000 nM for about a dozen multi-level observation wells under a landfill cap and less than 4 nM to ˜ 7300 nM from several nearby monitoring wells outside the landfill. Sulfide concentrations generally increased when oxygen reduction potential \\(ORP\\) values became more negative. Determination of sulfide should be carried out within 1 hr of sample collection. Samples taken by two methods, \\(1\\) PTFE syringes with luer-lock valves and \\(2\\) BOD bottles show a rapid decline of sulfide following sampling, with up to 90% and 60% losses, respectively, after 24 hrs of storage at 4 ° C. Despite the three orders of magnitude range of dissolved sulfide, arsenic and iron concentrations were all elevated in observational wells installed in a roughly 25 m by 20 m rectangle under the landfill cap, suggesting that As remains mobile under mildly sulfate-reducing conditions. In one well outside of the landfill area, with extremely negative ORP \\(-321 mV\\) and ˜ 7300 nM of dissolved sulfide, groundwater was very low in dissolved As, Fe, and sulfate, suggesting that precipitation of arsenopyrite could be a plausible mechanism for removing As in extremely reducing groundwaters.

  8. Distribution of dissolved and particulate radiocesium concentrations along rivers and the relations between radiocesium concentration and deposition after the nuclear power plant accident in Fukushima.

    PubMed

    Tsuji, Hideki; Yasutaka, Tetsuo; Kawabe, Yoshishige; Onishi, Takeo; Komai, Takeshi

    2014-09-01

    This study involved measurement of concentrations of dissolved and particulate radiocesium ((134)Cs and (137)Cs) in river water, and determination of the quantitative relations between the amount of deposited (137)Cs and (137)Cs concentrations in river waters after the Fukushima Daiichi nuclear power plant accident. First, the current concentrations of dissolved and particulate (134)Cs·(137)Cs were determined in a river watershed from 20 sampling locations in four contaminated rivers (Abukuma, Kuchibuto, Shakado, and Ota). Distribution characteristics of different (137)Cs forms varied with rivers. Moreover, a higher dissolved (137)Cs concentration was observed at the sampling location where the (137)Cs deposition occurred much more heavily. In contrast, particulate (137)Cs concentration along the river was quite irregular, because fluctuations in suspended solids concentrations occur easily from disturbance and heavy precipitation. A similar tendency with dissolved (137)Cs distribution was observed for the (137)Cs concentration per unit weight of suspended solids. Regression analysis between deposited (137)Cs and dissolved/particulate (137)Cs concentrations was performed for the four rivers. The results showed a strong correlation between deposited (137)Cs and dissolved (137)Cs, and a relatively weak correlation between deposited (137)Cs and particulate (137)Cs concentration for each river. However, if the particulate (137)Cs concentration was converted to (137)Cs concentration per unit weight of suspended solid, the values showed a strong correlation with deposited (137)Cs. PMID:24813506

  9. Assessing time-integrated dissolved concentrations and predicting toxicity of metals during diel cycling in streams

    USGS Publications Warehouse

    Balistrieri, Laurie S.; Nimick, David A.; Mebane, Christopher A.

    2012-01-01

    Evaluating water quality and the health of aquatic organisms is challenging in systems with systematic diel (24 h) or less predictable runoff-induced changes in water composition. To advance our understanding of how to evaluate environmental health in these dynamic systems, field studies of diel cycling were conducted in two streams (Silver Bow Creek and High Ore Creek) affected by historical mining activities in southwestern Montana. A combination of sampling and modeling tools was used to assess the toxicity of metals in these systems. Diffusive Gradients in Thin Films (DGT) samplers were deployed at multiple time intervals during diel sampling to confirm that DGT integrates time-varying concentrations of dissolved metals. Site specific water compositions, including time-integrated dissolved metal concentrations determined from DGT, a competitive, multiple-toxicant biotic ligand model, and the Windemere Humic Aqueous Model Version 6.0 (WHAM VI) were used to determine the equilibrium speciation of dissolved metals and biotic ligands. The model results were combined with previously collected toxicity data on cutthroat trout to derive a relationship that predicts the relative survivability of these fish at a given site. This integrative approach may prove useful for assessing water quality and toxicity of metals to aquatic organisms in dynamic systems and evaluating whether potential changes in environmental health of aquatic systems are due to anthropogenic activities or natural variability.

  10. New method for the direct determination of dissolved Fe(III) concentration in acid mine waters

    USGS Publications Warehouse

    To, T.B.; Nordstrom, D.K.; Cunningham, K.M.; Ball, J.W.; McCleskey, R.B.

    1999-01-01

    A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II) >> Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), AI(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2 ??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II)???Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), Al(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2/??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.

  11. 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.

  12. New method for the direct determination of dissolved Fe(III) concentration in acid mine waters

    SciTech Connect

    To, T.B.; Nordstrom, D.K.; Cunningham, K.M.; Ball, J.W.; McCleskey, R.B.

    1999-03-01

    A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II) {much_gt} Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), Al(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand. Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2 {micro}g/L using GFAAS and 20 {micro}g/L by colorimetry.

  13. The impact of seasonality and elevation on dissolved greenhouse gas concentrations in a northeastern Wyoming watershed

    NASA Astrophysics Data System (ADS)

    Kuhn, C.; Bettigole, C.; Raymond, P. A.; Glick, H.; Seegmiller, L.; Oliver, C.; Khadka, A.; Routh, D.

    2014-12-01

    Quantification of river and stream contributions to global carbon emission budgets using field-based measurements is key to understanding how freshwater streams act as conduits between terrestrial and atmospheric carbon pools. In order to better characterize drivers of this process, this study quantifies: a) emissions of carbon dioxide and methane from a semi-arid, high plains riverine system with montaine headwaters in order to establish baseline data for the watershed; b) the impact of stream order, seasonality and elevation on dissolved gas concentrations to better understand the spatial and temporal heterogeneity of dissolved carbon gases. To achieve the latter objective, we conducted field surveys in first and second order streams in the Clear Creek drainage of the Powder River Basin watershed. We took direct measurements of stream gases using headspace sampling at thirty sites along an elevation gradient ranging from 1,203-3,346 meters. We also intensely monitored five transects throughout the descending limb of spring runoff (June 8th-August 12th) to investigate how temperature and discharge volume impact greenhouse gas concentrations. Clear Creek, located in northeastern Wyoming, is approximately 118.4 km long with a drainage area of 2,968 km2. The creek flows east out of Bighorn National Forest where it turns northeast to converge with the Powder River about ten miles before the Montana border. The stream straddles the Middle Rockies and Northwestern Great Plains ecoregions and experiences an abrupt shift in soil type, riparian vegetation, underlying geology and stream geometry as the stream exits the mountains and enters the agricultural alluvial floodplain. These site specific biological and physical changes along the elevation gradient affect dissolved greenhouse gas concentrations.

  14. Influence of land use on total suspended solid and dissolved ion concentrations: Baton Rouge, Louisiana area

    NASA Astrophysics Data System (ADS)

    Carlson, D.

    2015-03-01

    Past studies in the Baton Rouge, Louisiana area considered streamwater quality during storm events but ignored water quality during low flow periods. This study includes determination of streamwater quality during low flow time periods for none watersheds in East Baton Rouge Parish, Louisiana. These samples were collected during dry-low flow periods as indicated by water levels at USGS stream gauging sites for each stream. Chemical analysis for ions was completed using colorimeters and gravimetric analysis for total dissolved solids (TDS) and total suspended solids (TSS). Land use appears to impact concentrations of ions, TDS and TSS in a variety of ways during periods of low flow. The two most rural watersheds, which are mainly underdeveloped, have higher concentrations of Fe and Mn. By contrast the three most urban watersheds, that are mainly commercial, industrial or residential, have higher concentrations of Si, SO4 and TDS.

  15. Relationships between nutrients and dissolved oxygen concentrations on the Texas-Louisiana shelf during summer of 2004 

    E-print Network

    Lahiry, Sudeshna

    2009-06-02

    stratification. In 2004, three shelf wide cruises (in April, June and August) were conducted on the Louisiana Shelf to understand the mechanisms controlling hypoxia on the shelf, and examine the relationship between dissolved oxygen and nutrient concentrations...

  16. Dissolved-solids sources, loads, yields, and concentrations in streams of the conterminous United States

    USGS Publications Warehouse

    Anning, David W.; Flynn, Marilyn E.

    2014-01-01

    Recent studies have shown that excessive dissolved-solids concentrations in water can have adverse effects on the environment and on agricultural, domestic, municipal, and industrial water users. Such effects motivated the U.S. Geological Survey’s National Water Quality Assessment Program to develop a SPAtially-Referenced Regression on Watershed Attributes (SPARROW) model that has improved the understanding of sources, loads, yields, and concentrations of dissolved solids in streams of the conterminous United States. Using the SPARROW model, long-term mean annual dissolved-solids loads from 2,560 water-quality monitoring stations were statistically related to several spatial datasets that are surrogates for dissolved-solids sources and land-to-water delivery processes. Specifically, sources in the model included variables representing geologic materials, road deicers, urban lands, cultivated lands, and pasture lands. Transport of dissolved solids from these sources was modulated by land-to-water delivery variables that represent precipitation, streamflow, soil, vegetation, terrain, population, irrigation, and artificial drainage characteristics. Where appropriate, the load estimates, source variables, and transport variables were statistically adjusted to represent conditions for the base year 2000. The nonlinear least-squares estimated SPARROW model was used to predict long-term mean annual conditions for dissolved-solids sources, loads, yields, and concentrations in a digital hydrologic network representing nearly 66,000 stream reaches and their corresponding incremental catchments that drain the Nation. Nationwide, the predominant source of dissolved solids yielded from incremental catchments and delivered to local streams is geologic materials in 89 percent of the catchments, road deicers in 5 percent of the catchments, pasture lands in 3 percent of the catchments, urban lands in 2 percent of the catchments, and cultivated lands in 1 percent of the catchments. Whereas incremental catchments with dissolved solids that originated predominantly from geologic sources or from urban lands are found across much of the Nation, incremental catchments with dissolved solids yields that originated predominantly from road deicers are largely found in the Northeast, and incremental catchments with dissolved solids that originated predominantly from cultivated or pasture lands are largely found in the West. The total amount of dissolved solids delivered to the Nation’s streams is 271.9 million metric tons (Mt) annually, of which 194.2 million Mt (71.4%) come from geologic sources, 37.7 million Mt (13.9%) come from road deicers, 18.2 million Mt (6.7%) come from pasture lands, 13.9 million Mt (5.1%) come from urban lands, and 7.9 million Mt (2.9%) come from cultivated lands. Nationwide, the median incremental-catchment yield delivered to local streams is 26 metric tons per year per square kilometer [(Mt/yr)/km2]. Ten percent of the incremental catchments yield less than 4 (Mt/yr)/km2, and 10 percent yield more than 90 (Mt/yr)/km2. Incremental-catchment yields greater than 50 (Mt/yr)/km2 mostly occur along the northern part of the West Coast and in a crescent shaped band south of the Great Lakes. For example, the median incremental-catchment yield is 81 (Mt/yr)/km2 for the Great Lakes, 78 (Mt/yr)/km2 for the Ohio, and 74 (Mt/yr)/km2 for the Upper Mississippi water-resources regions. Incremental-catchment yields less than 10 (Mt/yr)/km2 mostly occur in a wide band across the arid lowland of the interior West that excludes areas along the coast and the extensive, higher mountain ranges. For example, the median incremental-catchment yield is 3 (Mt/yr)/km2 for the Lower Colorado, 5 (Mt/yr)/km2 for the Rio Grande, and 8 (Mt/yr)/km2 for the Great Basin water-resources regions. Predicted incremental loads were cascaded down through the reach network, with loads accumulating from reach to reach. For most stream reaches, the entire incremental load of dissolved solids delivered to the reach was transported to either the ocean or to one of

  17. Problem set 2: Constructing a nutrient budget for Bellingham Bay In recent years the concentration of dissolved oxygen in bottom water in Bellingham Bay has been

    E-print Network

    Shull, David H.

    of dissolved oxygen in bottom water in Bellingham Bay has been dropping. Oxygen concentration below about 4 mg L1 is termed hypoxia. Hypoxia indicates that dissolved oxygen concentrations are low enough by 2014. How will this expansion affect nutrient concentrations and levels of dissolved oxygen

  18. Variations in dissolved organic nitrogen concentration in biofilters with different media during drinking water treatment.

    PubMed

    Zhang, Huining; Zhang, Kefeng; Jin, Huixia; Gu, Li; Yu, Xin

    2015-11-01

    Dissolved organic nitrogen (DON) is potential precursor of disinfection byproducts (DBPs), especially nitrogenous DBPs. In this study, we investigated the impact of biofilters on DON concentration changes in a drinking water plant. A small pilot plant was constructed next to a sedimentation tank in a drinking water plant and included activated carbon, quartz sand, anthracite, and ceramsite biofilters. As the biofilter layer depth increased, the DON concentration first decreased and then increased, and the variation in DON concentration differed among the biofilters. In the activated carbon biofilter, the DON concentration was reduced by the largest amount in the first part of the column and increased by the largest amount in the second part of the column. The biomass in the activated carbon filter was less than that in the quartz sand filter in the upper column. The heterotrophic bacterial proportion among bacterial flora in the activated carbon biofilter was the largest, which might be due to the significant reduction in DON in the first part of the column. Overall, the results indicate that the DON concentration in biofiltered water can be controlled via the selection of appropriate biofilter media. We propose that a two-layer biofilter with activated carbon in the upper layer and another media type in the lower layer could best reduce the DON concentration. PMID:25576130

  19. Prediction of dissolved oxygen and carbon dioxide concentration profiles in tubular photobioreactors for microalgal culture

    PubMed

    Rubio; Fernandez; Perez; Camacho; Grima

    1999-01-01

    A model is developed for prediction of axial concentration profiles of dissolved oxygen and carbon dioxide in tubular photobioreactors used for culturing microalgae. Experimental data are used to verify the model for continuous outdoor culture of Porphyridium cruentum grown in a 200-L reactor with 100-m long tubular solar receiver. The culture was carried out at a dilution rate of 0.05 h-1 applied only during a 10-h daylight period. The quasi-steady state biomass concentration achieved was 3.0 g. L-1, corresponding to a biomass productivity of 1.5 g. L-1. d-1. The model could predict the dissolved oxygen level in both gas disengagement zone of the reactor and at the end of the loop, the exhaust gas composition, the amount of carbon dioxide injected, and the pH of the culture at each hour. In predicting the various parameters, the model took into account the length of the solar receiver tube, the rate of photosynthesis, the velocity of flow, the degree of mixing, and gas-liquid mass transfer. Because the model simulated the system behavior as a function of tube length and operational variables (superficial gas velocity in the riser, composition of carbon dioxide in the gas injected in the solar receiver and its injection rate), it could potentially be applied to rational design and scale-up of photobioreactors. Copyright 1999 John Wiley & Sons, Inc. PMID:10099515

  20. Temporal Variability of Stemflow Dissolved Organic Carbon (DOC) Concentrations and Quality from Morphologically Contrasting Deciduous Canopies

    NASA Astrophysics Data System (ADS)

    van Stan, J. T.; Levia, D. F.; Inamdar, S. P.; Mitchell, M. J.; Mage, S. M.

    2010-12-01

    Dissolved organic carbon (DOC) inputs from canopy-derived hydrologic fluxes play a significant role in the terrestrial carbon budgets of forested ecosystems. However, no studies known to the authors have examined the variability of both DOC concentrations and quality for stemflow across time scales, nor has any study to date evaluated the effects of canopy structure on stemflow DOC characteristics. This investigation seeks to rectify this knowledge gap by examining the variability of stemflow DOC concentrations and quality across contrasting canopy morphologies and time scales (seasonal, storm and intrastorm). Bulk and intrastorm stemflow samples from a less dense, rough-barked, more plagiophile (Liriodendron tulipifera L. (tulip poplar)) and a denser, thin-barked, more erectophile (Fagus grandifolia Ehrh. (American beech)) canopy were collected and analyzed for DOC quality using metrics derived from UV-vis spectroscopy (E2:E3 ratio, SUVA254, select spectral slope (S), and spectral slope ratios (SR)). Our results suggest that stemflow DOC concentrations and quality change as crown architectural traits enhance or diminish hydrologic retention time within the canopy. The architecture of L. tulipifera canopies likely retards the flow of intercepted water, increasing chemical exchange with bark and foliar surfaces. UV-vis metrics indicated that this increased chemical exchange, particularly with bark surfaces, generally enhanced aromatic hydrocarbon content and increased molecular weight. Because leaf presence influenced DOC quality, stemflow DOC characteristics also varied seasonally in response to canopy condition. At the inter- and intrastorm scale, stemflow DOC concentration and quality varied with meteorological and antecedent canopy conditions. Since recent studies have linked stemflow production to preferential subsurface transport of dissolved chemistries, trends in DOC speciation and fluxes described in this study may impact soil environments within wooded ecosystems.

  1. Effects of reduced dissolved oxygen concentrations on physiology and fluorescence of hermatypic corals and benthic algae

    PubMed Central

    Smith, Jennifer E.; Thompson, Melissa

    2014-01-01

    While shifts from coral to seaweed dominance have become increasingly common on coral reefs and factors triggering these shifts successively identified, the primary mechanisms involved in coral-algae interactions remain unclear. Amongst various potential mechanisms, algal exudates can mediate increases in microbial activity, leading to localized hypoxic conditions which may cause coral mortality in the direct vicinity. Most of the processes likely causing such algal exudate induced coral mortality have been quantified (e.g., labile organic matter release, increased microbial metabolism, decreased dissolved oxygen availability), yet little is known about how reduced dissolved oxygen concentrations affect competitive dynamics between seaweeds and corals. The goals of this study were to investigate the effects of different levels of oxygen including hypoxic conditions on a common hermatypic coral Acropora yongei and the common green alga Bryopsis pennata. Specifically, we examined how photosynthetic oxygen production, dark and daylight adapted quantum yield, intensity and anatomical distribution of the coral innate fluorescence, and visual estimates of health varied with differing background oxygen conditions. Our results showed that the algae were significantly more tolerant to extremely low oxygen concentrations (2–4 mg L?1) than corals. Furthermore corals could tolerate reduced oxygen concentrations, but only until a given threshold determined by a combination of exposure time and concentration. Exceeding this threshold led to rapid loss of coral tissue and mortality. This study concludes that hypoxia may indeed play a significant role, or in some cases may even be the main cause, for coral tissue loss during coral-algae interaction processes. PMID:24482757

  2. Factors Controlling Dissolved Oxygen Concentration in the Hyporheic Zone Induced by Fish Egg Nests

    NASA Astrophysics Data System (ADS)

    Ford, A.; Cardenas, M. B.; Kaufman, M.; Zheng, L.; Kessler, A. J.

    2014-12-01

    There is currently limited research on the effects of bed depressions, such as those associated with fish nests, on hyporheic flow and biogeochemistry. A series of flume experiments are in progress, with the aim of understanding the effects of bed depressions on the hyporheic flow of oxygenated water. This study focuses on fish nests, also called redds, which represent a typical depression or scour feature. Previous research has shown that redd topography induces hyporheic circulation, but experiments regarding the oxygen concentration in and around the redds have not been conducted. We are determining the ways in which redds affect dissolved oxygen distribution and how this is controlled by hyporheic flow. The oxygen concentration across the cross-sectional plane of a fish nest is measured using a planar optode and microsensors. Hydraulic measurements include pressure measurements along the sediment-water interface and dye visualization. The redd design is based on a salmonid redd, which consists of a scour feature and a tailspin. The salmonid eggs are found in the tailspin. We hypothesize that the oxygen concentration will be greatest in close proximity to the gravel base of the redd and concentration will decrease with increasing depth and distance from the redd. Higher oxygen concentrations in the tailspin supports the placement of fish eggs within that area as opposed to a less oxygenated area of the streambed. Thus, fish nests are likely bio-engineered to optimize hyporheic flow and biogeochemistry to improve egg viability.

  3. High variability in dissolved iron concentrations in the vicinity of the Kerguelen Islands (Southern Ocean)

    NASA Astrophysics Data System (ADS)

    Quéroué, F.; Sarthou, G.; Planquette, H. F.; Bucciarelli, E.; Chever, F.; van der Merwe, P.; Lannuzel, D.; Townsend, A. T.; Cheize, M.; Blain, S.; d'Ovidio, F.; Bowie, A. R.

    2015-06-01

    Dissolved Fe (dFe) concentrations were measured in the upper 1300 m of the water column in the vicinity of the Kerguelen Islands as part of the second KErguelen Ocean Plateau compared Study (KEOPS2). Concentrations ranged from 0.06 nmol L-1 in offshore, Southern Ocean waters to 3.82 nmol L-1 within Hillsborough Bay, on the north-eastern coast of the Kerguelen Islands. Direct island runoff, glacial melting and resuspended sediments were identified as important inputs of dFe that could potentially fertilise the northern part of the plateau. A significant deep dFe enrichment was observed over the plateau with dFe concentrations increasing up to 1.30 nmol L-1 close to the seafloor, probably due to sediment resuspension and pore water release. Biological uptake was shown to induce a significant decrease in dFe concentrations between two visits (28 days apart) at a station above the plateau. Our work also considered other processes and sources, such as lateral advection of enriched seawater, remineralisation processes, and the influence of the polar front (PF) as a vector for Fe transport. Overall, heterogeneous sources of Fe over and off the Kerguelen Plateau, in addition to strong variability in Fe supply by vertical or horizontal transport, may explain the high variability in dFe concentrations observed during this study.

  4. Trace metal concentrations in post-hatching cuttlefish Sepia officinalis and consequences of dissolved zinc exposure.

    PubMed

    Le Pabic, Charles; Caplat, Christelle; Lehodey, Jean-Paul; Milinkovitch, Thomas; Koueta, Noussithé; Cosson, Richard Philippe; Bustamante, Paco

    2015-02-01

    In this study, we investigated the changes of 13 trace metal and metalloid concentrations (i.e. Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, V, Zn) and their subcellular fractionation in juvenile cuttlefish Sepia officinalis reared in controlled conditions between hatching and 2 months post-hatching. In parallel, metallothionein concentrations were determined. Our results highlighted contrasting changes of studied metals. Indeed, As and Fe concentrations measured in hatchlings suggested a maternal transfer of these elements in cuttlefish. The non-essential elements Ag and Cd presented the highest accumulation during our study, correlated with the digestive gland maturation. During the 6 first weeks of study, soluble fractions of most of essential trace metals (i.e. Co, Cr, Cu, Fe, Se, Zn) slowly increased consistently with the progressive needs of cuttlefish metabolism during this period. In order to determine for the first time in a cephalopod how metal concentrations and their subcellular distributions are impacted when the animals are trace metal-exposed, we studied previously described parameters in juveniles exposed to dissolved Zn at environmental (i.e. 50 ?g l(-1)) and sublethal (i.e. 200 ?g l(-1)) levels. Moreover, oxidative stress (i.e. glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase activities, and lipid peroxidation (LPO)) was assessed in digestive gland and gills after 1 and 2 months exposures. Our results highlighted no or low ability of this stage of life to regulate dissolved Zn accumulation during the studied period, consistently with high sensitivity of this organism. Notably, Zn exposures caused a concentration-dependent Mn depletion in juvenile cuttlefish, and an increase of soluble fraction of Ag, Cd, Cu without accumulation modifications, suggesting substitution of these elements (i.e. Mn, Ag, Cd, Cu) by Zn. In parallel, metallothionein concentrations decreased in individuals most exposed to Zn. Finally, no perturbations in oxidative stress management were detected in gills, whereas modifications of GST, SOD and catalase activity levels were recorded in digestive gland, resulting in an increase of LPO content after a 6-week exposure to low Zn concentration. Altogether, these perturbations are consistent with previously described high sensitivity of juvenile cuttlefish towards Zn. Our results underlined the need to study deeply contamination impact on this animal at this stage of life. PMID:25500620

  5. Long term in situ monitoring of total dissolved iron concentrations on the MoMAR observatory

    NASA Astrophysics Data System (ADS)

    Laes-Huon, Agathe; Legrand, Julien; Tanguy, Virginie; Cathalot, Cecile; Blandin, Jérôme; Rolin, Jean-Francois; Sarradin, Pierre-Marie

    2015-04-01

    Nowadays the scientific community wants relevant monitoring with an increase in spatial and temporal distribution of key chemicals. The hydrothermal ecosystems characterized by strong physico-chemical gradients are also of particular interest as they present an unique fauna, sustained by microbial chemosynthesis. The characterization of the chemical environment in the hydrothermal vent ecosystems implies the use of in situ instrumentation which is a serious challenge in the marine environment (Prien et al. 2007). The CHEMINI (CHEmical MINIaturised analyser), presented here, is a chemical in situ analyser specialized for deep sea uses (Vuillemin et al. 2007). It was first deployed on the autonomous deep sea observatory MoMAR (Monitoring of the Mid-Atlantic Ridge, FIXO3, Fixed point Open Ocean Observatories) in 2010. The first part of the presentation will focus on the description of the CHEMINI, then on the results obtained on the MoMAR observatory during the last 4 years. CHEMINI, implemented on the TEMPO ecological module determined total dissolved iron concentrations associated with an optode and a temperature probe. Several months of total iron concentrations, of T°C and videos were recorded permitting the study of the temporal dynamics of faunal assemblages and their habitat on the Lucky strike vent (-1700m, Cuvelier et al. 2011). Long term in situ analysis of total dissolved iron (31st of August 2013 - 23rd of February 2014, [DFe] = 7.12 +- 2.11 µmol L-1, n = 519) at the Eiffel Tower edifice is presented in details. The daily analyzed in situ standard (25µmol.L-1) showed an excellent reproducibility (1.07%, n=522). CHEMINI was reliable, robust over time for in situ analysis. The averaged total dissolved iron concentrations for the 6 months period remain low but they correlated significantly with temperature showing a spectra frequency with a maximal contribution around 4-5 days for both variables. The analytical results will be commented and the future technical challenges will be discussed in this presentation. References: Cuvelier, D, Sarrazin,J, Colaco A. Copley J.T., Glover A.G. Paul, A. Tyler, Serrao Santos R., Desbruyères D. (2011), Community dynamics over 14 years at the Eiffel Tower hydrothermal edifice on the Mid-Atlantic Ridge, Limnol. Oceanogr., 56(5), 1624-1640 Prien, R. (2007), The future of chemical in situ sensors, Mar. Chem., 107 (3), 422-432. Vuillemin, R., Le Roux, D., Dorval, P., Bucas, K., Sudreau, J.P., Hamon, M., Le Gall, C., Sarradin, P.M., 2009. CHEMINI: A new in situ CHEmical MINIaturized analyzer. Deep Sea Res. Part Oceanogr. Res. Pap. 56, 1391-1399.

  6. An anion-exchange method to concentrate dissolved DNA from aquifer water.

    PubMed

    Li, Zhen; Briggs, Brandon R; Sheridan, Peter P; Shields, Malcolm S

    2013-04-01

    A rapid DNA isolation method was developed to concentrate dissolved DNA (dDNA) in aquifer water for molecular analysis. The aquifer dDNA from the Eastern Snake River Plain Aquifer (ESRPA) was extracted and concentrated using a new method with an anion-exchange Mustang® Q membrane. The concentration of aquifer dDNA in this study ranged from 60 to 264.5 ng l?1 in ESRPA aquifer wells. DNA stability in ESRPA aquifer water was also tested in this study. The dDNA extracted from aquifer water samples was used for PCR amplification of bacterial 16S rRNA genes for terminal restriction fragment length polymorphism (T-RFLP) analysis and construction of 16S rRNA gene clone libraries. The ureC gene, IncP, IncQ and IncW plasmid genes were also PCR amplified from dDNA samples. Based on the results, dDNA is relatively stable in aquifer water and can be concentrated by Q membrane method for molecular analysis. The quality of isolated dDNA was suitable as a PCR template. PMID:23384828

  7. Variation of dissolved organic nitrogen concentration during the ultrasonic pretreatment to Microcystis aeruginosa.

    PubMed

    Liu, Cheng; Wang, Jie; Cao, Zhen; Chen, Wei; Bi, Hongkai

    2016-03-01

    Algae cells were the main sources of dissolved organic nitrogen (DON) in raw water with plenty of algae, and ultrasonic pretreatment was one of the algae-controlling methods through the damage of algae cells. However, the variation of DON concentration during the ultrasonic treatment process was not confirmed. Variation of DON concentration during the processes of low frequency ultrasound treatment of Microcystis aeruginosa was investigated. In addition, the effect of sonication on the metabolite concentration, algae cellar activity and the subsequent coagulation performance were discussed. The results showed that after a long duration of ultrasonic (60s), nearly 90% of the algal cells were damaged and the maximum concentration of DON attained more than 3mg/L. In order to control the leakage extent of DON, the sonication time should be less than 30s with power intensity of more than 1.0W/cm(3). In the mean time, ultrasonic treatment could inhibit the reactivation and the proliferation of algal, keep the algae cell wall integrity and enhance coagulation effectively under the same condition. However, ultrasound frequency had little effect on DON at the frequency range used in this study (20-150kHz). PMID:26585003

  8. Quantifying dissolved organic carbon concentrations in upland catchments using phenolic proxy measurements

    NASA Astrophysics Data System (ADS)

    Peacock, Mike; Burden, Annette; Cooper, Mark; Dunn, Christian; Evans, Chris D.; Fenner, Nathalie; Freeman, Chris; Gough, Rachel; Hughes, David; Hughes, Steve; Jones, Tim; Lebron, Inma; West, Mike; Zieli?ski, Piotr

    2013-01-01

    SummaryConcentrations of dissolved organic carbon (DOC) in soil and stream waters in upland catchments are widely monitored, in part due to the potential of DOC to form harmful by-products when chlorinated during treatment of water for public supply. DOC can be measured directly, though this is expensive and time-consuming. Light absorbance in the UV-vis spectrum is often used as a surrogate measurement from which a colour-carbon relationship between absorbance and DOC can be derived, but this relationship can be confounded by numerous variables. Through the analysis of data from eight sites in England and Wales we investigate the possibility of using the concentration of phenolic compounds in water samples as a proxy for DOC concentration. A general model using data from all the sites allowed DOC to be calculated from phenolics at an accuracy of 81-86%. A detailed analysis at one site revealed that a site-specific calibration was more accurate than the general model, and that this compared favourably with a colour-carbon calibration. We therefore recommend this method for use where estimates of DOC concentration are needed, but where time and money are limiting factors, or as an additional method to calculate DOC alongside colour-carbon calibrations. Tests demonstrated only small amounts of phenolic degradation over time; a loss of 0.92 mg L-1 after 8 months in storage, and so this method can be used on older samples with limited loss of accuracy.

  9. Quantitative consideration of flow structures (bubble swarms and liquid motion) and dissolved CO2 concentration transportation, in a bubbly flow

    NASA Astrophysics Data System (ADS)

    Shinohara, Daisuke; Saito, Takayuki

    2013-11-01

    The objective of the present study is to clarify the relationship between large scale flow structures (: bubble swarm and liquid motion) and dissolved CO2 concentration transportation, in a large-diameter bubble column. For this specific purpose, the time-series void fractions, dissolved CO2 concentration and liquid-phase-velocities were simultaneously measured by using a photoelectric optical fiber probe (POFP) and Laser Doppler Velocimetry. The POFP was newly developed in order to simultaneously measure bubble characteristics and dissolved CO2 concentration. We calculated the spatial scale of the bubble swarms and liquid motion based on the thinking of the integral length scale. The spatial scale of the bubble swarms and liquid motion was large in the bottom zone. Moreover, the size of this spatial scale changed with time; i.e. the flow structures changed with time in the bottom zone. The characteristics of the flow structures in the bottom zone faded out towards the upper zone of the column. The cross-correlation coefficients of dissolved CO2 concentration were calculated at several zones by height. As a result, the relationship between the flow structures and dissolved CO2 concentration transportation was found out.

  10. Evaluation of Electrodialysis as Part of an Improved Method to Concentrate Dissolved Organic Matter from Seawater

    NASA Astrophysics Data System (ADS)

    Chang, V.; Koprivnjak, J.; Ingall, E.; Pfromm, P.; Perdue, E. M.

    2004-12-01

    A major obstacle in the study of marine dissolved organic matter (DOM) has been isolating from seawater sufficient quantities for analysis of this highly dilute and chemically complex material. This research explores the application of electrodialysis (ED) in combination with reverse osmosis (RO) as a method to concentrate DOM from seawater. RO methods recover a significant fraction (90%) of DOM from fresh waters with little physical or chemical alteration, and similar high recoveries of DOM have been observed in preliminary tests using estuarine waters of varying salinity. Unfortunately, the extent to which DOM in saline waters can be concentrated by RO is very limited, because RO membranes co-concentrate inorganic salts with DOM. At an early stage of processing, osmotic pressures become too high and/or inorganic salts precipitate from solution and foul the RO membrane. To realize the potentially high recoveries of DOM from saline waters, RO must be coupled with an independent method for removal of inorganic salts. Electrodialysis, which is a well-established process for removal of inorganic salts from aqueous solutions, is such a method. In ED, a feed stream of the sample to be de-ionized and a receiving stream of a solution that will accept the removed ions are pumped through adjacent layers of a membrane stack, which consists of several layers of alternating anion and cation exchange membranes. The membranes are made from highly crosslinked polymers and are non-porous. The direction and velocity of diffusion of the cations and anions are further mediated by a DC electrical current that flows through the membrane stack. In the first stage of testing of the ED process, samples of near-seawater salinity (28 ppt) containing 4 ppm of dissolved organic carbon were collected at the Skidaway Institute of Oceanography in Savannah Georgia. Using ED, salinity was reduced by 87% in these samples with retention of more than 95% of the DOM. These experiments indicate that ED can significantly reduce salt concentrations in saline waters with little or no loss of DOM, thus making it possible to use efficient RO methods to concentrate marine DOM.

  11. Diminished Stream Nitrate Concentrations Linked to Dissolved Organic Carbon Dynamics After Leaf Fall

    NASA Astrophysics Data System (ADS)

    Sebestyen, S. D.; Shanley, J. B.; Boyer, E. W.; Doctor, D. H.; Kendall, C.

    2004-05-01

    Thermodynamic coupling of the nitrogen and carbon cycles has broad implications for controls on catchment nutrient fluxes. In the northeast US, leaf fall occurs in early October and the availability of organic carbon increases as the leaves decompose. At the Sleepers River Research Watershed in northeastern Vermont (USA), we sampled stream chemistry from seven nested catchments to determine how stream dissolved organic carbon (DOC) and nitrate vary as a function of flow conditions, land-use, and basin size in response to leaf fall. Following leaf fall, nitrate concentration patterns were quantitatively different from other times of the year. Under baseflow conditions, stream and soil water DOC concentrations were higher than normal, whereas nitrate concentrations declined sharply at the five smallest catchments and more modestly at the two largest catchments. Under high flow conditions, flushing of nitrate was observed, as is typical for stormflow response at Sleepers River. Our field data suggest that in-stream processing of nitrate is likely thermodynamically and kinetically favorable under baseflow but not at higher flow conditions when expanding variable source areas make hydrological connections between nitrate source areas and streams. We are working to evaluate this hypothesis with isotopic and other monitoring data, and to model the coupled interactions of water, DOC, and nitrate fluxes in these nested catchments.

  12. Effect of dissolved oxygen concentration on iron efficiency: Removal of three chloroacetic acids.

    PubMed

    Tang, Shun; Wang, Xiao-mao; Mao, Yu-qin; Zhao, Yu; Yang, Hong-wei; Xie, Yuefeng F

    2015-04-15

    The monochloroacetic, dichloroacetic and trichloroacetic acid (MCAA, DCAA and TCAA) removed by metallic iron under controlled dissolved oxygen conditions (0, 0.75, 1.52, 2.59, 3.47 or 7.09 mg/L DO) was investigated in well-mixed batch systems. The removal of CAAs increased first and then decreased with increasing DO concentration. Compared with anoxic condition, the reduction of MCAA and DCAA was substantially enhanced in the presence of O2, while TCAA reduction was significantly inhibited above 2.59 mg/L. The 1.52 mg/L DO was optimum for the formation of final product, acetic acid. Chlorine mass balances were 69-102%, and carbon mass balances were 92-105%. With sufficient mass transfer from bulk to the particle surface, the degradation of CAAs was limited by their reduction or migration rate within iron particles, which were dependent on the change of reducing agents and corrosion coatings. Under anoxic conditions, the reduction of CAAs was mainly inhibited by the available reducing agents in the conductive layer. Under low oxic conditions, the increasing reducing agents and thin lepidocrocite layer were favorable for CAA dechlorination. Under high oxic conditions, the redundant oxygen competing for reducing agents and significant lepidocrocite growth became the major restricting factors. Various CAA removal mechanisms could be potentially applied to explaining the effect of DO concentration on iron efficiency for contaminant reduction in water and wastewater treatment. PMID:25697696

  13. Novel method for online monitoring of dissolved N2O concentrations through a gas stripping device.

    PubMed

    Mampaey, Kris E; van Dongen, Udo G J M; van Loosdrecht, Mark C M; Volcke, Eveline I P

    2015-01-01

    Nitrous oxide emissions from wastewater treatment plants are currently measured by online gas phase analysis or grab sampling from the liquid phase. In this study, a novel method is presented to monitor the liquid phase N2O concentration for aerated as well as non-aerated conditions/reactors, following variations both in time and in space. The monitoring method consists of a gas stripping device, of which the measurement principle is based on a continuous flow of reactor liquid through a stripping flask and subsequent analysis of the N2O concentration in the stripped gas phase. The method was theoretically and experimentally evaluated for its fit for use in the wastewater treatment context. Besides, the influence of design and operating variables on the performance of the gas stripping device was addressed. This method can easily be integrated with online off-gas measurements and allows to better investigate the origin of the gas emissions from the treatment plant. Liquid phase measurements of N2O are of use in mitigation of these emissions. The method can also be applied to measure other dissolved gasses, such as methane, being another important greenhouse gas. PMID:25573615

  14. Influence of groundwater recharge and well characteristics on dissolved arsenic concentrations in southeastern Michigan groundwater

    USGS Publications Warehouse

    Meliker, J.R.; Slotnick, M.J.; Avruskin, G.A.; Haack, S.K.; Nriagu, J.O.

    2009-01-01

    Arsenic concentrations exceeding 10 ??g/l, the United States maximum contaminant level and the World Health Organization guideline value, are frequently reported in groundwater from bedrock and unconsolidated aquifers of southeastern Michigan. Although arsenic-bearing minerals (including arsenian pyrite and oxide/hydroxide phases) have been identified in Marshall Sandstone bedrock of the Mississippian aquifer system and in tills of the unconsolidated aquifer system, mechanisms responsible for arsenic mobilization and subsequent transport in groundwater are equivocal. Recent evidence has begun to suggest that groundwater recharge and characteristics of well construction may affect arsenic mobilization and transport. Therefore, we investigated the relationship between dissolved arsenic concentrations, reported groundwater recharge rates, well construction characteristics, and geology in unconsolidated and bedrock aquifers. Results of multiple linear regression analyses indicate that arsenic contamination is more prevalent in bedrock wells that are cased in proximity to the bedrock-unconsolidated interface; no other factors were associated with arsenic contamination in water drawn from bedrock or unconsolidated aquifers. Conditions appropriate for arsenic mobilization may be found along the bedrock-unconsolidated interface, including changes in reduction/oxidation potential and enhanced biogeochemical activity because of differences between geologic strata. These results are valuable for understanding arsenic mobilization and guiding well construction practices in southeastern Michigan, and may also provide insights for other regions faced with groundwater arsenic contamination. ?? Springer-Verlag 2008.

  15. The relationship between the dissolved inorganic carbon concentration and growth rate in marine phytoplankton.

    PubMed Central

    Clark, D R; Flynn, K J

    2000-01-01

    A range of marine phytoplankton was grown in closed systems in order to investigate the kinetics of dissolved inorganic carbon (DIC) use and the influence of the nitrogen source under conditions of constant pH. The kinetics of DIC use could be described by a rectangular hyperbolic curve, yielding estimations of KG(DIC) (the half saturation constant for carbon-specific growth, i.e. C mu) and mu max (the theoretical maximum C mu). All species attained a KG(DIC) within the range of 30-750 microM DIC. For most species, NH4+ use enabled growth with a lower KG(DIC) and/or, for two species, an increase in mu max. At DIC concentrations of > 1.6 mM, C mu was > 90% saturated for all species relative to the rate at the natural seawater DIC concentration of 2.0 mM. The results suggest that neither the rate nor the extent of primary productivity will be significantly limited by the DIC in the quasi-steady-state conditions associated with oligotrophic oceans. The method needs to be applied in the conditions associated with dynamic coastal (eutrophic) systems for clarification of a potential DIC rate limitation where cells may grow to higher densities and under variable pH and nitrogen supply. PMID:10874743

  16. Effects of Low Dissolved-Oxygen Concentrations on Poly-(3-Hydroxybutyrate-co-3-Hydroxyvalerate) Production by Alcaligenes eutrophus

    PubMed Central

    Lefebvre, G.; Rocher, M.; Braunegg, G.

    1997-01-01

    The bacterial copolyester poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) was produced with Alcaligenes eutrophus DSM 545 from glucose and sodium propionate in a fed-batch fermentation with both nitrogen limitation and low dissolved-oxygen concentrations. When the dissolved-oxygen content was kept between 1 and 4% of air saturation during the polymer accumulation phase, the yield of 3-hydroxybutyrate (3HB) monomer from glucose was not affected, but the propionate-to-3-hydroxyvalerate (3HV) monomer yield was two to three times (0.48 to 0.73 mol of 3HV mol of propionate consumed(sup-1)) that observed in a control experiment (0.25 mol mol(sup-1)), where the accumulation-phase dissolved-oxygen concentration was 50 to 70% of air saturation. The overall polymer productivity of the fermentation was somewhat decreased by low dissolved-oxygen contents, owing to a slower 3HB production rate. The effect of a low dissolved-oxygen concentration is probably attributable to a reduction of the oxygen-requiring decarbonylation of propionyl-coenzyme A (CoA) to acetyl-CoA. PMID:16535549

  17. Mesocosm validation of the marine No Effect Concentration of dissolved copper derived from a species sensitivity distribution.

    PubMed

    Foekema, E M; Kaag, N H B M; Kramer, K J M; Long, K

    2015-07-15

    The Predicted No Effect Concentration (PNEC) for dissolved copper based on the species sensitivity distribution (SSD) of 24 marine single species tests was validated in marine mesocosms. To achieve this, the impact of actively maintained concentrations of dissolved copper on a marine benthic and planktonic community was studied in 18 outdoor 4.6m(3) mesocosms. Five treatment levels, ranging from 2.9 to 31?g dissolved Cu/L, were created in triplicate and maintained for 82days. Clear effects were observed on gastropod and bivalve molluscs, phytoplankton, zooplankton, sponges and sessile algae. The most sensitive biological endpoints; reproduction success of the bivalve Cerastoderma edule, copepod population development and periphyton growth were significantly affected at concentrations of 9.9?g Cu/L and higher. The No Observed Effect Concentration (NOEC) derived from this study was 5.7?g dissolved Cu/L. Taking into account the DOC concentration of the mesocosm water this NOEC is comparable to the PNEC derived from the SSD. PMID:25829294

  18. Dissolved-solids concentrations and loads in return flows to the Colorado River from agricultural land in southern California

    USGS Publications Warehouse

    Klein, John M.; Bradford, Wesley L.

    1980-01-01

    The dissolved-solids concentration in Colorado River water increases from less than 50 mg/L (milligrams per liter) at the rivers 's origin to about 700 mg/L at the California border and to about 900 mg/L at the United States-Mexico boundary. Much of the latter increase is due to depletion by agricultural use and irrigation return water with salts leached from soils under cultivation. Forty sites in three agricultural areas--Fort Mojave, Bard Valley, and Palo Verde Valley--were sampled to describe the dissolved-solids concentrations in return flows. Emphasis was on Palo Verde Valley. In the Fort Mojave area, the dissolved-solids concentration of Colorado River water was about 700 mg/L, while the concentration in water at the tile-drain convergence averaged about 2,500 mg/L. In the closed sump that presently receives all irrigation return, concentrations ranged from 812 to 1,760 mg/L. In Bard Valley, water diverted from the river had an annual mean dissolved-solids concentration of about 835 mg/L. During the study, concentrations in two main drains carrying irrigation return water ranged from 953 to 1,290 mg/L. Selected drains in Palo Verde Valley were sampled several times to determine dissolved solids loads from subareas within the valley. Loads determined in this study were compared with those of an earlier study. In agreement with the earlier study, loads were found to be largest from three subareas in the southern half of the valley and comparatively small from the four subareas in the northern half. Smaller loads were found in this study from all subareas, however. The differences are thought to be due to generally lower water discharge observed in drains during this study. (USGS)

  19. Declines in dissolved silica concentrations in western Virginia streams (1988-2003): Gypsy moth defoliation stimulates diatoms?

    NASA Astrophysics Data System (ADS)

    Grady, Amy E.; Scanlon, Todd M.; Galloway, James N.

    2007-03-01

    Dissolved silica concentrations in western Virginia streams showed a significant bias toward declines (p < 0.0001) over the time period from 1988 to 2003. Streams with the greatest declines were those that had the highest mean dissolved silica concentrations, specific to watersheds underlain by basaltic and granitic bedrock. We examined potential geochemical, hydrological, and biological factors that could account for the observed widespread declines, focusing on six core watersheds where weekly stream chemistry data were available. No relationships were evident between stream water dissolved silica concentrations and pH, a finding supported by the results from a geochemical model applied to the dominant bedrock mineralogy. Along with changes in watershed acidity, changes in precipitation and discharge were also discounted since no significant trends were observed over the study period. Analyses of two longer-term data sets that extend back to 1979 revealed that the initiation of the dissolved silica declines coincided with the timing of a gypsy moth (Lymantria dispar) defoliation event. We develop a conceptual model centered on benthic diatoms, which are found within each of the six core watersheds but in greater abundance in the more silica-rich streams. Gypsy moth defoliation led to greater sunlight penetration and enhanced nitrate concentrations in the streams, which could have spurred population growth and silica uptake. The model can explain why the observed declines are primarily driven by decreased concentrations during low-flow conditions. This study illustrates lasting effects of disturbance on watershed biogeochemistry, in this case causing decadal-scale variability in stream water dissolved silica concentrations.

  20. A data reconnaissance on the effect of suspended-sediment concentrations on dissolved-solids concentrations in rivers and tributaries in the Upper Colorado River Basin

    USGS Publications Warehouse

    Tillman, Fred D; Anning, David W.

    2014-01-01

    The Colorado River is one of the most important sources of water in the western United States, supplying water to over 35 million people in the U.S. and 3 million people in Mexico. High dissolved-solids loading to the River and tributaries are derived primarily from geologic material deposited in inland seas in the mid-to-late Cretaceous Period, but this loading may be increased by human activities. High dissolved solids in the River causes substantial damages to users, primarily in reduced agricultural crop yields and corrosion. The Colorado River Basin Salinity Control Program was created to manage dissolved-solids loading to the River and has focused primarily on reducing irrigation-related loading from agricultural areas. This work presents a reconnaissance of existing data from sites in the Upper Colorado River Basin (UCRB) in order to highlight areas where suspended-sediment control measures may be useful in reducing dissolved-solids concentrations. Multiple linear regression was used on data from 164 sites in the UCRB to develop dissolved-solids models that include combinations of explanatory variables of suspended sediment, flow, and time. Results from the partial t-test, overall likelihood ratio, and partial likelihood ratio on the models were used to group the sites into categories of strong, moderate, weak, and no-evidence of a relation between suspended-sediment and dissolved-solids concentrations. Results show 68 sites have strong or moderate evidence of a relation, with drainage areas for many of these sites composed of a large percentage of clastic sedimentary rocks. These results could assist water managers in the region in directing field-scale evaluation of suspended-sediment control measures to reduce UCRB dissolved-solids loading.

  1. Glucose concentration alters dissolved oxygen levels in liquid cultures of Beauveria bassiana and affects formation and bioefficacy of blastospores.

    PubMed

    Mascarin, Gabriel Moura; Jackson, Mark A; Kobori, Nilce Naomi; Behle, Robert W; Dunlap, Christopher A; Delalibera Júnior, Ítalo

    2015-08-01

    The filamentous fungus Beauveria bassiana is an economically important pathogen of numerous arthropod pests and is able to grow in submerged culture as filaments (mycelia) or as budding yeast-like blastospores. In this study, we evaluated the effect of dissolved oxygen and high glucose concentrations on blastospore production by submerged cultures of two isolates of B. bassiana, ESALQ1432 and GHA. Results showed that maintaining adequate dissolved oxygen levels coupled with high glucose concentrations enhanced blastospore yields by both isolates. High glucose concentrations increased the osmotic pressure of the media and coincided with higher dissolved oxygen levels and increased production of significantly smaller blastospores compared with blastospores produced in media with lower concentrations of glucose. The desiccation tolerance of blastospores dried to less than 2.6 % moisture was not affected by the glucose concentration of the medium but was isolate dependent. Blastospores of isolate ESALQ1432 produced in media containing 140 g glucose L(-1) showed greater virulence toward whitefly nymphs (Bemisia tabaci) as compared with blastospores produced in media containing 40 g glucose L(-1). These results suggest a synergistic effect between glucose concentration and oxygen availability on changing morphology and enhancing the yield and efficacy of blastospores of B. bassiana, thereby facilitating the development of a cost-effective production method for this blastospore-based bioinsecticide. PMID:25947245

  2. Response of oxidative enzyme activities to nitrogen deposition affects soil concentrations of dissolved organic carbon

    USGS Publications Warehouse

    Waldrop, M.P.; Zak, D.R.

    2006-01-01

    Recent evidence suggests that atmospheric nitrate (NO3- ) deposition can alter soil carbon (C) storage by directly affecting the activity of lignin-degrading soil fungi. In a laboratory experiment, we studied the direct influence of increasing soil NO 3- concentration on microbial C cycling in three different ecosystems: black oak-white oak (BOWO), sugar maple-red oak (SMRO), and sugar maple-basswood (SMBW). These ecosystems span a broad range of litter biochemistry and recalcitrance; the BOWO ecosystem contains the highest litter lignin content, SMRO had intermediate lignin content, and SMBW leaf litter has the lowest lignin content. We hypothesized that increasing soil solution NO 3- would reduce lignolytic activity in the BOWO ecosystem, due to a high abundance of white-rot fungi and lignin-rich leaf litter. Due to the low lignin content of litter in the SMBW, we further reasoned that the NO3- repression of lignolytic activity would be less dramatic due to a lower relative abundance of white-rot basidiomycetes; the response in the SMRO ecosystem should be intermediate. We increased soil solution NO3- concentrations in a 73-day laboratory incubation and measured microbial respiration and soil solution dissolved organic carbon (DOC) and phenolics concentrations. At the end of the incubation, we measured the activity of ??-glucosidase, N-acetyl-glucosaminidase, phenol oxidase, and peroxidase, which are extracellular enzymes involved with cellulose and lignin degradation. We quantified the fungal biomass, and we also used fungal ribosomal intergenic spacer analysis (RISA) to gain insight into fungal community composition. In the BOWO ecosystem, increasing NO 3- significantly decreased oxidative enzyme activities (-30% to -54%) and increased DOC (+32% upper limit) and phenolic (+77% upper limit) concentrations. In the SMRO ecosystem, we observed a significant decrease in phenol oxidase activity (-73% lower limit) and an increase in soluble phenolic concentrations (+57% upper limit) in response to increasing NO 3- in soil solution, but there was no significant change in DOC concentration. In contrast to these patterns, increasing soil solution NO3- in the SMBW soil resulted in significantly greater phenol oxidase activity (+700% upper limit) and a trend toward lower DOC production (-52% lower limit). Nitrate concentration had no effect on microbial respiration or ??-glucosidase or N-acetyl-glucosaminidase activities. Fungal abundance and basidiomycete diversity tended to be highest in the BOWO soil and lowest in the SMBW, but neither displayed a consistent response to NO 3- additions. Taken together, our results demonstrate that oxidative enzyme production by microbial communities responds directly to NO3- deposition, controlling extracellular enzyme activity and DOC flux. The regulation of oxidative enzymes by different microbial communities in response to NO3- deposition highlights the fact that the composition and function of soil microbial communities directly control ecosystem-level responses to environmental change. ?? 2006 Springer Science+Business Media, Inc.

  3. Maximizing biomass concentration in baker's yeast process by using a decoupled geometric controller for substrate and dissolved oxygen.

    PubMed

    Chopda, Viki R; Rathore, Anurag S; Gomes, James

    2015-11-01

    Biomass production by baker's yeast in a fed-batch reactor depends on the metabolic regime determined by the concentration of glucose and dissolved oxygen in the reactor. Achieving high biomass concentration in turn is dependent on the dynamic interaction between the glucose and dissolved oxygen concentration. Taking this into account, we present in this paper the implementation of a decoupled input-output linearizing controller (DIOLC) for maximizing biomass in a fed-batch yeast process. The decoupling is based on the inversion of 2×2 input-output matrix resulting from global linearization. The DIOLC was implemented online using a platform created in LabVIEW employing a TCP/IP protocol via the reactor's built-in electronic system. An improvement in biomass yield by 23% was obtained compared to that using a PID controller. The results demonstrate superior capability of the DIOLC and that the cumulative effect of smoother control action contributes to biomass maximization. PMID:26233328

  4. Evaluation of planning alternatives for maintaining desirable dissolved-oxygen concentrations in the Willamette River, Oregon

    USGS Publications Warehouse

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

    1980-01-01

    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)

  5. Analysis of environmental issues related to small-scale hydroelectric development. VI. Dissolved oxygen concentrations below operating dams

    SciTech Connect

    Cada, G.F.; Kumar, K.D.; Solomon, J.A.; Hildebrand, S.G.

    1982-01-01

    Results are presented of an effort aimed at determining whether or not water quality degradation, as exemplified by dissolved oxygen concentrations, is a potentially significant issue affecting small-scale hydropower development in the US. The approach was to pair operating hydroelectric sites of all sizes with dissolved oxygen measurements from nearby downstream US Geological Survey water quality stations (acquired from the WATSTORE data base). The USGS data were used to calculate probabilities of non-compliance (PNCs), i.e., the probabilities that dissolved oxygen concentrations in the discharge waters of operating hydroelectric dams will drop below 5 mg/l. PNCs were estimated for each site, season (summer vs remaining months), and capacity category (less than or equal to 30 MW vs >30 MW). Because of the low numbers of usable sites in many states, much of the subsequent analysis was conducted on a regional basis. During the winter months (November through June) all regions had low mean PNCs regardless of capacity. Most regions had higher mean PNCs in summer than in winter, and summer PNCs were greater for large-scale than for small-scale sites. Among regions, the highest mean summer PNCs were found in the Great Basin, the Southeast, and the Ohio Valley. To obtain a more comprehensive picture of the effects of season and capacity on potential dissolved oxygen problems, cumulative probability distributions of PNC were developed for selected regions. This analysis indicates that low dissolved oxygen concentrations in the tailwaters below operating hydroelectric projects are a problem largely confined to large-scale facilities.

  6. Dissolved-solids concentration in water from the upper permeable zone of the Tertiary limestone aquifer system, southeastern United States

    USGS Publications Warehouse

    Sprinkle, Craig L.

    1982-01-01

    The Tertiary limestone aquifer system of the southeastern United States is a thick sequence of carbonate rocks that range from Paleocene to Miocene in age and are hydraulically connected in varying degrees. The upper permeable zone of the aquifer system consists of the Tampa, Suwannee, Ocala, and Avon Park Limestones. Based on analyses of water samples from 591 selected wells, a map is presented which shows dissolved-solids concentration in ranges of 0-250, 251-500, 501-1,000, and greater than 1,000 mg/. Dissolved-solids concentrations and hydrochemical facies developed within the aquifer system are related to the predevelopment and modern-day ground-water flow system. (USGS)

  7. Effect of water hardness and dissolved-solid concentration on hatching success and egg size in bighead carp

    USGS Publications Warehouse

    Chapman, Duane C.; Deters, Joseph E.

    2009-01-01

    Bighead carp Hypophthalmichthys nobilis is an Asian species that has been introduced to the United States and is regarded as a highly undesirable invader. Soft water has been said to cause the bursting of Asian carp eggs and thus has been suggested as a factor that would limit the spread of this species. To evaluate this, we subjected fertilized eggs of bighead carp to waters with a wide range of hardness and dissolved-solid concentrations. Hatching rate and egg size were not significantly affected by the different water qualities. These results, combined with the low hardness (28–84 mg/L) of the Yangtze River (the primary natal habitat of Hypophthalmichthys spp.), suggest that managers and those performing risk assessments for the establishment of Hypophthalmichthys spp. should be cautious about treating low hardness and dissolved-solid concentrations as limiting factors.

  8. A procedure for predicting concentrations of dissolved solids and sulfate ion in streams draining areas strip mined for coal

    USGS Publications Warehouse

    Bevans, H.E.

    1980-01-01

    Current trends in increased coal production necessitate the development of techniques to appraise the environmental degradation resulting from strip mining. A procedure is introduced for the prediction of dissolved-solids and sulfate-ion concentrations in streams draining strip-mined areas. Concentrations are a function of the percentage of the drainage area that has been strip mined. These relationships are expressed by regression equations computed from data collected in streams draining strip-mined areas of Cherokee and Crawford Counties in southeast Kansas. High correlation coefficients indicate that the relationships may be useful in the evaluation of present or future strip-mining operations. (USGS)

  9. Development of a pre-concentration system and auto-analyzer for dissolved methane, ethane, propane, and butane concentration measurements with a GC-FID

    NASA Astrophysics Data System (ADS)

    Chepigin, A.; Leonte, M.; Colombo, F.; Kessler, J. D.

    2014-12-01

    Dissolved methane, ethane, propane, and butane concentrations in natural waters are traditionally measured using a headspace equilibration technique and gas chromatograph with flame ionization detector (GC-FID). While a relatively simple technique, headspace equilibration suffers from slow equilibration times and loss of sensitivity due to concentration dilution with the pure gas headspace. Here we present a newly developed pre-concentration system and auto-analyzer for use with a GC-FID. This system decreases the time required for each analysis by eliminating the headspace equilibration time, increases the sensitivity and precision with a rapid pre-concentration step, and minimized operator time with an autoanalyzer. In this method, samples are collected from Niskin bottles in newly developed 1 L plastic sample bags rather than glass vials. Immediately following sample collection, the sample bags are placed in an incubator and individually connected to a multiport sampling valve. Water is pumped automatically from the desired sample bag through a small (6.5 mL) Liqui-Cel® membrane contactor where the dissolved gas is vacuum extracted and directly flushed into the GC sample loop. The gases of interest are preferentially extracted with the Liqui-Cel and thus a natural pre-concentration effect is obtained. Daily method calibration is achieved in the field with a five-point calibration curve that is created by analyzing gas standard-spiked water stored in 5 L gas-impermeable bags. Our system has been shown to substantially pre-concentrate the dissolved gases of interest and produce a highly linear response of peak areas to dissolved gas concentration. The system retains the high accuracy, precision, and wide range of measurable concentrations of the headspace equilibration method while simultaneously increasing the sensitivity due to the pre-concentration step. The time and labor involved in the headspace equilibration method is eliminated and replaced with the immediate and automatic analysis of a maximum of 13 sequential samples. The elapsed time between sample collection and analysis is reduced from approximately 12 hrs to < 10 min, enabling dynamic and highly resolved sampling plans.

  10. Dissolved Concentrations of PAHs and PCBs Are Often Over-predicted Using Sediment Concentrations and Literature Koc Values

    EPA Science Inventory

    There is an increasing amount of chemical and biological evidence that using sediment concentrations and commonly applied Koc values frequently overpredicts interstitial water concentrations of HOCs, and thereby overestimates uptake and/or effects of those chemicals on exposed or...

  11. Concentration and characterization of dissolved organic matter in the surface microlayer and subsurface water of the Bohai Sea, China

    NASA Astrophysics Data System (ADS)

    Chen, Yan; Yang, Gui-Peng; Wu, Guan-Wei; Gao, Xian-Chi; Xia, Qing-Yan

    2013-01-01

    A total of 19 sea-surface microlayer and corresponding subsurface samples collected from the Bohai Sea, China in April 2010 were analyzed for chlorophyll a, dissolved organic carbon (DOC) and its major compound classes including total dissolved carbohydrates (TDCHO, including monosaccharides, MCHO, and polysaccharides, PCHO) and total hydrolysable amino acids (THAA, including dissolved free, DFAA, and combined fraction, DCAA). The concentrations of DOC in the subsurface water ranged from 130.2 to 407.7 ?M C, with an average of 225.9±75.4 ?M C, while those in the surface microlayer varied between 140.1 and 330.9 ?M C, with an average of 217.8±56.8 ?M C. The concentrations of chlorophyll a, DOC, TDCHO and THAA in the microlayer were, respectively correlated with their subsurface water concentrations, implying that there was a strong exchange effect between the microlayer and subsurface water. The concentrations of DOC and TDCHO were negatively correlated with salinity, respectively, indicating that water mixing might play an important role in controlling the distribution of DOC and TDCHO in the water column. Major constituents of DCAA and DFAA present in the study area were glycine, alanine, glutamic acid, serine and histidine. Principal component analysis (PCA) was applied to examine the complex compositional differences that existed among the sampling sites. Our results showed that DFAA had higher mole percentages of glycine, valine and serine in the microlayer than in the subsurface water, while DCAA tended to have higher mole percentages of glutamic acid, aspartic acid, threonine, arginine, alanine, tyrosine, phenylalanine and leucine in the microlayer. The yields of TDCHO and THAA exhibited similar trends between the microlayer and subsurface water. Carbohydrate species displayed significant enrichment in the microlayer, whereas the DFAA and DCAA exhibited non-uniform enrichment in the microlayer.

  12. Dissolved, particulate and acid-leachable trace metal concentrations in North Atlantic precipitation collected on the Global Change Expedition

    SciTech Connect

    Lim, B.; Jickells, T.D. )

    1990-12-01

    Atmospheric inputs of trace metals into surface waters are an important pathway for the oceanic biogeochemical cycling of many trace constituents. Rainwater samples from six precipitation events were collected on board ship during legs 3 and 4 of the Global Change Expedition over the North Atlantic Ocean and analyzed for dissolved, particulate (Al and Pb), and acid-leachable trace metals (Al, Fe, Mn, Cd, Cu, Pb, Zn). Acid-leachable concentrations of the elements were similar to reported values from the North Atlantic and Pacific Oceans which were measured using comparable acidification procedures. Concentrations of dissolved and particulate Al and Pb were determined in rain events acid-leachable and total trace metal concentrations suggest that the acid-leachable fraction of metals can significantly underestimate total concentrations of crustal elements in rain. The solubilities of Al and Pb in precipitation were variable and mean solubilities of the elements were 13% and 45%, respectively. Recycled sea salt components were less than 14% for Al, Fe, Mn, Pb, Cd, Cu, and Zn, indicating that the net trace metal flux is from the atmosphere to the oceans. Deep sea particle fluxes for these metals through the western tropical North Atlantic exceed atmospheric deposition fluxes by a factor of 18 to 41. 57 refs., 2 figs., 12 tabs.

  13. Modelling the migration opportunities of diadromous fish species along a gradient of dissolved oxygen concentration in a European tidal watershed

    NASA Astrophysics Data System (ADS)

    Maes, J.; Stevens, M.; Breine, J.

    2007-10-01

    The relationship between poor water quality and migration opportunities for fish remains poorly documented, although it is an essential research step in implementing EU water legislation. In this paper, we model the environmental constraints that control the movements of anadromous and catadromous fish populations that migrate through the tidal watershed of River Scheldt, a heavily impacted river basin in Western Europe. Local populations of sturgeon, sea lamprey, sea trout, Atlantic salmon, houting and allis shad were essentially extirpated around 1900. For remaining populations (flounder, three-spined stickleback, twaite shad, thinlip mullet, European eel and European smelt), a data driven logistic model was parameterized. The presence or absence of fish species in samples taken between 1995 and 2004 was modelled as a function of temperature, dissolved oxygen concentration, river flow and season. Probabilities to catch individuals from all diadromous species but three-spined stickleback increased as a function of the interaction between temperature and dissolved oxygen. The hypoxic zone situated in the freshwater tidal part of the estuary was an effective barrier for upstream migrating anadromous spawners since it blocked the entrance to historical spawning sites upstream. Similarly, habitat availability for catadromous fish was greatly reduced and restricted to lower brackish water parts of the estuary. The model was applied to infer preliminary dissolved oxygen criteria for diadromous fish, to make qualitative predictions about future changes in fish distribution given anticipated changes in water quality and to suggest necessary measures with respect to watershed management.

  14. Benthic fluxes and porewater concentration profiles of dissolved organic carbon in sediments from the North Carolina continental slope

    SciTech Connect

    Alperin, M.J.; Martens, C.S.; Albert, D.B.; Suayah, I.B.; Benninger, L.K.; Blair, N.E.; Jahnke, R.A.

    1999-02-01

    Numerous studies of marine environments show that dissolved organic carbon (DOC) concentrations in sediments are typically tenfold higher than in the overlying water. Large concentration gradients near the sediment-water interface suggest that there may be a significant flux of organic carbon from sediments to the water column. Furthermore, accumulation of DOC in the porewater may influence the burial and preservation of organic matter by promoting geopolymerization and/or adsorption reactions. The authors measured DOC concentration profiles (for porewater collected by centrifugation and sipping) and benthic fluxes (with in situ and shipboard chambers) at two sites on the North Carolina continental slope to better understand the controls on porewater DOC concentrations and quantify sediment-water exchange rates. The authors also measured a suite of sediment properties (e.g., sediment accumulation and bioturbation rates, organic carbon content, and mineral surface area) that allow us to examine the relationship between porewater DOC concentrations and organic carbon preservation. Sediment depth-distributions of DOC from a downslope transect (300--1000 m water depth) follow a trend consistent with other porewater constituents ({summation}CO{sub 2} and SO{sub 4}{sup 2{minus}}) and a tracer of modern, fine-grained sediment, suggesting that DOC levels are regulated by organic matter remineralization. However, remineralization rates appear to be relatively uniform across the sediment transect. A simple diagenetic model illustrates that variations in DOC profiles at this site may be due to differences in the depth of the active remineralization zone, which in turn is largely controlled by the intensity of bioturbation. Comparison of porewater DOC concentrations, organic carbon burial efficiency, and organic matter sorption suggest that DOC levels are not a major factor in promoting organic matter preservation or loading on grain surfaces. The DOC benthic fluxes are difficult to detect, but suggest that only 2% of the dissolved organic carbon escapes remineralization in the sediments by transport across the sediment-water interface.

  15. Prediction of dissolved actinide concentrations in concentrated electrolyte solutions: a conceptual model and model results for the Waste Isolation Pilot Plant (WIPP)

    SciTech Connect

    Novak, C.F.; Moore, R.C.; Bynum, R.V.

    1996-10-25

    The conceptual model for WIPP dissolved concentrations is a description of the complex natural and artificial chemical conditions expected to influence dissolved actinide concentrations in the repository. By a set of physical and chemical assumptions regarding chemical kinetics, sorption substrates, and waste-brine interactions, the system was simplified to be amenable to mathematical description. The analysis indicated that an equilibrium thermodynamic model for describing actinide solubilities in brines would be tractable and scientifically supportable. This paper summarizes the conceptualization and modeling approach and the computational results as used in the WIPP application for certification of compliance with relevant regulations for nuclear waste repositories. The WIPP site contains complex natural brines ranging from sea water to 10x more concentrated than sea water. Data bases for predicting solubility of Am(III) (as well as Pu(III) and Nd(III)), Th(IV), and Np(V) in these brines under potential repository conditions have been developed, focusing on chemical interactions with Na, K, Mg, Cl, SO{sub 4}, and CO{sub 3} ions, and the organic acid anions acetate, citrate, EDTA, and oxalate. The laboratory and modeling effort augmented the Harvie et al. parameterization of the Pitzer activity coefficient model so that it could be applied to the actinides and oxidation states important to the WIPP system.

  16. Tolerance of Oncomelania hupensis quadrasi to varying concentrations of dissolved oxygen and organic pollution*

    PubMed Central

    Garcia, Rolando G.

    1972-01-01

    Ecological investigations were made of habitats containing natural populations of the snail Oncomelania hupensis quadrasi and of habitats free from the snail in the island of Leyte, Philippines. This species of snail is a vector of Schistosoma japonicum in the Philippines. Snail-infested habitats had dissolved oxygen levels of 3.8-9.85 ppm but snail-free habitats had levels of only 0.08-3.6 ppm. Snail-infested habitats were less polluted by organic matter than habitats that were snail-free. Larger numbers of chlorophyll-bearing algae were present in both the water and the soil of snail-infested habitats. Other factors, including temperature, pH, hydrogen carbonate alkalinity, and relative humidity, were also investigated. PMID:4538906

  17. How do changes in dissolved oxygen concentration influence microbially-controlled phosphorus cycling in stream biofilms?

    NASA Astrophysics Data System (ADS)

    Saia, S. M.; Locke, N. A.; Regan, J. M.; Carrick, H. J.; Buda, A. R.; Walter, M. T.

    2014-12-01

    Advances in molecular microbiology techniques (e.g. epi-fluorescent microscopy and PCR) are making it easier to study the influence of specific microorganisms on nutrient transport. Polyphosphate accumulating organisms (PAOs) are commonly used in wastewater treatment plants to remove excess phosphorus (P) from effluent water. PAOs have also been identified in natural settings but their ecological function is not well known. In this study, we tested the hypothesis that PAOs in natural environments would release and accumulate P during anaerobic and aerobic conditions, respectively. We placed stream biofilms in sealed, covered tubs and subjected them to alternating air (aerobic conditions) and N2 gas (anaerobic condition) bubbling for 12 hours each. Four treatments investigated the influence of changing dissolved oxygen on micribially-controlled P cycling: (1) biofilms bubbled continuously with air, (2) biofilms bubbled alternatively with air and N2, (3) biocide treated biofilms bubbled continuously with air, and (4) biocide treated biofilms bubbled alternatively with air and N2. Treatments 3 and 4 serve as abiotic controls to treatments 1 and 2. We analyzed samples every 12 hours for soluble reactive P (SRP), temperature, dissolved oxygen, and pH. We also used fluorescent microscopy (i.e. DAPI staining) and PCR to verify the presence of PAOs in the stream biofilms. SRP results over the course of the experiment support our hypothesis that anaerobic and aerobic stream conditions may impact PAO mediated P release and uptake, respectively in natural environments. The results of these experiments draw attention to the importance of microbiological controls on P mobility in freshwater ecosystems.

  18. Dissolved organic carbon concentration controls benthic primary production: results from in situ chambers in north-temperate lakes

    USGS Publications Warehouse

    Godwin, Sean C.; Jones, Stuart E.; Weidel, Brian C.; Solomon, Christopher T.

    2014-01-01

    We evaluated several potential drivers of primary production by benthic algae (periphyton) in north-temperate lakes. We used continuous dissolved oxygen measurements from in situ benthic chambers to quantify primary production by periphyton at multiple depths across 11 lakes encompassing a broad range of dissolved organic carbon (DOC) and total phosphorous (TP) concentrations. Light-use efficiency (primary production per unit incident light) was inversely related to average light availability (% of surface light) in 7 of the 11 study lakes, indicating that benthic algal assemblages exhibit photoadaptation, likely through physiological or compositional changes. DOC alone explained 86% of the variability in log-transformed whole-lake benthic production rates. TP was not an important driver of benthic production via its effects on nutrient and light availability. This result is contrary to studies in other systems, but may be common in relatively pristine north-temperate lakes. Our simple empirical model may allow for the prediction of whole-lake benthic primary production from easily obtained measurements of DOC concentration.

  19. Variations in concentrations and fluxes of dissolved inorganic nutrients related to catchment scale human interventions in Pamba River, Kerala, India

    NASA Astrophysics Data System (ADS)

    David, S. E.; Jennerjahn, T. C.; Chattopadhyay, S.

    2012-12-01

    River basins are geo-hydrological units. Water flowing out of the basin bears the imprint of natural factors such as geology, soil, vegetation and rainfall along with anthropogenic factors including the type and degree of human intervention within the basin. Pamba, a small mountainous river in the SW coast of India with a population density of ~1,400 persons km-2 was studied for its varying land use and human interventions as the global database are biased towards temperate regions while little is know about the smaller catchments from tropical regions. Land use comprised of dense forest in the highland region together with forest plantation and the human impacted Sabarimala temple- the second largest pilgrim, settlement with mixed tree crop (smt) in the midland and lowland paddy cultivated region. 50-60 million devotees visiting Sabarimala during November to January every year associated with the ritual bathing, discharge of human wastes emanating from the influx of millions of pilgrims due to inadequate number of sanitary latrines and the lack of facilities for sewage collection and treatment caused several ecological variations during pilgrim season. In order to asses the effect of land use and pilgrims in combination with seasonal variations in hydrology we investigated the seasonal and spatial variations in physicochemical and nutrient concentrations. Samples were collected from March 2010 to February 2012 during premonsoon (January-May), SW(June to September) and NE monsoon(October to December), from sites varying in land use. Nutrient budgets (load and yield) were calculated to quantify the inputs from various land use segments. Spatio-temporal variations in the physicochemical and dissolved nutrient concentrations were observed along the course of the river. Upstream forest region had highest dissolved oxygen(DO) and pH together with lowest dissolved inorganic nitrogen(DIN) values indicating almost pristine conditions. DIN in the temple region had the maximum value during the pre and NE monsoon. Highest DIN with ammonium(NH4+) as the major component in January were observed during the peak pilgrim season. Except for the temple locations NH4+ values were low in the rest of the catchment. Nitrate(NO3-) was dominant during SW monsoon in the midland and low land regions due to the various agricultural practices displaying variability along the course of the river. Maximum values for phosphate (PO43-) and silicate (Si(OH)4) were in the temple area during the premonsoon months. Average NPK fertilizer use in the basin was 80.2 kg ha-1.When compared to the average of all India (72 kg.ha-1) usage is high but lower than Western Europe and U.S (250 kg.ha-1).Yield calculated were 7186.6 kg km-2yr-1for DIN, 453.2 kg km-2yr-1for PO43--P and 17728.9 kg km-2yr- for dissolved Si. NH4+-N and dissolved Si yield were maximum in the temple and forest dominated regions, NO3--N and PO43--P in smt regions respectively. When compared to other tropical rivers, nutrient yield from the Pamba River found to be higher points to the significant hydrological and land use practices. To conclude, land use activities in the basin are the key factor contributing to varying water quality and nutrient concentrations and loading in the Pamba catchment the main being pilgrim event and agriculture in our study.

  20. Assessing the concentration, speciation, and toxicity of dissolved metals during mixing of acid-mine drainage and ambient river water downstream of the Elizabeth Copper Mine, Vermont, USA

    USGS Publications Warehouse

    Balistrieri, L.S.; Seal, R.R., II; Piatak, N.M.; Paul, B.

    2007-01-01

    The authors determine the composition of a river that is impacted by acid-mine drainage, evaluate dominant physical and geochemical processes controlling the composition, and assess dissolved metal speciation and toxicity using a combination of laboratory, field and modeling studies. Values of pH increase from 3.3 to 7.6 and the sum of dissolved base metal (Cd + Co + Cu + Ni + Pb + Zn) concentrations decreases from 6270 to 100 ??g/L in the dynamic mixing and reaction zone that is downstream of the river's confluence with acid-mine drainage. Mixing diagrams and PHREEQC calculations indicate that mixing and dilution affect the concentrations of all dissolved elements in the reach, and are the dominant processes controlling dissolved Ca, K, Li, Mn and SO4 concentrations. Additionally, dissolved Al and Fe concentrations decrease due to mineral precipitation (gibbsite, schwertmannite and ferrihydrite), whereas dissolved concentrations of Cd, Co, Cu, Ni, Pb and Zn decrease due to adsorption onto newly formed Fe precipitates. The uptake of dissolved metals by aquatic organisms is dependent on the aqueous speciation of the metals and kinetics of complexation reactions between metals, ligands and solid surfaces. Dissolved speciation of Cd, Cu, Ni and Zn in the mixing and reaction zone is assessed using the diffusive gradients in thin films (DGT) technique and results of speciation calculations using the Biotic Ligand Model (BLM). Data from open and restricted pore DGT units indicate that almost all dissolved metal species are inorganic and that aqueous labile or DGT available metal concentrations are generally equal to total dissolved concentrations in the mixing zone. Exceptions occur when labile metal concentrations are underestimated due to competition between H+ and metal ions for Chelex-100 binding sites in the DGT units at low pH values. Calculations using the BLM indicate that dissolved Cd and Zn species in the mixing and reaction zone are predominantly inorganic, which is consistent with the DGT results. Although the DGT method indicates that the majority of aqueous Cu species are inorganic, BLM calculations indicate that dissolved Cu is inorganic at pH 5.5. Integrated dissolved labile concentrations of Cd, Cu and Zn in the mixing and reaction zone are compared to calculated acute toxicity concentrations (LC50 values) for fathead minnows (Pimephales promelas) (Cd, Cu and Zn) and water fleas (Ceriodaphnia dubia) (Cd and Cu) using the BLM, and to national recommended water quality criteria [i.e., criteria maximum concentration (CMC) and criterion continuous concentration (CCC)]. Observed labile concentrations of Cd and Zn are below LC50 values and CMC for Cd, but above CCC and CMC for Zn at sites <30 m downstream of the confluence. In contrast, labile Cu concentrations exceed LC50 values for the organisms as well as CCC and CMC at sites <30 m downstream of the confluence. These results suggest that environmental conditions at sites closest to the confluence of the river and acid-mine drainage should not support healthy aquatic organisms. ?? 2007 Elsevier Ltd. All rights reserved.

  1. PHOTOCHEMICAL ALTERATION OF DISSOLVED ORGANIC MATTER: EFFECTS ON THE CONCENTRATION AND ACIDITIES OF IONIZABLE SITES IN DISSOLVED ORGANIC MATTER IN THE SATILLA RIVER OF GEORGIA, USA

    EPA Science Inventory

    The acid-base properties of humic substances, the major component of dissolved organic matter (DOM), area major control on the alkalinity, or acid neutralizing capacity of freshwater systems. Alkalinity is one of the fundamental parameters measured in aquatic sciences, and is an ...

  2. A simplified coulometric method for multi-sample measurements of total dissolved inorganic carbon concentration in marine waters.

    PubMed

    Amornthammarong, Natchanon; Ortner, Peter B; Hendee, James; Woosley, Ryan

    2014-10-21

    A new system requiring greatly reduced operator intervention has been developed for the determination of dissolved inorganic carbon concentration in marine waters. Based on a coulometric method, the system has an accuracy and precision comparable to more complex and expensive methods currently employed. A syringe pump equipped with a 12-port distribution valve is used to precisely dispense an acid solution and sample into a gas stripper. The system can autonomously measure eight discrete samples in duplicate or triplicate with no operator input. The best precision (%RSD) obtained was 0.022% (n = 14) or less than ±1.0 ?mol kg(-1). The system is calibrated against a certified reference material (CRM). Average offset from the CRM was 1.2 ?mol kg(-1). Sample throughput was 4 samples per h. Carryover effects are negligible but field sample analyses suggest that prefiltering may be necessary in highly turbid waters. PMID:25136787

  3. Direct analysis of ?13C and concentration of dissolved organic carbon (DOC) in environmental samples by TOC-IRMS

    NASA Astrophysics Data System (ADS)

    Kirkels, Frédérique; Cerli, Chiara; Federherr, Eugen; Kalbitz, Karsten

    2014-05-01

    Dissolved organic carbon (DOC) plays an important role in carbon cycling in terrestrial and aquatic systems. Stable isotope analysis (delta 13C) of DOC could provide valuable insights in its origin, fluxes and environmental fate. Precise and routine analysis of delta 13C and DOC concentration are therefore highly desirable. A promising, new system has been developed for this purpose, linking a high-temperature combustion TOC analyzer trough an interface with a continuous flow isotope ratio mass spectrometer (Elementar group, Hanau, Germany). This TOC-IRMS system enables simultaneous stable isotope (bulk delta 13C) and concentration analysis of DOC, with high oxidation efficiency by high-temperature combustion for complex mixtures as natural DOC. To give delta 13C analysis by TOC-IRMS the necessary impulse for broad-scale application, we present a detailed evaluation of its analytical performance for realistic and challenging conditions inclusive low DOC concentrations and environmental samples. High precision (standard deviation, SD predominantly < 0.15 permil) and accuracy (R2 = 0.9997, i.e. comparison TOC-IRMS and conventional EA-IRMS) were achieved by TOC-IRMS for a broad diversity of DOC solutions. This precision is comparable or even slightly better than that typically reported for EA-IRMS systems, and improves previous techniques for ?13C analysis of DOC. Simultaneously, very good precision was obtained for DOC concentration measurements. Assessment of natural abundance and slightly 13C enriched DOC, a wide range of concentrations (0.2-150 mgC/L) and injection volumes (0.05-3 ml), demonstrated good analytical performance with negligible memory effects, no concentration/volume effects and a wide linearity. Low DOC concentrations (< 2 mgC/L), were correctly analyzed without any pre-concentration. Moreover, TOC-IRMS was successfully applied to analyze DOC from diverse terrestrial, freshwater and marine environments (SD < 0.23 permil). In summary, the TOC-IRMS performs fast and reliable analysis of DOC concentration and ?13C in aqueous samples, without any pre-concentration/freeze-drying. Flexible usage is highlighted by automated, online analysis, a variable injection volume, high throughput and no extensive maintenance. Sample analysis is simple, using small aliquots and with minimal sample preparation. Further investigations should focus on complex, saline matrices and very low DOC concentrations, to achieve a potential lower limit of 0.2 mgC/L. High-resolution, routine delta 13C analysis of DOC by TOC-IRMS offers opportunities for wide-scale application in terrestrial, freshwater and marine research to elucidate the role of DOC in biogeochemical processes and ecosystem functioning.

  4. [Concentration and Source of Dissolved Organic Carbon in Snowpits of the Tibetan Plateau].

    PubMed

    Yan, Fang-ping; Kang, Shi-chang; Chen, Peng-fei; Bai, Jian-kun; Li, Yang; Hu, Zhao-fu; Li, Chao-liu

    2015-08-01

    Snowpit samples of three glaciers (Laohugou NO. 12 Glacier (LHG), Small Dongkemadi Glacier on Mount Tanggula (TGL) and East Ronghuk Glacier on Mount Everest (ZF)) in the Tibetan Plateau were collected. Concentrations of DOC and major ions were analyzed. The results showed that average DOC concentrations of the snowpits of LHG, TGL and ZF were (250.30 +/- 157.10), (216.92 +/- 142.82) and (152.50 +/- 56.11) microg x L(-1), respectively. DOC of TGL and ZF accounted for large parts of total values of DOC and ions. Correspondingly, DOC of LHG accounted for small part (only 5%), because LHG was located at north China and intensively influenced by natural mineral dust, which caused high concentrations of Ca2+ (the highest value could reach 5299.18 microg x L(-1)) and consequently low percentage of DOC of snowpit samples. Correlation and PCA analyses were used to study the sources of DOC. DOC was significantly correlated with Ca2+, Mg2+, K+ and SO4(2-). Additionally, PCA further indicated that the main potential source of DOC was the natural source of mineral dust. Meanwhile, anthropogenic pollutants (e.g., biomass, fossil combustion and agricultural related pollutants) could also not be ignored. Moreover, the carbon depositional fluxes of three snowpits were roughly estimated, and the values of LHG, TGL and ZF snowpits were 189.23, 132.76 and 128.44 mg (m2 x a)(-1), respectively, which played a significant role in the carbon cycle in this region and was also helpful for the study of glaciers fluctuation. PMID:26592009

  5. Impacts of Agricultural Practices on Concentrations and Fluxes of Dissolved Organic Carbon

    NASA Astrophysics Data System (ADS)

    Oh, N.; Pellerin, B. A.; Bachand, P. A.; Bergamaschi, B. A.; Horwath, W. R.

    2008-12-01

    Organic matter from the breakdown of plant and animal material is a significant concern for drinking water quality in California due to the potential formation of carcinogenic disinfection byproducts (DBPs) during water treatment with chlorine. Reducing DOC concentration at the source water is a possible management strategy being explored for the reduction of DBP precursors. We examined a variety of land use/land cover, i.e. natural grasslands and intensive agriculture in the Willow Slough Watershed (415 km2) in Yolo County, California to determine the temporal and spatial DOC dynamics. Surface water DOC concentrations ranged from 1.62 to 11.44 mg L-1 at the mouth of the watershed during the first two years, with about two times higher DOC concentrations measured downstream in an intensive agricultural subwatershed dominated by summer flood irrigation. The mean DOC yield was also the highest from the agricultural subwatershed at 0.74 g m-2 over the six months of active irrigation. Results suggest that there is a positive correlation between cropland area and DOC yield. Among many crop species examined, alfalfa showed the strongest positive linear relationship with R2 = 0.91 between the irrigation season DOC yield and percentage crop area of each subwatershed, indicating that agricultural practices such as flood irrigation have a greater impact on DOC loads than other irrigation systems. The results indicate that agricultural practices may deserve further attention for watershed management of DOC and DBP precursors and that flood irrigation practices should be targeted to reduce DOC loading within the main watershed.

  6. The effect of using different 0.45 ?m filter membranes on 'dissolved' element concentrations in natural waters

    USGS Publications Warehouse

    Hall, G.E.M.; Bonham-Carter, G. F.; Horowitz, A.J.; Lum, K.; Lemieux, C.; Quemerais, B.; Garbarino, J.R.

    1996-01-01

    The effect of 4 different 0.45 ??m pore size filter membrane systems on the 'dissolved' concentration of 28 elements in 5 natural water samples of varying matrix is reported. In 3 of the 5 waters, consistently higher concentrations of most elements (minor and trace) are obtained using Nucleopore 47 mm filter and the cellulose acetate/nitrate 47 mm filter than those measured using the 142 mm cellulose nitrate MFS filter or the Gelman capsule 47 mm filter. These distinct and coherent patterns in elemental behaviour disappear for the other 2 samples, an organic-rich peat water of high suspended load and a mineralised sample high in Si and Ca. Thus the nature and degree of filtration artifacts is matrix-dependent. These trends are evident in both data sets produced by 2 independent laboratories using different instrumentation, techniques and calibrating procedures. The average relative standard deviation in elemental concentration across the 4 filter types is in the range 9-21%. The presence of such filtration artifacts must be considered in projects where, for example, seasonal variability of water composition is under examination, data from various sources are being merged or hydrogeochemical surveys are being conducted.

  7. Evaluating Function of a Constructed Fen in Alberta's Oil Sands Region Using Dissolved Organic Carbon Concentration and Chemistry

    NASA Astrophysics Data System (ADS)

    Strack, M.; Khadka, B.

    2014-12-01

    Peatlands, mainly fens, account for close to 65% of the landscape in the oil sands region near Fort McMurray, Alberta. Since mine closure plans require landscape reclamation, methods for fen construction are being investigated. As reclamation goals include the return of ecosystem function, criteria for evaluation must be developed. In this study we compare soil concentrations and spectrophometric properties of dissolved organic carbon (DOC) from a constructed fen during its first growing season with that collected from three diverse, undisturbed reference fens in the region. The constructed fen had lower DOC concentration than all the reference fens. Based on E2/E3, E4/E6 and specific UV absorbance of the DOC, the constructed fen had DOC with significantly greater humic content, aromatic nature, and larger molecular size than the reference fens. Results from laboratory DOC production studies indicate that these patterns are likely due to the limited DOC contribution from the newly planted vegetation at the constructed fen, resulting in DOC largely derived from humified peat placed during construction. These preliminary results suggest that DOC concentration and chemistry provide information about the ecological development of the constructed system that could be useful for evaluating reclamation success through time.

  8. One year of Seaglider dissolved oxygen concentration profiles at the PAP site

    NASA Astrophysics Data System (ADS)

    Binetti, Umberto; Kaiser, Jan; Heywood, Karen; Damerell, Gillian; Rumyantseva, Anna

    2015-04-01

    Oxygen is one of the most important variables measured in oceanography, influenced both by physical and biological factors. During the OSMOSIS project, 7 Seagliders were used in 3 subsequent missions to measure a multidisciplinary suite of parameters at high frequency in the top 1000 m of the water column for one year, from September 2012 to September 2013. The gliders were deployed at the PAP time series station (nominally at 49° N 16.5° W) and surveyed the area following a butterfly-shaped path. Oxygen concentration was measured by Aanderaa optodes and calibrated using ship CTD O2 profiles during 5 deployment and recovery cruises, which were in turn calibrated by Winkler titration of discrete samples. The oxygen-rich mixed layer deepens in fall and winter and gets richer in oxygen when the temperature decreases. The spring bloom did not happen as expected, but instead the presence of a series of small blooms was measured throughout spring and early summer. During the summer the mixed layer become very shallow and oxygen concentrations decreased. A Deep Oxygen Maximum (DOM) developed along with a deep chlorophyll maximum during the summer and was located just below the mixed layer . At this depth, phytoplankton had favourable light and nutrient conditions to grow and produce oxygen, which was not subject to immediate outgassing. The oxygen concentration in the DOM was not constant, but decreased, then increased again until the end of the mission. Intrusions of oxygen rich water are also visible throughout the mission. These are probably due to mesoscale events through the horizontal transport of oxygen and/or nutrients that can enhance productivity, particularly at the edge of the fronts. We calculate net community production (NCP) by analysing the variation in oxygen with time. Two methods have been proposed. The classical oxygen budget method assumes that changes in oxygen are due to the sum of air-sea flux, isopycnal advection, diapycnal mixing and NCP. ERA-Interim provides climatological data to calculate air-sea gas exchange fluxes based on wind-speed parameterisations of the gas exchange coefficient. The second method exploits the high frequency of the measurements to determine the increment of oxygen over time during daylight hours to measure NCP. Together with the O2 concentration decrease during the night (due to community respiration), this method also allows us to derive gross oxygen production rates. The results of these two methods are compared.

  9. Seasonal Control of Surface-Water Dissolved Iron Concentrations by Suspended Particle Concentrations on the Northern Gulf of Alaska Continental Shelf and Slope

    NASA Astrophysics Data System (ADS)

    Crusius, J.; Schroth, A. W.; Campbell, R.; Cullen, J. T.; Dillman, D.; Resing, J.

    2012-12-01

    The continental shelf region of the northern Gulf of Alaska (GoA) supports a productive ecosystem including an important commercial fishery. Downwelling winds during most of the year imply that some mechanism other than upwelling must be supplying the essential nutrients iron and nitrate. Although it is well known that iron limits productivity offshore in the GoA, we have a poor understanding of the controls on Fe supply. Data from cruises from 2010 provide some new insight into the mechanisms of Fe supply. Cruises were carried out along a transect extending from the mouth of the Copper River to ~40 km beyond the shelf break three times per year including early April, early May, and late July. High-resolution surface-water sampling was carried out, as well as bottle casts at 5 stations. High, fairly uniform concentrations of "total dissolvable iron" (TDFe; unfiltered sample acidified to pH=1.7) as well as "dissolved" Fe (dFe) were observed spanning the shelf in April, suggesting sediment resuspension is an important source of dFe to surface waters at that time. By contrast, high dFe and TDFe concentrations in late July coincide with low-salinity surface water, which in this location indicates a glacial meltwater source. Throughout spring and summer high particle concentrations across much of the shelf appear to "buffer" dFe concentrations to ~3 nmol/kg, which are close to those observed by Lippiatt et al (2010) in the region. This is consistent with dFe concentrations being determined by the organic ligand concentrations that, in turn, are fairly constant. In late July, surface water dFe concentrations are ~0.5 nmol/kg on the outer shelf and up to ~50 km further offshore. These dFe concentrations on the outer shelf are much lower in July than earlier in the year, owing to Fe removal by phytoplankton uptake and by scavenging, as well as by the lack of particulate Fe sources to surface waters in July. However, the high surface-water dFe observed ~50 km beyond the shelf break suggest offshore transport of Fe in this location. These outer shelf and slope Fe concentrations are substantially higher than observed on the outer shelf and slope along the GAK line (offshore of Seward, AK) by Wu et al 2009 and Lippiatt et al, 2010. We suggest that the higher concentrations over the outer shelf and slope region in our work are due to offshore transport, whereas the GAK line experienced Ekman-induced onshore transport. We will explore possible mechanisms for offshore transport of Fe in surface waters in in our work. All of these studies have in common the suggestion that particles from the continental shelf exert an important control on dFe concentrations both over and beyond the shelf. Understanding the processes of cross-shelf transport will be important for understanding the high productivity in the region.

  10. An in situ method to quantitatively determine dissolved free drug concentrations in vitro in the presence of polymer excipients using pulsatile microdialysis (PMD).

    PubMed

    Vejani, Charchil; Bellantone, Robert A

    2015-12-30

    In drug formulations containing polymer excipients, the effects of the polymer on the dissolved free drug concentration and resulting dissolution or release can be important, especially for poorly soluble drugs. In this study, an in vitro method based on pulsatile microdialysis (PMD) was developed to quantitatively determine dissolved free concentrations of drugs in the presence of polymers in aqueous media in situ (e.g., in place within the system being characterized). Formulations were made by dissolving various ratios of the drug griseofulvin and polymer PVP K30 in water and allowing the mix to equilibrate. A PMD probe was immersed in each mixture and the dissolved free drug concentrations were determined in the PMD samples. The experimental procedure and the equations used for data analysis are presented. To assess the consistency of data, a binding model was fit to the data obtained using PMD by calculating the dissolved free drug fraction fD for each drug-polymer ratio in solution, and obtaining the product of the binding stoichiometry and binding constant (?K per mole of polymer) from the slope of a plot of (1-fD)/fD vs. the molar polymer concentration. For comparison, equilibrium binding experiments were also performed at 23C, and the determined value of ?K was similar to the value found using PMD. Experiments were performed at three temperatures, and a plot of ln (?K) vs. 1/T was linear and a binding enthalpy of -110.9±4.4J/mol of monomer was calculated from its slope. It was concluded that PMD can be used to determine the dissolved free drug concentrations in situ, which allows characterization of the drug-polymer interaction, even for low drug concentrations. This information may be important in modeling the dissolution or release of drugs from formulations containing polymers. PMID:26319635

  11. Dissolved Concentrations, Sources, and Risk Evaluation of Selected Metals in Surface Water from Mangla Lake, Pakistan

    PubMed Central

    Saleem, Muhammad; Iqbal, Javed; Shah, Munir H.

    2014-01-01

    The present study is carried out for the assessment of water quality parameters and selected metals levels in surface water from Mangla Lake, Pakistan. The metal levels (Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sr, and Zn) were determined by flame atomic absorption spectrophotometry. Average levels of Cd, Co, Cr, Ni, and Pb were higher than the allowable concentrations set by national and international agencies. Principal component analysis indicated significant anthropogenic contributions of Cd, Co, Cr, Ni, and Pb in the water reservoir. Noncarcinogenic risk assessment was then evaluated using Hazard Quotient (HQing/derm) and Hazard Index (HIing/derm) following USEPA methodology. For adults and children, Cd, Co, Cr, and Pb (HQing > 1) emerged as the most important pollutants leading to noncarcinogenic concerns via ingestion route, whereas there was no risk via dermal contact of surface water. This study helps in establishing pollutant loading reduction goal and the total maximum daily loads, and consequently contributes to preserve public health and develop water conservation strategy. PMID:24744690

  12. Synthesized mercaptopropyl nanoporous resins in DGT probes for determining dissolved mercury concentrations.

    PubMed

    Gao, Yue; De Canck, Els; Leermakers, Martine; Baeyens, Willy; Van Der Voort, Pascal

    2011-12-15

    3-Mercaptopropyl functionalized SBA-15 (SH-SBA) and 3-mercaptopropyl functionalized ethenylene bridged periodic mesoporous organosilica (SH-PMO) were included in a Diffusive Gradients in Thin film (DGT) probe and compared to similar commercially available resins also containing thiol functional groups, such as Sumichelate Q10R (SQR) and 3-mercaptopropyl functionalized silica gel (SH-KG), and also to the Chelex-100 resin for the determination of labile Hg concentrations. An agarose gel was used as the diffusive gel because the classic polyacrylamide gel shows more than 20% of Hg adsorption. According to our results, the Chelex-100 resin presents a much lower affinity for Hg than the thiol based resins. The non-linear accumulation profile of mercury with time for the Chelex-100 resin makes it in fact impossible to use Fick's law for estimating the diffusion coefficient of Hg. The 4 other resins all show a linear accumulation profile of Hg with time. Although the highest accumulation rate is observed for SH-PMO followed by SQR, SH-SBA and SH-KG, these values do not differ very much. PMID:22099677

  13. An Isotope Dilution Method for High-frequency Measurements of Dissolved Inorganic Carbon concentration in the Surface Ocean

    NASA Astrophysics Data System (ADS)

    Huang, K.; Bender, M. L.; Wanninkhof, R. H.; Cassar, N.

    2013-12-01

    Dissolved inorganic carbon (DIC) is one of the most important species in the ocean carbon system. An autonomous system using isotope dilution as its core method has been developed to obtain high-frequency measurements of dissolved inorganic carbon (DIC) concentrations in the surface ocean. This system accurately mixes a seawater sample and a 13C-labeled sodium bicarbonate solution (spike). The mixed solution is then acidified and sent through a gas permeable membrane contactor. CO2 derived from DIC in the mixture is extracted by a CO2-free gas stream, and is sent to a cavity ring-down spectrometer to analyze its 13C/12C ratio. [DIC] of the seawater can then be derived from the measured 13C/12C, the known mixing ratio and the [DI13C] of the spike. The method has been tested under a wide [DIC] range (1800-2800 ?mol/kg) in the laboratory. It has also been deployed on a cruise that surveyed ocean waters to the south of Florida. At a sampling resolution of 4 minutes (15 samples per hour), the relative standard deviation of DIC determined from the laboratory tests and the field deployment is ×0.07% and ×0.09%, respectively. The accuracy of the method is better than 0.1% except where [DIC] varies faster than 5 ?mol/kg per minute. Based on the laboratory and field evaluations, we conclude that this method can provide accurate underway [DIC] measurements at high resolution in most oceanic regions. Schematic illustration of the work flow.

  14. Dissolved inorganic carbon concentrations and stable carbon isotope ratios in streams polluted by variable amounts of acid mine drainage

    NASA Astrophysics Data System (ADS)

    Atekwana, Eliot A.; Fonyuy, Ernest W.

    2009-06-01

    SummaryDissolved inorganic carbon (DIC) concentrations and stable carbon isotopes of DIC (? 13C DIC) were determined in streams polluted by acid mine drainage (AMD). The aim was to assess the effects of variable AMD contamination on DIC dynamics and ? 13C DIC. The stream with relatively high metal (e.g., Fe, Al, Mn) concentrations exhibited downstream decreases in pH because production of protons by the chemical evolution of AMD exceeded the stream's buffering capacity. DIC dynamics in this stream was driven by proton-enhanced CO 2 degassing. In the stream with lower metal concentrations, the protons were neutralized by HCO3- and pH increased in the downstream direction. In this stream, DIC dynamics was driven by CO 2 loss due to higher partial pressure of CO 2 (pCO 2) in stream water compared to atmospheric. In both contaminated watersheds, CO 2 loss resulted in seasonal exports of <1-47% of stream DIC. The decreases in DIC concentrations were accompanied by a variable enrichment of ? 13C DIC which depended on the extent to which HCO3- was dehydrated to CO 2(aq), how CO 2 was lost from the streams, and if carbon in DIC was exchanged with atmospheric CO 2. The ? 13C DIC was enriched by <3.0‰ when CO 2 loss was proton enhanced and isotopic fractionation was controlled mostly by diffusion. The ? 13C DIC was enriched by >3.0‰ when CO 2 loss was neutralization induced and CO 2 loss was accompanied by partial exchange of carbon between DIC and atmospheric CO 2. We conclude that DIC loss and ? 13C DIC enrichment in AMD-contaminated streams depends on the rate of production and amount of protons produced by metal hydrolysis, the stream's buffering capacity, and the mechanism of CO 2 loss.

  15. Binding of mercury(II) to dissolved organic matter: The role of the mercury-to-DOM concentration ratio

    USGS Publications Warehouse

    Haitzer, M.; Aiken, G.R.; Ryan, J.N.

    2002-01-01

    The binding of Hg(II) to dissolved organic matter (DOM; hydrophobic acids isolated from the Florida Everglades by XAD-8 resin) was measured at a wide range of Hg-to-DOM concentration ratios using an equilibrium dialysis ligand exchange method. Conditional distribution coefficients (KDOM???) determined by this method were strongly affected by the Hg/DOM concentration ratio. At Hg/DOM ratios below approximately 1 ??g of Hg/mg of DOM, we observed very strong interactions (KDOM??? = 1023.2??1.0 L kg-1 at pH = 7.0 and I = 0.1), indicative of mercury-thiol bonds. Hg/DOM ratios above approximately 10 ??g of Hg/mg of DOM, as used in most studies that have determined Hg-DOM binding constants, gave much lower KDOM??? values (1010.7??1.0 L kg-1 at pH = 4.9-5.6 and I = 0.1), consistent with Hg binding mainly to oxygen functional groups. These results suggest that the binding of Hg to DOM under natural conditions (very low Hg/DOM ratios) is controlled by a small fraction of DOM molecules containing a reactive thiol functional group. Therefore, Hg/DOM distribution coefficients used for modeling the biogeochemical behavior of Hg in natural systems need to be determined at low Hg/DOM ratios.

  16. Effect of low dissolved oxygen concentration on planktonic foraminifera: results from laboratory culture experiments and implications for oceanic anoxic events

    NASA Astrophysics Data System (ADS)

    Kuroyanagi, A.; da Rocha, R. E.; Bijma, J.; Spero, H. J.; Russell, A. D.; Eggins, S. M.; Kawahata, H.

    2013-12-01

    During Cretaceous oceanic anoxic events (OAEs), substantial turnover of planktonic foraminiferal species occurred, however, the direct effects of the dissolved oxygen (DO) concentration on planktonic foraminifera remain obscure. Althogh culture experiments conducted under controlled conditions can quantify the relationships between foraminiferal ecology and environmental parameters, experiments controlling DO have yet to be conducted because it is difficult to maintain a stable oxygen concentration. In this study, we cultured two subtropical-transitional planktonic foraminifer species (one symbiotic species, Orbulina universa, and one nonsymbiotic species, Globigerina bulloides) under six different DO conditions (between 10% and 100% saturation). In both species, the gametogenesis rate was more than 60% even at a DO of 10%, suggesting that at least 'dysoxic' conditions (~0.7 mg O2 L-1) could not have directly caused the extinction of planktonic foraminifera during OAEs. Planktonic foraminifera originated from benthic lineages, and this origin is one possible explanation for their high tolerance to extremely low DO levels. Although the number of days to gametogenesis did not differ significantly among treatments in either species, final shell weight increased with increasing DO, suggesting that fossil foraminiferal shell weight could vary with past DO conditions. Our results suggest that the extinction of many planktonic foraminiferal species during OAEs may have been due to anoxic or euxinic conditions in the euphotic zone. The occurrence of these conditions can be explained either by the oxygen minimum layer model or by the stagnant ocean model combined with elevated riverine P input.

  17. Hydroclimatic Controls on the Seasonal and Inter-Annual Variability of Dissolved Phosphorus Concentration in a Lowland Agricultural Catchment

    NASA Astrophysics Data System (ADS)

    Dupas, R.; Gascuel-odoux, C.; Grimaldi, C.; Gruau, G.

    2014-12-01

    We investigated soluble reactive phosphorus (SRP) at the outlet of a lowland agricultural catchment (Kervidy-Naizin, France) to identify the hydroclimatic controls on the seasonal and inter-annual variability in concentrations. Six years of stream data have been used, including a regular 6-daily sampling and high-frequency monitoring of 52 floods. Both on an annual basis and during flood events, distinct export dynamics for SRP and particulate phosphorus (PP) revealed that SRP transport mechanism was independent from PP (Dupas et al., submitted). During most flood events, discharge-SRP hystereses were anticlockwise, which suggests that SRP was transferred to the stream via subsurface flow. Groundwater rise in wetland soils was likely the cause of this transfer, through the hydrological connectivity it created between the stream and P-rich soil horizons. SRP concentrations were highest in the beginning of the hydrological year (period A), when the stream started to flow again after the dry summer season and water table fluctuated in the wetland domain. Thus, wetland soils seemed to be a major source of SRP. Concentrations during period A were higher after a long summer period than after a short one, which suggest that a pool of labile P was constituted in soils during the dry summer period. During winter (period B), SRP concentration generally decreased compared to period A, both during floods and interflood. This could be due to depletion of a soil P pool in the wetland domain and/or dilution by deep groundwater with low P concentration from the upland domain. Concentration during period B barely decreased compared to A during wet years, probably due to increased connectivity with soils from the upland domain in wet conditions. During spring (period C), SRP concentration increased during baseflow periods. The possible mechanisms causing the release of SRP could involve reduction of Fe oxide-hydroxides in wetland soils or in-stream processes. At the same time, SRP and PP export during floods were synchronised and caused by erosion and overland flow. In-situ monitoring of soil solution and batch experiments are currently been performed to confirm hypotheses on biogeochemical mechanisms. Dupas R et al. Distinct export dynamics for dissolved and particulate phosphorus reveal independent transport mechanisms (subm.)

  18. Trends in chloride, dissolved-solids, and nitrate concentrations in ground water, Carson Valley and Topaz Lake Areas, Douglas County, Nevada, 1959-88

    USGS Publications Warehouse

    Thodal, C.E.

    1996-01-01

    Rapid population growth in Douglas County, an area of approximately 750 square miles in west-central Nevada, has led to concern about the present and future effects of development on ground water. This report describes the results of two nonparametric statistical procedures applied to detect trends in concentrations of chloride, dissolved solids, and nitrate in ground water. The water-quality data consist of analytical results from ground-water samples collected and analyzed by the U. S. Geological Survey and ground-water-quality data provided by the Nevada Bureau of Health Protection Services for the Carson Valley and Topaz Lake areas of Douglas County, Nevada. For purposes of this study, statistical significance, expressed as the p-value, was set at 0.1. The Mann-Whitney-Wilcoxan rank-sum test detected increasing step-trends for nitrate in one of seven residential areas and for dissolved-solids concentrations throughout the study area. Decreasing step-trends for chloride and dissolved-solids concentrations were detected in the west Carson Valley area. Kendall's Tau detected monotonic trends for increasing nitrate concentrations at four domestic wells and for increasing dissolved-solids concentrations at two domestic wells. No other statistically significant trends were indicated by either test. Land-use relations to areas where increasing trends were detected suggest that the density of individual wastewater-treatment systems may exceed the capacity of soils to treat wastewater leachate.

  19. Diurnal variations in, and influences on, concentrations of particulate and dissolved arsenic and metals in the mildly alkaline Wallkill River, New Jersey, USA

    USGS Publications Warehouse

    Barringer, J.L.; Wilson, T.P.; Szabo, Z.; Bonin, J.L.; Fischer, J.M.; Smith, N.P.

    2008-01-01

    Diurnal variations in particulate and dissolved As and metal concentrations were observed in mildly alkaline water from a wetlands site on the Wallkill River in northwestern New Jersey. The site, underlain by glacial sediments over dolomite bedrock, is 10 km downstream from a mined area of the Franklin Marble, host to Zn ores, also As and Mn minerals. In mid-September 2005, maxima and minima in dissolved-oxygen-concentration and pH, typically caused by photosynthesis and respiration, occurred at 2000 and 0800 hours. Concentrations of dissolved As (1.52-1.95 ??g/L) peaked at dusk (2000 hours), whereas dissolved Mn and Zn concentrations (76.5-96.9 and 8.55-12.8 ??g/L, respectively) were lowest at dusk and peaked at 1000 hours. These opposing cycles probably reflect sorption and desorption of As (an anion), and Mn and Zn (cations) as pH varied throughout the 24-h period. Doubly-peaked cycles of B, Cl, SO4, and nutrients also were observed; these may result from upstream discharges of septic-system effluent. Both recoverable amd particulate Al, Fe, Mn, and Zn concentrations peaked between 0200 and 0600 hours. The particulate metals cycle, with perturbations at 0400 hours, may be influenced by biological activity. ?? 2007 Springer-Verlag.

  20. Relationship between hydrological characteristics and dissolved organic carbon concentration and mass in northern prairie wetlands using a conservative tracer approach

    NASA Astrophysics Data System (ADS)

    Waiser, Marley J.

    2006-06-01

    The semiarid prairie pothole region of the North American Great Plains is characterized by millions of small, shallow, closed basin wetlands. These wetlands are hydrologically dynamic, often losing considerable water volume and depth seasonally in response to high evaporative stress and/or infiltration rates. However, the consequences of such water loss on wetland water chemistry parameters, in particular dissolved organic carbon (DOC), remain relatively unstudied. Seasonal changes in DOC concentrations in 12 freshwater and saline wetlands at the St. Denis National Wildlife Refuge near Saskatoon, Saskatchewan, Canada, were examined over an 8-year period (1993-2000). Specific conductivity in the study ponds ranged from 312 ?S cm-1 to 33,493 ?S cm-1 (seasonal means). DOC concentrations in all study ponds were high (>10 mg L-1) and increased across a gradient of increasing salinity (mean DOC values from fresh water to saline ranged from 19.7 mg L-1 to 102.7 mg L-1). In the majority of ponds, DOC concentrations increased seasonally from spring through fall. On average this increase was 21 mg L-1, with fall values averaging 60% greater than spring. The greatest DOC increases were observed in saline ponds which lost most of their water by evaporation. Although DOC in these ponds was highly correlated with the conservative tracer, chloride, the slopes of these regression lines were always less than 1 as were the DOC:chloride ratios, indicating nonconservative DOC behavior. Additionally, chloride concentrations increased much faster seasonally than did DOC. Taken together, these data indicated that although DOC was not behaving conservatively, at least some of the observed DOC increases could be explained by simple evapoconcentration. These data also suggested that saline ponds appeared to experience net seasonal removal of DOC. Possible removal mechanisms for DOC include infiltration to the pond margin, bacterial utilization, and photolysis. Freshwater ponds, which lost most of their water by infiltration to the pond margin, on the other hand, displayed less seasonal variation in DOC concentrations. In these ponds, the relationship between DOC and chloride ion was not as strong as in the saline ponds; the slope of this relationship was always >1, as were DOC:chloride ratios. These data indicated that although DOC was being lost to the pond margin as water infiltrated, freshwater ponds accumulated DOC seasonally. Decomposition and excretion of DOC by macrophytes, as well as by pelagic and attached phytoplankton, are the likely within pond sources of DOC here. The rapid response of these small, shallow aquatic systems to water loss make them ideal microcosms in which to study effects of climate on DOC concentrations and other water chemistry parameters.

  1. Characterization of the structure, clean-sand percentage, dissolved-solids concentrations, and estimated quantity of groundwater in the Upper Cretaceous Nacatoch Sand and Tokio Formation, Arkansas

    USGS Publications Warehouse

    Gillip, Jonathan A.

    2014-01-01

    The West Gulf Coastal Plain, Mississippi embayment, and underlying Cretaceous aquifers are rich in water resources; however, large parts of the aquifers are largely unusable because of large concentrations of dissolved solids. Cretaceous aquifers are known to have large concentrations of salinity in some parts of Arkansas. The Nacatoch Sand and the Tokio Formation of Upper Cretaceous age were chosen for investigation because these aquifers produce groundwater to wells near their outcrops and have large salinity concentrations away from their outcrop areas. Previous investigations have indicated that dissolved-solids concentrations of groundwater within the Nacatoch Sand, 2–20 miles downdip from the outcrop, render the groundwater as unusable for purposes requiring freshwater. Groundwater within the Tokio Formation also exhibits large concentrations of dissolved solids downdip. Water-quality data showing elevated dissolved-solids concentrations are limited for these Cretaceous aquifers because other shallower aquifers are used for water supply. Although not suitable for many uses, large, unused amounts of saline groundwater are present in these aquifers. Historical borehole geophysical logs were used to determine the geologic and hydrogeologic properties of these Cretaceous aquifers, as well as the quality of the groundwater within the aquifers. Based on the interpretation of borehole geophysical logs, in Arkansas, the altitude of the top of the Nacatoch Sand ranges from more than 200 to less than -4,000 feet; the structural high occurs in the outcrop area and the structural low occurs in southeastern Arkansas near the Desha Basin structural feature. The thickness of the Nacatoch Sand ranges from 0 to over 550 feet. The minimum thickness occurs where the formation pinches out in the outcrop area, and the maximum thickness occurs in the southwestern corner of Arkansas. Other areas of large thickness include the area of the Desha Basin structural feature in southeastern Arkansas and in an area on the border of Cross and St. Francis Counties in eastern Arkansas. The clean-sand percentage of the total Nacatoch Sand thickness ranges from less than 20 percent to more than 60 percent and generally decreases downdip. The Nacatoch Sand contains more than 120.5 million acre-feet of water with a dissolved-solids concentration between 1,000 and 10,000 milligrams per liter (mg/L), more than 57.5 million acre-feet of water with a dissolved-solids concentration between 10,000 and 35,000 mg/L, and more than 122.5 million acre-feet of water with a dissolved-solids concentration more than 35,000 mg/L. The altitude of the top of the Tokio Formation, in Arkansas, ranges from more than 200 feet to less than -4,400 feet; the structural high occurs in the outcrop area and the structural low occurs in southeastern Arkansas near the Desha Basin structural feature. The thickness of the Tokio Formation, in Arkansas, ranges from 0 to over 400 feet. The minimum thickness occurs where the formation pinches out in the outcrop area, and the maximum thickness occurs in the southwestern corner of Arkansas. The clean-sand percentage of the total Tokio Formation thickness ranges from less than 20 percent to more than 60 percent and generally decreases away from the outcrop area. The Tokio Formation contains more than 2.5 million acre-feet of water with a dissolved-solids concentration between 1,000 and 10,000 mg/L, more than 12.5 million acre-feet of water with a dissolved-solids concentration between 10,000 and 35,000 mg/L, and nearly 43.5 million acre-feet of water with a dissolved-solids concentration more than 35,000 mg/L.

  2. Influence of the Amazon River on dissolved and intra-cellular metal concentrations in Trichodesmium colonies along the western boundary of the sub-tropical North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Tovar-Sanchez, A.; Sañudo-Wilhelmy, S. A.

    2010-08-01

    Despite the ecological importance of Trichodesmium spp. for the global oceanic nitrogen budget, there is limited information on their trace metal composition in field samples. We report dissolved (<0.22 ?m) metal concentrations measured in surface waters (Ag, Cd, Co, Cu, Fe, Mo, Ni, P, Pb and V) and in the total and the intracellular pool (Ag, Al, Cd, Co, Cu, Fe, Mn, Mo, Ni, P, Pb, V) of Trichodesmium populations collected in the western subtropical North Atlantic Ocean (April-May 2003) within the influence of the Amazon River plume. Dissolved element distributions were strongly influenced by the River discharge, with concentrations of some elements varying directly (i.e. Cd, Mo and V) or inversely (Ag, Co, Cu, Fe, Ni, P and Pb) with surface salinity. Intracellular metal values to phosphorous ratios (mol:mol) for Cd, Co, Cu, Fe, Mn, Mo, Ni and V ranged from 9.0×10-6 for Cd to 4.4×10-2 for Fe. Although total metal composition was significantly correlated with the intracellular content in the Trichodesmium colonies for some elements (e.g., Co, Cu, V), metal pools in the phytoplankton did not co-vary with the dissolved metal concentrations, suggesting that water column measurements may not be good predictors of the intracellular metal concentrations. The impact of physical parameters and bioactive elements on biological processes in Trichodesmium such as nitrogen fixation, carbon drawdown and biomass production was explored by using a principal component analysis test (PCA). The analysis indicates that the biological drawdown of dissolved inorganic carbon (DIC) by Trichodesmium seems to be influenced by the internal content of Fe, Co, Cd, Cu and Mn, while nitrogen fixation seems more influenced by the internal concentration of Mo, Ni and V and by the dissolved phosphorous concentrations.

  3. Dissolved oxygen concentration profiles in the hyporheic zone through the use of a high density fiber optic measurement network

    NASA Astrophysics Data System (ADS)

    Reeder, W. J.; Quick, A. M.; Farrell, T. B.; Benner, S. G.; Feris, K. P.; Tonina, D.

    2013-12-01

    The hyporheic zone (HZ) is a potentially important source of the potent greenhouse gas, nitrous oxide (N2O); stream processes may account for up to 10% of global anthropogenic N2O emissions. However, mechanistic understanding and predictive quantification of this gas flux is hampered by complex temporally and spatially variable interactions between flow dynamics and biogeochemical processes. Reactive inorganic nitrogen (Nr) is typically present at low concentrations in natural stream waters, but many rural and urban streams suffer from an excess of Nr, typically in the form of ammonium (NH4+) and nitrate (NO3-). These reactive species are either assimilated by living biomass or transformed by microbial processes. The two primary microbial transformations of Nr are nitrification (NH4+ to NO3-) and denitrification (NO3- to N2). Denitrification, which occurs almost exclusively in the anoxic zone of the HZ, permanently removes between 30-70% of all Nr entering streams, other mechanisms may retain nitrogen. The mass transport of reactive species (i.e. O2, NO3- and N2O) by hyporheic flow strongly influences reaction rates, residence times, and subsequent N2O flux. By extension, stream flow and channel morphology presumably control, and may be effective predictors of, N2O generation rates. By recreating the stream processes in the University of Idaho flume, we are able to control the bed morphology, fluxes and residence times through the HZ and concentrations of Nr from exogenous (stream water) and endogenous (organic material in the streambed) sources. For the present experiment, the flume was divided into three streams, each with different morphologies (3, 6 and 9cm dunes) and all using the same source water. Stream water for this first experimental phase had no significant loading of Nr. As such, all reaction products were the result of endogenous sources of Nr. To measure dissolved oxygen (DO) concentrations we deployed 120 channels of a novel, fiber-optic optode system which was coupled with an advanced optical multiplexer that allowed us to cycle continuously through all 120 channels. Using this approach, we were able to accurately map the evolution and extent of the anoxic regions within the HZ and demonstrate that bed morphology exhibits significant control over residence times and the spatial temporal evolution of the anoxic region. In addition to the DO measurements, we deployed 240 Rhizon water samplers to extract pore water, which we used to measure Nr and N2O concentrations, and an ion Clark-type electrode sensor to measure N2O concentrations at the streambed surface (results discussed separately). Integrating these various results will allow us to refine the existing models for N2O emissions from urban and rural streams.

  4. Water quality in the Fort Cobb Watershed, USA: Spatial and temporal patterns of dissolved P stream concentrations

    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. The objective of this work is to identify spatial and temporal patterns in dissolved P [soluble reactive P (SRP) and bioavailable P (B...

  5. Dissolved methane concentration and flux in the coastal zone of the Southern California Bight-Mexican sector: Possible influence of wastewater

    EPA Science Inventory

    We measured dissolved methane concentrations ([CH4]) in the coastal zone of the Southern California Bight-Mexican sector (SCBMex) during two cruises: S1 in the USA–Mexico Border Area (BA) during a short rainstorm and S2 in the entire SCBMex during a drier period a few days later....

  6. Dissolved carbon dioxide and oxygen concentrations in purge of vacuum-packaged pork chops and the relationship to shelf life and models for estimating microbial populations.

    PubMed

    Adams, K R; Niebuhr, S E; Dickson, J S

    2015-12-01

    The objectives of this study were to determine the dissolved CO2 and O2 concentrations in the purge of vacuum-packaged pork chops over a 60 day storage period, and to elucidate the relationship of dissolved CO2 and O2 to the microbial populations and shelf life. As the populations of spoilage bacteria increased, the dissolved CO2 increased and the dissolved O2 decreased in the purge. Lactic acid bacteria dominated the spoilage microflora, followed by Enterobacteriaceae and Brochothrix thermosphacta. The surface pH decreased to 5.4 due to carbonic acid and lactic acid production before rising to 5.7 due to ammonia production. A mathematical model was developed which estimated microbial populations based on dissolved CO2 concentrations. Scanning electron microscope images were also taken of the packaging film to observe the biofilm development. The SEM images revealed a two-layer biofilm on the packaging film that was the result of the tri-phase growth environment. PMID:26143235

  7. Application of high-resolution spectral absorbance measurements to determine dissolved organic carbon concentration in remote areas

    NASA Astrophysics Data System (ADS)

    Avagyan, Armine; Runkle, Benjamin R. K.; Kutzbach, Lars

    2014-09-01

    Accurate quantification of dissolved organic carbon (DOC) in surface and soil pore waters is crucial for understanding changes in water resources under the influence of climate and land use changes. Sampling and laboratory analysis of DOC content at a sufficient temporal frequency are especially difficult to achieve for natural DOC sources like the extensive boreal and arctic mire landscapes due to their remoteness. Therefore, the goals of this paper are (1) to investigate the performance of a portable, high-resolution ultraviolet-visible light spectroscopic method for determining the DOC content of surface and soil pore water samples from a boreal mire complex and (2) to compare the spectroscopic method with other DOC measurement techniques, e.g., the wet heated persulfate oxidation method and a laboratory, expulsion-based spectrophotometric method and (3) to assess different multivariate models that relate absorbance measurements with DOC contents. The study indicates that high-resolution spectroscopic measurements provide a simple, robust and non-destructive method for measuring DOC content. These measurements are of short duration (<1 min) and the sample analysis is portable, rendering this method particularly advantageous for in situ investigations at remote field locations. The study also demonstrates that if absorbances at specific wavelengths are used as proxies for DOC concentration, it is recommended to create site-specific calibration models that include more than one wavelength to achieve the optimal accuracy of the proxy-based DOC quantification.

  8. Dissolved Trace Metal Concentrations over the Peru Shelf and in the Subsurface Oxygen Minimum Zone Off Peru

    NASA Astrophysics Data System (ADS)

    Parker, C.; Bruland, K. W.

    2014-12-01

    The Peru coast is the site of one of the largest fisheries in the world, and home to some of the highest f-ratios ever recorded. As a result of this highly productive surface water, an intense subsurface oxygen minimum zone (OMZ) persists. Despite the import of the effect of OMZs due to their predicted increase with global warming, there is very little trace metal data from this region. Here we present dissolved trace metal data from the U.S. GEOTRACES Eastern Pacific Zonal Transect over the Peru shelf and through the OMZ. Results suggest a sink of Pb, Cd, Sc, Cu and Ga in the suboxic region of the shelf, and a shelf source of Co and Fe. Trace metal concentrations within the OMZ will also be discussed. As many of these metals have not been analyzed in this region previously, this work can serve as a baseline for future comparison and adds to the understanding of global trace metal distributions.

  9. Temporal control on concentration, character, and export of dissolved organic carbon in two hemiboreal headwater streams draining contrasting catchments

    NASA Astrophysics Data System (ADS)

    Wallin, Marcus B.; Weyhenmeyer, Gesa A.; Bastviken, David; Chmiel, Hannah E.; Peter, Simone; Sobek, Sebastian; Klemedtsson, Leif

    2015-05-01

    Although lateral carbon (C) export from terrestrial to aquatic systems is known to be an important component in landscape C balances, most existing global studies are lacking empirical data on the soil C export. In this study, the concentration, character, and export of dissolved organic carbon (DOC) were studied during 2 years in two hemiboreal headwater streams draining catchments with different soil characteristics (mineral versus peat soils). The streams exposed surprisingly similar strong air temperature controls on the temporal variability in DOC concentration in spite of draining such different catchments. The temporal variability in DOC character (determined by absorbance metrics, specific ultraviolet absorbance 254 (SUVA254) as a proxy for aromaticity and a254/a365 ratio as a proxy for mean molecular weight) was more complex but related to stream discharge. While the two streams showed similar ranges and patterns in SUVA254, we found a significant difference in median a254/a354, suggesting differences in the DOC character. Both streams responded similarly to hydrological changes with higher a254/a365 at higher discharge, although with rather small differences in a254/a365 between base flow and high flow (<0.3). The DOC exports (9.6-25.2 g C m-2 yr-1) were among the highest reported so far for Scandinavia and displayed large interannual and intraannual variability mainly driven by irregular precipitation/discharge patterns. Our results show that air temperature and discharge affect the temporal variability in DOC quantity and character in different ways. This will have implications for the design of representative sampling programs, which in turn will affect the reliability of future estimates of landscape C budgets.

  10. Influence of the Amazon River on dissolved and intra-cellular metal concentrations in Trichodesmium colonies along the western boundary of the sub-tropical North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Tovar-Sanchez, A.; Sañudo-Wilhelmy, S. A.

    2011-01-01

    Despite the ecological importance of Trichodesmium spp. for the global oceanic nitrogen budget, there is limited information on their trace metal composition in field samples. We report dissolved (<0.22 ?m) metal concentrations measured in surface waters (Ag, Cd, Co, Cu, Fe, Mo, Ni, P, Pb and V) and in the total and the intracellular pool (Ag, Al, Cd, Co, Cu, Fe, Mn, Mo, Ni, P, Pb, V) of Trichodesmium populations collected in the western subtropical North Atlantic Ocean (April-May 2003) within the influence of the Amazon River plume. Dissolved element distributions were strongly influenced by the River discharge, with concentrations of some elements varying directly (i.e. Cd, Mo and V) or inversely (Ag, Co, Cu, Fe, Ni, P and Pb) with surface salinity. Intracellular metal values to phosphorous ratios (mol:mol) for Cd, Co, Cu, Fe, Mn, Mo, Ni and V ranged from 9.0 × 10-6 for Cd to 4.4 × 10-2 for Fe. Although total metal composition was significantly correlated with the intracellular content in the Trichodesmium colonies for some elements (e.g., Co, Cu, V), metal pools in the phytoplankton did not co-vary with the dissolved metal concentrations, suggesting that water column measurements may not be good predictors of the intracellular metal concentrations. The impact of physical parameters and bioactive elements on biological processes such as nitrogen fixation, carbon drawdown and biomass production in Trichodesmium colonies was explored by using a principal component analysis test (PCA). The analysis indicated that the biological drawdown of dissolved inorganic carbon (DIC) by Trichodesmium seems to be influenced by the internal content of Fe, Co, Cd, and Cu, while nitrogen fixation seems more influenced by mixed layer depth and dissolved Fe and Ni concentrations.

  11. Effects of Land Use on Stable Carbon Isotopic Composition and Concentration of Dissolved Organic Carbon (DOC) and Dissolved Inorganic Carbon (DIC) in Southeastern US Piedmont Headwater Streams

    EPA Science Inventory

    Stable carbon isotopic composition (delta 13C) and concentrations of DOC and DIC were measured in stream water samples collected monthly in 15 headwater streams from an area with extensive poultry and cattle production and a rapidly growing human population. Linear regression te...

  12. Land Use Controls on Stream and Lake Dissolved Silica Concentrations: A Case Study from the Finger Lakes, Central New York State, USA.

    NASA Astrophysics Data System (ADS)

    Halfman, J. D.

    2014-12-01

    Bedrock geology, climate and time are important controls on chemical weathering and release of dissolved silica. Forested land vs. other land uses was recently hypothesized as another control. The Finger Lakes region is an ideal natural laboratory to test this hypothesis as local watersheds vary in area, bedrock and agricultural to forested land cover in this rural setting. Annual mean dissolved silica data from 11 watersheds in our ongoing monitoring program ranged from 100 to 4,000 ?g/L Si, analyzing filtered (0.45 ?m) samples by spectrophotometer (molybdate indicator with metol/oxalic acid reagents). Like earlier work, only forested land use (12 to 73%) correlated to the mean silica concentrations (r2 = 0.3), which improves (r2 = 0.6) when a small, primarily (24%) developed watershed is excluded from the correlation. Bedrock (Devonian carbonates, 0 to 8% and clastics, 0 to 99% covered by till) and basin area (10 to 500 km2) did not correlate (r2 <= 0.1). Event and base flow samples of an agricultural (64%) watershed revealed peak to base flow fluctuations in silica concentrations that more closely mimic nitrates and other groundwater solutes than suspended particles, phosphates and other runoff signature parameters. Annual mean epilimnion and hypolimnion dissolved silica data from the 8 easternmost Finger Lakes in our ongoing monitoring program ranged from 250 to 1,500 ?g/L Si. Forested cover (30 to 75%) positively correlated to epilimnion silica concentrations (r2 = 0.6). Lake water residence time (1 to 17 yr) negatively correlated to hypolimnion silica concentrations (r2 = 0.5). Agricultural land use, bedrock, and productivity indicators (chlorophyll-a, total phosphate, and secchi disk depth) lacked correlation (r2 <= 0.1). It suggested that land use impacts stream and, surprisingly, lake dissolved silica chemistry. Biogeochemical processes in the lakes like diatom uptake appears to increasingly decrease silica concentrations in lakes with longer residence times.

  13. 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.

  14. Electrospray ionization fourier transform ion cyclotron resonance mass spectrometry of dissolved organic phosphorus species in a treatment wetland after selective isolation and concentration.

    PubMed

    Llewelyn, Jennifer M; Landing, William M; Marshall, Alan G; Cooper, William T

    2002-02-01

    A method for the selective concentration of dissolved organic phosphorus (DOP) from complex surface water samples for the first time allows mass spectral characterization of individual DOP compounds in phosphorus-limited ecosystems. The entire dissolved organic matter (DOM) pool is first separated according to molecular weight by tangential cross-flow ultrafiltration (CFF). DOP is selectively isolated and concentrated from CFF fractions by a barium precipitation procedure. The DOP precipitate is then reconstituted in distilled water and excess barium, and other cations are removed with an ion-exchange resin. The DOP isolation/concentration step can provide up to 15-fold concentration and 300-fold concentration of high molecular weight DOP when combined with the inherent concentration provided by CFF. The procedure also removes cations and most of the background DOM, leaving DOP in a matrix suitable for electrospray ionization and mass spectral characterization. Model organic phosphate standards representative of DOP species expected in aquatic environments were used to evaluate the technique. It was then applied to a series of high molecular weight (>1000) CFF retentates isolated from sites within the Everglades Nutrient Removal (ENR) treatment wetland. The elemental compositions of several individual DOP compounds observed at different sites within the ENR were determined by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. PMID:11838681

  15. An extensive study of the concentrations of particulate/dissolved radiocaesium derived from the Fukushima Dai-ichi Nuclear Power Plant accident in various river systems and their relationship with catchment inventory.

    PubMed

    Yoshimura, Kazuya; Onda, Yuichi; Sakaguchi, Aya; Yamamoto, Masayoshi; Matsuura, Yuki

    2015-01-01

    An extensive investigation of particulate radiocaesium in suspended solids and dissolved radiocaesium in river water was undertaken at 30 sites in Fukushima and Miyagi Prefectures in December 2012, and their relationships with catchment inventory and the solid/liquid distribution coefficient (Kd) were evaluated. Rivers located in the coastal region on the north side of the Fukushima Dai-ichi Nuclear Power Plant exhibited relatively higher particulate radiocaesium concentrations. Significant correlations were found between concentrations of particulate/dissolved radiocaesium and average catchment inventories, indicating that the concentrations of particulate/dissolved radiocaesium could be approximated from the catchment inventory. Particulate radiocaesium concentration was significantly correlated with dissolved radiocaesium concentration (with the exception of concentrations measured in estuaries), and the geometric mean Kd was calculated as 3.6 × 10(5) with a 95% confidence interval of 2.6-5.1 × 10(5). PMID:25242014

  16. Development of a continuous process for adjusting nitrate, zirconium, and free hydrofluoric acid concentrations in zirconium fuel dissolver product

    SciTech Connect

    Cresap, D.A.; Halverson, D.S.

    1993-04-01

    In the Fluorinel Dissolution Process (FDP) upgrade, excess hydrofluoric acid in the dissolver product must be complexed with aluminum nitrate (ANN) to eliminate corrosion concerns, adjusted with nitrate to facilitate extraction, and diluted with water to ensure solution stability. This is currently accomplished via batch processing in large vessels. However, to accommodate increases in projected throughput and reduce water production in a cost-effective manner, a semi-continuous system (In-line Complexing (ILC)) has been developed. The major conclusions drawn from tests demonstrating the feasibility of this concept are given in this report.

  17. Effect of Fenton oxidation on biodegradability, biotoxicity and dissolved organic matter distribution of concentrated landfill leachate derived from a membrane process.

    PubMed

    He, Ruo; Tian, Bao-Hu; Zhang, Qi-Qi; Zhang, Hong-Tao

    2015-04-01

    The treatment of concentrated landfill leachate from membrane process is a troublesome issue due to high concentrations of biorecalcitrant pollutants. In this study, the effect of Fenton process on dissolved organic matter (DOM) distribution (i.e. humic acid (HA), fulvic acid (FA) and hydrophilic fraction (HyI)), chemical forms of toxic organic compounds and metals, and their biotoxicity were investigated. In the concentrated leachate, toluene, ethylbenzene and chlorobenzene predominated in the HyI fraction, while phthalate esters (PAEs) were mainly absorbed on the HA and FA fractions. PAEs were more readily removed from the HA and FA fractions than that from the HyI fraction in the Fenton process. The complexing abilities of DOM varied with types of metal in the concentrated leachate. The biotoxicities of the DOM fractions to luminescent bacteria (Photobacterium phosphoreum T3 mutation) were HA > FA > - HyI. The biotoxicities of the hydrophobic organic contaminants to luminescent bacteria were not obvious in the concentrated leachate due to their low concentrations. Metals might be the main contributor to the biotoxicity to luminous bacteria in the concentrated leachate. These results indicated that Fenton process could influence the pollutants distribution in DOM and their biotoxicities through the breakdown of HA and FA in the concentrated leachate. PMID:25660905

  18. A Synthesis of Light Absorption Properties of the Arctic Ocean: Application to Semi-analytical Estimates of Dissolved Organic Carbon Concentrations from Space

    NASA Technical Reports Server (NTRS)

    Matsuoka, A.; Babin, M.; Doxaran, D.; Hooker, S. B.; Mitchell, B. G.; Belanger, S.; Bricaud, A.

    2014-01-01

    The light absorption coefficients of particulate and dissolved materials are the main factors determining the light propagation of the visible part of the spectrum and are, thus, important for developing ocean color algorithms. While these absorption properties have recently been documented by a few studies for the Arctic Ocean [e.g., Matsuoka et al., 2007, 2011; Ben Mustapha et al., 2012], the datasets used in the literature were sparse and individually insufficient to draw a general view of the basin-wide spatial and temporal variations in absorption. To achieve such a task, we built a large absorption database at the pan-Arctic scale by pooling the majority of published datasets and merging new datasets. Our results showed that the total non-water absorption coefficients measured in the Eastern Arctic Ocean (EAO; Siberian side) are significantly higher 74 than in the Western Arctic Ocean (WAO; North American side). This higher absorption is explained 75 by higher concentration of colored dissolved organic matter (CDOM) in watersheds on the Siberian 76 side, which contains a large amount of dissolved organic carbon (DOC) compared to waters off 77 North America. In contrast, the relationship between the phytoplankton absorption (a()) and chlorophyll a (chl a) concentration in the EAO was not significantly different from that in the WAO. Because our semi-analytical CDOM absorption algorithm is based on chl a-specific a() values [Matsuoka et al., 2013], this result indirectly suggests that CDOM absorption can be appropriately erived not only for the WAO but also for the EAO using ocean color data. Derived CDOM absorption values were reasonable compared to in situ measurements. By combining this algorithm with empirical DOC versus CDOM relationships, a semi-analytical algorithm for estimating DOC concentrations for coastal waters at the Pan-Arctic scale is presented and applied to satellite ocean color data.

  19. 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.

  20. 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.

  1. Concentration and flux of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids for monitored tributaries of Lake Champlain, 1990-2012

    USGS Publications Warehouse

    Medalie, Laura

    2014-01-01

    Annual and daily concentrations and fluxes of total and dissolved phosphorus, total nitrogen, chloride, and total suspended solids were estimated for 18 monitored tributaries to Lake Champlain by using the Weighted Regressions on Time, Discharge, and Seasons regression model. Estimates were made for 21 or 23 years, depending on data availability, for the purpose of providing timely and accessible summary reports as stipulated in the 2010 update to the Lake Champlain “Opportunities for Action” management plan. Estimates of concentration and flux were provided for each tributary based on (1) observed daily discharges and (2) a flow-normalizing procedure, which removed the random fluctuations of climate-related variability. The flux bias statistic, an indicator of the ability of the Weighted Regressions on Time, Discharge, and Season regression models to provide accurate representations of flux, showed acceptable bias (less than ±10 percent) for 68 out of 72 models for total and dissolved phosphorus, total nitrogen, and chloride. Six out of 18 models for total suspended solids had moderate bias (between 10 and 30 percent), an expected result given the frequently nonlinear relation between total suspended solids and discharge. One model for total suspended solids with a very high bias was influenced by a single extreme value; however, removal of that value, although reducing the bias substantially, had little effect on annual fluxes.

  2. Freely oriented portable superconducting magnet

    SciTech Connect

    Schmierer, Eric N.; Prenger, F. Coyne; Hill, Dallas D.

    2010-01-12

    A freely oriented portable superconducting magnet is disclosed. Coolant is supplied to the superconducting magnet from a repository separate from the magnet, enabling portability of the magnet. A plurality of support assemblies structurally anchor and thermally isolate the magnet within a thermal shield. A plurality of support assemblies structurally anchor and thermally isolate the thermal shield within a vacuum vessel. The support assemblies restrain movement of the magnet resulting from energizing and cooldown, as well as from changes in orientation, enabling the magnet to be freely orientable.

  3. Cloud water composition during HCCT-2010: Scavenging efficiencies, solute concentrations, and droplet size dependence of inorganic ions and dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    van Pinxteren, D.; Fomba, K. W.; Mertes, S.; Müller, K.; Spindler, G.; Schneider, J.; Lee, T.; Collett, J.; Herrmann, H.

    2015-09-01

    Cloud water samples were taken in September/October 2010 at Mt. Schmücke in a rural, forested area in Germany during the Lagrange-type Hill Cap Cloud Thuringia 2010 (HCCT-2010) cloud experiment. Besides bulk collectors, a 3-stage and a 5-stage collector were applied and samples were analysed for inorganic ions (SO42-, NO3-, NH4+, Cl-, Na+, Mg2+, Ca2+, K+), H2O2 (aq), S(IV), and dissolved organic carbon (DOC). Campaign volume-weighted mean concentrations were 191, 142, and 39 ?mol L-1 for ammonium, nitrate, and sulfate, respectively, between 4 and 27 ?mol L-1 for minor ions, 5.4 ?mol L-1 for H2O2 (aq), 1.9 ?mol L-1 for S(IV), and 3.9 mgC L-1 for DOC. The concentrations compare well to more recent European cloud water data from similar sites. On a mass basis, organic material (as DOC · 1.8) contributed 20-40 % (event means) to total solute concentrations and was found to have non-negligible impact on cloud water acidity. Relative standard deviations of major ions were 60-66 % for solute concentrations and 52-80 % for cloud water loadings (CWLs). Contrary to some earlier suggestions, the similar variability of solute concentrations and CWLs together with the results of back trajectory analysis and principal component analysis, suggests that concentrations in incoming air masses (i.e. air mass history), rather than cloud liquid water content (LWC) was the main factor controlling bulk solute concentrations at Mt. Schmücke. Droplet effective radius was found to be a somewhat better predictor for cloud water total ionic content (TIC) than LWC, even though no single explanatory variable can fully describe TIC (or solute concentration) variations in a simple functional relation due to the complex processes involved. Bulk concentrations typically agreed within a factor of 2 with co-located measurements of residual particle concentrations sampled by a counterflow virtual impactor (CV) and analysed by an aerosol mass spectrometer (AMS), with the deviations being mainly caused by systematic differences and limitations of the approaches (such as outgassing of dissolved gases during residual particle sampling). Scavenging efficiencies (SEs) of aerosol constituents were 0.56-0.94, 0.79-0.99, 0.71-98, and 0.67-0.92 for SO42-, NO3-, NH4+, and DOC, respectively, when calculated as event means with in-cloud data only. SEs estimated using data from an upwind site were substantially different in many cases, revealing the impact of gas-phase uptake (for volatile constituents) and mass losses across Mt. Schmücke likely due to physical processes such as droplet scavenging by trees and/or entrainment. Drop size-resolved cloud water concentrations of major ions SO42-, NO3-, and NH4+ revealed two main profiles: decreasing concentrations with increasing droplet size and "U"-shapes. In contrast, profiles of typical coarse particle mode minor ions were often increasing with increasing drop size, highlighting the importance of a species' particle concentration size distribution for the development of size-resolved solute concentration patterns. Concentration differences between droplet size classes were typically < 2 for major ions from the 3-stage collector and somewhat more pronounced from the 5-stage collector, while they were much larger for minor ions. Due to a better separation of droplet populations, the 5-stage collector was capable of resolving some features of solute size dependencies not seen in the 3-stage data, especially sharp concentration increases (up to a factor of 5-10) in the smallest droplets for many solutes.

  4. Kinks in experimental diffusion profiles of a dissolving semi-crystalline polymer explained by a concentration-dependent diffusion coefficient.

    PubMed

    Hermes, Helen E; Sitta, Christoph E; Schillinger, Burkhard; Löwen, Hartmut; Egelhaaf, Stefan U

    2015-06-28

    The dissolution of polyethylene oxide (PEO) tablets in water has been followed in situ by neutron radiography. When in contact with water, the crystalline phase of semi-crystalline PEO melts once a certain water content is attained. Polymer concentration profiles obtained from the neutron transmission images exhibited a pronounced kink which corresponds to a sharp front in the images and which is related to the melting transition. Sharp diffusion fronts and phase transitions are often linked to non-Fickian behaviour. However, by considering the time evolution of the complete concentration profiles in detail it is shown that the dissolution process can be explained using Fickian diffusion equations with a concentration-dependent diffusion coefficient. PMID:26018995

  5. Effects of anomalous high temperatures on carbon dioxide, methane, dissolved organic carbon and trace element concentrations in thaw lakes in Western Siberia in 2012

    NASA Astrophysics Data System (ADS)

    Pokrovsky, O. S.; Shirokova, L. S.; Kirpotin, S. N.; Kulizhsky, S. P.; Vorobiev, S. N.

    2013-04-01

    During the anomalous hot summer in 2012, surface air temperatures in Western Siberia were 5 to 10 °C higher than those observed during the previous period of > 30 yr. This unusual climate phenomenon provided an opportunity to examine the effects of short-term natural heating of water in thermokarst ponds and lakes in discontinuous permafrost zones and compare these observations to previous field results obtained when the temperature was normal during the summer of 2010 in the same region. Thermokarst bodies of water shrank significantly, water levels dropped approximately 50 cm in large lakes and small (< 10-100 m2) ponds, and shallow soil depressions disappeared. Based on samples from ~ 40 bodies of water collected previously and in 2012, first-order features of changes in chemical composition in response to increased water temperatures (from 14.1 ± 2.2 to 23.8 ± 2.3 °C in 2010 and 2012, respectively) were established. In these thermokarst bodies of water that covered a full range of surface areas, the average conductivity and pH were almost unchanged, whereas dissolved organic carbon (DOC), Cl- and SO42- concentrations were higher by a factor of ~ 2 during summer 2012 compared to periods with normal temperatures. Similarly, most divalent metals and insoluble trivalent and tetravalent elements were more concentrated by a factor of 1.7-2.4 in the summer of 2012 than normal periods. The average concentrations of dissolved CO2 and CH4 during the hot summer of 2012 increased by factors of 1.4 and 4.9, respectively. For most of the trace elements bound to colloids, the degree of colloidal binding decreased by a factor of 1.44 ± 0.33 (for an average of 40 elements) during the hot summer of 2012 compared to normal periods. Increases in CO2 and CH4 concentrations with the decreasing size of the body of water were well-pronounced during the hot summer of 2012. The concentrations of CO2 and CH4 significantly increased by factors of 5 and 150, respectively, in small (? 102 m2) compared to large (? 104 m2) thermokarst (thaw) lakes. Taken together, these trends suggest that, for a conservative scenario of lake size distribution, lake water warming at high latitudes will produce (1) a significant increase in methane emission capacity from thaw lake surfaces; (2) decrease of molecular sizes of TE complexes and increase of potential bioavailability of metal micronutrients in water columns; and (3) relatively conservative responses by CO2, DOC and trace element concentrations.

  6. Dissolved pesticide concentrations in the Sacramento-San Joaquin Delta and Grizzly Bay, California, 2011-12

    USGS Publications Warehouse

    Orlando, James L.; McWayne, Megan; Sanders, Corey; Hladik, Michelle

    2013-01-01

    Surface-water samples were collected from sites within the Sacramento-San Joaquin Delta and Grizzly Bay, California, during the spring in 2011 and 2012, and they were analyzed by the U.S. Geological Survey for a suite of 99 current-use pesticides and pesticide degradates. Samples were collected and analyzed as part of a collaborative project studying the occurrence and characteristics of phytoplankton in the San Francisco Estuary. Samples were analyzed by two separate laboratory methods employing gas chromatography/mass spectrometry or liquid chromatography with tandem mass spectrometry. Method detection limits ranged from 0.9 to 10.5 nanograms per liter (ng/L). Eighteen pesticides were detected in samples collected during 2011, and the most frequently detected compounds were the herbicides clomazone, diuron, hexazinone and metolachlor, and the diuron degradates 3,4-dichloroaniline and N-(3,4-dichlorophenyl)-N’-methylurea (DCPMU). Concentrations for all compounds were less than 75 ng/L, except for the rice herbicide clomazone and the fungicide tetraconazole, which had maximum concentrations of 535 and 511 ng/L, respectively. In samples collected in 2012, a total of 16 pesticides were detected. The most frequently detected compounds were the fungicides azoxystrobin and boscalid and the herbicides diuron, hexazinone, metolachlor, and simazine. Maximum concentrations for all compounds detected in 2012 were less than 75 ng/L, except for the fungicide azoxystrobin and the herbicides hexazinone and simazine, which were detected at up to 188, 134, and 140 ng/L, respectively.

  7. Photosynthetic fractionation of 13C and concentrations of dissolved CO2 in the central equatorial Pacific during the last 255,000 years

    NASA Technical Reports Server (NTRS)

    Jasper, J. P.; Hayes, J. M.; Mix, A. C.; Prahl, F. G.

    1994-01-01

    Carbon isotopically based estimates of CO2 levels have been generated from a record of the photosynthetic fractionation of 13C [is equivalent to epsilon(p)] in a central equatorial Pacific sediment core that spans the last approximately 255 ka. Contents of 13C in phytoplanktonic biomass were determined by analysis of C37 alkadienones. These compounds are exclusive products of Prymnesiophyte algae which at present grow most abundantly at depths of 70-90 m in the central equatorial Pacific. A record of the isotopic composition of dissolved CO2 was constructed from isotopic analyses of the planktonic foraminifera Neogloboquadrina dutertrei, which calcifies at 70-90 m in the same region. Values of epsilon(p), derived by comparison of the organic and inorganic delta values, were transformed to yield concentrations of dissolved CO2 [is equivalent to c(e)] based on a new, site-specific calibration of the relationship between epsilon(p) and c(e). The calibration was based on reassessment of existing epsilon(p) versus c(e) data, which support a physiologically based model in which epsilon(p) is inversely related to c(e). Values of PCO2, the partial pressure of CO2 that would be in equilibrium with the estimated concentrations of dissolved CO2, were calculated using Henry's law and the temperature determined from the alkenone-unsaturation index U(K/37). Uncertainties in these values arise mainly from uncertainties about the appropriateness (particularly over time) of the site-specific relationship between epsilon(p) and 1/c(e). These are discussed in detail and it is concluded that the observed record of epsilon(p) most probably reflects significant variations in delta pCO2, the ocean-atmosphere disequilibrium, which appears to have ranged from approximately 110 microatmospheres during glacial intervals (ocean > atmosphere) to approximately 60 microatmospheres during interglacials. Fluxes of CO2 to the atmosphere would thus have been significantly larger during glacial intervals. If this were characteristic of large areas of the equatorial Pacific, then greater glacial sinks for the equatorially evaded CO2 must have existed elsewhere. Statistical analysis of air-sea pCO2 differences and other parameters revealed significant (p<0.01) inverse correlations of delta pCO2 with sea surface temperature and with the mass accumulation rate of opal. The former suggests response to the strength of upwelling, the latter may indicate either drawdown of CO2 by siliceous phytoplankton or variation of [CO2]/[Si(OH)4] ratios in upwelling waters.

  8. Correlation between DNAPL distribution area and dissolved concentration in surfactant enhanced aquifer remediation effluent: A two-dimensional flow cell study.

    PubMed

    Wu, Bin; Li, Huiying; Du, Xiaoming; Zhong, Lirong; Yang, Bin; Du, Ping; Gu, Qingbao; Li, Fasheng

    2016-02-01

    During the process of surfactant enhanced aquifer remediation (SEAR), free phase dense non-aqueous phase liquid (DNAPL) may be mobilized and spread. The understanding of the impact of DNAPL spreading on the SEAR remediation is not sufficient with its positive effect infrequently mentioned. To evaluate the correlation between DNAPL spreading and remediation efficiency, a two-dimensional sandbox apparatus was used to simulate the migration and dissolution process of 1,2-DCA (1,2-dichloroethane) DNAPL in SEAR. Distribution area of DNAPL in the sandbox was determined by digital image analysis and correlated with effluent DNAPL concentration. The results showed that the effluent DNAPL concentration has significant positive linear correlation with the DNAPL distribution area, indicating the mobilization of DNAPL could improve remediation efficiency by enlarging total NAPL-water interfacial area for mass transfer. Meanwhile, the vertical migration of 1,2-DCA was limited within the boundary of aquifer in all experiments, implying that by manipulating injection parameters in SEAR, optimal remediation efficiency can be reached while the risk of DNAPL vertical migration is minimized. This study provides a convenient visible and quantitative method for the optimization of parameters for SEAR project, and an approach of rapid predicting the extent of DNAPL contaminant distribution based on the dissolved DNAPL concentration in the extraction well. PMID:26583297

  9. Computed solid phases limiting the concentration of dissolved constituents in basalt aquifers of the Columbia Plateau in eastern Washington. Geochemical modeling and nuclide/rock/groundwater interaction studies

    SciTech Connect

    Deutsch, W.J.; Jenne, E.A.; Krupka, K.M.

    1982-08-01

    A speciation-solubility geochemical model, WATEQ2, was used to analyze geographically-diverse, ground-water samples from the aquifers of the Columbia Plateau basalts in eastern Washington. The ground-water samples compute to be at equilibrium with calcite, which provides both a solubility control for dissolved calcium and a pH buffer. Amorphic ferric hydroxide, Fe(OH)/sub 3/(A), is at saturation or modestly oversaturated in the few water samples with measured redox potentials. Most of the ground-water samples compute to be at equilibrium with amorphic silica (glass) and wairakite, a zeolite, and are saturated to oversaturated with respect to allophane, an amorphic aluminosilicate. The water samples are saturated to undersaturated with halloysite, a clay, and are variably oversaturated with regard to other secondary clay minerals. Equilibrium between the ground water and amorphic silica presumably results from the dissolution of the glassy matrix of the basalt. The oversaturation of the clay minerals other than halloysite indicates that their rate of formation lags the dissolution rate of the basaltic glass. The modeling results indicate that metastable amorphic solids limit the concentration of dissolved silicon and suggest the same possibility for aluminum and iron, and that the processes of dissolution of basaltic glass and formation of metastable secondary minerals are continuing even though the basalts are of Miocene age. The computed solubility relations are found to agree with the known assemblages of alteration minerals in the basalt fractures and vesicles. Because the chemical reactivity of the bedrock will influence the transport of solutes in ground water, the observed solubility equilibria are important factors with regard to chemical-retention processes associated with the possible migration of nuclear waste stored in the earth's crust.

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

    PubMed

    Núñez, Eutimio Gustavo Fernández; Leme, Jaci; de Almeida Parizotto, Letícia; Chagas, Wagner Antonio; de Rezende, Alexandre Gonçalves; 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 4 × 10(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

  11. 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

  12. Dissolved and labile concentrations of Cd, Cu, Pb, and Zn in the South Fork Coeur d'Alene River, Idaho: Comparisons among chemical equilibrium models and implications for biotic ligand models

    USGS Publications Warehouse

    Balistrieri, L.S.; Blank, R.G.

    2008-01-01

    In order to evaluate thermodynamic speciation calculations inherent in biotic ligand models, the speciation of dissolved Cd, Cu, Pb, and Zn in aquatic systems influenced by historical mining activities is examined using equilibrium computer models and the diffusive gradients in thin films (DGT) technique. Several metal/organic-matter complexation models, including WHAM VI, NICA-Donnan, and Stockholm Humic model (SHM), are used in combination with inorganic speciation models to calculate the thermodynamic speciation of dissolved metals and concentrations of metal associated with biotic ligands (e.g., fish gills). Maximum dynamic metal concentrations, determined from total dissolved metal concentrations and thermodynamic speciation calculations, are compared with labile metal concentrations measured by DGT to assess which metal/organic-matter complexation model best describes metal speciation and, thereby, biotic ligand speciation, in the studied systems. Results indicate that the choice of model that defines metal/organic-matter interactions does not affect calculated concentrations of Cd and Zn associated with biotic ligands for geochemical conditions in the study area, whereas concentrations of Cu and Pb associated with biotic ligands depend on whether the speciation calculations use WHAM VI, NICA-Donnan, or SHM. Agreement between labile metal concentrations and dynamic metal concentrations occurs when WHAM VI is used to calculate Cu speciation and SHM is used to calculate Pb speciation. Additional work in systems that contain wide ranges in concentrations of multiple metals should incorporate analytical speciation methods, such as DGT, to constrain the speciation component of biotic ligand models. ?? 2008 Elsevier Ltd.

  13. Characterizing dissolved organic carbon concentrations and export in a boreal forest-peatland landscape under the influence of rapidly degrading discontinuous permafrost

    NASA Astrophysics Data System (ADS)

    Hanisch, J.; Connon, R.; Templeton, M.; Quinton, W. L.; Olefeldt, D.; Moore, T. R.; Roulet, N. T.; Sonnentag, O.

    2014-12-01

    Our current understanding of peatland energy, water and carbon (C) cycles implies that northern peatlands are vulnerable to projected climate change, and that the perturbation of these cycles might cause a strong positive or negative net feedback to the climate system. About one third of Canada's northern peatlands contain contain perennialy frozen ground (permafrost). Boreal forest-peatland ecosystems in the discontinuous permafrost zone (50-90% of frozen ground) are especially vulnerable to rising temperatures as permafrost is ice-rich, relatively warm and thin, and thus susceptible to complete disappearance causing ground surface subsidence and a decline in forest cover in response to water-logging. Several recent studies have substantially improved our understanding of northern peatland's role in the climate system by quantifying their net ecosystem C balance which includes atmospheric and aqueous C fluxes generally dominated by the export of dissolved organic C (DOC). We characterize seasonal and diurnal variations in DOC export from five catchments (0.02-0.05 km2) at Scotty Creek, a 152 km2-watershed under the influence of rapidly degrading and disappearing discontinuous permafrost near Fort Simpson, Northwest Territories, Canada. The five catchments are characterized by different fractions of forested peat plateaus with permafrost (38-73%) and permafrost-free collapse bogs (27-62%). Dissolved organic carbon concentrations at Scotty Creek appear to be higher in catchments where the percentage of peat plateaus is higher compared to bogs, independent of catchment size. Average DOC concentration for catchments with a lower percentage of peat plateaus is lower (~43 mg/l) than for those with a higher percentage of plateaus (~60 mg/l). These preliminary results suggest that lateral C losses from this rapidly changing landscape are at least partly controlled by the peat plateau-bog ratio. Over the year, DOC export from the five catchments is limited to around a week due to the relatively dry conditions at Scotty Creek over the hot summer months: only one of the catchments produces continuous measurable surface runoff. However, as indicated through water level recordings, additional unaccounted DOC export may occur through diffuse subsurface flow.

  14. Evaluation of high-frequency mean streamwater transit-time estimates using groundwater age and dissolved silica concentrations in a small forested watershed

    USGS Publications Warehouse

    Peters, Norman E.; Burns, Douglas A.; Aulenbach, Brent T.

    2014-01-01

    Many previous investigations of mean streamwater transit times (MTT) have been limited by an inability to quantify the MTT dynamics. Here, we draw on (1) a linear relation (r 2 = 0.97) between groundwater 3H/3He ages and dissolved silica (Si) concentrations, combined with (2) predicted streamwater Si concentrations from a multiple-regression relation (R 2 = 0.87) to estimate MTT at 5-min intervals for a 23-year time series of streamflow [water year (WY) 1986 through 2008] at the Panola Mountain Research Watershed, Georgia. The time-based average MTT derived from the 5-min data was ~8.4 ± 2.9 years and the volume-weighted (VW) MTT was ~4.7 years for the study period, reflecting the importance of younger runoff water during high flow. The 5-min MTTs are normally distributed and ranged from 0 to 15 years. Monthly VW MTTs averaged 7.0 ± 3.3 years and ranged from 4 to 6 years during winter and 8–10 years during summer. The annual VW MTTs averaged 5.6 ± 2.0 years and ranged from ~5 years during wet years (2003 and 2005) to >10 years during dry years (2002 and 2008). Stormflows are composed of much younger water than baseflows, and although stormflow only occurs ~17 % of the time, this runoff fraction contributed 39 % of the runoff during the 23-year study period. Combining the 23-year VW MTT (including stormflow) with the annual average baseflow for the period (~212 mm) indicates that active groundwater storage is ~1,000 mm. However, the groundwater storage ranged from 1,040 to 1,950 mm using WY baseflow and WY VW MTT. The approach described herein may be applicable to other watersheds underlain by granitoid bedrock, where weathering is the dominant control on Si concentrations in soils, groundwater, and streamwater.

  15. Correlation Between Surface Area and Dissolving Properties of Lead - A Step in the Investigation of Higher than Standard Lead Concentration in Drinking Water in Washington, D.C.

    NASA Astrophysics Data System (ADS)

    Hua, M.; Garduno, L.; Mondragon, J. D.; Cuff, K. E.

    2004-12-01

    Several recently published articles by the Washington Post exposing the alarming concentration of lead in drinking water from schools and homes in the Washington D.C. area sparked our interest in the correlation between lead-containing materials used in plumbing and rate of lead solubility. Elementary children who attend schools in various regions of the District were contacted by San Francisco Bay Area- based high school students who are participants in the NSF-sponsored Environmental Science Information Technology Activities (ESITA) project. After receiving a thorough explanation of required sampling procedures, the elementary school children sent 500 ml water samples from their homes and schools to Berkeley along with information on the locations from which the water samples were collected. These water samples were analyzed for lead content at the Environmental Science Research Program laboratory at Lawrence Hall of Science. The majority of the samples contained more than 15 ppb of lead, which is the EPA action level. We hypothesize that there are three possible sources of lead in the drinking water: 1) lead pipes in the water main; 2) lead pipes in the service main; and 3) lead soldering that was often previously used to connect piping. We chose to investigate the effect of lead-based solder on the overall lead concentration in water. Using a soldering iron, we melted lead solder to create discs ranging from one to five centimeter diameter and one to thirty-six grams of mass. These discs were then placed into a beaker with 500 ml of 7.1pH distilled water and allowed to stand for 48 hours. At the end of 48 hours, the water samples were prepared for analysis using the EPA approved lead-dithizone procedure. Results showed an exponential relationship between disc surface area and the concentration of dissolved lead measured in the sample. Therefore, lead-based solder can represent a possible major source of lead contamination.

  16. The effect of feed water dissolved organic carbon concentration and composition on organic micropollutant removal and microbial diversity in soil columns simulating river bank filtration.

    PubMed

    Bertelkamp, C; van der Hoek, J P; Schoutteten, K; Hulpiau, L; Vanhaecke, L; Vanden Bussche, J; Cabo, A J; Callewaert, C; Boon, N; Löwenberg, J; Singhal, N; Verliefde, A R D

    2016-02-01

    This study investigated organic micropollutant (OMP) biodegradation rates in laboratory-scale soil columns simulating river bank filtration (RBF) processes. The dosed OMP mixture consisted of 11 pharmaceuticals, 6 herbicides, 2 insecticides and 1 solvent. Columns were filled with soil from a RBF site and were fed with four different organic carbon fractions (hydrophilic, hydrophobic, transphilic and river water organic matter (RWOM)). Additionally, the effect of a short-term OMP/dissolved organic carbon (DOC) shock-load (e.g. quadrupling the OMP concentrations and doubling the DOC concentration) on OMP biodegradation rates was investigated to assess the resilience of RBF systems. The results obtained in this study imply that - in contrast to what is observed for managed aquifer recharge systems operating on wastewater effluent - OMP biodegradation rates are not affected by the type of organic carbon fraction fed to the soil column, in case of stable operation. No effect of a short-term DOC shock-load on OMP biodegradation rates between the different organic carbon fractions was observed. This means that the RBF site simulated in this study is resilient towards transient higher DOC concentrations in the river water. However, a temporary OMP shock-load affected OMP biodegradation rates observed for the columns fed with the river water organic matter (RWOM) and the hydrophilic fraction of the river water organic matter. These different biodegradation rates did not correlate with any of the parameters investigated in this study (cellular adenosine triphosphate (cATP), DOC removal, specific ultraviolet absorbance (SUVA), richness/evenness of the soil microbial population or OMP category (hydrophobicity/charge). PMID:26432535

  17. A SIMPLE PHOTOMETER FOR PRECISE DETERMINATION OF DISSOLVED OXYGEN CONCENTRATION BY THE WINKLER METHOD WITH RECOMMENDATIONS FOR IMPROVING RESPIRATION RATE MEASUREMENTS IN AQUATIC ORGANISMS

    EPA Science Inventory

    A simple inexpensive photometer designed for Winkler titration end-point detection is described. The precision of replicate dissolved oxygen measurements using this instrument was 0.06-0.22%. This high precision is needed to measure the small changes in dissolved oxygen concentra...

  18. Fast measurement of dissolved inorganic carbon concentration for small-volume interstitial water by acid extraction and nondispersive infrared gas analysis.

    PubMed

    Noguchi, Takuroh; Hatta, Mayumi; Yamanaka, Toshiro; Okamura, Kei

    2013-01-01

    We developed a system for measuring the total dissolved inorganic carbon (DIC) concentrations in interstitial water and hydrothermal fluid, which are hard to obtain in large volumes. The system requires a sample volume of only 500 ?L, and it takes only 150 s per one sample. The detection limit of this system was estimated to be 66.6 ?mol/kg with repeated analysis of CO(2)-free ultrapure water (n = 9). The precision of this nondispersive infrared (NDIR) system was ±3.1% of the relative standard deviations (2?) by repeated CRM batch 104 (n = 10). This result is much larger than the required precision for oceanographic studies, but is comparable to a previous result of interstitial water analysis. An on-site trial showed a significant DIC enrichment in interstitial water of hydrothermally altered sediment, and is considered to occur by the mixing of hydrothermal fluid. This procedure will achieve carbon dioxide flux calculations from hydrothermal activities, and will bring a more accurate feature on the global carbon cycle. PMID:23303077

  19. An Assessment of Habitat Quality Using Dissolved Oxygen Concentrations in Floodplain Water Bodies in Relation to River Flow and Mainstem Connectivity

    NASA Astrophysics Data System (ADS)

    Stofleth, J.; Andrews, E. S.; White, J. Q.

    2011-12-01

    The floodplains of the Apalachicola River, Florida include an intricate network of sloughs, lakes and wetlands. These floodplain water bodies provide essential spawning and nursery areas for a diverse array of aquatic organisms. The frequency and duration of Apalachicola River flows sufficient to hydraulically connect and thereby activate these floodplain features has decreased over time due to upstream dams, diversions, and modification to the channel geometry (incision and widening). The main objective of this study is to characterize the relationship between a key water quality parameter, dissolved oxygen (DO), to the hydraulic connectivity of the ecologically-important large slough systems within the Apalachicola River floodplain over a range of flow conditions. When DO concentrations drop, the quality of habitat for fish, invertebrates and other aquatic organisms are impacted. Hydraulic connection between the river and the floodplain sloughs contributes markedly to DO levels in the sloughs. To characterize the relationship between hydraulic connectivity and water quality, water level, DO, and temperature data were continuously monitored within four (4) major floodplain sloughs, one (1) oxbow lake, and mainstem (control) from August 2009 to January 2011. A comparison was made between statistically representative DO concentrations (daily mean, diurnal range, daily minimum and maximum) for each site and in the river. River discharge was estimated at each site from nearby gages. By examining distinct changes in DO signatures with increasing flow, it was possible to determine the approximate flow at which the sloughs and oxbow lakes begin to become activated or hydraulically connected (flowing condition) to the mainstem of the Apalachicola River, and at what flow rates these floodplain wetlands become fully connected. Based on this data, we drew conclusions about the availability of suitable habitat for native fish species in these slough systems across a range of Apalachicola River flow conditions. We also reviewed the historic flow record to infer how habitat availability has likely changed over time in response to a decline in the frequency of hydraulic connection between the river and its floodplain sloughs.

  20. Importance of Dissolved Neutral Hg-Sulfides, Energy Rich Organic Matter and total Hg Concentrations for Methyl Mercury Production in Sediments

    NASA Astrophysics Data System (ADS)

    Drott, A.; Skyllberg, U.

    2007-12-01

    Methyl mercury (MeHg) is the mercury form that biomagnifies to the greatest extent in aquatic food webs. Therefore information about factors determining MeHg concentrations is critical for accurate risk assessment of contaminated environments. The concentration of MeHg in wetlands and sediments is the net result of: 1) methylation rates, 2) demethylation rates, and 3) input/output processes. In this study, the main controls on Hg methylation rates and total concentrations of MeHg, were investigated at eight sites in Sweden with sediments that had been subjected to local Hg contamination either as Hg(0), or as phenyl-Hg. Sediments were selected to represent a gradient in total Hg concentration, temperature climate, salinity, primary productivity, and organic C content and quality. Most sediments were high in organic matter content due to wood fibre efflux from pulp and paper industry. The pore water was analysed for total Hg, MeHg, DOC, H2S(aq), pH, DOC, Cl and Br. The chemical speciation of Hg(II) and MeHg in pore water was calculated using equilibrium models. Potential methylation and demethylation rates in sediments were determined in incubation experiments at 23° C under N2(g) for 48 h, after addition of isotopically enriched 201Hg(II) and Me204Hg. In all surface (0-20 cm) sediments there was a significant (p<0.001) positive relationship between the experimentally determined specific potential methylation rate constant (Km, day-1) and % MeHg (concentrations of MeHg normalized to total Hg) in the sediment. This indicates that MeHg production overruled degradation and input/output processes of MeHg in surface sediments, and that % MeHg in surface sediments may be used as a proxy for net production of MeHg. To our knowledge, these are the first data showing significant positive relationships between short term (48 h) MeHg production and longer term accumulation of MeHg, across a range of sites with different properties (1). If MeHg was not normalized to total Hg, the relationship was not significant. For sub-sets of brackish waters (p<0.001, n=23), southern, high-productivity freshwaters (p<0.001, n=20) as well as northern, low-productivity freshwater (p=0.048, n=6), the sum of neutral Hg-sulfides [Hg(SH)20 (aq)] and [HgS0 (aq)] in the sediment pore water was significantly, positively correlated with both the potential methylation rate constant (Km) and total MeHg concentrations (2). This indicates that methylating sulphate reducing bacteria passively take up neutral Hg-sulfides, which are transformed to MeHg. Differences in slopes of the relationships were explained by differences in primary productivity and availability of energy-rich organic matter to methylating bacteria. High primary productivity at southern freshwater sites, reflected by a low C/N ratio (large contribution from free living algae and bacteria) in the sediment and a high annual temperature sum, resulted in high methylation rates. In conclusion, concentrations of neutral Hg-sulfides and availability of energy rich organic matter, but also total Hg concentrations in sediments are important factors behind net production and accumulation of MeHg . References: (1) Drott et. al. submitted, (2) Drott, A.; Lambertsson, L.; Björn, E.; Skyllberg, U. Importance of dissolved neutral mercury sulfides for methyl mercury production in contaminated sediments. Environmental Science & Technology 2007, 41, 2270-2276.

  1. Characterizing the production and retention of dissolved iron as Fe(II) across a natural gradient in chlorophyll concentrations in the Southern Drake Passage - Final Technical Report

    SciTech Connect

    Katherine Barbeau

    2007-04-10

    Recent mesoscale iron fertilization studies in the Southern Ocean (e.g. SOIREE, EisenEx, SOFeX) have demonstrated the importance of iron as a limiting factor for phytoplankton growth in these high nutrient, low-chlorophyll (HNLC) waters. Results of these experiments have demonstrated that factors which influence the biological availability of the iron supplied to phytoplankton are crucial in bloom development, longevity, and generation of carbon export flux. These findings have important implications for the future development of iron fertilization protocols to enhance carbon sequestration in high-latitude oceans. In particular, processes which lead to the mobilization and retention of iron in dissolved form in the upper ocean are important in promoting continued biological availability of iron. Such processes can include photochemical redox cycling, which leads to the formation of soluble reduced iron, Fe(II), within iron-enriched waters. Creation of effective fertilization schemes will thus require more information about Fe(II) photoproduction in Southern Ocean waters as a means to retain new iron within the euphotic zone. To contribute to our knowledge base in this area, this project was funded by DOE with a goal of characterizing the production and retention of dissolved Fe as Fe(II) in an area of the southern Drake Passage near the Shackleton Transverse Ridge, a region with a strong recurrent chlorophyll gradient which is believed to be a site of natural iron enrichment in the Southern Ocean. This area was the focus of a multidisciplinary NSF/OPP-funded investigation in February 2004 (OPP02-30443, lead PI Greg Mitchell, SIO/UCSD) to determine the influence of mesoscale circulation and iron transport with regard to the observed patterns in sea surface chlorophyll in the region near the Shackleton Transverse Ridge. A number of parameters were assessed across this gradient in order to reveal interactions between plankton community structure and iron distributions. As a co-PI in the NSF/OPP-funded project, I was responsible for iron addition incubation and radiotracer experiments, and analysis of iron chemistry, including iron-organic speciation. This final technical report describes the results of my DOE funded project to analyse reduced iron species using an FeLume flow injection analysis chemiluminescence system as an extension of my work on the NSF/OPP project. On the cruise in 2004, spatial and temporal gradients in Fe(II) were determined, and on-board incubations were conducted to study Fe(II) lifetime and production. Following the cruise a further series of experiments was conducted in my laboratory to study Fe(II) lifetimes and photoproduction under conditions typical of high latitude waters. The findings of this study suggest that, in contrast to results observed during mesoscale iron addition experiments, steady-state levels of Fe(II) are likely to remain low (below detection) even within a significant gradient in dissolved Fe concentrations produced as a result of natural iron enrichment processes. Fe(II) is likely to be produced, however, as a reactive intermediate associated with photochemical reactions in surface waters. While Fe(II) lifetimes measured in the field in this study were commensurate with those determined in previously published Southern Ocean work, Fe(II) lifetimes reflective of realistic Southern Ocean environmental conditions have proven difficult to determine in a laboratory setting, due to contamination by trace levels of H2O2. Laboratory experiments demonstrated that direct ligand-to-metal charge transfer reactions of strong Fe(III)-organic complexes do appear to be a viable source of available Fe(II) in Antarctic waters, and further studies are needed to characterize the temperature dependence of this phenomenon.

  2. Water type and concentration of dissolved solids, chloride, and sulfate in water from the St. Francois aquifer in Missouri, Arkansas, Kansas, and Oklahoma

    USGS Publications Warehouse

    Imes, Jeffrey L.; Davis, J.V.

    1990-01-01

    The St. Francois aquifer, the lowermost of three regional aquifers that form part of the Ozark Plateaus aquifer system, is composed of water-bearing sandstone and dolostone of Late Cambrian age. The aquifer was studied as part of the Central Midwest Regional Aquifer-System Analysis (CMRASA, Jorgensen and Signor, 1981), a study of regional aquifer systems in the midcontinent United States that includes parts of 10 States. Because of its significance as a source of freshwater in and adjacent to the Ozark Plateaus province (index map) of Missouri, Arkansas, Kansas, and Oklahoma, a subregional project was established to investigate the Ozark Plateaus aquifer system in more detail than the regional study could provide.The geologic and hydrologic relation between the Ozark Plateaus aquifer system and other regional aquifer systems of the Midwest is presented in Jorgensen an others (in press). The relation of the St. Francois aquifer to the Ozark Plateaus aquifer system is explained in Imes [in press (a)]. A companion publication, Imes [in press (b)], contains contour maps of the altitude of the top, thickness, and potentiometric surface of the St. Francois aquifer. This report contains maps that show water type and concentration of dissolved solids, chloride, and sulfate in water from the St. Francois aquifer. Most of the data from which these maps are compiled is stored in the CMRASA hydrochemical data base (R.B. Leonard, U.S. Geological Survey, written commun., 1986). Only water quality analyses that ionically balanced to within 10 percent are included in this report. Because few water wells are completed in the St. Francois aquifer beyond the vicinity of the St. Francois Mountains in southeastern Missouri (index map), water-quality data, with few exceptions, are limited to a relatively small area near the outcrop of the aquifer.

  3. Water type and concentration of dissolved solids, chloride, and sulfate in water from the Ozark aquifer in Missouri, Arkansas, Kansas, and Oklahoma

    USGS Publications Warehouse

    Imes, Jeffrey L.; Davis, J.V.

    1991-01-01

    The Ozark aquifer is a thick sequence of water-bearing dolostone, limestone, and sandstone of latest Cambrian through Middle Devonian age that is widely used as a source of water throughout the Ozark Plateaus province (index map). The Ozark aquifer is the largest of three aquifers that form part of the Ozark Plateaus aquifer system. The aquifer was studied as part of the Central Midwest Regional Aquifer-System Analysis (CMRASA; Jorgensen and Signor, 1981), a study of regional aquifer systems in the midcontinent United States that includes parts of 10States. Because of its significance as a source of freshwater in parts of Missouri, Arkansas, Kansas, and Oklahoma, a subregional project was established to investigate the Ozark Plateaus aquifer system in more detail than the regional study could provide.The geologic and hydrologic relation between the Ozark Plateaus aquifer system and other regional aquifer systems of the Midwest is presented in Jorgensen and others (in press). The relation of the Ozark aquifer to the Ozark Plateaus aquifer system is explained in Imes [in press (a)]. A companion publication, Imes [1990 (b)], contains contour maps of the altitude of the top, thickness, and potentiometric surface of the Ozark aquifer. This report contains maps that show water type and concentrations of dissolved solids, chloride, and sulfate in water from the Ozark aquifer. Most of the data from which these maps are compiled is stored in the CMRASA hydrochemical data base (R.B. Leonard, U.S. Geological Survey, written commun., 1986). Data for Oklahoma were also taken from data published by Havens (1978). The maps in this report on the Ozark subregion may contain small differences from maps in other CMRASA publications because the criteria for data selection may be different and the subregional maps may contain additional data. However, regional trends in these maps are consistent with other maps published as part of the regional project.

  4. Flow-adjusted trends in dissolved selenium load and concentration in the Gunnison and Colorado Rivers near Grand Junction, Colorado, water years 1986--2008

    USGS Publications Warehouse

    Mayo, John W.; Leib, Kenneth J.

    2012-01-01

    As a result of elevated selenium concentrations, many western Colorado rivers and streams are on the U.S. Environmental Protection Agency 2010 Colorado 303(d) list, including the main stem of the Colorado River from the Gunnison River confluence to the Utah border. Selenium is a trace metal that bioaccumulates in aquatic food chains and can cause reproductive failure, deformities, and other adverse impacts in birds and fish, including several threatened and endangered fish species. Salinity in the upper Colorado River has been the focus of source-control efforts for many years. Although salinity loads and concentrations have been previously characterized at the U.S. Geological Survey (USGS) streamflow-gaging stations at the Gunnison River near Grand Junction, Colo., and at the Colorado River near the Colorado-Utah State line, trends in selenium load and concentration at these two stations have not been studied. The USGS, in cooperation with the Bureau of Reclamation and the Colorado River Water Conservation District, evaluated dissolved selenium (herein referred to as "selenium") load and concentration trends at these two sites to inform decision makers on the status and trends of selenium. This report presents results of the evaluation of trends in selenium load and concentration for two USGS streamflow-gaging stations: the Gunnison River near Grand Junction, Colo. ("Gunnison River site"), USGS site 09152500, and the Colorado River near Colorado-Utah State line ("Colorado River site"), USGS site 09163500. Flow-adjusted selenium loads were estimated for the beginning water year (WY) of the study, 1986, and the ending WY of the study, 2008. The difference between flow-adjusted selenium loads for WY 1986 and WY 2008 was selected as the method of analysis because flow adjustment removes the natural variations in load caused by changes in mean-daily streamflow, emphasizing human-caused changes in selenium load and concentration. Overall changes in human-caused effects in selenium loads and concentrations during the period of study are of primary interest to the cooperators. Selenium loads for each of the 2 water years were calculated by using normalized mean-daily streamflow, measured selenium concentration, standard linear regression techniques, and data previously collected at the two study sites. Mean-daily streamflow was normalized for each site by averaging the daily streamflow for each day of the year over the 23-year period of record. Thus, for the beginning and ending water years, estimations could be made of loads that would have occurred without the effect of year-to-year streamflow variation. The loads thus calculated are illustrative of the change in loads between water years 1986 and 2008, and are not the actual loads that occurred in those 2 water years. The estimated 50th and 85th percentile selenium concentrations associated with the selenium loads were also calculated for WY 1986 and WY 2008 at each site. Time-trends in selenium concentration at the two sites were charted by using regression techniques for partial residuals for the entire study period (WY 1986 through WY 2008). Annual selenium load for the Gunnison River site was estimated to be 23,196 pounds for WY 1986 and 16,560 pounds for WY 2008, a 28.6 percent decrease. Lower and upper 95-percent confidence levels for WY 1986 annual load were 22,360 and 24,032 pounds. Lower and upper 95-percent confidence levels for WY 2008 annual load were 15,724 and 17,396 pounds. Estimated 50th percentile daily selenium concentrations decreased from 6.41 to 4.57 micrograms/liter from WY 1986 to WY 2008, whereas estimated 85th percentile daily selenium concentrations decreased from 7.21 to 5.13 micrograms/liter from WY 1986 to WY 2008. Annual selenium load for the Colorado River site was estimated to be 56,587 pounds for WY 1986 and 34,344 pounds for WY 2008, a 39.3 percent decrease. Lower and upper 95-percent confidence levels for WY 1986 annual load were 53,785 and 59,390 pounds. Lower and upper 95-percent confidence levels for WY 2008 annual load were 31,542 and 3

  5. Assessment of the Impact of Climate Change and Land Management Change on Soil Organic Carbon Content, Leached Carbon Rates and Dissolved Organic Carbon Concentrations

    NASA Astrophysics Data System (ADS)

    Stergiadi, Maria; de Nijs, Ton; van der Perk, Marcel; Bonten, Luc

    2014-05-01

    Climate change is projected to significantly affect the concentrations and mobility of contaminants, such as metals and pathogens, in soil, groundwater and surface water. Climate- and land management-induced changes in soil organic carbon and dissolved organic carbon levels may promote the transport of toxic substances, such as copper and cadmium, and pathogenic microorganisms, ultimately affecting the exposure of humans and ecosystems to these contaminants. In this study, we adopted the Century model to simulate past (1900 - 2010), present, and future (2010 - 2100) SOC and DOC levels for a sandy and a loamy soil typical for Central and Western European conditions under three land use types (forest, grassland and arable land) and several future scenarios addressing climate change and land management change. The climate scenarios were based on the KNMI'06 G+ and W+ scenarios from the Royal Dutch Meteorological Institute. The simulated current SOC levels were compared to observed SOC values derived from various Dutch soil databases, taking into account the different soil depths the simulated and observed values refer to. The simulated SOC levels were generally in line with the observed values for the different kinds of soil and land use types. Climate change scenarios resulted in a decrease in both SOC and DOC for the grassland systems, whereas in the arable land (on sandy soil) and in the forest systems, SOC was found to increase and DOC to decrease. A sensitivity analysis of the individual effects of changes in temperature and precipitation showed that the effect of temperature predominates over the effect of precipitation. A reduction in the application rates of artificial fertilizers leads to a decrease in the SOC stocks and the leached carbon rates in the arable land systems, but has a negligible effect on SOC and DOC levels of the grassland systems. This study demonstrated the ability of the Century model to simulate climate change and agricultural management effects on SOC dynamics. The following step of this study will involve the translation of the soil organic matter pools as simulated with Century model, into pools of different metal binding capacity to be used for the metal partitioning and leaching modelling.

  6. Vegetation, soil property and climatic controls over pore water dissolved organic carbon concentrations in a blanket peatland hosting a wind farm

    NASA Astrophysics Data System (ADS)

    Armstrong, Alona; Waldron, Susan; Whitaker, Jeanette; Ostle, Nick

    2013-04-01

    Rising dissolved organic carbon concentrations ([DOC]) in surface waters have prompted much research to elucidate the cause(s). Given that increases in [DOC] may indicate a destabalisation of carbon stores, increase water treatment costs and affect rates of primary production and respiration in aquatic ecosystems, identifying the causes of the increase is important. Research has demonstrated that [DOC] in peatlands are influenced by vegetation, soil property and climatic controls, including water table height, temperature and plant functional type (PFT). In this paper we present data from Black Law Wind Farm, Scotland, where we examined the effect of a predicted wind turbine-induced microclimatic gradient and PFT on pore water [DOC]. Moreover, we determined the role of vegetation, soil property and climatic variables as predictors of the variation in [DOC]. We measured [DOC] at 48 plots within Black Law Wind Farm at monthly intervals from May 2011 to April 2012. Four sampling sites were located along a predicted wind turbine-induced microclimatic gradient. At each site four blocks were established each with plots in areas dominated by mosses, sedges and shrubs. Plant biomass and PFT (vegetation factors); soil moisture, water table height, peat depth, C content, nitrogen (N) content and C:N (soil properties); and soil temperature and photosynthetically active radiation (PAR) (climatic variables) were measured. An analysis of variance (ANOVA) model based on the microclimatic gradient site, season, site*season and PFT*season explained 55 % of the variation in [DOC]. [DOC] generally increased along the predicted microclimatic gradient and increased from winter through to autumn. A parsimonious ANOVA model using the vegetation, soil property and climatic explanatory data explained 53 % of the variation in [DOC]. Published studies (Baidya Roy and Traiteur 2010; Zhou, Tian et al. 2012) and preliminary results from this study suggest that a wind turbine-induced microclimatic effect may exist. Consequently, given that the climatic variables, factors influenced by changes in the climate, and their interactions affect [DOC] fluxes, the operational effects of wind farms on peatland ecosystems may need to be taken into account when considering their full life cycle carbon budget. Baidya Roy, S. and J. J. Traiteur (2010). Impacts of wind farms on surface air temperatures, Proceedings of the National Academy of Sciences, 109: 15679-15684. Limpens, J. et al. (2008). Peatlands and the carbon cycle: from local processes to global implications - a synthesis, Biogeosciences, 5(5): 1475-1491. Zhou, L., et al. (2012). Impacts of wind farms on land surface temperature, Nature Climate Change, 2: 539-543.

  7. Application of isotope dilution method for measuring bioavailability of organic contaminants sorbed to dissolved organic matter (DOM).

    PubMed

    Delgado-Moreno, Laura; Wu, Laosheng; Gan, Jay

    2015-08-01

    Natural waters such as surface water and sediment porewater invariably contain dissolved organic matter (DOM). Association of strongly hydrophobic contaminants (HOCs) with DOM leads to decreased toxicity and bioavailability, but bioavailability of DOM-sorbed HOCs is difficult to measure. Current methods to estimate bioavailability of HOCs in water are based on only the freely dissolved concentration (Cfree). The ignorance of the exchangeable fraction of HOCs sorbed on DOM may result in an underestimation of the toxicity potential of HOCs to aquatic organisms. Here we explore the applicability of an isotope dilution method (IDM) to measuring the desorption fraction of DOM-sorbed pyrene and bifenthrin and determining their exchangeable pool (E) as an approximation of bioavailability. E values, expressed as percentage of the total concentration, ranged between 0.80 and 0.92% for pyrene and 0.74 and 0.85% for bifenthrin, depending primarily on the amount of chemical in the freely dissolved form. However, between 34 and 78% of the DOM-sorbed pyrene was exchangeable. This fraction ranged between 23% and 82% for bifenthrin. The ability of IDM to predict bioavailability was further shown from a significant relationship (r(2)>0.72, P<0.0001) between E and bioaccumulation into Daphnia magna. Therefore, IDM may be used to improve the bioavailability measurement and risk assessment of HOCs in aquatic systems. PMID:26037097

  8. Rapid behavioral responses of an invertebrate larva to dissolved settlement cue.

    PubMed

    Hadfield, Michael G; Koehl, M A R

    2004-08-01

    Larvae of the nudibranch Phestilla sibogae were used to study whether a natural dissolved settlement cue (from their prey, Porites compressa, an abundant coral on Hawaiian reefs) induces behavioral responses that can affect larval transport to suitable settlement sites. As cue and larvae are mixed in the turbulent flow over a reef, cue is distributed in fine-scale filaments that the larva experiences as rapid (seconds) on/off encounters. To examine larval responses in this setting, individual larvae were tethered in a small flume with flow simulating water velocity relative to a freely swimming larva, and their responses to realistic temporal patterns of cue encounter were videotaped. Competent larvae quickly ceased swimming in cue filaments and resumed swimming after exiting filaments. The threshold cue concentration eliciting a response was 3%-17% of concentrations within heads of P. compressa in nature. When moving freely in filtered seawater, competent larvae swam along straight paths in all directions at approximately 0.2 cm s(-1), whereas in water conditioned by P. compressa, most ceased swimming and sank at approximately 0.1 cm s(-1). The ability of larvae to rapidly respond (by sinking) to brief encounters with dissolved settlement cues can enhance their rapid transport to the substratum, even in wave-driven turbulent flow. PMID:15315941

  9. Predicting Polycyclic Aromatic Hydrocarbon Concentrations in Resident Aquatic Organisms Using Passive Samplers and Partial Least-Squares Calibration

    PubMed Central

    2015-01-01

    The current work sought to develop predictive models between time-weighted average polycyclic aromatic hydrocarbon (PAH) concentrations in the freely dissolved phase and those present in resident aquatic organisms. We deployed semipermeable membrane passive sampling devices (SPMDs) and collected resident crayfish (Pacifastacus leniusculus) at nine locations within and outside of the Portland Harbor Superfund Mega-site in Portland, OR. Study results show that crayfish and aqueous phase samples collected within the Mega-site had PAH profiles enriched in high molecular weight PAHs and that freely dissolved PAH profiles tended to be more populated by low molecular weight PAHs compared to crayfish tissues. Results also show that of several modeling approaches, a two-factor partial least-squares (PLS) calibration model using detection limit substitution provided the best predictive power for estimating PAH concentrations in crayfish, where the model explained ?72% of the variation in the data set and provided predictions within ?3× of measured values. Importantly, PLS calibration provided a means to estimate PAH concentrations in tissues when concentrations were below detection in the freely dissolved phase. The impact of measurements below detection limits is discussed. PMID:24800862

  10. Copyright 2002 Cisco Systems This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2002 Cisco Systems This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco VPN 3000 Series Concentrators® 3005, 3015, 3030, 3060, 3080 2002 Cisco Systems Page 2 of 18 This document may be freely reproduced and distributed whole and intact

  11. 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

  12. Passive Sampling to Measure Baseline Dissolved Persistent Organic Pollutant Concentrations in the Water Column of the Palos Verdes Shelf Superfund Site

    EPA Science Inventory

    Passive sampling was used to deduce water concentrations of persistent organic pollutants (POPs) in the vicinity of a marine Superfund site on the Palos Verdes Shelf, California, USA. Pre-calibrated solid phase microextraction (SPME) fibers and polyethylene (PE) strips that were...

  13. A freely-moving monkey treadmill model

    NASA Astrophysics Data System (ADS)

    Foster, Justin D.; Nuyujukian, Paul; Freifeld, Oren; Gao, Hua; Walker, Ross; Ryu, Stephen I.; Meng, Teresa H.; Murmann, Boris; Black, Michael J.; Shenoy, Krishna V.

    2014-08-01

    Objective. Motor neuroscience and brain-machine interface (BMI) design is based on examining how the brain controls voluntary movement, typically by recording neural activity and behavior from animal models. Recording technologies used with these animal models have traditionally limited the range of behaviors that can be studied, and thus the generality of science and engineering research. We aim to design a freely-moving animal model using neural and behavioral recording technologies that do not constrain movement. Approach. We have established a freely-moving rhesus monkey model employing technology that transmits neural activity from an intracortical array using a head-mounted device and records behavior through computer vision using markerless motion capture. We demonstrate the flexibility and utility of this new monkey model, including the first recordings from motor cortex while rhesus monkeys walk quadrupedally on a treadmill. Main results. Using this monkey model, we show that multi-unit threshold-crossing neural activity encodes the phase of walking and that the average firing rate of the threshold crossings covaries with the speed of individual steps. On a population level, we find that neural state-space trajectories of walking at different speeds have similar rotational dynamics in some dimensions that evolve at the step rate of walking, yet robustly separate by speed in other state-space dimensions. Significance. Freely-moving animal models may allow neuroscientists to examine a wider range of behaviors and can provide a flexible experimental paradigm for examining the neural mechanisms that underlie movement generation across behaviors and environments. For BMIs, freely-moving animal models have the potential to aid prosthetic design by examining how neural encoding changes with posture, environment and other real-world context changes. Understanding this new realm of behavior in more naturalistic settings is essential for overall progress of basic motor neuroscience and for the successful translation of BMIs to people with paralysis.

  14. Three-phase modeling of polycyclic aromatic hydrocarbon association with pore-water-dissolved organic carbon

    SciTech Connect

    Mitra, S. ); Dickhut, R.M. )

    1999-06-01

    Log-log plots of measured organic carbon-normalized sediment pore-water distribution coefficients (K[prime][sub OC]s) for several polycyclic aromatic hydrocarbons (PAHs) versus their octanol-water partition coefficients (K[prime][sub OW]s) at two sites in the Elizabeth River, Virginia, show large deviations from linearity. Organic-carbon normalized distribution coefficients for these PAHs between sediments and pore waters decreased by more than two orders of magnitude with depth as well. To determine to what extent pore water dissolved and colloidal organic carbon (DOC) was responsible for the observed nonlinearity and decrease in K[prime][sub OC], a three-phase model was used to estimate pore-water PAH-DOC binding coefficients (K[sub DOC]). Partitioning of PAHs to pore-water DOC (i.e., K[sub DOC])enhances the observed dissolved phase PAH concentration, especially for high-K[sub OW] compounds, contributing to the nonlinearity in K[prime][sub OC]-K[sub OW] plots. However, the application of the three-phase partitioning model to these data indicate that, at most, pore-water PAH-DOC binding accounts for one order of magnitude of the observed decrease in K[prime][sub OC] with depth in the sediment bed. The results of this study are consistent with three-phase partitioning theory for hydrophobic organic compounds between sediment organic matter, pore-water DOC, and freely dissolved aqueous phases in natural systems.

  15. Trends in concentrations of nitrate and total dissolved solids in public supply wells of the Bunker Hill, Lytle, Rialto, and Colton groundwater subbasins, San Bernardino County, California: Influence of legacy land use

    USGS Publications Warehouse

    Kent, Robert; Landon, Matthew K.

    2013-01-01

    Concentrations and temporal changes in concentrations of nitrate and total dissolved solids (TDS) in groundwater of the Bunker Hill, Lytle, Rialto, and Colton groundwater subbasins of the Upper Santa Ana Valley Groundwater Basin were evaluated to identify trends and factors that may be affecting trends. One hundred, thirty-one public-supply wells were selected for analysis based on the availability of data spanning at least 11 years between the late 1980s and the 2000s. Forty-one of the 131 wells (31%) had a significant (p < 0.10) increase in nitrate and 14 wells (11%) had a significant decrease in nitrate. For TDS, 46 wells (35%) had a significant increase and 8 wells (6%) had a significant decrease. Slopes for the observed significant trends ranged from ? 0.44 to 0.91 mg/L/yr for nitrate (as N) and ? 8 to 13 mg/L/yr for TDS. Increasing nitrate trends were associated with greater well depth, higher percentage of agricultural land use, and being closer to the distal end of the flow system. Decreasing nitrate trends were associated with the occurrence of volatile organic compounds (VOCs); VOC occurrence decreases with increasing depth. The relations of nitrate trends to depth, lateral position, and VOCs imply that increasing nitrate concentrations are associated with nitrate loading from historical agricultural land use and that more recent urban land use is generally associated with lower nitrate concentrations and greater VOC occurrence. Increasing TDS trends were associated with relatively greater current nitrate concentrations and relatively greater amounts of urban land. Decreasing TDS trends were associated with relatively greater amounts of natural land use. Trends in TDS concentrations were not related to depth, lateral position, or VOC occurrence, reflecting more complex factors affecting TDS than nitrate in the study area.

  16. A 17-year record of environmental tracers in spring discharge, Shenandoah National Park, Virginia, USA: use of climatic data and environmental conditions to interpret discharge, dissolved solutes, and tracer concentrations

    USGS Publications Warehouse

    Busenberg, Eurybiades; Plummer, L. Niel

    2014-01-01

    A 17-year record (1995–2012) of a suite of environmental tracer concentrations in discharge from 34 springs located along the crest of the Blue Ridge Mountains in Shenandoah National Park (SNP), Virginia, USA, reveals patterns and trends that can be related to climatic and environmental conditions. These data include a 12-year time series of monthly sampling at five springs, with measurements of temperature, specific conductance, pH, and discharge recorded at 30-min intervals. The monthly measurements include age tracers (CFC-11, CFC-12, CFC-113, CFC-13, SF6, and SF5CF3), dissolved gases (N2, O2, Ar, CO2, and CH4), stable isotopes of water, and major and trace inorganic constituents. The chlorofluorocarbon (CFC) and sulfur hexafluoride (SF6) concentrations (in pptv) in spring discharge closely follow the concurrent monthly measurements of their atmospheric mixing ratios measured at the Air Monitoring Station at Big Meadows, SNP, indicating waters 0–3 years in age. A 2-year (2001–2003) record of unsaturated zone air displayed seasonal deviations from North American Air of ±10 % for CFC-11 and CFC-113, with excess CFC-11 and CFC-113 in peak summer and depletion in peak winter. The pattern in unsaturated zone soil CFCs is a function of gas solubility in soil water and seasonal unsaturated zone temperatures. Using the increase in the SF6 atmospheric mixing ratio, the apparent (piston flow) SF6 age of the water varied seasonally between about 0 (modern) in January and up to 3 years in July–August. The SF6 concentration and concentrations of dissolved solutes (SiO2, Ca2+, Mg2+, Na+, Cl?, and HCO3?) in spring discharge demonstrate a fraction of recent recharge following large precipitation events. The output of solutes in the discharge of springs minus the input from atmospheric deposition per hectare of watershed area (mol ha?1 a?1) were approximately twofold greater in watersheds draining the regolith of Catoctin metabasalts than that of granitic gneisses and granitoid crystalline rocks. The stable isotopic composition of water in spring discharge broadly correlates with the Oceanic Niño Index. Below normal precipitation and enriched stable isotopic composition were observed during El Niño years.

  17. Experimental investigations on freely exposed ducted radiators

    NASA Technical Reports Server (NTRS)

    Linke, W

    1941-01-01

    This report deals with the relation between the open areas, the drag, and the air flow as observed on freely exposed, ducted radiators - the air conductivity being modified from zero to one unit. In conjunction with theoretical results, the individual components of the drag of ducted radiators are discussed and general rules established for low-loss ducts. The influence of the wall thickness of the ducts, of the length ratio of the exit, and the effects of sonic velocity on diffusers are dealt with by special measurement.

  18. Dissolved pesticide concentrations entering the Sacramento-San Joaquin Delta from the Sacramento and San Joaquin Rivers, California, 2012-13

    USGS Publications Warehouse

    Orlando, James L.; McWayne, Megan; Sanders, Corey; Hladik, Michelle

    2014-01-01

    Surface-water samples were collected from the Sacramento and San Joaquin Rivers where they enter the Sacramento–San Joaquin Delta, and analyzed by the U.S. Geological Survey for a suite of 99 current-use pesticides and pesticide degradates. Samples were collected twice per month from May 2012 through July 2013 and from May 2012 through April 2013 at the Sacramento River at Freeport, and the San Joaquin River near Vernalis, respectively. Samples were analyzed by two separate laboratory methods by using gas chromatography with mass spectrometry or liquid chromatography with tandem mass spectrometry. Method detection limits ranged from 0.9 to 10.5 nanograms per liter (ng/L). A total of 37 pesticides and degradates were detected in water samples collected during the study (18 herbicides, 11 fungicides, 7 insecticides, and 1 synergist). The most frequently detected pesticides overall were the herbicide hexazinone (detected in 100 percent of the samples); 3,4-dichloroaniline (97 percent), which is a degradate of the herbicides diuron and propanil; the fungicide azoxystrobin (83 percent); and the herbicides diuron (72 percent), simazine (66 percent), and metolachlor (64 percent). Insecticides were rarely detected during the study. Pesticide concentrations varied from below the method detection limits to 984 ng/L (hexazinone). Twenty seven pesticides and (or) degradates were detected in Sacramento River samples, and the average number of pesticides per sample was six. The most frequently detected compounds in these samples were hexazinone (detected in 100 percent of samples), 3,4-dichloroaniline (97 percent), azoxystrobin (88 percent), diuron (56 percent), and simazine (50 percent). Pesticides with the highest detected maximum concentrations in Sacramento River samples included the herbicide clomazone (670 ng/L), azoxystrobin (368 ng/L), 3,4-dichloroaniline (364 ng/L), hexazinone (130 ng/L), and propanil (110 ng/L), and all but hexazinone are primarily associated with rice agriculture. In addition to the twice monthly sampling, surface-water samples were collected from the Sacramento River on 5 consecutive days following a rainfall event in the Sacramento urban area. Samples collected following this event contained an average of 11 pesticides. The insecticides carbaryl, fipronil, and imidacloprid; the herbicide DCPA; and the fungicide imazalil were only detected in the Sacramento River during this storm-runoff event, and two detections of fipronil during this period exceeded the U.S. Environmental Protection Agency Aquatic Life Benchmark (11 ng/L) for chronic toxicity to invertebrates in freshwater. In San Joaquin River samples, 26 pesticides and (or) degradates were detected, and the average number detected per sample was 9. The most frequently detected compounds in these samples were hexazinone and metolachlor (detected in 100 percent of samples); diuron (96 percent); the fungicide boscalid (96 percent); the degradates 3,4-dicloroaniline (92 percent) and NN-(3,4-Dichlorophenyl)-N’-methylurea (DCPMU; 83 percent); simazine (83 percent); and azoxystrobin (75 percent). The pesticides with the highest detected maximum concentrations were hexazinone (984 ng/L), diuron (695 ng/L), simazine (524 ng/L), the herbicide prometryn (155 ng/L), metolachlor (127 ng/L), boscalid (112 ng/L), DCPMU (111 ng/L), and the herbicide pendimethalin (108 ng/L).

  19. Comparison of the activity of immobilised and freely suspended Streptomyces coelicolor A3(2).

    PubMed

    Ozergin-Ulgen, K; Mavituna, F

    1994-04-01

    Streptomyces coelicolor was immobilised "naturally" in porous support materials and its growth, glucose uptake and actinorhodin production were compared with freely suspended culture using defined and complex media. When the defined medium was used, the most pronounced difference between the two cultures was the accumulation of actinorhodin extracellularly in freely suspended and intracellularly in immobilised cultures. In the complex medium, however, actinorhodin was excreted by both cultures. In addition, the complex medium yielded 50 times as much actinorhodin compared to the defined medium. Further increases in product concentration were obtained by repeated batches of immobilised culture, which showed stability for at least 3 months. PMID:7764831

  20. Concentration, flux, and the analysis of trends of total and dissolved phosphorus, total nitrogen, and chloride in 18 tributaries to Lake Champlain, Vermont and New York, 1990–2011

    USGS Publications Warehouse

    Medalie, Laura

    2013-01-01

    Annual concentration, flux, and yield for total phosphorus, dissolved phosphorus, total nitrogen, and chloride for 18 tributaries to Lake Champlain were estimated for 1990 through 2011 using a weighted regression method based on time, tributary streamflows (discharges), and seasonal factors. The weighted regression method generated two series of daily estimates of flux and concentration during the period of record: one based on observed discharges and a second based on a flow-normalization procedure that removes random variation due to year-to-year climate-driven effects. The flownormalized estimate for a given date is similar to an average estimate of concentration or flux that would be made if all of the observed discharges for that date were equally likely to have occurred. The flux bias statistic showed that 68 of the 72 flux regression models were minimally biased. Temporal trends in the concentrations and fluxes were determined by calculating percent changes in flow-normalized annual fluxes for the full period of analysis (1990 through 2010) and for the decades 1990–2000 and 2000–2010. Basinwide, flow-normalized total phosphorus flux decreased by 42 metric tons per year (t/yr) between 1990 and 2010. This net result reflects a basinwide decrease in flux of 21 metric tons (t) between 1990 and 2000, followed by a decrease of 20 t between 2000 and 2010; both results were largely influenced by flux patterns in the large tributaries on the eastern side of the basin. A comparison of results for total phosphorus for the two separate decades of analysis found that more tributaries had decreasing concentrations and flux rates in the second decade than the first. An overall reduction in dissolved phosphorus flux of 0.7 t/yr was seen in the Lake Champlain Basin during the full period of analysis. That very small net change in flux reflects substantial reductions between 1990 and 2000 from eastern tributaries, especially in Otter Creek and the LaPlatte and Winooski Rivers that largely were offset by increases in the Missisquoi and Saranac Rivers in the second decade (between 2000 and 2010). The number of tributaries that had increases in dissolved phosphorus concentrations stayed constant at 13 or 14 during the period of analysis. Total nitrogen concentration and flux for most of the monitored tributaries in the Lake Champlain Basin have decreased since 1990. Between 1990 and 2010, flow-normalized total nitrogen flux decreased by 386 t/yr, which reflects an increase of 440 t/yr between 1990 and 2000 and a decrease of 826 t/yr between 2000 and 2010. All individual tributaries except the Winooski River had decreases in total nitrogen concentration and flux between 2000 and 2010. The decrease in total nitrogen flux over the period of record could be related to the decrease in nitrogen from atmospheric deposition observed in Vermont or to concurrent benefits realized from the implementation of agricultural best-management practices in the Lake Champlain Basin that were designed primarily to reduce phosphorus runoff. For chloride, large increases in flow-normalized concentrations and flux between 1990 and 2000 for 17 of the 18 tributaries diminished to small increases or decreases between 2000 and 2010. Between 1990 and 2010, flow-normalized flux increased by 32,225 t/yr, 78 percent of which (25,163 t) was realized during the first decade, from 1990 through 2000. The five tributaries that had decreasing concentration and flux of chloride between 2000 and 2010 were all on the eastern side of Lake Champlain, possibly related to reductions since 1999 in winter road salt application in Vermont. Positive correlations of phosphorus flux and changes in phosphorus concentration and flux in tributaries with phosphorus inputs to basins from point sources, suggest that point sources have an effect on stream phosphorus chemistry. Several measures of changes in agricultural statistics, such as agricultural land use, acres of land in farms, acres of cropland, and acres of corn for grain or seed, are positively correlated with changes in phosp

  1. Testing the sensitivity of boreal headwaters using a forest clear-cutting experiment: The impact of changing flow-pathways and soil warming on dissolved organic carbon concentrations in streams

    NASA Astrophysics Data System (ADS)

    Schelker, J.; Grabs, T.; Bishop, K. H.; Laudon, H.

    2014-12-01

    Forest disturbance such as clear-cutting has been identified as an important factor for increasing dissolved organic carbon (DOC) concentrations in boreal streams. We used a long-term dataset of soil temperature, soil moisture, shallow ground water (GW) levels and stream DOC concentrations from three boreal first-order streams to investigate mechanisms causing these increases. Clear-cutting was found to alter soil conditions with warmer and wetter soils during summer. The application of a riparian flow concentration integration model (RIM) explained a major part of variation in stream [DOC] arising from changing flow-pathways in riparian soils during the pre-treatment period (r2= 0.4-0.7), but less well after the harvest. Model residuals were highly sensitive to changes in soil temperature. The linear regression models for the temperature dependence of [DOC] in soils were not different in the disturbed and undisturbed catchments, whereas a non-linear response to soil moisture was found. Overall these results suggest that the increased DOC mobilization after forest disturbance is caused by (i) increased GW levels leading to increased water fluxes in shallow flow-path in riparian soils and (ii) increased soil temperature increasing the DOC availability in soils during summer. These relationships indicate that the mechanisms of DOC mobilization after forest disturbance are not different to those of undisturbed catchments, but that catchment soils respond to the higher hydro-climatic variation observed after clear-cutting. This highlights the sensitivity of boreal streams to changes in the energy and water balance, which may be altered as a result of both land management and climate change.

  2. Use of Passive Samplers to Measure Dissolved Organic Contaminants in a Temperate Estuary

    EPA Science Inventory

    Measuring dissolved concentrations of organic contaminants can be challenging given their low solubilities and high particle association. However, to perform accurate risk assessments of these chemicals, knowing the dissolved concentration is critical since it is considered to b...

  3. Children's Interpretation of Dissolving.

    ERIC Educational Resources Information Center

    Longden, Ken; And Others

    1991-01-01

    Children of 2 different age groups (11-12, n=246; and 13-14, n=196) were asked to draw and write about dissolving in 2 different ways. Greater percentage of children at both ages gave accurate particle interpretation that accurate view of observable process. Consistency between two ways of looking at dissolving was not found to improve with age.…

  4. EFFECT OF DISSOLVED ORGANIC SUBSTANCES ON OYSTERS

    E-print Network

    EF·FECT OF DISSOLVED ORGANIC SUBSTANCES· ON OYSTERS BY ALBERT COLLIER, S. M. RAY, A. W. MAGNITZKY gapes ~f !ileveral oysters recorded simultaneously indicated a parallel reaction to the concentration of carbohydrates in sea water. The oysters responded to increases in the carbohydrate concentration by pumping

  5. ORIGINAL PAPER Benthic sediment influence on dissolved phosphorus

    E-print Network

    Lottig, Noah R.

    ORIGINAL PAPER Benthic sediment influence on dissolved phosphorus concentrations in a headwater with inorganic sedi- ment particles through sorption reactions in streams. Collectively, this phosphorus (P determining ambi- ent stream P concentrations. Keywords Phosphorus retention Á Sediments Á Equilibrium

  6. Influence of Dissolved Organic Matter on Tetracycline Bioavailability to an Antibiotic-Resistant Bacterium.

    PubMed

    Chen, Zeyou; Zhang, Yingjie; Gao, Yanzheng; Boyd, Stephen A; Zhu, Dongqiang; Li, Hui

    2015-09-15

    Complexation of tetracycline with dissolved organic matter (DOM) in aqueous solution could alter the bioavailability of tetracycline to bacteria, thereby alleviating selective pressure for development of antibiotic resistance. In this study, an Escherichia coli whole-cell bioreporter construct with antibiotic resistance genes coupled to green fluorescence protein was exposed to tetracycline in the presence of DOM derived from humic acids. Complexation between tetracycline and DOM diminished tetracycline bioavailability to E. coli, as indicated by reduced expression of antibiotic resistance genes. Increasing DOM concentration resulted in decreasing bioavailability of tetracycline to the bioreporter. Freely dissolved tetracycline (not complexed with DOM) was identified as the major fraction responsible for the rate and magnitude of antibiotic resistance genes expressed. Furthermore, adsorption of DOM on bacterial cell surfaces inhibited tetracycline diffusion into the bioreporter cells. The magnitude of the inhibition was related to the amount of DOM adsorbed and tetracycline affinity for the DOM. These findings provide novel insights into the mechanisms by which the bioavailability of tetracycline antibiotics to bacteria is reduced by DOM present in water. Agricultural lands receiving livestock manures commonly have elevated levels of both DOM and antibiotics; the DOM could suppress the bioavailability of antibiotics, hence reducing selective pressure on bacteria for development of antibiotic resistance. PMID:26370618

  7. 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.

  8. Dissolved Oxygen a practical guide to dissolved oxygen measurements

    E-print Network

    Serianni, Anthony S.

    ..............................................................................................5 YsI optical Dissolved oxygen Instruments ............................................6 optical sensing element............................................................................7 How

  9. Freely propagating open premixed turbulent flames stabilized by swirl

    SciTech Connect

    Chan, C.K.; Lau, K.S.; Chin, W.K.; Cheng, R.K.

    1991-12-01

    A novel means has been developed for using weak swirl to stabilize freely propagating open premixed turbulent flames (swirl numbers between 0.05 to 0.3). By injecting a small amount of air tangentially into the co-flow of a concentric burner, stationary flames can be maintained above the burner exit for a large range of mixture, turbulence and flow conditions. The absence of physical surfaces in the vicinity of the flame provides free access to laser diagnostics. Laser Doppler anemometry and laser Mie scattering measurements of four flames with and without incident turbulence show that their features are typical of wrinkled laminar flames. The most distinct characteristics is that flame stabilization does not rely on flow recirculation. Centrifugal force induced by swirl causes flow divergence, and the flame is maintained at where the local mass flux balances the burning rate. The flame speeds can be estimated based on the centerline velocity vector, which is locally normal to the flame brush. This flame geometry is the closest approximation to the 1-D planar flame for determining fundamental properties to advance turbulent combustion theories. 18 refs.

  10. Flagellar waveform dynamics of freely swimming algal cells

    E-print Network

    Kurtuldu, H.

    We present quantitative measurements of time-dependent flagellar waveforms for freely swimming biflagellated algal cells, for both synchronous and asynchronous beating. We use the waveforms in conjunction with resistive ...

  11. 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…

  12. 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 ...

  13. The marine biogeochemistry of dissolved and colloidal iron

    E-print Network

    Fitzsimmons, Jessica Nicole

    2013-01-01

    Iron is a redox active trace metal micronutrient essential for primary production and nitrogen acquisition in the open ocean. Dissolved iron (dFe) has extremely low concentrations in marine waters that can drive phytoplankton ...

  14. DISSOLVED OXYGEN, TEMPERATURE, SURVIVAL OF YOUNG AT FISH SPAWNING SITES

    EPA Science Inventory

    Fluctuations of dissolved oxygen concentrations and water temperatures in their natural spawning sites were measured during embryo through larva stages of northern pike (Esox lucius), and during embryo and sac larva stages of bluegills (Lepomis macrochirus) and pumpkinseeds (Lepo...

  15. EFFECTS OF TEMPERATURE VARIATION ON CRITICAL STREAM DISSOLVED OXYGEN

    EPA Science Inventory

    The classical assumption that the lowest dissolved oxygen (DO) occurs at the highest temperature may not always hold. The DO saturation concentration decreases monotonically with increasing temperature, lowering the DO, but the reaeration coefficient increases monotonically with ...

  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. Long-time tails in freely cooling granular gases

    E-print Network

    Hisao Hayakawa; Michio Otsuki

    2007-08-28

    The long-time behavior of the current auto-correlation functions for the velocity, the shear stress and the heat flux is investigated in freely cooling granular gases. It is found that the correlation functions for the velocity and the shear stress have the long-time tails obeying $\\tau^{-d/2}$, while the correlation function of heat flux decays as $\\tau^{-(d+2)/2} \\exp(-\\zeta^* \\tau)$ with the dimensionless cooling rate $\\zeta^*$, the spatial dimension $d$ and the scaled time $\\tau$ in terms of the collision frequency. The result of our numerical simulation of the freely cooling granular gases is consistent with the theoretical prediction.

  18. Growth, metabolic activity, and productivity of immobilized and freely suspended CHO cells in perfusion culture.

    PubMed

    Hilal-Alnaqbi, Ali; Hu, Alan Y C; Zhang, Zhibing; Al-Rubeai, Mohamed

    2013-01-01

    Chinese hamster ovary (CHO) cells producing ?-galactosidase (?-gal) were successfully cultured on silicone-based porous microcarriers (ImmobaSil FS) in a 1 L stirred-tank perfusion bioreactor. We studied the growth, metabolism, and productivity of free and immobilized cells to understand cellular activity in immobilized conditions. CHO cells attached to ImmobaSil FS significantly better than to other microcarriers. Scanning electron microscope images showed that the CHO cells thoroughly colonized the porous surfaces of the ImmobaSil FS, exhibiting a spherical morphology with microvilli that extended to anchorage cells on the silicone surface. In perfusion culture, the concentration of the attached cells reached 8 × 10(8) cells/mL of carrier, whereas those that remained freely suspended reached 2 × 10(7) cells/mL medium. The ?-gal concentration reached more than 5 unit/mL in perfusion culture, more than fivefold that of batch culture. The maximum concentration per microcarrier was proportional to the initial cell density. The specific growth rate, the specific ?-gal production rate, the percentage of S phase, and the oxygen uptake rate were all relatively lower for immobilized cells than freely suspended cells in the same bioreactor, indicating that not only do cells survive and grow to a greater extent in a free suspension state, but they are also metabolically more active than viable cells inside the pores of the microcarriers. PMID:23701045

  19. The equation xp and groups that act freely

    E-print Network

    Brady, Noel

    and CAT(-1) groups which do not act freely on any -tree. 2000 Mathematics Subject Classification: 20E08, 20F65. Key words: free actions, -trees, hyperbolic groups, CAT(-1). 1 Introduction There has recently on the exponents. We would like to point out one intriguing difference in the behaviour of the equation x2y2 = z2

  20. 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 (?56Fe) 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 ?56Fe 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.

  1. 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

  2. Magnetic tracking of eye position in freely behaving chickens

    PubMed Central

    Schwarz, Jason S.; Sridharan, Devarajan; Knudsen, Eric I.

    2013-01-01

    Research on the visual system of non-primates, such as birds and rodents, is increasing. Evidence that neural responses can differ dramatically between head-immobilized and freely behaving animals underlines the importance of studying visual processing in ethologically relevant contexts. In order to systematically study visual responses in freely behaving animals, an unobtrusive system for monitoring eye-in-orbit position in real time is essential. We describe a novel system for monitoring eye position that utilizes a head-mounted magnetic displacement sensor coupled with an eye-implanted magnet. This system is small, lightweight, and offers high temporal and spatial resolution in real time. We use the system to demonstrate the stability of the eye and the stereotypy of eye position during two different behavioral tasks in chickens. This approach offers a viable alternative to search coil and optical eye tracking techniques for high resolution tracking of eye-in-orbit position in behaving animals. PMID:24312023

  3. Characterization of Urban Runoff Pollution between Dissolved and Particulate Phases

    PubMed Central

    Wei, Zhang; Simin, Li; Fengbing, Tang

    2013-01-01

    To develop urban stormwater management effectively, characterization of urban runoff pollution between dissolved and particulate phases was studied by 12 rainfall events monitored for five typical urban catchments. The average event mean concentration (AEMC) of runoff pollutants in different phases was evaluated. The AEMC values of runoff pollutants in different phases from urban roads were higher than the ones from urban roofs. The proportions of total dissolved solids, total dissolved nitrogen, and total dissolved phosphorus in total ones for all the catchments were 26.19%–30.91%, 83.29%–90.51%, and 61.54–68.09%, respectively. During rainfall events, the pollutant concentration at the initial stage of rainfall was high and then sharply decreased to a low value. Affected by catchments characterization and rainfall distribution, the highest concentration of road pollutants might appear in the later period of rainfall. Strong correlations were also found among runoffs pollutants in different phases. Total suspended solid could be considered as a surrogate for particulate matters in both road and roof runoff, while dissolved chemical oxygen demand could be regarded as a surrogate for dissolved matters in roof runoff. PMID:23935444

  4. FIELD MEASUREMENT OF DISSOLVED OXYGEN: A COMPARISON OF METHODS

    EPA Science Inventory

    The ability to confidently measure the concentration of dissolved oxygen (D.O.) in ground water is a key aspect of remedial selection and assessment. Presented here is a comparison of the commonly practiced methods for determining D.O. concentrations in ground water, including c...

  5. Distribution of dissolved silver in marine waters

    NASA Astrophysics Data System (ADS)

    Barriada, J. L.; Achterberg, E. P.; Tappin, A.; Truscott, J.

    2003-04-01

    Silver is one of the most toxic heavy metals, surpassed only by mercury [1-3]. Monitoring of dissolved silver concentrations in natural waters is therefore of great importance. The determination of dissolved silver in waters is not without challenges, because of its low (picomolar) concentrations. Consequently, there are only a few reported studies in marine waters, which have been performed in USA [4-6] and Japan [7]. The analytical techniques used in the reported studies for the determination of silver in seawater were Graphite Furnace Atomic Absorption Spectroscopy (GFAAS) after solvent extraction [2,4,5], and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after solvent extraction or solid phase extraction [7,8]. In this contribution, we will present an optimised Magnetic Sector (MS) ICP-MS technique for the determination of dissolved silver in marine waters. The MS-ICP-MS method used anion exchange column to preconcentrate silver from saline waters, and to remove the saline matrix. The ICP-MS method has been used successfully to determine total dissolved silver in estuarine and oceanic samples. Bibliography 1. H. T. Ratte, Environ. Toxicol. Chem. 1999, 18: p. 89-108. 2. R. T. Herrin, A. W. Andren and D. E. Armstrong, Environ. Sci. Technol. 2001, 35: 1953-1958. 3. D. E. Schildkraut, P. T. Dao, J. P. Twist, A. T. Davis and K. A. Robillard, Environ. Toxicol. Chem. 1998, 17: 642-649. 4. E. Breuer, S. A. Sanudo-Wilhelmy and R. C. Aller, Estuaries. 1999, 22:603-615. 5. A. R. Flegal, S. A. Sanudowilhelmy and G. M. Scelfo, Mar. Chem. 1995, 49: 315-320. 6. S. N. Luoma, Y. B. Ho and G. W. Bryan, Mar. Pollut. Bull. 1995, 31: 44-54. 7. Y. Zhang, H. Amakawa and Y. Nozaki, Mar. Chem. 2001, 75: 151-163. 8. L. Yang and R. E. Sturgeon, J. Anal. At. Spectrom. 2002, 17: 88-93.

  6. Occurrence and potential combined toxicity of dissolved organic contaminants in the Forth estuary and Firth of Forth, Scotland assessed using passive samplers and an algal toxicity test.

    PubMed

    Emelogu, Emmanuel S; Pollard, Pat; Dymond, Peter; Robinson, Craig D; Webster, Lynda; McKenzie, Craig; Dobson, Judy; Bresnan, Eileen; Moffat, Colin F

    2013-09-01

    As an alternative procedure to conventional water quality assessment, the presence and combined toxicity of dissolved organic contaminants in water at five sites in the Forth estuary and the Firth of Forth, Scotland, United Kingdom was investigated using silicone rubber passive sampling devices (SR-PSDs) and an algal growth inhibition bioassay. SR-PSDs were deployed in water at the five sites for ~2 months. Following retrieval, extracts from the deployed SR-PSDs were assessed for both algal growth inhibition and the occurrence of a wide range of organic contaminants, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and a variety of plant protection products (PPPs; commonly referred to collectively as 'pesticides'). The 72 h algal growth inhibition test was performed using a native marine phytoplankton (Diacronema lutheri) in 24 well microplates. Freely dissolved (e.g. bioavailable) concentrations of PAHs and PCBs were determined using performance reference compounds (PRCs). The algal toxicity tests exhibited varied effects at the five sites indicating the presence of, and exposure to, phytotoxic compounds and their potential toxicity in the Forth. The individual and total dissolved concentrations of 40 PAHs and 32 PCBs measured in the study were relatively low and showed input of petrogenic, atmospheric and sewage related sources. Several pesticides of diverse polarities were identified in the water suggesting sources from both riverine input and direct discharges. The study thus illustrates the value of combining bioassays and chemical analysis (with effective sampling technique) for a realistic and rapid assessment of organic contaminants in the aquatic environment. PMID:23728064

  7. Dissolved organic matter discharge in the six largest arctic rivers-chemical composition and seasonal variability 

    E-print Network

    Rinehart, Amanda J.

    2009-05-15

    watershed characteristics influence DOM composition. Dissolved organic carbon (DOC) concentrations followed the hydrograph with highest concentrations measured during peak river flow. The chemical composition of peak-flow DOM indicates a dominance of freshly...

  8. Wastewater Discharge, Nutrient Loading, and Dissolved Oxygen Dynamics in a Shallow Texas Bay 

    E-print Network

    Schroer, Lee Allen

    2014-05-07

    . Variables measured were water temperature (oC), pH, salinity (ppt), conductivity (mS), depth (meters), turbidity (nephilometric turbidity units), dissolved oxygen in both % saturation and concentration (mg/L), and chlorophyll-? concentration (?g/L). Grab...

  9. Single-molecule-sensitive fluorescence resonance energy transfer in freely-diffusing attoliter droplets

    NASA Astrophysics Data System (ADS)

    Rahmanseresht, Sheema; Milas, Peker; Ramos, Kieran P.; Gamari, Ben D.; Goldner, Lori S.

    2015-05-01

    Fluorescence resonance energy transfer (FRET) from individual, dye-labeled RNA molecules confined in freely-diffusing attoliter-volume aqueous droplets is carefully compared to FRET from unconfined RNA in solution. The use of freely-diffusing droplets is a remarkably simple and high-throughput technique that facilitates a substantial increase in signal-to-noise for single-molecular-pair FRET measurements. We show that there can be dramatic differences between FRET in solution and in droplets, which we attribute primarily to an altered pH in the confining environment. We also demonstrate that a sufficient concentration of a non-ionic surfactant mitigates this effect and restores FRET to its neutral-pH solution value. At low surfactant levels, even accounting for pH, we observe differences between the distribution of FRET values in solution and in droplets which remain unexplained. Our results will facilitate the use of nanoemulsion droplets as attoliter volume reactors for use in biophysical and biochemical assays, and also in applications such as protein crystallization or nanoparticle synthesis, where careful attention to the pH of the confined phase is required.

  10. Single-molecule-sensitive fluorescence resonance energy transfer in freely-diffusing attoliter droplets

    SciTech Connect

    Rahmanseresht, Sheema; Ramos, Kieran P.; Gamari, Ben D.; Goldner, Lori S.; Milas, Peker

    2015-05-11

    Fluorescence resonance energy transfer (FRET) from individual, dye-labeled RNA molecules confined in freely-diffusing attoliter-volume aqueous droplets is carefully compared to FRET from unconfined RNA in solution. The use of freely-diffusing droplets is a remarkably simple and high-throughput technique that facilitates a substantial increase in signal-to-noise for single-molecular-pair FRET measurements. We show that there can be dramatic differences between FRET in solution and in droplets, which we attribute primarily to an altered pH in the confining environment. We also demonstrate that a sufficient concentration of a non-ionic surfactant mitigates this effect and restores FRET to its neutral-pH solution value. At low surfactant levels, even accounting for pH, we observe differences between the distribution of FRET values in solution and in droplets which remain unexplained. Our results will facilitate the use of nanoemulsion droplets as attoliter volume reactors for use in biophysical and biochemical assays, and also in applications such as protein crystallization or nanoparticle synthesis, where careful attention to the pH of the confined phase is required.

  11. On the losses of dissolved CO(2) during champagne serving.

    PubMed

    Liger-Belair, Gérard; Bourget, Marielle; Villaume, Sandra; Jeandet, Philippe; Pron, Hervé; Polidori, Guillaume

    2010-08-11

    Pouring champagne into a glass is far from being consequenceless with regard to its dissolved CO(2) concentration. Measurements of losses of dissolved CO(2) during champagne serving were done from a bottled Champagne wine initially holding 11.4 +/- 0.1 g L(-1) of dissolved CO(2). Measurements were done at three champagne temperatures (i.e., 4, 12, and 18 degrees C) and for two different ways of serving (i.e., a champagne-like and a beer-like way of serving). The beer-like way of serving champagne was found to impact its concentration of dissolved CO(2) significantly less. Moreover, the higher the champagne temperature is, the higher its loss of dissolved CO(2) during the pouring process, which finally constitutes the first analytical proof that low temperatures prolong the drink's chill and helps it to retain its effervescence during the pouring process. The diffusion coefficient of CO(2) molecules in champagne and champagne viscosity (both strongly temperature-dependent) are suspected to be the two main parameters responsible for such differences. Besides, a recently developed dynamic-tracking technique using IR thermography was also used in order to visualize the cloud of gaseous CO(2) which flows down from champagne during the pouring process, thus visually confirming the strong influence of champagne temperature on its loss of dissolved CO(2). PMID:20681665

  12. Leachability of dissolved chromium in asphalt and concrete surfacing materials.

    PubMed

    Kayhanian, Masoud; Vichare, Akshay; Green, Peter G; Harvey, John

    2009-08-01

    Leachate metal pollutant concentrations produced from different asphalt and concrete pavement surfacing materials were measured under controlled laboratory conditions. The results showed that, in general, the concentrations of most metal pollutants were below the reporting limits. However, dissolved chromium was detected in leachate from concrete (but not asphalt) specimens and more strongly in the early-time leachate samples. As the leaching continued, the concentration of Cr decreased to below or close to the reporting limit. The source of the chromium in concrete pavement was found to be cement. The concentration of total Cr produced from leachate of different cement coming from different sources that was purchased from retail distributors ranged from 124 to 641mug/L. This result indicates that the potential leachability of dissolved Cr from concrete pavement materials can be reduced through source control. The results also showed that the leachability of dissolved Cr in hardened pavement materials was substantially reduced. For example, the concentration of dissolved Cr measured in actual highway runoff was found to be much lower than the Cr concentration produced from leachate of both open and dense graded concrete pavement specimens under controlled laboratory study. It was concluded that pavement materials are not the source of pollutants of concern in roadway runoff; rather most pollutants in roadway surface runoff are generated from other road-use or land-use sources, or from (wet or dry) atmospheric deposition. PMID:19604624

  13. 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...

  14. The Role of Dissolved Oxygen in Hard Clam Aquaculture1 Kerry Weber, Elise Hoover, Leslie Sturmer, and Shirley Baker2

    E-print Network

    Florida, University of

    the brown-black iodine color disappears. The concentration of dissolved oxygen can be calculated fromFA152 The Role of Dissolved Oxygen in Hard Clam Aquaculture1 Kerry Weber, Elise Hoover, Leslie. Larry Arrington, Dean What Is Dissolved Oxygen? Oxygen is a chemical element and a major component (21

  15. Fate of polychlorinated biphenyls in a contaminated lake ecosystem: Combining equilibrium passive sampling of sediment and water with total concentration measurements of biota.

    PubMed

    Mäenpää, Kimmo; Leppänen, Matti T; Figueiredo, Kaisa; Mayer, Philipp; Gilbert, Dorothea; Jahnke, Annika; Gil-Allué, Carmen; Akkanen, Jarkko; Nybom, Inna; Herve, Sirpa

    2015-11-01

    Equilibrium sampling devices can be applied to study and monitor the exposure and fate of hydrophobic organic chemicals on a thermodynamic basis. They can be used to determine freely dissolved concentrations and chemical activity ratios and to predict equilibrium partitioning concentrations of hydrophobic organic chemicals in biota lipids. The authors' aim was to assess the equilibrium status of polychlorinated biphenyls (PCBs) in a contaminated lake ecosystem and along its discharge course using equilibrium sampling devices for measurements in sediment and water and by also analyzing biota. The authors used equilibrium sampling devices (silicone rubber and polyethylene [PE]) to determine freely dissolved concentrations and chemical activities of PCBs in the water column and sediment porewater and calculated for both phases the corresponding equilibrium concentrations and chemical activities in model lipids. Overall, the studied ecosystem appeared to be in disequilibrium for the studied phases: sediment, water, and biota. Chemical activities of PCBs were higher in sediment than in water, which implies that the sediment functioned as a partitioning source of PCBs and that net diffusion occurred from the sediment to the water column. Measured lipid-normalized PCB concentrations in biota were generally below equilibrium lipid concentrations relative to the sediment (CLip ?Sed ) or water (CLip ?W ), indicating that PCB levels in the organisms were below the maximum partitioning levels. The present study shows the application versatility of equilibrium sampling devices in the field and facilitates a thermodynamic understanding of exposure and fate of PCBs in a contaminated lake and its discharge course. Environ Toxicol Chem 2015;34:2463-2474. © 2015 SETAC. PMID:26053463

  16. Modeling and Understanding Combination pMDI Formulations with Both Dissolved and Suspended Drugs.

    PubMed

    Stein, Stephen W; Sheth, Poonam; Younis, Usir S; Mogalian, Erik; Myrdal, Paul B

    2015-09-01

    A simulation model has been established to predict the residual aerodynamic particle size distribution (APSD) of dual-component pressurized metered dose inhalers (pMDIs). More specifically, this model estimates the APSD of pMDI formulations containing dissolved and suspended compounds for various formulations, and has been verified experimentally. Simulated and experimental data illustrate that APSDs of the dissolved and suspended components of the pMDI are influenced by concentrations of the dissolved and micronized suspended drugs, along with suspended drug size. Atomized droplets from such combination formulations may contain varying number of suspended drug particles and a representative concentration of dissolved drug. These sub-populations of atomized droplets may explain the residual APSDs. The suspended drug follows a monomodal, lognormal distribution and is more greatly impacted by the size and concentration of the suspended drug in comparison to the concentration of dissolved drug. On the other hand, dissolved drug illustrates a bimodal, lognormal residual particle size distribution both theoretically and experimentally. The smaller mode consists of residual particles made of dissolved drug only, while the larger mode consists of residual particles that contain both dissolved and suspended drugs. The model effectively predicted the size distributions of both the dissolved and suspended components of combination formulations (r(2) value of 0.914 for the comparison of simulated versus experimental MMAD values for the formulations examined). The results demonstrate that this model is a useful tool that may be able to expedite the development of combination pMDI formulation. PMID:26258647

  17. A freely falling magneto-optical trap drop tower experiment

    NASA Astrophysics Data System (ADS)

    Könemann, T.; Brinkmann, W.; Göklü, E.; Lämmerzahl, C.; Dittus, H.; van Zoest, T.; Rasel, E. M.; Ertmer, W.; Lewoczko-Adamczyk, W.; Schiemangk, M.; Peters, A.; Vogel, A.; Johannsen, G.; Wildfang, S.; Bongs, K.; Sengstock, K.; Kajari, E.; Nandi, G.; Walser, R.; Schleich, W. P.

    2007-12-01

    We experimentally demonstrate the possibility of preparing ultracold atoms in the environment of weightlessness at the earth-bound short-term microgravity laboratory Drop Tower Bremen, a facility of ZARM - University of Bremen. Our approach is based on a freely falling magneto-optical trap (MOT) drop tower experiment performed within the ATKAT collaboration (“Atom-Catapult”) as a preliminary part of the QUANTUS pilot project (“Quantum Systems in Weightlessness”) pursuing a Bose-Einstein condensate (BEC) in microgravity at the drop tower [1, 2]. Furthermore we give a complete account of the specific drop tower requirements to realize a compact and robust setup for trapping and cooling neutral rubidium 87Rb atoms in microgravity conditions. We also present the results of the first realized freely falling MOT and further accomplished experiments during several drops. The goal of the preliminary ATKAT pilot project is to initiate a basis for extended atom-optical experiments which aim at realizing, observing and investigating ultracold quantum matter in microgravity.

  18. Wireless Neural Stimulation in Freely Behaving Small Animals

    PubMed Central

    Arfin, Scott K.; Long, Michael A.; Fee, Michale S.; Sarpeshkar, Rahul

    2009-01-01

    We introduce a novel wireless, low-power neural stimulation system for use in freely behaving animals. The system consists of an external transmitter and a miniature, implantable wireless receiver–stimulator. The implant uses a custom integrated chip to deliver biphasic current pulses to four addressable bipolar electrodes at 32 selectable current levels (10 ?A to 1 mA). To achieve maximal battery life, the chip enters a sleep mode when not needed and can be awakened remotely when required. To test our device, we implanted bipolar stimulating electrodes into the songbird motor nucleus HVC (formerly called the high vocal center) of zebra finches. Single-neuron recordings revealed that wireless stimulation of HVC led to a strong increase of spiking activity in its downstream target, the robust nucleus of the arcopallium. When we used this device to deliver biphasic pulses of current randomly during singing, singing activity was prematurely terminated in all birds tested. Thus our device is highly effective for remotely modulating a neural circuit and its corresponding behavior in an untethered, freely behaving animal. PMID:19386759

  19. Structure and Dynamics of Freely Suspended Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Clark, Noel A.

    2004-01-01

    Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1 D) periodic arrays of layers, each layer being between one and two molecular lengths thick. In the least ordered smectic phases, the smectics A and C, each layer is a two dimensional (2D) liquid. Additionally there are a variety of more ordered smectic phases having hexatic short range translational order or 2D crystalline or quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enables the long term stabilization of freely suspended, single component, layered fluid films as thin as 30A, a single molecular layer. The layering forces the films to be an integral number of smectic layers thick, quantizing their thickness in layer units and forcing a film of a particular number of layers to be physically homogeneous with respect to its layer structure over its entire area. Optical reflectivity enables the precise determination of the number of layers. These ultrathin freely suspended liquid crystal films are structures of fundamental interest in condensed matter and fluid physics. They are the thinnest known stable fluid structures and have the largest surface-to-volume ratio of any stable fluid preparation, making them ideal for the study of the effects of reduced dimensionality on phase behavior and on fluctuation and interface phenomena. Their low vapor pressure and quantized thickness enable the effective use of microgravity to extend the study of basic capillary phenomena to ultrathin fluid films. Freely suspended films have been a wellspring of new LC physics. They have been used to provide unique experimental conditions for the study of condensed phase transitions in two dimensions. They are the only system in which the hexatic has been unambiguously identified as a phase of matter, and the only physical system in which fluctuations of a 2D XY system and Kosterlitz Thouless phase transition has been observed and 2D XY quasi long range order verified. Smectic films have enabled the precise determination of smectic layer electron density and positional fluctuation profiles and have been used to show that the interlayer interactions in antiferroelectric tilted smectics do not extend significantly beyond nearest neighbors. Freely suspended films played a pivotal role in the recent discovery of macroscopic chiral-polar ordering in fluids of achiral molecules. The interactions which are operative in liquid crystals are generally weak in comparison to those in crystalline phases, leading to the facile manipulation of the order in liquid crystals by external agents such as applied fields and surfaces. Effects arising from weak ordering are significantly enhanced in ultrathin free films and filaments, in which the intermolecular coupling is effectively further reduced by loss of neighbors. Over the past four years this research, which we now detail, has produced a host of exciting new discoveries and unexpected results, maintaining the study of freely suspended liquid crystal structures as one of most exciting and fruitful areas of complex fluid physics. In addition, a class of experiments on the behavior of 1D interfaces in 2D films have been pursued with results that point to potentially quite interesting effects in microgravity.

  20. Cruise summary for P-1-02-SC: acoustic imaging of natural oil and gas seeps and measurement of dissolved methane concentration in coastal waters near Pt. Conception, California

    USGS Publications Warehouse

    Lorenson, T.D.; Dougherty, Jennifer A.; Ussler, William, III; Paull, Charles K.

    2003-01-01

    Water-column acoustic anomalies and methane concentrations were documented in coastal waters surrounding Pt. Conception, California, in March 2002. The purpose of this survey, supported by the Minerals Management Service, was to locate active oil and gas seeps in the area as a background for further studies to determine hydrocarbon flux, mainly oil, into the environment. Objectives in reaching this goal are to (1) document the locations and geochemically fingerprint natural seeps within the offshore southern Santa Maria Basin; (2) geochemically fingerprint coastal tar residues and potential sources, both onshore and offshore, in this region; (3) establish chemical correlations between offshore active seeps and coastal residues thus linking seep sources to oil residues; (4) measure the rate of natural seepage of individual seeps and attempt to assess regional natural oil and gas seepage rates; (5) attempt to predict transport pathways of oil from seep sources to the coastline and; (6) interpret the petroleum system history for the natural seeps. This survey, addressing objective 1, focused on the area from offshore Surf Beach to the north and Gaviota to the south in water depths ranging from 20 to 500m. In addition, nine stations were sampled outside this area to provide a regional context. Water-column methane concentrations were measured in water samples collected from the R/V Point Sur with Niskin bottles from various depths. A total of 724 water samples from 94 stations were collected.

  1. The effects of dissolved methane upon liquid argon scintillation light

    NASA Astrophysics Data System (ADS)

    Jones, B. J. P.; Alexander, T.; Back, H. O.; Collin, G.; Conrad, J. M.; Greene, A.; Katori, T.; Pordes, S.; Toups, M.

    2013-12-01

    In this paper we report on measurements of the effects of dissolved methane upon argon scintillation light. We monitor the light yield from an alpha source held 20 cm from a cryogenic photomultiplier tube (PMT) assembly as methane is injected into a high-purity liquid argon volume. We observe significant suppression of the scintillation light yield by dissolved methane at the 10 part per billion (ppb) level. By examining the late scintillation light time constant, we determine that this loss is caused by an absorption process and also see some evidence of methane-induced scintillation quenching at higher concentrations (50-100 ppb). Using a second PMT assembly we look for visible re-emission features from the dissolved methane which have been reported in gas-phase argon methane mixtures, and we find no evidence of visible re-emission from liquid-phase argon methane mixtures at concentrations between 10 ppb and 0.1%.

  2. Solid-Phase Speciation of Arsenic As the Primary Control on Dissolved As Concentrations in a Glacial Aquifer System: Quantifying Speciation of Arsenic in Glacial Aquifer Solids with ?XAS Mapping.

    NASA Astrophysics Data System (ADS)

    Nicholas, S. L.; Gowan, A. S.; Knaeble, A. R.; Erickson, M. L.; Woodruff, L. G.; Marcus, M.; Toner, B. M.

    2014-12-01

    Western Minnesota, USA, is a regional locus of drinking-water wells with high arsenic (As) (As>10µgL-1). Arsenic concentrations vary widely among neighboring wells with otherwise similar water chemistry [1,2]. As(III) should be the most mobile As species in Minnesota well waters (median Eh in As affected wells is -50mV). This As is geogenic, sourced from glacial deposits derived from Cretaceous sedimentary bedrock (dolostone, limestone, shale). Our hypothesis is that As speciation in the solid phase is the important factor controlling the introduction of As to groundwater—more significant in this region than absolute As concentrations or landscape variability. Our previous research used micro-X-ray absorption spectroscopy (µXAS) speciation mapping [3] on archived glacial tills (stored dry at room temperature in air). µXAS results from this material showed that As in a reduced chemical state within the till aquitard is spatially correlated with iron sulfide at the micron scale. Conversley, As in aquifer sediments was mainly oxidized As(V). At the aquifer-aquitard contact As was observed as a mixture of both reduced and oxidized forms. This suggests that the aquifer-aquitard contact is a geochemically active zone in which reduced As species present within glacial till are converted to As(V) through complex redox processes, and subsequently release into aquifer sediments. Our current research applies the same methods to describe As speciation in samples collected from fresh cores of glacial sediment and frozen under argon in the field. Preliminary results are similar to our previous work in that As is, in general, more reduced in aquitard sediments, and more oxidized at the contact and in aquifer sediments. Arsenic(III) was preserved as a minor consitutent in ambient archived cores but is a more significant constituent in fresh, anaerobically preserved cores. Results will be presented comparing anaerobic samples with ambient-air aliquots of the same sample to document changes in the relative abundance of As species depending on sample preservation. This work was supported by LBNL-ALS, ANL-APS, USGS-MNWSC, MGS, and CURA. [1]Berndt & Soule (1999) Minnesota Arsenic Research Study: Report on Geochemistry. [2] Erickson & Barnes (2005) Water Research 39 4029-4039. [3] Toner et al. (2014) Env. Chem. 11 4-9.

  3. 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.

  4. Novel System for Continuous Measurements of Dissolved Gases in Liquids

    NASA Astrophysics Data System (ADS)

    Baer, D. S.; Liem, J.; Owano, T. G.; Gupta, M.

    2014-12-01

    Measurements of dissolved gases in lakes, rivers and oceans may be used to quantify underwater greenhouse gas generation, air-surface exchange, and pollution migration. Studies involving quantification of dissolved gases typically require obtaining water samples (from streams, lakes, or ocean water) and transporting them to a laboratory, where they are degased. The gases obtained are then generally measured using gas chromatography and isotope ratio mass spectrometry for concentrations and isotope ratios, respectively. This conventional, off-line, discrete-sample methodology is time consuming and labor intensive, and thus severely inhibits detailed spatial and temporal mapping of dissolved gases. In this work, we describe the commercial development of a new portable membrane-based gas extraction system (18.75" x 18.88" x 10.69", 16 kg, 85 watts) that interfaces directly to our cavity enhanced laser absorption based (or Off-Axis ICOS) gas analyzers to continuously and quickly measure concentrations and isotope ratios of dissolved gases. By accurately controlling the water flow rate through the membrane contactor, gas pressure on the outside and water pressure on the inside of the membrane, the system can generate precise and highly reproducible results. Furthermore, the gas-phase mole fractions (parts per million, ppm) may be converted into dissolved gas concentrations (nM), by accurately measuring the gas flow rates in and out of the extraction system. We will present detailed laboratory test data that quantifies the performance (linearity, precision, and dynamic range) of the system for measurements of the concentrations and isotope ratios of dissolved greenhouse gases (methane, carbon dioxide, and nitrous oxide) continuously and in real time.

  5. 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.

  6. 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.

  7. The near wake of a freely flying European starling

    NASA Astrophysics Data System (ADS)

    Kirchhefer, Adam J.; Kopp, Gregory A.; Gurka, Roi

    2013-05-01

    The wake of a freely flying European starling (Sturnus vulgaris) has been measured using high speed, time-resolved, particle image velocimetry, simultaneously with high speed cameras which imaged the bird. These have been used to generate vector maps that can be associated with the bird's location and wing configuration in the wind tunnel. Time series of measurements have been expressed as composite wake plots which depict segments of the wing beat cycle for various spanwise locations in the wake. Measurements indicate that downwash is not produced during the upstroke, suggesting that the upstroke does not generate lift. As well, the wake velocities imply the presence of streamwise vortical structures, in addition to tip vortices. These two characteristics indicate similarities between the wake of a bird and the wake of a bat, which may be general features of the wakes of flapping wings.

  8. Structure, Hydrodynamics, and Phase Transition of Freely Suspended Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Clark, Noel A.

    2000-01-01

    Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1D) periodic arrays of layers, each layer being between one and two molecular lengths thick. In the least ordered smectic phases, the smectics A and C, each layer is a two dimensional (2D) liquid. Additionally there are a variety of more ordered smectic phases having hexatic short range translational order or 2D crystalline quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enable the long term stabilization of freely suspended, single component, layered fluid films as thin as 30A, a single molecular layer. The layering forces the films to be an integral number of smectic layers thick, quantizing their thickness in layer units and forcing a film of a particular number of layers to be physically homogeneous with respect to its layer structure over its entire area. Optical reflectivity enables the precise determination of the number of layers. These ultrathin freely suspended liquid crystal films are structures of fundamental interest in condensed matter and fluid physics. They are the thinnest known stable condensed phase fluid structures and have the largest surface-to-volume ratio of any stable fluid preparation, making them ideal for the study of the effects of reduced dimensionality on phase behavior and on fluctuation and interface phenomena. Their low vapor pressure and quantized thickness enable the effective use of microgravity to extend the study of basic capillary phenomena to ultrathin fluid films. Freely suspended films have been a wellspring of new liquid crystal physics. They have been used to provide unique experimental conditions for the study of condensed phase transitions in two dimensions. They are the only system in which the hexatic has been unambiguously identified as a phase of matter, and the only physical system in which fluctuations of a 2D XY system and Kosterlitz Thouless phase transition has been observed and 2D XY quasi long range order verified. Smectic films have enabled the precise determination of smectic layer electron density and positional fluctuation profile and have been used to show that the interlayer interactions in anti-ferroelectric tilted smectics do not extend significantly beyond nearest neighbors. The interactions which are operative in liquid crystals are generally weak in comparison to those in crystalline phases, leading to the facile manipulation of the order in liquid crystals by external agents such as applied fields and surfaces. Effects arising from weak ordering are significantly enhanced in ultrathin free films and filaments wherein the intermolecular coupling is effectively reduced by loss of neighbors. Over the past four years this research, which we now detail, has produced a host of exciting new discoveries and unexpected results, maintaining the position of the study of freely suspended liquid crystal structures as one of most exciting and fruitful areas of complex fluid physics. In addition, several potentially interesting microgravity free film experiments have been identified.

  9. Chronic detachable headphones for acoustic stimulation in freely moving animals

    PubMed Central

    Nodal, Fernando R.; Keating, Peter; King, Andrew J.

    2010-01-01

    A growing number of studies of auditory processing are being carried out in awake, behaving animals, creating a need for precisely controlled sound delivery without restricting head movements. We have designed a system for closed-field stimulus presentation in freely moving ferrets, which comprises lightweight, adjustable headphones that can be consistently positioned over the ears via a small, skull-mounted implant. The invasiveness of the implant was minimized by simplifying its construction and using dental adhesive only for attaching it to the skull, thereby reducing the surgery required and avoiding the use of screws or other anchoring devices. Attaching the headphones to a chronic implant also reduced the amount of contact they had with the head and ears, increasing the willingness of the animals to wear them. We validated sound stimulation via the headphones in ferrets trained previously in a free-field task to localize stimuli presented from one of two loudspeakers. Noise bursts were delivered binaurally over the headphones and interaural level differences (ILDs) were introduced to allow the sound to be lateralized. Animals rapidly transferred from the free-field task to indicate the perceived location of the stimulus presented over headphones. They showed near perfect lateralization with a 5 dB ILD, matching the scores achieved in the free-field task. As expected, the ferrets’ performance declined when the ILD was reduced in value. This closed-field system can easily be adapted for use in other species, and provides a reliable means of presenting closed-field stimuli whilst monitoring behavioral responses in freely moving animals. PMID:20346981

  10. Respiratory sinus arrhythmia in freely moving and anesthetized rats.

    PubMed

    Bouairi, Evguenia; Neff, Robert; Evans, Cory; Gold, Allison; Andresen, Michael C; Mendelowitz, David

    2004-10-01

    Heart rate increases during inspiration and slows during postinspiration; this respiratory sinus arrhythmia helps match pulmonary blood flow to lung inflation and maintain an appropriate diffusion gradient of oxygen in the lungs. This cardiorespiratory pattern is found in neonatal and adult humans, baboons, dogs, rabbits, and seals. Respiratory sinus arrhythmia occurs mainly due to inhibition of cardioinhibitory parasympathetic cardiac vagal neurons during inspiration. Surprisingly, however, a recent study in anesthetized rats paradoxically found an enhancement of cardiac vagal activity during inspiration, suggesting that rats have an inverted respiratory sinus arrhythmia (Rentero N, Cividjian A, Trevaks D, Pequignot JM, Quintin L, and McAllen RM. Am J Physiol Regul Integr Comp Physiol 283: R1327-R1334, 2002). To address this controversy, this study examined respiratory sinus arrhythmia in conscious freely moving rats and tested whether the commonly used experimental anesthetics urethane, pentobarbital sodium, or ketamine-xylazine alter respiratory sinus arrhythmia. Heart rate significantly increased 21 beats/min during inspiration in conscious rats, a pattern similar to the respiratory sinus arrhythmia that occurs in other species. However, anesthetics altered normal respiratory sinus arrhythmia. Ketamine-xylazine (87 mg/kg and 13 mg/kg) depressed and pentobarbital sodium (60 mg/kg) abolished normal respiratory sinus arrhythmia. Urethane (1 g/kg) inverted the cardiorespiratory pattern so that heart rate significantly decreased during inspiration. Our study demonstrates that heart rate normally increases during inspiration in conscious, freely moving rats, similar to the respiratory sinus arrhythmia pattern that occurs in other species but that this pattern is disrupted in the presence of general anesthetics, including inversion in the case of urethane. The presence and consequences of anesthetics need to be considered in studying the parasympathetic control of heart rate. PMID:15155710

  11. Measurement of associations of pharmaceuticals with dissolved humic substances using solid phase extraction.

    PubMed

    Ding, Yunjie; Teppen, Brian J; Boyd, Stephen A; Li, Hui

    2013-04-01

    An innovative method was developed to determine association of carbadox, lincomycin and tetracycline with dissolved humic acids using solid phase extraction (SPE). Dissolved organic matter (DOM) and DOM-bound pharmaceuticals passed through the SPE cartridge while the cartridge retained freely dissolved pharmaceuticals from water. This method was validated by comparison with the results measured using the common equilibrium dialysis technique. For the SPE method pharmaceutical interaction with DOM required ?30h to approach the equilibration, whereas 50-120h was needed for the equilibrium dialysis technique. The uneven distributions of freely membrane-penetrating pharmaceuticals and protons inside vs. outside of the dialysis cell due to the Donnan effect resulted in overestimates of pharmaceutical affinity with DOM for the equilibrium dialysis method. The SPE technique eliminates the Donnan effect, and demonstrates itself as a more efficient, less laborious and more accurate method. The measured binding coefficients with DOM followed the order of carbadox

  12. TOTAL DISSOLVED AND BIOAVAILABLE METALS AT LAKE TEXOMA MARINAS

    EPA Science Inventory

    Dissolved metals in water and total metals in sediments have been measured at marina areas in Lake Texoma during June 1999 to October 2001, and October 2001, respectively. The metals most often found in the highest concentrations in marina water were Na and Ca, followed by Mg an...

  13. REDUCED DISSOLVED OXYGEN TEST SYSTEM FOR MARINE ORGANISMS

    EPA Science Inventory

    A flow-through test system was designed to examine minimum dissolved oxygen (D.O.) requirements of marine animals. he system provides up to six treatment concentrations between 0.3 mg D.O./I and saturation. ea water is degassed in a vacuum-evacuated packed column and the treatmen...

  14. MATHEMATICAL SIMULATION TOOLS FOR DEVELOPING DISSOLVED OXYGEN TMDLS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This paper presents an extended abstract of a research paper describing four commonly used dissolved oxygen (DO) simulation models. The concentration of DO in surface waters is one of the most commonly used indicators of river and stream health. Regulators and other professionals are increasingly r...

  15. 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...

  16. SIMULATION OF DISSOLVED OXYGEN PROFILES IN A TRANSPARENT, DIMICTIC LAKE

    EPA Science Inventory

    Thrush Lake is a small, highly transparent lake in northeastern Minnesota. rom 1986 to 1991, vertical profiles of water temperature, dissolved oxygen, chlorophyll a concentration, underwater light irradiance, and Secchi depths were measured at monthly intervals during the ice-fre...

  17. Influence of dissolved organic materials on turbid water optical properties and remote-sensing reflectance

    NASA Technical Reports Server (NTRS)

    Witte, W. G.; Whitlock, C. H.; Harriss, R. C.; Usry, J. W.; Poole, L. R.; Houghton, W. M.; Morris, W. D.; Gurganus, E. A.

    1982-01-01

    The effects of dissolved organic materials on turbid-water optical properties are assessed, by means of field measurements and laboratory simulations in which upwelled reflectance, attenuation, absorption, and backscatter spectral properties at wavelengths from 450 to 800 nm are examined in relation to water chemistry. The data show that dissolved organic materials decrease upwelled reflectance from turbid waters, and that the decrease in reflectance is a nonlinear function of concentration with the largest gradients at low carbon concentrations, depending on wavelength. Upwelled reflectance is found to be highly correlated with two backscatter-absorption parameters used in some optical models, which are nonlinear with dissolved organic material concentration change.

  18. 2011 Quantum Corporation. May be freely distributed in its entirety without modification. Quantum Corporation

    E-print Network

    © 2011 Quantum Corporation. May be freely distributed in its entirety without modification. Quantum ...................................................................................................................................3 1. Cryptographic SKM Specification.....................................................................................................4 1.2. Cryptographic SKM Boundary

  19. Dissolved oxygen stratification in two micro-tidal partially-mixed estuaries

    E-print Network

    Mallin, Michael

    Dissolved oxygen stratification in two micro-tidal partially-mixed estuaries Jing Lin a,*, Lian Xie online 21 August 2006 Abstract The controlling physical factors for vertical oxygen stratification that vertical stratification of dissolved oxygen (DO) concentration can be explained by the extended Hansen

  20. 40 CFR 795.70 - Indirect photolysis screening test: Sunlight photolysis in waters containing dissolved humic...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...Sunlight photolysis in waters containing dissolved humic...near-surface, conditions in fresh water bodies. (7...the chemical dissolve in water at sufficient concentrations...clear-sky period to obtain the best results. Testing...five-fold less than its water solubility of...

  1. 40 CFR 795.70 - Indirect photolysis screening test: Sunlight photolysis in waters containing dissolved humic...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Sunlight photolysis in waters containing dissolved humic...near-surface, conditions in fresh water bodies. (7...the chemical dissolve in water at sufficient concentrations...clear-sky period to obtain the best results. Testing...five-fold less than its water solubility of...

  2. 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...

  3. UNDERSTANDING AND MANAGING RISKS POSED BY BRINES CONTAINING DISSOLVED CARBON DIOXIDE

    EPA Science Inventory

    Geologic disposal of supercritical carbon dioxide in saline aquifers and depleted oil and gas fields will cause large volumes of brine to become saturated with dissolved CO2 at concentrations of 50 g/l or more.  As CO2 dissolves in brine, the brine de...

  4. Dissolved Solids in Streams of the Conterminous United States

    NASA Astrophysics Data System (ADS)

    Anning, D. W.; Flynn, M.

    2014-12-01

    Studies have shown that excessive dissolved-solids concentrations in water can have adverse effects on the environment and on agricultural, municipal, and industrial water users. Such effects motivated the U.S. Geological Survey's National Water-Quality Assessment Program to develop a SPAtially-Referenced Regression on Watershed Attributes (SPARROW) model to improve the understanding of dissolved solids in streams of the United States. Using the SPARROW model, annual dissolved-solids loads from 2,560 water-quality monitoring stations were statistically related to several spatial datasets serving as surrogates for dissolved-solids sources and transport processes. Sources investigated in the model included geologic materials, road de-icers, urban lands, cultivated lands, and pasture lands. Factors affecting transport from these sources to streams in the model included climate, soil, vegetation, terrain, population, irrigation, and artificial-drainage characteristics. The SPARROW model was used to predict long-term mean annual conditions for dissolved-solids sources, loads, yields, and concentrations in about 66,000 stream reaches and corresponding incremental catchments nationwide. The estimated total amount of dissolved solids delivered to the Nation's streams is 272 million metric tons (Mt) annually, of which 194 million Mt (71%) are from geologic sources, 38 million Mt (14%) are from road de-icers, 18 million Mt (7%) are from pasture lands, 14 million Mt (5 %) are from urban lands, and 8 million Mt (3%) are from cultivated lands. The median incremental-catchment yield delivered to local streams is 26 metric tons per year per square kilometer [(Mt/yr)/km2]. Ten percent of the incremental catchments yield less than 4 (Mt/yr)/km2, and 10 percent yield more than 90 (Mt/yr)/km2. In 13% of the reaches, predicted flow-weighted concentrations exceed 500 mg/L—the U.S. Environmental Protection Agency secondary non-enforceable drinking-water standard.

  5. 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 ?-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% ?-cellulose and 89% brightness after D0EpD1EpD1 bleaching. The produced dissolving pulp can be used in rayon production. PMID:25439866

  6. DISSOLVED OXYGEN DIURNAL FLUX STUDY

    EPA Science Inventory

    Stream monitoring study of a 24 Western Corn Belt Plains streams designed to assess any correlation of nutrient loads and the level of dissolved oxygen in wadeable streams and any subsequent affect on aquatic life. Study currently being conducted under a cooperative agreement be...

  7. 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`

  8. Thermodynamic properties of gases dissolved in electrolyte solutions.

    NASA Technical Reports Server (NTRS)

    Tiepel, E. W.; Gubbins, K. E.

    1973-01-01

    A method based on perturbation theory for mixtures is applied to the prediction of thermodynamic properties of gases dissolved in electrolyte solutions. The theory is compared with experimental data for the dependence of the solute activity coefficient on concentration, temperature, and pressure; calculations are included for partial molal enthalpy and volume of the dissolved gas. The theory is also compared with previous theories for salt effects and found to be superior. The calculations are best for salting-out systems. The qualitative feature of salting-in is predicted by the theory, but quantitative predictions are not satisfactory for such systems; this is attributed to approximations made in evaluating the perturbation terms.

  9. Nano-Enriched and Autonomous Sensing Framework for Dissolved Oxygen

    PubMed Central

    Shehata, Nader; Azab, Mohammed; Kandas, Ishac; Meehan, Kathleen

    2015-01-01

    This paper investigates a nano-enhanced wireless sensing framework for dissolved oxygen (DO). The system integrates a nanosensor that employs cerium oxide (ceria) nanoparticles to monitor the concentration of DO in aqueous media via optical fluorescence quenching. We propose a comprehensive sensing framework with the nanosensor equipped with a digital interface where the sensor output is digitized and dispatched wirelessly to a trustworthy data collection and analysis framework for consolidation and information extraction. The proposed system collects and processes the sensor readings to provide clear indications about the current or the anticipated dissolved oxygen levels in the aqueous media. PMID:26287211

  10. A Dissolved Oxygen Threshold for Shifts in Bacterial Community Structure in a Seasonally Hypoxic Estuary

    PubMed Central

    Spietz, Rachel L.; Williams, Cheryl M.; Rocap, Gabrielle; Horner-Devine, M. Claire

    2015-01-01

    Pelagic ecosystems can become depleted of dissolved oxygen as a result of both natural processes and anthropogenic effects. As dissolved oxygen concentration decreases, energy shifts from macrofauna to microorganisms, which persist in these hypoxic zones. Oxygen-limited regions are rapidly expanding globally; however, patterns of microbial communities associated with dissolved oxygen gradients are not yet well understood. To assess the effects of decreasing dissolved oxygen on bacteria, we examined shifts in bacterial community structure over space and time in Hood Canal, Washington, USA?a glacial fjord-like water body that experiences seasonal low dissolved oxygen levels known to be detrimental to fish and other marine organisms. We found a strong negative association between bacterial richness and dissolved oxygen. Bacterial community composition across all samples was also strongly associated with the dissolved oxygen gradient, and significant changes in bacterial community composition occurred at a dissolved oxygen concentration between 5.18 and 7.12 mg O2 L-1. This threshold value of dissolved oxygen is higher than classic definitions of hypoxia (<2.0 mg O2 L-1), suggesting that changes in bacterial communities may precede the detrimental effects on ecologically and economically important macrofauna. Furthermore, bacterial taxa responsible for driving whole community changes across the oxygen gradient are commonly detected in other oxygen-stressed ecosystems, suggesting that the patterns we uncovered in Hood Canal may be relevant in other low oxygen ecosystems. PMID:26270047

  11. Simulated effects of surface coal mining and agriculture on dissolved solids in the Redwater River, east-central Montana

    USGS Publications Warehouse

    Ferreira, R.F.; Lambing, J.H.

    1985-01-01

    Dissolved solids concentrations in five reaches of the Redwater River in east-central Montana were simulated to evaluate the effects of surface coal mining and agriculture. A mass-balance model of streamflow and dissolved solids load developed for the Tongue River in southeastern Montana was modified and applied to the Redwater River. Mined acreages, dissolved solids concentrations in mined spoils, and irrigated acreage can be varied in the model to study relative changes in the dissolved solids concentration in consecutive reaches of the river. Because of extreme variability and a limited amount of data, the model was not consecutively validated. Simulated mean and median monthly mean streamflows and consistently larger than those calculated from streamflow records. Simulated mean and median monthly mean dissolved solids loads also are consistently larger than regression-derived values. These discrepancies probably result from extremely variable streamflow, overestimates of streamflow from ungaged tributaries, and weak correlations between streamflow and dissolved solids concentrations. The largest increases in simulated dissolved solids concentrations from mining and agriculture occur from September through January because of smaller streamflows and dissolved solids loads. Different combinations of agriculture and mining under mean flow conditions resulted in cumulative percentage increases of dissolved solids concentrations of less than 5% for mining and less than 2% for agriculture. (USGS)

  12. DISSOLVED ORGANIC CARBON AND DISSOLVED CARBON DIOXIDE CONCENTRATIONS AND EXPORT IN GEORGIA PIEDMONT HEADWATER STREAMS

    EPA Science Inventory

    The South Fork Broad River (SFBR) drains about 550 km2 of the Georgia Piedmont. The SFBR watershed is primarily rural and undeveloped although the human population increased by about 25% between 1990 and 2000. Forestry and agriculture are the main land uses. Agriculture consis...

  13. More on the losses of dissolved CO(2) during champagne serving: toward a multiparameter modeling.

    PubMed

    Liger-Belair, Gérard; Parmentier, Maryline; Cilindre, Clara

    2012-11-28

    Pouring champagne into a glass is far from being inconsequential with regard to the dissolved CO(2) concentration found in champagne. Three distinct bottle types, namely, a magnum bottle, a standard bottle, and a half bottle, were examined with regard to their loss of dissolved CO(2) during the service of successively poured flutes. Whatever the bottle size, a decreasing trend is clearly observed with regard to the concentration of dissolved CO(2) found within a flute (from the first to the last one of a whole service). Moreover, when it comes to champagne serving, the bottle size definitely does matter. The higher the bottle volume, the better its buffering capacity with regard to dissolved CO(2) found within champagne during the pouring process. Actually, for a given flute number in a pouring data series, the concentration of dissolved CO(2) found within the flute was found to decrease as the bottle size decreases. The impact of champagne temperature (at 4, 12, and 20 °C) on the losses of dissolved CO(2) found in successively poured flutes for a given standard 75 cL bottle was also examined. Cold temperatures were found to limit the decreasing trend of dissolved CO(2) found within the successively poured flutes (from the first to the last one of a whole service). Our experimental results were discussed on the basis of a multiparameter model that accounts for the major physical parameters that influence the loss of dissolved CO(2) during the service of a whole bottle type. PMID:23110303

  14. Freely Falling Finite Frames Near a Black Hole

    E-print Network

    Tarun Biswas

    2015-04-01

    It is well-known that the Riemann curvature tensor has no discontinuity at the black hole horizon. It is also well-known that a freely falling observer takes finite time to reach the horizon from an outside point. However, the usual assumption is that such an observer resides in a frame of reference (spaceship) of infinitesimal size. This assumption is justified as long as the coordinates are continuous enough to assume that the observer's frame is small compared to the variations of the metric from a local flat metric. Such an assumption may be invalid when the coordinate system has not only a discontinuity but a singularity like the one at the horizon. Hence, here, the characteristics of a finite frame (a spaceship) near a black hole horizon is discussed. It is shown that clocks placed at the front and rear ends have different time scales even in the limit when they reach the horizon at the same time. This renders such a frame physically meaningless. It is also argued that the forces that are expected to keep a realistic frame (like a spaceship) in one piece tend to zero near the horizon. So, a physical spaceship is expected to fall apart near the horizon.

  15. Freely Falling Finite Frames Near a Black Hole

    E-print Network

    Biswas, Tarun

    2015-01-01

    It is well-known that the Riemann curvature tensor has no discontinuity at the black hole horizon. It is also well-known that a freely falling observer takes finite time to reach the horizon from an outside point. However, the usual assumption is that such an observer resides in a frame of reference (spaceship) of infinitesimal size. This assumption is justified as long as the coordinates are continuous enough to assume that the observer's frame is small compared to the variations of the metric from a local flat metric. Such an assumption may be invalid when the coordinate system has not only a discontinuity but a singularity like the one at the horizon. Hence, here, the characteristics of a finite frame (a spaceship) near a black hole horizon is discussed. It is shown that clocks placed at the front and rear ends have different time scales even in the limit when they reach the horizon at the same time. This renders such a frame physically meaningless. It is also argued that the forces that are expected to ke...

  16. Localizing and Beamforming Freely Drifting VLF Acoustic Sensors.

    NASA Astrophysics Data System (ADS)

    Culver, Richard Lee

    Self-contained, freely-drifting Swallow floats capable of recording ambient ocean noise in the 1 to 25 Hz band have been designed, built and deployed by the Marine Physical Laboratory, Scripps Institution of Oceanography, University of California, San Diego, California. The buoys are ballasted to neutral buoyancy at midwater depth where they record the components of particle velocity from which sound pressure levels may be derived. Float positions are estimated using an 8 kHz acoustic ranging system and a Kalman tracking filter. Individual float times series are then combined to obtain passive, directional acoustic measurements from 1 to 25 Hz which are not contaminated by flow noise or tether strumming. The float localization and beamforming techniques are illustrated using measurements from a September 1986 Swallow float experiment conducted approximately 50 miles west of San Diego, California. A distant target of opportunity (apparently a surface ship) provides six spectral lines between 9 and 22.5 Hz which are tracked for about 90 minutes. The complex bathymetry of the experiment site complicates signal propagation, but the signal level in the beamformer output indicates that the element time series are being properly combined.

  17. Studying the freely-behaving brain with fMRI

    PubMed Central

    Maguire, Eleanor A.

    2012-01-01

    Given that the brain evolved to function in the real world then it seems reasonable to want to examine how it operates in that context. But of course the world is complex, as are the brain's responses to it, and MRI scanners are inherently restrictive environments. This combination of challenges makes the prospect of studying the freely-behaving brain with fMRI disconcerting to anyone sensible. When designing naturalistic fMRI experiments it is necessary to ensure that the thoughts or behaviours under scrutiny are not unduly perturbed or constrained by the imaging process, while still being amenable to experimental manipulation and control, and result in meaningful and interpretable data. This is difficult to achieve. Here, briefly, and in a highly subjective and selective manner, I consider: why we might want to deploy free-behaviour designs in an fMRI context, how to go about it, review some examples of it in action, and decide finally whether it is worth it (it is). PMID:22245643

  18. Freely decaying turbulence in force-free electrodynamics

    E-print Network

    Zrake, Jonathan

    2015-01-01

    Freely decaying relativistic force-free turbulence is studied for the first time. We initiate the magnetic field at a short wavelength and simulate its relaxation toward equilibrium on two and three dimensional periodic domains, in both helical and non-helical settings. Force-free turbulent relaxation is found to exhibit an inverse cascade in all settings, and in 3D to have a magnetic energy spectrum consistent with the Kolmogorov $5/3$ power law. 3D relaxations also obey the Taylor hypothesis; they settle promptly into the lowest energy configuration allowed by conservation of the total magnetic helicity. But in 2D, the relaxed state is a force-free equilibrium whose energy greatly exceeds the Taylor minimum, and which contains persistent force-free current layers and isolated flux tubes. We explain this behavior in terms of additional topological invariants that exist only in two dimensions, namely the helicity enclosed within each level surface of the magnetic potential function. The speed and completeness...

  19. Freely decaying turbulence in two-dimensional electrostatic gyrokinetics

    SciTech Connect

    Tatsuno, T.; Plunk, G. G.; Barnes, M.; Dorland, W.; Howes, G. G.; Numata, R.

    2012-12-15

    In magnetized plasmas, a turbulent cascade occurs in phase space at scales smaller than the thermal Larmor radius ('sub-Larmor scales') [Tatsuno et al., Phys. Rev. Lett. 103, 015003 (2009)]. When the turbulence is restricted to two spatial dimensions perpendicular to the background magnetic field, two independent cascades may take place simultaneously because of the presence of two collisionless invariants. In the present work, freely decaying turbulence of two-dimensional electrostatic gyrokinetics is investigated by means of phenomenological theory and direct numerical simulations. A dual cascade (forward and inverse cascades) is observed in velocity space as well as in position space, which we diagnose by means of nonlinear transfer functions for the collisionless invariants. We find that the turbulence tends to a time-asymptotic state, dominated by a single scale that grows in time. A theory of this asymptotic state is derived in the form of decay laws. Each case that we study falls into one of three regimes (weakly collisional, marginal, and strongly collisional), determined by a dimensionless number D{sub *}, a quantity analogous to the Reynolds number. The marginal state is marked by a critical number D{sub *}=D{sub 0} that is preserved in time. Turbulence initialized above this value become increasingly inertial in time, evolving toward larger and larger D{sub *}; turbulence initialized below D{sub 0} become more and more collisional, decaying to progressively smaller D{sub *}.

  20. Intersegmental coupling and recovery from perturbations in freely running cockroaches.

    PubMed

    Couzin-Fuchs, Einat; Kiemel, Tim; Gal, Omer; Ayali, Amir; Holmes, Philip

    2015-01-15

    Cockroaches are remarkably stable runners, exhibiting rapid recovery from external perturbations. To uncover the mechanisms behind this important behavioral trait, we recorded leg kinematics of freely running animals in both undisturbed and perturbed trials. Functional coupling underlying inter-leg coordination was monitored before and during localized perturbations, which were applied to single legs via magnetic impulses. The resulting transient effects on all legs and the recovery times to normal pre-perturbation kinematics were studied. We estimated coupling architecture and strength by fitting experimental data to a six-leg-unit phase oscillator model. Using maximum-likelihood techniques, we found that a network with nearest-neighbor inter-leg coupling best fitted the data and that, although coupling strengths vary among preparations, the overall inputs entering each leg are approximately balanced and consistent. Simulations of models with different coupling strengths encountering perturbations suggest that the coupling schemes estimated from our experiments allow animals relatively fast and uniform recoveries from perturbations. PMID:25609786

  1. Intersegmental coupling and recovery from perturbations in freely running cockroaches

    PubMed Central

    Couzin-Fuchs, Einat; Kiemel, Tim; Gal, Omer; Ayali, Amir; Holmes, Philip

    2015-01-01

    Cockroaches are remarkably stable runners, exhibiting rapid recovery from external perturbations. To uncover the mechanisms behind this important behavioral trait, we recorded leg kinematics of freely running animals in both undisturbed and perturbed trials. Functional coupling underlying inter-leg coordination was monitored before and during localized perturbations, which were applied to single legs via magnetic impulses. The resulting transient effects on all legs and the recovery times to normal pre-perturbation kinematics were studied. We estimated coupling architecture and strength by fitting experimental data to a six-leg-unit phase oscillator model. Using maximum-likelihood techniques, we found that a network with nearest-neighbor inter-leg coupling best fitted the data and that, although coupling strengths vary among preparations, the overall inputs entering each leg are approximately balanced and consistent. Simulations of models with different coupling strengths encountering perturbations suggest that the coupling schemes estimated from our experiments allow animals relatively fast and uniform recoveries from perturbations. PMID:25609786

  2. Functional Brain Mapping in Freely Moving Rats During Treadmill Walking

    PubMed Central

    Holschneider, D. P.; Maarek, J.-M. I.; Yang, J.; Harimoto, J.; Scremin, O. U.

    2014-01-01

    Summary A dilemma in functional neuroimaging is that immobilization of the subject, necessary to avoid movement artifact, extinguishes all but the simplest behaviors. Recently, we developed an implantable microbolus infusion pump (MIP) that allows bolus injection of radiotracers by remote activation in freely moving, nontethered animals. The MIP is examined as a tool for brain mapping in rats during a locomotor task. Cerebral blood flow–related tissue radioactivity (CBF-TR) was measured using [14C]-iodoantipyrine with an indicator-fractionation method, followed by autoradiography. Rats exposed to walking on a treadmill, compared to quiescent controls, showed increases in CBF-TR in motor circuits (primary motor cortex, dorsolateral striatum, ventrolateral thalamus, midline cerebellum, copula pyramis, paramedian lobule), in primary somatosensory cortex mapping the forelimbs, hindlimbs and trunk, as well as in secondary visual cortex. These results support the use of implantable pumps as adjunct tools for functional neuroimaging of behaviors that cannot be elicited in restrained or tethered animals. PMID:12902836

  3. Coupled heat and vapor transport: The thermostat effect of a freely evaporating land surface

    E-print Network

    Szilagyi, Jozsef

    Coupled heat and vapor transport: The thermostat effect of a freely evaporating land surface Jozsef for a freely evaporating vegetated land area (assuming negligible ground heat conduction) within a drier, Nebraska, USA Abstract Analytical solutions of the 2-D heat and vapor transport equations for a surface

  4. FREELY BRAIDED ELEMENTS IN COXETER GROUPS, II R.M. Green and J. Losonczy

    E-print Network

    Green, Richard M.

    FREELY BRAIDED ELEMENTS IN COXETER GROUPS, II R.M. Green and J@e-math.ams.org Abstract. We continue the study of freely braided elements of simply lace* *d Coxeter groups, which classes of reduced expressions for an element of a * *simply laced Coxeter group is shown

  5. Optogenetic control of selective neural activity in multiple freely moving Drosophila adults

    E-print Network

    Hsu, Winston H.

    Optogenetic control of selective neural activity in multiple freely moving Drosophila adults Ming memory in fruit flies (Drosophila melanogaster). ALTOMS comprises an intelligent central control module freely moving Drosophila adults. By using ALTOMS to monitor and compute the locations, orientations, wing

  6. Evaporation of freely suspended single droplets: experimental, theoretical and computational simulations

    E-print Network

    Evaporation of freely suspended single droplets: experimental, theoretical and computational IN PHYSICS Rep. Prog. Phys. 76 (2013) 034601 (19pp) doi:10.1088/0034-4885/76/3/034601 Evaporation of freely 2012 Published 25 February 2013 Online at stacks.iop.org/RoPP/76/034601 Abstract Evaporation

  7. Firing properties of dopamine neurons in freely moving dopamine-deficient mice: Effects of dopamine

    E-print Network

    Firing properties of dopamine neurons in freely moving dopamine-deficient mice: Effects of dopamine 15, 2004 To examine the regulation of midbrain dopamine neurons, record- ings were obtained from single neurons of freely moving, genet- ically engineered dopamine-deficient (DD) mice. DD mice were

  8. THE BUBBLE STRIPPING METHOD FOR DETERMINING DISSOLVED HYDROGEN (H2) IN WELL WATER

    EPA Science Inventory

    The Bubble Strip Method was developed for determining concentrations of dissolved H2 in ground water (1). This information canaid in assessing the viability of employing the strategyof monitored natural attenuation (MNA) to restore sites contaminated with chlorinated hydrocarbon...

  9. Spatial variability of total dissolved copper and copper speciation in the inshore waters of Bermuda.

    PubMed

    Oldham, V E; Swenson, M M; Buck, K N

    2014-02-15

    Total dissolved copper (Cu) and Cu speciation were examined from inshore waters of Bermuda, in October 2009 and July-August 2010, to determine the relationship between total dissolved Cu, Cu-binding ligands and bioavailable, free, hydrated Cu(2+) concentrations. Speciation was performed using competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV). Mean total dissolved Cu concentrations ranged from 1.4 nM to 19.2 nM, with lowest concentrations at sites further from shore, consistent with previous measurements in the Sargasso Sea, and localized Cu enrichment inshore in enclosed harbors. Ligand concentrations exceeded dissolved [Cu] at most sites, and [Cu(2+)] were correspondingly low at those sites, typically <10(-13) M. One site, Hamilton Harbour, was found to have [Cu] in excess of ligands, resulting in [Cu(2+)] of 10(-10.7) M, and indicating that Cu may be toxic to phytoplankton here. PMID:24461699

  10. DISSOLVED ORGANIC CARBON TRENDS RESULTING FROM CHANGES IN ATMOSPHERIC DEPOSITION CHEMISTRY

    EPA Science Inventory

    Several hypotheses have been proposed to explain recent, widespread increases in concentrations of dissolved organic carbon (DOC) in the surface waters of glaciated landscapes across eastern North America and northern and central Europe. Some invoke anthropogenic forcing through ...

  11. Quantification of dissolved iron sources to the North Atlantic Ocean.

    PubMed

    Conway, Tim M; John, Seth G

    2014-07-10

    Dissolved iron is an essential micronutrient for marine phytoplankton, and its availability controls patterns of primary productivity and carbon cycling throughout the oceans. The relative importance of different sources of iron to the oceans is not well known, however, and flux estimates from atmospheric dust, hydrothermal vents and oceanic sediments vary by orders of magnitude. Here we present a high-resolution transect of dissolved stable iron isotope ratios (?(56)Fe) and iron concentrations ([Fe]) along a section of the North Atlantic Ocean. The different iron sources can be identified by their unique ?(56)Fe signatures, which persist throughout the water column. This allows us to calculate the relative contribution from dust, hydrothermal venting and reductive and non-reductive sedimentary release to the dissolved phase. We find that Saharan dust aerosol is the dominant source of dissolved iron along the section, contributing 71-87 per cent of dissolved iron. Additional sources of iron are non-reductive release from oxygenated sediments on the North American margin (10-19 per cent), reductive sedimentary dissolution on the African margin (1-4 per cent) and hydrothermal venting at the Mid-Atlantic Ridge (2-6 per cent). Our data also indicate that hydrothermal vents in the North Atlantic are a source of isotopically light iron, which travels thousands of kilometres from vent sites, potentially influencing surface productivity. Changes in the relative importance of the different iron sources through time may affect interactions between the carbon cycle and climate. PMID:25008528

  12. Method for dissolving delta-phase plutonium

    DOEpatents

    Karraker, David G. (1600 Sherwood Pl., SE., Aiken, SC 29801)

    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.

  13. Dissolved Solids in Basin-Fill Aquifers and Streams in the Southwestern United States - Executive Summary

    USGS Publications Warehouse

    Anning, David W.

    2008-01-01

    The U.S. Geological Survey (USGS) recently completed a regional study in the Southwestern United States to characterize dissolved-solids conditions in major water supplies, including important rivers and aquifers. High concentrations of dissolved solids can degrade a water supply's suitability for important uses, such as drinking water or crop irrigation. In an effort to ensure the continued availability of clean surface and groundwater, USGS scientists identified areas where there have been both increasing and decreasing trends in dissolved-solids concentrations.

  14. A study of trends in dissolved oxygen and fecal coliform bacteria at NASQAN stations

    USGS Publications Warehouse

    Smith, Richard A.; Alexander, Richard B.

    1982-01-01

    Most stations in the U.S. Geological Survey's National Stream Quality Accounting Network show no significant trend in either dissolved oxygen concentration or fecal coliform bacteria population for the period October 1974. through October 1981. Of the stations which do show trends, however, most show improved water quality: thirty-one of a total of 276 stations show rising dissolved oxygen concentrations, while only 17 show decreasing concentrations. Decreases in fecal coliform populations have occurred at 21 stations while increases have occurred at only 12 stations. Approximately half of the stations showing improving trends in dissolved oxygen and fecal coliform bacteria are in the Missouri-Mississippi-Ohio River system. Decreases in dissolved oxygen have occurred at scattered locations in the Western and South-Central States. Rising bacterial populations occur most frequently in the Eastern and Central States Trends in dissolved oxygen concentration resulting from temperature changes occurring during the study period can be separated from trends caused by chemical or biological processes by analyzing computed values of dissolved oxygen deficit. About half of the observed trends in dissolved oxygen appear to be the result of changes in water temperature.

  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. Refining the Use of Sodium Azide to Counteract Nitrite Interference in Dissolved Oxygen Analysis of Seawater

    NASA Astrophysics Data System (ADS)

    Miller, M. T.

    2014-12-01

    High nitrite concentrations are known to interfere with the analysis of dissolved oxygen in seawater samples, though the affected range has yet to be defined. This error can be counteracted by the addition of sodium azide to the hydroxide-iodide pickling reagent. The 2013 US GEOTRACES zonal transect included stations off the coast of Peru with nitrite values up to 10?mol/kg in the upper 400 meters of the water column. Low concentrations of dissolved oxygen were also present in the upper 800 meters, providing an opportunity to study the effect of high nitrite levels on dissolved oxygen analysis over a range of concentrations. Without the addition of azide, the error in dissolved oxygen measurement increased linearly with nitrite concentration. The interference was only significant in samples with nitrite concentrations higher than 1.5 ?mol/kg, all of which also had low dissolved oxygen concentrations (<45?mol/kg). The unique combination of high nitrite and low dissolved oxygen is present in such well known and relatively small areas of the world's oceans that the addition of azide is not necessary as a standard procedure for the vast majority of oceanographic measurements.

  17. Satellite Meteorology Education Resources Freely Available from COMET°

    NASA Astrophysics Data System (ADS)

    Abshire, W. E.; Dills, P. N.

    2011-12-01

    The COMET° Program (www.comet.ucar.edu) receives funding from NOAA NESDIS, EUMETSAT, and the Meteorological Service of Canada to support education and training efforts in satellite meteorology. These partnerships enable COMET to create educational materials of global interest on the application of products from geostationary and polar-orbiting remote sensing platforms. Recently, COMET's satellite education programs have focused on both current and next generation satellites and their relevance to operational forecasters and other communities. By partnering with experts from the Naval Research Laboratory, NOAA-NESDIS and its Cooperative Institutes, MSC, and other user communities, COMET stimulates greater utilization of satellite data and products. COMET also continues to broaden the scope of its training to include materials on the EUMETSAT Polar-orbiting System (EPS) and Meteosat geostationary satellites. EPS represents an important contribution to the Initial Joint Polar System between NOAA and EUMETSAT, while Meteosat Second Generation imaging capabilities provide an authentic proving ground for the next-generation GOES-R imager. This presentation provides an overview of COMET's recent satellite education efforts including courses and publications that focus on topics like multispectral RGB products, detecting atmospheric dust, and climate monitoring from satellites. Over 50 satellite-focused self-paced online materials are freely available via the Satellite Topic area of the MetEd Web site (www.meted.ucar.edu/topics/modules/satellite) and COMET's Environmental Satellite Resource Center (ESRC)(www.meted.ucar.edu/esrc). The ESRC, another important resource developed for use by the geosciences and education communities, is a searchable, database driven Web site that provides easy access to a wide range of useful information and training materials on Earth-observing satellites. Simple free online registration is required to access all training materials and the ESRC.

  18. Variability of swallowing performance in intact, freely feeding Aplysia

    PubMed Central

    Lum, Cecilia S.; Zhurov, Yuriy; Cropper, Elizabeth C.; Weiss, Klaudiusz R.; Brezina, Vladimir

    2005-01-01

    Variability in nervous systems is often taken to be merely “noise.” Yet in some cases it may play a positive, active role in the production of behavior. The central pattern generator (CPG) that drives the consummatory feeding behaviors of Aplysia generates large, quasi-random variability in the parameters of the feeding motor programs from one cycle to the next; the variability then propagates through the firing patterns of the motor neurons to the contractions of the feeding muscles. We have proposed that, when the animal is faced with a new, imperfectly known feeding task in each cycle, the variability implements a trial-and-error search through the space of possible feeding movements. Although this strategy will not be successful in every cycle, over many cycles it may be the optimal strategy for feeding in an uncertain and changing environment. To play this role, however, the variability must actually appear in the feeding movements and, presumably, in the functional performance of the feeding behavior. Here we have tested this critical prediction. We have developed a technique to measure, in intact, freely feeding animals, the performance of Aplysia swallowing behavior, by continuously recording with a length transducer the movement of the seaweed strip being swallowed. Simultaneously, we have recorded with implanted electrodes activity at each of the internal levels, the CPG, motor neurons, and muscles, of the feeding neuromusculature. Statistical analysis of a large dataset of these recordings suggests that functional performance is not determined strongly by one or a few parameters of the internal activity, but weakly by many. Most importantly, the internal variability does emerge in the behavior and its functional performance. Even when the animal is swallowing a long, perfectly regular seaweed strip, remarkably, the length swallowed from cycle to cycle is extremely variable, as variable as the parameters of the activity of the CPG, motor neurons, and muscles. PMID:15944235

  19. Dissolved amino acids in oceanic basaltic basement fluids

    NASA Astrophysics Data System (ADS)

    Lin, Huei-Ting; Amend, Jan P.; LaRowe, Douglas E.; Bingham, Jon-Paul; Cowen, James P.

    2015-09-01

    The oceanic basaltic basement contains the largest aquifer on Earth and potentially plays an important role in the global carbon cycle as a net sink for dissolved organic carbon (DOC). However, few details of the organic matter cycling in the subsurface are known because great water depths and thick sediments typically hinder direct access to this environment. In an effort to examine the role of water-rock-microorganism interaction on organic matter cycling in the oceanic basaltic crust, basement fluid samples collected from three borehole observatories installed on the eastern flank of the Juan de Fuca Ridge were analyzed for dissolved amino acids. Our data show that dissolved free amino acids (1-13 nM) and dissolved hydrolyzable amino acids (43-89 nM) are present in the basement. The amino acid concentrations in the ridge-flank basement fluids are at the low end of all submarine hydrothermal fluids reported in the literature and are similar to those in deep seawater. Amino acids in recharging deep seawater, in situ amino acid production, and diffusional input from overlying sediments are potential sources of amino acids in the basement fluids. Thermodynamic modeling shows that amino acid synthesis in the basement can be sustained by energy supplied from inorganic substrates via chemolithotrophic metabolisms. Furthermore, an analysis of amino acid concentrations and compositions in basement fluids support the notion that heterotrophic activity is ongoing. Similarly, the enrichment of acidic amino acids and depletion of hydrophobic ones relative to sedimentary particulate organic matter suggests that surface sorption and desorption also alters amino acids in the basaltic basement. In summary, although the oceanic basement aquifer is a net sink for deep seawater DOC, similar amino acid concentrations in basement aquifer and deep seawater suggest that DOC is preferentially removed in the basement over dissolved amino acids. Our data also suggest that organic carbon cycling occurs in the oceanic basaltic basement, where an active subsurface biosphere is likely responsible for amino acid synthesis and degradation.

  20. 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)

  1. 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.

  2. Effect of rheological properties of dissolved cellulose/microfibrillated cellulose blend suspensions on film forming.

    PubMed

    Saarikoski, Eve; Rissanen, Marja; Seppälä, Jukka

    2015-03-30

    Enzymatically treated cellulose was dissolved in a NaOH/ZnO solvent system and mixed together with microfibrillated cellulose (MFC) in order to find the threshold in which MFC fibers form a percolation network within the dissolved cellulose solution and in order to improve the properties of regenerated cellulose films. In the aqueous state, correlations between the rheological properties of dissolved cellulose/MFC blend suspensions and MFC fiber concentrations were investigated and rationalized. In addition, rheological properties of diluted MFC suspensions were characterized and a correlation with NaOH concentration was found, thus partly explaining the flow properties of dissolved cellulose/MFC blend suspensions. Finally, based on results from Dynamic Mechanical Analysis (DMA), MFC addition had strengthening/plasticizing effect on regenerated cellulose films if low concentrations of MFC, below the percolation threshold (5.5-6 wt%, corresponding to 0.16-0.18 wt% of MFC in the blend suspensions), were used. PMID:25563945

  3. Structural Defects and Instabilities in Freely Suspended Liquid Crystal Films.

    NASA Astrophysics Data System (ADS)

    Pang, Jinzhong

    1995-01-01

    Ultrathin freely suspended liquid crystal films (FSLCFs) are layered two-dimensional (2D) systems which are ideal for the study of 2D physics because of their rich phase and symmetry breaking behavior and almost exclusively internal interactions. We have studied structural defects and instabilities in tilted smectic FSLCFs of many different materials over a wide range of layer numbers. Our observations show that the range of possible phases, structural defects and instabilities in these films is considerably broader than previously realized. Here, we report our studies of string defects, twist-bend instabilities and splay instabilities in FSLCFs. Until now, the defects identified in tilted smectic films are point topological defects of unit topological charge, in which the tilt orientation changes by +/-2pi upon traveling once around the defect point. We have discovered a variety of new defects in 2D tilted smectic systems (the "string" defects) in which there is discontinuity in tilt orientation along a line. We also find associated fractionally charged topological point defect structures. Our observations indicate the presence of additional stabilization mechanisms for 2D line defects and open the way for study of line defects in 2D systems. Some of the most interesting structures in liquid crystals arise as a result of internal frustration. These are situations in which the local energetically ideal configuration cannot be extended to fill space, but must be accommodated by the appearance of defects, often in periodic arrays. We have discovered two new frustrated phases in FSLCFs: the twist-bend stripe phase and the splay stripe phase. The twist-bend stripe phase is formed in an achiral compound with one aliphatic and one perfluoroalkyl chain and is a novel example of spontaneous chiral-symmetry breaking. This phase transition is mainly driven by the interior twist field generated by the steric interaction of molecules in non-polar films. The splay stripe phase, on the other hand, arises as a result of a polar ordering phase separation, and the instability of the ensuing domain boundaries.

  4. 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.

  5. An implantable CMOS device for blood-flow imaging during experiments on freely moving rats

    NASA Astrophysics Data System (ADS)

    Haruta, Makito; Kitsumoto, Chikara; Sunaga, Yoshinori; Takehara, Hironari; Noda, Toshihiko; Sasagawa, Kiyotaka; Tokuda, Takashi; Ohta, Jun

    2014-01-01

    An observation technique for animal brain activity under freely moving conditions is important to understand brain functions because brain activity under an anesthetized condition is different from that under a nonanesthetized condition. We have developed an ultrasmall CMOS imaging device for brain activity observation under freely moving conditions. This device is composed of a CMOS image sensor chip and nine LEDs for illumination. It weighs only 0.02 g and its small size enables experiments to be performed without restricting animal movement. This feature is advantageous for brain imaging, particularly in freely moving situations. In this study, we have demonstrated blood-flow imaging using the device for the stable observation of brain activity over a long period. The blood flow can be observed without staining the brain during optical imaging. We have successfully estimated the blood-flow velocity under freely moving conditions.

  6. Intersegmental coupling and recovery from perturbations in freely-running cockroaches

    E-print Network

    Holmes, Philip

    Intersegmental coupling and recovery from perturbations in freely-running cockroaches E. Couzin and Princeton Neuroscience Institute, Princeton University, USA. November 6, 2014 Abstract Cockroaches Cockroaches are renowned for their ability to maintain dynamic stability when running over uneven terrain

  7. available freely to all at bigbangonline.org! new online suite of cosmology codes!

    E-print Network

    available freely to all at bigbangonline.org! new online suite of cosmology codes! Michael Smith in cosmology to explore the details of big bang element synthesis for themselves Community Building - file

  8. 77 FR 25452 - Applications for New Awards; Territories and Freely Associated States Education Grant Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-30

    ...DEPARTMENT OF EDUCATION Applications for New Awards...and Freely Associated States Education Grant Program AGENCY: Office...assistance from the Department of Education (34 CFR 100.4, 104.5...financially stable; has a history of unsatisfactory...

  9. View of a stone age adze cutting tool floating freely in the flight deck.

    NASA Technical Reports Server (NTRS)

    1992-01-01

    View of a stone age adze cutting tool floating freely in the forward flight deck and framed by the forward and side windows. On the Earth below, the big island of Hawaii can be seen through the window.

  10. Long-term synchronized electrophysiological and behavioral wireless monitoring of freely moving animals.

    PubMed

    Grand, Laszlo; Ftomov, Sergiu; Timofeev, Igor

    2013-01-30

    Parallel electrophysiological recording and behavioral monitoring of freely moving animals is essential for a better understanding of the neural mechanisms underlying behavior. In this paper we describe a novel wireless recording technique, which is capable of synchronously recording in vivo multichannel electrophysiological (LFP, MUA, EOG, EMG) and activity data (accelerometer, video) from freely moving cats. The method is based on the integration of commercially available components into a simple monitoring system and is complete with accelerometers and the needed signal processing tools. LFP activities of freely moving group-housed cats were recorded from multiple intracortical areas and from the hippocampus. EMG, EOG, accelerometer and video were simultaneously acquired with LFP activities 24-h a day for 3 months. These recordings confirm the possibility of using our wireless method for 24-h long-term monitoring of neurophysiological and behavioral data of freely moving experimental animals such as cats, ferrets, rabbits and other large animals. PMID:23099345

  11. Seasonal variability of total dissolved fluxes and origin of major dissolved elements within a large tropical river: The Orinoco, Venezuela

    NASA Astrophysics Data System (ADS)

    Laraque, Alain; Moquet, Jean-Sébastien; Alkattan, Rana; Steiger, Johannes; Mora, Abrahan; Adèle, Georges; Castellanos, Bartolo; Lagane, Christèle; Lopez, José Luis; Perez, Jesus; Rodriguez, Militza; Rosales, Judith

    2013-07-01

    Seasonal variations of total dissolved fluxes of the lower Orinoco River were calculated taking into account four complete hydrological cycles during a five-year period (2005-2010). The modern concentrations of total dissolved solids (TDS) of the Orinoco surface waters were compared with data collected during the second half of the last century published in the literature. This comparison leads to the conclusion that chemical composition did not evolve significantly at least over the last thirty to forty years. Surface waters of the Orinoco at Ciudad Bolivar are between bicarbonated calcic and bicarbonated mixed. In comparison to mean values of concentrations of total dissolved solids (TDS) of world river surface waters (89.2 mg l-1), the Orinoco River at Ciudad Bolivar presents mainly low mineralized surface waters (2005-10: TDS 30 mg l-1). The TDS fluxes passing at this station in direction to the Atlantic Ocean between 2005 and 2010 were estimated at 30 × 106 t yr-1, i.e. 36 t km-2 yr-1. It was observed that the seasonal variations (dry season vs wet season) of total dissolved fluxes (TDS and dissolved organic carbon (DOC)) are mainly controlled by discharge variations. Two groups of elements have been defined from dilution curves and molar ratio diagrams. Ca2+, Mg2+, HCO3-, Cl- and Na+ mainly come from the same geographic and lithologic area, the Andes. K+ and SiO2 essentially come from the Llanos and the Guayana Shield. These findings are important for understanding fundamental geochemical processes within the Orinoco River basin, but also as a baseline study in the perspective of the development of numerous mining activities related with aluminum and steel industries; and the plans of the Venezuelan government to construct new fluvial ports on the lower Orinoco for the transport of hydrocarbons.

  12. Dependence of riverine nitrous oxide emissions on dissolved oxygen levels

    NASA Astrophysics Data System (ADS)

    Rosamond, Madeline S.; Thuss, Simon J.; Schiff, Sherry L.

    2012-10-01

    Nitrous oxide is a potent greenhouse gas, and it destroys stratospheric ozone. Seventeen per cent of agricultural nitrous oxide emissions come from the production of nitrous oxide in streams, rivers and estuaries, in turn a result of inorganic nitrogen input through leaching, runoff and sewage. The Intergovernmental Panel on Climate Change and global nitrous oxide budgets assume that riverine nitrous oxide emissions increase linearly with dissolved inorganic nitrogen loads, but data are sparse and conflicting. Here we report measurements over two years of nitrous oxide emissions in the Grand River, Canada, a seventh-order temperate river that is affected by agricultural runoff and outflow from a waste-water treatment plant. Emissions were disproportionately high in urban areas and during nocturnal summer periods. Moreover, annual emission estimates that are based on dissolved inorganic nitrogen loads overestimated the measured emissions in a wet year and underestimated them in a dry year. We found no correlations of nitrous oxide emissions with nitrate or dissolved inorganic nitrogen, but detected negative correlations with dissolved oxygen, suggesting that nitrate concentrations did not limit emissions. We conclude that future increases in nitrate export to rivers will not necessarily lead to higher nitrous oxide emissions, but more widespread hypoxia most likely will.

  13. 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.

  14. Utilizing Colored Dissolved Organic Matter to Derive Dissolved Black Carbon Export by Arctic Rivers

    NASA Astrophysics Data System (ADS)

    Stubbins, Aron; Spencer, Robert; Mann, Paul; Holmes, R.; McClelland, James; Niggemann, Jutta; Dittmar, Thorsten

    2015-10-01

    Wildfires have produced black carbon (BC) since land plants emerged. Condensed aromatic compounds, a form of BC, have accumulated to become a major component of the soil carbon pool. Condensed aromatics leach from soils into rivers, where they are termed dissolved black carbon (DBC). The transport of DBC by rivers to the sea is a major term in the global carbon and BC cycles. To estimate Arctic river DBC export, 25 samples collected from the six largest Arctic rivers (Kolyma, Lena, Mackenzie, Ob’, Yenisey and Yukon) were analyzed for dissolved organic carbon (DOC), colored dissolved organic matter (CDOM), and DBC. A simple, linear regression between DOC and DBC indicated that DBC accounted for 8.9 ± 0.3% DOC exported by Arctic rivers. To improve upon this estimate, an optical proxy for DBC was developed based upon the linear correlation between DBC concentrations and CDOM light absorption coefficients at 254 nm (a254). Relatively easy to measure a254 values were determined for 410 Arctic river samples between 2004 and 2010. Each of these a254 values was converted to a DBC concentration based upon the linear correlation, providing an extended record of DBC concentration. The extended DBC record was coupled with daily discharge data from the six rivers to estimate riverine DBC loads using the LOADEST modeling program. The six rivers studied cover 53% of the pan-Arctic watershed and exported 1.5 ± 0.1 million tons of DBC per year. Scaling up to the full area of the pan-Arctic watershed, we estimate that Arctic rivers carry 2.8 ± 0.3 million tons of DBC from land to the Arctic Ocean each year. This equates to ~8% of Arctic river DOC export, slightly less than indicated by the simpler DBC vs DOC correlation-based estimate. Riverine discharge is predicted to increase in a warmer Arctic. DBC export was positively correlated with river runoff, suggesting that the export of soil BC to the Arctic Ocean is likely to increase as the Arctic warms.

  15. The Distribution and Stabilisation of Dissolved Fe in Deep-sea Hydrothermal Plumes

    NASA Astrophysics Data System (ADS)

    Bennett, S. A.; Achterberg, E. P.; Connelly, D. P.; Statham, P. J.; Fones, G. R.; German, C. R.

    2007-12-01

    Iron (Fe) is an essential micronutrient for oceanic phytoplankton, yet the debate over its sources and sinks persists. Dissolved Fe(II) in hydrothermal vent fluids is enriched ca. 106-fold over open ocean values, but as vent-fluids enter the base of the water column, abundant polymetallic particulate phases are formed: predominantly Fe-rich sulfides and Fe oxyhydroxides. More recently in hydrothermal plumes, deviation from first order Fe oxidation kinetics has suggested the occurrence of organically stabilised dissolved Fe. Such stabilisation could have implications on the hydrothermal Fe flux to the deep-ocean. To study Fe stabilisation in non-buoyant hydrothermal plumes, we have investigated the plume system at 5°S, Southern Mid-Atlantic Ridge, for dissolved Fe concentrations and Fe-complexing ligands. Six CTD stations were occupied for this study that intercepted non-buoyant plumes. Along-axis flow dominated the dispersion of plume material within the ridge segment and, 2.5 km down-plume from the nearest vent-site, high concentrations of dissolved Fe (20 nM) were still present. These high levels of "dissolved" Fe could be due to the presence of Fe colloids and/or organic Fe complexes. With the use of Competitive Ligand Exchange- Cathodic Stripping Voltammetry (CLE-CSV), we have detected stabilised dissolved Fe complexes within this "dissolved" Fe fraction, on the edges of a plume. We calculate that such a stabilised Fe fraction in hydrothermal plumes, 2.9 to 5.6 times greater than deep-ocean dissolved Fe concentrations (0.7 nM), could be sufficient to provide 10-20% of the global deep-ocean dissolved Fe budget.

  16. In Vitro Evaluation of Domperidone Mouth Dissolving Tablets

    PubMed Central

    Patra, S.; Sahoo, R.; Panda, R. K.; Himasankar, K.; Barik, B. B.

    2010-01-01

    In the present research work mouth dissolving tablets of domperidone were developed with superdisintegrants like crospovidone, croscarmellose sodium and sodium starch glycollate in various concentrations like 3%, 4% and 6% w/w by direct compression method. All formulations were evaluated for physical characteristics of compressed tablets such as weight variation, hardness, friability, content uniformity, in vitro disintegration time, wetting time and in vitro dissolution study. Among all, the formulation F3 (containing 6% w/w concentration of crospovidone) was considered to be the best formulation, having disintegration time of 9 s, wetting time of 15 s and in vitro drug release of 99.22% in 15 min. PMID:21969764

  17. In vitro evaluation of domperidone mouth dissolving tablets.

    PubMed

    Patra, S; Sahoo, R; Panda, R K; Himasankar, K; Barik, B B

    2010-11-01

    In the present research work mouth dissolving tablets of domperidone were developed with superdisintegrants like crospovidone, croscarmellose sodium and sodium starch glycollate in various concentrations like 3%, 4% and 6% w/w by direct compression method. All formulations were evaluated for physical characteristics of compressed tablets such as weight variation, hardness, friability, content uniformity, in vitro disintegration time, wetting time and in vitro dissolution study. Among all, the formulation F3 (containing 6% w/w concentration of crospovidone) was considered to be the best formulation, having disintegration time of 9 s, wetting time of 15 s and in vitro drug release of 99.22% in 15 min. PMID:21969764

  18. The Influence of Dissolved Carbon Dioxide on Cavitation Intensity in Ultrasound Cleaning Systems

    NASA Astrophysics Data System (ADS)

    Brems, Steven; Hauptmann, Marc; Camerotto, Elisabeth; Pacco, Antoine; Struyf, Herbert; Mertens, Paul; Gottschalk, Christiane; De Gendt, Stefan

    2013-06-01

    A study is made of the effect of dissolved CO2 on cavitation inception and activity in an ultrasound system with a sound frequency of 928 kHz. It is shown that measurable cavitation activity is completely absent at moderate acoustic power densities (?1.7 W cm-2) when only CO2 is dissolved in ultra pure water. It is suggested that the enhanced stability of CO2 bubbles against coalescence might be the origin of the delayed cavitation inception when compared to other dissolved gases. A combination of dissolved O2 and CO2 can lead to a measurable cavitation activity at an acoustic power of 420 mW cm-2, but an increase of the dissolved CO2 level reduces, in general, the observed cavitation activity. In order to compare results with different dissolved gas concentrations, measurements are performed with acoustic pulses and the pulse off time is varied. An optimal pulse-off time exists, where a maximum of cavitation activity is observed. However, the pulse-off time interval with enhanced cavitation activity is narrowed with increasing dissolved CO2 concentrations. Again, a decrease in bubble coalescence might explain the narrowing of the “enhancement peak”.

  19. Evaluation of sampling strategies to characterize dissolved oxygen conditions in northern Gulf of Mexico estuaries

    SciTech Connect

    Summers, J.K.; Engle, V.D.

    1993-01-01

    Dissolved oxygen was continuously monitored in eight sites of northern Gulf of Mexico estuaries in August, 1990. Monte Carlo analyses on subsamples of the data were used to evaluate several commonly used monitoring strategies. Monitoring strategies which involve single point sampling of dissolved oxygen may often misclassify an estuary as having good water quality. In the case of shallow, often well-mixed estuaries that experience diurnal cycles, such monitoring often does not occur at night, during the time of lowest dissolved oxygen concentration. The authors' objective was to determine the minimum sampling effort required to correctly classify a site in terms of the observed frequency of hypoxia. Tests concluded that the most successful classification strategy used the minimum dissolved oxygen concentration from a continuously sampled 24-hour period. (Copyright (c) 199e Kluwer Academic Publishers.)

  20. Dialysate With High Dissolved Hydrogen Facilitates Dissociation of Indoxyl Sulfate From Albumin

    PubMed Central

    Tange, Yoshihiro; Takesawa, Shingo; Yoshitake, Shigenori

    2015-01-01

    Background: Protein-bound toxins such as indoxyl sulfate (IS) are not efficiently removed by conventional hemodialysis (HD). Objectives: To improve the removal of IS, we performed an in vitro study to evaluate the effects of high dissolved hydrogen on the dissociation of IS from albumin using simulated HD. Materials and Methods: Wasted dialysate from peritoneal dialysis was concentrated a hundred times using extracorporeal ultrafiltration method. Dialysate with high dissolved hydrogen was made by mixing concentrated dialysis solution and electrolyzed-reduced water. The amounts of free fractions of IS were determined by high performance liquid chromatography. Results: IS was significantly dissociated from albumin using dialysate with high dissolved hydrogen compared with conventional dialysate (P < 0.05). Conclusions: Effective removal of IS is expected using a dialysate with high dissolved hydrogen. PMID:25883914

  1. Is Low Dissolved Oxygen in Spawning Areas an Impediment to Lake Herring Restoration and Recruitment in the Great Lakes?

    E-print Network

    documented very low (oxygen (DO) concentrations near lake bottom and on lake bottomIs Low Dissolved Oxygen in Spawning Areas an Impediment to Lake Herring Restoration and Recruitment dissolved oxygen conditions caused by eutrophication and paper mill discharges, in conjunction

  2. Method 366.0 Determination of Dissolved Silicate in Estuarine and Coastal Watersby Gas Segmented Continuous Flow Colorimetric Analysis

    EPA Science Inventory

    This method provides a procedure for the determination of dissolved silicate concentration in estuarine and coastal waters. The dissolved silicate is mainly in the form of silicic acid, H SiO , in estuarine and 4 4 coastal waters. All soluble silicate, including colloidal silici...

  3. Dissolved organic carbon and nitrogen in the Western Black Sea Hugh W. Ducklow a,, Dennis A. Hansell b

    E-print Network

    Hansell, Dennis

    Dissolved organic carbon and nitrogen in the Western Black Sea Hugh W. Ducklow a,, Dennis A October 2006; accepted 16 January 2007 Available online 3 February 2007 Abstract Dissolved organic carbon and nitrogen (DOC and DON) concentrations were measured in the Black Sea during May­June 2001. Sampling

  4. SEASONAL VARIATIONS IN NUTRIENT CONCENTRATIONS AND RIVER FLOW IN A NORTHWESTERN USA WATERSHED

    EPA Science Inventory

    Dissolved nutrient concentrations were measured in the Yaquina River, Oregon from 1998 through 2001 to determine the watershed loading to Yaquina estuary. The effects of storms on dissolved nutrient transport were investigated relative to stream discharge for three storm events,...

  5. Summary of Tests to Determine Effectiveness of Gelatin Strike on SS{ampersand}C Dissolver Solutions

    SciTech Connect

    Murray, A.M.; Karraker, D.G.

    1998-05-01

    The solutions from the dissolution of sand, slag, and crucible (SS&C) material are sufficiently different from previous solutions processed via the F-Canyon Purex process that the effectiveness of individual process steps needed to be ascertained. In this study, the effectiveness of gelatin strike was tested under a variety of conditions. Specifically, several concentrations of silica, fluoride, nitric acid (HNO{sub 3}), boric acid (H{sub 3}BO{sub 3}), and aluminium nitrate nonahydrate (ANN) were studied. The disengagement times of surrogate and plant SS&C dissolver solutions from plant solvent also were measured. The results of the tests indicate that gelatin strike does not coagulate the silica at the low concentration of silica ({tilde 30} ppm) expected in the SS&C dissolver solutions because the silicon is complexed with fluoride ions (e.g., SiF{sub 6}{sup -2}). The silicon fluoride complex is expected to remain with the aqueous phase during solvent extraction. The disengagement times of the dissolver solutions from the plant solvent were not affected by the presence of low concentrations of silica and no third phase formation was observed in the disengagement phase with the low silica concentrations. Tests of surrogate SS&C dissolver solutions with higher concentration of silica (less than 150 ppm) did show that gelatin strike followed by centrifugation resulted in good phase disengagement of the surrogate SS{ampersand}C dissolver solution from the plant dissolver solution. At the higher silica concentrations, there is not sufficient fluoride to complex with the silica, and the silica must be entrained by the gelatin and removed from the dissolver solution prior to solvent extraction.

  6. 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…

  7. 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...

  8. 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

  9. RELATIONSHIPS BETWEEN NEAR-BOTTOM DISSOLVED OXYGEN AND SEDIMENT PROFILE CAMERA MEASUREMENTS

    EPA Science Inventory

    The United States Environmental Protection Agency (U.S. EPA) and other environmental authorities regulate concentrations of dissolved oxygen (DO) as a measure of nutrient-related eutrophication in estuarine and coastal waters. However, in situ DO concentrations are extremely var...

  10. UV-SENSITIVE COMPLEX PHOSPHORUS: ASSOCIATION WITH DISSOLVED HUMIC MATERIALS AND IRON IN A BOG LAKE

    EPA Science Inventory

    The concentration of UV-sensitive complex phosphorus compounds in water from an acid bog lake was linearly related to the concentration of dissolved high molecular weight humic material (DHM) both seasonally and diurnally. The first-order rate of photoreduction (Fe(+3) to Fe(+2) ...

  11. Characteristics and source identification of dissolved trace elements in the Jinshui River of the South Qinling Mts., China.

    PubMed

    Bu, Hongmei; Wang, Weibo; Song, Xianfang; Zhang, Quanfa

    2015-09-01

    Dissolved trace elements and physiochemical parameters were analyzed to investigate their physicochemical characteristics and identify their sources at 12 sampling sites of the Jinshui River in the South Qinling Mts., China from October 2006 to November 2008. The two-factor ANOVA indicated significant temporal variations of the dissolved Cu, Fe, Sr, Si, and V (p?concentrations of the dissolved trace elements displayed that dissolved Cu, Fe, Sr, Si, V, and Cr were originated from chemical weathering and leaching from the soil and bedrock. Dissolved Cu, Fe, Sr, As, and Si were also from anthropogenic inputs (farming and domestic effluents). Correlation and regression analysis showed that the chemical and physical processes of dissolved Cu was influenced by water temperature and dissolved oxygen (DO) to some degree. Dissolved Fe and Sr were affected by colloid destabilization or sedimentary inputs. Concentrations of dissolved Si were slightly controlled by biological uptake. Principal component analysis confirmed that Fe, Sr, and V resulted from domestic effluents, agricultural runoff, and confluence, whereas As, Cu, and Si were from agricultural activities, and Cr and Zn through natural processes. The research results provide a reference for ecological restoration and protection of the river environment in the Qinling Mts., China. PMID:25971808

  12. A Wearable Multi-Channel fNIRS System for Brain Imaging in Freely Moving Subjects

    PubMed Central

    Piper, Sophie K.; Krueger, Arne; Koch, Stefan P.; Mehnert, Jan; Habermehl, Christina; Steinbrink, Jens; Obrig, Hellmuth; Schmitz, Christoph H.

    2013-01-01

    Functional near infrared spectroscopy (fNIRS) is a versatile neuroimaging tool with an increasing acceptance in the neuroimaging community. While often lauded for its portability, most of the fNIRS setups employed in neuroscientific research still impose usage in a laboratory environment. We present a wearable, multi-channel fNIRS imaging system for functional brain imaging in unrestrained settings. The system operates without optical fiber bundles, using eight dual wavelength light emitting diodes and eight electro-optical sensors, which can be placed freely on the subject's head for direct illumination and detection. Its performance is tested on N = 8 subjects in a motor execution paradigm performed under three different exercising conditions: (i) during outdoor bicycle riding, (ii) while pedaling on a stationary training bicycle, and (iii) sitting still on the training bicycle. Following left hand gripping, we observe a significant decrease in the deoxyhemoglobin concentration over the contralateral motor cortex in all three conditions. A significant task-related ?HbO2 increase was seen for the non-pedaling condition. Although the gross movements involved in pedaling and steering a bike induced more motion artifacts than carrying out the same task while sitting still, we found no significant differences in the shape or amplitude of the HbR time courses for outdoor or indoor cycling and sitting still. We demonstrate the general feasibility of using wearable multi-channel NIRS during strenuous exercise in natural, unrestrained settings and discuss the origins and effects of data artifacts. We provide quantitative guidelines for taking condition-dependent signal quality into account to allow the comparison of data across various levels of physical exercise. To the best of our knowledge, this is the first demonstration of functional NIRS brain imaging during an outdoor activity in a real life situation in humans. PMID:23810973

  13. Pathways and transformations of dissolved methane and dissolved inorganic carbon in Arctic tundra soils: Evidence from analysis of stable isotopes

    NASA Astrophysics Data System (ADS)

    Throckmorton, H.; Perkins, G.; Muss, J. D.; Smith, L. J.; Conrad, M. E.; Torn, M. S.; Heikoop, J. M.; Newman, B. D.; Wilson, C. J.; Wullschleger, S. D.

    2014-12-01

    Arctic soils contain a large pool of terrestrial C and are of great interest because of their potential for releasing significant amounts of carbon dioxide (CO2) and methane (CH4) to the atmosphere. Few attempts have been made, however, to derive quantitative budgets of CO2 and CH4 budgets for high-latitude ecosystems. Therefore, this study used naturally occurring geochemical and isotopic tracers to estimate production pathways and transformations of dissolved inorganic carbon (DIC = ? (total) dissolved CO2) and dissolved CH4 in soil pore waters from 17 locations (drainages) in Barrow, Alaska (USA) in July and September, 2013; and to approximate a complete balance of belowground C cycling at our sampling locations. Results suggest that CH4 was primarily derived from biogenic acetate fermentation, with a shift at 4 locations from July to September towards CO2 reduction as the dominant methanogenic pathway. A large majority of CH4 produced at the frost table methane was transferred directly to the atmosphere via plant roots and ebullition (94.0 ± 1.4% and 96.6 ± 5.0% in July and September). A considerable fraction of the remaining CH4 was oxidized to CO2 during upward diffusion in July and September, respectively. Methane oxidization produced <1% of CO2 relative to alternative production mechanisms in deep subsurface pore waters. The majority of subsurface CO2 was produced from anaerobic respiration, likely due to reduction of Fe oxides and humics (52 ± 6 to 100 ± 13%, on average) while CO2 produced from methanogenesis accounted for the remainder (0 ± 13% to 47 ± 6%, on average) for July and September, respectively. Dissolved CH4 and dissolved CO2 concentrations correlated with thaw depth, suggesting that Arctic ecosystems will likely produce and release a greater amount of greenhouse gasses under projected warming and deepening of active layer thaw depth under future climate change scenarios.

  14. Chemical characterization of dissolved organic compounds from coastal sea surface microlayers (Baltic Sea, Germany).

    PubMed

    van Pinxteren, Manuela; Müller, Conny; Iinuma, Yoshiteru; Stolle, Christian; Herrmann, Hartmut

    2012-10-01

    The physicochemical properties of the sea surface microlayer (SML), i.e. the boundary layer between the air and the sea, and its impact on air-sea exchange processes have been investigated for decades. However, a detailed description about these processes remains incomplete. In order to obtain a better chemical characterization of the SML, in a case study three pairs of SML and corresponding bulk water samples were taken in the southern Baltic Sea. The samples were analyzed for dissolved organic carbon and dissolved total nitrogen, as well as for several organic nitrogen containing compounds and carbohydrates, namely aliphatic amines, dissolved free amino acids, dissolved free monosaccharides, sugar alcohols, and monosaccharide anhydrates. Therefore, reasonable analytical procedures with respect to desalting and enrichment were established. All aliphatic amines and the majority of the investigated amino acids (11 out of 18) were found in the samples with average concentrations between 53 ng L(-1) and 1574 ng L(-1). The concentrations of carbohydrates were slightly higher, averaging 2900 ng L(-1). Calculation of the enrichment factor (EF) between the sea surface microlayer and the bulk water showed that dissolved total nitrogen was more enriched (EF: 1.1 and 1.2) in the SML than dissolved organic carbon (EF: 1.0 and 1.1). The nitrogen containing organic compounds were generally found to be enriched in the SML (EF: 1.9-9.2), whereas dissolved carbohydrates were not enriched or even depleted (EF: 0.7-1.2). Although the investigated compounds contributed on average only 0.3% to the dissolved organic carbon and 0.4% to the total dissolved nitrogen fraction, these results underline the importance of single compound analysis to determine SML structure, function, and its potential for a transfer of compounds into the atmosphere. PMID:22475414

  15. Variability in dissolved oxygen off Eastern Luzon, Philippines

    NASA Astrophysics Data System (ADS)

    San Diego-McGlone, M.; Escobar, M.; Jacinto, G.; Villanoy, C. L.

    2013-12-01

    The eastern coast and shelf of Luzon is a unique area encompassed by the bifurcation of the western boundary North Equatorial Current (NEC) into the Kuroshio and Mindanao Currents. This region is also productive and has become a rich fishing ground. Of interest is how biogeochemistry in this area is influenced by variability in the bifurcation driven by ENSO events, as well as by production and remineralization processes. Results from 2011 and 2012 oceanographic cruises show changes in dissolved oxygen (DO) off Eastern Luzon in both spatial and temporal scales. Between 2011 and 2012, there was a southern shift of the bifurcation latitude. Water masses from the NEC and the Kuroshio Recirculation Gyre (KRG) east of Luzon have inherent low and higher DO concentrations, respectively. A subsurface oxygen minimum layer was seen at 150-200m. Waters with this low dissolved oxygen signature comes from a 400m-deep sill basin (Lamon Deep) off Eastern Luzon. Apart from low ventilation rates, organic matter decomposition contributes to depletion of DO. Proximity of the basin to the coast is evident in the high particulate organic carbon concentration that is delivered from land through run-off and the nearby river. The low DO water is advected offshore and contributes to the spatial variability of DO in the area. Linear regression of particulate organic carbon, dissolved organic carbon, dissolved inorganic carbon, and nutrients with AOU strongly correlate organic matter remineralization to the change in DO with depth. The variability in DO off Eastern Luzon is analyzed with the large-scale variability offshore of source waters to determine the relative influence of biogeochemical cycling in the area.

  16. Permafrost Disturbance Impacts on Dissolved Ion Loads and Nitrogen Dynamics

    NASA Astrophysics Data System (ADS)

    Lafreniere, M. J.; Louiseize, N. L.; Lamoureux, S. F.; Hastings, M. G.

    2014-12-01

    Physical disturbance (slope failure) and thermal perturbation (deep thaw) of the active layer alter the physical hydrology and the dissolved loads of solutes and nutrients of arctic watersheds and downstream water bodies, however the seasonality and duration of these changes, and the processes responsible for them, are poorly understood. To examine these dimensions of permafrost change, we investigated the seasonal fluxes of major ions and dissolved N species from small catchments that were affected by recent slope failures. The catchments represent a range of disturbance extent and hydrological connectivity, including an undisturbed control catchment. Key differences in the impacts of slope disturbance on the fluvial export of major ions, and nitrogen from these headwater catchments were observed. The export of ions increased for all streams (disturbed and undisturbed) in response to deep thaw in warm years. However, the impact of physical disturbance was largely limited to increased ion concentrations late in the season when baseflow was driven by rainfall and soil water drainage. In contrast, nitrate (NO3-) concentrations were substantially affected by physical disturbance. A comparison of a disturbed and undisturbed catchment shows the two streams had similar concentrations of all dissolved N prior to slope failure, yet five years following failure, NO3- concentrations in the disturbed watershed were two orders of magnitude higher than in the undisturbed catchment. NO3- was especially high following late season rainfall and isotopic evidence shows that late season NO3-is not from rainfall but microbially produced (mineralized). Results indicate that the impact of disturbance on ion and N loads is limited by discharge and hydrological connectivity of the disturbed areas, that the drainage of upper permafrost (soils below normal active layer depth) is the likely source of enhanced ion and mineralized NO3-, and that impacts are evident several years after disturbance.

  17. Global effects of agriculture on fluvial dissolved organic matter

    PubMed Central

    Graeber, Daniel; Boëchat, Iola G.; Encina-Montoya, Francisco; Esse, Carlos; Gelbrecht, Jörg; Goyenola, Guillermo; Gücker, Björn; Heinz, Marlen; Kronvang, Brian; Meerhoff, Mariana; Nimptsch, Jorge; Pusch, Martin T.; Silva, Ricky C. S.; von Schiller, Daniel; Zwirnmann, Elke

    2015-01-01

    Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing. PMID:26541809

  18. Global effects of agriculture on fluvial dissolved organic matter.

    PubMed

    Graeber, Daniel; Boëchat, Iola G; Encina-Montoya, Francisco; Esse, Carlos; Gelbrecht, Jörg; Goyenola, Guillermo; Gücker, Björn; Heinz, Marlen; Kronvang, Brian; Meerhoff, Mariana; Nimptsch, Jorge; Pusch, Martin T; Silva, Ricky C S; von Schiller, Daniel; Zwirnmann, Elke

    2015-01-01

    Agricultural land covers approximately 40% of Earth's land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing. PMID:26541809

  19. Global effects of agriculture on fluvial dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Graeber, Daniel; Boëchat, Iola G.; Encina-Montoya, Francisco; Esse, Carlos; Gelbrecht, Jörg; Goyenola, Guillermo; Gücker, Björn; Heinz, Marlen; Kronvang, Brian; Meerhoff, Mariana; Nimptsch, Jorge; Pusch, Martin T.; Silva, Ricky C. S.; von Schiller, Daniel; Zwirnmann, Elke

    2015-11-01

    Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea, and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks, and resulting in higher ecosystem productivity and CO2 outgassing.

  20. PATTERNS AND CONTROLS OF DISSOLVED ORGANIC MATTER EXPORT BY MAJOR RIVERS: A NEW SEASONAL, SPATIALLY EXPLICIT, GLOBAL MODEL

    EPA Science Inventory

    River-derived dissolved organic matter (DOM) influences metabolism, light attenuation, and bioavailability of metals and nutrients in coastal ecosystems. Recent work suggests that DOM concentrations in surface waters vary seasonally because different organic matter pools are mobi...

  1. SPATIAL AND TEMPORAL DISTRIBUTION OF COLOURED DISSOLVED ORGANIC MATTER (CDOM) IN NARRAGANSETT BAY, RI: IMPLICATIONS FOR PHYTOPLANKTON IN COASTAL WATERS

    EPA Science Inventory

    One indicator of health in estuarine and coastal ecosystems is the ability of local waters to transmit sunlight to planktonic, macrophytic, and other submerged vegetation for photosynthesis. The concentration of coloured dissolved organic matter (CDOM) is a primary factor affecti...

  2. Real-time imaging of brain activity in freely moving rats using functional ultrasound.

    PubMed

    Urban, Alan; Dussaux, Clara; Martel, Guillaume; Brunner, Clément; Mace, Emilie; Montaldo, Gabriel

    2015-09-01

    Innovative imaging methods help to investigate the complex relationship between brain activity and behavior in freely moving animals. Functional ultrasound (fUS) is an imaging modality suitable for recording cerebral blood volume (CBV) dynamics in the whole brain but has so far been used only in head-fixed and anesthetized rodents. We designed a fUS device for tethered brain imaging in freely moving rats based on a miniaturized ultrasound probe and a custom-made ultrasound scanner. We monitored CBV changes in rats during various behavioral states such as quiet rest, after whisker or visual stimulations, and in a food-reinforced operant task. We show that fUS imaging in freely moving rats could efficiently decode brain activity in real time. PMID:26192084

  3. 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.

  4. Assessing the Effects of Water Rights Purchases on Dissolved Oxygen, Stream Temperatures, and Fish Habitat

    NASA Astrophysics Data System (ADS)

    Mouzon, N. R.; Null, S. E.

    2014-12-01

    Human impacts from land and water development have degraded water quality and altered the physical, chemical, and biological integrity of Nevada's Walker River. Reduced instream flows and increased nutrient concentrations affect native fish populations through warm daily stream temperatures and low nightly dissolved oxygen concentrations. Water rights purchases are being considered to maintain instream flows, improve water quality, and enhance habitat for native fish species, such as Lahontan cutthroat trout. This study uses the River Modeling System (RMSv4), an hourly, physically-based hydrodynamic and water quality model, to estimate streamflows, temperatures, and dissolved oxygen concentrations in the Walker River. We simulate thermal and dissolved oxygen changes from increased streamflow to prioritize the time periods and locations that water purchases most enhance native trout habitat. Stream temperatures and dissolved oxygen concentrations are proxies for trout habitat. Monitoring results indicate stream temperature and dissolved oxygen limitations generally exist in the 115 kilometers upstream of Walker Lake (about 37% of the study area) from approximately May through September, and this reach currently acts as a water quality barrier for fish passage.

  5. Dissolved Organic Matter Dynamics in a Suburbanizing Watershed: The Importance of Wetlands, People, and Flowpaths

    NASA Astrophysics Data System (ADS)

    Koenig, L.; Daley, M. L.; Potter, J.; McDowell, W. H.

    2013-12-01

    Human development of a watershed often yields fundamental and quantifiable changes in water quality and inorganic nutrient cycling. The effects of suburban development on the cycling of dissolved organic matter (DOM), however, have received relatively less attention, and the understanding of local dissolved organic matter dynamics is rarely a stated goal of watershed management. In this study, we examine the effects of suburbanization on concentrations of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) as well as the optical properties of DOM using 17 study sites in the Lamprey River watershed, NH that integrate varying levels of human development and population density. We show that concentration of DOC and DON is related to wetland cover but is not correlated with population density. Further, we observed no response in DOC concentration with increased flow at the mainstem site, while DON concentration is diluted. The optical properties of dissolved organic matter, however, showed different trends. Fluorescence Index (FI) decreases with increasing wetland cover and lower population density. We show that in a coastal watershed, while DOM quantity is driven by the presence of wetlands, DOM quality changes with both wetland cover and human development. The decoupling of DOM quantity and quality in this suburbanizing watershed indicate that DOM quality may be an important yet overlooked control on watershed-scale biogeochemical cycling and nutrient export.

  6. Heat release in freely-propagating lean premixed hydrogen-methane mixtures

    NASA Astrophysics Data System (ADS)

    Gao, Xinfeng; Day, Marcus; Bell, John

    2009-11-01

    Freely-propagating lean premixed hydrogen-air flames are thermo-diffusively unstable and burn in localized regions of intensified reaction. The flames propagate by the ``active species-diffusion'' mechanism, rather than the ``thermal propagation mode'' adopted by lean methane mixtures. We are interested in understanding mechanisms potentially explaining the influence of hydrogen on the flame structure of hydrogen-methane-air flames. The combustion behavior of hydrogen-methane fuel mixtures is then described with a set of relations derived from the heat release structures. The heat release characteristics of freely propagating flames resemble those of flat steady flames across a broad range of inlet fuel mixtures.

  7. 27 CFR 19.455 - Dissolving of denaturants.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Dissolving of denaturants. 19.455 Section...Articles Denaturation § 19.455 Dissolving of denaturants. Denaturants...27 CFR part 21. Any spirits used in dissolving denaturants and contained in the...

  8. Dissolved iron and macronutrient distributions in the southern California Current System

    NASA Astrophysics Data System (ADS)

    King, Andrew L.; Barbeau, Katherine A.

    2011-03-01

    The distribution of dissolved iron in the southern California Current System (sCCS) is presented from seven research cruises between 2002 and 2006. Dissolved iron concentrations were generally low in most of the study area (<0.5 nM), although high mixed layer and water column dissolved iron concentrations (up to 8 nM) were found to be associated with coastal upwelling, both along the continental margin and some island platforms. A significant supply of iron was probably not from a deep remineralized source but rather from the continental shelf and bottom boundary layer as identified in previous studies along the central and northern California coast. With distance offshore, dissolved iron decreased more rapidly relative to nitrate in a transition zone 10-250 km offshore during spring and summer, resulting in relatively high ratios of nitrate:dissolved iron. Higher nitrate:dissolved iron ratios could be the result of utilization and scavenging in addition to an overall lower supply of iron relative to nitrate in the offshore transition zones. The low supply of iron leads to phytoplankton iron limitation and a depletion in silicic acid relative to nitrate in the coastal upwelling and transition zones of the sCCS.

  9. Abiotic effects on effluent dissolved organic nitrogen along an estuarine transect.

    PubMed

    Funkey, Carolina P; Latour, Robert J; Bronk, Deborah A

    2015-03-01

    Biological nutrient removal is a process commonly used in water resource recovery facilities to reduce dissolved inorganic nitrogen (DIN) concentrations in effluent; this process is less effective at removing all of the effluent dissolved organic nitrogen (EDON). The goal of this study was to investigate the fate of EDON after it undergoes the disinfection process and enters receiving waters. The authors quantified the abiotic effects of effluent exposure to sunlight, increased salinity, and a combination of the two factors. Effluent dissolved organic nitrogen showed significant breakdown during the disinfection process (UV and chlorine) and when exposed to sunlight and increasing salinity. Approximately 7% of the EDON was transformed to DIN and dissolved primary amines after exposure to 9 hours of sunlight and a salinity increase from 0 to 33. The production of DIN and primary amines should be taken into account when considering sources of labile nitrogen to aquatic ecosystems. PMID:25842537

  10. Dissolved oxygen sensing based on fluorescence quenching of ceria nanoparticles

    NASA Astrophysics Data System (ADS)

    Shehata, Nader; Meehan, Kathleen; Leber, Donald

    2012-10-01

    The development of oxygen sensors has positively impacted the fields of medical science, bioengineering, environmental monitoring, solar cells, industrial process control, and a number of military applications. Fluorescent quenching sensors have an inherent high sensitivity, chemical selectivity, and stability when compared to other types of sensors. While cerium oxide thin films have been used to monitor oxygen in the gas phase, the potential of cerium oxide (ceria) nanoparticles as the active material in sensor for oxygen gas has only recently been investigated. Ceria nanoparticles are one of the most unique nanomaterials that are being studied today due to the diffusion and reactivity of its oxygen vacancies, which contributes to its high oxygen storage capability. The reactivity of the oxygen vacancies, which is also related to conversion of cerium ion from the Ce+4 to Ce+3 state, affects the fluorescence properties of the ceria nanoparticles. Our research demonstrates that the ceria nanoparticles (~7 nm in diameter) have application as a fluorescence quenching sensor to measure dissolved oxygen in water. We have found a strong inverse correlation between the amplitude of the fluorescence emission (?excitation = 430 nm and ?peak = 520 nm) and the dissolved oxygen concentration between 5 - 13 mg/L. The Stern-Volmer constant, which is an indication of the sensitivity of gas sensing is 184 M-1 for the ceria nanoparticles. The results show that ceria nanoparticles can be used in an improved, robust fluorescence sensor for dissolved oxygen in a liquid medium.

  11. Release of dissolved nitrogen from water during depressurization

    NASA Technical Reports Server (NTRS)

    Simoneau, R. J.

    1978-01-01

    Experiments were run to study depressurization of water containing various concentrations of dissolved nitrogen gas, the primary case being room temperature water saturated with nitrogen at 4 MPa. In a static depressurization experiment, water with very high nitrogen content was depressurized at rates from 0.09 to 0.50 MPa per second and photographed with high speed movies. The pictures showed that the bubble population at a given pressure increased strongly with decreasing depressurization rate. Flow experiments were performed in an axisymmetric converging-diverging nozzle and in a two-dimensional converging nozzle with glass sidewalls. Depressurization gradients were roughly 500 to 1200 MPa per second. Both nozzles exhibited choked flow behavior even at nitrogen concentration levels as low as 4 percent of saturated. The flow rates were independent of concentration level and could be computed as incompressible water flow based on the difference between stagnation and throat pressures; however, the throat pressures were significantly different between the two nozzles.

  12. Measuring Spatial and Temporal Heterogeneity of Dissolved Oxygen in Streambed Sediments Using Pressure Sensitive Paint (PSP)

    NASA Astrophysics Data System (ADS)

    Huynh, K. T.; Salus, A.; Xie, M.; Roche, K. R.; Packman, A. I.

    2014-12-01

    Pressure sensitive paints (PSP) have been largely used in aerodynamic applications to measure pressure distributions on complex bodies such as aircraft. One common family of PSPs employ fluorescent pigments that are quenched in the presence of oxygen, yielding an inverse relationship between fluorescence intensity and oxygen concentration that is used to measure pressure in aerodynamic applications through the partial pressure of oxygen. These PSPs offer unexplored potential for visualizing dissolved oxygen (DO) concentration distributions on surfaces underwater. PSP was used to measure dissolved oxygen concentrations in streambed sediments in a laboratory flume. Two PSP-coated 2.5 cm diameter spheres were emplaced in a bed of similar material, and imaged under varying DO concentrations. Calibration curves relating fluorescence intensity to dissolved oxygen concentration were developed on a pixel-by-pixel basis, enabling spatial patterns of oxygen to be resolved in the sediment bed. This method of measuring dissolved oxygen concentration is advantageous because of its fast response time and ability to measure heterogeneous oxygen distributions in sediments. Future work will explore the combined effects of stream flow and biofilm growth on oxygen distributions in streambed sediments.

  13. 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.

  14. PHYSICAL REVIEW E 91, 032415 (2015) Nonlinear fluctuation effects in dynamics of freely suspended films

    E-print Network

    Lebedev, Vladimir

    2015-01-01

    of physical properties of the freestanding liquid-crystalline films and fluid membranes are devoted in freely suspended films is analyzed. We consider isotropic films that, say, can be pulled from bulk smectic-A liquid crystals. The key feature of such objects is possibility of bending deformations

  15. Emotions in freely varying and mono-pitched vowels, acoustic and EGG analyses.

    PubMed

    Waaramaa, Teija; Palo, Pertti; Kankare, Elina

    2015-12-01

    Vocal emotions are expressed either by speech or singing. The difference is that in singing the pitch is predetermined while in speech it may vary freely. It was of interest to study whether there were voice quality differences between freely varying and mono-pitched vowels expressed by professional actors. Given their profession, actors have to be able to express emotions both by speech and singing. Electroglottogram and acoustic analyses of emotional utterances embedded in expressions of freely varying vowels [a:], [i:], [u:] (96 samples) and mono-pitched protracted vowels (96 samples) were studied. Contact quotient (CQEGG) was calculated using 35%, 55%, and 80% threshold levels. Three different threshold levels were used in order to evaluate their effects on emotions. Genders were studied separately. The results suggested significant gender differences for CQEGG 80% threshold level. SPL, CQEGG, and F4 were used to convey emotions, but to a lesser degree, when F0 was predetermined. Moreover, females showed fewer significant variations than males. Both genders used more hypofunctional phonation type in mono-pitched utterances than in the expressions with freely varying pitch. The present material warrants further study of the interplay between CQEGG threshold levels and formant frequencies, and listening tests to investigate the perceptual value of the mono-pitched vowels in the communication of emotions. PMID:24998780

  16. HermesC: RF Wireless Low-Power Neural Recording System for Freely Behaving Primates

    E-print Network

    Shenoy, Krishna V.

    HermesC: RF Wireless Low-Power Neural Recording System for Freely Behaving Primates Cynthia AC, a system for recording neural activity from electrode arrays implanted in rhesus monkeys and transmitting amplifies, digitizes, and transmits neural data across a ~900 MHz wireless channel. The wireless

  17. 34 CFR 300.701 - Outlying areas, freely associated States, and the Secretary of the Interior.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 34 Education 2 2010-07-01 2010-07-01 false Outlying areas, freely associated States, and the Secretary of the Interior. 300.701 Section 300.701 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF SPECIAL EDUCATION AND REHABILITATIVE SERVICES, DEPARTMENT OF EDUCATION ASSISTANCE TO STATES FOR THE EDUCATION...

  18. 34 CFR 300.701 - Outlying areas, freely associated States, and the Secretary of the Interior.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 2 2011-07-01 2010-07-01 true Outlying areas, freely associated States, and the Secretary of the Interior. 300.701 Section 300.701 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF SPECIAL EDUCATION AND REHABILITATIVE SERVICES, DEPARTMENT OF...

  19. Fabrication of freely suspended nanostructures by nanoimprint lithography C. C. Huang

    E-print Network

    Ekinci, Kamil

    Fabrication of freely suspended nanostructures by nanoimprint lithography C. C. Huang Department; accepted 19 January 2006; published online 1 March 2006 We describe an innovative approach to fabricate, the imprint polymer serves as both the pattern mask and the sacrificial layer. The fabrication involves

  20. Concentrator Systems

    NASA Astrophysics Data System (ADS)

    Luque-Heredia, Ignacio; Luque, Antonio

    2015-10-01

    The following sections are included: * Introduction * The early development of CPV * Concentrator solar cells * Optics for photovoltaic concentrators * Photovoltaic concentration modules * Tracking systems for photovoltaic concentration * High-concentration systems * Rating and performance * Cost considerations * Conclusions * References

  1. Accumulation of cadmium from the dissolved and particulate phases by the freshwater mussel, Elliptio complanata

    SciTech Connect

    Yankovich, T.

    1995-12-31

    The primary objective of the current study was to quantify cadmium accumulation by Elliptio complanata from suspended particulates relative to the dissolved phase. Results obtained from this study suggest that particle physico-chemical properties and their associated cadmium concentrations may play a role in cadmium bioaccumulation by E. complanata. This accumulation of cadmium is due to direct uptake from the particulate phase and/or accumulation of dissolved cadmium which has leached off particles. The importance of the particulate phase in cadmium uptake is related to the type of particle to which mussels are exposed. No significant cadmium bioaccumulation was observed when mussels consumed Cd-contaminated kaolinite or illite clay particles. Significant uptake was observed by mussels exposed to Cd-contaminated montmorillonite clay particles at high bound cadmium levels; however, the dissolved phase accounted for all observed Cd accumulation, suggesting that equilibrium partitioning into the aqueous phase represented the key route of cadmium uptake from clay particles. Cadmium uptake did not occur when mussels were exposed to natural sediment particles containing low organic carbon concentrations, but significant bioaccumulation was observed when mussels consumed Cd-contaminated sediments with relatively high organic carbon contents. Dissolved cadmium concentrations present in sediment suspensions with low and high organic carbon contents were similar, suggesting that the particulate phase was the source of cadmium uptake. These results indicate that particle processing and selective feeding behaviors by filter-feeding bivalves may play a key role in determining the relative importance of dissolved and particulate phases in cadmium bioaccumulation.

  2. Nutrients, Water Temperature, and Dissolved Oxygen: Are Water Quality Standards Achievable for Forest Streams?

    NASA Astrophysics Data System (ADS)

    Ice, G. G.

    2002-12-01

    Water quality standards provide a performance measure for watershed managers. Three of the most important standards for rivers and streams are the key nutrients, nitrogen and phosphorus; water temperature; and dissolved oxygen. The concentration of nitrogen and phosphorus in waterbodies affects primary production and productivity. Too little nutrients and streams are sterile and unproductive. Too much and they are eutrophic. Water temperature is important because it influences chemical reaction rates in streams and metabolic rates in fish. Dissolved oxygen is necessary for respiration. Salmon, the focus of much of the conservation efforts in the Northwest, are known as organisms that require cool, highly oxygenated water to thrive. Still, it is important when setting a performance standard to determine if those standards are achievable. A survey of nutrient data for small forested streams has found that the ecoregion guidelines proposed by EPA are often unachievable, sometimes even for small, unmanaged reference watersheds. A pilot survey of water temperatures in Oregon wilderness areas and least impaired watersheds has found temperatures frequently exceed the state standards. While natural temperature exceedances are addressed in the water quality standards for Oregon for unmanaged watersheds, these temperatures for managed watersheds might be presumed to result from management activities, precipitating an expensive Total Maximum Daily Load (TMDL) assessment. Less is known about dissolved oxygen for small forest streams because work 20 years ago showed little risk of significant dissolved oxygen concentrations where shade was maintained near the stream and fine slash was kept out of the stream. However, work from the 1970's on intergravel dissolved oxygen also shows that stream with greater large woody debris (LWD) can have lower intergravel dissolved oxygen concentrations, presumably due to trapping of fine organic and inorganic materials. Efforts to add LWD to streams could potentially depress intergravel dissolved oxygen. To avoid making inappropriate decisions based on these performance standards, watershed managers need to understand expected water quality patterns based on the physical, chemical, and biological factors that influence water quality.

  3. Dynamics of dissolved and particulate phosphorus influenced by seasonal hypoxia in Green Bay, Lake Michigan.

    PubMed

    Lin, Peng; Klump, J Val; Guo, Laodong

    2016-01-15

    Despite major investments in point source reductions, portions of the Great Lakes, like Green Bay, remain hypereutrophic and are subject to persistent seasonal hypoxia. Phosphorus (P) is generally a limiting nutrient in the Great Lakes ecosystem, but not all P species are equally bioavailable, and the dynamics of nutrients and their correlation to algal bloom remain poorly characterized, in part, due to a lack of adequate quantification of P chemical speciation. During summer 2014, water samples were collected from seasonally hypoxic Green Bay for measurements of dissolved and particulate inorganic and organic P to examine P cycling dynamics along a steep nutrient gradient ranging from Fox River inflow dominated eutrophic waters in the southern bay to mesotrophic northern waters near the bay's connection with open Lake Michigan. River-derived dissolved and particulate P was quickly removed from the water column in southern Green Bay through biological uptake and sedimentation. Concentrations of phosphate or dissolved inorganic P (DIP) dramatically decreased from 828±216nM in the Fox River, comprising 57±1% of the total dissolved P, to 24±9nM in northern Green Bay where dissolved organic P (DOP) became predominant (>80%). Generally low phosphate concentrations and extremely high dissolved organic C/P ratios (2090±1160 in August 2014) suggested high DOP turnover rates and active transformation between DOP and DIP through organic degradation during P-limited conditions in Green Bay. Elevated DIP levels were accompanied by low dissolved oxygen in deeper waters (10-15m) of central Green Bay where hypoxia-development occurred, suggesting the release of DIP through particle regeneration under hypoxic conditions enhanced by lateral transport and sediment resuspension. High partition coefficients (Kd) of both inorganic and organic P and their significant negative correlation with suspended particulate matter concentrations indicated the particle-reactive nature of P in freshwater environments and may imply that DOP could also be bioavailable under P-limitation. PMID:26473709

  4. Calibration of a dissolved-solids model for the Yampa River basin between Steamboat Springs and Maybell, northwestern Colorado

    USGS Publications Warehouse

    Parker, R.S.; Litke, D.W.

    1987-01-01

    The cumulative effects of changes in dissolved solids from a number of coal mines are needed to evaluate effects on downstream water use. A model for determining cumulative effects of streamflow, dissolved-solids concentration, and dissolved-solids load was calibrated for the Yampa River and its tributaries in northwestern Colorado. The model uses accounting principles. It establishes nodes on the stream system and sums water quantity and quality from node to node in the downstream direction. The model operates on a monthly time step for the study period that includes water years 1976 through 1981. Output is monthly mean streamflow, dissolved-solids concentration, and dissolved-solids load. Streamflow and dissolved-solids data from streamflow-gaging stations and other data-collection sites were used to define input data sets to initiate and to calibrate the model. The model was calibrated at four nodes and generally was within 10 percent of the observed values. The calibrated model can compute changes in dissolved-solids concentration or load resulting from the cumulative effects of new coal mines or the expansion of old coal mines in the Yampa River basin. (USGS)

  5. Tidal impact on the dynamic behavior of dissolved pharmaceuticals in the Yangtze Estuary, China.

    PubMed

    Zhao, Heng; Zhou, Jun Liang; Zhang, Jing

    2015-12-01

    The dynamic behavior of 24 dissolved pharmaceuticals over tidal cycles in the Yangtze Estuary, China was studied to assess the tidal impact on the fate of pharmaceutical residues. The results show that most pharmaceuticals were frequently detected with concentrations from below detection to 27.2 ng/L, with sulfamethoxazole, sulfamethazine, erythromycin, thiamphenicol and florfenicol dominating. During tidal cycles, pharmaceutical concentrations decreased during tidal rise, then increasing during tidal receding for all locations, except at site S2 which showed an opposite trend due to unique water movement there. It was observed that most compounds showed a non-conservative behavior, while diazepam and sulfamethoxazole displayed a conservative behavior. The pharmaceutical concentrations were found to increase with dissolved organic carbon (DOC) concentration, suggesting DOC as a carrier of pharmaceuticals. In addition, many compounds showed a significant negative relationship with suspended particulate matter (SPM) concentration, indicating SPM-water interactions as a control of pharmaceutical behavior in estuarine environment. PMID:26094800

  6. Export Fluxes of Dissolved Organic Carbon From the Yukon River

    NASA Astrophysics Data System (ADS)

    Guo, L.; Cai, Y.; Belzile, C.; MacDonald, R.

    2005-12-01

    Quantitative determination of export fluxes of carbon species through Arctic rivers is required to constrain the carbon budget in the Arctic Ocean and to understand the biogeochemical consequence of climate change in Northern drainage basins. In order to quantify the annual riverine export flux from the Yukon River, monthly or bimonthly water samples were collected at Pilot Station from July 2004 to July 2005 and analyzed for concentrations of dissolved organic carbon (DOC), particulate organic carbon (POC) and dissolved inorganic carbon (DIC). Concentration of DOC varied from 182 to 1683 uM (average 441 uM), with the highest concentration during river ice opening and the lowest in April under the ice. In contrast, DIC concentration increased from ice opening in May (1178 uM) to winter frozen season (2128 uM), with an average of 1588 uM. In addition to the DOC maximum during ice opening, an elevated DOC concentration was observed during the early stage of river ice formation, suggesting the rejection of DOC from ice during its formation. There was a positive correlation of DOC with freshwater flow rate whereas DIC correlated negatively with flow, indicating a hydrological control on both components but different source terms and transport mechanisms. Integrated annual export flux during 2004/2005 was 2.78x1012 g-C/y for DOC and 4.53x1012 g-C/y for DIC. Within the annual fluxes, only 5% of DOC and 17% of DIC were exported during the winter period when the river was frozen over. Long-term observations of DOC and DIC together with their molecular and isotopic signatures are needed to understand how the Yukon River Basin responds to a changing climate.

  7. Violation of the Porod Law in a Freely Cooling Granular Gas in One Dimension Mahendra Shinde,1

    E-print Network

    Ravindran, Rajesh

    Violation of the Porod Law in a Freely Cooling Granular Gas in One Dimension Mahendra Shinde,1 this equivalence, the struc- ture functions of the sticky gas can be inferred to obey the Porod law [21]. Numerical 7 August 2007; published 6 December 2007) We study a model of freely cooling inelastic granular gas

  8. Copyright 2004 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2004 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Sun Microsystems Sun Cryptographic Accelerator 4000 Firmware 2004 SUN MICROSYSTEMS Page 2 of 18 This document may be freely reproduced and distributed whole

  9. Copyright 2004 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2004 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Sun Microsystems Sun Cryptographic Accelerator 4000 Firmware;© Copyright 2004 SUN MICROSYSTEMS Page 2 of 21 This document may be freely reproduced and distributed whole

  10. Copyright 2008 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2008 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Sun Microsystems Sun Crypto Accelerator 6000 Bootstrap Version 1;© Copyright 2007 SUN MICROSYSTEMS Page 2 of 23 This document may be freely reproduced and distributed whole

  11. Copyright 2004 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2004 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Sun Microsystems Sun Cryptographic Accelerator 4000 Firmware 2004 SUN MICROSYSTEMS Page 2 of 20 This document may be freely reproduced and distributed whole

  12. Copyright 2008 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2008 SUN MICROSYSTEMS This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Sun Microsystems Sun Crypto Accelerator 6000 Bootstrap Version 1;© Copyright 2008 SUN MICROSYSTEMS Page 2 of 26 This document may be freely reproduced and distributed whole

  13. Largo(q.=44) Copyright 2009 by George Peter Bird. This edition may be freely distributed, duplicated, performed, and recorded.

    E-print Network

    Bird, Peter

    Largo(q.=44) Copyright © 2009 by George Peter Bird. This edition may be freely distributed, duplicated, performed, and recorded. PETER BIRD Mars: 1. Waiting for rain Flute Vibraphone mp or synthesizer by George Peter Bird. This edition may be freely distributed, duplicated, performed, and recorded. PETER

  14. Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco 1841 and Cisco 2801 Integrated Services Router FIPS 140 #12;© Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole

  15. Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco 2811 and Cisco 2821 Integrated Services Routers with AIM;© Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact

  16. Copyright 2004 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2004 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco 3220 Mobile Access Router Card Cisco 3251 Mobile Access #12;© Copyright 2004 Cisco Systems, Inc. Page 2 of 18 This document may be freely reproduced

  17. Copyright 2006 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2006 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco Systems, Inc. 1801, 1802, 1803, 1811, and 1812 Integrated.12 August 28, 2006 #12;© Copyright 2006 Cisco Systems, Inc. Page 2 of 15 This document may be freely

  18. Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

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  19. Copyright 2006 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2006 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco Systems, Inc. ASA 5510, ASA 5520, and ASA 5540 FIPS 140;© Copyright 2006 Cisco Systems, Inc. Page 2 of 17 This document may be freely reproduced and distributed whole

  20. Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco 3825 and Cisco 3845 Integrated Services Routers with AIM;© Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact

  1. Copyright 2006 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2006 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco Systems, Inc. 7206VXR NPE-G1 and 7301 with VAM2+ FIPS 140;© Copyright 2006 Cisco Systems, Inc. Page 2 of 17 This document may be freely reproduced and distributed whole

  2. Copyright 2006 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice.

    E-print Network

    © Copyright 2006 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco Systems, Inc. 871, 876, 877, and 878 Integrated Services.13 September 20, 2006 #12;© Copyright 2006 Cisco Systems, Inc. Page 2 of 14 This document may be freely

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    E-print Network

    © Copyright 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact including this Copyright Notice. Cisco 2851 Integrated Services Router with AIM-VPN/EPII-Plus FIPS 2009 Cisco Systems, Inc. This document may be freely reproduced and distributed whole and intact

  5. Fluxes of Dissolved Trace Metals Evaluated Using Paired Thorium Isotopes

    NASA Astrophysics Data System (ADS)

    Robinson, L. F.; Huang, K.; Anderson, R. F.; Fleisher, M. Q.; Edwards, R.; Cheng, H.; Moran, S.

    2012-12-01

    This study examines the distribution of the long-lived thorium isotopes 232Th and 230Th in the Atlantic Ocean. 232Th in the ocean is derived from the partial dissolution of lithogenic minerals. 230Th is produced at a predictable rate by the decay of uranium, and its subsequent removal by efficient reversible scavenging onto settling particles provides a method to quantify 232Th fluxes to the ocean, and eventually to the seafloor. As such, combining analysis of these two isotopes in seawater has the potential to improve our ability to calculate present and past detrital fluxes to the ocean. Challenges to using this approach are both analytical, for example 232Th contamination issues encountered by many labs during the international GEOTRACES intercalibration, and the lack of systematically collected sample sets. The GEOTRACES program is helping to overcome these issues, giving deeper insights into the processes controlling the sources, sinks and cycling of thorium isotopes in the ocean. In this study, dissolved 232Th was measured in the subtropical North Atlantic, in a region of high Saharan aerosol flux, along the U.S. GEOTRACES section occupied in 2010 and 2011. The section ran from Portugal to Mauritania, under the plume of Saharan dust, and from there via Bermuda to Woods Hole. High concentration of dissolved 232Th were observed in the upper parts of the stations closest to Saharan dust plume as expected for an aerosol supply of lithogenic material to the ocean. However, high dissolved 232Th concentrations were also observed on the western side of the Atlantic basin away from the direct effects of the dust plume indicative of additional surface water lithogenic input sources. Assumptions and prospects for future development will be discussed.

  6. Distributions of dissolved vitamin B 12 and Co in coastal and open-ocean environments

    NASA Astrophysics Data System (ADS)

    Panzeca, Caterina; Beck, Aaron J.; Tovar-Sanchez, Antonio; Segovia-Zavala, Jose; Taylor, Gordon T.; Gobler, Christopher J.; Sañudo-Wilhelmy, Sergio A.

    2009-11-01

    Distributions of dissolved vitamin B 12 and total dissolved Co were measured to gain an understanding of the cycling of these interdependent micronutrients in six marine settings including; an upwelling location, a semi-enclosed bay, two urban coastal systems, and two open ocean locations. Along the coast of Baja California, Mexico, concentrations of B 12 and dissolved Co varied from 0.2 to 11 pM and 180 to 990 pM, respectively. At a nearby upwelling station, vitamin B 12 and Co concentrations ranged from 0.3 to 7.0 pM and 22 to 145 pM, and concentrations did not correlate with upwelling intensity. Concentrations of B 12 were highest within Todos Santos Bay, a semi-enclosed bay off the coast of Baja California, Mexico, during a dinoflagellate bloom, ranging from 2 to 61 pM, while Co concentrations varied between 61 and 194 pM. In the anthropogenically impacted Long Island Sound, NY, U.S.A., B 12 levels were between 0.1 and 23 pM and Co concentrations varied from 60 to 1900 pM. However, anthropogenic inputs were not evident in B 12 levels in the San Pedro Basin, located outside Los Angeles, Ca, U.S.A., where concentrations of B 12 were 0.2-1.8 pM, approximating observed open ocean B 12 concentrations. In the Southern Ocean and North Atlantic Ocean, B 12 levels were 0.4-4 pM and 0.2-2 pM, respectively. Total Co concentrations in the Southern Ocean and North Atlantic tended to be low; measuring 26-59 pM and 15-80 pM, respectively. These low Co concentrations may limit B 12 synthesis and its availability to B 12-requiring phytoplankton because the total dissolved Co pool is not necessarily entirely bioavailable.

  7. Dissolved solids, hardness, and orthophosphate of surface-water runoff in the Suwannee River Water Management District, Florida

    USGS Publications Warehouse

    Earle, J.E.

    1975-01-01

    Historical water-quality data collected from January 1965 to September 1970 were used to prepare maps showing the generalized distribution of dissolved solids, hardness, and orthophosphate in streams and lakes in the Suwannee River Water Management District. The regional concentration patterns shown on the maps are generalized and local variations may be expected. The dissolved-solids concentrations generally range from 15 to 300 milligrams per liter. Higher concentrations are found in the coastal area on tide affected streams. The concentrations of hardness as CaCO3 generally range from 10 to 200 milligrams per liter. The concentrations of dissolved orthophosphate generally range from 0 to 3 milligrams per liter. These maps provide information to those concerned with water resources management and establish a basis for comparing future quality data. (Woodard-USGS)

  8. Dissolved solids, hardness, and orthophosphate of surface-water runoff in the Northwest Florida Water Management District

    USGS Publications Warehouse

    Earle, J.E.

    1976-01-01

    Historical water-quality data collected from January 1965 to September 1970 were used to prepare maps showing the generalized distribution of dissolved solids, hardness, and orthophosphate in streams and lakes in the Northwest Florida Water Management District. The regional concentration patterns shown on the maps are generalized and local variations may be expected. The dissolved-solids concentrations generally range from 10 to 150 milligrams per liter. Higher concentrations are found in the coastal area on tide affected streams. The concentrations of hardness as CaCO3 generally range from 5 to 140 milligrams per liter. The concentrations of dissolved orthophosphate generally range from 0 to 0.75 milligrams per liter. These maps provide information to those concerned with water resources management and establish a basis for comparing future water-quality data. (Woodard-USGS)

  9. Differences in dissolved cadmium and zinc uptake among stream insects: Mechanistic explanations

    USGS Publications Warehouse

    Buchwalter, D.B.; Luoma, S.N.

    2005-01-01

    This study examined the extent to which dissolved Cd and Zn uptake rates vary in several aquatic insect taxa commonly used as indicators of ecological health. We further attempted to explain the mechanisms underlying observed differences. By comparing dissolved Cd and Zn uptake rates in several aquatic insect species, we demonstrated that species vary widely in these processes. Dissolved uptake rates were not related to gross morphological features such as body size or gill size-features that influence water permeability and therefore have ionoregulatory importance. However, finer morphological features, specifically, the relative numbers of ionoregulatory cells (chloride cells), appeared to be related to dissolved metal uptake rates. This observation was supported by Michaelis-Menten type kinetics experiments, which showed that dissolved Cd uptake rates were driven by the numbers of Cd transporters and not by the affinities of those transporters to Cd. Calcium concentrations in exposure media similarly affected Cd and Zn uptake rates in the caddisfly Hydropsyche californica. Dissolved Cd and Zn uptake rates strongly co-varied among species, suggesting that these metals are transported by similar mechanisms.

  10. Distribution and molecular characterization of dissolved DNA in aquatic environments

    SciTech Connect

    DeFlaun, M.F.

    1987-01-01

    The distribution of dissolved DNA in oceanic, estuarine and freshwater environments in southwest Florida and the Gulf of Mexico was determined by using a method for the measurement of dissolved DNA based on the fluorescence of Hoechst 33258-DNA complexes. A wide range of molecular weights (determined by agarose gel electrophoresis) was found for extracellular DNA concentrated from various aquatic environments. A model system for probing extracellular DNA from aquatic environments was developed using the plasmid pS{beta}TK2.0 containing the herpes simplex thymidine kinase (TK) gene. Plasmid DNA and the TK gene fragment added to artificial seawater were concentrated and probed with ({sup 35}S) labelled TK to establish percent recovery and detection limits for the method. The degradation of plasmid DNA added to a natural seawater sample was monitored over a 36 h period by probing with the TK gene probe. Intact plasmid was detected for up to 4 h and DNA hybridizable to the TK probe was detected for up to 24 h. These methods were used to probe for the TK gene in environmental samples of extracellular DNA. Hybridization to the TK probe was detected in both freshwater and estuarine samples.

  11. 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.

  12. Temporal variations in dissolved selenium in Lake Kinneret (Israel)

    USGS Publications Warehouse

    Nishri, A.; Brenner, I.B.; Hall, G.E.M.; Taylor, H.E.

    1999-01-01

    Selenium is an essential micronutrient for the growth of the dinoflagellate Peridinium gatunense that dominates the spring algal bloom in Lake Kinneret (LK). The relationship between the levels of dissolved selenium species and the occurance of algal blooms in this lake was studied. During algal blooms of P. gatunense in spring and of the blue-green Aphanizomenon ovalisporum in fall (in 1994) the concentration of epilimnetic dissolved organic Se (Se(org)) increased whereas that of selenite (SeIV) decreased, to levels below the limit of detection: 5 ng/l. The disappearance of SeIV during these blooms is attributed to algal uptake and it is suggested that the growth of both algae may have depended on Se(org) regeneration. A budget performed for selenate (SeVI) suggests that this species is also consumed by algae but to a lesser extent than SeIV (in 1994 ~40% of the epilimnetic load). During the stratification period the hypolimnion of Lake Kinneret becomes anoxic, with high levels of dissolved sulfide. The affects of this environment on the distribution of Se oxy-anions, selenite (SeIV) and selenate(SeVI), were also studied. At the onset of thermal stratification (March) about 35% of the lake inventory of both Se oxidized species are entrapped in the hypolimnion. During stages of oxygen depletion and H2S accumulation, SeIV is completely and SeVI partially removed from this layer. The removal is attributed to reduction followed by formation of particulate reduced products, such as elemental selenium Se(o). The ratio between SeVI to total dissolved selenium (SE(T)) in water sources to the lake is ~0.84, about twice the corresponding ratio in the lake (~0.44, during holomixis). In the lake about 75% of annual SeVI inflow from external sources undergoes reduction to selenide (Se-II) and Se(o) through epilimnetic algal assimilation and hypolimnetic anoxic reduction, respectively. It is suggested that the latter oxidation of the dissolved organic selenide released from biogenic particles and of Se(o) only to the tetravalent species is the cause for the lower ratio of SeVI/Se(T) in the lake.

  13. Speaking Freely

    ERIC Educational Resources Information Center

    Watson, Jamal Eric

    2012-01-01

    Ask Princeton University's Dr. Cornel West about his views on Black History Month, and somehow the conversation ends up with a sharp critique of the Obama administration. This article profiles West who pulls no punches when it comes to his advocacy for impoverished Americans. For more than three decades, the 58-year-old philosopher has combined…

  14. Dilution limits dissolved organic carbon utilization in the deep ocean

    NASA Astrophysics Data System (ADS)

    Arrieta, Jesús M.; Mayol, Eva; Hansman, Roberta L.; Herndl, Gerhard J.; Dittmar, Thorsten; Duarte, Carlos M.

    2015-04-01

    Oceanic dissolved organic carbon (DOC) is the second largest reservoir of organic carbon in the biosphere. About 72% of the global DOC inventory is stored in deep oceanic layers for years to centuries, supporting the current view that it consists of materials resistant to microbial degradation. An alternative hypothesis is that deep-water DOC consists of many different, intrinsically labile compounds at concentrations too low to compensate for the metabolic costs associated to their utilization. Here, we present experimental evidence showing that low concentrations rather than recalcitrance preclude consumption of a substantial fraction of DOC, leading to slow microbial growth in the deep ocean. These findings demonstrate an alternative mechanism for the long-term storage of labile DOC in the deep ocean, which has been hitherto largely ignored.

  15. 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 ?M 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 ?M are iron mats able to form. Enrichment cultures of iron oxidizers, however, grow easily at levels exceeding 100 ?M 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.

  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. 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.

  18. Process for coal liquefaction in staged dissolvers

    DOEpatents

    Roberts, George W. (Emmaus, PA); Givens, Edwin N. (Bethlehem, PA); Skinner, Ronald W. (Allentown, PA)

    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.

  19. 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...

  20. EFFECT OF DISSOLVED SOLIDS ON LIMESTONE FGD (FLUE GAS DESULFURIZATION) SCRUBBING CHEMISTRY

    EPA Science Inventory

    The paper gives results of experiments in a 0.1 MW pilot plant to determine the effects of high concentrations of chloride ions and dissolved salts on flue gas desulfurization (FGD) scrubbing chemistry, both in the natural and forced oxidation modes of operation. (Note: The tight...

  1. Multivariate Curve Resolution Methods Illustrated Using Infrared Spectra of an Alcohol Dissolved in Carbon Tetrachloride

    ERIC Educational Resources Information Center

    Grung, Bjorn; Nodland, Egil; Forland, Geir Martin

    2007-01-01

    The analysis of the infrared spectra of an alcohol dissolved in carbon tetrachloride gives a better understanding of the various multivariate curve resolution methods. The resulting concentration profile is found to be very useful for calculating the degree of association and equilibrium constants of different compounds.

  2. DETECTION OF EXOGENOUS GENE SEQUENCES IN DISSOLVED DNA FROM AQUATIC ENVIRONMENTS

    EPA Science Inventory

    A method for the concentration and detection of gene sequences in the dissolved DNA from freshwater and marine environments has been developed. he limit of detection in the dot blot format was 167 fg/ml (100 ml sample) for exogenous herpes simplex thymidine kinase (TK) gene that ...

  3. DETERMINATION OF DISSOLVED KEPONE BY DIRECT ADDITION OF XAD-2 RESIN TO WATER

    EPA Science Inventory

    Analytical procedures are described for the determination of Kepone in water, using benzene, toulene-ethyl acetate, or ethyl ether-hexane as solvents. The procedure is presently being used to quantify dissolved Kepone concentrations of less than 15 ng/l in the James River and thu...

  4. PII S0016-7037(99)00277-X The speciation of dissolved water in rhyolitic melt

    E-print Network

    Zhang, Youxue

    PII S0016-7037(99)00277-X The speciation of dissolved water in rhyolitic melt PHILLIP D. IHINGER) Abstract--Concentrations of water molecules and hydroxyl groups have been measured in rhyolitic glasses be used as a rough approximation for modeling the solution of water in rhyolitic melts with less than 2

  5. DISSOLVED ORGANIC CARBON LOSS FROM FIELD PLOTS AND WATERSHEDS IN NORTHEASTERN INDIANA, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transport of carbon (C) from hillslopes to adjacent ditches, streams and watersheds can represent a significant loss of C. While carbon associated with eroding sediments is often measured, the concentrations of dissolved organic carbon (DOC) in runoff water is rarely measured. A rainfall simulator ...

  6. Turbidity and chlorophyll introduce high uncertainty in remote sensing of Chromophoric Dissolved Organic Matter

    E-print Network

    Yu, Qian

    Abstract Turbidity and chlorophyll introduce high uncertainty in remote sensing of Chromophoric Dissolved Organic Matter (CDOM) in riverine and coastal water. To reduce the uncertainty, we developed underwater CDOM concentrations and concurrent in situ above-surface hyperspectral remote sensing reflectance

  7. Determining net dissolved organic carbon production in the hydrographically complex western Arctic Ocean

    E-print Network

    Hansell, Dennis

    Station for Research, Inc., 17 Biological Station Lane, Ferry, Bermuda, GE01 Lee W. Cooper Department experiences a short but intense phytoplankton bloom that is controlled by sea ice cover, nutrient availability, and river runoff. During the bloom, dissolved inorganic carbon (DIC) concentrations are drawn down

  8. ELEVATED LEVELS OF DISSOLVED SULFIDES IN SURFICIAL SEDIMENTS OF YAQUINA BAY ESTUARY, OREGON

    EPA Science Inventory

    Concentrations of dissolved sulfides were measured via the standard colorimetric method in porewater of surficial sediments collected during 2000 from two sites in Yaquina Bay estuary, Oregon. The first site, Idaho Point, is an area where drift green macroalgae (principally Ulva...

  9. ELEVATED DISSOLVED SULFIDES IN SURFICIAL SEDIMENTS OF YAQUINA BAY ESTUARY, OREGON

    EPA Science Inventory

    Dissolved sulfide concentrations were measured in porewater of surficial sediments collected from two exposed intertidal sites in Yaquina Bay, Oregon. Idaho Pt. (IP) is an area where drift green macroalgae is known to accumulate, and the odor of hydrogen sulfide gas (H2S) on th...

  10. CHEMISTRY OF DISSOLVED ORGANIC CARBON AND ORGANIC ACIDS IN TWO STREAMS DRAINING FORESTED WATERSHEDS

    EPA Science Inventory

    The concentration, major fractions, and contribution of dissolved organic carbon (DOG) to stream chemistry were examined in two paired streams draining upland catchments in eastern Maine. oncentrations of DOC in East and West Bear Brooks were 183 +/- 73 and 169 +/- 70 umol CL-1 (...

  11. DETERMINATION OF LETHAL DISSOLVED OXYGEN LEVELS FOR SELECTED MARINE AND ESTUARINE FISHES, CRUSTACEANS AND A BIVALVE

    EPA Science Inventory

    The objective of this study was to provide a database of the incipient lethal concentrations for reduced dissolved oxygen (DO) for selected marine and estuarine species including 12 species of fish, 9 crustaceans, and 1 bivalve. All species occur in the Virginian Province, USA, w...

  12. Comment on "Dilution limits dissolved organic carbon utilization in the deep ocean".

    PubMed

    Jiao, Nianzhi; Legendre, Louis; Robinson, Carol; Thomas, Helmuth; Luo, Ya-Wei; Dang, Hongyue; Liu, Jihua; Zhang, Rui; Tang, Kai; Luo, Tingwei; Li, Chao; Wang, Xiaoxue; Zhang, Chuanlun

    2015-12-18

    Arrieta et al. (Reports, 17 April 2015, p. 331) propose that low concentrations of labile dissolved organic carbon (DOC) preclude prokaryotic consumption of a substantial fraction of DOC in the deep ocean and that this dilution acts as an alternative mechanism to recalcitrance for long-term DOC storage. Here, we show that the authors' data do not support their claims. PMID:26680188

  13. LOSS OF DISSOLVED ORGANIC CARBON FROM WATERSHEDS IN NORTHEASTERN INDIANA, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transport of carbon from hillslopes to adjacent ditches, streams, and watersheds can represent a significant loss of C. While carbon associated with eroding sediments is often measured, the concentration of dissolved organic carbon (DOC) in runoff water is rarely measured. As part of a larger proj...

  14. RESEARCH AT THE GULF ECOLOGY DIVISION ON THE EFFECTS OF LOW DISSOLVED OXYGEN ON ESTUARINE ANIMALS

    EPA Science Inventory

    Concerns about hypoxia and its effects on saltwater organisms are increasing as environmental conditions in the inshore and nearshore marine environments are better understood. Along the Gulf of Mexico coast, periods of very low dissolved oxygen (D.O.) concentrations have been re...

  15. ISOLATION OF DISSOLVED ORGANIC MATTER FROM THE SUWANNEE RIVER USING REVERSE OSMOSIS

    EPA Science Inventory

    A portable reverse osmosis (RO) system was constructed and used to concentrate dissolved organic matter (DOM) from the Suwannee River in southeastern Georgia. sing this RO system, 150-180 1/h of river water could be processed with 90% recovery of DOM. fter further cation exchange...

  16. Identification of dissolved-constituent sources in mine-site ground water using batch mixing

    USGS Publications Warehouse

    Clark, Gregory M.; Williams, Robert S., Jr.

    1991-01-01

    Batch-mixing experiments were used to help identify lithologic and mineralogic sources of increased concentrations of dissolved solids in water affected by surface coal mining in northwestern Colorado. Ten overburden core samples were analyzed for mineral composition and mixed with distilled water for 90 days until mineral-water equilibrium was reached. Between one day and 90 days after initial contact, specific conductance in the sample mixtures had a median increase of 306 percent. Dissolved-solids concentrations ranged from 200 to 8,700 mg/L in water samples extracted from the mixtures after 90 days. Mass-balance simulations were conducted using the geochemical models BALANCE and WATEQF to quantify mineral-water interactions occurring in five selected sample mixtures and in water collected from a spring at a reclaimed mine site. The spring water is affected by mineral-water interactions occurring in all of the lithologic units comprising the overburden. Results of the simulations indicate that oxidation of pyrite, dissolution of dolomite, gypsum, and epsomite, and cation-exchange reactions are the primary mineral-water interactions occurring in the overburden. Three lithologic units in the overburden (a coal, a sandstone, and a shale) probably contribute most of the dissolved solids to the spring water. Water sample extracts from mixtures using core from these three units accounted for 85 percent of the total dissolved solids in the 10 sample extracts. Other lithologic units in the over-burden probably contribute smaller quantities of dissolved solids to the spring water.

  17. Dissolved organic matter in anoxic pore waters from Mangrove Lake, Bermuda

    USGS Publications Warehouse

    Orem, W.H.; Hatcher, P.G.; Spiker, E. C.; Szeverenyi, N.M.; Maciel, G.E.

    1986-01-01

    Dissolved organic matter and dissolved inorganic chemical species in anoxic pore water from Mangrove Lake, Bermuda sediments were studied to evaluate the role of pore water in the early diagenesis of organic matter. Dissolved sulphate, titration alkalinity, phosphate, and ammonia concentration versus depth profiles were typical of many nearshore clastic sediments and indicated sulphate reduction in the upper 100 cm of sediment. The dissolved organic matter in the pore water was made up predominantly of large molecules, was concentrated from large quantities of pore water by using ultrafiltration and was extensively tudied by using elemental and stable carbon isotope analysis and high-resolution, solid state 13C nuclear magnetic resonance and infrared spectroscopy. The results indicate that this material has a predominantly polysaccharide-like structure and in addition contains a large amount of oxygen-containing functional groups (e.g., carboxyl groups). The 13C nulcear magnetic resonance spectra of the high-molecular-weight dissolved organic matter resemble those of the organic matter in the surface sediments of Mangrove Lake. We propose that this high-molecular-weight organic matter in pore waters represents the partially degraded, labile organic components of the sedimentary organic matter and that pore waters serve as a conduit for removal of these labile organic components from the sediments. The more refractory components are, thus, selectively preserved in the sediments as humic substances (primarily humin). ?? 1986.

  18. Ocean metabolism and dissolved organic matter: How do small dissolved molecules persist in the ocean?

    NASA Astrophysics Data System (ADS)

    Benner, Ronald

    2010-05-01

    The ocean reservoir of dissolved organic matter (DOM) is among the largest global reservoirs (~700 Pg C) of reactive organic carbon. Marine primary production (~50 Pg C/yr) by photosynthetic microalgae and cyanobacteria is the major source of organic matter to the ocean and the principal substrate supporting marine food webs. The direct release of DOM from phytoplankton and other organisms as well as a variety of other processes, such as predation and viral lysis, contribute to the ocean DOM reservoir. Continental runoff and atmospheric deposition are relatively minor sources of DOM to the ocean, but some components of this material appear to be resistant to decomposition and to have a long residence time in the ocean. Concentrations of DOM are highest in surface waters and decrease with depth, a pattern that reflects the sources and diagenesis of DOM in the upper ocean. Most (70-80%) marine DOM exists as small molecules of low molecular weight (<1 kDalton). Surprisingly, high-molecular-weight (>1 kDalton) DOM is relatively enriched in major biochemicals, such as combined neutral sugars and amino acids, and is more bioavailable than low-molecular-weight DOM. The observed relationships among the size, composition, and reactivity of DOM have led to the size-reactivity continuum model, which postulates that diagenetic processes lead to the production of smaller molecules that are structurally altered and resistant to microbial degradation. The radiocarbon content of these small dissolved molecules also indicates these are the most highly aged components of DOM. Chemical signatures of bacteria are abundant in DOM and increase during diagenesis, indicating bacteria are an important source of slowly cycling biochemicals. Recent analyses of DOM isolates by ultrahigh-resolution mass spectrometry have revealed an incredibly diverse mixture of molecules. Carboxyl-rich alicyclic molecules are abundant in DOM, and they appear to be derived from diagenetically-altered terpenoids, such as sterols and hopanoids. Thermally-altered molecules, including black carbon, also appear to be important components of DOM, but their origins are unclear. We are rapidly acquiring novel information about the composition and molecular identity of DOM, and novel insights about the origins, transformations and fates this vast reservoir of DOM are emerging. This presentation will review and synthesize this information for comparison with non-living organic matter in other systems.

  19. Optogenetic control of freely behaving adult Drosophila using a red-shifted channelrhodopsin

    PubMed Central

    Inagaki, Hidehiko K.; Jung, Yonil; Hoopfer, Eric D.; Wong, Allan M.; Mishra, Neeli; Lin, John Y.; Tsien, Roger Y.; Anderson, David J.

    2014-01-01

    Optogenetics allows the manipulation of neural activity in freely moving animals with millisecond precision, but its application in Drosophila has been limited. Here we show that a recently described Red activatable Channelrhodopsin (ReaChR) permits control of complex behavior in freely moving adult flies, at wavelengths that are not thought to interfere with normal visual function. This tool affords the opportunity to control neural activity over a broad dynamic range of stimulation intensities. Using time-resolved activation, we show that the neural control of male courtship song can be separated into probabilistic, persistent and deterministic, command-like components. The former, but not the latter, neurons are subject to functional modulation by social experience, supporting the idea that they constitute a locus of state-dependent influence. This separation is not evident using thermogenetic tools, underscoring the importance of temporally precise control of neuronal activation in the functional dissection of neural circuits in Drosophila. PMID:24363022

  20. Whole-brain calcium imaging with cellular resolution in freely behaving C. elegans

    E-print Network

    Nguyen, Jeffrey P; Linder, Ashley N; Plummer, George S; Shaevitz, Joshua W; Leifer, Andrew M

    2015-01-01

    The ability to acquire large-scale recordings of neuronal activity in awake and unrestrained animals poses a major challenge for studying neural coding of animal behavior. We present a new instrument capable of recording intracellular calcium transients from every neuron in the head of a freely behaving C. elegans with cellular resolution while simultaneously recording the animal's position, posture and locomotion. We employ spinning-disk confocal microscopy to capture 3D volumetric fluorescent images of neurons expressing the calcium indicator GCaMP6s at 5 head-volumes per second. Two cameras simultaneously monitor the animal's position and orientation. Custom software tracks the 3D position of the animal's head in real-time and adjusts a motorized stage to keep it within the field of view as the animal roams freely. We observe calcium transients from 78 neurons and correlate this activity with the animal's behavior. Across worms, multiple neurons show significant correlations with modes of behavior correspo...

  1. Multiple leading edge vortices of unexpected strength in freely flying hawkmoth

    PubMed Central

    Johansson, L. Christoffer; Engel, Sophia; Kelber, Almut; Heerenbrink, Marco Klein; Hedenström, Anders

    2013-01-01

    The Leading Edge Vortex (LEV) is a universal mechanism enhancing lift in flying organisms. LEVs, generally illustrated as a single vortex attached to the wing throughout the downstroke, have not been studied quantitatively in freely flying insects. Previous findings are either qualitative or from flappers and tethered insects. We measure the flow above the wing of freely flying hawkmoths and find multiple simultaneous LEVs of varying strength and structure along the wingspan. At the inner wing there is a single, attached LEV, while at mid wing there are multiple LEVs, and towards the wingtip flow separates. At mid wing the LEV circulation is ~40% higher than in the wake, implying that the circulation unrelated to the LEV may reduce lift. The strong and complex LEV suggests relatively high flight power in hawmoths. The variable LEV structure may result in variable force production, influencing flight control in the animals. PMID:24253180

  2. Dual-modal (OIS/LSCI) imager of cerebral cortex in freely moving animals

    NASA Astrophysics Data System (ADS)

    Lu, Hongyang; Miao, Peng; Liu, Qi; Li, Yao; Tong, Shanbao

    2012-03-01

    Optical intrinsic signals (OIS) and laser speckle contrast imaging (LSCI) have been used for years in the study of the cerebral blood flow (CBF) and hemodynamic responses to the neural activity under functional stimulation. So far, most in vivo rodent experiments are based on the anesthesia model when the animals are in unconscious and restrained conditions. The influences of anesthesia on the neural activity have been documented in literature. In this study, we designed a miniature head-mounted dual-modal imager in freely moving animals that could monitor in real time the coupling of local oxygen consumption and blood perfusion of CBF by integrating different imaging modalities of OIS and LSCI. The system facilitates the study the cortical hemodynamics and neural-hemodynamic coupling in real time in freely moving animals.

  3. Dual-modal (OIS/LSCI) imager of cerebral cortex in freely moving animals

    NASA Astrophysics Data System (ADS)

    Lu, Hongyang; Miao, Peng; Liu, Qi; Li, Yao; Tong, Shanbao

    2011-11-01

    Optical intrinsic signals (OIS) and laser speckle contrast imaging (LSCI) have been used for years in the study of the cerebral blood flow (CBF) and hemodynamic responses to the neural activity under functional stimulation. So far, most in vivo rodent experiments are based on the anesthesia model when the animals are in unconscious and restrained conditions. The influences of anesthesia on the neural activity have been documented in literature. In this study, we designed a miniature head-mounted dual-modal imager in freely moving animals that could monitor in real time the coupling of local oxygen consumption and blood perfusion of CBF by integrating different imaging modalities of OIS and LSCI. The system facilitates the study the cortical hemodynamics and neural-hemodynamic coupling in real time in freely moving animals.

  4. Chronic, Wireless Recordings of Large Scale Brain Activity in Freely Moving Rhesus Monkeys

    PubMed Central

    Schwarz, David A.; Lebedev, Mikhail A.; Hanson, Timothy L.; Dimitrov, Dragan F.; Lehew, Gary; Meloy, Jim; Rajangam, Sankaranarayani; Subramanian, Vivek; Ifft, Peter J.; Li, Zheng; Ramakrishnan, Arjun; Tate, Andrew; Zhuang, Katie; Nicolelis, Miguel A.L.

    2014-01-01

    Advances in techniques for recording large-scale brain activity contribute to both the elucidation of neurophysiological principles and the development of brain-machine interfaces (BMIs). Here we describe a neurophysiological paradigm for performing tethered and wireless large-scale recordings based on movable volumetric three-dimensional (3D) multielectrode implants. This approach allowed us to isolate up to 1,800 units per animal and simultaneously record the extracellular activity of close to 500 cortical neurons, distributed across multiple cortical areas, in freely behaving rhesus monkeys. The method is expandable, in principle, to thousands of simultaneously recorded channels. It also allows increased recording longevity (5 consecutive years), and recording of a broad range of behaviors, e.g. social interactions, and BMI paradigms in freely moving primates. We propose that wireless large-scale recordings could have a profound impact on basic primate neurophysiology research, while providing a framework for the development and testing of clinically relevant neuroprostheses. PMID:24776634

  5. Development of implantable optoelectronic module for optical brain tissue stimulation in freely moving mice

    NASA Astrophysics Data System (ADS)

    Rusakov, Konstantin; Czajkowski, Rafa?; Ka?mierczak, Andrzej

    2015-09-01

    The research aims to design and manufacture of wireless optogenetics devices for freely moving animals in cages IntelliCage system. The purpose of the device is to stimulate specific brain regions using light. The constructed device consists of a light source and optical fibre structure responsible for delivering light into the corresponding region of the brain of the animal. The size of the animal (mouse) and the fact that it is freely moving imposes substantial limitations with respect to the size and weight of the optoelectronic device. The present paper describes research on optical fibre structure fabrication, assembling it to the small size (less than 500 × 500 ?m2 top surface) LED chip and experimental validation of the optoelectronic stimulator.

  6. Environmental photoinactivation of extracellular phosphatases and the effects of dissolved organic matter.

    PubMed

    Janssen, Elisabeth M L; McNeill, Kristopher

    2015-01-20

    Alkaline phosphatases are ubiquitous extracellular enzymes in aquatic systems and play a central role in the biogeochemical cycling of phosphorus. Yet, the photochemical stability of phosphatase and effects of natural organic matter (DOM) are not completely understood. We demonstrate that phosphatase activity in natural biofilm samples decreased during sunlight exposure similar to well-defined bacterial phosphatase solutions. Direct photoinactivation was slowed by more than 50% in the presence of redox-active dissolved organic matter (DOM, 10 mgC L(–1)) or a model antioxidant (esculetin, 50 ?M), even after light screening effects had been accounted for. Thus, DOM can not only inhibit enzymes (in the dark) or sensitize photodegradation by producing photochemically produced reactive intermediates but can also significantly quench direct photoinactivation of phosphatase. Our data further suggest that direct photooxidation of tryptophan residues within the protein structure are significantly involved in the photoinactivation of phosphatase because a loss of tryptophan-like fluorescence paralleled photoinactivation kinetics and because DOM acted as an antioxidant toward photoinactivation, a phenomenon recently established for the photooxidation of freely dissolved tryptophan. Thus, photoinactivation of phosphatase can be significantly slowed in the presence of naturally occurring antioxidants like DOM. The mechanistic link between tryptophan photooxidation and inactivation of phosphatase may have applicability to other extracellular enzymes but remains to be established. PMID:25495644

  7. Surface Enhanced Raman Scattering Monitoring of Chain Alignment in Freely Suspended Nanomembranes

    NASA Astrophysics Data System (ADS)

    Jiang, Chaoyang; Lio, Wilber Y.; Tsukruk, Vladimir V.

    2005-09-01

    The molecular chain reorganization in freely standing membranes with encapsulated gold nanoparticles was studied with surface enhanced Raman scattering (SERS) in the course of their elastic deformations. The efficient SERS was enabled by optimizing the design of gold nanoparticle forming chainlike aggregates, thus creating an exceptional ability to conduct in situ monitoring. Small deformations resulted in the radial orientation of side phenyl rings of polymer backbones while larger deflections led to the polymer chains bridging adjacent nanoparticles within one-dimensional aggregates.

  8. Using dislocations to probe surface reconstruction in thick freely suspended liquid crystalline films

    E-print Network

    J. A. Collett; Daniel Martinez Zambrano

    2015-08-14

    Surface interactions can cause freely suspended thin liquid crystalline films to form phases different from the bulk material, but it is not known what happens at the surface of thick films. Edge dislocations can be used as a marker for the boundary between the bulk center and the reconstructed surface. We use noncontact mode atomic force microscopy to determine the depth of edge dislocations below the surface of freely suspended thick films of 4-n-heptyloxybenzylidene-4-n-heptylaniline (7O.7) in the crystalline B phase. 3.0 +/- 0.1 nm high steps are found with a width that varies with temperature between 56 C and 59 C. Using a strain model for the profile of liquid crystalline layers above an edge dislocation to estimate the depth of the dislocation, we find that the number of reconstructed surface layers increases from 4 to 50 layers as the temperature decreases from 59 C to 56 C. This trend tracks the behavior of the phase boundary in the thickness dependent phase diagram of freely suspended films of 7O.7, suggesting that the surface may be reconstructed into a smectic F region.

  9. Using dislocations to probe surface reconstruction in thick freely suspended liquid crystalline films

    NASA Astrophysics Data System (ADS)

    Collett, J. A.; Martinez Zambrano, Daniel

    2015-10-01

    Surface interactions can cause freely suspended thin liquid crystalline films to form phases different from the bulk material, but it is not known what happens at the surface of thick films. Edge dislocations can be used as a marker for the boundary between the bulk center and the reconstructed surface. We use noncontact mode atomic force microscopy to determine the depth of edge dislocations below the surface of freely suspended thick films of 4-n -heptyloxybenzylidene-4-n -heptylaniline (7O.7) in the crystalline B phase. Here, 3.0 ±0.1 nm high steps are found with a width that varies with temperature between 56 and 59 ?C. Using a strain model for the profile of liquid crystalline layers above an edge dislocation to estimate the depth of the dislocation, we find that the number of reconstructed surface layers increases from 4 to 50 layers as the temperature decreases from 59 to 56 ?C . This trend tracks the behavior of the phase boundary in the thickness dependent phase diagram of freely suspended films of 7O.7, suggesting that the surface may be reconstructed into a smectic F region.

  10. Changes in dissolved organic carbon and total dissolved nitrogen fluxes across subtropical forest ecosystems at different successional stages

    NASA Astrophysics Data System (ADS)

    Yan, Junhua; Li, Kun; Wang, Wantong; Zhang, Deqiang; Zhou, Guoyi

    2015-05-01

    Lateral transports of carbon and nitrogen are important processes linking terrestrial ecosystems and aquatic systems. Most previous studies made in temperate forests found that fluxes of carbon and nitrogen by runoff water varied in different forests, but few studies have been made in subtropical forests. This study was to investigate dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) fluxes at the catchment scale along a subtropical forest succession gradient from pine forest (pioneer) to coniferous and broadleaved mixed forest (transitional) to broadleaved forest (mature). Our results showed that DOC concentration significantly decreased (p<0.001) while TDN concentration significantly increased (p<0.001) in runoff water from pioneer to mature forests, which in turn resulted in a decrease in DOC flux and an increase in TDN flux, as mean annual runoff did not vary significantly among three succession forest catchments. The mean (±standard deviation) annual DOC flux was 118.1±43.6, 88.3±16.7 and 77.2±11.7 kg ha-1 yr-1for pioneer, transitional and mature forest catchments, respectively; and the mean annual TDN flux was 9.9 ±2.7, 18.2±3.0 and 21.2 ±4.5 kg ha-1 yr-1for pioneer, transitional and mature forest catchments, respectively. The mature forest reduced DOC flux by increased soil chemical adsorption and physical protection. An increase in TDN flux from pioneer to mature forests was consistent with the previous finding that mature forest was nitrogen saturated while pioneer forest was nitrogen limited. Therefore large-scale conversion of pioneer forests to transitional or mature forests in subtropical China will reduce DOC concentration and increase TDN concentration in the down-stream water, which may have significant impact on its water quality and aquatic biological activities.

  11. 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.

  12. Optical Characterization of Dissolved Organic Matter in Maine Rivers

    NASA Astrophysics Data System (ADS)

    White, D. P.; Roesler, C. S.; Bourakovsky, A.; Drapeau, S.; Huntington, T. G.; Billmire, M.; Camill, P.

    2014-12-01

    The coastal waters of the Gulf of Maine are significantly impacted by the input of fresh water from a distributed river system. In this study, we focus on the four largest watersheds (Androscoggin, Kennebec, Penobscot and St. John) that contribute to the freshwater inputs. In particular, we investigated the input of dissolved organic carbon via PARAFAC analysis of excitation/emission matrix fluorescence spectroscopy. Monthly sampling of over 65 stations for three years has yielded a wealth of information about tributary characteristics. Specifically, we investigated the role of water quality properties and landscape coverage in the mobilization and flux of different components of DOC and how those properties vary spatially across the landscape and temporally over seasons and between years. Across all rivers, humic-like materials were the most prevalent components at the river mouths; accumulating along the rivers due to sequential tributary inputs. The concentration of humic-like materials increased latitudinally from the Androscoggin to St John, a geographic progression in source material also correlated to climate variations, land coverage or bedrock acidity. Dissolved proteins displayed positive relationships with climatological Chlorophyll a and total Nitrogen values. In all rivers, peak fluorescence of dissolved proteins was observed during summer months, with the maximum intensity observed in the Androscoggin River. The magnitude and pattern of seasonal flux of fluorescent materials into the Gulf of Maine was very similar between the Penobscot and the Kennebec rivers. The flux of all DOM components was highest during the spring freshet, with a secondary peak during fall precipitation maxima and lowest during August, likely due to both low mobilization and photo degradation of river borne materials.

  13. Formulation and evaluation of aceclofenac mouth-dissolving tablet

    PubMed Central

    Solanki, Shailendra Singh; Dahima, Rashmi

    2011-01-01

    Aceclofenac has been shown to have potent analgesic and anti-inflammatory activities similar to indomethacin and diclofenac, and due to its preferential Cox-2 blockade, it has a better safety than conventional Non steroidal anti-inflammatory drug (NSAIDs) with respect to adverse effect on gastrointestinal and cardiovascular systems. Aceclofenac is superior from other NSAIDs as it has selectivity for Cox-2, a beneficial Cox inhibitor is well tolerated, has better Gastrointestinal (GI) tolerability and improved cardiovascular safety when compared with other selective Cox-2 inhibitor. To provide the patient with the most convenient mode of administration, there is need to develop a fast-disintegrating dosage form, particularly one that disintegrates and dissolves/disperses in saliva and can be administered without water, anywhere, any time. Such tablets are also called as “melt in mouth tablet.” Direct compression, freeze drying, sublimation, spray drying, tablet molding, disintegrant addition, and use of sugar-based excipients are technologies available for mouth-dissolving tablet. Mouth-dissolving tablets of aceclofenac were prepared with two different techniques, wet granulation and direct compression, in which different formulations were prepared with varying concentration of excipients. These tablets were evaluated for their friability, hardness, wetting time, and disintegration time; the drug release profile was studied in buffer Phosphate buffered Saline (PBS) pH 7.4. Direct compression batch C3 gave far better dissolution than the wet granulation Batch F2, which released only 75.37% drug, and C3, which released 89.69% drug in 90 minutes. PMID:22171305

  14. 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...

  15. Mississippi river methods comparison study: Implications for water quality monitoring of dissolved trace elements

    USGS Publications Warehouse

    Taylor, H.E.

    1995-01-01

    Recent reports have questioned the validity of dissolved trace element concentrations reported by the U.S. Geological Survey's National Stream Quality Accounting Network (NASQAN) as well as by other water-quality monitoring programs. To address these concerns and to evaluate the NASQAN protocols, the U.S. Geological Survey undertook the Mississippi River Methods Comparison Study. We report here the major results and implications of this study. In particular, we confirm the possible inaccuracy of previous NASQAN dissolved trace element data. The results suggest that all steps of the NASQAN protocol (sampling, processing, and analysis) require revision, though the sample filtration step appears to be of particular concern.

  16. Dissolved and Particulate 230Th - 232Th systematics in the Central Equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Lopez, G. I.; Marcantonio, F.

    2013-12-01

    To complement our work in the eastern Equatorial Pacific, we have measured total and dissolved 230Th and 232Th in the central Equatorial Pacific at two sites, one at 8°N and the other at the equator (ML1208-03CTD; 00° 13.166' S, 155° 57.668' W and ML1208-12CTD; 8° 19.989' N, 159° 18.000' W). The two seawater casts were collected in May 2012 during an NSF-funded "Line Islands" cruise to test for the extent of advection or diffusion of dissolved 230Th from the oligotrophic North Pacific gyre (low particle flux) to the more productive equatorial region (high particle flux). Our thorium results are similar to previous data published for the western and central North Pacific Ocean. Dissolved 230Th concentrations range from 1.1 fg/kg at 100 m to 30.8 fg/kg at 4400 m, while dissolved 232Th concentrations span from 8.1 pg/kg at 900 m to 19.7 pg/kg at 4400 m. The pattern of the dissolved 230Th profile at 8°N is essentially linear from the surface to 2000 m. From 2000 m to 3000 m, the dissolved 230Th concentrations are constant, and then from 3000 m to the bottom, the profile is linear again. At the same site, the particulate fraction of the total seawater 230Th increases exponentially from about 0% at the surface to 38% at 4400 m. From 0 to 3000 m at 8°N, dissolved 232Th concentrations display a relatively constant pattern (variability of about 20%). From 3000 m to 4400 m, dissolved 232Th contents are more variable, but generally increase toward greater depths. The proportion of 232Th in the particulate fraction of the total seawater sample increases exponentially with depth to a value of 58% in the bottommost sample. We will present additional data from the equator and assess the particulate dynamics that control the distribution of thorium isotopes in central equatorial Pacific seawater.

  17. A wireless beta-microprobe based on pixelated silicon for in vivo brain studies in freely moving rats

    NASA Astrophysics Data System (ADS)

    Märk, J.; Benoit, D.; Balasse, L.; Benoit, M.; Clémens, J. C.; Fieux, S.; Fougeron, D.; Graber-Bolis, J.; Janvier, B.; Jevaud, M.; Genoux, A.; Gisquet-Verrier, P.; Menouni, M.; Pain, F.; Pinot, L.; Tourvielle, C.; Zimmer, L.; Morel, C.; Laniece, P.

    2013-07-01

    The investigation of neurophysiological mechanisms underlying the functional specificity of brain regions requires the development of technologies that are well adjusted to in vivo studies in small animals. An exciting challenge remains the combination of brain imaging and behavioural studies, which associates molecular processes of neuronal communications to their related actions. A pixelated intracerebral probe (PIXSIC) presents a novel strategy using a submillimetric probe for beta+ radiotracer detection based on a pixelated silicon diode that can be stereotaxically implanted in the brain region of interest. This fully autonomous detection system permits time-resolved high sensitivity measurements of radiotracers with additional imaging features in freely moving rats. An application-specific integrated circuit (ASIC) allows for parallel signal processing of each pixel and enables the wireless operation. All components of the detector were tested and characterized. The beta+ sensitivity of the system was determined with the probe dipped into radiotracer solutions. Monte Carlo simulations served to validate the experimental values and assess the contribution of gamma noise. Preliminary implantation tests on anaesthetized rats proved PIXSIC's functionality in brain tissue. High spatial resolution allows for the visualization of radiotracer concentration in different brain regions with high temporal resolution.

  18. Inhibition of NADH oxidation by chloramphenicol in the freely moving rat measured by picosecond time-resolved emission spectroscopy.

    PubMed

    Mottin, Stéphane; Laporte, Pierre; Cespuglio, Raymond

    2003-02-01

    Owing to the lack of methods capable to monitor the energetic processes taking place within small brain regions (i.e. nucleus raphe dorsalis, nRD), the neurotoxicity of various categories of substances, including antibiotics and psycho-active drugs, still remains difficult to evaluate. Using an in vivo picosecond optical spectroscopy imaging method, we report that chloramphenicol (CAP), besides its well-known ability to inhibit the mitochondria protein synthesis, also influences the NADH/NAD+ redox processes of the respiratory chain. At a 200-mg/kg dose, CAP indeed produces a marked increase in the fluorescent signal of the nRD which, according to clear evidence, is likely to be related to the NADH concentration. This effect also implies an efficient inhibition of complex I of the respiratory chain by CAP. It refers to the mechanism through which the adverse effects of the antibiotic may take place. It could explain why paradoxical sleep, a state needing aerobic energy to occur, is suppressed after CAP administration. The present approach constitutes the first attempt to determine by fluorescence methods the effects of substances on deep brain structures of the freely moving animal. It points out that in vivo ultrafast optical methods are innovative and adequate tools for combined neurochemical and behavioural approaches. PMID:12562508

  19. PCBs, PCDD/Fs and PAHs in dissolved, suspended and settling particulate matrixes from the Baltic Sea

    SciTech Connect

    Naef, C.; Broman, D.; Zebuehr, Y.

    1994-12-31

    The occurrence and dynamics of polychlorinated biphenyls (PCBs), dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs) are discussed on the basis of results from samples taken at pristine coastal and off shore locations in the Baltic Sea. The sampling techniques used were high volume cross flow filtration and sediment traps for suspended and settling particulate matter, respectively, and polyurethane foam adsorbents for the compounds associated with the apparently dissolved fractions. All samples were Soxhlet extracted with toluene and separated on a HPLC system followed by quantification on GS/MS. The importance of parameters such as concentrations of particulate lipids, particulate organic carbon and dissolved organic carbon, etc. for the distribution of the compounds between the suspended and settling particulate matrixes and the dissolved phase in the water are discussed. In situ determined particulate organic carbon-water partition coefficients as well as predicted dissolved organic carbon-water partition coefficients and approximations of the average ``truly`` dissolved concentrations are presented. The particulate and dissolved concentrations in the mixed surface layer are discussed in perspective to the particulate flux of PCBs, PCDD/Fs and PAHs.

  20. Seasonal Changes in Arctic Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Boot, C. M.; Wallenstein, M. D.; Schimel, J.

    2011-12-01

    The Arctic is a landscape in flux. Temperatures are shifting upward and plant communities are transitioning from tussock to shrub tundra in some regions. Decomposition processes sensitive to temperature, moisture, and plant inputs are controls on the source/sink dynamics of the Arctic C pool. The response of decomposition to warming will, in part, determine if the Arctic C pool feeds back positively or negatively to climate change. The portion of the C pool immediately available to decomposers is dissolved organic matter (DOM). The aim of this is study is to examine the molecular composition of DOM to determine which components vary seasonally in soil pore water among three vegetation types at Toolik Field Station in Alaska. Vegetation types include wet sedge (Carex aquatilis and Eriophorum angustifolium), moist acidic tussock (E. vaginatum) and shrub tundra (Betula nana and Salix sp.). These sites were sampled during winter/summer transitions in 2010 in order to capture both growing season and winter dynamics. We expected the chemical composition of DOM in pore water to be distinct among plant communities due to differences in root exudates, litter chemistry and microbial community; and vary seasonally due to shifting temperature and water availability and their impacts on decomposition of DOM. Soil pore water was isolated through centrifugation and is being characterized with ultra high performance liquid chromatography (UPLC) in line with a quadrupole time of flight mass spectrometer (QTOF-MS) as well as with specific UV absorbance at 254 nm (SUVA), and excitation emission matrices (EEMs) generated by fluorescence spectroscopy. The DOM concentrations across vegetation types show consistent seasonal patterns, spiking at thaw, and declining through late summer. As soils freeze these patterns diverge-in tussock soils DOM concentration decreases slightly, while in shrub and wet sedge sites it increases. SUVA values (indicator of aromaticity) were consistent among vegetation types across seasons; starting low in late winter and at thaw, increasing over the course of the summer and decreasing at the summer to winter transition. Metabolite profiles generated with UPLC-MS were evaluated using principle component analysis. Sampling date explained the most variation in this dataset, with metabolite profiles of the DOM most different in the summer to winter transition. Over 6000 mass features were detected in the metabolite profiles and at least 1500 of these features were significantly different between late summer and early winter. Fluorescence EEMs have been collected for the complete dataset and analysis is underway. Overall, these data suggest the composition of DOM varies more due to season than vegetation type, with changes in quantity, aromaticity, and shifts in the metabolite profiles occurring at seasonal transitions. Efforts are continuing to identify some of the most variable components with MS and EEMs data. By understanding which chemical components of DOM shift seasonally, we can anticipate what portions of the DOM are most subject to change in a warming arctic; and how the gain/loss of those components will play into the sink/source C dynamics under future climate scenarios.

  1. 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.

  2. 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)

  3. Feasibility of using alginate to absorb dissolved copper from aqueous media

    SciTech Connect

    Jang, L.K.; Brand, W.; Resong, M.; Mainieri, W.; Geesey, G.G. )

    1990-11-01

    Alginate (a biopolymer from kelp and some bacterial strains) is known to absorb copper favorably in the presence of other cations. In this work, the feasibility of using a 2-liter batch three-phase (air/liquid/alginate gel) loop fluidized bed reactor to polish water containing 10-150 ppm dissolved copper was investigated. Three methods were tested: (1) calcium alginate spheres, prepared by dispensing sodium alginate (3.2 wt. % in water) into a 0.05 M calcium nitrate solution, were used as the absorbent, (2) the alginate spheres were formed in situ by dispensing the sodium alginate solution directly into the reactor fluid, and (3) same as (2) except that a trace amount of EDTA was added to the alginate solution. Batch absorption data showed that Method 3 yielded the best result; the concentration of dissolved copper was successfully reduced from 140 ppm to 10 ppm with 3.2 g sodium alginate and 0.2 g EDTA used. However, when the initial concentration was below 40 ppm, both Method 2 and Method 3 are not recommended because the concentration of dissolved copper was too low to allow in situ formation of alginate spheres. Method 1 was found to be useful for treating water containing 10 ppm dissolved copper. But the competition from calcium seriously affected the effective capacity of the alginate for copper. The application of the classical shell progressive model to describe the absorption kinetics was discussed.

  4. Dissolved Organic Matter Quality in a Shallow Aquifer of Bangladesh: Implications for Arsenic Mobility.

    PubMed

    Mladenov, Natalie; Zheng, Yan; Simone, Bailey; Bilinski, Theresa M; McKnight, Diane M; Nemergut, Diana; Radloff, Kathleen A; Rahman, M Moshiur; Ahmed, Kazi Matin

    2015-09-15

    In some high arsenic (As) groundwater systems, correlations are observed between dissolved organic matter (DOM) and As concentrations, but in other systems, such relationships are absent. The role of labile DOM as the main driver of microbial reductive dissolution is not sufficient to explain the variation in DOM-As relationships. Other processes that may also influence As mobility include complexation of As by dissolved humic substances, and competitive sorption and electron shuttling reactions mediated by humics. To evaluate such humic DOM influences, we characterized the optical properties of filtered surface water (n = 10) and groundwater (n = 24) samples spanning an age gradient in Araihazar, Bangladesh. Further, we analyzed large volume fulvic acid (FA) isolates (n = 6) for optical properties, C and N content, and (13)C NMR spectroscopic distribution. Old groundwater (>30 years old) contained primarily sediment-derived DOM and had significantly higher (p < 0.001) dissolved As concentration than groundwater that was younger than 5 years old. Younger groundwater had DOM spectroscopic signatures similar to surface water DOM and characteristic of a sewage pollution influence. Associations between dissolved As, iron (Fe), and FA concentration and fluorescence properties of isolated FA in this field study suggest that aromatic, terrestrially derived FAs promote As-Fe-FA complexation reactions that may enhance As mobility. PMID:26192081

  5. Tracing origin and fate of dissolved greenhouse gases in Malaysian peat-draining rivers

    NASA Astrophysics Data System (ADS)

    Müller, Denise; Warneke, Thorsten; Rixen, Tim; Denis, Nastassia; Müller, Moritz; Notholt, Justus

    2014-05-01

    Tropical peatlands are known to store large amounts of organic carbon. Peat-draining rivers in these regions receive considerable amounts of carbon from these soils, yet, its fate remains poorly studied. Although a number of recent studies investigated greenhouse gas production and emission from inland waters, only a small number focused on tropical freshwaters, and data from tropical peat-draining rivers are particularly lacking. We investigated rivers in a peat-dominated catchment in Sarawak, Malaysia. Dissolved greenhouse gases (GHG) were measured with Fourier Transform InfraRed (FTIR) spectroscopy. It allows for the simultaneous and continuous measurement of major GHG (CO2 and ?13C in CO2, CH4, N2O, and CO) with high accuracy and precision. We found that concentrations of dissolved CO, CO2 and CH4 were higher than the respective atmospheric equilibrium concentration, suggesting that those rivers are a source of these GHG to the atmosphere. Enhanced N2O concentrations were only found around some cultivated areas. In order to trace the origin of the GHG, we quantified dissolved organic carbon (DOC), particulate organic carbon (POC), inorganic nutrients and different parameters that describe water chemistry. Stable carbon isotope analysis of dissolved inorganic carbon (DIC) yielded indications of a terrestrial source of inorganic carbon in the river, suggesting that in-situ respiration of organic matter might play an important role.

  6. Dissolved Solids in Basin-Fill Aquifers and Streams in the Southwestern United States

    USGS Publications Warehouse

    Anning, David W.; Bauch, Nancy J.; Gerner, Steven J.; Flynn, Marilyn E.; Hamlin, Scott N.; Moore, Stephanie J.; Schaefer, Donald H.; Anderholm, Scott K.; Spangler, Lawrence E.

    2007-01-01

    The U.S. Geological Survey National Water-Quality Assessment Program performed a regional study in the Southwestern United States (Southwest) to describe the status and trends of dissolved solids in basin-fill aquifers and streams and to determine the natural and human factors that affect dissolved solids. Basin-fill aquifers, which include the Rio Grande aquifer system, Basin and Range basin-fill aquifers, and California Coastal Basin aquifers, are the most extensively used ground-water supplies in the Southwest. Rivers, such as the Colorado, the Rio Grande, and their tributaries, are also important water supplies, as are several smaller river systems that drain internally within the Southwest, or drain externally to the Pacific Ocean in southern California. The study included four components that characterize (1) the spatial distribution of dissolved-solids concentrations in basin-fill aquifers, and dissolved-solids concentrations, loads, and yields in streams; (2) natural and human factors that affect dissolved-solids concentrations; (3) major sources and areas of accumulation of dissolved solids; and (4) trends in dissolved-solids concentrations over time in basin-fill aquifers and streams, and the relation of trends to natural or human factors. Dissolved-solids concentrations of ground water in the basin-fill aquifers of the Southwest ranged from less than 500 milligrams per liter near basin margins where ground water is recharged from nearby mountains to more than 10,000 milligrams per liter in topographically low areas of some basins or in areas adjacent to specific streams or rivers in the Basin and Range and Rio Grande aquifer systems. The area of the basin-fill aquifer systems with dissolved-solids concentrations less than or equal to 500 milligrams per liter was about 57 percent for the Rio Grande aquifer system, 63 percent for the Basin and Range basin-fill aquifers, and 44 percent for the California Coastal Basin aquifers. At least 70 percent of the area of these three basin-fill aquifer systems had dissolved-solids concentrations less than or equal to 1,000 milligrams per liter. Dissolved solids in streams were described on the basis of median daily concentration, median annual load, and median annual yield data for 420 surface-water-quality monitoring sites. The time period with dissolved-solids data for individual sites varied but was at least 10 or more years between 1974 and 2003. Median daily dissolved-solids concentrations vary substantially among the sites in the Southwest, ranging between 22 and 13,800 milligrams per liter, and also vary between different sites on the same stream. Median daily concentrations generally increased in a downstream direction for sites on the Rio Grande, Colorado River, Yampa River, White River, Green River, San Juan River, Gila River, Bear River, and Sevier River. Median annual dissolved-solids loads ranged from 60 tons per year for a site on Elk Creek, a headwater tributary to the Colorado River, to 7.86 million tons per year at Colorado River below Hoover Dam, Arizona-Nevada. Typically, streams with the highest flows have the highest dissolved-solids loads. Median annual loads for sites on these rivers generally increased in the downstream direction, except where streamflow decreased substantially due to diversions and (or) streambed infiltration, typically in the downstream part of the river system. Median annual yields ranged from 0.69 to 7,510 tons per year per square mile, and the mean for all 420 sites was 125 tons per year per square mile. Most (104 of 112) sites with median annual yields greater than 100 tons per year per square mile were in the Colorado River basin upstream from Lees Ferry and in the Bear and Great Salt Lake hydrologic subregions. A conceptual model was developed for the effects of natural and human factors on dissolved-solids concentrations in basin-fill aquifers and streams. Factors affecting concentrations in streamflow of upland mountain

  7. Dynamics of dissolved organic matter in fjord ecosystems: Contributions of terrestrial dissolved organic matter in the deep layer

    NASA Astrophysics Data System (ADS)

    Yamashita, Youhei; McCallister, S. Leigh; Koch, Boris P.; Gonsior, Michael; Jaffé, Rudolf

    2015-06-01

    Annually, rivers and inland water systems deliver a significant amount of terrestrial organic matter (OM) to the adjacent coastal ocean in both particulate and dissolved forms; however, the metabolic and biogeochemical transformations of OM during its seaward transport remains one of the least understood components of the global carbon cycle. This transfer of terrestrial carbon to marine ecosystems is crucial in maintaining trophic dynamics in coastal areas and critical in global carbon cycling. Although coastal regions have been proposed as important sinks for exported terrestrial materials, most of the global carbon cycling data, have not included fjords in their budgets. Here we present distributional patterns on the quantity and quality of dissolved OM in Fiordland National Park, New Zealand. Specifically, we describe carbon dynamics under diverse environmental settings based on dissolved organic carbon (DOC) depth profiles, oxygen concentrations, optical properties (fluorescence) and stable carbon isotopes. We illustrate a distinct change in the character of DOC in deep waters compared to surface and mid-depth waters. Our results suggest that, both, microbial reworking of terrestrially derived plant detritus and subsequent desorption of DOC from its particulate counterpart (as verified in a desorption experiment) are the main sources of the humic-like enriched DOC in the deep basins of the studied fjords. While it has been suggested that short transit times and protection of OM by mineral sorption may ultimately result in significant terrestrial carbon burial and preservation in fjords, our data suggests the existence of an additional source of terrestrial OM in the form of DOC generated in deep, fjord water.

  8. Role of dissolved organic matter in ice photochemistry.

    PubMed

    Grannas, Amanda M; Pagano, Lisa P; Pierce, Brittany C; Bobby, Rachel; Fede, Alexis

    2014-09-16

    In this study, we provide evidence that dissolved organic matter (DOM) plays an important role in indirect photolysis processes in ice, producing reactive oxygen species (ROS) and leading to the efficient photodegradation of a probe hydrophobic organic pollutant, aldrin. Rates of DOM-mediated aldrin loss are between 2 and 56 times faster in ice than in liquid water (depending on DOM source and concentration), likely due to a freeze-concentration effect that occurs when the water freezes, providing a mechanism to concentrate reactive components into smaller, liquid-like regions within or on the ice. Rates of DOM-mediated aldrin loss are also temperature dependent, with higher rates of loss as temperature decreases. This also illustrates the importance of the freeze-concentration effect in altering reaction kinetics for processes occurring in environmental ices. All DOM source types studied were able to mediate aldrin loss, including commercially available fulvic and humic acids and an authentic Arctic snow DOM sample isolated by solid phase extraction, indicating the ubiquity of DOM in indirect photochemistry in environmental ices. PMID:25157605

  9. PREDICTION OF DISSOLVER LIFETIMES THROUGH NON-DESTRUCTIVE EVALUATION AND LABORATORY TESTING

    SciTech Connect

    Mickalonis, J.; Woodsmall, T.; Hinz, W.; Edwards, T.

    2011-10-03

    Non-destructive evaluation was used as the primary method of monitoring the corrosion degradation of nuclear material dissolvers and assessing the remaining lifetimes. Materials were typically processed in nitric acid based (4-14M) solutions containing fluoride concentrations less than 0.2 M. The primary corrosion issue for the stainless steel dissolvers is the occurrence of localized corrosion near the tank bottom and the heat affected zones of the welds. Laboratory data for a range of operational conditions, including solution chemistry and temperature, was used to assess the impact of processing changes on the dissolver corrosion rate. Experimental and NDE-based general corrosion rates were found to be in reasonable agreement for standard dissolution chemistries consisting of nitric acid with fluorides and at temperatures less than 95 C. Greater differences were observed when chloride was present as an impurity and temperatures exceeded 100 C.

  10. 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

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    E-print Network

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  16. Export of Dissolved Lignin from Coastal Wetlands to the Louisiana Shelf

    NASA Astrophysics Data System (ADS)

    Bianchi, T. S.; Dimarco, S. F.; Smith, R. W.; Schreiner, K. M.

    2008-12-01

    Here we report on spatial and temporal changes in the concentration and composition of dissolved lignin- phenols in surface and bottom waters off the Louisiana coast (USA). Samples were collected at 7 stations on 2 cruises (April, and July, 2008) along a transect that spanned from inside Terrebonne Bay, Louisiana (12 m water depth) to the outer-most station on the inner Louisiana shelf (21 m water depth). The highest average concentration of dissolved organic carbon (DOC) and dissolved lignin, during both cruises, occurred at the interface between Terrebonne Bay and the inner shelf. Average DOC and dissolved lignin concentrations were significantly higher in April than in July across most stations. Based on hydrologic data, these higher concentrations clearly reflect a combined mixing of DOM from plume waters to the west and local marsh inputs. The cinnamyl/vanillyl (C/V) and syringyl/vanillyl (S/V) ratios indicated that the predominant source of lignin was from non-woody angiosperms - likely the dominant species of wetland plants Spartina alterniflora and S. patens (Spartina spp.) that border the entire bay. The high vanillic acid to vanillin (Ad/Al)v ratios for all stations were typical of that found near estuarine boundaries, where biologically- and photochemically-mediated lignin decay processes are important. This preliminary data indicates that wetlands provide another source of dissolved organic matter (DOM) to the Louisiana shelf that likely contributes to microbial food resources and hence hypoxia, especially in the context of the instability and extensive erosion of these marshes over the past ca. 50 years. This has important implications for the current management plan to reduce hypoxia in the GOM, particularly in those regions that extend west of the nutrient-rich highly productive near-field zones of Atchafalaya-Mississippi river plumes.

  17. 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%.

  18. Autoclave leaching kinetics of a leucoxene concentrate with alkaline solutions

    NASA Astrophysics Data System (ADS)

    Zablotskaya, Yu. V.; Sadykhov, G. B.; Gocharenko, T. V.

    2015-01-01

    The autoclave leaching kinetics of a leucoxene concentrate from the Yaregskoe deposit (Komi Republic, Russia) with NaOH and Na2SiO3 solutions is studied. The changes in the activation energy and reaction order are determined as a function of the degree of desiliconization of a leucoxene concentrate. A steplike character of quartz leaching is shown: "internal" quartz dissolves at the first stage and then free quartz dissolves.

  19. [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

  20. Biogeochemical controls on Diel cycling of stable isotopes of dissolved O2 and dissolved inorganic carbon in the Big Hole River, Montana.

    PubMed

    Parker, Stephen R; Poulson, Simon R; Gammons, Christopher H; DeGrandpre, Michael D

    2005-09-15

    Rivers with high biological productivity typically show substantial increases in pH and dissolved oxygen (DO) concentration during the day and decreases at night, in response to changes in the relative rates of aquatic photosynthesis and respiration. These changes, coupled with temperature variations, may impart diel (24-h) fluctuations in the concentration of trace metals, nutrients, and other chemical species. A better understanding of diel processes in rivers is needed and will lead to improved methods of data collection for both monitoring and research purposes. Previous studies have used stable isotopes of dissolved oxygen (DO) and dissolved inorganic carbon (DIC) as tracers of geochemical and biological processes in streams, lakes, and marine systems. Although seasonal variation in 6180 of DO in rivers and lakes has been documented, no study has investigated diel changes in this parameter. Here, we demonstrate large (up to 13%o) cycles in delta18O-DO for two late summer sampling periods in the Big Hole River of southwest Montana and illustrate that these changes are correlated to variations in the DO concentration, the C-isotopic composition of DIC, and the primary productivity of the system. The magnitude of the diel cycle in delta18O-DO was greater in August versus September because of the longer photoperiod and warmer water temperatures. This study provides another biogeochemical tool for investigating the O2 and C budgets in rivers and may also be applicable to lake and groundwater systems. PMID:16201639

  1. Assessment of water quality and factors affecting dissolved oxygen in the Sangamon River, Decatur to Riverton, Illinois, summer 1982

    USGS Publications Warehouse

    Schmidt, A.R.; Stamer, J.K.

    1987-01-01

    Water quality and processes that affect the dissolved-oxygen concentration in a 45.9 mile reach of the Sangamon River from Decatur to Riverton, Illinois, were determined from data collected during low-flow periods in the summer of 1982. Relations among dissolved oxygen, water discharge, biochemical oxygen demand, ammonia and nitrite plus nitrate concentrations, and photosynthetic-oxygen production were simulated using a one-dimensional, steady-state computer model. Average dissolved oxygen concentrations ranged from 8.0 milligrams per liter at the upstream end of the study reach at Decatur to 5.2 milligrams per liter 12.2 miles downstream. Ammonia concentrations ranged from 45 milligrams per liter at the mouth of Stevens Creek (2.6 miles downstream from Decatur) to 0.03 milligram per liter at the downstream end of the study reach. Un-ionized ammonia concentrations exceeded the maximum concentration specified in the State water quality standard (0.04 milligram per liter) throughout most of the study reach. Model simulations indicated that oxidation of ammonia to form nitrite plus nitrate was the most significant process leading to low dissolved oxygen concentrations in the river. (USGS)

  2. Free zinc ion and dissolved orthophosphate effects on phytoplankton from Coeur d'Alene Lake, Idaho

    USGS Publications Warehouse

    Kuwabara, J.S.; Topping, B.R.; Woods, P.F.; Carter, J.L.

    2007-01-01

    Coeur d'Alene Lake in northern Idaho is fed by two major rivers: the Coeur d'Alene River from the east and the St. Joe River from the south, with the Spokane River as its outlet to the north. This phosphorus-limited lake has been subjected to decades of mining (primarily for zinc and silver) and other anthropogenic inputs. A 32 full-factorial experimental design was used to examine the interactive effects of free (uncomplexed) zinc ion and dissolved-orthophosphate concentrations on phytoplankton that were isolated from two sites along a longitudinal zinc-concentration gradient in Coeur d'Alene Lake. The two sites displayed different dominant taxa. Chlorella minutissima, a dominant species near the southern St. Joe River inlet, exhibited greater sensitivity to free Zn ions than Asterionella formosa, collected nearer the Coeur d'Alene River mouth with elevated dissolved-zinc concentrations. Empirical phytoplankton-response models were generated to describe phytoplankton growth in response to remediation strategies in the surrounding watershed. If dissolved Zn can be reduced in the water column from >500 nM (i.e., current concentrations near and down stream of the Coeur d'Alene River plume) to <3 nM (i.e., concentrations near the southern St. Joe River inlet) such that the lake is truly phosphorus limited, management of phosphorus inputs by surrounding communities will ultimately determine the limnologic state of the lake.

  3. Integrated wireless fast-scan cyclic voltammetry recording and electrical stimulation for reward-predictive learning in awake, freely moving rats

    NASA Astrophysics Data System (ADS)

    Li, Yu-Ting; Wickens, Jeffery R.; Huang, Yi-Ling; Pan, Wynn H. T.; Chen, Fu-Yu Beverly; Chen, Jia-Jin Jason

    2013-08-01

    Objective. Fast-scan cyclic voltammetry (FSCV) is commonly used to monitor phasic dopamine release, which is usually performed using tethered recording and for limited types of animal behavior. It is necessary to design a wireless dopamine sensing system for animal behavior experiments. Approach. This study integrates a wireless FSCV system for monitoring the dopamine signal in the ventral striatum with an electrical stimulator that induces biphasic current to excite dopaminergic neurons in awake freely moving rats. The measured dopamine signals are unidirectionally transmitted from the wireless FSCV module to the host unit. To reduce electrical artifacts, an optocoupler and a separate power are applied to isolate the FSCV system and electrical stimulator, which can be activated by an infrared controller. Main results. In the validation test, the wireless backpack system has similar performance in comparison with a conventional wired system and it does not significantly affect the locomotor activity of the rat. In the cocaine administration test, the maximum electrically elicited dopamine signals increased to around 230% of the initial value 20 min after the injection of 10 mg kg-1 cocaine. In a classical conditioning test, the dopamine signal in response to a cue increased to around 60 nM over 50 successive trials while the electrically evoked dopamine concentration decreased from about 90 to 50 nM in the maintenance phase. In contrast, the cue-evoked dopamine concentration progressively decreased and the electrically evoked dopamine was eliminated during the extinction phase. In the histological evaluation, there was little damage to brain tissue after five months chronic implantation of the stimulating electrode. Significance. We have developed an integrated wireless voltammetry system for measuring dopamine concentration and providing electrical stimulation. The developed wireless FSCV system is proven to be a useful experimental tool for the continuous monitoring of dopamine levels during animal learning behavior studies of freely moving rats.

  4. Do dissolving objects converge to a universal shape?

    PubMed

    Nakouzi, Elias; Goldstein, Raymond E; Steinbock, Oliver

    2015-04-14

    Surprisingly, macroscopic objects such as melting ice cubes and growing stalactites approach nonintuitive geometric ideals. Here we investigate the shape of dissolving cylinders in a large volume of water. The cylinders are oriented vertically and consist of amorphous glucose or poly(ethylene glycol). The dissolution causes density differences in the surrounding fluid, which induce gravity-driven convection downward along the object. The resulting concentration gradient shapes the cylinder according to fast dissolution at the tip and slow dissolution at the base. The contour of the object approaches a power law of the form z ? R(2), where z is the vertical distance from the tip and R is the corresponding radius. We suggest that this paraboloidal shape is the geometric attractor for the dissolution of noncrystalline objects in the presence of gravity. PMID:25409279

  5. Why dissolved organic matter (DOM) enhances photodegradation of methylmercury

    SciTech Connect

    Qian, Yun; Yin, Xiangping Lisa; Brooks, Scott C; Liang, Liyuan; Gu, Baohua

    2014-01-01

    Methylmercury (MeHg) is known to degrade photochemically, but it remains unclear what roles naturally dissolved organic matter (DOM) and complexing organic ligands play in MeHg photodegradation. Here we investigate the rates and mechanisms of MeHg photodegradation using DOM samples with varying oxidation states and origins as well as organic ligands with known molecular structures. All DOM and organic ligands increased MeHg photodegradation under solar irradiation, but the first-order rate constants varied depending on the oxidation state of DOM and the type and concentration of the ligands. Compounds containing both thiols and aromatics (e.g., thiosalicylate and reduced DOM) increased MeHg degradation rates far greater than those containing only aromatic or thiol functional groups (e.g., salicylate or glutathione). Our results suggest that, among other factors, the synergistic effects of thiolate and aromatic moieties in DOM greatly enhance MeHg photodegradation.

  6. Transport of dissolving colloidal particles in porous media

    NASA Astrophysics Data System (ADS)

    Corapcioglu, M. Yavuz; Jiang, Shiyan; Kim, Seung-Hyun

    1999-11-01

    A mathematical model was developed to simulate the transport and dissolution of colloidal particles with a water-soluble component in a porous medium. The model is based on mass balance equations describing the mass transport, dissolution, sorption, capture, and release of colloids in a three-phase medium consisting of a solid matrix, an aqueous phase, and colloids. Colloid dissolution, contaminant sorption on solid matrix, and colloid capture mechanisms are represented by first-order kinetics. A numerical comparison of the model of a water-soluble component associated with fly ash-mobilized transport and transport due only to dissolved component migration indicates that the presence of colloids significantly increases the aqueous phase contaminant concentration.

  7. Sparingly soluble pesticide dissolved in ionic liquid aqueous.

    PubMed

    Fan, Tengfei; Wu, Xuemin; Peng, Qingrong

    2014-10-01

    Ionic liquids may be considered as "environment-friendly solvents" for sparingly soluble pesticides. In this study, a series of aqueous ionic liquids (ILs) with different cations and different anions was used as environment-friendly alternative to harmful organic solvents sparingly dissolved in soluble pesticides (metolachlor, acetochlor, clethodim, thiamethoxam, and prochloraz). The aggregation behavior of aqueous ILs was investigated through surface tension measurement. Minimum area per IL molecule (Amin) values from the surface tension measurement showed that alkyl chain length and the halide anions strongly affect the aggregation behavior of ILs and the solubilization of pesticides. The solubility of metolachlor, acetochlor, clethodim, thiamethoxam, nitenpyram, and prochloraz in aqueous ILs increased. More importantly, the solubility of prochloraz in [C10mim][I] became 5771-fold higher than that in pure water. The substantially enhanced solubility of the above pesticides proved that aqueous ILs are promising environment-friendly solvents for pesticides that are commercially processed in emulsifiable concentrate (EC) formulation. PMID:25222470

  8. Effect of dissolved oxygen on phenols breakthrough from GAC adsorbers

    SciTech Connect

    Vidic, R.D.; Suidan, M.T.

    1992-01-01

    The study demonstrates that molecular oxygen plays an important role in the adsorption of organic compounds from water by activated carbon. It was determined that the adsorptive capacity of granular activated carbon (GAC) for o-cresol can increase by almost 200% as a result of the presence of molecular oxygen in the test environment (oxic conditions). This increase in adsorptive capacity is not due to biological activity but can be totally attributed to the polymerization of o-cresol on the carbon surface under oxic conditions. The rate of adsorbate polymerization is such that the presence of molecular oxygen does not influence adsorption kinetics during the first 12 hours of adsorbent-adsorbate contact. However, the concentration of dissolved oxygen in the feed to a GAC adsorber can significantly influence the breakthrough of adsorbate. (Copyright (c) 1992 IAWPRC.)

  9. Formulation and evaluation of mouth dissolving tablets of cinnarizine.

    PubMed

    Patel, B P; Patel, J K; Rajput, G C; Thakor, R S

    2010-07-01

    The purpose of this research was to develop mouth dissolve tablets of cinnarizine by effervescent, superdisintegrant addition and sublimation methods. All the three formulations were evaluated for disintegration time, hardness and friability, among these superdisintegrant addition method showed lowest disintegration time; hence it was selected for further studies. Further nine batches (B1-B9) were prepared by using crospovidone, croscarmellose sodium and L-HPC in different concentrations such as 5, 7.5 and 10%. All the formulations were evaluated for weight variation, hardness, friability, drug content, in vitro disintegration time, wetting time, in vitro dissolution. Formulation with 10% L-HPC showed the less disintegration time (25.3 s) and less wetting time (29.1 s). In vitro dissolution studies showed total drug release at the end of 6 min. PMID:21218071

  10. Decoding of intentional actions from scalp electroencephalography (EEG) in freely-behaving infants.

    PubMed

    Hernandez, Zachery R; Cruz-Garza, Jesus; Tse, Teresa; Contreras-Vidal, Jose L

    2014-01-01

    The mirror neuron system (MNS) in humans is thought to enable an individual's understanding of the meaning of actions performed by others and the potential imitation and learning of those actions. In humans, electroencephalographic (EEG) changes in sensorimotor a-band at central electrodes, which desynchronizes both during execution and observation of goal-directed actions (i.e., ? suppression), have been considered an analog to MNS function. However, methodological and developmental issues, as well as the nature of generalized ? suppression to imagined, observed, and performed actions, have yet to provide a mechanistic relationship between EEG ?-rhythm and MNS function, and the extent to which EEG can be used to infer intent during MNS tasks remains unknown. In this study we present a novel methodology using active EEG and inertial sensors to record brain activity and behavioral actions from freely-behaving infants during exploration, imitation, attentive rest, pointing, reaching and grasping, and interaction with an actor. We used 5-band (1-4Hz) EEG as input to a dimensionality reduction algorithm (locality-preserving Fisher's discriminant analysis, LFDA) followed by a neural classifier (Gaussian mixture models, GMMs) to decode the each MNS task performed by freely-behaving 6-24 month old infants during interaction with an adult actor. Here, we present results from a 20-month male infant to illustrate our approach and show the feasibility of EEG-based classification of freely occurring MNS behaviors displayed by an infant. These results, which provide an alternative to the ?-rhythm theory of MNS function, indicate the informative nature of EEG in relation to intentionality (goal) for MNS tasks which may support action-understanding and thus bear implications for advancing the understanding of MNS function. PMID:25570402

  11. PROGRAM DROP: A computer program for prediction of evaporation from freely falling multicomponent drops

    SciTech Connect

    Gavin, P.M.

    1996-12-01

    PROGRAM DROP consists of a series of FORTRAN routine which together are used to model the evaporation of a freely falling, multicomponent drop composed of an arbitrary number of volatile species and a single nonvolatile, inert component. The physics underlying the model are clearly identified, and the model`s relationship to previous work in the literature is described. Test cases are used to illustrate the viability of the model and to highlight its potential usefulness in the accurate prediction of multicomponent droplet vaporization in a variety of applications.

  12. Trapped modes around freely floating bodies in a two-layer fluid channel

    PubMed Central

    Cal, Filipe S.; Dias, Gonçalo A. S.; Videman, Juha H.

    2014-01-01

    Unlike the trapping of time-harmonic water waves by fixed obstacles, the oscillation of freely floating structures gives rise to a complex nonlinear spectral problem. Still, through a convenient elimination scheme the system simplifies to a linear spectral problem for a self-adjoint operator in a Hilbert space. Under symmetry assumptions on the geometry of the fluid domain, we present conditions guaranteeing the existence of trapped modes in a two-layer fluid channel. Numerous examples of floating bodies supporting trapped modes are given. PMID:25294970

  13. Distribution and mobilization of dissolved selenium in ground water of the irrigated grand and Uncompahgre Valleys, Western Colorado

    USGS Publications Warehouse

    Wright, Winfield G.; Butler, David L.

    1993-01-01

    Distribution of dissolved selenium in ground water of the irrigated Grand and Uncompahgre Valleys is affected by the aqueous geochemical environment of the shallow ground-water system composed of alluvium and shale residuum. Selenium concentrations are as high as 1,300 micrograms per liter in water from shallow wells. The highest concentrations of dissolved selenium were in water from wells completed in alluvium overlying the Mancos Shale of Cretaceous Age, and the lowest concentrations were in water from wells completed in terrace deposits on the western side of the Uncompahgre Valley and in water from wells completed in Mancos Shale residuum. Factors controlling the mobilization of dissolved selenium in the Grand and Uncompahgre Valleys could include oxidation/reduction, adsorption/desorption, and(or) ion exchange. Infiltration of irrigation water provides oxidizing conditions for mobilization of selenium from alluvium and shale residuum and transport to streams and irrigation drains tributary to the Uncompahgre, Gunnison and Colorado Rivers.

  14. Dissolved organic carbon pools and export from the coastal ocean

    NASA Astrophysics Data System (ADS)

    Barrón, Cristina; Duarte, Carlos M.

    2015-10-01

    The distribution of dissolved organic carbon (DOC) concentration across coastal waters was characterized based on the compilation of 3510 individual estimates of DOC in coastal waters worldwide. We estimated the DOC concentration in the coastal waters that directly exchange with open ocean waters in two different ways, as the DOC concentration at the edge of the shelf break and as the DOC concentration in coastal waters with salinity close to the average salinity in the open ocean. Using these estimates of DOC concentration in the coastal waters that directly exchange with open ocean waters, the mean DOC concentration in the open ocean and the estimated volume of water annually exchanged between coastal and open ocean, we estimated a median ± SE (and average ± SE) global DOC export from coastal to open ocean waters ranging from 4.4 ± 1.0 Pg C yr-1 to 27.0 ± 1.8 Pg C yr-1 (7.0 ± 5.8 Pg C yr-1 to 29.0 ± 8.0 Pg C yr-1) depending on the global hydrological exchange. These values correspond to a median and mean median (and average) range between 14.7 ± 3.3 to 90.0 ± 6.0 (23.3 ± 19.3 to 96.7 ± 26.7) Gg C yr-1 per km of shelf break, which is consistent with the range between 1.4 to 66.1 Gg C yr-1 per km of shelf break of available regional estimates of DOC export. The estimated global DOC export from coastal to open ocean waters is also consistent with independent estimates of the net metabolic balance of the coastal ocean. The DOC export from the coastal to the open ocean is likely to be a sizeable flux and is likely to be an important term in the carbon budget of the open ocean, potentially providing an important subsidy to support heterotrophic activity in the open ocean.

  15. Microbial dissolved organic phosphorus utilization in the Hudson River Estuary

    SciTech Connect

    Ammerman, J.W. ); Angel, D.L. )

    1990-01-09

    The Hudson River Estuary has large inputs of phosphorus and other nutrients from sewage discharge. Concentrations of soluble reactive phosphorus (SRP) reach at least 4 uM during the summer low-flow period. Biological utilization of phosphorus and other nutrients is usually minimal because of the high turbidity and short residence time of the water. Therefore SRP is normally a conservative tracer of salinity, with maximum concentrations found off Manhattan and decreasing to the north. Despite this abundance of SRP, some components of the dissolved organic phosphorus (DOP) appear to be rapidly cycled by microbes. The objective of this study was to measure this DIP cycling during both the high- and low-flow periods. We measured the concentrations of SRP and DOP, the SRP turnover rate, algal and bacterial biomass, and the substrate turnover rates of two microbial cell-surface phosphatases, alkaline phosphatase (AP) and 5[prime] - nucleotidase (5PN). SRP concentrations ranged from about 0.5-4 uM, DOP was usually less than 1 uM. SRP and AP turnover were slow (generally < 5%/h), but 5PN substrate turnover was high with a median rate of 100%/h. Furthermore, over 30% of the phosphate hydrolyzed by 5PN was immediately taken up. If the nucleotide-P concentration is conservatively assumed to be 5 nM, than the rate of phosphate utilization from DOP is nearly equal to that from SRP. That is paradoxical considering the large SRP concentration, but suggests that much of this SRP may be biologically unavailable due to complexation with iron or other processes.

  16. Concurrent photolytic degradation of aqueous methylmercury and dissolved organic matter

    USGS Publications Warehouse

    Fleck, Jacob A.; Gill, Gary W.; Bergamaschi, Brian A.; Kraus, Tamara E.C.; Downing, Bryan D.; Alpers, Charles N.

    2014-01-01

    Monomethyl mercury (MeHg) is a potent neurotoxin that threatens ecosystem viability and human health. In aquatic systems, the photolytic degradation of MeHg (photodemethylation) is an important component of the MeHg cycle. Dissolved organic matter (DOM) is also affected by exposure to solar radiation (light exposure) leading to changes in DOM composition that can affect its role in overall mercury (Hg) cycling. This study investigated changes in MeHg concentration, DOM concentration, and the optical signature of DOM caused by light exposure in a controlled field-based experiment using water samples collected from wetlands and rice fields. Filtered water from all sites showed a marked loss in MeHg concentration after light exposure. The rate of photodemethylation was 7.5 × 10-3 m2 mol-1 (s.d. 3.5 × 10-3) across all sites despite marked differences in DOM concentration and composition. Light exposure also caused changes in the optical signature of the DOM despite there being no change in DOM concentration, indicating specific structures within the DOM were affected by light exposure at different rates. MeHg concentrations were related to optical signatures of labile DOM whereas the percent loss of MeHg was related to optical signatures of less labile, humic DOM. Relationships between the loss of MeHg and specific areas of the DOM optical signature indicated that aromatic and quinoid structures within the DOM were the likely contributors to MeHg degradation, perhaps within the sphere of the Hg-DOM bond. Because MeHg photodegradation rates are relatively constant across freshwater habitats with natural Hg–DOM ratios, physical characteristics such as shading and hydrologic residence time largely determine the relative importance of photolytic processes on the MeHg budget in these mixed vegetated and open-water systems.

  17. Concurrent photolytic degradation of aqueous methylmercury and dissolved organic matter.

    PubMed

    Fleck, Jacob A; Gill, Gary; Bergamaschi, Brian A; Kraus, Tamara E C; Downing, Bryan D; Alpers, Charles N

    2014-06-15

    Monomethyl mercury (MeHg) is a potent neurotoxin that threatens ecosystem viability and human health. In aquatic systems, the photolytic degradation of MeHg (photodemethylation) is an important component of the MeHg cycle. Dissolved organic matter (DOM) is also affected by exposure to solar radiation (light exposure) leading to changes in DOM composition that can affect its role in overall mercury (Hg) cycling. This study investigated changes in MeHg concentration, DOM concentration, and the optical signature of DOM caused by light exposure in a controlled field-based experiment using water samples collected from wetlands and rice fields. Filtered water from all sites showed a marked loss in MeHg concentration after light exposure. The rate of photodemethylation was 7.5×10(-3)m(2)mol(-1) (s.d. 3.5×10(-3)) across all sites despite marked differences in DOM concentration and composition. Light exposure also caused changes in the optical signature of the DOM despite there being no change in DOM concentration, indicating specific structures within the DOM were affected by light exposure at different rates. MeHg concentrations were related to optical signatures of labile DOM whereas the percent loss of MeHg was related to optical signatures of less labile, humic DOM. Relationships between the loss of MeHg and specific areas of the DOM optical signature indicated that aromatic and quinoid structures within the DOM were the likely contributors to MeHg degradation, perhaps within the sphere of the Hg-DOM bond. Because MeHg photodegradation rates are relatively constant across freshwater habitats with natural Hg-DOM ratios, physical characteristics such as shading and hydrologic residence time largely determine the relative importance of photolytic processes on the MeHg budget in these mixed vegetated and open-water systems. PMID:23642571

  18. Modeling impact of storage zones on stream dissolved oxygen

    USGS Publications Warehouse

    Chapra, S.C.; Runkel, R.L.

    1999-01-01

    The Streeter-Phelps dissolved oxygen model is modified to incorporate storage zones. A dimensionless number reflecting enhanced decomposition caused by the increased residence time of the biochemical oxygen demand in the storage zone parameterizes the impact. This result provides a partial explanation for the high decomposition rates observed in shallow streams. An application suggests that the storage zone increases the critical oxygen deficit and moves it closer to the point source. It also indicates that the storage zone should have lower oxygen concentration than the main channel. An analysis of a dimensionless enhancement factor indicates that the biochemical oxygen demand decomposition in small streams could be up to two to three times more than anticipated based on the standard Streeter-Phelps model without storage zones. For larger rivers, enhancements of up to 1.5 could occur.The Streeter-Phelps dissolved oxygen model is modified to incorporate storage zones. A dimensionless number reflecting enhanced decomposition caused by the increased residence time of the biochemical oxygen demand in the storage zone parameterizes the impact. This result provides a partial explanation for the high decomposition rates observed in shallow streams. An application suggests that the storage zone increases the critical oxygen deficit and moves it closer to the point source. It also indicates that the storage zone should have lower oxygen concentration than the main channel. An analysis of a dimensionless enhancement factor indicates that the biochemical oxygen demand decomposition in small streams could be up to two to three times more than anticipated based on the standard Streeter-Phelps model without storage zones. For larger rivers, enhancements of up to 1.5 could occur.

  19. Dissolved organic carbon (DOC) in Arctic ground ice

    NASA Astrophysics Data System (ADS)

    Fritz, M.; Opel, T.; Tanski, G.; Herzschuh, U.; Meyer, H.; Eulenburg, A.; Lantuit, H.

    2015-01-01

    Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have been accumulated in late Pleistocene and Holocene unconsolidated deposits. Their vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change is largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements, which are important for ecosystems and carbon cycling. Here we show, using geochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage with a maximum of 28.6 mg L-1 (mean: 9.6 mg L-1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly stored in ground ice, especially in ice wedges, even before further degradation. In the Yedoma region ice wedges represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a fresh-water reservoir of 4172 km3. This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost carbon pool for ecosystems and climate feedback upon mobilization.

  20. Dissolved organic carbon (DOC) in Arctic ground ice

    NASA Astrophysics Data System (ADS)

    Fritz, M.; Opel, T.; Tanski, G.; Herzschuh, U.; Meyer, H.; Eulenburg, A.; Lantuit, H.

    2015-04-01

    Thermal permafrost degradation and coastal erosion in the Arctic remobilize substantial amounts of organic carbon (OC) and nutrients which have accumulated in late Pleistocene and Holocene unconsolidated deposits. Permafrost vulnerability to thaw subsidence, collapsing coastlines and irreversible landscape change are largely due to the presence of large amounts of massive ground ice such as ice wedges. However, ground ice has not, until now, been considered to be a source of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and other elements which are important for ecosystems and carbon cycling. Here we show, using biogeochemical data from a large number of different ice bodies throughout the Arctic, that ice wedges have the greatest potential for DOC storage, with a maximum of 28.6 mg L-1 (mean: 9.6 mg L-1). Variation in DOC concentration is positively correlated with and explained by the concentrations and relative amounts of typically terrestrial cations such as Mg2+ and K+. DOC sequestration into ground ice was more effective during the late Pleistocene than during the Holocene, which can be explained by rapid sediment and OC accumulation, the prevalence of more easily degradable vegetation and immediate incorporation into permafrost. We assume that pristine snowmelt is able to leach considerable amounts of well-preserved and highly bioavailable DOC as well as other elements from surface sediments, which are rapidly frozen and stored in ground ice, especially in ice wedges, even before further degradation. We found that ice wedges in the Yedoma region represent a significant DOC (45.2 Tg) and DIC (33.6 Tg) pool in permafrost areas and a freshwater reservoir of 4200 km2. This study underlines the need to discriminate between particulate OC and DOC to assess the availability and vulnerability of the permafrost carbon pool for ecosystems and climate feedback upon mobilization.

  1. 40 CFR 430.10 - Applicability; description of the dissolving kraft subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...Applicability; description of the dissolving kraft subcategory. 430.10...PAPERBOARD POINT SOURCE CATEGORY Dissolving Kraft Subcategory § 430.10 Applicability; description of the dissolving kraft subcategory. The...

  2. 40 CFR 430.40 - Applicability; description of the dissolving sulfite subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...Applicability; description of the dissolving sulfite subcategory. 430.40...PAPERBOARD POINT SOURCE CATEGORY Dissolving Sulfite Subcategory § 430.40 Applicability; description of the dissolving sulfite subcategory. The...

  3. 40 CFR 430.10 - Applicability; description of the dissolving kraft subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Applicability; description of the dissolving kraft subcategory. 430.10...PAPERBOARD POINT SOURCE CATEGORY Dissolving Kraft Subcategory § 430.10 Applicability; description of the dissolving kraft subcategory. The...

  4. 40 CFR 430.40 - Applicability; description of the dissolving sulfite subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...Applicability; description of the dissolving sulfite subcategory. 430.40...PAPERBOARD POINT SOURCE CATEGORY Dissolving Sulfite Subcategory § 430.40 Applicability; description of the dissolving sulfite subcategory. The...

  5. Composition, Dynamics, and Fate of Leached Dissolved Organic Matter

    E-print Network

    Neff, Jason

    Composition, Dynamics, and Fate of Leached Dissolved Organic Matter in Terrestrial Ecosystems Fluxes of dissolved organic matter (DOM) are an important vector for the movement of carbon (C dissolve organic carbon (DOC) and dis- solved organic nitrogen (DON) fractions], as well as DOM chemical

  6. GEOC: Division of Geochemistry 163 -Ternary complexation of dissolved organic

    E-print Network

    Sparks, Donald L.

    GEOC: Division of Geochemistry 163 - Ternary complexation of dissolved organic matter in kaolinite-Fe(III)-organic-INRA-AgroParisTech, Thiverval-Grignon, France Abstract:Chemical interactions of dissolved organic matter (DOM) with minerals of aqueous Fe(III). In this study, two common soil containing dissolved organic acids (DOA, malic and citric

  7. Investigating Students' Understanding of the Dissolving Process

    NASA Astrophysics Data System (ADS)

    Naah, Basil M.; Sanger, Michael J.

    2013-04-01

    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 symbolic-level questions were based on balanced equations, and the particulate-level questions used multiple-choice questions involving dynamic animations or static pictures. This paper analyzes students' responses to these questions to look for associations among four variables—Answer (the correct answer and three misconceptions), Representation (symbolic or particulate question), Visualization (static or animated pictures), and Representation Order (symbolic questions before or after the particulate questions). The results indicate that the correct answer and the acid-base misconception were more popular than the ion-pair or subscript error misconceptions, the ion-pair misconception was more popular for the particulate questions than the symbolic questions, and that participants were more likely to select the correct answer when viewing static particulate questions compared to animated particulate questions, especially if the particulate questions are seen first. These results suggest that the animated motion of dissolving these compounds in water may be distracting for students.

  8. Cope with dissolved gases in pump calculations

    SciTech Connect

    Chen, C.C. )

    1993-10-01

    The pressure of the liquid at the inlet of a centrifugal pump must be high enough to prevent vaporization within the pump, because this vaporization hinders the pumping and can damage the impellers. This pressure requirement must be taken into account when deciding how high to place the pump feed vessel relative to the height of the pump itself. Basically, the pump suction pressure must be greater than the fluid's vapor pressure at the pumping temperature. The difference between pump suction pressure and vapor pressure is the net positive suction head (NPSH). For cases in which the liquid contains no dissolved gases, the vapor-pressure determination is straightforward. With dissolved gases, the situation is more complicated, because vapor-pressure data for such systems are usually not at hand. Adding to the complication is the fact that centrifugal pumps generally can, as it happens, tolerate a small amount of vapor at the impeller eye. If the solubility of the dissolved gas is low and the temperature is far below the boiling point of liquid, the amount of vapor released in a pump is likely not to exceed the tolerable value unless the pressure reduction is substantial.

  9. Spatiotemporal variation characteristics and related affecting factors of dissolved carbohydrates in the East China Sea

    NASA Astrophysics Data System (ADS)

    He, Zhen; Wang, Qi; Yang, Gui-Peng; Gao, Xian-Chi; Wu, Guan-Wei

    2015-10-01

    Carbohydrates are the largest identified fraction of dissolved organic carbon and play an important role in biogeochemical cycling in the ocean. Seawater samples were collected from the East China Sea (ECS) during June and October 2012 to study the spatiotemporal distributions of total dissolved carbohydrates (TCHOs) constituents, including dissolved monosaccharides (MCHOs) and polysaccharides (PCHOs). The concentrations of TCHOs, MCHOs and PCHOs showed significant differences between summer and autumn 2012, and exhibited an evident diurnal variation, with high values occurring in the daytime. Phytoplankton biomass was identified as the primary factor responsible for seasonal and diurnal variations of dissolved carbohydrates in the ECS. The TCHOs, MCHOs and PCHOs distributions in the study area displayed similar distribution patterns, with high concentrations appearing in the coastal water. The influences of chlorophyll-a, salinity and nutrients on the distributions of these carbohydrates were examined. A carbohydrate enrichment in the near-bottom water was found at some stations, implying that there might be an important source of carbohydrate in the deep water or bottom sediment.

  10. Seasonal Variation and Sources of Dissolved Nutrients in the Yellow River, China

    PubMed Central

    Gong, Yao; Yu, Zhigang; Yao, Qingzhen; Chen, Hongtao; Mi, Tiezhu; Tan, Jiaqiang

    2015-01-01

    The rapid growth of the economy in China has caused dramatic growth in the industrial and agricultural development in the Yellow River (YR) watershed. The hydrology of the YR has changed dramatically due to the climate changes and water management practices, which have resulted in a great variation in the fluxes of riverine nutrients carried by the YR. To study these changes dissolved nutrients in the YR were measured monthly at Lijin station in the downstream region of the YR from 2002 to 2004. This study provides detailed information on the nutrient status for the relevant studies in the lower YR and the Bohai Sea. The YR was enriched in nitrate (average 314 ?mol·L?1) with a lower concentration of dissolved silicate (average 131 ?mol·L?1) and relatively low dissolved phosphate (average 0.35 ?mol·L?1). Nutrient concentrations exhibited substantial seasonal and yearly variations. The annual fluxes of dissolved inorganic nitrogen, phosphate, and silicate in 2004 were 5.3, 2.5, and 4.2 times those in 2002, respectively, primarily due to the increase in river discharge. The relative contributions of nutrient inputs to nitrogen in the YR were: wastewater > fertilizer > atmospheric deposition > soil; while to phosphorus were: wastewater > fertilizer > soil > atmospheric deposition. The ratios of N, P and Si suggest that the YR at Lijin is strongly P-limited with respect to potential phytoplankton growth. PMID:26287226

  11. Light-mediated release of dissolved organic carbon by phytoplankton

    NASA Astrophysics Data System (ADS)

    Cherrier, Jennifer; Valentine, SarahKeith; Hamill, Barbara; Jeffrey, Wade H.; Marra, John F.

    2015-07-01

    Laboratory and field studies were carried out to examine the effects of irradiance variability on dissolved organic carbon (DOC) extracellular release by phytoplankton (ER) and the response of natural bacteria assemblages. In axenic laboratory cultures, ER was 3× greater in cultures shifted to 330 ?mol photons m-2 s-1 compared to cultures kept at their cultured irradiance, 110 ?mol photons m-2 s-1. Natural bacterial assemblages incubated in the dark for 24 h in algal-free culture filtrate generated from both light treatments consumed the DOC from the high-light treatment at a faster rate than that for the low-light treatment. Field measurements in the coastal waters of the northeastern Gulf of Mexico (GOM) and the Eastern North Pacific (ENP) mirrored the laboratory findings, with short-term increases in DOC concentrations occurring concurrently with short-term increases in irradiance, followed by rapid consumption by bacteria. Where no diurnal irradiance increase was observed (overcast skies), no increase in DOC concentration was observed. An experiment using 14C as a tracer for plankton interactions (GOM) was consistent with data on bulk DOC concentrations. For all the field measurements, the rate of irradiance change was correlated with the quantity of DOC released. Collectively these results indicated that release of DOC by phytoplankton populations as a function of incident irradiance can be significant and may have important implications for estimates of ocean carbon flux.

  12. Field observation of diurnal dissolved oxygen fluctuations in shallow groundwater.

    PubMed

    Schilling, Keith E; Jacobson, Peter

    2015-01-01

    Dissolved oxygen (DO) concentrations influence many biogeochemical processes in groundwater systems but studies of temporal variability in DO are lacking. In this study, we used an optical DO probe to measure rapid changes in concentration due to plant-groundwater interaction at an alluvial aquifer field site in Iowa. Diurnal DO concentrations were observed during mid- to late-summer when soil conditions were dry, fluctuating approximately 0.2 to 0.3 mg/L on a daily basis. DO fluctuations in groundwater were out-of-phase with diurnal water table fluctuations, increasing during the day and decreasing at night. DO consumption at night is likely due to increased soil autotrophic and heterotrophic respiration linked with patterns of carbon supply derived from daytime photosynthetic activity, and consistent with available literature on diurnal soil respiration patterns. Although more work is needed to quantify specific processes, our results indicate the potential usefulness of the new optical DO technology to reveal insights regarding many ecohydrological processes. PMID:24841899

  13. Total Dissolved Cobalt and Labile Cobalt in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Saito, M. A.; Noble, A.

    2012-12-01

    This study presents the total and labile dissolved cobalt distributions from the North Atlantic GEOTRACES Zonal Transect expeditions of the fall of 2010 and 2011. Labile cobalt was detected in much of the water column below the euphotic zone, suggesting that strong cobalt binding ligands were not present in excess of the total cobalt concentration. Near complete complexation of cobalt was observed in surface waters, and linear relationships were observed when both total and labile cobalt were compared to phosphate in surface waters, indicative of a strong biological influence on cobalt cycling. Decoupling of cobalt and macronutrients in the surface waters was observed approaching the North American coast, and a relationship between cobalt and salinity was observed, suggesting that coastal inputs may dominate the distributions of cobalt there. In deep waters, both total and labile cobalt were generally lower in concentration than at intermediate depths, which is evidence of scavenging processes removing cobalt from the water column. Elevated concentrations of labile and total cobalt were observed in samples taken within the TAG hydrothermal plume, and a reverse relationship between cobalt and oxygen was observed in the western basin OMZ.

  14. 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.

  15. Trace element behaviour at cold seeps and the potential export of dissolved iron to the ocean

    NASA Astrophysics Data System (ADS)

    Lemaitre, Nolwenn; Bayon, Germain; Ondréas, Hélène; Caprais, Jean-Claude; Freslon, Nicolas; Bollinger, Claire; Rouget, Marie-Laure; de Prunelé, Alexis; Ruffine, Livio; Olu-Le Roy, Karine; Sarthou, Géraldine

    2014-10-01

    Seawater samples were collected by submersible above methane seeps in the Gulf of Guinea (Regab and Baboon pockmarks) in order to investigate the behaviour of iron (Fe), manganese (Mn) and rare earth elements (REE) during fluid seepage. Our aim was to determine whether cold seeps may represent potential sources of dissolved chemical species to the ocean. Dissolved (<0.45 ?m filtered samples) and total dissolvable (unfiltered samples) concentrations were determined over ?50 m long vertical transects above the seafloor and at various discrete locations within the pockmarks. We show that substantial amounts of Fe and Mn are released into seawater during seepage of methane-rich fluids. Mn is exported almost quantitatively in the dissolved form (more than 90% of total Mn; mean MnDISS?12±11 nmol/kg). Although a significant fraction of Fe is bound to particulate phases, the dissolved iron pool still accounts on average for approximately 20 percent of total iron flux at vent sites (mean FeDISS?22±11 nmol/kg). This dissolved Fe fraction also appears to remain stable in the water column. In contrast, there was no evidence for any significant benthic fluxes of pore water REE associated with fluid seepage at the studied sites. Overall, our results point towards distinct trace element behaviour during fluid seepage, with potential implications for the marine geochemical budget. The absence of any dissolved REE enrichments in bottom waters clearly indicates effective removal in sub-surface sediments. Most likely, precipitation of authigenic mineral phases at cold seeps (i.e. carbonates) represents a net sink for these elements. While Mn appears to behave near-conservatively during fluid seepage, the observed relative stability of dissolved Fe in the water column above seepage sites could be explained by complexation with strong organic ligands and/or the presence of Fe-bearing sulfide nanoparticles, as reported previously for submarine hydrothermal systems. Considering the ubiquitous occurrence of methane vents at ocean margins, cold seeps could represent a previously unsuspected source of dissolved Fe to the deep ocean.

  16. Simultaneous optogenetic manipulation and calcium imaging in freely moving C. elegans

    PubMed Central

    Shipley, Frederick B.; Clark, Christopher M.; Alkema, Mark J.; Leifer, Andrew M.

    2014-01-01

    Understanding how an organism's nervous system transforms sensory input into behavioral outputs requires recording and manipulating its neural activity during unrestrained behavior. Here we present an instrument to simultaneously monitor and manipulate neural activity while observing behavior in a freely moving animal, the nematode Caenorhabditis elegans. Neural activity is recorded optically from cells expressing a calcium indicator, GCaMP3. Neural activity is manipulated optically by illuminating targeted neurons expressing the optogenetic protein Channelrhodopsin. Real-time computer vision software tracks the animal's behavior and identifies the location of targeted neurons in the nematode as it crawls. Patterned illumination from a DMD is used to selectively illuminate subsets of neurons for either calcium imaging or optogenetic stimulation. Real-time computer vision software constantly updates the illumination pattern in response to the worm's movement and thereby allows for independent optical recording or activation of different neurons in the worm as it moves freely. We use the instrument to directly observe the relationship between sensory neuron activation, interneuron dynamics and locomotion in the worm's mechanosensory circuit. We record and compare calcium transients in the backward locomotion command interneurons AVA, in response to optical activation of the anterior mechanosensory neurons ALM, AVM or both. PMID:24715856

  17. Non-linear fluctuation effects in dynamics of freely suspended film

    E-print Network

    E. I. Kats; V. V. Lebedev

    2015-01-27

    Long-scale dynamic fluctuation phenomena in freely suspended films is analyzed. We consider isotropic films that, say, can be pulled from bulk smectic A liquid crystals. The key feature of such objects is possibility of bending deformations of the film. The bending (also known as flexular) mode turns out to be anomalously weakly attenuated. In the harmonic approximation there is no viscous-like damping of the bending mode, proportional to q^2 (q is the wave vector of the mode), since it is forbidden by the rotational symmetry. Therefore the bending mode is strongly affected by non-linear dynamic fluctuation effects. We calculate the dominant fluctuation contributions to the damping of the bending mode due to its coupling to the in-plane viscous mode, that restores the viscous-like q^2 damping of the bending mode. Our calculations are performed in the framework of the perturbation theory where the coupling of the modes is assumed to be small, then the bending mode damping is relatively weak. We discuss our results in the context of existing experiments and numeric simulations of the freely suspended films and propose possible experimental observations of our predictions.

  18. Force estimation and turbulence in the wake of a freely flying European Starling

    NASA Astrophysics Data System (ADS)

    Ben-Gida, Hadar; Kirchhefer, Adam; Kopp, Gregory; Gurka, Roi

    2011-11-01

    Flapping wings are one of the most complex yet widespread propulsion method found in nature. Although aeronautical technology has advanced rapidly over the past 100 years, natural flyers, which have evolved over millions of years, still feature higher efficiency and represent one of nature's finest locomotion methods. One of the key questions is the role of the unsteady motion in the flow due to the wing flapping and its contribution to the forces acting on a bird during downstroke and upstroke. The wake of a freely flying European Starling is investigated as a case study of unsteady wing aerodynamics. Measurements of the near wake have been taken using long duration high-speed PIV in the wake behind a freely flying bird in a specially designed avian wind tunnel. The wake has been characterized by means of velocity and vorticity fields. The measured flow field is decomposed based on the wing position phases. Drag and lift have been estimated using the mean velocity deficit and the circulation at the wake region. In addition, kinematic analysis of the wing motion and the body has been performed using additional high-speed cameras that recorded the bird movement simultaneously with the PIV. Correlations between the wing kinematics and the flow field characteristics are presented as well as the time evolution of the velocity, vorticity and additional turbulence parameters.

  19. Optogenetic control of selective neural activity in multiple freely moving Drosophila adults.

    PubMed

    Wu, Ming-Chin; Chu, Li-An; Hsiao, Po-Yen; Lin, Yen-Yin; Chi, Chen-Chieh; Liu, Tsung-Ho; Fu, Chien-Chung; Chiang, Ann-Shyn

    2014-04-01

    We present an automated laser tracking and optogenetic manipulation system (ALTOMS) for studying social memory in fruit flies (Drosophila melanogaster). ALTOMS comprises an intelligent central control module for high-speed fly behavior analysis and feedback laser scanning (?40 frames per second) for targeting two lasers (a 473-nm blue laser and a 593.5-nm yellow laser) independently on any specified body parts of two freely moving Drosophila adults. By using ALTOMS to monitor and compute the locations, orientations, wing postures, and relative distance between two flies in real time and using high-intensity laser irradiation as an aversive stimulus, this laser tracking system can be used for an operant conditioning assay in which a courting male quickly learns and forms a long-lasting memory to stay away from a freely moving virgin female. With the equipped lasers, channelrhodopsin-2 and/or halorhodopsin expressed in selected neurons can be triggered on the basis of interactive behaviors between two flies. Given its capacity for optogenetic manipulation to transiently and independently activate/inactivate selective neurons, ALTOMS offers opportunities to systematically map brain circuits that orchestrate specific Drosophila behaviors. PMID:24706830

  20. The WURM project - a web-based freely accessible database of computed physical properties for minerals

    NASA Astrophysics Data System (ADS)

    Bobocioiu, E.; Caracas, R.

    2009-12-01

    This project aims to build a freely accessible web-based database of computed physical properties for minerals. The database provides for each mineral various physical properties: the crystal structure used in the calculation, the dynamical charges and the dielectric tensors, the refractive index, the Raman spectra with both peak position and intensity and the infrared spectra with peak position. Additional information comprises the parameters of the calculation, to ensure reproducibility of the results. The vibrational information makes the bulk of the database and constitutes the major computational effort. For each vibrational mode in the zone-center we determine the frequency, the symmetry assignment, the atomic displacement patterns, and the Raman tensors. The Raman spectra are represented in both single crystal and powder with different possible laser polarizations. For the infrared modes we give both the TO and the LO components. The database is freely available on the web at http://www.wurm.info and is highly interactive. Jmol-powered applets incorporated in the website allow the quick visualization of the crystal structure and of the atomic displacement patters of all vibrational modes. Further developments include development of a virtual microscope on top of the computed refractive indexes and the analysis of the elastic properties based on the computed elastic constants tensor. All the results are exclusively obtained from first-principles calculations performed using the local density approximation of density functional theory and density functional perturbation theory in the ABINIT implementation [http://www.abinit.org], based on planewaves and pseudopotentials.

  1. The WURM project - a web-based freely available database of computed physical properties for minerals

    NASA Astrophysics Data System (ADS)

    Caracas, R.; Bobocioiu, E.

    2013-12-01

    Teaching of vibrational spectra for minerals is highly improved by visual media support. The atomic vibrations are usually described by words such as breathing, symmetric or asymmetric stretching, bending, rolling and so on. However only the visualization of these modes can bring a thorough understanding of the dynamics of a crystalline lattice. Here we present the WURM database, whose aim is to build a freely accessible web-based repository of computed physical properties for minerals. Apart from the crystal structure used in the calculation, the dynamical charges and the dielectric tensors, and the refractive index, the WURM database presents at length the Raman spectra with both peak position and intensity and the infrared peak positions. In fact the vibrational information makes the bulk of the database and constitutes the major computational effort. For each vibrational mode in the zone-center we determine the frequency, the symmetry assignment, the atomic displacement patterns, and the Raman tensors. The database is freely available on the web at http://www.wurm.info and is highly interactive. Jmol-powered applets incorporated in the website allow the quick visualization of the crystal structure and of the atomic displacement patters of all vibrational modes. All the results are exclusively obtained from first-principles calculations performed using the local density approximation of density functional theory and density functional perturbation theory in the ABINIT implementation [http://www.abinit.org], based on planewaves and pseudopotentials.

  2. Measuring Whole-Brain Neural Dynamics and Behavior of Freely-Moving C. elegans

    NASA Astrophysics Data System (ADS)

    Shipley, Frederick; Nguyen, Jeffrey; Plummer, George; Shaevitz, Joshua; Leifer, Andrew

    2015-03-01

    Bridging the gap between an organism's neural dynamics and its ultimate behavior is the fundamental goal of neuroscience. Previously, to probe neural dynamics, we have been limited to measuring from a limited number of neurons, whether by electrode or optogenetic measurements. Here we present an instrument to simultaneously monitor neural activity from every neuron in a freely moving Caenorhabditis elegans' head, while recording behavior at the same time. Previously, whole-brain imaging has been demonstrated in C. elegans, but only in restrained and anesthetized animals (1). For studying neural coding of behavior it is crucial to study neural activity in freely behaving animals. Neural activity is recorded optically from cells expressing a calcium indicator, GCaMP6. Real time computer vision tracks the worm's position in x-y, while a piezo stage sweeps through the brain in z, yielding five brain-volumes per second. Behavior is recorded under infrared, dark-field imaging. This tool will allow us to directly correlate neural activity with behavior and we will present progress toward this goal. Thank you to the Simons Foundation and Princeton University for supporting this research.

  3. Electrical high frequency stimulation modulates GABAergic activity in the nucleus accumbens of freely moving rats.

    PubMed

    Varatharajan, Ramya; Joseph, Kevin; Neto, Sonya Carvalho; Hofmann, Ulrich G; Moser, Andreas; Tronnier, Volker

    2015-11-01

    Deep brain stimulation (DBS) of the nucleus accumbens (NAc) is an effective treatment option for those affected by obsessive compulsive disorder, who do not respond to pharmacological treatment strategies. Yet, little is known about the mechanism by which DBS achieve its therapeutic effects. Previous studies have shown an increase in GABA levels due to high frequency stimulation (HFS) in the rat caudate putamen. Here, the effect of high frequency stimulation in the nucleus accumbens of conscious and freely moving rats was characterized using unilateral but simultaneous microdialysis and HFS with a frequency of 124 Hz and 0.5 mA current. Extracellular levels of neurotransmitters - GABA, glutamate, dopamine, serotonin and their metabolites were quantified by means of HPLC with electrochemical detection. Basal levels of GABA were significantly increased in animals of the stimulation group compared to the control group without HFS. The levels of other neurotransmitters were unaffected. The influence of NMDA receptor antagonist, memantine (5 mg/kg) on the effect of HFS was investigated by subcutaneous administration of memantine on the day of the experiment. Memantine (without stimulation) enhanced basal GABA and dopamine levels. However, under the influence of both memantine and HFS, GABA levels were not affected by HFS whereas dopamine levels decreased during the stimulation period. The results of our study demonstrate that HFS in the nucleus accumbens of freely moving rats induces selective increase in GABA outflow and show a possible involvement of NMDA receptors in the mechanistic action of HFS. PMID:26449310

  4. Determination of dissolved methane in natural waters using headspace analysis with cavity ring-down spectroscopy.

    PubMed

    Roberts, Hannah M; Shiller, Alan M

    2015-01-26

    Methane (CH4) is the third most abundant greenhouse gas (GHG) but is vastly understudied in comparison to carbon dioxide. Sources and sinks to the atmosphere vary considerably in estimation, including sources such as fresh and marine water systems. A new method to determine dissolved methane concentrations in discrete water samples has been evaluated. By analyzing an equilibrated headspace using laser cavity ring-down spectroscopy (CRDS), low nanomolar dissolved methane concentrations can be determined with high reproducibility (i.e., 0.13 nM detection limit and typical 4% RSD). While CRDS instruments cost roughly twice that of gas chromatographs (GC) usually used for methane determination, the process presented herein is substantially simpler, faster, and requires fewer materials than GC methods. Typically, 70-mL water samples are equilibrated with an equivalent amount of zero air in plastic syringes. The equilibrated headspace is transferred to a clean, dry syringe and then drawn into a Picarro G2301 CRDS analyzer via the instrument's pump. We demonstrate that this instrument holds a linear calibration into the sub-ppmv methane concentration range and holds a stable calibration for at least two years. Application of the method to shipboard dissolved methane determination in the northern Gulf of Mexico as well as river water is shown. Concentrations spanning nearly six orders of magnitude have been determined with this method. PMID:25542359

  5. A comparison of in situ vs. ex situ filtration methods on the assessment of dissolved and particulate metals at hydrothermal vents

    NASA Astrophysics Data System (ADS)

    Cotte, Laura; Waeles, Matthieu; Pernet-Coudrier, Benoît; Sarradin, Pierre-Marie; Cathalot, Cécile; Riso, Ricardo D.

    2015-11-01

    The objective of this study was to assess the impact of the filtration method (in situ vs. ex situ) on the dissolved/particulate partitioning of 12 elements in hydrothermal samples collected from the Lucky Strike vent field (Mid-Atlantic Ridge; MAR). To do so, dissolved (<0.45 ?m) and particulate Mg, Li, Mn, U, V, As, Ba, Fe, Zn, Cd, Pb and Cu were measured using different techniques (HR-ICP-MS, ICP-AES and CCSA). Using in situ filtration as a baseline, we showed that ex situ filtration (on-board and on shore after freezing) resulted in an underestimation of the dissolved pool, which was counterbalanced by an overestimation of the particulate pool for almost all the elements studied. We also showed that on-board filtration was acceptable for the assessment of dissolved and particulate Mn, Mg, Li and U for which the measurement bias for the dissolved fraction did not exceed 3%. However, in situ filtration appeared necessary for the accurate assessment of the dissolved and particulate concentrations of V, As, Fe, Zn, Ba, Cd, Pb and Cu. In the case of Fe, on-board filtration underestimated the dissolved pool by up to 96%. Laboratory filtration (after freezing) resulted in a large bias in the dissolved and particulate concentrations, unambiguously discounting this filtration method for deep-sea chemical speciation studies. We discuss our results in light of the precipitation processes that can potentially affect the accuracy of ex situ filtration methods.

  6. Oceanic Methane Concentrations in Three Mexican Regions

    EPA Science Inventory

    The atmospheric concentration of methane has increased significantly over the last several decades. Methane is an important greenhouse gas, and it is important to better quantify methane sources and sinks. Dissolved methane in the ocean is produced by biological and hydrothermal ...

  7. Dissolved and particulate 230Th-232Th in the Central Equatorial Pacific Ocean: Evidence for far-field transport of the East Pacific Rise hydrothermal plume

    NASA Astrophysics Data System (ADS)

    Lopez, Grecia I.; Marcantonio, Franco; Lyle, Mitch; Lynch-Stieglitz, Jean

    2015-12-01

    We assess the distribution of 230Th and 232Th along a latitudinal gradient in the Central Equatorial Pacific Ocean (?155°W-159°W) at two sites: 8°N and the equator. The dissolved 230Th concentration profile at 8°N increases nearly linearly from the surface to 2000 m, exhibiting behavior consistent with thermodynamic reversible scavenging. However, from 2000 m to 3000 m, the dissolved 230Th concentrations exhibit little change, before increasing slightly from