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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.

  2. Measuring freely dissolved water concentrations of PCBs using LDPE passive samplers and performance reference compounds (PRCs)

    EPA Science Inventory

    Low-Density polyethylene (LDPE) sheets are often used as passive samplers for aquatic environmental monitoring to measure the dissolved concentrations of hydrophobic organic contaminants (HOCs). These concentrations are then used to evaluate the potential for ecological and human...

  3. Distribution of polycyclic aromatic hydrocarbons in southern Chesapeake Bay surface water: Evaluation of three methods for determining freely dissolved water concentrations

    SciTech Connect

    Gustafson, K.E.; Dickhut, R.M.

    1997-03-01

    Gas sparging, semipermeable-membrane devices (SPMDs), and filtration with sorption of dissolved polycyclic aromatic hydrocarbons (PAHs) to XAD-2 resin were evaluated for determining the concentrations of freely dissolved PAHs in estuarine waters of southern Chesapeake Bay at sites ranging from rural to urban and highly industrialized. Gas sparging had significant sampling artifacts due to particle scavenging by rising bubbles, and SPMDs were kinetically limited for four-ring and larger PAHs relative to short-term temporal changes in water concentrations. Filtration with sorption of the dissolved contaminant fraction to XAD-2 resin was found to be the most accurate and feasible method for determining concentrations of freely dissolved PAHs in estuarine water. Concentrations and distribution coefficients of dissolved and particulate PAHs were measured using the filtration/XAD-2 method. Concentrations of PAHs in surface waters of southern Chesapeake Bay were higher than those reported for the northern bay; concentrations in the Elizabeth River were elevated relative to all other sites. A gradient for particulate PAHs was observed from urban to remote sites. No seasonal trends were observed in dissolved or particle-bound PAH fractions at any site. Distributions of dissolved and particulate PAHs in surface waters of the Chesapeake Bay are near equilibrium at all locations and during all seasons.

  4. Bioaccumulation of native polycyclic aromatic hydrocarbons from sediment by a polychaete and a gastropod: freely dissolved concentrations and activated carbon amendment.

    PubMed

    Cornelissen, Gerard; Breedveld, Gijs D; Naes, Kristoffer; Oen, Amy M P; Ruus, Anders

    2006-09-01

    The present paper describes a study on the bioaccumulation of native polycyclic aromatic hydrocarbons (PAHs) from three harbors in Norway using the polychaete Nereis diversicolor and the gastropod Hinia reticulata. First, biota-sediment accumulation factors (BSAFs) were measured in laboratory bioassays using the original sediments. Median BSAFs were 0.004 to 0.01 kg organic carbon/kg lipid (10 PAHs and 6 organism-sediment combinations), which was a factor of 89 to 240 below the theoretical BSAF based on total sediment contents (which is approximately one). However, if BSAFs were calculated on the basis of measured freely dissolved PAH concentrations in the pore water (measured with polyoxymethylene passive samplers), it appeared that these BSAFfree values agreed well with the measured BSAFs, within a factor of 1.7 to 4.3 (median values for 10 PAHs and six organism-sediment combinations). This means that for bioaccumulation, freely dissolved pore-water concentrations appear to be a much better measure than total sediment contents. Second, we tested the effect of 2% (of sediment dry wt) activated carbon (AC) amendments on BSAE The BSAFs were significantly reduced by a factor of six to seven for N. diversicolor in two sediments (i.e., two of six organism-sediment combinations), whereas no significant reduction was observed for H. reticulata. This implies that either site-specific evaluations of AC amendment are necessary, using several site-relevant benthic organisms, or that the physiology of H. reticulata caused artifactually high BSAF values in the presence of AC.

  5. 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...

  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 μM (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).

  7. 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 Σ16 PAHs in RBP varied from 449 to 6147 μg/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 Σ16 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.

  8. Spatial and temporal variation of freely dissolved PAHs in an urban river undergoing Superfund remediation

    PubMed Central

    Sower, GJ; Anderson, K.A.

    2014-01-01

    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 pre-cap average of 440 ± 422 ng/L to 8 ± 3 ng/L post-capping. 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. PMID:19174872

  9. Equilibrium sampling through membranes of freely dissolved chlorophenols in water samples with hollow fiber supported liquid membrane.

    PubMed

    Liu, Jing-fu; Jönsson, Jan Ake; Mayer, Philipp

    2005-08-01

    The freely dissolved concentration (C(free)) of pollutants is generally believed to be bioavailable and thus responsible for toxic effects. The C(free) of organic weak acids and bases consists of a dissociated and a nondissociated fraction. By using chlorophenols as model compounds, a negligible-depletion extraction technique, equilibrium sampling through membranes (ESTM), was developed for the measurement of the nondissociated part of the C(free). Polypropylene hollow fiber membranes (280-microm i.d., 50-microm wall thickness, 0.1-microm pore size, 15-cm length) were impregnated with undecane in the pores in the fiber wall as liquid membrane and filled with buffer solution in the lumen as acceptor. Then, the hollow fiber membranes were placed into the sample (donor) for an equilibrium extraction after sealing the two ends. The chlorophenol concentrations in the acceptor were then determined by direct injection into a HPLC system. Finally, the C(free) of the nondissociated and the dissociated species of a chlorophenol were calculated based on its measured concentration in the acceptor, its pK(a) value, and the measured pH in sample and acceptor. Theoretically calculated distribution coefficients (D = 8-970) agree well with the experimental enrichment factors (E(e(max)) = 6-1124), and the equilibration time was observed to increase with increasing distribution coefficients (hours to days). The freely dissolved concentration of five chlorophenols, with a wide range of pK(a) (4.9-9.2) and log K(ow) (2.35-5.24), were successfully determined in model solutions of humic acids and at low-ppb levels in river and leachate water. PMID:16053291

  10. 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.

  11. Determining air-water exchange, spatial and temporal trends of freely dissolved PAHs in an urban estuary using passive polyethylene samplers.

    PubMed

    Lohmann, Rainer; Dapsis, Meredith; Morgan, Eric J; Dekany, Victoria; Luey, Pamela J

    2011-04-01

    Passive polyethylene (PE) samplers were deployed at six locations within Narragansett Bay (RI, USA) to determine sources and trends of freely dissolved and gas-phase polycyclic aromatic hydrocarbons (PAHs) from May to November 2006. Freely dissolved aqueous concentrations of PAHs were dominated by fluoranthene, pyrene, and phenanthrene, at concentrations ranging from tens to thousands of pg/L. These were also the dominant PAHs in the gas phase, at hundreds to thousands of pg/m3. All stations mostly followed the same temporal trends, with highest concentrations (up to 7300 pg/L for sum PAHs) during the second of 11 deployments, coinciding with a major rainstorm. Strong correlations of sum PAHs with river flows and wastewater treatment plant discharges highlighted the importance of rainfall in mobilizing PAHs from a combination of runoff and atmospheric washout. PAH concentrations declined through consecutive deployments III to V, which could be explained by an exponential decay due to flushing with cleaner ocean water during tides. The estimated residence time (tres) of the PAH pulse was 24 days, close to an earlier estimate of tres of 26 days for freshwater in the Bay. Air-water exchange gradients indicated net volatilization of most PAHs closest to Providence. Further south in the Bay, gradients had changed to mostly net uptake of the more volatile PAHs, but net volatilization for the less volatile PAHs. Based on characteristic PAH ratios, freely dissolved PAHs at most sites originated from the combustion of fossil fuels; only two sites were at times affected by fuel spill-derived PAHs. PMID:21351793

  12. 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...

  13. Summary of Dissolved Concentration Limits

    SciTech Connect

    Yueting Chen

    2001-06-11

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

  14. 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.

  15. 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 ...

  16. 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...

  17. 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

  18. 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

  19. 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

  20. Gaseous and Freely-Dissolved PCBs in the Lower Great Lakes Based on Passive Sampling: Spatial Trends and Air-Water Exchange.

    PubMed

    Liu, Ying; Wang, Siyao; McDonough, Carrie A; Khairy, Mohammed; Muir, Derek C G; Helm, Paul A; Lohmann, Rainer

    2016-05-17

    Polyethylene passive sampling was performed to quantify gaseous and freely dissolved polychlorinated biphenyls (PCBs) in the air and water of Lakes Erie and Ontario during 2011-2012. In view of differing physical characteristics and the impacts of historical contamination by PCBs within these lakes, spatial variation of PCB concentrations and air-water exchange across these lakes may be expected. Both lakes displayed statistically similar aqueous and atmospheric PCB concentrations. Total aqueous concentrations of 29 PCBs ranged from 1.5 pg L(-1) in the open lake of Lake Erie (site E02) in 2011 spring to 105 pg L(-1) in Niagara (site On05) in 2012 summer, while total atmospheric concentrations were 7.7-634 pg m(-3) across both lakes. A west-to-east gradient was observed for aqueous PCBs in Lake Erie. River discharge and localized influences (e.g., sediment resuspension and regional alongshore transport) likely dominated spatial trends of aqueous PCBs in both lakes. Air-water exchange fluxes of Σ7PCBs ranged from -2.4 (±1.9) ng m(-2) day(-1) (deposition) in Sheffield (site E03) to 9.0 (±3.1) ng m(-2) day(-1) (volatilization) in Niagara (site On05). Net volatilization of PCBs was the primary trend across most sites and periods. Almost half of variation in air-water exchange fluxes was attributed to the difference in aqueous concentrations of PCBs. Uncertainty analysis in fugacity ratios and mass fluxes in air-water exchange of PCBs indicated that PCBs have reached or approached equilibrium only at the eastern Lake Erie and along the Canadian shore of Lake Ontario sites, where air-water exchange fluxes dominated atmospheric concentrations.

  1. Gaseous and Freely-Dissolved PCBs in the Lower Great Lakes Based on Passive Sampling: Spatial Trends and Air-Water Exchange.

    PubMed

    Liu, Ying; Wang, Siyao; McDonough, Carrie A; Khairy, Mohammed; Muir, Derek C G; Helm, Paul A; Lohmann, Rainer

    2016-05-17

    Polyethylene passive sampling was performed to quantify gaseous and freely dissolved polychlorinated biphenyls (PCBs) in the air and water of Lakes Erie and Ontario during 2011-2012. In view of differing physical characteristics and the impacts of historical contamination by PCBs within these lakes, spatial variation of PCB concentrations and air-water exchange across these lakes may be expected. Both lakes displayed statistically similar aqueous and atmospheric PCB concentrations. Total aqueous concentrations of 29 PCBs ranged from 1.5 pg L(-1) in the open lake of Lake Erie (site E02) in 2011 spring to 105 pg L(-1) in Niagara (site On05) in 2012 summer, while total atmospheric concentrations were 7.7-634 pg m(-3) across both lakes. A west-to-east gradient was observed for aqueous PCBs in Lake Erie. River discharge and localized influences (e.g., sediment resuspension and regional alongshore transport) likely dominated spatial trends of aqueous PCBs in both lakes. Air-water exchange fluxes of Σ7PCBs ranged from -2.4 (±1.9) ng m(-2) day(-1) (deposition) in Sheffield (site E03) to 9.0 (±3.1) ng m(-2) day(-1) (volatilization) in Niagara (site On05). Net volatilization of PCBs was the primary trend across most sites and periods. Almost half of variation in air-water exchange fluxes was attributed to the difference in aqueous concentrations of PCBs. Uncertainty analysis in fugacity ratios and mass fluxes in air-water exchange of PCBs indicated that PCBs have reached or approached equilibrium only at the eastern Lake Erie and along the Canadian shore of Lake Ontario sites, where air-water exchange fluxes dominated atmospheric concentrations. PMID:26642083

  2. Concentration of frequencies of trapped waves in problems on freely floating bodies

    SciTech Connect

    Nazarov, Sergei A

    2012-09-30

    It is shown that by choosing the shape of two identical bodies floating freely in a channel with symmetric cross-section it is possible to form any pre-assigned number of linearly independent trapped waves (localized solutions). Bibliography: 27 titles.

  3. 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.

  4. 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.

  5. Dissolved oxygen concentration affects hybrid striped bass growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  6. Iron oxides, dissolved silica, and regulation of marine phosphate concentration

    NASA Astrophysics Data System (ADS)

    Planavsky, N.; Reinhard, C.; Lyons, T.

    2008-12-01

    Phosphorous concentrations in iron oxide-rich sediments reflect orthophosphate levels in the water column from which iron oxides precipitated. Sediment P/Fe ratios are also strongly influenced by the concentrations of dissolved species that inhibit orthophosphate-to-ferrihydrite sorption, most notably silica. It may, therefore, be possible to use P/Fe ratios in iron oxide-rich sediments to estimate past dissolved P concentrations, if one considers the evolution of the silica cycle. A compilation of Fe and P data in iron oxide-rich sediments through time reveals an increase in P/Fe ratios after the Jurassic. We propose that this trend indicates evolution of the iron-oxide phosphate removal mechanism caused by decreasing levels of sorption inhibition by dissolved silica. The large difference in P/Fe ratios in Cenozoic versus older iron-oxide rich sediments can be linked with Si drawdown caused by the proliferation of siliceous plankton in the Cretaceous. There is also a late Mesozoic or Cenozoic increase in V/Fe ratios, which provides additional evidence for lower ferrihydrite anion sorption efficiency prior to diatom radiation. P/Fe ratios in iron oxide-rich sediments from the early and middle Phanerozoic are comparable to the ratios in iron formations previously presented as evidence for an early Precambrian phosphate crisis (Bjerrum and Canfield, 2002, Nature, 417:159-162). Given the compelling evidence for higher Si concentrations in the Precambrian compared to the Phanerozoic and dissolved P concentrations comparable to modern levels throughout the Phanerozoic, the presented trend of P/Fe ratios suggests dissolved P concentrations were higher in Precambrian than Phanerozoic oceans. High dissolved P levels in the Precambrian may have been linked to inhibited carbonate fluorapatite (CFA) formation as a result of persistently high levels of carbonate supersaturation. Carbonate ion substitution into CFA scales with the ambient carbonate ion activity and increases

  7. 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)

  8. Dissolved gas concentrations of the geothermal fluids in Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Ai-Ti; Yang, Tsanyao Frank

    2010-05-01

    Taiwan, a geologically active island, is located on the boundary of the Philippine Sea Plate and the Eurasian Plate. High heat flow and geothermal gradient generated by the complex collision and orogeny, warm up the meteoric water and/or the ground water. The heated water becomes geothermal fluids. In previous studies, researchers tried to categorize hot springs based on the appearance, chemical compositions and lithological areas. Because of the chemical inertness, the concentrations and isotopic composition of dissolved noble gases are good indicators of the mantle degassing, geothermal conditions, and so on. In this study, 55 hot springs were collected from different tectonic units. It is the first time to systematically study the hot springs in Taiwan in terms of dissolved gases. Hot spring water is sampled and stored in pre-evacuated glass bottles for analyzing gas compositions. The abundances of noble gases were determined by a quadrupole mass spectrometer based on the isotope dilution technique. Samples with glass vials are introduced to RAD 7 and GC for dissolved Rn and major dissolved gases analyses. Furthermore, helium isotopic ratios and helium-neon ratios are measured on a conventional noble gas mass spectrometer. For hydrochemistry analysis, water samples are analyzed by IC, ICP-MS and titration. We can classify the hot springs samples into three major groups from main anion concentration data; and then, subdivide them into nine minor groups by cation concentration data. Moreover, according to major dissolved gases compositions, three major gas components: CH4, N2 and CO2, are identified. Dissolved noble gases provided more detailed clues about hot springs sources in Taiwan, such as the degree of mixing between meteoric water and deep-source water, which will be further discussed in this study.

  9. Effect of dissolved oxygen concentration on sludge settleability.

    PubMed

    Martins, A M P; Heijnen, J J; van Loosdrecht, M C M

    2003-10-01

    This laboratory study presents a detailed evaluation of the effects of dissolved oxygen concentration and accumulation of storage polymers on sludge settleability in activated sludge systems with an aerobic selector. The oxygen and substrate availability regime were simulated in laboratory sequencing batch reactor systems. The experiments showed that low dissolved oxygen concentration (< or =1.1 mg O2 l(-1)) had a strong negative effect on sludge settleability, leading to the proliferation of filamentous bacteria (Thiothrix spp., Type 021N and Type 1851). This negative effect was stronger at high chemical oxygen demand loading rate. This indicates that a compartmentalised (plug flow) aerobic contact tank, designed at short hydraulic residence time to guarantee a strong substrate gradient, with low dissolved oxygen concentration, might be worse for sludge settleability than an "overdesigned" completely mixed contact tank. Contrary to the general hypothesis, the maximum specific acetate uptake rate, poly-beta-hydroxybutyrate production rate, and resistance to short starvation periods are similar in both poor- and well-settling sludge. The results of this study support our previous hypothesis on the importance of substrate gradients for the development of filamentous structures in biological flocs, from soluble organic substrate gradients to dissolved oxygen gradients in sludge flocs.

  10. Measurement of Relative Dissolved Gas Concentrations Using Underwater Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Bell, R. J.; Toler, S.; van Amerom, F. H.; Wenner, P.; Hall, M.; Edkins, J.; Gassig, S.; Short, R.; Byrne, R.

    2004-12-01

    The deployment of underwater mass spectrometer (UMS) systems in marine and lacustrine environments has provided chemical data of exceptional temporal and spatial resolution. UMS instruments operate moored, tethered, remotely, or autonomously, allowing users to customize deployments to suit a wide variety of situations. The ability to collect and analyze real-time data enables prompt, intelligent sampling decisions based on observed analyte distributions. UMS systems can simultaneously detect a wide variety of analytes generated by biological, chemical, physical, geothermal and anthropogenic activities. A polydimethylsiloxane (PDMS) membrane separates the sample-stream from the spectrometer's vacuum chamber. This membrane is selective against water and charged species, yet highly permeable to volatile organic compounds (VOC) and simple gases. Current detection limits for dissolved gases and VOCs are on the order of ppm and ppb respectively. Semi-quantitative proof-of-concept applications have included horizontal mapping of gas gradients, characterization of geothermal vent water, and observation of dissolved gas profiles. Horizontal gradients in dissolved gas concentrations were determined in Lake Maggiore, St Petersburg, Florida. The UMS was positioned on a remotely-guided surface vehicle, and real-time gas concentration data were transmitted to shore via wireless ethernet. Real-time observations allowed intensive sampling of areas with strong gas gradients. Oxygen and CO2 exhibited patchy distributions and their concentrations varied inversely, presumably in response to biological activity. The UMS signal for methane depended on the instrument's proximity to organic rich sediments. Geothermal vent water was characterized while the UMS was deployed in Yellowstone Lake, Wyoming, on a tethered Eastern Oceanics remotely operated vehicle (ROV). Observations of dissolved vent-gas compositions were obtained to depths of 30m. Distinct differences in dissolved vent

  11. Dissolved oxygen concentration in culture medium: assumptions and pitfalls.

    PubMed

    Newby, D; Marks, L; Lyall, F

    2005-04-01

    Oxygen is a key factor in the regulation of cytotrophoblast differentiation, proliferation and invasion in early pregnancy. Abnormalities in oxygen concentration have also been linked to a number of pregnancy disorders. Cell culture models have been used to study the effect of oxygen on cytotrophoblast behaviour in vitro, however, there is often little or no validation of oxygen levels in these cell culture systems. In this study, dissolved oxygen levels in culture medium maintained in standard culture conditions (18% O(2)) measured 18%. On transfer to a low oxygen environment (2% O(2)), oxygen levels decreased to 6-8% after 4h and reached 2% only after 24h in culture. Culture medium pre-gassed with nitrogen to remove dissolved oxygen quickly absorbed oxygen when exposed to ambient air during dispensing and required further incubation in a 2% oxygen environment before dissolved oxygen levels equilibrated to 2%. Thus, cultured cells placed in a low oxygen environment would be exposed to varying levels of oxygen before the desired level of oxygen exposure is reached. This study highlights the importance of validation of oxygen levels and potential problems associated with in vitro studies on the regulatory effects of oxygen.

  12. 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...

  13. Corals concentrate dissolved inorganic carbon to facilitate calcification.

    PubMed

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

    2014-12-22

    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.

  14. An advanced passive diffusion sampler for the determination of dissolved gas concentrations

    NASA Astrophysics Data System (ADS)

    Gardner, P.; Solomon, D. K.

    2009-06-01

    We have designed and tested a passive headspace sampler for the collection of noble gases that allows for the precise calculation of dissolved gas concentrations from measured gas mixing ratios. Gas permeable silicon tubing allows for gas exchange between the headspace in the sampler volume and the dissolved gases in the adjacent water. After reaching equilibrium, the aqueous-phase concentration is related to the headspace concentration by Henry's law. Gas exchange between the water and headspace can be shut off in situ, preserving the total dissolved gas pressure upon retrieval. Gas samples are then sealed in an all metal container, retaining even highly mobile helium. Dissolved noble gas concentrations measured in these diffusion samplers are in good agreement with traditional copper tube aqueous-phase samples. These significantly reduce the laboratory labor in extracting the gases from a water sample and provide a simple and robust method for collecting dissolved gas concentrations in a variety of aqueous environments.

  15. DISSOLVED ORGANIC CARBON (DOC) CONCENTRATIONS IN SMALL STREAMS OF THE GEORGIA PIEDMONT

    EPA Science Inventory

    Dissolved organic matter (DOM) supports microbial activity and contributes to transport of N and P in streams. We have studied the impact of land uses on dissolved organic carbon (DOC) concentrations in 17 Georgia Piedmont headwater streams since January 2001. We classified the w...

  16. [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

  17. [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.

  18. The measurement of dissolved and gaseous carbon dioxide concentration

    NASA Astrophysics Data System (ADS)

    Zosel, J.; Oelßner, W.; Decker, M.; Gerlach, G.; Guth, U.

    2011-07-01

    In this review the basic principles of carbon dioxide sensors and their manifold applications in environmental control, biotechnology, biology, medicine and food industry are reported. Electrochemical CO2 sensors based on the Severinghaus principle and solid electrolyte sensors operating at high temperatures have been manufactured and widely applied already for a long time. Besides these, nowadays infrared, non-dispersive infrared and acoustic CO2 sensors, which use physical measuring methods, are being increasingly used in some fields of application. The advantages and drawbacks of the different sensor technologies are outlined. Electrochemical sensors for the CO2 measurement in aqueous media are pointed out in more detail because of their simple setup and the resulting low costs. A detailed knowledge of the basic detection principles and the windows for their applications is necessary to find an appropriate decision on the technology to be applied for measuring dissolved CO2. In particular the pH value and the composition of the analyte matrix exert important influence on the results of the measurements.

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

    USGS Publications Warehouse

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

    1996-01-01

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

  20. 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.

  1. 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

  2. Hypolimnetic concentrations of dissolved oxygen, nutrients, and trace elements in Coeur d'Alene Lake, Idaho

    USGS Publications Warehouse

    Woods, P.F.

    1989-01-01

    A reconnaissance study of Coeur d'Alene Lake, Idaho 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 refinement of the sampling protocol in a U.S. Geological Survey research proposal for a large-scale investigation of nutrient enrichment and trace element contamination problems affecting the 129.5 sq kilometer lake in northern Idaho. Hypolimnetic dissolved-oxygen concentrations as low as 4.1 mg/L in November and the frequent occurrence of supersaturated dissolved-oxygen concentrations during June through August indicated nutrient enrichment. Secchi-disc depths in the lake 's central and southern areas were typical of mesotrophic conditions, whereas oligotrophic conditions prevailed in the northern area. Throughout the study, hypolimnetic concentrations of total recoverable zinc exceeded chronic and acute toxicity criteria for freshwater aquatic life. (USGS)

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  5. Effect of dissolved oxygen concentration on growth of fingerling hybrid striped bass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Management of dissolved oxygen (DO) concentration in production ponds is important because fish growth and yield are greater in ponds with higher DO concentrations. The purpose of this study was to evaluate growth and metabolic responses of hybrid striped bass (Morone chrysops x M. saxatilis; HSB) f...

  6. Effect of daily minimum pond dissolved oxygen concentration on hybrid striped bass fingerling yield

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Management of dissolved oxygen (DO) concentration in ponds at night during the growing season is important because fish growth and yield are greater in ponds with higher nightly DO concentrations. The purpose of this study was to quantify the production and water quality responses of hybrid striped ...

  7. Dissolved Phosphorus Concentrations in the Mississippi River Valley Alluvial Aquifer, Northwestern Mississippi

    NASA Astrophysics Data System (ADS)

    Rose, C. E.; Welch, H. L.

    2010-12-01

    The Mississippi River Valley alluvial (MRVA) aquifer is the most heavily used aquifer in the state of Mississippi with more than 1.3 billion gallons of water per day being withdrawn primarily for irrigation. In a study conducted in 1998, median concentrations of dissolved phosphorus in water from 25 wells screened in the Holocene alluvium and 29 wells screened in the Pleistocene valley train deposits, two subunits of the MRVA aquifer, were 0.65 and 0.11 milligrams per liter (mg/L), respectively. Both values are considerably higher than the typical average concentration of 0.02 mg/L for dissolved phosphorus in groundwater; and more than 0.1 mg/L, which is the U.S. Environmental Protection Agency’s water-quality criteria for dissolved phosphorus in streams for the prevention of nuisance plant growth. Approximately 67 percent of the water samples exceeded the EPA criteria. A general association between elevated phosphorus concentrations and high concentrations of dissolved iron suggests that reducing conditions that mobilize iron in the MRVA aquifer also may facilitate transport of phosphorus. These elevated concentrations of phosphorus in the two subunits may represent a source of phosphorus to streams and rivers in the study area through irrigation return flow and groundwater discharge during stream base-flow conditions. Fifty irrigation wells were sampled during the summer 2010 for total dissolved phosphorus, iron, manganese, calcium, arsenic, silica, and field parameters (pH, specific conductance, turbidity, and alkalinity) to further characterize the occurrence of phosphorus in the aquifer, as well as the factors that might contribute to high dissolved phosphorus concentrations in the aquifer.

  8. Effect of oxygen reduction rate and constant low dissolved oxygen concentrations on two estuarine fish

    SciTech Connect

    Burton, D.T.; Richardson, L.B.; Moore, C.J.

    1980-09-01

    The relationship between mean lethal oxygen concentration and rate of reduction of dissolved oxygen that induces fish kills was determined for Atlantic menhaden (Brevoortia tyrannus). Reduction of dissolved oxygen at hourly rates of 1.00 to 0.08 mg/liter had no effect on the mean lethal oxygen concentrations. There was an inverse relationship between the median time to death (LT50) and rate of oxygen reduction that can be used to estimate how quickly a fish kill may occur when oxygen concentrations decrease at a constant rate. Atlantic menhaden were less resistant than spot (Leiostomus xanthurus) when both species were exposed to constant low concentrations of oxygen. The lethal threshold concentrations for Atlantic menhaden and spot at 28/sup 0/C were approximately 1.1 and 0.7 mg/liter, respectively, whereas, the 96-hour, 5% lethal concentrations were approximately 1.6 and 0.8 mg/liter, respectively.

  9. 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

  10. 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.

  11. Tracking Dissolved Methane Concentrations near Active Seeps and Gas Hydrates: Sea of Japan.

    NASA Astrophysics Data System (ADS)

    Snyder, G. T.; Aoki, S.; Matsumoto, R.; Tomaru, H.; Owari, S.; Nakajima, R.; Doolittle, D. F.; Brant, B.

    2015-12-01

    A number of regions in the Sea of Japan are known for active gas venting and for gas hydrate exposures on the sea floor. In this investigation we employed several gas sensors mounted on a ROV in order to determine the concentrations of dissolved methane in the water near these sites. Methane concentrations were determined during two-second intervals throughout each ROV deployment during the cruise. The methane sensor deployments were coupled with seawater sampling using Niskin bottles. Dissolved gas concentrations were later measured using gas chromatography in order to compare with the sensor results taken at the same time. The observed maximum dissolved methane concentrations were much lower than saturation values, even when the ROV manipulators were in contact with gas hydrate. Nonetheless, dissolved concentrations did reach several thousands of nmol/L near gas hydrate exposures and gas bubbles, more than two orders of magnitude over the instrumental detection limits. Most of the sensors tested were able to detect dissolved methane concentrations as low as 10 nmol/L which permitted detection when the ROV approached methane plume sites, even from several tens of meters above the sea floor. Despite the low detection limits, the methane sensors showed variable response times when returning to low-background seawater (~5nM). For some of the sensors, the response time necessary to return to background values occurred in a matter of minutes, while for others it took several hours. Response time, as well as detection limit, should be an important consideration when selecting methane sensors for ROV or AUV investigations. This research was made possible, in part, through funding provided by the Japanese Ministry of Economy, Trade and Industry (METI).

  12. 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

  13. 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.

  14. 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, ...

  15. Occurrence and concentration of dissolved silver in rivers in England and Wales.

    PubMed

    Peters, A; Simpson, P; Merrington, G; Rothenbacher, K; Sturdy, L

    2011-06-01

    There is a paucity of monitoring data for silver in freshwater environments in Europe. There are several reasons for this, including the relatively low levels of silver in the aquatic environment and the requirement for commensurately low levels of detection (<100 ng l⁻¹), which are generally not routinely achieved in analytical laboratories. In this study 425 separate analytical determinations for dissolved (<0.45 μm) silver from 84 Environment Agency monitoring stations were carried out. Sampling was carried out on a monthly basis over a period of 6 months. Of the 425 samples, 346 were reported as having dissolved silver concentrations below the limit of quantification (6.6 ng l⁻¹) and, of these, 280 samples were reported as below the reporting limit of detection (3 ng l⁻¹). The mean of the maximum dissolved silver concentrations reported at each station was calculated as 6.1 ng l⁻¹ using a statistical extrapolation technique to allow for the high level of censorship in the dataset. The maximum mean dissolved silver concentration recorded at a station was 19.8 ng l⁻¹. A freshwater Predicted No Effect Concentration (PNEC) of 40 ng l⁻¹ was used in this study. PMID:21516451

  16. [Influence of the Concentration of Dissolved Oxygen on Embryonic Development of the Common Toad (Bufo bufo)].

    PubMed

    Dmitrieva, E V

    2015-01-01

    Several series of experiments investigating the influence of dissolved oxygen concentrations on the growth rates and mortality in the embryogenesis of the common toad Bufo bufo were carried out. The experiments showed that, when the eggs develop singly, the lack of oxygen does not lead to an increase in mortality by the time of hatching and results only in a change in the dynamics of mortality: mortality occurs at an earlier stage of development than in the conditions of normal access to oxygen. Taking into account the combined effect of the density of eggs and the dissolved oxygen concentration, we increase the accuracy of analysis of the experimental results and improve the interpretation of the results. In the conditions of different initial density of eggs, the impact of the concentration of dissolved oxygen on mortality and rates of development of the common toad embryos is manifested in different ways. At high density, only a small percentage of embryos survives by the time of hatching, and the embryos are significantly behind in their development compared with the individuals that developed in normal oxygen conditions. The lack of oxygen dissolved in the water slows down the development of embryos of the common toad.

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

    USGS Publications Warehouse

    Lum, W. E.; 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)

  18. Linking CDOM spectral absorption to dissolved organic carbon concentrations and loadings in boreal estuaries

    NASA Astrophysics Data System (ADS)

    Asmala, Eero; Stedmon, Colin A.; Thomas, David N.

    2012-10-01

    The quantity of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) in three Finnish estuaries (Karjaanjoki, Kyrönjoki and Kiiminkijoki) was investigated, with respect to predicting DOC concentrations and loadings from spectral CDOM absorption measurements. Altogether 87 samples were collected from three estuarine transects which were studied in three seasons, covering a salinity range between 0 and 6.8, and DOC concentrations from 1572 μmol l-1 in freshwater to 222 μmol l-1 in coastal waters. CDOM absorption coefficient, aCDOM(375) values followed the trend in DOC concentrations across the salinity gradient and ranged from 1.67 to 33.4 m-1. The link between DOC and CDOM was studied using a range of wavelengths and algorithms. Wavelengths between 250 and 270 nm gave the best predictions with single linear regression. Total dissolved iron was found to influence the prediction in wavelengths above 520 nm. Despite significant seasonal and spatial differences in DOC-CDOM models, a universal relationship was tested with an independent data set and found to be robust. DOC and CDOM yields (loading/catchment area) from the catchments ranged from 1.98 to 5.44 g C m-2 yr-1, and 1.67 to 11.5 aCDOM(375) yr-1, respectively.

  19. 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

  20. 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.

  1. 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 hour) 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 were 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. Thermodynamic speciation calculations using site specific water compositions, including time-integrated dissolved metal concentrations determined from DGT, and a competitive, multiple-metal biotic ligand model incorporated into the Windemere Humic Aqueous Model Version 6.0 (WHAM VI) were used to determine the chemical 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.

  2. 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.

  3. Laser induced fluorescence measurements of dissolved oxygen concentration fields near air bubble surfaces

    NASA Astrophysics Data System (ADS)

    Roy, Sabita; Duke, Steve R.

    2000-09-01

    This article describes a laser-induced fluorescence (LIF) technique for measuring dissolved oxygen concentration gradients in water near the surface of an air bubble. Air bubbles are created at the tip of a needle in a rectangular bubble column filled with water that contains pyrenebutyric acid (PBA). The fluorescence of the PBA is induced by a planar pulse of nitrogen laser light. Oxygen transferring from the air bubble to the deoxygenated water quenches the fluorescence of the PBA. Images of the instantaneous and two-dimensional fluorescence field are obtained by a UV-intensified charge-coupled device (CCD) camera. Quenching of fluorescence intensity is determined at each pixel in the CCD image to measure dissolved oxygen concentration. Two-dimensional concentration fields are presented for a series of measurements of oxygen transfer from 1.6 mm bubbles suspended on the tip of a needle in a quiescent fluid. The images show the spatially varying concentration profiles, gradients, and boundary layer thicknesses at positions around the bubble surfaces. These direct and local measurements of concentration behavior within the mass transfer boundary layer show the potential of this LIF technique for the development of general and mechanistic models for oxygen transport across the air-water interface.

  4. 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 μg⋅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 μg⋅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 μm) of 2.7 ± 0.9 μg⋅L(-1), which is significantly higher than the world-average baseline for river water (0.83 μg⋅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

  5. 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 μg⋅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 μg⋅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 μm) of 2.7 ± 0.9 μg⋅L(-1), which is significantly higher than the world-average baseline for river water (0.83 μg⋅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.

  6. Spatial variability of dissolved phosphorous concentrations and alkaline phosphatase activity in the East China Sea

    NASA Astrophysics Data System (ADS)

    Liu, H.; Chang, J.; Ho, T.; Gong, G.

    2010-12-01

    The concentrations of dissolved inorganic phosphorus (DIP) and alkaline phosphatase activity (APA) have been determined at about 25 sampling stations in the East China Sea since 2003. The stations are mainly distributed from the Changjiang river mouth to northern Taiwan and east to the shelf break. In addition to the Changjiang discharge, we have found a specific nutrient source around a coastal site (122° 2’30’’ E, 28° 40’ N). Elevated DIP and nitrate concentrations have been constantly observed around the sampling station for 8 years, where the surface DIP concentrations are generally around 0.3 µM. The nutrient source may either originate from ground water discharge or coastal upwelling, where lower temperature has been observed in the water column around the station. In general, APA has been negatively correlated with DIP concentrations in the studies sites, with lowest APA around the high DIP station and the Changjiang river mouth.

  7. 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.

  8. Dissolved organic matter concentration and quality influences upon structure and function of freshwater microbial communities.

    PubMed

    Docherty, Kathryn M; Young, Katherine C; Maurice, Patricia A; Bridgham, Scott D

    2006-10-01

    Past studies have suggested that the concentration and quality of dissolved organic matter (DOM) may influence microbial community structure. In this study, we cross-inoculated the bacterial communities from two streams and a dystrophic lake that varied in DOM concentration and chemistry, to yield nine fully crossed treatments. We measured dissolved organic carbon (DOC) concentration and heterotrophic microbial community productivity throughout a 72-h incubation period, characterized DOM quality by molecular weight, and determined microbial community structure at the initial and final time points. Our results indicate that all bacterial inoculate sources had similar effects upon DOC concentration and DOM quality, regardless of the DOM source. These effects included an overall decrease in DOM M (W) and an initial period of DOC concentration variability between 0-24h. In contrast, microbial communities and their metabolic rates converged to profiles that reflected the DOM source upon which they were growing, regardless of the initial bacterial inoculation. The one exception was that the bacterial community from the low-concentration and low-molecular-weight DOM source exhibited a greater denaturing gradient gel electrophoresis (DGGE) band richness when grown in its own DOM source than when grown in the highest concentration and molecular weight DOM source. This treatment also exhibited a higher rate of productivity. In general, our data suggest that microbial communities are selected by the DOM sources to which they are exposed. A microbial community will utilize the low-molecular-weight (or labile) DOM sources as well as parts of the high-molecular-weight (refractory) DOM, until a community develops that can efficiently metabolize the more abundant high-molecular-weight source. This experiment examines some of the complex interactions between microbial community selection and the combined factors of DOM quality and concentration. Our data suggest that the roles of

  9. The concentrations, appearance and taste of nine sedating drugs dissolved in four different beverages.

    PubMed

    Olsen, Vigdis; Gustavsen, Ingebjørg; Bramness, Jørgen G; Hasvold, Inger; Karinen, Ritva; Christophersen, Asbjørg S; Mørland, Jørg

    2005-07-16

    Sedating drugs are reported to be used in cases where people have been drugged unwittingly. In the present experiments we studied whether nine sedating medicinal drugs would dissolve in four different beverages to reach concentrations which could possibly cause impairment and whether the drugs altered the appearance and taste of the beverages. Nine sedating medicinal drugs were added separately to water, beer, Coca-Cola and ethanol. Drug concentrations were measured 5, 10, 20 and 40 min after spiking. The amount of drug in one swallow (50 mL) was calculated. Appearance and taste were recorded after 10 min. Flunipam, Sobril, Valium and Xanor dissolved faster than Rohypnol, Imovane, Somadril, Rivotril and Dolcontin. Ten minutes after adding Flunipam, Sobril, Imovane (in beer and Coca-Cola), Valium and Xanor, the concentrations had reached more than 50% of maximum theoretical concentration. Most of the drugs caused sediment, pieces and/or turbidity in one or more of the beverages. Some of the solutions were dyed from added Rohypnol (turquoise or green), Dolcontin (red) and Valium (yellow). Flunipam and Valium caused extensive frothing in beer. The tastes of Imovane and Somadril were distinct in all the beverages, while the taste of other drug solutions was less distinct. The ingestion of all solutions could probably have caused impairment. All the nine drugs were, however, apparent to the consumer from the altered appearance and/or taste of the beverages.

  10. Rheological behaviors in the regimes from dilute to concentrated in cellulose solutions dissolved at low temperature.

    PubMed

    Lue, Ang; Zhang, Lina

    2009-05-13

    Cellulose was dissolved rapidly in 9.5 wt.-% NaOH/4.5 wt.-% thiourea aqueous solution pre-cooled to -5 degrees C to prepare cellulose solution with different concentrations. The rheological properties of the cellulose solutions in wide concentration regimes from dilute (0.008 wt.-%) to concentrated (4.0 wt.-%) at 25 degrees C were investigated. On the basis of data from the steady-shear flow test, the critical overlap (c*), the entanglement (c(e)) and the gel (c(g)) concentrations of the cellulose solution at 25 degrees C were determined, respectively, to be 0.10 wt.-%, 0.53 wt.-% and 2.50 wt.-%, in accordance with the results of storage modulus (G') versus c by dynamic test. Moreover, the Cox-Merz deviation at relatively low concentrations was in good agreement with the micro-gel particles in dilute regime. As the cellulose concentration increased, a homogeneous 3-dimensional network formed in the cellulose solution in the concentrated regime, and further increasing of the concentration led to micro-phase separation as determined by the time-temperature superposition (tTS). So far, this complex cellulose solution has been successfully described by the concentration regime theory for the first time, and the relatively molecular morphologies in each regime have been determined, providing useful information for the applications of the cellulose solution systems. PMID:19039777

  11. 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

  12. Trends in nitrate and dissolved-solids concentrations in ground water, Carson Valley, Douglas County, Nevada, 1985-2001

    USGS Publications Warehouse

    Rosen, Michael R.

    2003-01-01

    Analysis of trends in nitrate and total dissolved-solids concentrations over time in Carson Valley, Nevada, indicates that 56 percent of 27 monitoring wells that have long-term records of nitrate concentrations show increasing trends, 11 percent show decreasing trends, and 33 percent have not changed. Total dissolved-solids concentrations have increased in 52 percent of these wells and are stable in 48 percent. None of these wells show decreasing trends in total dissolved-solids concentrations. The wells showing increasing trends in nitrate and total dissolved-solids concentrations were always in areas that use septic waste-disposal systems. Therefore, the primary cause of these increases is likely the increase in septic-tank usage over the past 40 years.

  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. Frequency-duration analysis of dissolved-oxygen concentrations in two southwestern Wisconsin streams

    USGS Publications Warehouse

    Greb, Steven R.; Graczyk, David J.

    2007-01-01

    Historically, dissolved-oxygen (DO) data have been collected in the same manner as other water-quality constituents, typically at infrequent intervals as a grab sample or an instantaneous meter reading. Recent years have seen an increase in continuous water-quality monitoring with electronic dataloggers. This new technique requires new approaches in the statistical analysis of the continuous record. This paper presents an application of frequency-duration analysis to the continuous DO records of a cold and a warm water stream in rural southwestern Wisconsin. This method offers a quick, concise way to summarize large time-series data bases in an easily interpretable manner. Even though the two streams had similar mean DO concentrations, frequency-duration analyses showed distinct differences in their DO-concentration regime. This type of analysis also may be useful in relating DO concentrations to biological effects and in predicting low DO occurrences.

  16. Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

    NASA Astrophysics Data System (ADS)

    Prasetyaningrum, A.; Ratnawati, Jos, B.

    2015-12-01

    Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O3) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flow rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.

  17. Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

    SciTech Connect

    Prasetyaningrum, A. Ratnawati,; Jos, B.

    2015-12-29

    Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O{sub 3}) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flow rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.

  18. 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

  19. Concentrations of dissolved herbicides and pharmaceuticals in a small river in Luxembourg.

    PubMed

    Meyer, Berenike; Pailler, Jean-Yannick; Guignard, Cédric; Hoffmann, Lucien; Krein, Andreas

    2011-09-01

    Urban and agricultural areas affect the hydraulic patterns as well as the water quality of receiving drainage systems, especially of catchments smaller than 50 km(2). Urban runoff is prone to contamination due to pollutants like pesticides or pharmaceuticals. Agricultural areas are possible sources of nutrient and herbicide contamination for receiving water bodies. The pollution is derived from leaching by subsurface flow, as well as wash-off and erosion caused by surface runoff. In the Luxembourgish Mess River catchment, the pharmaceutical and pesticide concentrations are comparable with those detected by other authors in different river systems worldwide. Some investigated pesticide concentrations infringe current regulations. The maximum allowable concentration for diuron of 1.8 μg l( - 1) is exceeded fourfold by measured 7.41 μg l( - 1) in a flood event. The load of dissolved pesticides reaching the stream gauge is primarily determined by the amount applied to the surfaces within the catchment area. Storm water runoff from urban areas causes short-lived but high-pollutant concentrations and moderate loads, whereas moderate concentrations and high loads are representative for agricultural inputs to the drainage system. Dissolved herbicides, sulfonamides, tetracyclines, analgesics and hormones can be used as indicators to investigate runoff generation processes, including inputs from anthropogenic sources. The measurements prove that the influence of kinematic wave effects on the relationship between hydrograph and chemographs should not be neglected in smaller basins. The time lag shows that it is not possible to connect analysed substances of defined samples to the corresponding section of the hydrograph.

  20. Estimating dissolved organic carbon concentration in turbid coastal waters using optical remote sensing observations

    NASA Astrophysics Data System (ADS)

    Cherukuru, Nagur; Ford, Phillip W.; Matear, Richard J.; Oubelkheir, Kadija; Clementson, Lesley A.; Suber, Ken; Steven, Andrew D. L.

    2016-10-01

    Dissolved Organic Carbon (DOC) is an important component in the global carbon cycle. It also plays an important role in influencing the coastal ocean biogeochemical (BGC) cycles and light environment. Studies focussing on DOC dynamics in coastal waters are data constrained due to the high costs associated with in situ water sampling campaigns. Satellite optical remote sensing has the potential to provide continuous, cost-effective DOC estimates. In this study we used a bio-optics dataset collected in turbid coastal waters of Moreton Bay (MB), Australia, during 2011 to develop a remote sensing algorithm to estimate DOC. This dataset includes data from flood and non-flood conditions. In MB, DOC concentration varied over a wide range (20-520 μM C) and had a good correlation (R2 = 0.78) with absorption due to coloured dissolved organic matter (CDOM) and remote sensing reflectance. Using this data set we developed an empirical algorithm to derive DOC concentrations from the ratio of Rrs(412)/Rrs(488) and tested it with independent datasets. In this study, we demonstrate the ability to estimate DOC using remotely sensed optical observations in turbid coastal waters.

  1. 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.

  2. Seasonal variations in concentration and lability of dissolved organic carbon in Tokyo Bay

    NASA Astrophysics Data System (ADS)

    Kubo, A.; Yamamoto-Kawai, M.; Kanda, J.

    2015-01-01

    Concentrations of recalcitrant and bioavailable dissolved organic carbon (DOC) and their seasonal variations were investigated at three stations in Tokyo Bay, Japan, and in two freshwater sources flowing into the bay. On average, recalcitrant DOC (RDOC), as a remnant of DOC after 150 days of bottle incubation, accounted for 78% of the total DOC in Shibaura sewage treatment plant (STP) effluent, 67% in the upper Arakawa River water, 66% in the lower Arakawa River water, and 78% in surface bay water. Bioavailable DOC (BDOC) concentrations, defined as DOC minus RDOC, were lower than RDOC at all stations. In freshwater environments, RDOC concentrations were almost constant throughout the year. In the bay, RDOC was higher during spring and summer than in autumn and winter because of freshwater input and biological production. The relative concentration of RDOC in the bay derived from phytoplankton, terrestrial, and open-oceanic waters was estimated to be 8-10, 21-32, and 59-69%, respectively, based on multiple regression analysis of RDOC, salinity, and chl a. In addition, comparison with previous data from 1972 revealed that concentrations of RDOC and BDOC have decreased by 33 and 74% at freshwater sites and 39 and 76% in Tokyo Bay, while the ratio of RDOC to DOC has increased. The change in DOC concentration and composition was probably due to increased amounts of STP effluent entering the system. Tokyo Bay exported mostly RDOC to the open ocean because of the remineralization of BDOC.

  3. Fast-freezing with liquid nitrogen preserves bulk dissolved organic matter concentrations, but not its composition

    NASA Astrophysics Data System (ADS)

    Thieme, Lisa; Graeber, Daniel; Kaupenjohann, Martin; Siemens, Jan

    2016-08-01

    Freezing can affect concentrations and spectroscopic properties of dissolved organic matter (DOM) in water samples. Nevertheless, water samples are regularly frozen for sample preservation. In this study we tested the effect of different freezing methods (standard freezing at -18 °C and fast-freezing with liquid nitrogen) on DOM concentrations measured as organic carbon (DOC) concentrations and on spectroscopic properties of DOM from different terrestrial ecosystems (forest and grassland). Fresh and differently frozen throughfall, stemflow, litter leachate and soil solution samples were analyzed for DOC concentrations, UV-vis absorption and fluorescence excitation-emission matrices combined with parallel factor analysis (PARAFAC). Fast-freezing with liquid nitrogen prevented a significant decrease of DOC concentrations observed after freezing at -18 °C. Nonetheless, the share of PARAFAC components 1 (EXmax < 250 nm (340 nm), EXmax: 480 nm) and 2 (EXmax: 335 nm, EXmax: 408 nm) to total fluorescence and the humification index (HIX) decreased after both freezing treatments, while the shares of component 3 (EXmax: < 250 nm (305 nm), EXmax: 438 nm) as well as SUVA254 increased. The contribution of PARAFAC component 4 (EXmax: 280 nm, EXmax: 328 nm) to total fluorescence was not affected by freezing. We recommend fast-freezing with liquid nitrogen for preservation of bulk DOC concentrations of samples from terrestrial sources, whereas immediate measuring is preferable to preserve spectroscopic properties of DOM.

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

    PubMed

    Haas, Andreas F; Smith, Jennifer E; Thompson, Melissa; Deheyn, Dimitri D

    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.

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

    PubMed

    Haas, Andreas F; Smith, Jennifer E; Thompson, Melissa; Deheyn, Dimitri D

    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

  6. 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

  7. An Estimate of the Dissolved oxygen Concentration in Subglacial Lake Vostok

    NASA Astrophysics Data System (ADS)

    Lipenkov, V.; Istomin, V.; Bulat, S.; Raynaud, D.; Petit, J.

    2002-05-01

    The upper section of 3.5 km thick glacier ice overlying Lake Vostok is characterized by abundance of air bubbles trapped during pore closure near the surface of the ice sheet. As the pressure increases with depth, the air occluded in ice gradually transforms to mixed air clathrate hydrate. In the region of interest the bubble-to-hydrate transition is complete at about 1300 mbs below which depth most of the air (about 99%) in the ice sheet is located within hydrate crystals. The basal-ice melting prevails in the north of Lake Vostok and the ice accretion occurs in the south. The concentration of air in the melting glacier ice is typically about 113 mg l-1 (86 mg N2 L-1 + 27 mg O2 L-1), whereas that in accreted ice is nearly zero. This suggests a net transfer of the atmospheric air (in the form of gas hydrate) through the ice-sheet thickness to Lake Vostok water. Available laboratory data and thermodynamic models indicate that, under conditions appropriate to Lake Vostok, the air-hydrate crystals released from the melting ice will persist within the water body provided there is enough air present in the system for a hydrate phase to coexist with dissolved N2 and O2. Neglecting biogeochemical inputs and losses of dissolved gases we have calculated the solubility of nitrogen (2.25 103 mg L-1) and oxygen (1.3 103 mg L-1) in equilibrium with air hydrate in lake water. Accordingly, the dissolved oxygen concentration is predicted to be between 27 and 1.3 103 mg L-1 (compare to 15 mg O2 L-1 for standard conditions). Assuming a steady state and taking 20 kyr for the residence time of the lake water, we have estimated that a 630 kyr period is needed to reach the upper bond of the dissolved O2 concentration, which is a prerequisite for air hydrate stability in the lake. Metabolic consumption of oxygen in the lake could only make this transition longer. We also demonstrate that strong hydrate-forming gases such as CO2 and CH4, if present in the lake together with N2 and O2

  8. Impact of environmental factors on dissolved organic carbon concentrations in German bogs under grassland

    NASA Astrophysics Data System (ADS)

    Frank, Stefan; Tiemeyer, Bärbel; Freibauer, Annette

    2013-04-01

    Peatlands cover about 5% of Germany's land area. Agricultural use combined with drainage increases the greenhouse gas emissions and alters the dissolved organic carbon (DOC) concentrations in the soil- and groundwater of these ecosystems. Cycling of DOC is influenced by a complex interaction of environmental factors such as peat characteristics, groundwater level, meteorological conditions, pH-value and ionic strength. Reasons for elevated DOC concentrations are debated in literature, but only a few studies on the dynamic of DOC in raised bogs in Germany have been conducted so far. In Germany, raised bogs are mainly used as grassland. Therefore, five grassland study sites and one natural reference have been selected. The bog "Ahlenmoor" has a deep, medium to weakly decomposed peat layer. There, three study sites represent different land use intensities with a corresponding groundwater table (intensive grassland, extensive grassland, natural reference). The bog relict "Großes Moor" is characterised by a shallow amorphous peat layer, which is partly mixed with sand. There, three sites in an extensive grassland were chosen to study the effects of soil carbon concentrations (9 to 48 %) and groundwater levels. At each site, nine suction plates (three replicates in each depth) and three tensiometers were installed in 15, 30 and 60 cm. Soil water was sampled fortnightly from June 2011 to December 2012 and analysed for electrical conductivity, pH-value and DOC concentration. Compared to most literature values, DOC concentrations at our study sites were very high (on average, 197 to 55 mg/L). At the "Ahlenmoor", an increase in agricultural intensity and a lower groundwater table increases both the DOC concentrations and their variability in the soil water in order intensive grassland > extensive grassland > natural site. Surprisingly, soil carbon concentration and groundwater table gradients as investigated in the "Großes Moor" did only lead to minor differences in the

  9. Hydrologic control of dissolved organic matter concentration and quality in a semiarid artificially drained agricultural catchment

    NASA Astrophysics Data System (ADS)

    Bellmore, Rebecca A.; Harrison, John A.; Needoba, Joseph A.; Brooks, Erin S.; Kent Keller, C.

    2015-10-01

    Agricultural practices have altered watershed-scale dissolved organic matter (DOM) dynamics, including in-stream concentration, biodegradability, and total catchment export. However, mechanisms responsible for these changes are not clear, and field-scale processes are rarely directly linked to the magnitude and quality of DOM that is transported to surface water. In a small (12 ha) agricultural catchment in eastern Washington State, we tested the hypothesis that hydrologic connectivity in a catchment is the dominant control over the concentration and quality of DOM exported to surface water via artificial subsurface drainage. Concentrations of dissolved organic carbon (DOC) and humic-like components of DOM decreased while the Fluorescence Index and Freshness Index increased with depth through the soil profile. In drain discharge, these characteristics were significantly correlated with drain flow across seasons and years, with drain DOM resembling deep sources during low-flow and shallow sources during high flow, suggesting that DOM from shallow sources bypasses removal processes when hydrologic connectivity in the catchment is greatest. Assuming changes in streamflow projected for the Palouse River (which contains the study catchment) under the A1B climate scenario (rapid growth, dependence on fossil fuel, and renewable energy sources) apply to the study catchment, we project greater interannual variability in annual DOC export in the future, with significant increases in the driest years. This study highlights the variability in DOM inputs from agricultural soil to surface water on daily to interannual time scales, pointing to the need for a more nuanced understanding of agricultural impacts on DOM dynamics in surface water.

  10. 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

  11. Regulation of the dissolved phosphate concentration of a mountainous stream, Kitakyushu, southwestern Japan.

    PubMed

    Koga, Masaaki; Yoshimura, Kazuhisa

    2012-07-01

    The phosphate concentration in mountainous stream water can be a measure of the forest condition, because its concentration will be low when the biomass in the forest is increasing and vice versa when the forest is declining. To investigate the seasonal change in the dissolved phosphate concentration of the mountainous stream water of the Yamakami River, Kitakyushu, from June 2009 to August 2010, and the regulation mechanism of the phosphate concentration, solid-phase spectrophotometry, which can be applicable to natural water without any pretreatment procedures, was employed for the determination of phosphate at μg P L(-1) levels in natural water. The phosphate concentrations in the mountainous stream waters at 6 sites ranged from 2.2 to 13 μg P L(-1), and those from the catchment area of the steady state forest were 5.3 ± 1.6 (±1 SD) μg P L(-1). Changes in the concentration were fairly small even during a storm runoff. The average phosphate concentration of rain was 2.8 ± 0.7 μg P L(-1), about half of the concentration in the stream water. The rate of runoff in forest areas is generally considered to be about 50% of the total precipitation. For a forest under a climax condition, the phosphate concentration is estimated to be regulated by the fallout and evapotranspiration (α = 0.05). At one of the sites, an upstream tributary, where a fairly big landslide occurred before July in 2009, the phosphate concentration was the highest, suggesting that the biomass may still be decreasing. For all of the six sites examined, a characteristic seasonal change in phosphate concentration was observed, reflecting the local budget between the biological decomposition of plant matter and the consumption by the biomass. The increase in the phosphate concentration during late spring and early summer may result from the extensive decomposition of plant litter mainly supplied in autumn and of plant matter relating to spring blooming such as fallen flowers, pollen and immature

  12. Regulation of the dissolved phosphate concentration of a mountainous stream, Kitakyushu, southwestern Japan.

    PubMed

    Koga, Masaaki; Yoshimura, Kazuhisa

    2012-07-01

    The phosphate concentration in mountainous stream water can be a measure of the forest condition, because its concentration will be low when the biomass in the forest is increasing and vice versa when the forest is declining. To investigate the seasonal change in the dissolved phosphate concentration of the mountainous stream water of the Yamakami River, Kitakyushu, from June 2009 to August 2010, and the regulation mechanism of the phosphate concentration, solid-phase spectrophotometry, which can be applicable to natural water without any pretreatment procedures, was employed for the determination of phosphate at μg P L(-1) levels in natural water. The phosphate concentrations in the mountainous stream waters at 6 sites ranged from 2.2 to 13 μg P L(-1), and those from the catchment area of the steady state forest were 5.3 ± 1.6 (±1 SD) μg P L(-1). Changes in the concentration were fairly small even during a storm runoff. The average phosphate concentration of rain was 2.8 ± 0.7 μg P L(-1), about half of the concentration in the stream water. The rate of runoff in forest areas is generally considered to be about 50% of the total precipitation. For a forest under a climax condition, the phosphate concentration is estimated to be regulated by the fallout and evapotranspiration (α = 0.05). At one of the sites, an upstream tributary, where a fairly big landslide occurred before July in 2009, the phosphate concentration was the highest, suggesting that the biomass may still be decreasing. For all of the six sites examined, a characteristic seasonal change in phosphate concentration was observed, reflecting the local budget between the biological decomposition of plant matter and the consumption by the biomass. The increase in the phosphate concentration during late spring and early summer may result from the extensive decomposition of plant litter mainly supplied in autumn and of plant matter relating to spring blooming such as fallen flowers, pollen and immature

  13. Dissolved organic matter conformation and its interaction with pyrene as affected by water chemistry and concentration.

    PubMed

    Pan, Bo; Ghosh, Saikat; Xing, Baoshan

    2008-03-01

    Water chemistry and concentration of dissolved organic matter (DOM) have been reported to affect DOM conformation and binding properties with hydrophobic organic contaminants (HOCs). However, relationship between DOM conformation and its binding properties remains unclear. We designed a multibag equilibration system (MBES) to investigate the variation of carbon-normalized sorption coefficients (K(DOC)) of pyrene at different DOM concentrations based on an identical free solute concentration at different pHs and in the presence of Al ions. In addition, we studied the conformation of DOM under different conditions via atomic force microscopy (AFM) imaging, dynamic light scattering, and zeta potential measurements. Zeta potential measurements indicated that intra- and intermolecular interaction was facilitated at low pH or with the presence of Al ions, and a more organized molecular aggregate (such as a micelle-like structure) could form, thus, enhancing K(DOC). As DOM concentration increased, DOM molecular aggregation was promoted in a way reducing K(DOC). This research is a first attempt to correlate DOM conformation with K(DOC). Aggregation of DOM molecules resulting from increased zeta potential (less negative) generally led to an increased K(DOC). Further study in this area will provide valuable information on HOC-DOM interactions, thus, leading to more accurate predictions of K(DOC).

  14. 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 (60 s), nearly 90% of the algal cells were damaged and the maximum concentration of DON attained more than 3 mg/L. In order to control the leakage extent of DON, the sonication time should be less than 30 s with power intensity of more than 1.0 W/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 (20-150 kHz). PMID:26585003

  15. 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; Zieliński, 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.

  16. Raising and controlling study of dissolved oxygen concentration in closed-type aeration tank.

    PubMed

    Chen, C K; Lo, S L

    2005-07-01

    This study investigated the promotion and control of dissolved oxygen (DO) concentration of the closed-type aeration tank via practical experiments in the wastewater treatment system of a 5-star hotel in Taipei. As with limited and treasured space in Taiwan, before the completion of the sewer system construction in cities, to utilize the mat foundation under large buildings as the space of sewage treatment plant still has been one of the alternatives of those sewage treatments. However, aeration tanks constructed in the mat foundation of buildings have smaller effective water depth, which will cause a lower total transfer amount of DO. Controlling the total exhaust gas flow rate can increase the pressure on such closed-type aeration tanks. The DO concentration thus may increase according to Henry's Law. Furthermore, it may enable operators to adjust the DO concentration of the aeration tank more precisely and thus sustain optimal operating conditions in these treatment facilities. Practical experiments indicated that the DO concentration of aeration tank maintains an average of 3.8 mg l(-1), obtaining the optimum operating conditions. The efficiency of the biological treatment facilities in the mat foundation could be markedly improved. PMID:16080335

  17. 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

  18. Freely floating smectic films.

    PubMed

    May, Kathrin; Harth, Kirsten; Trittel, Torsten; Stannarius, Ralf

    2014-05-19

    We have investigated the dynamics of freely floating smectic bubbles using high-speed optical imaging. Bubbles in the size range from a few hundred micrometers to several centimeters were prepared from collapsing catenoids. They represent ideal model systems for the study of thin-film fluid dynamics under well-controlled conditions. Owing to the internal smectic layer structure, the bubbles combine features of both soap films and vesicles in their unique shape dynamics. From a strongly elongated initial shape after pinch-off, they relax towards the spherical equilibrium, first by a slow redistribution of the smectic layers, and finally by weak, damped shape oscillations. In addition, we describe the rupture of freely floating smectic bubbles, and the formation and stability of smectic filaments. PMID:24692347

  19. Freely floating smectic films.

    PubMed

    May, Kathrin; Harth, Kirsten; Trittel, Torsten; Stannarius, Ralf

    2014-05-19

    We have investigated the dynamics of freely floating smectic bubbles using high-speed optical imaging. Bubbles in the size range from a few hundred micrometers to several centimeters were prepared from collapsing catenoids. They represent ideal model systems for the study of thin-film fluid dynamics under well-controlled conditions. Owing to the internal smectic layer structure, the bubbles combine features of both soap films and vesicles in their unique shape dynamics. From a strongly elongated initial shape after pinch-off, they relax towards the spherical equilibrium, first by a slow redistribution of the smectic layers, and finally by weak, damped shape oscillations. In addition, we describe the rupture of freely floating smectic bubbles, and the formation and stability of smectic filaments.

  20. 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.

  1. The effect of decreased atmospheric sulphur deposition on soil dissolved organic carbon concentration and quality

    NASA Astrophysics Data System (ADS)

    Ekström, Sara; Kritzberg, Emma; Berggren, Dan; Graneli, Wilhelm; Bergkvist, Bo

    2010-05-01

    Increasing concentrations of dissolved organic carbon (DOC) has been observed in aquatic systems throughout the Northern Hemisphere the last decades. The reduction in sulphur deposition has been identified as one of the major mechanisms behind this trend, where several reports show correlations between DOC and sulphur concentrations in surface waters. The reasoning is that as sulphur deposition decreases, pH in soil increase and ionic strength decrease thereby making DOC more soluble and mobile. With a more mobile DOC, the transport of DOC from the terrestrial to the aquatic system will increase. However, most of these conclusions are based solely on monitoring data that generally only include the period of decreasing sulphur deposition, and little experimental evidence exist. In this study we wanted to test the effect of sulphur deposition on the concentration and quality of the DOC in soil water. This was done in a field experiment with artificial precipitation of 12 50*50 cm plots in a boreal-nemoral forest. There was one low and one high sulphate treatment and the soil water was collected every second week using zero-tension lysimeters placed just below the O-horizon and analyzed for both quantitative and qualitative DOC variables. The experiment lasted 2 years. After about one year the low acid treatment had significantly higher absorbance at a wavelength of 420 nm, while DOC concentration did not differ between the low and the high acid treatment. Rather than the expected increase in DOC concentration in the low acid treatment, a change in DOC quality was observed as characterized by absorbance, fluorescence and high performance size exclusion chromatography. DOC in the low acid treatment tended to be more aromatic and of greater molecular weight. A change in DOC quality will affect the fate of the DOC as it moves through the terrestrial and into the aquatic system. The susceptibility of DOC to photooxidation, biodegradation and flocculation may be greatly

  2. Dissolved Organic Matter Characteristics Control Filtered Total Mercury Concentrations in an Adirondack River Basin

    NASA Astrophysics Data System (ADS)

    Burns, D. A.; Aiken, G.; Bradley, P. M.; Journey, C.

    2011-12-01

    Dissolved organic carbon (DOC) plays important roles in the transport and biogeochemical processes that affect mercury (Hg) cycling in the environment. Previous investigations have shown strong correlations between DOC and Hg concentrations in surface waters. Commonly, other DOC-related measures such as ultraviolet absorbance (UV254), and hydrophobic acid content (HPOA) show even stronger positive correlations with Hg in waters indicating the importance of the more aromatic fraction of DOC in Hg cycling. Finally, in-situ optical sensor-derived DOC concentrations have proven useful as inexpensive proxies for estimating Hg concentrations in some surface waters. Here, we describe results from the 493 km2 Upper Hudson River basin in the Adirondack Mountains of New York in which stream water samples were collected for filtered total Hg (FTHg) concentrations, DOC concentrations, UV254, HPOA, and specific ultraviolet absorbance (SUVA, derived from the absorbance and DOC measurements) at two temporal and spatial scales during 2006-09: (1) biweekly to monthly in a 66 km2 basin, and (2) seasonally at 27 synoptic sites distributed across the larger Upper Hudson basin. These results indicate that SUVA values are more strongly correlated with FTHg concentrations than are those of DOC concentrations, especially during summer. The presence of numerous open water bodies in this basin appears to greatly affect DOC and FTHg concentrations and SUVA values as reflected by data collected upstream and downstream of ponds and lakes. Multivariate regression models developed to examine the landscape factors that control spatial variation in SUVA values among synoptic sites indicate that open water area is inversely correlated with these values, reflecting autochthonous carbon sources in lakes/ponds that are more aliphatic in character than that found in streams. In contrast, metrics such as percent riparian area that reflect the influence of soils with high organic carbon content are

  3. Salicylhydroxamic acid (SHAM) inhibition of the dissolved inorganic carbon concentrating process in unicellular green algae

    SciTech Connect

    Goyal, A.; Tolbert, N.E. )

    1990-03-01

    Rates of photosynthetic O{sub 2} evolution, for measuring K{sub 0.5}(CO{sub 2} + HCO{sub 3}{sup {minus}}) at pH 7, upon addition of 50 micromolar HCO{sub 3}{sup {minus}} to air-adapted Chlamydomonas, Dunaliella, or Scenedesmus cells, were inhibited up to 90% by the addition of 1.5 to 4.0 millimolar salicylhydroxamic acid (SHAM) to the aqueous medium. The apparent K{sub i}(SHAM) for Chlamydomonas cells was about 2.5 millimolar, but due to low solubility in water effective concentrations would be lower. Salicylhydroxamic acid did not inhibit oxygen evolution or accumulation of bicarbonate by Scenedesmus cells between pH 8 to 11 or by isolated intact chloroplasts from Dunaliella. Thus, salicylhydroxamic acid appears to inhibit CO{sub 2} uptake, whereas previous results indicate that vanadate inhibits bicarbonate uptake. These conclusions were confirmed by three test procedures with three air-adapted algae at pH 7. Salicylhydroxamic acid inhibited the cellular accumulation of dissolved inorganic carbon, the rate of photosynthetic O{sub 2} evolution dependent on low levels of dissolved inorganic carbon (50 micromolar NaHCO{sub 3}), and the rate of {sup 14}CO{sub 2} fixation with 100 micromolar ({sup 14}C)HCO{sub 3}{sup {minus}}. Salicylhydroxamic acid inhibition of O{sub 2} evolution and {sup 14}CO{sub 2}-fixation was reversed by higher levels of NaHCO{sub 3}. Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO{sub 2} accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

  4. Salicylhydroxamic Acid (SHAM) Inhibition of the Dissolved Inorganic Carbon Concentrating Process in Unicellular Green Algae.

    PubMed

    Goyal, A; Tolbert, N E

    1990-03-01

    Rates of photosynthetic O(2) evolution, for measuring K(0.5)(CO(2) + HCO(3) (-)) at pH 7, upon addition of 50 micromolar HCO(3) (-) to air-adapted Chlamydomonas, Dunaliella, or Scenedesmus cells, were inhibited up to 90% by the addition of 1.5 to 4.0 millimolar salicylhydroxamic acid (SHAM) to the aqueous medium. The apparent K(1)(SHAM) for Chlamydomonas cells was about 2.5 millimolar, but due to low solubility in water effective concentrations would be lower. Salicylhydroxamic acid did not inhibit oxygen evolution or accumulation of bicarbonate by Scenedesmus cells between pH 8 to 11 or by isolated intact chloroplasts from Dunaliella. Thus, salicylhydroxamic acid appears to inhibit CO(2) uptake, whereas previous results indicate that vanadate inhibits bicarbonate uptake. These conclusions were confirmed by three test procedures with three air-adapted algae at pH 7. Salicylhydroxamic acid inhibited the cellular accumulation of dissolved inorganic carbon, the rate of photosynthetic O(2) evolution dependent on low levels of dissolved inorganic carbon (50 micromolar Na-HCO(3)), and the rate of (14)CO(2) fixation with 100 micromolar [(14)C] HCO(3) (-). Salicylhydroxamic acid inhibition of O(2) evolution and (14)CO(2)-fixation was reversed by higher levels of NaHCO(3). Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO(2) accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

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

    PubMed

    Meliker, Jaymie R; Slotnick, Melissa J; Avruskin, Gillian A; Haack, Sheridan K; Nriagu, Jerome O

    2009-02-01

    Arsenic concentrations exceeding 10 microg/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.

  6. 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.

  7. Concentration, sources and flux of dissolved organic carbon of precipitation at Lhasa city, the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Li, C.

    2015-12-01

    Dissolved organic carbon (DOC) plays important role in climate system, but few data are available on the Tibetan Plateau (TP). In this study 89 precipitation samples were collected at Lhasa, the largest city of southern Tibet, from March to December 2013. The average concentration and wet deposition fluxes of DOC was 1.10 mg C/L and 0.62 g C m-2.yr-1, respectively. Seasonally, low DOC concentration and high flux appeared during monsoon period, which were in line with heavy precipitation amount, reflecting dilution effect of precipitation for the DOC. Compared to other regions, the values of Lhasa were lower than those of large cites (e.g. Beijing and Seoul) mainly because of less air pollution of Lhasa. The relationship between DOC and ion analysis showed that DOC of Lhasa was derived mainly from the natural sources, followed by burning activities. Furthermore, △14C value of DOC indicated that fossil combustion contributed around 20% of the precipitation DOC of Lhasa, indicating that the atmosphere of Lhasa has been influenced by vehicle emissions. Therefore, although atmosphere of Lhasa is relatively clean, pollutants emitted from local sources cannot be ignored.

  8. In vivo noninvasive monitoring of dissolved oxygen concentration within an implanted tissue-engineered pancreatic construct.

    PubMed

    Goh, Fernie; Sambanis, Athanassios

    2011-09-01

    The function of an implanted tissue-engineered pancreatic construct is influenced by many in vivo factors; however, assessing its function is based primarily on end physiologic effects. As oxygen significantly affects cell function, we established a dual perfluorocarbon method that utilizes (19)F nuclear magnetic resonance spectroscopy, with perfluorocarbons as oxygen concentration markers, to noninvasively monitor dissolved oxygen concentration (DO) in βTC-tet cell-containing alginate beads and at the implantation milieu. Beads were implanted in the peritoneal cavity of normal and streptozotocin-induced diabetic mice. Using this method, the feasibility of acquiring real-time in vivo DO measurements was demonstrated. Results showed that the mouse peritoneal environment is hypoxic and the DO is further reduced when βTC-tet cell constructs were implanted. The DO within cell-containing beads decreased considerably over time and could be correlated with the relative changes in the number of viable encapsulated cells. The reduction of construct DO due to the metabolic activity of the βTC-tet cells was also compatible with the implant therapeutic function, as observed in the reversal of hyperglycemia in diabetic mice. The importance of these findings in assessing implant functionality and host animal physiology is discussed.

  9. Dissolved oxygen concentration in the medium during cell culture: Defects and improvements.

    PubMed

    Zhang, Kuan; Zhao, Tong; Huang, Xin; He, Yunlin; Zhou, Yanzhao; Wu, Liying; Wu, Kuiwu; Fan, Ming; Zhu, Lingling

    2016-03-01

    In vitro cell culture has provided a useful model to study the effects of oxygen on cellular behavior. However, it remains unknown whether the in vitro operations themselves affect the medium oxygen levels and the living states of cells. In addition, a prevailing controversy is whether reactive oxygen species (ROS) production is induced by continuous hypoxia or reoxygenation. In this study, we have measured the effects of different types of cell culture containers and the oxygen environment where medium replacement takes place on the actual oxygen tension in the medium. We found that the deviations of oxygen concentrations in the medium are much greater in 25-cm(2) flasks than in 24-well plates and 35-mm dishes. The dissolved oxygen concentrations in the medium were increased after medium replacement in normoxia, but remained unchanged in glove boxes in which the oxygen tension remained at a low level (11.4, 5.7, and 0.5% O2 ). We also found that medium replacement in normoxia increased the number of ROS-positive cells and reduced the cell viability; meanwhile, medium replacement in a glove box did not produce the above effects. Therefore, we conclude that the use of 25-cm(2) flasks should be avoided and demonstrate that continuous hypoxia does not produce ROS, whereas the reoxygenation that occurs during the harvesting of cells leads to ROS and induces cell death.

  10. 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.

  11. 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

  12. Dissolved methane concentration profiles and air-sea fluxes from 41°S to 27°N

    NASA Astrophysics Data System (ADS)

    Kelley, Cheryl A.; Jeffrey, Wade H.

    2002-07-01

    Water column samples from a transect cruise from southern Chile through the Panama Canal to the Gulf of Mexico were used to determine dissolved methane depth profiles and air-sea methane fluxes. In the Gulf of Mexico, surface concentrations were approximately 40% supersaturated with respect to the atmosphere, whereas near the equator and in the Peru upwelling region, 10-20% supersaturation generally occurred. These saturation ratios translate into an average flux of methane from the sea surface to the atmosphere of 0.38 μmol m-2 d-1. In addition, water column profiles of dissolved methane indicate that subsurface maxima in dissolved methane concentrations are a consistent feature of the open ocean, except near the equator. At the equator, the subsurface peak at the base of the mixed layer may be bowed down by the Equatorial Undercurrent. The highest methane concentration (12 nM) was observed in the Peru upwelling region.

  13. Elevated concentrations of dissolved Ba, Fe and Mn in a mangrove subterranean estuary: Consequence of sea level rise?

    NASA Astrophysics Data System (ADS)

    Sanders, Christian J.; Santos, Isaac R.; Barcellos, Renato; Silva Filho, Emmanoel V.

    2012-07-01

    Groundwater underlying a mangrove habitat was studied to determine the geochemical nature of Ba, Fe and Mn as related to dissolved organic carbon (DOC), SO4 and salinity (Sepetiba Bay, Brazil). Wells were placed across geobotanic facies and sampled monthly for a year. We observed non-conservative behavior and elevated concentrations of dissolved metals relative to local end-members (i.e., fresh river water and seawater). Average Ba concentrations were near 2000 nM in an area with low salinity (˜5.3). Dissolved Fe (up to 654 μM) was two orders of magnitude greater in fresh groundwater than in the seaward sampling stations. Manganese concentrations were greatest (112 μM) in the high salinity (˜65) zone, being directly influenced by salinity. Groundwater Ba, Fe and Mn showed differing site specific concentrations, likely related to ion exchange processes and redox-controlled cycling along distinct mangrove facies. The results of this work show that metal concentrations are altered relative to conservative mixing between terrestrial and marine endmembers, illustrating the importance of mangrove subterranean estuaries as biogeochemical reactors. Roughly-estimated submarine groundwater discharge-derived dissolved Ba, Fe and Mn fluxes were at least one order of magnitude greater than river-derived fluxes into Sepetiba Bay.

  14. The episodic acidification of a stream with elevated concentrations of dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Wellington, Brian I.; Driscoll, Charles T.

    2004-10-01

    Organic acids are generally thought to play a minor role in the episodic acidification of streams in the USA. In this study, we investigated the episodic acidification of a stream at the Hubbard Brook Experimental Forest in New Hampshire with high concentrations of dissolved organic carbon and naturally occurring organic acids. We studied three events in 2001: spring snowmelt, which occurred from 6 April to 14 May and resulted in two distinct melt events; and two rain events, one on 17 June and the other on 17 July. During snowmelt events organic acids were a minor contributor to the short-term acidification of stream water, with increases in NO3- and dilution of base cations being the dominant mechanisms. During summer rainfall events, however, increases in inputs of organic acids were the dominant mechanism of episodic acidification when soil water was the dominant contributor to stream discharge (59 to 66% of peak stream discharge). We also found that precipitation events occurring after relatively wet antecedent conditions (17 July event) resulted in more severe acid episodes than events that followed drier antecedent conditions (17 June event). The minimum acid neutralizing capacity (ANC) was only -19 μeq l-1 for the 17 June event, whereas the minimum ANC for the 17 July event was much lower (-62 μeq l-1) although the total rainfall amount was similar for the two events.

  15. Concentrations and radiocarbon signatures of dissolved organic matter in the Pacific Ocean

    SciTech Connect

    Druffel, E.R.M. ); Williams, P.M. ); Suzuki, Yoshimi )

    1989-09-01

    The authors present evidence suggesting that only a portion of the dissolved organic carbon (DOC) in the seawater analyzed previously by Williams and Druffel (1987) was oxidized by the UV-radiation method. High temperature catalytic (HTC) methods (Sugimura and Suzuki, 1988) used to reoxidize the central North Pacific gyre water samples reveal that the total DOC (DOC{sub HTC}) is about twice that of the UV-oxidizable DOC (DOC{sub UV}). Indications from the original study suggest that this additional DOC contains higher concentrations of radiocarbon than in the DOC{sub UV} (Williams and Druffel, 1987). This evidence implies that DOC is older and thus more refractory with respect to biological utilization, yet is more chemically reactive with respect to photooxidation, than the fraction resistant to UV (DOC{sub res}). The authors report accelerator mass spectrometry (AMS) {Delta}{sup 14}C measurements of humic, fulvic and hydrophilic acid fractions isolated from water collected at 180 m in the North Pacific (19{degree}N, 158{degree}W) using XAD macroreticular resins. {Delta}{sup 14} values of the humic material are less than those of DOC{sub UV} from a similar depth 1,200 km further north (Williams and Druffel, 1987) indicating that these humic substances are part of the old recycled DOC{sub UV} in the ocean.

  16. Direct measurement of local dissolved oxygen concentration spatial profiles in a cell culture environment.

    PubMed

    Kagawa, Yuki; Matsuura, Katsuhisa; Shimizu, Tatsuya; Tsuneda, Satoshi

    2015-06-01

    Controlling local dissolved oxygen concentration (DO) in media is critical for cell or tissue cultures. Various biomaterials and culture methods have been developed to modulate DO. Direct measurement of local DO in cultures has not been validated as a method to test DO modulation. In the present study we developed a DO measurement system equipped with a Clark-type oxygen microelectrode manipulated with 1 μm precision in three-dimensional space to explore potential applications for tissue engineering. By determining the microelectrode tip position precisely against the bottom plane of culture dishes with rat or human cardiac cells in static monolayer culture, we successfully obtained spatial distributions of DO in the medium. Theoretical quantitative predictions fit the obtained data well. Based on analyses of the variance between samples, we found the data reflected "local" oxygen consumption in the vicinity of the microelectrode and the detection of temporal changes in oxygen consumption rates of cultured cells was limited by the diffusion rate of oxygen in the medium. This oxygen measuring system monitors local oxygen consumption and production with high spatial resolution, and can potentially be used with recently developed oxygen modulating biomaterials to design microenvironments and non-invasively monitor local DO dynamics during culture.

  17. Hydrologically Driven Dynamics of Dissolved Organic Carbon Concentration and Composition in a Headwater Stream Ecosystem

    NASA Astrophysics Data System (ADS)

    Kaplan, L. A.; McLaughlin, C.; Hogan, K. R.; Newbold, J. D.

    2011-12-01

    A 34-year record of dissolved organic carbon (DOC) concentrations and compositions was used to assess the role of hydrologic variability in the carbon cycle of a headwater stream. The DOC concentration record is characterized by sharply increasing values during storms and annual minima associated with soil freezing in winter (Fig. 1). Baseflow discharge accounts for approximately 67% of the total runoff in this 3rd-order stream in the Pennsylvania Piedmont but storm flows transport approximately 75% of the DOC flux. The annual DOC flux varies as much as 3-fold and this variability is driven by unusual events such as major storms and prolonged droughts. During storms DOC quality changes as water moves to the stream through organic matter-rich upper soil horizons, by passing terrestrial controls on DOC content. The pool of biodegradable DOC (BDOC) as a percentage of total DOC increases from 33% to 73% with the most labile BDOC class increasing 4-fold while the semi-labile BDOC pool increases 2-fold. Storms also alter the structure and productivity of benthic bacterial communities that metabolize DOC in streams, though the impacts are tempered by stability of streambed substrata. For example, a February storm reduced the biomass and productivity of bacteria attached to sediments by 48% and 90%, respectively, while reducing the biomass of bacteria attached to rocks by 21% but increasing bacterial productivity by 22%. Molecular fingerprints of community compositions revealed a stable "climax community" whose alteration is influenced by the magnitude of the storm flows and eventually returns to its original composition. Actual measurements of carbon cycling based on whole-stream releases and sampling the stream bed microbial community are not feasible during storms, but we argue that for headwater streams it is the post-disturbance condition rather than any processing which occurs during storm flows that shapes the magnitude and dynamics of carbon cycling.

  18. The soil organic carbon content of anthropogenically altered organic soils effects the dissolved organic matter quality, but not the dissolved organic carbon concentrations

    NASA Astrophysics Data System (ADS)

    Frank, Stefan; Tiemeyer, Bärbel; Bechtold, Michel; Lücke, Andreas; Bol, Roland

    2016-04-01

    Dissolved organic carbon (DOC) is an important link between terrestrial and aquatic ecosystems. This is especially true for peatlands which usually show high concentrations of DOC due to the high stocks of soil organic carbon (SOC). Most previous studies found that DOC concentrations in the soil solution depend on the SOC content. Thus, one would expect low DOC concentrations in peatlands which have anthropogenically been altered by mixing with sand. Here, we want to show the effect of SOC and groundwater level on the quantity and quality of the dissolved organic matter (DOM). Three sampling sites were installed in a strongly disturbed bog. Two sites differ in SOC (Site A: 48%, Site B: 9%) but show the same mean annual groundwater level of 15 and 18 cm below ground, respectively. The SOC content of site C (11%) is similar to Site B, but the groundwater level is much lower (-31 cm) than at the other two sites. All sites have a similar depth of the organic horizon (30 cm) and the same land-use (low-intensity sheep grazing). Over two years, the soil solution was sampled bi-weekly in three depths (15, 30 and 60 cm) and three replicates. All samples were analyzed for DOC and selected samples for dissolved organic nitrogen (DON) and delta-13C and delta-15N. Despite differences in SOC and groundwater level, DOC concentrations did not differ significantly (A: 192 ± 62 mg/L, B: 163 ± 55 mg/L and C: 191 ± 97 mg/L). At all sites, DOC concentrations exceed typical values for peatlands by far and emphasize the relevance even of strongly disturbed organic soils for DOC losses. Individual DOC concentrations were controlled by the temperature and the groundwater level over the preceding weeks. Differences in DOM quality were clearer. At site B with a low SOC content, the DOC:DON ratio of the soil solution equals the soil's C:N ratio, but the DOC:DON ratio is much higher than the C:N ratio at site A. In all cases, the DOC:DON ratio strongly correlates with delta-13C. There is no

  19. Trends in soil solution dissolved organic carbon (DOC) concentrations across European forests

    NASA Astrophysics Data System (ADS)

    Camino-Serrano, Marta; Graf Pannatier, Elisabeth; Vicca, Sara; Luyssaert, Sebastiaan; Jonard, Mathieu; Ciais, Philippe; Guenet, Bertrand; Gielen, Bert; Peñuelas, Josep; Sardans, Jordi; Waldner, Peter; Etzold, Sophia; Cecchini, Guia; Clarke, Nicholas; Galić, Zoran; Gandois, Laure; Hansen, Karin; Johnson, Jim; Klinck, Uwe; Lachmanová, Zora; Lindroos, Antti-Jussi; Meesenburg, Henning; Nieminen, Tiina M.; Sanders, Tanja G. M.; Sawicka, Kasia; Seidling, Walter; Thimonier, Anne; Vanguelova, Elena; Verstraeten, Arne; Vesterdal, Lars; Janssens, Ivan A.

    2016-10-01

    Dissolved organic carbon (DOC) in surface waters is connected to DOC in soil solution through hydrological pathways. Therefore, it is expected that long-term dynamics of DOC in surface waters reflect DOC trends in soil solution. However, a multitude of site studies have failed so far to establish consistent trends in soil solution DOC, whereas increasing concentrations in European surface waters over the past decades appear to be the norm, possibly as a result of recovery from acidification. The objectives of this study were therefore to understand the long-term trends of soil solution DOC from a large number of European forests (ICP Forests Level II plots) and determine their main physico-chemical and biological controls. We applied trend analysis at two levels: (1) to the entire European dataset and (2) to the individual time series and related trends with plot characteristics, i.e., soil and vegetation properties, soil solution chemistry and atmospheric deposition loads. Analyses of the entire dataset showed an overall increasing trend in DOC concentrations in the organic layers, but, at individual plots and depths, there was no clear overall trend in soil solution DOC. The rate change in soil solution DOC ranged between -16.8 and +23 % yr-1 (median = +0.4 % yr-1) across Europe. The non-significant trends (40 %) outnumbered the increasing (35 %) and decreasing trends (25 %) across the 97 ICP Forests Level II sites. By means of multivariate statistics, we found increasing trends in DOC concentrations with increasing mean nitrate (NO3-) deposition and increasing trends in DOC concentrations with decreasing mean sulfate (SO42-) deposition, with the magnitude of these relationships depending on plot deposition history. While the attribution of increasing trends in DOC to the reduction of SO42- deposition could be confirmed in low to medium N deposition areas, in agreement with observations in surface waters, this was not the case in high N deposition areas. In

  20. 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.

  1. Periodical bubble formation and the oscillatory change in dissolved oxygen concentration in a catalase-hydrogen peroxide system.

    PubMed

    Sasaki, Satoshi

    2006-06-01

    The relationship between the periodical bubble forming and the oscillatory change in the dissolved oxygen (DO) concentration in a catalase-hydrogen peroxide system was studied. Photographs of the bubbles and the responses from the DO electrode indicated that large bubbles were generated periodically, and that the DO profile depended on the geometrical relationship between the electrode and the bubbles. PMID:16772694

  2. Use of dissolved H2 concentrations to determine distribution of microbially catalyzed redox reactions in anoxic groundwater

    USGS Publications Warehouse

    Lovley, D.R.; Chapelle, F.H.; Woodward, J.C.

    1994-01-01

    The potential for using concentrations of dissolved H2 to determine the distribution of redox processes in anoxic groundwaters was evaluated. In pristine aquifers in which standard geochemical measurements indicated that Fe-(III) reduction, sulfate reduction, or methanogenesis was the terminal electron accepting process (TEAP), the H2 concentrations were similar to the H2 concentrations that have previously been reported for aquatic sediments with the same TEAPs. In two aquifers contaminated with petroleum products, it was impossible with standard geochemical analyses to determine which TEAPs predominated in specific locations. However, the TEAPs predicted from measurements of dissolved H2 were the same as those determined directly through measurements of microbial processes in incubated aquifer material. These results suggest that H2 concentrations may be a useful tool for analyzing the redox chemistry of nonequilibrium groundwaters.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    Tillman, Fred D.; Anning, David W.

    2014-11-01

    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.

  5. 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

  6. Closed-loop identification and control application for dissolved oxygen concentration in a full-scale coke wastewater treatment plant.

    PubMed

    Yoo, C K; Cho, J H; Kwak, H J; Choi, S K; Chun, H D; Lee, I

    2001-01-01

    The objective of this paper is to apply a closed-loop identification to actual dissolved oxygen control system in the coke wastewater treatment plant. It approximates the dissolved oxygen dynamics to a high order model using the integral transform method and reduces it to the first-order plus time delay (FOPTD) or second-order plus time delay (SOPTD) for the PID controller tuning. To experiment the process identification on the real plant, a simple set-point change of the speed of surface aerator under the closed-loop control without any mode change was used as an activation signal of the identification. The full-scale experimental results show a good identification performance and a good tracking ability for set-point change. As a result of improved control performance, the fluctuation of dissolved oxygen concentration variation has been decreased and the electric power saving has been accomplished.

  7. Closed-loop identification and control application for dissolved oxygen concentration in a full-scale coke wastewater treatment plant.

    PubMed

    Yoo, C K; Cho, J H; Kwak, H J; Choi, S K; Chun, H D; Lee, I

    2001-01-01

    The objective of this paper is to apply a closed-loop identification to actual dissolved oxygen control system in the coke wastewater treatment plant. It approximates the dissolved oxygen dynamics to a high order model using the integral transform method and reduces it to the first-order plus time delay (FOPTD) or second-order plus time delay (SOPTD) for the PID controller tuning. To experiment the process identification on the real plant, a simple set-point change of the speed of surface aerator under the closed-loop control without any mode change was used as an activation signal of the identification. The full-scale experimental results show a good identification performance and a good tracking ability for set-point change. As a result of improved control performance, the fluctuation of dissolved oxygen concentration variation has been decreased and the electric power saving has been accomplished. PMID:11385849

  8. Dissolved Pesticide and Organic Carbon Concentrations Detected in Surface Waters, Northern Central Valley, California, 2001-2002

    USGS Publications Warehouse

    Orlando, James L.; Jacobson, Lisa A.; Kuivila, Kathryn M.

    2004-01-01

    Field and laboratory studies were conducted to determine the effects of pesticide mixtures on Chinook salmon under various environmental conditions in surface waters of the northern Central Valley of California. This project was a collaborative effort between the U.S. Geological Survey (USGS) and the University of California. The project focused on understanding the environmental factors that influence the toxicity of pesticides to juvenile salmon and their prey. During the periods January through March 2001 and January through May 2002, water samples were collected at eight surface water sites in the northern Central Valley of California and analyzed by the USGS for dissolved pesticide and dissolved organic carbon concentrations. Water samples were also collected by the USGS at the same sites for aquatic toxicity testing by the Aquatic Toxicity Laboratory at the University of California Davis; however, presentation of the results of these toxicity tests is beyond the scope of this report. Samples were collected to characterize dissolved pesticide and dissolved organic carbon concentrations, and aquatic toxicity, associated with winter storm runoff concurrent with winter run Chinook salmon out-migration. Sites were selected that represented the primary habitat of juvenile Chinook salmon and included major tributaries within the Sacramento and San Joaquin River Basins and the Sacramento?San Joaquin Delta. Water samples were collected daily for a period of seven days during two winter storm events in each year. Additional samples were collected weekly during January through April or May in both years. Concentrations of 31 currently used pesticides were measured in filtered water samples using solid-phase extraction and gas chromatography-mass spectrometry at the U.S. Geological Survey's organic chemistry laboratory in Sacramento, California. Dissolved organic carbon concentrations were analyzed in filtered water samples using a Shimadzu TOC-5000A total organic carbon

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

    USGS Publications Warehouse

    Cravotta, C.A.

    2008-01-01

    Water-quality data for discharges from 140 abandoned mines in the Anthracite and Bituminous Coalfields of Pennsylvania reveal complex relations among the pH and dissolved solute concentrations that can be explained with geochemical equilibrium models. Observed values of pH ranged from 2.7 to 7.3 in the coal-mine discharges (CMD). Generally, flow rates were smaller and solute concentrations were greater for low-pH CMD samples; pH typically increased with flow rate. Although the frequency distribution of pH was similar for the anthracite and bituminous discharges, the bituminous discharges had smaller median flow rates; greater concentrations of SO4, Fe, Al, As, Cd, Cu, Ni and Sr; comparable concentrations of Mn, Cd, Zn and Se; and smaller concentrations of Ba and Pb than anthracite discharges with the same pH values. The observed relations between the pH and constituent concentrations can be attributed to (1) dilution of acidic water by near-neutral or alkaline ground water; (2) solubility control of Al, Fe, Mn, Ba and Sr by hydroxide, sulfate, and/or carbonate minerals; and (3) aqueous SO4-complexation and surface-complexation (adsorption) reactions. The formation of AlSO4+ and AlHSO42 + complexes adds to the total dissolved Al concentration at equilibrium with Al(OH)3 and/or Al hydroxysulfate phases and can account for 10-20 times greater concentrations of dissolved Al in SO4-laden bituminous discharges compared to anthracite discharges at pH of 5. Sulfate complexation can also account for 10-30 times greater concentrations of dissolved FeIII concentrations at equilibrium with Fe(OH)3 and/or schwertmannite (Fe8O8(OH)4.5(SO4)1.75) at pH of 3-5. In contrast, lower Ba concentrations in bituminous discharges indicate that elevated SO4 concentrations in these CMD sources could limit Ba concentrations by the precipitation of barite (BaSO4). Coprecipitation of Sr with barite could limit concentrations of this element. However, concentrations of dissolved Pb, Cu, Cd, Zn

  10. Diatom stratigraphy and long-term dissolved silica concentrations in the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Olli, Kalle; Clarke, Annemarie; Danielsson, Åsa; Aigars, Juris; Conley, Daniel J.; Tamminen, Timo

    2008-10-01

    In many parts of the world coastal waters with anthropogenic eutrophication have experienced a gradual depletion of dissolved silica (DSi) stocks. This could put pressure on spring bloom diatom populations, e.g. by limiting the intensity of blooms or by causing shifts in species composition. In addition, eutrophication driven enhanced diatom growth is responsible for the redistribution of DSi from the water phase to the sediments, and changes in the growth conditions may be reflected in the sediment diatom stratigraphy. To test for changes in diatom communities we have analyzed four sediment cores from the Baltic Sea covering approximately the last 100 years. The sediment cores originate from the western Gulf of Finland, the Kattegat, the Baltic Proper and the Gulf of Riga. Three out of the four cores reveal only minor changes in composition of diatom assemblages, while the Gulf of Riga core contains major changes, occurring after the second World War. This area is set apart from the other Baltic Sea basins by a high frequency of low after spring bloom DSi concentrations (< 2 µmol L - 1 ) during a relatively well defined time period from 1991-1998. In 1991 to 1993 a rapid decline of DSi spring concentrations and winter stocks (down to 5 µmol L - 1 ) in the Gulf was preceded by exceptionally intense diatom spring blooms dominated by the heavily silicified species Thalassiosira baltica (1991-1992; up to 5.5 mg ww L - 1 ). T. baltica has been the principal spring bloom diatom in the Gulf of Riga since records began in 1975. DSi consumption and biomass yield experiments with cultured T. baltica suggest that intense blooms can potentially exhaust the DSi stock of the water column and exceed the annual Si dissolution in the Gulf of Riga. The phytoplankton time series reveals another exceptional T. baltica bloom period in 1981-1983 (up to 8 mg L - 1 ), which, however, took place before the regular DSi measurements. These periods may be reflected in the conspicuous

  11. 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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Our knowledge of dynamic natural habitats could be improved through the deployment of automated sensor technology. Dissolved organic carbon concentrations, [DOC], are of interest to water companies as purification removes this pool and currently in environmental science, due in part to rising DOC levels and also as respiration of this C pool can lead to an increased CO2 efflux. Manual sampling of catchment drainage systems has revealed seasonal patterns in DOC (Williams, P.J.L., 1995) and that hydrological events export most DOC(Raymond, P.A. and J.E. Saiers, 2010). However, manual sampling precludes detailed characterisation of the dynamic fluctuation of DOC over shorter but important time periods e.g. immediately prior to an event; the transition from base flow to a surface run-off dominated system as surface flow pathways defrost. Such insight is only gained through deployment of continuous-monitoring equipment. Since autumn 2010 we have deployed an S::CAN Spectrolyser (which from absorbance gives a measurement of [DOC]) in a 7.5 kilometre squared peaty catchment draining Europe's largest windfarm, Whitelee. Since autumn 2011, we have an almost complete time series of [DOC] every 30. Here [DOC] has ranged from 12.2 to 58.4 mg/l C and during event flow DOC had a maximum variation of 23.5 mg/l within a single day. Simultaneously with the Spectrolyser, we have logged stage height, pH and conductivity using an In-Situ Inc MD Troll 9000. Generally there is an inverse relationship between [DOC] and both pH and conductivity, but a positive relationship (albeit with seasonal differences) with [DOC] and stage height, from which we can infer hydrological changes in the source of the DOC. Here, in addition to presenting the time series of the data, and a more accurate export budget estimate, I will explore statistical methods for the handling of large datasets. Trends in the data of such large and dynamic data sets are challenging to model. Simple relationships with stage

  13. Concentration and characteristics of dissolved carbon in the Sanjiang Plain influenced by long-term land reclamation from marsh.

    PubMed

    Guo, Y D; Lu, Y Z; Song, Y Y; Wan, Z M; Hou, A X

    2014-01-01

    Since the 1960s, the marshes in the Sanjiang Plain, Northeast China, which are an important reservoir for dissolved carbon, have undergone long-term reclamation to farmland, resulting in elevated marsh loss and degradation on a large scale. This study compared the concentrations of dissolved carbon, as well as the chemical characteristics of dissolved organic carbon (DOC), in natural marshes, a degraded marsh, and drainage ditches sampled during the growing seasons between 2008 and 2010 to clarify the temporal-spatial variability of the dissolved carbon in the fluvial system influenced by the long-term reclamation. The results show that the average concentrations of total dissolved carbon (TDC) and DOC are considerably greater in the natural marshes than in the degraded marsh and drainage ditches. The average DOC concentration for the natural marshes, approximately 35.53 ± 5.15 mg L(-1), is approximately 2.39 times that in the degraded marsh (14.84 ± 4.21 mg L(-1)) and 2.77 times the average value in the ditches (12.84 ± 4.49 mg L(-1)). The dissolved inorganic carbon (DIC) exhibits increased trends in the drainage ditches compared with the natural marshes, whereas the hydrophobic fraction of DOC is present at lower concentrations in the degraded marsh and ditches. Fluorescence indices also indicate that the DOC in the degraded marsh and ditches has a simpler humification structure. In total, the long-term reclamation has led to great variability in the DOC concentration and chemical characteristics in the fluvial system. Changes in the DOC production potential and hydrological regimes due to sustained reclamation are deemed the predominant causes of this effect. The continuously decreased DOC concentration and high variability of DOC in the surface fluvial systems are inevitable if reclamation continues in the Sanjiang Plain. More importantly, the presence of tyrosine and tryptophan-like substances in the ditches indicates that there has been extensive

  14. Concentration and characteristics of dissolved carbon in the Sanjiang Plain influenced by long-term land reclamation from marsh.

    PubMed

    Guo, Y D; Lu, Y Z; Song, Y Y; Wan, Z M; Hou, A X

    2014-01-01

    Since the 1960s, the marshes in the Sanjiang Plain, Northeast China, which are an important reservoir for dissolved carbon, have undergone long-term reclamation to farmland, resulting in elevated marsh loss and degradation on a large scale. This study compared the concentrations of dissolved carbon, as well as the chemical characteristics of dissolved organic carbon (DOC), in natural marshes, a degraded marsh, and drainage ditches sampled during the growing seasons between 2008 and 2010 to clarify the temporal-spatial variability of the dissolved carbon in the fluvial system influenced by the long-term reclamation. The results show that the average concentrations of total dissolved carbon (TDC) and DOC are considerably greater in the natural marshes than in the degraded marsh and drainage ditches. The average DOC concentration for the natural marshes, approximately 35.53 ± 5.15 mg L(-1), is approximately 2.39 times that in the degraded marsh (14.84 ± 4.21 mg L(-1)) and 2.77 times the average value in the ditches (12.84 ± 4.49 mg L(-1)). The dissolved inorganic carbon (DIC) exhibits increased trends in the drainage ditches compared with the natural marshes, whereas the hydrophobic fraction of DOC is present at lower concentrations in the degraded marsh and ditches. Fluorescence indices also indicate that the DOC in the degraded marsh and ditches has a simpler humification structure. In total, the long-term reclamation has led to great variability in the DOC concentration and chemical characteristics in the fluvial system. Changes in the DOC production potential and hydrological regimes due to sustained reclamation are deemed the predominant causes of this effect. The continuously decreased DOC concentration and high variability of DOC in the surface fluvial systems are inevitable if reclamation continues in the Sanjiang Plain. More importantly, the presence of tyrosine and tryptophan-like substances in the ditches indicates that there has been extensive

  15. 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

    Results from the trend analysis and from the SPARROW model indicate that, compared to monitoring stations with no trends or decreasing trends, stations with increasing trends are associated with a smaller percentage of the predicted dissolved-solids load originating from geologic sources, and a larger percentage originating from urban lands and road deicers. Conversely, compared to stations with increasing trends or no trends, stations with decreasing trends have a larger percentage of the predicted dissolved-solids load originating from geologic sources and a smaller percentage originating from urban lands and road deicers. Stations with decreasing trends also have larger percentages of predicted dissolved-solids load originating from cultivated lands and pasture lands, compared to stations with increasing trends or no trends.

  16. 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.

  17. Concentrations of dissolved methane (CH sub 4 ) and nitrogen (N sub 2 ) in groundwaters from the Hanford Site, Washington

    SciTech Connect

    Early, T.O.

    1986-03-14

    This document reports all available dissolved gas concentration data for groundwaters from the Hanford Site as of June 1985. Details of the computational procedures required to reduce data obtained from the field measurements made by the Basalt Waste Isolation Project are provided in the appendix. Most measured values for methane concentration from reference repository boreholes are in the range of from 350 to 700 mg/L for the Cohassett flow top. Because of the uncertainties associated with these measurements, it is currently recommended that a conservative methane concentration of 1200 mg/L (methane saturated) in groundwater be considered the most reasonable upper-bounding value. 16 refs., 2 figs., 2 tabs.

  18. 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.

  19. Long-term trends in dissolved iron and DOC concentration linked to nitrate depletion in riparian soils

    NASA Astrophysics Data System (ADS)

    Musolff, Andreas; Selle, Benny; Fleckenstein, Jan H.; Oosterwoud, Marieke R.; Tittel, Jörg

    2016-04-01

    The instream concentrations of dissolved organic carbon (DOC) are rising in many catchments of the northern hemisphere. Elevated concentrations of DOC, mainly in the form of colored humic components, increase efforts and costs of drinking water purification. In this study, we evaluated a long-term dataset of 110 catchments draining into German drinking water reservoirs in order to assess sources of DOC and drivers of a potential long-term change. The average DOC concentrations across the wide range of different catchments were found to be well explained by the catchment's topographic wetness index. Higher wetness indices were connected to higher average DOC concentrations, which implies that catchments with shallow topography and pronounced riparian wetlands mobilize more DOC. Overall, 37% of the investigated catchments showed a significant long-term increase in DOC concentrations, while 22% exhibited significant negative trends. Moreover, we found that increasing trends in DOC were positively correlated to trends in dissolved iron concentrations at pH≤6 due to remobilization of DOC previously sorbed to iron minerals. Both, increasing trends in DOC and dissolve iron were found to be connected to decreasing trends and low concentrations of nitrate (below ~6 mg/L). This was especially observed in forested catchments where atmospheric N-depositions were the major source for nitrate availability. In these catchments, we also found long-term increases of phosphate concentrations. Therefore, we argue that dissolved iron, DOC and phosphate were jointly released under iron-reducing conditions when nitrate as a competing electron acceptor was too low in concentrations to prevent the microbial iron reduction. In contrast, we could not explain the observed increasing trends in DOC, iron and phosphate concentrations by the long-term trends of pH, sulfate or precipitation. Altogether this study gives strong evidence that both, source and long-term increases in DOC are

  20. Decadal-scale changes in dissolved-solids concentrations in groundwater used for public supply, Salt Lake Valley, Utah

    USGS Publications Warehouse

    Thiros, Susan; Spangler, Larry

    2010-01-01

    Basin-fill aquifers are a major source of good-quality water for public supply in many areas of the southwestern United States and have undergone increasing development as populations have grown over time. During 2005, the basin-fill aquifer in Salt Lake Valley, Utah, provided approximately 75,000 acre-feet, or about 29 percent of the total amount of water used by a population of 967,000. Groundwater in the unconsolidated basin-fill deposits that make up the aquifer occurs under unconfined and confined conditions. Water in the shallow unconfined part of the groundwater system is susceptible to near-surface contamination and generally is not used as a source of drinking water. Groundwater for public supply is withdrawn from the deeper unconfined and confined parts of the system, termed the principal aquifer, because yields generally are greater and water quality is better (including lower dissolved-solids concentrations) than in the shallower parts of the system. Much of the water in the principal aquifer is derived from recharge in the adjacent Wasatch Range (mountain-block recharge). In many areas, the principal aquifer is separated from the overlying shallow aquifer by confining layers of less permeable, fine-grained sediment that inhibit the downward movement of water and any potential contaminants from the surface. Nonetheless, under certain hydrologic conditions, human-related activities can increase dissolved-solids concentrations in the principal aquifer and result in groundwater becoming unsuitable for consumption without treatment or mixing with water having lower dissolved-solids concentrations. Dissolved-solids concentrations in areas of the principal aquifer used for public supply typically are less than 500 milligrams per liter (mg/L), the U.S. Environmental Protection Agency (EPA) secondary (nonenforceable) drinking-water standard. However, substantial increases in dissolved-solids concentrations in the principal aquifer have been documented in some

  1. Spatial variability in dissolved organic matter and inorganic nitrogen concentrations in a semiarid stream, San Pedro River, Arizona

    NASA Astrophysics Data System (ADS)

    Brooks, Paul D.; Lemon, Michelle M.

    2007-09-01

    We performed synoptic sampling of a 95-km reach of the San Pedro River, Arizona, to identify the effects of regional hydrology and land use on dissolved carbon and nitrogen concentrations. Six synoptic surveys, two before, two during, and two after the 2002 monsoon season, encompassed periods of both low and high stream discharge. Chloride concentrations and δ18O values during low-flow periods indicated the river was divided into three hydrologically distinct reaches each roughly 30 km long. Upper and lower reaches were characterized by areas of localized groundwater input followed by downstream evapo-concentration gradients, limited downstream solute transport, and highly variable carbon and nitrogen concentrations. In contrast, the middle reach was characterized by widespread groundwater input, continuous downstream hydrologic connectivity, and less variable carbon and nitrogen concentrations. During the monsoon season, base flow discharge increased five- to ten-fold, dissolved organic matter and inorganic N increased two- to ten-fold, Fluorescence Index (FI) values indicated a large input of terrestrial solutes, and both chloride concentrations and δ18O values indicated that stream water and alluvial groundwater were well mixed along the entire 95 km reach. Concurrently, the middle reach that exhibited continuous hydrologic connectivity during the nonmonsoon season was a net sink for N, while the reaches characterized by limited hydrologic connectivity during the low-flow season exhibited net N export. Our data suggest that instream biogeochemical cycling during the monsoon season is influenced by antecedent conditions, specifically hydrologic connectivity, during the dry season.

  2. 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)

  3. 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

  4. 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...

  5. Natural and anthropogenic factors controlling the dissolved organic carbon concentrations and fluxes in a large tropical river, India.

    PubMed

    Balakrishna, K; Kumar, Itta Arun; Srinikethan, G; Mugeraya, Gopal

    2006-11-01

    Carbon studies in tropical rivers have gained significance since it was realized that a significant chunk of anthropogenic CO(2) emitted into the atmosphere returns to the biosphere, that is eventually transported by the river and locked up in coastal sediments for a few thousand years. Carbon studies are also significant because dissolved organic carbon (DOC) is known to complex the toxic trace metals in the river and carry them in the dissolved form. For the first time, this work has made an attempt to study the variations in DOC concentrations in space and time for a period of 19 months, and estimate their fluxes in the largest peninsular Indian river, the Godavari at Rajahmundry. Anthropogenic influence on DOC concentrations possibly from the number of bathing ghats along the banks and domestic sewage discharge into the river are evident during the pre-monsoon of 2004 and 2005. The rise in DOC concentrations at the onset of monsoon could be due to the contributions from flood plains and soils from the river catchment. Spatial variations highlighted that the DOC concentrations in the river are affected more by the anthropogenic discharges in the downstream than in the upstream. The discharge weighted DOC concentrations in the Godavari river is 3-12 times lower than Ganga-Brahmaputra, Indus and major Chinese rivers. The total carbon fluxes from the Godavari into the Bay of Bengal is insignificant (0.5%) compared to the total carbon discharges by major rivers of the world into oceans.

  6. Natural and anthropogenic factors controlling the dissolved organic carbon concentrations and fluxes in a large tropical river, India.

    PubMed

    Balakrishna, K; Kumar, Itta Arun; Srinikethan, G; Mugeraya, Gopal

    2006-11-01

    Carbon studies in tropical rivers have gained significance since it was realized that a significant chunk of anthropogenic CO(2) emitted into the atmosphere returns to the biosphere, that is eventually transported by the river and locked up in coastal sediments for a few thousand years. Carbon studies are also significant because dissolved organic carbon (DOC) is known to complex the toxic trace metals in the river and carry them in the dissolved form. For the first time, this work has made an attempt to study the variations in DOC concentrations in space and time for a period of 19 months, and estimate their fluxes in the largest peninsular Indian river, the Godavari at Rajahmundry. Anthropogenic influence on DOC concentrations possibly from the number of bathing ghats along the banks and domestic sewage discharge into the river are evident during the pre-monsoon of 2004 and 2005. The rise in DOC concentrations at the onset of monsoon could be due to the contributions from flood plains and soils from the river catchment. Spatial variations highlighted that the DOC concentrations in the river are affected more by the anthropogenic discharges in the downstream than in the upstream. The discharge weighted DOC concentrations in the Godavari river is 3-12 times lower than Ganga-Brahmaputra, Indus and major Chinese rivers. The total carbon fluxes from the Godavari into the Bay of Bengal is insignificant (0.5%) compared to the total carbon discharges by major rivers of the world into oceans. PMID:16738757

  7. Behavior of dissolved and total phosphorus concentration and stream discharge: The form of hysteresis during storm events

    NASA Astrophysics Data System (ADS)

    Pradhanang, S. M.; Samal, N. R.; Pierson, D. C.; Schneiderman, E. M.; Zion, M. S.

    2013-12-01

    The forms, rotational patterns and trends of hysteretic loops of dissolved and total phosphorus were investigated in the watershed of a New York City drinking water reservoir. We evaluated two biogeochemical parameters summarizing the changes in solute concentrations and the overall dynamics of each hysteretic loop and seven hydrological parameters that characterize the hydrograph formation of particular storm events. The objectives of this study are: (1) to examine whether the characteristics of solute hysteretic loops monitored during the summer, winter and spring seasons followed a consistent and recurring pattern, (2) to identify hydrological parameters which could potentially influence features of dissolved and total phosphorus hysteresis. Relationships between hysteresis features and hydrological parameters at the watershed outlet were explored using multivariate redundancy analysis (RDA).

  8. A combined process of activated carbon adsorption, ion exchange resin treatment and membrane concentration for recovery of dissolved organics in pre-hydrolysis liquor of the kraft-based dissolving pulp production process.

    PubMed

    Shen, Jing; Kaur, Ishneet; Baktash, Mir Mojtaba; He, Zhibin; Ni, Yonghao

    2013-01-01

    To recover dissolved organics in pre-hydrolysis liquor (PHL) of the kraft-based dissolving pulp production process, a new combined process concept of sequential steps of activated carbon adsorption, ion exchange resin treatment, and membrane concentration, was proposed. The removal of lignin in the PHL was achieved in the activated carbon adsorption step, which also facilitates the subsequent operations, such as the membrane filtration and ion exchange resin treatment. The ion exchange resin treatment resulted in the removal/concentration of acetic acid, which opens the door for acetic acid recovery. The membrane filtration is to recover/concentrate the dissolved sugars. The combined process resulted in the production of PHL-based concentrate with relatively high concentration of hemicellulosic sugars, i.e., 22.13%.

  9. Sources, transformations, and hydrological processes that control stream nitrate and dissolved organic matter concentrations during snowmelt in an upland forest

    USGS Publications Warehouse

    Sebestyen, S.D.; Boyer, E.W.; Shanley, J.B.; Kendall, C.; Doctor, D.H.; Aiken, G.R.; Ohte, N.

    2008-01-01

    We explored catchment processes that control stream nutrient concentrations at an upland forest in northeastern Vermont, USA, where inputs of nitrogen via atmospheric deposition are among the highest in the nation and affect ecosystem functioning. We traced sources of water, nitrate, and dissolved organic matter (DOM) using stream water samples collected at high frequency during spring snowmelt. Hydrochemistry, isotopic tracers, and end-member mixing analyses suggested the timing, sources, and source areas from which water and nutrients entered the stream. Although stream-dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) both originated from leaching of soluble organic matter, flushing responses between these two DOM components varied because of dynamic shifts of hydrological flow paths and sources that supply the highest concentrations of DOC and DON. High concentrations of stream water nitrate originated from atmospheric sources as well as nitrified sources from catchment soils. We detected nitrification in surficial soils during late snowmelt which affected the nitrate supply that was available to be transported to streams. However, isotopic tracers showed that the majority of nitrate in upslope surficial soil waters after the onset of snowmelt originated from atmospheric sources. A fraction of the atmospheric nitrogen was directly delivered to the stream, and this finding highlights the importance of quick flow pathways during snowmelt events. These findings indicate that interactions among sources, transformations, and hydrologic transport processes must be deciphered to understand why concentrations vary over time and over space as well as to elucidate the direct effects of human activities on nutrient dynamics in upland forest streams. Copyright 2008 by the American Geophysical Union.

  10. 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 μM C, with an average of 225.9±75.4 μM C, while those in the surface microlayer varied between 140.1 and 330.9 μM C, with an average of 217.8±56.8 μM 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.

  11. 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.

  12. Characterization and biotoxicity assessment of dissolved organic matter in RO concentrate from a municipal wastewater reclamation reverse osmosis system.

    PubMed

    Sun, Ying-Xue; Gao, Yue; Hu, Hong-Ying; Tang, Fang; Yang, Zhe

    2014-12-01

    Reverse osmosis (RO) concentrate from municipal wastewater reclamation reverse osmosis (mWRRO) system containing organic compounds may associate with toxic risk, and its discharge might pose an environmental risk. To identify a basis for the selection of feasible technology in treating RO concentrates, the characteristics and biotoxicity of different fractions of dissolved organic matter (DOM) in RO concentrates from an mWRRO system were investigated. The results indicated that the hydrophilic neutrals (HIN), hydrophobic acids (HOA) and hydrophobic bases (HOB) accounted for 96% of the dissolved organic carbon (DOC) of the total DOM in the RO concentrate. According to the SEC chromatograph detected at 254 nm wavelength of UV, the DOM with molecular weight (MW) 1-3 kDa accounted for the majority of the basic and neutral fractions. The fluorescence spectra of the excitation emission matrix (EEM) indicated that most aromatic proteins, humic/fulvic acid-like and soluble microbial by-product-like substances existed in the fractions HOA and hydrophobic neutrals (HON). The genotoxicity and anti-estrogenic activity of the RO concentrate were 1795.6 ± 57.2 μg 4-NQOL(-1) and 2.19 ± 0.05 mg TAM L(-1), respectively. The HIN, HOA, and HOB contributed to the genotoxicity of the RO concentrate, and the HIN was with the highest genotoxic level of 1007.9 ± 94.8 μg 4-NQOL(-1). The HOA, HON, and HIN lead to the total anti-estrogenic activity of the RO concentrate, and HOA occupied approximately 60% of the total, which was 1.3 ± 0.17 mg TAM L(-1).

  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. Dissolved greenhouse gas concentrations as proxies for emissions: First results from a survey of 43 Alpine lakes

    NASA Astrophysics Data System (ADS)

    Pighini, Sylvie; Wohlfahrt, Georg; Miglietta, Franco

    2015-04-01

    Up to very recently, freshwater ecosystems were neglected in assessments of the global carbon cycle and considered merely as passive 'pipes' which transport carbon from the land to the oceans. This view has been challenged by an increasing number of studies showing that freshwater ecosystems may negate a substantial fraction of the carbon sink through carbon dioxide (CO2) and in particular methane (CH4) emissions and thus rather should be viewed as 'reactors' which process a large fraction of the terrigenous carbon. Most of our knowledge on freshwater CO2 and CH4 emissions to date derives from studies in tropical and boreal regions, while temperate freshwater ecosystems are understudied. This study is focused on lakes from the Alpine area and their content in dissolved greenhouse gases, CH4 and CO2. We mostly aim to assess the content of dissolved methane and carbon dioxide from the Alpine lakes in order to understand whether Alpine lakes could be potential CH4 and CO2 emitters. We also would like to relate concentrations to lake characteristics and potential biotic and abiotic driving forces. A diverse set of 43 lakes, from Trentino, South Tirol (Italy) and North Tirol (Austria), was selected resulting in a gradient with respect to elevation (from 240 to 1700 m a.s.l.) and latitude (from 45.52° to 47.38°). Complementary to dissolved CH4 and CO2 surface water samples, dissolved oxygen and temperature were measured. Only water surface samples were considered. Analyses were done with a gas chromatographer equipped with a flame ionization detector (FID) for CH4 and a thermal conductivity detector (TCD) for CO2 determination. The first results show that all the sampled lakes were super-saturated in dissolved methane and carbon dioxide concentrations, at least partly to a degree that in the literature has been shown to result in substantial emissions to the atmosphere. To estimate emissions, CO2 and CH4 fluxes will be quantified using the eddy covariance and floating

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

    PubMed

    Garcia, R 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.

  16. 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.

  17. Experimental whole-lake increase of dissolved organic carbon concentration produces unexpected increase in crustacean zooplankton density

    USGS Publications Warehouse

    Kelly, Patrick T.; Craig, Nicola; Solomon, Christopher T.; Weidel, Brian C.; Zwart, Jacob A.; Jones, Stuart E.

    2016-01-01

    The observed pattern of lake browning, or increased terrestrial dissolved organic carbon (DOC) concentration, across the northern hemisphere has amplified the importance of understanding how consumer productivity varies with DOC concentration. Results from comparative studies suggest these increased DOC concentrations may reduce crustacean zooplankton productivity due to reductions in resource quality and volume of suitable habitat. Although these spatial comparisons provide an expectation for the response of zooplankton productivity as DOC concentration increases, we still have an incomplete understanding of how zooplankton respond to temporal increases in DOC concentration within a single system. As such, we used a whole-lake manipulation, in which DOC concentration was increased from 8 to 11 mg L−1 in one basin of a manipulated lake, to test the hypothesis that crustacean zooplankton production should subsequently decrease. In contrast to the spatially derived expectation of sharp DOC-mediated decline, we observed a small increase in zooplankton densities in response to our experimental increase in DOC concentration of the treatment basin. This was due to significant increases in gross primary production and resource quality (lower seston carbon-to-phosphorus ratio; C:P). These results demonstrate that temporal changes in lake characteristics due to increased DOC may impact zooplankton in ways that differ from those observed in spatial surveys. We also identified significant interannual variability across our study region, which highlights potential difficulty in detecting temporal responses of organism abundances to gradual environmental change (e.g., browning).

  18. [Effect of the change in sulphate and dissolved oxygen mass concentration on metal release in old cast iron distribution pipes].

    PubMed

    Wu, Yong-li; Shi, Bao-you; Sun, Hui-fang; Zhang, Zhi-huan; Gu, Jun-nong; Wang, Dong-sheng

    2013-09-01

    To understand the processes of corrosion by-product release and the consequent "red water" problems caused by the variation of water chemical composition in drinking water distribution system, the effect of sulphate and dissolved oxygen (DO) concentration on total iron release in corroded old iron pipe sections historically transporting groundwater was investigated in laboratory using small-scale pipe section reactors. The release behaviors of some low-level metals, such as Mn, As, Cr, Cu, Zn and Ni, in the process of iron release were also monitored. The results showed that the total iron and Mn release increased significantly with the increase of sulphate concentration, and apparent red water occurred when sulphate concentration was above 400 mg x L(-1). With the increase of sulfate concentration, the effluent concentrations of As, Cr, Cu, Zn and Ni also increased obviously, however, the effluent concentrations of these metals were lower than the influent concentrations under most circumstances, which indicated that adsorption of these metals by pipe corrosion scales occurred. Increasing DO within a certain range could significantly inhibit the iron release.

  19. Experimental whole-lake increase of dissolved organic carbon concentration produces unexpected increase in crustacean zooplankton density.

    PubMed

    Kelly, Patrick T; Craig, Nicola; Solomon, Christopher T; Weidel, Brian C; Zwart, Jacob A; Jones, Stuart E

    2016-08-01

    The observed pattern of lake browning, or increased terrestrial dissolved organic carbon (DOC) concentration, across the northern hemisphere has amplified the importance of understanding how consumer productivity varies with DOC concentration. Results from comparative studies suggest these increased DOC concentrations may reduce crustacean zooplankton productivity due to reductions in resource quality and volume of suitable habitat. Although these spatial comparisons provide an expectation for the response of zooplankton productivity as DOC concentration increases, we still have an incomplete understanding of how zooplankton respond to temporal increases in DOC concentration within a single system. As such, we used a whole-lake manipulation, in which DOC concentration was increased from 8 to 11 mg L(-1) in one basin of a manipulated lake, to test the hypothesis that crustacean zooplankton production should subsequently decrease. In contrast to the spatially derived expectation of sharp DOC-mediated decline, we observed a small increase in zooplankton densities in response to our experimental increase in DOC concentration of the treatment basin. This was due to significant increases in gross primary production and resource quality (lower seston carbon-to-phosphorus ratio; C:P). These results demonstrate that temporal changes in lake characteristics due to increased DOC may impact zooplankton in ways that differ from those observed in spatial surveys. We also identified significant interannual variability across our study region, which highlights potential difficulty in detecting temporal responses of organism abundances to gradual environmental change (e.g., browning).

  20. 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.

  1. Predicting dissolved oxygen concentration using kernel regression modeling approaches with nonlinear hydro-chemical data.

    PubMed

    Singh, Kunwar P; Gupta, Shikha; Rai, Premanjali

    2014-05-01

    Kernel function-based regression models were constructed and applied to a nonlinear hydro-chemical dataset pertaining to surface water for predicting the dissolved oxygen levels. Initial features were selected using nonlinear approach. Nonlinearity in the data was tested using BDS statistics, which revealed the data with nonlinear structure. Kernel ridge regression, kernel principal component regression, kernel partial least squares regression, and support vector regression models were developed using the Gaussian kernel function and their generalization and predictive abilities were compared in terms of several statistical parameters. Model parameters were optimized using the cross-validation procedure. The proposed kernel regression methods successfully captured the nonlinear features of the original data by transforming it to a high dimensional feature space using the kernel function. Performance of all the kernel-based modeling methods used here were comparable both in terms of predictive and generalization abilities. Values of the performance criteria parameters suggested for the adequacy of the constructed models to fit the nonlinear data and their good predictive capabilities. PMID:24338099

  2. Lake transparency: a window into decadal variations in dissolved organic carbon concentrations in Lakes of Acadia National Park, Maine

    USGS Publications Warehouse

    Collin Roesler,; Culbertson, Charles W.

    2016-01-01

    A forty year time series of Secchi depth observations from approximately 25 lakes in Acadia National Park, Maine, USA, evidences large variations in transparency between lakes but relatively little seasonal cycle within lakes. However, there are coherent patterns over the time series, suggesting large scale processes are responsible. It has been suggested that variations in colored dissolved organic matter (CDOM) are primarily responsible for the variations in transparency, both between lakes and over time and further that CDOM is a robust optical proxy for dissolved organic carbon (DOC). Here we present a forward model of Secchi depth as a function of DOC based upon first principles and bio-optical relationships. Inverting the model to estimate DOC concentration from Secchi depth observations compared well with the measured DOC concentrations collected since 1995 (RMS error < 1.3 mg C l-1). This inverse model allows the time series of DOC to be extended back to the mid 1970s when only Secchi depth observations were collected, and thus provides a means for investigating lake response to climate forcing, changing atmospheric chemistry and watershed characteristics, including land cover and land use.

  3. 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.

  4. Spatial and Seasonal Variation of Dissolved Organic Carbon (DOC) Concentrations in Irish Streams: Importance of Soil and Topography Characteristics

    NASA Astrophysics Data System (ADS)

    Liu, Wen; Xu, Xianli; McGoff, Nicola M.; Eaton, James M.; Leahy, Paul; Foley, Nelius; Kiely, Gerard

    2014-05-01

    Dissolved organic carbon (DOC) concentrations have increased in many sites in Europe and North America in recent decades. High DOC concentrations can damage the structure and functions of aquatic ecosystems by influencing water chemistry. This study investigated the spatial and seasonal variation of DOC concentrations in Irish streams across 55 sites at seven time occasions over 1 year (2006/2007). The DOC concentrations ranged from 0.9 to 25.9 mg/L with a mean value of 6.8 and a median value of 5.7 mg/L and varied significantly over the course of the year. The DOC concentrations from late winter (February: 5.2 ± 3.0 mg/L across 55 sites) and early spring (April: 4.5 ± 3.5 mg/L) had significantly lower DOC concentrations than autumn (October: mean 8.3 ± 5.6 mg/L) and early winter (December: 8.3 ± 5.1 mg/L). The DOC production sources (e.g., litterfall) or the accumulation of DOC over dry periods might be the driving factor of seasonal change in Irish stream DOC concentrations. Analysis of data using stepwise multiple linear regression techniques identified the topographic index (TI, an indication of saturation-excess runoff potential) and soil conditions (organic carbon content and soil drainage characteristics) as key factors in controlling DOC spatial variation in different seasons. The TI and soil carbon content (e.g., soil organic carbon; peat occurrence) are positively related to DOC concentrations, while well-drained soils are negatively related to DOC concentrations. The knowledge of spatial and seasonal variation of DOC concentrations in streams and their drivers are essential for optimum riverine water resources management.

  5. Spatial and Seasonal Variation of dissolved organic carbon (DOC) concentrations in Irish streams: importance of soil and topography characteristics.

    PubMed

    Liu, Wen; Xu, Xianli; McGoff, Nicola M; Eaton, James M; Leahy, Paul; Foley, Nelius; Kiely, Gerard

    2014-05-01

    Dissolved organic carbon (DOC) concentrations have increased in many sites in Europe and North America in recent decades. High DOC concentrations can damage the structure and functions of aquatic ecosystems by influencing water chemistry. This study investigated the spatial and seasonal variation of DOC concentrations in Irish streams across 55 sites at seven time occasions over 1 year (2006/2007). The DOC concentrations ranged from 0.9 to 25.9 mg/L with a mean value of 6.8 and a median value of 5.7 mg/L and varied significantly over the course of the year. The DOC concentrations from late winter (February: 5.2 ± 3.0 mg/L across 55 sites) and early spring (April: 4.5 ± 3.5 mg/L) had significantly lower DOC concentrations than autumn (October: mean 8.3 ± 5.6 mg/L) and early winter (December: 8.3 ± 5.1 mg/L). The DOC production sources (e.g., litterfall) or the accumulation of DOC over dry periods might be the driving factor of seasonal change in Irish stream DOC concentrations. Analysis of data using stepwise multiple linear regression techniques identified the topographic index (TI, an indication of saturation-excess runoff potential) and soil conditions (organic carbon content and soil drainage characteristics) as key factors in controlling DOC spatial variation in different seasons. The TI and soil carbon content (e.g., soil organic carbon; peat occurrence) are positively related to DOC concentrations, while well-drained soils are negatively related to DOC concentrations. The knowledge of spatial and seasonal variation of DOC concentrations in streams and their drivers are essential for optimum riverine water resources management.

  6. Dissolved organic carbon concentrations and compositions, and trihalomethane formation potentials in waters from agricultural peat soils, Sacramento-San Joaquin Delta, California; implications for drinking-water quality

    USGS Publications Warehouse

    Fujii, Roger; Ranalli, Anthony J.; Aiken, George R.; Bergamaschi, Brian A.

    1998-01-01

    Water exported from the Sacramento-San Joaquin River delta (Delta) is an important drinking-water source for more than 20 million people in California. At times, this water contains elevated concentrations of dissolved organic carbon and bromide, and exceeds the U.S. Environmental Protection Agency's maximum contaminant level for trihalomethanes of 0.100 milligrams per liter if chlorinated for drinking water. About 20 to 50 percent of the trihalomethane precursors to Delta waters originates from drainage water from peat soils on Delta islands. This report elucidates some of the factors and processes controlling and affecting the concentration and quality of dissolved organic carbon released from peat soils and relates the propensity of dissolved organic carbon to form trihalomethanes to its chemical composition.Soil water was sampled from near-surface, oxidized, well-decomposed peat soil (upper soil zone) and deeper, reduced, fibrous peat soil (lower soil zone) from one agricultural field in the west central Delta over 1 year. Concentrations of dissolved organic carbon in the upper soil zone were highly variable, with median concentrations ranging from 46.4 to 83.2 milligrams per liter. Concentrations of dissolved organic carbon in samples from the lower soil zone were much less variable and generally slightly higher than samples from the upper soil zone, with median concentrations ranging from 49.3 to 82.3 milligrams per liter. The dissolved organic carbon from the lower soil zone had significantly higher aromaticity (as measured by specific ultraviolet absorbance) and contained significantly greater amounts of aromatic humic substances (as measured by XAD resin fractionation and carbon-13 nuclear magnetic resonance analysis of XAD isolates) than the dissolved organic carbon from the upper soil zone. These results support the conclusion that more aromatic forms of dissolved organic carbon are produced under anaerobic conditions compared to aerobic conditions

  7. 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.

  8. An Analysis of Dissolved Oxygen Concentrations in Tail Waters of Hydroelectric Dams and the Implications for Small-Scale Hydropower Development

    NASA Astrophysics Data System (ADS)

    Cada, Glenn F.; Kumar, K. D.; Solomon, Jean A.; Hildebrand, Stephen G.

    1983-08-01

    One of the environmental issues affecting small-scale hydropower development in the United States is water quality degradation. The extent of this potential problem, as exemplified by low dissolved oxygen concentrations in reservoir tail waters, was analyzed by pairing operating hydroelectric sites with dissolved oxygen measurements from nearby downstream U.S. Geological Survey water quality stations. These data were used to calculate probabilities of noncompliance (PNC's), that is, the probabilities that dissolved oxygen concentrations in the discharge waters of operating hydroelectric dams will drop below 5 mg/l. The continental states were grouped into eight regions based on geographic and climatic similarities. Most regions had higher mean PNC's in summer than in winter, and summer PNC's were greater for large-scale than for small-scale hydropower facilities. Cumulative probability distributions of PNC also indicated that low dissolved oxygen concentrations in the tail waters of operating hydroelectric dams are phenomena largely confined to sites with large-scale facilities.

  9. Use of pore-water composition to reconstruct past dissolved inorganic carbon concentration and alkalinity in Pacific bottom water

    NASA Astrophysics Data System (ADS)

    Sauvage, J. F.; Spivack, A. J.; D'Hondt, S. L.; Integrated Ocean Drilling Program Expedition 329 shipboard scientific party

    2011-12-01

    The carbonate system is a crucial component in controlling the pH of the world's oceans and the distribution of CO2 within the ocean, as well as between the ocean and atmosphere. Consequently, dissolved inorganic carbon (DIC) and alkalinity reconstructions bear lots of promise for improving understanding of the ocean's role in the global carbon cycle and climate. We propose and test a method to quantify in situ concentrations of deep-sea carbonate-system components (DIC, alkalinity, CO32-, Ca2+, and minor component concentrations) in pore fluid of deep-sea sediment cores. These concentrations can in turn be used to reconstruct deep-sea carbonate-system chemistry of the geologic past. Alkalinity, DIC and Ca2+ concentrations measured on research vessels differ from in situ values because temperature and pressure changes during core recovery, storage and extraction induce calcium carbonate precipitation and in this way alter the original composition. To reconstruct in situ values, we developed a method that takes advantage of the mathematically over-determined state of the system if three components are measured, given that CaCO3 is saturated and the dissolved carbonate system is at equilibrium in situ. As a result, based on the measured alkalinity, DIC and Ca2+ concentrations, in situ CO2aq, HCO3-, CO32-, and minor species concentrations are calculated by applying an iteration process. This approach allows us to calculate the amount of CaCO3 precipitated during sediment recovery from the seafloor, and hence in situ carbonate system components. We apply our model to pore-water data from two SPG sites rich in calcium carbonate and drilled by Integrated Ocean Drilling Program Expedition 329 (Sites 1367 and 1368). We compared two sample types for this study, (i) samples squeezed and processed within minutes of recovery (rapidly processed) and (ii) samples processed in the following hours/days, and as consequence prone to some substantial alteration (slowly processed

  10. Effects of over-winter green cover on groundwater nitrate and dissolved organic carbon concentrations beneath tillage land.

    PubMed

    Premrov, Alina; Coxon, Catherine E; Hackett, Richard; Kirwan, Laura; Richards, Karl G

    2012-11-01

    Application of over-winter green cover (e.g. cover crops) as a measure for reducing nitrate losses from tillage land has been frequently investigated, especially in the unsaturated zone. Monitoring of groundwater is less common in these studies. Studies on groundwater responses to different land treatments can be challenging because they can be influenced by various conditions, such as recharge, seasonal variations, and aquifer properties, often occurring at different time scales than surface water processes. The aim of this study was to evaluate groundwater nitrate (NO(3)(-)N) and dissolved organic carbon (DOC) concentration responses to different over-winter green covers: mustard, natural regeneration and no cover. A field experiment was designed and run for three years on tillage land underlain by a vulnerable sand and gravel aquifer in the south-east of Ireland. Results showed that over-winter green cover growth on tillage land can be an effective measure to reduce groundwater NO(3)(-)N concentrations. A significant decrease in groundwater NO(3)(-)N concentrations was observed under the mustard cover compared to no cover. All treatments, including no cover, showed a decline in groundwater NO(3)(-)N concentrations over time. A significant increase in groundwater DOC was also observed under the mustard cover. Although the overall groundwater DOC concentrations were low, the increased DOC occurrence in groundwater should be accounted for in carbon balances and could potentially enhance groundwater denitrification in cases where aquifer conditions may favour it.

  11. River bank restoration effects on dissolved organic carbon concentrations in groundwater during floods

    NASA Astrophysics Data System (ADS)

    Derx, J.; Blaschke, A. P.

    2012-04-01

    Estimating the effect of river restoration on groundwater quality is important in the view of nationwide implementations demanded by e.g. the EU Water Framework Directive. DOC transport during river infiltration conditions was examined based on 3D flow and contaminant transport simulations with transient groundwater-surface water interaction. In a scenario setting the effects of river restoration on DOC concentrations, travel time and distance from the river required for DOC reduction in groundwater during river floods were investigated. River restoration was assumed to cause scouring of the riverbank, which a) affects the bank geometry and provides more chance of the river to interact with groundwater and b) reduces bank sediment clogging. A shallow unconfined alluvial aquifer of gravel and sandy gravel media was assumed which was either well connected to the river or was confined by a thin clogging layer at the top of the river bed and bank at natural infiltration conditions. Scenario results showed that riverbank restoration facilitates DOC transport into the aquifer during floods. Even if riverbank permeability remained unchanged, floods caused significantly higher DOC concentrations at a restored than at a channelised riverbank. At the same time, DOC concentration peaks in groundwater arrived earlier and the required distance from the river reducing DOC to background concentrations increased. These effects were explained by changes in bank geometry, and thus a greater ability of the river to interact with groundwater.

  12. Manifestation of cryptic fibroblast tissue factor occurs at detergent concentrations which dissolve the plasma membrane.

    PubMed

    Carson, S D

    1996-04-01

    Cultured fibroblasts treated with increasing concentrations of detergents expressed only encrypted levels of tissue factor activity (measured by fX activation in the presence of fVIIa), characteristic of undamaged cells, until each detergent reached a critical concentration at which the cryptic tissue factor activity was manifested. Beyond the narrow ranges of concentrations over which the detergents stimulated tissue factor activity, the detergents were inhibitory. Studies with Triton X-100 and octyl glucoside revealed that manifestation of tissue factor activity coincided with breakdown of the plasma membrane. The magnitude of the increased tissue factor activity differed among detergents, with octyl glucoside giving the largest response. The tissue factor that was active after Triton X-100 treatment remained mostly associated with the insoluble cell residue, whereas the concentration of octyl glucoside which stimulated activity released tissue factor activity into the supernatant. Radiolabeled antibody against human tissue factor was used to show that a small percentage of the total accessible tissue factor remained in the insoluble fraction after treatment with either non-ionic detergent. Chromatographic analysis of lipids extracted from cells treated with detergents and dansyl chloride showed dansyl-reactivity of phosphatidylserine on intact cells, and solubilization of membrane lipids at sublytic concentrations of detergents. These findings reveal that there is a critical level of detergent-induced membrane damage at which tissue factor activity is maximally expressed, in essentially an all-or-none manner. The results are consistent with a major role for phospholipid asymmetry in regulation of tissue factor specific activity, but require either maintenance of asymmetry during sublytic detergent perturbation of the plasma membrane or additional control mechanisms.

  13. [Characteristics of Dissolved CH₄ and N₂O Concentrations of Weihe River in Xinxiang Section in Spring].

    PubMed

    Hou, Cui-cui; Zhang, Fang; Li, Ying-chen; Wang, Qi-bo; Liu, Sai

    2016-05-15

    Distributions of CH₄ and N₂O concentrations in Weihe River in Xinxiang City were monitored in spring of 2015, and their influencing factors were discussed. The result showed that CH₄ and N₂O were super-saturated in surface water of Weihe River. The variation ranges of two gases' saturations in the surface water of Weihe River were 147.59-2667.85 (CH₄) and 4.06-188.25 (N₂O). In the urban area, significant correlation existed between N₂O and NH₄⁺-N concentrations (P < 0.01), but in the new district, dissolved N₂O concentration showed sharp increase because of the water input from the urban sewage plants, illustrating that the controlling mechanism on N₂O production varied as pollutant characteristics changed. Stepwise regression analysis showed that CH₄ concentrations could be explained by NH₄⁺-N concentrations and water temperature, and CH₄ concentrations in the surface water of Weihe River was significantly correlated with NH₄⁺-N concentrations (R² = 0.70, P < 0.01), suggesting that NH₄⁺-N was the key factor in regulating the production and assumption of CH₄oxidation in Weihe River in spring. Besides, this study showed that when there was less NO₃⁻-N but more NH₄⁺-N in river water, CH₄and N₂O concentrations would be positively correlated, indicating that different nitrogen sources would impact the coupling mechanism of CH₄and N₂O productions.

  14. [Characteristics of Dissolved CH₄ and N₂O Concentrations of Weihe River in Xinxiang Section in Spring].

    PubMed

    Hou, Cui-cui; Zhang, Fang; Li, Ying-chen; Wang, Qi-bo; Liu, Sai

    2016-05-15

    Distributions of CH₄ and N₂O concentrations in Weihe River in Xinxiang City were monitored in spring of 2015, and their influencing factors were discussed. The result showed that CH₄ and N₂O were super-saturated in surface water of Weihe River. The variation ranges of two gases' saturations in the surface water of Weihe River were 147.59-2667.85 (CH₄) and 4.06-188.25 (N₂O). In the urban area, significant correlation existed between N₂O and NH₄⁺-N concentrations (P < 0.01), but in the new district, dissolved N₂O concentration showed sharp increase because of the water input from the urban sewage plants, illustrating that the controlling mechanism on N₂O production varied as pollutant characteristics changed. Stepwise regression analysis showed that CH₄ concentrations could be explained by NH₄⁺-N concentrations and water temperature, and CH₄ concentrations in the surface water of Weihe River was significantly correlated with NH₄⁺-N concentrations (R² = 0.70, P < 0.01), suggesting that NH₄⁺-N was the key factor in regulating the production and assumption of CH₄oxidation in Weihe River in spring. Besides, this study showed that when there was less NO₃⁻-N but more NH₄⁺-N in river water, CH₄and N₂O concentrations would be positively correlated, indicating that different nitrogen sources would impact the coupling mechanism of CH₄and N₂O productions. PMID:27506045

  15. 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

  16. 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 ...

  17. Assessment of dissolved Pb concentration and isotopic composition in surface waters of the modern global ocean

    NASA Astrophysics Data System (ADS)

    Pinedo-Gonzalez, P.; West, A. J.; Sanudo-Wilhelmy, S. A.

    2015-12-01

    Lead (Pb) produced by human activities, mainly from leaded gasoline combustion and high-temperature industries, dominates Pb in our present-day oceans. Previous studies have shown that surface ocean Pb concentrations and isotope ratios have varied in time and space, reflecting the changes in the amount of inputs and sources of anthropogenic Pb. However, data on surface ocean Pb is quite limited, especially for some basins like the Indian Ocean. In the present study, Pb concentrations and stable isotopes (208, 207, and 206) have been analyzed in surface water samples (3m depth) collected during the Malaspina Circumnavigation Expedition, 2010. Our results are compared with data from the literature to i) evaluate the changing status of metal contamination in surface waters of the global ocean over the last 30 years, and ii) propose potential sources of modern Pb to the oceans. Our results show that Pb concentrations in surface waters of the North Atlantic Ocean have decreased ~ 40% since 1975, attributable to the phase-out of leaded gasoline in North America. This result is corroborated by stable Pb isotope measurements. Furthermore, the isotopic gradient observed in surface waters of the studied transects in the north tropical and subtropical Atlantic Ocean can be attributed to simple mixing of European and African aerosols and Saharan Holocene loess. Results from an understudied transect in the Southern Indian Ocean give an indication of the source region of Pb delivered to this region. Although comparison with literature data is limited, mixing of Australian ores and African and Australian coals could potentially explain the measured Pb isotope composition. This study provides an opportunity to build on the work of previous oceanographic campaigns, enabling us to assess the impact of anthropogenic Pb inputs to the ocean and the relative importance of various Pb sources, providing new insights into the transport and fate of Pb in the oceans.

  18. 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.

  19. Relative control of dissolved organic matter (DOM) composition and concentration for carbon-mineral complexation

    NASA Astrophysics Data System (ADS)

    Pan, W.; Inamdar, S. P.; Sparks, D. L.; Aufdenkampe, A. K.; Yoo, K.

    2012-12-01

    Growing concern about climate change has evoked considerable interest in the soil carbon (C) pool, the second largest C-sink on the earth. C-mineral complexation formed by ligand exchange between DOM and soil is considered as the dominant mechanism for DOM sorption and stabilization in soil. Despite intensive sorption studies, our understanding of how DOM composition influences sorption is still fairly limited. The objectives of the proposed study are: (a) to investigate the relative control of DOM composition and concentration on C-mineral complexation and (b) to determine the DOM composition metrics that are associated with irreversible binding between carbon and mineral surfaces. To address these objectives, we investigated the sorption of DOM isolated and extracted from 12 different watershed sources to goethite (a-FeOOH) with batch sorption and desorption experiments. Fluorescence-EEM and UV-absorbance methods were used to characterize DOM composition through a variety of metrics. DOM composition varied considerably for the 12 DOM solutions. With all DOM solutions adjusted to a DOC concentration of 30mgC/L, humification index (HIX) value ranged from 0.18 to 0.8 and the specific UV absorbance (SUVA) ranged from 1.12 to 3.70. The increase of 2 pH units after sorption indicated ligand exchange was likely the dominant process during sorption. The aromatic and humic-like DOM substances were preferentially sorbed. Preliminary results suggest that carbon mineral complexation (OC/SSA) was influenced by both, the concentration as well as the composition of the DOM. The explanatory power of the regression equations predicting DOM sorption to goethite was increased by the including of DOM composition matrix. The sorption isotherm revealed that DOM composition has a significant influence on the shape of the isotherms.

  20. [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

  1. [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.

  2. 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

  3. Evaluation of capillary electrophoresis for determining the concentration of dissolved silica in geothermal brines.

    PubMed

    Santoyo, E; García, R; Aparicio, A; Verma, Surendra P; Verma, M P

    2005-04-15

    The determination of silica concentrations in geothermal brines is widely recognized as a difficult analytical task due to its complex chemical polymerization kinetics that occurs during sample collection and chemical analysis. Capillary electrophoresis (CE) has been evaluated as a new reliable analytical method to measure silica (as silicates) in geothermal brines. Synthetic and geothermal brine samples were used to evaluate CE methodology. A capillary electrophoresis instrument, Quanta 4000 (Waters-Millipore) coupled with a Waters 820 workstation was used to carry out the experimental work. The separation of silicates was completed in approximately 5.5 min using a conventional fused-silica capillary (75 microm i.d. x 375 microm o.d. x 60 cm total length). A hydrostatic injection (10 cm for 20 s at 25 degrees C) was employed for introducing the samples. The carrier electrolyte consisted of 10 mM sodium chromate, 3 mM tetradecyltrimethyl-ammonium hydroxide (TTAOH), 2 mM sodium carbonate, and 1 mM sodium hydroxide, adjusted to a pH 11.0 +/- 0.1. Silicates were determined using an indirect UV detection at a wavelength of 254 nm with a mercury lamp and with a negative power supply (-15 kV). A good reproducibility in the migration times (%R.S.D. approximately 1.6%) based on six non-consecutive injections of synthetic brine solutions was obtained. A linear response between silica concentration and corrected peak area was observed. Ordinary (OLR) and weighted (WLR) linear regression models were used for calculating silica concentrations in all samples using the corresponding fitted calibration curves. The analytical results of CE were finally compared with the most probable values of synthetic reference standards of silica using the Student's t-test. No significant differences were found between them at P = 0.01. Similarly, the atomic absorption spectrometry (AAS) results were also compared with the most probable concentrations of the same reference standards, finding

  4. Influence of environmental parameters on the concentration of subsurface dissolved methane in two hydroelectric power plants in Brazil

    NASA Astrophysics Data System (ADS)

    Silva, M. G.; Marani, L.; Alvala, P. C.

    2013-12-01

    Methane (CH4) is a trace gas in the atmosphere of great importance for atmospheric chemistry as one of the main greenhouse gases. There are different sources with the largest individual production associated with the degradation of organic matter submerged in flooded areas. The amount of dissolved methane that reaches the surface depends on the production in the sediments and consumption in the water column. Both processes are associated with microbial activity and consequently dependent on the physico-chemical environmental conditions. The construction of hydroelectric dams cause flooding of areas near the river that can change the characteristics of the environment and cause changes in subsurface methane concentration. In this work, we studied two hydroelectric plants located in Brazil: Batalha (17°20'39.52"S, 47°29'34.29"W), under construction when the samples were take, and Itaipu (25°24'45.00"S, 54°35'39.00"W) which has been floated over 30 years ago. The water samples to determine dissolved methane were collected approximately 5 cm near the surface. In each collection point was measured depth, water temperature, pH and redox potential. The range of dissolved methane between the two dams was similar: 0.07-10.33 μg/l (Batalha) and 0.15-10.93 μg/l (Itaipu). However, the Batalha's average (4.04 × 3.43 μg/l; median = 3.66 μg/l) was higher than that observed in Itaipu (2.15 × 1.59 μg/l; median = 2.53 μg/l). The influence of environmental parameters on the concentration of dissolved methane was evaluated by multivariate statistical techniques (Principal Component Analysis - PCA). All of the parameters had some correlation with dissolved methane, however, the greatest contribution in Batalha was associated with pH while in Itaipu was the depth. The pH variation of the various points studied in Batalha may be associated with periods of drought and flooding of the river and hence the incorporation of organic matter in the environment. The organisms

  5. Generalized regression neural network-based approach for modelling hourly dissolved oxygen concentration in the Upper Klamath River, Oregon, USA.

    PubMed

    Heddam, Salim

    2014-08-01

    In this study, a comparison between generalized regression neural network (GRNN) and multiple linear regression (MLR) models is given on the effectiveness of modelling dissolved oxygen (DO) concentration in a river. The two models are developed using hourly experimental data collected from the United States Geological Survey (USGS Station No: 421209121463000 [top]) station at the Klamath River at Railroad Bridge at Lake Ewauna. The input variables used for the two models are water, pH, temperature, electrical conductivity, and sensor depth. The performances of the models are evaluated using root mean square errors (RMSE), the mean absolute error (MAE), Willmott's index of agreement (d), and correlation coefficient (CC) statistics. Of the two approaches employed, the best fit was obtained using the GRNN model with the four input variables used.

  6. Comparison of land-based sources with ambient estuarine concentrations of total dissolved nitrogen in Jiaozhou Bay (China)

    NASA Astrophysics Data System (ADS)

    Lu, Dongliang; Yang, Nannan; Liang, Shengkang; Li, Keqiang; Wang, Xiulin

    2016-10-01

    Seasonal, land-sea synchronous surveys were conducted from 2012 to 2013 to characterize the relationship between the composition of land-based total dissolved nitrogen (TDN) and the concentration of dissolved inorganic nitrogen (DIN) in Jiaozhou Bay (JZB). A total of 11 freshwater riverine sampling sites were selected at the river mouths and at waste water outfalls around JZB, while a total 23 Bay stations were established in JZB. Among them, 11 Bay stations were located near the 11 outfalls. Each land-sea sampling was conducted synchronously during a semi-tidal cycle. The contribution of NO3sbnd N, NO2sbnd N, NH4sbnd N, and dissolved organic nitrogen (DON) to TDN in land-based freshwater were similar to those in JZB seawater, while the contribution of the sum of NO3sbnd N and NO2sbnd N to TDN and the contribution of DON to TDN were about 3.2 and 4.1 times higher than the contribution of NH4sbnd N to TDN, respectively. These results showed that inputs of all land-based forms of nitrogen impact the DIN in seawater. Spatial distributions of DIN and DON, showing a gradual decrease from inner bay to the mouth of the bay, were negatively correlated with S in different seasons. In summer and winter, the ratio of DIN to DON in seawater (Rs) gradually decreased from the inner bay to the center of the bay, and the ratio of land-based DIN to DON (RL) was less than RS, indicating net transformation from land-based DON into marine DIN. However, in spring and autumn, the distribution of Rs was opposite to that in summer and winter, and RL was greater than RS, indicating net conversion from land-based DIN into marine DON. Throughout the whole year, net land-based DON was transformed into marine DIN. We provided direct evidence that the variation in DIN concentration in JZB was affected both by land-based TDN inputs and by their hydrodynamic transport and biogeochemical transformation processes.

  7. Direct analysis of δ13C 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 δ13C 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

  8. 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.; 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

  9. Dissolved organic nitrogen (DON) during batch denitrification of low concentrations of nitrate using suspended and attached biomass.

    PubMed

    Brandão, D N; Spanjers, H; van Lier, J B

    2015-01-01

    The occurrence and removal of dissolved organic nitrogen (DON) is an issue of increasing importance for the reclamation of treated wastewater. Effluent DON may act as a precursor of disinfection by-products during wastewater disinfection and may contribute to eutrophication of receiving surface waters. The aim of this study was to understand the effect of the post-denitrification process on final effluent DON (organic nitrogen filtered by 0.45 μm pore size) concentration to further gain knowledge on how to optimize denitrifying filtration, in order to reach the required discharge standards. To evaluate DON variation, denitrification batch experiments were carried out with suspended and attached biomass under different shear conditions. For both conditions, with suspended and attached biomass, DON concentration did not increase or decrease during the denitrification process with addition of an external carbon source. Moreover, the increase of shear rate did not affect the DON concentration. Apparently, there is no direct link between DON evolution and the denitrification process itself. PMID:26606082

  10. Influence of dissolved oxygen concentration on the start-up of the anammox-based process: ELAN®.

    PubMed

    Morales, N; Val del Río, A; Vázquez-Padín, J R; Gutiérrez, R; Fernández-González, R; Icaran, P; Rogalla, F; Campos, J L; Méndez, R; Mosquera-Corral, A

    2015-01-01

    The anammox-based process ELAN® was started-up in two different sequencing batch reactor (SBR) pilot plant reactors treating municipal anaerobic digester supernatant. The main difference in the operation of both reactors was the dissolved oxygen (DO) concentration in the bulk liquid. SBR-1 was started at a DO value of 0.4 mg O2/L whereas SBR-2 was started at DO values of 3.0 mg O2/L. Despite both reactors working at a nitrogen removal rate of around 0.6 g N/(L d), in SBR-1, granules represented only a small fraction of the total biomass and reached a diameter of 1.1 mm after 7 months of operation, while in SBR-2 the biomass was mainly composed of granules with an average diameter of 3.2 mm after the same operational period. Oxygen microelectrode profiling revealed that granules from SBR-2 where only fully penetrated by oxygen with DO concentrations of 8 mg O2/L while granules from SBR-1 were already oxygen penetrated at DO concentrations of 1 mg O2/L. In this way granules from SBR-2 performed better due to the thick layer of ammonia oxidizing bacteria, which accounted for up to 20% of all the microbial populations, which protected the anammox bacteria from non-suitable liquid media conditions. PMID:26247749

  11. 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.

  12. Influence of increased dissolved oxygen concentration on the formation of secondary metabolites by manumycin-producing Streptomyces parvulus.

    PubMed

    Kaiser, D; Onken, U; Sattler, I; Zeeck, A

    1994-05-01

    The influence of increased dissolved O2 concentrations (DOC) on cell growth and production of the secondary metabolite manumycin by a strain of Streptomyces parvulus (Tü 64) was investigated in a stirred tank fermentor. DOC is given as the O2 partial pressure (po2) in the gas phase in an equilibrium state with the liquid phase. Growth of S. parvulus was not influenced up to DOC equivalent to po2 = 1260 mbar. At po2 = 2205 mbar the maximum biomass concentration was lowered by 40%. Production of manumycin was markedly influenced by DOC and reached the maximal concentration at po2 = 315 mbar. At increased DOC three new metabolites were observed. Two of them, 64p-A and 64p-B, were identified as carboxamides, which represent the branched side chain of the manumycin molecule and a derivative with a shorter chain length. The third metabolite, 64p-C, was a manumycin derivative containing an aromatic ring system. Feeding of glycerol during the production phase increased the total yield and showed a similar effect of DOC. Since DOC has significant regulation effects on product formation and selectivity, it should be used as a major parameter in development strategies of aerobic microbial processes.

  13. The effect of using different 0.45 μm 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.

  14. Dissolved organic nitrogen (DON) during batch denitrification of low concentrations of nitrate using suspended and attached biomass.

    PubMed

    Brandão, D N; Spanjers, H; van Lier, J B

    2015-01-01

    The occurrence and removal of dissolved organic nitrogen (DON) is an issue of increasing importance for the reclamation of treated wastewater. Effluent DON may act as a precursor of disinfection by-products during wastewater disinfection and may contribute to eutrophication of receiving surface waters. The aim of this study was to understand the effect of the post-denitrification process on final effluent DON (organic nitrogen filtered by 0.45 μm pore size) concentration to further gain knowledge on how to optimize denitrifying filtration, in order to reach the required discharge standards. To evaluate DON variation, denitrification batch experiments were carried out with suspended and attached biomass under different shear conditions. For both conditions, with suspended and attached biomass, DON concentration did not increase or decrease during the denitrification process with addition of an external carbon source. Moreover, the increase of shear rate did not affect the DON concentration. Apparently, there is no direct link between DON evolution and the denitrification process itself.

  15. 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

  16. Estimation of Suspended and Dissolved Matter Concentration In Sea Water On Shelves By Satellite Remote Sensing

    NASA Astrophysics Data System (ADS)

    Pelevin, V.; Rostovtseva, V.

    Falling of rivers into the seas or surging in shallow aquatoria cause the violation of the balance between living and dead matter occurring in the open ocean ( Pelevin and Rostovtseva, 2001). That means in littoral arias the one-parameter model of sea waters optical properties developed for the open ocean (Pelevin and Rostovtseva, 1997) is not valid. We suggest to use the three-parameters model of light scattering and absorbing prop- erties of sea water for the most arias on shelves. The three parameters are: the coeffi- cient of light absorption by coloured matter at 500 nm (coloured matter includes both chlorophyll pigments and "yellow substance"), the coefficient of light absorption by suspended matter and the coefficient of light backscattering by suspended matter. For some specific shelf arias with coloured suspended matter we suggest to add the fourth parameter taking into account the spectral dependence of backscattering by suspended matter. The method of such type arias determination is also given. The algorithm of solution of the inverse problem of these parameters estimation using optical remote sensing data obtained from satellites is developed. It consists of two steps: the rough determination of the parameters values by some spectral characteris- tics and then the minimization of real and model spectra discrepancy. The suggested algorithm was used for spectral distribution of upward radiation mea- sured in the Black, Marmora and Baltic Seas. Comparison of the obtained results with some data of direct measurements carried out in these aquatoria proved the validity of the model for these shelf waters and showed the efficiency of the suggested approach. V.N.Pelevin and V.V.Rostovtseva , 1997, Estimation of lightscattering and lightabsorb- ing admixture concentration in open ocean waters of different types.- Atmospheric and Oceanic Optics, 10(9), 989-995. V.N.Pelevin and V.V.Rostovtseva, 2001, Modelling of optic- biological parameters of open ocean waters

  17. Estimation of Concentration and Bonding Environment of Water Dissolved in Common Solvents Using Near Infrared Absorptivity

    PubMed Central

    Dickens, Brian; Dickens, Sabine H.

    1999-01-01

    Integrated near infrared (NIR) absorbance has been used to determine the absorptivity of the υ2 + υ3 combination band of the asymmetric stretch (υ2) and the bending vibration (υ3) for water in several organic solvents. Absorptivity measured in this way is essentially constant across the absorption envelope and is found to be 336 L mol−1 cm−1 with a standard deviation of 4 L mol−1 cm−1 as estimated from a least squares fit of a straight line to data from water concentrations between 0.01 mol/L and 0.06 mol/L. Absorptivity measured from the peak maximum of the υ2 + υ3 combination band of water varies with the type of hydrogen bonding of the water molecule because the shape of the NIR absorption envelope changes with the hydrogen bonding. Because the integrated NIR absorptivity of the υ2 + υ3 combination band of water is essentially constant across the absorption envelope, the NIR absorption envelope reflects the distribution of hydrogen bonding of the water. The shape and location of the absorption envelope appear to be governed mostly by the number of hydrogen bonds from the water molecules to easily polarized atoms. Water that is a donor in hydrogen bonds to atoms which are not easily polarized (such as the oxygen of a typical carbonyl group) absorbs near 5240 cm−1 to 5260 cm−1. Water that donates one hydrogen bond to an easily polarized atom (such as a water molecule oxygen) absorbs near 5130 cm−1 to 5175 cm−1, and water that donates two hydrogen bonds to easily polarized atoms is estimated to absorb near 5000 cm−1 to 5020 cm−1. Water donating two hydrogen bonds to other water molecules may be said to be in a water-like environment. In no case does a small amount of water absorbed in a host material appear to have a water-like environment.

  18. 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, William Jeffrey; Quick, Annika; Farrell, Tiffany B.; Benner, Shawn G.; Feris, Kevin P.; Tonina, Daniele

    2015-04-01

    The majority of chemical reactions in riverine systems occur within the hyporheic zone (HZ). Hyporheic exchange, flow into and out of the hyporheic zone, represents a primary control over those reactions because the flow rate will determine the residence time and amount of chemical constituents in the HZ. Hyporheic flow can be conceptualized as discreet streamlines that collectively represent a broad distribution of residence times. Within this context, dissolved oxygen (DO) concentration becomes a primary indicator of the redox and biochemical state of the HZ including, for example, the fate of carbon, contaminant behavior, nutrient cycling, stream DO levels and nitrous oxide (N2O) production. River systems have been identified as a significant source of N2O emissions, contributing an estimated 10% of anthropogenically generated N2O. The primary biochemical transformations that lead to N2O production are nitrification (NH4+ to NO3-) and denitrification (NO3- to N2) reactions that are mediated by microbes living in the HZ. Current theory describes a process in which DO enters the stoss side of the HZ and is consumed by respiration and nitrification in the upstream, oxic portion of the streamlines leading to a progressive partitioning of the HZ from oxic to anoxic. This conceptualization, however, has not been well validated in a physical sense, due to inherent difficulties associated with measuring chemical concentrations in the HZ. To test current theory, we measured HZ DO concentrations, in a large-scale flume experiment, almost continuously for five months using a multiplexed optical network and a precision robotic surface probe system. We were able to measure DO at higher spatial and temporal resolution than has been previously demonstrated. These measurements, coupled with detailed numerical modeling of HZ flowlines, allowed us to map HZ DO concentrations spatially and over time. Our findings validate the models that describe the consumption of DO through

  19. Changes in Dissolved Carbon and Nitrogen Concentrations Along a Hill Slope Flow Path in Siberian Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Theberge, J.; Schade, J. D.; Fiske, G. J.; Loranty, M. M.; Zimov, N.

    2014-12-01

    Permafrost soils contain a large pool of carbon that has accumulated for thousands of years, and remains frozen in organic form. As climate warms, permafrost thaw will lead to active cycling of old organic materials, possibly leading to release of carbon to the atmosphere or to export of organic carbon to the oceans. Organic matter breakdown may also release reactive forms of nitrogen, which may significantly impact ecosystem processes. We currently have limited understanding of where in Arctic landscapes breakdown of organic materials will occur, or whether this will influence the strength and direction of feedback loops that may occur in response to changes in C and N cycling. In this work, we studied changes in dissolved forms of C and N in water moving down a hillslope linking upland terrestrial environments to lowland floodplains within the Kolyma River watershed in the East Siberian Arctic tundra in July, 2014. The hill slope consisted of a mosaic of dry and saturated soils, generally with drier soils on the periphery and saturated soils in and around pools or short reaches of flowing surface water. We established transects at regular intervals downslope, installing wells in the center of the flow path and 5 meters laterally north and south. We analyzed pore-water from wells and surface water from pools at each transect for dissolved organic carbon (DOC) and total dissolved nitrogen (TDN). We used patterns in water chemistry to develop a conceptual model for biogeochemical changes as water moved downslope through soils, pools and runs. Pore-water analysis showed significantly higher DOC in lateral wells than in surface water and pore water in the center of the flow path, suggesting possible processing of C as water moves laterally towards the valley bottom. In contrast, DOC increased modestly down the center of the flow path, suggesting either higher hydrologic inputs or production of new DOC downslope. TDN concentration decreased downslope, suggesting

  20. 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 μmol/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 μmol/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.

  1. Response of dissolved carbon and nitrogen concentrations to moderate nutrient additions in a tropical montane forest of south Ecuador

    NASA Astrophysics Data System (ADS)

    Velescu, Andre; Valarezo, Carlos; Wilcke, Wolfgang

    2016-05-01

    In the past two decades, the tropical montane rain forests in south Ecuador experienced increasing deposition of reactive nitrogen mainly originating from Amazonian forest fires, while Saharan dust inputs episodically increased deposition of base metals. Increasing air temperature and unevenly distributed rainfall have allowed for longer dry spells in a perhumid ecosystem. This might have favored mineralization of dissolved organic matter (DOM) by microorganisms and increased nutrient release from the organic layer. Environmental change is expected to impact the functioning of this ecosystem belonging to the biodiversity hotspots of the Earth. In 2007, we established a nutrient manipulation experiment (NUMEX) to understand the response of the ecosystem to moderately increased nutrient inputs. Since 2008, we have continuously applied 50 kg ha-1 a-1 of nitrogen (N), 10 kg ha-1 a-1 of phosphorus (P), 50 kg + 10 kg ha-1 a-1 of N and P and 10 kg ha-1 a-1 of calcium (Ca) in a randomized block design at 2000 m a.s.l. in a natural forest on the Amazonia-exposed slopes of the south Ecuadorian Andes. Nitrogen concentrations in throughfall increased following N+P additions, while separate N amendments only increased nitrate concentrations. Total organic carbon (TOC) and dissolved organic nitrogen (DON) concentrations showed high seasonal variations in litter leachate and decreased significantly in the P and N+P treatments, but not in the N treatment. Thus, P availability plays a key role in the mineralization of DOM. TOC/DON ratios were narrower in throughfall than in litter leachate but their temporal course did not respond to nutrient amendments. Our results revealed an initially fast, positive response of the C and N cycling to nutrient additions which declined with time. TOC and DON cycling only change if N and P supply are improved concurrently, while NO3-N leaching increases only if N is separately added. This indicates co-limitation of the microorganisms by N and P

  2. Concentrations and fluxes of dissolved uranium in the Yellow River estuary: seasonal variation and anthropogenic (Water-Sediment Regulation Scheme) impact.

    PubMed

    Juanjuan, Sui; Zhigang, Yu; Bochao, Xu; Wenhua, Dong; Dong, Xia; Xueyan, Jiang

    2014-02-01

    The Water-Sediment Regulation Scheme (WSRS) of the Yellow River is a procedure implemented annually from June to July to expel sediments deposited in Xiaolangdi and other large middle-reach reservoirs and to scour the lower reaches of the river, by controlling water and sediment discharges. Dissolved uranium isotopes were measured in river waters collected monthly as well as daily during the 2010 WSRS (June 19-July 16) from Station Lijin (a hydrologic station nearest to the Yellow River estuary). The monthly samples showed dissolved uranium concentrations of 3.85-7.57 μg l(-1) and (234)U/(238)U activity ratios of 1.24-1.53. The concentrations were much higher than those reported for other global major rivers, and showed seasonal variability. Laboratory simulation experiments showed significant uranium release from bottom and suspended sediment. The uranium concentrations and activity ratios differed during the two stages of the WSRS, which may reflect desorption/dissolution of uranium from suspended river sediments of different origins. An annual flux of dissolved uranium of 1.04 × 10(8) g y(-1) was estimated based on the monthly average water discharge and dissolved uranium concentration in the lower reaches of the Yellow River. The amount of dissolved uranium (2.65 × 10(7) g) transported from the Yellow River to the sea during the WSRS constituted about 1/4 of the annual flux.

  3. Dissolved low-molecular weight thiol concentrations from the U.S. GEOTRACES North Atlantic Ocean zonal transect

    NASA Astrophysics Data System (ADS)

    Swarr, Gretchen J.; Kading, Tristan; Lamborg, Carl H.; Hammerschmidt, Chad R.; Bowman, Katlin L.

    2016-10-01

    Low-molecular weight thiols, including cysteine and glutathione, are biomolecules involved in a variety of metabolic pathways and act as important antioxidant and metal buffering agents. In this last capacity, they represent a potential mechanism for modulating the bioavailability and biogeochemistry of many trace elements in the ocean, particularly for chalcophilic elements (e.g., Cu, Zn, Cd, Ag and Hg). For this reason, and in the context of the international GEOTRACES program that seeks to understand the biogeochemistry of trace elements in the ocean, we measured the concentration of individual dissolved low-molecular weight thiols during the U.S. GEOTRACES North Atlantic Zonal Transect (USGNAZT). Only two thiols were identified, cysteine and glutathione, in contrast to results from the northeast subarctic Pacific Ocean, where the dipeptides glycine-cysteine and arginine-cysteine were also present and γ-glutamylcysteine was dominant. Concentrations of cysteine and glutathione in the North Atlantic Ocean were lower than in the Pacific and ranged from below detection ( 0.01 nM) to 0.61 nM of cysteine and up to 1.0 nM of glutathione, with cysteine generally more abundant than glutathione. Vertical profiles of cysteine and glutathione were broadly consistent with their biological production, being more abundant in surface water and usually below detection at depths greater than about 200 m. Subsurface concentration maxima, often co-incident with the deep chlorophyll maximum, were frequently observed but not universal. We conclude that cysteine and glutathione do not make up significant portions of complexation capacity for Cu and Zn in the upper open ocean but could be important for Cd, Hg, and potentially other chalcophiles. Extremely low concentrations of cysteine and glutathione in deep water suggest that higher molecular-weight thiols are a more important ligand class for chalcophiles in that portion of the ocean.

  4. Effects of dissolved organic matter (DOM) at environmentally relevant carbon concentrations on atrazine degradation by Chelatobacter heintzii SalB.

    PubMed

    Cheyns, Karlien; Calcoen, Jasper; Martin-Laurent, Fabrice; Bru, David; Smolders, Erik; Springael, Dirk

    2012-09-01

    The dissolved organic matter (DOM) is the term used for organic components of natural origin present in the soil solution and is probably the most available C-source that primes microbial activity in subsoils. Contrasting effects of organic C components on pesticide degradation have been reported; however, most studies have used model organic compounds with compositions and concentrations which differ substantially from those found in the environment. Degradation of atrazine (AT) by Chelatobacter heintzii SalB was monitored in liquid batch assays in the absence or presence of well-defined model C compounds (glucose, gluconate and citrate) as model DOM (mDOM) or complex, less-defined, environmental DOM solutions (eDOM: isolated humic substances, soil and plant residue extracts) at environmentally relevant concentrations. Glucose significantly increased AT degradation rate by more than a factor of 8 at and above 2.5 mg C L( - 1). Optical density measurements showed that this stimulation is related to microbial growth. Gluconate and citrate had no effects unless at non-relevant concentrations (1,000 mg DOC L( - 1)) at which stimulations (gluconate) or inhibitions (citrate) were found. The effects of eDOM added at 10 mg DOC L( - 1) on AT degradation were generally small. The AT degradation time was reduced by factors 1.4-1.9 in the presence of humic acids and eDOM from soils amended with plant residues; however, no effects were found for fulvic acids or eDOM from a soil leachate solution or extracted from unamended peat or forest soil. In conclusion, DOM supplied as both mDOM and eDOM did not inhibit AT degradation at environmentally relevant concentrations, and stimulation can be found for selected DOM samples and this is partly related to its effect on growth. PMID:22159734

  5. Dissolved trace element concentrations in the East River-Long Island Sound system: relative importance of autochthonous versus allochthonous sources.

    PubMed

    Buck, Nathaniel J; Gobler, Christopher J; Sañudo-Wilhelmy, Sergio A

    2005-05-15

    Dissolved trace metal (Ag, Cd, Cu, Fe, Ni, Pb, and Zn), inorganic nutrient (NO3, NH4, PO4, H4SiO4), and DOC concentrations were measured at 43 stations during low (July 2000) and high (April 2001) river discharge conditions in surface waters of Long Island Sound (LIS). To evaluate the impact of fluvial sources to the total metal budget of the sound, samples were collected from major tributaries discharging into LIS (Thames, Quinnipiac, Housatonic, Connecticut, and East Rivers). To compare LIS with other coastal embayments, samples were also collected from five LIS coastal embayments (Manhassett Bay, Huntington Harbor, Oyster Bay, Hempstead Harbor, and Port Jefferson Harbor), which are monitored by the U.S. National Status and Trends Program. Metal and nutrient distributions identified two biogeochemical regimes within LIS: an area of relatively high nutrient and metal concentrations in the East River/Narrows region in western LIS and an area in the eastern region of the sound that had comparatively lower concentrations. Mass balance estimates indicated that, during low flow conditions, the East River was the dominant allochthonous source of most trace metals (Ag, Cd, Cu, Ni, Zn) and inorganic nutrients (NO3 and PO4); during high flow conditions, the most influential source of these constituents was the Connecticut River. Mass balance estimates also evidenced a large autochthonous source of Cu, Ni, and Zn, as their spatial distributions displayed elevated concentrations away from point sources such as the East River. Principal component analysis suggested that metal and nutrient distributions in the LIS system were influenced by different seasonal processes: remobilization from contaminated sediments, anthropogenic inputs from sewage discharges and phytoplankton scavenging during the spring freshet, and benthic remobilization during summer conditions.

  6. Modeling hourly dissolved oxygen concentration (DO) using two different adaptive neuro-fuzzy inference systems (ANFIS): a comparative study.

    PubMed

    Heddam, Salim

    2014-01-01

    This article presents a comparison of two adaptive neuro-fuzzy inference systems (ANFIS)-based neuro-fuzzy models applied for modeling dissolved oxygen (DO) concentration. The two models are developed using experimental data collected from the bottom (USGS station no: 420615121533601) and top (USGS station no: 420615121533600) stations at Klamath River at site KRS12a nr Rock Quarry, Oregon, USA. The input variables used for the ANFIS models are water pH, temperature, specific conductance, and sensor depth. Two ANFIS-based neuro-fuzzy systems are presented. The two neuro-fuzzy systems are: (1) grid partition-based fuzzy inference system, named ANFIS_GRID, and (2) subtractive-clustering-based fuzzy inference system, named ANFIS_SUB. In both models, 60 % of the data set was randomly assigned to the training set, 20 % to the validation set, and 20 % to the test set. The ANFIS results are compared with multiple linear regression models. The system proposed in this paper shows a novelty approach with regard to the usage of ANFIS models for DO concentration modeling.

  7. Biological phosphorus and nitrogen removal in sequencing batch reactors: effects of cycle length, dissolved oxygen concentration and influent particulate matter.

    PubMed

    Ginige, Maneesha P; Kayaalp, Ahmet S; Cheng, Ka Yu; Wylie, Jason; Kaksonen, Anna H

    2013-01-01

    Removal of phosphorus (P) and nitrogen (N) from municipal wastewaters is required to mitigate eutrophication of receiving water bodies. While most treatment plants achieve good N removal using influent carbon (C), the use of influent C to facilitate enhanced biological phosphorus removal (EBPR) is poorly explored. A number of operational parameters can facilitate optimum use of influent C and this study investigated the effects of cycle length, dissolved oxygen (DO) concentration during aerobic period and influent solids on biological P and N removal in sequencing batch reactors (SRBs) using municipal wastewaters. Increasing cycle length from 3 to 6 h increased P removal efficiency, which was attributed to larger portion of N being removed via nitrite pathway and more biodegradable organic C becoming available for EBPR. Further increasing cycle length from 6 to 8 h decreased P removal efficiencies as the demand for biodegradable organic C for denitrification increased as a result of complete nitrification. Decreasing DO concentration in the aerobic period from 2 to 0.8 mg L(-1) increased P removal efficiency but decreased nitrification rates possibly due to oxygen limitation. Further, sedimented wastewater was proved to be a better influent stream than non-sedimented wastewater possibility due to the detrimental effect of particulate matter on biological nutrient removal.

  8. Modeling hourly dissolved oxygen concentration (DO) using two different adaptive neuro-fuzzy inference systems (ANFIS): a comparative study.

    PubMed

    Heddam, Salim

    2014-01-01

    This article presents a comparison of two adaptive neuro-fuzzy inference systems (ANFIS)-based neuro-fuzzy models applied for modeling dissolved oxygen (DO) concentration. The two models are developed using experimental data collected from the bottom (USGS station no: 420615121533601) and top (USGS station no: 420615121533600) stations at Klamath River at site KRS12a nr Rock Quarry, Oregon, USA. The input variables used for the ANFIS models are water pH, temperature, specific conductance, and sensor depth. Two ANFIS-based neuro-fuzzy systems are presented. The two neuro-fuzzy systems are: (1) grid partition-based fuzzy inference system, named ANFIS_GRID, and (2) subtractive-clustering-based fuzzy inference system, named ANFIS_SUB. In both models, 60 % of the data set was randomly assigned to the training set, 20 % to the validation set, and 20 % to the test set. The ANFIS results are compared with multiple linear regression models. The system proposed in this paper shows a novelty approach with regard to the usage of ANFIS models for DO concentration modeling. PMID:24057665

  9. 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.

  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 (νK 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 νK was similar to the value found using PMD. Experiments were performed at three temperatures, and a plot of ln (νK) 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.

  11. 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

  12. Dissolved heavy metal concentrations of the Kralkızı, Dicle and Batman dam reservoirs in the Tigris River basin, Turkey.

    PubMed

    Varol, Memet

    2013-10-01

    Water samples were collected at monthly intervals during 1 year of monitoring from Kralkızı, Dicle and Batman dam reservoirs in the Tigris River basin to assess the concentrations of dissolved heavy metals and to determine their spatial and seasonal variations. The results indicated that dissolved heavy metal concentrations in the reservoirs were very low, reflecting the natural background levels. The lowest total metal concentrations in the three dam reservoirs were detected at sampling sites close to the dam wall. However, the highest total concentrations were observed at sites, which are located at the entrance of the streams to the reservoirs. Fe, Cr and Ni were the most abundant elements in the reservoirs, whereas Cd and As were the less abundant. The mean concentrations of dissolved metals in the dam reservoirs never exceeded the maximum permitted concentrations established by EC (European Community), WHO and USEPA drinking water quality guidelines. All heavy metals showed significant seasonal variations. As, Cd, Cr, Cu, Fe, Ni and Pb displayed higher values in the dry season, while higher values for Zn in the wet season. Cluster analysis grouped all ten sampling sites into three clusters. Clusters 1 and 2, and cluster 3 corresponded to relatively low polluted and moderate polluted regions, respectively. PCA/FA demonstrated the dissolved metals in the dam reservoirs controlled by natural sources.

  13. Water Mass Distribution and Particle Flux in the Arctic Ocean From Dissolved 10Be and 9Be Concentrations

    NASA Astrophysics Data System (ADS)

    Frank, M.; Porcelli, D.; Andersson, P.; Halliday, A. N.; Kubik, P. W.; Hattendorf, B.; Guenther, D.

    2002-12-01

    The Arctic Ocean basin is confined by landmasses similar to the Mediterranean. There is only little deep water formed seasonally on the shelves of the Arctic Ocean despite the low temperatures. This is due to a freshwater lid at the surface which originates from the Arctic rivers. The deeper Arctic Ocean water masses can thus only be renewed at comparatively low rates through the only deep connection to the Atlantic Ocean, the Fram Strait. At the same time the biogenic particulate fluxes in the central Arctic Ocean are very low due to perennial sea ice cover and the organic matter produced in the surface waters is remineralised efficiently. Detrital particle fluxes from either eolian or riverine sources are also very low. We will present the first combined dissolved 10Be (cosmogenic) and 9Be (continental sources) depth profiles from water samples of the major deep basins of the Arctic Ocean collected during the Swedish Arctic Ocean 2001 expedition. Be is 5-10 times less particle-reactive than other previously investigated radionuclides such as Th or Pa and should therefore even at the relatively low Arctic Ocean renewal rates serve as a quasi-conservative tracer for different origins of water masses (Atlantic Ocean/Norwegian Sea, Pacific Ocean, Arctic Shelves). 9Be and Nd isotope analyses provide complementary information on the pathways of dissolved material originating from the Arctic continents. Results obtained ten years ago at similar locations as in our study indicated a uniform distribution of 10Be at low values of 500 +/- 100 atoms/g suggesting restricted input and efficient homogenisation. In contrast, our new results show that in 2001 the inflowing waters from the Atlantic are traced by 10Be concentrations of up to 1100 atoms/g. In addition, the surface concentrations vary considerably. It will be discussed wether this is a consequence of a seasonal/decadal variability in the distribution of surface water masses, which has been deduced from oceanographic

  14. Effects of climate change on stream temperature, dissolved oxygen, and sediment concentration in the Sierra Nevada in California

    NASA Astrophysics Data System (ADS)

    Ficklin, Darren L.; Stewart, Iris T.; Maurer, Edwin P.

    2013-05-01

    Warmer temperatures are expected to raise mountain stream temperatures, affecting water quality and ecosystem health. We demonstrate the importance of climate-driven changes in hydrology as fundamental to understanding changes in the local water quality. In particular, we focus on changes in stream temperature, dissolved oxygen (DO) concentrations, and sediment transport in mountainous, snowmelt-dominated, and water-limited systems, using the Sierra Nevada as our case study. Downscaled output from an ensemble of general circulation model projections for the A2 (higher greenhouse gas) emission scenario was used to drive the Soil and Water Assessment Tool with a new integrated stream temperature model on the subbasin scale. Spring and summer stream temperature increase by 1°C-5.5°C, with varying increases among subbasins. The highest projected stream temperatures are in the low-elevation subbasins of the southern Sierra Nevada, while the northern Sierra Nevada, with distinct impacts on snowmelt and subsurface flow contributions to streamflow, shows moderated increases. The spatial pattern of stream temperature changes was the result of differences in surface and subsurface hydrologic, snowmelt, and air temperature changes. Concurrent with stream temperature increases and decreases in spring and summer flows, simulations indicated decreases in DO (10%) and sediment (50%) concentrations by 2100. Stream temperature and DO concentrations for several major streams decline below survival thresholds for several native indicator species. These results highlight that climatic changes in water-limited mountain systems may drive changes in water quality that have to be understood on the reach scale for developing adaptive management options.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  16. Effect of phytoremediation on concentrations of benzene, toluene, naphthalene, and dissolved oxygen in groundwater at a former manufactured gas plant site, Charleston, South Carolina, USA, 1998–2014

    USGS Publications Warehouse

    Landmeyer, James E.; Effinger, Thomas N.

    2016-01-01

    Concentrations of benzene, toluene, naphthalene, and dissolved oxygen in groundwater at a former manufactured gas plant site near Charleston, South Carolina, USA, have been monitored since the installation of a phytoremediation system of hybrid poplar trees in 1998. Between 2000 and 2014, the concentrations of benzene, toluene, and naphthalene (BT&N) in groundwater in the planted area have decreased. For example, in the monitoring well containing the highest concentrations of BT&N, benzene concentrations decreased from 10,200 µg/L to less than 4000 µg/L, toluene concentrations decreased from 2420 µg/L to less than 20 µg/L, and naphthalene concentrations decreased from 6840 µg/L to less than 3000 µg/L. Concentrations of BT&N in groundwater in all wells were observed to be lower during the summer months relative to the winter months of a particular year during the first few years after installing the phytoremediation system, most likely due to increased transpiration and contaminant uptake by the hybrid poplar trees during the warm summer months; this pathway of uptake by trees was confirmed by the detection of benzene, toluene, and naphthalene in trees during sampling events in 2002, and later in the study in 2012. These data suggest that the phytoremediation system affects the groundwater contaminants on a seasonal basis and, over multiple years, has resulted in a cumulative decrease in dissolved-phase contaminant concentrations in groundwater. The removal of dissolved organic contaminants from the aquifer has resulted in a lower demand on dissolved oxygen supplied by recharge and, as a result, the redox status of the groundwater has changed from anoxic to oxic conditions. This study provides much needed information for water managers and other scientists on the viability of the long-term effectiveness of phytoremediation in decreasing groundwater contaminants and increasing dissolved oxygen at sites contaminated by benzene, toluene, and naphthalene.

  17. 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.

  18. 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.

  19. Water uptake and growth of cucumber plants (Cucumis sativus L.) under control of dissolved O2 concentration in hydroponics.

    PubMed

    Yoshida, S; Kitano, M; Eguchi, H

    1996-12-01

    Dissolved O2 concentration ([O2]) in nutrient solution was controlled at 0.01, 0.10 and 0.20 mM with accuracy of +/- 0.005 mM in a newly developed hydroponic system, and the effects of [O2] on water uptake and growth of cucumber plants (Cucumis sativus L.) were analyzed. For evaluating water uptake rate under the control of [O2], water flux at the stem base was measured on-line with +/-5% in accuracy, 1 mg s-1 in resolution and 1 min in time constant by heat flux control (HFC) method. Water uptake rate was drastically increased by lighting to the plant at each [O2], and water uptake per day was depressed in proportion to decrease in [O2]. In the plants grown for 10 days, leaf area, fresh weight and dry weight of leaves decreased at lower [O2], while stem length and number of leaves were scarcely affected. These facts suggest that membrane permeability of root cells reduces at lower [O2] through respiration-dependent processes, and growth is inhibited through leaf turgor loss caused by the depressed water uptake of roots in O2-deficient nutrient solution in hydroponics.

  20. Contribution of groundwater discharge to the coastal dissolved nutrients and trace metal concentrations in Majorca Island: karstic vs detrital systems.

    PubMed

    Tovar-Sánchez, Antonio; Basterretxea, Gotzon; Rodellas, Valentí; Sánchez-Quiles, David; García-Orellana, Jordi; Masqué, Pere; Jordi, Antoni; López, José M; Garcia-Solsona, Ester

    2014-10-21

    Submarine groundwater discharge (SGD) and derived nutrient (NO2(-), NO3(-), NH4(+), PO4(3-), and SiO2) and trace element (Cd, Co, Cu, Fe, Mo, Ni, Pb, V and Zn) loadings to the coastal sea were systematically assessed along the coast of Majorca Island, Spain, in a general survey around the island and in three representative coves during 2010. We estimated that brackish water discharges through the shoreline are important contributors to the DIN, SiO2, Fe, and Zn budgets of the nearshore waters. Furthermore, our results showed that SGD-derived elements are conditioned by the hydrogeological formations of the aquifer and discharge type. Thus, while rapid discharges through karstic conduits are enriched in SiO2 and Zn, the large detrital aquifers of the island typically present enhanced concentrations of Fe. The estimated total annual inputs of chemicals constituents discharged by SGD to the coastal waters were as follows: DIN: 610 × 10(3) kg yr(-1), SiO2: 1400 × 10(3) kg yr(-1), Fe: 3.2 × 10(3) kg yr(-1), and Zn: 2.0 × 10(3) kg yr(-1). Our results provide evidence that SGD is a major contributor to the dissolved pool of inorganic nutrients and trace metals in the nearshore waters of Majorca.

  1. Contribution of groundwater discharge to the coastal dissolved nutrients and trace metal concentrations in Majorca Island: karstic vs detrital systems.

    PubMed

    Tovar-Sánchez, Antonio; Basterretxea, Gotzon; Rodellas, Valentí; Sánchez-Quiles, David; García-Orellana, Jordi; Masqué, Pere; Jordi, Antoni; López, José M; Garcia-Solsona, Ester

    2014-10-21

    Submarine groundwater discharge (SGD) and derived nutrient (NO2(-), NO3(-), NH4(+), PO4(3-), and SiO2) and trace element (Cd, Co, Cu, Fe, Mo, Ni, Pb, V and Zn) loadings to the coastal sea were systematically assessed along the coast of Majorca Island, Spain, in a general survey around the island and in three representative coves during 2010. We estimated that brackish water discharges through the shoreline are important contributors to the DIN, SiO2, Fe, and Zn budgets of the nearshore waters. Furthermore, our results showed that SGD-derived elements are conditioned by the hydrogeological formations of the aquifer and discharge type. Thus, while rapid discharges through karstic conduits are enriched in SiO2 and Zn, the large detrital aquifers of the island typically present enhanced concentrations of Fe. The estimated total annual inputs of chemicals constituents discharged by SGD to the coastal waters were as follows: DIN: 610 × 10(3) kg yr(-1), SiO2: 1400 × 10(3) kg yr(-1), Fe: 3.2 × 10(3) kg yr(-1), and Zn: 2.0 × 10(3) kg yr(-1). Our results provide evidence that SGD is a major contributor to the dissolved pool of inorganic nutrients and trace metals in the nearshore waters of Majorca. PMID:25215451

  2. 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

  3. Effect of the spatiotemporal variability of rainfall inputs in water quality integrated catchment modelling for dissolved oxygen concentrations

    NASA Astrophysics Data System (ADS)

    Moreno Ródenas, Antonio Manuel; Cecinati, Francesca; ten Veldhuis, Marie-Claire; Langeveld, Jeroen; Clemens, Francois

    2016-04-01

    Maintaining water quality standards in highly urbanised hydrological catchments is a worldwide challenge. Water management authorities struggle to cope with changing climate and an increase in pollution pressures. Water quality modelling has been used as a decision support tool for investment and regulatory developments. This approach led to the development of integrated catchment models (ICM), which account for the link between the urban/rural hydrology and the in-river pollutant dynamics. In the modelled system, rainfall triggers the drainage systems of urban areas scattered along a river. When flow exceeds the sewer infrastructure capacity, untreated wastewater enters the natural system by combined sewer overflows. This results in a degradation of the river water quality, depending on the magnitude of the emission and river conditions. Thus, being capable of representing these dynamics in the modelling process is key for a correct assessment of the water quality. In many urbanised hydrological systems the distances between draining sewer infrastructures go beyond the de-correlation length of rainfall processes, especially, for convective summer storms. Hence, spatial and temporal scales of selected rainfall inputs are expected to affect water quality dynamics. The objective of this work is to evaluate how the use of rainfall data from different sources and with different space-time characteristics affects modelled output concentrations of dissolved oxygen in a simplified ICM. The study area is located at the Dommel, a relatively small and sensitive river flowing through the city of Eindhoven (The Netherlands). This river stretch receives the discharge of the 750,000 p.e. WWTP of Eindhoven and from over 200 combined sewer overflows scattered along its length. A pseudo-distributed water quality model has been developed in WEST (mikedhi.com); this is a lumped-physically based model that accounts for urban drainage processes, WWTP and river dynamics for several

  4. 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.

  5. Effects of dissolved organic carbon and second substrates on the biodegradation of organic compounds at low concentrations

    SciTech Connect

    Schmidt, S.K.; Alexander, M.

    1985-04-01

    Pseudomonas acidovorans and Pseudomonas sp. strain ANL but not Salmonella typhimurium grew in an inorganic salts solution. The growth of P. acidovorans in this solution was not enhanced by the addition of 2.0 ..mu..g of phenol per liter, but the phenol was mineralized. Mineralization of 2.0 ..mu..g of phenol per liter by P. acidovorans was delayed 16 h by 70 ..mu..g of acetate per liter, and the delay was lengthened by increasing acetate concentrations, whereas phenol and acetate were utilized simultaneously at concentrations of 2.0 and 13 ..mu..g/liter, respectively. Growth of Pseudomonas sp. in the inorganic salts solution was not affected by the addition of 3.0 ..mu..g each of glucose and aniline per liter, nor was mineralization of the two compounds detected during the initial period of growth. However, mineralization of both substrates by this organism occurred simultaneously during the latter phases of growth and after growth had ended at the expense of the uncharacterized dissolved organic compounds in the salts solution. In contrast, when Pseudomonas sp. was grown in the salts solution supplemented with 300 ..mu..g each of glucose and aniline, the sugar was mineralized first, and aniline was mineralized only after much of the glucose carbon was converted to CO/sub 2/. S. typhimurium failed to multiply in the salts solution with 1.0 ..mu..g of glucose per liter. It grew slightly but mineralized little of the sugar at 5.0 ..mu..g/liter, but its population density rose at 10 ..mu..g of glucose per liter or higher. The hexose could be mineralized at 0.5 ..mu..g/liter, however, if the solution contained 5.0 mg of arabinose per liter.

  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. 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....

  8. Mercury, monomethyl mercury, and dissolved organic carbon concentrations in surface water entering and exiting constructed wetlands treated with metal-based coagulants, Twitchell Island, California

    USGS Publications Warehouse

    Stumpner, Elizabeth B.; Kraus, Tamara E.C.; Fleck, Jacob A.; Hansen, Angela M.; Bachand, Sandra M.; Horwath, William R.; DeWild, John F.; Krabbenhoft, David P.; Bachand, Philip A.M.

    2015-09-02

    Following coagulation, but prior to passage through the wetland cells, coagulation treatments transferred dissolved mercury and carbon to the particulate fraction relative to untreated source water: at the wetland cell inlets, the coagulation treatments decreased concentrations of filtered total mercury by 59–76 percent, filtered monomethyl mercury by 40–70 percent, and dissolved organic carbon by 65–86 percent. Passage through the wetland cells decreased the particulate fraction of mercury in wetland cells that received coagulant-treated water. Changes in total mercury, monomethyl mercury, and dissolved organic carbon concentrations resulting from wetland passage varied both by treatment and season. Despite increased monomethyl mercury in the filtered fraction during wetland passage between March and August, the coagulation-wetland systems generally decreased total mercury (filtered plus particulate) and monomethyl mercury (filtered plus particulate) concentrations relative to source water. Coagulation—either alone or in association with constructed wetlands—could be an effective way to decrease concentrations of mercury and dissolved organic carbon in surface water as well as the bioavailability of mercury in the Sacramento–San Joaquin Delta.

  9. Contrasting distributions of dissolved gaseous mercury concentration and evasion in the North Pacific Subarctic Gyre and the Subarctic Front

    NASA Astrophysics Data System (ADS)

    Kim, Hyunji; Rhee, Tae Siek; Hahm, Doshik; Hwang, Chung Yeon; Yang, Jisook; Han, Seunghee

    2016-04-01

    The distribution of dissolved gaseous mercury (DGM) and the oxidation-reduction processes of mercury (Hg) in the surface and subsurface ocean are currently understudied despite their importance in ocean-atmosphere interactions. We investigated the Hg(0) evasion and the DGM distribution at water depths of 2-500 m in the Subarctic Front, Western Subarctic Gyre, and Bering Sea of the Northwestern Pacific. The mean DGM concentration in the surface mixed water (<10 m) and the mean Hg(0) evasion flux were significantly higher in the Subarctic Front (125±5.0 fM and 15 pmol m-2 h-1, respectively), which typically has lower nutrient levels and higher primary production, than in the Western Subarctic Gyre and the Bering Sea (74±18 fM and 3.2±1.2 pmol m-2 h-1, respectively). The variation in the chlorophyll-a concentration and extracellular protease activity predicted 54% and 48% of the DGM variation, respectively, in the euphotic zone (2-50 m). The DGM concentration in aphotic intermediate water (415±286 fM) was positively correlated to the apparent oxygen utilization (AOU; r2=0.94 and p<0.001 for the Western Subarctic Gyre and the Bering Sea; r2=0.61 and p=0.01 for the Subarctic Front), emphasizing the importance of microbial oxidation of organic matter. The DGM-to-AOU ratio in aphotic water was significantly (p<0.05, ANCOVA) higher at the Western Subarctic Gyre and Bering Sea sites (2.5±0.14) than the ratio at the Subarctic Front sites (0.89±0.27) that mainly consisted of newly formed North Pacific Intermediate Water. The overall results imply that variation of DGM and Hg(0) evasion is closely linked to primary production in euphotic water and organic remineralization in aphotic intermediate water. The oceanic alterations in these factors may induce significant modification in Hg redox speciation in the Northwestern Pacific.

  10. 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...

  11. Using in-situ spectrophotometric sensors to monitoring dissolved organic carbon concentration: our S::CAN experience

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Dissolved organic carbon, (DOC), is the component of the organic carbon that can pass through a membrane filter, with the accepted maximum pore size of 0.7 μm. There is growing interest in high resolution time series of such data e.g. heterotrophic respiration of DOC in freshwater systems can fuel atmospheric CO2 efflux so observing variation in DOC concentration, [DOC], is meaningful. Field deployable sensors, capable of measuring [DOC] on a continuous basis, have the potential to provide us with a far higher resolution time series data than we can obtain through manual sampling. At a catchment area draining Europe's largest windfarm, Whitelee, we have deployed an S::CAN Spectrolyser. This device scans wavelengths from 200 to 735nm, generating a spectral fingerprint and then, using an inbuilt algorithm, returns a value for the DOC concentration, termed DOC-equivalent, [DOC-eq]. The Spectrolyser also estimates other parameters such as total organic carbon and the true colour of the water. Unfortunately, our field Spectrolyser [DOC] are different from lab based measurement of [DOC] of the same field filtered samples (measured using a Thermalox high temperature catalytic oxidation system). Comparing 28 lab measured [DOC] with Spectrolyser [DOC-eq] shows an average difference of 7.6 mg/l C. Here we discuss our interpretation of why this disparity exists and how to accommodate this offset such that accuracy is improved. We have tried various methods of keeping the lens and path length clean through brushing, acid cleaning and the recent installation of a high pressure air hose (recommended by S::CAN). We will compare output before and after this installation. Further complexity is added because light may be absorbed by other components of the field sample, such as particulate material, and this could compromise the estimated [DOC-eq]. [DOC] may be estimated using absorption measurements made at 254nm and 340nm (Tipping et al, 2009). We have implemented this formula

  12. Microbial community evolution during simulated managed aquifer recharge in response to different biodegradable dissolved organic carbon (BDOC) concentrations.

    PubMed

    Li, Dong; Alidina, Mazahirali; Ouf, Mohamed; Sharp, Jonathan O; Saikaly, Pascal; Drewes, Jörg E

    2013-05-01

    This study investigates the evolution of the microbial community in laboratory-scale soil columns simulating the infiltration zone of managed aquifer recharge (MAR) systems and analogous natural aquifer sediment ecosystems. Parallel systems were supplemented with either moderate (1.1 mg/L) or low (0.5 mg/L) biodegradable dissolved organic carbon (BDOC) for a period of six months during which time, spatial (1 cm, 30 cm, 60 cm, 90 cm, and 120 cm) and temporal (monthly) analyses of sediment-associated microbial community structure were analyzed. Total microbial biomass associated with sediments was positively correlated with BDOC concentration where a significant decline in BDOC was observed along the column length. Analysis of 16S rRNA genes indicated dominance by Bacteria with Archaea comprising less than 1 percent of the total community. Proteobacteria was found to be the major phylum in samples from all column depths with contributions from Betaproteobacteria, Alphaproteobacteria and Gammaproteobacteria. Microbial community structure at all the phylum, class and genus levels differed significantly at 1 cm between columns receiving moderate and low BDOC concentrations; in contrast strong similarities were observed both between parallel column systems and across samples from 30 to 120 cm depths. Samples from 1 cm depth of the low BDOC columns exhibited higher microbial diversity (expressed as Shannon Index) than those at 1 cm of moderate BDOC columns, and both increased from 5.4 to 5.9 at 1 cm depth to 6.7-8.3 at 30-120 cm depths. The microbial community structure reached steady state after 3-4 months since the initiation of the experiment, which also resulted in an improved DOC removal during the same time period. This study suggested that BDOC could significantly influence microbial community structure regarding both composition and diversity of artificial MAR systems and analogous natural aquifer sediment ecosystems.

  13. Factors affecting dissolved phosphorus and nitrate concentrations in ground and surface water for a valley dairy farm in the northeastern United States.

    PubMed

    Flores-López, Francisco; Easton, Zachary M; Geohring, Larry D; Steenhuis, Tammo S

    2011-02-01

    Agriculture often is considered to be a contributor of soluble reactive phosphorus (SRP) and nitrate-N (NO3- -N) to surface waters. This research analyzed SRP and NO3- -N concentrations in groundwater and in a creek fed by groundwater on a valley dairy farm in the Cannonsville basin of the New York City (NYC) watershed. A total of 37 groundwater piezometers were installed to depths of 0.3 to 1.5 m. Water-table depth and concentrations of SRP, NO3- -N, dissolved organic carbon (DOC), and dissolved oxygen were measured at regular intervals over a three-year period. A multivariate mixed model analysis of variance indicated that the SRP and NO3- -N concentrations were controlled primarily by three classes of variables: environmental variables, including precipitation and water table depth; source variables, including manure applied and crop type; and chemical variables, including DOC and dissolved oxygen concentrations in groundwater. The highest groundwater concentrations of N03- -N and SRP were found at the shallowest water-table depths, which has implications for agricultural nutrient management in areas with shallow groundwater.

  14. Viral Lysis of Cells Influences The Concentration and Compostion of Dissolved Organic Matter and The Formation of Organic Aggregates (marine Snow)

    NASA Astrophysics Data System (ADS)

    Weinbauer, M. G.; Peduzzi, P.

    The effect of moderately (ca. 2.5 fold) increasing the concentration of the virus-size fraction (VSF) of seawater on the chemical composition of the dissolved organic mat- ter (DOM) pool during the formation of organic aggregates (marine snow) was tested experimentally with seawater samples collected in the Northern Adriatic Sea. The VSF enrichment did not significantly change the concentration of selected DOM com- pounds, whereas viral abundance was ca. 2-fold higher. During long-term experiments (40 - 200 hrs), bacterial abundance was on average 25% lower in the VSF amended than in the control incubations, and the frequency of visibly infected cells was stimu- lated by ca. 50%. VSF delayed the development of phytoplankton blooms (diatoms), but in the end of the experiments, Chl a concentrations in the VSF amended incuba- tions exceeded those in the control incubations. The VSF enrichment caused an enrich- ment of Serine and Threonine in the dissolved hydrolysable amino acid (AA) fraction indicative of viral lysis of diatoms. Bulk dissolved free AA acid and monomeric car- bohydrate (CHO) concentrations were repressed, whereas bulk dissolved hydrolysable AA and CHO concentrations were stimulated in the VSF enriched incubations. Viral lysis was likely the major reason for the stimulation of hydrolysable DOM. The for- mation of organic aggregates was repressed by the VSF enrichment, but the aggregates were larger and more persistent in the VSF amended than in the control incubations. Stimulation of hydrolysable DOM and sticky viral lysis products might be the reason for the larger and more persistent aggregates. This demonstrates that bioactive mate- rial in the VSF of seawater can have major implications for primary production and the cycling of organic carbon in the ocean.

  15. 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 μg/L Si, analyzing filtered (0.45 μm) 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 μg/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

  16. Application of a novel sampling bailer device for the analysis of dissolved methane concentrations in municipal wastewater during and following anaerobic treatment.

    PubMed

    Beale, David J; Muster, Tim H; Low, Jason; Trickey, Mark

    2016-01-01

    Modern wastewater utilities need to be able to measure and quantify the amount of methane from their treatment facilities in order to understand the potential energy that can be produced and the amount of methane being lost. This paper describes the application of a novel sampling bailer designed for the collection of wastewater samples that minimises methane losses. Samples collected during and following anaerobic treatment from a wastewater treatment plant using a novel sampling bailer were analysed using a previously optimised analytical method. Analysis of wastewater and anaerobic pond samples using current industry approaches resulted in dissolved methane concentrations ranging from 0.01 to 14.33 mg L(-1). In comparison, the modified sampling protocol resulted in concentrations ranging from 0.08 to 18.73 mg L(-1). The relative standard deviations (RSD%) of low level spikes (5.0 mg L(-1) and 0.1 mg L(-1) methane; n = 5) were found to be 2.3 and 10.3, respectively. Statistical analysis of the dissolved methane concentrations using the two different approaches demonstrated a significant difference in the recovered dissolved methane concentrations, indicating there is a greater methane recovery potential in wastewater treatment plants than previously realised, when collected using the novel sampling bailer and analysed following the optimised analytical protocol. PMID:27332839

  17. Application of a novel sampling bailer device for the analysis of dissolved methane concentrations in municipal wastewater during and following anaerobic treatment.

    PubMed

    Beale, David J; Muster, Tim H; Low, Jason; Trickey, Mark

    2016-01-01

    Modern wastewater utilities need to be able to measure and quantify the amount of methane from their treatment facilities in order to understand the potential energy that can be produced and the amount of methane being lost. This paper describes the application of a novel sampling bailer designed for the collection of wastewater samples that minimises methane losses. Samples collected during and following anaerobic treatment from a wastewater treatment plant using a novel sampling bailer were analysed using a previously optimised analytical method. Analysis of wastewater and anaerobic pond samples using current industry approaches resulted in dissolved methane concentrations ranging from 0.01 to 14.33 mg L(-1). In comparison, the modified sampling protocol resulted in concentrations ranging from 0.08 to 18.73 mg L(-1). The relative standard deviations (RSD%) of low level spikes (5.0 mg L(-1) and 0.1 mg L(-1) methane; n = 5) were found to be 2.3 and 10.3, respectively. Statistical analysis of the dissolved methane concentrations using the two different approaches demonstrated a significant difference in the recovered dissolved methane concentrations, indicating there is a greater methane recovery potential in wastewater treatment plants than previously realised, when collected using the novel sampling bailer and analysed following the optimised analytical protocol.

  18. Impact of minimum daily dissolved oxygen concentration on production performance of hybrid female channel catfish x male blue catfish

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hybrid Catfish (female Channel Catfish Ictalurus punctatus X male Blue Catfish I. furcatus) were reared during two years as single-batch crops under two different dissolved oxygen (DO) regimes each year; a high-DO (control) treatment in which the minimum daily DO was maintained above 3.8 ppm during ...

  19. Sources and concentrations of dissolved solids and selenium in the San Joaquin River and its tributaries, California, October 1985 to March 1987

    SciTech Connect

    Clifton, D.G.; Gilliom, R.J.

    1989-01-01

    Sources and concentrations of dissolved solids and selenium in the San Joaquin River and its tributaries, California, were assessed by a mass-balance approach to determine the effects of tile-drain water and irrigation-return flows on the river. The study included low-flow periods from October 1985 to mid-February 1986 and mid-May 1986 through March 1987, and a high-flow period from mid-February to mid-May 1985. During the combined low-flow period, the dissolved-solids load from eastside tributaries and the upper San Joaquin River accounted for only 18% of the total load at Vernalis, located farthest downstream, even though they accounted for 71% of the stream flow. Salt and Mud Sloughs contributed 40% of the dissolved-solids load but only 9% of stream flow. Unmeasured sources of dissolved solids contributed about 42% of the total load during low flow. In contrast, Salt and Mud Sloughs, which receive most of the tile-drain water that enters the river, contributed almost 80% of the total selenium load to the river, and loading of selenium concentrations were highest in Salt and Mud Sloughs and decreased downstream in the San Joaquin River with dilution from eastside tributaries. A State standard for dissolved solids of 500 mg/L was exceeded 11% of the time in the San Joaquin River at Vernalis. The US Environmental Protection Agency's 4-day average aquatic-life criterion of 5 micrograms/L of selenium was exceeded in more than 60% of the samples from the sloughs and in about 20% of the samples from the San Joaquin River, just downstream of the Merced River. 23 refs., 8 figs., 6 tabs.

  20. Influence of in-stream diel concentration cycles of dissolved trace metals on acute toxicity to one-year-old cutthroat trout (Oncorhynchus clarki lewisi)

    USGS Publications Warehouse

    Nimick, D.A.; Harper, D.D.; Farag, A.M.; Cleasby, T.E.; MacConnell, Elizabeth; Skaar, D.

    2007-01-01

    Extrapolating results of laboratory bioassays to streams is difficult, because conditions such as temperature and dissolved metal concentrations can change substantially on diel time scales. Field bioassays conducted for 96 h in two mining-affected streams compared the survival of hatchery-raised, metal-nai??ve westslope cutthroat trout (Oncorhynchus clarki lewisi) exposed to dissolved (0.1-??m filtration) metal concentrations that either exhibited the diel variation observed in streams or were controlled at a constant value. Cadmium and Zn concentrations in these streams increased each night by as much as 61 and 125%, respectively, and decreased a corresponding amount the next day, whereas Cu did not display a diel concentration cycle. In High Ore Creek (40 km south of Helena, MT, USA), survival (33%) after exposure to natural diel-fluctuating Zn concentrations (range, 214-634 ??g/L; mean, 428 ??g/L) was significantly (p = 0.008) higher than survival (14%) after exposure to a controlled, constant Zn concentration (422 ??g/L). Similarly, in Dry Fork Belt Creek (70 km southeast of Great Falls, MT, USA), survival (75%) after exposure to diel-fluctuating Zn concentrations (range, 266-522 ??g/L; mean, 399 ??g/L) was significantly (p = 0.022) higher than survival (50%) in the constant-concentration treatment (392 ??g/L). Survival likely was greater in these diel treatments, both because the periods of lower metal concentrations provided some relief for the fish and because toxicity during periods of higher metal concentrations was lessened by the simultaneous occurrence each night of lower water temperatures, which reduce the rate of metal uptake. Based on the present study, current water-quality criteria appear to be protective for streams with diel concentration cycles of Zn (and, perhaps, Cd) for the hydrologie conditions tested. ?? 2007 SETAC.

  1. Mercury dynamics in relation to dissolved organic carbon concentration and quality during high flow events in three northeastern U.S. streams

    NASA Astrophysics Data System (ADS)

    Dittman, Jason A.; Shanley, James B.; Driscoll, Charles T.; Aiken, George R.; Chalmers, Ann T.; Towse, Janet E.; Selvendiran, Pranesh

    2010-07-01

    Mercury (Hg) contamination is widespread in remote areas of the northeastern United States. Forested uplands have accumulated a large reservoir of Hg in soil from decades of elevated anthropogenic deposition that can be released episodically to stream water during high flows. The objective of this study was to evaluate spatial and temporal variations in stream water Hg species and organic matter fractions over a range of hydrologic conditions in three forested upland watersheds (United States). Mercury and organic matter concentrations increased with discharge at all three sites; however, the partitioning of Hg fractions (dissolved versus particulate) differed among sites and seasons. Associated with increased discharge, flow paths shifted from mineral soil under base flow to upper soil horizons. As flow paths shifted, greater concentrations of dissolved organic carbon (DOC) richer in aromatic substances were flushed from upper soil horizons to stream water. The hydrophobic organic matter associated with humic material from upper soils appears to have had a greater capacity to bind Hg. Because of the strong correlation between Hg and DOC, we hypothesize that there was a concurrent shift in the source of Hg with DOC from lower mineral soil to upper soil horizons. Our study suggests that stream discharge is an effective predictor of dissolved total Hg flux.

  2. Influence of domestic pets on soil concentrations of dissolved organic carbon, nitrogen, and phosphorus under turfgrass in apartment complexes of Central Texas, USA

    NASA Astrophysics Data System (ADS)

    Steele, M.; Aitkenhead-Peterson, J. A.

    2009-12-01

    High nitrogen (N) and phosphorus (P) watershed loading rates increases the concentration and loads present in urban streams and rivers, resulting in eutrophication and degradation of surface water quality. Domestic pet animal feed may represent a significant proportion of nitrogen loading in urban watersheds, and because it is deposited directly on the watershed surface may have a large effect on N loads in urban surface waters (Baker et al. 2001). Animal manure has long been used to increase soil N and phosphorus concentrations for the purpose of growing agricultural crops; however, little is known about unintentional urban manuring resulting from a high density of domesticated pets. The purpose of this study is to determine if the presence of domesticated animals in high density urban developments results in increased concentrations of soil dissolved organic carbon (DOC), N, and P and the potential to contribute to loading of urban streams. Composite soil samples from the 0 to 5 cm and 5 to 10 cm soil depth were collected from apartment complexes in Bryan/College Station (BCS) and San Antonio, Texas during August, 2009. Apartment complexes were randomly located around the city and were chosen based on their rules regarding pet ownership. Four apartment complexes that allowed all domestic pets were compared to four that did not allow any domestic pets on the property. A 10:1 water extraction of field moist soil was conducted immediately after sampling. Soil water extracts were analyzed for DOC, total dissolved nitrogen (TDN), nitrate-N, ammonium-N, dissolved organic N, and orthophosphate-P. Results indicated significantly increased concentrations of DOC and N species at both depths in BCS apartments that allowed pets compared to those that did not; however, opposite trends were found in San Antonio. There is a trend for increased concentrations of orthophosphate-P at both locations. Baker, L.A., D. Hope, Y. Xu, et al. 2001. Nitrogen balance for the central Arizona

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

    PubMed

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

    2009-08-01

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

  4. 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

  5. Seasonal changes in concentrations of dissolved pesticides and organic carbon in the Sacramento-San Joaquin delta, California, 1994-1996

    USGS Publications Warehouse

    Orlando, James L.; Kuivila, Kathryn M.

    2006-01-01

    The Sacramento-San Joaquin Delta (Delta) of California is an ecologically rich and hydrologically complex region that receives runoff from nearly one-quarter of the state. Water-quality studies of surface water in the region have found dissolved pesticides in winter storm runoff at concentrations toxic to some aquatic invertebrates. However, scientists have little information on pesticide concentrations in the Delta on a seasonal timescale or the importance of pesticide contributions from within-Delta sources. Consequently, the U.S. Geological Survey conducted a study from 1994 to 1996 during which water samples were collected seasonally from 31 sites located within the Delta and on major tributaries to the Delta. Water samples were analyzed for 20 current-use pesticides and dissolved organic carbon. During the study, 11 current-use pesticides were detected; maximum concentrations ranging from 17 ng/L (for trifluralin) to 1,160 ng/L (for metolachlor). The highest concentrations of five pesticides (carbaryl, carbofuran, metolachlor, molinate, and simazine) were greater than 900 ng/L. The greatest number of pesticides was detected in the summer of 1994, whereas the least number were detected in the winter of 1994. The herbicides metolachlor and simazine were the most frequently detected pesticides and were detected in five of the six sampling seasons. The herbicides molinate and EPTC were detected only during the three summer sampling seasons. A comparison of pesticides detected during the spring and summer of 1995 showed some seasonal variability. Comparison of the three summer seasons sampled showed that a larger number of pesticides were detected, and with generally higher maximum concentrations, in 1994 than in 1995 or 1996. Dissolved organic carbon (DOC) concentrations ranged, over the course of the study, from 1.4 mg/L to 10.4 mg/L, and had a median concentration of 3.8 mg/L. On a seasonal basis, the lowest maximum DOC concentrations occurred during the summer

  6. Corrosion investigations on zircaloy-4 and titanium dissolver materials for MOX fuel dissolution in concentrated nitric acid containing fluoride ions

    NASA Astrophysics Data System (ADS)

    Jayaraj, J.; Krishnaveni, P.; Krishna, D. Nanda Gopala; Mallika, C.; Mudali, U. Kamachi

    2016-05-01

    Aqueous reprocessing of plutonium-rich mixed oxide fuels require fluoride as a dissolution catalyst in boiling nitric acid for an effective dissolution of the spent fuel. High corrosion rates were obtained for the candidate dissolver materials zircaloy-4 (Zr-4) and commercial pure titanium (CP-Ti grade 2) in boiling 11.5 M HNO3 + 0.05 M NaF. Complexing the fluoride ions either with Al(NO3)3 or ZrO(NO3)2 aided in decreasing the corrosion rates of Zr-4 and CP-Ti. From the obtained corrosion rates it is concluded that CP-Ti is a better dissolver material than Zr-4 for extended service life in boiling 11.5 M HNO3 + 0.05 M NaF, when complexed with 0.15 M ZrO(NO3)2. XPS analysis confirmed the presence of TiO2 and absence of fluoride on the surface of CP-Ti samples, indicating that effective complexation had occurred in solution leading to passivation of the metal and imparting high corrosion resistance.

  7. 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.

  8. Recovering/concentrating of hemicellulosic sugars and acetic acid by nanofiltration and reverse osmosis from prehydrolysis liquor of kraft based hardwood dissolving pulp process.

    PubMed

    Ahsan, Laboni; Jahan, M Sarwar; Ni, Yonghao

    2014-03-01

    This work investigated the feasibility of recovering and concentrating sugars and acetic acid (HAc) from prehydrolysis liquor (PHL) of the kraft-based dissolving pulp process prior to fermentation of hemicellulosic sugars, by the combination of activated carbon adsorption, nanofiltration (NF) and reverse osmosis (RO) processes. To reduce the fouling PHL was subjected to adsorption on activated carbon, then the treated PHL (TPHL) passed through a nanofiltration (NF DK) membrane to retain the sugars, and the permeate of acetic acid rich solution was passed through a reverse osmosis membrane (RO SG). It was found that for NF process sugars were concentrated from 48 to 227g/L at a volume reduction factor (VRF) of 5 while 80 to 90% of acetic acid was permeated. For the reverse osmosis process, 68% of acetic acid retention was achieved at pH 4.3 and 500 psi pressure and the HAc concentration increased from 10 to 50g/L.

  9. Recovering/concentrating of hemicellulosic sugars and acetic acid by nanofiltration and reverse osmosis from prehydrolysis liquor of kraft based hardwood dissolving pulp process.

    PubMed

    Ahsan, Laboni; Jahan, M Sarwar; Ni, Yonghao

    2014-03-01

    This work investigated the feasibility of recovering and concentrating sugars and acetic acid (HAc) from prehydrolysis liquor (PHL) of the kraft-based dissolving pulp process prior to fermentation of hemicellulosic sugars, by the combination of activated carbon adsorption, nanofiltration (NF) and reverse osmosis (RO) processes. To reduce the fouling PHL was subjected to adsorption on activated carbon, then the treated PHL (TPHL) passed through a nanofiltration (NF DK) membrane to retain the sugars, and the permeate of acetic acid rich solution was passed through a reverse osmosis membrane (RO SG). It was found that for NF process sugars were concentrated from 48 to 227g/L at a volume reduction factor (VRF) of 5 while 80 to 90% of acetic acid was permeated. For the reverse osmosis process, 68% of acetic acid retention was achieved at pH 4.3 and 500 psi pressure and the HAc concentration increased from 10 to 50g/L. PMID:24434701

  10. 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

  11. Relationships between 222Rn dissolved in ground water supplies and indoor 222Rn concentrations in some Colorado front range houses.

    PubMed

    Folger, P F; Nyberg, P; Wanty, R B; Poeter, E

    1994-09-01

    Indoor 222Rn concentrations were measured in 37 houses with alpha track detectors placed in water-use rooms near water sources (bathrooms, laundry rooms, and kitchens) and in non-water-use living rooms, dining rooms, and bedrooms away from water sources. Results show that relative contributions of 222Rn to indoor air from water use are insignificant when soil-gas concentrations are high but become increasingly important as the ratio of 222Rn-in-water: 222Rn-in-soil gas increases. High soil-gas 222Rn concentrations may mask 222Rn contributions from water even when waterborne 222Rn concentrations are as high as 750 kBq m-3. Ground water in Precambrian Pikes Peak granite averages 340 kBq m-3 222Rn, vs. 170 kBq m-3 in Precambrian migmatite, but average 222Rn concentrations in soil gas are also lower in migmatite. Because the ratio of 222Rn-in-water: 222Rn-in-soil gas may be consistently higher for houses in migmatite than in Pikes Peak granite, indoor air in houses built on migmatite may have a greater relative contribution from water use even though average 222Rn concentrations in the water are lower. Continuous monitoring of 222Rn concentrations in air on 15-min intervals also indicates that additions to indoor concentrations from water use are significant and measurable only when soil-gas concentrations are low and concentrations in water are high. When soil-gas concentrations were mitigated to less than 150 Bq m-3 in one house, water contributes 20-40% of the annual indoor 222Rn concentration in the laundry room (222Rn concentration in water of 670 kBq m-3). Conversely, when the mitigation system is inactive, diurnal fluctuations and other variations in the soil-gas 222Rn contribution swamp the variability due to water use in the house. Measurable variations in indoor concentrations from water use were not detected in one house despite a low soil-gas contribution of approximately 150 Bq m-3 because waterborne 222Rn concentrations also are low (80 kBq m-3). This

  12. 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.

  13. Functional imaging in freely moving animals.

    PubMed

    Kerr, Jason N D; Nimmerjahn, Axel

    2012-02-01

    Uncovering the relationships between animal behavior and cellular activity in the brain has been one of the key aims of neuroscience research for decades, and still remains so. Electrophysiological approaches have enabled sparse sampling from electrically excitable cells in freely moving animals that has led to the identification of important phenomena such as place, grid and head-direction cells. Optical imaging in combination with newly developed labeling approaches now allows minimally invasive and comprehensive sampling from dense networks of electrically and chemically excitable cells such as neurons and glia during self-determined behavior. To achieve this two main imaging avenues have been followed: Optical recordings in head-restrained, mobile animals and miniature microscope-bearing freely moving animals. Here we review progress made toward functional cellular imaging in freely moving rodents, focusing on developments over the past few years. We discuss related challenges and biological applications.

  14. 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 μmol L-1 for ammonium, nitrate, and sulfate, respectively, between 4 and 27 μmol L-1 for minor ions, 5.4 μmol L-1 for H2O2 (aq), 1.9 μmol 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

  15. 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, Dominik; Wadinga Fomba, Khanneh; Mertes, Stephan; Müller, Konrad; Spindler, Gerald; Schneider, Johannes; Lee, Taehyoung; Collett, Jeffrey L.; Herrmann, Hartmut

    2016-03-01

    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 three-stage and a five-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 µmol L-1 for ammonium, nitrate, and sulfate respectively, between 4 and 27 µmol L-1 for minor ions, 5.4 µmol L-1 for H2O2 (aq), 1.9 µmol 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). 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), were the main factor controlling bulk solute concentrations for the cloud studied. 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 (CVI) and analysed by an aerosol mass spectrometer (AMS), with the deviations being mainly caused by systematic

  16. What drove Dissolved Organic Carbon (DOC) concentration variability in the River Thames (UK) between 1884 and 2014?

    NASA Astrophysics Data System (ADS)

    Noacco, Valentina; Wagener, Thorsten; Howden, Nicholas; Duffy, Christopher

    2016-04-01

    Climate and atmospheric circulation patterns influence the variability of basin hydrochemistry, therefore understanding their influence is essential to put short-term water quality trends into the right context and to predict future hydrochemistry responses in the face of climate change. We investigate the drivers of DOC concentration variability in the Thames basin over 130 years. Our previous work has shown that increased urbanization since the 1880s in the Thames basin was the major driver for the increase in riverine DOC, but it does not explain DOC variability. Our current work investigates the links between hydro-climatic variability (temperature, precipitation and runoff) and teleconnections (ENSO and NAO), and the variability in DOC concentration. Moreover we compare the impact of hydro-climatic variability on riverine DOC, to the impact of land-use change and population increase. We use singular spectrum analysis to identify and then compare the dominant oscillatory components of hydro-climatic and hydro-biogeochemical variables. We use phase-plane trajectories of the noise-free, intra-annual to inter-annual reconstructed components to elucidate the biogeochemical and hydro-climatic dynamics of the system. This allows us to elucidate the links between the variability of hydro-climatic variables and DOC. Moreover they enable the identification of points in time where the dynamics of the system have changed, e.g. due to anthropogenic influences. Further, lag-correlations between teleconnections, DOC and flow are explored, to consider the hydrological memory of the catchment due to the permeable geology present. We show that the high seasonal to inter-annual variability in DOC concentration is linked to the variability of precipitation and runoff, rather than temperature. The dominant inter-annual modes of variability in DOC are connected to the ENSO oscillatory components. During strong El Niño and La Niña years there is statistically significant positive

  17. Tracing water and suspended matter in Raritan and Lower New York Bays using dissolved and particulate elemental concentrations

    USGS Publications Warehouse

    Paulson, A.J.

    2005-01-01

    The concentrations of 22 elements also were measured in the suspended matter of Raritan and Lower New York Bays and brackish water sources. The elemental composition of the suspended matter in surface and bottom waters was correlated with Fe concentrations, which ranged between 50 and 900 μmol g− 1. Statistical differences among the geographical regions were detected in the relationships of Ti, Ni, Co, As, and U with Fe, with particulate As being an especially strong geochemical indicator of Raritan River particles. The geochemical signatures of Lower New York Bay particles were similar to those of Upper New York Bay. The geochemical signatures of Raritan River particles were distinctly different than those of the Upper New York Bay, but the influence of Raritan River particles appeared to be limited to only inner Raritan Bay. This study illustrates the utility of trace elements for characterization of physical processes in complex estuaries.

  18. Electrolytic dissolver

    DOEpatents

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

    1975-08-26

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

  19. 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.

  20. Calibration of UV/Vis spectrophotometers: A review and comparison of different methods to estimate TSS and total and dissolved COD concentrations in sewers, WWTPs and rivers.

    PubMed

    Lepot, Mathieu; Torres, Andres; Hofer, Thomas; Caradot, Nicolas; Gruber, Günter; Aubin, Jean-Baptiste; Bertrand-Krajewski, Jean-Luc

    2016-09-15

    UV/Vis spectrophotometers have been used for one decade to monitor water quality in various locations: sewers, rivers, wastewater treatment plants (WWTPs), tap water networks, etc. Resulting equivalent concentrations of interest can be estimated by three ways: i) by manufacturer global calibration; ii) by local calibration based on the provided global calibration and grab sampling; iii) by advanced calibration looking for relations between UV/Vis spectra and corresponding concentrations from grab sampling. However, no study has compared the applied methods so far. This collaborative work presents a comparison between five different methods. A Linear Regression (LR), Support Vector Machine (SVM), EVOlutionary algorithm method (EVO) and Partial Least Squares (PLS) have been applied on various data sets (sewers, rivers, WWTPs under dry, wet and all weather conditions) and for three water quality parameters: TSS, COD total and dissolved. Two criteria (r(2) and Root Mean Square Error RMSE) have been calculated - on calibration and verification data subsets - to evaluate accuracy and robustness of the applied methods. Values of criteria have then been statistically analysed for all and separated data sets. Non-consistent outcomes come through this study. According to the Kruskal-Wallis test and RMSEs, PLS and SVM seem to be the best methods. According to uncertainties in laboratory analysis and ranking of methods, LR and EVO appear more robust and sustainable for concentration estimations. Conclusions are mostly independent of water matrices, weather conditions or concentrations investigated.

  1. Calibration of UV/Vis spectrophotometers: A review and comparison of different methods to estimate TSS and total and dissolved COD concentrations in sewers, WWTPs and rivers.

    PubMed

    Lepot, Mathieu; Torres, Andres; Hofer, Thomas; Caradot, Nicolas; Gruber, Günter; Aubin, Jean-Baptiste; Bertrand-Krajewski, Jean-Luc

    2016-09-15

    UV/Vis spectrophotometers have been used for one decade to monitor water quality in various locations: sewers, rivers, wastewater treatment plants (WWTPs), tap water networks, etc. Resulting equivalent concentrations of interest can be estimated by three ways: i) by manufacturer global calibration; ii) by local calibration based on the provided global calibration and grab sampling; iii) by advanced calibration looking for relations between UV/Vis spectra and corresponding concentrations from grab sampling. However, no study has compared the applied methods so far. This collaborative work presents a comparison between five different methods. A Linear Regression (LR), Support Vector Machine (SVM), EVOlutionary algorithm method (EVO) and Partial Least Squares (PLS) have been applied on various data sets (sewers, rivers, WWTPs under dry, wet and all weather conditions) and for three water quality parameters: TSS, COD total and dissolved. Two criteria (r(2) and Root Mean Square Error RMSE) have been calculated - on calibration and verification data subsets - to evaluate accuracy and robustness of the applied methods. Values of criteria have then been statistically analysed for all and separated data sets. Non-consistent outcomes come through this study. According to the Kruskal-Wallis test and RMSEs, PLS and SVM seem to be the best methods. According to uncertainties in laboratory analysis and ranking of methods, LR and EVO appear more robust and sustainable for concentration estimations. Conclusions are mostly independent of water matrices, weather conditions or concentrations investigated. PMID:27295626

  2. Changes in the Dissolved Organic Carbon Concentrations of Stream and Soil Water in Response to a Watershed-Scale Calcium Addition and Recovery from Acidification

    NASA Astrophysics Data System (ADS)

    Fuss, C. B.; Driscoll, C. T.; Ard, G. R.

    2014-12-01

    Positive trends in surface water dissolved organic carbon (DOC) concentrations have been observed in recent decades across many, but not all, surface water monitoring sites in eastern North America and northern Europe. The drivers of these trends are not necessarily clear, although declining acidic deposition is often cited as a likely cause for increased DOC mobilization. Here we used long-term records (16-31 years) of monthly streamwater and soil solution chemistry data from two headwater catchments at the Hubbard Brook Experimental Forest (NH, USA) to evaluate DOC trends in response to the recovery from acidification. We compared the concentrations and trends of DOC in Hubbard Brook's Watershed 6 (W6) and Watershed 1 (W1). W6 is the biogeochemical reference watershed and W1 underwent a treatment with calcium silicate in 1999 to mitigate the effects of long-term acid deposition. Streamwater DOC in W6 initially decreased through the 1980s and 1990s, but has leveled over the past 10-15 years, coincident with a period of modest pH increase. In contrast, W1 streamwater DOC concentrations have significantly increased since the calcium treatment which has led to more marked increases in pH. Greater mobilization of DOC in soil solution in W1 appears to be driving the higher streamwater DOC concentrations. We are analyzing these trends spatially within the watersheds and in conjunction with major solute chemistry to further explain the observed changes in DOC.

  3. 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 (

  4. 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

  5. Nitritating-anammox biomass tolerant to high dissolved oxygen concentration and C/N ratio in treatment of yeast factory wastewater.

    PubMed

    Zekker, Ivar; Rikmann, Ergo; Tenno, Toomas; Seiman, Andrus; Loorits, Liis; Kroon, Kristel; Tomingas, Martin; Vabamäe, Priit; Tenno, Taavo

    2014-01-01

    Maintaining stability of low concentration (< 1 g L(-1)) floccular biomass in the nitritation-anaerobic ammonium oxidation (anammox) process in the sequencing batch reactor (SBR) system for the treatment of high COD (> 15,000 mg O2 L(-1)) to N (1680 mg N L(-1)) ratio real wastewater streams coming from the food industry is challenging. The anammox process was suitable for the treatment of yeast factory wastewater containing relatively high and abruptly increased organic C/N ratio and dissolved oxygen (DO) concentrations. Maximum specific total inorganic nitrogen (TIN) loading and removal rates applied were 600 and 280 mg N g(-1) VSS d(-1), respectively. Average TIN removal efficiency over the operation period of 270 days was 70%. Prior to simultaneous reduction of high organics (total organic carbon > 600mg L(-1)) and N concentrations > 400 mg L(-1), hydraulic retention time of 15 h and DO concentrations of 3.18 (+/- 1.73) mg O2 L(-1) were applied. Surprisingly, higher DO concentrations did not inhibit the anammox process efficiency demonstrating a wider application of cultivated anammox biomass. The SBR was fed rapidly over 5% of the cycle time at 50% volumetric exchange ratio. It maintained high free ammonia concentration, suppressing growth of nitrite-oxidizing bacteria. Partial least squares and response surface modelling revealed two periods of SBR operation and the SBR performances change at different periods with different total nitrogen (TN) loadings. Anammox activity tests showed yeast factory-specific organic N compound-betaine and inorganic N simultaneous biodegradation. Among other microorganisms determined by pyrosequencing, anammox microorganism (uncultured Planctomycetales bacterium clone P4) was determined by polymerase chain reaction also after applying high TN loading rates.

  6. 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.

  7. Determination of isotopic composition of dissolved copper in seawater by multi-collector inductively coupled plasma mass spectrometry after pre-concentration using an ethylenediaminetriacetic acid chelating resin.

    PubMed

    Takano, Shotaro; Tanimizu, Masaharu; Hirata, Takafumi; Sohrin, Yoshiki

    2013-06-19

    Copper is an essential trace metal that shows a vertical recycled-scavenged profile in the ocean. To help elucidate the biogeochemical cycling of Cu in the present and past oceans, it is important to determine the distribution of Cu isotopes in seawater. However, precise isotopic analysis of Cu has been impaired by the low concentrations of Cu as well as co-existing elements that interfere with measurements by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The objective of this study is to develop a simple Cu pre-concentration method using Nobias-chelate PA1 resin (Hitachi High Technologies). This extraction followed by anion exchange, allows precise analysis of the Cu isotopic composition in seawater. Using this method, Cu was quantitatively concentrated from seawater and >99.9999% of the alkali and alkaline earth metals were removed. The technique has a low procedural blank of 0.70 ng for Cu for a 2L sample and the precision of the Cu isotopic analysis was ±0.07‰ (±2SD, n=6). We applied this method to seawater reference materials (i.e., CASS-5 and NASS-6) and seawater samples obtained from the northwestern Pacific Ocean. The range of dissolved δ(65)Cu was 0.40-0.68‰.

  8. Carbon nanofiber multiplexed array and Wireless Instantaneous Neurotransmitter Concentration Sensor for simultaneous detection of dissolved oxygen and dopamine

    PubMed Central

    Marsh, Michael P.; Koehne, Jessica E.; Andrews, Russell J.; Meyyappan, M.; Bennet, Kevin E.; Lee, Kendall H.

    2014-01-01

    Purpose While the mechanism of Deep Brain Stimulation (DBS) remains poorly understood, previous studies have shown that it evokes release of neurochemicals and induces activation of functional magnetic resonance imaging (fMRI) blood oxygen level-dependent signal in distinct areas of the brain. Therefore, the main purpose of this paper is to demonstrate the capabilities of the Wireless Instantaneous Neurotransmitter Concentration Sensor system (WINCS) in conjunction with a carbon nanofiber (CNF) multiplexed array electrode as a powerful tool for elucidating the mechanism of DBS through the simultaneous detection of multiple bioactive-molecules. Methods Patterned CNF nanoelectrode arrays were prepared on a 4-inch silicon wafer where each device consists of 3 × 3 electrode pads, 200 μm square, that contain CNFs spaced at 1μm intervals. The multiplexed carbon nanofiber CNF electrodes were integrated with WINCS to detect mixtures of dopamine (DA) and oxygen (O2) using fast scan cyclic voltammetry (FSCV) in vitro. Results First, simultaneous detection of O2 at two spatially different locations, 200 um apart, was demonstrated. Second, simultaneous detection of both O2 and DA at two spatially different locations, using two different decoupled waveforms was demonstrated. Third, controlled studies demonstrated that the waveform must be interleaved to avoid electrode crosstalk artifacts in the acquired data. Conclusions Multiplexed CNF nanoelectrode arrays for electrochemical detection of neurotransmitters show promise for the detection of multiple analytes with the application of time independent decoupled waveforms. Electrochemistry on CNF electrodes may be helpful in elucidating the mechanism of DBS, and may also provide the precision and sensitivity required for future applications in feedback modulated DBS neural control systems. PMID:24688800

  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. 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

  11. Using environmental isotopes and dissolved methane concentrations to constrain hydrochemical processes and inter-aquifer mixing in the Galilee and Eromanga Basins, Great Artesian Basin, Australia

    NASA Astrophysics Data System (ADS)

    Moya, Claudio E.; Raiber, Matthias; Taulis, Mauricio; Cox, Malcolm E.

    2016-08-01

    Groundwater recharge processes, water-rock interaction and the hydraulic connectivity between aquifers of the Galilee and Eromanga Basins in central Queensland, Australia, were investigated using stable (δ2H, δ18O, δ13C and 87Sr/86Sr) and radiogenic (36Cl) isotopes and dissolved methane concentrations, complemented by major ion chemistry. The central Eromanga and the upper sequence of the Galilee basins are both sub-basins of the Great Artesian Basin (GAB), and the coal seams of the Galilee Basin are currently explored for their potential as commercial coal seam gas deposits. In order to understand the potential influence of depressurisation of coal seams required to release the gas on adjacent aquifers, a detailed understanding of recharge processes and groundwater hydraulics of these basins prior to any development is required. Each of the different isotope systems were used in this study to provide different information on specific processes. For example, the assessment of δ13C and 87Sr/86Sr ratios suggested that carbonate dissolution is one of the major processes controlling the water chemistry within some aquifers. In addition, the combined assessment of δ2H, δ18O and major ion chemistry indicates that transpiration is the primary process controlling the solute concentration in the GAB recharge area, whereas evaporation appears to be less significant. Groundwaters in the Galilee Basin recharge area (outside the limits of the GAB) are different to any groundwater within the GAB units. This difference is attributed to the dissolution of potassium-bearing micas, which are absent in the GAB. Groundwater age estimates based on 36Cl/Cl ratios suggest that there is a steady increase along the flow paths, and this lack of anomalous age estimates from the recharge areas to the deeper parts of the basin indicates that there is no evidence for regional inter-aquifer mixing based in isotopes only. However, dissolved methane concentrations and groundwater chemistry

  12. Freely Suspended Smectic Films in Aqueous Environment

    NASA Astrophysics Data System (ADS)

    Peddireddy, Karthik; Bahr, Christian

    2012-02-01

    Smectic liquid crystals easily form thin films which are freely suspended on a solid frame in air. These systems have been thoroughly studied for various purposes such as structural studies of smectic phases, investigating phase transitions in two-dimensional systems, and studying various physical properties of liquid crystals. In the present study, we explore the preparation of freely suspended smectic films in water. A prerequisite is the presence of a surfactant which accumulates at the liquid-crystal/water interface and induces a homeotropic anchoring of the director, so that the smectic layers align parallel to the two film surfaces. The presence of the surfactant might also serve as a handle to tune properties such as the surface tension of the films (which is hardly possible for freely suspended films in air). We study the formation of films in water using different frames and different surfactants, and we focus especially on the thinning behaviour which occurs when the temperature is increased towards the smectic - nematic or smectic - isotropic transition.

  13. 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.

  14. Biofilm formation of a bacterial consortium on linuron at micropollutant concentrations in continuous flow chambers and the impact of dissolved organic matter.

    PubMed

    Horemans, Benjamin; Hofkens, Johan; Smolders, Erik; Springael, Dirk

    2014-04-01

    Bacterial multispecies biofilms are catalysts for pollutant degradation in aqueous ecosystems. Their activity in systems where xenobiotics occur as micropollutants (μg L(-1) level) and natural dissolved organic matter provides carbon and energy instead remains uncharacterized. Biofilm formation of a bacterial consortium consisting of the linuron-degrading Variovorax sp. WDL1 and metabolite-degrading strains Comamonas sp. WDL7 and Hyphomicrobium sp. WDL6 at micropollutant linuron concentrations and the impact of auxiliary carbon sources on degradation and biofilm composition were investigated. Biofilms formed at concentrations of 1000, 100, and 10 μg L(-1) linuron. The highest biomass, organized in mixed-species mounds, was observed at 1000 μg L(-1) linuron, while at 100 and 10 μg L(-1) , thin layers of cells occurred. Linuron removal efficiencies decreased from c. 85% when fed with 100 and 1000 μg L(-1) linuron to 30% in case of 10 μg L(-1) linuron due to reduced specific activity. Biofilms grown on 10 μg L(-1) linuron were subsequently fed with easily and less degradable carbon sources in addition to 10 μg L(-1) linuron. Although co-feeding with more degradable C-sources increased biofilm biomass, linuron removal remained 30%. Calculations based on biofilm volume measurements pointed toward reduced specific activity, compensated by a higher biomass. Uncertainties about biofilm heterogeneity and cell volume can undo this explanation. PMID:24410802

  15. Dissolved pesticide concentrations detected in storm-water runoff at selected sites in the San Joaquin River basin, California, 2000-2001

    USGS Publications Warehouse

    Orlando, James L.; Kuivila, Kathryn M.; Whitehead, Andrew

    2003-01-01

    As part of a collaborative study involving the United States Geological Survey Toxics Substances Hydrology Project (Toxics Project) and the University of California, Davis, Bodega Marine Laboratory (BML), water samples were collected at three sites within the San Joaquin River Basin of California and analyzed for dissolved pesticides. Samples were collected during, and immediately after, the first significant rainfall (greater than 0.5 inch per day) following the local application of dormant spray, organophosphate insecticides during the winters of 2000 and 2001. All samples were collected in conjunction with fish-caging experiments conducted by BML researchers. Sites included two locations potentially affected by runoff of agricultural chemicals (San Joaquin River near Vernalis, California, and Orestimba Creek at River Road near Crows Landing, California, and one control site located upstream of pesticide input (Orestimba Creek at Orestimba Creek Road near Newman, California). During these experiments, fish were placed in cages and exposed to storm runoff for up to ten days. Following exposure, the fish were examined for acetylcholinesterase concentrations and overall genetic damage. Water samples were collected throughout the rising limb of the stream hydrograph at each site for later pesticide analysis. Concentrations of selected pesticides were measured in filtered water samples using solid-phase extraction (SPE) and gas chromatography-mass spectrometry (GC/MS) at the U.S. Geological Survey organic chemistry laboratory in Sacramento, California. Results of these analyses are presented.

  16. Modelling seasonal and long-term patterns in stream dissolved organic carbon concentration in mire and forest dominated landscape elements at Svartberget, Sweden using INCA-C

    NASA Astrophysics Data System (ADS)

    Futter, M.; Koehler, S. J.; Bishop, K. H.

    2009-04-01

    We present an application of the INCA-C (Integrated Catchments model for Carbon) to the Svartberget catchment in central Sweden. The INCA-C model is a catchment-scale, semi-distributed, process-based model of dissolved organic carbon (DOC) that has been used previously to simulate intra- and inter-annual patterns in surface water DOC concentration and flux in boreal and temperate forested catchments (Futter et al. 2007). The 50 ha Svartberget catchment provides an ideal location for evaluating the performance of INCA-C as it contains two mire and upland landscape elements, where the output from each element has been monitored separately for a decade. Previous work has shown that these two landscape elements have markedly different intra-annual patterns of DOC concentration and export as well as the importance of the riparian zone in controlling surface water DOC concentration from the forested sub-catchment (Köhler et al. 2008). The 19 ha mire sub-catchment is dominated by bog communities with Scots pine in the upland areas. The 13 ha forested sub-catchment stream joins the main stem of the stream just above the confluence. It is dominated by Scots pine and Norway spruce. A third sub-catchment between the mire and the catchment outflow has a similar vegetation cover to that of the forested sub-catchment. INCA is designed to model different landscape elements, and combine them to simulate downstream locations. Like most complex, process-based models, however, INCA-C is over-determined. Insufficient data are available to constrain all processes and pool-sizes. As a result, similar in-stream DOC concentrations may be obtained by varying either aquatic or terrestrial rate parameters. The Svartberget catchment provides an opportunity to constrain the model parameter space for the entire catchment as there is information for the two major constituent elements, forest and mire. Additionally soil solution data from the riparian zone in the forest area together with a

  17. 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).

  18. Use of dissolved chloride concentrations in tributary streams to support geospatial estimates of Cl contamination potential near Skiatook Lake, northeastern Oklahoma

    USGS Publications Warehouse

    Rice, C.A.; Abbott, M.M.; Zielinski, R.A.

    2007-01-01

    Releases of NaCl-rich (>100 000 mg/L) water that is co-produced from petroleum wells can adversely affect the quality of ground and surface waters. To evaluate produced water impacts on lakes, rivers and streams, an assessment of the contamination potential must be attainable using reliable and cost-effective methods. This study examines the feasibility of using geographic information system (GIS) analysis to assess the contamination potential of Cl to Skiatook Lake in the Hominy Creek drainage basin in northeastern Oklahoma. GIS-based predictions of affects of Cl within individual subdrainages are supported by measurements of Cl concentration and discharge in 19 tributaries to Skiatook Lake. Dissolved Cl concentrations measured in October, 2004 provide a snapshot of conditions assumed to be reasonably representative of typical inputs to the lake. Chloride concentrations ranged from 5.8 to 2300 mg/L and compare to a value of 34 mg/L in the lake. At the time of sampling, Hominy Creek provided 63% of the surface water entering the lake and 80% of the Cl load. The Cl load from the other tributaries is relatively small (150 mg/L) were generally in subdrainages with greater well density (>15 wells/km2), relatively large numbers of petroleum wells in close proximity (>2 proximity wells/stream km), and relatively small discharge (<0.005 m3/s). GIS calculations of subdrainage areas can be used to estimate the expected discharge of the tributary for each subdrainage. GIS-based assessment of Cl contamination potential at Skiatook Lake and at other lakes surrounded by oil fields can proceed even when direct measurements of Cl or discharge in tributary streams may be limited or absent.

  19. 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

  20. 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.

  1. Comparison of dialysis and solid-phase extraction for isolation and concentration of dissolved organic matter prior to Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Tfaily, Malak M; Hodgkins, Suzanne; Podgorski, David C; Chanton, Jeffrey P; Cooper, William T

    2012-08-01

    We compare two methods, solid-phase extraction (SPE) and dialysis, commonly used for extraction and concentration of dissolved organic matter (DOM) prior to molecular characterization by electrospray ionization (ESI) and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry. Spectra of DOM samples from Minnesota and Sweden peatlands that were extracted with styrene divinyl benzene polymer SPE sorbents included ions with formulas that had higher oxygen to carbon (O/C) ratios than spectra of DOM from the same samples after de-salting by dialysis. The SPE method was not very effective in extracting several major classes of DOM compounds that had high ESI efficiencies, including carboxylic acids and organo-sulfur compounds, and that out-competed other less-functionalized compounds (e.g., carbohydrates) for charge in the ESI source. The large abundance of carboxylic acids in the dialysisextracted DOM, likely the result of in situ microbial production, makes it difficult to see other (mainly hydrophilic) compounds with high O/C ratios. Our results indicate that, while dialysis is generally preferable for the isolation of DOM, for samples with high microbial inputs, the use of both isolation methods is recommended for a more accurate molecular representation.

  2. Concentrations of dissolved solids and nutrients in water sources and selected streams of the Santa Ana Basin, California, Octoger 1998 - September 2001

    USGS Publications Warehouse

    Kent, Robert; Belitz, Kenneth

    2004-01-01

    Concentrations of total dissolved solids (TDS) and nutrients in selected Santa Ana Basin streams were examined as a function of water source. The principal water sources are mountain runoff, wastewater, urban runoff, and stormflow. Rising ground water also enters basin streams in some reaches. Data were collected from October 1998 to September 2001 from 6 fixed sites (including a mountain site), 6 additional mountain sites (including an alpine indicator site), and more than 20 synoptic sites. The fixed mountain site on the Santa Ana River near Mentone appears to be a good representative of reference conditions for water entering the basin. TDS can be related to water source. The median TDS concentration in base-flow samples from mountain sites was 200 mg/L (milligrams per liter). Base-flow TDS concentrations from sites on the valley floor typically ranged from 400 to 600 mg/L; base flow to most of these sites is predominantly treated wastewater, with minor contributions of rising ground water and urban runoff. Sparse data suggest that TDS concentrations in urban runoff are about 300 mg/L. TDS concentrations appear to increase on a downstream gradient along the main stem of the Santa Ana River, regardless of source inputs. The major-ion compositions observed in samples from the different sites can be related to water source, as well as to in-stream processes in the basin. Water compositions from mountain sites are categorized into two groups: one group had a composition close to that of the alpine indicator site high in the watershed, and another group had ionic characteristics closer to those in tributaries on the valley floor. The water composition at Warm Creek, a tributary urban indicator site, was highly variable but approximately intermediate to the compositions of the upgradient mountain sites. Water compositions at the Prado Dam and Imperial Highway sites, located 11 miles apart on the Santa Ana River, were similar to one another and appeared to be a mixture

  3. Temporal and spatial changes in dissolved organic carbon concentration and fluorescence intensity of fulvic acid like materials in mountainous headwater catchments

    NASA Astrophysics Data System (ADS)

    Terajima, Tomomi; Moriizumi, Mihoko

    2013-02-01

    SummaryDissolved organic carbon (DOC) such as humic substances are key to understanding the aquatic environment in catchments, because they, containing a large number of phenolic and carboxylic acid groups, adsorb many kinds of inorganic materials and also affect nutrition and carbon transport in catchments. To understand the detailed DOC dynamics, we conducted hydrological observations at mountainous headwater catchments dominated by different vegetation types (planted evergreen coniferous forest of 1.29 ha and natural deciduous broadleaf forest of 1.28 ha). The relationship between DOC concentrations and fluorescence intensity of fulvic acid-like materials (F-FAM) were positively correlated in both catchments but different between soil extracts, baseflow, and near surface flow represented by biomat flow. The ratios of change in F-FAM to that in DOC concentration (F-FAM/DOC) were higher in the baseflow (about 6 in both catchments) and lower in the soil extracts (about 4.5 in both catchments, respectively). However, the relationship in stormflow was distributed between the trends of baseflow and soil extracts. The higher F-FAM/DOC in baseflow may thus indicate that DOC (and FAM) in groundwater discharge mainly contributed to the stream flow, and the stormflow mainly reflect subsurface flow through soil during most rainstorms. In contrast, a high F-FAM/DOC ratio (>6) appeared in the stormflow of both catchments especially during large storms of short duration and high intensity following a dry antecedent period. The F-FAM/DOC in biomat flow developing distinctly in the coniferous catchment was high (about 6.5). Thus, rapid shallow subsurface flow through the biomat or near-surface of slopes might explain the unique transport dynamics of DOC and FAM in stormflows with the high F-FAM/DOC ratio. These results imply that the DOC and FAM relationship responds variably depending on both the distribution of soil organic matter and rainwater flow paths in steep slopes as

  4. 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

  5. Concentration, composition, bioavailability, and N-nitrosodimethylamine formation potential of particulate and dissolved organic nitrogen in wastewater effluents: A comparative study.

    PubMed

    Hu, Haidong; Ma, Haijun; Ding, Lili; Geng, Jinju; Xu, Ke; Huang, Hui; Zhang, Yingying; Ren, Hongqiang

    2016-11-01

    Wastewater-derived organic nitrogen (org-N) can act as both nutrients and carcinogenic nitrogenous disinfection byproduct precursors. In this study, the concentration, composition, bioavailability, and N-nitrosodimethylamine (NDMA) formation potential of particulate organic nitrogen (PON) from three different municipal wastewater treatment plants were characterized and compared with that of effluent dissolved organic nitrogen (DON). The average effluent PON and DON concentrations ranged from 0.09 to 0.55mgN/L and from 0.91 to 1.88mgN/L, respectively. According to principal component analysis, org-N composition and characterization differed in PON and DON samples (n=20). Compared with DON, PON tended to be enriched in protein and nucleic acids, and showed a more proteinaceous character. Composition of org-N functional groups estimated from the X-ray photoelectron spectroscopy N 1s spectra indicate no significant differences in the molecular weight distribution of the protein-like materials between PON and DON. Moreover, PON exhibited a significantly higher bioavailability (61.0±13.3%) compared to DON (38.5±12.4%, p˂0.05, t-test) and a significantly higher NDMA yields (791.4±404.0ng/mg-N) compared to DON (374.8±62.5ng/mg-N, p˂0.05, t-test). Accordingly, PON contributed to approximately 12.3-41.7% of the total bioavailable org-N and 22.0-38.4% of the total NDMA precursors in wastewater effluents. Thus, the potential adverse effects of PON on wastewater discharge and reuse applications should not be overlooked, even though it only accounted for 7.4-26.8% of the total effluent org-N.

  6. Concentration, composition, bioavailability, and N-nitrosodimethylamine formation potential of particulate and dissolved organic nitrogen in wastewater effluents: A comparative study.

    PubMed

    Hu, Haidong; Ma, Haijun; Ding, Lili; Geng, Jinju; Xu, Ke; Huang, Hui; Zhang, Yingying; Ren, Hongqiang

    2016-11-01

    Wastewater-derived organic nitrogen (org-N) can act as both nutrients and carcinogenic nitrogenous disinfection byproduct precursors. In this study, the concentration, composition, bioavailability, and N-nitrosodimethylamine (NDMA) formation potential of particulate organic nitrogen (PON) from three different municipal wastewater treatment plants were characterized and compared with that of effluent dissolved organic nitrogen (DON). The average effluent PON and DON concentrations ranged from 0.09 to 0.55mgN/L and from 0.91 to 1.88mgN/L, respectively. According to principal component analysis, org-N composition and characterization differed in PON and DON samples (n=20). Compared with DON, PON tended to be enriched in protein and nucleic acids, and showed a more proteinaceous character. Composition of org-N functional groups estimated from the X-ray photoelectron spectroscopy N 1s spectra indicate no significant differences in the molecular weight distribution of the protein-like materials between PON and DON. Moreover, PON exhibited a significantly higher bioavailability (61.0±13.3%) compared to DON (38.5±12.4%, p˂0.05, t-test) and a significantly higher NDMA yields (791.4±404.0ng/mg-N) compared to DON (374.8±62.5ng/mg-N, p˂0.05, t-test). Accordingly, PON contributed to approximately 12.3-41.7% of the total bioavailable org-N and 22.0-38.4% of the total NDMA precursors in wastewater effluents. Thus, the potential adverse effects of PON on wastewater discharge and reuse applications should not be overlooked, even though it only accounted for 7.4-26.8% of the total effluent org-N. PMID:27450243

  7. Mapping brain function in freely moving subjects

    PubMed Central

    Holschneider, Daniel P.; Maarek, Jean-Michel I.

    2014-01-01

    Expression of many fundamental mammalian behaviors such as, for example, aggression, mating, foraging or social behaviors, depend on locomotor activity. A central dilemma in the functional neuroimaging of these behaviors has been the fact that conventional neuroimaging techniques generally rely on immobilization of the subject, which extinguishes all but the simplest activity. Ideally, imaging could occur in freely moving subjects, while presenting minimal interference with the subject’s natural behavior. Here we provide an overview of several approaches that have been undertaken in the past to achieve this aim in both tethered and freely moving animals, as well as in nonrestrained human subjects. Applications of specific radiotracers to single photon emission computed tomography and positron emission tomography are discussed in which brain activation is imaged after completion of the behavioral task and capture of the tracer. Potential applications to clinical neuropsychiatry are discussed, as well as challenges inherent to constraint-free functional neuroimaging. Future applications of these methods promise to increase our understanding of the neural circuits underlying mammalian behavior in health and disease. PMID:15465134

  8. 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

    . 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.

  9. 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.

  10. 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

  11. Surface-water-quality assessment of the lower Kansas River basin, Kansas and Nebraska; distribution of trace-element concentrations in dissolved and suspended phases, streambed sediment, and fish samples, May 1987 through April 1990

    USGS Publications Warehouse

    Tanner, D.Q.

    1995-01-01

    The distribution of trace elements in dissolved and suspended phases, streambed sediment, and fish samples is described for principal streams in the lower Kansas River Basin, Kansas and Nebraska, from May 1987 through April 1990. Large median concentrations of dissolved lithium and strontium in the Kansas River were related to saline ground-water discharge, and large median concentrations of dissolved strontium in Mill Creek near Paxico, Kansas were related to Permian limestone and shale. Large concentrations of arsenic, chromium, and lead in water were identified downstream from three reservoirs, which may be attributed to resuspension of bed sediment in turbulent flow near the dams or release of water from near the bottom of the reservoirs. Trace elements in streambed sediments greater than background concentrations were identified downstream from the Aurora, Nebraska, wastewater-treatment plant, from industrial or urban areas near Kansas City, Kansas, and from the dam at Perry Lake, Kansas. Median and 90th-percentile concentrations of mercury in fish-tissue samples approximately doubled from 1979-86 to 1987-90. However, concentrations in samples collected during the latter period were less than the National Academy of Sciences and National Academy of Engineering 1972 criterion of 500 micrograms per kilogram for mercury in fish tissue.

  12. 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.

  13. 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.

  14. Changes between early development (1930–60) and recent (2005–15) groundwater-level altitudes and dissolved-solids and nitrate concentrations In and near Gaines, Terry, and Yoakum Counties, Texas

    USGS Publications Warehouse

    Thomas, Jonathan V.; Teeple, Andrew P.; Payne, Jason D.; Ikard, Scott

    2016-06-21

    During the recent period, median dissolved-solids concentrations of less than 1,000 milligrams per liter (mg/L) were predominantly measured in the western part of the study area, and median concentrations of more than 1,000 mg/L were predominantly measured in the eastern part of the study area. A general pattern of increasing nitrate concentrations from west to the northeast was evident in the study area. Nitrate concentrations measured in samples collected from 16 wells completed in the Ogallala aquifer for the recent period were equal to or greater than 10 mg/L, the primary drinking water standard for finished drinking water.

  15. Methods for evaluating temporal groundwater quality data and results of decadal-scale changes in chloride, dissolved solids, and nitrate concentrations in groundwater in the United States, 1988-2010

    USGS Publications Warehouse

    Lindsey, Bruce D.; Rupert, Michael G.

    2012-01-01

    Decadal-scale changes in groundwater quality were evaluated by the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program. Samples of groundwater collected from wells during 1988-2000 - a first sampling event representing the decade ending the 20th century - were compared on a pair-wise basis to samples from the same wells collected during 2001-2010 - a second sampling event representing the decade beginning the 21st century. The data set consists of samples from 1,236 wells in 56 well networks, representing major aquifers and urban and agricultural land-use areas, with analytical results for chloride, dissolved solids, and nitrate. Statistical analysis was done on a network basis rather than by individual wells. Although spanning slightly more or less than a 10-year period, the two-sample comparison between the first and second sampling events is referred to as an analysis of decadal-scale change based on a step-trend analysis. The 22 principal aquifers represented by these 56 networks account for nearly 80 percent of the estimated withdrawals of groundwater used for drinking-water supply in the Nation. Well networks where decadal-scale changes in concentrations were statistically significant were identified using the Wilcoxon-Pratt signed-rank test. For the statistical analysis of chloride, dissolved solids, and nitrate concentrations at the network level, more than half revealed no statistically significant change over the decadal period. However, for networks that had statistically significant changes, increased concentrations outnumbered decreased concentrations by a large margin. Statistically significant increases of chloride concentrations were identified for 43 percent of 56 networks. Dissolved solids concentrations increased significantly in 41 percent of the 54 networks with dissolved solids data, and nitrate concentrations increased significantly in 23 percent of 56 networks. At least one of the three - chloride, dissolved solids, or

  16. 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

  17. The Measurement of Dissolved Oxygen

    ERIC Educational Resources Information Center

    Thistlethwayte, D.; And Others

    1974-01-01

    Describes an experiment in environmental chemistry which serves to determine the dissolved oxygen concentration in both fresh and saline water. Applications of the method at the undergraduate and secondary school levels are recommended. (CC)

  18. 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

  19. Testing watershed size and slope, soil C:N and carbon storage as indicators of riverine dissolved organic carbon concentration and export

    NASA Astrophysics Data System (ADS)

    Alexander, J.; Aitkenhead-Peterson, J. A.; Clair, T. A.

    2001-12-01

    Several predictors of riverine dissolved organic carbon export have been presented over the last decade. The relationship between dissolved organic carbon export and a) watershed size and slope, b) mean watershed carbon storage and c) mean biome soil C:N ratio have all had measurable success as predictors of riverine DOC export. We tested each of these major predictors within a cool temperate conifer biome in Nova Scotia and New Brunswick, Canada. Soil cores were taken from thirteen watersheds, and the organic and mineral soil horizons were analyzed for carbon and nitrogen. The number of soil cores taken from each watershed depended on the size of the watershed. We retrieved 12 cores from the smallest and 35 from the largest watersheds. Bulk density was calculated for each soil sample so that watershed carbon storage could be derived. Watershed area, forest cover, slope and altitude were also logged for each soil sample point. Watershed size ranged from 6.3 x 103 ha to 1.25 x 105 ha. Altitude from 88 to 1458 ft. Individual soil C:N ratios ranged from 16.5 to 48.9 in organic soil horizons and from 6.1 to 29.8 in mineral soil horizons. Dissolved organic carbon export for each of the watersheds was calculated and range between 29.9 and 123.5 kg DOC ha-1 yr-1. Ten watersheds were used to derive empirical relationships between DOC export and each of aforementioned major predictors of DOC export. The remaining three watersheds, not included in empirical modeling were used for testing each model.

  20. 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

  1. METHOD OF DISSOLVING URANIUM METAL

    DOEpatents

    Slotin, L.A.

    1958-02-18

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

  2. Visualizing Nanoscopic Topography and Patterns in Freely Standing Thin Films

    NASA Astrophysics Data System (ADS)

    Sharma, Vivek; Zhang, Yiran; Yilixiati, Subinuer

    Thin liquid films containing micelles, nanoparticles, polyelectrolyte-surfactant complexes and smectic liquid crystals undergo thinning in a discontinuous, step-wise fashion. The discontinuous jumps in thickness are often characterized by quantifying changes in the intensity of reflected monochromatic light, modulated by thin film interference from a region of interest. Stratifying thin films exhibit a mosaic pattern in reflected white light microscopy, attributed to the coexistence of domains with various thicknesses, separated by steps. Using Interferometry Digital Imaging Optical Microscopy (IDIOM) protocols developed in the course of this study, we spatially resolve for the first time, the landscape of stratifying freely standing thin films. We distinguish nanoscopic rims, mesas and craters, and follow their emergence and growth. In particular, for thin films containing micelles of sodium dodecyl sulfate (SDS), these topological features involve discontinuous, thickness transitions with concentration-dependent steps of 5-25 nm. These non-flat features result from oscillatory, periodic, supramolecular structural forces that arise in confined fluids, and arise due to complex coupling of hydrodynamic and thermodynamic effects at the nanoscale.

  3. 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.

  4. Bioavailability of benzo(a)pyrene and dehydroabietic acid from a few lake waters containing varying dissolved organic carbon concentrations to Daphnia magna

    SciTech Connect

    Oikari, A.; Kukkonen, J. )

    1990-07-01

    Dissolved organic carbon (DOC) in natural waters consists of a great variety of organic molecules. Some of these molecules have been identified but most of them cannot be identified. This unidentified group of heterogeneous organic macromolecules is considered as humic substances. The role of humic substances in water chemistry and in aquatic toxicology is receiving increasing attention. The effects of DOC on the bioavailability of organic pollutants have been demonstrated in several studies. A decreased bioavailability has been demonstrated in most cases. Both the quantity and the quality of DOC are suggested determinants of this apparent ecotoxicological buffer of inland waters worldwide. In this study, the authors measured the bioaccumulation of benzo(a)pyrene (BaP) and dehydroabietic acid (DHAA) in Daphnia magna using a wide range of naturally occurring DOC levels. Another objective was to associate the reduced bioavailability with the chemical characteristics of water and DOC.

  5. 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).

  6. Do Ions Flow Freely Through Confined DNA?

    NASA Astrophysics Data System (ADS)

    Azad, Zubair; Riehn, Robert

    Double-stranded DNA in an aqueous solution is characterized by a strongly localized counter-ion cloud. Classical experiments have shown that the mobility of large DNA coils is independent of the number of basepairs, leading to an interpretation that the molecule can be understood as a collection of segments with constant mobility whose interactions are effectively screened from each other. This ``free-draining'' assumption posits that DNA and other electrolytes will not influence each other's mobility. In this talk, we call this assumption into question when the local concentration of DNA is increased beyond that of a self-avoiding random walk by nanoconfinement. We present translocation of DNA and fluorescent tracer ions under established chemical gradients, pressure-driven flow, and electrophoresis in nanochannels with cross sections that are 100 nm x 100 nm. We present evidence that interactions between the DNA and ionic tracers are a non-linear function of the applied fields.

  7. Variability of the dissolved nutrient (N, P, Si) concentrations in the Bay of Annaba in relation to the inputs of the Seybouse and Mafragh estuaries.

    PubMed

    Ounissi, Makhlouf; Ziouch, Omar-Ramzi; Aounallah, Ouafia

    2014-03-15

    Dissolved inorganic nitrogen (DIN), phosphate (PO₄) and silicic acid (Si(OH)₄) loads from the Seybouse and the Mafragh estuaries into the Bay of Annaba, Algeria, were assessed at three stations of the Bay over three years. The Seybouse inputs had high levels of DIN and PO₄, in contrast to the Mafragh estuary's near-pristine inputs; Si(OH)₄ levels were low in both estuaries. The DIN:PO₄ molar ratios were over 30 in most samples and the Si(OH)4:DIN ratio was less than 0.5 in the Seybouse waters, but nearly balanced in the Mafragh. The specific fluxes of Si-Si(OH)₄ (400-540 kg Si km⁻² yr⁻¹) were comparable in the two catchments, but those of DIN were several-fold higher in the Seybouse (373 kg N km⁻² yr⁻¹). The inner Bay affected by the Seybouse inputs had high levels of all nutrients, while the Mafragh plume and the outer marine station were less enriched.

  8. Influence of carbon nanotubes with preloaded and coexisting dissolved organic matter on the bioaccumulation of polycyclic aromatic hydrocarbons to Chironomus plumosus larvae in sediment.

    PubMed

    Shen, Mohai; Xia, Xinghui; Zhai, Yawei; Zhang, Xiaotian; Zhao, Xiuli; Zhang, Pu

    2014-01-01

    The ubiquity of dissolved organic matter (DOM) in an aqueous environment may have influence on the carbonaceous material's impact on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) to benthonic organisms in contaminated sediment. In the present study, 1 multiwalled carbon nanotube (MWNT); 2 types of DOM (fulvic acid and tannic acid), and 2 PAHs (pyrene and chrysene) were selected to study the influence of MWNT with preloaded and coexisting DOM on the bioaccumulation of PAHs to Chironomus plumosus larvae in sediment. Moreover, the freely dissolved concentrations of PAHs were measured to explore the influence mechanisms. The results showed that despite the presence or absence of preloaded or coexisting DOM, the presence of 1% MWNT in sediments suppressed the biota-sediment accumulation factor (BSAF) and elevated the water-based bioaccumulation factor (BAF) of PAHs. However, the BSAF and BAF values generally decreased with the increase of 2 forms of both DOM; this was caused by the combined impact of DOM and MWNT on the freely dissolved concentrations of PAHs and the ingestion behavior of benthic organisms.

  9. Crank inertial load affects freely chosen pedal rate during cycling.

    PubMed

    Hansen, Ernst Albin; Jørgensen, Lars Vincents; Jensen, Kurt; Fregly, Benjamin Jon; Sjøgaard, Gisela

    2002-02-01

    Cyclists seek to maximize performance during competition, and gross efficiency is an important factor affecting performance. Gross efficiency is itself affected by pedal rate. Thus, it is important to understand factors that affect freely chosen pedal rate. Crank inertial load varies greatly during road cycling based on the selected gear ratio. Nevertheless, the possible influence of crank inertial load on freely chosen pedal rate and gross efficiency has never been investigated. This study tested the hypotheses that during cycling with sub-maximal work rates, a considerable increase in crank inertial load would cause (1) freely chosen pedal rate to increase, and as a consequence, (2) gross efficiency to decrease. Furthermore, that it would cause (3) peak crank torque to increase if a constant pedal rate was maintained. Subjects cycled on a treadmill at 150 and 250W, with low and high crank inertial load, and with preset and freely chosen pedal rate. Freely chosen pedal rate was higher at high compared with low crank inertial load. Notably, the change in crank inertial load affected the freely chosen pedal rate as much as did the 100W increase in work rate. Along with freely chosen pedal rate being higher, gross efficiency at 250W was lower during cycling with high compared with low crank inertial load. Peak crank torque was higher during cycling at 90rpm with high compared with low crank inertial load. Possibly, the subjects increased the pedal rate to compensate for the higher peak crank torque accompanying cycling with high compared with low crank inertial load. PMID:11784546

  10. Plant induced changes in concentrations of caesium, strontium and uranium in soil solution with reference to major ions and dissolved organic matter.

    PubMed

    Takeda, Akira; Tsukada, Hirofumi; Takaku, Yuichi; Akata, Naofumi; Hisamatsu, Shun'ichi

    2008-06-01

    For a better understanding of the soil-to-plant transfer of radionuclides, their behavior in the soil solution should be elucidated, especially at the interface between plant roots and soil particles, where conditions differ greatly from the bulk soil because of plant activity. This study determined the concentration of stable Cs and Sr, and U in the soil solution, under plant growing conditions. The leafy vegetable komatsuna (Brassica rapa L.) was cultivated for 26 days in pots, where the rhizosphere soil was separated from the non-rhizosphere soil by a nylon net screen. The concentrations of Cs and Sr in the rhizosphere soil solution decreased with time, and were controlled by K+NH(4)(+) and Ca, respectively. On the other hand, the concentration of U in the rhizosphere soil solution increased with time, and was related to the changes of DOC; however, this relationship was different between the rhizosphere and non-rhizosphere soil.

  11. 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...

  12. Extracellular Wire Tetrode Recording in Brain of Freely Walking Insects

    PubMed Central

    Guo, Peiyuan; Pollack, Alan J.; Varga, Adrienn G.; Martin, Joshua P.; Ritzmann, Roy E.

    2014-01-01

    Increasing interest in the role of brain activity in insect motor control requires that we be able to monitor neural activity while insects perform natural behavior. We previously developed a technique for implanting tetrode wires into the central complex of cockroach brains that allowed us to record activity from multiple neurons simultaneously while a tethered cockroach turned or altered walking speed. While a major advance, tethered preparations provide access to limited behaviors and often lack feedback processes that occur in freely moving animals. We now present a modified version of that technique that allows us to record from the central complex of freely moving cockroaches as they walk in an arena and deal with barriers by turning, climbing or tunneling. Coupled with high speed video and cluster cutting, we can now relate brain activity to various parameters of the movement of freely behaving insects. PMID:24747699

  13. Real Time Monitoring of Dissolved Organic Carbon Concentration and Disinfection By-Product Formation Potential in a Surface Water Treatment Plant with Simulaneous UV-VIS Absorbance and Fluorescence Excitation-Emission Mapping

    NASA Astrophysics Data System (ADS)

    Gilmore, A. M.

    2015-12-01

    This study describes a method based on simultaneous absorbance and fluorescence excitation-emission mapping for rapidly and accurately monitoring dissolved organic carbon concentration and disinfection by-product formation potential for surface water sourced drinking water treatment. The method enables real-time monitoring of the Dissolved Organic Carbon (DOC), absorbance at 254 nm (UVA), the Specific UV Absorbance (SUVA) as well as the Simulated Distribution System Trihalomethane (THM) Formation Potential (SDS-THMFP) for the source and treated water among other component parameters. The method primarily involves Parallel Factor Analysis (PARAFAC) decomposition of the high and lower molecular weight humic and fulvic organic component concentrations. The DOC calibration method involves calculating a single slope factor (with the intercept fixed at 0 mg/l) by linear regression for the UVA divided by the ratio of the high and low molecular weight component concentrations. This method thus corrects for the changes in the molecular weight component composition as a function of the source water composition and coagulation treatment effects. The SDS-THMFP calibration involves a multiple linear regression of the DOC, organic component ratio, chlorine residual, pH and alkalinity. Both the DOC and SDS-THMFP correlations over a period of 18 months exhibited adjusted correlation coefficients with r2 > 0.969. The parameters can be reported as a function of compliance rules associated with required % removals of DOC (as a function of alkalinity) and predicted maximum contaminant levels (MCL) of THMs. The single instrument method, which is compatible with continuous flow monitoring or grab sampling, provides a rapid (2-3 minute) and precise indicator of drinking water disinfectant treatability without the need for separate UV photometric and DOC meter measurements or independent THM determinations.

  14. Energy Decay in Three-Dimensional Freely Cooling Granular Gas

    NASA Astrophysics Data System (ADS)

    Pathak, Sudhir N.; Jabeen, Zahera; Das, Dibyendu; Rajesh, R.

    2014-01-01

    The kinetic energy of a freely cooling granular gas decreases as a power law t-θ at large times t. Two theoretical conjectures exist for the exponent θ. One based on ballistic aggregation of compact spherical aggregates predicts θ =2d/(d+2) in d dimensions. The other based on Burgers equation describing anisotropic, extended clusters predicts θ =d/2 when 2≤d≤4. We do extensive simulations in three dimensions to find that while θ is as predicted by ballistic aggregation, the cluster statistics and velocity distribution differ from it. Thus, the freely cooling granular gas fits to neither the ballistic aggregation or a Burgers equation description.

  15. Single-molecule diffusion in freely suspended smectic films.

    PubMed

    Schulz, Benjamin; Mazza, Marco G; Bahr, Christian

    2014-10-01

    We present a study of the molecular diffusion in freely suspended smectic-A liquid crystal films with thicknesses ranging from 20 down to only two molecular layers. The molecular mobility is directly probed by determining the trajectories of single, fluorescent tracer molecules. We demonstrate, using several different smectic compounds, that a monotonic increase of the diffusion coefficient with decreasing film thickness is a general phenomenon. In two-layer films, the diffusion is enhanced by a factor of 3 to 5 compared to the corresponding bulk smectic phase. Molecular dynamics simulations of freely suspended smectic films are presented which support the experimental results.

  16. METHOD OF DISSOLVING METALLIC URANIUM

    DOEpatents

    Schulz, W.W.

    1959-07-28

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

  17. Sequential Determination of Free Acidity and Plutonium Concentration in the Dissolver Solution of Fast-Breeder Reactor Spent Fuels in a Single Aliquot.

    PubMed

    Dhamodharan, K; Pius, Anitha

    2016-01-01

    A simple potentiometric method for determining the free acidity without complexation in the presence of hydrolysable metal ions and sequentially determining the plutonium concentration by a direct spectrophotometric method using a single aliquot was developed. Interference from the major fission products, which are susceptible to hydrolysis at lower acidities, had been investigated in the free acidity measurement. This method is applicable for determining the free acidity over a wide range of nitric acid concentrations as well as the plutonium concentration in the irradiated fuel solution prior to solvent extraction. Since no complexing agent is introduced during the measurement of the free acidity, the purification step is eliminated during the plutonium estimation, and the resultant analytical waste is free from corrosive chemicals and any complexing agent. Hence, uranium and plutonium can be easily recovered from analytical waste by the conventional solvent extraction method. The error involved in determining the free acidity and plutonium is within ±1% and thus this method is superior to the complexation method for routine analysis of plant samples and is also amenable for remote analysis. PMID:27063711

  18. Sequential Determination of Free Acidity and Plutonium Concentration in the Dissolver Solution of Fast-Breeder Reactor Spent Fuels in a Single Aliquot.

    PubMed

    Dhamodharan, K; Pius, Anitha

    2016-01-01

    A simple potentiometric method for determining the free acidity without complexation in the presence of hydrolysable metal ions and sequentially determining the plutonium concentration by a direct spectrophotometric method using a single aliquot was developed. Interference from the major fission products, which are susceptible to hydrolysis at lower acidities, had been investigated in the free acidity measurement. This method is applicable for determining the free acidity over a wide range of nitric acid concentrations as well as the plutonium concentration in the irradiated fuel solution prior to solvent extraction. Since no complexing agent is introduced during the measurement of the free acidity, the purification step is eliminated during the plutonium estimation, and the resultant analytical waste is free from corrosive chemicals and any complexing agent. Hence, uranium and plutonium can be easily recovered from analytical waste by the conventional solvent extraction method. The error involved in determining the free acidity and plutonium is within ±1% and thus this method is superior to the complexation method for routine analysis of plant samples and is also amenable for remote analysis.

  19. Acute toxicity of the cationic surfactant C12-benzalkonium in different bioassays: how test design affects bioavailability and effect concentrations.

    PubMed

    Chen, Yi; Geurts, Marc; Sjollema, Sascha B; Kramer, Nynke I; Hermens, Joop L M; Droge, Steven T J

    2014-03-01

    Using an ion-exchange-based solid-phase microextraction (SPME) method, the freely dissolved concentrations of C12-benzalkonium were measured in different toxicity assays, including 1) immobilization of Daphnia magna in the presence or absence of dissolved humic acid; 2) mortality of Lumbriculus variegatus in the presence or absence of a suspension of Organisation for Economic Co-Operation and Development (OECD) sediment; 3) photosystem II inhibition of green algae Chlorella vulgaris; and 4) viability of in vitro rainbow trout gill cell line (RTgill-W1) in the presence or absence of serum proteins. Furthermore, the loss from chemical adsorption to the different test vessels used in these tests was also determined. The C12-benzalkonium sorption isotherms to the different sorbent phases were established as well. Our results show that the freely dissolved concentration is a better indicator of the actual exposure concentration than the nominal or total concentration in most test assays. Daphnia was the most sensitive species to C12-benzalkonium. The acute Daphnia and Lumbriculus tests both showed no enhanced toxicity from possible ingestion of sorbed C12-benzalkonium in comparison with water-only exposure, which is in accordance with the equilibrium partitioning theory. Moreover, the present study demonstrates that commonly used sorbent phases can strongly affect bioavailability and observed effect concentrations for C12-benzalkonium. Even stronger effects of decreased actual exposure concentrations resulting from sorption to test vessels, cells, and sorbent phases can be expected for more hydrophobic cationic surfactants. PMID:24273010

  20. Automated microextraction sample preparation coupled on-line to FT-ICR-MS: application to desalting and concentration of river and marine dissolved organic matter.

    PubMed

    Morales-Cid, Gabriel; Gebefugi, Istvan; Kanawati, Basem; Harir, Mourad; Hertkorn, Norbert; Rosselló-Mora, Ramón; Schmitt-Kopplin, Philippe

    2009-10-01

    Sample preparation procedures are in most cases sample- and time-consuming and commonly require the use of a large amount of solvents. Automation in this regard can optimize the minimal-needed injection volume and the solvent consumption will be efficiently reduced. A new fully automated sample desalting and pre-concentration technique employing microextraction by packed sorbents (MEPS) cartridges is implemented and coupled to an ion cyclotron resonance Fourier-transform mass spectrometer (ICR-FT/MS). The performance of non-target mass spectrometric analysis is compared for the automated versus off-line sample preparation for several samples of aqueous natural organic matter. This approach can be generalized for any metabolite profiling or metabolome analysis of biological materials but was optimized herein using a well characterized but highly complex organic mixture: a surface water and its well-characterized natural organic matter and a marine sample having a highly salt charge and enabling to validate the presented automatic system for salty samples. The analysis of Suwannee River water showed selective C18-MEPS enrichment of chemical signatures with average H/C and O/C elemental ratios and loss of both highly polar and highly aromatic structures from the original sample. Automated on-line application to marine samples showed desalting and different chemical signatures from surface to bottom water. Relative comparison of structural footprints with the C18-concentration/desalting procedure however enabled to demonstrate that the surface water film was more concentrated in surface-active components of natural (fatty acids) and anthropogenic origin (sulfur-containing surfactants). Overall, the relative standard deviation distribution in terms of peak intensity was improved by automating the proposed on-line method. PMID:19685041

  1. On-line estimation of the dissolved zinc concentration during ZnS precipitation in a continuous stirred tank reactor (CSTR).

    PubMed

    Grootscholten, T I M; Keesman, K J; Lens, P N L

    2008-01-01

    In this paper a method is presented to estimate the reaction term of zinc sulphide precipitation and the zinc concentration in a CSTR, using the read-out signal of a sulphide selective electrode. The reaction between zinc and sulphide is described by a non-linear model and therefore classical observer theory cannot be applied directly, as this theory was initially developed for linear systems. However, by linear reparametrization of this non-linear system, the linear observer theory can be applied in an effective way. This is illustrated by a zinc sulphide example using real data.

  2. 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.

  3. 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.

    PubMed

    Kent, Robert; Landon, Matthew K

    2013-05-01

    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. PMID:23500406

  4. 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.

    PubMed

    Kent, Robert; Landon, Matthew K

    2013-05-01

    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.

  5. Pore water dating by 129I: What do 36Cl/Cl ratio, dissolved 4He concentration, δ37Cl and 129I/127I ratio suggest in the Mobara Gas field, Japan?

    NASA Astrophysics Data System (ADS)

    Mahara, Y.; Ohta, T.; Tokunaga, T.

    2010-12-01

    Total 24-brine samples were collected from hot springs and the Mobara gas wells in the Southern Kanto Gas field, where is not only the major production area for dissolved natural gas in Japan but for iodine in the world. Isotopic ratios of 129I/127I and 36Cl/Cl, and noble gases concentration dissolved into pore water were measured for estimating residence time of brine. Iodine concentration in brines increases from 10 mg/L in the northern Kanto plain to more than 100 mg/L in the south edge of the gas field, and finally reaches 170 mg/L. In contrast, the isotopic ratio of 129I/127I decreases 5×10-13 in north to 1.7×10-13 in south. Both distributions were presumably controlled by the thickness of the Kazusa group as natural gas reservoirs. The average 129I/127I ratio was estimated to be 2.33 ± 0.11×10-13 at the Mobara area. Average ages of brines are estimated to be 42 Ma by using the initial 129I/127I ratio (1.5×10-12), if the origin of 129I were cosmogenic. On the other hand, we deduced 0.2 - 0.9 Ma as the residence time of brine from comparison with the secular equilibrium 36Cl/Cl ratio (6.46 ± 2.24×10-15) for the reservoir formation of Pleistocene. The concentration of 4He dissolved in pore water in the bored rock core suggests that residence time of brines vertically ranges 0.12 - 1.05 Ma and it is also harmonized with the formation age (of 0.45 - 2.5 Ma). Furthermore, δ37Cl (- 0.14±0.13 ~ + 0.45±0.07 ‰) in pore water were measured under the chloride concentration increasing 5000 mg/L to 17000 mg/L at the depth from 642 m to 1902 m below the ground surface. The simulating analyses of δ37Cl was conducted under the boundary conditions of washing out by freshwater at the depth of 600 m below the ground surface, chloride concentration gradient of 17000/500 (mg/L/m) and diffusion alone without advection flow during the past 0.12 Ma. The fractionation factor for 35Cl and 37Cl was 1.0012 (Desauliniers et al., 1986). The analyses indicated that the

  6. 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

  7. Measuring in situ dissolved methane concentrations in gas hydrate-rich systems, Part 1: Investigating the correlation between tectonics and methane release from sediments

    NASA Astrophysics Data System (ADS)

    Lapham, L.; Wilson, R. M.; Paull, C. K.; Chanton, J.; Riedel, M.

    2010-12-01

    In 2009, an area of extended methane venting at 1200 meters water depth was found with high resolution AUV bathymetry scans on the Northern Cascadia Margin that was previously unknown. When visited by ROV, we found seafloor cracks with active bubble streams and thin bacterial mats suggesting shallow gas and possible pore-fluid saturation. Upon coring into the cracks, a hard-substrate (carbonate or gas hydrate) was punctured and gas flows began. With these observations, we asked the question “is this shallow gas released from the seafloor from regional tectonic activity, and, if so, what is the temporal variability of such release events?” To answer this, we deployed a long term pore-water collection device at one of these gas crack sites, informally named “bubbly gulch”, for 9 months. The device is made up of 4 OsmoSamplers that were each plumbed to a port along a 1-meter probe tip using small diameter tubing. By osmosis, the samplers collected water samples slowly through the ports and maintained them within a 300 meter-long copper tubing coil. Because of the high methane concentrations anticipated, in situ pressures were maintained within the coil by the addition of a high pressure valve. Water samples were collected from the overlying water, at the sediment-water interface, and 6 and 10 cm into the sediments. Bottom water temperatures were also measured over the time series to determine pumping rates of the samplers but also to look for any temporal variability. In May 2010, the samplers were retrieved by ROV during efforts to install seafloor instruments for Neptune Canada. In a land-based lab, the coils were sub-sampled by cutting every 4 meters of tubing. With a pumping rate of 0.5 mL/day, this allowed a temporal resolution of 6 days. To date, one sampler coil has been sub-sampled and measured for methane concentrations and stable carbon isotopes. Preliminary results from this coil show pore-fluids nearly saturated with respect to methane, ~45 m

  8. 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

  9. Methods to Identify Changes in Background Water-Quality Conditions Using Dissolved-Solids Concentrations and Loads as Indicators, Arkansas River and Fountain Creek, in the Vicinity of Pueblo, Colorado

    USGS Publications Warehouse

    Ortiz, Roderick F.

    2004-01-01

    Effective management of existing water-storage capacity in the Arkansas River Basin is anticipated to help satisfy the need for water in southeastern Colorado. A strategy to meet these needs has been developed, but implementation could affect the water quality of the Arkansas River and Fountain Creek in the vicinity of Pueblo, Colorado. Because no known methods are available to determine what effects future changes in operations will have on water quality, the U.S. Geological Survey, in cooperation with the Southeastern Colorado Water Activity Enterprise, began a study in 2002 to develop methods that could identify if future water-quality conditions have changed significantly from background (preexisting) water-quality conditions. A method was developed to identify when significant departures from background (preexisting) water-quality conditions occur in the lower Arkansas River and Fountain Creek in the vicinity of Pueblo, Colorado. Additionally, the methods described in this report provide information that can be used by various water-resource agencies for an internet-based decision-support tool. Estimated dissolved-solids concentrations at five sites in the study area were evaluated to designate historical background conditions and to calculate tolerance limits used to identify statistical departures from background conditions. This method provided a tool that could be applied with defined statistical probabilities associated with specific tolerance limits. Drought data from 2002 were used to test the method. Dissolved-solids concentrations exceeded the tolerance limits at all four sites on the Arkansas River at some point during 2002. The number of exceedances was particularly evident when streamflow from Pueblo Reservoir was reduced, and return flows and ground-water influences to the river were more prevalent. No exceedances were observed at the site on Fountain Creek. These comparisons illustrated the need to adjust the concentration data to account for

  10. 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

  11. Flyception: imaging brain activity in freely walking fruit flies.

    PubMed

    Grover, Dhruv; Katsuki, Takeo; Greenspan, Ralph J

    2016-07-01

    Genetically encoded calcium sensors have enabled monitoring of neural activity in vivo using optical imaging techniques. Linking neural activity to complex behavior remains challenging, however, as most imaging systems require tethering the animal, which can impact the animal's behavioral repertoire. Here, we report a method for monitoring the brain activity of untethered, freely walking Drosophila melanogaster during sensorially and socially evoked behaviors to facilitate the study of neural mechanisms that underlie naturalistic behaviors. PMID:27183441

  12. Soot Formation in Freely-Propagating Laminar Premixed Flames

    NASA Technical Reports Server (NTRS)

    Lin, K.-C.; Hassan, M. I.; Faeth, G. M.

    1997-01-01

    Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

  13. 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

  14. Dissolved Fe(II) in a river-estuary system rich in dissolved organic matter

    NASA Astrophysics Data System (ADS)

    Hopwood, Mark J.; Statham, Peter J.; Milani, Ambra

    2014-12-01

    Reduced iron, Fe(II), accounts for a significant fraction of dissolved Fe across many natural surface waters despite its rapid oxidation under oxic conditions. Here we investigate the temporal and spatial variation in dissolved Fe redox state in a high dissolved organic matter (DOM) estuarine system, the River Beaulieu. We couple manual sample collection with the deployment of an autonomous in situ analyser, designed to simultaneously measure dissolved Fe(II) and total dissolved Fe, in order to investigate processes operating on the diurnal timescale and to evaluate the performance of the analyser in a high DOM environment. Concentrations of dissolved Fe available to the ligand ferrozine are elevated throughout the estuary (up to 21 μM in freshwater) and notably higher than those previously reported likely due to seasonal variation. Fe(II) is observed to account for a large, varying fraction of the dissolved Fe available to ferrozine (25.5 ± 12.5%) and this fraction decreases with increasing salinity. We demonstrate that the very high DOM concentration in this environment and association of this DOM with dissolved Fe, prevents the accurate measurement of dissolved Fe concentrations in situ using a sensor reliant on rapid competitive ligand exchange.

  15. Modelling hourly dissolved oxygen concentration (DO) using dynamic evolving neural-fuzzy inference system (DENFIS)-based approach: case study of Klamath River at Miller Island Boat Ramp, OR, USA.

    PubMed

    Heddam, Salim

    2014-01-01

    In this study, we present application of an artificial intelligence (AI) technique model called dynamic evolving neural-fuzzy inference system (DENFIS) based on an evolving clustering method (ECM), for modelling dissolved oxygen concentration in a river. To demonstrate the forecasting capability of DENFIS, a one year period from 1 January 2009 to 30 December 2009, of hourly experimental water quality data collected by the United States Geological Survey (USGS Station No: 420853121505500) station at Klamath River at Miller Island Boat Ramp, OR, USA, were used for model development. Two DENFIS-based models are presented and compared. The two DENFIS systems are: (1) offline-based system named DENFIS-OF, and (2) online-based system, named DENFIS-ON. The input variables used for the two models are water pH, temperature, specific conductance, and sensor depth. The performances of the models are evaluated using root mean square errors (RMSE), mean absolute error (MAE), Willmott index of agreement (d) and correlation coefficient (CC) statistics. The lowest root mean square error and highest correlation coefficient values were obtained with the DENFIS-ON method. The results obtained with DENFIS models are compared with linear (multiple linear regression, MLR) and nonlinear (multi-layer perceptron neural networks, MLPNN) methods. This study demonstrates that DENFIS-ON investigated herein outperforms all the proposed techniques for DO modelling. PMID:24705953

  16. Perfusion Imaging with a Freely Diffusible Hyperpolarized Contrast Agent

    PubMed Central

    Grant, Aaron K.; Vinogradov, Elena; Wang, Xiaoen; Lenkinski, Robert E.; Alsop, David C.

    2011-01-01

    Contrast agents that can diffuse freely into or within tissue have numerous attractive features for perfusion imaging. Here we present preliminary data illustrating the suitability of hyperpolarized 13C labeled 2-methylpropan-2-ol (also known as dimethylethanol, tertiary butyl alcohol and tert-butanol) as a freely diffusible contrast agent for magnetic resonance perfusion imaging. Dynamic 13C images acquired in rat brain with a balanced steady-state free precession (bSSFP) sequence following administration of hyperpolarized 2-methylpropan-2-ol show that this agent can be imaged with 2–4s temporal resolution, 2mm slice thickness, and 700 micron in-plane resolution while retaining adequate signal-to-noise ratio. 13C relaxation measurements on 2-methylpropan-2-ol in blood at 9.4T yield T1=46±4s and T2=0.55±0.03s. In the rat brain at 4.7T, analysis of the temporal dynamics of the bSSFP image intensity in tissue and venous blood indicate that 2-methylpropan-2-ol has a T2 of roughly 2–4s and a T1 of 43±24s. In addition, the images indicate that 2-methylpropan-2-ol is freely diffusible in brain and hence has a long residence time in tissue; this in turn makes it possible to image the agent continuously for tens of seconds. These characteristics show that 2-methylpropan-2-ol is a promising agent for robust and quantitative perfusion imaging in the brain and body. PMID:21432901

  17. Assessing the relation between anthropogenic pressure and PAH concentrations in surface water in the Seine River basin using multivariate analysis.

    PubMed

    Uher, Emmanuelle; Mirande-Bret, Cécile; Gourlay-Francé, Catherine

    2016-07-01

    Understanding the relation between polycyclic aromatic hydrocarbons (PAHs) in freshwater and anthropogenic pressure is fundamental to finding a solution to reduce the presence of PAHs in water, and thus their potential impact on aquatic life. In this paper we propose to gain greater insight into the variability, sources and partitioning of PAHs in labile (or freely dissolved=not associated to the organic matter), dissolved and particulate phases in freshwater. This study was conducted using land use data as a marker of anthropogenic pressure and coupling it with chemical measurements. This study was conducted on 30 sites in the Seine River basin, which is subjected to a strong human impact and exhibits a wide range of land uses. Half of the sites were studied twice. Labile PAHs were measured by semi-permeable membrane devices (SPMDs), and dissolved and particulate phases by grab samples. Partial least squares regressions were performed between chemical measurements and data of anthropogenic pressure. The results indicate different sources for the dissolved phase and particles. Dissolved and labile phases were more related to the population density of the watershed, while particles were more related to a local pressure. Season and land use data are necessary information to correctly interpret and compare PAH concentrations from different sites. Furthermore, the whole data set of the 45 field deployments comprising labile, dissolved, total and particulate PAH concentrations as well as the physico-chemical parameters is available in the supplementary information. PMID:27037876

  18. An experimental study of magnesite dissolution rates at neutral to alkaline conditions and 150 and 200 °C as a function of pH, total dissolved carbonate concentration, and chemical affinity

    NASA Astrophysics Data System (ADS)

    Saldi, Giuseppe D.; Schott, Jacques; Pokrovsky, Oleg S.; Oelkers, Eric H.

    2010-11-01

    Steady-state magnesite dissolution rates were measured in mixed-flow reactors at 150 and 200 °C and 4.6 < pH < 8.4, as a function of ionic strength (0.001 M ⩽ I ⩽ 1 M), total dissolved carbonate concentration (10 -4 M < ΣCO 2 < 0.1 M), and distance from equilibrium. Rates were found to increase with increasing ionic strength, but decrease with increasing temperature from 150 to 200 °C, pH, and aqueous CO 32- activity. Measured rates were interpreted using the surface complexation model developed by Pokrovsky et al. (1999a) in conjunction with transition state theory ( Eyring, 1935). Within this formalism, magnesite dissolution rates are found to be consistent with r=k{>MgOH2+}41-exp (-4ART), where rd represents the BET surface area normalized dissolution rate, {>MgOH2+} stands for the concentration of hydrated magnesium centers on the magnesite surface, kMg designates a rate constant, A refers to the chemical affinity of the overall reaction, R denotes the gas constant, and T symbolizes absolute temperature. Within this model decreasing rates at far-from-equilibrium conditions (1) at constant pH with increasing temperature and (2) at constant temperature with increasing pH and ΣCO 2 stem from a corresponding decrease in {>MgOH2+}. This decrease in {>MgOH2+} results from the increasing stability of the >MgCO3- and >MgOH° surface species with increasing temperature, pH and CO 32- activity. The decrease in constant pH dissolution rates yields negative apparent activation energies. This behavior makes magnesite resistant to re-dissolution if formed as part of mineral carbon sequestration efforts in deep geologic formations.

  19. Flagellar waveform dynamics of freely swimming algal cells

    NASA Astrophysics Data System (ADS)

    Kurtuldu, H.; Tam, D.; Hosoi, A. E.; Johnson, K. A.; Gollub, J. P.

    2013-07-01

    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 force theory as well as a singularity method to predict a cell's time-dependent velocity for comparison with experiments. While net propulsion is thought to arise from asymmetry between the power and recovery strokes, we show that hydrodynamic interactions between the flagella and cell body on the return stroke make an important contribution to enhance net forward motion.

  20. Velocity measurements around a freely swimming fish using PIV

    NASA Astrophysics Data System (ADS)

    Kamran Siddiqui, M. H.

    2007-01-01

    Two-dimensional velocity fields around a freely swimming goldfish in a vertical plane have been measured using the particle image velocimetry (PIV) technique. A novel scheme has been developed to detect the fish body in each PIV image. The scheme is capable of detecting the bodies of fish and other aquatic animals with multicolour skin and different patterns. In this scheme, the body portions brighter and darker than the background are extracted separately and then combined together to construct the entire body. The velocity fields show that the fins and tail produce jets. Vortices are also observed in the wake region.

  1. Erosion patterns on dissolving blocks

    NASA Astrophysics Data System (ADS)

    Courrech du Pont, Sylvain; Cohen, Caroline; Derr, Julien; Berhanu, Michael

    2016-04-01

    Patterns in nature are shaped under water flows and wind action, and the understanding of their morphodynamics goes through the identification of the physical mechanisms at play. When a dissoluble body is exposed to a water flow, typical patterns with scallop-like shapes may appear [1,2]. These shapes are observed on the walls of underground rivers or icebergs. We experimentally study the erosion of dissolving bodies made of salt, caramel or ice into water solutions without external flow. The dissolving mixture, which is created at the solid/liquid interface, undergoes a buoyancy-driven instability comparable to a Rayleigh-Bénard instability so that the dissolving front destabilizes into filaments. This mechanism yields to spatial variations of solute concentration and to differential dissolution of the dissolving block. We first observe longitudinal stripes with a well defined wavelength, which evolve towards chevrons and scallops that interact and move again the dissolving current. Thanks to a careful analysis of the competing physical mechanisms, we propose scaling laws, which account for the characteristic lengths and times of the early regime in experiments. The long-term evolution of patterns is understood qualitatively. A close related mechanism has been proposed to explain structures observed on the basal boundary of ice cover on brakish lakes [3] and we suggest that our experiments are analogous and explain the scallop-like patterns on iceberg walls. [1] P. Meakin and B. Jamtveit, Geological pattern formation by growth and dissolution in aqueous systems, Proc. R. Soc. A 466, 659-694 (2010). [2] P.N. Blumberg and R.L. Curl, Experimental and theoretical studies of dissolution roughness, J. Fluid Mech. 65, 735-751 (1974). [3] L. Solari and G. Parker, Morphodynamic modelling of the basal boundary of ice cover on brakish lakes, J.G.R. 118, 1432-1442 (2013).

  2. Wireless neural stimulation in freely behaving small animals.

    PubMed

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

    2009-07-01

    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 microA 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

  3. Nonlinear fluctuation effects in dynamics of freely suspended films

    NASA Astrophysics Data System (ADS)

    Kats, E. I.; Lebedev, V. V.

    2015-03-01

    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 q2 (q is the wave vector of the mode), since it is forbidden by the rotational symmetry. Therefore, the bending mode is strongly affected by nonlinear dynamic fluctuation effects. We calculate the dominant fluctuation contributions to the damping of the bending mode due to its coupling to the inplane viscous mode, which restores the viscous-like q2 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.

  4. 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.

  5. Freely-tunable broadband polarization rotator for terahertz waves

    NASA Astrophysics Data System (ADS)

    Peng, Ru-Wen; Fan, Ren-Hao; Zhou, Yu; Jiang, Shang-Chi; Xiong, Xiang; Huang, Xian-Rong; Wang, Mu

    It is known that commercially-available terahertz (THz) emitters usually generate linearly polarized waves only along certain directions, but in practice, a polarization rotator that is capable of rotating the polarization of THz waves to any direction is particularly desirable and it will have various important applications. In this work, we demonstrate a freely tunable polarization rotator for broadband THz waves using a three-rotating-layer metallic grating structure, which can conveniently rotate the polarization of a linearly polarized THz wave to any desired direction with nearly perfect conversion efficiency. The device performance has been experimentally demonstrated by both THz transmission spectra and direct imaging. The polarization rotation originates from multi wave interference in the three-layer grating structure based on the scattering-matrix analysis. We can expect that this active broadband polarization rotator has wide applications in analytical chemistry, biology, communication technology, imaging, etc.. Reference: R. H. Fan, Y. Zhou, X. P. Ren, R. W. Peng, S. C. Jiang, D. H. Xu, X. Xiong, X. R. Huang, and Mu Wang, Advanced Materials 27,1201(2015). Freely-tunable broadband polarization rotator for terahertz waves.

  6. 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

  7. Dissolver vessel bottom assembly

    DOEpatents

    Kilian, Douglas C.

    1976-01-01

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

  8. Enhanced glucose tolerance by intravascularly administered piceatannol in freely moving healthy rats.

    PubMed

    Oritani, Yukihiro; Okitsu, Teru; Nishimura, Eisaku; Sai, Masahiko; Ito, Tatsuhiko; Takeuchi, Shoji

    2016-02-12

    Piceatannol is a phytochemical in the seeds of passion fruit that has a hypoglycemic effect when orally administered. To elucidate the contribution of intact and metabolites of piceatannol after gastro-intestinal absorption to hypoglycemic effect, we examined the influence of piceatannol and isorhapontigenin on blood glucose concentrations during fasting and glucose tolerance tests by administering them intravascularly to freely moving healthy rats. We found that intravascularly administered piceatannol reduced the blood glucose concentrations during both fasting and glucose tolerance tests, but isorhapontigenin did not during either of them. Furthermore, we found that piceatannol increased the insulinogenic index during glucose tolerance tests and that piceatannol had no influence on insulin sensitivity by performing hyperinsulinemic euglycemic clamping tests. These results suggest that piceatannol orally intaken may enhance glucose tolerance by the effect of intact piceatannol through enhanced early-phase secretion of insulin. Therefore, oral intake of piceatannol might contribute to proper control of postprandial glycemic excursions in healthy subjects.

  9. 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...

  10. Simulation of hydrodynamics, temperature, and dissolved oxygen in Bull Shoals Lake, Arkansas, 1994-1995

    USGS Publications Warehouse

    Galloway, Joel M.; Green, W. Reed

    2003-01-01

    and dissolved-oxygen concentration through time. However, results from both scenarios for water temperature and dissolved-oxygen concentration were within the boundaries of the error between measured and simulated water column profile values.

  11. 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.

  12. Bioaccumulation of perfluoroalkyl substances by Daphnia magna in water with different types and concentrations of protein.

    PubMed

    Xia, Xinghui; Rabearisoa, Andry H; Jiang, Xiaoman; Dai, Zhineng

    2013-10-01

    Perfluoroalkyl substances (PFASs) are sometimes regarded as proteinophilic compounds, however, there is no research report about the effect of environmental protein on the bioaccumulation of PFASs in waters. In the present study we investigated influences of protein on the bioaccumulation of six kinds of PFASs by Daphnia magna in water; it included perfluorooctane sulfonate, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, and perfluorododecanoic acid. Two types of protein including bovine albumin from animal and soy peptone from plant were compared and the effects of protein concentration were investigated. Both types of protein at high concentrations (10 and 20 mg L(-1)) suppressed the bioaccumulation of PFASs. When protein concentration increased from 0 to 20 mg L(-1), the decreasing ratios of the PFAS body burden (35.3-52.9%) in Daphnia magna induced by bovine albumin were significantly higher than those (22.0-36.6%) by soy peptone. The dialysis bag experiment results showed that the binding of PFASs to protein followed the Freundlich isotherm, suggesting it is not a linear partitioning process but an adsorption-like process. The partition coefficients of PFASs between bovine albumin and water were higher compared to soy peptone; this resulted in higher reducing rates of freely dissolved concentrations of PFASs with increasing bovine albumin concentration, leading to a stronger suppression of PFAS bioaccumulation. However, the presence of both types of protein with a low concentration (1 mg L(-1)) enhanced the bioaccumulation of PFASs. Furthermore, the water-based bioaccumulation factor based on the freely dissolved concentrations of PFASs even increased with and the depuration rate constants of PFASs from Daphnia magna decreased with protein concentration, suggesting that protein would not only reduce the bioavailable concentrations and uptake rates of PFASs but also lower the elimination rates of PFASs in

  13. 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.

  14. Optogenetic manipulation of neural activity in freely moving Caenorhabditis elegans

    PubMed Central

    Leifer, Andrew M; Fang-Yen, Christopher; Gershow, Marc; Alkema, Mark J; Samuel, Aravinthan D T

    2011-01-01

    We present an optogenetic illumination system capable of real-time light delivery with high spatial resolution to specified targets in freely moving Caenorhabditis elegans. A tracking microscope records the motion of an unrestrained worm expressing Channelrhodopsin-2 or Halorhodopsin/NpHR in specific cell types. Image processing software analyzes the worm’s position within each video frame, rapidly estimates the locations of targeted cells, and instructs a digital micromirror device to illuminate targeted cells with laser light of the appropriate wavelengths to stimulate or inhibit activity. Since each cell in an unrestrained worm is a rapidly moving target, our system operates at high speed (~50 frames per second) to provide high spatial resolution (~30 µm). To demonstrate the accuracy, flexibility, and utility of our system, we present optogenetic analyses of the worm motor circuit, egg-laying circuit, and mechanosensory circuits that were not possible with previous methods. PMID:21240279

  15. Flagellar Waveform Dynamics of Freely Swimming Algal Cells

    NASA Astrophysics Data System (ADS)

    Gollub, Jerry; Kurtuldu, Huseyin; Johnson, Karl

    2012-02-01

    We study the time-dependent conformation patterns of flagella driving freely swimming algal cells, and use this information to determine the time-dependent forces acting on the cells, the induced cell velocities, and the power injected into the surrounding fluid. Conformational waves are evident along the flagella, as are synchronization transitions. The observed dynamics relate directly to the behavior of the dynein molecular motors ``walking'' along the microtubules of the flagella. We find that the irreversibility giving rise to net propulsion is due to the hydrodynamic interactions between the flagella and cell body. We determine the time-dependent power injected into the fluid by the cell body and flagella, and show that the propulsion efficiency is only about 3%.

  16. Numerical simulation of the dynamics of freely falling discs

    NASA Astrophysics Data System (ADS)

    Chrust, Marcin; Bouchet, Gilles; Dušek, Jan

    2013-04-01

    We present a comprehensive parametric study of the transition scenario of freely falling discs. The motion of the discs is investigated by a direct numerical simulation of the solid-fluid interaction. The discs are assumed to be homogeneous and infinitely thin. The problem is shown to depend on two independent parameters, the Galileo number expressing the ratio between effects of gravity and viscosity and the non-dimensionalized mass characterizing the inertia of the disc. The obtained results are in agreement with known experimental and numerical data and provide both detailed and comprehensive picture of the transition scenario in the two-parameter plane defined by the Galileo number and the non-dimensionalized mass.

  17. 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

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

    PubMed

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

    2010-05-30

    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.

  19. 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

  20. PROCESS OF DISSOLVING ZIRCONIUM ALLOYS

    DOEpatents

    Shor, R.S.; Vogler, S.

    1958-01-21

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

  1. Real-time monitoring of brain tissue oxygen using a miniaturized biotelemetric device implanted in freely moving rats.

    PubMed

    Bazzu, Gianfranco; Puggioni, Giulia G M; Dedola, Sonia; Calia, Giammario; Rocchitta, Gaia; Migheli, Rossana; Desole, Maria S; Lowry, John P; O'Neill, Robert D; Serra, Pier A

    2009-03-15

    A miniaturized biotelemetric device for the amperometric detection of brain tissue oxygen is presented. The new system, derived from a previous design, has been coupled with a carbon microsensor for the real-time detection of dissolved O(2) in the striatum of freely moving rats. The implantable device consists of a single-supply sensor driver, a current-to-voltage converter, a microcontroller, and a miniaturized data transmitter. The oxygen current is converted to a digital value by means of an analog-to-digital converter integrated in a peripheral interface controller (PIC). The digital data is sent to a personal computer using a six-byte packet protocol by means of a miniaturized 434 MHz amplitude modulation (AM) transmitter. The receiver unit is connected to a personal computer (PC) via a universal serial bus. Custom developed software allows the PC to store and plot received data. The electronics were calibrated and tested in vitro under different experimental conditions and exhibited high stability, low power consumption, and good linear response in the nanoampere current range. The in vivo results confirmed previously published observations on oxygen dynamics in the striatum of freely moving rats. The system serves as a rapid and reliable model for studying the effects of different drugs on brain oxygen and brain blood flow and it is suited to work with direct-reduction sensors or O(2)-consuming biosensors. PMID:19222224

  2. 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.

  3. Natural versus wastewater derived dissolved organic carbon: implications for the environmental fate of organic micropollutants.

    PubMed

    Neale, Peta A; Antony, Alice; Gernjak, Wolfgang; Leslie, Greg; Escher, Beate I

    2011-08-01

    The interaction of organic micropollutants with dissolved organic carbon (DOC) can influence their transport, degradation and bioavailability. While this has been well established for natural organic carbon, very little is known regarding the influence of DOC on the fate of micropollutants during wastewater treatment and water recycling. Dissolved organic carbon-water partition coefficients (K(DOC)) for wastewater derived and reference DOC were measured for a range of micropollutants using a depletion method with polydimethylsiloxane disks. For micropollutants with an octanol-water partition coefficient (log K(OW)) greater than 4 there was a significant difference in K(DOC) between reference and wastewater derived DOC, with partitioning to wastewater derived DOC over 1000 times lower for the most hydrophobic micropollutants. The interaction of nonylphenol with wastewater derived DOC from different stages of a wastewater and advanced water treatment train was studied, but little difference in K(DOC) was observed. Organic carbon characterisation revealed that reference and wastewater derived DOC had very different properties due to their different origins. Consequently, the reduced sorption capacity of wastewater derived DOC may be related to their microbial origin which led to reduced aromaticity and lower molecular weight. This study suggests that for hydrophobic micropollutants (log K(OW) > 4) a higher concentration of freely dissolved and thus bioavailable micropollutants is expected in the presence of wastewater derived DOC than predicted using K(DOC) values quantified using reference DOC. The implication is that naturally derived DOC may not be an appropriate surrogate for wastewater derived DOC as a matrix for assessing the fate of micropollutants in engineered systems. PMID:21703657

  4. 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.

  5. Studying the freely-behaving brain with fMRI.

    PubMed

    Maguire, Eleanor A

    2012-08-15

    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).

  6. Hydrodynamics of Inclusions in Freely Suspended Liquid Crystal Films

    NASA Astrophysics Data System (ADS)

    Qi, Zhiyuan

    Hydrodynamic interaction of pairs of circular inclusions in two-dimensional (2D), fluid smectic membranes suspended in air has been studied systematically. By analyzing their Brownian motion, it is found that the radial mutual mobilities of identical inclusions are independent of their size but that the angular coupling becomes strongly size-dependent when their radius exceeds a characteristic hydrodynamic length. These observations are described well for arbitrary inclusion separations by a model that generalizes the Levine/MacKintosh theory of point-force response functions and uses a boundary-element approach to calculate the mobility matrix for inclusions of finite extent. Beyond that, 2D flow fields generated by a rigid, oscillating post inserted in the film have been measured by analyzing the motion of tracer particles and provide a detailed understanding of the hydrodynamic behavior in the film/gas system. The Brownian diffusion of micron-scale inclusions in freely suspended smectic A liquid crystal films a few nanometers thick and several millimeters in diameter depends strongly on the air surrounding the film. Near atmospheric pressure, the three-dimensionally coupled film/gas system is well described by Hughes/Pailthorpe/White hydrodynamic theory but at lower pressure, the diffusion coefficient increases substantially, tending in high vacuum toward the two-dimensional limit where it is determined by film size. In the absence of air, the films are found to be a nearly ideal physical realization of a two-dimensional, incompressible Newtonian fluid.

  7. Freely Decaying Turbulence in Force-free Electrodynamics

    NASA Astrophysics Data System (ADS)

    Zrake, Jonathan; East, William E.

    2016-02-01

    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 nonhelical settings. Force-free turbulent relaxation is found to exhibit an inverse cascade in all settings and in three dimensions to have a magnetic energy spectrum consistent with the Kolmogorov 5/3 power law. Three-dimensional relaxations also obey the Taylor hypothesis; they settle promptly into the lowest-energy configuration allowed by conservation of the total magnetic helicity. However, in two dimensions, the relaxed state is a force-free equilibrium whose energy greatly exceeds the Taylor minimum and that 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 of turbulent magnetic free-energy discharge could help account for rapidly variable gamma-ray emission from the Crab Nebula, gamma-ray bursts, blazars, and radio galaxies.

  8. 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 *}.

  9. 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

  10. Near and far wake structures behind freely flying bats

    NASA Astrophysics Data System (ADS)

    Schunk, Cosima; Swartz, Sharon M.; Breuer, Kenneth S.

    2014-11-01

    While pseudo-volumetric reconstructions of the wakes of flying animals, based on transverse (Trefftz) wake measurements, have become a well-established tool in the study of animal aerodynamics in recent years, there are a number of concerns that persist regarding their use in estimating drag and flight efficiency. Here we report on stereo particle image velocimetry (PIV) measurements behind freely flying bats (Eptesicus fuscus) in both the transverse and streamwise planes. The streamwise plane measurements are taken on the wing as well as in the near and far wake region up to eight chord lengths behind the bat. By organizing the data according to the flight speed, wingbeat phase and the spanwise position of the laser sheet on the wing we are able to connect specific features of the wing and body geometry with observed wake structures and thereby construct a detailed time-space map of the wake. Furthermore, we can quantitatively assess wake distortion and assess the validity of lift and drag estimates based on transverse wake measurements. Supported by AFOSR.

  11. Microdroplets Impinging on Freely Suspended Smectic Films: Three Impact Regimes.

    PubMed

    Dölle, Sarah; Stannarius, Ralf

    2015-06-16

    We employ high-speed video imaging to study microdroplets of a few picoliters volume impacting freely suspended smectic liquid-crystal films. Depending on the impact parameters, in particular, droplet velocity and mass, three different regimes are observed such as trapping, rebounding, and tunneling. Fast droplets penetrate the films completely. After they have passed the film, they are coated with a layer of film material while the original smectic film remains intact. Droplets in a certain intermediate velocity range bounce back from the film. After impact, the film deforms and hurls the droplet back, depleting a substantial share of the initial kinetic energy. Slow droplets are caught and embedded in the film. During impact and tunneling, an appreciable amount of kinetic energy is lost. The energy is partially dissipated during droplet impact and during subsequent mechanical vibrations and oscillations of the film and the droplet. The tunneling process of high-speed droplets can be exploited to prepare smectic shells of well-defined sizes that enclose picoliters of an immiscible liquid.

  12. Method for dissolving plutonium oxide with HI and separating plutonium

    DOEpatents

    Vondra, Benedict L.; Tallent, Othar K.; Mailen, James C.

    1979-01-01

    PuO.sub.2 -containing solids, particularly residues from incomplete HNO.sub.3 dissolution of irradiated nuclear fuels, are dissolved in aqueous HI. The resulting solution is evaporated to dryness and the solids are dissolved in HNO.sub.3 for further chemical reprocessing. Alternatively, the HI solution containing dissolved Pu values, can be contacted with a cation exchange resin causing the Pu values to load the resin. The Pu values are selectively eluted from the resin with more concentrated HI.

  13. 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…

  14. 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

  15. Neuronal correlates of siphon withdrawal in freely behaving Aplysia.

    PubMed

    Kanz, J E; Eberly, L B; Cobbs, J S; Pinsker, H M

    1979-11-01

    1. Central neuronal mechanisms of siphon withdrawal in Aplysia were studied for the first time in intact, freely behaving animals by means of population recordings from implanted whole-nerve cuff electrodes. Intracellular follow-up studies were then conducted when the same animal was reduced to a semi-intact preparation. 2. Background spontaneous activity in the siphon nerve consisted of low-frequency firing of a population of efferent units containing identified siphon motoneurons. 3. Spontaneous patterned bursts of efferent activity occurred irregularly and were associated with all-or-nothing contractions of the parapodia, gill, and siphon. Spontaneous bursts were due to centrally generated activity in the interneuron II (INT II) network, an oscillatory network with endogenous pacemaker properties. 4. In intact animals, even weak tactile stimuli to the siphon typically triggered an INTII burst shortly after the stimulus-locked efferent activity. Thus, the stimulus can phase-advance the INT II oscillator. In semi-intact preparations, short-latency INT II bursts were triggered less less frequently and required more intense stimuli. 5. With weak to moderate-intensity stimuli in intact animals, the presence of short-latency triggered INT II bursts largely determined the duration of the siphon component and amplitude of the gill component of the withdrawal reflex. 6. When stimuli were repeated over a range of interstimulus intervals (from 60 to 1 min), the likelihood of triggering a short-latency INT II burst die not change systematically. Thus, the ability of the siphon stimulus to stably entrain the all-or-none INT II component over a wide range of intervals will interact behaviorally with the decrement of the monosynaptic component of the reflex with repetition.

  16. Three-dimensional spatial representation in freely swimming fish.

    PubMed

    Burt de Perera, Theresa; Holbrook, Robert I

    2012-08-01

    Research on spatial cognition has focused on how animals encode the horizontal component of space. However, most animals travel vertically within their environments, particularly those that fly or swim. Pelagic fish move with six degrees of freedom and must integrate these components to navigate accurately--how do they do this? Using an assay based on associative learning of the vertical and horizontal components of space within a rotating Y-maze, we found that fish (Astyanax fasciatus) learned and remembered information from both horizontal and vertical axes when they were presented either separately or as an integrated three-dimensional unit. When information from the two components conflicted, the fish used the previously learned vertical information in preference to the horizontal. This not only demonstrates that the horizontal and vertical components are stored separately in the fishes' representation of space (simplifying the problem of 3D navigation), but also suggests that the vertical axis contains particularly salient spatial cues--presumably including hydrostatic pressure. To explore this latter possibility, we developed a physical theoretical model that shows how fish could determine their absolute depth using pressure. We next considered full volumetric spatial cognition. Astyanax were trained to swim towards a reward in a Y-maze that could be rotated, before the arms were removed during probe trials. The subjects were tracked in three dimensions as they swam freely through the surrounding cubic tank. The results revealed that fish are able to accurately encode metric information in a volume, and that the error accrued in the horizontal and vertical axes whilst swimming in probe trials was similar. Together, these experiments demonstrate that unlike in surface-bound rats, the vertical component of the representation of space is vitally important to fishes. We hypothesise that the representation of space in the brain of vertebrates could ultimately be

  17. Bioconcentration of perfluoroalkyl substances by Chironomus plumosus larvae in water with different types of dissolved organic matters.

    PubMed

    Wen, Wu; Xia, Xinghui; Chen, Xi; Wang, Haotian; Zhu, Baotong; Li, Husheng; Li, Yang

    2016-06-01

    The effects of four types of dissolved organic matters (DOM) on the bioconcentration of perfluoroalkyl substances (PFASs) in Chironomus plumosus larvae have been studied. The PFASs included perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnA), and perfluorododecanoic acid (PFDoA). The DOM included humic acid (HA), fulvic acid (FA), tannic acid (TA), and a protein, peptone (PEP), and their concentrations ranged from 0 to 50 mg L(-1). The results showed that, upon bioconcentration equilibrium, the body burdens of longer perfluoroalkyl chain PFASs (PFOS, PFDA, PFUnA and PFDoA) decreased with PEP and HA concentrations while increased with FA and TA concentrations. When FA and TA concentrations increased from 0 to 50 mg L(-1), body burdens of these PFASs increased by 7.5%-148.8% and 5.7%-37.1%, respectively. However, the DOM had no significant impact on the body burdens of shorter perfluoroalkyl chain PFASs (PFOA and PFNA). All of the four types of DOM lowered not only the uptake rate constants (ku) of PFASs due to the decrease of freely dissolved PFAS concentrations, but also the elimination rate constants (ke) due to the inhibition effect of DOM on the PFAS elimination from the larvae. The reduction in the two constants varied with both DOM and PFAS types. In the presence of PEP and HA with larger molecular weights, the ku values decreased more than ke, leading to the decreased body burdens of longer perfluoroalkyl chain PFASs. As for FA and TA with smaller molecular weights, the ke values decreased more than ku, resulting in increased body burdens of longer perfluoroalkyl chain PFASs. This study suggests that the effects of DOM on PFAS bioconcentration depend not only on the concentration but also on the molecule weight of DOM, which should be considered in the bioavailability assessment of PFASs. PMID:26925752

  18. Effects of quantity, quality, and contact time of dissolved organic matter on bioconcentration of benzo[a]pyrene in the nematode Caenorhabditis elegans

    SciTech Connect

    Haitzer, M.; Hoess, S. |; Burnison, B.K.; Traunspurger, W.; Steinberg, C.E.W.

    1999-03-01

    Quantity and quality of dissolved organic matter (DOM) and the time allowed for DOM to interact with organic contaminants can influence their bioavailability. The authors studied the effect of natural aquatic DOM that had been in contact with benzo[a]pyrene (B[a]P) for 1 to 12 d on the bioconcentration of B[a]P in the nematode Caenorhabditis elegans. Dissolved organic matter quality and quantity was varied by using DOM from three different sources, each in three different concentrations. A model, based on the assumption that only freely dissolved B[a]P is bioavailable, was employed to estimate biologically determined partition coefficients [K{sub p}(biol.)]. Expressing the data for each combination of DOM source and contact time in a single K{sub p} (biol.) value allowed a direct comparison of the effects of different DOM qualities and contact times. The results show that the effect of DOM from a specific source was dependent on DOM quantity, but they also observed a distinct effect of DOM quality (represented by different sampling locations) on the bioconcentration of B[a]P. Contact time had no significant influence for the effects of two DOM sources on the bioconcentration of B[a]P. However, the third DOM source was significantly more effective with increased contact time, leading to lower B[a]P bioconcentration in the nematodes.

  19. [Using ultraviolet-visible ( UV-Vis) absorption spectrum to estimate the dissolved organic matter (DOM) concentration in water, soils and sediments of typical water-level fluctuation zones of the Three Gorges Reservoir areas].

    PubMed

    Li, Lu-lu; Jiang, Tao; Lu, Song; Yan, Jin-long; Gao, Jie; Wei, Shi-qiang; Wang, Ding-yong; Guo, Nian; Zhao, Zhena

    2014-09-01

    Dissolved organic matter (DOM) is a very important component in terrestrial ecosystem. Chromophoric dissolved organic matter (CDOM) is a significant constituent of DOM, which can be measured by ultraviolet-visible (UV-Vis) absorption spectrum. Thus the relationship between CDOM and DOM was investigated and established by several types of models including single-wavelength model, double-wavelength model, absorption spectrum slope (S value) model and three-wavelength model, based on the UV-Vis absorption coefficients of soil and sediment samples (sampled in July of 2012) and water samples (sampled in November of 2012) respectively. The results suggested that the three-wavelength model was the best for fitting, and the determination coefficients of water, soil and sediment data were 0. 788, 0. 933 and 0. 856, respectively. Meanwhile, the nominal best model was validated with the UV-Vis data of 32 soil samples and 36 water samples randomly collected in 2013, showing the RRMSE and MRE were 16. 5% and 16. 9% respectively for soil DOM samples, 10. 32% and 9. 06% respectively for water DOM samples, which further suggested the prediction accuracy was higher in water DOM samples as compared with that in soil DOM samples.

  20. 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.

  1. Using solid-phase microextraction to determine partition coefficients to humic acids and bioavailable concentrations of hydrophobic chemicals

    SciTech Connect

    Ramos, E.U.; Meijer, S.N.; Vaes, W.H.J.; Verhaar, H.J.M.; Hermens, J.L.M.

    1998-11-01

    In the current study, the suitability of negligible depletion solid-phase microextraction (nd-SPME) to determine free fractions of chemicals in aquatic environments was explored. The potential interferences of the dissolved matrix (i.e., humic acids) with the SPME measurements were tested. Results show that nd-SPME measures only the freely dissolved fraction and that the measurements are not disturbed by the humic acids. In addition, nd-SPME was used to determine partition coefficients between dissolved organic carbon and water for four hydrophobic chemicals. Obtained values are in excellent agreement with previously reported data. Finally, the bioaccumulation of hexachlorobenzene and PCB 77 to Daphnia magna was determined in the presence and absence of humic acids. The bioconcentration factors (BCF) were calculated based on total as well as on free concentration. Lower BCF values are obtained in the presence of humic acids using total concentrations, whereas equal BCFs are found using free concentrations measured with nd-SPME. Therefore, the authors can conclude that negligible depletion SPME is a good technique to determine bioavailable concentrations of hydrophobic chemicals in aquatic environments.

  2. 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.

  3. The marine geochemistry of dissolved gallium: A comparison with dissolved aluminum

    SciTech Connect

    Orians, K.J.; Bruland, K.W. )

    1988-12-01

    Dissolved Ga concentrations in the pacific Ocean range from 2 to 30 picomolar: they are low in surface waters (2-12 pM), with a subsurface maximum at 150-300 m (6-17 pM), a mid-depth minimum from 500 to 1,000 m (4-10 pM) and increasing values with depth to a maximum in the bottom waters (12-30 pM). The highest concentrations are in the central gyre, with lower values toward the north and east where productivity and particle scavenging increase. Dissolved Ga concentrations in the surface waters of the northwest Atlantic are nearly an order of magnitude higher than in the central North pacific, with higher values in the Gulf Stream than in the continental slope boundary region. The vertical distributions and horizontal transects indicate three sources of dissolved Ga to the oceans. The surface distribution reflects an eolian source with no net fluvial input to the open ocean; the subsurface maximum (a feature not seen for North Pacific dissolved Al) is attributed to vertical exchange processes; the source for the deep waters of the North Pacific is from a sediment surface remineralization process or a pore water flux. Scavenging removal throughout the water column is evident in the vertical profiles for both dissolved Ga and Al, with intensified removal in the boundary regions where productivity and particle scavenging are at a maximum. Residence times of dissolved Ga in surface waters are nearly an order of magnitude longer than the corresponding values for Al.

  4. Total dissolvable and dissolved iron isotopes in the water column of the Peru upwelling regime

    NASA Astrophysics Data System (ADS)

    Chever, Fanny; Rouxel, Olivier J.; Croot, Peter L.; Ponzevera, Emmanuel; Wuttig, Kathrin; Auro, Maureen

    2015-08-01

    Vertical distributions of iron (Fe) concentrations and isotopes were determined in the total dissolvable and dissolved pools in the water column at three coastal stations located along the Peruvian margin, in the core of the Oxygen Minimum Zone (OMZ). The shallowest station 121 (161 m total water depth) was characterized by lithogenic input from the continental plateau, yielding concentrations as high as 456 nM in the total dissolvable pool. At the 2 other stations (stations 122 and 123), Fe concentrations of dissolved and total dissolvable pools exhibited maxima in both surface and deep layers. Fe isotopic composition (δ56Fe) showed a fractionation toward lighter values for both physical pools throughout the water column for all stations with minimum values observed for the surface layer (between -0.64 and -0.97‰ at 10-20 m depth) and deep layer (between -0.03 and -1.25‰ at 160-300 m depth). An Fe isotope budget was established to determine the isotopic composition of the particulate pool. We observed a range of δ56Fe values for particulate Fe from +0.02 to -0.87‰, with lightest values obtained at water depth above 50 m. Such light values in the both particulate and dissolved pools suggest sources other than atmospheric dust deposition in the surface ocean, including lateral transport of isotopically light Fe. Samples collected at station 122 closest to the sediment show the lightest isotope composition in the dissolved and the particulate pools (-1.25 and -0.53‰ respectively) and high Fe(II) concentrations (14.2 ± 2.1 nM) consistent with a major reductive benthic Fe sources that is transferred to the ocean water column. A simple isotopic model is proposed to link the extent of Fe(II) oxidation and the Fe isotope composition of both particulate and dissolved Fe pools. This study demonstrates that Fe isotopic composition in OMZ regions is not only affected by the relative contribution of reductive and non-reductive shelf sediment input but also by

  5. Knowledge and understanding of dissolved solids in the Rio Grande–San Acacia, New Mexico, to Fort Quitman, Texas, and plan for future studies and monitoring

    USGS Publications Warehouse

    Moyer, Douglas; Anderholm, Scott K.; Hogan, James F.; Phillips, Fred M.; Hibbs, Barry J.; Witcher, James C.; Matherne, Anne Marie; Falk, Sarah E.

    2013-01-01

    -Focused Hydrogeology Studies at Inflow Sources: Map dissolved-solids concentrations in the Rio Grande and underlying alluvial aquifer; perform hydrogeologic characterization of subsurface areas containing unusually high concentrations of dissolved solids. -Modeling of Dissolved Solids: Develop models to simulate the transport and storage of dissolved solids in both surface-water and groundwater systems.

  6. Method for dissolving plutonium dioxide

    DOEpatents

    Tallent, Othar K.

    1978-01-01

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

  7. Chronic monitoring of cortical hemodynamics in behaving, freely-moving rats using a miniaturized head-mounted optical microscope

    NASA Astrophysics Data System (ADS)

    Sigal, Iliya; Gad, Raanan; Koletar, Margaret; Ringuette, Dene; Stefanovic, Bojana; Levi, Ofer

    2016-03-01

    Growing interest within the neurophysiology community in assessing healthy and pathological brain activity in animals that are awake and freely-behaving has triggered the need for optical systems that are suitable for such longitudinal studies. In this work we report label-free multi-modal imaging of cortical hemodynamics in the somatosensory cortex of awake, freely-behaving rats, using a novel head-mounted miniature optical microscope. The microscope employs vertical cavity surface emitting lasers (VCSELs) at three distinct wavelengths (680 nm, 795 nm, and 850 nm) to provide measurements of four hemodynamic markers: blood flow speeds, HbO, HbR, and total Hb concentration, across a > 2 mm field of view. Blood flow speeds are extracted using Laser Speckle Contrast Imaging (LSCI), while oxygenation measurements are performed using Intrinsic Optical Signal Imaging (IOSI). Longitudinal measurements on the same animal are made possible over the course of > 6 weeks using a chronic window that is surgically implanted into the skull. We use the device to examine changes in blood flow and blood oxygenation in superficial cortical blood vessels and tissue in response to drug-induced absence-like seizures, correlating motor behavior with changes in blood flow and blood oxygenation in the brain.

  8. Chemical characterization of dissolvable tobacco products promoted to reduce harm.

    PubMed

    Rainey, Christina L; Conder, Paige A; Goodpaster, John V

    2011-03-23

    In 2009, the R. J. Reynolds Tobacco Co. released a line of dissolvable tobacco products that are marketed as an alternative to smoking in places where smoking is prohibited. These products are currently available in Indianapolis, IN, Columbus, OH, and Portland, OR. This paper describes the chemical characterization of four such products by gas chromatography-mass spectrometry (GC-MS). The dissolvable tobacco products were extracted and prepared by ultrasonic extraction using acetone, trimethylsilyl derivatization, and headspace solid phase microextraction (SPME). The following compounds were identified in the dissolvables using either ultrasonic extractions or trimethylsilyl derivatization: nicotine, ethyl citrate, palmitic acid, stearic acid, sorbitol, glycerol, and xylitol. The following compounds were identified in the dissolvables using headspace SPME: nicotine, ethyl citrate, cinnamaldehyde, coumarin, vanillin, and carvone. With the exception of nicotine, the compounds identified thus far in the dissolvables are either flavoring compounds or binders. The concentration of free nicotine in the dissolvables was determined from the Henderson-Hasselbalch equation and by measuring the pH and nicotine concentration by GC-MS. The results presented here are the first to reveal the complexity of dissolvable tobacco products and may be used to assess potential oral health effects.

  9. 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

  10. The effects of systemically administered taurine and N-pivaloyltaurine on striatal extracellular dopamine and taurine in freely moving rats.

    PubMed

    Salimäki, J; Scriba, G; Piepponen, T P; Rautolahti, N; Ahtee, L

    2003-08-01

    The second most abundant cerebral amino acid, taurine, is widely consumed in the so-called "energy drinks". Therefore, its possible actions on the brain are of great interest. In the present experiments taurine was given intraperitoneally to rats in order to study if it can be administered systemically in large enough amounts to alter cerebral dopaminergic transmission or to induce hypothermia. In addition, the effects of subcutaneously administered lipophilic taurine analogue, N-pivaloyltaurine, were studied. The extracellular striatal taurine and dopamine concentrations were estimated using in vivo microdialysis in awake and freely moving rats, and the rectal temperatures were measured. Taurine at the total dose of 45 mmol/kg i.p. led to a maximally 8-fold increased striatal extracellular taurine concentration, induced a long-lasting hypothermia, and significantly reduced the striatal extracellular dopamine concentration. The latter effect was strengthened by co-treatment with reuptake inhibitor nomifensine. N-pivaloyltaurine (15 mmol/kg in total, s.c.) only slightly elevated the striatal extracellular taurine concentration, failed to alter the rectal temperature, and in contrast to taurine somewhat elevated the striatal extracellular dopamine concentration suggesting a different mechanism or locus of action from that of taurine. Finally, our experiments using brain microdialysis confirmed the earlier findings that taurine is slowly eliminated from the brain. The results clearly indicate that systemically given taurine enters the brain in concentrations that induce pharmacological effects. PMID:12898127

  11. Method of dissolving organic filter cake

    SciTech Connect

    Hollenbeck, K.H.; Norman, L.R.

    1989-03-07

    A method of dissolving a polysaccharide-containing filter cake present in a subterranean formation is described, comprising: injecting an effective amount of a treatment fluid comprising a water soluble source of fluoride ions present in an amount sufficient to provide a molar concentration of from about 0.01 to about 0.5 and a source of hydrogen ions present in an amount sufficient to produce a pH in the treatment fluid in the range of from about 2 to about 4 into a subterranean formation wherein a filter cake is present; and maintaining the treatment fluid within the subterranean formation and in contact with the filter cake for a sufficient time to dissolve at least a portion of the filter cake.

  12. A wearable multi-channel fNIRS system for brain imaging in freely moving subjects.

    PubMed

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

    2014-01-15

    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 ΔHbO2 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. 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 ΔHbO2 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

  14. Preservation of samples for dissolved mercury

    USGS Publications Warehouse

    Hamlin, S.N.

    1989-01-01

    Water samples for dissolved mercury requires special treatment because of the high chemical mobility and volatility of this element. Widespread use of mercury and its compounds has provided many avenues for contamination of water. Two laboratory tests were done to determine the relative permeabilities of glass and plastic sample bottles to mercury vapor. Plastic containers were confirmed to be quite permeable to airborne mercury, glass containers were virtually impermeable. Methods of preservation include the use of various combinations of acids, oxidants, and complexing agents. The combination of nitric acid and potassium dichromate successfully preserved mercury in a large variety of concentrations and dissolved forms. Because this acid-oxidant preservative acts as a sink for airborne mercury and plastic containers are permeable to mercury vapor, glass bottles are preferred for sample collection. To maintain a healthy work environment and minimize the potential for contamination of water samples, mercury and its compounds are isolated from the atmosphere while in storage. Concurrently, a program to monitor environmental levels of mercury vapor in areas of potential contamination is needed to define the extent of mercury contamination and to assess the effectiveness of mercury clean-up procedures.Water samples for dissolved mercury require special treatment because of the high chemical mobility and volatility of this element. Widespread use of mercury and its compounds has provided many avenues for contamination of water. Two laboratory tests were done to determine the relative permeabilities of glass and plastic sample bottles to mercury vapor. Plastic containers were confirmed to be quite permeable to airborne mercury, glass containers were virtually impermeable. Methods of preservation include the use of various combinations of acids, oxidants, and complexing agents. The combination of nitric acid and potassium dichromate successfully preserved mercury in a

  15. 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.

  16. 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

  17. Visually evoked activity in cortical cells imaged in freely moving animals

    PubMed Central

    Sawinski, Juergen; Wallace, Damian J.; Greenberg, David S.; Grossmann, Silvie; Denk, Winfried; Kerr, Jason N. D.

    2009-01-01

    We describe a miniaturized head-mounted multiphoton microscope and its use for recording Ca2+ transients from the somata of layer 2/3 neurons in the visual cortex of awake, freely moving rats. Images contained up to 20 neurons and were stable enough to record continuously for >5 min per trial and 20 trials per imaging session, even as the animal was running at velocities of up to 0.6 m/s. Neuronal Ca2+ transients were readily detected, and responses to various static visual stimuli were observed during free movement on a running track. Neuronal activity was sparse and increased when the animal swept its gaze across a visual stimulus. Neurons showing preferential activation by specific stimuli were observed in freely moving animals. These results demonstrate that the multiphoton fiberscope is suitable for functional imaging in awake and freely moving animals. PMID:19889973

  18. 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...

  19. Effects of the lampricide 3-trifluoromethyl-4-nitrophenol on dissolved oxygen in aquatic systems

    USGS Publications Warehouse

    Dawson, V.K.; Johnson, D.A.; Sullivan, J.F.

    1992-01-01

    The effects of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) on dissolved oxygen and other water- quality characteristics were evaluated in a series of test chambers under selected combinations of water, sediment, TFM, and exposure to sunlight. Concentrations of TFM gradually decreased over time, especially in the presence of sediment and sunlight. The lampricide did not directly cause a reduction in dissolved oxygen concentration, but appeared to inhibit photosynthetic production of oxygen during daylight. Dissolved oxygen concentrations were significantly reduced by the presence of TFM in chambers exposed to sunlight. Concentrations of total ammonia were significantly higher in chambers with sediment than in those without sediment. In chambers that contained river water and were exposed to sunlight, ammonia concentrations were low because of either oxidation by the elevated dissolved oxygen concentrations or the assimilation of nutrients by algae. The observed changes in dissolved oxygen and ammonia because of the presence of TFM were subtle, but statistically significant.

  20. Instrumentation for fast-scan cyclic voltammetry combined with electrophysiology for behavioral experiments in freely moving animals

    PubMed Central

    Takmakov, Pavel; McKinney, Collin J.; Carelli, Regina M.; Wightman, R. Mark

    2011-01-01

    Fast-scan cyclic voltammetry is a unique technique for sampling dopamine concentration in the brain of rodents in vivo in real time. The combination of in vivo voltammetry with single-unit electrophysiological recording from the same microelectrode has proved to be useful in studying the relationship between animal behavior, dopamine release and unit activity. The instrumentation for these experiments described here has two unique features. First, a 2-electrode arrangement implemented for voltammetric measurements with the grounded reference electrode allows compatibility with electrophysiological measurements, iontophoresis, and multielectrode measurements. Second, we use miniaturized electronic components in the design of a small headstage that can be fixed on the rat's head and used in freely moving animals. PMID:21806203

  1. Ring-pattern dynamics in smectic-C* and smectic-C*A freely suspended liquid crystal films.

    PubMed

    Link, D R; Radzihovsky, L; Natale, G; Maclennan, J E; Clark, N A; Walsh, M; Keast, S S; Neubert, M E

    2000-06-19

    Ring patterns of concentric 2pi solitons in molecular orientation form in freely suspended chiral smectic-C films in response to an in-plane rotating electric field. We present measurements of the driven dynamics of ring formation under conditions of synchronous winding and of the zero-field relaxation of ring patterns, and propose a simple model which enables their quantitative description in low polarization DOBAMBC. In smectic-C*A TFMHPOBC we observe an odd-even layer number effect, with odd layer number films exhibiting order of magnitude slower relaxation rates than even layer films. We show that this rate difference is due to a much larger spontaneous polarization in odd layer number films. PMID:10991051

  2. Cellular partitioning of nanoparticulate versus dissolved metals in marine phytoplankton.

    PubMed

    Bielmyer-Fraser, Gretchen K; Jarvis, Tayler A; Lenihan, Hunter S; Miller, Robert J

    2014-11-18

    Discharges of metal oxide nanoparticles into aquatic environments are increasing with their use in society, thereby increasing exposure risk for aquatic organisms. Separating the impacts of nanoparticle from dissolved metal pollution is critical for assessing the environmental risks of the rapidly growing nanomaterial industry, especially in terms of ecosystem effects. Metal oxides negatively affect several species of marine phytoplankton, which are responsible for most marine primary production. Whether such toxicity is generally due to nanoparticles or exposure to dissolved metals liberated from particles is uncertain. The type and severity of toxicity depends in part on whether phytoplankton cells take up and accumulate primarily nanoparticles or dissolved metal ions. We compared the responses of the marine diatom, Thalassiosira weissflogii, exposed to ZnO, AgO, and CuO nanoparticles with the responses of T. weissflogii cells exposed to the dissolved metals ZnCl2, AgNO3, and CuCl2 for 7 d. Cellular metal accumulation, metal distribution, and algal population growth were measured to elucidate differences in exposure to the different forms of metal. Concentration-dependent metal accumulation and reduced population growth were observed in T. weissflogii exposed to nanometal oxides, as well as dissolved metals. Significant effects on population growth were observed at the lowest concentrations tested for all metals, with similar toxicity for both dissolved and nanoparticulate metals. Cellular metal distribution, however, markedly differed between T. weissflogii exposed to nanometal oxides versus those exposed to dissolved metals. Metal concentrations were highest in the algal cell wall when cells were exposed to metal oxide nanoparticles, whereas algae exposed to dissolved metals had higher proportions of metal in the organelle and endoplasmic reticulum fractions. These results have implications for marine plankton communities as well as higher trophic levels, since

  3. Cellular partitioning of nanoparticulate versus dissolved metals in marine phytoplankton.

    PubMed

    Bielmyer-Fraser, Gretchen K; Jarvis, Tayler A; Lenihan, Hunter S; Miller, Robert J

    2014-11-18

    Discharges of metal oxide nanoparticles into aquatic environments are increasing with their use in society, thereby increasing exposure risk for aquatic organisms. Separating the impacts of nanoparticle from dissolved metal pollution is critical for assessing the environmental risks of the rapidly growing nanomaterial industry, especially in terms of ecosystem effects. Metal oxides negatively affect several species of marine phytoplankton, which are responsible for most marine primary production. Whether such toxicity is generally due to nanoparticles or exposure to dissolved metals liberated from particles is uncertain. The type and severity of toxicity depends in part on whether phytoplankton cells take up and accumulate primarily nanoparticles or dissolved metal ions. We compared the responses of the marine diatom, Thalassiosira weissflogii, exposed to ZnO, AgO, and CuO nanoparticles with the responses of T. weissflogii cells exposed to the dissolved metals ZnCl2, AgNO3, and CuCl2 for 7 d. Cellular metal accumulation, metal distribution, and algal population growth were measured to elucidate differences in exposure to the different forms of metal. Concentration-dependent metal accumulation and reduced population growth were observed in T. weissflogii exposed to nanometal oxides, as well as dissolved metals. Significant effects on population growth were observed at the lowest concentrations tested for all metals, with similar toxicity for both dissolved and nanoparticulate metals. Cellular metal distribution, however, markedly differed between T. weissflogii exposed to nanometal oxides versus those exposed to dissolved metals. Metal concentrations were highest in the algal cell wall when cells were exposed to metal oxide nanoparticles, whereas algae exposed to dissolved metals had higher proportions of metal in the organelle and endoplasmic reticulum fractions. These results have implications for marine plankton communities as well as higher trophic levels, since

  4. 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; 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.

  5. Tracing natural gas transport into shallow groundwater using dissolved nitrogen and alkane chemistry in Parker County, Texas

    NASA Astrophysics Data System (ADS)

    Larson, T.; Nicot, J. P.; Mickler, P. J.; Darvari, R.

    2015-12-01

    Dissolved methane in shallow groundwater drives public concern about the safety of hydraulic fracturing. We report dissolved alkane and nitrogen gas concentrations and their stable isotope values (δ13C and δ15N, respectively) from 208 water wells in Parker county, Texas. These data are used to differentiate 'stray' natural gas and low temperature microbial methane, and (2) estimate the ratio of stray gas to groundwater. The ratio of (gas-phase) stray natural gas to groundwater is estimated by correlating dissolved methane and nitrogen concentrations and dissolved nitrogen δ15N values. Our hypothesis is groundwater exposed to high volumes of stray natural gas have high dissolved methane concentrations and low dissolved nitrogen concentrations and δ15N values. Alternatively, groundwater exposed to low volumes of stray gas-phase natural gas have elevated dissolved methane, but the concentration of dissolved nitrogen and its d15N value is atmospheric. A cluster of samples in Parker county have high concentrations of dissolved methane (>10mg/L) with d13Cmethane and alkane ratios (C1/C2+C3) typical of natural gas from the Barnett Shale and the Strawn Formation. Coupling dissolved nitrogen concentrations and δ15N values with these results, we suggest that few of the wells in this cluster preserve large gas to water ratios. Many samples with high dissolved methane concentrations have atmospheric dissolved nitrogen concentrations and δ15N values, providing evidence against high flux natural gas transport into shallow groundwater. These results demonstrate that dissolved nitrogen chemistry, in addition to dissolved alkane and noble gas measurements, may be useful to discern sources of dissolved methane and estimate ratios of stray natural gas-water ratios.

  6. 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…

  7. Thermal and Isotopic Anomalies when pd Cathodes are Electrolyzed in Electrolytes Containing Th-Hg Salts Dissolved at Micromolar Concentration in C2H5OD/D2O Mixtures

    NASA Astrophysics Data System (ADS)

    Celani, F.; Spallone, A.; Righi, E.; Trenta, G.; Catena, C.; D'Agostaro, G.; Quercia, P.; Andreassi, V.; Marini, P.; di Stefano, V.; Nakamura, M.; Mancini, A.; Sona, P. G.; Fontana, F.; Gamberale, L.; Garbelli, D.; Falcioni, F.; Marchesini, M.; Novaro, E.; Mastromatteo, U.

    2005-12-01

    Discussed in this paper is the evolution of work that started by using the M. Fleischmann and S. Pons method and ended by using thin palladium wires electrolyzed in an electrolyte consisting of slightly acidic heavy alcohol-water solution containing thorium (Th) and mercury (Hg) salts at micromolar concentrations. The resulting large and dynamic loading of the Pd wires was studied. The recent use of thorium instead of strontium resulted in thermal anomalies and detection of new elements in larger amounts. The results with Sr are qualitatively in agreement with what was found by Y. Iwamura (Mitsubishi Heavy Industries) using multilayers of Pd-CaO-Pd-Sr in flowing deuterium gas. Most results seem to be in agreement with a "multi-body resonance fusion of deuterons" model recently developed by A.Takahashi (Osaka University).

  8. Distributions of dissolved and particulate biogenic thiols in the subartic Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Dupont, Christopher L.; Moffett, James. W.; Bidigare, Robert R.; Ahner, Beth A.

    2006-12-01

    Dissolved and particulate concentrations of the biogenic thiols cysteine (Cys), arginine-cysteine (Arg-Cys), glutamine-cysteine (Gln-Cys), γ-glutamate-cysteine ( γ-Glu-Cys) and glutathione (GSH) were measured in the subartic Pacific Ocean in the summer of 2003 using high performance liquid chromatography (HPLC) with precolumn derivatization as reported in previous work. In this study, a preconcentration protocol for the derivatized thiols was utilized to extend detection limits of dissolved thiols to picomolar levels. The measured concentrations of particulate and dissolved thiols were uncoupled, with distinctive depth profiles and large differences in the particulate to dissolved ratios between individual compounds. Glutathione was the most abundant particulate thiol whereas the most abundant dissolved thiol was γ-Glu-Cys, with concentrations as high as 15 nM. Given the relatively small pool of intracellular γ-Glu-Cys and the very low dissolved concentrations of GSH, we hypothesize that glutathione released from cells is rapidly converted to the potentially degradation resistant γ-Glu-Cys outside the cell. The relatively high concentrations of other dissolved thiols compared to particulate concentrations implies both biological exudation and slow degradation rates. Some thiols appear to vary with changes in nutrient availability but this effect is difficult to decouple from changes in community structure inferred from pigment analyses. Dissolved thiol concentrations also exceed typical metal concentrations in the subartic Pacific, supporting previous arguments that they may be important in metal speciation.

  9. 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).

  10. 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 μXAS 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

  11. 34 CFR 300.701 - Outlying areas, freely associated States, and the Secretary of the Interior.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... States—(1) Funds reserved. From the amount appropriated for any fiscal year under section 611(i) of the... State received for fiscal year 2003 under Part B of the Act, but only if the freely associated State— (A... Public Law 95-134, permitting the consolidation of grants by the outlying areas, do not apply to...

  12. 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.

  13. 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

  14. Spontaneous and repetitive cardiac slowdown in the freely moving spiny lobster, Panulirus japonicus.

    PubMed

    Yazawa, T; Katsuyama, T

    2001-12-01

    The fluctuation of heartbeat interval was investigated to assess cardio-regulatory nervous function in freely moving spiny lobsters. This was performed by time series analysis of the heartbeat interval recorded from restrained animals, freely moving animals, and isolated hearts. The heart rate of freely moving animals exhibited on/off switching: i.e., an elevated and maintained rate was repetitively interrupted by periods of decreased rate. Each period was initiated by a sudden decrease in rate and was terminated by an exponential return to normal activity. In order to explain this characteristic change in heart rate, we have constructed a neurotransmitter release-reuptake model for such bi-stable activity of cardio-regulatory nerves. The model was successful in reproducing the characteristic observed fluctuation. In freely moving animals, the brain seems to regulate the heart through the inhibitory nerve in an "on/off" manner. In the hearts of restrained animals and isolated hearts, the heart rate exhibited white-noise like fluctuation. This implies that stress impairs the normal bi-stable regulatory mode. PMID:11800038

  15. Spatial distribution of dissolved constituents in Icelandic river waters

    NASA Astrophysics Data System (ADS)

    Oskarsdottir, Sigrídur Magnea; Gislason, Sigurdur Reynir; Snorrason, Arni; Halldorsdottir, Stefanía Gudrún; Gisladottir, Gudrún

    2011-02-01

    SummaryIn this study we map the spatial distribution of selected dissolved constituents in Icelandic river waters using GIS methods to study and interpret the connection between river chemistry, bedrock, hydrology, vegetation and aquatic ecology. Five parameters were selected: alkalinity, SiO 2, Mo, F and the dissolved inorganic nitrogen and dissolved inorganic phosphorus mole ratio (DIN/DIP). The highest concentrations were found in rivers draining young rocks within the volcanic rift zone and especially those draining active central volcanoes. However, several catchments on the margins of the rift zone also had high values for these parameters, due to geothermal influence or wetlands within their catchment area. The DIN/DIP mole ratio was higher than 16 in rivers draining old rocks, but lowest in rivers within the volcanic rift zone. Thus primary production in the rivers is limited by fixed dissolved nitrogen within the rift zone, but dissolved phosphorus in the old Tertiary catchments. Nitrogen fixation within the rift zone can be enhanced by high dissolved molybdenum concentrations in the vicinity of volcanoes. The river catchments in this study were subdivided into several hydrological categories. Importantly, the variation in the hydrology of the catchments cannot alone explain the variation in dissolved constituents. The presence or absence of central volcanoes, young reactive rocks, geothermal systems and wetlands is important for the chemistry of the river waters. We used too many categories within several of the river catchments to be able to determine a statistically significant connection between the chemistry of the river waters and the hydrological categories. More data are needed from rivers draining one single hydrological category. The spatial dissolved constituent distribution clearly revealed the difference between the two extremes, the young rocks of the volcanic rift zone and the old Tertiary terrain.

  16. Development of mediator-type biosensor to wirelessly monitor whole cholesterol concentration in fish.

    PubMed

    Takase, Mai; Murata, Masataka; Hibi, Kyoko; Huifeng, Ren; Endo, Hideaki

    2014-04-01

    We developed a wireless monitoring system to monitor fish condition by tracking the change in whole cholesterol concentration. The whole cholesterol concentration of fish is a source of steroid hormones or indicator of immunity level, which makes its detection important for tracking physiological condition of fish. Wireless monitoring system comprises of mediator-type biosensor and wireless transmission device. Biosensor is implantable to fish body, and transmission device is so light, in that fish is allowed to swim freely during monitoring. Cholesterol esterase and oxidase were fixated on to the detection site of biosensor and used to detect the whole cholesterol concentration. However, cholesterol oxidase incorporates oxidation-reduction reaction of oxygen for detection, which concentration fluctuates easily due to change in environmental condition. Meanwhile, mediator-type biosensor enables monitoring of whole cholesterol concentration by using mediator to substitute that oxidation-reduction reaction of oxygen. Characteristic of fabricated mediator-type biosensor was tested. The sensor output current of mediator-type biosensor remained stable compared to output current of non-mediator-type biosensor under fluctuating oxygen concentration of 0-8 ppm, which implied that this sensor is less affected by change in dissolved oxygen concentration. That biosensor was then implanted into fish for wireless monitoring. As a result, approximately 48 h of real-time monitoring was successful.

  17. 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.

  18. 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.

  19. 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

  20. Leaching of dissolved phosphorus from tile-drained agricultural areas.

    PubMed

    Andersen, H E; Windolf, J; Kronvang, B

    2016-01-01

    We investigated leaching of dissolved phosphorus (P) from 45 tile-drains representing animal husbandry farms in all regions of Denmark. Leaching of P via tile-drains exhibits a high degree of spatial heterogeneity with a low concentration in the majority of tile-drains and few tile-drains (15% in our investigation) having high to very high concentration of dissolved P. The share of dissolved organic P (DOP) was high (up to 96%). Leaching of DOP has hitherto been a somewhat overlooked P loss pathway in Danish soils and the mechanisms of mobilization and transport of DOP needs more investigation. We found a high correlation between Olsen-P and water extractable P. Water extractable P is regarded as an indicator of risk of loss of dissolved P. Our findings indicate that Olsen-P, which is measured routinely in Danish agricultural soils, may be a useful proxy for the P leaching potential of soils. However, we found no straight-forward correlation between leaching potential of the top soil layer (expressed as either degree of P saturation, Olsen-P or water extractable P) and the measured concentration of dissolved P in the tile-drain. This underlines that not only the source of P but also the P loss pathway must be taken into account when evaluating the risk of P loss. PMID:27332841

  1. Reducing Emissions from Uranium Dissolving

    SciTech Connect

    Griffith, W.L.

    1992-01-01

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

  2. Selected methods for dissolved iron (II, III) and dissolved sulfide (-II) determinations in geothermal waters

    USGS Publications Warehouse

    Vivit, D.V.; Jenne, E.A.

    1985-01-01

    Dissolved sulfide (-II) and dissolved iron (II, III) were determined in geothermal well water samples collected at Cerro Prieto, Mexico. Most samples consisted of liquid and gas (two phases) at the instant of collection; and a subset of samples, referred to as ' flashed ' samples, consisted of pressurized steam samples which were allowed to condense. Sulfide was determined by sulfide specific ion electrode; Fe(II) and Fe(III) plus Fe(II) were determined spectrophotometrically. The precision and accuracy of the methods were evaluated for these high-silica waters with replicate analyses, spike recoveries, and an alternate method. Direct current (d.c.) argon plasma emission spectrometry was the alternate method used for Fe(III)-plus-Fe(II) analyses. Mean dissolved iron concentrations ranged from 20.2 to 834 micrograms/L (ug/L) as Fe(II) and 26.8 to 904 ug/L as Fe(III) plus Fe(II). Mean sulfide concentrations ranged from about 0.01 to 5.3 mg/L (S-II) Generally, higher S(-II) values and larger Fe(II)/Fe(III) ratios were found in the two-phase samples. These findings suggest that the ' flashed ' samples are at a less reduced state than the two-phase samples. (Author 's abstract)

  3. Dissolved-Solids Transport in Surface Water of the Muddy Creek Basin, Utah

    USGS Publications Warehouse

    Gerner, Steven J.

    2008-01-01

    Muddy Creek is located in the southeastern part of central Utah and is a tributary of the Dirty Devil River, which, in turn, is a tributary of the Colorado River. Dissolved solids transported from the Muddy Creek Basin may be stored in the lower Dirty Devil River Basin, but are eventually discharged to the Colorado River and impact downstream water users. This study used selected dissolved-solids measurements made by various local, State, and Federal agencies from the 1970s through 2006, and additional dissolved-solids data that were collected by the U.S. Geological Survey during April 2004 through November 2006, to compute dissolved-solids loads, determine the distribution of dissolved-solids concentrations, and identify trends in dissolved-solids concentration in surface water of the Muddy Creek Basin. The dissolved-solids concentration values measured in water samples collected from Muddy Creek during April 2004 through October 2006 ranged from 385 milligrams per liter (mg/L) to 5,950 mg/L. The highest dissolved-solids concentration values measured in the study area were in water samples collected at sites in South Salt Wash (27,000 mg/L) and Salt Wash (4,940 to 6,780 mg/L). The mean annual dissolved-solids load in Muddy Creek for the periods October 1976 to September 1980 and October 2005 to September 2006 was smallest at a site near the headwaters (9,670 tons per year [tons/yr]) and largest at a site at the mouth (68,700 tons/yr). For this period, the mean annual yield of dissolved solids from the Muddy Creek Basin was 44 tons per square mile. During October 2005 to September 2006, direct runoff transported as much as 45 percent of the annual dissolved-solids load at the mouth of Muddy Creek. A storm that occurred during October 5?7, 2006 resulted in a peak streamflow at the mouth of Muddy Creek of 7,150 cubic feet per second (ft3/s) and the transport of an estimated 35,000 tons of dissolved solids, which is about 51 percent of the average annual dissolved

  4. Dissolved platinum in rainwater, river water and seawater around Tokyo Bay and Otsuchi Bay in Japan

    NASA Astrophysics Data System (ADS)

    Mashio, Asami Suzuki; Obata, Hajime; Tazoe, Hirofumi; Tsutsumi, Makoto; Ferrer i Santos, Antoni; Gamo, Toshitaka

    2016-10-01

    Platinum, among the rarest elements in the earth's crust, is now widely used in various products such as catalytic converters in automobiles and anticancer drugs. Consequently, the concentration of Pt in urban aquatic environments might be increasing. However, little is known about the distributions and geochemical cycles of Pt in aquatic environments because its overall concentration remains low. In this study, we examined dissolved Pt in river water and seawater around Tokyo Bay and Otsuchi Bay (Iwate Prefecture, Japan) and rainwater in the Tokyo area. To determine sub-picomolar levels of dissolved Pt, we used isotope-dilution Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after column preconcentration with an anion exchange resin. We observed seasonal variation in the dissolved Pt concentrations in Tokyo rainwater in 2002; higher concentrations were found from January to March, which might be related to the pH of rainwaters. At the source of the Arakawa River in the greater Tokyo area, the dissolved Pt concentration was found to be similar to that in rainwater. Further downstream, the dissolved Pt concentration increased sharply, which seemingly reflects the anthropogenic input of Pt into the river. In a rural area in Japan (Otsuchi Bay), the dissolved Pt concentrations were lower than in Tokyo Bay. In this area, a sharp increase in dissolved Pt concentrations was observed in a high salinity region. Contrasting Pt distribution patterns between urban and rural areas indicate that strong anthropogenic Pt sources exist in urban estuaries and that geochemical processes within estuaries affect the Pt distribution.

  5. 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...

  6. Columnar transmitter based wireless power delivery system for implantable device in freely moving animals.

    PubMed

    Eom, Kyungsik; Jeong, Joonsoo; Lee, Tae Hyung; Lee, Sung Eun; Jun, Sang Bum; Kim, Sung June

    2013-01-01

    A wireless power delivery system is developed to deliver electrical power to the neuroprosthetic devices that are implanted into animals freely moving inside the cage. The wireless powering cage is designed for long-term animal experiments without cumbersome wires for power supply or the replacement of batteries. In the present study, we propose a novel wireless power transmission system using resonator-based inductive links to increase power efficiency and to minimize the efficiency variations. A columnar transmitter coil is proposed to provide lateral uniformity of power efficiency. Using this columnar transmitter coil, only 7.2% efficiency fluctuation occurs from the maximum transmission efficiency of 25.9%. A flexible polymer-based planar type receiver coil is fabricated and assembled with a neural stimulator and an electrode. Using the designed columnar transmitter coil, the implantable device successfully operates while it moves freely inside the cage. PMID:24110073

  7. Navier-Stokes hydrodynamics of thermal collapse in a freely cooling granular gas.

    PubMed

    Kolvin, Itamar; Livne, Eli; Meerson, Baruch

    2010-08-01

    We show that, in dimension higher than one, heat diffusion and viscosity cannot arrest thermal collapse in a freely evolving dilute granular gas, even in the absence of gravity. Thermal collapse involves a finite-time blowup of the gas density. It was predicted earlier in ideal, Euler hydrodynamics of dilute granular gases in the absence of gravity, and in nonideal, Navier-Stokes granular hydrodynamics in the presence of gravity. We determine, analytically and numerically, the dynamic scaling laws that characterize the gas flow close to collapse. We also investigate bifurcations of a freely evolving dilute granular gas in circular and wedge-shaped containers. Our results imply that, in general, thermal collapse can only be arrested when the gas density becomes comparable with the close-packing density of grains. This provides a natural explanation to the formation of densely packed clusters of particles in a variety of initially dilute granular flows.

  8. Between soap bubbles and vesicles: The dynamics of freely floating smectic bubbles

    NASA Astrophysics Data System (ADS)

    Stannarius, Ralf; May, Kathrin; Harth, Kirsten; Trittel, Torsten

    2013-03-01

    The dynamics of droplets and bubbles, particularly on microscopic scales, are of considerable importance in biological, environmental, and technical contexts. We introduce freely floating bubbles of smectic liquid crystals and report their unique dynamic properties. Smectic bubbles can be used as simple models for dynamic studies of fluid membranes. In equilibrium, they form minimal surfaces like soap films. However, shape transformations of closed smectic membranes that change the surface area involve the formation and motion of molecular layer dislocations. These processes are slow compared to the capillary wave dynamics, therefore the effective surface tension is zero like in vesicles. Freely floating smectic bubbles are prepared from collapsing catenoid films and their dynamics is studied with optical high-speed imaging. Experiments are performed under normal gravity and in microgravity during parabolic flights. Supported by DLR within grant OASIS-Co.

  9. 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

  10. 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.

  11. 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.

  12. Miniature microscopes for large-scale imaging of neuronal activity in freely behaving rodents.

    PubMed

    Ziv, Yaniv; Ghosh, Kunal K

    2015-06-01

    Recording neuronal activity in behaving subjects has been instrumental in studying how information is represented and processed by the brain. Recent advances in optical imaging and bioengineering have converged to enable time-lapse, cell-type specific recordings of neuronal activities from large neuronal populations in deep-brain structures of freely behaving rodents. We will highlight these advancements, with an emphasis on miniaturized integrated microscopy for large-scale imaging in freely behaving mice. This technology potentially enables studies that were difficult to perform using previous generation imaging and current electrophysiological techniques. These studies include longitudinal and population-level analyses of neuronal representations associated with different types of naturalistic behaviors and cognitive or emotional processes. PMID:25951292

  13. Miniature microscopes for large-scale imaging of neuronal activity in freely behaving rodents.

    PubMed

    Ziv, Yaniv; Ghosh, Kunal K

    2015-06-01

    Recording neuronal activity in behaving subjects has been instrumental in studying how information is represented and processed by the brain. Recent advances in optical imaging and bioengineering have converged to enable time-lapse, cell-type specific recordings of neuronal activities from large neuronal populations in deep-brain structures of freely behaving rodents. We will highlight these advancements, with an emphasis on miniaturized integrated microscopy for large-scale imaging in freely behaving mice. This technology potentially enables studies that were difficult to perform using previous generation imaging and current electrophysiological techniques. These studies include longitudinal and population-level analyses of neuronal representations associated with different types of naturalistic behaviors and cognitive or emotional processes.

  14. Development of implantable optoelectronic module for optical brain tissue stimulation in freely moving mice

    NASA Astrophysics Data System (ADS)

    Rusakov, Konstantin; Czajkowski, Rafał; Kaźmierczak, 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 μm2 top surface) LED chip and experimental validation of the optoelectronic stimulator.

  15. Navier-Stokes hydrodynamics of thermal collapse in a freely cooling granular gas.

    PubMed

    Kolvin, Itamar; Livne, Eli; Meerson, Baruch

    2010-08-01

    We show that, in dimension higher than one, heat diffusion and viscosity cannot arrest thermal collapse in a freely evolving dilute granular gas, even in the absence of gravity. Thermal collapse involves a finite-time blowup of the gas density. It was predicted earlier in ideal, Euler hydrodynamics of dilute granular gases in the absence of gravity, and in nonideal, Navier-Stokes granular hydrodynamics in the presence of gravity. We determine, analytically and numerically, the dynamic scaling laws that characterize the gas flow close to collapse. We also investigate bifurcations of a freely evolving dilute granular gas in circular and wedge-shaped containers. Our results imply that, in general, thermal collapse can only be arrested when the gas density becomes comparable with the close-packing density of grains. This provides a natural explanation to the formation of densely packed clusters of particles in a variety of initially dilute granular flows. PMID:20866801

  16. Long-term Potentiation of Perforant Pathway-dentate Gyrus Synapse in Freely Behaving Mice

    PubMed Central

    Blaise, J. Harry

    2013-01-01

    Studies of long-term potentiation of synaptic efficacy, an activity-dependent synaptic phenomenon having properties that make it attractive as a potential cellular mechanism underlying learning and information storage, have long been used to elucidate the physiology of various neuronal circuits in the hippocampus, amygdala, and other limbic and cortical structures. With this in mind, transgenic mouse models of neurological diseases represent useful platforms to conduct long-term potentiation (LTP) studies to develop a greater understanding of the role of genes in normal and abnormal synaptic communication in neuronal networks involved in learning, emotion and information processing. This article describes methodologies for reliably inducing LTP in the freely behaving mouse. These methodologies can be used in studies of transgenic and knockout freely behaving mouse models of neurodegenerative diseases. PMID:24327052

  17. Dissolving pulp from jute stick.

    PubMed

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

    2015-01-22

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

  18. 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`

  19. Dissolving pulp from jute stick.

    PubMed

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

    2015-01-22

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

  20. Experimental measurement of the flow field around a freely swimming microorganism

    NASA Astrophysics Data System (ADS)

    Polin, Marco; Drescher, Knut; Goldstein, Raymond; Michel, Nicolas; Tuval, Idan

    2010-03-01

    Despite their small size, the fluid flows produced by billions of microscopic swimmers in nature can have dramatic macroscopic effects (e.g. biogenic mixing in the ocean). Understanding the flow structure of a single swimming microorganism is essential to explain and model these macroscopic phenomena. Here we report the first detailed measurement of the flow field around an isolated, freely swimming microorganism, the spherical alga Volvox, and discuss the implications of this measurement for other species.

  1. Hybrid Metameterials Enable Fast Electrical Modulation Of Freely Propagating Terahertz Waves

    SciTech Connect

    Chen, Hou-tong; O' Hara, John F; Taylor, Antoinette J

    2008-01-01

    We demonstrate fast electrical modulation of freely propagating THz waves at room temperature using hybrid metamaterial devices. the devices are planar metamaterials fabricated on doped semiconducor epitaxial layers, which form hybrid metamaterial - Schottky diode structures. With an applied ac voltage bias, we show modulation of THz radiation at inferred frequencies over 2 MHz. The modulation speed is limited by the device depletion capacitance which may be reduced for even faster operation.

  2. A novel synthetic route to freely adjust the crystal structures of Ni-P compounds

    NASA Astrophysics Data System (ADS)

    Xu, Hanghui; Lu, Shaoxiang; Ren, Lili

    2016-10-01

    Crystal-structure-controllable Ni-P compounds were synthesized using nickel chloride, nontoxic red phosphorus and polyethylene glycol. The hexagonal Ni2P and tetragonal Ni12P5 could be freely transformed via adjusting the amount of polyethylene glycol, and the mechanism of phase transformation was discussed. The catalytic performances of Ni-P compounds were promoted markedly with moderate quantity of PEG. However, excessive PEG will cover the active sites of catalysts and decrease the catalytic activity.

  3. Labyrinthine instability in freely suspended films of a polarization-modulated smectic phase

    NASA Astrophysics Data System (ADS)

    Eremin, Alexey; Kornek, Ulrike; Stannarius, Ralf; Weissflog, Wolfgang; Nádasi, Hajnalka; Araoka, Fumito; Takezoe, Hideo

    2013-12-01

    We report on fingering and labyrinthine instabilities of the layer dislocation lines in freely suspended polar liquid-crystalline films. These polar fingerlike and labyrinth structures reversibly form upon a transition into a modulated phase. External electric fields of several kV/m applied in the film plane can reversibly influence the formation of the finger textures. We show that the labyrinthine pattern is intrinsically related to regular splay deformations of the polarization.

  4. 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.

  5. Nanoscopic Terraces, Mesas, and Ridges in Freely Standing Thin Films Sculpted by Supramolecular Oscillatory Surface Forces.

    PubMed

    Zhang, Yiran; Yilixiati, Subinuer; Pearsall, Collin; Sharma, Vivek

    2016-04-26

    Freely standing thin liquid films containing supramolecular structures including micelles, nanoparticles, polyelectrolyte-surfactant complexes, and smectic liquid crystals undergo drainage via stratification. The layer-by-layer removal of these supramolecular structures manifests as stepwise thinning over time and a coexistence of domains and nanostructures of discretely different thickness. The layering of supramolecular structures in confined thin films contributes additional non-DLVO, supramolecular oscillatory surface forces to disjoining pressure, thus influencing both drainage kinetics and stability of thin films. Understanding and characterizing the spontaneous creation and evolution of nanoscopic topography of stratifying, freely standing thin liquid films have been long-standing challenges due to the absence of experimental techniques with the requisite spatial (thickness <10 nm) and temporal resolution (<1 ms). Using Interferometry Digital Imaging Optical Microscopy (IDIOM) protocols developed herein, we visualize and characterize size, shape, and evolution kinetics of nanoscopic mesas, terraces, and ridges. The exquisite thickness maps created using IDIOM protocols provide much needed and unprecedented insights into the role of supramolecular oscillatory surface forces in driving growth of such nanostructures as well as in controlling properties and stability of freely standing thin films and, more generally, of colloidal dispersions like foams.

  6. [Long-term potentiation and unit evoked responses in the cingulate cortex of freely moving rats].

    PubMed

    Gorkin, A G; Reymann, K G; Aleksandrov, Iu I

    2002-01-01

    Long-term potentiation (LTP) of synaptic efficacy is considered to be the most probable physiological mechanism of long-term memory. However, lack of understanding of cellular and subcellular mechanisms of LTP induction in freely behaving animals does not correspond to the importance of the problem. It was tested whether the characteristics of potentiation in the cingulate cortex after tetanization of the subiculocingulate tract (SCT) meet the criteria of true LTP (that passes all known stages in its development and lasts for more than a day in freely-behaving animals). Additionally, characteristics of spike responses to SCT stimulation and the effects of application of different glutamate receptor blockers were studied. Without application of GABA receptor blockers, the LTP lasted for more than 24 hours. Application of NMDA glutamate receptor blockers significantly inhibited field potentials evoke by testing stimulation. Short-latency spike responses to SCT stimulation were recorded with low probability that increased with stimulation intensity. The obtained data reveal the possibility to compare the involvement of cingulate neurons in acquisition of adaptive behavior and changes in their spike responses during the LTP development in freely-moving rats. PMID:12528373

  7. 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...

  8. 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.

  9. Dissolved-oxygen quenching of in-situ fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Chudyk, Wayne; Tonaszuck, David; Pohlig, Kenneth

    1993-04-01

    In-situ fluorescence measurements of aromatic organic ground water contaminants do not always agree with gas chromatographic methods. Dissolved oxygen quenching of fluorescence may be an interferant in field measurements. Two standard fluorescent aromatics, quinine sulfate and naphthalene, were evaluated in this study. Over the range of dissolved oxygen concentrations expected to be encountered in the field, no effects of oxygen quenching on fluorescence of these compounds was observed. Quenching of quinine sulfate fluorescence by sodium chloride was observed using this system. Sodium chloride quenching was shown to follow the Stern-Volmer relation.

  10. 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.

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

    PubMed

    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

  12. 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.

  13. Dissolved methane in Indian freshwater reservoirs.

    PubMed

    Narvenkar, G; Naqvi, S W A; Kurian, S; Shenoy, D M; Pratihary, A K; Naik, H; Patil, S; Sarkar, A; Gauns, M

    2013-08-01

    Emission of methane (CH4), a potent greenhouse gas, from tropical reservoirs is of interest because such reservoirs experience conducive conditions for CH4 production through anaerobic microbial activities. It has been suggested that Indian reservoirs have the potential to emit as much as 33.5 MT of CH4 per annum to the atmosphere. However, this estimate is based on assumptions rather than actual measurements. We present here the first data on dissolved CH4 concentrations from eight freshwater reservoirs in India, most of which experience seasonal anaerobic conditions and CH4 buildup in the hypolimnia. However, strong stratification prevents the CH4-rich subsurface layers to ventilate CH4 directly to the atmosphere, and surface water CH4 concentrations in these reservoirs are generally quite low (0.0028-0.305 μM). Moreover, only in two small reservoirs substantial CH4 accumulation occurred at depths shallower than the level where water is used for power generation and irrigation, and in the only case where measurements were made in the outflowing water, CH4 concentrations were quite low. In conjunction with short periods of CH4 accumulation and generally lower concentrations than previously assumed, our study implies that CH4 emission from Indian reservoirs has been greatly overestimated. PMID:23397538

  14. 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

  15. Geochemical behavior of dissolved manganese in the East China Sea: Seasonal variation, estuarine removal, and regeneration under suboxic conditions

    NASA Astrophysics Data System (ADS)

    Wang, Zhao-Wei; Ren, Jing-Ling; Jiang, Shuo; Liu, Su-Mei; Xuan, Ji-Liang; Zhang, Jing

    2016-02-01

    To better understand the geochemical cycle of dissolved manganese (Mn) in the East China Sea (ECS), the distribution of dissolved Mn across the ECS was investigated during three field studies in 2011 (May, August, and November). The concentration of dissolved Mn decreased across the ECS with distance from the coast. Mn-rich ECS shelf waters could export to the Kuroshio Waters, and had the potential to influence the northwest Pacific Ocean as well as the Japan Sea. The Kuroshio Waters were devoid of dissolved Mn, so its incursion could be tracked as it entered the ECS continental shelf region (approximately 50 m isobath). Seasonal variations of dissolved Mn in the ECS were significant, with the highest concentrations occurring in summer. Dissolved Mn in the Changjiang Estuary was nonconservative, and significant quantities were removed by net sorption onto suspended particulate matter. A model describing the sorption processes was applied to data for the Changjiang Estuary. Regeneration of dissolved Mn took place in near-bottom waters of the suboxic zone in August 2011, following extensive consumption of oxygen. The benthic flux of dissolved Mn was estimated based on Mn concentrations in the overlying waters and the near-bottom waters. A preliminary box model was established to develop a dissolved Mn budget for the ECS. Based on the dissolved Mn content in the ECS and the total input flux, a residence time of 76-350 days for dissolved Mn in the ECS was inferred.

  16. Method for dissolving delta-phase plutonium

    DOEpatents

    Karraker, David G.

    1992-01-01

    A process for dissolving plutonium, and in particular, delta-phase plutonium. The process includes heating a mixture of nitric acid, hydroxylammonium nitrate (HAN) and potassium fluoride to a temperature between 40.degree. and 70.degree. C., then immersing the metal in the mixture. Preferably, the nitric acid has a concentration of not more than 2M, the HAN approximately 0.66M, and the potassium fluoride 0.1M. Additionally, a small amount of sulfamic acid, such as 0.1M can be added to assure stability of the HAN in the presence of nitric acid. The oxide layer that forms on plutonium metal may be removed with a non-oxidizing acid as a pre-treatment step.

  17. X-ray fluorescence measurements of dissolved gas and cavitation

    NASA Astrophysics Data System (ADS)

    Duke, Daniel J.; Kastengren, Alan L.; Swantek, Andrew B.; Matusik, Katarzyna E.; Powell, Christopher F.

    2016-10-01

    The dynamics of dissolved gas and cavitation are strongly coupled, yet these phenomena are difficult to measure in-situ. Both create voids in the fluid that can be difficult to distinguish. We present an application of X-ray fluorescence in which liquid density and total noncondensible gas concentration (both dissolved and nucleated) are simultaneously measured. The liquid phase is doped with 400 ppm of a bromine tracer, and dissolved air is removed and substituted with krypton. Fluorescent emission at X-ray wavelengths is s