Note: This page contains sample records for the topic freely dissolved concentration from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Field testing of equilibrium passive samplers to determine freely dissolved native polycyclic aromatic hydrocarbon concentrations.  

PubMed

Equilibrium passive samplers are promising tools to determine freely dissolved aqueous concentrations (C(W,free)) of hydrophobic organic compounds. Their use in the field, however, remains a challenge. In the present study on native polycyclic aromatic hydrocarbons (PAHs) in Oslo Harbor, Norway, two different passive sampler materials, polyoxymethylene (POM; thickness, 55 microm [POM-55] and 500 microm [POM-500]) and polydimethylsiloxane (PDMS; thickness, 200 microm), were used to determine in the laboratory C(W,free) in sediment pore water (C(PW,free)), and the suitability of five passive samplers for determination of C(W,free) in overlying surface water was tested under field conditions. For laboratory determinations of C(PW,free), both POM-55 and PDMS turned out to be suitable. In the field, the shortest equilibrium times (approximately one month) were observed for POM-55 and PDMS (thickness, 28 microm) coatings on solid-phase microextraction fibers, with PDMS tubing as a good alternative. Low-density polyethylene (thickness, 100 microm) and POM-500 did not reach equilibrium within 119 d in the field. Realistic values were obtained for dissolved organic carbon-water partition coefficients in the field (approximately one log unit under log K(OW)), which strengthened the conclusion that equilibrium was established in field-exposed passive samplers. At all four stations, chemical activity ratios between pore water and overlying water were greater than one for all PAHs, indicating that the sediment was a PAH diffusion source and that sediment remediation may be an appropriate treatment for PAH contamination in Oslo Harbor. PMID:18516795

Cornelissen, Gerard; Pettersen, Arne; Broman, Dag; Mayer, Philipp; Breedveld, Gijs D

2008-03-01

2

Measuring low picogram per liter concentrations of freely dissolved polychlorinated biphenyls in sediment pore water using passive sampling with polyoxymethylene.  

PubMed

Studies into bioaccumulation of polychlorinated biphenyls (PCBs) have increasingly focused on congeners that are freely dissolved in sediment interstitial pore water. Because of their low water solubilities and their tendency to persist and concentrate as they progress in the food chain, interest has grown in methods capable of measuring individual PCB congeners at low part-per-quadrillion (picogram per liter) concentrations. Obtaining large volumes of pore water is difficult (or impossible), which makes conventional analytical approaches incapable of attaining suitable detection limits. In the present study, nondepletive sampling is used to achieve very low detection limits of freely dissolved PCBs, while requiring no separation of the sediment and water slurry. Commercially available 76 microm thick polyoxymethylene (POM) coupons were placed directly into wet sediments and left to reach equilibrium with the pore water and sediment PCBs for up to 84 days, with 28 days found to be sufficient. Freely dissolved concentrations were then calculated by dividing the PCB concentration found in the POM by its POM/water partitioning coefficient (K(POM)). The K(POM) values required for determining water concentrations were measured using two spiked sediments and two historically contaminated sediments for all 62 PCB congeners that are present at greater than trace concentrations in commercial Aroclors. Log K(POM) values ranged from ca. 4.6 for dichloro-congeners to ca. 7.0 for octachloro-congeners and correlate well with octanol/water coefficients (K(OW)) (r(2) = 0.947) so that a simple linear equation can be used to calculate dissolved concentrations within a factor of 2 or better for congeners having no measured K(POM) value. Detection limits for freely dissolved PCBs ranged from ca. 20 pg/L (part-per-quadrillion) for dichloro-congeners down to ca. 0.2 pg/L for higher-molecular-weight congeners. Sorption isotherms were found to be linear (r(2) > 0.995) over at least 3 orders of magnitude for all congeners, demonstrating good quantitative linearity of the method for determining freely dissolved PCB concentrations at environmentally relevant levels. PMID:19908907

Hawthorne, Steven B; Miller, David J; Grabanski, Carol B

2009-11-15

3

Using disposable solid-phase microextraction (SPME) to determine the freely dissolved concentration of polybrominated diphenyl ethers (PBDEs) in sediments.  

PubMed

Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants (BFRs). The ubiquity and persistence of PBDEs in sediment have raised concerns over their environmental fate and ecological risks. Due to strong affinity for sediment organic matter, environmental fate and bioavailability of PBDEs closely depend on their phase distribution. In this study, disposable polydimethylsiloxane (PDMS) fiber was used to derive the freely dissolved concentration (C(free)) of PBDEs in sediment porewater as a measurement of bioavailability. The PDMS-to-water partition coefficient (log K(PDMS)) was 5.46-5.83 for BDE 47, 99, and 153. In sediments, PBDEs were predominantly sorbed to the sediment phase, with C(free) accounting for <0.012% of the total chemical mass. The C(free) of PBDEs decreased as their bromination or sediment organic carbon content increased. The strong association with dissolved organic matter (DOM) implies a potential for facilitated offsite transport and dispersion in the environment that depends closely on the stability of sediment aggregates. PMID:22522316

Jia, Fang; Cui, Xinyi; Wang, Wei; Delgado-Moreno, Laura; Gan, Jay

2012-04-21

4

Passive equilibrium sampler for in situ measurements of freely dissolved concentrations of hydrophobic organic chemicals in sediments.  

PubMed

In this study, an equilibrium passive sampling device is introduced that facilitates the in situ measurement of hydrophobic organic chemicals bioavailability in sediments in terms of freely dissolved concentrations. The new field sampler allows SPME fibers and silicone hollow fibers to be immersed and equilibrated in situ, whereas an automated liner exchanger (ALEX) facilitates the quantitative transfer of analytes to the GC without the use of extraction solvents. The sampler was developed for environmental monitoring as follows: (1) It is of very solid construction and can be reused practically ad infinitum. (2) Fibers with varying surface to volume ratios can be exposed in parallel in order to confirm that equilibrium was reached between sampler and sediment. (3) The equilibrium times allow a temporal resolution that is suited for monitoring of both long-term trends and seasonal effects. The automated thermal desorption reduced sample treatment to a minimum and ensured cost- and time-efficient measurements while minimizing potential error sources after the sampling. The sampler is applicable in a multitude of aquatic environments, especially where currents are low and sediments are muddy and well-mixed, e.g. by bioturbation. Examples for such environments are mud flats, harbor basins, river banks, and lakes. PMID:23819657

Witt, Gesine; Lang, Susann-Cathrin; Ullmann, Dagny; Schaffrath, Gotja; Schulz-Bull, Detlef; Mayer, Philipp

2013-07-02

5

Measuring binding and speciation of hydrophobic organic chemicals at controlled freely dissolved concentrations and without phase separation.  

PubMed

The binding and speciation of hydrophobic organic chemicals (HOCs) in aqueous solutions were determined by controlling chemical activity and measuring total concentrations. Passive dosing was applied to control chemical activities of HOCs in aqueous solutions by equilibrium partitioning from a poly(dimethylsiloxane) polymer preloaded with the chemicals. The HOC concentrations in the equilibrated solutions [C(solution(eq))] and water [C(water(eq))] were then measured. Free fractions of the HOCs were determined as C(water(eq))/C(solution(eq)), whereas enhanced capacities (E) of the solutions for HOCs were determined as C(solution(eq))/C(water(eq)). A mixture of polycyclic aromatic hydrocarbons served as model analytes, while humic acid, sodium dodecyl sulfate, hydroxypropyl-?-cyclodextrin, and NaCl served as model medium constituents. The enhanced capacities were plotted versus the concentrations of medium constituents, and simple linear regression provided precise partition ratios, salting out constants, and critical micelle concentrations. These parameters were generally in good agreement with published values obtained by solid phase microextraction and fluorescence quenching. The very good precision was indicated by the low relative standard errors for the partition ratios of 0.5-8%, equivalent to 0.002-0.03 log unit. This passive dosing approach allows binding and speciation of HOCs to be studied without any phase separation steps or mass balance assumptions. PMID:22148547

Gouliarmou, Varvara; Smith, Kilian E C; de Jonge, Lis Wollesen; Mayer, Philipp

2012-01-06

6

Matrix solid-phase microextraction for measuring freely dissolved concentrations and chemical activities of PAHs in sediment cores from the western Baltic Sea.  

PubMed

Sediment-pore water partitioning of polycyclic aromatic hydrocarbons (PAHs) was studied in sediment cores of a dumping area in the western Baltic Sea and compared to a reference site. Freely dissolved concentrations (C(free)) of nine PAHs were measured in sediment samples using solid-phase microextraction (SPME), a cost and time-efficient method with detection limits in the lower ng L(-1) range. Elevated levels of C(free) were measured at the dumping site, where concentration peaks in the core correlated with the presence of the dumped material, which was conspicuous in its color and consistency. Sediment concentrations of PAHs were three orders of magnitude higher at the dumping site than at the reference site, whereas C(free) was only one order of magnitude greater. Chemical activities of the PAHs in the sediment cores were calculated from C(free) to predict the baseline toxic potential of the contaminant mixture. Finally, gradients in C(free) and chemical activity were used to determine the direction of diffusion within the sediment and to obtain a spatial characterization of the PAH exposure. C(free) and chemical activity are important exposure parameters for the prediction of bioconcentration and toxicity in sediment organisms, and their measurement should be included in risk-assessment and pollution-management strategies. PMID:19000629

Witt, Gesine; Liehr, Gladys A; Borck, Dörthe; Mayer, Philipp

2008-11-08

7

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

EPA Science Inventory

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

8

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

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 <1nM-1?M (well below the CMC). Using the C18/SCX-SPME fibers, linear sorption isotherms to Aldrich humic acid at pH 6 (ionic strength 0.015M) were measured over a broad concentration range with a sorption coefficient of 10(5.3). PMID:24094752

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

2013-09-14

9

Experimental verification of a model describing solid phase microextraction (SPME) of freely dissolved organic pollutants in sediment porewater  

Microsoft Academic Search

To verify a theoretical mass balance and multiple compartment partitioning model developed to predict freely dissolved concentrations (FDCs) of hydrophobic organic chemicals (HOCs) using negligible depletion-solid phase microextraction (nd-SPME), a series of sediment slurry experiments were performed using disposable poly(dimethyl)siloxane (PDMS) coated-SPME fibers and 14C-radiolabeled HOC analogs. First, pre-calibration of disposable PDMS coated fibers for four model compounds (phenanthrene, PCB

Ze-Yu Yang; Keith A. Maruya; Darrin Greenstein; David Tsukada; Eddy Y. Zeng

2008-01-01

10

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

PubMed

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

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

2005-08-01

11

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

SciTech Connect

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.

Aregory James Sower; Kim A. Anderson [Oregon State University, Corvallis, OR (USA). Environmental and Molecular Toxicology Department

2008-12-15

12

Experimental verification of a model describing solid phase microextraction (SPME) of freely dissolved organic pollutants in sediment porewater.  

PubMed

To verify a theoretical mass balance and multiple compartment partitioning model developed to predict freely dissolved concentrations (FDCs) of hydrophobic organic chemicals (HOCs) using negligible depletion-solid phase microextraction (nd-SPME), a series of sediment slurry experiments were performed using disposable poly(dimethyl)siloxane (PDMS) coated-SPME fibers and (14)C-radiolabeled HOC analogs. First, pre-calibration of disposable PDMS coated fibers for four model compounds (phenanthrene, PCB 52, PCB 153 and p,p'-DDE) with good precision (concentrations in sediment porewater using solid-phase microextraction. Chemosphere 66, 1408-1414]. Moreover, the SPME-measured FDCs (C(pw,SPME)) followed the order of phenanthrene>PCB 52>PCB 153, and the measured and predicted C(pw) values were not substantially different from empirically determined values except for p,p'-DDE. PMID:18597813

Yang, Ze-Yu; Maruya, Keith A; Greenstein, Darrin; Tsukada, David; Zeng, Eddy Y

2008-07-01

13

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

PubMed

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

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

2011-02-25

14

Development of negligible depletion hollow fiber-protected liquid-phase microextraction for sensing freely dissolved triazines.  

PubMed

A new sampling method, termed negligible depletion hollow fiber-protected liquid-phase microextraction, was developed for sensing the freely dissolved concentration (C(free)) and evaluating the availability of atrazine (ATR), desethyl atrazine (DEA), and simazine (SIM) in water. The sampling device was prepared by impregnating 1-octanol to both the pores and the lumen of a piece of polypropylene microporous hollow fiber membrane. After equilibrium and negligible depletion extraction, the 1-octanol in the lumen of the hollow fiber (10 microl) was collected for determination of triazines. Determination of C(free) and the distribution coefficient to 1-octanol (D(ow)) can be performed with this technique. A wide linear working range (1-200 microg/L) and low detection limits (0.1-1 microg/L) were obtained for triazines. Measured log D(ow) values of DEA (1.44 +/- 0.04), SIM (2.06 +/- 0.06), and ATR (2.33 +/- 0.05) agreed well with those reported in the literature. The measured D(ow) values were independent of the chemical concentration and sample pH (pH 3-10) and negligibly affected by the sample salinity (0-500 mM), suggesting that environmentally relevant pH and salinity have no significant effects on the availability of triazines. Although a slight (< or = 31%) increase of C(free) was observed, one-way analysis of variance indicated the C(free) of triazines were not significantly affected by the presence of Aldrich humic acid, Acros humic acid, and bovine albumin V (dissolved organic carbon [DOC], 0-100 mg/L). From 3 to 36% of the spiked triazines, however, were found to associate with the dissolved organic matter (DOM) in surface-water samples (DOC, 32.0-61.9 mg/L), suggesting the origin of the DOM is a key parameter in determining its association with and, thus, the availability of triazines. PMID:18937535

Hu, Xialin; Liu, Jingfu; Jönsson, Jan A; Jiang, Guibin

2009-02-01

15

DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS  

SciTech Connect

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.

NA

2004-11-22

16

DISSOLVED CONCENTRATION LIMITS OF RADIOACTIVE ELEMENTS  

SciTech Connect

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

P. Bernot

2005-07-13

17

Ionic liquid assisted dissolution of dissolved organic matter and PAHs from soil below the critical micelle concentration.  

PubMed

Increased use and production of ionic liquids (ILs) may result in emissions into the environment. Particularly vulnerable are industrial areas and landfills where ILs are utilized and ultimately disposed of. This study investigates how IL contamination can affect soil properties and the sorption of pre-existing contaminants. The commonly used IL 1-methyl-3-octyl imidazolium chloride ([OMIM][Cl]) was added at various quantities to a landfill soil contaminated with polycyclic aromatic hydrocarbons (PAHs). Subsequently, the release of PAHs and dissolved organic matter (DOM) from this soil was thoroughly investigated. Two fractions of PAH release into the porewater were measured, the freely dissolved fraction (measured using a passive sampler) and the total PAH concentration (which includes the freely dissolved molecules as well as those associated with colloids, micelles and DOM). As expected the highest levels of total PAH porewater concentration occurred when the critical micelle concentration (CMC) of the IL was exceeded. However, as we report here for the first time, enhanced amounts of freely dissolved PAHs were released by sub-CMC concentrations of IL. Additionally, enhanced levels of DOM, due to dissolution of soil organic matter by IL, were also observed upon addition of sub-CMC IL concentrations. Based on this, enhanced release of pre-existing contaminants and DOM is suggested as a potential risk from IL emissions at trace concentrations well below the CMC. Potential mechanisms of this sub-CMC release are discussed. PMID:23627900

Markiewicz, Marta; Jungnickel, Christian; Arp, Hans Peter H

2013-05-14

18

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

NASA Astrophysics Data System (ADS)

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 the solubility of the CFA. Substitution of the carbonate ion into the fluorapatite structure, therefore, results in an exponential increase in the levels of dissolved P needed for CFA precipitation. Elevated dissolved P concentrations in Precambrian oceans likely resulted in nitrogen-limited primary production on geological time scales.

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

2008-12-01

19

Dissolved oxygen concentration profiles in a production-scale bioreactor  

Microsoft Academic Search

A five-compartment model for the liquid flow and the oxygen transfer into the liquid phase of a large-scale bioreactor is presented. The aim of the model is to predict the following reactor operating variables: 1) the overall oxygen transfer capacity of the reactor; 2) the local liquid dissolved oxygen concentrations, for estimation of bad aerated zones which can introduce negative

N. M. G. Oosterhuis; N. W. F. Kossen

1984-01-01

20

Investigating Factors that Affect Dissolved Oxygen Concentration in Water  

ERIC Educational Resources Information Center

|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)|

Jantzen, Paul G.

1978-01-01

21

Dissolved gas concentrations of the geothermal fluids in Taiwan  

NASA Astrophysics Data System (ADS)

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.

Chen, Ai-Ti; Yang, Tsanyao Frank

2010-05-01

22

Measurement of Relative Dissolved Gas Concentrations Using Underwater Mass Spectrometry  

NASA Astrophysics Data System (ADS)

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-gas compositions at different sites point to diverse geothermal conditions beneath the lake. Oxygen concentrations were low at most vents, while hydrogen sulfide, methane and carbon dioxide concentrations were highly variable. Dissolved gas depth profiles were obtained using the UMS system in Saanich Inlet, Canada. Due to degradation of organic material, the inlet's deep water is typically anoxic, and rich in methane, carbon dioxide, and reduced sulfur compounds. Relative gas concentrations were obtained between the surface and 200m. A thermocline was detected as the instrument entered anoxic bottom water at 100m. Below this depth oxygen signal intensity declined sharply to background levels. In contrast, carbon dioxide increased sharply below 100m until a reproducible maximum was observed at 120m. Methane and hydrogen sulfide increased steadily with depth below 100 m, and exhibited no local maxima. Fully quantitative UMS measurements require characterization of the influence of salinity, and especially temperature and pressure, on the performance of the internal PDMS membrane. Temperature exerts a strong influence on gas diffusion across the PDMS membrane and the behavior of residual gases in the vacuum chamber; therefore, precise thermostating methods must be adopted. Other technical issues being examined in the laboratory include variations in UMS response attributable to pressure-induced membrane compression, and variable hydrodynamic conditions at the sample/membrane boundary. Experiments are being developed to address the issue of calibrating the ion signal intensity for dissolved gas concentrations.

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

2004-12-01

23

Arterial gas tensions and hemoglobin concentrations of the freely diving Weddell seal.  

PubMed

Heart rate, body temperature, arterial blood gas tensions, pHa and hemoglobin concentrations were measured during and after free diving of the Weddell seal (Leptonychotes weddelli), beneath the fast ice of McMurdo Sound, Antarctica. To examine arterial nitrogen tensions (PaN2), 47 samples of arterial blood were obtained from 4 seals diving up to 23 min to depths of 230 m. Peak arterial nitrogen tensions between 2000 and 2500 mmHg were recorded at depths of 40-80 m during descent, indicating that the seal's lung collapses by 25-50 m. Then arterial blood nitrogen tensions slowly decreased to about 1500 mmHg near surfacing. Thus during diving alveolar collapse and redistribution of blood nitrogen allow the seal to avoid nitrogen narcosis and decompression sickness. The arterial PO2 (PaO2) at rest (78 +/- 13 mmHg, mean +/- SD) increased with diving compression to a maximum measured value of 232 mmHg and then rapidly decreased to 25-35 mmHg. The lowest diving PaO2 was 18 mmHg just before the seal surfaced from a 27-min dive. A consistent increase of arterial hemoglobin concentrations occurred during each dive. We suggest that an extension of the sympathetic outflow of the diving reflex caused profound contraction of the Weddell seal's spleen. PMID:2800051

Zapol, W M; Hill, R D; Qvist, J; Falke, K; Schneider, R C; Liggins, G C; Hochachka, P W

1989-09-01

24

Effect of Concentration of Dissolved Oxygen on Survival of Trout and Roach in Lethal Temperatures  

Microsoft Academic Search

IN the freshwater environment high temperature may be associated with low concentrations of dissolved oxygen, particularly in rivers receiving both heated and oxidizable effluents. Since the toxicity of some poisons is increased by lowering the dissolved oxygen concentration1 and asphyxial levels of dissolved oxygen are increased by an increase in temperature2, it is likely that lethal temperatures will be reduced

J. S. Alabaster; R. L. Welcomme

1962-01-01

25

Rainwater dissolved organic carbon: Concentrations and global flux  

NASA Astrophysics Data System (ADS)

Dissolved organic carbon (DOC) is a major component of both marine (23 ?M) and continental (161 ?M) rain, present in concentrations greater than nitric and sulfuric acids combined. Rain is a significant source of DOC to surface seawater (90 × 1012 g C yr-1), equivalent to the magnitude of river input of DOC to the open ocean and half the magnitude of carbon buried in marine sediments per year on a global scale. Current models of global carbon cycling focus primarily on inorganic forms of carbon and are unable to account for approximately 20% of the global carbon dioxide, suggesting a significant missing carbon sink. Quantification of the average DOC concentration in marine rain allows calculation of the global rainwater flux of DOC of 430 ± 150 × 1012 g C yr-1. When inorganic carbon is included, this rainwater carbon flux becomes 510 ± 170 × 1012 g C yr-1, which, although not the same carbon, is equivalent in magnitude to over one third of the missing carbon sink.

Willey, Joan D.; Kieber, Robert J.; Eyman, Mary S.; Avery, G. Brooks

2000-03-01

26

What controls dissolved iron concentrations in the world ocean?  

Microsoft Academic Search

Dissolved (< 0.4 ?m) iron has been measured in 354 samples at 30 stations in the North and South Pacific, Southern Ocean and North Atlantic by the Trace Metals Laboratory at Moss Landing Marine Laboratories. These stations are all more than 50 km from a continental margin. The global distribution of dissolved iron, which is derived from these profiles, is

Kenneth S. Johnson; R. Michael Gordon; Kenneth H. Coale

1997-01-01

27

Influence of dissolved oxygen concentration and aeration time on nitrite accumulation in partial nitrification process  

Microsoft Academic Search

This study investigated the influence of dissolved oxygen concentration and aeration time on nitrification and nitrite accumulation in an attempt to optimize the recently developed biological-partial-nitritation process for the treatment of strong nitrogen wastewaters. Investigation of dissolved oxygen concentration on ammonium and nitrite oxidation was carried out in a batch reactor. The dissolved oxygen concentration of 0.5 mg O2\\/L inhibited

X. Guo; J. H. Kim; S. K. Behera

28

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

Microsoft Academic Search

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

David A. Nimick; Thomas E. Cleasby; R. Blaine McCleskey

2005-01-01

29

Dissolved Organic Matter Concentration and Quality Influences upon Structure and Function of Freshwater Microbial Communities  

Microsoft Academic Search

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

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

2006-01-01

30

Dissolved Organic Matter concentration and composition in the forests and streams of Olympic National Park, WA  

Microsoft Academic Search

Dissolved organic carbon (DOC) concentration and dissolved organic matter (DOM) character were investigated in soil water (15 and 40 cm) and streams at eleven sites in Olympic National Park. In addition, the effect of added nitrogen on soil water DOM concentration and composition was tested. Forested plots covering a gradient of precipitation, climate, slope, and aspect in Olympic National Park

R. M. Cory; S. A. Green; K. S. Pregitzer

2004-01-01

31

Freely dissolved PCDD\\/F concentrations in the Frierfjord, Norway: comparing equilibrium passive sampling with “active” water sampling  

Microsoft Academic Search

Introduction  Equilibrium passive samplers consisting of 55-µm polyoxymethylene (POM) and 170-µm polydimethylsiloxane were tested for the\\u000a analysis of polychlorinated dibenzodioxin\\/furan (PCDD\\/F) in the pore water and overlying water of the Frierfjord, a bay in\\u000a southern Norway. This fjord is heavily polluted with PCDD\\/Fs due to emissions from a former Mg smelter.\\u000a \\u000a \\u000a \\u000a \\u000a Results and Discussion  Field exposures of both equilibrium passive sampler types

Gerard Cornelissen; Dag Broman; Kristoffer Næs

2010-01-01

32

Stability of complexed Rover dissolver solutions containing high concentrations of niobium, fluoride-ion, and aluminum  

Microsoft Academic Search

The processing of nuclear rocket (Rover) fuels requires high ;\\u000a concentrations of hydrofluoric acid and nitric acid in the dissolver solution to ;\\u000a dissolve the uranium and niobium. The resulting dissolver solutlon is highly ;\\u000a corrosive and requires the addition of aluminum nitrate to complex the free ;\\u000a fluoride'' and reduce corrosion on stainless steel processing equipment located ;\\u000a downstream

Rindfleisch

1974-01-01

33

Elevated air carbon dioxide concentrations increase dissolved carbon leaching from a cropland soil  

Microsoft Academic Search

Increasing leaching losses of carbon from soils due to accelerated weathering and increasing concentrations of dissolved carbon\\u000a as a result of intensified soil respiration are suspected to provide a negative feedback on rising atmospheric CO2 concentrations. We tested this hypothesis by studying concentrations of dissolved carbon and groundwater recharge at the\\u000a Braunschweig free air carbon dioxide enrichment (FACE) experiment under

Jan Siemens; Andreas Pacholski; Katia Heiduk; Anette Giesemann; Ulrike Schulte; René Dechow; Martin Kaupenjohann; Hans-Joachim Weigel

34

A model for predicting the temporal evolution of dissolved oxygen concentration in shallow estuaries  

Microsoft Academic Search

The design of sewage discharge systems in estuaries needs to consider the dissolved oxygen concentration among other water quality indicators. Due to the great number of factors affecting the dissolved oxygen, the prediction of the temporal evolution of this element requires the use of mathematical tools. In the case of shallow estuaries with extensive intertidal zones, the complexity of this

A. García; J. A. Revilla; R. Medina; C. Álvarez; J. A. Juanes

2002-01-01

35

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

USGS Publications Warehouse

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

Fogelman, Ronald P.

1982-01-01

36

Development of an Instrument for Measuring the Concentration of Dissolved Oxygen in Sea Water in Situ.  

National Technical Information Service (NTIS)

An instrument is described consisting of a commercially available oxygen sensor and of a newly developed telemetering and digitizing system which permits measurement of the concentration of dissolved oxygen even in great oceanic depths. The instrument emp...

V. Graefe

1970-01-01

37

The measurement of dissolved and gaseous carbon dioxide concentration  

NASA Astrophysics Data System (ADS)

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.

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

2011-07-01

38

Dissolved oxygen concentration in culture medium: assumptions and pitfalls  

Microsoft Academic Search

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

D. Newby; L. Marks; F. Lyall

2005-01-01

39

Effects of cyanide and dissolved oxygen concentration on biological Au recovery.  

PubMed

The number of discarded electric devices containing traces of Au is currently increasing. It is desirable to recover this Au because of its valuable physicochemical properties. Au is usually dissolved with relatively high concentrations of cyanide, which is associated with environmental risk. Chromobacterium violaceum is able to produce and detoxify small amounts of cyanide, and may thus be able to recover Au from discarded electric devices. This study investigated the effects of cyanide and dissolved oxygen concentration on biological Au recovery. Cyanide production by C. violaceum was sufficient to dissolve Au, while maintaining a high cyanide concentration did not enhance Au dissolution. Increased oxygen concentration enhanced Au dissolution from 0.04 to 0.16 mmol/l within the test period of 70 h. Electrochemical measurement clarified this phenomenon; the rest potential of Au in the cyanide solution produced by C. violaceum increased from -400 to -200 mV, while in the sterile cyanide solution, it was constant in cyanide concentrations ranging from 0 to 1.5 mmol/l and increased in dissolved oxygen concentrations ranging from 0 to 0.25 mmol/l. Therefore, it was clarified that dissolved oxygen concentration is the main factor affecting the efficiency of cyanide leaching of gold by using bacteria. PMID:16567012

Kita, Yoshito; Nishikawa, Hiroshi; Takemoto, Tadashi

2006-03-29

40

Preliminary assessment of total dissolved trace metal concentrations in Sava River water  

Microsoft Academic Search

This study provides the preliminary data set for total dissolved trace metal concentrations in the surface water of the Sava\\u000a River in Croatia and the assessment of Sava River water quality status. The highest levels of total dissolved metals were\\u000a observed for Fe, Mn, and Zn (12.6 ± 7.8 ?g L???1, 3.44 ± 3.95 ?g L???1, and 2.27 ± 1.53 ?g L???1, respectively),

Zrinka Dragun; Vibor Roje; Nevenka Mikac; Biserka Raspor

2009-01-01

41

Dissolved volatile concentrations in an ore-forming magma  

USGS Publications Warehouse

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

Lowenstern, J. B.

1994-01-01

42

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

USGS Publications Warehouse

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)

Woods, P. F.

1989-01-01

43

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

NASA Astrophysics Data System (ADS)

Substantial diel (24-hour) 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 in southwestern Montana. The stream was alkaline (pH of 7.65-9.06), and dissolved metal concentrations were relatively low (1.8-7.1 ? g/L for As, 18-57 ? g/L for Mn, and 12-123 ? 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.

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

2004-12-01

44

Fluxes and concentrations of dissolved organic carbon and nitrogen – a synthesis for temperate forests  

Microsoft Academic Search

Dissolved organic carbon (DOC) and nitrogen (DON)represent an important part of the C and N cycles inforest ecosystems. Little is known about the controlson fluxes and concentrations of these compounds insoils under field conditions. Here we compiledpublished data on concentrations and fluxes of DOC andDON from 42 case studies in forest ecosystems of thetemperate zone in order to evaluate controls

B. Michalzik; K. Kalbitz; J.-H. Park; S. Solinger; E. Matzner

2001-01-01

45

Role of Natural Dissolved Organic Compounds in Determining the Concentrations of Americium in Natural Waters.  

National Technical Information Service (NTIS)

Concentrations of sup 241 Am, both in solution and bound to suspended particulate matter, have been measured in several North American lakes. Dissolved concentrations vary from 0.4 mu Bq/L to 85 mu Bq/L. The sup 241 Am in these lakes originated solely fro...

D. M. Nelson K. A. Orlandini

1985-01-01

46

INCREASED TOXICITY OF AMMONIA TO RAINBOW TROUT 'SALMO GAIRDNERI' RESULTING FROM REDUCED CONCENTRATIONS OF DISSOLVED OXYGEN  

EPA Science Inventory

The median lethal concentration (LC50) of aqueous ammonia at reduced dissolved oxygen (D.O.) concentrations was tested in acute toxicity tests with rainbow trout (Salmo gairdneri) fingerlings. Fifteen 96-h flow-through tests were conducted over the D.O. range 2.6-8.6 mg/L, the fo...

47

Effect of Iron Bioavailability on Dissolved Hydrogen Concentrations During Microbial Iron Reduction  

Microsoft Academic Search

Dissolved hydrogen (H2) concentrations have been shown to correlate with specific terminal electron accepting processes (TEAPs) in aquifers. The research presented herein examined the effect of iron bioavailability on H2 concentrations during iron reduction in flow-through column experiments filled with soil obtained from the uncontaminated background area of the Field Research Center (FRC), Oak Ridge, TN and amended with acetate

John Komlos; Peter R. Jaffe ´

2004-01-01

48

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

Microsoft Academic Search

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

David A. Nimick; Christopher H. Gammons; Thomas E. Cleasby; James P. Madison; Don Skaar; Christine M. Brick

2003-01-01

49

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

Microsoft Academic Search

Substantial diel (24-hour) cycles in dissolved (0.1-mum 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

David A. Nimick; Christopher H. Gammons; Thomas E. Cleasby; James P. Madison; Don Skaar; Christine M. Brick

2003-01-01

50

Dissolved phosphorus concentrations in a natural salt-marsh of Delaware  

Microsoft Academic Search

Dissolved phosphorus concentrations, salinity, pH, and related physical parameters were used to evaluate the variations in a natural salt-marsh. Diel, tidal, lunar, and seasonal variations in phosphorus concentrations were evaluated for a three year period in a natural marsh, situated along the southwestern coast of the Delaware Estuary.

Robert J. Reimold; Franklin C. Daiber

1970-01-01

51

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

Microsoft Academic Search

This study determined the effects of the minimum daily dissolved oxygen (DO) concentration on the production parameters of channel catfish Ictalurus punctatus in earthen ponds. Fifteen 1-acre ponds (five ponds per treatment) were managed as high-oxygen (minimum DO concentrations averaging 4.37 ppm or 54% air saturation from June through September), medium-oxygen (minimum DO concentrations averaging 2.68 ppm or 33.2% air

Eugene L. Torrans

2008-01-01

52

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

NASA Astrophysics Data System (ADS)

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.

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

2006-12-01

53

Behavioral responses of red hake, Urophycis chuss , to decreasing concentrations of dissolved oxygen  

Microsoft Academic Search

Synopsis Laboratory experiments were conducted to examine changes in behavior of red hake,Urophycis chuss, under decreasing concentrations of dissolved oxygen (DO). Since the ecological requirements of this species change with age, responses were measured for three different groups: (1) age 0+, = 89 mm total length (TL); (2) age 1+, = 238 mm TL; and (3) age 2–3+, = 397

Allen J. Bejda; Anne L. Studholme; Bori L. Olla

1987-01-01

54

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

Microsoft Academic Search

A model is developed for prediction of axial concentration profiles of dissolved oxygen and carbon dioxide in tubular photobioreactors used for culturing microalgae. Experimental data are used to verify the model for continuous outdoor culture of Porphyridium cruentum grown in a 200-L reactor with 100-m long tu- bular solar receiver. The culture was carried out at a di- lution rate

F. Camacho Rubio; E. Molina Grima

1999-01-01

55

Influence of dissolved oxygen concentration and shear rate on the production of pullulan by Aureobasidium pullulans  

Microsoft Academic Search

Summary Experiments were carried out withA. pullulans (ATCC 9348) at constant dissolved oxygen concentration (DO=100 and 50% related to air saturation at 1 bar) and at constant stirrer speeds (n=500 and 150 [min-1]). The highest pullulan yield was achieved at decreased constant DO in connection with decreased shear rate. Biomass production was not affected.

A. Wecker; U. Onken

1991-01-01

56

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

Microsoft Academic Search

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

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

2010-01-01

57

Spawning Success of the Black Crappie, 'Pomoxis nigromaculatus', at Reduced Dissolved Oxygen Concentration.  

National Technical Information Service (NTIS)

Mature black crappies (Pomoxis nigromaculatus) were exposed to constant dissolved oxygen (DO) concentrations near or at 2.5, 3.5, 5.0, or 6.5 mg/liter, and near air saturation (control) to determine the effects of reduced DO on spawning success. The fish ...

R. E. Siefert L. J. Herman

1977-01-01

58

SPAWNING SUCCESS OF THE BLACK CRAPPIE, 'POMOXIS NIGROMACULATUS', AT REDUCED DISSOLVED OXYGEN CONCENTRATION  

EPA Science Inventory

Mature black crappies (Pomoxis nigromaculatus) were exposed to constant dissolved oxygen (DO) concentrations near or at 2.5, 3.5, 5.0, or 6.5 mg/liter, and near air saturation (control) to determine the effects of reduced DO on spawning success. The fish spawned successfully 39 t...

59

Landscape predictors of stream dissolved organic matter concentration and physicochemistry in a Lake Superior river watershed  

Microsoft Academic Search

.  We examined landscape predictors of dissolved organic matter (DOM) concentration, molecular weight (Mw), and molar absorptivity at 280 nm (?280) in 60 streams from the Ontonagon River watershed in northern Michigan. During our sampling period (September 19–22, 2002),\\u000a DOM concentration ranged from 4 to 35 mg C L?1 across streams. DOM Mw and ?280 also showed considerable variation among streams. Multiple factor

Paul C. Frost; James H. Larson; Carol A. Johnston; Katie C. Young; Patricia A. Maurice; Gary A. Lamberti; Scott D. Bridgham

2006-01-01

60

Concentration level of dissolved cadmium and its variation in surface seawater of Urasoko Bay, Ishigaki Island  

Microsoft Academic Search

From April 2005 to March 2006, the concentration of dissolved cadmium (Cd) was monitored in the surface seawater of Urasoko\\u000a Bay, which is in a subtropical area of the North Pacific Ocean and is surrounded by a well-developed fringing reef. During\\u000a this period, the observed salinity and Cd concentrations varied in a range of approximately 16–34.5 and 4.8–77.8 pM, respectively.

Kazuo Abe; Ishigaki Tropical Station

2007-01-01

61

Spawning Success of the Black Crappie, Pomoxis nigromaculatus, at Reduced Dissolved Oxygen Concentrations  

Microsoft Academic Search

Mature black crappies (Pomoxis nigromaculatus) were exposed to constant dissolved oxygen (DO) concentrations near or at 2.5, 3.5, 5.0, or 6.5 mg\\/liter, and near air saturation (control) to determine the effects of reduced DO on spawning success. The fish spawned successfully 39 times in laboratory tanks under a simulated natural temperature and light regime at all DO concentrations tested. Fish

Richard E. Siefert; Lawrence J. Herman

1977-01-01

62

Exposure to low concentrations of dissolved ammonia promotes growth rate in walleye Sander vitreus.  

PubMed

The objective of the current study was to examine whether sublethal (moderate) levels of dissolved ammonia may be beneficial to growth in juvenile walleye Sander vitreus (recent evidence in juvenile rainbow trout Oncorhynchus mykiss has shown significant increases in protein synthesis in the presence of moderately elevated concentrations of dissolved ammonia). Moderately elevated dissolved ammonia concentrations between 100 and 300 micromol l(-1) suppressed routine aerobic metabolic activity by 20% during acute trials (2 h), while promoting specific growth rate (>50%) and elevating whole body soluble protein content by 20% in the early stages (14-42 days) in chronic ammonia exposure experiments. Juvenile S. vitreus held at ammonia concentrations between 107.6 +/- 5.5 and 225.5 +/- 4.7 micromol l(-1) (mean +/-s.e.) grew significantly faster than control fish and significantly reduced plasma cortisol levels (<3 microg dl(-1)). Results from this study suggest that chronic exposure to moderate amounts of dissolved ammonia significantly increase growth rates in juvenile S. vitreus by increasing nitrogen accessible for supplementary protein deposition leading to somatic development. PMID:20735605

Madison, B N; Dhillon, R S; Tufts, B L; Wang, Y S

2009-03-01

63

Dissolved nitrous oxide concentrations and fluxes from the eutrophic San Joaquin River, California.  

PubMed

Agriculturally impacted ecosystems can be a source of the greenhouse gas, nitrous oxide (N(2)O); yet in situ measurements of N(2)O fluxes are sparse, particularly in streams and rivers. Dissolved N(2)O was measured from 9 sites over a 13-month period and a gas exchange model was used to predict N(2)O fluxes. N(2)O fluxes were measured at 4 sites on 7 sampling dates using floating chambers. In addition, dissolved N(2)O in porewaters was measured at 4 sites at various depths from 2 to 30 cm. Dissolved N(2)O-N concentrations in surface waters (0.31-1.60 ?g L(-1)) varied seasonally with highest concentrations in late fall and early summer and lowest in winter. Estimated N(2)O-N fluxes (26.2-207 ?g m(-2) hr(-1)) were in relative agreement with measured N(2)O fluxes using floating chambers (9.5-372 ?g m(-2) hr(-1)) and correlated strongly with temperature and nitrate concentrations (R(2) = 0.86). Maximum dissolved N(2)O-N:NO(3)(-)-N ratios were higher in sediment-porewaters at 0.16, compared to surface waters (0.010). The calculated EF5-r value (mean = 0.0028; range = 0.0012-0.0069) was up to 3 times greater than the current IPCC EF5-r emissions factor (0.0025 kg N(2)O-N emitted per kg of NO(3)(-)-N leached). The highest EF5-r values were found in the high-flow sampling events when dissolved N(2)O and NO(3)(-) concentrations were low, highlighting potential constraints in the IPCC methodology for large rivers. PMID:23259867

Hinshaw, Sarra E; Dahlgren, Randy A

2013-01-17

64

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

USGS Publications Warehouse

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)

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

1984-01-01

65

Pyrite oxidation by Acidithiobacillus ferrooxidans at various concentrations of dissolved oxygen  

Microsoft Academic Search

Pyrite oxidation rates were examined at various concentrations of dissolved oxygen (DO) in the presence of the sulfur and iron oxidizer Acidithiobacillus ferrooxidans. Five different batch experiments were performed at room temperature for 75 days under various DO levels (273, 129, 64.8, 13.2, and ?0.006 ?M), containing pyrite grains (particle size 63–250 ?m) and a modified 9K nutrient medium at

Magdalena Gleisner; Roger B. Herbert; Paul C. Frogner Kockum

2006-01-01

66

Amplitude and Phase Fluorescence-Spectroscopy Methods for Dissolved Oxygen Concentration Evaluation: Comparative Practical Results  

Microsoft Academic Search

This paper shows the practical results from a detailed comparative study of amplitude and phase fluorescence-spectroscopy methods for dissolved oxygen concentration evaluation. These results were obtained with an implemented optoelectronic measurement system that guarantees near-optimal operation conditions for both methods and a commercial fluorescence optical-fiber sensor, which is excited by a continuous-regulated sinusoidal-amplitude modulated light beam. The comparison was made

Gustavo J. Grillo; Miguel A. Pérez; Marta Valledor; Rubén Ramos

2005-01-01

67

in situ interlaboratory comparisons for dissolved oxygen concentration and pH  

Microsoft Academic Search

Organization, benefits, and possible drawbacks of in situ interlaboratory comparison are discussed using the example of dissolved oxygen concentration and pH measurements organized\\u000a at the University of Tartu.\\u000a \\u000a \\u000a In situ interlaboratory comparisons are intercomparison measurements, where all the participants (with their technical equipment\\u000a and using their own competence) are measuring the same sample continuously at the same time, at the

Lauri Jalukse; Viktor Vabson; Ivo Leito

2006-01-01

68

A stormflow\\/baseflow comparison of dissolved organic matter concentrations and bioavailability in an Appalachian stream  

Microsoft Academic Search

Patterns of dissolved organic carbon (DOC) and nitrogen (DON) delivery were compared between times of stormflow and baseflow in Paine Run, an Appalachian stream draining a 12.4 km2 forested catchment in the Shenandoah National Park (SNP), Virginia. The potential in-stream ecological impact of altered concentrations and\\/or chemical composition of DOM during storms also was examined, using standardized bacterial bioassays. DOC

ISHI BUFFAM; JAMES N. GALLOWAY; LINDA K. BLUM; KAREN J. McGLATHERY

2001-01-01

69

Long cold winters give higher stream water dissolved organic carbon (DOC) concentrations during snowmelt  

NASA Astrophysics Data System (ADS)

We show that long cold winters enhanced the stream water dissolved organic carbon (DOC) concentrations during the following spring flood. Using a 15 year stream record from a boreal catchment, we demonstrate that the interannual variation in DOC concentrations during spring flood was related to the discharge, and winter climate. That discharge is important for DOC concentration agrees with previous studies. By controlling for discharge we could detect that the winter climatic conditions during the preceding winter affected the soil water DOC concentrations, which in turn affected the concentrations in the stream. The results from the stream time-series were also supported by a riparian soil frost experiment, which showed that a long period of soil frost promoted high DOC concentrations in the soil water.

Gren, A. Ã.; Haei, M.; Köhler, S.; Bishop, K.; Laudon, H.

2010-06-01

70

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

USGS Publications Warehouse

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.

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

2003-01-01

71

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

PubMed

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. PMID:22481055

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

2012-04-04

72

The Influence of Dissolved Oxygen Concentration on the Respiration and Glucose Metabolism of Klebsiella aerogenes during Growth  

Microsoft Academic Search

SUMMARY The influence of dissolved oxygen concentration on the metabolism and respiration of growing Klebsiella aerogenes NCTC 8017 was studied by means of a continuous-flow culture technique. Different dissolved oxygen tensions (equivalent partial pressures) were obtained by varying the partial pressure of oxygen in the gas phase. The respiration rate (oxygen uptake rate per unit mass organism) was independent of

D. E. F. HARRISON; S. J. PIRT

1967-01-01

73

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

Microsoft Academic Search

Geochemical tracers were used to examine the mixing of water and particles in Lower New York and Raritan Bays in August 1999 during low-flow conditions. Four brackish water masses (20?S?28) originating in the Raritan and Shrewsbury Rivers, Arthur Kill, and Upper New York Bay were characterized by their dissolved metals concentrations. The mixing lines of dissolved Cu, Ni, and Pb

Anthony J. Paulson

2005-01-01

74

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

SciTech Connect

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

To, T.B.; Nordstrom, D.K.; Cunningham, K.M.; Ball, J.W.; McCleskey, R.B. [Geological Survey, Boulder, CO (United States)

1999-03-01

75

Concentrations of particulate and dissolved cylindrospermopsin in 21 Aphanizomenon-dominated temperate lakes.  

PubMed

The cyanobacterial toxin cylindrospermopsin (CYN) is widely distributed in German lakes, but volumetric data for risk assessment are lacking and it is unclear which cyanobacterial species produce CYN in Europe. We therefore analyzed CYN concentration and cyanobacterial composition of 21 German lakes in 2005. CYN was detected in 19 lakes (102 of 115 samples). In total, 45 samples contained particulate CYN only, and 57 contained both dissolved and particulate CYN. The concentrations were 0.002-0.484 microg L(-1) for particulate CYN and 0.08-11.75 microg L(-1) for dissolved CYN with a maximum of 12.1 microg L(-1) total CYN. A drinking water guideline value of 1 microg L(-1) proposed by Humpage and Falconer [2003. Oral toxicity of the cyanobacterial toxin CYN in male Swiss albino mice: determination of no observed adverse effect level for deriving a drinking water guideline value. Environ. Toxicol. 18, 94-103] was exceeded in 18 samples from eight lakes due to high concentrations of dissolved CYN. CYN occurrence in the German lakes could not be ascribed to the three known CYN-producing species Cylindrospermopsis raciborskii, Anabaena bergii and Aphanizomenon flos-aquae, which were detected in some lakes in low abundances. The highest correlation coefficients were observed between particulate CYN and the native Aphanizomenon gracile. It occurred in 98 CYN-positive samples, was the most abundant Nostocales and was the only Nostocales in five samples. This indicates that A. gracile is a potential CYN producer in German lakes. PMID:17804031

Rücker, Jacqueline; Stüken, Anke; Nixdorf, Brigitte; Fastner, Jutta; Chorus, Ingrid; Wiedner, Claudia

2007-07-04

76

Concentrations of dissolved oxygen in the lower Puyallup and White rivers, Washington, August and September 2000 and 2001  

USGS Publications Warehouse

The U.S. Geological Survey, Washington State Department of Ecology, and Puyallup Tribe of Indians conducted a study in August and September 2001 to assess factors affecting concentrations of dissolved oxygen in the lower Puyallup and White Rivers, Washington. The study was initiated because observed concentrations of dissolved oxygen in the lower Puyallup River fell to levels ranging from less than 1 milligram per liter (mg/L) to about 6 mg/L on several occasions in September 2000. The water quality standard for the concentration of dissolved oxygen in the Puyallup River is 8 mg/L.This study concluded that inundation of the sensors with sediment was the most likely cause of the low concentrations of dissolved oxygen observed in September 2000. The conclusion was based on (1) knowledge gained when a dissolved-oxygen sensor became covered with sediment in August 2001, (2) the fact that, with few exceptions, concentrations of dissolved oxygen in the lower Puyallup and White Rivers did not fall below 8 mg/L in August and September 2001, and (3) an analysis of other mechanisms affecting concentrations of dissolved oxygen.The analysis of other mechanisms indicated that they are unlikely to cause steep declines in concentrations of dissolved oxygen like those observed in September 2000. Five-day biochemical oxygen demand ranged from 0.22 to 1.78 mg/L (mean of 0.55 mg/L), and river water takes only about 24 hours to flow through the study reach. Photosynthesis and respiration cause concentrations of dissolved oxygen in the lower Puyallup River to fluctuate as much as about 1 mg/L over a 24-hour period in August and September. Release of water from Lake Tapps for the purpose of hydropower generation often lowered concentrations of dissolved oxygen downstream in the White River by about 1 mg/L. The effect was smaller farther downstream in the Puyallup River at river mile 5.8, but was still observable as a slight decrease in concentrations of dissolved oxygen caused by photosynthesis and respiration. The upper limit on oxygen demand caused by the scour of anoxic bed sediment and subsequent oxidation of reduced iron and manganese is less than 1 mg/L. The actual demand, if any, is probably negligible.In August and September 2001, concentrations of dissolved oxygen in the lower Puyallup River did not fall below the water-quality standard of 8 mg/L, except at high tide when the saline water from Commencement Bay reached the monitor at river mile 2.9. The minimum concentration of dissolved oxygen (7.6 mg/L) observed at river mile 2.9 coincided with the maximum value of specific conductance. Because the dissolved-oxygen standard for marine water is 6.0 mg/L, the standard was not violated at river mile 2.9. The concentration of dissolved oxygen at river mile 1.8 in the White River dropped below the water-quality standard on two occasions in August 2001. The minimum concentration of 7.8 mg/L occurred on August 23, and a concentration of 7.9 mg/L was recorded on August 13. Because there was some uncertainty in the monitoring record for those days, it cannot be stated with certainty that the actual concentration of dissolved oxygen in the river dropped below 8 mg/L. However, at other times when the quality of the monitoring record was good, concentrations as low as 8.2 mg/L were observed at river mile 1.8 in the White River.

Ebbert, J. C.

2002-01-01

77

Long-term changes in dissolved oxygen concentrations in the ocean caused by protracted global warming  

NASA Astrophysics Data System (ADS)

In the Earth's geological record massive marine ecological change has been attributed to the occurrence of widespread anoxia in the ocean [, 2002; , 2002; , 1996]. Climate change projection till the end of this century predict a 4 to 7% decline in the dissolve oxygen in the ocean [, 2002; , 2000; , 2001; , 1998] suggesting the potential for global warming to eventually drive the deep ocean anoxic. To examine the multicentury impact of protracted global warming on oceanic concentrations of dissolved oxygen, we use a climate system model and a low-order oceanic biogeochemical model. The models are integrated for an atmospheric equivalent CO2 concentration, which is specified to triple according to a standard scenario from the late nineteenth to the late twenty-first century, and then is subsequently held constant at that elevated level for an additional 6 centuries. For the present day, the model successfully reproduced the large-scale features of the dissolved oxygen field in the ocean. In the global warming simulation, the physical model displays marked changes in high-latitude oceanic stratification and overturning, including near-cessation of deep water renewal for depths greater than about 1.5 km during the period of elevated stable CO2 concentration. Our model predicts a decline in oxygen concentration through most of the subsurface ocean. Concentration changes in the thermocline waters result mainly from solubility changes in the upstream source waters, while changes in the deep waters result mainly from lack of ventilation and ongoing consumption of oxygen by remineralization of sinking particulate organic matter. Changes in the upper 2 km of the ocean generally show signs of equilibration by the end of the integration, but at greater depths, there occurs a slow but steady decline through to the end of the integration. By the end of the integration, we simulate a doubling of the volume of hypoxic water (less than 10 ?mol/kg) in the thermocline of the eastern equatorial Pacific Ocean. During the integration deep ocean oxygen concentrations generally decline by between 20 and 40%, but, significantly, no extensive deep ocean anoxia develops during the period of integration, nor does it appear that it would likely do so for at least a further 4000 years of integration. Subsurface oxygen decline is moderated by an overall reduction in export production of particulate organic matter, which reduces oxygen consumption in the ocean interior due to the remineralization of this material.

Matear, R. J.; Hirst, A. C.

2003-12-01

78

Influence of dissolved oxygen concentration on growth, mitochondrial function and antibody production of hybridoma cells in batch culture  

Microsoft Academic Search

The effects of dissolved oxygen concentration on hybridoma cell growth, metabolism, and antibody production were studied. A mouse hybridoma cell line producing an IgG1 directed at a consensus a-interferon was grown in batch cultures in a 5 dm3 stirred bioreactor at dissolved oxygen (DO) concentrations of 5, 30, 90 and 95% or air saturation. High oxygen tension (95% of air

E. Meilhoc; K. D. Wittrup; J. E. Bailey

1990-01-01

79

Numerical simulation of dissolved oxygen concentration in water flow over stepped spillways.  

PubMed

This study developed an improved Eulerian model for the simulation of an air-water flow field over stepped spillways. The improved drag model applied different drag coefficients for bubbles and for free surface flows or gas cavities. Void fraction and turbulence correction were used in determining the bubble drag coefficient. The calculated air entrainment and air-water velocity could be adapted using these parameters. With the improved drag model, the Eulerian simulations predicted the location of the inception point, the distributions of air void fraction, velocity distributions, and pressure distributions. The change in the dissolved oxygen (DO) concentration from upstream of the stepped spillways, to downstream, was simulated based on the improved computational fluid dynamics model and the transport equation for DO transferring. The numerical DO concentration coincided with the experimental results. Therefore, the improved CFD model and the numerical methods presented here can provide possible optimization tools for strong air entrainment flows. PMID:23789573

Cheng, Xiangju; Chen, Xuewei

2013-05-01

80

Establishing and controlling dissolved concentrations of hydrophobic organics by partitioning from a solid phase  

SciTech Connect

Bioavailable concentrations of hydrophobic organic substances in aqueous tests often decrease as a result of (bio)sorption, volatilization, or degradation. In the present study, partitioning driven administering (PDA) is introduced as an approach to maintain constant exposure levels of hydrophobic organics in aqueous tests. The working principle of PDA is to control dissolved concentrations by partitioning from a dominating solid phase. For this purpose, test compounds are loaded on an octadecyl Empore disk, which subsequently is placed in an aqueous test system. Stable aqueous concentrations for a range of halogenated aromatic substances were established within minutes to hours, and the resulting concentrations indicate that equilibrium partitioning governs the release from the disk. Furthermore, PDA`s capability to maintain stable concentrations against a depletion process was demonstrated, and PDA was successfully applied to dose 1,3,5-tribromobenzene and hexachlorobenzene in algal toxicity tests. Finally, the feasibility to administer concentrations up to aqueous solubility, to administer mixtures, and to dominate the fugacity of multicompartment systems is discussed.

Mayer, P.; Wernsing, J.; Tolls, J.; Maagd, P.G.J. de; Sijm, D.T.H.M. [Utrecht Univ. (Netherlands). Environmental Toxicology and Chemistry

1999-07-01

81

[Interpretation of spatial distribution pattern for dissolved inorganic nitrogen concentration in coastal estuary using hyperspectral data].  

PubMed

Choosing dissolved inorganic nitrogen (DIN) as one of the representative nutritional salt monitoring indexes, a hyperspectral remotely sensed inversion model was built and applied to quantitatively retrieve water quality parameters with its spatial distribution patterns in coastal estuary with high suspended sediment concentration (SSC). It was found that when SSC was larger than 0.1 kg/m3, DIN concentration had a notable inverse correlation with SSC and the correlation coefficient R2 reached 0.617. Based on this conclusion, firstly the in-situ observed water surface remote sensing reflectance was resampled according to the spectral response characters of Hyperion sensor. And then, statistical correlation analysis between reflectance and DIN concentration was carried out. The results showed that band reflectance of R804 and R630 representing the second and first reflectance peak of water spectrum curve were sensitive to the variation of DIN concentration. And then, a pseudo remotely sensed sand parameter index R804 x R630/(R804 - R630) was calculated for the construction of the nonlinear DIN quantitative reversion model. Correlation coefficient R2 between observed and simulated DIN concentrations for 29 calibrating samples and 10 validating samples were 0.746 and 0.67, while their mean absolute errors reached 109.07 and 147.58 microg/L, respectively. The model was then applied on Hyperion hyperspectral image to get the spatial distribution character of DIN concentration in Sheyanghe river estuary and the DIN concentration was between 52 to 513 microg/L. Results indicated that in coastal estuary which was dominated by suspended sediments, the diffusive trends of DIN concentration reversed by remote sensing techniques had an intimate relationship with motions of tidal current and transportation attributes of SSC. As the hydrodynamic conditions were unclear, hyperspectral remote sensing technique was an effective technical way for dynamic survey of DIN concentration. PMID:20698253

Zhang, Dong; Xu, Yong; Zhang, Ying; Li, Huan

2010-06-01

82

Technical Note: Comparison between a direct and the standard, indirect method for dissolved organic nitrogen determination in freshwater environments with high dissolved inorganic nitrogen concentrations  

NASA Astrophysics Data System (ADS)

Research on dissolved organic nitrogen (DON) in aquatic systems with high dissolved inorganic nitrogen (DIN, the sum of NO3-, NO2- and NH4+) concentrations is often hampered by high uncertainties regarding the determined DON concentration. The reason is that DON is determined indirectly as the difference between total dissolved nitrogen (TDN) and DIN. In this standard approach to determine DON concentrations, even small relative measurement errors of the DIN and TDN concentrations propagate into high absolute errors of DON concentrations at high DIN : TDN ratios. To improve the DON measurement accuracy at high DIN : TDN ratios, we investigated the DON measurement accuracy of this standard approach according to the DIN : TDN ratio and compared it to the direct measurement of DON by size-exclusion chromatography (SEC) for freshwater systems. For this, we used standard compounds and natural samples with and without DIN enrichment. We show that for the standard approach, large errors of the determined DON concentrations at DIN : TDN ratios >0.6 occur for both standard compounds and natural samples. In contrast, measurements of DON by SEC always gave low errors at high DIN : TDN ratios due to the successful separation of DON from DIN. For SEC, DON recovery rates were 91-108% for five pure standard compounds and 89-103% for two standard compounds, enriched with DIN. Moreover, SEC resulted in 93-108% recovery rates for DON concentrations of natural samples at a DIN : TDN ratio of 0.8 and the technique was successfully applied to a range of samples from waste water treatment plants to forest and agricultural streams. With 2.5 h of measurement time per sample, SEC is slower, but more accurate than the standard approach for determination of DON concentrations in freshwaters with DIN : TDN ratios >0.6. To sum up, the direct DON measurement by SEC enables better understanding of the nitrogen cycle of urban and agricultural freshwater systems.

Graeber, D.; Gelbrecht, J.; Kronvang, B.; Gücker, B.; Pusch, M. T.; Zwirnmann, E.

2012-11-01

83

Variability in the concentration and character of blanket bog pore water dissolved organic carbon  

NASA Astrophysics Data System (ADS)

Rising dissolved organic carbon (DOC) concentrations in surface waters have prompted much research to elucidate the cause(s). Given that increases in DOC concentrations, [DOC], may indicate a destabalisation of carbon stores, increase water treatment costs and affect rates of primary production and respiration in aquatic ecosystems, identifying the causes of the increase is important. The majority of studies measure [DOC] but rarely is DOC composition considered contemporaneously - yet this important as it potentially indicates provenance, reprocessing and fate. Moreover, surface water samples are usually collected at a low spatial density within a catchment. For one year we have sampled pore water from 48 piezometers and 48 tension samplers across a 12 km2 area of a Scottish blanket bog hosting a wind farm. The sampling sites are divided into four sites along a hypothesized wind farm-induced microclimatic gradient. At each site twelve sampling plots were established, four each in areas dominated by mosses, sedges and shrubs. From each plot samples were collected from piezometers and tension samplers, representing free-flowing pore water and that held under tension respectively. Dissolved organic carbon concentration and absorbance (190 to 1100 nm), were measured for each sample. Ratios, established to indicate DOC character, were calculated from the absorbance data. We found [DOC] ranged from 2-197 mg l-1 and was significantly associated with sampling location, time of year and the interaction between site and time of year, but not with plant functional type. The water held under tension had a significantly higher [DOC] compared with the free-flowing pore water sampled from the same plot. Preliminary data analysis also indicates variations in the DOC character between sites and with time. These results demonstrate the variable nature of DOC production which is partially obscured when sampling at a catchment scale but needs to be better understood to further understanding of trends in [DOC].

Armstrong, A.; Waldron, S.; Ostle, N.; Whitaker, J.

2012-04-01

84

On chip steady liquid-gas phase separation for flexible generation of dissolved gas concentration gradient.  

PubMed

In this study, steady liquid-gas phase separation is realized by applying a hydrophobic small microchannel array (SMA) to bridge two large microchannels, one for liquid phase and one for gas phase. In this structure, a capillary pressure difference between that in the SMA and the larger channel results in a steady liquid-gas interface. The generated liquid-gas interface allows for fast gas dissolving speed. By coupling the liquid-gas interface with a one directional fluidic field, a steady dissolved gas concentration gradient (DgCG) is generated. The DgCG distribution is easily designable for linear or exponential modes, providing improved flexibility for gas participated processes on chip. To demonstrate its applicability, a CO(2) DgCG chip is fabricated and applied for screening CaCO(3) crystal growth conditions in the DgCG chip. Crystals with transitional structures are successfully fabricated, which is consistent with the CO(2) DgCG distribution. PMID:22336913

Xu, Bi-Yi; Hu, Shan-Wen; Yan, Xiao-Na; Xia, Xing-Hua; Xu, Jing-Juan; Chen, Hong-Yuan

2012-02-15

85

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

NASA Astrophysics Data System (ADS)

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 DOC concentrations. At these sites, the highest DOC concentrations were measured in the zone of transition between peat and mineral layer. No consistent relationship between DOC concentrations and electrical conductivity or pH-value could be found. In the "Ahlenmoor", seasonal variations of temperature and water table position influence DOC concentrations. The highest values were measured in late summer after warm and dry periods. At the study sites of the "Großes Moor", the seasonal variation of temperature and groundwater table had no impact on DOC concentrations. Our results show that while it is difficult to unravel all factors controlling DOC concentrations, drainage and physical disturbance clearly increase DOC concentrations.

Frank, Stefan; Tiemeyer, Bärbel; Freibauer, Annette

2013-04-01

86

Behavioral response of fish larvae to low dissolved oxygen concentrations in a stratified water column  

Microsoft Academic Search

Density stratification and respiration lead to vertical gradients in dissolved oxygen in many aquatic habitats. The behavioral responses of fish larvae to low dissolved oxygen in a stratified water column were examined during 1990–1991 with the goal of understanding how vertical gradients in dissolved oxygen may directly affect the distribution and survival of fish larvae in Chesapeake Bay, USA. In

D. L. Breitburg

1994-01-01

87

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

PubMed

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 ?g P L(-1) levels in natural water. The phosphate concentrations in the mountainous stream waters at 6 sites ranged from 2.2 to 13 ?g P L(-1), and those from the catchment area of the steady state forest were 5.3 ± 1.6 (±1 SD) ?g 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 ?g 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 (? = 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 fruits. The proposed method using the phosphate concentration in surface stream waters without the period of the seasonal change mentioned above is expected to be very helpful in diagnosing the condition of forests. PMID:22673628

Koga, Masaaki; Yoshimura, Kazuhisa

2012-06-07

88

The effects of varied dissolved oxygen concentrations and temperature on the wood-boring isopod genus Limnoria  

Microsoft Academic Search

Three species of the marine wood-boring genus Limnoria were subjected to low dissolved oxygen concentrations at different temperatures under laboratory conditions. 28-day median tolerance limits (TLm) were 1.0 mg\\/l of dissolved oxygen at 15° to 16°C and 19° to 20°C for L. lignorum, 0.75 and 0.60 mg\\/l at 15° to 16°C and 22° to 25°C, respectively, for L. quadripunctata, and

J. W. Anderson; D. J. Reish

1967-01-01

89

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

90

Glucose fluxes and concentrations of dissolved combined neutral sugars (polysaccharides) in the Ross Sea and Polar Front Zone, Antarctica  

NASA Astrophysics Data System (ADS)

We hypothesized that dissolved carbohydrates would be large components of the labile dissolved organic carbon (DOC) pool and would support much bacterial growth in Antarctic waters, especially the Ross Sea, since previous work had observed extensive phytoplankton blooms with potentially high production rates of carbohydrates in Antarctic seas. These hypotheses were tested on cruises in the Ross Sea and Antarctic Polar Front Zone as part of the US JGOFS program. Concentrations and fluxes of free glucose (the only free sugar detected) were very low, but dissolved polysaccharides appeared to be important components of the DOC pool. Concentrations of dissolved combined neutral sugars increased >3-fold during the phytoplankton bloom in the Ross Sea and were a large fraction (ca. 50%) of the semi-labile fraction of DOC. The relatively high concentrations of dissolved combined neutral sugars, which are thought to be quite labile, appear to explain why DOC accumulated during the phytoplankton bloom was degraded so quickly once the bloom ended. Some of the polysaccharides appeared to be more refractory, however, since dissolved combined neutral sugars were observed in deep waters (>550 m) and in early spring (October) in the Ross Sea, apparently having survived degradation for >8 months. The molecular composition of these refractory polysaccharides differed from that of polysaccharides sampled during the phytoplankton bloom. Fluxes of DOC were low in the Ross Sea compared to standing stocks and fluxes of particulate material, but the DOC that did accumulate during the phytoplankton bloom appeared to be sugar-rich and relatively labile.

Kirchman, David L.; Meon, Benedikt; Ducklow, Hugh W.; Carlson, Craig A.; Hansell, Dennis A.; Steward, Grieg F.

91

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

NASA Astrophysics Data System (ADS)

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.

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

2004-05-01

92

[Study on colored dissolved organic matter concentration retrieved from Landsat/TM imagery at Taihu Lake].  

PubMed

At the lake ecosystem, the CDOM (colored dissolved organic matter) not only is an important source of nutrients, but also is major component of carbon cycle. Based on the fieldworks of water qualities experiments at Taihu lake, China, on 27 and 28 October, 2003, the present paper used the Landsat/TM imageries to study and estimate the distribution pattern of CDOM concentration at Taihu lake. According to the study results, it was found that CDOM was a strong absorber at TM1 band, where there was a wave trough at that corresponding wavelength. Taking the reflectance at TM1 as a remote sensing parameter, the remote sensing technology could perfectly retrieval the CDOM concentration from the Landsat/TM imagery at TM1 band. Compared with the validation dataset at two stations, the mean bias between modeled prediction and in situ measurements was 0. 922 mg x L(-1), and the corresponding relative bias was 14.85%. Additionally, the retrieval results show that the spatial distribution of CDOM concentration was higher in the south and center of the lake, but lower in the east and west lake. PMID:21428050

Chen, Jun; Wang, Bao-Jun; Sun, Ji-Hong; Fu, Jun

2011-01-01

93

The effect of dissolved oxygen concentration on the structure, size and size distribution of activated sludge flocs  

Microsoft Academic Search

The variations in activated sludge floc structure, size and size distribution were studied for different dissolved oxygen (DO) concentrations in pilot scale completely mixed reactors. The size distribution by volume for flocs larger than about 10?m fitted well to log–normal distribution functions. No clear relationship between DO concentration and average floc diameter could be found; there was only a trend

Britt-Marie Wilén; Peter Balmér

1999-01-01

94

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

SciTech Connect

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.

Goyal, A.; Tolbert, N.E. (Michigan State Univ., East Lansing (USA))

1990-03-01

95

Freely Suspended Nematic Films  

Microsoft Academic Search

Using one of the most commonly studied synthetic molecule, 4-Cyano-4'-pentylbiphenyl (5CB), we were able to pull freely suspended membranes of different thicknesses into circular frames of up to 20mm diameter. Films pulled this way were distorted using a speaker, while a laser light was shone onto them for studying the far field reflection and learn about resonant frequency modes and

Wilder Iglesias; Jeffrey Choi; Elizabeth K. Mann; Antal Jakli

2011-01-01

96

Freely Suspended Nematic Films  

NASA Astrophysics Data System (ADS)

Using one of the most commonly studied synthetic molecule, 4-Cyano-4'-pentylbiphenyl (5CB), we were able to pull freely suspended membranes of different thicknesses into circular frames of up to 20mm diameter. Films pulled this way were distorted using a speaker, while a laser light was shone onto them for studying the far field reflection and learn about resonant frequency modes and subtract valuable information about the viscoelastic terms that hold the membrane stable.

Iglesias, Wilder; Choi, Jeffrey; Mann, Elizabeth K.; Jakli, Antal

2011-03-01

97

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

PubMed Central

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

Clark, D R; Flynn, K J

2000-01-01

98

Concentration studies of collision-induced fundamental absorption of hydrogen dissolved in liquid neon  

NASA Astrophysics Data System (ADS)

We report further and more detailed results of our recent investigation [W. A. Herrebout, B. J. van der Veken, and A. P. Kouzov, Phys. Rev. Lett. 101, 093001 (2008)] on the collision-induced fundamental absorption by hydrogen dissolved in liquid neon (T ~ 25 K). The band shapes were studied in a wide range of concentrations (0.003-0.05 mole fractions) as well as for different ortho/para ratios and at much higher level of accuracy and resolution than before. Due to almost unhindered rotation of the hydrogen molecule and low temperature, an unprecedently rich frequency-domain picture produced by different terms of the interaction-induced polarization was observed. While some of them are conspicuous via fast intracell motion of a light guest (H2), others--induced by the electrostatic field of the guest--give rise to lines whose shapes are imprinted by fluctuations of the nearest surrounding. Strong motional narrowing observed on the guest-guest induced lines shows up in their Lorentzian shapes which are signatures of microscopic-scale diffusion. Near-Lorentzian peaks were also detected at the tops of the diffuse lines induced by isolated guests. Their formation may be associated with a long-living defect (vacancy) emerging in the vicinity of the polarization inductor. Altogether, our results give the first unambiguous spectroscopic evidence on the diffusional evolution of isolated binary interactions that emerge in dense chaotic media.

Herrebout, W. A.; van der Veken, B. J.; Kouzov, A. P.

2012-08-01

99

Concentration studies of collision-induced fundamental absorption of hydrogen dissolved in liquid neon.  

PubMed

We report further and more detailed results of our recent investigation [W. A. Herrebout, B. J. van der Veken, and A. P. Kouzov, Phys. Rev. Lett. 101, 093001 (2008)] on the collision-induced fundamental absorption by hydrogen dissolved in liquid neon (T ? 25 K). The band shapes were studied in a wide range of concentrations (0.003-0.05 mole fractions) as well as for different ortho/para ratios and at much higher level of accuracy and resolution than before. Due to almost unhindered rotation of the hydrogen molecule and low temperature, an unprecedently rich frequency-domain picture produced by different terms of the interaction-induced polarization was observed. While some of them are conspicuous via fast intracell motion of a light guest (H(2)), others--induced by the electrostatic field of the guest--give rise to lines whose shapes are imprinted by fluctuations of the nearest surrounding. Strong motional narrowing observed on the guest-guest induced lines shows up in their Lorentzian shapes which are signatures of microscopic-scale diffusion. Near-Lorentzian peaks were also detected at the tops of the diffuse lines induced by isolated guests. Their formation may be associated with a long-living defect (vacancy) emerging in the vicinity of the polarization inductor. Altogether, our results give the first unambiguous spectroscopic evidence on the diffusional evolution of isolated binary interactions that emerge in dense chaotic media. PMID:22938252

Herrebout, W A; van der Veken, B J; Kouzov, A P

2012-08-28

100

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

USGS Publications Warehouse

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

Klein, John M.; Bradford, Wesley L.

1980-01-01

101

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

102

Long term trend in dissolved iron concentration in the Amur River basin: Observation and modeling, possible causes of abrupt increase in the late 1990s'  

Microsoft Academic Search

Recent studies revealed that significant part of iron which limits primary production of the Sea of Okhotsk is delivered from the Amur River basin with the form of dissolved iron. Thus, it is very important to understand dissolved iron producion mechanism of the basin. With long term trend analysis in dissolved iron concentration, we found that abrupt increase in the

T. Onishi; M. Yoh; H. Shibata; S. Nagao; M. Kawahigashi; V. Shamov

2009-01-01

103

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

NASA Astrophysics Data System (ADS)

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.

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

2007-03-01

104

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

Microsoft Academic Search

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

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

1994-01-01

105

GROWTH AND SURVIVAL OF CHANNEL CATFISH AND YELLOW PERCH EXPOSED TO LOWERED CONSTANT AND DIURNALLY FLUCTUATING DISSOLVED OXYGEN CONCENTRATIONS  

EPA Science Inventory

Growth and survival were determined for duplicate lots of juvenile channel catfish (Ictalurus punctatus) and yellow perch (Perca flavescens) exposed for 69 and 67 days, respectively, to nearly constant dissolved oxygen (DO) concentrations at near air saturation (control), 6.5, 5....

106

Image analyzing method to evaluate in situ bioluminescence from an obligate anaerobe cultivated under various dissolved oxygen concentrations.  

PubMed

An image analyzing method was developed to evaluate in situ bioluminescence expression, without exposing the culture sample to the ambient oxygen atmosphere. Using this method, we investigated the effect of dissolved oxygen concentration on bioluminescence from an obligate anaerobe Bifidobacterium longum expressing bacterial luciferase which catalyzes an oxygen-requiring bioluminescent reaction. PMID:23040354

Ninomiya, Kazuaki; Yamada, Ryuji; Matsumoto, Masami; Fukiya, Satoru; Katayama, Takane; Ogino, Chiaki; Shimizu, Nobuaki

2012-10-04

107

Effect of exchangeable cation concentration on sorption and desorption of dissolved organic carbon in saline soils.  

PubMed

Sorption is a very important factor in stabilization of dissolved organic carbon (DOC) in soils and thus C sequestration. Saline soils have significant potential for C sequestration but little is known about the effect of type and concentration of cations on sorption and release of DOC in salt-affected soils. To close this knowledge gap, three batch sorption and desorption experiments were conducted using soils treated with solutions either low or high in salinity. In Experiment 1, salinity was developed with either NaCl or CaCl2 to obtain an electrical conductivity (EC) in a 1:5 soil: water extract (EC1:5) of 2 and 4dSm(-1). In Experiments 2 and 3, NaCl and CaCl2 were added in various proportions (between 25 and 100%) to obtain an EC1:5 of 0.5 and 4dSm(-1), respectively. At EC1:5 of 4dSm(-1), the sorption of DOC (derived from wheat straw) was high even at a low proportion of added Ca(2+) and did not change with proportion of Ca added, but at EC1:5 of 0.5dSm(-1) increasing proportion of Ca(2+) added increased DOC sorption. This can be explained by the differences in exchangeable Ca(2+) at the two salinity levels. At EC1:5 of 4dSm(-1), the exchangeable Ca(2+) concentration did not increase beyond a proportion of 25% Ca(2+), whereas it increased with increasing Ca(2+) proportion in the treatments at EC1:5 of 0.5dSm(-1). The DOC sorption was lowest with a proportion of 100% as Na(+). When Ca(2+) was added, DOC sorption was highest, but least was desorbed (with deionised water), thus sorption and desorption of added DOC were inversely related. The results of this study suggest that DOC sorption in salt-affected soils is mainly controlled by the levels of exchangeable Ca(2+) irrespective of the Ca(2+) concentration in the soil solution which has implications on carbon stabilization in salt-affected soils. PMID:23374419

Setia, Raj; Rengasamy, Pichu; Marschner, Petra

2013-01-29

108

Effect of pH and redox potential on concentration of dissolved nutrients in an estuarine sediment  

Microsoft Academic Search

A study was conducted on sediment suspensions maintained under condition of controlled pH (5.0, 6.5, and 8.0) and redox potentials (-200, 0, 250, and 500 mv) to determine the effect of these parameters on concentrations of dissolved organic C, P, NH\\/sub 4+\\/, Fe, and Mn in an estuarine sediment. Concentration of these nutrients was strongly influenced by changes in sediment

R. D. Deluane; C. N. Reddy; W. H. Jr. Patrick

1981-01-01

109

Modeling stream dissolved organic carbon concentrations during spring flood in the boreal forest: A simple empirical approach for regional predictions  

Microsoft Academic Search

Changes in dissolved organic carbon (DOC) concentration are clearly seen for streams in which chemistry is measured on a high-frequency\\/episode basis, but these high-frequency data are not available in long-term monitoring programs. Here we develop statistical models to predict DOC concentrations during spring flood from easily available geographic information system data and base flow chemistry. Two response variables were studied,

Anneli Ågren; Ishi Buffam; Kevin Bishop; Hjalmar Laudon

2010-01-01

110

Effects of constant and shifting dissolved oxygen concentration on the growth and antibiotic activity of Xenorhabdus nematophila  

Microsoft Academic Search

To evaluate the effects of dissolved oxygen (DO) control strategy on cell growth and the production of antibiotic (cyclo(2-Me-BABA-Gly)) by Xenorhabdus nematophila. The effects of different agitation speeds and DO concentrations on cell growth and antibiotic activity of X. nematophila YL001 were examined. Experiments showed that higher agitation speeds and DO concentrations at earlier fermentation stage were favorable for cell

Yong-Hong Wang; Xiang-Ling Fang; Yu-Ping Li; Xing Zhang

2010-01-01

111

Dissolved organic carbon concentrations in runoff from shallow heathland catchments: effects of frequent excessive leaching in summer and autumn  

Microsoft Academic Search

Transport and turnover of dissolved organic carbon (DOC) is important in the C cycle of organic soils. The concentration of\\u000a DOC in soil water is buffered by adsorption to the soil matrix, and has been hypothesized to depend on the pool size of adsorbed\\u000a DOC. We have studied the effect of frequent artificial excessive leaching events on concentration and flux

S. Haaland; J. Mulder

2010-01-01

112

Dissolved Hydrocarbons and Related Microflora in a Fjordal Seaport: Sources, Sinks, Concentrations, and Kinetics  

PubMed Central

The continuous addition of toluene as a solute of treated ballast water from oil tankers into a well-defined estuary facilitated the study of the dynamics of dissolved hydrocarbon metabolism in seawater. Most rates of toluene oxidation were in the range of 1 to 30 pg/liter per h at 0.5 ?g of toluene per liter. Near the ballast water injection point, a layer of warm ballast water, rich in bacteria, that was trapped below the less-dense fresh surface water was located. Toluene residence times were approximately 2 weeks in this layer, 2 years elsewhere in Port Valdez, and 2 decades in the surface water of a more oceanic receiving estuary adjacent. Mixing was adequate for a steady-state treatment which showed that 98% of the toluene was flushed from Port Valdez before metabolism and gave a steady-state concentration of 0.18 ?g/liter. Total bacterial biomass from direct counts and organism size data was usually near 0.1 mg/liter, but ranged up to 0.8 mg/liter in the bacteria-rich layer. The origin of bacteria in this layer was traced to growth in oil tanker ballast during shipments. The biomass of toluene oxidizers in water samples was estimated from the average affinity of pure-culture isolates for toluene (28 liters per g of cells per h) and observed toluene oxidation kinetics. Values ranged from nearly all of the total bacterial biomass within the bacteria-rich layer down to 0.2% at points far removed. Because the population of toluene oxidizers was large with respect to the amount of toluene consumed and because water from a nearby nonpolluted estuary was equally active in facilitating toluene metabolism, we searched for an additional hydrocarbon source. It was found that terpenes could be washed from spruce trees by simulated rainfall, which suggested that riparian conifers provide an additional and significant hydrocarbon source to seawater. Images

Button, D. K.; Robertson, Betsy R.; Craig, Kathleen S.

1981-01-01

113

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

USGS Publications Warehouse

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

Cravotta, III, C. A.

2008-01-01

114

Influence of temperature and origin of dissolved organic matter on the partitioning behavior of polycyclic aromatic hydrocarbons  

Microsoft Academic Search

Background, aim, and scope  The behavior of polycyclic aromatic hydrocarbons (PAHs) is affected by dissolved organic matter (DOM) present in pore water\\u000a of soils and sediments. Since partitioning to DOM reduces the bioavailable or freely dissolved PAH concentration in pore water,\\u000a it is important to assess the effect of environmental variables on the magnitude of dissolved organic matter to water partition

Joris J. H. Haftka; Harrie A. J. Govers; John R. Parsons

2010-01-01

115

Dissolved Oxygen and Temperature  

Microsoft Academic Search

Dissolved oxygen and temperature are two of the fundamental variables in lake and pond ecology. By measuring dissolved oxygen and temperature, scientists can gauge the overall condition of waterbodies. Aquatic organisms need dissolved oxygen for their survival. While water temperature also directly influences aquatic organ- isms, it regulates dissolved oxygen concentrations within a lake. Dissolved oxygen and temperature are also

Kelly Addy; Linda Green

116

Dissolved and labile concentrations of Cd, Cu, Pb, and Zn in aged ferrihydrite-organic matter systems  

SciTech Connect

The relative efficiencies of an organic and a mineral component of soils in controlling Zn, Cd, Cu, and Pb solubility and dissolution initially and during aging at pH 5.5 for up to 200 days in investigated. Metal retention by a natural organic matter and a mineral model system (ferrihydrite) were tested for the organic and hydrous ferric oxide components separately (ORG and HFO) and in a mixed system (HFO-ORG). Total dissolved and labile concentrations of metals in solution were measured. Initial Cd and Zn solubility in the systems followed the order: HFO > HFO-ORG > ORG. After aging for about 200 days, however, Cd and Zn solubility was HFO = HFO-ORG > ORG. Thus, the organic adsorbate proved to be more efficient in Zn and Cd removal from solution under the conditions used in this study. The HFO system resulted in the highest Cu solubility at intermediate aging times. However, during longer aging, total dissolved Cu increased in the ORG system whereas that in the HFO decreased, so that Cu solubility was lower in HFO after about 200 days. Lead solubility generally remained very low except in the ORG system in which the total dissolved Pb reached 0.25 {micro}M. The ORG system shows that about 75% of total dissolved Cu and 80% of total dissolved Pb exist as nonlabile organo-metal complexes, while soluble nonlabile complexes account for about 40% of dissolved Zn. Cadmium complexation in the ORG system was minimal, thus Cd exists mostly in the free ionic form or as weak (labile) organic complexes.

Martinez, C.E.; McBride, M.B. [Cornell Univ., Ithaca, NY (United States). Dept. of Soil, Crop, and Atmospheric Sciences

1999-03-01

117

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

NASA Astrophysics Data System (ADS)

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 (in 0.4% v/v HNO3) 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 concurrently sampled. Comparisons between acid-leachable and total (dissolved plus particulate) trace metal concentrations suggest that the acid-leachable fraction of metals can significantly underestimate total concentrations of crustal elements (e.g., Al) 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 18-41.

Lim, B.; Jickells, T. D.

1990-12-01

118

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

SciTech Connect

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.

Early, T.O.

1986-03-14

119

Longterm changes in dissolved oxygen concentrations in the ocean caused by protracted global warming  

Microsoft Academic Search

In the Earths geological record massive marine ecological change has been attributed to the occurrence of widespread anoxia in the ocean [Jahren, 2002; White, 2002; Wignall and Twitchett, 1996]. Climate change projection till the end of this century predict a 4 to 7 decline in the dissolve oxygen in the ocean [Bopp et al., 2002; Matear et al., 2000; Plattner

R. J. Matear; A. C. Hirst

2003-01-01

120

Long-term changes in dissolved oxygen concentrations in the ocean caused by protracted global warming  

Microsoft Academic Search

In the Earth's geological record massive marine ecological change has been attributed to the occurrence of widespread anoxia in the ocean [Jahren, 2002; White, 2002; Wignall and Twitchett, 1996]. Climate change projection till the end of this century predict a 4 to 7% decline in the dissolve oxygen in the ocean [Bopp et al., 2002; Matear et al., 2000; Plattner

R. J. Matear; A. C. Hirst

2003-01-01

121

Overview of a continuous rotary dissolver concept with concentration on motor control and fabrication techniques  

SciTech Connect

A joint agreement between the Power Reactor and Nuclear Fuel Development Corporation of Japan and the US Department of Energy to develop breeder reactor fuel reprocessing technology has resulted in a project to design, fabricate, and test a continuous rotary dissolver and associated systems. The continuous rotary dissolver provides the functions to react oxide fuels with nitric acid during the dissolution process. Design requirements dictated that welding be restricted to a minimum, that the dissolver would be remotely maintainable, that the drive system must be controlled for stage transfer and agitation, and that bearing/seal performance must be an improvement from previous designs. Welding was virtually eliminated by machining the helical auger from a 4960-kg (11,000-lb) forging, then shrink fitting a centrifugal casting to the auger. Remote maintenance requirements were achieved by utilizing module design, specifically a unique bearing/seal/taper coupling assembly. Ceramic bearings were selected, fabricated, and installed, non-lubricatable. The drive unit and its control system were tested and programmed to transfer solids and liquids, while providing agitation to assist the dissolution process. The drive control provides angular feedback from a radiation-hardened resolver. Fabrication was accomplished on schedule and within projected costs. Installation has been completed and the dissolver is now being tested at the Oak Ridge National Laboratory.

Ladd, L.D.; Abston, R.A.

1991-06-01

122

Survival and Growth Rate of Channel Catfish as a Function of Dissolved-Oxygen Concentration.  

National Technical Information Service (NTIS)

Channel catfish were raised in water-recirculating systems for several periods of about six months duration each. Initial stock was fingerling size fish (10 to 20 grams). At dissolved-oxygen levels below 2.5 parts per million, mortality was high. Fish rai...

R. W. Raible

1975-01-01

123

Temperature and dissolved oxygen concentration as parameters of Azotobacter chroococcum cultivation for use in biofertilizers  

Microsoft Academic Search

Azotobacter chroococcum was grown in continuous culture at two temperatures (30 °C and 20 °C) and different dissolved oxygen tensions (DOT) (30 % to 40 % and 70 % to 80 % of air saturation), respectively. At the temperature of 30 °C and low DOT a relatively high volumetric productivity and efficiency of nitrogen fixation were obtained. After lowering the

Božidar Šantek; Vladimir Mari?

1995-01-01

124

The relationship between dissolved oxygen concentration and maximum size in deep-sea turrid gastropods: an application of quantile regression  

Microsoft Academic Search

Bathymetric gradients in body size are the most well-known patterns of geographic variation in deep-sea organisms. The causes of size-depth relationships remain uncertain, but most have been attributed to rates of nutrient input. Chapelle and Peck (1999, Nature 399:114-115) recently hypothesized that body size in marine invertebrates is a function of dissolved oxygen concentration. We tested this hypothesis by using

C. McClain; M. Rex

2001-01-01

125

Impact of Minimum Dissolved Oxygen Concentration on Grow-Out Performance of Blue Catfish with Comparison to Channel Catfish  

Microsoft Academic Search

Feed intake, the feed conversion ratio (FCR), and the production of blue catfish Ictalurus furcatus and channel catfish I. punctatus were examined in 1-acre ponds maintained at either a high or low minimum dissolved oxygen (DO) concentration (mean values of 4.29 and 2.54 ppm [55% and 32% air saturation], respectively). Two additional studies were conducted examining only blue catfish in

Les Torrans; Brian Ott; Brian Bosworth

2012-01-01

126

Optimum concentration of dissolved oxygen for the survival of virulent Treponema pallidum under conditions of low oxidation-reduction potential  

Microsoft Academic Search

A maintenance medium with a low oxidation-reduction (redox) potential, when gently bubbled with 5% oxygen in nitrogen or with air for various periods of time, gave a range of dissolved oxygen concentrations between 1.6 and 5.8 micrograms\\/l. Virulent Treponema pallidum (Nichols strain) inoculated into these media were assayed 24 and 48 hours later for motility and virulence and were compared

S Graves; T Billington

1979-01-01

127

The Effect of Temperature and Dissolved Oxygen Concentration on the Electrochemical Behavior of Al-Zn-Inbased Anodes  

Microsoft Academic Search

The electrochemical behavior of three types of aluminium anode at different temperatures and dissolved oxygen concentrations was studied. Current efficiency tests were carried out. SEM and EDX were also conducted. The results suggest that when the temperature is much lower than room temperature, the dissolution morphologies of Al-Zn-In and Al-Zn-In-Cd anodes are non-uniform, and the Al-Zn-In-Mg-Ti anode exhibits uniform dissolution

Weili Li; Yonggui Yan; Guang Chen; Ma Li

2011-01-01

128

Formation and stability of iron(II) oxidation products under natural concentrations of dissolved silica  

Microsoft Academic Search

Model solutions were used to evaluate the effect of dissolved silica on the mineralogy and stability of Fe(II) oxidation products. Mineralogy was evaluated with scanning electron microscopy (SEM) and X-ray diffraction. Stability was evaluated by measuring the decrease in turbidity of colloidal suspensions with time. At SiFe molar ratios of 0.1 or less, oxidation of Fe(II) produced lepidocrocite, a moderately

Timothy D. Mayer; Wesley M. Jarrell

1996-01-01

129

An On-Site Cooling Tower Treated by Stand-Alone Low-Concentration Dissolved Ozone  

Microsoft Academic Search

We report on an on-site 500 RT cooling tower ozone treatment process, in which chemicals other than ozone itself were completely eliminated. Ozone in an amount leading to less than 0.1 ppm of dissolved ozone was continuously introduced via side-stream injection into the circulating water returning from the chiller. The ozonated water was initially made to flow from the distributor

Huei Tarng Liou

2009-01-01

130

Regulation of stream water dissolved organic carbon (DOC) concentrations during snowmelt; the role of discharge, winter climate and memory effects  

NASA Astrophysics Data System (ADS)

Using a 15 year stream record from a northern boreal catchment, we demonstrate that the inter-annual variation in dissolved organic carbon (DOC) concentrations during snowmelt was related to discharge, winter climate and previous DOC export. A short and intense snowmelt gave higher stream water DOC concentrations, as did long winters, while a high previous DOC export during the antecedent summer and autumn resulted in lower concentrations during the following spring. By removing the effect of discharge we could detect that the length of winter affected the modeled soil water DOC concentrations during the following snowmelt period, which in turn affected the concentrations in the stream. Winter climate explained more of the stream water DOC variations than previous DOC export during the antecedent summer and autumn.

Ågren, A..; Haei, M.; Köhler, S. J.; Bishop, K.; Laudon, H.

2010-09-01

131

A comparison of the copper sensitivity of six invertebrate species in ambient salt water of varying dissolved organic matter concentrations.  

PubMed

The copper sensitivity of four saltwater invertebrates (the mussel Mytilus galloprovincialis, the oyster Crassostrea virginica, the sand dollar Dendraster excentricus, and the sea urchin Strongylocentrotus purpuratus) was determined experimentally using chronic-estimator embryo-larval test procedures. The effect of sample dissolved organic matter (DOM) content on Cu bioavailability was determined for these species using commonly prescribed test procedures. Comparisons were made among these test results and test results reported previously for two other invertebrate species: the mussel Mytilus edulis and the copepod Eurytemora affinis. All six species exhibited a direct and significant relationship between the sample dissolved organic carbon (DOC; a surrogate measure of DOM) and either the dissolved Cu median lethal concentration (LC50) values or median effect concentration (EC50) values. This relationship is significant even when the DOM has different quality as evidenced by molecular fluorescence spectroscopy. Once normalized for the effects of DOM, the Cu sensitivity of these species from least to most sensitive were E. affinis < D. excitricus < C. virginica approximately S. purpuratus approximately M. edulis approximately M. galloprovincialis. This ranking of species sensitivity differs from the saltwater species sensitivity distribution proposed in 2003 by the U.S. Environmental Protection Agency. These results support the need to account for factors that modify Cu bioavailability in future saltwater Cu criteria development efforts. More specifically, Cu saltwater species sensitivity distribution data will need to be normalized by factors affecting Cu bioavailability to assure that accurate and protective criteria are subsequently developed for saltwater species and their uses. PMID:20821449

Arnold, W Ray; Cotsifas, Jeffrey S; Ogle, R Scott; Depalma, Sarah G S; Smith, D Scott

2010-02-01

132

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

PubMed

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

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

2006-11-01

133

Modulation of extracellular monoamine transmitter concentrations in the hippocampus after weak and strong tetanization of the perforant path in freely moving rats.  

PubMed

Hippocampal long-term potentiation (LTP) is considered as a cellular model of memory formation. Specific, electrical weak tetanization of distinct afferents such as the medial perforant path results in a short-lasting, protein synthesis-independent early-LTP (up to 4 h) within the dentate gyrus. A stronger tetanization leads to late-LTP (>4 h), which is protein synthesis-dependent and requires heterosynaptic activation during its induction, the latter of which can be provided by afferents from cortical brain regions or subcortical nuclei during memory formation in the behaving animal. In particular, noradrenaline (NA) is required for late-LTP in the dentate gyrus and dopamine for late-LTP in the apical CA1-dendrites. However, little is known about the concentrations and temporal dynamics of such neuromodulators like NA, serotonin (5-HT) and dopamine (DA) during LTP. We now implemented the microdialysis method to study this topic after stimulating the dentate gyrus in more detail. A weak tetanus of the perforant path, which normally leads to early-LTP, transiently but significantly decreased the concentration of NA (3 h) and increased the concentration of 5-HT (about 2 h) and DA (about 1 h) in the hippocampus. A strong tetanus, normally resulting in late-LTP, increased concentrations of NA and DA significantly and long-lasting (for about 5 h), whereas 5-HT concentration was increased with a delay (after about 30 min) and only for a short time (30 min). Thus different stimulation protocols resulted in different release patterns of neuromodulators, that may support discriminative processing of incoming information in the hippocampus. PMID:19345680

Neugebauer, Frank; Korz, Volker; Frey, Julietta U

2009-04-02

134

Diurnal variations of total mercury, reactive mercury, and dissolved gaseous mercury concentrations and water/air mercury flux in warm and cold seasons from freshwaters of southwestern China.  

PubMed

Diurnal variations of water total Hg, reactive Hg, and dissolved gaseous Hg concentrations and mercury flux were monitored at 2 sites in warm and cold seasons in an alkaline reservoir in southwestern China. Concentrations of total Hg and reactive Hg, as well as Hg fluxes, usually exhibited a consistent diurnal trend, with elevated values observed during the day. The increasing reactive Hg concentrations and Hg fluxes were highly related to the incident intensity of solar radiation, suggesting that sunlight-induced processes played an important role in the transformation of Hg in the study area. Dissolved gaseous Hg concentrations experienced different diurnal variations among the sampling sites, with peak dissolved gaseous Hg at midday under sunny weather conditions and in the early morning under cloudy and/or partially cloudy weather conditions. The peak values of dissolved gaseous Hg observed at midday agree well with previous results and highlight the sunlight-induced production of dissolved gaseous Hg in freshwaters, whereas dissolved gaseous Hg peaks at night suggest that microbial activity might be an additional mechanism for dissolved gaseous Hg production in surface waters. Total Hg, reactive Hg, and dissolved gaseous Hg concentrations and Hg fluxes in the warm season were consistently higher than those in the cold season; this is probably attributable to the combined effect of seasonal variations of environmental parameters, transformation of Hg species, and microbial activities. PMID:23832677

Fu, Xuewu; Feng, Xinbin; Yin, Runsheng; Zhang, Hui

2013-10-01

135

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

NASA Astrophysics Data System (ADS)

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.

Sebestyen, Stephen D.; Boyer, Elizabeth W.; Shanley, James B.; Kendall, Carol; Doctor, Daniel H.; Aiken, George R.; Ohte, Nobuhito

2008-12-01

136

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

USGS Publications Warehouse

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.

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

2008-01-01

137

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

138

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...

139

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

SciTech Connect

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.

Lim, B.; Jickells, T.D. (Univ. of East Anglia, Norwich (United Kingdom))

1990-12-01

140

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)

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.

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

2007-10-01

141

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

PubMed Central

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.

Garcia, Rolando G.

1972-01-01

142

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

SciTech Connect

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

Alperin, M.J.; Martens, C.S.; Albert, D.B.; Suayah, I.B.; Benninger, L.K. [Univ. of North Carolina, Chapel Hill, NC (United States); Blair, N.E. [North Carolina State Univ., Raleigh, NC (United States). Dept. of Marine, Earth, and Atmospheric Sciences; Jahnke, R.A. [Skidaway Inst. of Oceanography, Savannah, GA (United States)

1999-02-01

143

Sardine Sardinops sagax and anchovy Engraulis encrasicolus larvae avoid regions with low dissolved oxygen concentration in the northern Benguela Current system.  

PubMed

Larvae of sardine Sardinops sagax and anchovy Engraulis encrasicolus in the northern Benguela upwelling system were distributed predominantly in waters with dissolved oxygen concentrations >2.0 ml l(-1) and oxygen saturations >75%. PMID:20735538

Kreiner, A; Stenevik, E K; Ekau, W

2009-01-01

144

Intercomparison experiment on isotope dilution thermal ionisation mass spectrometry using plutonium-239 spike for the determination of plutonium concentration in dissolver solution of irradiated fuel.  

National Technical Information Service (NTIS)

Determination of plutonium concentration in the dissolver solution of irradiated fuel is one of the key measurements in the nuclear fuel cycle. This report presents the results of an intercomparison experiment performed between Fuel Chemistry Division (FC...

S. K. Aggarwal P. M. Shah M. K. Saxena H. C. Jain P. B. Gurba

1996-01-01

145

Variation in solute concentration within the River Almond and its effect on the estimated dissolved load  

Microsoft Academic Search

Solute concentrations monitored over one complete year in the River Almond, Scotland, ranged between 47 and 88 mg I- . The responses to water level and seasonal variations were evaluated and separate summer and winter solution load rating curves established. Generally summer concentrations were higher than those of winter and a simple dilution model holds for the River Almond, with

M. H. AL-JABBARI

1983-01-01

146

Long term trend in dissolved iron concentration in the Amur River basin: Observation and modeling, possible causes of abrupt increase in the late 1990s’  

NASA Astrophysics Data System (ADS)

Recent studies revealed that significant part of iron which limits primary production of the Sea of Okhotsk is delivered from the Amur River basin with the form of dissolved iron. Thus, it is very important to understand dissolved iron producion mechanism of the basin. With long term trend analysis in dissolved iron concentration, we found that abrupt increase in the late 1990s’ was observed at the Khabarovsk station. Abrupt increases were also recorded at many observation stations, and are spreading over wide range of the basin. Potential drivers of these increases are considered, including temperature, rainfall, and land cover change. It was suggested that both temperature and land cover change may have significant effect on increasing dissolved iron concentration. Especially, drastic increase in groundwater pumping wells for paddy water irrigation which contains high concentrated dissolved iron has a significant impact on dissolved iron concentration of the basin. However, modeling study which considers possible mechanism of dissolved iron increase indicates that temperature change and land cover change can not fully reproduce the increase amount. In the presentation, several new possibilities of increase will also be discussed.

Onishi, T.; Yoh, M.; Shibata, H.; Nagao, S.; Kawahigashi, M.; Shamov, V.

2009-12-01

147

Effect of dissolved oxygen concentration (microaerobic and aerobic) on selective enrichment culture for bioaugmentation of acidic industrial wastewater.  

PubMed

The successful application of bioaugmentation is largely dependent on the selective enrichment of culture with regards to pH, temperature, salt, or specific toxic organic pollutants. In this study, we investigated the effect of dissolved oxygen (DO) concentrations (aerobic, >2 mg L(-1); microaerobic, <1 mg L(-1)) on yeast enrichment culture for bioaugmentation of acidic industrial wastewater (pH 3.9-4.7). Clone library analyses revealed that the yeast community shifted in response to different DO levels, and that Candida humilis and Candida pseudolambica were individually dominant in the aerobic and microaerobic enrichment cultures. This would significantly influence the isolation results, and further hinder bioaugmentation due to differences in DO environments during the enrichment and application periods. However, differences in the selective enrichment culture cannot be predicted based on differences in pollutant removal performance. Thus, DO concentrations (aerobic/microaerobic) should be considered a secondary selective pressure to achieve successful bioaugmentation. PMID:22776258

Quan, Ying; Han, Hui; Zheng, Shaokui

2012-06-16

148

Dissolved organic carbon (DOC) concentrations in UK soils and the influence of soil, vegetation type and seasonality.  

PubMed

Given the lack of studies which measured dissolved organic carbon (DOC) over long periods, especially in non-forest habitat, the aim of this study was to expand the existing datasets with data of mainly non-forest sites that were representative of the major soil and habitat types in the UK. A further aim was to predict DOC concentrations from a number of biotic and abiotic explanatory variables such as rainfall, temperature, vegetation type and soil type in a multivariate way. Pore water was sampled using Rhizon or Prenart samplers at two to three week intervals for 1 year. DOC, pH, organic carbon, carbon/nitrogen (C:N) ratios of soils and slope were measured and data on vegetation, soil type, temperature and precipitation were obtained. The majority of the variation in DOC concentrations between the UK sites could be explained by simple empirical models that included annual precipitation, and soil C:N ratio with precipitation being negatively related to DOC concentrations and C:N ratio being positively related to DOC concentrations. Our study adds significantly to the data reporting DOC concentrations in soils, especially in grasslands, heathlands and moorlands. Broad climatic and site factors have been identified as key factors influencing DOC concentrations. PMID:22542300

van den Berg, Leon J L; Shotbolt, Laura; Ashmore, Mike R

2012-04-28

149

Lisdexamfetamine and immediate release d-amfetamine - differences in pharmacokinetic/pharmacodynamic relationships revealed by striatal microdialysis in freely-moving rats with simultaneous determination of plasma drug concentrations and locomotor activity.  

PubMed

Lisdexamfetamine mesylate (Vyvanse(®)) is a novel prodrug approved for attention deficit hyperactivity disorder (ADHD). It is metabolised to d-amfetamine and l-lysine. In drug-experienced humans, lisdexamfetamine evoked lower "Drug liking" scores on Drug Rating Questionnaire (DRQ) scales than immediate-release (IR) d-amfetamine. This study investigated why lisdexamfetamine may have lower abuse potential and a better therapeutic window than d-amfetamine. We compared the pharmacokinetic/pharmacodynamic relationships of lisdexamfetamine and IR d-amfetamine in freely-moving rats by measuring simultaneously extracellular concentrations of striatal dopamine, plasma concentrations of d-amfetamine and lisdexamfetamine, and locomotor activity. At equivalent doses (1.5 mg/kg d-amfetamine base), lisdexamfetamine produced smaller, but more sustained, increases in striatal dopamine efflux than d-amfetamine and substantially less locomotor activation. Consistent with it being a prodrug, increased striatal dopamine and locomotion correlated with plasma concentration of its metabolite, d-amfetamine, but not the parent compound. Compared with IR d-amfetamine, lisdexamfetamine produced an identical AUC for plasma d-amfetamine, but a 50% lower C(max) and significantly delayed t(max). Where a hysteresis relationship did exist between plasma concentrations of d-amfetamine and striatal dopamine or locomotor activity, they were anticlockwise in direction for lisdexamfetamine and IR d-amfetamine. For extracellular striatal dopamine (neurochemical mediator) and locomotor activity (functional outcome), it was anticlockwise for lisdexamfetamine, but clockwise for IR d-amfetamine. This shows that lisdexamfetamine produced less pronounced behavioural activation as dopamine concentrations increased, but activity was maintained for longer when they declined. These findings help explain why the unusual pharmacokinetics of lisdexamfetamine evoked lower "Drug liking" scores than IR d-amfetamine and also suggest therapeutic window between efficacy and stimulant side-effects will be larger. PMID:22796358

Rowley, H L; Kulkarni, R; Gosden, J; Brammer, R; Hackett, D; Heal, D J

2012-07-14

150

Modification of nitrifying biofilm into nitritating one by combination of increased free ammonia concentrations, lowered HRT and dissolved oxygen concentration.  

PubMed

Nitrifying biomass on ring-shaped carriers was modified to nitritating one in a relatively short period of time (37 days) by limiting the air supply, changing the aeration regime, shortening the hydraulic retention time and increasing free ammonia (FA) concentration in the moving-bed biofilm reactor (MBBR). The most efficient strategy for the development and maintenance of nitritating biofilm was found to be the inhibition of nitrifying activity by higher FA concentrations (up to 6.5 mg/L) in the process. Reject water from sludge treatment from the Tallinn Wastewater Treatment Plant was used as substrate in the MBBR. The performance of high-surfaced biocarriers taken from the nitritating activity MBBR was further studied in batch tests to investigate nitritation and nitrification kinetics with various FA concentrations and temperatures. The maximum nitrite accumulation ratio (96.6%) expressed as the percentage of NO2(-)-N/NOx(-)-N was achieved for FA concentration of 70 mg/L at 36 degrees C. Under the same conditions the specific nitrite oxidation rate achieved was 30 times lower than the specific nitrite formation rate. It was demonstrated that in the biofilm system, inhibition by FA combined with the optimization of the main control parameters is a good strategy to achieve nitritating activity and suppress nitrification. PMID:22125903

Zekker, Ivar; Rikmann, Ergo; Tenno, Toomas; Menert, Anne; Lemmiksoo, Vallo; Saluste, Alar; Tenno, Taavo; Tomingas, Martin

2011-01-01

151

Modification of nitrifying biofilm into nitritating one by combination of increased free ammonia concentrations, lowered HRT and dissolved oxygen concentration  

Microsoft Academic Search

Nitrifying biomass on ring-shaped carriers was modified to nitritating one in a relatively short period of time (37 days) by limiting the air supply, changing the aeration regime, shortening the hydraulic retention time and increasing free ammonia (FA) concentration in the moving-bed biofilm reactor (MBBR). The most efficient strategy for the development and maintenance of nitritating biofilm was found to

Ivar Zekker; Ergo Rikmann; Toomas Tenno; Anne Menert; Vallo Lemmiksoo; Alar Saluste; Taavo Tenno; Martin Tomingas

2011-01-01

152

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 ...

153

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

PubMed

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. PMID:22982940

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

2012-09-13

154

Effects of constant and shifting dissolved oxygen concentration on the growth and antibiotic activity of Xenorhabdus nematophila.  

PubMed

To evaluate the effects of dissolved oxygen (DO) control strategy on cell growth and the production of antibiotic (cyclo(2-Me-BABA-Gly)) by Xenorhabdus nematophila. The effects of different agitation speeds and DO concentrations on cell growth and antibiotic activity of X. nematophila YL001 were examined. Experiments showed that higher agitation speeds and DO concentrations at earlier fermentation stage were favorable for cell growth and antibiotic production. At mid- and later-stage, properly decreasing DO concentration can strengthen cell growth and antibiotic production. Based on the kinetic information about the effects of agitation speeds and DO concentrations on the fermentation, the two-stage DO control strategy in which DO concentration was controlled to 70% in the first 18 h, and then switched to 50% after 18 h, was established to improve the biomass and antibiotic activity. By applying this DO-shift strategy in X. nematophila YL001 fermentation, maximal antibiotic activity and biomass reached 252.0+/-6.10 U/mL and 30.04+/-2.50 g/L, respectively, thus was 18.99% and 15.36% more than in the cultures at constantly 50% DO. PMID:20488698

Wang, Yong-Hong; Fang, Xiang-Ling; Li, Yu-Ping; Zhang, Xing

2010-05-21

155

In situ Raman-based measurements of high dissolved methane concentrations in hydrate-rich ocean sediments  

NASA Astrophysics Data System (ADS)

Ocean sediment dissolved CH4 concentrations are of interest for possible climate-driven venting from sea floor hydrate decomposition, for supporting the large-scale microbial anaerobic oxidation of CH4 that holds the oceanic CH4 budget in balance, and for environmental issues of the oil and gas industry. Analyses of CH4 from recovered cores near vent locations typically show a maximum of ˜1 mM, close to the 1 atmosphere equilibrium value. We show from novel in situ measurement with a Raman-based probe that geochemically coherent profiles of dissolved CH4 occur rising to 30 mM (pCH4 = 3 MPa) or an excess pressure ˜3× greater than CO2 in a bottle of champagne. Normalization of the CH4 Raman ?1 peak to the ubiquitous water ?2 bending peak provides a fundamental internal calibration. Very large losses of CH4 and fractions of other gases (CO2, H2S) must typically occur from recovered cores at gas rich sites. The new data are consistent with observations of microbial biomass and observed CH4 oxidation rates at hydrate rich sites and support estimates of a greatly expanded near surface oceanic pore water CH4 reservoir.

Zhang, Xin; Hester, Keith C.; Ussler, William; Walz, Peter M.; Peltzer, Edward T.; Brewer, Peter G.

2011-04-01

156

The effect of dissolved gas concentration on bubble-enhanced heating in tissue-mimetic materials  

NASA Astrophysics Data System (ADS)

Bubble-enhanced heating is a key mechanism to cause tissue damage in ultrasound surgery. We have conducted experiments in an agar-based tissue phantom. We found that the difference of air concentration in the tissue phantom has a small but measurable effect on the enhanced heating. Notably, high air concentration samples exhibit very good repeatability. We have passively monitored broadband acoustic emissions from the bubbles in order to determine if diagnostic information could be gleaned from such signals. Finally we investigate the effect of bubble size distribution on bubble-enhanced heating by employing bubble-based contrast agents to control the initial bubble size distribution. [Work supported by DARPA and the U.S. Army.

Yang, Xinmai; Roy, Ronald A.; Holt, R. Glynn

2002-11-01

157

Wetland types and wetland maps differ in ability to predict dissolved organic carbon concentrations in streams.  

PubMed

Three categories of digital wetland maps widely available in the United States were used to develop models relating wetlands to DOC: (1) wetlands mapped by the U.S. National Wetlands Inventory (NWI) (2) wetland vegetation cover mapped by the U.S. National Land Cover Dataset (NLCD), and (3) maps of hydric soils. Data extracted from these maps for 27 headwater catchments of the Ontonagon River in northern Michigan, USA were used with DOC concentrations measured in catchment streams to develop stepwise multiple regressions based on wetland area and type. The catchments of the 27 tributaries ranged in area from 2 to 66 km(2) and wetlands constituted 10 to 53% of their area. Although all three databases provided regressions that were highly significant (p<0.001), the variance explained was greater for NWI maps (R(2)=0.75) than for NLCD (R(2)=0.61) or soil maps (R(2)=0.60). Wetland-stream relationships were strongest during September 2002, but were significant for nine out of ten dates sampled during subsequent seasons. The individual wetland type most highly correlated (r>0.62) with stream DOC concentrations was conifer peatland, represented on the NWI maps as Palustrine Needle-leaved Forest, the NLCD maps as woody wetland, and the soil maps as organic soils. For the NWI dataset, DOC was negatively correlated with area of palustrine emergent wetlands (i.e., sedge meadows and graminoid fens) and bog shrubs, inferring that these wetland types may be sinks for DOC. Because of the different effects of wetland vegetation types on DOC, a GIS data source such as the NWI which depicts those wetland types is superior for predicting landscape contributions to stream DOC concentrations. PMID:18054999

Johnston, Carol A; Shmagin, Boris A; Frost, Paul C; Cherrier, Christine; Larson, James H; Lamberti, Gary A; Bridgham, Scott D

2007-12-04

158

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

PubMed

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 significant differences at P = 0.01. PMID:15865194

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

2005-04-15

159

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

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

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

2007-01-01

160

Temporal and spatial variability of dissolved inorganic carbon in a boreal stream network: Concentrations and downstream fluxes  

NASA Astrophysics Data System (ADS)

Carbon dioxide (CO2) and dissolved inorganic carbon (DIC) concentrations and export were analyzed throughout a 67 km2 boreal stream network in northern Sweden. 700 DIC and CO2 samples from 14 subcatchments were collected in 2006 and 2007. All sites were consistently supersaturated in CO2 with respect to the atmosphere. Temporal variability of DIC and CO2 concentration was best correlated with discharge, with concentrations generally diluting at high discharge. However, the variability in CO2 concentration was also dependent on the specific pH range of the stream, as variability was greatest in acidic headwater streams and lowest in larger circumneutral streams. In the larger ones the increase in the CO2 proportion of DIC at increased discharge counteracts the dilution of CO2. The shift toward proportionally more CO2 of the DIC at higher discharge is caused by decline in pH. Spatial patterns showed that DIC and CO2 concentrations were best correlated with peatland coverage of the subcatchment. The highest concentrations were found in headwater streams draining peatlands. The downstream export of DIC from the catchment outlet constitutes 19% of the total downstream export of carbon (DIC + DOC), or 0.7 (±0.09) g C m-2 yr-1. This study demonstrates the importance of including fluvial fluxes of inorganic carbon in landscape carbon budgets via runoff, and also highlights the need to account for stream evasion of CO2 to the atmosphere in such estimates since it can be larger than the downstream DIC export.

Wallin, Marcus; Buffam, Ishi; Öquist, Mats; Laudon, Hjalmar; Bishop, Kevin

2010-06-01

161

Dissolved heavy metal(Cd, Pb, Cr, Ni) concentrations in surface water and porewater from Bahía Blanca estuary tidal flats.  

PubMed

The concentrations of dissolved cadmium, lead, chromium and níquel were determined in surface water column and pore water, collected from the extensive tidal plain at Bahía Blanca estuary, Argentina. Three different polluted areas were selected to study the spatial variation of these metals. The concentration ranges within the water column were slightly variable (Cd: 0.18-2.48 microg L(-1); Pb: 0.38-7.53 microg L(-1); Cr: 0.89-5.83 microg L(-1); Ni: 0.81-3.49 microg L(-1)), and displayed a clear gradient respect to the industrial area. Significant differences (contrast tests) between sites were detected for Cd, Pb and Ni. Very similar concentrations of Cd (0.18-3.41 microg L(-1)), Pb (0.38-5.83 microg L(-1)), Cr (0.89-9.37 microg L(-1)), Ni (0.81-6.56 microg L(-1)) were found in the porewater at all sites. The results suggested that both environmental compartments (water column and tidal flats porewater) may be affected by similar point and non-point heavy metal sources. PMID:17639330

Botté, Sandra E; Freije, R Hugo; Marcovecchio, Jorge E

2007-07-18

162

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

PubMed

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

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

2011-10-17

163

Comparison of ovarian functions for keeping embryos by measurement of dissolved oxygen concentrations in ovaries of copulatory and non-copulatory oviparous fishes and viviparous fishes  

Microsoft Academic Search

To investigate causes of anomalous development of embryos facultatively fertilized in the ovary of a non-copulatory oviparous fish Hemilepidotus gilberti (Scorpaeniformes: Cottdae), dissolved oxygen (DO) concentrations were measured in ovaries of copulatory oviparous (Alcichthys alcicornis, Bero elegans), non-copulatory oviparous (H. gilberti, Hexagrammus otakii), and viviparous (Sebastes taczanowskii, Zoarces elongatus) fishes. DO concentrations changed during vitellogenesis and ovulation cycles, and also

Youichi Hayakawa; Hiroyuki Munehara

2003-01-01

164

Changes in the concentration, biodegradability, and fluorescent properties of dissolved organic matter during stormflows in coastal temperate watersheds  

NASA Astrophysics Data System (ADS)

Dissolved organic matter (DOM) transport during storms is studied because it is important in the annual watershed export budget for dissolved organic carbon (DOC). We sampled stream water from two watersheds (upland and wetland-dominated) and three subcatchments (bog, forested wetland, and mineral forest) located within the wetland-dominated watershed during a fall and summer storm to investigate changes in the magnitude and chemical quality of DOM during stormflows. Stormflow export of DOC ranged from 2.3 kg C ha-1 in the upland watershed to 13.9 kg C ha-1 in the bog subcatchment. Biodegradable DOC (BDOC) export for these same storms ranged from 0.6 kg C ha-1 in the upland watershed to 4.2 kg C ha-1 in the bog subcatchment. The percent BDOC decreased during both storms in the upland watershed, while percent BDOC increased in the three wetland streams. Parallel factor analysis (PARAFAC) modeling of fluorescence excitation-emission matrices further showed that as stream water DOM concentrations increased during stormflows in the upland watershed, the contribution of protein-like fluorescence decreased and humic-like fluorescence increased. However, the contribution of protein-like fluorescence increased and humic-like fluorescence decreased slightly in the three wetland streams. These results indicate that shifts in the biodegradability and chemical quality of DOM are different for upland and wetland watersheds. Taken together, our findings suggest stormflows are responsible for substantial export of BDOC from coastal temperate watersheds. Moreover, we found that PARAFAC modeling of fluorescent DOM is an effective tool for elucidating shifts in the quality of stream water DOM during storms.

Fellman, Jason B.; Hood, Eran; Edwards, Richard T.; D'Amore, David V.

2009-03-01

165

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

USGS Publications Warehouse

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.

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

2002-01-01

166

Concentrations and fluxes of dissolved organic carbon in runoff from a forested catchment: insights from high frequency measurements  

NASA Astrophysics Data System (ADS)

Concentrations of dissolved organic carbon (DOC) in runoff from catchments are often subject to substantial short-term variations. The aim of this study was to identify the compartmental sources of DOC in a forested catchment and the causes for short-term variations in runoff. Furthermore, we investigated the implication of short-term variations for the calculation of annual runoff fluxes. High frequency measurements (30 min intervals) of DOC in runoff, of discharge and groundwater table were conducted for one year in the 4.2 km2 forested Lehstenbach catchment, Germany. Riparian wetland soils represent about 30% of the catchment area. The quality of DOC was investigated by three dimensional fluorescence excitation-emission matrices in samples taken from runoff, deep groundwater and shallow groundwater from the riparian wetland soils. The concentrations of DOC in runoff were highly variable at an hourly to daily time scale, ranging from 2.6 mg L-1 to 34 mg L-1 with an annual average of 9.2 mg L-1. The concentrations were positively related to discharge, with a counter clockwise hysteresis. Relations of DOC to discharge were steeper and the degree of hysteresis larger in the summer/fall than in the winter/spring period. Dynamics of groundwater table, discharge, DOC concentrations and DOC quality parameters indicated that DOC in runoff originated mainly from the riparian wetland soils, both under low and high flow conditions. The annual export of DOC from the catchment was 84 kg C ha-1 yr-1 when calculated from the high frequency measurements. If the annual export was calculated by simulated samplings of >2 days intervals substantial deviations resulted. Predicted changes in precipitation and discharge patterns as well as generally increasing temperatures likely will cause raising DOC exports from this catchment.

Strohmeier, S.; Knorr, K.-H.; Reichert, M.; Frei, S.; Fleckenstein, J. H.; Peiffer, S.; Matzner, E.

2013-02-01

167

Concentrations and fluxes of dissolved organic carbon in runoff from a forested catchment: insights from high frequency measurements  

NASA Astrophysics Data System (ADS)

Concentrations of dissolved organic carbon (DOC) in runoff from catchments are often subject to substantial short term variations. The aim of this study was to identify the spatial sources of DOC and the causes for short term variations in runoff from a forested catchment. Furthermore, we investigated the implication of short term variations for the calculation of annual runoff fluxes. High frequency measurements (30 min intervals) of DOC in runoff, of discharge and groundwater table were conducted for one year in the 4.2 km2 forested Lehstenbach catchment, Germany. Riparian wetland soils represent about 30% of the catchment area. The quality of DOC was investigated by three dimensional fluorescence excitation-emission matrices in samples taken from runoff, deep groundwater and shallow groundwater from the riparian wetland soils. The concentrations of DOC in runoff were highly variable at an hourly to daily time scale, ranging from 2.6 mg l-1 to 34 mg l-1 with an annual average of 9.2 mg l-1. The concentrations were positively related to discharge, with a pronounced, counter clockwise hysteresis. Relations of DOC to discharge were steeper in the summer/fall than in the winter/spring season. Dynamics of groundwater table, discharge, DOC concentrations and DOC quality parameters indicated that DOC in runoff originated mainly from the riparian wetland soils, both under low and high flow conditions. The annual export of DOC from the catchment was 84 kg C ha-1 yr-1 when calculated from the high frequency measurements. If the annual export was calculated by simulated random fortnightly samplings, the range was 47 to 124 kg C ha-1 yr-1. Calculations of DOC export fluxes might result in significant errors when based on infrequent (e.g. fortnightly) sampling intervals. Future changes in the precipitation and discharge patterns will influence the DOC dynamics in this catchment, with largest effects in the summer season.

Strohmeier, S.; Knorr, K.-H.; Reichert, M.; Frei, S.; Fleckenstein, J. H.; Peiffer, S.; Matzner, E.

2012-08-01

168

Riparian soil temperature modification of the relationship between flow and dissolved organic carbon concentration in a boreal stream  

NASA Astrophysics Data System (ADS)

Discharge is often strongly correlated to the temporal variability of dissolved organic carbon concentrations ([DOC]) in watercourses. One recently proposed way to model this is the riparian flow-concentration integration model (RIM) concept that accounts for the role of flow pathway control on [DOC] dynamics in streams. However, in boreal systems, there is also commonly a seasonal pattern, which cannot be explained by variability in discharge alone. The objectives with this study were to (1) demonstrate RIM as a tool for studying variability in stream water chemistry, (2) investigate factors related to stream water DOC variability, and (3) modify RIM to account for these factors. RIM was used with 14 years of daily discharge and almost 500 stream measurements of [DOC] from a forested boreal headwater stream. We used the calibrated RIM to account for discharge influences and then investigated variables that could be related to DOC variability (air and soil temperature, soil moisture, precipitation, antecedent flow and stream sulfate). Five alternative formulations of RIM, with temporally varying soil concentration profiles based on the variability in soil temperature and/or antecedent flow, were evaluated. The model where only the effects of riparian soil temperature on dynamics in DOC depth profiles were included performed best overall. This dynamic RIM improved the Nash-Sutcliffe to 0.58 compared to 0.42 for the flow-only formulation and reduced the median absolute error from 3.0 to 2.1 mg L-1. This study demonstrates that RIM is a simple way of modeling stream DOC and exploring controls on stream water chemistry.

Winterdahl, Mattias; Futter, Martyn; KöHler, Stephan; Laudon, Hjalmar; Seibert, Jan; Bishop, Kevin

2011-08-01

169

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

NASA Astrophysics Data System (ADS)

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

Waiser, Marley J.

2006-06-01

170

Changes in the concentration, biodegradability, and fluorescent properties of dissolved organic matter during stormflows in coastal temperate watersheds  

Microsoft Academic Search

Dissolved organic matter (DOM) transport during storms is studied because it is important in the annual watershed export budget for dissolved organic carbon (DOC). We sampled stream water from two watersheds (upland and wetland-dominated) and three subcatchments (bog, forested wetland, and mineral forest) located within the wetland-dominated watershed during a fall and summer storm to investigate changes in the magnitude

Jason B. Fellman; Eran Hood; Richard T. Edwards; David V. D'Amore

2009-01-01

171

Dust deposition to the surface waters of the western and central North Pacific inferred from surface water dissolved aluminum concentrations  

Microsoft Academic Search

Dissolved Al was determined on ?3500 surface water samples collected in the NW Pacific during the 2002 Intergovernmental Oceanographic Commission (IOC) Contaminant Baseline survey. In addition, dissolved Al was determined on samples collected at 9 vertical stations occupied along the cruise track. Surface water Al distributions, when converted to annual mineral dust deposition (Measures and Brown, 1996), imply extremely low

C. I. Measures; M. T. Brown; S. Vink

2005-01-01

172

Challenges of Using Polyethylene Passive Samplers to Determine Dissolved Concentrations of Parent and Alkylated PAHs under Cold and Saline Conditions.  

PubMed

Passive samplers can be useful tools for determining truly dissolved concentrations of organic contaminants in the water. Polyethylene (PE) samplers were validated for measuring polycyclic aromatic hydrocarbons (PAHs), with a focus on alkylated PAHs that can dominate in an oil spill. Equilibrium partition coefficients between water and PE passive samplers (KPEw) were measured for 41 PAHs both at ambient conditions (20 °C, no salt) and down to -15 °C with up to 245 psu present in ice brine. For each additional alkylated carbon, log KPEw increased by an average of 0.40 (±0.20) log units, close to predictions. The increase per aromatic carbon was only 0.33 (±0.02) log units. Apparent PE-water distributions of pyrene and deuterated pyrene (performance reference compound) were within 0.1 log unit for all experiments at 20 and 2 °C but started to diverge by 0.8 log units at -4 °C (100 psu) and by 3.1 log units at -15 °C (245 psu). The delay in equilibrating PAHs in these experiments was dominated by increases in the water viscosity, which, in turn, affected both the aqueous diffusivities of the PAHs and the thickness of the water boundary layer. In a simulated marine oil spill in the laboratory, PE-based results were within a factor of 2 of conventional sampling results for the most abundant PAHs. PMID:23919389

Reitsma, Pamela J; Adelman, Dave; Lohmann, Rainer

2013-09-09

173

Defining Dissolving  

NSDL National Science Digital Library

In this introductory activity, learners discover that sugar and food coloring dissolve in water but neither dissolves in oil. Based on their observations, learners can conclude that both solids and liquids can dissolve, but they don't necessarily dissolve in all liquids. Through this activity, learners will refine their definition of dissolve.

Kessler, James H.; Galvan, Patricia M.

2007-01-01

174

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

PubMed

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. PMID:23490107

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

2013-02-26

175

Effects of forestry operations on dissolved organic carbon concentrations and export in boreal first-order streams  

NASA Astrophysics Data System (ADS)

The purpose of this study was to quantify the effects of clear-cutting and site preparation on dissolved organic carbon (DOC) concentrations and export in four boreal headwater streams in northern Sweden. The data set included intensive stream water monitoring from 2 years of pretreatment conditions (2004-2005), a 2 year post-clear-cut period (2006-2007), and a 2 year period after site preparation (2008-2009). To investigate differences in [DOC], an analysis of variance on ranks was performed on the data sets. Clear-cutting increased the median DOC concentrations significantly from 15.9 to 20.4 mg L-1, which represents a net increase (treatment versus control) of 3.0 mg L-1 in the 2006-2007 period. Site preparation had an even more profound effect on DOC levels; an increase from 20.4 to 27.6 mg L-1was found in the site-prepared catchments, whereas the control sites increased slightly from 17.4 to 21.4 mg L-1during the wetter years of 2008-2009. Riverine C fluxes increased significantly by 100% after clear-cutting and by 79% after site preparation (92% and 195%, respectively, if compared to pretreatment conditions). When comparing these yearly C fluxes (183 kg C ha-1 yr-1after clear-cutting; 280 kg C ha-1 yr-1after site preparation) to the net ecosystem exchange (NEE) of a forest in the region, the DOC flux represented 10% of NEE before harvest, increased to 18% after the clear-cut, and increased to 28% after site preparation. These results underline the large impact of forestry operations on stream water quality as well as DOC exports leaving managed boreal forests.

Schelker, J.; EklöF, K.; Bishop, K.; Laudon, H.

2012-03-01

176

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

PubMed Central

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 micrograms of phenol per liter, but the phenol was mineralized. Mineralization of 2.0 micrograms of phenol per liter by P. acidovorans was delayed 16 h by 70 micrograms 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 micrograms/liter, respectively. Growth of Pseudomonas sp. in the inorganic salts solution was not affected by the addition of 3.0 micrograms 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 micrograms each of glucose and aniline, the sugar was mineralized first, and aniline was mineralized only after much of the glucose carbon was converted to CO2. S. typhimurium failed to multiply in the salts solution with 1.0 micrograms of glucose per liter. It grew slightly but mineralized little of the sugar at 5.0 micrograms/liter, but its population density rose at 10 micrograms of glucose per liter or higher. The hexose could be mineralized at 0.5 micrograms/liter, however, if the solution contained 5.0 mg of arabinose per liter.(ABSTRACT TRUNCATED AT 250 WORDS)

Schmidt, S K; Alexander, M

1985-01-01

177

Enhanced porcine interferon-? production by recombinant Pichia pastoris with a combinational control strategy of low induction temperature and high dissolved oxygen concentration  

Microsoft Academic Search

Porcine interferon-? (pIFN-?) production by recombinant Pichia pastoris with standard induction strategy at 30°C often suffers problems such as low antiviral activity, long cells adaptation period, etc. To solve these problems, a combinational induction strategy by simultaneously controlling induction temperature at 20°C and dissolved oxygen concentration (DO) over 50% was proposed and the relevant fermentation runs were conducted in a

Hu Jin; Guoqiang Liu; Xiaofei Ye; Zuoying Duan; Zhen Li; Zhongping Shi

2010-01-01

178

The biogeochemical effect of seaweeds upon close-to natural concentrations of dissolved iodate and iodide in seawater – Preliminary study with Laminaria digitata and Fucus serratus  

Microsoft Academic Search

Toward assessing the biogeochemical significance of seaweeds in relation to dissolved iodine in seawater, the effect of whole seaweeds (Laminaria digitata and Fucus serratus) upon iodide and iodate, at essentially natural concentrations, has been studied. The weeds were carefully removed from the sub-littoral zone of the Menai Straits and exposed to iodide and iodate at their natural temperature (6°C), but

Victor W. Truesdale

2008-01-01

179

Seasonal changes in the concentration and chemical quality of dissolved organic matter exported from wetland soils to streams in coastal temperate watersheds  

Microsoft Academic Search

The concentration and chemical quality of dissolved organic matter (DOM) fluxes from terrestrial to aquatic ecosystems is an important indicator of watershed-scale hydrologic and biogeochemical processes. Understanding the relative magnitude and chemical character of these DOM fluxes is critical because DOM influences an array of biological, chemical, and physical processes. We used PARAFAC modeling of excitation- emission (EEM) fluorescence spectroscopy

J. B. Fellman; E. Hood; D. V. D'Amore; R. T. Edwards; J. Berkowitz

2007-01-01

180

Diel variation in concentration, assimilation and respiration of dissolved free amino acids in relation to planktonic primary and secondary production in two eutrophic lakes  

Microsoft Academic Search

Concentration of dissolved free amino acids (DFAA) and assimilation of the 5 most abundant DFAA (glutamic acid, serine, glycine, alanine and ornithine) were measured at 3-h intervals over 27 h in two Danish, eutrophic lakes. The carbon flux of the amino acid assimilation was compared with the major routes of carbon flux, including primary production, bacterial production and zooplankton grazing.

Niels O. G. Jorgensen; Morten Sondergaard; Hans J. Hansen; Suzanne Bosselmann; Bo Riemann

1983-01-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

182

Influence of temperature, pH and dissolved oxygen concentration on enhanced biological phosphorus removal under strictly aerobic conditions.  

PubMed

Previous research has suggested that enhanced biological phosphorus removal (EBPR) from wastewater can be achieved under continuous aerobic conditions over the short term. However, little is known how environmental conditions might affect aerobic EBPR performance. Consequently we have investigated the impact of temperature, pH and dissolved oxygen (DO) concentrations on EBPR performance under strictly aerobic conditions. A sequencing batch reactor (SBR) was operated for 108 days on a six-hour cycle (four cycles a day). The SBR ran under alternating anaerobic-aerobic conditions as standard and then operated under strictly aerobic conditions for one cycle every three or four days. SBR operational temperature (10, 15, 20, 25 and 30°C), pH (6, 7, 8 and 9) and DO concentration (0.5, 2.0 and 3.5mg/L) were changed consecutively during the aerobic cycle. Recorded increases in mixed liquor phosphorus (P) concentrations during aerobic carbon source uptake (P release) were affected by the biomass P content rather than the imposed changes in the operational conditions. Thus, P release levels increased with biomass P content. By contrast, subsequent aerobic P assimilation (P uptake) levels were both affected by changes in operational temperature and pH, and peaked at 20-25°C and pH 7-8. Highest P uptake detected under these SBR operating conditions was 15.4 mg Pg-MLSS(-1) (at 25°C, pH 7 and DO 2.0mg/L). The ability of the community for linked aerobic P release and P uptake required the presence of acetate in the medium, a finding which differs from previous data, where these are reported to occur in the absence of any exogenous carbon source. Fluorescence in situ hybridization was performed on samples collected from the SBR, and Candidatus 'Accumulibacter phosphatis' cells were detected with PAOmix probes through the operational periods. Thus, Candidatus 'Accumulibacter phosphatis' seemed to perform P removal in the SBR as shown in previous studies on P removal under strictly aerobic conditions. PMID:21718809

Nittami, Tadashi; Oi, Hiroshi; Matsumoto, Kanji; Seviour, Robert J

2011-06-28

183

Effects of dissolved oxygen levels and the role of extra- and intracellular amino acid concentrations upon the metabolism of mammalian cell lines during batch and continuous cultures  

Microsoft Academic Search

The effects of dissolved oxygen and the concentration of essential amino acids upon the metabolism of two mammalian cell lines\\u000a (rCHO producing human active (t-PA) and a mouse-mouse hybridoma) were investigated in batch, chemostat, and perfusion cultures.\\u000a Intracellular amino acid concentrations were measured for both cell lines during repeated batch cultures and the KS-values for the essential amino acids were

Rüdiger Heidemann; Dirk Lütkemeyer; Heino Büntemeyer; Jürgen Lehmann

1998-01-01

184

Impact of dissolved oxygen concentration on acetate accumulation and physiology of E. coli BL21, evaluating transcription levels of key genes at different dissolved oxygen conditions  

Microsoft Academic Search

High density growth of Escherichia coli especially in large bioreactors may temporarily expose the cells to oxygen limitation as a result of a local inadequate oxygen supply or intermittently high concentrations of cells and nutrients. Although short, these periods can potentially alter bacterial metabolism, affecting both growth and recombinant proteins production capability, and thus lowering process productivity. When E. coli

Je-Nie Phue; Joseph Shiloach

2005-01-01

185

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...

186

Impacts of dust deposition on dissolved trace metal concentrations (Mn, Al and Fe) during a mesocosm experiment  

NASA Astrophysics Data System (ADS)

The deposition of atmospheric dust is the primary process supplying trace elements abundant in crustal rocks (e.g. Al, Mn and Fe) to the surface ocean. Upon deposition, the residence time in surface waters for each of these elements differs according to their chemical speciation and biological utilization. Presently however their behavior after atmospheric deposition is poorly constrained, principally because of the difficulty in following natural dust events in-situ. In the present work we examined the temporal changes in the biogeochemistry of crustal metals (in particular Al, Mn and Fe) after an artificial dust deposition event. The experiment was contained inside trace metal clean mesocosms (0-12.5 m depths) deployed in the surface waters of the Northwestern Mediterranean, close to the coast of Corsica in the frame of the DUNE project (a DUst experiment in a low Nutrient low chlorophyll Ecosystem). Two consecutive artificial dust deposition events, each mimicking a wet deposition of 10 g m-2 of dust, were performed during the course of this DUNE-2 experiment. The changes in dissolved manganese (dMn), iron (dFe) and aluminium (dAl) concentrations were followed immediately and over the following week and their inventories and loss or dissolution rates were determined. The evolution of the inventories after the two consecutive additions of dust showed distinct behaviors for dMn, dAl and dFe. Even though the mixing conditions differed from one seeding to the other, dMn and dAl showed clear increases directly after both seedings due to dissolution processes. Three days after the dust additions, dAl concentrations decreased as a consequence of scavenging on sinking particles. dAl appeared to be highly affected by the concentrations of biogenic particles, with an order of magnitude difference in its loss rates related to the increase of biomass after the addition of dust. For dFe concentrations, the first dust addition decreased the concentrations through scavenging of the dust particles, whereas the second seeding induced dissolution of Fe from the dust particles. This difference, which might be related to a change in Fe-binding ligand concentration in the mesocosms, highlights the complex processes that control the solubility of Fe. Based on the inventories at the mesocosm scale, the estimations of solubility of metals from dust particles in seawater were 1% for Al and 40% for Mn which were in good agreement with laboratory based estimates. Overall, the trace metal dataset presented here makes a significant contribution to enhancing our knowledge on the processes influencing trace metals release from Saharan dust and the subsequent processes of bio-uptake and scavenging in a low nutrient low chlorophyll area.

Wuttig, K.; Wagener, T.; Bressac, M.; Dammshäuser, A.; Streu, P.; Guieu, C.; Croot, P. L.

2012-10-01

187

Estimating absorption coefficients of colored dissolved organic matter (CDOM) using a semi-analytical algorithm for Southern Beaufort Sea (Canadian Arctic) waters: application to deriving concentrations of dissolved organic carbon from space  

NASA Astrophysics Data System (ADS)

A series of papers have suggested that freshwater discharge, including a large amount of dissolved organic matter (DOM), has increased since the middle of the 20th century. In this study, a semi-analytical algorithm for estimating light absorption coefficients of the colored fraction of DOM (CDOM) was developed for Southern Beaufort Sea waters using remote sensing reflectance at six wavelengths in the visible spectral domain corresponding to MODIS ocean color sensor. This algorithm allows to separate colored detrital matter (CDM) into CDOM and non-algal particles (NAP) by determining NAP absorption using an empirical relationship between NAP absorption and particle backscattering coefficients. Evaluation using independent datasets, that were not used for developing the algorithm, showed that CDOM absorption can be estimated accurately to within an uncertainty of 35% and 50% for oceanic and turbid waters, respectively. In situ measurements showed that dissolved organic carbon (DOC) concentrations were tightly correlated with CDOM absorption (r2 = 0.97). By combining the CDOM absorption algorithm together with the DOC versus CDOM relationship, it is now possible to estimate DOC concentrations in the near-surface layer of the Southern Beaufort Sea using satellite ocean color data. DOC concentrations in the surface waters were estimated using MODIS ocean color data, and the estimates showed reasonable values compared to in situ measurements. We propose a routine and near real-time method for deriving DOC concentrations from space, which may open the way to an estimate of DOC budgets for Arctic coastal waters.

Matsuoka, A.; Hooker, S. B.; Bricaud, A.; Gentili, B.; Babin, M.

2012-10-01

188

The effect of dissolve gas concentration in the initial growth stage of multi cavitation bubbles. Differences between vacuum degassing and ultrasound degassing.  

PubMed

The sonochemical luminescence intensity from luminol was measured at a sampling rate of several kilohertz. This was noted at three different periods: first, the latent period in which no light emission occurs at all; second, the increased emission period from the start of light emission to the time when a steady state is reached; and third, the steady state period in which light emission occurs at the steady state value. When irradiated with ultrasound of different intensities, the times of the latent period and increased emission period are shorter for higher ultrasound intensities. To know how the dissolved oxygen content is involved in early-stage cavitation growth, an experiment was conducted using solutions with varying dissolved oxygen contents from 100% to 37%. For dissolved air content of 50% or less, it was found that the latent period was 30 times longer in a saturated condition. It was also found that the increased emission period was 10 times longer. However, the emission intensity in the steady state did not change at all even when the initial dissolved gas concentration of the sample was changed. From this, it was found that the reuse of collapsed bubbles takes place efficiently in the steady state. Dissolved oxygen was reduced by the use of a vacuum pump and by the degassing action of ultrasound, and it was discovered that the behavior of transient emission differed for the two ways of degassing. PMID:17681864

Yanagida, Hirotaka

2007-06-27

189

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)

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.

Weinbauer, M. G.; Peduzzi, P.

190

The influence of ammonium, nitrate, and dissolved oxygen concentrations on uptake, nitrification, and denitrification rates associated with prairie stream substrata  

Microsoft Academic Search

Substrata samples were collected from Kings Creek on Konza Prairie Biological Station (Manhattan, Kansas) and incubated with varying levels of ammonium (NH ), nitrate (NO ), and dissolved oxygen (O2) to examine the 12 43 response of nitrogen (N) uptake and transformation rates. Substrata collected were fine benthic organic matter (FBOM), coarse benthic organic matter, filamentous green algae, bryophytes, suspended

Melody J. Kemp; Walter K. Dodds

2002-01-01

191

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

Microsoft Academic Search

The semiarid prairie pothole region of the North American Great Plains is characterized by millions of small, shallow, closed basin wetlands. These wetlands are hydrologically dynamic, often losing considerable water volume and depth seasonally in response to high evaporative stress and\\/or infiltration rates. However, the consequences of such water loss on wetland water chemistry parameters, in particular dissolved organic carbon

Marley J. Waiser

2006-01-01

192

Concentrations and fluxes of dissolved organic carbon and nitrogen in a Picea abies chronosequence on former arable land in Sweden  

Microsoft Academic Search

Shifting land use from agriculture to forestry induces major changes in the carbon (C) and nitrogen (N) cycles, including fluxes of dissolved organic carbon (DOC) and nitrogen (DON). This study investigated the long-term effects of afforestation on ecosystem DOC and DON dynamics using a chronosequence approach comprising four arable fields and nine differently aged (10–92 years) Norway spruce stands growing

Lars Rosenqvist; Dan B. Kleja; Maj-Britt Johansson

2010-01-01

193

Activated carbon and biochar amendments decrease pore-water concentrations of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge.  

PubMed

The aim of the research was to determine the influence of biochar and activated carbon (AC) on the freely dissolved concentration of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge. Two different biochars (MSB and PMW) and two ACs (CP1 and BP2) were used in the present experiment. Addition of AC/biochar to sewage sludge caused significant decrease of freely dissolved PAHs concentration. Depending on the dose, the reduction of freely dissolved PAHs ranged from 56% to 95% (ACs) and from 0% to 57% (biochars). Only for the biochars was there a significant difference between short 7-d and long 30/60-d mixing time. It is concluded that both AC and biochar are effective at reducing PAH pore-water concentrations, the more expensive and non-carbon negative AC having the greatest effect. PMID:22391590

Oleszczuk, Patryk; Hale, Sarah E; Lehmann, Johannes; Cornelissen, Gerard

2012-02-12

194

Interannual variability of water transport by the East Kamchatka and East Sakhalin Currents and their influence on dissolved oxygen concentration in the Sea of Okhotsk and subarctic pacific  

Microsoft Academic Search

The influence of interannual variability of water transport by the East Kamchatka Current, the Oyashio, and the East Sakhalin\\u000a Current on the dissolved oxygen concentration in the western subarctic Pacific and the Sea of Okhotsk is considered for studying\\u000a climate change impact on sea water chemical parameters. It is shown that statistically significant relation is observed between\\u000a the calculated with

A. G. Andreev; G. V. Shevchenko

2008-01-01

195

Modeling the liquid-phase oxidation of hydrocarbons over a range of temperatures and dissolved oxygen concentrations with pseudo-detailed chemical kinetics  

Microsoft Academic Search

The ability of pseudo-detailed chemical kinetic modeling to simulate the oxidation behavior of Exxsol D-80, a paraffin blend whose oxidative characteristics are representative of severely hydrotreated jet fuels, is assessed. The effects of temperature and initial dissolved O2 concentration on oxidation are considered. A 17-step pseudo-detailed mechanism is shown to provide reasonable simulations of Exxsol D-80 oxidation over a range

Nicholas J. Kuprowicz; Jamie S. Ervin; Steven Zabarnick

2004-01-01

196

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

Microsoft Academic Search

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

D. G. Clifton; R. J. Gilliom

1989-01-01

197

Estimating absorption coefficients of colored dissolved organic matter (CDOM) using a semi-analytical algorithm for southern Beaufort Sea waters: application to deriving concentrations of dissolved organic carbon from space  

NASA Astrophysics Data System (ADS)

A series of papers have suggested that freshwater discharge, including a large amount of dissolved organic matter (DOM), has increased since the middle of the 20th century. In this study, a semi-analytical algorithm for estimating light absorption coefficients of the colored fraction of DOM (CDOM) was developed for southern Beaufort Sea waters using remote sensing reflectance at six wavelengths in the visible spectral domain corresponding to MODIS ocean color sensor. This algorithm allows the separation of colored detrital matter (CDM) into CDOM and non-algal particles (NAP) through the determination of NAP absorption using an empirical relationship between NAP absorption and particle backscattering coefficients. Evaluation using independent datasets, which were not used for developing the algorithm, showed that CDOM absorption can be estimated accurately to within an uncertainty of 35% and 50% for oceanic and coastal waters, respectively. A previous paper (Matsuoka et al., 2012) showed that dissolved organic carbon (DOC) concentrations were tightly correlated with CDOM absorption in our study area (r2 = 0.97). By combining the CDOM absorption algorithm together with the DOC versus CDOM relationship, it is now possible to estimate DOC concentrations in the near-surface layer of the southern Beaufort Sea using satellite ocean color data. DOC concentrations in the surface waters were estimated using MODIS ocean color data, and the estimates showed reasonable values compared to in situ measurements. We propose a routine and near real-time method for deriving DOC concentrations from space, which may open the way to an estimate of DOC budgets for Arctic coastal waters.

Matsuoka, A.; Hooker, S. B.; Bricaud, A.; Gentili, B.; Babin, M.

2013-02-01

198

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

PubMed

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-naïve westslope cutthroat trout (Oncorhynchus clarki lewisi) exposed to dissolved (0.1-microm 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 microg/L; mean, 428 microg/L) was significantly (p = 0.008) higher than survival (14%) after exposure to a controlled, constant Zn concentration (422 microg/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 microg/L; mean, 399 microg/L) was significantly (p = 0.022) higher than survival (50%) in the constant-concentration treatment (392 microg/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 hydrologic conditions tested. PMID:18020695

Nimick, David A; Harper, David D; Farag, Aïda M; Cleasby, Thomas E; MacConnell, Elizabeth; Skaar, Don

2007-12-01

199

Neurophysiological recordings in freely moving monkeys  

Microsoft Academic Search

Recordings of neuronal activity in freely moving rats are common in experiments where electrical signals are transmitted using cables. Such techniques are not common in monkeys because their prehensile abilities are thought to preclude such techniques. However, analysis of brain mechanisms underlying spatial navigation and cognition require the subject to walk. We have developed techniques for recordings in freely moving

Ning Lei Sun; Yan Lin Lei; Byoung-Hoon Kim; Jae-Wook Ryou; Yuan-Ye Ma; Fraser A. W. Wilson

2006-01-01

200

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)

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-Phoenix (CAP) ecosystem. Ecosystems 4: 582-602.

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

2009-12-01

201

Chemical characteristics of dissolved organic matter (DOM) in relation to heavy metal concentrations in soil water from boreal peatlands after clear-cut harvesting  

NASA Astrophysics Data System (ADS)

Boreal peatlands form an important terrestrial carbon reserve and are a major source of dissolved organic matter (DOM) to surface waters, particularly when disturbed through forestry practices such as draining or timber harvesting. Heavy metals show a strong affinity to organic matter and so, along with DOM, heavy metals can be mobilized and transported from the soil to surface waters and sediments where they may become toxic to aquatic organisms and pass up the food chain. The complexation of heavy metals with DOM can be expected to be related and determined by the chemical characteristics of DOM and oxidation/reducing conditions in the peat. We extracted interstitial water from peat samples and determined the concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and Al, Cu, Zn and Fe in various fractions of DOM isolated by adsorption properties (XAD-8 fractionation) and molecular-weight (ultrafiltration). The peat samples were taken from 0-30 and 30-50 cm depth in drained peatland catchments two years after whole-tree or stem-only clear-cut harvesting (Scots pine or Norway spruce) had been carried out. The samples from the upper layer had been subject to alternating saturation/aeration conditions while the deeper layer had been continuously under the water table. The fractionation of DOC and DON according to both adsorption properties and molecular-weight fractions clearly differed between the upper and lower peat layers. While the hydrophobic acid fraction contained proportionally more DOC and DON than the hydrophilic acid fraction in the upper peat layer the results were vice versa in the lower peat layer. High-molecular-weight compounds (> 100 kDa) were proportionally more abundant in the upper and low-molecular-weight compounds (< 1 kDa) in the lower peat layer. These differences are assumed to reflect differences in the aerobic/ anaerobic conditions and degree of decomposition between the two layers. The concentrations of Zn, Al, Fe and DON correlated positively with DOC concentrations whereas the concentration Cu did not correlate with DOC concentrations. Heavy metal concentrations in different molecular-weight fractions indicated that Al, Cu, Zn and Fe were mostly associated with high-molecular-weight compounds and only a small fraction existed as free metal ions in solution. There were no clear differences in the chemical characteristics of DOC or DON or heavy metal concentrations between the two harvesting treatments.

Kiikkilä, O.; Nieminen, T.; Starr, M.; Ukonmaanaho, L.

2012-04-01

202

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

USGS Publications Warehouse

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

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

2009-01-01

203

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

USGS Publications Warehouse

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-3222Rn, 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 result suggests that 222Rn concentrations in water near the recommended EPA limit in drinking water of 11 kBq m-3 may not contribute measurable amounts of 222Rn to indoor air in most houses.

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

1994-01-01

204

Effect of low dissolved oxygen concentrations on behavior and predation rates on red sea bream Pagrus major larvae by the jellyfish Aurelia aurita and by juvenile Spanish mackerel Scomberomorus niphonius  

Microsoft Academic Search

A shift in outcomes of predator-prey interactions in plankton community may occur at sublethal dissolved oxygen concentrations that commonly occur in coastal waters. Laboratory experiments were conducted to investigate how a decline in dissolved oxygen concentration alters the predation rate on fish larvae by two estuarine predators. Behavior and consumption of larval fish by moon jellyfish Aurelia aurita (103.1±12.4 mm in

J. Shoji; R. Masuda; Y. Yamashita; M. Tanaka

2005-01-01

205

Using the critical body residue approach to determine the acute toxicity of cadmium at varying levels of water hardness and dissolved organic carbon concentrations.  

PubMed

The linkage between acute adverse effects of cadmium and internal cadmium levels were investigated for the oligochaete worm Lumbriculus variegatus in water at varying degrees of hardness and two different dissolved organic carbon (DOC) concentrations. The LC??s for the effect of cadmium on the survival of the worms greatly differed depending on water hardness and DOC. We found less variability in internal metal toxicity metrics (lethal residue; LR??s) than in external toxicity metrics (lethal concentration; LC??s): LC??s varied from 2.4 to 66.1 ?mol/L, while LR??s varied only from 226 to 413 ?mol/kg wet weight. The cadmium body burden appeared to be independent of exposure conditions. From our experimental data, a critical cadmium body residue (324 ± 78 ?mol/kg wet weight) associated with 50% lethality was derived. The protective role of DOC and water hardness against cadmium toxicity was evident. PMID:21481932

Penttinen, S; Malk, V; Väisänen, A; Penttinen, O-P

2011-04-09

206

Dramatic changes in the dissolved 230Th concentration of seawater in Canada Basin between 1995 and 2009: a transient Arctic circulation signal?  

NASA Astrophysics Data System (ADS)

A dissolved 230Th profile measured in the Arctic Ocean in 1983 under permanent ice cover (Alpha Ridge; 85°50'N, 108°50'W) documented concentrations substantially higher than in any other ocean basins, reflecting very low particle flux and scavenging intensity (Bacon et al., 1989). In contrast, similar measurements closer to the ice edge conducted in Canada Basin in 1995 (72°32'N, 143°50'W, 3500 m) found much lower concentrations, reflecting higher rates of particle flux and particle scavenging (Edmonds et al, 1998). In November 2007, we measured dissolved 230Th at two Canada Basin stations (KC2000; 71°44'N, 135°30'W, 1925m; KC2700; 72°28'N, 136°56'W, 2490m) and compared these profiles to that obtained in 1995. While the earlier 230Th profile displayed a linear increase in concentration with depth, as predicted by a simple reversible absorption model which neglects water mass transport, the 2007 profile obtained at KC2700 documented very large deviations from linearity, with a prominent maximum centered within the Atlantic Water. The profile taken closer to the shelf (KC2000) did not show this feature. These observations suggested that the prominent maximum in 230Th concentration at KC2700 could have been produced by entrainment of water from the permanently ice-covered Arctic interior into the warm Atlantic Water which is slowly penetrating into the eastern sector of Canada Basin and as such could provide information on the path of Atlantic Water intrusion. New data obtained from the same area in September 2009 during the Canadian IPY-GEOTRACES program documents the evolution of this signal. Reference: Bacon et al. (1989), Earth and Planet. Sci. Letters, 95, 15-22. Edmonds et al. (1998), Science, 280, 405-407.

Francois, Roger; Soon, Maureen

2010-05-01

207

Variovorax sp.-mediated biodegradation of the phenyl urea herbicide linuron at micropollutant concentrations and effects of natural dissolved organic matter as supplementary carbon source.  

PubMed

In nature, pesticides are often present as micropollutants with concentrations too low for efficient biodegradation and growth of heterotrophic pollutant-degrading bacteria. Instead, organic carbon present in environmental dissolved organic matter (eDOM) constitutes the main carbon source in nature. Information on how natural organic carbon affects degradation of pollutants and micropollutants, in particular, is however poor. Linuron-degrading Variovorax sp. strains SRS16, WDL1, and PBLH6 and a triple-species bacterial consortium, from which WDL1 originated, were examined for their ability to degrade linuron at micropollutant concentrations and the effect hereon of different eDOM formulations of varying biodegradability as supplementary C-source was explored. Individual strains and the consortium degraded linuron at initial concentrations as low as 1 ?g?L(-1) till concentrations below 4 ng?L(-1). Degradation kinetics differed among strains with rates that differed up to 70-fold at the lowest linuron concentrations and with lag phases ranging from 0 to 7 days. Linuron biodegradation by the individual strains was inhibited by an easily biodegradable compound such as citrate but stimulated by eDOM at a linuron concentration of 10 mg?L(-1). Effects were strongly reduced or became non-existent at micropollutant linuron concentrations. Effects of eDOM on degradation at 10 mg?L(-1) linuron by WDL1 were reduced when WDL1 was incubated together with its original consortium members. This is the first report on eDOM effects on degradation of pesticides at micropollutant concentrations and indicates these effects are limited and depend on linuron and eDOM concentrations, eDOM quality, and the bacterial culture. PMID:23339013

Horemans, Benjamin; Vandermaesen, Johanna; Vanhaecke, Lynn; Smolders, Erik; Springael, Dirk

2013-01-22

208

Formation of bromoform in irradiated titanium dioxide suspensions with varying photocatalyst, dissolved organic carbon and bromide concentrations  

Microsoft Academic Search

We report the formation of bromoform in TiO2 suspensions (P25) under simulated solar UV irradiation at different concentrations of photocatalyst (0.5–1.5 g L?1) as well as initial concentrations of bromide ions (1–3mg L?1) and 2,4-dihydroxybenzoic acid (2–10mg L?1). The extent of bromoform formation (3–17?g L?1) was most strongly affected by the amount of photocatalyst present and by the initial bromide

Luis A. Tercero Espinoza; Maximilian Rembor; Clara Arribas Matesanz; Axel Heidt; Fritz H. Frimmel

2009-01-01

209

In situ measurements of dissolved gases (CO2 and CH4) in a wide range of concentrations in a tropical reservoir using an equilibrator.  

PubMed

An equilibrator system connected to an infrared photo acoustic gas analyzer was used in order to measure directly in situ the concentrations of dissolved CO2 and CH4 in waters of a tropical reservoir (Petit Saut, French Guiana). The performance of the system was tested both on a vertical profile in the stratified water body of the reservoir and in the surface waters of the river downstream the dam. Results agreed with conventional GC analysis at +/-15% in a wide range of concentrations (CO2:50-400 micromol l-1 and CH4:0.5-350 micromol l-1 corresponding to gas partial pressures of respectively 1700-13,000 and 12-8800 microatm). The time needed for in situ measurements was equivalent to water sampling, time for GC analysis in the laboratory being suppressed. The continuous monitoring of gas concentrations for 24 h in the reservoir surface waters revealed rapid changes in concentrations highly significant in the daily emission budget. The system opens new perspectives for the monitoring of gas concentrations in highly dynamic systems like tropical reservoirs. PMID:16398998

Abril, Gwenaël; Richard, Sandrine; Guérin, Frédéric

2005-03-16

210

The effects of harmful algal species and food concentration on zooplankton grazer production of dissolved organic matter and inorganic nutrients  

Microsoft Academic Search

Harmful algal blooms (HABs), including toxic species, have been increasing in frequency, range, and duration over the past several decades. The effect of a harmful or toxic algal diet on zooplankton nutrient regeneration, however, has not been previously examined. In this study, we determined the effects of non-bloom and bloom concentrations of non-toxic and toxic cultures of HAB species Prorocentrum

Grace K. Saba; Deborah K. Steinberg; Deborah A. Bronk

2011-01-01

211

Rare earth precipitation and coprecipitation behavior: The limiting role of PO 4 3- on dissolved rare earth concentrations in seawater  

Microsoft Academic Search

Formation of rare earth phosphate coprecipitates, ( M i ) PO 4 ( s ), may set limits on the maximum REE concentrations observed in seawater. Examination of rare earth phosphate solubility products, as well as oceanic { M 3+ } { PO 4 3- } activity products, indicates that below approximately 300 m, the oceans are at saturation with

Robert H. Byrne; Ki-Hyun Kim

1993-01-01

212

Seasonal changes in the concentration and chemical quality of dissolved organic matter exported from wetland soils to streams in coastal temperate watersheds  

NASA Astrophysics Data System (ADS)

The concentration and chemical quality of dissolved organic matter (DOM) fluxes from terrestrial to aquatic ecosystems is an important indicator of watershed-scale hydrologic and biogeochemical processes. Understanding the relative magnitude and chemical character of these DOM fluxes is critical because DOM influences an array of biological, chemical, and physical processes. We used PARAFAC modeling of excitation- emission (EEM) fluorescence spectroscopy and biodegradable dissolved organic carbon (BDOC) incubations to investigate changes in the chemical quality of DOM along a soil-stream gradient in two watersheds in coastal Southeastern Alaska. Within each watershed, two sub-catchments (bog and forested wetland) were selected and soil solution from the sub-catchment soils, sub-catchment outlet streams and the watershed outlet streams were sampled weekly from May to October. Throughout the sampling period, concentrations of dissolved organic carbon (DOC) and BDOC were greatest in the soil solution and generally decreased in both the sub-catchment and watershed outlet streams. DOC concentrations at all sites were lowest during the spring runoff, increased during the summer growing season and decreased gradually with the onset of the fall wet season. In contrast, BDOC at all sites was highest during the spring runoff, decreased during the growing season and increased briefly during the fall wet season. The results from PARAFAC modeling indicate a strong seasonal linkage between soil solution and streams during the spring runoff and fall wet season, as demonstrated by the similar contribution of PARAFAC components in soil solution and the sub-catchment and watershed outlet streams. In particular, the relative contribution of two fluorescent amino acids, which have been attributed to tyrosine and tryptophan-like fluorescence, were very similar in both the soil solution and streams during the spring runoff and fall wet season. However, during the summer growing season, the contribution of both amino acids remained high in soil solution but drastically decreased in streams. Moreover, PARAFAC modeling of fluorescence EEMs revealed that the seasonal and longitudinal changes in the fluorescent amino acids were positively correlated with BDOC for all sites. These findings suggest that wetland soils in southeast, Alaska contribute abundant labile DOM to streams in the spring and fall. However, biological uptake of DOM along the soil-stream gradient appears to alter the character of DOM moving from terrestrial to aquatic ecosystems during the summer growing season. Our findings further suggest that DOM characterization and BDOC measurements are useful tools for evaluating seasonal changes in the biogeochemical coupling between terrestrial and aquatic ecosystems and thus, have the potential to be used as a tracer to evaluate the movement of DOM along soil-stream gradients.

Fellman, J. B.; Hood, E.; D'Amore, D. V.; Edwards, R. T.; Berkowitz, J.

2007-12-01

213

Dissolved VOC concentrations and salt contents affecting air-sweat equilibrium partition of hydrophilic and hydrophobic VOCs  

Microsoft Academic Search

Workers have frequently disregarded long-term dermal exposure to low concentration of gaseous volatile organic compounds (VOCs). To assess dermal exposure risk to gaseous VOCs, equilibrium partitioning coefficients (pc) at the air-sweat interface on human skin surface must be examined. This study analyzed the pc values of hydrophilic iso-propanol (IPA), methyl ethyl ketone (MEK), and hydrophobic benzene, toluene, ethylbenzene, o-xylene, m-xylene,

Wen-Hsi Cheng

2007-01-01

214

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

USGS Publications Warehouse

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.

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

2013-01-01

215

The Use of Semipermeable Membrane Devices to Concentrate Chemicals in Oil Refinery Effluent on the Mackenzie River  

Microsoft Academic Search

To concentrate natural and refinery-derived inducers of mixed function oxygenase (MFO), semipermeable membrane devices (SPMDs) were deployed for 11 - 12 days in Norman Wells refinery effluent and upstream and downstream on the Mackenzie River, Northwest Territories, Canada. SPMDs, which are layflat polyethylene membrane tubes containing a thin film of purified triolein, absorb freely dissolved neutral organic chemicals that diffuse

JOANNE L. PARROTT; SEAN M. BACKUS; ANNE I. BORGMANN; MURRAY SWYRIPA

216

Dissolved mercury concentrations and reactivity in mangrove waters from the Itacurussa Experimental Forest, Sepetiba Bay, SE Brazil  

Microsoft Academic Search

Mangrove waters from the Itacurussa Experimental Forest (IEF), SE Brazilare enriched in reactive-Hg (15 ± 2.0 pM) and total-Hg (28 ±2.5 pM) relative to open bay waters (4.5 ± 3.0 pM and 19 ±8.5 pM, for reactive-Hg and total-Hg respectively). Mercury concentrationsand reactivity varied according to tidal flux in mangrove creek waters.Reactive-Hg concentrations were higher in ebb tide waters ranging

L. D. Lacerda; L. F. F. Silva; R. V. Marins; S. Mounier; H. H. M. Paraquetti; J. Benaim

2001-01-01

217

The effect of wind turbine-induced microclimates and plant functional types on peatland greenhouse gas emissions and pore water dissolved organic carbon concentrations  

NASA Astrophysics Data System (ADS)

Wind turbines can affect the local climate by removing energy from the wind and increasing air turbulence with a recent study showing a cooling effect of 1.5C during the day (Baidya & Roy, 2010). Wind farms are commonly located on peatlands where both greenhouse gas carbon dioxide (CO2) and methane (CH4) fluxes and dissolved organic carbon concentrations ([DOC]) are significantly influenced by temperature and water table depth. In this paper we present data from Black Law Wind Farm, Scotland, where we examined the effect of wind turbines on (1) Microclimate - peatland surface and subsurface temperatures, soil moisture and water table depth and (2) Carbon cycling - greenhouse gas fluxes and pore water dissolved organic carbon concentrations. Within our experimental framework we examined the impact of the three main peatland plant functional types (shrubs, mosses and sedges) and their interactions with wind microclimate changes on ecosystem CO2 and CH4 fluxes and [DOC]. The sampling plots are divided into four sites along a hypothesized wind turbine-induced microclimatic gradient. At each site twelve sampling plots were established, four in areas dominated by mosses, four in areas dominated by sedges and four in areas dominated by shrubs. The results show that there are significant relationships between plot location on the hypothesized microclimatic gradient, plant functional type and their interactions and CO2 and CH4 fluxes and [DOC]. Consequently, the long-term effects of wind farms on peatland microclimates may need to be taken into account when considering their life cycle carbon budget.

Armstrong, A.; Waldron, S.; Ostle, N.; Whitaker, J.

2012-04-01

218

Addition of freely independent random variables  

Microsoft Academic Search

A direct proof is given of Voiculescu's addition theorem for freely independent real-valued random variables, using resolvents of self-adjoint operators. In contrast to the original proof, no assumption is made on the existence of moments above the second.

HANS MAASSEN

1992-01-01

219

Experimental realization of freely propagating teleported qubits  

Microsoft Academic Search

Quantum teleportation is central to quantum communication, and plays an important role in a number of quantum computation protocols. Most information-processing applications of quantum teleportation include the subsequent manipulation of the qubit (the teleported photon), so it is highly desirable to have a teleportation procedure resulting in high-quality, freely flying qubits. In our previous teleportation experiment, the teleported qubit had

Jian-Wei Pan; Sara Gasparoni; Markus Aspelmeyer; Thomas Jennewein; Anton Zeilinger

2003-01-01

220

Perennial ponds are not an important source of water or dissolved organic matter to groundwaters with high arsenic concentrations in West Bengal, India  

NASA Astrophysics Data System (ADS)

Arsenic (As) concentrations and stable hydrogen (?2H) and oxygen (?18O) isotope ratios of surface and groundwaters from a representative site in West Bengal, India, are reported. Shallow groundwaters (?35 m) from the study site have among the highest As concentrations measured in the entire Bengal Basin, reaching values in excess of 4600 ?g kg-1. Stable isotope ratios of waters from constructed, perennial ponds indicate the ponds are chiefly recharged during the summer monsoon, and subsequently undergo extensive evaporation during the dry (winter) season. In contrast, groundwaters with high As concentrations plot along the local meteoric water line (LMWL) near where the annual, volume-weighted mean precipitation values for ?2H and ?18O would plot. The stable isotope data demonstrate that groundwaters are directly recharged by local precipitation without significant evaporation, and thus are not recharged by, nor mixed with, the pond waters. Furthermore, reactive transport modeling indicates that dissolved organic matter (DOM) derived from pond waters does not fuel microbial respiration and As mobilization at depth in the underlying aquifer because travel times for pond-derived DOM exceed groundwater ages by thousands of years. Instead, organic matter within the aquifer sediments must drive dissimilatory iron reduction and As release to groundwaters.

Datta, Saugata; Neal, Andrew W.; Mohajerin, T. Jade; Ocheltree, Troy; Rosenheim, Brad E.; White, Christopher D.; Johannesson, Karen H.

2011-10-01

221

Application of extraction chromatography to the separation of thorium and uranium dissolved in a solution of high salt concentration.  

PubMed

Extraction chromatography with commercially available UTEVA resin (for uranium and tetravalent actinide) was applied for the separation of Th and U from control solutions prepared from a multi-element control solution and from sample solutions of solidified simulated waste. Thorium and U in control solutions with 1-5mol/dm(3) HNO(3) were extracted with UTEVA resin and recovered with a solution containing 0.1mol/dm(3) HNO(3) and 0.05mol/dm(3) oxalic acid to be separated from the other metallic elements. Extraction behavior of U in the sample solutions was similar to that in the control solutions, but extraction of Th was dependent on the concentration of HNO(3). Thorium was extracted from 5mol/dm(3) HNO(3) sample solutions but not from 1mol/dm(3) HNO(3) sample solutions. We conjecture that thorium fluoride formation interferes with extraction of Th. Addition of Al(NO(3))(3) and Fe(NO(3))(3), which have higher stability constant with fluoride ion than Th, does improve extractability of Th from 1mol/dm(3) HNO(3) sample solution. PMID:17161412

Fujiwara, Asako; Kameo, Yutaka; Hoshi, Akiko; Haraga, Tomoko; Nakashima, Mikio

2006-12-11

222

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

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.

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

1982-08-01

223

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

USGS Publications Warehouse

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.

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

2003-01-01

224

Freely Suspended Smectic Films in Aqueous Environment  

NASA Astrophysics Data System (ADS)

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.

Peddireddy, Karthik; Bahr, Christian

2012-02-01

225

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

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.

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

2008-01-01

226

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

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

Katherine Barbeau

2007-04-10

227

Mapping brain function in freely moving subjects.  

PubMed

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

Holschneider, Daniel P; Maarek, Jean-Michel I

2004-09-01

228

METHOD OF DISSOLVING MASSIVE PLUTONIUM  

DOEpatents

Massive plutonium can be dissolved in a hot mixture of concentrated nitric acid and a small quantity of hydrofluoric acid. A preliminary oxidation with water under superatmospheric pressure at 140 to 150 deg C is advantageous

Facer, J.F.; Lyon, W.L.

1960-06-28

229

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

230

Use of a long endurance solar powered autonomous underwater vehicle (SAUV II) to measure dissolved oxygen concentrations in Greenwich Bay, Rhode Island, U.S.A  

Microsoft Academic Search

As hypoxic water masses increase worldwide in duration and extent due to coastal eutrophication, advanced technology water quality monitoring by autonomous vehicles can increase our capability to document and respond to these environmental perturbations. We evaluated the use of a long endurance autonomous underwater vehicle (AUV) to map dissolved oxygen levels to determine the extent of hypoxia in a small

Denise Crimmins; C. Deacutis; E. Hinchey; M. Chintala; G. Cicchetti; Dick Blidberg

2005-01-01

231

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

232

The contribution of capsaicin-sensitive sensory nerves to xylene-induced visceral pain in conscious, freely moving rats  

Microsoft Academic Search

1.Intravesical instillation of xylene (10–100%, dissolved in silicone oil) through a catheter implanted into the bladder of conscious, freely-moving rats produced behavioural effects (licking of lower abdomen or perineal region) suggestive of intense visceral pain, not mimicked by topical application of the irritant on the urethral outlet.2.The xylene-induced visceral pain was prevented, to the same extent, by systemic desensitization to

Luigi Abelli; Bruno Conte; Vincenzo Somma; Carlo Alberto Maggi; Sandro Giuliani; Pierangelo Geppetti; Massimo Alessandri; Elvar Theodorsson; Alberto Meli

1988-01-01

233

Dissolved Oxygen Protocol  

NSDL National Science Digital Library

The purpose of this resource is to measure the amount of oxygen dissolved in water. Students use a dissolved oxygen kit or meter to measure the dissolved oxygen in the water at their hydrology site. The exact procedure depends on the instructions in the dissolved oxygen kit or meter used. The meter requires calibration before use.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

234

Chemistry Review: Dissolving  

NSDL National Science Digital Library

This resource clearly defines and summarizes all the aspects of the dissolving of liquids, with detailed examples of different substances dissolving together. There are videos that show dissolving examples, as well as models that show substances at their molecular level. The chemical make-up of substances such as water and oil are included to better understand the dissolving process and to learn which substances dissolve and which ones do not.

Kessler, James; Galvan, Patti

2010-01-01

235

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

SciTech Connect

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.

Oikari, A.; Kukkonen, J. (Univ. of Joensuu (Finland))

1990-07-01

236

Documentation of hydrochemical-facies data and ranges of dissolved-solids concentrations for the northern Atlantic Coastal Plain aquifer system, New Jersey, Delaware, Maryland, Virginia and North Carolina supplement to Professional paper 1404-L  

USGS Publications Warehouse

Hydrochemical-facies data and ranges of dissolved- solids concentrations used to construct hydrochemical-facies maps and sections for U.S. Geological Survey Professional Paper 1404-L have not been previously published. In this report, the data are contained on a 3-1/2 high-density diskette in a file presented in American International Standard Code for Information Exchange (ASCII) format. The file requires about 0.2 megabyte of disk space on an IBM-compatible microcomputer using the MS-DOS operating system.

Meisler, Harold; Knobel, L. L.

1994-01-01

237

Freely propagating open premixed turbulent flames stabilized by swirl  

SciTech Connect

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.

Chan, C.K.; Lau, K.S.; Chin, W.K. (Hong Kong Polytechnic, Kowloon (Hong Kong)); Cheng, R.K. (Lawrence Berkeley Lab., CA (United States))

1991-12-01

238

Effect of low dissolved oxygen concentrations on the ventilation rhythm of three tubicolous crustaceans, with special reference to the phenomenon of intermittent ventilation  

Microsoft Academic Search

The pleopod ventilatory activity of the tube-dwelling amphipods Corophium volutator (Pallas) and C. arenariumCrawford is intermittent. Unlike the free-living amphipod Marinogammarus obtusatus (Dahl), which increases its rate of pleopod beating, the pleopod beat rate of both Corophium species is unaffected by low oxygen concentrations. However, the nature of the intermittent ventilation rhythm is altered so that, at low oxygen concentrations,

J. C. Gamble

1970-01-01

239

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

Microsoft Academic Search

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

Peter F. Folger; R. B. Wanty; E. Poeter; P. Nyberg

1994-01-01

240

An exploration of how litter controls drainage water DIN, DON and DOC dynamics in freely draining acid grassland soils  

Microsoft Academic Search

Surface and subsurface litter fulfil many functions in the biogeochemical cycling of C and N in terrestrial ecosystems. These\\u000a were explored using a microcosm study by monitoring dissolved inorganic nitrogen (DIN) (NH4\\u000a +–N + NO3\\u000a ?–N), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations and fluxes in drainage water under\\u000a ambient outdoor temperatures. Subsurface litter remarkably reduced the DIN concentrations

Muhammad RiazIshaq; Ishaq A. Mian; Ambreen Bhatti; Malcolm S. Cresser

241

Crank inertial load affects freely chosen pedal rate during cycling.  

PubMed

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

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

2002-02-01

242

Combined effects of dissolved oxygen concentration and water temperature on embryonic development and larval shell secretion in the marine snail Chorus giganteus (Gastropoda: Muricidae)  

Microsoft Academic Search

The present study was undertaken to determine the effects of both extracapsular oxygen concentration and temperature on embryonic development in Chorus giganteus. In normoxia increasing water temperature from 12°C to 18°C reduced by 15 days the median time required for the capsules to hatch. Hypoxia (oxygen content at 50% of air saturation) generated a low development rate and totally prevented

J. M. Cancino; J. A. Gallardo; F. A. Torres

2003-01-01

243

A feeding inhibition based prediction of the toxic effect of dissolved metal mixtures upon Echinogammarus marinus (Crustacea: Amphipoda) at field relevant concentrations across a latitudinal gradient.  

PubMed

Risk assessment of metals in the environment is performed mainly with toxicity evaluations on single metals, which is largely inadequate since these substances occur in mixtures. The development of models predicting combined toxic effects on the basis of the concentration-response relationships of individual compounds has emerged as an answer. In the present study, metal effects on post-exposure anorexia (the concept of FdC(50)--concentration causing 50% of feeding inhibition--is implemented) in Echinogammarus marinus, a widely distributed gammarid amphipod, were assessed and compared with modelled ones obtained through the application of the concentration addition (CA) model, which represents a reasonable worst-case scenario for the risk assessment of metal mixtures. Data were validated using in situ experiments performed along a latitudinal gradient (Iceland, Scotland and Portugal) aiming at establishing a geographic profile of autochthonous population susceptibilities to metals. For all of the metals studied concentrations in the water column at exposure sites were in good agreement with feeding inhibition levels. Models gave low to relatively high percentage agreement between predictions and experimental data. Boreal populations demonstrated higher susceptibility to single metals, but not to mixture exposures. Meridional populations denoted lower susceptibilities with higher FdC(50). PMID:22048725

Pastorinho, M Ramiro; Telfer, Trevor C; Soares, Amadeu M V M; Nogueira, António J A

2011-11-03

244

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...

245

Passive sampling to measure baseline dissolved persistent organic pollutant concentrations in the water column of the Palos Verdes Shelf Superfund site.  

PubMed

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. Precalibrated solid phase microextraction (SPME) fibers and polyethylene (PE) strips that were preloaded with performance reference compounds (PRCs) were codeployed for 32 d along an 11-station gradient at bottom, surface, and midwater depths. Retrieved samplers were analyzed for DDT congeners and their breakdown products (DDE, DDD, DDMU, and DDNU) and 43 PCB congeners using GC-EI- and NCI-MS. PRCs were used to calculate compound-specific fractional equilibration achieved in situ for the PE samplers, using both an exponential approach to equilibrium (EAE) and numerical integration of Fickian diffusion (NI) models. The highest observed concentrations were for p,p'-DDE, with 2200 and 990 pg/L deduced from PE and SPME, respectively. The difference in these estimates could be largely attributed to uncertainty in equilibrium partition coefficients, unaccounted for disequilibrium between samplers and water, or different time scales over which the samplers average. The concordance between PE and SPME estimated concentrations for DDE was high (R(2) = 0.95). PCBs were only detected in PE samplers, due to their much larger size. Near-bottom waters adjacent to and down current from sediments with the highest bulk concentrations exhibited aqueous concentrations of DDTs and PCBs that exceeded Ambient Water Quality Criteria (AWQC) for human and aquatic health, indicating the need for future monitoring to determine the effectiveness of remedial activities taken to reduce adverse effects of contaminated surface sediments. PMID:23062073

Fernandez, Loretta A; Lao, Wenjian; Maruya, Keith A; White, Carmen; Burgess, Robert M

2012-10-26

246

Vertical profiles of CH 4 concentrations, dissolved substrates and processes involved in CH 4 production in a flooded Italian rice field  

Microsoft Academic Search

Vertical profiles were measured in soil cores taken from flooded rice fields in the Po valley during July and August 1990.\\u000a Methane concentrations generally increased with depth and reached maximum values of 150–500 ?M in 5–13 cm depth. However,\\u000a the shape of the profiles was very different when studying different soil cores. The CH4 content of gas bubbles showed a

Franz Rothfuss; Ralf Conrad

1992-01-01

247

Relative importance of hydrogen-ion concentration, temperature, dissolved oxygen, and carbon dioxide tension on habitat selection by brook-trout. [Brook  

Microsoft Academic Search

While certain stream conditions such as protecting obstructions, riffled feeding beds, and the like are selected by brook-trout and determine to some extent their local distribution, it has been shown that streams tolerable to brook-trout cannot be determined upon such characteristics. The range of voluntary toleration of hydrogen-ion concentration by brook-trout is greater than the maximum and minimum values found

Creaser

1930-01-01

248

Concentration of Mn and separation from Fe in sediments--I. Kinetics and stoichiometry of the reaction between birnessite and dissolved Fe(II) at 10°C  

Microsoft Academic Search

Redox reactions between Fe 2+ in solution and Mn-oxides are proposed as a mechanism for concentration of Mn in sediments both during weathering and diagenesis in marine sediments, e.g. the formation of Mn-nodules. If such a mechanism is to be effective, then reaction rates between Fe 2+ and Mn-oxides should be fast. The kinetics and stoichiometry of the reaction between

Dieke Postma

1985-01-01

249

Spatial and Temporal Variability in Dissolved Organic Matter (DOM) Concentrations Along a 90km Reach of the San Pedro River, AZ.  

NASA Astrophysics Data System (ADS)

River and stream systems of the arid and semi-arid southwestern U.S. are quantitatively and qualitatively different from rivers in more mesic systems. Water sources are localized in both space (e.g. mountain fronts) and time (e.g. monsoon precipitation) resulting in high seasonality in discharge. Furthermore, losing reaches often dominate the length of the river, interspersed with isolated groundwater inflows that regenerate flow. Consequently, the distance water and solutes at any one point may travel or "spiral" downstream is likely to vary significantly due to changes in flow regime. Five synoptic sampling events were performed along the San Pedro River in Southeastern AZ to understand how seasonal changes in discharge affect the biogeochemical linkages between upstream and downstream reaches in this perennial stream. During baseflow periods before the summer monsoon both conservative solutes (Cl- and Br-) and DOM reflected local sources and sinks with little indication of significant solute transport between upstream and downstream reaches. During the monsoon season baseflow (between storms) discharge increased by a factor of 2 to 5, Cl- and Br- decreased by a factor of 2 to 3, and DOM concentrations approximately doubled. Stable Cl- and Br- concentrations during the monsoon suggest the entire 90 km reach was linked hydrologically and changes in DOM concentrations reflected variable sources and sinks of organic matter. As the monsoon season ended hydrologic and biogeochemical connectivity along the 90 km reach was broken and solute concentrations began to reflect more and more localized sources, similar to the pattern observed pre-monsoon. These data suggest that the increase in discharge associated with monsoon season precipitation connects previously isolated stream reaches not only during flood, but during elevated summer baseflow.

Lemon, M. M.; Brooks, P. D.; Huth, A. K.; Villinski, J.

2002-12-01

250

Dissolving Ag from Au-Ag Alloy Nanoboxes with H2O2: A Method for Both Tailoring the Optical Properties and Measuring the H2O2 Concentration  

PubMed Central

This article describes a method for generating Au-based nanocages with controlled wall thickness, porosity, and optical properties by dissolving Ag from Au-Ag alloy nanoboxes with H2O2. It involves two steps: i) formation of Au-Ag alloy nanoboxes with some pure Ag left behind by titrating Ag nanocubes with aqueous HAuCl4; and ii) removal of Ag atoms from both the pure Ag remaining in the nanoboxes and the alloy walls via H2O2 etching. The optical properties of the resultant Au-Ag nanocages can be easily tailored by controlling the amount of H2O2 added into the reaction system. Due to the changes to the optical spectra, the Au-Ag alloy nanoboxes can also be employed to detect H2O2 with a more or less linear readout in the range of concentration from 5×10?2 M down to 5×10?7 M.

Zhang, Qiang; Cobley, Claire M.; Zeng, Jie; Wen, Long-Ping; Chen, Jingyi; Xia, Younan

2010-01-01

251

Pore water dating by 129I: What do 36Cl/Cl ratio, dissolved 4He concentration, ?37Cl and 129I/127I ratio suggest in the Mobara Gas field, Japan?  

NASA Astrophysics Data System (ADS)

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, ?37Cl (- 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 ?37Cl 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 variation of ?37Cl was significantly happened by diffusion alone. This suggested that pore water was such stagnant that 35Cl atoms were slightly separated from 37Cl atoms by diffusion. The origin of brines at Mobara was estimated to be connate seawater left in pore of sediments thickly depositing on the deep sea floor. Consequently, iodine in brine at Mobara was not transported from long distant other places or deep stratum, but was released into pore water from the deposited sediments that iodine was retained with a high concentration under a strong reducing condition. In conclusion, we cannot simply date pore water by using 129I/127I ratio, without deeply considering the origin of iodine and enrichment process. Reference D. E. Desaulniers, R. S. Kaufmann, J. A. Cherry and H. W. Bentley (1986) 37Cl-35Cl variations in a diffusion-controlled groundwater system.

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

2010-12-01

252

Regulation of stream water dissolved organic carbon concentrations ([DOC]) during snowmelt in forest streams; the role of discharge, winter climate and memory effects  

NASA Astrophysics Data System (ADS)

Using 15 year stream records from two forested northern boreal catchments, coupled with soil frost experiments in the riparian zone, we demonstrate the complex inter-annual control on [DOC] and export during snowmelt. Stream [DOC] varied by a factor of 2 during those 15 years with no consistent trend. Based on our long-term analysis, we demonstrate, for the first time, that stream water [DOC] is strongly linked to the climatic conditions during the preceding winter, but that there is also a long-term memory effect in the catchment soils, related to the extent of the previous export from the catchment. Hydrology had a first order control on the inter-annual variation in concentrations, and the length of the winter was more important than the memory effect. By removing the effect of discharge on [DOC], using a conceptual hydrological model, we could detect processes that would otherwise have been overshadowed. A short and intense snowmelt gave higher [DOC] in the stream. During a prolonged snowmelt, one soil layer at the time might have been "flushed" from easily exported DOC, resulting in slightly lower stream [DOC] during such years. We found that longer and colder winters resulted in higher [DOC] during the subsequent snowmelt. A soil frost manipulation experiment in the riparian soils of the study catchment showed that the DOC concentrations in the soil water increased with the duration of the soil frost. A high antecedent DOC export during the preceding summer and autumn resulted in lower concentrations during the following spring, indicating a long-term "memory effect" of the catchment soils. In a nearby stream draining mire, we found a different response to hydrology but similar response to climate and memory effect. The inter-annual variation in snowmelt DOC exports was mostly controlled by the amount of runoff, but the variability in [DOC] also exerted a significant control on the exports, accounting for 15% of the variance in exports. We conclude that winter climatic conditions can play a substantial role in controlling stream [DOC] in ways not previously understood. These findings are especially important for northern latitude regions expected to be most affected by climate change. It's difficult to directly translate this to a future climate change prediction. If warmer winters with less insulating snow cover increase the soil frost, the results from the soil frost manipulation experiment then suggest increasing [DOC] in a future climate. At the same time the statistical analysis of the stream records suggest that a shorter and warmer winter would decrease the [DOC]. Our results do, however, highlight the role of winter climate for regulating DOC in areas with seasonally frozen soils which should be considered when resolving the sensitivity of stream [DOC] to global environmental change.

Ågren, A.; Haei, M.; Öquist, M.; Buffam, I.; Ottosson-Löfvenius, M.; Kohler, S.; Bishop, K.; Blomkvist, P.; Laudon, H.

2011-12-01

253

A Freely Available Automatically Generated Thesaurus of Related Words  

Microsoft Academic Search

A freely available English thesaurus of related words is presented that has been automatically compiled by analyzing the distributional similarities of words in the British National Corpus. The quality of the results has been evaluated by comparison with human judg- ments as obtained from non-native and native speakers of English who were asked to provide rankings of word similarities. According

Reinhard Rapp

2004-01-01

254

Reshaping of freely propagating terahertz pulses by diffraction  

Microsoft Academic Search

We discuss the application of diffraction theory to the reshaping of freely propagating terahertz pulses by narrow apertures. This is accomplished by using two separate electrooptic sampling detectors. The first contains a narrow electrode geometry that does not modify the frequency content of the incident terahertz field, while the second contains a narrow gap between two large electrodes. The latter

Ajay Nahata; Tony F. Heinz

1996-01-01

255

Optogenetic manipulation of neural activity in freely moving Caenorhabditis elegans  

Microsoft Academic Search

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 in specific cell types. Image processing software analyzes the worm's position in each video frame, rapidly estimates the locations of targeted cells and

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

2011-01-01

256

High-speed, miniaturized fluorescence microscopy in freely moving mice  

PubMed Central

A central goal in biomedicine is to explain organismic behavior in terms of causal cellular processes. However, concurrent observation of mammalian behavior and underlying cellular dynamics has been a longstanding challenge. We describe a miniaturized (1.1 g mass) epifluorescence microscope for cellular-level brain imaging in freely moving mice, and its application to imaging microcirculation and neuronal Ca2+ dynamics.

Flusberg, Benjamin A; Nimmerjahn, Axel; Cocker, Eric D; Mukamel, Eran A; Barretto, Robert P J; Ko, Tony H; Burns, Laurie D; Jung, Juergen C; Schnitzer, Mark J

2010-01-01

257

Evaluation of modal stress resultants in freely vibrating plates  

Microsoft Academic Search

In the dynamic analysis of a very large floating structure (VLFS), it is crucial that the stress resultants are accurately determined for design purposes. This paper highlights some problems in obtaining accurate modal stress-resultant distributions in freely vibrating rectangular plates (for modeling box-like VLFSs) using various conventional methods. First, it is shown herein that if one adopts the classical thin

C. M. Wang; Y. Xiang; T. Utsunomiya; E. Watanabe

2001-01-01

258

Stormflow Dynamics of Dissolved Organic Carbon and Total Dissolved Nitrogen in a Small Urban Watershed  

Microsoft Academic Search

We examined patterns of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) loading to a small urban stream during baseflow and stormflow. We hypothesized that lower DOC and TDN contributions from impervious surfaces would dilute natural hydrologic flowpath (i.e., riparian) contributions during storm events in an urban watershed, resulting in lower concentrations of DOC and TDN during storms. We

Aaron M. Hook; J. Alan Yeakley

2005-01-01

259

Photochemical and microbial degradation of dissolved lignin phenols: Implications for the fate of terrigenous dissolved organic matter in marine environments  

Microsoft Academic Search

Molecular level characterizations of dissolved lignin were conducted in Mississippi River plume waters to study the impact of various removal mechanisms (photooxidation, microbial degradation, and flocculation) on dissolved organic material (DOM) concentrations and compositions. Prior to analysis, dissolved (1 kDalton) and low molecular weight (LMW; <1 kDalton) components. At salinities 25 psu, photooxidation was a dominant factor influencing lignin compositions

Peter J. Hernes; Ronald Benner

2003-01-01

260

Water What-ifs: Water Quality and Dissolved Oxygen  

NSDL National Science Digital Library

This Science Junction website features general information and three lesson plans about dissolved oxygen geared toward middle and high school students. Lessons cover topics such as what dissolved oxygen is, why it is important, and how decomposition of organic material affects dissolved oxygen. The third lesson includes an activity in which students are instructed to design an experiment to test effects of changes in dissolved oxygen concentration. The lessons meet several National Science Education Standards, Delaware science standards, and North Carolina competency goals.

Cleveland, April J.; Science Junction, Nc S.

261

Dissolver vessel bottom assembly  

DOEpatents

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.

Kilian, Douglas C. (Kennewick, WA)

1976-01-01

262

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

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

Medalie, Laura

2013-01-01

263

Relative entropy of a freely cooling granular gas  

NASA Astrophysics Data System (ADS)

The time evolution and stationary values of the entropy per particle of a homogeneous freely cooling granular gas, relative to the maximum entropy consistent with the instantaneous translational and rotational temperatures, is analyzed by means of a Sonine approximation involving fourth-degree cumulants. The results show a rich variety of dependencies of the relative entropy on time and on the coefficients of normal and tangential restitution, including a peculiar behavior in the quasi-smooth limit.

Santos, Andrés; Kremer, Gilberto M.

2012-11-01

264

Strength training reduces freely chosen pedal rate during submaximal cycling  

Microsoft Academic Search

The freely chosen pedal rate is relatively high and energetically inefficient during submaximal cycling, which is a paradox\\u000a since the rate of energy expenditure is considered important for voluntary motor behavior in other cyclical activities as,\\u000a e.g., running. For example, it has been suggested that subjects pedal fast to reduce the perception of force. In this study,\\u000a we investigated the

Ernst Albin Hansen; Truls Raastad; Jostein Hallén

2007-01-01

265

Electrochemistry of Dissolved Gases.  

National Technical Information Service (NTIS)

The electrochemistry of various dissolved gases has been investigated as a function of the gas, solution pH, supporting electrolyte, electrode material, and the preconditioning of the electrode surfaces. These investigations have been conducted through th...

D. T. Sawyer

1965-01-01

266

Dissolving Ag from Au-Ag Alloy Nanoboxes with H(2)O(2): A Method for Both Tailoring the Optical Properties and Measuring the H(2)O(2) Concentration.  

PubMed

This article describes a method for generating Au-based nanocages with controlled wall thickness, porosity, and optical properties by dissolving Ag from Au-Ag alloy nanoboxes with H(2)O(2). It involves two steps: i) formation of Au-Ag alloy nanoboxes with some pure Ag left behind by titrating Ag nanocubes with aqueous HAuCl(4); and ii) removal of Ag atoms from both the pure Ag remaining in the nanoboxes and the alloy walls via H(2)O(2) etching. The optical properties of the resultant Au-Ag nanocages can be easily tailored by controlling the amount of H(2)O(2) added into the reaction system. Due to the changes to the optical spectra, the Au-Ag alloy nanoboxes can also be employed to detect H(2)O(2) with a more or less linear readout in the range of concentration from 5×10(-2) M down to 5×10(-7) M. PMID:20495675

Zhang, Qiang; Cobley, Claire M; Zeng, Jie; Wen, Long-Ping; Chen, Jingyi; Xia, Younan

2010-03-01

267

Dissolved silver in the Baltic Sea  

Microsoft Academic Search

The increased use of silver as a biocide in nanoparticle formulations has heightened concern on possible environmental implications owing to its toxicity. There is however very little data on the concentration levels of silver in marine and freshwaters. Here, I report data on dissolved (<0.4?m filter) silver concentration in the surface waters of the Baltic Sea, the first such data

Kuria Ndungu

2011-01-01

268

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

USGS Publications Warehouse

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.

Galloway, Joel M.; Green, W. Reed

2003-01-01

269

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...

270

PROCESS OF DISSOLVING ZIRCONIUM ALLOYS  

DOEpatents

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.

Shor, R.S.; Vogler, S.

1958-01-21

271

Developing Standards for Dissolved Iron in Seawater  

NASA Astrophysics Data System (ADS)

In nearly a dozen open-ocean fertilization experiments conducted by more than 100 researchers from nearly 20 countries, adding iron at the sea surface has led to distinct increases in photosynthesis rates and biomass. These experiments confirmed the hypothesis proposed by the late John Martin that dissolved iron concentration is a key variable that controls phytoplankton processes in ocean surface waters. However, the measurement of dissolved iron concentration in seawater remains a difficult task with significant interlaboratory differences apparent at times. The availability of a seawater reference solution with well-known dissolved iron (Fe) concentrations similar to open-ocean values, which could be used for the calibration of equipment or other tasks, would greatly alleviate these problems.

Johnson, Kenneth S.; Boyle, Edward; Bruland, Kenneth; Coale, Kenneth; Measures, Chris; Moffett, James; Aguilar-Islas, Ana; Barbeau, Katherine; Bergquist, Bridget; Bowie, Andrew; Buck, Kristen; Cai, Yihua; Chase, Zanna; Cullen, Jay; Doi, Takashi; Elrod, Virginia; Fitzwater, Steve; Gordon, Michael; King, Andrew; Laan, Patrick; Laglera-Baquer, Luis; Landing, William; Lohan, Maeve; Mendez, Jeffrey; Milne, Angela; Obata, Hajime; Ossiander, Lia; Plant, Joshua; Sarthou, Geraldine; Sedwick, Peter; Smith, Geoffrey J.; Sohst, Bettina; Tanner, Sara; Van den Berg, Stan; Wu, Jingfeng

2007-03-01

272

Freely accessible water does not decrease consumption of ethanol liquid diets.  

PubMed

In experimental studies, liquid ethanol diets are usually given as the sole source of nutrition and fluid. Two series of experiments were conducted to examine the effect of freely accessible water on the consumption of ethanol liquid diets in male Long-Evans rats. The consumption of diets and subsequent learning ability of rats were first examined in animals given twice-daily saline injections. One group received diet with no access to water for 12 weeks and was subsequently given free access to water with diets for an additional 12 weeks. A second group was given diet and water ad libitum for 24 weeks. Control animals received an isocaloric sucrose-containing diet (with or without ad libitum access to water). Subsequently, rats were tested for active avoidance learning. In the first 12 weeks, animals with ad libitum access to water drank more diet than did water-restricted animals, and previously water-restricted animals increased their diet consumption when access to water was freely available. All water-restricted animals, in both ethanol- and sucrose-treated groups, showed deficits in active avoidance learning, whereas only ethanol-treated animals in groups with ad libitum access to water showed learning deficits. In the second series of experiments, the effect of saline injections on diet consumption, both in the presence and absence of water, was examined. Although saline injections were associated with decreased diet consumption, there was no effect of free access to water. No differences in blood ethanol concentration were seen among groups. Findings obtained from both series of studies demonstrate that consumption of a Sustacal-based liquid ethanol diet does not decrease if access to water is freely available. PMID:12782247

de Fiebre, NancyEllen C; de Fiebre, Christopher M

2003-02-01

273

Dissolved Oxygen in Water  

Microsoft Academic Search

\\u000a After performing this experiment, the student shall be able to:\\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a Determine the level of dissolved oxygen in a sample of water using Winkler’s method.\\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a Analyze the effects of various factors on the level of dissolved oxygen in a water sample (e.g., salt content, temperature,\\u000a degree of mixing, and the presence of reducing compounds).

Jorge G. Ibanez; Margarita Hernandez-Esparza; Carmen Doria-Serrano; Arturo Fregoso-Infante; Mono Mohan Singh

274

Melting and dissolving  

NASA Astrophysics Data System (ADS)

The different modes of convection which may arise in diffusion-governed melting of a pure solid into a binary melt, when the interface between the solid and the melt is horizontal are investigated. It is shown that, in the dissolving regime, a relatively warm solid may dissolve into a relatively cold liquid. The nature of the convection which may arise as the geometry and the melt composition are varied is determined by calculating the difference between the density of the melt at the solid interface and the density of the liquid far from the interface. The analysis is generalized by considering binary solid solutions.

Woods, Andrew W.

1992-06-01

275

Dissolved Oxygen Activity  

NSDL National Science Digital Library

One of the most important measures of the health of the stream is the level of dissolved oxygen (DO) in the water. Oxygen (O2) dissolves in water through the mixing of the water surface with the atmosphere. The oxygen is used by fish and other animals in the water to "breath" through their gills or other respiratory systems and by plants. If the levels fall too low, many species of fish, macroinvertebrates, and plants cannot survive. At very low levels of oxygen, the stream becomes "septic" and smells rotten because low oxygen sulfur bacteria begin to dominate.

Gordon, Steve

276

Dissolved Oxygen Model  

NSDL National Science Digital Library

One of the most important measures of the health of the stream is the level of dissolved oxygen (DO) in the water. Oxygen (O2) dissolves in water through the mixing of the water surface with the atmosphere. The oxygen is used by fish and other animals in the water to "breath" through their gills or other respiratory systems and by plants. If the levels fall too low, many species of fish, macroinvertebrates, and plants cannot survive. At very low levels of oxygen, the stream becomes "septic" and smells rotten because low oxygen sulfur bacteria begin to dominate.

Gordon, Steve

277

Temperature Affects Dissolving  

NSDL National Science Digital Library

In this activity will compare how well cocoa mix dissolves in cold and hot water. They will see that cocoa mix dissolves much better in hot water. There is a downloadable activity sheet that will be very helpful to educators, and will help students stay on track. An assessment sheet is also available on the activity page to keep track of students progress. There is also a step by step guide as to how to perform the experiment, and how to introduce it t the students.

Kessler, James; Galvan, Patti

2010-01-01

278

Ovariectomy improves neovascularization and microcirculation of freely transplanted ovarian follicles.  

PubMed

To investigate the influence of ovariectomy on the physiological process of neovascularization of ovarian follicles, we harvested follicles with a theca interna at 48 h after pregnant mare's serum gonadotropin (PMSG) treatment of Syrian golden hamsters, for subsequent transplantation onto striated muscle tissue of chronically implanted skinfold chambers of non-ovariectomized PMSG-synchronized hamsters and bilaterally ovariectomized hamsters. Non-ovariectomized non-PMSG-treated animals served as controls. During a 2 week period after transplantation, neovascularization of these freely transplanted grafts was quantified in vivo by assessment of the newly developed microvascular follicular network, its microvessel density, the diameter of microvessels and their volumetric blood flow using fluorescence microscopic techniques. At day 3 after transplantation, capillary sprouts could be observed in all groups studied, finally developing a complete glomerulum-like microvascular network within 5-10 days. In ovariectomized animals, however, vascularization of follicular tissue was found to be accelerated and enhanced when compared with the follicles in both groups of non-ovariectomized animals. This was associated with significantly higher capillary blood perfusion, which may in part represent the graft's adaptive response to pro-angiogenic stimuli due to elevated gonadotropin levels, but might in particular be mediated by gonadotropin-induced release of vasoactive substances. Interestingly, small preantral follicles lacking a theca interna failed to vascularize in either of the groups. In conclusion, the study demonstrates that ovariectomy improves neovascularization and microcirculation of freely transplanted ovarian follicles. PMID:11874702

Laschke, M W; Menger, M D; Vollmar, B

2002-03-01

279

A freely falling magneto-optical trap drop tower experiment  

NASA Astrophysics Data System (ADS)

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.

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

280

Wireless Neural Stimulation in Freely Behaving Small Animals  

PubMed Central

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

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

2009-01-01

281

Optogenetic control of targeted peripheral axons in freely moving animals.  

PubMed

Optogenetic control of the peripheral nervous system (PNS) would enable novel studies of motor control, somatosensory transduction, and pain processing. Such control requires the development of methods to deliver opsins and light to targeted sub-populations of neurons within peripheral nerves. We report here methods to deliver opsins and light to targeted peripheral neurons and robust optogenetic modulation of motor neuron activity in freely moving, non-transgenic mammals. We show that intramuscular injection of adeno-associated virus serotype 6 enables expression of channelrhodopsin (ChR2) in motor neurons innervating the injected muscle. Illumination of nerves containing mixed populations of axons from these targeted neurons and from neurons innervating other muscles produces ChR2-mediated optogenetic activation restricted to the injected muscle. We demonstrate that an implanted optical nerve cuff is well-tolerated, delivers light to the sciatic nerve, and optically stimulates muscle in freely moving rats. These methods can be broadly applied to study PNS disorders and lay the groundwork for future therapeutic application of optogenetics. PMID:23991144

Towne, Chris; Montgomery, Kate L; Iyer, Shrivats M; Deisseroth, Karl; Delp, Scott L

2013-08-21

282

ADDING REALISM TO NUCLEAR MATERIAL DISSOLVING ANALYSIS  

SciTech Connect

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.

Williamson, B.

2011-08-15

283

Littoral-Pelagial Interactions: The Role of Dissolved Humic Materials.  

National Technical Information Service (NTIS)

Relationships between ultraviolet absorbance, fluorescence, and concentrations of dissolved organic carbon (DOC) were examined in four model humic materials. Fluorescence was consistently a poor predictor of DOC concentration, and absorbance correctly pre...

A. J. Stewart

1980-01-01

284

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

PubMed

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

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

2011-06-07

285

Lap-Dissolve Slides  

ERIC Educational Resources Information Center

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

Fine, Leonard W.; And Others

1977-01-01

286

Dissolving a Partnership Efficiently  

Microsoft Academic Search

Several partners jointly own an asset that may be traded among them. Each partner has a valuation for the asset. The valuations are known privately and drawn independently from a common probability distribution. The authors characterize the set of all incentive- compatible and interim individually-rational trading mechanisms, and give a simple necessary and sufficient condition for such mechanisms to dissolve

Peter Cramton; Robert Gibbons; PAUL KLEMPERERI

1987-01-01

287

Using polyacrylate-coated SPME fibers to quantify sorption of polar and ionic organic contaminants to dissolved organic carbon.  

PubMed

A passive sampling method using polyacrylate-coated solid-phase microextraction (SPME) fibers was applied to determine sorption of polar and ionic organic contaminants to dissolved organic carbon (DOC). The tested contaminants included pharmaceuticals, industrial chemicals, hormones, and pesticides and represented neutral, anionic, and cationic structures. Prior to the passive sampler application, sorption of the chemicals to the fibers was characterized. This was needed in order to accurately translate concentrations measured in fibers to freely dissolved aqueous concentrations during the sorption tests with DOC. Sorption isotherms of neutral compounds to the fiber were linear, whereas isotherms of basic chemicals covered a nonlinear and a linear range. Sorption of acidic and basic compounds to the fiber was pH-dependent and was dominated by sorption of the neutral sorbate species. Fiber- and DOC-water partition coefficients of neutral compounds were both linearly related to octanol-water partition coefficients (log Kow). The results of this study show that polyacrylate fibers can be used to quantify sorption to DOC of neutral and ionic contaminants, having multiple functional groups and spanning a wide hydrophobicity range (log Kow = 2.5-7.5). PMID:23586731

Haftka, Joris J-H; Scherpenisse, Peter; Jonker, Michiel T O; Hermens, Joop L M

2013-04-29

288

Pore water profiles of dissolved N2 concentrations and ?15N-N2 in the Santa Barbara Basin: Evidence for non-diffusive nitrate flux into the sediment column  

NASA Astrophysics Data System (ADS)

Recently constructed global N budgets indicate that sedimentary denitrification removes about 75 % of biologically available nitrogen from the ocean, which makes it the most important sink for the oceanic nitrate. However, the uncertainty of a factor of two or three exists in the estimates of benthic denitrification. The challenge of accurately quantifying the contribution of this process to the global nitrogen budget arises, in part, from the lack of detailed knowledge of the nitrogen metabolism of benthic microbial communities participating in the processes collectively termed as ''sedimentary denitrification''. Nitrogen isotopic gradients of pore water ammonium and nitrate have been previously used to place budgetary constraints on some of the microbial processes in anoxic and suboxic marine sediments. Here we present the profiles of concentrations and isotopic composition of dissolved N2 as well as N2/Ar ratios from the pore waters of anoxic sediments collected in the center of Santa Barbara Basin in May 2005. Concentration and N2/Ar ratio gradients indicate a 20 to 40 uM downcore increase in N2 over the upper 4 to 5 cm. Addition of N2 to the pore waters continues below 5 cm into the sediments, even though the concentrations of pore water nitrate approach the detection limit within 2 to 3 cm below the sediment surface. The newly added N2 is most likely of biological origin, as follows from the N2/Ar ratios. The downcore increase in N2 concentration is 2 to 3 times greater than predicted from denitrified bottom water nitrate (25 uM). The increase in N2 concentrations is accompanied by an increase in dinitrogen ?15N, from 0.4-0.7 per mil at the sediment-water interface to 0.9 - 1.3 per mil at depth (the range reflecting variations between stations). Isotopic mass balance requires that the added N2 has a ?15N of 7.5 - 12.5 per mil (± 3 per mil). The ?15N composition of organic matter deposited on the ocean floor is 7.5 per mil, while the ?15N of ammonium produced from the organic matter is ~ 10 per mil. The ?15N of the bottom water nitrate is between 8 and 12 per mil, depending on the magnitude of the nitrate deficit at the time of measurements. Therefore, our isotope data are consistent with N2 production from both organic nitrogen derived NH4+ and the bottom water NO3-, as in the anammox reaction. The deep N2 production and the amplitude of the deep N2 excess require a non-diffusive mechanism for NO3- supply, unless in situ oxidation of ammonium is producing excess NO3- or NO2- at depth.

Prokopenko, M. G.; Sigman, D. M.; Hammond, D. E.; Barnett, B. A.; Bender, M.; Berelson, W.

2005-12-01

289

Cyclothiazide induces seizure behavior in freely moving rats.  

PubMed

We have previously demonstrated that cyclothiazide (CTZ) is a potent convulsant drug inducing robust epileptiform activity in hippocampal neurons both in vitro and in vivo. Here we further establish an animal model for CTZ-induced behavioral seizures in freely moving rats. Microinjection of CTZ into the left ventricle dose-dependently induced robust seizure behaviors within 3h after administration. At a dose of 0.75 ?mol, CTZ induced Racine score IV-V seizure behaviors in 71% (n=14) of the rats were tested. In addition, CTZ also induced epileptiform EEG activity accompanying behavioral seizures. The convulsant action of CTZ on both behavior and EEG was blocked by pretreatment with clinical anticonvulsant drug diazepam (n=5). In conclusion, our results demonstrate that CTZ is capable of inducing behavioral seizures in intact animals. Since CTZ acts on both GABAergic and glutamatergic systems, this new animal epilepsy model will be useful for anticonvulsant drug testing and general epilepsy research. PMID:20678492

Kong, Shuzhen; Qian, Binbin; Liu, Jianhui; Fan, Mingxin; Chen, Gong; Wang, Yun

2010-07-30

290

Autonomous head-mounted electrophysiology systems for freely behaving primates.  

PubMed

Recent technological advances have led to new light-weight battery-operated systems for electrophysiology. Such systems are head mounted, run for days without experimenter intervention, and can record and stimulate from single or multiple electrodes implanted in a freely behaving primate. Here we discuss existing systems, studies that use them, and how they can augment traditional, physically restrained, 'in-rig' electrophysiology. With existing technical capabilities, these systems can acquire multiple signal classes, such as spikes, local field potential, and electromyography signals, and can stimulate based on real-time processing of recorded signals. Moving forward, this class of technologies, along with advances in neural signal processing and behavioral monitoring, have the potential to dramatically expand the scope and scale of electrophysiological studies. PMID:20655733

Gilja, Vikash; Chestek, Cindy A; Nuyujukian, Paul; Foster, Justin; Shenoy, Krishna V

2010-07-23

291

The near wake of a freely flying European starling  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

292

``Reverse'' Lock-in Regime on a Freely Oscillating Cylinder  

NASA Astrophysics Data System (ADS)

DPIV and flow visualizations were used to characterize the flow in the near wake of a freely oscillating cylinder. A rigid cylinder with a low mass ratio was fixed at one end to a leaf spring and free to oscillate, pendulum-like, at the other end in the cross stream plane. It was found that only a subset of the synchronization range follows the behavior of a ``classical'' lock-in, i.e., when the difference between the natural Strouhal frequency and the natural frequency of the cylinder is small enough, vortex shedding frequency deviates from the linear Strouhal dependence and follows instead the cylinder natural frequency. However, over a range of flow speed in which the response amplitude of the cylinder is significant, it was found that the frequency of oscillation and of vortex shedding follow instead the natural Strouhal frequency, instead of the mechanical natural frequency.

Atsavapranee, P.; Voorhees, A. V.; Benaroya, H.; Wei, T.

1998-11-01

293

Fatal freely mobile left atrial thrombus: fallout of anticoagulation?  

PubMed

Rheumatic heart disease with moderate mitral stenosis and a large left atrial (LA) thrombus was diagnosed in a 45-year-old woman at a peripheral hospital. Oral anticoagulation was administered, and the patient was referred for further management. During the intervening period, sudden worsening of dyspnea developed in the patient and a repeat echocardiogram revealed a large thrombus freely vacillating within the left atrium. Urgent open mitral valvotomy and LA thrombus removal were planned. However, as the patient was being prepared for surgery, she had a fatal cardiorespiratory arrest and could not be revived. Warfarin is known to influence thrombus lysis, and it is possible that it may have severed the LA thrombus from the posterior LA wall by partially lysing it, leading to the formation of a ball-valve thrombus, which is a well-known risk factor for sudden death. PMID:19560665

Roy, Ambuj; Naik, Nitish; Nagesh, Chamarajnagar M; Saxena, Anita

2009-07-01

294

Method for dissolving plutonium oxide with HI and separating plutonium  

DOEpatents

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.

Vondra, Benedict L. (Oak Ridge, TN); Tallent, Othar K. (Oak Ridge, TN); Mailen, James C. (Oak Ridge, TN)

1979-01-01

295

Bioaccumulation of Perfluoroalkyl Substances by Daphnia magna in Water with Different Types and Concentrations of Protein.  

PubMed

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 Daphnia magna. Because these two opposite effects would change with different protein concentrations in water, the net effect of protein on PFAS bioaccumulation would also vary with protein concentration. PMID:23968486

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

2013-09-09

296

Chronic detachable headphones for acoustic stimulation in freely moving animals  

PubMed Central

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.

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

2010-01-01

297

Dissolved Nitrogen Dynamics and Dissolved Organic Carbon Biogeochemistry in an Ombrotrophic Bog  

NASA Astrophysics Data System (ADS)

As an extension of an ongoing study on carbon cycling and sequestration, Mer Bleue bog near Ottawa, Ontario was studied for dissolved nitrogen dynamics. Since nitrogen is an important nutrient for plant growth, the retention and export by the bog could reflect the impact of nitrogen deposition on bog productivity and carbon sequestration. Dissolved inorganic and organic nitrogen (DIN, DON) and dissolved organic carbon (DOC) inputs, export, and groundwater concentrations were measured over the 2003 field season (from May 21 to November 18, 2003). Nitrogen inputs were found to be entering the bog dissolved in precipitation in very small concentrations, ranging from 0 to 6 mg/L, and were dominated by NH4+. Export DON and DOC concentrations followed similar patterns, increasing with a decrease in outflow discharge with drier bog conditions throughout the season. Rough budget estimates for DOC, DON and DIN for the 2003 field season are roughly 0.034, 0.101, and 2.861 g m-2 t-1, respectively. The bog was also characterized for groundwater concentrations of DIN, DON, and DOC in the saturated and unsaturated zones of the bog. The general patterns of concentrations show dominance of NH4+ deeper in the saturated zone, and DON dominating in the unsaturated, biologically active zone. Although deposited nitrogen is dominated by inorganic forms, the internal processing of nitrogen results in DON export correlated to DOC. The results provide greater insight as to the influence and importance of dissolved nitrogen on carbon retention and sequestration.

Rattle, J. M.; Roulet, N. T.; Moore, T. R.

2004-05-01

298

Developing Standards for Dissolved Iron in Seawater  

Microsoft Academic Search

In nearly a dozen open-ocean fertilization experiments conducted by more than 100 researchers from nearly 20 countries, adding iron at the sea surface has led to distinct increases in photosynthesis rates and biomass. These experiments confirmed the hypothesis proposed by the late John Martin that dissolved iron concentration is a key variable that controls phytoplankton processes in ocean surface waters.

Kenneth S. Johnson; Edward Boyle; Kenneth Bruland; Kenneth Coale; Chris Measures; James Moffett; Ana Aguilar-Islas; Katherine Barbeau; Bridget Bergquist; Andrew Bowie; Kristen Buck; Yihua Cai; Zanna Chase; Jay Cullen; Takashi Doi; Virginia Elrod; Steve Fitzwater; Michael Gordon; Andrew King; Patrick Laan; Luis Laglera-Baquer; William Landing; Maeve Lohan; Jeffrey Mendez; Angela Milne; Hajime Obata; Lia Ossiander; Joshua Plant; Geraldine Sarthou; Peter Sedwick; Geoffrey J. Smith; Bettina Sohst; Sara Tanner; Stan Van den Berg; Jingfeng Wu

2007-01-01

299

A Dissolving Challenge  

NSDL National Science Digital Library

In this activity, learners add objects and substances to carbonated water to discover that added objects increase the rate at which dissolved gas comes out of solution. Learners are then challenged to make a lemon soda that retains as much carbonation as possible, by using carbonated water, sugar, and lemon juice. Learners identify the difficulty in making a fizzy lemon soda, develop a better method, and then test it.

Kessler, James H.; Galvan, Patricia M.

2007-01-01

300

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

Microsoft Academic Search

We generated suspended sediment solutions using river sediments and river water at concentrations similar to those observed during 1.5 year floods (Q1.5) and a dam removal (?325 mg L?1) on the Deep River, North Carolina. Suspended sediment solutions were exposed to simulated solar radiation, equivalent to one clear, summer day at the study site (35°N). Concentrations of dissolved organic carbon

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

2008-01-01

301

On the contribution of natural and restored wetlands to changes in the concentration and composition of dissolved organic material in the Sacramento-San Joaquin Delta and San Francisco Estuary.  

NASA Astrophysics Data System (ADS)

The amount and quality of wetland-derived dissolved organic material (DOM) entering delta and estuary environments remains poorly characterized even though DOM has two roles of societal significance: 1) it supports estuarine foodwebs, commonly habitat for endangered species, and 2) it presents problems when it occurs in drinking water supplies, forming carcinogenic byproducts on treatment. The Sacramento-San Joaquin Delta is a source of drinking water for over 20 million people and contributes 80% of the DOM entering the San Francisco Estuary, nearly doubling the concentration of DOM in the influent river water. The majority of the Delta is composed of below-sea level peat islands maintained in agricultural production by continuous pumping of DOM-rich drain water into Delta channels. Previous studies have shown that changes in the composition of the DOM in water that passes through the Delta are not consistent with addition of peat island drain water, and are more consistent with addition of wetland-derived material, suggesting that wetlands may contribute substantially to DOM export to the Estuary. Although wetlands currently contribute only 14% of the Delta, restoration is planned that would more than double this area, potentially altering DOM quality and content in the Delta and Estuary waters. Over the past several years we have examined the seasonal variation in the quality of DOM added by a variety of wetland types and island drains within the Delta and Estuary. In the current study, thirteen sites were each sampled five times. To date, we have analyzed the samples to determine the content of hydrophobic DOM, characterize the UV absorbance and fluorescence properties, and quantify the susceptibility to biodegradation both before and after photo-exposure. Samples were humic-rich, averaging over 75% hydrophobic content and varying from 74 to 86% with the variation in hydrophobic content between samples corresponding to changes in the optical properties. Samples typically were refractory with respect to biodegradation, with an average of 11% of the DOM susceptible to biodegradation prior to photoexposure, but the range was from 1% to 48%. Following photoexposure, samples were generally more refractory rather than more labile. Wetland DOM was found to react to form more drinking water disinfection byproducts than influent waters, but some wetland types appeared to contribute fewer precursors. Seasonal variation in biodegradation and chemical parameters was much greater than variation among wetland types, and the peak of biodegradeability was not related to the seasonal peak in DOM. This suggests addition of DOM through the Delta is controlled by changes in the nature of the source material rather than changes in efficiency or extent of remineralization.

Bergamaschi, B.; Stepanauskas, R.; Fram, M.; Hollibaugh, J.; Fujii, R.

2002-12-01

302

The Contribution of Natural and Restored Wetlands to Changes in the Concentration and Composition of Dissolved Organic Material in the Sacramento-San Joaquin Delta and San Francisco Estuary  

NASA Astrophysics Data System (ADS)

The quantity and quality of wetland-derived dissolved organic material (DOM) entering delta and estuary environments remains poorly characterized, even though DOM has two roles of societal significance: 1) it supports estuarine foodwebs, which commonly are a habitat for endangered species, and 2) it presents problems when it occurs in drinking water supplies, because it forms carcinogenic byproducts when treated. The Sacramento-San Joaquin Delta is a source of drinking water for more than 20 million people and contributes 80% of the DOM entering the San Francisco estuary, nearly doubling the concentration of DOM in the influent river water. The majority of the Delta is composed of below-sea-level peat islands that are maintained in agricultural production by continuous pumping of DOM-rich drain water into Delta channels. Previous studies indicate that changes in DOM composition in water passing through the Delta are not consistent with the addition of peat island drain water, and are more consistent with the addition of wetland-derived material. Therefore, wetlands may contribute substantially to DOM export to the estuary. Although wetlands currently constitute only 14% of the Delta, restoration is planned that would more than double this wetland area, potentially altering DOM quality and content in the Delta and estuary waters. During the past several years, the seasonal variation in the quality of DOM added by a variety of wetland types and island drains within the Delta and estuary has been examined. In this study, 13 sites were sampled 5 times. As of September 2002, the samples have been analyzed to determine the content of hydrophobic DOM, characterize the ultraviolet absorbance and fluorescence properties, and quantify the susceptibility to biodegradation before and after photoexposure. Samples were humic-rich, averaging more than 75% hydrophobic content and varying from 74 to 86%, with the variation in hydrophobic content between samples corresponding to changes in the optical properties. Samples typically were refractory with respect to biodegradation, having an average of 11% of the DOM being susceptible to biodegradation prior to photoexposure, but the range was from 1% to 48%. Following photoexposure, samples generally were more refractory rather than more labile. Wetland DOM reacted to form more drinking water disinfection byproducts than influent waters, but some wetland types seemed to contribute fewer precursors. Seasonal variation in biodegradation and chemical parameters was much greater than variation among wetland types, and the peak of biodegradability was not related to the seasonal peak in DOM. Therefore, the addition of DOM through the Delta is controlled by changes in the nature of the source material rather than changes in efficiency or extent of remineralization.

Bergamaschi, B. A.; Stepanauskas, R.; Fram, M.; Hollibaugh, J. T.; Fujii, R.

2002-12-01

303

CASAA Dissolvables - Attachment 6 1  

Center for Biologics Evaluation and Research (CBER)

Text Version... CASAA Dissolvables - Attachment 6 1 Content withheld for copyright purposes Page 2. CASAA Dissolvables - Attachment 6 2 ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

304

Dissolved trace elements in the Mississippi River: Seasonal, interannual, and decadal variability  

Microsoft Academic Search

A monthly trace element sampling of the lower Mississippi River, utilizing ultra-clean methods, was conducted from October 1991 to December 1993. Dissolved concentrations were determined for Fe, Mn, Zn, Ph, V, Mo, U, Cu, Ni, Cd, Rb, and Ba. The results show significant seasonal dissolved concentration changes for a number of elements. Specifically, dissolved Mn and Fe are found to

Alan M. Shiller

1997-01-01

305

Partial nitrification under limited dissolved oxygen conditions  

Microsoft Academic Search

Partial nitrification to nitrite is technically feasible and economically favourable, especially when wastewaters contained high ammonium concentrations or low C\\/N ratios. Partial nitrification can be obtained by selectively inhibiting nitrite-oxidizing bacteria (NOB) through appropriate regulation of the pH, temperature and dissolved oxygen (DO) concentrations. The effect of pH, DO levels and temperature on ammonia oxidation rate and nitrite accumulation was

Wang Jianlong; Yang Ning

2004-01-01

306

Transport of dissolved oxygen through silicone rubber membrane  

Microsoft Academic Search

The transport of dissolved oxygen in water through a silicone rubber membrane was studied theoretically and experimentally. The apparent oxygen permeability coefficients of silicone rubber were measured at various membrane thicknesses, temperatures, and concentration levels. The permeation flux was measured under both steady-and unsteady-state conditions. For the first time, the thickness effect of dissolved gas permeation has been studied. It

Sun-Tak Hwang; Thomas E. S. Tang; Karl Kammermeyer

1971-01-01

307

Dissolved P in streams in dry years and wet years  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dissolved phosphorus (P) has often been identified as the nutrient of concern in lakes, reservoirs, and streams especially where there is evidence of eutrophication. We analyzed contiguous-spatial and temporal variability of dissolved P [soluble reactive P (SRP)] stream concentrations during times ...

308

Characterization of Dissolved Solids in Water Resources of Agricultural Lands Near Manila, Utah, 2004-05.  

National Technical Information Service (NTIS)

Agricultural lands near Manila, Utah, have been identified as contributing dissolved solids to Flaming Gorge Reservoir. Concentrations of dissolved solids in water resources of agricultural lands near Manila, Utah, ranged from 35 to 7,410 milligrams per l...

B. A. Kimball D. L. Naftz L. E. Spangler S. J. Gerner

2007-01-01

309

Dissolved Organic Metals in the Hydrothermal Plume  

NASA Astrophysics Data System (ADS)

In the hydrothermal plume, there are the unique microbiological communities and the microorganism utilizes various chemical substances. The interactions between heavy metals and microorganisms in the hydrothermal plume are important to comprehend the oceanic geochemical cycles of heavy metals. It is considered that the heavy metals in hydrothermal plume are organically bound with dissolved organic matter derived from the hydrothermal microorganism. This study funded by the O`Archaean ParkO_L project of MEXT is a first attempt to observe the bioavailability of heavy metals in hydrothermal plume. The hydrothermal plume samples were taken from two different kinds of hydrothermal sites, the Suiyo Seamount caldera and the Central Indian Ridge. The mini CTDT-RMS mounted twelve 1.2L Niskin bottles was installed on the manned submersible, and the hydrothermal plume samples were collected by taking the distance from the hydrothermal vents gradually. The solid phase extraction technique in C18 Sep-Pak cartridge (Millipore Waters) was used to extract the dissolved organic matter from the hydrothermal plume samples. Dissolved heavy metals (Al, Mn, Fe, Cu, Zn, Co, Ni, As, Mo, Cd and Pb) bound with C18 Sep-Pak extractable organic matter, dissolved organic metals, were analyzed by GFAAS. In all measured heavy metals, the dissolved organic metals existed in the hydrothermal plume samples collected from two sites. The concentration of the dissolved organic metals ranged from 0.5nM to 30nM and was about 1/1000~1/100 of the total dissolved heavy metals concentration. It suggests that these heavy metals were bound with organic matter originated in the hydrothermal microorganism. Though the abundance of the organism in the Central Indian Ridge is larger than that in the Suiyo Seamount caldera, the concentration of the dissolved organic metals in the plume samples at the Suiyo Seamount caldera was higher than that at the Central Indian Ridge. These results indicate that the bioavailability of heavy metals is different in two sites.

Shitashima, K.

2003-12-01

310

Spin polarization in a freely evolving sample of cold atoms  

NASA Astrophysics Data System (ADS)

We have implemented and optimized a technique of spin polarization by optical pumping in a caesium atomic fountain, gaining a nearly fivefold increase in the useful cold atom signal in detection. This allows an improvement of the fountain clock stability without compromising its accuracy. We present a detailed study of optical pumping in a freely evolving cloud of cold caesium atoms: we have investigated theoretically and experimentally the dynamics of the pumping process and the associated heating due to random photon scattering. The heating limits the potential gain in the fountain signal due to an additional cloud expansion. A high degree of spin polarization was achieved with accumulation of up to 97 % of the population in a single magnetic ( m F = 0) sublevel of the ground state. Factors affecting the achievable spin polarizations, such as the purity of the pumping light polarization and the shadowing effect in the cloud, were considered. This technique may also be used in atom interferometers and for other alkali metal systems.

Szymaniec, Krzysztof; Noh, Heung-Ryoul; Park, Sang Eon; Takamizawa, Akifumi

2013-05-01

311

3-D worm tracker for freely moving C. elegans.  

PubMed

The manner in which the nervous system regulates animal behaviors in natural environments is a fundamental issue in biology. To address this question, C. elegans has been widely used as a model animal for the analysis of various animal behaviors. Previous behavioral assays have been limited to two-dimensional (2-D) environments, confining the worm motion to a planar substrate that does not reflect three-dimensional (3-D) natural environments such as rotting fruits or soil. Here, we develop a 3-D worm tracker (3DWT) for freely moving C. elegans in 3-D environments, based on a stereoscopic configuration. The 3DWT provides us with a quantitative trajectory, including the position and movement direction of the worm in 3-D. The 3DWT is also capable of recording and visualizing postures of the moving worm in 3-D, which are more complex than those in 2-D. Our 3DWT affords new opportunities for understanding the nervous system function that regulates animal behaviors in natural 3-D environments. PMID:23437394

Kwon, Namseop; Pyo, Jaeyeon; Lee, Seung-Jae; Je, Jung Ho

2013-02-21

312

3-D Worm Tracker for Freely Moving C. elegans  

PubMed Central

The manner in which the nervous system regulates animal behaviors in natural environments is a fundamental issue in biology. To address this question, C. elegans has been widely used as a model animal for the analysis of various animal behaviors. Previous behavioral assays have been limited to two-dimensional (2-D) environments, confining the worm motion to a planar substrate that does not reflect three-dimensional (3-D) natural environments such as rotting fruits or soil. Here, we develop a 3-D worm tracker (3DWT) for freely moving C. elegans in 3-D environments, based on a stereoscopic configuration. The 3DWT provides us with a quantitative trajectory, including the position and movement direction of the worm in 3-D. The 3DWT is also capable of recording and visualizing postures of the moving worm in 3-D, which are more complex than those in 2-D. Our 3DWT affords new opportunities for understanding the nervous system function that regulates animal behaviors in natural 3-D environments.

Kwon, Namseop; Pyo, Jaeyeon; Lee, Seung-Jae; Je, Jung Ho

2013-01-01

313

Monitoring pulse oximetry via radiotelemetry in freely-moving lambs.  

PubMed

This study was aimed at validating the use of a custom-made wireless pulse oximeter in freely moving lambs, using radiotelemetry transmission. First, measurements obtained simultaneously using the new, wireless oximeter and a standard commercially-available pulse oximeter (Nonin 8500) were compared in five lambs during 5min episodes of normoxia, hypoxia and hyperoxia. Correlation between the two oximeters for both SpO(2) and heart rate was very good, regardless of oxygenation conditions. Secondly, the capabilities of our device were assessed during more than 45h of polysomnographic recordings in seven lambs. According to the plethysmographic pulse waveform, reliable SpO(2) values were obtained in more than 85% of recording time. Multiple decreases in SpO(2) were readily observed after spontaneous apneas in preterm lambs. It is concluded that our wireless pulse oximeter performs as reliably as a standard pulse oximeter for monitoring SpO(2) variations in lambs, and offers new perspectives for researchers interested in continuous monitoring of oxygenation throughout sleep stages and wakefulness. PMID:15848124

Reix, Philippe; Dumont, Sylvain; Duvareille, Charles; Cyr, Jonathan; Moreau-Bussière, François; Arsenault, Julie; Praud, Jean-Paul

2005-05-12

314

Energy decay of freely cooling granular gases in three dimensions  

NASA Astrophysics Data System (ADS)

Freely cooling granular gases, wherein a dilute system of macroscopic particles with uncorrelated initial velocities lose energy through inelastic collisions, have been extensively studied both as a simple model for granular systems as well as a nonequilibrium system showing nontrivial coarsening at late times. As the system cools, inelasticity induces clustering, making the system inhomogeneous. While the form of energy decay (E(t)˜t^-?) in the initial homogeneous regime is well established by Haff's law (?=2), the energy decay in the clustered regime is still unresolved in higher dimensions. Within mean field theory, ?=2 d/(d+2) (where d is the spatial dimension), while a correspondence to Burgers equation implies an exponent ?= 2/3 (d=1), d/2 (d>1). In one and two dimensions, the two formulae predict the same exponents. By performing extensive event driven molecular dynamics simulations, we show that in three dimensions, the energy decays asymptotically with a power 1.2, for all coefficients of restitution r<1, consistent with the mean field exponent. However, we argue that the mean field arguments fail due to non local interactions between mass clusters.

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

2012-02-01

315

Functional brain mapping in freely moving rats during treadmill walking.  

PubMed

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

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

2003-08-01

316

Stimulated release of lactate in freely moving rats is dependent on the uptake of glutamate.  

PubMed Central

1. Physiological stimulation of neuronal activity induces an increase in extracellular lactate. Experiments were designed to determine the role of the reuptake of neuronally released glutamate in lactate delivery to the extracellular compartment. 2. In vivo microdialysis was used in freely moving rats. The lactate concentration in striatal dialysate was assayed using an enzyme-based on-line assay at 1 min intervals. Drugs were given locally through the dialysis probe. 3. The extracellular concentration of lactate, determined using the zero net flux method, was 346 +/- 21 microM. 4. Induced grooming caused a maximal increase in lactate concentration in striatal dialysate of 58 +/- 10%. 5. Administration of 100 microM glutamate caused a transient increase in dialysate lactate concentration of 72 +/- 17%. 6. A 20 min infusion of the glutamate uptake blockers beta-D,L-threohydroxyaspartate (THA) or pirrolidine-2-4-dicarboxylate (PDC) produced an increase in basal lactate, which was sustained in response to THA and transient in response to PDC. 7. Grooming induced during the infusion of PDC produced no significant increase in lactate. 8. Grooming induced after the infusion of the glutamate uptake blockers gave rise to a reduced increase in lactate. 9. These results support the hypothesis that stimulated release of lactate is dependent on the uptake of glutamate.

Demestre, M; Boutelle, M; Fillenz, M

1997-01-01

317

Dissolved organic carbon on Georges Bank  

NASA Astrophysics Data System (ADS)

Dissolved organic carbon (DOC) in sea water from Georges Bank was measured by a high temperature combustion/direct injection (HTC/DI) technique during the spring bloom period in April 1993. Concentrations in surface waters (72-85 ?M) and deep waters (54-56 ?M) were similar to DOC concentrations measured in the oligotrophic north-west Atlantic Ocean by a number of other investigators by various techniques. Although surface values for Chl- a concentrations ranged from 2 to 5 ?g l -1, NO 3- ranged from 3 to 9 ?M and particulate organic carbon (POC) concentrations ranged from 1.0 to 10?M, DOC concentrations only varied by <18‰ DOC was slightly higher (˜5 ?M) in the highly productive central bank region than in surrounding stratified surface waters. Relatively constant stable carbon isotopes (DO 13C = -22.0 ± 0.5 could not be used to identify a source for these small variations. Slight decreases of DOC (5-12?M) and dissolved organic nitrogen (DON) (0.5-1.0 ?M) in filtered sea water kept in the dark was observed over six months, suggesting the presence of a small, labile pool of dissolved organic matter in addition to a large, more refractory reservoir of DOC (˜70 ?M) during the spring bloom period on Georges Bank.

Chen, Robert F.; Fry, Brian; Hopkinson, Chuck S.; Repeta, Daniel J.; Peltzer, Edward T.

1996-04-01

318

Dissolved vanadium in rivers and estuaries  

NASA Astrophysics Data System (ADS)

New measurements of dissolved vanadium in a variety of rivers and estuaries are presented here. The data indicate that the average concentration of dissolved vanadium in major rivers entering the ocean is ˜ 15 nmol/kg. Weathering rate and type of source rock, rather than solution chemistry or anthropogenic influences, appear to be the important factors in determining fluvial dissolved vanadium concentrations. Laboratory experiments suggest that in oxic waters vanadium is found predominantly in its most oxidized, anionic form (V(V)). Complexation with organic matter and formation of large colloidal species appear to be unimportant. Adsorption also appears to be a less important influence for vanadium than for some other trace elements such as zinc. In estuaries, vanadium behaves as a bioactive element, showing a close correspondence with the distribution of phosphate. The extent of estuarine vanadium removal is presently uncertain but may be low due to rapid remineralization of this element. Based on the river flux, the oceanic residence time for dissolved vanadium is estimated to be 100,000 years.

Shiller, Alan M.; Boyle, Edward A.

1987-12-01

319

Simplified Method for Dissolved DNA Determination in Aquatic Environments  

PubMed Central

A method was developed for the determination of dissolved DNA in aquatic environments. The method is based upon the concentration of dissolved DNA by ethanol precipitation of 0.2-?m-pore-size filtered water. The DNA in concentrated extracts was quantified by the fluorescence of Hoechst 33258-DNA complexes. Fluorescence not attributable to DNA was corrected for by DNase I digestion of the extracts and averaged 25% of the total fluorescence for all samples. The effectiveness of the procedure for concentrating dissolved DNA was demonstrated by the efficient (>90%) recovery of internal standards. Concentrations of dissolved DNA from a variety of marine and freshwater environments ranged from 0.2 to 44 ?g/liter, with the highest values being obtained for estuarine and river environments. The method is simple, specific for DNA, and more sensitive than previously described methods for the determination of extracellular DNA.

DeFlaun, Mary F.; Paul, John H.; Davis, Dean

1986-01-01

320

EFFECTS OF TEMPERATURE VARIATION ON CRITICAL STREAM DISSOLVED OXYGEN  

EPA Science Inventory

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

321

Three-dimensional spatial representation in freely swimming fish.  

PubMed

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 shaped by the number of the degrees of freedom of movement that binds the navigating animal. PMID:22915259

Burt de Perera, Theresa; Holbrook, Robert I

2012-08-01

322

Droplet and cluster formation in freely falling granular streams.  

PubMed

Particle beams are important tools for probing atomic and molecular interactions. Here we demonstrate that particle beams also offer a unique opportunity to investigate interactions in macroscopic systems, such as granular media. Motivated by recent experiments on streams of grains that exhibit liquid-like breakup into droplets, we use molecular dynamics simulations to investigate the evolution of a dense stream of macroscopic spheres accelerating out of an opening at the bottom of a reservoir. We show how nanoscale details associated with energy dissipation during collisions modify the stream's macroscopic behavior. We find that inelastic collisions collimate the stream, while the presence of short-range attractive interactions drives structure formation. Parameterizing the collision dynamics by the coefficient of restitution (i.e., the ratio of relative velocities before and after impact) and the strength of the cohesive interaction, we map out a spectrum of behaviors that ranges from gaslike jets in which all grains drift apart to liquid-like streams that break into large droplets containing hundreds of grains. We also find a new, intermediate regime in which small aggregates form by capture from the gas phase, similar to what can be observed in molecular beams. Our results show that nearly all aspects of stream behavior are closely related to the velocity gradient associated with vertical free fall. Led by this observation, we propose a simple energy balance model to explain the droplet formation process. The qualitative as well as many quantitative features of the simulations and the model compare well with available experimental data and provide a first quantitative measure of the role of attractions in freely cooling granular streams. PMID:21728520

Waitukaitis, Scott R; Grütjen, Helge F; Royer, John R; Jaeger, Heinrich M

2011-05-12

323

Benthic foraminiferal dissolved-oxygen index and dissolved-oxygen levels in the modern ocean  

Microsoft Academic Search

Changes in oxygen concentrations at the sediment-water interface play a major role in controlling benthic foraminiferal assemblages and morphologic characteristics; such changes are reflected in size, wall thickness, porosity, and also taxa (genera and species) of foraminifera present. These morphologic and taxonomic differences have been quantified as a dissolved-oxygen index. This paper demonstrates that the foraminiferal oxygen index derived from

Kunio Kaiho

1994-01-01

324

Dissolved silver in the Baltic Sea.  

PubMed

The increased use of silver as a biocide in nanoparticle formulations has heightened concern on possible environmental implications owing to its toxicity. There is however very little data on the concentration levels of silver in marine and freshwaters. Here, I report data on dissolved (<0.4 ?m filter) silver concentration in the surface waters of the Baltic Sea, the first such data reported for a European coastal water body. Levels of dissolved silver in the Baltic are comparable to those reported for other American estuarine waters and range from non-detectable in the open Baltic Sea Proper (<1 pM) to 9.4 pM (1 ng/L) in the Stockholm Archipelago, with a mean of 2.8 pM (0.2 ng/L). Inputs from wastewater treatment are clearly discernable and might constitute the main source of silver to the Stockholm Archipelago and possibly the Baltic Sea Proper. PMID:21075364

Ndungu, Kuria

2010-11-13

325

Fast dissolving films made of maltodextrins  

Microsoft Academic Search

This work aimed to study maltodextrins (MDX) with a low dextrose equivalent as film forming material and their application in the design of oral fast-dissolving films. The suitable plasticizer and its concentration were selected on the basis of flexibility, tensile strength and stickiness of MDX films, and the MDX\\/plasticizer interactions were investigated by ATR-FTIR spectroscopy. Flexible films were obtained by

Francesco Cilurzo; Irma E. Cupone; Paola Minghetti; Francesca Selmin; Luisa Montanari

2008-01-01

326

The Dynamics of Freely Oscillating Gas-Vapor Bubbles  

NASA Astrophysics Data System (ADS)

This dissertation describes experimental and theoretical studies of the dynamics of freely oscillating gas-vapor bubbles. Longuet-Higgins has predicted that bubble surface modes can produce, through nonlinear coupling, monopole sound radiation. The first part of this dissertation is devoted to an experimental investigation of this phenomenon. A hydrophone and needle were submerged in water in a small sealed cell that was connected to a regulated evacuation system. The sound produced by releasing a bubble from the needle was monitored by a hydrophone and displayed on an oscilloscope. Two high speed video cameras simultaneously recorded the bubble motion and the displayed sound trace. At pressures of a few cm-Hg, it was seen that after the bubble -generation sound died out, there followed a sound of the same frequency but lower magnitude. Because this sound amplitude increased as the ambient pressure decreased and had its maximum value at resonance, it appeared that this sound was evidence for a surface-mode induced volume-mode. Careful data analysis shows that there exists a mutual interaction between these surface and volume modes. The second half of the dissertation contains the development of a theory, in which the resonance frequency omega_{x} and damping constant omega_{y} for free volume oscillations of a spherical bubble in an infinite medium are derived from the linearized, fundamental equations of fluid dynamics. There are three possible wave propagation modes that satisfy the governing equations for the gas-vapor mixture inside the bubble. Outside it, only two modes need be considered because gas diffusion across the bubble surface into the liquid appears negligible for free oscillations. Two parameters omega _{x} and omega_ {y} are values such that the boundary conditions can be satisfied. The dependence of omega_{x} and omega _{y} on many physical parameters is examined. For a bubble containing mostly gas, the values of omega_{x} and omega_{y} agree with previous theories. For a bubble containing mostly vapor, significant additional damping occurs from the effects of vapor evaporation-condensation. We also find that there exists only one resonance frequency for free oscillations, in contrast to the predictions of Finch and Neppiras who suggested that two resonances are possible.

Mao, Yi.

327

Dissolved zirconium in the north Pacific Ocean  

SciTech Connect

Picomolar levels of dissolved Zr in seawater were measured using an analytical technique developed with a Chelex-100 extraction/concentration step and subsequent detection by isotope-dilution inductively-coupled-plasma mass spectrometry (ID-ICP-MS). Here the authors present the first vertical profile of Zr in the oceans, from the central-North Pacific, and a horizontal surface transect across the western Pacific. Dissolved Zr ranges from 12--95 pmol/kg in the surface waters then increases linearly with depth to a maximum of 300 pmol/kg in the deep water. The vertical profile shows a strong correlation with Si in the mid-waters, with higher Zr/Si ratios in the surface and bottom waters. There is evidence of both a bottom source and a coastal source of dissolved Zr to the oceans. A comparison with dissolved Ti and Be shows similar depth dependence, but an enrichment in Zr/Ti and a depletion in Zr/Be ratios in seawater relative to average crustal materials. Zirconium appears to have a reactivity intermediate between these two elements. 24 refs., 4 figs., 1 tab.

McKelvey, B.A.; Orians, K.J. (Univ. of British Columbia, Vancouver (Canada))

1993-08-01

328

Dissolved zirconium in the North Pacific Ocean  

NASA Astrophysics Data System (ADS)

Picomolar levels of dissolved Zr in seawater were measured using an analytical technique developed with a Chelex-100 extraction/concentration step and subsequent detection by isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). Here we present the first vertical profile of Zr in the oceans, from the central-North Pacific, and a horizontal surface transect across the western Pacific. Dissolved Zr ranges from 12-95 pmol/kg in the surface waters then increases linearly with depth to a maximum of 300 pmol/kg in the deep water. The vertical profile shows a strong correlation with Si in the mid-waters, with higher Zr/Si ratios in the surface and bottom waters. There is evidence of both a bottom source and a coastal source of dissolved Zr to the oceans. A comparison with dissolved Ti and Be shows similar depth dependence, but an enrichment in Zr/Ti and a depletion in Zr/Be ratios in seawater relative to average crustal materials. Zirconium appears to have a reactivity intermediate between these two elements.

McKelvey, Brad A.; Orians, Kristin J.

1993-08-01

329

A fully implantable telemetry system for the chronic monitoring of brain tissue oxygen in freely moving rats.  

PubMed

The ability to monitor tissue oxygen concentration in a specific region of the brain in a freely moving animal could provide a new paradigm in neuroscience research. We have developed a fully implantable telemetry system for the continuous and chronic recording of brain tissue oxygen (PO(2,BR)) in conscious animals. A telemetry system with a sampling rate of 2kHz was combined with a miniaturized potentiostat to amperiometrically detect oxygen concentration with carbon paste electrodes. Wireless power was employed to recharge the telemeter battery transcutaneously for potential lifetime monitoring. Rats were implanted with the telemeter in the peritoneal cavity and electrodes stereotaxically implanted into the brain (striatum or medulla oblongata). While the animals were living in their home cages the sensitivity to changes in oxygen was validated by repeatedly altering the inspired oxygen (10%, 100%, respectively) or a pharmacological stimulus (carbonic anhydrase inhibitor: acetazolamide 50mg/kg IP). Basal level of PO(2,BR) was monitored for 3weeks and showed good overall stability and good correlation to movement such as grooming. During hypoxia, PO(2,BR) decreased significantly by -51%±2% from baseline, whereas it increased by 34%±3% during hyperoxia. Following the systemic administration of acetazolamide, PO(2,BR) increased by 38%±4%. We propose this new technology provides a robust method to measure changes in oxygen concentration in specific areas of the brain, in conscious freely moving rats. The ability to track long term changes with disease progression or drug treatment may be enabled. PMID:22123353

Russell, David M; Garry, Emer M; Taberner, Andrew J; Barrett, Carolyn J; Paton, Julian F R; Budgett, David M; Malpas, Simon C

2011-11-19

330

Method for dissolving plutonium dioxide  

DOEpatents

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.

Tallent, Othar K. (Oak Ridge, TN)

1978-01-01

331

How to Measure Dissolved Oxygen  

NSDL National Science Digital Library

This web page, hosted by the Washington State Department of Ecology, offers a general overview of dissolved oxygen and how it is measured. It includes protocols for measuring dissolved oxygen in turbulent waters as well as using the Winkler titration method. The site also features links to measuring other water quality parameters such as pH, nutrients, and turbidity.

Ecology, Washington S.

332

Nitric oxide (NO)--production and regulation of insulin secretion in islets of freely fed and fasted mice.  

PubMed

Production of nitric oxide through the action of nitric oxide synthase (NOS) has been detected in the islets of Langerhans. The inducible isoform of NOS (iNOS) is induced by cytokines and might contribute to the development of type-1 diabetes, while the constitutive isoform (cNOS) is thought to be implicated in the physiological regulation of insulin secretion. In the present study we have detected and quantified islet cNOS- and iNOS-derived NO production concomitant with measuring its influence on insulin secretion in the presence of different secretagogues: glucose, L-arginine, L-leucine and ?-ketoisocaproic acid (KIC) both during fasting and freely fed conditions. In intact islets from freely fed mice both cNOS- and iNOS-activity was greatly increased by glucose (20 mmol/l). Fasting induced islet iNOS activity at both physiological (7 mmol/l) and high (20 mmol/l) glucose concentrations. NOS blockade increased insulin secretion both during freely fed conditions and after fasting. L-arginine stimulated islet cNOS activity and did not affect islet iNOS activity. l-leucine or KIC, known to enter the TCA cycle without affecting glycolysis, did not affect either islet cNOS- or iNOS activity. Accordingly, insulin secretion stimulated by L-leucine or KIC was unaffected by addition of L-NAME both during feeding and fasting. We conclude that both high glucose concentrations and fasting increase islet total NO production (mostly iNOS derived) which inhibit insulin secretion. The insulin secretagogues L-leucine and KIC, which do not affect glycolysis, do not interfere with the islet NO-NOS system. PMID:22120830

Eckersten, Dag; Henningsson, Ragnar

2011-11-24

333

The distribution of dissolved aluminum in the Yellow and East China Seas  

Microsoft Academic Search

Water samples containing dissolved aluminum were collected from the Yellow and East China Seas in October–November 2000. The\\u000a average concentrations of dissolved Al in the Yellow Sea (YS) and East China Sea (ECS) were 0.042 and 0.056 ?molL?1, respectively. The concentration of dissolved aluminum decreased gradually across the continental shelf. The lower concentrations\\u000a appeared in the YS cold water center

Jianbing Li; Jingling Ren; Jing Zhang; Sumei Liu

2008-01-01

334

Dissolved Vanillin as Tracer for Estuarine Lignin Conversion  

NASA Astrophysics Data System (ADS)

Lignin is produced only by vascular plants and therefore can be used as a tracer for terrestrial organic carbon input to the estuarine and marine environments. Lignin measurements have been done by analyses of the oxidation products such as vanillin or 4-hydroxybenzaldehyde. In the Elbe Estuary, free dissolved vanillin was analysed in order to test whether such measurements yield information on terrestrial carbon inputs into the Estuary and on the vanillin derived from lignin oxidation. In the period 1990-1992, concentrations of dissolved vanillin in the Elbe ranged from 0 to 60 ? g l -1(mean: 8 ?g l -1). Higher values were found in areas of increased microbial activity such as the turbidity zone and the river mouth where the water chemistry is influenced by large tidal flats. No correlation was found between dissolved vanillin and suspended matter concentrations, although lignin is normally associated with suspended particulate matter, nor was a covariance seen between dissolved vanillin and the terrestrial carbon inputs into the Estuary. Apparently, biological conversion of lignin was faster than the transport processes, and local sources were more dominant for the vanillin concentration than riverine sources. The dissolved vanillin turnover was fast and, consequently, a significant amount of lignin may be converted within an estuary. In sediments from the Estuary, the concentrations of dissolved vanillin were similar to those found in the water phase and showed no clear vertical profile. The sediment is unlikely to be the source for vanillin.

Edelkraut, F.

1996-12-01

335

Chemical characterization of dissolvable tobacco products promoted to reduce harm.  

PubMed

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. PMID:21332188

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

2011-02-18

336

Method of dissolving organic filter cake  

SciTech Connect

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.

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

1989-03-07

337

Chemical and Biological Microassays in Freely Suspended Droplets on Novel Fluidic Chips.  

National Technical Information Service (NTIS)

We developed the principles of a platform for manipulation of freely suspended micro- and nanoliter droplets for micromanipulation and microassays. The liquid transport in such chips requires very low energy input due to the lack of microchannels or solid...

O. D. Velev

2004-01-01

338

Characterization of locomotor-related spike activity in protocerebrum of freely walking cricket.  

PubMed

To characterize the neural elements involved in the higher-order control of spontaneous walking in insects, we recorded extracellular spike activity in the protocerebrum of freely walking crickets (Gryllus bimaculatus). Locomotor behavior was simultaneously recorded using a newly developed motion tracking system. We focused on spike units that altered their firing patterns during walking. According to their activity patterns with reference to walking bouts, these locomotor-related spike units were classified into the following four types: continuously activated unit during walking (type 1); continuously inhibited unit during walking (type 2); transiently activated unit at the onset of walking (type 3); and transiently activated unit at the termination of walking (type 4). The type 1 unit was the most dominant group (25 out of 33 units), whereas only a few units each were recorded for types 2-4. Some of the locomotor-related units tended to change firing pattern before the onset or termination of walking bouts. Spike activity in some type 1 units was found to be closely correlated with walking speed. When firing timing was compared between unit pairs, their temporal relationships (synchronization/desynchronization) altered, depending on the behavioral state (standing/walking). Mechanical stimuli applied to the body surface elicited excitatory responses in the majority of the units. Histological observations revealed that the recorded sites were concentrated near or within the mushroom body and central complex in the protocerebrum. PMID:23829220

Kai, Kazuki; Okada, Jiro

2013-07-01

339

Distribution of dissolved silver in marine waters  

NASA Astrophysics Data System (ADS)

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.

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

2003-04-01

340

Photodegradation of fluorescent dissolved organic matter in river waters  

Microsoft Academic Search

Photodegradation of dissolved organic matter (DOM), collected from two upstream and one downstream sites in the Lake Biwa watershed in Japan, was investigated using fluorescence properties of three-dimensional excitation emission matrix (3-D EEM). Solar irradiation caused a decrease in the dissolved organic carbon (DOC) concentration and in the fluorescence peak intensity (FI) of fulvic acid (FA)- and protein-like substances in

KHAN M. G. MOSTOFA; TAKAHITO YOSHIOKA; EIICHI KONOHIRA; EIICHIRO TANOUE

341

The solubility control of rare earth elements in natural terrestrial waters and the significance of PO 4 3? and CO 3 2? in limiting dissolved rare earth concentrations: A review of recent information  

Microsoft Academic Search

Rare earth element (REE) concentrations in alkaline lakes, circumneutral pH groundwaters, and an acidic freshwater lake were determined along with the free carbonate, free phosphate, and free sulfate ion concentrations. These parameters were used to evaluate the saturation state of these waters with respect to REE phosphate and carbonate precipitates. Our activity product estimates indicate that the alkaline lake waters

Kevin H. Johannesson; W. Berry Lyons; Klaus J. Stetzenbach; Robert H. Byrne

1995-01-01

342

Dissolved mercury behaviour in the Saint Lawrence estuary  

NASA Astrophysics Data System (ADS)

Dissolved mercury concentrations have been measured in the waters of the St Lawrence estuary. The typical concentration of the riverine end-member is 12·0±3·0 p M; the oceanic end-member samples exhibit a mean mercury concentration of 2·4 p M. The graphical pattern of the relationship between mercury concentration and salinity shows a departure from a dilution line. We suggest that a removal of mercury from the dissolved phase during the estuarine mixing is responsible for this observation. Based on the results, the actual input of dissolved mercury from the St Lawrence River to the Gulf is evaluated to be approximately 0·52 T a -1.

Cossa, Daniel; Gobeil, Charles; Courau, Philippe

1988-02-01

343

Dissolved oxygen in lower Hudson Estuary: 1978--93  

Microsoft Academic Search

During summer months, dissolved oxygen (DO) concentrations in the lower Hudson estuary were usually lower than atmospheric equilibrium values. Distributions of DO along the axis of the estuary can be described by three general characteristics. Firstly, surface and bottom values lie on a single trend when plotted against salinity. Secondly, maximum DO concentrations were observed 50--75 km upstream of Manhattan

Jordan F. Clark; H. James Simpson; Richard F. Bopp; Bruce L. Deck

1995-01-01

344

Dissolved organic carbon in a northern boreal landscape  

Microsoft Academic Search

I examined concentrations and fluxes of dissolved organic carbon (DOC) in precipitation, upland forest throughfall, stemflow and soil water, peatland pore water, beaver ponds, and streams from May to September 1994 in the BOREAS Northern Study Area, near Thompson, Manitoba, Canada. Concentrations of DOC in precipitation were large (8 mg L?1) compared to other boreal locations, possibly associated with a

T. R. Moore

2003-01-01

345

Dissolved organic carbon in a northern boreal landscape  

Microsoft Academic Search

I examined concentrations and fluxes of dissolved organic carbon (DOC) in precipitation, upland forest throughfall, stemflow and soil water, peatland pore water, beaver ponds, and streams from May to September 1994 in the BOREAS Northern Study Area, near Thompson, Manitoba, Canada. Concentrations of DOC in precipitation were large (8 mg L-1) compared to other boreal locations, possibly associated with a

T. R. Moore

2003-01-01

346

Dissolved organic carbon in a northern boreal landscape  

Microsoft Academic Search

I examined concentrations and fluxes of dissolved organic carbon (DOC) in precipitation, upland forest throughfall, stemflow and soil water, peatland pore water, beaver ponds, and streams from May to September 1994 in the BOREAS Northern Study Area, near Thompson, Manitoba, Canada. Concentrations of DOC in precipitation were large (8 mg L1) compared to other boreal locations, possibly associated with a

T. R. Moore

2003-01-01

347

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...

348

Reducing emissions from uranium dissolving  

SciTech Connect

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.

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

1992-10-01

349

Reducing emissions from uranium dissolving  

SciTech Connect

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.

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

1992-10-01

350

The exchange rate between dissolved tripalmitin and tripalmitin crystals.  

PubMed

The focus of this paper is on understanding the exchange between dissolved fats and fat crystals in dispersions by quantifying the rate of the exchange between the fats in solution and in crystals. In the studies reported here, tripalmitin (PPP) was used as model fat. The dispersions contained PPP crystals and dissolved radio-labelled PPP (14C-PPP, used as the probe) in a medium chain triglyceride oil (MCT). The exchange process between the dissolved 14C-PPP and unlabelled PPP crystals was followed using a radio-detector. The effect of the crystal concentration on the exchange rate was studied. The results suggested that the rate of the exchange is dependent upon both the dissolution of the surface of the crystals and also diffusion and crystallisation of the dissolved compounds. PMID:11377952

Haghshenas, N; Smith, P; Bergenståhl, B

2001-07-01

351

Increased dissolved oxygen in Pacific intermediate waters due to lower rates of carbon oxidation in sediments  

Microsoft Academic Search

Concentrations of dissolved oxygen in the ocean seem to correlate well with climate instabilities over the past 100,000 years. For example, the concentration of dissolved oxygen in Pacific intermediate waters was considerably higher during Pleistocene glacial periods than it is today. This has been inferred from the presence of bioturbated sediments, implying that oxygen levels were sufficient for burrowing organisms

Lowell D. Stott; William Berelson; Robert Douglas; Donn Gorsline

2000-01-01

352

Dissolved inorganic constituents as conservative tracers of a leachate plume from a municipal landfill, Memphis, Tennessee  

Microsoft Academic Search

Selected dissolved inorganic constituents were used to trace the path of a leachate plume emanating from the Shelby County landfill, a municipal landfill at Memphis, Tennessee. Concentrations of dissolved solids, ammonia nitrogen, barium, boron, calcium, sodium, strontium, and other constituents were measured in water samples from wells screened in the alluvial aquifer downgradient from the landfill. Concentrations of the named

J. E. Mirecki; W. S. Parks

1992-01-01

353

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

NASA Astrophysics Data System (ADS)

Dissolved and particulate concentrations of the biogenic thiols cysteine (Cys), arginine-cysteine (Arg-Cys), glutamine-cysteine (Gln-Cys), ?-glutamate-cysteine ( ?-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 ?-Glu-Cys, with concentrations as high as 15 nM. Given the relatively small pool of intracellular ?-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 ?-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.

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

2006-12-01

354

Storm event exports of dissolved organic nitrogen (DON) across multiple catchments in a glaciated forested watershed  

Microsoft Academic Search

Storm event patterns of dissolved organic nitrogen (DON) were studied for multiple events across four catchments (1.6–696 ha) in a forested, glaciated watershed in western New York State. Highest concentrations of DON in the watershed were recorded for litter leachate followed by throughfall. Storm event concentrations of DON consistently peaked at or before peak discharge while dissolved organic carbon (DOC)

Shreeram P. Inamdar; Myron J. Mitchell

2007-01-01

355

Tracing dissolved organic substances and nutrients from the Lena River through Laptev Sea (Arctic)  

Microsoft Academic Search

Dissolved organic substances and inorganic nutrients were determined in the central and northern Laptev Sea north of the Lena delta region in August 1995. These results are discussed with data from the Lena River from July 1994. Enhanced concentrations of dissolved organic matter (DOM) and silicate in the Lena River generate a concentration gradient extending towards the oceanic regions of

G Kattner; J. M Lobbes; H. P Fitznar; R Engbrodt; E.-M Nöthig; R. J Lara

1999-01-01

356

Dissolving a Substance in Different Liquids  

NSDL National Science Digital Library

In this activity, learners make colored sugar and add it to water, alcohol, and oil to discover some interesting differences in dissolving. The sugar will dissolve to a different extent in each liquid, and the color may or may not dissolve depending on the liquid. Learners also have an opportunity to refine their definition of the term dissolve. Adult supervision recommended.

Kessler, James H.; Galvan, Patricia M.

2007-01-01

357

Three representative UK moorland soils show differences in decadal release of dissolved organic carbon in response to environmental change  

NASA Astrophysics Data System (ADS)

Moorland carbon reserves in organo-mineral soils may be crucial to predicting landscape-scale variability in soil carbon losses, an important component of which is dissolved organic carbon (DOC). Surface water DOC trends are subject to a range of scaling, transport and biotic processes that disconnect them from signals in the catchment's soils. Long-term soil datasets are vital to identify changes in DOC release at source and soil C depletion. Here we show, that moorland soil solution DOC concentrations at three key UK Environmental Change Network sites increased between 1993-2007 in both surface- and sub- soil of a freely-draining Podzol (48 % and 215 % increases in O and Bs horizons, respectively), declined in a gleyed Podzol and showed no change in a Peat. Our principal findings were that: (1) considerable heterogeneity in DOC response appears to exist between different soils that is not apparent from the more consistent observed trends for streamwaters, and (2) freely-draining organo-mineral Podzol showed increasing DOC concentrations, countering the current scientific focus on soil C destabilization in peats. We discuss how the key solubility controls on DOC associated with coupled physico-chemical factors of ionic strength, acid deposition recovery, soil hydrology and temperature cannot readily be separated. Yet, despite evidence that all sites are recovering from acidification the soil-specific responses to environmental change have caused divergence in soil DOC concentration trends. The study shows that the properties of soils govern their specific response to an approximately common set of broad environmental drivers. Key soil properties are indicated to be drainage, sulphate and DOC sorption capacity. Soil properties need representation in process-models to understand and predict the role of soils in catchment to global C budgets. Catchment hydrological (i.e. transport) controls may, at present, be governing the more ubiquitous rises in river DOC concentration trends, but soil (i.e. source) controls provide the key to prediction of future C loss to waters and the atmosphere.

Stutter, M. I.; Lumsdon, D. G.; Rowland, A. P.

2011-08-01

358

Three representative UK moorland soils show differences in decadal release of dissolved organic carbon in response to environmental change  

NASA Astrophysics Data System (ADS)

Moorland carbon reserves in organo-mineral soils may be crucial to predicting landscape-scale variability in soil carbon losses, an important component of which is dissolved organic carbon (DOC). Surface water DOC trends are subject to a range of scaling, transport and biotic processes that disconnect them from signals in the catchment's soils. Long-term soil datasets are vital to identify changes in DOC release at source and soil C depletion. Here we show, that moorland soil solution DOC concentrations at three key UK Environmental Change Network sites increased between 1993-2007 in both surface- and sub- soil of a freely-draining Podzol (48 % and 215 % increases in O and Bs horizons, respectively), declined in a gleyed Podzol and showed no change in a Peat. Our principal findings were that: (1) considerable heterogeneity in DOC response appears to exist between different soils that is not apparent from the more consistent observed trends for streamwaters, and (2) freely-draining organo-mineral Podzol showed increasing DOC concentrations, countering the current scientific focus on soil C destabilization in peats. We discuss how the key solubility controls on DOC associated with coupled physico-chemical factors of ionic strength, acid deposition recovery, soil hydrology and temperature cannot readily be separated. Yet, despite evidence that all sites are recovering from acidification the soil-specific responses to environmental change have caused divergence in soil DOC concentration trends. The study shows that the properties of soils govern their specific response to an approximately common set of broad environmental drivers. Key soil properties are indicated to be drainage, sulphate and DOC sorption capacity. Soil properties need representation in process-models to understand and predict the role of soils in catchment to global C budgets. Catchment hydrological (i.e. transport) controls may, at present, be governing the more ubiquitous rises in river DOC concentration trends, but soil (i.e. source) controls provide the key to prediction of future C loss to waters and the atmosphere.

Stutter, M. I.; Lumsdon, D. G.; Rowland, A. P.

2011-12-01

359

Continuous mineralization of concentrated phenol dissolved in an electrolyte?containing tap water by integrating biological–photocatalytic treatment with TiO2 separation: utilization of sunlight and reuse of TiO2  

Microsoft Academic Search

The continuous mineralization of concentrated phenol (200 mg l) in an electrolyte?containing tap water was investigated using a biological–photocatalytic treatment integrated with TiO2 separation. Black light and sunlight were used as the light source, and the reuse of TiO2 was also studied. The mineralization of phenol in tap water and the reuse of TiO2 were conducted in a flow system

D. Suryaman; K. Hasegawa; S. Kagaya; T. Yoshimura

2009-01-01

360

Dissolving Different Liquids in Water  

NSDL National Science Digital Library

In this activity, students add different liquids to water and apply their working definition of âdissolvingâ to their observations. After observing isopropyl rubbing alcohol, vegetable oil, and corn syrup in water, students can conclude that while some liquids may dissolve in water, different liquids dissolve in water to different extents. There is a downloadable activity sheet that will be very helpful to educators, and will help students stay on track. An assessment sheet is also available on the activity page to keep track of students progress. There is also a step by step guide as to how to perform the experiment, and how to introduce it t the students.

Kessler, James; Galvan, Patti

2010-01-01

361

Influence of sorption to dissolved humic substances on transformation reactions of hydrophobic organic compounds in water. Part II: hydrolysis reactions.  

PubMed

The effect of dissolved humic acid (HA) on two types of hydrolysis reactions was investigated: (I) dehydrochlorination of gamma-hexachlorocyclohexane (HCH) and 1,1,2,2-tetrachloroethane (TeCA) as a reaction involving hydroxide ions (OH(-)) and (II) hydrolysis of 1-octyl acetate (OA) which is catalyzed by H(+) at the applied pH value (pH 4.5). The rate of TeCA hydrolysis was not affected by addition of 2 g l(-1) of HA at pH 10 (k' = 0.33 h(-1)) but HCH hydrolysis was significantly inhibited (k' = 4.6 x 10(-3) h(-1) without HA and 2.8 x 10(-3)h(-1) at 2 g l(-1) HA). HCH is sorbed by 51% whereas TeCA sorption is insignificant at this HA concentration. Sorbed HCH molecules are effectively protected due to electrostatic repulsion of OH(-) by the net negative charge of the HA molecules. In contrast, OA hydrolysis at pH 4.5 (k' = 1.6 x 10(-5) h(-1)) was drastically accelerated after addition of 2 g l(-1) HA (k' = 1.1 x 10(-3) h(-1)). The ratio of the pseudo-first-order rate constants of the sorbed and the freely dissolved ester fraction is about 70. H(+) accumulation in the microenvironment of the negatively charged HA molecules was suggested to contribute to the higher reaction rate for the sorbed fraction in case of this H(+)-catalyzed reaction. Analogous effects from anionic surfactants are known as micellar catalysis. PMID:18237760

Georgi, Anett; Trommler, Ulf; Reichl, Annett; Kopinke, Frank-Dieter

2008-01-30

362

Investigating the significance of dissolved organic contaminants in aquatic environments: coupling passive sampling with in vitro bioassays.  

PubMed

We investigated the feasibility of coupling passive sampling and in vitro bioassay techniques for both chemical and ecotoxicological assessment of complex mixtures of organic contaminants in water. Silicone rubber passive sampling devices (SR-PSDs) were deployed for 8-9 weeks in four streams and an estuary of an agricultural catchment in North East (NE) Scotland. Extracts from the SR-PSDs were analysed for freely dissolved hydrophobic organic contaminants (HOCs) and screened for wide range of pesticides. The total concentrations of dissolved PAHs (?PAH(40), parent and branched) in the water column of the catchment varied from 38 to 69 ng L(-1), whilst PCBs (?PCB(32)) ranged 0.02-0.06 ng L(-1). A number and level of pesticides and acid/urea herbicides of varying hydrophobicity (logK(OW)s ~2.25 to ~5.31) were also detected in the SR extracts, indicating their occurrence in the catchment. The acute toxicity and EROD induction potentials of SR extracts from the study sites were evaluated with rainbow trout liver (Oncorhynchus mykiss; RTL-W1) cell line. Acute cytotoxicity was not observed in cells following 48 h exposure to the SR extracts using neutral red uptake assay as endpoint. But, on a sublethal level, for every site, statistically significant EROD activity was observed to some degree following 72 h exposure to extracts, indicating the presence of compounds with dioxin-like effect that are bioavailable to aquatic organisms in the water bodies of the catchment. Importantly, only a small fraction of the EROD induction could be attributed to the PAHs and PCBs that were determined. This preliminary study demonstrates that the coupling of silicone rubber passive sampling techniques with in vitro bioassays is feasible and offers a cost effective early warning signal on water quality deterioration. PMID:22850278

Emelogu, Emmanuel S; Pollard, Pat; Robinson, Craig D; Smedes, Foppe; Webster, Lynda; Oliver, Ian W; McKenzie, Craig; Seiler, T B; Hollert, Henner; Moffat, Colin F

2012-07-31

363

Kinetics of desorption of organic compounds from dissolved organic matter.  

PubMed

This study presents a new experimental technique for measuring rates of desorption of organic compounds from dissolved organic matter (DOM) such as humic substances. The method is based on a fast solid-phase extraction of the freely dissolved fraction of a solute when the solution is flushed through a polymer-coated capillary. The extraction interferes with the solute-DOM sorption equilibrium and drives the desorption process. Solutes which remain sorbed to DOM pass through the extraction capillary and can be analyzed afterward. This technique allows a time resolution for the desorption kinetics from subseconds up to minutes. It is applicable to the study of interaction kinetics between a wide variety of hydrophobic solutes and polyelectrolytes. Due to its simplicity it is accessible for many environmental laboratories. The time-resolved in-tube solid-phase microextraction (TR-IT-SPME) was applied to two humic acids and a surfactant as sorbents together with pyrene, phenanthrene and 1,2-dimethylcyclohexane as solutes. The results give evidence for a two-phase desorption kinetics: a fast desorption step with a half-life of less than 1 s and a slow desorption step with a half-life of more than 1 min. For aliphatic solutes, the fast-desorbing fraction largely dominates, whereas for polycyclic aromatic hydrocarbons such as pyrene, the slowly desorbing, stronger-bound fraction is also important. PMID:22035249

Kopinke, Frank-Dieter; Ramus, Ksenia; Poerschmann, Juergen; Georgi, Anett

2011-11-10

364

New potentiomentric dissolved oxygen sensors in thick film technology  

Microsoft Academic Search

New designed dissolved oxygen potentiometric sensors in thick film technology based in the use of RuO2 as active material and TiO2 or polyisoftalamide diphenylsulphone (PIDS) as membranes have been developed. TiO2-coated RuO2 electrodes showed a linear response as a function of the logarithm of the dissolved oxygen concentration in the 0.5–8ppm range (log[O2], ?4.82 to ?3.60; concentration of O2 in

Ramón Mart??nez-Máñez; Juan Soto; Josefa Lizondo-Sabater; Eduardo Garc??a-Breijo; Luis Gil; Javier Ibáñez; Isabel Alcaina; Silvia Alvarez

2004-01-01

365

Annihilation of freely migrating defects by cascade remnants in Cu-1% Au alloys  

NASA Astrophysics Data System (ADS)

The effects of cascade remnants on freely migrating defects (FMD) were studied by measuring radiation-induced segregation in Cu-1%Au at 400°C during simultaneous irradiation with 1.5 MeV He and (400-800) keV heavy ions (Ne, Ar or Cu). Radiation induced segregation during single-ion irradiation with He, Ne, Ar and Cu, and the effects of pre-irradiation with the same ions, were also investigated. The large segregation observed during 1.5 MeV He-only irradiation was dramatically suppressed under simultaneous Cu irradiation. This suppression disappeared immediately after the Cu irradiation ceased, indicating that it was caused by a transient population of cascade remnants, i.e., vacancy and/or interstitial clusters. For simultaneous inert-gas (He and Ne or Ar) irradiation, a similar suppression of the radiation induced segregation was observed. However, in contrast to the Cu-irradiation results, the suppression persisted after the Ne or Ar beam was turned off. The present results demonstrate that the energetic displacement cascades created by heavy ions introduce additional point-defect annihilation sites, which reduce the steady-state concentration of FMD. This finding implies that recombination dominates defect annihilation under the present irradiation conditions, which is indeed what is observed experimentally. As the cascade remnants produced by the Cu ions are thermally unstable at 400°C, the suppression of radiation induced segregation occurs only during simultaneous irradiation. During Ne and Ar irradiation, the inert gas atoms which accumulate in the specimen apparently stabilize the cascade remnants, allowing the suppression to persist during subsequent He-only irradiation.

Iwase, A.; Rehn, L. E.; Baldo, P. M.; Funk, L.

1996-11-01

366

Friction-based stabilization of juxtacellular recordings in freely moving rats.  

PubMed

Virtually nothing is known about the activity of morphologically identified neurons in freely moving mammals. Here we describe stabilization and positioning techniques that allow juxtacellular recordings from labeled single neurons in awake, freely moving animals. This method involves the use of a friction-based device that allows stabilization of the recording pipette by friction forces. Friction is generated by a clamplike mechanism that tightens a sliding pipette holder to a preimplanted pipette guide. The interacting surfaces are smoothed to optical quality (<5-nm roughness) to enable micrometer stepping precision of the device during operation. Our method allows recordings from identified neurons in freely moving animals, and thus opens new perspectives for analyzing the role of identified neurons in the control of behavior. PMID:22514297

Herfst, Lucas; Burgalossi, Andrea; Haskic, Kurt; Tukker, John J; Schmidt, Martin; Brecht, Michael

2012-04-18

367

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

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.

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

2003-01-01

368

Dynamics of dissolved organic nitrogen in subalpine Castle Lake, California  

Microsoft Academic Search

Dissolved organic nitrogen (DON) concentrations were measured in meso-oligotrophic Castle Lake, California during the ice-free season in 1982, 1983 and 1984. No consistent relationships were found between DON and particulate-N, primary productivity rates or chlorophyll concentrations. However, increases in DON concentrations were observed in the early growing season of 1982 and 1984 when water temperature was rising and a diatom

J. P. Zehr; S. G. Paulsen; R. P. Axler; C. R. Goldman

1988-01-01

369

Laser speckle contrast imaging of cerebral blood flow in freely moving animals  

NASA Astrophysics Data System (ADS)

We designed a miniature laser speckle imager that weighs ~20 g and is 3.1-cm high for full-field high-resolution imaging of cerebral blood flow (CBF) in freely moving animals. Coherent laser light illuminates the cortex through a multimode optical fiber bundle fixed onto the supporting frame of the imager. The reflected lights are then collected by a miniature macrolens system and imaged by a high-resolution CMOS camera at a high frame rate (50 fps). Using this miniature imager, we achieve high spatiotemporal resolution laser speckle contrast imaging of CBF in freely moving animals in real time.

Miao, Peng; Lu, Hongyang; Liu, Qi; Li, Yao; Tong, Shanbao

2011-09-01

370

Laser speckle contrast imaging of cerebral blood flow in freely moving animals.  

PubMed

We designed a miniature laser speckle imager that weighs ?20 g and is 3.1-cm high for full-field high-resolution imaging of cerebral blood flow (CBF) in freely moving animals. Coherent laser light illuminates the cortex through a multimode optical fiber bundle fixed onto the supporting frame of the imager. The reflected lights are then collected by a miniature macrolens system and imaged by a high-resolution CMOS camera at a high frame rate (50 fps). Using this miniature imager, we achieve high spatiotemporal resolution laser speckle contrast imaging of CBF in freely moving animals in real time. PMID:21950906

Miao, Peng; Lu, Hongyang; Liu, Qi; Li, Yao; Tong, Shanbao

2011-09-01

371

Blood pressure measurement in freely moving rats by the tail cuff method.  

PubMed

Inconsistency in consecutive blood pressure values is one of the most frequently observed problems in tail cuff method. The aim of this study was to measure blood pressure using the tail cuff method in rats without heating, anesthesia, and movement restriction. In this study, it has been shown that blood pressure measurement could be obtained without problem using the tail cuff method in freely moving rats in their cage environment. Also, the reliability of consecutive blood pressure values obtained from freely moving rats was higher than ether anesthesia and restricted groups. PMID:22571543

Erken, Haydar Ali; Erken, Gülten; Genç, Osman

2012-05-09

372

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

NASA Astrophysics Data System (ADS)

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.

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

2011-07-01

373

Dissolved oxygen and fish behavior  

Microsoft Academic Search

Synopsis This essay reviews the behavioral responses of fish to reduced levels of dissolved oxygen from the perspective of optimization theory as used in contemporary behavioral ecology. A consideration of oxygen as a resource suggests that net oxygen gain per unit of energy expenditure will be the most useful currency for ecological models of breathing. In the process of oxygen

Donald L. Kramer

1987-01-01

374

Dissolving Pulp Industry. Market Trends.  

National Technical Information Service (NTIS)

The report presents a worldwide overview of the dissolving pulp industry and highlights of the industry in Alaska. It describes trends in world markets and major end-use markets, with special emphasis on the manufacture and use of textile, fibers in the U...

I. Durbak

1993-01-01

375

Phase fluorometric dissolved oxygen sensor  

Microsoft Academic Search

The design and performance of a ruggedised dissolved oxygen (DO) probe, which is based on phase fluorometric detection of the quenched fluorescence of an oxygen-sensitive ruthenium complex, is reported. The complex is entrapped in a porous hydrophobic sol–gel matrix that has been optimised for this application. The LED excitation and photodiode detection are employed in a dipstick probe configuration, with

C. McDonagh; C. Kolle; A. K. McEvoy; D. L. Dowling; A. A. Cafolla; S. J. Cullen; B. D. MacCraith

2001-01-01

376

Survival, Development, and Growth of Fall Chinook Salmon Embryos, Alevins, and Fry Exposed to Variable Thermal and Dissolved Oxygen Regimes  

Microsoft Academic Search

Some fall Chinook salmon Oncorhynchus tshawytscha initiate spawning in the Snake River downstream of Hells Canyon Dam at temperatures that exceed 13°C and at intergravel dissolved oxygen concentrations that are less than 8 mg O2\\/L. Although water temperature declines and dissolved oxygen increases soon after spawning, the initial temperature and dissolved oxygen levels do not meet the water quality standards

David R. Geist; C. Scott Abernethy; Kristine D. Hand; Valerie I. Cullinan; James A. Chandler; Phillip A. Groves

2006-01-01

377

Wet-oxidation and automated colorimetry for simultaneous determination of organic carbon, nitrogen and phosphorus dissolved in seawater  

Microsoft Academic Search

We developed a simple and reliable method which allows simultaneous determination of organic forms of carbon (DOC), nitrogen (DON) and phosphorus (DOP) dissolved in seawater. Conversion of dissolved organic matter (DOM) to inorganic products (carbon dioxide, nitrate+nitrite and soluble reactive phosphate) is performed by a persulfate wet-oxidation in low alkaline condition. After oxidation, the concentration of the inorganic products dissolved

Patrick Raimbault; Wilfried Pouvesle; Frédéric Diaz; Nicole Garcia; Richard Sempéré

1999-01-01

378

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

USGS Publications Warehouse

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-solids load at the mouth of Muddy Creek. A significant downward trend in dissolved-solids concentrations from 1973 to 2006 was determined for Muddy Creek at a site just downstream of that portion of the basin containing agricultural land. Dissolved-solids concentrations decreased about 2.1 percent per year; however, the rate of change was a decrease of 1.8 percent per year when dissolved-solids concentrations were adjusted for flow.

Gerner, Steven J.

2008-01-01

379

Dissolved aluminium in the Southern Ocean  

NASA Astrophysics Data System (ADS)

Dissolved aluminium (Al) occurs in a wide range of concentrations in the world oceans. The concentrations of Al in the Southern Ocean are among the lowest ever observed. An all-titanium CTD sampling system makes it possible to study complete deep ocean sections of Al and other trace elements with the same high vertical resolution of 24 depths as normal for traditional CTD/Rosette sampling. Overall, 470 new data points of Al are reported for 22 full depth stations and 24 surface sampling positions along one transect. This transect consisted of 18 stations on the zero meridian proper from 51°57' S until 69°24'S, and 4 stations somewhat to the northeast towards Cape Town from 42°20'S, 09°E to 50°17'S, 01°27'E. The actual concentrations of Al in the Southern Ocean were lower than previously reported. The concentration of Al in the upper 25 m was relatively elevated with an average concentration of 0.71 nM ( n=22; S.D.=0.43 nM), most likely due to atmospheric input by a suggested combination of direct atmospheric (wet and dry) input and indirect atmospheric input via melting sea ice. Below the surface waters there was a distinct Al minimum with an average concentration of 0.33 nM ( n=22; S.D.=0.13 nM) at an average depth of 120 m. In the deep southernmost Weddell Basin the concentration of Al increased with depth to ˜0.8 nM at 4000 m, and a higher concentration of ˜1.5 nM in the ˜4500-5200 m deep Weddell Sea Bottom Water. Over the Bouvet triple junction region, where three deep ocean ridges meet, the concentration of Al increased to ˜1.4 nM at about 2000 m depth over the ridge crest. In the deep basin north of the Bouvet region the concentration of Al increased to higher deep values of 4-6 nM due to influence of North Atlantic Deep Water. In general the intermediate and deep distribution of Al results from the mixing of water masses with different origins, the formation of deep water and additional input from sedimentary sources at sea floor elevations. No significant correlation between Al and silicate (Si) was observed. This is in contrast to some other ocean regions. In the Southern Ocean the supply of Al is extremely low and any signal from Al uptake and dissolution with biogenic silica is undetectable against the high dissolved Si and low dissolved Al concentrations. Here the Al-Si relation in the deep ocean is uncoupled. This is due to the scavenging and subsequent loss of the water column of Al, whereas the concentration of Si increases in the deep ocean due to its input from deep dissolution of biogenic diatom frustules settling from the surface layer.

Middag, R.; van Slooten, C.; de Baar, H. J. W.; Laan, P.

2011-12-01

380

Technique for Measurements of the Evaporation Rate of Single, Freely Falling, Droplets  

Microsoft Academic Search

An ex perimental setup has been developed in order to determine evaporation rates of freely falling droplets. The droplets may consist of pure liquids, of a mixture of different liquids, or of a solution. After a droplet has been produced by a droplet on deman d generator, it falls downwards along a vertical observation channel. Meanwhile a laser beam is

N. Roth; J. Wilms; B. Weigand

381

Optical Light Curves of HZ Her in the Model of Freely Precessing Neutron Star.  

National Technical Information Service (NTIS)

Optical light curves to be observed from HZ Herculis are simulated numerically. THe model of freely precessing neutron star in Her X-1 is applied. The comparison with extended B-photometrical data covering a 16 year interval is performed. The best fit par...

I. B. Voloshina V. M. Lyutyi

1989-01-01

382

Telemetric monitoring of blood pressure in freely moving mice: a preliminary study  

Microsoft Academic Search

Summary This paper describes for the first time the possibility for recording the systolic pressure (SPI, diastolic pressure (DP), and the mean arterial pressure (MAP) as well as the heart rate (HR) and locomotor activity (LA) in freely moving mice, using a commercially available telemetry and data acquisition system. The system comprises a new, small radio-telemetry transmitter implanted in the

Klaas Kramer; Hans-Peter Voss; Joop A. Grimbergen; Perry A. Mills; Daniel Huetteman; Lynn Zwiers; Brian Brockway

2000-01-01

383

Improved optimal seam selection blending for fast video stitching of videos captured from freely moving devices  

Microsoft Academic Search

We investigate the problem of stitching timely synchronized video streams captured by freely moving devices. Recently, it was shown that using frame-to-frame correlation can greatly enhance the efficiency and effectiveness of video stitching algorithms [19]. In this paper, we address some of the shortcomings in [19], namely the simple blending approach, causing almost a third of stitching errors and the

Motaz El-Saban; Mostafa Izz; Ayman Kaheel; Mahmoud Refaat

2011-01-01

384

Optical Trapping of Disk-Shaped Islands on Freely Suspended Bubbles of Smectic Liquid Crystal  

Microsoft Academic Search

We have constructed an optical system for observing the layer and director structure of freely suspended smectic liquid crystal bubbles and for optical trapping of micrometer-sized objects using a reflected light microscope. Liquid crystal bubbles can have thicker circular regions (islands) which may easily be generated either by shrinking the bubble diameter or using laminar air jet flow. The diameters

Apichart Pattanaporkratana

2003-01-01

385

The WURM project - a web-based freely accessible database of computed physical properties for minerals  

Microsoft Academic Search

This project aims to build a freely accessible web-based database of computed physical properties for minerals. The database provides for each mineral various physical properties: the crystal structure used in the calculation, the dynamical charges and the dielectric tensors, the refractive index, the Raman spectra with both peak position and intensity and the infrared spectra with peak position. Additional information

E. Bobocioiu

2009-01-01

386

The Evaporation, Temperature and Thermal Relaxation-Time of Freely Falling Waterdrops  

Microsoft Academic Search

A theoretical and experimental study of the physical behavior of freely falling waterdrops is carried out. The influence of ventilation and environment upon the evaporation and equilibrium temperature is formulated in quantitative terms.The theoretical approach emphasizes the vapor and heat transferred to packets of environmental air that make transient contact with the liquid sphere. The basic psychrometric equation is derived

Gilbert D. Kinzer; Ross Gunn

1951-01-01

387

Diffusion-controlled Aggregation of Bucky Balls on Freely Suspended Smectic Liquid Crystal Films  

Microsoft Academic Search

Bucky balls (BB) have the tendency to clump together, making it hard to have them suspended in a solvent. We find that in highly viscous bulk 8CB, a smectic liquid crystal at room temperature, the aggregation happens more slowly. As the result, a freely suspended film made from the 8CB-BB mixture contains mostly small BB clumps. The diffusion coefficients of

Zoom Nguyen; Tatyana Malinina; Cheol Park; Joseph Maclennan; Matthew Glaser; Noel Clark

2011-01-01

388

HermesC: RF wireless low-power neural recording system for freely behaving primates  

Microsoft Academic Search

Neural prosthetics for motor systems is a rapidly growing field with the potential to provide treatment for amputees or patients suffering from neurological injury and disease. To determine whether a physically active patient such as an amputee can take advantage of these systems, we seek to develop an animal model of freely moving humans. Therefore, we have developed and tested

Cynthia A. Chestek; Vikash Gilja; Paul Nuyujukian; Stephen I. Ryu; Krishna V. Shenoy; Ryan J. Kier

2008-01-01

389

Wireless Neural\\/EMG Telemetry Systems for Small Freely Moving Animals  

Microsoft Academic Search

We have developed miniature telemetry systems that capture neural, EMG, and acceleration signals from a freely moving insect or other small animal and transmit the data wire- lessly to a remote digital receiver. The systems are based on custom low-power integrated circuits (ICs) that amplify, filter, and digitize four biopotential signals using low-noise circuits. One of the chips also digitizes

Reid R. Harrison; Haleh Fotowat; Raymond Chan; Ryan J. Kier; Robert Olberg; Anthony Leonardo; Fabrizio Gabbiani

2011-01-01

390

Freely flying bees discriminate between stationary and moving objects: performance and possible mechanisms  

Microsoft Academic Search

Freely flying honeybees are innately attracted to moving objects, as revealed by their spontaneous preference for a moving disc over an identical, but stationary disc. We have exploited this spontaneous preference to explore the visual cues by which a bee, which is herself in motion, recognizes a moving object. We find that the moving disc is not detected on the

Miriam Lehrer; Mandyam V. Srinivasan

1992-01-01

391

A rapid and simple cannulation technique for repeated sampling of cerebrospinal fluid in freely moving rats  

Microsoft Academic Search

A cannulation technique for frequent sampling of cerebrospinal fluid (CSF) in unanaesthetized freely moving rats is described. A permanent stainless steel cannula, constructed in such a way that no loss of CSF occurs, is placed into the rat's cisterna magna and fixed to the skull by anchoring screws and dental cement. A special CSF outflow opening of the cannula is

H. J. Bouman; T. B. van Wimersma Greidanus

1979-01-01

392

Optetrode: a multichannel readout for optogenetic control in freely moving mice  

Microsoft Academic Search

Recent advances in optogenetics have improved the precision with which defined circuit elements can be controlled optically in freely moving mammals; in particular, recombinase-dependent opsin viruses, used with a growing pool of transgenic mice expressing recombinases, allow manipulation of specific cell types. However, although optogenetic control has allowed neural circuits to be manipulated in increasingly powerful ways, combining optogenetic stimulation

Polina Anikeeva; Aaron S Andalman; Ilana Witten; Melissa Warden; Inbal Goshen; Logan Grosenick; Lisa A Gunaydin; Loren M Frank; Karl Deisseroth

2011-01-01

393

Applications of a total dissolved gas pressure probe in ground water studies.  

PubMed

Measurements of dissolved gases have numerous applications in ground water hydrology, and it is now possible to measure the total dissolved gas pressure in situ using a probe. Dissolved gas pressure is measured by submerging a headspace volume with a gas-permeable membrane, allowing dissolved gases in the water to equilibrate with gases in the headspace, then measuring the pressure in the headspace with a pressure transducer. Total dissolved gas pressure (TGP) probes have many potential uses in ground water studies employing dissolved gases, including: (1) determining approximate excess air levels, which may provide information about the time and location of recharge; (2) screening wells for air contamination, which can compromise the accuracy of dissolved gas tracer techniques: (3) detecting a trapped gas phase, which can significantly reduce hydraulic conductivity and impede the transport of dissolved solutes and gases; (4) enabling the use of gas-filled passive diffusion samplers for determining accurate dissolved gas concentrations; and (5) determining relative concentrations of CH4 and CO2 when they are known to be highly abundant. Although TGP probes designed for surface water have been available for several years, TGP probes suitable for ground water applications have only recently become available. Herein we present what are, to our knowledge, the first reported ground water dissolved gas data collected using a TGP probe. We also explain the basic operating principles of these probes and discuss the potential applications listed. PMID:12873007

Manning, Andrew H; Solomon, D Kip; Sheldon, Amy L

394

The diffusion of dissolved silica in dilute aqueous solution  

NASA Astrophysics Data System (ADS)

The diffusion coefficient of dissolved silica at 25.5 ± .5° C was determined as a function of concentration using a non-steady-state method whereby agar-gelled solutions containing dissolved silica from 0.09 to 1.50 mM ( pH = 5.5) were placed in contact with distilled water in glass cells. Diffusion coefficients were obtained by measuring the dissolved silica content of the distilled water after a given length of time. The measured diffusion coefficients decreased as a function of increasing dissolved silica concentration, which is thought to reflect an increase in dimeric silica according to the equilibrium: 2 Si ( OH ) 4 = Si 2 O ( OH ) 6 + H 2 O . The tracer diffusion coefficients for Si(OH) 4 and Si 2 O(OH) 6 and an association constant for the above reaction were determined by fitting the following equation to the experimental data: D obs = D monomer + (1 - ) D dimer where is the fraction of total dissolved silica which is Si(OH) 4 . The best fit yielded tracer D 's for Si(OH) 4 and Si 2 O(OH) 6 of 2.2 and 1.0 (in units of 10 -5 cm 2 sec -1 ), respectively, and an association constant of 330.

Applin, Kenneth R.

1987-08-01

395

Retardation of dissolved oxygen due to a trapped gas phase in porous media  

Microsoft Academic Search

Information on the transport of dissolved gases in ground water is needed to design ways to increase dissolved gas concentrations in ground water for use in in situ bioremediation (e.g., Oâ and CHâ) and to determine if dissolved gases are conservative tracers of ground-water flow (e.g., He). A theoretical model was developed to describe the effect of small quantities of

Virginia A. Fry; Jonathan D. Istok; Lewis Semprini; Kirk T. O'Reilly; Timothy E. Buscheck

1995-01-01

396

A new pH-ISFET based dissolved oxygen sensor by employing electrolysis of oxygen  

Microsoft Academic Search

A new dissolved oxygen sensor based on a pH-ISFET is discussed. A working electrode surrounding a pH-sensing gate of the pH-ISFET electrolyzes dissolved oxygen, resulting in a corresponding pH change near the pH-sensing gate. The pH-ISFET is expected to determine dissolved oxygen concentration by detecting this pH change. The results suggest that the proposed sensor operated by a combined mechanism

Byung-Ki Sohn; Chang-Soo Kim

1996-01-01

397

Speaking Freely  

ERIC Educational Resources Information Center

|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…

Watson, Jamal Eric

2012-01-01

398

Speaking Freely.  

ERIC Educational Resources Information Center

|In this interview, Albert Shanker, president of the United Federation of Teachers of New York City, executive vice president of the American Federation of Teachers, and vice president of the AFL/CIO, discussed such topics as the following: his participation in a meeting of labor leaders with President Ford on September 11; the potential influence…

Shanker, Albert

399

Reduced Dissolved Oxygen Test System for Marine Organisms.  

National Technical Information Service (NTIS)

A flow-through test system was designed to examine minimum dissolved oxygen (D.O.) requirements of marine animals. The system provides up to six treatment concentrations between 0.3 mg D.O./l and saturation. Sea water is degassed in a vacuum-evacuated pac...

D. C. Miller D. E. Body J. C. Sinnett S. L. Poucher J. Sewall D. J. Sleczkowski

1994-01-01

400

Predicting Diel Dissolved Oxygen Dynamics in the Carson River, Nevada  

Microsoft Academic Search

The Carson River originates in eastern Alpine County California, flows northeast into western Nevada through Carson City, and terminates in the Carson Sink. Elevated nutrient levels from agricultural return flows allow for excess attached algal (periphyton) growth. Periods of low flow, coupled with an abundance of periphyton, harbor an environment capable of producing dissolved oxygen concentrations less than 5 mg

Z. B. Latham; J. J. Warwick; C. H. Fritsen

2005-01-01

401

DISSOLVED OXYGEN AND OXIDATION-REDUCTION POTENTIALS IN GROUND WATER  

EPA Science Inventory

Water samples were collected from various depths in a pristine sand and gravel water table aquifer at monthly intervals over a period of one year. Dissolved oxygen concentrations were near saturation 9 feet below the water table and decreased to nearly zero at 78 feet below the w...

402

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...

403

Electrochemical determination of dissolved uranium in Krka river estuary  

Microsoft Academic Search

The applicability of the previously developed method for electrochemical determination of dissolved uranium concentration has been tested on natural water samples taken from the Krka river estuary during various seasons and along different depth profiles. The method is based on the following treatment of the sample: destroying the uranyl-carbonato complexes by adjusting the pH to 3, enabling the formation of

R Djogi?; M Branica

2001-01-01

404

REDUCED DISSOLVED OXYGEN TEST SYSTEM FOR MARINE ORGANISMS  

EPA Science Inventory

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

405

Agricultural Practices Influence Dissolved Nutrients Leaching through Intact Soil Cores  

Microsoft Academic Search

high water table was set in the Netherlands (Breeuwsma et al., 1995). Agricultural practices such as tillage, crop- Nitrogen and P leaching from agricultural land to ground water ping systems, and fertilizer applications influence soil poses a threat to water quality, but it may be possible to control nutrient concentrations and drainage rates, leading us dissolved nutrient leaching by choosing

You Jiao; William H. Hendershot; Joann K. Whalen

2004-01-01

406

MATHEMATICAL SIMULATION TOOLS FOR DEVELOPING DISSOLVED OXYGEN TMDLS  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

407

Salmonid Bioassay of Supersaturated Dissolved Air in Water.  

National Technical Information Service (NTIS)

Tests were conducted in shallow (0.25 m) and deep (2.5 m) tanks of water at 10C with concentrations of dissolved atmospheric gas ranging from 100% to 127% of air saturation to determine the lethal and sublethal effects on juvenile fall chinook salmon (Onc...

E. Dawley B. Monk M. Schiewe F. Ossiander W. Ebel

1976-01-01

408

Preservation of samples for dissolved mercury  

SciTech Connect

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 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.

Hamlin, S.N. (Geological Survey, Sacramento, CA (United States))

1989-04-01

409

Dissolved-oxygen analysis with temperature dependence  

SciTech Connect

Water-quality models to predict oxygen dynamics in streams require estimates of rates of reaeration, respiration, and primary production, which are often evaluated through diel studies. Simple, approximate methods of parameter estimation are desirable at the scoping level, and are often used for waste-load allocation studies. Scoping methods often assume that reaeration and respiration are constant over the diel period. Use of such methods, however, can yield unrealistic parameter estimates for shallow streams with a significant range of diel water temperatures, because both reaeration and respiration rates as well as the saturation concentration of dissolved oxygen are temperature-dependent. Based on this work on the Santa Margarita River in Southern California, this paper presents a modified approach to dissolved-oxygen-rate parameter estimation that takes temperature variation into account. Using a simple finite-difference approximation, temperature-normalized parameter estimates are readily optimized in a spreadsheet application. The approach is applicable to many shallow streams in which diel temperature variability is significant.

Butcher, J.B. [Cadmus Group, Durham, NC (United States); Covington, S. [Cadmus Group, Laramie, WY (United States)

1995-10-01

410

Dissolved organic carbon fluxes under bare soil.  

PubMed

The flux of dissolved organic carbon (DOC) in soil facilitates transport of nutrients and contaminants in soil. There is little information on DOC fluxes and the relationship between DOC concentration and water flux in agricultural soils. The DOC fluxes and concentrations were measured during 2.5 yr using 30 automatic equilibrium tension plate lysimeters (AETPLs) at 0.4 m and 30 AETPLs at 1.20-m depth in a bare luvisol, previously used as an arable soil. Average annual DOC fluxes of the 30 AETPLS were 4.9 g C m(-2) y(-1) at 0.4 m and 2.4 g C m(-2) y(-1) at 1.2 m depth. The average leachate DOC concentrations were 17 mg C L(-1) (0.4 m) and 9 mg C L(-1) (1.2 m). The DOC concentrations were unrelated to soil moisture content or average temperature and rarely dropped below 9 mg C L(-1) (0.4 m) and 5 mg C L(-1) (1.2 m). The variability in cumulative DOC fluxes among the plates was positively related to leachate volume and not to average DOC concentrations at both depths. This suggests that water fluxes are the main determinants of spatial variability in DOC fluxes. However, the largest DOC concentrations were inversely proportional to the mean water velocity between succeeding sampling periods, suggesting that the maximal net DOC mobilization rate in the topsoil is limited. Elevated DOC concentrations, up to 90 mg C L(-1), were only observed at low water velocities, reducing the risks of DOC-facilitated transport of contaminants to groundwater. The study emphasizes that water flux and velocity are important parameters for DOC fluxes and concentrations. PMID:17332264

Mertens, Jan; Vanderborght, Jan; Kasteel, Roy; Pütz, Thomas; Merckx, Roel; Feyen, Jan; Smolders, Erik

2007-03-01

411

Toxic and carcinogenic constituents in dissolvable tobacco ...  

Center for Biologics Evaluation and Research (CBER)

Text Version... Page 8. Tobacco-specific N-nitrosamines in Camel dissolvable products ... Page 9. Tobacco-specific N-nitrosamines in Camel dissolvable products ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

412

Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

This Environmental Protection Agency (EPA) website provides general information about dissolved oxygen, including what it is, sampling and equipment considerations, and sampling and analysis protocols. The site also features a chart of dissolved oxygen solubility as a function of temperature.

2010-03-02

413

Dissolved Oxygen and Biochemical Oxygen Demand  

NSDL National Science Digital Library

This EPA website provides general information about dissolved oxygen, including what it is, sampling and equipment considerations, and sampling and analysis protocols. The site also features a chart of dissolved oxygen solubility as a function of temperature.

Agency, U. S.

414

Delta-plutonium dissolving: A HAN process.  

National Technical Information Service (NTIS)

This report describes preliminary studies in the development of a nitrate-based method for dissolving delta-phase plutonium. The dissolving solution, a mixture of nitric acid, hydroxylammonium nitrate (HAN) and fluoride offers substantial advantages over ...

D. G. Karraker

1990-01-01

415

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...

416

Asymmetrical relationships between absorbance, fluorescence, and dissolved organic carbon  

SciTech Connect

Relationships between ultraviolet absorbance, fluorescence, and concentrations of dissolved organic carbon (DOC) were examined in four model materials fractionated by gel permeation chromatography. Fluorescence was consistently a poor predictor of DOC concentration, and absorbance correctly predicted DOC concentration only in the more labile materials. Asymmetry between DOC and the two optical parameters was related to the apparent molecular weight of the dissolved organic matter (DOM) and could be explained by greater levels of internal quenching and shielding in compounds of larger apparent molecular weight. A lake-to-lake comparison (n = 55) showed a calcium-related selective loss of high molecular weight humic materials, which invalidates the use of either optical characteristic as a good predictor of DOC concentration in hard-water systems. Calcium-related seasonal and between-lake differences in the relative molecular weight of the DOM may selectively alter trace metal availability.

Stewart, A.J.; Wetzl, R.G.

1981-01-01

417

Dissolved-oxygen quenching of in-situ fluorescence measurements  

NASA Astrophysics Data System (ADS)

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.

Chudyk, Wayne; Tonaszuck, David; Pohlig, Kenneth

1993-04-01