These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

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

PubMed

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

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

2014-08-01

2

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

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

2013-11-01

3

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

PubMed Central

Urban rivers with a history of industrial use can exhibit spatial and temporal variations in contaminant concentrations that may significantly affect risk evaluations and even the assessment of remediation efforts. Concentrations of 15 biologically available priority pollutant polycyclic aromatic hydrocarbons (PAHs) were measured over five years along 18.5 miles of the lower Willamette River using passive sampling devices and HPLC. The study area includes the Portland Harbor Superfund megasite with several PAH sources including remediation operations for coal tar at RM 6.3 west and an additional Superfund site, McCormick and Baxter, at RM 7 east consisting largely of creosote contamination. Study results show that organoclay capping at the McCormick and Baxter Superfund Site reduced PAHs from a pre-cap average of 440 ± 422 ng/L to 8 ± 3 ng/L post-capping. Results also reveal that dredging of submerged coal tar nearly tripled nearby freely dissolved PAH concentrations. For apportioning sources, fluoranthene/ pyrene and phenanthrene/anthracene diagnostic ratios from passive sampling devices were established for creosote and coal tar contamination and compared to published sediment values. PMID:19174872

Sower, GJ; Anderson, K.A.

2014-01-01

4

Summary of Dissolved Concentration Limits  

SciTech Connect

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

Yueting Chen

2001-06-11

5

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

2011-04-01

6

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

7

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

8

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

USGS Publications Warehouse

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

Gale, Robert W.

2007-01-01

9

Relationship between the concentrations of dissolved organic matter and polycyclic aromatic hydrocarbons in a typical U.K. upland stream.  

PubMed

Concentrations of total and freely dissolved polycyclic aromatic hydrocarbons (PAHs) and dissolved organic carbon (DOC) were measured in water collected during four sampling events at five sites from the River Wyre. The sites are typical of streams draining upland organically rich soils in northwest U.K. Freely dissolved PAHs were separated from those associated with DOC using a flocculation method. The sum of concentrations of the total and freely dissolved PAHs analyzed ranged from 2.71 to 18.9 ng/L and 2.61 to 16.8 ng/L, respectively. PAH concentrations and PAH fluxes derived from concentrations and water flow rates generally increased downstream, the trend in the latter being more pronounced. The concentration of individual PAHs containing five or more aromatic rings was found to be strongly correlated to the DOC concentration (p < 0.0001), suggesting common terrestrial sources and hydrological pathways. In contrast, no significant relationships were observed between concentrations of PAHs with four or fewer rings and DOC. Concentrations of PAHs with more than four rings showed similar seasonal variation as DOC concentration (peaking in the late summer), while variation in two or three ring PAHs was out of phase with DOC (peaking in the winter). As the PAH-DOC relationship appeared partly dependent on the molecular weight of the PAHs, a linear regression function that included an interaction between this variable and DOC concentration was used to model PAH concentrations over a 2 year period to estimate annual fluxes. The relationship identified between PAH concentrations and DOC should help to enhance interpretation of PAH monitoring data that are currently sparse both spatially and temporally and, thus, enable more robust assessments of the potential risks of these environmental pollutants to sensitive aquatic organisms and human water supplies. PMID:24308296

Moeckel, Claudia; Monteith, Donald T; Llewellyn, Neville R; Henrys, Peter A; Pereira, M Glória

2014-01-01

10

The effect of membrane filtration on dissolved trace element concentrations  

USGS Publications Warehouse

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

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

1996-01-01

11

Effect of membrane filtration artifacts on dissolved trace element concentrations  

USGS Publications Warehouse

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

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

1992-01-01

12

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

13

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

14

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

15

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

16

Seasonal ice and hydrologic controls on dissolved organic carbon and nitrogen concentrations in a borealrich fen  

E-print Network

Seasonal ice and hydrologic controls on dissolved organic carbon and nitrogen concentrations and hydrologic controls on dissolved organic carbon and nitrogen concentrations in a borealrich fen, J. Geophys of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) across an experimental manipulation

Turetsky, Merritt

17

Corals concentrate dissolved inorganic carbon to facilitate calcification.  

PubMed

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

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

2014-01-01

18

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

19

Abstract Low dissolved oxygen concentrations present numerous challenges for non-air-breathing aquatic or-  

E-print Network

Abstract Low dissolved oxygen concentrations present numerous challenges for non- pact of dissolved oxygen on predator-prey interactions, and suggest that outcomes depend on the respiratory ecology of both predator and prey. Key words Air-breathing · Rana catesbeiana · Dissolved oxygen

McIntyre, Peter

20

Impact of high Saharan dust inputs on dissolved iron concentrations in the Mediterranean Sea  

E-print Network

Impact of high Saharan dust inputs on dissolved iron concentrations in the Mediterranean Sea C) in the Mediterranean Sea, dissolved iron concentrations in seawater and iron and aluminium concentrations in aerosols of Saharan origin on the iron cycle in the Mediterranean Sea. INDEX TERMS: 1065 Geochemistry: Trace elements

Guieu, Cécile

21

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

22

Respiratory and Behavioral Responses of Juvenile Dolphin Fish to Dissolved Oxygen Concentration  

Microsoft Academic Search

Understanding the responses of juvenile dolphins (Coryphaena hippurus) to physical variables may help increase survival during culture. The purposes of this study were to (1) describe the respiratory and gross behavioral responses of juveniles to dissolved oxygen concentration and (2) find the short-term tolerance limit to low levels of dissolved oxygen. Three hundred eight cultured juvenile dolphins (44–70 d old)

Marvin M. F. Lutnesky; James P. Szyper

1990-01-01

23

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

EPA Science Inventory

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

24

The effect of benthic sediments on dissolved nutrient concentrations and fluxes  

Microsoft Academic Search

The Ria Formosa is a meso-tidal coastal lagoon experiencing enhanced nutrient concentrations. Assessment of sediment–seawater interaction is essential if nutrient dynamics and the risk of eutrophication are to be fully understood. Pore water concentrations of dissolved inorganic and organic phosphorus, ammonium, nitrate and nitrite were determined in cores from six sites. Changes in nutrients concentrations were measured in intertidal pools

L. G. Murray; S. M. Mudge; A. Newton; J. D. Icely

2006-01-01

25

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

PubMed

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

Shaler, T A; Klecka, G M

1986-05-01

26

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

USGS Publications Warehouse

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

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

2005-01-01

27

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

28

MCM LTER METADATA FILE TITLE: Dissolved Inorganic Carbon concentrations in lakes of the McMurdo Dry Valleys  

E-print Network

, Collection Date, Depth (m), DIC (mg L-1 ), DIC (mM), Comments KEYWORDS: Dissolved inorganic carbon, DIC, lakeMCM LTER METADATA FILE TITLE: Dissolved Inorganic Carbon concentrations in lakes of the McMurdo Dry and quantifies dissolved inorganic carbon concentrations at specific depths in McMurdo Dry Valley lakes

Priscu, John C.

29

The effect of membrane filtration artifacts on dissolved trace element concentrations  

USGS Publications Warehouse

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

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

1992-01-01

30

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

31

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...

32

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

SciTech Connect

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

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

1980-09-01

33

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

USGS Publications Warehouse

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

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

1996-01-01

34

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...

35

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

E-print Network

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

Scanlon, Todd

36

Effect of cycling dissolved oxygen concentrations on product formation in penicillin fermentations  

Microsoft Academic Search

Limitations in mass and momentum transfer coupled with high hydrostatic pressures create significant spatial variations in dissolved gas concentrations in large fermenters. Microorganisms are subjected to fluctuating environmental conditions as they pass through the zones in a stirred vessel or along a closed loop fermenter.

F. Vardar; M. D. Lilly

1982-01-01

37

The Effects of Photosynthesis and Cellular Respiration on Dissolved Oxygen Concentration  

Microsoft Academic Search

Photosynthesis and cellular respiration are two processes that transform energy and affect concentrations of carbon dioxide and oxygen in air and water. In this lesson, middle school students use graphing calculators and calculator-based laboratory units to measure dissolved oxygen in water and graph their results to gain an under-standing of the relationship between photosynthesis and cellular respiration.

Darren Proppe; Sherry Harrel

2007-01-01

38

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

39

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

40

ACUTE SENSITIVITY OF JUVENILE SHORTNOSE STURGEON TO LOW DISSOLVED OXYGEN CONCENTRATIONS  

EPA Science Inventory

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

41

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

42

Effect of dissolved oxygen concentration on nar promoter activity in batch and semi-continuous cultivations  

Microsoft Academic Search

The level of the dissolved oxygen concentration could significantly affect thenar promoter activity in the induction of the gene expression under the anaerobic condition. In batch culture, the ?-galactosidase\\u000a activity was about 12000 units\\/min\\/g cell under the anaerobic condition. The optimum DO concentration for the induction of\\u000a the gene expression was 0% in both batch and continuous cultivations. In semi-continuous

Eock Kee Hong; Kwang Soo Kim

1999-01-01

43

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

44

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

PubMed

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

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

2014-03-01

45

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

46

High dissolved methane concentrations in the deep-water Ulleung Basin, East Sea of Korea  

NASA Astrophysics Data System (ADS)

As a part of the Korean National Gas Hydrate Program, a production test in the Ulleung Basin is planned to be performed in 2015. The targets are the gas hydrate-bearing sand reservoirs, which were found during the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) in 2010. To ensure a safe production test, an environmental program has been conducted by the Korea Institute of Geoscience and Mineral Resources (KIGAM) since 2012. This program includes a baseline survey using a KIGAM Seafloor Observation System (KISOS) and R/V TAMHAE II of KIGAM, development of a KIGAM Seafloor Monitoring System (KIMOS), and seafloor monitoring on various potential hazards associated with the dissociated gas from gas hydrates using the KIMOS during the production test. A survey for measuring the dissolved methane concentrations in the area at and nearby the gas hydrate production testing site was performed using R/V TAMHAE II and the KISOS. The water samples were also collected and analyzed to measure the dissolved methane concentrations by the SBE carousel water sampler installed in the KISOS and gas chromatography (GC) at KIGAM. The dissolved methane concentrations were also measured using a Frantech METS methane sensor installed in the KISOS. No dissolved methane anomaly was detected at the site where any evidence of gas hydrate presence has not been observed. On the other hand, the water analysis showed high dissolved methane concentrations at the water depth above and within the gas hydrate stability zone (GHSZ) at the site where gas hydrates were identified by drilling. However, these dissolved methane anomalies within the GHSZ were not detected by methane sensor. To examine these uncertain dissolved methane anomalies within the GHSZ, the water samples will be collected and analyzed once again, and the analytical result will be also carefully compared with the data collected using the methane sensor and deep ocean mass spectrometer (DOMS) developed by the University of Hawaii. The results of baseline surveys will be used to set up the KIMOS efficiently.

Ryu, Byong-Jae; Chun, Jong-Hwa

2014-05-01

47

Predation on fish larvae by moon jellyfish Aurelia aurita under low dissolved oxygen concentrations  

Microsoft Academic Search

Laboratory experiments were conducted to test the hypothesis that low dissolved oxygen concentrations have the potential to\\u000a enhance the predation rate on fish larvae by moon jellyfish Aurelia aurita which is increasing in abundance in the coastal waters of Japan. Larvae of the red sea bream Pagrus major in four size classes (2.9, 4.1, 6.2 and 8.6 mm in standard

Jun Shoji; Reiji Masuda; Yoh Yamashita; Masaru Tanaka

2005-01-01

48

Elevated concentrations of formate, acetate and dissolved organic carbon found at the Lost City hydrothermal field  

NASA Astrophysics Data System (ADS)

Fluids from the ultramafic-hosted Lost City hydrothermal field were analyzed for total dissolved organic carbon and dissolved organic acids. Formate (36-158 ?mol/kg) and acetate (1-35 ?mol/kg) concentrations are higher than in other fluids from unsedimented hydrothermal vents, and are a higher ratio of the total dissolved organic carbon than has been found in most marine geothermal systems. Isotopic evidence is consistent with an abiotic formation mechanism for formate, perhaps during serpentinization processes in the sub-surface. Further support comes from previous studies where the abiological formation of low molecular weight organic acids has been shown to be thermodynamically favorable during hydrothermal alteration of olivine, and laboratory studies in which the reduction of carbon dioxide to formate has been confirmed. As the second most prevalent carbon species after methane, formate may be an important substrate to microbial communities in an environment where dissolved inorganic carbon is limited. Acetate is found in locations where sulfate reduction is believed to be important and is likely to be a microbial by-product, formed either directly by autotrophic metabolic activity or indirectly during the fermentative degradation of larger organic molecules. Given the common occurrence of exposed ultramafic rocks and active serpentinization within the worlds ocean basins, the abiotic formation of formate may be an important process supporting life in these high pH environments and may have critical implications to understanding the organic precursors from which life evolved.

Lang, Susan Q.; Butterfield, David A.; Schulte, Mitch; Kelley, Deborah S.; Lilley, Marvin D.

2010-02-01

49

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

USGS Publications Warehouse

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.

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

2012-01-01

50

Spatial variation in concentrations of dissolved nitrogen species in an upland blanket peat catchment.  

PubMed

The concentration of nitrogen (N), particularly as nitrate (NO3-N), in upland streams, lakes and rivers is frequently used as a diagnostic of the vulnerability of upland ecosystems to increased atmospheric nitrogen deposition and N saturation. The N content of running waters, however, is generally assessed on the basis of sampling at a limited number of points in space and time within the catchment under investigation. The current study was conducted at Trout Beck, an 11.5 km2 blanket peat-dominated catchment in the North Pennine uplands of the UK. Results from sampling at 33 sites within this catchment demonstrated that the concentrations of all dissolved N species were highly variable, even over short distances. Statistical relationships between the concentrations of NO3-N and dissolved organic nitrogen (DON) and percentage catchment cover of Calluna/Eriophorum and Eriophorum vegetation were found. However, it was also noted that in catchments containing limestone outcrops, NO3-N concentration was much higher than in catchments where runoff was sourced directly from the blanket peat surface. It is possible that NH4-N and DON leached from the blanket peat are mineralised and nitrified, providing a source for the NO3-N found in the river channels. Overall, the current study suggests that interpretations of N-saturation based on river water chemistry measurements at a single point must be treated cautiously, and that the influence of catchment-scale physical factors, such as vegetation and geology cover on the concentration of dissolved N species in upland river waters should not be ignored. PMID:17182088

Cundill, A P; Chapman, P J; Adamson, J K

2007-02-01

51

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

PubMed

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

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

2014-09-01

52

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

53

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)] [Geological Survey, Boulder, CO (United States)

1999-03-01

54

Levels and activities of nitrogenase proteins in Azotobacter vinelandii grown at different dissolved oxygen concentrations.  

PubMed

Azotobacter vinelandii was grown diazotrophically at different dissolved oxygen concentrations (in the range of 3 to 216 microM) in sucrose-limited continuous culture. The specific nitrogenase activity, measured on the basis of acetylene reduction in situ, was dependent solely on the growth rate and was largely independent of oxygen and sucrose concentration. FeMo (Av1) and Fe (Av2) nitrogenase proteins were quantified after Western blotting (immunoblotting). When the cultures were grown at a constant dilution rate (D, representing the growth rate, mu) of 0.15.h-1, the cellular levels of both proteins were constant regardless of different dissolved oxygen concentrations. The same was true when the organisms were grown at D values above 0.15.h-1. At a lower growth rate (D = 0.09.h-1), however, and at lower oxygen concentrations cellular levels of both nitrogenase proteins were decreased. This means that catalytic activities of nitrogenase proteins were highest at low oxygen concentrations, but at higher oxygen concentrations they increased with growth rate. Under all conditions tested, however, the Av1:Av2 molar ratio was 1:(1.45 +/- 0.12). Cellular levels of flavodoxin and FeS protein II were largely constant as well. In order to estimate turnover of nitrogenase proteins in the absence of protein synthesis, chloramphenicol was added to cultures adapted to 3 and 216 microM oxygen, respectively. After 2 h of incubation, no significant decrease in the cellular levels of Av1 and Av2 could be observed. This suggests that oxygen has no significant effect on the breakdown of nitrogenase proteins. PMID:3162907

Dingler, C; Kuhla, J; Wassink, H; Oelze, J

1988-05-01

55

Levels and activities of nitrogenase proteins in Azotobacter vinelandii grown at different dissolved oxygen concentrations.  

PubMed Central

Azotobacter vinelandii was grown diazotrophically at different dissolved oxygen concentrations (in the range of 3 to 216 microM) in sucrose-limited continuous culture. The specific nitrogenase activity, measured on the basis of acetylene reduction in situ, was dependent solely on the growth rate and was largely independent of oxygen and sucrose concentration. FeMo (Av1) and Fe (Av2) nitrogenase proteins were quantified after Western blotting (immunoblotting). When the cultures were grown at a constant dilution rate (D, representing the growth rate, mu) of 0.15.h-1, the cellular levels of both proteins were constant regardless of different dissolved oxygen concentrations. The same was true when the organisms were grown at D values above 0.15.h-1. At a lower growth rate (D = 0.09.h-1), however, and at lower oxygen concentrations cellular levels of both nitrogenase proteins were decreased. This means that catalytic activities of nitrogenase proteins were highest at low oxygen concentrations, but at higher oxygen concentrations they increased with growth rate. Under all conditions tested, however, the Av1:Av2 molar ratio was 1:(1.45 +/- 0.12). Cellular levels of flavodoxin and FeS protein II were largely constant as well. In order to estimate turnover of nitrogenase proteins in the absence of protein synthesis, chloramphenicol was added to cultures adapted to 3 and 216 microM oxygen, respectively. After 2 h of incubation, no significant decrease in the cellular levels of Av1 and Av2 could be observed. This suggests that oxygen has no significant effect on the breakdown of nitrogenase proteins. PMID:3162907

Dingler, C; Kuhla, J; Wassink, H; Oelze, J

1988-01-01

56

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 of 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 in dependence of DIN:TDN ratio and compared it to the direct measurement of DON by size-exclusion chromatography (SEC). 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 resulted in low errors at high DIN:TDN ratios due to the successful separation of DON from DIN. For SEC, DON recovery rates were 90.7-107.9% for five pure standard compounds and 89-103% for two standard compounds, enriched with DIN. Moreover, SEC resulted in 93-101% recovery rates for DON concentrations of natural samples at a DIN:TDN ratio of 0.8. With 2.5 h of measurement time per sample, SEC is a moderately fast and accurate alternative to the standard approach for the determination of DON concentrations in freshwaters with DIN:TDN ratios >0.6. The direct DON measurement by SEC will enable the scientific community to gather accurate information on DON concentrations, especially in anthropogenically disturbed systems with high DIN concentrations.

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

2012-06-01

57

How Does the Changing Environment Affect Concentrations, Fluxes and Properties of Dissolved Organic Matter in Soils?  

NASA Astrophysics Data System (ADS)

Environmental conditions influencing the release and fate of dissolved organic matter (DOM) in terrestrial and aquatic ecosystems have changed in the past and continue to change in the future. I studied effects of declining acidic deposition on concentrations and fluxes of dissolved organic carbon (DOC) using long-term soil solution data of two forest sites. The response of DOM to increased decomposition of soil organic matter caused by land use change (clear-cutting) and subsequently increased temperature will be examined at one forest site. Effects of an increased or decreased productivity of forests on DOM were studied by experimental manipulation of litter input to two forest soils. The central idea of all experiments carried out in the field was the response of DOM as a key driver in terrestrial and aquatic ecosystems to the changing environment. From the results of these experiments I conclude that accelerated decomposition of organic matter caused by temperature rise or land use changes should result in increasing concentrations and fluxes of DOC from soils into aquatic ecosystems. The larger stability of this additional DOM increases the importance of DOM for C sequestration in soils. The expected increased productivity of forest ecosystems should also result in increased DOC fluxes from soils. On the other hand, declining acidic deposition might result in smaller DOC fluxes into aquatic ecosystem if water passes through well developed soils with the capacity to sorb DOC.

Kalbitz, K.

2004-05-01

58

Adaptive predictive control of dissolved oxygen concentration in a laboratory-scale bioreactor.  

PubMed

We present an algorithm for the adaptive control of dissolved oxygen concentration in a bioreactor, based on the agitation rate. The dynamics are represented by an incremental first-order model with variable dead-time and parameters. These are estimated on-line by a recursive least-squares identification method with a forgetting factor and a constant sensitivity. The model is employed to predict the behaviour of the dissolved oxygen concentration over a finite horizon, using an original method which requires little computation. Then, a Generalized Predictive Control optimisation strategy computes the agitation rate from the predictions and the desired set point, while gradually updating the controller smoothness. This algorithm, which requires little preliminary knowledge, has been implemented on a laboratory-scale fed-batch bioreactor for which the use of conventional controllers showed limited performance, due to the unpredictable and evolutive nature of the dynamics. The new controller proved to be robust and effective over a wide range of operating conditions, while requiring no operator adjustments. PMID:8573319

Diaz, C; Dieu, P; Feuillerat, C; Lelong, P; Salomé, M

1995-11-21

59

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

60

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

E-print Network

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

Shull, David H.

61

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

PubMed Central

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

Smith, Jennifer E.; Thompson, Melissa

2014-01-01

62

Dissolved organic nitrogen transformation in river water: Effects of suspended sediment and organic nitrogen concentration  

NASA Astrophysics Data System (ADS)

SummaryHigh suspended sediment (SPS) concentration exists in many Asian rivers. In addition, human activities and climate change can change river runoff, leading to the variation of SPS and pollutant concentrations. In this research, the effects of SPS and dissolved organic nitrogen (DON) concentration on DON transformation in river systems were studied through simulation experiments with samples collected from the Yellow River which is famous for its high SPS concentration. The results indicated that high DON concentration resulted in a longer retention time of NH4+-N and NO2--N in the system due to the inhibition effect of ammonia on nitrification. The re-suspension of sediment accelerated DON transformation, and both the ammonification and nitrification rates increased with SPS concentration. The ammonification rate constants obtained from the first-order kinetics were 0.286, 0.332, 0.538 day-1; the nitrification rate constants obtained from the Logistic model were 0.0018, 0.0038, 0.005 day-1 ?mol-1 L-1 for the systems with SPS concentration of 0, 5, 10 g L-1, respectively. Bacteria tended to attach onto SPS, and the specific growth rate in the systems with SPS was approximately two orders of magnitude higher than that without SPS in the first 3 days of cultivation, which resulted in an increase of DON transformation rate with SPS concentration. This study implied that DON transformation rate may be lower in the dry season than that in the wet season, and nitrogen transformation will be affected by the variation of river runoff and SPS concentration.

Xia, Xinghui; Liu, Ting; Yang, Zhifeng; Zhang, Xueqing; Yu, Zhongbo

2013-03-01

63

Dissolved oxygen concentrations in Lake Erie (U.S.A.-Canada). 2. A statistical model for dissolved oxygen in the Central Basin of Lake Erie  

NASA Astrophysics Data System (ADS)

In this paper, which is a continuation of the work laid down in Part 1 in this issue, a statistical model is developed for dissolved oxygen (DO) concentrations in the hypolimnion of the Central Basin of Lake Erie. The model uses the lake water level, the hypolimnion temperature and the total phosphorus (TP) concentrations as explanatory variables. The model estimates the probability of anoxia occurrence in the Central Basin and predicts the TP concentration when the DO depletion rate and the water level are specified. The use of the model for regulation and for setting standards are also outlined.

El-Shaarawi, A. H.

1984-06-01

64

High variability of dissolved iron concentrations in the vicinity of Kerguelen Island (Southern Ocean)  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

65

Seasonal variations in concentration and composition of dissolved organic carbon in Tokyo Bay  

NASA Astrophysics Data System (ADS)

Concentrations of recalcitrant and bioavailable dissolved organic carbon (DOC) and their seasonal variations were investigated at three stations in Tokyo Bay, Japan, and in two freshwater sources flowing into the bay to evaluate the significance of DOC degradation for the carbon budget in coastal waters and carbon export to the open ocean. Recalcitrant DOC (RDOC) was differentiated from bioavailable DOC (BDOC) as a remnant of DOC after 150 days of bottle incubation. On average, RDOC accounted for 78% of the total DOC in Shibaura sewage treatment plant (STP) effluent, 67% in the upper Arakawa River water, 66% in the lower Arakawa River water, and 78% in surface bay water. RDOC concentrations were higher than BDOC at all stations. In freshwater environments, RDOC concentrations were almost constant throughout the year. In the bay, RDOC was higher during spring and summer than during autumn and winter. The relative abundance of RDOC in the bay derived from phytoplankton, terrestrial, and open oceanic waters was estimated to be 9%, 33%, and 58%, respectively, by multiple regression analysis of RDOC, salinity, and chl a. In addition, comparison with previous data from 1972 revealed that concentrations of RDOC and BDOC have decreased by 33% and 74% at freshwater sites and 39% and 76% at Tokyo Bay, while the ratio of RDOC to DOC has increased. The change in DOC concentration and composition was probably due to increased amounts of sewage treatment plant effluent entering the system. Tokyo Bay exported DOC, mostly RDOC, to the open ocean because of remineralization of BDOC.

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

2014-07-01

66

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

67

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

68

Factors affecting total dissolved solids concentration of ?-ray-irradiated aqueous hexamethylenetetramine solution: A dosimetric study.  

PubMed

A new ?-ray-radiation dosimetric system (TDS-HMTA), comprising a 'total dissolved solids (TDS)' meter and 0.02 M aqueous hexamethylenetetramine (HMTA) solution, is introduced for medical and biological applications. Gamma-ray radiolysis of aqueous HTMA solutions increases the concentrations (ppm) of TDS, which is measured by the TDS meter. The effects of HMTA concentration, absorbed radiation dose, absorbed dose rate, and storage time on the TDS concentration of irradiated HMTA solutions were studied. It was found that 0.02 M aqueous HMTA solution yields the highest sensitivity to ?-ray-radiation according to TDS concentration measurements. The effect of absorbed radiation dose was studied in the range 1.64-435.5 kGy. The TDS concentration increases linearly up to the maximum of the studied absorbed radiation dose range (R(2) = 0.9965). The overall coefficient of variation (CV %) associated with TDS concentration measurements of 0.02 M HMTA solution as a function of absorbed dose was found to be 0.732%. The effect of dose rate on the TDS concentration was studied in the range 0.33-3.31 kGy/h. It was found, also, that the TDS concentration is relatively stable over a storage period of 144 h after irradiation with different doses. The tissue equivalency of 0.02 M aqueous HMTA solutions allow it to be used for radiation dose measurement during sterilization in human tissue banks. Therefore, this system (TDS-HMTA) could be considered as a promising candidate for ?-ray radiation dosimetry in technical, medical and research fields. PMID:25288526

Sife-Eldeen, Kh A

2014-12-01

69

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

PubMed

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

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

2015-02-01

70

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

2012-07-01

71

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

PubMed

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

Chen, C K; Lo, S L

2005-07-01

72

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

73

Concentrations of dissolved radon-222 in water from selected wells and springs in Idaho, 1989-91  

SciTech Connect

Concentrations of dissolved radon-222, a naturally occurring radioactive gas, are found in water in Idaho. The U.S. Geological Survey collected water samples for radon-222 analyses from 338 Idaho wells and springs during 1989-91. These water samples were collected as part of ongoing monitoring programs with the Idaho Department of Water Resources and the U.S. Department of Energy. Concentrations of dissolved radon-222 in 372 of the water samples ranged from -58{+-}30 to 5,715{+-}66 picocuries per liter; the mean and median concentrations were 446{+-}35 and 242{+-}25 picocuries per liter, respectively.

Cecil, L.D.; Parliman, D.J.; Edwards, D.D.; Young, H.W.

1994-11-01

74

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

75

Effect of dissolved oxygen concentration on the bioflocculation process in high loaded MBRs.  

PubMed

High-loaded membrane bioreactors (HL-MBRs), i.e. MBRs which are operated at extremely short sludge and hydraulic retention times, can be applied to flocculate and concentrate sewage organic matter. The concentrated organics can be used for energy recovery, or for the production of more valuable organic chemicals. Little is known about the effect of the dissolved oxygen concentration (DO) on this bioflocculation process. To examine this effect, two HL-MBRs were operated, respectively at a low (1 mg L(-1)) and a higher (4 mg L(-1)) DO. The higher DO resulted in a better flocculation efficiency, i.e. 92% of the colloidal COD in the sewage flocculated compared to 69% at the lower DO. The difference was attributed to a higher microbial production of extracellular polymeric substances at a DO of 4 mg L(-1) and to more multivalent cations (calcium, iron and aluminium) being distributed to the floc matrix. In addition, the HL-MBR that was operated at a DO of 4 mg L(-1) gave a bigger mean floc size, a lower supernatant turbidity, better settleability and better membrane filterability than the HL-MBR that was operated at a DO of 1 mg L(-1). PMID:25213685

Faust, L; Temmink, H; Zwijnenburg, A; Kemperman, A J B; Rijnaarts, H H M

2014-12-01

76

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

E-print Network

oxygen in the northern Gulf of Mexico Walter K Dodds The "dead zone", an area with reduced concentrations that forms each summer in the northern Gulf of Mexico. This hypoxic zone (HZ) is formally defined as an areaThe "dead zone" is a large area of decreased dissolved oxygen concentration in bottom waters

Kaufman, Glennis A.

77

Effects of Dissolved Oxygen Concentration on Oxygen Consumption and Development of Channel Catfish Eggs and Fry: Implications for Hatchery Management  

Technology Transfer Automated Retrieval System (TEKTRAN)

Channel catfish spawns were incubated under controlled conditions to determine the effect of dissolved oxygen (DO) concentration on development and survival. Routine metabolic rate and limiting oxygen concentration were determined on eggs, sac fry and swim-up fry. Eight channel catfish spawns were s...

78

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

79

Measurement of dissolved organic carbon by wet chemical oxidation with persulfate: influence of chloride concentration and reagent volume  

Microsoft Academic Search

The influence of chloride content and reagent volume on the analysis of dissolved organic carbon by wet chemical oxidation with persulfate was evaluated. A strong hyperbolic relationship was found between measured DOC concentration and volume of persulfate added for oxidation in both marine and artificially chlorinated (NaCl) freshwater samples. Freshwater samples showed no such relationship. Precision of measured DOC concentrations

James H. McKenna; Peter H. Doering

1995-01-01

80

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

81

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

82

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

USGS Publications Warehouse

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

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

2009-01-01

83

Concentration dynamics and biodegradability of dissolved organic matter in wetland soils subjected to experimental warming.  

PubMed

Dissolved organic matter (DOM) is the most bioavailable soil organic pool. Understanding how DOM responds to elevated temperature is important for forecasting soil carbon (C) dynamics under climate warming. Here a 4.5-year field microcosm experiment was carried out to examine temporal DOM concentration dynamics in soil pore-water from six different subtropical wetlands. Results are compared between control (ambient temperature) and warmed (+5°C) treatments. UV-visible and fluorescence spectroscopy was performed to reveal DOM structural complexity at the end of the warming incubation. Elevated temperature resulted in initially (1 to 2.5 years) high pore-water DOM concentrations in warmed samples. These effects gradually diminished over longer time periods. Of the spectral indices, specific UV absorbance at 280 nm and humification index were significantly higher, while the signal intensity ratio of the fulvic-like to humic-like fluorescence peak was lower in warmed samples, compared to the control. Fluorescence regional integration analysis further suggested that warming enhanced the contribution of humic-like substances to DOM composition for all tested wetlands. These spectral fingerprints implied a declined fraction of readily available substrates in DOM allocated to microbial utilization in response to 4.5 years of warming. As a negative feedback, decreased DOM biodegradability may have the potential to counteract initial DOM increases and alleviate C loss in water-saturated wetland soils. PMID:24239698

Wang, Hang; Holden, Joseph; Zhang, Zhijian; Li, Meng; Li, Xia

2014-02-01

84

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

PubMed Central

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

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

1997-01-01

85

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

86

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

NASA Astrophysics Data System (ADS)

We present evidence suggesting that only a portion of the dissolved organic carbon (DOC) in the seawater analyzed previously by Williams and Druffel (1987) was oxidized by the UV-radiation method. High temperature catalytic (HTC) methods (Sugimura and Suzuki, 1988) used to reoxidize the central North Pacific gyre water samples reveal that the total DOC (DOCHTC) is about twice that of the UV-oxidizable DOC (DOCuv). Indications from the original study suggest that this additional DOC contains higher concentrations of radiocarbon than in the DOCuv(Williams and Druffel, 1987). This evidence implies that DOC is older and thus more refractory with respect to biological utilization, yet is more chemically reactive with respect to photooxidation, than the fraction resistant to UV (DOCres). We report accelerator mass spectrometry (AMS) ?14C measurements of humic, fulvic and hydrophilic acid fractions isolated from water collected at 180 m in the North Pacific (19°N, 158°W) using XAD macroreticular resins. ?14C values of the humic material are less than those of DOCuv from a similar depth 1200 km further north (Williams and Druffel, 1987) indicating that these humic substances are part of the ‘old’ recycled DOCuv in the ocean.

Druffel, Ellen R. M.; Williams, Peter M.; Suzuki, Yoshimi

87

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

SciTech Connect

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

Druffel, E.R.M. (Woods Hole Oceanographic Institution, MA (USA)); Williams, P.M. (Scripps Institution of Oceanography, La Jolla, CA (USA)); Suzuki, Yoshimi (Meteorological Research Institute, Tsukuba (Japan))

1989-09-01

88

Discrete-element model for simulating hydrodynamic conditions and absorbed and dissolved radioisotope concentrations in estuaries  

SciTech Connect

A model has been developed to simulate one-dimensional model for simulating hydrodynamic and thermal conditions and dissolved radionuclide concentrations in tidal estuaries was merged with an improved version of the SEDTRN model, a multisediment-size class model of bedload and suspended sediment transport. The improved SEDTRN model, which employs a velocity-based rather than an energy-based sediment transport rate calculation and accounts for nonzero channel bed slope, is given credibility by comparing its results in stand-alone form to those obtained using the parent model. Results of the latter model have been shown to compare favorably to field measurements. The combined model is called HOTSED. The HOTSED model has been applied to the Hudson River under tidal-transient conditions and the transport of tagged or radioisotope-bearing sediment simulated. The code is designed specifically for applications with dominant tidal cycling. It requires, for a 76-element channel system, 270 thousand bytes of storage, and for a simulation of 25 hours, has an execution time of approximately five minutes on an IBM System 360/91 computer. 10 references, 7 figures.

Fields, D.E.

1984-01-01

89

Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea  

NASA Astrophysics Data System (ADS)

Concentrations of oxygen (O2) and other dissolved gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes; for example, in the context of net and gross biological production estimates. The mixed layer depth (zmix) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that zmix defined using O2 may be different to zmix defined using temperature or density. Here, we propose to define an O2-based mixed layer depth, zmix(O2), as the depth where the relative difference between the O2 concentration and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by numerical analysis of O2 profiles in coastal areas of the Southern Ocean and corroborated by visual inspection. Comparisons of zmix(O2) with zmix based on potential temperature differences, i.e. zmix(?? = 0.2 °C) and zmix(?? = 0.5 °C), and potential density differences, i.e. zmix(??? = 0.03 kg m-3) and zmix(??? = 0.125 kg m-3), showed that zmix(O2) closely follows zmix(??? = 0.03 kg m-3). Further comparisons with published zmix climatologies and zmix derived from World Ocean Atlas 2005 data were also performed. To establish zmix for use with biological production estimates in the absence of O2 profiles, we suggest using zmix(??? = 0.03 kg m-3), which is also the basis for the climatology by de Boyer Montégut et al. (2004).

Castro-Morales, K.; Kaiser, J.

2011-06-01

90

Comparative production of channel catfish and channel x blue hybrid catfish subjected to two minimum dissolved oxygen concentrations  

Technology Transfer Automated Retrieval System (TEKTRAN)

The effect of daily minimum dissolved oxygen concentration on growth and yield (kg/ha) of the channel catfish (Ictalurus punctatus) and the channel x blue hybrid catfish (I. punctatus female x I. furcatus male), which shared the Jubilee strain of channel catfish as the maternal parent, was evaluated...

91

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....

92

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

USGS Publications Warehouse

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

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

1994-01-01

93

Dissolved-solids concentrations and hydrochemical facies in water of the Edwards-Trinity aquifer system, west-central Texas  

USGS Publications Warehouse

Much of the Edwards-Trinity aquifer system contains freshwater, but sizable parts contain marginally fresh or slightly saline water. The predominant water type in the aquifer system is calcium bicarbonate; however, one of seven other hydrochemical facies characterizes the water in places. The median dissolved-solids concentration of water samples from the Edwards aquifer in the Balcones fault zone is 297 mg/L (milligrams per liter); the interquartile range is 93 mg/L. In the freshwater zone of the Edwards aquifer updip of a freshwater/saline-water transition zone, the water is almost exclusively calcium bicarbonate. The median dissolved-solids concentration of water samples from the Trinity aquifer in the Hill Country is 537 mg/L and the interquartile range is 573 mg/L. Four bicarbonate and sulfate facies, spread vertically throughout the saturated section, characterize most of the Hill Country analyses; calcium bicarbonate predominates. The median concentration of dissolved solids in water samples from the Edwards-Trinity aquifer in the Edwards Plateau is 379 mg/L and the interquartile range is 547 mg/L. Freshwater is nearly everywhere in the southern and northeastern parts of the aquifer, and mostly slightly saline water is in the northwestern part. The distribution of hydrochemical facies shows a similar pattern to dissolved-solids concentration, with bicarbonate water nearly everywhere in the southern and northeastern parts of the aquifer. Sulfate and chloride facies characterize the northwestern part of the Edwards Plateau. The median concentration of dissolved solids among water samples from the Edwards-Trinity aquifer in the Trans-Pecos is 929 mg/L and the interquartile range is 1,626 mg/L. Fresh, calcium bicarbonate water predominates in the southern part, and more saline mixed and sulfate waters are the most common in the northwestern part.

Bush, P.W.; Ulery, R.L.; Rittmaster, R.L.

1994-01-01

94

Dissolved oxygen concentration field measurement in micro-scale water flows using PtOEP\\/PS film sensor  

Microsoft Academic Search

A planar optode system based on an oxygen quenchable luminophore platinum (II) octaethyporphrin (PtOEP) bound with thin polystyrene (PS) film and UV light-emitting diodes (UV-LEDs) was developed to measure the dissolved oxygen (DO) concentration field in micro-scale water flows. An intensity-based method adopting a pixel-to-pixel in situ calibration technique was used to visualize DO concentration fields around an impinging micro-nozzle.

Dae Hun Song; Hyun Dong Kim; Kyung Chun Kim

2012-01-01

95

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

USGS Publications Warehouse

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

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

2006-01-01

96

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 4 dS m(-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 4 dS m(-1), respectively. At EC1:5 of 4 dS m(-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 0.5 dS m(-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 4 dS m(-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 0.5 dS m(-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

2013-11-01

97

Dissolved gaseous mercury concentrations and mercury volatilization in a frozen freshwater fluvial lake.  

PubMed

In situ mesocosm experiments were performed to examine dissolved gaseous mercury (DGM), mercury volatilization, and sediment interactions in a frozen freshwater fluvial lake (Lake St. Louis, Beauharnois, QC). Two large in situ mesocosm cylinders, one open-bottomed and one close-bottomed (no sediment diffusion), were used to isolate the water column and minimize advection. Mercury volatilization over the closed-bottom mesocosm did not display a diurnal pattern and was low (mean = -0.02 ng m(-2) h(-1), SD = 0.28, n=71). Mercury volatilization over the open-bottom mesocosm was also low (mean = 0.24 ng m(-2) h(-1), SD = 0.08, n=96) however a diurnal pattern was observed. Low and constant concentrations of DGM were observed in surface water in both the open-bottomed and close-bottomed mesocosms (combined mean = 27.6 pg L(-1), SD = 7.2, n=26). Mercury volatilization was significantly correlated with solar radiation in both the close-bottomed (Pearson correlation = 0.33, significance = 0.005) and open-bottomed (Pearson correlation = 0.52, significance = 0.001) mesocosms. However, DGM and mercury volatilization were not significantly correlated (at the 95% level) in either of the mesocosms (significance = 0.09 in the closed mesocosm and significance = 0.9 in the open mesocosm). DGM concentrations decreased with depth (from 62 to 30 pg L(-1)) in the close-bottomed mesocosm but increased with depth (from 30 to 70 pg L(-1)) in the open-bottomed mesocosm suggesting a sediment source. DGM concentrations were found to be high in samples of ice melt (mean 73.6 pg L(-1), SD = 18.9, n=6) and snowmelt (mean 368.2 pg L(-1), SD = 115.8, n=4). These results suggest that sediment diffusion of mercury and melting snow and ice are important to DGM dynamics in frozen Lake St. Louis. These processes may also explain the lack of significant correlations observed in the DGM and mercury volatilization data. PMID:18754358

O'Driscoll, N J; Poissant, L; Canário, J; Lean, D R S

2008-07-15

98

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

NASA Astrophysics Data System (ADS)

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

Tillman, Fred D.; Anning, David W.

2014-11-01

99

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

USGS Publications Warehouse

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

Tillman, Fred D.; Anning, David W.

2014-01-01

100

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

USGS Publications Warehouse

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

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

1980-01-01

101

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, C.A., III

2008-01-01

102

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

NASA Astrophysics Data System (ADS)

In many parts of the world coastal waters with anthropogenic eutrophication have experienced a gradual depletion of dissolved silica (DSi) stocks. This could put pressure on spring bloom diatom populations, e.g. by limiting the intensity of blooms or by causing shifts in species composition. In addition, eutrophication driven enhanced diatom growth is responsible for the redistribution of DSi from the water phase to the sediments, and changes in the growth conditions may be reflected in the sediment diatom stratigraphy. To test for changes in diatom communities we have analyzed four sediment cores from the Baltic Sea covering approximately the last 100 years. The sediment cores originate from the western Gulf of Finland, the Kattegat, the Baltic Proper and the Gulf of Riga. Three out of the four cores reveal only minor changes in composition of diatom assemblages, while the Gulf of Riga core contains major changes, occurring after the second World War. This area is set apart from the other Baltic Sea basins by a high frequency of low after spring bloom DSi concentrations (< 2 µmol L - 1 ) during a relatively well defined time period from 1991-1998. In 1991 to 1993 a rapid decline of DSi spring concentrations and winter stocks (down to 5 µmol L - 1 ) in the Gulf was preceded by exceptionally intense diatom spring blooms dominated by the heavily silicified species Thalassiosira baltica (1991-1992; up to 5.5 mg ww L - 1 ). T. baltica has been the principal spring bloom diatom in the Gulf of Riga since records began in 1975. DSi consumption and biomass yield experiments with cultured T. baltica suggest that intense blooms can potentially exhaust the DSi stock of the water column and exceed the annual Si dissolution in the Gulf of Riga. The phytoplankton time series reveals another exceptional T. baltica bloom period in 1981-1983 (up to 8 mg L - 1 ), which, however, took place before the regular DSi measurements. These periods may be reflected in the conspicuous accumulation of T. baltica frustules in the sediment core corresponding to ca. 1975-1985.

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

2008-10-01

103

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

104

Role of wetlands and developed land use on dissolved organic nitrogen concentrations and DON\\/TDN in northeastern U.S. rivers and streams  

Microsoft Academic Search

Previous studies have shown that watersheds with significant human development (i.e., urban and agricultural land use) generally have higher concentrations and fluxes of dissolved inorganic nitrogen (DIN) in comparison to less-developed or forested watersheds. However, the impact of watershed development on dissolved organic nitrogen (DON) concentrations in drainage waters has received little attention. We present data from 39 watersheds in

Brian A. Pellerin; Wilfred M. Wollheim; Charles S. Hopkinson; William H. McDowell; Michael R. Williams; Charles J. Vörösmarty; Michelle L. Daley

2004-01-01

105

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

USGS Publications Warehouse

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

Sprinkle, Craig L.

1982-01-01

106

Calibration of a reflectance FTIR method for determination of dissolved CO 2 concentration in rhyolitic glasses  

Microsoft Academic Search

A technique based upon infrared reflectance spectroscopy is developed as an alternative to the Fourier transform infrared (FTIR) transmission method for the quantitative measurement of dissolved molecular carbon dioxide in aluminosilicate glasses. The technique has the advantage that only a single sample surface need be polished, and no thickness measurement is necessary. The reflectance spectrum is analyzed by Kramers–Kronig relations

Gordon Moore; Andrew Chizmeshya; Paul F McMillan

2000-01-01

107

Effect of daily minimum dissolved oxygen concentration on production of channel x blue hybrid catfish  

Technology Transfer Automated Retrieval System (TEKTRAN)

As the channel x blue hybrid catfish is stocked by an increasing number of catfish farmers, it is important to quantify the production response of this fish to pond dissolved oxygen management strategies. The purpose of this study was to quantify the production and water quality responses of the cha...

108

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

109

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

NASA Astrophysics Data System (ADS)

We performed synoptic sampling of a 95-km reach of the San Pedro River, Arizona, to identify the effects of regional hydrology and land use on dissolved carbon and nitrogen concentrations. Six synoptic surveys, two before, two during, and two after the 2002 monsoon season, encompassed periods of both low and high stream discharge. Chloride concentrations and ?18O values during low-flow periods indicated the river was divided into three hydrologically distinct reaches each roughly 30 km long. Upper and lower reaches were characterized by areas of localized groundwater input followed by downstream evapo-concentration gradients, limited downstream solute transport, and highly variable carbon and nitrogen concentrations. In contrast, the middle reach was characterized by widespread groundwater input, continuous downstream hydrologic connectivity, and less variable carbon and nitrogen concentrations. During the monsoon season, base flow discharge increased five- to ten-fold, dissolved organic matter and inorganic N increased two- to ten-fold, Fluorescence Index (FI) values indicated a large input of terrestrial solutes, and both chloride concentrations and ?18O values indicated that stream water and alluvial groundwater were well mixed along the entire 95 km reach. Concurrently, the middle reach that exhibited continuous hydrologic connectivity during the nonmonsoon season was a net sink for N, while the reaches characterized by limited hydrologic connectivity during the low-flow season exhibited net N export. Our data suggest that instream biogeochemical cycling during the monsoon season is influenced by antecedent conditions, specifically hydrologic connectivity, during the dry season.

Brooks, Paul D.; Lemon, Michelle M.

2007-09-01

110

Effects of inoculum type and bulk dissolved oxygen concentration on achieving partial nitrification by entrapped-cell-based reactors.  

PubMed

An entrapment of nitrifiers into gel matrix is employed as a tool to fulfill partial nitrification under non-limiting dissolved oxygen (DO) concentrations in bulk solutions. This study aims to clarify which of these two attributes, inoculum type and DO concentration in bulk solutions, is the decisive factor for partial nitrification in an entrapped-cell based system. Four polyvinyl alcohol entrapped inocula were prepared to have different proportions of nitrite-oxidizing bacteria (NOB) and nitrite-oxidizing activity. At a DO concentration of 3 mg l(-1), the number of active NOB cells in an inoculum was the decisive factor for partial nitrification enhancement. However, when the DO concentration was reduced to 2 mg l(-1), all entrapped cell inocula showed similar degrees of partial nitrification. The results suggested that with the lower bulk DO concentration, the preparation of entrapped cell inocula is not useful as the DO level becomes the decisive factor for achieving partial nitrification. PMID:24862001

Rongsayamanont, Chaiwat; Limpiyakorn, Tawan; Khan, Eakalak

2014-07-01

111

Analysis of dissolved organic carbon concentration and 13C isotopic signature by TOC-IRMS - assessment of analytical performance  

NASA Astrophysics Data System (ADS)

Stable carbon isotopes provide a powerful tool to assess carbon pools and their dynamics. Dissolved organic carbon (DOC) has been recognized to play an important role in ecosystem functioning and carbon cycling and has therefore gained increased research interest. However, direct measurement of 13C isotopic signature of carbon in the dissolved phase is technically challenging particularly using high temperature combustion. Until recently, mainly custom-made systems existed which were modified for coupling of TOC instruments with IRMS for simultaneous assessment of C content and isotopic signature. The variety of coupled systems showed differences in their analytical performances. For analysis of DOC high temperature combustion is recognized as best performing method, owing to its high efficiency of conversion to CO2 also for highly refractory components (e.g. humic, fulvic acids) present in DOC and soil extracts. Therefore, we tested high temperature combustion TOC coupled to IRMS (developed by Elementar Group) for bulk measurements of DOC concentration and 13C signature. The instruments are coupled via an Interface to exchange the carrier gas from O2 to He and to concentrate the derived CO2 for the isotope measurement. Analytical performance of the system was assessed for a variety of organic compounds characterized by different stability and complexity, including humic acid and DOM. We tested injection volumes between 0.2-3 ml, thereby enabling measurement of broad concentration ranges. With an injection volume of 0.5 ml (n=3, preceded by 1 discarded injection), DOC and 13C signatures for concentrations between 5-150 mg C/L were analyzed with high precision (standard deviation (SD) predominantly <0.1‰), good accuracy and linearity (overall SD <0.9‰). For the same settings, slightly higher variation in precision was observed among the lower concentration range and depending upon specific system conditions. Differences in 13C signatures of about 50‰ among samples did not affect the precision of the analysis of natural abundance and labeled samples. Natural DOM, derived from different soils and assessed at various concentrations, was measured with similar good analytical performance, and also tested for the effect of freezing and re-dissolving. We found good performance of TOC-IRMS in comparison with other systems capable of determining C concentration and isotopic signatures. We recognize the advantages of this system providing: - High sample throughput, short measurement time (15 minutes), flexible sample volume - Easy maintenance, handling, rapid sample preparation (no pretreatment) This preliminary assessment highlights wide-ranging opportunities for further research on concentrations and isotopic signatures by TOC-IRMS to elucidate the role of dissolved carbon in terrestrial and aquatic systems.

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

2013-04-01

112

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

USGS Publications Warehouse

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

Bevans, H.E.

1980-01-01

113

Dissolved Heavy Metal (Cd, Pb, Cr, Ni) Concentrations in Surface Water and Porewater from Bahía Blanca Estuary Tidal Flats  

Microsoft Academic Search

The concentrations of dissolved cadmium, lead, chromium and n?quel were determined in surface water column and pore water,\\u000a collected from the extensive tidal plain at Bah?a Blanca estuary, Argentina. Three different polluted areas were selected\\u000a to study the spatial variation of these metals. The concentration ranges within the water column were slightly variable (Cd:\\u000a 0.18–2.48 ?g L?1; Pb: 0.38–7.53?g L?1; Cr: 0.89–5.83 ?g L?1; Ni:

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

2007-01-01

114

The influence of sulfur and iron on dissolved arsenic concentrations in the shallow subsurface under changing redox conditions.  

PubMed

The chemical speciation of arsenic in sediments and porewaters of aquifers is the critical factor that determines whether dissolved arsenic accumulates to potentially toxic levels. Sequestration of arsenic in solid phases, which may occur by adsorption or precipitation processes, controls dissolved concentrations. We present synchrotron x-ray absorption spectra of arsenic in shallow aquifer sediments that indicate the local structure of realgar (AsS) as the primary arsenic-bearing phase in sulfate-reducing conditions at concentrations of 1-3 mmol.kg(-1), which has not previously been verified in sediments at low temperature. Spectroscopic evidence shows that arsenic does not substitute for iron or sulfur in iron sulfide minerals at the molecular scale. A general geochemical model derived from our field and spectroscopic observations show that the ratio of reactive iron to sulfur in the system controls the distribution of solid phases capable of removing arsenic from solution when conditions change from oxidized to reduced, the rate of which is influenced by microbial processes. Because of the difference in solubility of iron versus arsenic sulfides, precipitation of iron sulfide may remove sulfide from solution but not arsenic if precipitation rates are fast. The lack of incorporation of arsenic into iron sulfides may result in the accumulation of dissolved As(III) if adsorption is weak or inhibited. Aquifers particularly at risk for such geochemical conditions are those in which oxidized and reduced waters mix, and where the amount of sulfate available for microbial reduction is limited. PMID:15356340

O'Day, Peggy A; Vlassopoulos, Dimitri; Root, Robert; Rivera, Nelson

2004-09-21

115

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

116

Regulation of responsiveness of phosphorescence toward dissolved oxygen concentration by modulating polymer contents in organic-inorganic hybrid materials.  

PubMed

Platinum(II) octaethylporphyrin (PtOEP)-loaded organic-inorganic hybrids were obtained via the microwave-assisted sol-gel condensation with methyltrimethoxysilane and poly(vinylpyrrolidone). From transparent and homogeneous hybrid films, the strong phosphorescence from PtOEP was observed. Next, the resulting hybrids were immersed in the aqueous buffer, and the emission intensity was monitored by changing the dissolved oxygen level in the buffer. When the hybrid with relatively-higher amount of the silica element, the strong phosphorescence was observed even under the aerobic conditions. In contrast, the emission from the hybrids with lower amounts of the silica element was quenched under the hypoxic conditions. This is, to the best of our knowledge, the first example to demonstrate that the responsiveness of the phosphorescence intensity of PtOEP in hybrid films to the dissolved oxygen concentration in water can be modulated by changing the percentage of the contents in the material. PMID:24794749

Okada, Hiroshi; Tanaka, Kazuo; Chujo, Yoshiki

2014-06-15

117

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

118

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

PubMed

Reverse osmosis (RO) concentrate from municipal wastewater reclamation reverse osmosis (mWRRO) system containing organic compounds may associate with toxic risk, and its discharge might pose an environmental risk. To identify a basis for the selection of feasible technology in treating RO concentrates, the characteristics and biotoxicity of different fractions of dissolved organic matter (DOM) in RO concentrates from an mWRRO system were investigated. The results indicated that the hydrophilic neutrals (HIN), hydrophobic acids (HOA) and hydrophobic bases (HOB) accounted for 96% of the dissolved organic carbon (DOC) of the total DOM in the RO concentrate. According to the SEC chromatograph detected at 254nm wavelength of UV, the DOM with molecular weight (MW) 1-3kDa accounted for the majority of the basic and neutral fractions. The fluorescence spectra of the excitation emission matrix (EEM) indicated that most aromatic proteins, humic/fulvic acid-like and soluble microbial by-product-like substances existed in the fractions HOA and hydrophobic neutrals (HON). The genotoxicity and anti-estrogenic activity of the RO concentrate were 1795.6±57.2?g4-NQOL(-1) and 2.19±0.05mgTAML(-1), respectively. The HIN, HOA, and HOB contributed to the genotoxicity of the RO concentrate, and the HIN was with the highest genotoxic level of 1007.9±94.8?g4-NQOL(-1). The HOA, HON, and HIN lead to the total anti-estrogenic activity of the RO concentrate, and HOA occupied approximately 60% of the total, which was 1.3±0.17mgTAML(-1). PMID:25277967

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

2014-12-01

119

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

120

Seasonal ice and hydrologic controls on dissolved organic carbon and nitrogen concentrations in a boreal-rich fen  

NASA Astrophysics Data System (ADS)

Boreal wetland carbon cycling is vulnerable to climate change in part because hydrology and the extent of frozen ground have strong influences on plant and microbial functions. We examined the response of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) across an experimental manipulation of water table position (both raised and lowered water table treatments) in a boreal-rich fen in interior Alaska. DOC and TDN responses to water table manipulation exhibited an interaction with seasonal ice dynamics. We observed consistently higher DOC and TDN concentrations in the lowered water table treatment (71.7 ± 6.5 and 3.0 ± 0.3 mg-L) than in both the control (55.6 ± 5.1 and 2.3 ± 0.2 mg-L) and raised (49.1 ± 4.3 and 1.9 ± 0.1 mg L-1, respectively) water table treatments. Across all plots, pore water DOC concentrations at 20 cm increased as the depth to water table increased (R2 = 0.43, p < 0.001). DOC concentrations also increased as the seasonal thaw depth increased, with solutes increasing most rapidly in the drained plot (R2 = 0.62, p < 0.001). About half of the TDN pool was composed of dissolved organic N (DON). Inorganic N and DON were both highly correlated with changes in DOC, and their respective constraints to mineralization are discussed. These results demonstrate that a declining water table position and dryer conditions affect thaw depth and peat temperatures, and interactions among these ecosystem properties will likely increase DOC and TDN loading and potential for export in these systems.

Kane, Evan S.; Turetsky, Merritt R.; Harden, Jennifer W.; McGuire, A. David; Waddington, James M.

2010-12-01

121

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. PMID:4538906

Garcia, Rolando G.

1972-01-01

122

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

PubMed

To understand the processes of corrosion by-product release and the consequent "red water" problems caused by the variation of water chemical composition in drinking water distribution system, the effect of sulphate and dissolved oxygen (DO) concentration on total iron release in corroded old iron pipe sections historically transporting groundwater was investigated in laboratory using small-scale pipe section reactors. The release behaviors of some low-level metals, such as Mn, As, Cr, Cu, Zn and Ni, in the process of iron release were also monitored. The results showed that the total iron and Mn release increased significantly with the increase of sulphate concentration, and apparent red water occurred when sulphate concentration was above 400 mg x L(-1). With the increase of sulfate concentration, the effluent concentrations of As, Cr, Cu, Zn and Ni also increased obviously, however, the effluent concentrations of these metals were lower than the influent concentrations under most circumstances, which indicated that adsorption of these metals by pipe corrosion scales occurred. Increasing DO within a certain range could significantly inhibit the iron release. PMID:24288993

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

2013-09-01

123

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

USGS Publications Warehouse

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

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

2014-01-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

125

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

USGS Publications Warehouse

Water exported from the Sacramento-San Joaquin River delta (Delta) is an important drinking-water source for more than 20 million people in California. At times, this water contains elevated concentrations of dissolved organic carbon and bromide, and exceeds the U.S. Environmental Protection Agency's maximum contaminant level for trihalomethanes of 0.100 milligrams per liter if chlorinated for drinking water. About 20 to 50 percent of the trihalomethane precursors to Delta waters originates from drainage water from peat soils on Delta islands. This report elucidates some of the factors and processes controlling and affecting the concentration and quality of dissolved organic carbon released from peat soils and relates the propensity of dissolved organic carbon to form trihalomethanes to its chemical composition.Soil water was sampled from near-surface, oxidized, well-decomposed peat soil (upper soil zone) and deeper, reduced, fibrous peat soil (lower soil zone) from one agricultural field in the west central Delta over 1 year. Concentrations of dissolved organic carbon in the upper soil zone were highly variable, with median concentrations ranging from 46.4 to 83.2 milligrams per liter. Concentrations of dissolved organic carbon in samples from the lower soil zone were much less variable and generally slightly higher than samples from the upper soil zone, with median concentrations ranging from 49.3 to 82.3 milligrams per liter. The dissolved organic carbon from the lower soil zone had significantly higher aromaticity (as measured by specific ultraviolet absorbance) and contained significantly greater amounts of aromatic humic substances (as measured by XAD resin fractionation and carbon-13 nuclear magnetic resonance analysis of XAD isolates) than the dissolved organic carbon from the upper soil zone. These results support the conclusion that more aromatic forms of dissolved organic carbon are produced under anaerobic conditions compared to aerobic conditions. Dissolved organic carbon concentration, trihalomethane formation potential, and ultraviolet absorbance were all highly correlated, showing that trihalomethane precursors increased with increasing dissolved organic carbon and ultraviolet absorbance for whole water samples. Contrary to the generally accepted conceptual model for trihalomethane formation that assumes that aromatic forms of carbon are primary precursors to trihalomethanes, results from this study indicate that dissolved organic carbon aromaticity appears unrelated to trihalomethane formation on a carbon-normalized basis. Thus, dissolved organic carbon aromaticity alone cannot fully explain or predict trihalomethane precursor content, and further investigation of aromatic and nonaromatic forms of carbon will be needed to better identify trihalomethane precursors.

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

1998-01-01

126

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

PubMed

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

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

2014-05-01

127

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

128

Simultaneous nitrogen and organic carbon removal in aerobic granular sludge reactors operated with high dissolved oxygen concentration.  

PubMed

Simultaneous nitrification and denitrification (SND) together with organic removal in granules is usually carried out without Dissolved Oxygen (DO) concentration control, at "low DO" (with a DO<30-50% of the saturation value, about 3-4 mg/L) to promote anoxic conditions within the aggregates. These conditions can sometimes be in detrimental of the stability of the granules itself due to a lack of shear force. In this work, the authors achieved SND without oxygen control with big sized granules. More specifically, the paper presents a experimentation focused on the analysis of two Sequencing Batch Reactors (SBRs), in bench scale, working with different aerobic sludge granules, in terms of granule size, and high DO concentration, (with concentration varying from anoxic conditions, about DO ?0 mg/L, to values close to those of saturation, >7-8 mg/L, during feast and famine conditions respectively). In particular, different strategies of cultivation and several organic and nitrogen loading rate have been applied, in order to evaluate the efficiencies in SND process without dissolved oxygen control. The results show that, even under conditions of high DO concentration, nitrogen and organic matter can be simultaneously removed, with efficiency >90%. Nevertheless, the biological conditions in the inner layer of the granule may change significantly between small and big granules, during the feast and famine periods. From point of view of granule stability, it is also interesting that with a particle size greater than 1.5mm, after the cultivation start-up, the granules are presented stable for a long period (about 100 days) and, despite the variations of operational conditions, the granules breaking was always negligible. PMID:23751809

Di Bella, Gaetano; Torregrossa, Michele

2013-08-01

129

Influence of dissolved oxygen concentration on intracellular pH for regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor.  

PubMed

In this paper we report the regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor. For this, the influence of dissolved oxygen concentration in a medium on intracellular pH values and consequently on overall microbial metabolism was emphasized. Intracellular pH of mycelium grown under different concentrations of dissolved oxygen in the medium was determined. Sensitivity of proteins toward proton concentration is well recognized, therefore pH influences on the activities of key regulatory enzymes of Aspergillus niger were determined at pH values similar to those detected in the cells grown under lower dissolved oxygen concentrations. The results have shown significantly reduced specific activities of hexokinase, 6-phosphofructokinase and glucose-6-phosphate dehydrogenase in more acidic environment, while pyruvate kinase was found to be relatively insensitive towards higher proton concentration. As expected, due to the reduced specific activities of regulatory enzymes under more acidic conditions, overall metabolism should be hindered in the medium with lower dissolved oxygen concentration which was confirmed by detecting the reduced specific growth rates. From the studies, we conclude that dissolved oxygen concentration affects the intracellular pH and thus growth rate of Aspergillus niger during the fermentation process. PMID:15951848

Haq, Ikram-Ul; Ali, Sikander; Qadeer, M A

2005-01-01

130

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

E-print Network

that Raman spectroscopy with these Teflon®-AF LCOFs is stable enough for quantitative concentration Instrumentation Engineers. [DOI: 10.1117/1.1917842] Keywords: Raman; spectroscopy; LCOF; waveguide; urine; PLS for publication Oct. 29, 2004; published online May 11, 2005. 1 Introduction Raman spectroscopy is a useful method

Berger, Andrew J.

131

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 ...

132

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

133

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

PubMed

In this study, a comparison between generalized regression neural network (GRNN) and multiple linear regression (MLR) models is given on the effectiveness of modelling dissolved oxygen (DO) concentration in a river. The two models are developed using hourly experimental data collected from the United States Geological Survey (USGS Station No: 421209121463000 [top]) station at the Klamath River at Railroad Bridge at Lake Ewauna. The input variables used for the two models are water, pH, temperature, electrical conductivity, and sensor depth. The performances of the models are evaluated using root mean square errors (RMSE), the mean absolute error (MAE), Willmott's index of agreement (d), and correlation coefficient (CC) statistics. Of the two approaches employed, the best fit was obtained using the GRNN model with the four input variables used. PMID:24956755

Heddam, Salim

2014-08-01

134

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, R.R., II; Piatak, N.M.; Paul, B.

2007-01-01

135

The role of phytoplankton in the modulation of dissolved and oyster cadmium concentrations in Deep Bay, British Columbia, Canada.  

PubMed

We previously identified dissolved cadmium (Cd(diss)) as the main source of this metal in cultured Pacific oysters, Crassostrea gigas, in Deep Bay, British Columbia, Canada (Lekhi et al., 2008). Total suspended particulate Cd (Cd(part)) was not found to be a significant source of oyster Cd (Cd(oys)), with Cd(part) >20 ?m negatively correlated with Cd(oys) concentration. High phytoplankton abundance in spring and summer was hypothesized to reduce Cd(oys) indirectly by drawing down Cd(diss) and increasing oyster growth. In the present study we expanded on these results by examining specifically how the phytoplankton community composition modulates both Cd(diss) and Cd(oys) concentrations in Deep Bay. Based on calculations of nutrients and Cd(diss) drawdown, phytoplankton accounted for approximately 90% of the overall summer reduction in Cd(diss) in the bay. Diatoms were the dominant phytoplankton group, being correlated negatively with Cd(oys) and positively with Cd(part). This suggests that diatom growth mediates the transfer of Cd from the dissolved to the particulate phase, resulting in lower Cd(oys). Spring blooms and sporadic harmful algal blooms may mediate a large flux of Cd(part) to the sediments. Thus, phytoplankton act as a sink, rather than a source, of Cd to oysters in Deep Bay and have a crucial role in the seasonality of Cd(oys) by reducing the concentration of Cd(diss) during the summer. Based on environmental variables, two descriptive models for annual Cd(oys) concentrations were developed using multiple linear regression. The first model (R(2)=0.870) was created to explain the maximum variability in Cd(oys) concentrations throughout the year, while the second (R(2)=0.806) was based on parameters that could be measured easily under farm conditions. Oyster age heavily affected both models, with the first model being secondarily affected by temperature and the second one being more sensitive to changes in salinity. PMID:21820696

Cassis, David; Lekhi, Priyanka; Pearce, Christopher M; Ebell, Nadene; Orians, Kristin; Maldonado, Maria T

2011-09-15

136

Generalised Additive Models to understand long-term trends of dissolved organic carbon concentrations in surface waters  

NASA Astrophysics Data System (ADS)

In the literature, several causes of recently increasing dissolved organic carbon (DOC) concentrations in surface waters across eastern North America and northern and central Europe have been debated. One of the most likely drivers of the widespread increase of DOC concentrations since the early to mid 1990s were decreasing atmospheric acid depositions. More specifically, it was observed that the spatial distribution of linear trends between DOC and sulphate concentrations was consistent for surface waters in Canada, Finland, Norway, Sweden, the UK and the USA. However, to the best of our knowledge, non-linear methods have not been applied to examine temporal trends of DOC and surrogates of acid deposition such as sulphate concentrations and pH. This type of analysis could provide a refined understanding of how deceasing acid deposition affected DOC concentrations over time. In this study, we used Generalised Additive Models (GAM) to detect non-linear trends of DOC and pH during the last 20 years for three streams draining forested headwater catchments of the Mulde River in the Ore Mountains, East Germany. The analysis accounted for both seasonal patterns and the influence of stream flow on DOC. We found consistent temporal non-linear trends for DOC and pH. Furthermore, trends of DOC and pH may be decoupled during the last 5 years. While DOC concentrations were still increasing, pH tended to level off. Overall, our GAM analysis appeared to be a promising tool to gain further insight into potential drivers of increasing DOC trends in surface waters.

Selle, Benny; Tittel, Jörg

2014-05-01

137

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

138

Dissolved hydrogen concentrations as a rapidly measured indicator of nitrogen fixation rates in the surface ocean  

NASA Astrophysics Data System (ADS)

A major source of hydrogen in the marine environment is release by diazotrophs during the process of nitrogen fixation. While the net release differs among various diazotrophs, the highest net release per unit nitrogen fixed is from Trichodesmium which is widely reported to be the predominant source of fixed nitrogen in the oceans. Unlike direct measurements of nitrogen fixation rates, typically made through N15 uptake incubations, which are time consuming and labour intensive, hydrogen analyses can be made on a semi-automatic basis on continuously pumped surface waters. An extensive data set of such measurements made during an Atlantic Meridional Transect cruise (AMT 20) in 2010 will be presented. We propose that hydrogen measurements have the potential to improve our ability to quantify the extent and variability of nitrogen fixation in ocean surface waters, for example, by guiding or optimising sampling for N15 uptake measurements. Also, the detailed spatial coverage possible for hydrogen concentrations could be used to better define the short-term relationship between nitrogen fixation rates and iron concentrations,and hence dust fluxes to the ocean surface.

Moore, R. M.; Fraser, M.

2012-12-01

139

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

USGS Publications Warehouse

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

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

1996-01-01

140

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

PubMed Central

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

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

2014-01-01

141

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

2011-12-15

142

Dissolved concentrations, sources, and risk evaluation of selected metals in surface water from Mangla Lake, Pakistan.  

PubMed

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

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

2014-01-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

144

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

145

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

PubMed

Dissolved trace metal (Ag, Cd, Cu, Fe, Ni, Pb, and Zn), inorganic nutrient (NO3, NH4, PO4, H4SiO4), and DOC concentrations were measured at 43 stations during low (July 2000) and high (April 2001) river discharge conditions in surface waters of Long Island Sound (LIS). To evaluate the impact of fluvial sources to the total metal budget of the sound, samples were collected from major tributaries discharging into LIS (Thames, Quinnipiac, Housatonic, Connecticut, and East Rivers). To compare LIS with other coastal embayments, samples were also collected from five LIS coastal embayments (Manhassett Bay, Huntington Harbor, Oyster Bay, Hempstead Harbor, and Port Jefferson Harbor), which are monitored by the U.S. National Status and Trends Program. Metal and nutrient distributions identified two biogeochemical regimes within LIS: an area of relatively high nutrient and metal concentrations in the East River/Narrows region in western LIS and an area in the eastern region of the sound that had comparatively lower concentrations. Mass balance estimates indicated that, during low flow conditions, the East River was the dominant allochthonous source of most trace metals (Ag, Cd, Cu, Ni, Zn) and inorganic nutrients (NO3 and PO4); during high flow conditions, the most influential source of these constituents was the Connecticut River. Mass balance estimates also evidenced a large autochthonous source of Cu, Ni, and Zn, as their spatial distributions displayed elevated concentrations away from point sources such as the East River. Principal component analysis suggested that metal and nutrient distributions in the LIS system were influenced by different seasonal processes: remobilization from contaminated sediments, anthropogenic inputs from sewage discharges and phytoplankton scavenging during the spring freshet, and benthic remobilization during summer conditions. PMID:15952355

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

2005-05-15

146

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

147

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

PubMed

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

Heddam, Salim

2014-01-01

148

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

149

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

NASA Astrophysics Data System (ADS)

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

Mammitzsch, K.; Jost, G.; Jürgens, K.

2012-12-01

150

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

151

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

USGS Publications Warehouse

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

Thodal, C.E.

1996-01-01

152

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

153

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

USGS Publications Warehouse

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

Gillip, Jonathan A.

2014-01-01

154

HOTSED: a discrete element model for simulating hydrodynamic conditions and adsorbed and dissolved radioisotope concentrations in estuaries  

SciTech Connect

A model has been developed to study the feasibility of simulating one-dimensional transport of radioisotope-tagged sediment in tidal-dominated estuaries. A preliminary one-dimensional model for simulating hydrodynamic, thermal, and dissolved radionuclide concentrations in tidal estuaries was merged with an improved version of the SEDTRN model, a multi-sediment-size class model of bedload and suspended sediment transport. The improved SEDTRN model, which employs a velocity-based rather than an energy-based sediment transport rate calculation and accounts for nonzero channel bed slope, is given credence by comparing its results in stand-alone form to those obtained using the parent model. Results of the latter model have been shown to compare favorably to field measurements. The combined preliminary model is called HOTSED. Details of model modifications, the addition of printer plot output capability, and a discussion of input and output structures are included. The HOTSED model is applied to the Hudson River under tidal-transient conditions and the transport ''tagged'' or radioisotope-bearing sediment is simulated. The code is designed specifically for applications with dominant tidal cycling. It requires, for a 76-element channel system, 270 thousand bytes of storage and, for a simulation of 25 hours, has an execution time of approximately five minutes on the IBM System 360/91 computer.

Fields, D.E.; Hetrick, D.M.

1978-12-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

156

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

PubMed

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

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

2014-10-21

157

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 in Trichodesmium such as nitrogen fixation, carbon drawdown and biomass production was explored by using a principal component analysis test (PCA). The analysis indicates that the biological drawdown of dissolved inorganic carbon (DIC) by Trichodesmium seems to be influenced by the internal content of Fe, Co, Cd, Cu and Mn, while nitrogen fixation seems more influenced by the internal concentration of Mo, Ni and V and by the dissolved phosphorous concentrations.

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

2010-08-01

158

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

EPA Science Inventory

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

159

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

160

EFFECTS OF DISSOLVED ORGANIC CARBON AND SECOND SUBSTRATES ON THE BIODEGRADATION OF ORGANIC COMPOUNDS AT LOW CONCENTRATIONS  

EPA Science Inventory

Pseudomonas acidovorans and Pseudomonas sp. strain ANL but not Salmonella typhimurium grew in an inorganic salts solution. Results indicate that second substrates and uncharacterized dissolved organic carbon may play an important role in controlling the rate and extent of biodegr...

161

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

162

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

163

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

NASA Astrophysics Data System (ADS)

Dissolved organic carbon, (DOC), is the component of the organic carbon that can pass through a membrane filter, with the accepted maximum pore size of 0.7 ?m. There is growing interest in high resolution time series of such data e.g. heterotrophic respiration of DOC in freshwater systems can fuel atmospheric CO2 efflux so observing variation in DOC concentration, [DOC], is meaningful. Field deployable sensors, capable of measuring [DOC] on a continuous basis, have the potential to provide us with a far higher resolution time series data than we can obtain through manual sampling. At a catchment area draining Europe's largest windfarm, Whitelee, we have deployed an S::CAN Spectrolyser. This device scans wavelengths from 200 to 735nm, generating a spectral fingerprint and then, using an inbuilt algorithm, returns a value for the DOC concentration, termed DOC-equivalent, [DOC-eq]. The Spectrolyser also estimates other parameters such as total organic carbon and the true colour of the water. Unfortunately, our field Spectrolyser [DOC] are different from lab based measurement of [DOC] of the same field filtered samples (measured using a Thermalox high temperature catalytic oxidation system). Comparing 28 lab measured [DOC] with Spectrolyser [DOC-eq] shows an average difference of 7.6 mg/l C. Here we discuss our interpretation of why this disparity exists and how to accommodate this offset such that accuracy is improved. We have tried various methods of keeping the lens and path length clean through brushing, acid cleaning and the recent installation of a high pressure air hose (recommended by S::CAN). We will compare output before and after this installation. Further complexity is added because light may be absorbed by other components of the field sample, such as particulate material, and this could compromise the estimated [DOC-eq]. [DOC] may be estimated using absorption measurements made at 254nm and 340nm (Tipping et al, 2009). We have implemented this formula using 255 and 340nm (the closest wavelengths) to compare the results with the automatically generated [DOC-eq], and also our laboratory measurements. As a field-deployed sensor measuring unfiltered samples, to compensate for turbidity we have incorporated the asborption measurement at 735nm in the calculation. With this approach, the average difference between lab measured and calculated decreases to 4.5mg/l. Tipping, E., et al. (2009), Quantification of natural DOM from UV absorption at two wavelengths. Environmental Chemistry, 6,6, 472-476.

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

2013-04-01

164

Production of channel catfish and channel x blue hybrid catfish subjected to two minimum dissolved oxygen concentrations  

Technology Transfer Automated Retrieval System (TEKTRAN)

As the channel x blue hybrid catfish is stocked by an increasing number of catfish farmers, it is important to quantify the production response of this fish to dissolved oxygen management strategies. The purpose of this study was to compare the production and water quality responses of the channel x...

165

Freely oriented portable superconducting magnet  

DOEpatents

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

Schmierer, Eric N. (Los Alamos, NM); Prenger, F. Coyne (Los Alamos, NM); Hill, Dallas D. (Los Alamos, NM)

2010-01-12

166

Typhoon- and earthquake-enhanced concentration and inventory of dissolved and particulate trace metals along two submarine canyons off southwestern Taiwan  

NASA Astrophysics Data System (ADS)

The influence of typhoon and earthquake events on the distributions of dissolved and particulate trace metals (Al, Fe, Mn, Cd, Cu, Pb, Zn) is evaluated along the Gaoping Canyon and Fangliao Canyon in a tectonically active margin off southwestern Taiwan. The Fangliao Canyon was mightily struck by a large Pingtung Earthquake (ML 7.0) in winter when terrestrial inputs were insignificant. This large earthquake clearly enhanced the concentration and inventory of total suspended matter (TSM), dissolved and particulate metals by 2-5 fold in Fangliao Canyon and nearby Gaoping Canyon, as compared to those in normal winter conditions. The Gaoping Canyon is typically inundated with massive amounts of terrestrial materials during summer typhoons from the mountainous Gaoping River. Strong contrast of particle and metal distributions can be found between summer and winter and between typhoon and regular summer periods in the Gaoping Canyon, which was apparently caused by various strengths of river inputs followed by sediment resuspension and lateral advection at intermediate and near-bottom depths along the canyon. The water-column and canyon-wide inventories of TSM, dissolved and particulate metals increased up to 2-fold higher during the post-typhoon period than during the rainy period in summer in the Gaoping Canyon. After extreme events, most metals tend to increase their release into the dissolved phase through the increase of TSM concentration. In addition to huge river inputs during typhoon, both typhoon and earthquake induce energetic sea conditions that cause sediment resuspension and enhance the concentration and inventory of particles and metals in submarine canyons.

Hung, J.-J.; Ho, C.-Y.

2014-01-01

167

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

168

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

PubMed

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

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

2009-08-01

169

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

PubMed

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

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

2015-01-01

170

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

171

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

172

Automation of a flow injection system for the determination of dissolved silver at picomolar concentrations in seawater with inductively coupled plasma mass spectrometry.  

PubMed

An automated flow injection system for the determination of dissolved silver at ultratrace concentrations in seawater, and controlled under LabVIEW, is described. The flow injection system allows online processing of seawater samples before their analysis using a magnetic sector inductively coupled plasma mass spectrometry (MS-ICP-MS) instrument. Samples were analysed with a minimum amount of manipulation, thereby reducing the risk of contamination. In addition, the flow injection approach with incorporation of an anion exchange minicolumn allowed ready removal of analytical interferences caused by the saline matrix. The software allowed full control of all flow injection components (valves and pumps) and removed manual time control and, therefore, operator errors. The optimized system was capable of five sample injections per h, including preconcentration and wash steps. The limit of detection was 0.5 pM for a 240-s sample load time, which allowed the determination of dissolved silver in open ocean waters, where picomolar concentration levels are typically encountered. PMID:18924719

Barriada, Jose L; Truscott, Jason B; Achterberg, Eric P

2003-01-01

173

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

174

A novel method for the determination of dissolved methylmercury concentrations using diffusive gradients in thin films technique.  

PubMed

A novel DGT probe and analysis protocol were developed for the determination of MeHg concentrations in aquatic system. The DGT probe consisted of an agarose (AG) gel as the diffusive hydrogel and a 3-mercaptoproply functionalised silica resin gel as the resin gel. The polyacrylamide (PA) hydrogel which is commonly used in DGT probes to assess trace metal concentrations in aquatic system appeared to be unsuitable for the determination of MeHg. The affinity of the PA hydrogel for MeHg is very high reducing its accumulation by the resin. In contrast, the AG hydrogel presents a by far lower affinity towards MeHg, which makes it suitable as diffusive layer in a DGT probe for MeHg determinations. Two extraction procedures to liberate MeHg from the resin were studied: one is involving thiourea as complexing agent, the other a simple acidic extraction. The extraction step was followed by an ethylation reaction of the liberated MeHg to determine low concentrations of MeHg species by Headspace-Gas Chromatography-Atomic Fluorescence (HS-GC-AFS). With the thiourea extraction method the recovery of the adsorbed MeHg compounds was extremely low while the recovery with the acid extraction method was 100%. The reliability of the novel DGT probe and analysis protocol was studied. A linear dependency between the amount of MeHg accumulated on the resin gel and both the deployment time and the gel thickness were demonstrated. From those experiments a diffusion coefficient of MeHg in AG gel was determined: 5.1±0.20×10(-6) cm(2) s(-1). Additional experiments showed that the new DGT method can be used in most natural waters independent of the ionic strength and within a pH range of 3-8. PMID:24468398

Gao, Yue; De Craemer, Sam; Baeyens, Willy

2014-03-01

175

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

176

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

177

Silicic magma accumulation beneath Mount Mazama, Oregon, 71 ka to 24 ka constrained by SHRIMP measurements of dissolved volatile concentrations in melt inclusions  

NASA Astrophysics Data System (ADS)

Dissolved volatile contents of melt inclusions trapped in pyroxene and plagioclase crystals from 7 silicic eruptions preceding the climactic ~7.7 ka Mazama eruption were measured by SIMS with the Stanford-USGS SHRIMP-RG. Melt inclusions in crystals were intersected, polished, and crystals were mounted in indium in Al mounts. A 1.2-3.0 nA (depending on the session), O2- primary beam was accelerated and focused to a 15-25 ?m spot on the sample surface, which generated positive secondary ions of analyzed Li, Be, B, C, OH, F, Mg, Si, SiH, S, Cl, Ca, AlO, KO, Rb, and Sr. Measurements were made at high mass resolution (6000-7000). Trace element and volatile concentrations were calculated using a best-fit regression to count rate ratios (normalized to 30Si) vs. variable known concentrations in experimental and natural rhyolite glass standards. Pumiceous samples were chosen from dacitic to rhyodacitic eruptive deposits, consisting of the 71ka dacite of Pumice Castle, 70ka dacite below Llao Rock, 50ka dacite of the Watchman, 35ka dacite of Munson Valley, 35ka Williams Crater tephra, 27ka Redcloud Cliff rhyodacite, and 24ka andesite S of Bear Bluff. Melt inclusions are abundant in spongy, mineral-inclusion-rich interiors of pyroxene crystals in early (71-35ka) eruptive deposits and are less abundant throughout pyroxenes from later eruptions (35-24ka) and in plagioclase crystals. Over the entire time interval, most trace element and volatile concentrations remain approximately constant between melt inclusion populations. However, there are some variations in water and carbon dioxide concentration. A large proportion of inclusions in the smaller eruptive deposits (0.003-0.4 km3) of the dacite of the Watchman, dacite of Munson Valley, and Williams Crater tephra have low water contents, ~1 wt% H2O, corresponding to a saturation pressure of 25MPa, or ~1km depth (at 870°, approximate average temperature for these deposits, e.g., Druitt and Bacon, Contrib Mineral Petrol 1989; with 2200 kg/m3 overburden density), potentially reflecting shallow storage immediately preceding eruption. Furthermore, compositional differences between melt inclusions hosted in orthopyroxene, clinopyroxene, and plagioclase crystals are small, with the exception of lower water content in plagioclase than pyroxene from some, but not all, deposits, which we attribute to diffusive water loss during decompression. The largest cluster of high-water-content volatile data lies at ~4 wt% H2O, with maximum water contents at 6 wt%. CO2 concentrations range from below detection to almost 800 ppm. The combined dissolved H2O and CO2 data indicate dominant saturation pressures between 75 and 150 MPa, ~3.5-7 km depth, similar to saturation pressures calculated for the climactic and pre-climactic Llao and Cleetwood eruptive products. Further, calculated CO2 concentrations are higher in early eruptive products than late. We interpret these water and CO2 data to reflect a limited range of storage depths (with similar water contents), with a progressive increase in the extent of passive degassing, culminating in a climactic chamber that contained ˜no dissolved CO2 (Bacon et al., Amer Mineral 1992; Mandeville et al., Geochim Cosmochim Acta 2009).

Wright, H. M.; Bacon, C. R.; Vazquez, J. A.; Sisson, T. W.

2010-12-01

178

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

PubMed Central

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

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

2014-01-01

179

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

180

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

PubMed

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

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

2014-08-01

181

Impact of dissolved inorganic carbon concentrations and pH on growth of the chemolithoautotrophic epsilonproteobacterium Sulfurimonas gotlandica GD1T  

PubMed Central

Epsilonproteobacteria have been found globally distributed in marine anoxic/sulfidic areas mediating relevant transformations within the sulfur and nitrogen cycles. In the Baltic Sea redox zones, chemoautotrophic epsilonproteobacteria mainly belong to the Sulfurimonas gotlandica GD17 cluster for which recently a representative strain, S. gotlandica GD1T, could be established as a model organism. In this study, the potential effects of changes in dissolved inorganic carbon (DIC) and pH on S. gotlandica GD1T were examined. Bacterial cell abundance within a broad range of DIC concentrations and pH values were monitored and substrate utilization was determined. The results showed that the DIC saturation concentration for achieving maximal cell numbers was already reached at 800??mol?L?1, which is well below in situ DIC levels. The pH optimum was between 6.6 and 8.0. Within a pH range of 6.6–7.1 there was no significant difference in substrate utilization; however, at lower pH values maximum cell abundance decreased sharply and cell-specific substrate consumption increased. PMID:24376054

Mammitzsch, Kerstin; Jost, Günter; Jürgens, Klaus

2014-01-01

182

Concentrations of total and dissolved Hg in snow and vapor deposition collected during Atmospheric Mercury Depletion Events (AMDEs) in Barrow, Alaska during the BROMEX campaign  

NASA Astrophysics Data System (ADS)

During the Bromine, Ozone, and Mercury Experiment (BROMEX) in March and April 2012, we characterized surface snow concentrations of mercury and major ions near Barrow, Alaska, in order to assess effects of Atmospheric Mercury Depletion Events (AMDE) on surface snow chemistry. During AMDEs, gaseous elemental mercury is oxidized to divalent Hg forms which, due to their high deposition velocities, can lead to increased Hg deposition to snow and ice surfaces. Daily collections of surface snow (top 2 cm) analyzed for total Hg (THg) showed average concentrations of 14 ppt at both an Out-On-The-Ice (OOTI) site on Arctic Ocean first year sea ice 2 km from the shore and at a terrestrial site on tussock tundra 5 km inland. Both sites showed similar concentration variability (THg ranging from 3.9 to 29.3 ppt). The OOTI site, however, showed substantially higher percentages of Hg that was in the dissolved phase (DHg; filtered by 0.45 ?m filter), averaging 68% versus 27% at the inland site. These differences were unlikely linked to atmospheric Hg dynamics as both sites showed similar concentrations and temporal patterns of gaseous and oxidized atmospheric Hg. A higher DHg fraction may indicate a different behavior of snow on land versus snow on sea ice snow in regards to accumulating, retaining, or re-emitting mercury. Overall, surface snow Hg concentrations at both sites were weakly and inversely correlated with the daily average atmospheric elemental Hg concentration, showing that depletions of atmospheric Hg and their associated formation of divalent Hg may translate into small surface snow Hg enhancements. A snow transect collected between 2 km out on the sea ice and 6 km inland also showed no inherent differences in THg between inland and sites on the sea ice and confirmed the higher DHg fraction in snow on sea ice. To collect vapor phase ice samples from the lower atmosphere- snow surface interface we designed and deployed a novel "cold plate" sampler that allowed for daily collection of vapor phase (condensate) deposition through cooling of a clean stainless-steel surface to ~20° below ambient air temperature. Collected deposition averaged 12.0 and 15.6 ppt, which was similar to THg levels observed in surface snow. This indicates that water directly extracted from the atmosphere showed surprisingly similar THg concentrations to surface snow nearby.

Obrist, D.; Moore, C. W.; Douglas, T. A.; Steffen, A.; Staebler, R. M.; Pearson, C.

2012-12-01

183

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

184

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

USGS Publications Warehouse

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

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

2007-01-01

185

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

EPA Science Inventory

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

186

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

NASA Astrophysics Data System (ADS)

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

Terajima, Tomomi; Moriizumi, Mihoko

2013-02-01

187

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

188

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

NASA Astrophysics Data System (ADS)

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

Drott, A.; Skyllberg, U.

2007-12-01

189

The Measurement of Dissolved Oxygen  

ERIC Educational Resources Information Center

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

Thistlethwayte, D.; And Others

1974-01-01

190

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

191

Effects of wind farm construction on concentrations and fluxes of dissolved organic carbon and suspended sediment from peat catchments at Braes of Doune, central Scotland  

Microsoft Academic Search

SUMMARY This paper assesses the impacts of disturbance associated with the construction of a wind farm on fluxes of dissolved organic carbon (DOC) and suspended sediment from a blanket peat catchment in central Scotland during the period immediately following completion. Six streams draining the site were sampled on six dates from October 2006, when construction was completed, and an additional

I. Grieve; D. Gilvear

192

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

193

A freely-moving monkey treadmill model  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

194

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

195

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

196

Experimental investigations on freely exposed ducted radiators  

NASA Technical Reports Server (NTRS)

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

Linke, W

1941-01-01

197

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

PubMed

Dissolved inorganic nitrogen (DIN), phosphate (PO?) and silicic acid (Si(OH)?) loads from the Seybouse and the Mafragh estuaries into the Bay of Annaba, Algeria, were assessed at three stations of the Bay over three years. The Seybouse inputs had high levels of DIN and PO?, in contrast to the Mafragh estuary's near-pristine inputs; Si(OH)? levels were low in both estuaries. The DIN:PO? molar ratios were over 30 in most samples and the Si(OH)4:DIN ratio was less than 0.5 in the Seybouse waters, but nearly balanced in the Mafragh. The specific fluxes of Si-Si(OH)? (400-540 kg Si km?² yr?¹) were comparable in the two catchments, but those of DIN were several-fold higher in the Seybouse (373 kg N km?² yr?¹). The inner Bay affected by the Seybouse inputs had high levels of all nutrients, while the Mafragh plume and the outer marine station were less enriched. PMID:24486043

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

2014-03-15

198

Biotransformation of codeine to morphine in freely suspended cells and immobilized cultures of Spirulina platensis  

Microsoft Academic Search

Both freely suspended cells and immobilized cultures of Spirulina platensis, a blue-green alga, biotransformed exogenously fed codeine, an opium alkaloid, to morphine. The external addition of codeine to the culture medium did not affect the growth of S. platensis. Immobilization of Spirulina in a calcium alginate gel matrix was optimized by using 2% (w\\/v) sodium alginate and reducing the concentration

S. Ramachandra Rao; Usha Tripathi; G. A. Ravishankar

1999-01-01

199

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...

200

Method for dissolving clay  

Microsoft Academic Search

A method is described for dissolving clay which comprises contacting the clay alternately with separate slugs of a hydrogen ion-containing chemical and a fluoride ion-containing chemical. The hydrogen ions and fluoride ions react on the surface of the clay to produce hydrofluoric acid to dissolve the clay. The method is particularly valuable in dissolving the clay in a mixture of

Hall

1977-01-01

201

Concentration  

NSDL National Science Digital Library

This is the NCTM Android app of their familiar on line Illuminations game, "Concentration" ( cataloged separately ) which challenges a user to match whole numbers, shapes, fractions, or multiplication facts to equivalent representations. This game can be played by one or two players taking turns and can be played in clear pane mode, or for added challenge, with the windows closed.

2011-08-11

202

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

203

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

USGS Publications Warehouse

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

Busenberg, Eurybiades; Plummer, L. Niel

2014-01-01

204

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

205

Background Subtraction for Freely Moving Cameras Yaser Sheikh1  

E-print Network

Background Subtraction for Freely Moving Cameras Yaser Sheikh1 Omar Javed2 Takeo Kanade1 yaser, PA 15213 2 ObjectVideo Inc., Reston, VA 20191 Abstract Background subtraction algorithms define, we extend the concept of `subtract- ing' areas at rest to apply to video captured from a freely

Zhu, Zhigang

206

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

USGS Publications Warehouse

Effective management of existing water-storage capacity in the Arkansas River Basin is anticipated to help satisfy the need for water in southeastern Colorado. A strategy to meet these needs has been developed, but implementation could affect the water quality of the Arkansas River and Fountain Creek in the vicinity of Pueblo, Colorado. Because no known methods are available to determine what effects future changes in operations will have on water quality, the U.S. Geological Survey, in cooperation with the Southeastern Colorado Water Activity Enterprise, began a study in 2002 to develop methods that could identify if future water-quality conditions have changed significantly from background (preexisting) water-quality conditions. A method was developed to identify when significant departures from background (preexisting) water-quality conditions occur in the lower Arkansas River and Fountain Creek in the vicinity of Pueblo, Colorado. Additionally, the methods described in this report provide information that can be used by various water-resource agencies for an internet-based decision-support tool. Estimated dissolved-solids concentrations at five sites in the study area were evaluated to designate historical background conditions and to calculate tolerance limits used to identify statistical departures from background conditions. This method provided a tool that could be applied with defined statistical probabilities associated with specific tolerance limits. Drought data from 2002 were used to test the method. Dissolved-solids concentrations exceeded the tolerance limits at all four sites on the Arkansas River at some point during 2002. The number of exceedances was particularly evident when streamflow from Pueblo Reservoir was reduced, and return flows and ground-water influences to the river were more prevalent. No exceedances were observed at the site on Fountain Creek. These comparisons illustrated the need to adjust the concentration data to account for varying streamflow. As such, similar comparisons between flow-adjusted data were done. At the site Arkansas River near Avondale, nearly all the 2002 flow-adjusted concentration data were less than the flow-adjusted tolerance limit which illustrated the effects of using flow-adjusted concentrations. Numerous exceedances of the flow-adjusted tolerance limits, however, were observed at the sites Arkansas River above Pueblo and Arkansas River at Pueblo. These results indicated that the method was able to identify a change in the ratio of source waters under drought conditions. Additionally, tolerance limits were calculated for daily dissolved-solids load and evaluated in a similar manner. Several other mass-load approaches were presented to help identify long-term changes in water quality. These included comparisons of cumulative mass load at selected sites and comparisons of mass load contributed at the Arkansas River near Avondale site by measured and unmeasured sources.

Ortiz, Roderick F.

2004-01-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

208

Determination of Dissolved Oxygen in the Cryosphere: A Comprehensive  

E-print Network

Determination of Dissolved Oxygen in the Cryosphere: A Comprehensive Laboratory and Field communities, whose function and dynamics are often controlled by the concentrations of dissolved oxygen (DO tests and superior to traditional methods. Introduction Dissolved oxygen (DO) is a key parameter

Fountain, Andrew G.

209

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

210

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

211

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

PubMed

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

Heddam, Salim

2014-08-01

212

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

213

Bathymetric influence on dissolved methane in hydrothermal plumes revealed by concentration and stable carbon isotope measurements at newly discovered venting sites on the Central Indian Ridge (11-13°S)  

NASA Astrophysics Data System (ADS)

Methane is a useful tracer for studying hydrothermal discharge, especially where the source fluids are of low temperature and lack metal precipitates. However, the dual origins of deep-sea methane, both chemical and biological, complicate the interpretation of methane observations. Here, we use both the concentration and stable carbon isotopic composition (?13C) of dissolved methane to trace hydrothermal plumes and identify the source and behavior of methane at two sites of newly discovered hydrothermal activity on the Central Indian Ridge (11-13°S). At both sites, methane and optical anomalies between 2500 and 3500 m at all stations indicate active hydrothermal discharge. We compared methane concentrations and ?13C at three stations, two (CTIR110136 and CTIR110208) with the most prominent anomalies at each site, and a third (CTIR110140) with near-background methane values. At stations CTIR110136 and CTIR110208, the concentration and ?13C of methane in distinct plumes ranged from 3.3 to 42.3 nmol kg-1 and -30.0 to -15.4‰, respectively, compared to deep-water values of 0.5 to 1.2 nmol kg-1 and -35.1 to -28.9‰ at the station with a near-background distal plume (CTIR110140). ?13C was highest in the center of the plumes at CTIR110136 (-15.4‰) and CTIR110208 (-17.8‰). From the plume values we estimate that the ?13C of methane in the hydrothermal fluids at these stations was approximately -19‰ and thus the methane was most likely derived from magmatic outgassing or the chemical synthesis of inorganic matter. We used the relationship between ?13C and methane concentration to examine the behavior of methane at the plume stations. In the CTIR110208 plume, simple physical mixing was likely the major process controlling the methane profile. In the CTIR110136 plume we interpret a more complicated relationship as resulting from microbial oxidation as well as physical mixing. We argue that this difference in methane behavior between the two areas stems from a distinct bathymetric dissimilarity between the two stations. The location of CTIR110208 on the open slope of a ridge allowed rapid plume dispersion and physical mixing, whereas the location of CTIR110136 in a small basin surrounded by wall structures inhibited physical mixing and enhanced microbial oxidation.

You, Ok-Rye; Son, Seung Kyu; Baker, Edward T.; Son, Juwon; Kim, Mi Jin; Barcelona, Michael J.; Kim, Moonkoo

2014-09-01

214

Pill Dissolving Demo  

NSDL National Science Digital Library

In a class demonstration, the teacher places different pill types ("chalk" pill, gel pill, and gel tablet) into separate glass beakers of vinegar, representing human stomach acid. After 20-30 minutes, the pills dissolve. Students observe which dissolve the fastest, and discuss the remnants of the various pills. What they learn contributes to their ongoing objective to answer the challenge question presented in lesson 1 of this unit.

Vu Bioengineering Ret Program

215

Voltammetric determination of dissolved iron and its speciation in freshwater  

Microsoft Academic Search

Analytical methods were developed to determine the concentration of total dissolved iron and its chemical speciation in freshwater using cathodic stripping voltammetry (CSV) with 1-nitroso-2-naphthol (NN) at pH 8.1. The concentrations of total dissolved iron in river water that iron concentration was certified and in natural water samples from Lake Kasumigaura were determined successfully. The natural iron ligand concentration and

Takashi Nagai; Akio Imai; Kazuo Matsushige; Kunihiko Yokoi; Takehiko Fukushima

2004-01-01

216

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

217

Extracellular wire tetrode recording in brain of freely walking insects.  

PubMed

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

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

2014-01-01

218

The relationship of dissolved Pb to some dissolved trace metals (Al, Cr, Mn, and Zn) and to dissolved nitrate and phosphate in a freshwater aquatic system in Mauritius.  

PubMed

The relationship of some dissolved trace metals (Al, Cr, Mn, Zn, and Pb) with one another and to dissolved phosphate and nitrate in a freshwater aquatic system at Flic en Flac and Grand River North West (GRNW) in Mauritius (1850 km2, 20 degrees S and 57 degrees E, Western Indian ocean) is reported following trace metal determination using inductively coupled plasma mass spectrometry (ICP-MS). Dissolved Al (<200 ng ml(-1)), Cr (<50 ng ml(-1)), Mn (<50 ng ml(-1)), Zn (< 100 ng ml(-1)), and Pb (<50 ng ml(-1)) upstream, downstream GRNW and in the marshes and rivulet at Flic en Flac were found to be below the recommended EEC maximum admissible concentrations and within the ambient drinking water quality standards in Mauritius. Dissolved Pb was significantly positively correlated to both dissolved Cr and Zn suggesting that the cycling for dissolved Pb is linked to the cycling of both dissolved Cr and Zn along GRNW. The common influential cycling of Pb and Zn was further reinforced as both dissolved Pb and Zn were significantly positively correlated to dissolved phosphate, which suggested a biological role in the cycling of Zn and Pb. The role of biological activity or adsorption to biological systems in Pb cycling along GRNW is further suggested as dissolved Pb was significantly correlated to dissolved nitrate. The apparent absence of the dissolved Al, Cr, and Mn with dissolved nitrate and phosphate could be attributed to factors such as the lower sensitivity of the GRNW to metal uptake during biological activity during the time frame considered. The cycling of dissolved Al and Mn was also not linked to the cycling of Cr, Zn, and Pb as no significant correlation was found along GRNW. PMID:11341289

Ramessur, R T; Parry, S J; Ramjeawon, T

2001-04-01

219

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

220

Acoustic tracking of a freely drifting sonobuoy field: experimental results  

Microsoft Academic Search

This paper describes a regularized acoustic inversion algorithm for tracking individual elements of a freely drifting sonobuoy field using measured acoustic arrival times from a series of impulsive sources. The acoustic experiment involved 11 sonobuoys distributed over an 8×6-km field, with a total of six sources deployed over 72 min. The inversion solves for an independent track for each sonobuoy

Nicole E. B. Collison; Stan E. Dosso

2003-01-01

221

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

222

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

223

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

224

Free Zinc Ion and Dissolved Orthophosphate Effects on  

E-print Network

Free Zinc Ion and Dissolved Orthophosphate Effects on Phytoplankton from Coeur d'Alene Lake, Idaho. This phosphorus-limited lake has been subjected to decades of mining (primarily for zinc and silver) and other of free (uncomplexed) zinc ion and dissolved- orthophosphate concentrations on phytoplankton that were

225

Decomposition of dissolved organic matter from the continental margin  

Microsoft Academic Search

Decomposition of dissolved organic carbon, nitrogen and phosphorus (DOC, DON, DOP) was measured for surface and bottom waters of the middle Atlantic bight (MAB) and deep slope water adjacent to the MAB on two occasions in March and August 1996. We used standard bottle incubation techniques to measure the decrease in dissolved organic matter (DOM) concentrations over a 180-day interval.

Charles S. Hopkinson Jr; Joseph J. Vallino; Amy Nolin

2002-01-01

226

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 ...

227

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

228

Dissolving Different Liquids in Water  

NSDL National Science Digital Library

In this activity, learners add different liquids to water and apply their working definition of “dissolving” to their observations. After observing isopropyl rubbing alcohol, vegetable oil, and corn syrup in water, learners can conclude that while some liquids may dissolve in water, different liquids dissolve in water to different extents. Adult supervision recommended.

James H. Kessler

2007-01-01

229

Magnetic tracking of eye position in freely behaving chickens  

PubMed Central

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

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

2013-01-01

230

Freely floating structures trapping time-harmonic water waves (revisited)  

E-print Network

We study the coupled small-amplitude motion of the mechanical system consisting of infinitely deep water and a structure immersed in it. The former is bounded above by a free surface, whereas the latter is formed by an arbitrary finite number of surface-piercing bodies floating freely. The mathematical model of time-harmonic motion is a spectral problem in which the frequency of oscillations serves as the spectral parameter. It is proved that there exist axisymmetric structures consisting of $N \\geq 2$ bodies; every structure has the following properties: (i) a time-harmonic wave mode is trapped by it; (ii) some of its bodies (may be none) are motionless, whereas the rest of the bodies (may be none) are heaving at the same frequency as water. The construction of these structures is based on a generalization of the semi-inverse procedure applied earlier for obtaining trapping bodies that are motionless although float freely.

Nikolay Kuznetsov; Oleg Motygin

2014-10-22

231

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 ...

232

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

EPA Science Inventory

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

233

Fish embryos are damaged by dissolved PAHs, not oil particles.  

PubMed

To distinguish the toxicity of whole oil droplets from compounds dissolved in water, responses of zebrafish embryos exposed to particulate-laden, mechanically dispersed Alaska North Slope crude oil (mechanically dispersed oil (MDO)) were compared to those of embryos protected from direct oil droplet contact by an agarose matrix. Most polycyclic aromatic hydrocarbons (PAHs) in MDO were contained in oil droplets; about 16% were dissolved. The agarose precluded embryo contact with particulate oil but allowed diffusive passage of dissolved PAHs. The incidence of edema, hemorrhaging, and cardiac abnormalities in embryos was dose-dependent in both MDO and agarose and the biological effects in these compartments were identical in character. Although mean total PAH (TPAH) concentrations in MDO were about 5-9 times greater than in agarose, dissolved PAH concentrations were similar in the two compartments. Furthermore, mean differences in paired embryo responses between compartments were relatively small (14-23%, grand mean 17%), typically with a larger response in embryos exposed to MDO. Therefore, the embryos reacted only to dissolved PAHs and the response difference between compartments is explained by diffusion. Averaged over 48 h, the estimated mean TPAH concentration in agarose was about 16% less than the dissolved TPAH concentration in MDO. Thus, PAHs dissolved from oil are toxic and physical contact with oil droplets is not necessary for embryotoxicity. PMID:18479765

Carls, Mark G; Holland, Larry; Larsen, Marie; Collier, Tracy K; Scholz, Nathaniel L; Incardona, John P

2008-06-23

234

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

235

Dissolved Oxygen Sensing in a Flow Stream using Molybdenum Chloride Optical Indicators  

E-print Network

Dissolved Oxygen Sensing in a Flow Stream using Molybdenum Chloride Optical Indicators Reza Loloee1@msu.edu Abstract--Dissolved oxygen concentration is considered the most important water quality variable in fish culture. Reliable and continuous (24/7) oxygen monitoring of dissolved oxygen (DO) in the 1 ­ 11 mg

Ghosh, Ruby N.

236

Characterization of dissolved organic matter from source to sea using fluorescence and absorbance spectroscopy  

Microsoft Academic Search

Dissolved organic matter fluorescence, absorbance and dissolved organic carbon were measured from source to sea in the River Tyne catchment, of ?2935 km2 and encompassing areas of contrasting land use. The catchment has three major tributaries: the North Tyne which has good water quality, high dissolved organic carbon concentrations and visible water colour from the high proportion of peat in

Andy Baker; Robert G. M. Spencer

2004-01-01

237

Dissolved aluminum in the Gulf of Mexico  

E-print Network

and unswerving Rickness, IMAX. Vl TABLE OF CONTENTS Page ABSTRACT ACKNOWLEDGEMENTS TABLE OF CONTENTS Vi LIST OF TABLES V1. 1. LIST OF FIGURES INTRODUCTION THE NORTHWESTERN GULF OF MEXICO PRECIPITATION AND DISSOLUTION OF ALUMINUM THE CONCENTRATION... and residence time estimates 4) Mississippi River flux and residence time estimates V I I I LIST OF FIGURES Figure Page 1) Location map, Northwestern Gulf of Mexico 2) Aluminum hydroxide pH diagram 3) Clay dissolution in sea water 4) Dissolved aluminum...

Myre, Peggy Lynne

2012-06-07

238

Flagellar waveform dynamics of freely swimming algal cells  

NASA Astrophysics Data System (ADS)

We present quantitative measurements of time-dependent flagellar waveforms for freely swimming biflagellated algal cells, for both synchronous and asynchronous beating. We use the waveforms in conjunction with resistive force theory as well as a singularity method to predict a cell's time-dependent velocity for comparison with experiments. While net propulsion is thought to arise from asymmetry between the power and recovery strokes, we show that hydrodynamic interactions between the flagella and cell body on the return stroke make an important contribution to enhance net forward motion.

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

2013-07-01

239

Dissolved organic nitrogen measurement using dialysis pretreatment.  

PubMed

Dissolved organic nitrogen (DON) is important for ecological and engineering researches. Quantification of low DON concentrations in waters with elevated dissolved inorganic nitrogen (DIN) using existing methods is inaccurate. In this study, a dialysis-based pretreatment technique was optimized and adopted to reduce the interference from DIN to the quantification of DON in natural water. A cellulose ester dialysis tube (nominal molecular weight cutoff = 100 Da) was used in batch and continuous-flow dialysis steps with model compounds, natural organic matter isolates, and bulk waters to develop a dialysis pretreatment approach that selectively reduces DIN from solutions containing DON. By reducing DIN concentrations, propagation of analytical variance in total dissolved nitrogen (TDN) and DIN species concentrations allows more accurate determination of DON (DON = TDN - NO3 - NO2- - NH3/NH4+). Dialysis for 24 h against continuously flowing distilled water reduced DIN species by 70%. With dialysis pretreatment, DON recoveries of more than 95% were obtained for surface water and finished drinking water, but wastewater experienced a slight loss (approximately 10%) of DON possibly due to the adsorption of organics onto the dialysis membrane, permeation of low molecular weight fractions, or biodegradation. Dialysis experiments using surface water spiked with different DIN/TDN ratios concluded that dialysis pretreatment leads to more accurate DON determination than no dialysis when DIN/TDN ratios exceed 0.6 mg of N/mg of N. PMID:15757353

Lee, Wontae; Westerhoff, Paul

2005-02-01

240

Dissolved inorganic phosphorus, dissolved iron, and Trichodesmium in the oligotrophic South China Sea  

Microsoft Academic Search

Dissolved inorganic phosphorus (DIP) concentrations in the oligotrophic surface waters of the South China Sea decrease from ~20 nM in March 2000 to ~5 nM in July 2000, in response to seasonal water column stratification. These minimum DIP concentrations are one order of magnitude higher than those in the P-limited, iron-replete stratified surface waters of the western North Atlantic, suggesting

Jingfeng Wu; Shi-Wei Chung; Liang-Saw Wen; Kon-Kee Liu; Yuh-ling Lee Chen; Houng-Yung Chen; David M. Karl

2003-01-01

241

Application of MODIS on monitoring dissolved inorganic nitrogen and dissolved inorganic phosphorus in Haizhou Gulf  

NASA Astrophysics Data System (ADS)

Red tides have been increasingly observed in the gulf of Haizhou and considered a serious environmental problem from the beginning of the new century. Eutrophication of water is an important reason of red tide occurrence. This paper used the observation data of the concentration of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) in Haizhou Gulf from 2004 to 2006 and selected synchronous MODIS Terra 1B data with 500m spatial resolution in this period of time. We established factors with single band and multi-bands, and then calculated the correlation of each factor with DIN concentration, DIP concentration, and their logarithm respectively. The factors with stronger correlation were used to establish regression models of DIN and DIP's concentration. After comparing these models, we chose the linear model of DIN concentration established by factor ) 4, 3 ( 11 F and inverse model of the logarithm of DIP concentration established by factor ) 5, 6 ( 7 F as their final regression model. The relative accuracy of DIN concentration model achieved about 70%; the retrieving results of DIN concentration were consistent well with real conditions. The relative accuracy of the logarithm of DIP concentration achieved about 90%. The results prove the feasibility of monitoring DIN concentration and the exponential order of DIP concentration in offshore of Jiangsu Province.

Xu, Yong; Zhang, Ying; Zhang, Dong; Liu, Jitang

2008-10-01

242

Mobility Measurements of Freely-Standing Cyclic PS Films  

NASA Astrophysics Data System (ADS)

Reductions in the glass transition temperature Tg have been observed for thin, freely-standing films of linear polystyrene (PS) (Forrest et al.), PRE 61, R53 (2000); Dalnoki-Veress et al., PRE, in press., which indicates increased segmental mobility. Despite topological differences between cyclic and linear PS, their bulk rheological properties are similar, apart from a factor of approximately two difference in zero shear viscosity, plateau modulus, and steady state recoverable compliance (McKenna et al.), Macromolecules 20, 489 (1987); 22, 1834 (1989).. We investigate the mobility of freely-standing films of cyclic and linear PS chains with molecular weight Mw ~ 200k and thicknesses 20 nm < h < 150 nm. Using ellipsometry, we have measured the temperature dependence of h and the index of refraction n of the films. In all cyclic PS films, we observe irreversible changes in h for temperatures T > 90^circC. For the thinnest cyclic PS films, irreversible changes in n are also observed for T > 90^circC. We relate the results of these measurements to the determination of T_g, chain diffusion and anisotropy within the films. Chain diffusion was further studied using optical microscopy to measure hole growth in the films as a function of h and T.

Murray, Chris A.; Dutcher, John R.; McKenna, Gregory B.

2001-03-01

243

Structure and Dynamics of Freely Suspended Liquid Crystals  

NASA Technical Reports Server (NTRS)

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

Clark, Noel A.

2004-01-01

244

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

SciTech Connect

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

Ramos, E.U.; Meijer, S.N.; Vaes, W.H.J.; Verhaar, H.J.M.; Hermens, J.L.M. [Utrecht Univ. (Netherlands). Research Inst. of Toxicology

1998-11-01

245

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

PubMed

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

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

2009-03-15

246

PII S0016-7037(99)00084-8 Dissolved sulfide distributions in the water column and sediment pore waters  

E-print Network

sites (550 and 590 m) with low ( 10 M) bottom-water dissolved-oxygen concentrations. Pore-water profilesPII S0016-7037(99)00084-8 Dissolved sulfide distributions in the water column and sediment pore) Abstract--Dissolved sulfide concentrations in the water column and in sediment pore waters were measured

van Geen, Alexander

247

Linkages among runoff, dissolved organic carbon, and the stable oxygen isotope composition of seawater and other water mass  

E-print Network

Linkages among runoff, dissolved organic carbon, and the stable oxygen isotope composition 2005; published 7 December 2005. [1] Flow-weighted dissolved organic carbon (DOC) concentrations and d responding to chromophoric dissolved organic matter (CDOM) was not correlated with DOC concentrations

Hansell, Dennis

248

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.

Washington State University Department of Ecology

249

Superhydrophobic porous surfaces: dissolved oxygen sensing.  

PubMed

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

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

2015-02-18

250

Colored dissolved organic matter in Tampa Bay, Florida  

Microsoft Academic Search

Absorption and fluorescence of colored dissolved organic matter (CDOM) and concentrations of dissolved organic carbon (DOC), chlorophyll and total suspended solids in Tampa Bay and its adjacent rivers were examined in June and October of 2004. Except in Old Tampa Bay (OTB), the spatial distribution of CDOM showed a conservative relationship with salinity in June, 2004 (aCDOM(400)=?0.19×salinity+6.78, R2=0.98, n=17, salinity

Zhiqiang Chen; Chuanmin Hu; Robyn N. Conmy; Frank Muller-Karger; Peter Swarzenski

2007-01-01

251

Clustering instability in a freely falling granular jet  

E-print Network

This paper investigates a clustering instability of a freely falling granular jet composed of 100 micron glass spheres. The granular flow out of a circular nozzle starts out spatially uniform and then, further downstream, breaks up into well defined clusters. The role of air is investigated in this phenomenon by changing the ambient air pressure down to 1/5000th atm. An optical method is used that measures inhomogeneities in the flow in order to quantify the growth of the clusters. Clustering is observed down to the lowest pressure and the presence of air leads to larger drops but does not initiate the drop formation. The analysis shows that the drop size is set by fluctuations on the order of the size of the particles at the nozzle.

Matthias E. Möbius

2006-04-03

252

Aeromechanic Analysis of a Missile with Freely Spinning Tailfins  

NASA Technical Reports Server (NTRS)

The objective of the present work is to demonstrate the utility of Chimera overset grid methods for missiles with freely spinning tailfins. Computations on grids with two levels of resolution and three levels of geometric detail are used to assess grid convergence and the significance of the different geometric features of the missile. The grid convergence is good for overall force and moment vectors. The numerous protuberances on the missile have a limited influence on the overall forces. A yaw maneuver is computed on a medium resolution grid with 17 million gridpoints. The tail spins in response to the computed tail rolling moment. The asymmetric inflow to the tail results in a spin-rate of approximately 2000 revolutions per minute. The results are in excellent agreement with an unstructured grid CFD model, and in fair agreement with experimental results. Overall, the Chimera overset method seems to be well suited for geometrically complex moving body configurations.

Nygaard, Tor A.

2003-01-01

253

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

254

Optogenetic manipulation of neural activity in freely moving Caenorhabditis elegans  

PubMed Central

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

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

2011-01-01

255

Flagellar Waveform Dynamics of Freely Swimming Algal Cells  

NASA Astrophysics Data System (ADS)

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

Gollub, Jerry; Kurtuldu, Huseyin; Johnson, Karl

2012-02-01

256

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

NASA Technical Reports Server (NTRS)

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

Clark, Noel A.

2000-01-01

257

Chronic detachable headphones for acoustic stimulation in freely moving animals.  

PubMed

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

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

2010-05-30

258

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

259

Characterization of urban runoff pollution between dissolved and particulate phases.  

PubMed

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

Wei, Zhang; Simin, Li; Fengbing, Tang

2013-01-01

260

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...

261

Flux of dissolved organic carbon from U.K. rivers  

Microsoft Academic Search

The rise in dissolved organic carbon (DOC) concentrations in the Northern Hemisphere in recent decades has been taken as indicative of increased turnover of terrestrial carbon and in particular in the vital reserve of peat. Hypotheses for this rise have been hotly debated in the literature. This study proposes that, although trends in concentration have been the main focus of

F. Worrall; T. P. Burt

2007-01-01

262

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

USGS Publications Warehouse

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

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

1992-01-01

263

Pharmacokinetics of di-isononyl phthalate in freely moving rats by UPLC-MS/MS.  

PubMed

Di-isononyl phthalate (DINP) is a general-purpose plasticizer for polyvinyl chloride. However, this industrial chemical plasticizer used as a clouding agent has recently contaminated food and beverages that had been inspected by Taiwan Food and Drug Administration. This study develops a sensitive and specific method combining ultra-performance liquid chromatography with electrospray ionization tandem mass spectrometry (UPLC-MS/MS) to investigate the pharmacokinetics of DINP in freely moving rats. Multiple reaction monitoring (MRM) was used to monitor the transition of the protonated molecule m/z of 419 [M+H](+) to the product ion 149 for DINP. The analyte was analyzed by UPLC-MS/MS with C18 column (100×2.1mm, 1.7 ?m) which was equilibrated and eluted with an isocratic mixture of acetonitrile-ammonium acetate water solution (90:10, v/v) at a flow rate of 0.3 mL/min. Linear calibration curves were obtained for DINP concentration ranges of 0.05-2.5 ?g/mL in plasma and feces. The feces were homogenized mechanically using 50% acetonitrile as the medium. The pharmacokinetic curve demonstrates that the disposition of DINP in rat plasma was fitted well by the two-compartment model after DINP administration (10 mg/kg, i.v.). The elimination half-life of DINP was 364±146 min and 150±58 min for intravenous (10 mg/kg) and oral (100 mg/kg) administration, respectively. The pharmacokinetic data indicate that the oral bioavailability of DINP in freely moving rats was about 1.19%. The total DINP excretion up to 48 h was 13.64±3.99% in feces. PMID:23618960

Hou, Mei-Ling; Chang, Li-Wen; Chiang, Chang-Jung; Tsuang, Yang-Hwei; Lin, Chi-Hung; Tsai, Tung-Hu

2013-06-25

264

Characterisation of dissolved combined amino acids in marine waters.  

PubMed

Dissolved combined amino acids (DCAA) are important constituents of the dissolved organic nitrogen (DON) pool in marine environments, although little is known about their sources, dynamics and sinks. The DCAA pool consists of various compounds including proteins and peptides, proteins linked to sugars and amino acids adsorbed to humic and fulvic acids, clays and other materials. The proportions of each of these components and the extent to which they are used by microplankton living within the photic zone are not known. An investigation was carried out, using (15)N isotope dilution techniques, to determine the concentration and composition of dissolved amino acid pools in the marine environment. A near-shore seawater sample was collected and split into fractions to determine the concentrations of dissolved free amino acids (DFAA), DCAA and a <3 kDa dissolved peptide fraction (DPEP; obtained by ultrafiltration). DCAA and DPEP fractions were hydrolysed to yield free amino acids and all samples were analysed by gas chromatography/mass spectrometry (GC/MS) as isobutyloxycarbonyl/tert-butyldimethylsilyl derivatives. The DFAA was the smallest fraction representing approximately 1% of total dissolved amino acids. The majority of DCAA was contained in the low molecular weight DPEP fraction (90%) and was probably as a result of release from phytoplankton and degradation by heterotrophic bacteria. PMID:11466786

Sommerville, K; Preston, T

2001-01-01

265

Localizing and Beamforming Freely Drifting VLF Acoustic Sensors.  

NASA Astrophysics Data System (ADS)

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

Culver, Richard Lee

266

Revascularization and microcirculation of freely grafted islets of Langerhans.  

PubMed

A considerable number of experimental studies have demonstrated that the reestablishment of an appropriate microvascular supply is an essential prerequisite for successful pancreatic islet transplantation. Freely transplanted islets show the first signs of angiogenesis (i.e., capillary sprout formation and protrusion) as early as 2 days after transplantation, and the entire vascularization process is completed after 10 to 14 days. Cryopreservation and culture of the isolated islets before transplantation and hyperglycemia of the transplant recipient seem not to affect the vascularization process essentially. In addition, immunosuppressive drugs, such as cyclosporin A and 15-deoxyspergualin, do not or only slightly inhibit revascularization of syngeneic islets; however, they are not able to prevent completely xenograft-induced microvascular perfusion failure. In contrast, novel immunosuppressants (e.g., RS-61443) or dietary supplementation of the antioxidant vitamin E were shown to prevent microvascular graft rejection almost completely, including leukocyte recruitment and capillary perfusion failure. Thus the development of novel strategies to improve posttransplant islet function should include concepts that accelerate the vascularization process and protect the newly formed microvasculature from rejection-mediated injury. The improvement of islet graft vascularization and the maintenance of adequate microvascular perfusion will contribute to the increased success of pancreatic islet transplantation. PMID:11344405

Menger, M D; Yamauchi, J; Vollmar, B

2001-04-01

267

Intersegmental coupling and recovery from perturbations in freely running cockroaches.  

PubMed

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

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

2015-01-15

268

Freely decaying turbulence in two-dimensional electrostatic gyrokinetics  

SciTech Connect

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

Tatsuno, T. [Department of Physics and IREAP, University of Maryland, College Park, Maryland 20742 (United States); Department of Communication Engineering and Informatics, University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); Plunk, G. G. [Department of Physics and IREAP, University of Maryland, College Park, Maryland 20742 (United States); Max-Planck-Institut fuer Plasmaphysik, 17491 Greifswald (Germany); Barnes, M. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Dorland, W. [Department of Physics and IREAP, University of Maryland, College Park, Maryland 20742 (United States); Howes, G. G. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States); Numata, R. [Department of Physics and IREAP, University of Maryland, College Park, Maryland 20742 (United States); Graduate School of Simulation Studies, University of Hyogo, Kobe, Hyogo 650-0047 (Japan)

2012-12-15

269

Intersegmental coupling and recovery from perturbations in freely running cockroaches  

PubMed Central

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

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

2015-01-01

270

Acoustic tracking of a freely drifting sonobuoy field  

NASA Astrophysics Data System (ADS)

This paper develops an acoustic inversion algorithm to track a field of freely drifting sonobuoys using travel-time measurements from a series of nonsimultaneous impulsive sources deployed around the field. In this scenario, the time interval between sources can be sufficiently long that significant independent movement of the individual sonobuoys occurs. In addition, the source transmission instants are unknown, and the source positions and initial sonobuoy positions are known only approximately. The formulation developed here solves for the track of each sonobuoy (parametrized by the sonobuoy positions at the time of each source transmission), allowing arbitrary, independent sonobuoy motion between transmissions, as well as for the source positions and transmission instants. This leads to a strongly underdetermined inverse problem. However, regularized inversion provides meaningful solutions by incorporating a priori information consisting of prior estimates (with uncertainties) for the source positions and initial sonobuoy positions, and a physical model for preferred sonobuoy motion. Several models for sonobuoy motion are evaluated, with the best results obtained by minimizing the second spatial derivative of the tracks to obtain the minimum-curvature or smoothest track, subject to fitting the acoustic data to a statistically appropriate level.

Dosso, Stan E.; Collison, Nicole E. B.

2002-05-01

271

Acoustic tracking of a freely drifting sonobuoy field.  

PubMed

This paper develops an acoustic inversion algorithm to track a field of freely drifting sonobuoys using travel-time measurements from a series of nonsimultaneous impulsive sources deployed around the field. In this scenario, the time interval between sources can be sufficiently long that significant independent movement of the individual sonobuoys occurs. In addition, the source transmission instants are unknown, and the source positions and initial sonobuoy positions are known only approximately. The formulation developed here solves for the track of each sonobuoy (parametrized by the sonobuoy positions at the time of each source transmission), allowing arbitrary, independent sonobuoy motion between transmissions, as well as for the source positions and transmission instants. This leads to a strongly underdetermined inverse problem. However, regularized inversion provides meaningful solutions by incorporating a priori information consisting of prior estimates (with uncertainties) for the source positions and initial sonobuoy positions, and a physical model for preferred sonobuoy motion. Several models for sonobuoy motion are evaluated, with the best results obtained by minimizing the second spatial derivative of the tracks to obtain the minimum-curvature or smoothest track, subject to fitting the acoustic data to a statistically appropriate level. PMID:12051436

Dosso, Stan E; Collison, Nicole E B

2002-05-01

272

Firing Rate Homeostasis in Visual Cortex of Freely Behaving Rodents  

PubMed Central

Summary It has been postulated that homeostatic mechanisms maintain stable circuit function by keeping neuronal firing within a set-point range, but such firing rate homeostasis has never been demonstrated in vivo. Here we use chronic multielectrode recordings to monitor firing rates in visual cortex of freely behaving rats during chronic monocular visual deprivation (MD). Firing rates in V1 were suppressed over the first 2 d of MD, but then rebounded to baseline over the next 2–3 d despite continued MD. This drop and rebound in firing was accompanied by bi-directional changes in mEPSC amplitude measured ex vivo. The rebound in firing was independent of sleep-wake state but was cell-type specific, as putative FS and regular spiking neurons responded to MD with different time-courses. These data establish for the first time that homeostatic mechanisms within the intact CNS act to stabilize neuronal firing rates in the face of sustained sensory perturbations. PMID:24139038

Hengen, Keith B.; Lambo, Mary E.; Van Hooser, Stephen D.; Katz, Donald B; Turrigiano, Gina G

2013-01-01

273

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

E-print Network

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

274

A Predictive Model of Bacterial Foraging by Means of Freely Released Extracellular Enzymes  

E-print Network

A Predictive Model of Bacterial Foraging by Means of Freely Released Extracellular Enzymes Y T Extracellular enzymes are important agents for microbial foraging and material cycling in diverse natural immobile microbe, of freely releasing extracellular enzymes into a fluid- bathed, stable matrix of both

Jumars, Pete

275

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

276

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

277

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

278

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

279

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.

James H. Kessler

2007-01-01

280

MCM LTER METADATA FILE TITLE: Dissolved organic carbon in the lakes of the McMurdo Dry Valleys.  

E-print Network

, Collection Date, Depth (m), DOC (mg L-1 ), DOC (mM), Comments KEYWORDS: Dissolved organic carbon, DOC, lakeMCM LTER METADATA FILE TITLE: Dissolved organic carbon in the lakes of the McMurdo Dry Valleys dissolved organic carbon concentrations at specific depths in McMurdo Dry Valley lakes. PRINCIPAL

Priscu, John C.

281

Mechanism studies of seasonal variability of dissolved oxygen in Mass Bay: A multi-scale FVCOM/UG-RCA application  

E-print Network

Mechanism studies of seasonal variability of dissolved oxygen in Mass Bay: A multi-scale FVCOM Accepted 7 December 2013 Available online 14 December 2013 Keywords: Coastal Modeling Dissolved oxygen Mass that the dissolved oxygen (DO) concentration in Mass Bay exhibits a well-defined seasonal cycle, highest in March

Chen, Changsheng

282

The Influence of Dissolved Oxygen on Winter Habitat Selection by Largemouth Bass: An Integration of Field Biotelemetry Studies  

E-print Network

143 The Influence of Dissolved Oxygen on Winter Habitat Selection by Largemouth Bass with habitat availability to assess whether fish were selecting for spe- cific dissolved oxygen concentrations largemouth bass acclimated to winter tem- peratures. Results from the dissolved oxygen measurements made

Cooke, Steven J.

283

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

2013-01-01

284

Chronic measurement of left ventricular pressure in freely moving rats.  

PubMed

Measurements of left ventricular pressure (LVP) in conscious freely moving animals are uncommon, yet could offer considerable opportunity for understanding cardiovascular disease progression and treatment. The aim of this study was to develop surgical methods and validate the measurements of a new high-fidelity, solid-state pressure-sensor telemetry device for chronically measuring LVP and dP/dt in rats. The pressure-sensor catheter tip (2-Fr) was inserted into the left ventricular chamber through the apex of the heart, and the telemeter body was implanted in the abdomen. Data were measured up to 85 days after implant. The average daytime dP/dt max was 9,444 ± 363 mmHg/s, ranging from 7,870 to 10,558 mmHg/s (n = 7). A circadian variation in dP/dt max and heart rate (HR) was observed with an average increase during the night phase in dP/dt max of 918 ± 84 mmHg/s, and in HR of 38 ± 3 bpm. The ?-adrenergic-agonist isoproterenol, ?1-adrenergic agonist dobutamine, Ca(2+) channel blocker verapamil, and the calcium sensitizer levosimendan were administered throughout the implant period, inducing dose-dependent time course changes and absolute changes in dP/dt max of -6,000 to +13,000 mmHg/s. The surgical methods and new technologies demonstrated long-term stability, sensitivity to circadian variation, and the ability to measure large drug-induced changes, validating this new solution for chronic measurement of LVP in conscious rats. PMID:24114699

Stehlin, Ellyce; Malpas, Simon C; Budgett, David M; Barrett, Carolyn J; McCormick, Daniel; Whalley, Gillian; Fu, Fumin; Beil, Michael; Rigel, Dean F; Guild, Sarah-Jane

2013-12-01

285

Satellite Meteorology Education Resources Freely Available from COMET°  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

286

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

287

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

288

Influences of land use and stream size on particulate and dissolved materials in a small Amazonian stream network  

Microsoft Academic Search

We investigated the influences of forest or pasture land use and stream size on particulate and dissolved material concentrations in a network of second to third order streams in Rondônia, in the Brazilian Amazon. During the dry season, a second order stream originating in pasture had lower concentrations of dissolved oxygen and nitrate, higher concentrations of chlorophyll, total suspended solids,

Suzanne M. Thomas; Christopher Neill; Linda A. Deegan; Alex V. Krusche; Victoria M. Ballester; Reynaldo L. Victoria

2004-01-01

289

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

290

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

291

Wormhole formation in dissolving fractures  

Microsoft Academic Search

We investigate the dissolution of artificial fractures with three-dimensional, pore-scale numerical simulations. The fluid velocity in the fracture space was determined from a lattice Boltzmann method, and a stochastic solver was used for the transport of dissolved species. Numerical simulations were used to study conditions under which long conduits (wormholes) form in an initially rough but spatially homogeneous fracture. The

P. Szymczak; A. J. C. Ladd

2009-01-01

292

DISSOLVED OXYGEN DIURNAL FLUX STUDY  

EPA Science Inventory

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

293

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

294

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

295

Dissolving pulp from jute stick.  

PubMed

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

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

2015-01-22

296

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 = Si2O( OH) 6 + H2O. The tracer diffusion coefficients for Si(OH) 4 and Si 2O(OH) 6 and an association constant for the above reaction were determined by fitting the following equation to the experimental data: Dobs = ?Dmonomer + (1 - ?) Ddimer 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 2O(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

297

RESPONSE OF LEAD SOLUBILITY TO DISSOLVED CARBONATE IN DRINKING WATER  

EPA Science Inventory

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

298

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...

299

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...

300

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...

301

SIMULATION OF DISSOLVED OXYGEN PROFILES IN A TRANSPARENT, DIMICTIC LAKE  

EPA Science Inventory

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

302

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

303

Relationships between Water Flow and Dissolved Solids Discharge in the Major Tributaries of Lake Baikal  

Microsoft Academic Search

Data of long-term observations of water and hydrochemical regimes were used to characterize relationships between water flow and dissolved solids discharge in the three major tributaries of Lake Baikal, which account for about two-thirds of the total water inflow into the lake. The total dissolved solids content (TDS) of these rivers' water and the concentrations of the principal ions are

V. N. Sinyukovich

2003-01-01

304

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

EPA Science Inventory

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

305

Total Dissolved Gas Monitoring in Chum Salmon Spawning Gravels Below Bonneville Dam  

Microsoft Academic Search

At the request of the U.S. Army Corps of Engineers (Portland District), Pacific Northwest National Laboratory (PNNL) conducted research to determine whether total dissolved gas concentrations are elevated in chum salmon redds during spring spill operations at Bonneville Dam. The study involved monitoring the total dissolved gas levels at egg pocket depth and in the river at two chum salmon

Evan V. Arntzen; David R. Geist; Jennifer L. Panther; Earl Dawley

2007-01-01

306

The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes  

Microsoft Academic Search

We have conducted a study of hydrothermal plumes overlying the Mid-Atlantic Ridge near 5° S to investigate whether there is a significant export flux of dissolved Fe from hydrothermal venting to the oceans. Our study combined measurements of plume-height Fe concentrations from a series of 6 CTD stations together with studies of dissolved Fe speciation in a subset of those

Sarah A. Bennett; Eric P. Achterberg; Douglas P. Connelly; Peter J. Statham; Gary R. Fones; Christopher R. German

2008-01-01

307

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

E-print Network

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

Mallin, Michael

308

Dissolved organic matter in the Baltic Sea  

NASA Astrophysics Data System (ADS)

Several factors highlight the importance of dissolved organic matter (DOM) in coastal ecosystems such as the Baltic Sea: 1) DOM is the main energy source for heterotrophic bacteria in surface waters, thus contributing to the productivity and trophic state of bodies of water. 2) DOM functions as a nutrient source: in the Baltic Sea, more than one-fourth of the bioavailable nutrients can occur in the dissolved organic form in riverine inputs and in surface water during summer. Thus, DOM also supports primary production, both directly (osmotrophy) and indirectly (via remineralization). 3) Flocculation and subsequent deposition of terrestrial DOM within river estuaries may contribute to production and oxygen consumption in coastal sediments. 4) Chromophoric DOM, which is one of the major absorbers of light entering the Baltic Sea, contributes highly to water color, thus affecting the photosynthetic depth as well as recreational value of the Baltic Sea. Despite its large-scale importance to the Baltic Sea ecosystem, DOM has been of minor interest compared with inorganic nutrient loadings. Information on the concentrations and dynamics of DOM in the Baltic Sea has accumulated since the late 1990s, but it is still sporadic. This review provides a coherent view of the current understanding of DOM dynamics in the Baltic Sea.

Hoikkala, L.; Kortelainen, P.; Soinne, H.; Kuosa, H.

2015-02-01

309

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...

310

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

PubMed Central

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

Grand, Laszlo; Ftomov, Sergiu; Timofeev, Igor

2012-01-01

311

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

312

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.

313

EFFECT OF DISSOLVED ORGANIC SUBSTANCES ON OYSTERS  

E-print Network

_____________________________________________________ 168 Effects of filtering and centrifuging'______________________________ 168 Variations______________________________________ 183 Description of sampling device ~ ______________________________ 183 #12;EFFECT OF DISSOLVED

314

Validating the use of performance reference compounds in passive samplers to assess porewater concentrations in sediment beds.  

PubMed

Hydrophobic organic compounds (HOCs) like polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) tend to accumulate in sediment beds when they are released into aquatic environments. Due to this buildup of HOCs in the sediment, the highest water concentrations are often in the pore water. Passive samplers can be used in the field (i.e., in situ) to measure freely dissolved porewater concentrations if target contaminants diffusing through the sediment and into the sampler exhibit the same diffusive retardation factors as performance reference compounds (PRCs) that are diffusing out of the sampler and into the sediment. To test this assumption, polyethylene (PE) passive samplers were placed in an organic- and black- carbon-rich sediment bed in the laboratory with samplers removed every 30 days for 4 months. The concentrations of target contaminants in the PE at each time point, corrected using measures of the losses of PRCs, were in good agreement with separately measured equilibrium concentrations in a well-mixed system. Concentrations in the PE passive samplers, normalized by their polyethylene-water partition coefficients, were also in good agreement with directly measured porewater concentrations. Finally, PE-deduced porewater concentrations were compared with the traditional equilibrium partitioning models and showed that considering sorption to only organic carbon substantially overestimated porewater concentrations. However, predictions improved greatly if sorption to black carbon was also considered. PMID:25093866

Apell, Jennifer N; Gschwend, Philip M

2014-09-01

315

Method for dissolving delta-phase plutonium  

DOEpatents

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

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

1992-01-01

316

Method for dissolving delta-phase plutonium  

SciTech Connect

A process for dissolving plutonium, and in particular, delta-phase plutonium. The process includes heating a mixture of nitric acid, hydroxylammonium nitrate and potassium fluoride (HAN) to a temperature between 40 and 70 C, then immersing the metal in the mixture. Preferably, the nitric acid has a concentration of not ore than 2M, the HAN approximately 0.66M, and the potassium fluoride 1M. Additionally, a small amount of sulfamic acid, such as 0.1M can be added to assure stability of the HAN in the presence of nitric acid. The oxide layer that forms on plutonium metal may be removed with a non-oxidizing acid as a pre-treatment step.

Karraker, D.G.

1992-12-31

317

Removal of dissolved metals by plant tissue  

SciTech Connect

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

Scott, C.D. (Oak Ridge National Lab., TN (United States))

1992-04-25

318

Quantification of dissolved iron sources to the North Atlantic Ocean  

NASA Astrophysics Data System (ADS)

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

Conway, Tim M.; John, Seth G.

2014-07-01

319

Scavenging rates of dissolved manganese in a hydrothermal vent plume  

NASA Astrophysics Data System (ADS)

The biogeochemical scavenging of dissolved manganese (Mn) from hydrothermal plumes was investigated using radiotracer ( 54Mn) techniques. The measured scavenging rate constant, k 1, was lowest in the buoyant plume (<0.2 y -1), increasing to ˜2 y -1 in the non-buoyant plume at distances of 20 km from the ridge valley axis. The direct biological contribution to the dissolved Mn scavenging rate (i.e the fraction suppressed by the addition of a metabolic poison) also increased over the same distances, being minor or absent at plume depths in the proximal plume, yet the major component at distal plume stations. These and other data suggest that the capacity for scavenging dissolved Mn onto particles evolves with increasing age of the plume, suggestive of a microbial response to changing conditions within the plume. Estimated maximum scavenging rates of dissolved Mn onto particles ( RDMn = k 1 [DMn])were noted at plume depths for all stations, a function of very high dissolved Mn concentrations in the case of the buoyant plume and proximal non-buoyant plume. RDMn values, integrated over plume depths, ranged from 3.4 to 1.7 mM m -2 y -1 for the non-buoyant plume at on-axis and off-axis stations, respectively. The application of the data to the dispersal of hydrothermal constituents and to plume aging is discussed.

Cowen, James P.; Massoth, Gary J.; Feely, Richard A.

1990-10-01

320

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

USGS Publications Warehouse

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

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

1985-01-01

321

Dissolved organic carbon and chromophoric dissolved organic matter properties of rivers in the USA  

USGS Publications Warehouse

Dissolved organic carbon (DOC) concentration and chromophoric dissolved organic matter (CDOM) parameters were measured over a range of discharge in 30 U.S. rivers, covering a diverse assortment of fluvial ecosystems in terms of watershed size and landscape drained. Relationships between CDOM absorption at a range of wavelengths (a254, a350, a440) and DOC in the 30 watersheds were found to correlate strongly and positively for the majority of U.S. rivers. However, four rivers (Colorado, Colombia, Rio Grande and St. Lawrence) exhibited statistically weak relationships between CDOM absorption and DOC. These four rivers are atypical, as they either drain from the Great Lakes or experience significant impoundment of water within their watersheds, and they exhibited values for dissolved organic matter (DOM) parameters indicative of autochthonous or anthropogenic sources or photochemically degraded allochthonous DOM and thus a decoupling between CDOM and DOC. CDOM quality parameters in the 30 rivers were found to be strongly correlated to DOM compositional metrics derived via XAD fractionation, highlighting the potential for examining DOM biochemical quality from CDOM measurements. This study establishes the ability to derive DOC concentration from CDOM absorption for the majority of U.S. rivers, describes characteristics of riverine systems where such an approach is not valid, and emphasizes the possibility of examining DOM composition and thus biogeochemical function via CDOM parameters. Therefore, the usefulness of CDOM measurements, both laboratory-based analyses and in situ instrumentation, for improving spatial and temporal resolution of DOC fluxes and DOM dynamics in future studies is considerable in a range of biogeochemical studies.

Spencer, Robert G.M.; Butler, Kenna D.; Aiken, George R.

2012-01-01

322

Dissolved organic carbon and chromophoric dissolved organic matter properties of rivers in the USA  

NASA Astrophysics Data System (ADS)

Dissolved organic carbon (DOC) concentration and chromophoric dissolved organic matter (CDOM) parameters were measured over a range of discharge in 30 U.S. rivers, covering a diverse assortment of fluvial ecosystems in terms of watershed size and landscape drained. Relationships between CDOM absorption at a range of wavelengths (a254, a350, a440) and DOC in the 30 watersheds were found to correlate strongly and positively for the majority of U.S. rivers. However, four rivers (Colorado, Colombia, Rio Grande and St. Lawrence) exhibited statistically weak relationships between CDOM absorption and DOC. These four rivers are atypical, as they either drain from the Great Lakes or experience significant impoundment of water within their watersheds, and they exhibited values for dissolved organic matter (DOM) parameters indicative of autochthonous or anthropogenic sources or photochemically degraded allochthonous DOM and thus a decoupling between CDOM and DOC. CDOM quality parameters in the 30 rivers were found to be strongly correlated to DOM compositional metrics derived via XAD fractionation, highlighting the potential for examining DOM biochemical quality from CDOM measurements. This study establishes the ability to derive DOC concentration from CDOM absorption for the majority of U.S. rivers, describes characteristics of riverine systems where such an approach is not valid, and emphasizes the possibility of examining DOM composition and thus biogeochemical function via CDOM parameters. Therefore, the usefulness of CDOM measurements, both laboratory-based analyses and in situ instrumentation, for improving spatial and temporal resolution of DOC fluxes and DOM dynamics in future studies is considerable in a range of biogeochemical studies.

Spencer, Robert G. M.; Butler, Kenna D.; Aiken, George R.

2012-09-01

323

Determination of dissolved aluminum in water samples  

USGS Publications Warehouse

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

Afifi, A.A.

1983-01-01

324

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

EPA Science Inventory

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

325

DISSOLVED ORGANIC CARBON TRENDS RESULTING FROM CHANGES IN ATMOSPHERIC DEPOSITION CHEMISTRY  

EPA Science Inventory

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

326

Lipid class and fatty acid distributions in particulate and dissolved fractions in the north Adriatic sea  

Microsoft Academic Search

Lipid classes (Iatroscan TLC\\/FID method) and fatty acids (GC\\/MS) of settling particles and dissolved fraction were investigated in the north Adriatic sea in June 1995. The differences in composition and concentrations were examined according to distance from Isonzo river Estuary, depth and fraction (particulate versus dissolved). Total particulate lipids showed large variations, from 32.6 to 139.5?g\\/l. The highest concentration was

S. Derieux; J. Fillaux; A. Saliot

1998-01-01

327

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

USGS Publications Warehouse

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

Smith, Richard A.; Alexander, Richard B.

1982-01-01

328

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

PubMed Central

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

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

2011-01-01

329

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

PubMed

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

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

2014-01-15

330

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

PubMed Central

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

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

2013-01-01

331

In-situ measurement of dissolved nitrogen and oxygen in the ocean  

NASA Astrophysics Data System (ADS)

Motivated by the need to separate changes in dissolved gas concentrations due to air-sea fluxes from biological production, a novel method of inferring dissolved nitrogen in the ocean is described. The method requires a local measurement of gas tension, dissolved oxygen, water temperature and salinity. Such instrumentation has been developed and tested at sea. Preliminary open ocean data are presented. The measurements during periods of low wind speed show a clear diurnal dissolved oxygen signal, incorporating biological photosynthetic response, solar heating and nocturnal convective mixing. The diurnal variability of the inferred nitrogen signal is approximately 10% that of the measured oxygen diurnal variability. The nitrogen diurnal variability is attributed to a 10 m separation between the primary measurements of gas tension and dissolved oxygen rather than any intrinsic change in dissolved nitrogen. These results are, however, consistent with the relative insensitivity of dissolved gaseous nitrogen to biological activity compared to that of dissolved oxygen. The open ocean results give good evidence for the integrity of the measurement scheme and indicate the potential for simultaneous measurement of dissolved nitrogen and oxygen in the study of biological cycling as well as gas transfer in the upper ocean.

McNeil, Craig L.; Johnson, Bruce D.; Farmer, David M.

1995-05-01

332

The potential source of dissolved aluminum from resuspended sediments to the North Atlantic deep water  

SciTech Connect

Laboratory and field studies were conducted to investigate the significance of resuspended sediments as a source of dissolved Al to the deep northwest Atlantic. Sediment resuspension experiments demonstrate the effect on dissolved Al concentration (initially 11 nM) of adding natural suspended sediments (ca. 0.1-10 mg/L) to seawater. The concentration of dissolved Al increased by the resuspension of sediments; for example, addition of 0.15 mg/L sediments caused dissolved Al to increase by 10 nM. Distributions of dissolved and leachable particulate Al off the tail of the Grand Banks, near the high-energy western boundary current, show elevated levels in the near-bottom waters. The authors suggest that resuspended sediments associated with nepheloid layers along the western boundary of the North Atlantic are a source of dissolved Al. Strong western boundary currents provide the energy to resuspend and maintain intense nepheloid layers of sediments. Continued resuspension and deposition of sediments within the nepheloid layer promotes the release of Al from sediments to the overlying water. The Al-rich terrigenous sediments that predominate along the deep boundary of the Denmark Strait, Labrador Sea, Newfoundland and off Nova Scotia constitute a potentially significant source of dissolved Al. Release of Al from resuspended sediments associated with nepheloid layers at a more northern location (e.g., Denmark Strait) may contribute to the near-linear increase in dissolved Al with depth observed in the deep northwest Atlantic.

Moran, S.B.; Moore, R.M. (Dalhousie Univ., Halifax, Nova Scotia (Canada))

1991-10-01

333

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

PubMed

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

Saarikoski, Eve; Rissanen, Marja; Seppälä, Jukka

2015-03-30

334

Water dissolved nitrous oxide from paddy agroecosystem in China  

Microsoft Academic Search

Although nitrous oxide emission from agricultural leaching and runoff is thought to constitute a globally important source of this greenhouse gas, water dissolved N2O in paddy ecosystems is poorly understood and scarcely reported where large amounts of fertilizer nitrogen are applied. This paper gives the results of a study assessing variability of the relationships between N2O and NO3? concentration in

Z. Q. Xiong; G. X. Xing; Z. L. Zhu

2006-01-01

335

Crucial tests of macrorealist and semi-classical gravity models with freely falling mesoscopic nanospheres  

E-print Network

Recently, several proposals have been made to test the quantum superposition principle in the mesoscopic regime. Most of these tests consist of a careful measurement of the loss of interference due to decoherence. Here we propose to measure, instead, the spread in position of a freely falling nanosphere. As we shall show, this parameter is not only sensitive to various sources of decoherence (exotic and non-exotic) but also to self-gravity. Moreover, our numerical estimates establish that a measurement of the spread of freely falling nanospheres can reveal an interesting interplay between self-gravity and decoherence.

Samuel Colin; Thomas Durt; Ralph Willox

2014-12-24

336

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

337

Production of Dissolved and Particulate Hydrogen Sulfide by Marine Phytoplankton  

NASA Astrophysics Data System (ADS)

Hydrogen sulfide is a reactive gas that in its dissolved form can be found as dissociated ions and meta-sulfide complexes, or in the particulate state as insoluble metal-sulfides. In oxygenated surface seawater the source of this hydrogen sulfide is the hydrolysis of dissolved carbonyl sulfide, but also emissions from marine phytoplankton. In this way, the phytoplankton production of hydrogen sulfide can affect the cycling of dissolved trace metals such as zinc, copper, and mercury. To examine phytoplankton production of hydrogen sulfide, four different phytoplankton species were grown in batch cultures and the concentrations of dissolved (<0.4 um) and particulate sulfide (>0.4 um) monitored over time. The chlorophyte Dunaliella produced the most hydrogen sulfide (diss>part), followed by the diatom Skeletonema (part>diss), the chryptophyte Rhodomonas (diss>part), and finally the prymnesiophyte E. huxleyi. (part>diss). Thus, all of the phytoplankton cultured emitted hydrogen sulfide, and the fact that particulate sulfide was present demonstrated that it reacts with metals to form insoluble metal sulfides, thus affecting metal cycling.

Grace, C.; Davis, J. A.; Cutter, G. A.

2002-12-01

338

Specific Conductance and Dissolved-Solids Characteristics for the Green River and Muddy Creek, Wyoming, Water Years 1999-2008  

USGS Publications Warehouse

Southwestern Wyoming is an area of diverse scenery, wildlife, and natural resources that is actively undergoing energy development. The U.S. Department of the Interior's Wyoming Landscape Conservation Initiative is a long-term science-based effort to assess and enhance aquatic and terrestrial habitats at a landscape scale, while facilitating responsible energy development through local collaboration and partnerships. Water-quality monitoring has been conducted by the U.S. Geological Survey on the Green River near Green River, Wyoming, and Muddy Creek near Baggs, Wyoming. This monitoring, which is being conducted in cooperation with State and other Federal agencies and as part of the Wyoming Landscape Conservation Initiative, is in response to concerns about potentially increased dissolved solids in the Colorado River Basin as a result of energy development. Because of the need to provide real-time dissolved-solids concentrations for the Green River and Muddy Creek on the World Wide Web, the U.S. Geological Survey developed regression equations to estimate dissolved-solids concentrations on the basis of continuous specific conductance using relations between measured specific conductance and dissolved-solids concentrations. Specific conductance and dissolved-solids concentrations were less varied and generally lower for the Green River than for Muddy Creek. The median dissolved-solids concentration for the site on the Green River was 318 milligrams per liter, and the median concentration for the site on Muddy Creek was 943 milligrams per liter. Dissolved-solids concentrations ranged from 187 to 594 milligrams per liter in samples collected from the Green River during water years 1999-2008. Dissolved-solids concentrations ranged from 293 to 2,485 milligrams per liter in samples collected from Muddy Creek during water years 2006-08. The differences in dissolved-solids concentrations in samples collected from the Green River compared to samples collected from Muddy Creek reflect the different basin characteristics. Relations between specific conductance and dissolved-solids concentrations were statistically significant for the Green River (p-value less than 0.001) and Muddy Creek (p-value less than 0.001); therefore, specific conductance can be used to estimate dissolved-solids concentrations. Using continuous specific conductance values to estimate dissolved solids in real-time on the World Wide Web increases the amount and improves the timeliness of data available to water managers for assessing dissolved-solids concentrations in the Colorado River Basin.

Clark, Melanie L.; Davidson, Seth L.

2009-01-01

339

Greenhouse gases dissolved in soil solution - often ignored, but important?  

NASA Astrophysics Data System (ADS)

Flux measurements of climate-relevant trace gases from soils are frequently undertaken in contemporary ecosystem studies and substantially contribute to our understanding of greenhouse gas balances of the biosphere. While the great majority of such investigations builds on closed chamber and eddy covariance measurements, where upward gas fluxes to the atmosphere are measured, fewest concurrently consider greenhouse gas dissolution in the seepage and leaching of dissolved gases via the vadose zone to the groundwater. Here we present annual leaching losses of dissolved N2O and CO2 from arable, grassland, and forest lysimeter soils from three sites differing in altitude and climate. We aim to assess their importance in comparison to direct N2O emission, soil respiration, and further leaching parameters of the C- and N cycle. The lysimeters are part of the Germany-wide lysimeter network initiative TERENO-SoilCan, which investigates feedbacks of climate change to the pedosphere on a long-term scale. Soil water samples were collected weekly from different depths of the profiles by means of suction cups. A laboratory pre-experiment proved that no degassing occurred under those sampling conditions. We applied the headspace equilibration technique to determine dissolved gas concentrations by gas chromatography. The seepage water of all lysimeters was consistently supersaturated with N2O and CO2 compared to water equilibrated ambient air. In terms of N2O, leaching losses increased in the ascending order forest, grassland, and arable soils, respectively. In case of the latter soils, we observed a strong variability of N2O, with dissolved concentrations up to 23 ?g N L-1. However, since seepage discharge of the arable lysimeters was comparatively small and mostly limited to the hydrological winter season, leached N2O appeared to be less important than direct N2O emissions. In terms of dissolved CO2,our measurements revealed considerable leaching losses from the mountainous forest and grassland soils, based on concentrations up to 24 mg C L-1 and high seepage discharge. Such losses turned out to be similarly important like soil respiration, particularly during winter when temperature-dependent soil respiration declined. In conclusion, the results of the first year of our measurements provide evidence that dissolved greenhouse gases should be considered in studies which aim to assess full greenhouse gas balances, particularly in ecosystems where hydrological conditions favour microbial activity and high leaching losses.

Weymann, Daniel; Brueggemann, Nicolas; Puetz, Thomas; Vereecken, Harry

2014-05-01

340

Pharmacokinetics of venlafaxine and its major metabolite o-desmethylvenlafaxine in freely moving mice using automated dosing/sampling system  

PubMed Central

Objective: To assess the pharmacokinetics of venlafaxine (VEN) and its major metabolite o-desmethylvenlafaxine (ODV) in freely moving mice using automated dosing/infusion (ADI) and automated blood sampling (ABS) systems. In addition, concentration of VEN and its metabolite ODV were also measured in brain by microdialysis. Materials and Methods: Venlafaxine was administered directly via jugular vein or gastric catheterization and blood samples were collected through carotid artery. A series of samples with 10 ?l of blood was collected from the mouse using ADI/ABS and analyzed with a validated LC-MS/MS system. Extracellular concentrations of VEN and ODV in brain were investigated by using microdialysis procedure. Results: The bioavailability of VEN was 11.6%. The percent AUC ratios of ODV to VEN were 18% and 39% following intravenous and intragastric administration, respectively. The terminal half-life of venlafaxine was about two hours. Extracellular concentration of VEN contributed 3.4% of the blood amount, while ODV was not detected in dialysate. Conclusion: This study suggests that besides rapid absorption of VEN, the first-pass metabolism is likely to contribute for its lower bioavailability in the mouse. The proposed automated technique can be used easily to conduct pharmacokinetic studies and is applicable to high-throughput manner in mouse model. PMID:22345864

Aryal, Bijay; Aryal, Dipendra; Kim, Eun-Joo; Kim, Hyung-Gun

2012-01-01

341

How Cheap Is Soaring Flight in Raptors? A Preliminary Investigation in Freely-Flying Vultures  

E-print Network

the costs of soaring, gliding and flapping flight in raptors is challenging, but essential for understanding. himalayensis) trained for freely-flying. HR increased three-fold at take-off (characterized by prolonged. Weather conditions influenced flight performance and HR was noticeably higher during cloudy compared

Boyer, Edmond

342

tinual recirculation. The strain measurements from the compliant members of the freely rotating 4-bar  

E-print Network

#12;tinual recirculation. The strain measurements from the compliant members of the freely rotating of the empirical function relating strain measurement to leg configura- tion. Section 4 concerns the data for measurement of strain, := R+ , which varies as a function of leg configuration. The gauge is located

Lin, Pei-Chun

343

Making an automatic speech recognition service freely available on the web Stuart N. Wrigley, Thomas Hain  

E-print Network

Making an automatic speech recognition service freely available on the web Stuart N. Wrigley, Sheffield S1 4DP, UK s.wrigley@dcs.shef.ac.uk, t.hain@dcs.shef.ac.uk Abstract The state-of-the-art speech been made available as a web service. The service provides free access to ASR aimed specifically

Hain, Thomas

344

High-speed tracking of rupture and clustering in freely falling granular streams  

E-print Network

­12 . Granular systems in Hele­Shaw geometries or impinging on stationary targets have recently been shown. 13) and more recently observed within the context of granular jets4,5 , we investi- gated freely, USA. {Present address: School of Physics, Trinity College Dublin, Dublin 2, Ireland. z 2 mm Nozzle a b

Jaeger, Heinrich M.

345

The activity pattern of limb muscles in freely moving normal and deafferented newts  

Microsoft Academic Search

Bipolar silver electrodes were implanted into eight forelimb muscles of normal and deafferented newts. In freely moving animals muscle potentials were recorded with the aid of a Hellige EEG apparatus combined with a set of transistorized preamplifiers of high input impedance. The steps, as the animals lifted up and put down the limb, were electrically signalled. The myograms revealed a

Gy. Székely; G. Czéh; Gy. Vöeös

1969-01-01

346

Virally mediated optogenetic excitation and inhibition of pain in freely moving nontransgenic mice  

Microsoft Academic Search

Primary nociceptors are the first neurons involved in the complex processing system that regulates normal and pathological pain. Because of constraints on pharmacological and electrical stimulation, noninvasive excitation and inhibition of these neurons in freely moving nontransgenic animals has not been possible. Here we use an optogenetic strategy to bidirectionally control nociceptors of nontransgenic mice. Intrasciatic nerve injection of adeno-associated

Shrivats Mohan Iyer; Kate L Montgomery; Chris Towne; Soo Yeun Lee; Charu Ramakrishnan; Karl Deisseroth; Scott L Delp

2014-01-01

347

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

348

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

E-print Network

Optogenetic control of selective neural activity in multiple freely moving Drosophila adults Ming present an automated laser tracking and optogenetic manipula- tion system (ALTOMS) for studying social for optogenetic manipula- tion to transiently and independently activate/inactivate selective neurons, ALTOMS

Huang, Haimei

349

Two useful methods for evaluating antihypertensive drugs in conscious freely moving rats1  

Microsoft Academic Search

AIM: Computerized analysis of blood pressure in conscious freely moving rats is a sound technique for physiologi- cal and pharmacological studies. The present work, based on this technique, was designed to introduce two useful methods for the evaluation of antihypertensive drugs in conscious spontaneously hypertensive rat (SHR). They were the directly intragastric administration of drugs and modified probability sum test

Ding-feng SU; Li-ping XU; Chao-yu MIAO; He-hui XIE; Fu-ming SHEN; Yuan-ying JIANG

350

Hippocampal place units in the freely moving rat: Why they fire where they fire  

Microsoft Academic Search

Place units in the dorsal hippocampus of the freely-moving rat signal the animal's position in an environment (place field). In the present experiments, thirty four place units were recorded in two different environments: one, a small platform where the rat had received neither training nor reward; the other, an elevated T-maze inside a set of black curtains where the rat

J. O'Keefe; D. H. Conway

1978-01-01

351

In vitro determination of aceclofenac Mouth Dissolving Tablets.  

PubMed

In the present study, Mouth Dissolving Tablets (MDTs) of aceclofenac were formulated by direct compression technique. Sodium starch glycolate and crospovidone were employed as superdisintegrants in various concentrations like 2%, 3% and 4% w/w. All prepared tablets were evaluated for weight variation, hardness, drug content, friability, disintegration time, in vitro wetting time and percent drug release. MDTs containing 4% w/w concentration of crospovidone give best results and is therefore considered as the best formula. It has shown 30 s disintegration time, 25 s wetting time and 79.34% in vitro release of drug in 25 min. PMID:24596037

Shobhit, Shobhit; Gupta, Satish Kumar

2013-01-01

352

Toxicity of dissolved ozone to fish eggs and larvae  

SciTech Connect

To find levels of dissolved residual ozone lethal to fish eggs and larvae during brief exposures, continuous-flow toxicity tests were performed with eggs and larvae of yellow perch (Perca flavescens), and fathead minnow (Pimephales promelas), eggs of white sucker (Catastomus commersoni), and larvae of bluegill sunfish (Lepomis macrochirus). The 50 and 99% lethal concentrations with confidence limits were calculated. Eggs of the species tested were more tolerant than larvae, which were destroyed by very brief exposures (less than 2 minutes) to residuals less than 0.1 mg/1. Because of the sensitivity of the larvae, residual ozone concentrations in natural waters should remain well below 50 ..mu..g/1.

Asbury, C.; Coler, R.

1980-07-01

353

Photochemical and microbial consumption of dissolved organic carbon and dissolved oxygen in the Amazon River system  

Microsoft Academic Search

Bacterial and photochemical mineralization of dissolved organic matter were investigated in the Amazon River system. Dissolved oxygen, dissolved organic carbon (DOC), and bacterial growth were measured during incubations conducted under natural sunlight and in the dark. Substrate addition experiments indicated that the relatively low rates of bacterial activity in Amazon River water were caused by C limitation. Experiments to determine

R. M. W. Amon; R. Benner

1996-01-01

354

Investigating Students' Understanding of the Dissolving Process  

ERIC Educational Resources Information Center

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

Naah, Basil M.; Sanger, Michael J.

2013-01-01

355

Dissolved Oxygen Data for Coos Estuary (Oregon)  

EPA Science Inventory

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

356

Photochemical degradation of dissolved organic matter and dissolved lignin phenols from the Congo River  

NASA Astrophysics Data System (ADS)

Photochemical degradation of Congo River dissolved organic matter (DOM) was investigated to examine the fate of terrigenous DOM derived from tropical ecosystems. Tropical riverine DOM receives greater exposure to solar radiation, particularly in large river plumes discharging directly into the open ocean. Initial Congo River DOM exhibited dissolved organic carbon (DOC) concentration and compositional characteristics typical of organic rich blackwater systems. During a 57 day irradiation experiment, Congo River DOM was shown to be highly photoreactive with a decrease in DOC, chromophoric DOM (CDOM), lignin phenol concentrations (?8) and carbon-normalized yields (?8), equivalent to losses of ˜45, 85-95, >95 and >95% of initial values, respectively, and a +3.1 ‰ enrichment of the ?13C-DOC signature. The loss of ?8 and enrichment of ?13C-DOC during irradiation was strongly correlated (r = 0.99, p < 0.01) indicating tight coupling between these biomarkers. Furthermore, the loss of CDOM absorbance was correlated to the loss of ?8 (e.g., a355 versus ?8; r = 0.98, p < 0.01) and ?13C-DOC (e.g., a355 versus ?13C; r = 0.97, p < 0.01), highlighting the potential of CDOM absorbance measurements for delineating the photochemical degradation of lignin and thus terrigenous DOM. It is apparent that these commonly used measurements for examination of terrigenous DOM in the oceans have a higher rate of photochemical decay than the bulk DOC pool. Further process-based studies are required to determine the selective removal rates of these biomarkers for advancement of our understanding of the fate of this material in the ocean.

Spencer, Robert G. M.; Stubbins, Aron; Hernes, Peter J.; Baker, Andy; Mopper, Kenneth; Aufdenkampe, Anthony K.; Dyda, Rachael Y.; Mwamba, Vincent L.; Mangangu, Arthur M.; Wabakanghanzi, Jose N.; Six, Johan

2009-09-01

357

Fast dissolving films made of maltodextrins.  

PubMed

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 using 16-20% w/w glycerin (GLY). This basic formulation was adapted to the main production technologies, casting and solvent evaporation (Series C) or hot-melt extrusion (Series E), by adding sorbitan monoleate (SO) or cellulose microcrystalline (MCC), respectively. MCC decreased the film ductility and significantly affected the film disintegration time both in vitro and in vivo (Series C<10s; Series E approximately 1min). To assess the film loading capacity, piroxicam (PRX), a water insoluble drug, was selected. The loading of a drug as a powder decreased the film ductility, but the formulation maintained satisfactory flexibility and resistance to elongation for production and packaging procedures. The films present a high loading capacity, up to 25mg for a surface of 6cm(2). The PRX dissolution rate significantly improved in Series C films independently of the PRX/MDX ratio. PMID:18667164

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

2008-11-01

358

Methanex, Hoechst Celanese dissolve methanol partnership  

SciTech Connect

One of the many joint venture alliances recently announced in the petrochemical sector is ending in divorce. Hoechst Celanese Chemical (Dallas) and Methanex Corp. (Vancouver) are in the process of dissolving the partnership they had formed to restart Hoechst Celanese's methanol plant at Clear Lake, TX. Hoechst Celanese says it is actively seeking replacement partners and has several likely prospects, while Methanex is concentrating on its other ventures. Those include its just-completed acquisition of Fletcher Challenge's (Auckland, NZ) methanol business and a joint venture with American Cyanamid to convert an ammonia plant at Fortier, LA to methanol. Methanex will still be the world's largest producer of methanol. Officially, the negotiations between Methanex and Hoechst Celanese just broke down over the last month or so,' says Steve Yurich, operations manager for the Clear Lake plant. Market sources, however, say that Methanex found itself with too many irons in the fire' and pulled out before it ran into financial or perhaps even antitrust difficulties.

Morris, G.D.L.

1993-03-31

359

Measurement and interpretation of low levels of dissolved oxygen in ground water  

USGS Publications Warehouse

A Rhodazine-D colorimetric technique was adapted to measure low-level dissolved oxygen concentrations in ground water. Prepared samples containing between 0 and 8.0 ??moles L-1 dissolved oxygen in equilibrium with known gas mixtures produced linear spectrophotometric absorbance with a lower detection limit of 0.2 ??moles L-1. Excellent reproducibility was found for solutions ranging in composition from deionized water to sea water with chemical interferences detected only for easily reduced metal species such as ferric ion, cupric ion, and hexavalent chromium. Such effects were correctable based on parallel reaction stoichiometries relative to oxygen. The technique, coupled with a downhole wire line tool, permitted low-level monitoring of dissolved oxygen in wells at the selenium-contaminated Kesterson Reservoir in California. Results indicated a close association between low but measurable dissolved oxygen concentrations and mobility of oxidized forms of selenium. -from Authors

White, A.F.; Peterson, M.L.; Solbau, R.D.

1990-01-01

360

Dissolved organic matter fluorescence as a water-flow tracer in the tropical wetland of Pantanal of Nhecolândia, Brazil  

Microsoft Academic Search

The Nhecolândia is a sub-region of the Brazilian Pantanal wetland, where saline and freshwater lakes coexist in close proximity. Measurements of dissolved organic carbon (DOC) content and analysis of fluorescence excitation–emission matrices (EEM) were conducted in an effort to characterize spatial variability in concentration and source of dissolved organic matter (DOM) and to further understand the hydrochemical functioning of this

Mélody Mariot; Yves Dudal; Sônia Furian; Arnaldo Sakamoto; Vincent Vallès; Monique Fort; Laurent Barbiero

2007-01-01

361

Decoupled adaptive control of glucose and dissolved oxygen for fed-batch methionine production using linear reference model  

Microsoft Academic Search

In this paper, the design of a decoupled adaptive controller for controlling the dissolved oxygen and glucose feeding simultaneously in fed-batch fermentation of methionine production is proposed. The synthesis of methionine at the cellular level is strictly regulated and its process dynamics shows a nonlinear interaction between dissolved oxygen and glucose concentration. The adaptive controller developed using a linear reference

Amalendu P. Ranjan; James Gomes

2010-01-01

362

Removal of Cs from Dissolved Hanford Tank Saltcake by Treatment with IONSIV IE?911  

Microsoft Academic Search

This paper describes the removal of Cs from dissolved Hanford tank saltcake. A composite feed solution was prepared by dissolving archived saltcake samples from Hanford single shell tanks 241?S?101, 241?S?109, 241?S?110, 241?S?111, 241?U?106, and 241?U?109 and adjusting the solution to approximately 5 M Na. This composite feed solution was treated by ion exchange with IONSIV IE?911, which effectively reduced the concentration

Brian M. Rapko; Serguei I. Sinkov; Tatiana G. Levitskaia

2005-01-01

363

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

USGS Publications Warehouse

The tailwaters of Beaver Lake and other White River reservoirs support a cold-water trout fishery of significant economic yield in northwestern Arkansas. The Arkansas Game and Fish Commission has requested an increase in existing minimum flows through the Beaver Lake dam to increase the amount of fishable waters downstream. Information is needed to assess the impact of additional minimum flows on temperature and dissolved-oxygen qualities of reservoir water above the dam and the release water. A two-dimensional, laterally averaged hydrodynamic, thermal and dissolved-oxygen model was developed and calibrated for Beaver Lake, Arkansas. The model simulates surface-water elevation, currents, heat transport and dissolved-oxygen dynamics. The model was developed to assess the impacts of proposed increases in minimum flows from 1.76 cubic meters per second (the existing minimum flow) to 3.85 cubic meters per second (the additional minimum flow). Simulations included assessing (1) the impact of additional minimum flows on tailwater temperature and dissolved-oxygen quality and (2) increasing initial water-surface elevation 0.5 meter and assessing the impact of additional minimum flow on tailwater temperatures and dissolved-oxygen concentrations. The additional minimum flow simulation (without increasing initial pool elevation) appeared to increase the water temperature (<0.9 degrees Celsius) and decrease dissolved oxygen concentration (<2.2 milligrams per liter) in the outflow discharge. Conversely, the additional minimum flow plus initial increase in pool elevation (0.5 meter) simulation appeared to decrease outflow water temperature (0.5 degrees Celsius) and increase dissolved oxygen concentration (<1.2 milligrams per liter) through time. However, results from both minimum flow scenarios for both water temperature and dissolved oxygen concentration were within the boundaries or similar to the error between measured and simulated water column profile values.

Haggard, Brian; Green, W. Reed

2002-01-01

364

Dissolved and particulate-adsorbed hydrocarbons in the waters of shatt al-Arab River, Iraq  

Microsoft Academic Search

N-alkanes were measured both in dissolved and particulate-adsorbed phases of water samples collected from five stations located along Shatt al-Arab River in Iraq. The aim of this study was to provide a background information on the presence, origin, and distribution of n-alkanes in the waters of Shatt al-Arab River. Total concentrations of n-alkanes were lower in the dissolved phase (29.37

Hassan M. Bedair; Hamid T. Al-Saad

1992-01-01

365

Molecular indicators of the sources and transformations of dissolved organic matter in the Mississippi river plume  

Microsoft Academic Search

The dynamics of dissolved organic matter (DOM) in the Mississippi river plume were investigated during four cruises to the region in 1990–1993. During each cruise, large-volume water samples were collected from a broad salinity gradient (0–36 psu) for the determination of dissolved organic carbon (DOC) concentrations and the isolation of DOM by tangential-flow ultrafiltration. The fraction of DOC recovered by

Ronald Benner; Stephen Opsahl

2001-01-01

366

Dissolved gas and ultrasonic cavitation--a review.  

PubMed

The physics and chemistry of nonlinearly oscillating acoustic cavitation bubbles are strongly influenced by the dissolved gas in the surrounding liquid. Changing the gas alters among others the luminescence spectrum, and the radical production of the collapsing bubbles. An overview of experiments with various gas types and concentration described in literature is given and is compared to mechanisms that lead to the observed changes in luminescence spectra and radical production. The dissolved gas type changes the bubble adiabatic ratio, thermal conductivity, and the liquid surface tension, and consequently the hot spot temperature. The gas can also participate in chemical reactions, which can enhance radical production or luminescence of a cavitation bubble. With this knowledge, the gas content in cavitation can be tailored to obtain the desired output. PMID:22705074

Rooze, Joost; Rebrov, Evgeny V; Schouten, Jaap C; Keurentjes, Jos T F

2013-01-01

367

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

SciTech Connect

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

Murray, A.M. [Westinghouse Savannah River Company, AIKEN, SC (United States); Karraker, D.G.

1998-05-01

368

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

E-print Network

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

Bird, Peter

369

Seasonal variability of dissolved organic carbon and total dissolved nitrogen in Arctic streams and rivers  

NASA Astrophysics Data System (ADS)

Changes in the quantity, seasonality, and flow paths of water through catchments have been documented throughout much of the Arctic, with further changes projected to occur over the coming century due to increasing temperatures and altered precipitation regimes. These changes in hydrology are expected to have a significant impact on biogeochemical cycles in Arctic watersheds. An improved understanding of the controls that impact water chemistry in Arctic rivers under varying hydrologic conditions will help to better project how these systems may respond to anticipated climate change. During 2009 and 2010, we collected surface waters from six streams on the North Slope of Alaska from mid-May through mid-October. The catchments of all six streams are underlain by continuous permafrost and range in size from 1.6 km2 to 610 km2. Three of the catchments drain predominantly tussock tundra while the other three are located in more mountainous terrain with exposed bedrock and less tundra coverage. This presentation will focus on the seasonality of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) in these streams. As observed in previous studies, DOC concentrations are highest during the spring snowmelt period and decline as the summer progresses. Concentrations of TDN show similar patterns to those of DOC during the spring and early summer. However, the pattern for TDN diverges from that of DOC later in the summer, with a substantial increase at some locations that is primarily attributed to the nitrate fraction. While the seasonal patterns are qualitatively similar in the tundra and mountain streams, DOC concentrations are much higher in the tundra streams and nitrate concentrations are much higher in the mountain streams. Our study places particular emphasis on dynamics during the spring and fall. Historically, these are times of the year that Arctic streams and rivers have been understudied. However, these are also times when the anticipated responses to warming in the Alaskan Arctic are most likely to be manifest: an earlier spring melt transition from winter to summer and the downward movement of the seasonally thawed “active” layer. During the spring, frozen ground largely constrains water flow to the organic-rich soil surface, whereas maximum thaw depths (active layer) in the fall facilitate water flow thorough deeper soil layers.

Khosh, M. S.; McClelland, J. W.; Douglas, T. A.; Jacobson, A. D.; Lehn, G. O.; Barker, A.

2010-12-01

370

Biocidal Efficacy of Dissolved Ozone, Formaldehyde and Sodium Hypochlorite Against Total Planktonic Microorganisms in Produced Water  

NASA Astrophysics Data System (ADS)

The performance of three biocides (dissolved ozone, formaldehyde and sodium hypochlorite) in eliminating the bacteria and fungi in produced water is investigated experimentally. The analysis involves monitoring the microbial population in nine conical flasks each containing the same volume of a mixture of produced water, culture medium that sustains the growth of microorganisms and a known concentration of biocide. The concentrations of each biocide used in the study are 0.1, 0.2 and 0.5 ppm. It is shown that dissolved ozone exhibits the best biocidal characteristics and a concentration of 0.5 ppm eliminated all the microorganisms in the produced water after 150 min contact time.

Puyate, Y. T.; Rim-Rukeh, A.

371

Variability in dissolved oxygen off Eastern Luzon, Philippines  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

372

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

PubMed

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

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

2014-04-01

373

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

EPA Science Inventory

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

374

Particulate and dissolved elemental loads in the Kuji River related to discharge rate  

Microsoft Academic Search

In order to investigate influences of discharge rates on fluvial transport behavior of elements in the Kuji River, Japan, suspended and dissolved phase concentrations in the river water were measured together with the water flow rates. The concentrations of suspended particulate matter (SPM) increased by two or three orders of magnitude with the water discharge, and also had seasonal variations.

T. Nagano; N. Yanase; K. Tsuduki; S. Nagao

2003-01-01

375

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

EPA Science Inventory

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

376

Dissolved copper-complexing ligands in cultures of marine bacteria and estuarine water  

Microsoft Academic Search

We have determined concentrations and conditional stability constants of dissolved copper-complexing ligands in chemostat cultures of autotrophic (Synechococcus) and heterotrophic (Vibrio) marine bacteria, and in estuarine waters. Ligands with high affinity for copper were detected in Vibrio and Synechococcus cultures, and ligand production by Vibrio was dependent on the copper concentration in the medium. While Synechococcus cultures produced ligands in

Andrew S Gordon; John R Donat; Reyaz A Kango; Brian J Dyer; Lisa M Stuart

2000-01-01

377

Intracellular flux analysis applied to the effect of dissolved oxygen on hybridomas  

Microsoft Academic Search

Quantitative estimates of intracellular fluxes and measurements of intracellular concentrations were used to evaluate the e?ect of dissolved oxygen (DO) concentration on CRL 1606 hybridoma cells in batch culture. The estimates of intracellular fluxes were gen- erated by combining material balances with measure- ments of extracellular metabolite rates of change. Ex- periments were performed at DO levels of 60% and

C. Zupke; A. J. Sinskey; G. Stephanopoulos

1995-01-01

378

Total dissolved nitrogen analysis: comparisons between the persulfate, UV and high temperature oxidation methods  

Microsoft Academic Search

We compared the persulfate (PO), ultraviolet (UV), and high temperature oxidation (HTO) methods used to analyze total dissolved nitrogen (TDN) concentrations in aquatic samples to determine whether the three methods differed in terms of standard parameters (blanks, limits of detection and linearity, and precision) or in oxidation efficiency of standard compounds and field samples of varying salinity. The TDN concentrations

Deborah A. Bronk; Michael W. Lomas; Patricia M. Glibert; Karyn J. Schukert; Marta P. Sanderson

2000-01-01

379

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

USGS Publications Warehouse

Outflow from Norfork Lake and other White River reservoirs support a cold-water trout fishery of significant economic yield in north-central Arkansas and south-central Missouri. The Arkansas Game and Fish Commission has requested an increase in existing minimum flows through the Norfork Lake dam to increase the amount of fishable waters downstream. Information is needed to assess the impact of increased minimum flows on temperature and dissolved-oxygen concentrations of reservoir water and the outflow. A two-dimensional, laterally averaged, hydrodynamic, temperature, and dissolved-oxygen model was developed and calibrated for Norfork Lake, located on the Arkansas-Missouri State line. The model simulates water-surface elevation, heat transport, and dissolved-oxygen dynamics. The model was developed to assess the impacts of proposed increases in minimum flow from 1.6 cubic meter per second (the existing minimum flow) to 8.5 cubic meters per second (the increased minimum flow). Simulations included assessing the impact of (1) increased minimum flows and (2) increased minimum flows with increased water-surface elevation of 1.1 meter in Norfork Lake on outflow temperatures and dissolved-oxygen concentrations. The increased minimum flow simulation (without increasing initial water-surface elevation) appeared to increase the water temperature and decrease dissolved-oxygen concentration in the outflow. Conversely, the increased minimum flow and initial increase in water-surface elevation (1.1 meter) simulation appeared to decrease outflow water temperature and increase dissolved-oxygen concentration through time. However, results from both scenarios for water temperature and dissolved-oxygen concentration were within the boundaries or similar to the error between measured and simulated water column profile values.

Galloway, Joel M.; Green, W. Reed

2002-01-01

380

Suspended sediment, dissolved organic carbon, and dissolved nitrogen export during the dam removal process  

NASA Astrophysics Data System (ADS)

Total suspended solids (TSS), dissolved organic carbon (DOC), and total dissolved nitrogen (TDN) loads were calculated for all stages of the dam removal process (dewatering, breaching, and removal) at various points upstream, within, and downstream of Lowell Mill Impoundment on the Little River, North Carolina. The impoundment dewatering exported loads of TSS, DOC, and TDN which were all 1-2 orders of magnitude less than loads associated with historic floods. Conversely, floods exiting the former impoundment following dam removal produced TSS, DOC, and TDN loads comparable to, but slightly greater (1.2-1.75 times) than historic floods. Exported loads were greatest following the complete removal of the dam, most likely because of increased channel gradient. We assert that the disturbances (i.e., concentrations and loads) associated with dam removal should be compared to those generated by floods within the same system rather than comparing the impacts of dam removal with base flow conditions. During the dewatering, impounded floodplain wetlands were found to contribute the following percentages to total impoundment loads: 44% of stored water, 12.6 % of TSS, 49% of DOC, and 33% of TDN. Moreover, the dewatering flood wave was sampled at various points along a 19.2-km reach below the dam to characterize the routing of TSS, DOC, and TDN. TSS released by the impoundment was retained within 10 km of the dam, while TDN and DOC loads increased slightly. Finally, we used our results with those from other removals to provide insight into regional and morphologic controls on exports of impounded materials following dam removal.

Riggsbee, J. Adam; Julian, Jason P.; Doyle, Martin W.; Wetzel, Robert G.

2007-09-01

381

Mechanical properties of freely suspended semiconducting graphene-like layers based on MoS2  

NASA Astrophysics Data System (ADS)

We fabricate freely suspended nanosheets of molybdenum disulphide (MoS2) which are characterized by quantitative optical microscopy and high-resolution friction force microscopy. We study the elastic deformation of freely suspended nanosheets of MoS2 using an atomic force microscope. The Young's modulus and the initial pre-tension of the nanosheets are determined by performing a nanoscopic version of a bending test experiment. MoS2 sheets show high elasticity and an extremely high Young's modulus (0.30 TPa, 50% larger than steel). These results make them a potential alternative to graphene in applications requiring flexible semiconductor materials. PACS, 73.61.Le, other inorganic semiconductors, 68.65.Ac, multilayers, 62.20.de, elastic moduli, 81.40.Jj, elasticity and anelasticity, stress-strain relations.

Castellanos-Gomez, Andres; Poot, Menno; Steele, Gary A.; van der Zant, Herre; Agraït, Nicolás; Rubio-Bollinger, Gabino

2012-04-01

382

Multiple leading edge vortices of unexpected strength in freely flying hawkmoth  

NASA Astrophysics Data System (ADS)

The Leading Edge Vortex (LEV) is a universal mechanism enhancing lift in flying organisms. LEVs, generally illustrated as a single vortex attached to the wing throughout the downstroke, have not been studied quantitatively in freely flying insects. Previous findings are either qualitative or from flappers and tethered insects. We measure the flow above the wing of freely flying hawkmoths and find multiple simultaneous LEVs of varying strength and structure along the wingspan. At the inner wing there is a single, attached LEV, while at mid wing there are multiple LEVs, and towards the wingtip flow separates. At mid wing the LEV circulation is ~40% higher than in the wake, implying that the circulation unrelated to the LEV may reduce lift. The strong and complex LEV suggests relatively high flight power in hawmoths. The variable LEV structure may result in variable force production, influencing flight control in the animals.

Johansson, L. Christoffer; Engel, Sophia; Kelber, Almut; Heerenbrink, Marco Klein; Hedenström, Anders

2013-11-01

383

Multiple leading edge vortices of unexpected strength in freely flying hawkmoth.  

PubMed

The Leading Edge Vortex (LEV) is a universal mechanism enhancing lift in flying organisms. LEVs, generally illustrated as a single vortex attached to the wing throughout the downstroke, have not been studied quantitatively in freely flying insects. Previous findings are either qualitative or from flappers and tethered insects. We measure the flow above the wing of freely flying hawkmoths and find multiple simultaneous LEVs of varying strength and structure along the wingspan. At the inner wing there is a single, attached LEV, while at mid wing there are multiple LEVs, and towards the wingtip flow separates. At mid wing the LEV circulation is ~40% higher than in the wake, implying that the circulation unrelated to the LEV may reduce lift. The strong and complex LEV suggests relatively high flight power in hawmoths. The variable LEV structure may result in variable force production, influencing flight control in the animals. PMID:24253180

Johansson, L Christoffer; Engel, Sophia; Kelber, Almut; Heerenbrink, Marco Klein; Hedenström, Anders

2013-01-01

384

Optogenetic control of freely behaving adult Drosophila using a red-shifted channelrhodopsin  

PubMed Central

Optogenetics allows the manipulation of neural activity in freely moving animals with millisecond precision, but its application in Drosophila has been limited. Here we show that a recently described Red activatable Channelrhodopsin (ReaChR) permits control of complex behavior in freely moving adult flies, at wavelengths that are not thought to interfere with normal visual function. This tool affords the opportunity to control neural activity over a broad dynamic range of stimulation intensities. Using time-resolved activation, we show that the neural control of male courtship song can be separated into probabilistic, persistent and deterministic, command-like components. The former, but not the latter, neurons are subject to functional modulation by social experience, supporting the idea that they constitute a locus of state-dependent influence. This separation is not evident using thermogenetic tools, underscoring the importance of temporally precise control of neuronal activation in the functional dissection of neural circuits in Drosophila. PMID:24363022

Inagaki, Hidehiko K.; Jung, Yonil; Hoopfer, Eric D.; Wong, Allan M.; Mishra, Neeli; Lin, John Y.; Tsien, Roger Y.; Anderson, David J.

2014-01-01

385

Whole-brain calcium imaging with cellular resolution in freely behaving C. elegans  

E-print Network

The ability to acquire large-scale recordings of neuronal activity in awake and unrestrained animals poses a major challenge for studying neural coding of animal behavior. We present a new instrument capable of recording intracellular calcium transients from every neuron in the head of a freely behaving C. elegans with cellular resolution while simultaneously recording the animal's position, posture and locomotion. We employ spinning-disk confocal microscopy to capture 3D volumetric fluorescent images of neurons expressing the calcium indicator GCaMP6s at 5 head-volumes per second. Two cameras simultaneously monitor the animal's position and orientation. Custom software tracks the 3D position of the animal's head in real-time and adjusts a motorized stage to keep it within the field of view as the animal roams freely. We observe calcium transients from 78 neurons and correlate this activity with the animal's behavior. Across worms, multiple neurons show significant correlations with modes of behavior correspo...

Nguyen, Jeffrey P; Linder, Ashley N; Plummer, George S; Shaevitz, Joshua W; Leifer, Andrew M

2015-01-01

386

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

NASA Astrophysics Data System (ADS)

The dynamics of droplets and bubbles, particularly on microscopic scales, are of considerable importance in biological, environmental, and technical contexts. We introduce freely floating bubbles of smectic liquid crystals and report their unique dynamic properties. Smectic bubbles can be used as simple models for dynamic studies of fluid membranes. In equilibrium, they form minimal surfaces like soap films. However, shape transformations of closed smectic membranes that change the surface area involve the formation and motion of molecular layer dislocations. These processes are slow compared to the capillary wave dynamics, therefore the effective surface tension is zero like in vesicles. Freely floating smectic bubbles are prepared from collapsing catenoid films and their dynamics is studied with optical high-speed imaging [1]. Experiments are performed under normal gravity and in microgravity during parabolic flights.[4pt] [1] K. May et al. EPL 100 16003 (2012).

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

2013-03-01

387

Temporal activity patterns in thermosensory neurons of freely moving Caenorhabditis elegans encode spatial thermal gradients.  

PubMed

Our understanding of the operation of neurons and neuronal circuits has come primarily from probing their activity in dissected, anesthetized, or restrained animals. However, the behaviorally relevant operation of neurons and neuronal circuits occurs within intact animals as they freely perform behavioral tasks. The small size and transparency of the nematode Caenorhabditis elegans make it an ideal system for noninvasive, optical measurements of neuronal activity. Here, we use a high signal-to-noise version of cameleon, a fluorescent calcium-binding protein, to quantify the activity of the AFD thermosensory neuron of individual worms freely navigating spatial thermal gradients. We find that AFD activity is directly coupled to the worm's exploratory movements in spatial thermal gradients. We show that the worm is able, in principle, to evaluate and guide its own thermotactic behaviors with respect to ambient spatial thermal gradients by monitoring the activity of this single thermosensory neuron. PMID:17553981

Clark, Damon A; Gabel, Christopher V; Gabel, Harrison; Samuel, Aravinthan D T

2007-06-01

388

Aerial and aquatic oxygen uptake by freely-diving snapping turtles ( Chelydra serpentina )  

Microsoft Academic Search

Aerial oxygen consumption of unrestrained, freely-diving warm-and cold-acclimated snapping turtles, Chelydra serpentina, was measured at 10, 20, and 30°C. Also, simultaneous determinations of aerial and aquatic oxygen uptake by voluntarilydiving animals were made at 4 and 20°C. The standard rates of aerial oxygen consumption are equivalent in cold-and warm-acclimated animals in water and in cold-acclimated ones in air; these rates

Robert E. Gatten

1980-01-01

389

Computational complexity Freely using various textbooks, mainly the one by Arora-Barak  

E-print Network

Computational complexity Freely using various textbooks, mainly the one by Arora-Barak P´eter G. In the notes, section numbers and titles generally refer to the book: Arora-Barak: Computational Complexity with \\. a \\le b for a b, a_i for ai, a^{25} for a25, x \\in A for x A, X \\cup Y for X Y, X \\cap Y for X Y, X

Gacs, Peter

390

Simulation and experimental validation of a freely bubbling bed of FCC catalyst  

Microsoft Academic Search

A validation and mesh refinement study has been performed for the simulation of a freely bubbling bed of fluid catalytic cracking (FCC) catalyst operating at superficial gas velocities in the range of 0.05 to 0.20 m\\/s, using the two-fluid computational fluid dynamics (CFD) code Multiphase Flow with Interphase eXchanges (MFIX). The simulation results have been compared to experimental data collected

Tim McKeen; Todd Pugsley

2003-01-01

391

Comparison of Four Freely Available Frameworks for Image Processing and Visualization That Use ITK  

Microsoft Academic Search

Most image processing and visualization applications allow users to configure computation parameters and manipulate the resulting visualizations. SCIRun, VoIView, MeVisLab, and the Medical Interaction Toolkit (MITK) are four image processing and visualization frameworks that were built for these purposes. All frameworks are freely available and all allow the use of the ITK C++ library. In this paper, the benefits and

Ingmar Bitter; Robert L. Van Uitert Jr.; Ivo Wolf; Luis Ibáñez; Jan-martin Kuhnigk

2007-01-01

392

On the mechanism of d-amphetamine-induced changes in glutamate, ascorbic acid and uric acid release in the striatum of freely moving rats  

PubMed Central

The effects of systemic, intrastriatal or intranigral administration of d-amphetamine on glutamate, aspartate, ascorbic acid (AA), uric acid, dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in dialysates from the striatum of freely-moving rats were evaluated using microdialysis. d-Amphetamine (2?mg?kg?1) given subcutaneously (s.c.) increased DA, AA and uric acid and decreased DOPAC+HVA, glutamate and aspartate dialysate concentrations over a 3?h period after d-amphetamine. 5-HIAA concentrations were unaffected. Individual changes in glutamate and AA dialysate concentrations were negatively correlated. d-Amphetamine (0.2?mM), given intrastriatally, increased DA and decreased DOPAC+HVA and aspartate dialysate concentrations, but failed to change those of glutamate, AA uric acid or 5-HIAA, over a 2?h period after d-amphetamine. Haloperidol (0.1?mM), given intrastriatally, increased aspartate concentrations without affecting those of glutamate or AA. d-Amphetamine (0.2?mM), given intranigrally, increased AA and uric acid dialysate concentrations and decreased those of glutamate, aspartate and DA; DOPAC+HVA and 5-HIAA concentrations were unaffected. These results suggest that d-amphetamine-induced increases in AA and uric acid and decreases in glutamate concentrations are triggered at nigral sites. The changes in aspartate levels may be evoked by at least two mechanisms: striatal (mediated by inhibitory dopaminergic receptors) and nigral (activation of amino acid carrier-mediated uptake). PMID:10711358

Miele, Maddalena; Mura, Maria A; Enrico, Paolo; Esposito, Giovanni; Serra, Pier A; Migheli, Rossana; Zangani, Danilo; Miele, Egidio; Desole, Maria S

2000-01-01

393

Similar Odor Discrimination Behavior in Head-Restrained and Freely Moving Mice  

PubMed Central

A major challenge in neuroscience is relating neuronal activity to animal behavior. In olfaction limited techniques are available for these correlation studies in freely moving animals. To solve this problem, we developed an olfactory behavioral assay in head-restrained mice where we can monitor behavioral responses with high temporal precision. Mice were trained on a go/no-go operant conditioning paradigm to discriminate simple monomolecular odorants, as well as complex odorants such as binary mixtures of monomolecular odorants or natural odorants. Mice learned to discriminate both simple and complex odors in a few hundred trials with high accuracy. We then compared the discrimination performance of head-restrained mice to the performance observed in freely moving mice. Discrimination accuracies were comparable in both behavioral paradigms. In addition, discrimination times were measured while the animals performed well. In both tasks, mice discriminated simple odors in a few hundred milliseconds and took additional time to discriminate the complex mixtures. In conclusion, mice showed similar and efficient discrimination behavior while head-restrained compared with freely moving mice. Therefore, the head-restrained paradigm offers a relevant approach to monitor neuronal activity while animals are actively engaged in olfactory discrimination behaviors. PMID:23272168

Abraham, Nixon M.; Guerin, Delphine; Bhaukaurally, Khaleel; Carleton, Alan

2012-01-01

394

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

SciTech Connect

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

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

1984-01-01

395

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

NASA Astrophysics Data System (ADS)

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

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

396

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

EPA Science Inventory

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

397

Release of dissolved nitrogen from water during depressurization  

NASA Technical Reports Server (NTRS)

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

Simoneau, R. J.

1978-01-01

398

Short term variability of dissolved lipid classes during summer to autumn transition in the Ligurian sea (NW Mediterranean)  

Microsoft Academic Search

Changes in concentration and composition of dissolved lipid classes (Iatroscan TLC\\/FID) were examined at daily to month scale, in relation to the hydrological and biological situation at a central site of the Ligurian sea, NW Mediterranean during the PECHE-DYNAPROC 2 experiment (14 September to 17 October). Dissolved lipid concentrations (TLd) and lipid to DOC ratios varied in the range 5.3-48.5

M. Goutx; C. Guigue; D. Aritio; J. Ghiglione; M. Pujo-Pay; V. Andersen

2009-01-01

399

Bacterial Production in the Recently Flooded Sep Reservoir: Diel Changes in Relation to Dissolved Carbohydrates and Combined Amino Acids  

Microsoft Academic Search

The spatial distribution of bacterial abundance and production were measured every 4 h in a recently flooded oligo-mesotrophic\\u000a reservoir (the Sep Reservoir, Puy-De-Dôme, France), in relation to concentrations of dissolved carbohydrates and combined\\u000a amino acids. The concentration of dissolved organic matter (DOM) components in the recently flooded Sep Reservoir were higher\\u000a than those measured in other lakes of similar trophic status.

Louis-B. Jugnia; M. Richardot; D. Debroas; J. Dévaux

2006-01-01

400

Natural and man-caused factors affecting the abundance and cycling of dissolved organic substances in precambrian shield lakes  

Microsoft Academic Search

Effects of natural factors (drought and forest fire), and experimental perturbations (fertilization and acidification) on\\u000a dissolved organic carbon (DOC) concentrations and ratios to other nutrients in lakes of the Experimental Lakes Area are examined\\u000a using data obtained over a period of 20 years. DOC concentration, and the ratio of dissolved iron to DOC in lakes of the area\\u000a were strongly

D. W. Schindler; S. E. Bayley; P. J. Curtis; B. R. Parker; M. P. Stainton; C. A. Kelly

1992-01-01

401

A wireless beta-microprobe based on pixelated silicon for in vivo brain studies in freely moving rats.  

PubMed

The investigation of neurophysiological mechanisms underlying the functional specificity of brain regions requires the development of technologies that are well adjusted to in vivo studies in small animals. An exciting challenge remains the combination of brain imaging and behavioural studies, which associates molecular processes of neuronal communications to their related actions. A pixelated intracerebral probe (PIXSIC) presents a novel strategy using a submillimetric probe for beta(+) radiotracer detection based on a pixelated silicon diode that can be stereotaxically implanted in the brain region of interest. This fully autonomous detection system permits time-resolved high sensitivity measurements of radiotracers with additional imaging features in freely moving rats. An application-specific integrated circuit (ASIC) allows for parallel signal processing of each pixel and enables the wireless operation. All components of the detector were tested and characterized. The beta(+) sensitivity of the system was determined with the probe dipped into radiotracer solutions. Monte Carlo simulations served to validate the experimental values and assess the contribution of gamma noise. Preliminary implantation tests on anaesthetized rats proved PIXSIC's functionality in brain tissue. High spatial resolution allows for the visualization of radiotracer concentration in different brain regions with high temporal resolution. PMID:23760022

Märk, J; Benoit, D; Balasse, L; Benoit, M; Clémens, J C; Fieux, S; Fougeron, D; Graber-Bolis, J; Janvier, B; Jevaud, M; Genoux, A; Gisquet-Verrier, P; Menouni, M; Pain, F; Pinot, L; Tourvielle, C; Zimmer, L; Morel, C; Laniece, P

2013-07-01

402

A wireless beta-microprobe based on pixelated silicon for in vivo brain studies in freely moving rats  

NASA Astrophysics Data System (ADS)

The investigation of neurophysiological mechanisms underlying the functional specificity of brain regions requires the development of technologies that are well adjusted to in vivo studies in small animals. An exciting challenge remains the combination of brain imaging and behavioural studies, which associates molecular processes of neuronal communications to their related actions. A pixelated intracerebral probe (PIXSIC) presents a novel strategy using a submillimetric probe for beta+ radiotracer detection based on a pixelated silicon diode that can be stereotaxically implanted in the brain region of interest. This fully autonomous detection system permits time-resolved high sensitivity measurements of radiotracers with additional imaging features in freely moving rats. An application-specific integrated circuit (ASIC) allows f