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1

Contribution ratio of freely to total dissolved concentrations of polycyclic aromatic hydrocarbons in natural river waters.  

PubMed

The bioavailability and ecological risk of hydrophobic organic compounds (HOCs) in aquatic environments largely depends on their freely dissolved concentrations. In this work, the freely dissolved concentrations of polycyclic aromatic hydrocarbons (PAHs) including phenanthrene, pyrene, and chrysene were determined for the Yellow River, Haihe River and Yongding River of China using polyethylene devices (PEDs). The results indicated that the order of ratios of freely to total dissolved concentrations of the three PAHs was phenanthrene (66.8±20.1%)>pyrene (48.8±26.4%)>chrysene (5.5±3.3%) for the three rivers. The ratios were significantly negatively correlated with the logK(ow) values of the PAHs. In addition, the ratios were negatively correlated with the suspended sediment (SPS) and dissolved organic carbon (DOC) concentrations in the river water, and the characteristics of the SPS and DOC were also important factors. Simulation experiments showed that the ratio of freely to total dissolved concentrations of pyrene in the aqueous phase decreased with increasing SPS concentration; when the sediment concentration increased from 2 g L(-1) to 10 g L(-1), the ratio decreased from 67.6% to 38.4% for Yellow River sediment and decreased from 50.4% to 33.6% for Haihe River sediment. This was because with increasing SPS concentration, more and more DOC, small particles and colloids (<0.45 ?m) would enter the aqueous phase. Because high SPS and DOC concentrations exist in many rivers, their effect on the freely dissolved concentrations of HOCs should be considered when conducting an ecological risk assessment. PMID:22963877

Xia, Xinghui; Zhai, Yawei; Dong, Jianwei

2013-02-01

2

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. Environ Toxicol Chem 2014;33:1739-1746. © 2014 SETAC. PMID:24839192

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

2014-08-01

3

Analyzing freely dissolved concentrations of cationic surfactant utilizing ion-exchange capability of polyacrylate coated solid-phase microextraction fibers.  

PubMed

A 7-?m polyacrylate (PA) coated fiber was successfully employed to determine freely dissolved concentrations of cationic surfactants by solid-phase microextraction (SPME) and utilizing the capability of the PA-coating to sorb organic cations via ion-exchange at carboxylic groups. Measured fiber-water partitioning coefficients (K(fw)) were constant below a fiber loading of 2mmol per liter polyacrylate, allowing for simple and accurate analysis in a concentration range that is relevant from a risk assessment point of view. Ion-exchange was confirmed to be the main sorption mechanism because of a decreasing K(fw) with either higher CaCl(2) concentrations or lower pH, and maximum fiber uptake at the polyacrylate cation-exchange capacity (CEC, at 30mmol/L PA). Fiber-water sorption isotherms were established in various aqueous media in toxicological relevant concentrations. The developed SPME method has a high potential for application in ecotoxicological studies, as demonstrated in sorption studies with humic acid in different electrolyte solutions at aqueous concentrations down to the sub nM range. Cationic surfactant sorption affinities for humic acid also depend on medium composition but are orders of magnitude higher than to the PA fiber on a sorbent weight basis. PMID:22818738

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

2012-08-24

4

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

EPA Science Inventory

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

5

Stabilization of sewage sludge by different biochars towards reducing freely dissolved polycyclic aromatic hydrocarbons (PAHs) content.  

PubMed

The objective of the study was to identify the effect of various biochars on the content of freely dissolved (Cfree) PAHs in sewage sludge. Apart from the evaluation of biochars obtained from various materials, the study also included the determination of the effects of biochar particle sizes and biochar production temperature on their ability to bind PAHs in sewage sludge. Increase in biochar dose caused a gradual reduction of Cfree PAHs content, but only up to the biochar dose of 5%. Depending on the kind of initial material from which the biochar was produced, the reduction of Cfree PAHs content in sewage sludge varied from 17.4% to 58.0%. Both the temperature and the particle size of biochar had an effect on PAH free concentration reduction. Biochars characterised by a low polarity index (O/C or (O+N)/C) reduced the level of Cfree PAHs better than biochars with a higher polarity index value. PMID:24495539

Oleszczuk, Patryk; Zieli?ska, Anna; Cornelissen, Gerard

2014-03-01

6

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

SciTech Connect

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

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

2008-12-15

7

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

PubMed

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

Sower, Gregory James; Anderson, Kim A

2008-12-15

8

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

9

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

10

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

11

Effect of dissolved oxygen concentration on sludge settleability  

Microsoft Academic Search

This laboratory study presents a detailed evaluation of the effects of dissolved oxygen concentration and accumulation of storage polymers on sludge settleability in activated sludge systems with an aerobic selector. The oxygen and substrate availability regime were simulated in laboratory sequencing batch reactor systems. The experiments showed that low dissolved oxygen concentration (=1.1 mg O 2 l -1) had a strong negative effect

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

2003-01-01

12

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

13

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

SciTech Connect

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

Nazarov, Sergei A [Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, St.-Petersburg (Russian Federation)

2012-09-30

14

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

15

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

16

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

17

Estival Distribution of Dissolved Metal Concentrations in Liaodong Bay  

Microsoft Academic Search

Abstact  The temporal and spatial distributions of Cu, Pb, Zn, and Cd in surface water of the Liaodong Bay were studied based on samples\\u000a collected at 16 sites in June and August from 2001 to 2005. The temporal distribution showed decreasing trends. The concentrations\\u000a of dissolved metals in the Liaodong Bay were 4.34, 3.21, 31.54, and 0.995 ?g\\/L for Cu, Pb, Zn,

L. Wan; N. B. Wang; Q. B. Li; Z. C. Zhou; B. Sun; K. Xue; Z. Q. Ma; J. Tian; N. Du

2008-01-01

18

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

19

Dissolved Neodymium Isotopes and Concentrations in the South Pacific  

NASA Astrophysics Data System (ADS)

The isotopic composition of dissolved Neodymium (expressed as ?Nd) in seawater is becoming increasingly established as a tracer for present and past water mass structure and flow paths. The South Pacific represents the largest sector of the Southern Ocean and harbors major areas of bottom and intermediate water mass formation and is therefore a key area for understanding present and past deep ocean circulation. While more dissolved Nd data are becoming available from different ocean basins, the South Pacific is still understudied with respect to the distribution of Nd isotopes and concentrations. In this study we have analyzed dissolved Nd isotopes and concentrations from 11 water column profiles across the South Pacific between 46°S and 69°S that sample all water masses. Our data show that the bottom water in the vicinity of the Ross Sea (Ross Sea Bottom water, RSBW) is represented by an ?Nd value of ~ -7, while the overlying Circumpolar Deep Water (CDW) carries a signature of ?Nd = -8 to -9. The characteristic Nd isotopic signal of RSBW can be tracked along its flow path into the southeast Pacific where it progressively looses its signal through interaction with ambient CDW. The easternmost stations, closer to South America, exhibit an excursion towards radiogenic ?Nd at ?2000 m water depth. This change towards more positive ?Nd coincides with low oxygen and high phosphate concentrations representing Pacific Deep Water (PDW) and possibly indicates water mass mixing of CDW with more radiogenic PDW. While the Nd isotopic composition shows apparent variations between stations and different water masses, the concentration profiles show a rather uniform and gradual increase with depth, a pattern typical for open ocean settings. Spatial and vertical contrasts in Nd isotopic values throughout the South Pacific indicate that Nd isotopes can be used as a water mass tracer in this region. It is reasonable to infer that local lithology in the Ross Sea influenced the Nd isotopic signature of newly formed RSBW, thereby tagging it with an ?Nd signal distinct from other water masses in the South Pacific. This suggests that ?Nd can be used in downcore studies to better understand past fluctuations of deep water advection in the South Pacific.

Basak, C.; Pahnke, K.

2013-12-01

20

Aerobic sludge digestion under low dissolved oxygen concentrations.  

PubMed

Low dissolved oxygen (DO) concentrations occur commonly in aerobic digesters treating thickened sludge, with benefits of smaller digester size, much reduced aeration cost, and higher digestion temperature (especially important for plants in colder areas). The effects of low DO concentrations on digestion kinetics were studied using the sludge from municipal wastewater treatment plants in Akron, Ohio, and Los Lunas, New Mexico. The experiments were conducted in both batch digestion and a mixed mode of continuous, fed-batch, and batch operations. The low DO condition was clearly advantageous in eliminating the need for pH control because of the simultaneous occurrence of nitrification and denitrification. However, when compared with fully aerobic (high DO) systems under constant pH control (rare in full-scale plants), low DO concentrations and a higher solids loading had a negative effect on the specific volatile solids (VS) digestion kinetics. Nonetheless, the overall (volumetric) digestion performance depends not only on the specific digestion kinetics, but also the solids concentration, pH, and digester temperature. All of the latter factors favor the low DO digestion of thickened sludge. The significant effect of temperature on low DO digestion was confirmed in the mixed-mode study with the Akron sludge. When compared with the well-known empirical correlation between VS reduction and the product (temperature x solids retention time), the experimental data followed the same trend, but were lower than the correlation predictions. The latter was attributed to the lower digestible VS in the Akron sludge, the slower digestion at low DO concentrations, or both. Through model simulation, the first-order decay constant (kd) was estimated as 0.004 h(-1) in the mixed-mode operations, much lower than those (0.011 to 0.029 h(-1)) obtained in batch digestion. The findings suggested that the interactions among sludges with different treatment ages may have a substantially negative effect on digestion kinetics. The use of multistage digesters, especially with small front-end reactors, may be advantageous in both "process" kinetics and "biological reaction" kinetics for sludge digestion. PMID:15523791

Arunachalam, RaviSankar; Shah, Hemant K; Ju, Lu-Kwang

2004-01-01

21

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

Microsoft Academic Search

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

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

22

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

Microsoft Academic Search

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

Gerard Cornelissen; Dag Broman; Kristoffer Næs

2010-01-01

23

Factors controlling concentration, export, and decomposition of dissolved organic nutrients in the Everglades of Florida  

Microsoft Academic Search

Water draining from the Everglades marshes of southern Florida contains high concentrations of dissolved organic C (DOC), N (DON), and in some locations, P (DOP). These dissolved organic nutrients carry over 90% of the N and organic C, and about 25% of the P exported downstream in the Everglades. Our objectives were to describe the most important aspects of the

ROBERT G. QUALLS; CURTIS J. RICHARDSON

2002-01-01

24

Factors controlling concentration, export, and decomposition of dissolved organic nutrients in the Everglades of Florida  

Microsoft Academic Search

Water draining from the Everglades marshes of southern Florida containshigh concentrations of dissolved organic C (DOC), N (DON), and in somelocations, P (DOP). These dissolved organic nutrients carry over 90% of the Nand organic C, and about 25% of the P exported downstream in the Everglades.Ourobjectives were to describe the most important aspects of the origin and fateofdissolved organic matter

Robert G. Qualls; Curtis J. Richardson

2003-01-01

25

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...

26

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

USGS Publications Warehouse

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

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

1996-01-01

27

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

28

Dissolved volatile concentrations in an ore-forming magma  

USGS Publications Warehouse

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

Lowenstern, J. B.

1994-01-01

29

Riparian control on NO 3 ? , DOC, and dissolved Fe concentrations in mountainous streams, northern Japan  

Microsoft Academic Search

We evaluated (1) the longitudinal pattern of stream chemistry and (2) the effects of the riparian zone on this longitudinal\\u000a pattern for nitrate (NO3\\u000a ?), dissolved organic carbon (DOC), and total dissolved iron (Fe). We selected two small watersheds; the “southern watershed”\\u000a had an extending riparian wetland and the “northern watershed” had a narrow riparian area. Stream NO3\\u000a ? concentrations

Yasunori Nakagawa; Hideaki Shibata; Fuyuki Satoh; Kaichiro Sasa

2008-01-01

30

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

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

Influence of dissolved-air concentration on spatial distribution of bubbles for sonochemistry.  

PubMed

The pulsation of ultrasonic cavitation bubbles at various dissolved-air concentration in a sonochemical reaction field of standing-wave type is investigated experimentally by laser-light scattering. When a thin light sheet, finer than half the wavelength of sound, is introduced into the cavitation bubbles at an antinode of sound pressure, the scattered light intensity oscillates. The peak-to-trough light intensity is correlated with the number of bubbles that contribute to the sonochemical reaction. It is shown that as the dissolved air concentration becomes higher, the weighted center of the spatial distribution of the peak-to-trough intensity tends to shift towards the liquid surface. At higher concentration of the dissolved air, a great deal of bubbles with size distribution generated due to coalescence between bubbles disturbs sound propagation to change the sound phase easily. A standing wave to trap tiny oscillating bubbles is established only at the side which is nearer to the liquid surface. Also at higher concentration, liquid flow induced by drag motion of bubbles by the action of radiation force becomes apparent and position-unstable region of bubble is enlarged from the side of sound source towards the liquid surface. Therefore, the position of oscillating bubbles active for sonochemical reaction is limited at the side which is nearer to the liquid surface at higher concentration of the dissolved air. PMID:16780909

Tuziuti, Toru; Yasui, Kyuichi; Sivakumar, Manickam; Iida, Yasuo

2006-12-22

33

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

PubMed

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

Henssge, Antje; Acker, Jörg; Müller, Constanze

2006-01-15

34

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

35

Concentration of viruses and dissolved DNA from aquatic environments by vortex flow filtration.  

PubMed

Vortex flow filtration (VFF) was used to concentrate viruses and dissolved DNA from freshwater and seawater samples taken in Florida, the Gulf of Mexico, and the Bahamas Bank. Recoveries of T2 phage and calf thymus DNA added to artificial seawater and concentrated by VFF were 72.8 and 80%, respectively. Virus concentrations determined by transmission electron microscopy of VFF-concentrated samples ranged from 3.4 x 10(7)/ml for a eutrophic Tampa Bay sample to 2.4 x 10(5) for an oligotrophic oceanic surface sample from the southeastern Gulf of Mexico. Viruslike particles were also observed in a sample taken from a depth of 1,500 m in the subtropical North Atlantic Ocean. Filtration of samples through Nuclepore or Durapore filters (pore size, 0.2 micron) prior to VFF reduced phage counts by an average of two-thirds. Measurement of dissolved-DNA content by Hoechst 33258 fluorescence in environmental samples concentrated by VFF yielded values only ca. 35% of those obtained for samples concentrated by ethanol precipitation (the standard dissolved-DNA method). However, ethanol precipitation of VFF-concentrated extracts resulted in an increase in measurable DNA, reaching 80% of the value obtained by the standard method. These results indicate that a portion of the naturally occurring dissolved DNA is in a form inaccessible to nucleases and Hoechst stain, perhaps bound to protein or other polymeric material, and is released upon ethanol precipitation. Viral DNA contents estimated from viral counts averaged only 3.7% (range, 0.9 to 12.3%) of the total dissolved DNA for samples from freshwater, estuarine, and offshore oligotrophic environments.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1768090

Paul, J H; Jiang, S C; Rose, J B

1991-08-01

36

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

37

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, ...

38

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...

39

Effect of dissolved oxygen concentration on red pigment and citrinin production by Monascus purpureus ATCC 36928  

Microsoft Academic Search

The present study investigated the effects of agitation speed, N (200, 500, 600 or 700 rpm), and dissolved oxygen concentration, C (120, >70, 70, 60, 10 or î 10%), on red pigment and citrinin production by Monascus purpureus ATCC 36928, cultivated in liquid medium by a batch process. The gas flow rate was the same for all runs with C

D. G. Pereira; A. Tonso; B. V. Kilikian

2008-01-01

40

Concentrations of Total Dissolved Solids Preferred or Avoided by Endangered Colorado River Fishes  

Microsoft Academic Search

Juveniles (age 0–1) of three endangered Colorado River fishes were subjected to a gradient of total dissolved solids (TDS) to determine the concentrations that they preferred or avoided. Preferred and avoided TDS concentrations, respectively, for juveniles of each species were: Colorado squawfish Ptychocheilus lucius, 560–1,150 mg\\/liter and greater than 4,400 mg\\/liter; humpback chub Gila cypha, 1,000–2,500 mg\\/liter and greater than

R. Pimentel; R. V. Bulkley

1983-01-01

41

Longitudinal patterns of dissolved organic carbon concentration and suspended bacterial density along a blackwater river  

Microsoft Academic Search

Dissolved organic carbon (DOC) is the dominant form of carbon in transport in blackwater rivers, and bacteria are the major\\u000a biological agents of its utilization. This study describes longitudinal patterns in DOC concentration and relates them to\\u000a suspended bacterial populations in the channel. Concentrations of total DOC, three molecular weight fractions, and bacterial\\u000a numbers were determined at 12 sites along

Francesc Sabater; Judy L. Meyer; Rick T. Edwards

1993-01-01

42

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

PubMed

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

Hinshaw, Sarra E; Dahlgren, Randy A

2013-02-01

43

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

44

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

45

Catchment-scale dissolved carbon concentrations and export estimates across six subarctic streams in northern Sweden  

NASA Astrophysics Data System (ADS)

Climatic change is currently enhancing permafrost thawing and the flow of water through the landscape in subarctic and arctic catchments, with major consequences for the carbon export to aquatic ecosystems. We studied stream water carbon export in several tundra-dominated catchments in northern Sweden. There were clear seasonal differences in both dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. The highest DOC concentrations occurred during the spring freshet while the highest DIC concentrations were always observed during winter baseflow conditions for the six catchments considered in this study. Long-term trends for the period 1982 to 2010 for one of the streams showed that DIC concentrations has increased by 9% during the 28 yr of measurement while no clear trend was found for DOC. Similar increasing trends were also found for conductivity, Ca and Mg. When trends were discretized into individual months, we found a significant linear increase in DIC concentrations with time for September, November and December. In these subarctic catchments, the annual mass of C exported as DIC was in the same order of magnitude as DOC; the average proportion of DIC to the total dissolved C exported was 61% for the six streams. Furthermore, there was a direct relationship between total runoff and annual dissolved carbon fluxes for these six catchments. These relationships were more prevalent for annual DIC exports than annual DOC exports in this region. Our results also highlight that both DOC and DIC can be important in high-latitude ecosystems. This is particularly relevant in environments where thawing permafrost and changes to subsurface ice due to global warming can influence stream water fluxes of C. The large proportion of stream water DIC flux also has implications on regional C budgets and needs to be considered in order to understand climate-induced feedback mechanisms across the landscape.

Giesler, R.; Lyon, S. W.; Mörth, C.-M.; Karlsson, J.; Karlsson, E. M.; Jantze, E. J.; Destouni, G.; Humborg, C.

2014-01-01

46

Dissolved organic matter (DOM) concentration and quality in a forested mid-Atlantic watershed, USA  

Microsoft Academic Search

Understanding the quantity and quality of dissolved organic matter (DOM) in potential watershed sources is critical for explaining\\u000a and quantifying the exports of DOM in stream runoff. Here, we examined the concentration and quality of DOM for ten watershed\\u000a sources in a 12 ha forested catchment over a two-year period. DOM composition was evaluated for: throughfall, litter leachate,\\u000a soil water (zero

Shreeram Inamdar; Nina Finger; Shatrughan Singh; Myron Mitchell; Delphis Levia; Harsh Bais; Durelle Scott; Patrick McHale

47

in situ interlaboratory comparisons for dissolved oxygen concentration and pH  

Microsoft Academic Search

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

Lauri Jalukse; Viktor Vabson; Ivo Leito

2006-01-01

48

Measurement of dissolved oxygen concentration field in a microchannel using PtOEP\\/PS film  

Microsoft Academic Search

\\u000a Abstract  A planar optode system based on an oxygen quenchable luminophore platinum (II) octaethyporphrin (PtOEP) bound with thin polystyrene\\u000a (PS) film and UV light-emitting diodes (UV-LEDs) was developed to measure the dissolved oxygen (DO) concentration field in\\u000a microscale water flows. An intensity-based method adopting a pixel-to-pixel in situ calibration technique was used to visualize\\u000a DO concentration fields in a Y-shaped microchannel.

Dae Hun Song; Hyun Dong Kim; Kyung Chun Kim

49

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

PubMed

Evaluating water quality and the health of aquatic organisms is challenging in systems with systematic diel (24 h) or less predictable runoff-induced changes in water composition. To advance our understanding of how to evaluate environmental health in these dynamic systems, field studies of diel cycling were conducted in two streams (Silver Bow Creek and High Ore Creek) affected by historical mining activities in southwestern Montana. A combination of sampling and modeling tools was used to assess the toxicity of metals in these systems. Diffusive Gradients in Thin Films (DGT) samplers were deployed at multiple time intervals during diel sampling to confirm that DGT integrates time-varying concentrations of dissolved metals. Site specific water compositions, including time-integrated dissolved metal concentrations determined from DGT, a competitive, multiple-toxicant biotic ligand model, and the Windemere Humic Aqueous Model Version 6.0 (WHAM VI) were used to determine the equilibrium speciation of dissolved metals and biotic ligands. The model results were combined with previously collected toxicity data on cutthroat trout to derive a relationship that predicts the relative survivability of these fish at a given site. This integrative approach may prove useful for assessing water quality and toxicity of metals to aquatic organisms in dynamic systems and evaluating whether potential changes in environmental health of aquatic systems are due to anthropogenic activities or natural variability. PMID:22481055

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

2012-05-15

50

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

PubMed

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

Lue, Ang; Zhang, Lina

2009-05-13

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

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

53

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

PubMed

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

Cheng, Xiangju; Chen, Xuewei

2013-05-01

54

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

55

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

PubMed

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

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

2014-01-01

56

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

PubMed

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

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

2010-06-01

57

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

58

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

PubMed

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

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

2012-04-01

59

Concentration of Dissolved Gases in the Williamette, Cowlitz, and Boise Rivers, 1970-1972.  

National Technical Information Service (NTIS)

Data on dissolved nitrogen, dissolved oxygen, total gas pressure, and water temperatures are presented for the Willamette, Cowlitz, and Boise rivers. Water samples were taken upstream and downstream of dams and over a wide range of river and dam discharge...

B. H. Monk E. Dawley K. Beiningen

1975-01-01

60

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

61

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

PubMed

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

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

2013-04-01

62

Acquiring reproducible fluorescence spectra of dissolved organic matter at very low concentrations.  

PubMed

A method that would allow for fast and reliable measurements of dissolved organic matter (DOM), both at low and high concentration levels would be a valuable tool for online monitoring of DOM. This could have applications in a variety of areas including membrane treatment systems for drinking water applications which is of interest to our group. In this study, the feasibility of using fluorescence spectroscopy for monitoring DOM at very low concentration levels was demonstrated with an emphasis on optimizing the instrument parameters necessary to obtain reproducible fluorescence signals. Signals were acquired using a cuvette or a fibre optic probe assembly, the latter which may have applications for on-line or in-line monitoring. The instrument parameters such as photomultiplier tube (PMT) voltage, scanning rate and slit width were studied in detail to find the optimum parameter settings required. The results showed that larger excitation and emission slit widths were preferred, over larger PMT voltage or lower scanning rates, to obtain reproducible and rapid measurements when measuring very low concentration levels of DOM. However, this approach should be implemented with caution to avoid any reduction of the signal resolution. PMID:19759440

Peiris, B R H; Budman, H; Moresoli, C; Legge, R L

2009-01-01

63

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

64

The Influence of Subsurface Processes on the Concentration and Composition of Dissolved Organic Matter  

NASA Astrophysics Data System (ADS)

Microbial and geochemical interactions in the subsurface can result in chemical alteration and fractionation of organic matter thereby altering the nature and composition of dissolved organic matter (DOM) in groundwater and in surface waters dominated by ground water inflow. In this paper, the results of a study designed to determine the effectiveness of subsurface processes for removing DOM from two surface waters in Southern California will be presented. The recharge zones immediately underneath two infiltration basins, Anaheim Lake and Kraemer Basin, were found to be very active with respect to changes in the amounts and reactivities of the DOM. In all cases, dissolved organic carbon (DOC) concentrations decrease as water moves from the basins into the regional aquifer system. Data obtained from relatively shallow wells located near the infiltration basins (travel times less than 30 days) indicate that a large amount of DOM is removed during the first stages of transport in the subsurface. Parcels of water from both basins were followed for up to 360 days as the water moved away from the infiltration basins. DOC concentrations and specific ultraviolet absorbance (SUVA), an excellent indicator of aromatic carbon content of DOM, continued to decrease substantially with a general decrease in DOC concentration of about 70%. Regardless of initial DOC concentrations present in the infiltration basins, values decreased to approximately 1.3 mg C/L at the furthest points sampled. Analyses of organic matter isolates obtained by chromatographic methods indicated greater removal of aromatic molecules and preservation of branched chain aliphatic and alicyclic structures more resistant to biodegradation. Compared to samples from a wide range of environments, the DOM in the down gradient wells most closely resembled similar materials obtained from other groundwater systems and those of microbial origin. These results suggest that subsurface processes are significant in the metabolism of terrestrially derived material and contribute to the evolution of DOM pools from ones dominated by terrestrially derived material to those of microbial origin. Ultimately, these processes exert strong controls on the composition and reactivity of DOM in ground water and contribute to the pools of compounds comprising DOM in surface water systems receiving ground water discharge.

Aiken, G.

2004-12-01

65

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

66

Optimization of pulsed feeding in a Baker's yeast process with dissolved oxygen concentration as a control parameter  

Microsoft Academic Search

The aim of the study was to optimize nutrient inflow in baker's yeast cultivation where the nutrient was dosed in portions, according to the cyclic changes in dissolved oxygen concentration; the optimization criterion being a simultaneous maximization of biomass yield and specific growth rate. The maximization of such a criterion required that the glucose concentration in the culture medium should

Andrzej Kasperski; Tadeusz Mi?kiewicz

2008-01-01

67

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

68

Salicylhydroxamic Acid (SHAM) Inhibition of the Dissolved Inorganic Carbon Concentrating Process in Unicellular Green Algae 1  

PubMed Central

Rates of photosynthetic O2 evolution, for measuring K0.5(CO2 + HCO3?) at pH 7, upon addition of 50 micromolar HCO3? 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 K1(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 CO2 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 O2 evolution dependent on low levels of dissolved inorganic carbon (50 micromolar Na-HCO3), and the rate of 14CO2 fixation with 100 micromolar [14C] HCO3?. Salicylhydroxamic acid inhibition of O2 evolution and 14CO2-fixation was reversed by higher levels of NaHCO3. Thus, salicylhydroxamic acid inhibition was apparently not affecting steps of photosynthesis other than CO2 accumulation. Although salicylhydroxamic acid is an inhibitor of alternative respiration in algae, it is not known whether the two processes are related.

Goyal, Arun; Tolbert, N. Edward

1990-01-01

69

Freely floating smectic films.  

PubMed

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

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

2014-05-19

70

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

PubMed Central

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

Clark, D R; Flynn, K J

2000-01-01

71

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

72

Dissolved heavy metal concentrations of the Kralk?z?, Dicle and Batman dam reservoirs in the Tigris River basin, Turkey.  

PubMed

Water samples were collected at monthly intervals during 1 year of monitoring from Kralk?z?, Dicle and Batman dam reservoirs in the Tigris River basin to assess the concentrations of dissolved heavy metals and to determine their spatial and seasonal variations. The results indicated that dissolved heavy metal concentrations in the reservoirs were very low, reflecting the natural background levels. The lowest total metal concentrations in the three dam reservoirs were detected at sampling sites close to the dam wall. However, the highest total concentrations were observed at sites, which are located at the entrance of the streams to the reservoirs. Fe, Cr and Ni were the most abundant elements in the reservoirs, whereas Cd and As were the less abundant. The mean concentrations of dissolved metals in the dam reservoirs never exceeded the maximum permitted concentrations established by EC (European Community), WHO and USEPA drinking water quality guidelines. All heavy metals showed significant seasonal variations. As, Cd, Cr, Cu, Fe, Ni and Pb displayed higher values in the dry season, while higher values for Zn in the wet season. Cluster analysis grouped all ten sampling sites into three clusters. Clusters 1 and 2, and cluster 3 corresponded to relatively low polluted and moderate polluted regions, respectively. PCA/FA demonstrated the dissolved metals in the dam reservoirs controlled by natural sources. PMID:23800586

Varol, Memet

2013-10-01

73

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

74

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

75

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

76

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

Microsoft Academic Search

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

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

2009-01-01

77

Research Note: Effects of Ozonated Water Spray Droplet Size and Distance on the Dissolved Ozone Concentration at the Spray Target  

Microsoft Academic Search

Dissolved ozone concentration (DOC) of ozonated water (OW) sprayed from four different distances using three different droplet sizes (expressed in terms of Sauter mean diameter; small, medium, large) was measured at the spray target to obtain fundamental data for improving disease control efficacy when spraying OW onto plants. DOC in the OW at the spray target decreased with decreasing droplet

Kazuhiro Fujiwara; Takuya Fujii

2004-01-01

78

EFFECTS OF LOWERED DISSOLVED OXYGEN CONCENTRATION ON THE TOXICITY OF 1,2,4-TRICHLOROBENZENE TO FATHEAD MINNOWS  

EPA Science Inventory

Fathead minnows Pimephales promelas were exposed for 32 days, starting with embryos and continuing through early juvenile development, to five concentrations of 1,2,4-trichlorobenzene (1,2,4-TCB) with a control. Each series of treatments was completed at three dissolved oxygen (D...

79

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....

80

Effect of Dissolved Oxygen Concentrations on Fish and Invertebrates in Large Experimental Channels.  

National Technical Information Service (NTIS)

The responses of fish (smallmouth bass, channel catfish, golden shiners, and bluegill), zooplankton, and benthic macroinvertebrates to various levels of dissolved oxygen (DO) were monitored in six large outdoor channels at TVA's Aquatic Research Laborator...

J. H. Heuer W. M. Seawell

1987-01-01

81

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

82

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

83

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

84

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

USGS Publications Warehouse

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

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

2004-01-01

85

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

USGS Publications Warehouse

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

Cravotta, III, C. A.

2008-01-01

86

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

87

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

PubMed

Workers have frequently disregarded long-term dermal exposure to low concentration of gaseous volatile organic compounds (VOCs). To assess dermal exposure risk to gaseous VOCs, equilibrium partitioning coefficients (p(c)) at the air-sweat interface on human skin surface must be examined. This study analyzed the p(c) values of hydrophilic iso-propanol (IPA), methyl ethyl ketone (MEK), and hydrophobic benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene (BTEXs) at the air-water and air-sweat interfaces at 27-47 degrees C. The hydrophilic VOCs were dissolved in pure water and artificial human sweat liquors at approximately 10-125 mg/L, and hydrophobic VOCs were at approximately 0.55 mg/L. According to experimental results, the dissolved VOC concentration and salt contents simultaneously have a co-effect on p(c) during human dermal exposure to gaseous VOCs. The salt effect resulted in increase of p(c) for hydrophilic and hydrophobic VOCs, and the dissolved VOC concentration effect resulted in a reduction in p(c), which is dominant for hydrophilic compounds of high concentrations of aqueous VOCs. The p(c) data were utilized for further assessment of risk due to dermal exposure to VOCs. PMID:18161563

Cheng, Wen-Hsi

2008-01-01

88

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

SciTech Connect

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

Early, T.O.

1986-03-14

89

New Spectrophotometric Method for Determination of Dissolved Proteins in Low Concentration Range.  

National Technical Information Service (NTIS)

The objective of this research was to introduce a new spectrophotometric method for determination of dissolved proteins in the 10-2500 mg/l range using carbonate-tartrate reagent phosphomolybdic-phosphotungstic reagent, and copper sulfate. The new analyti...

L. K. Wang A. E. Thayer

1983-01-01

90

Isotopic Chemical and Dissolved Gas Concentrations in Groundwater Near Venterstad, Cape Province.  

National Technical Information Service (NTIS)

Groundwater was collected for a multi parameter investigation from 27 boreholes within a radius of 120 km from Venterstad (Cape Province). The samples were analysed for the isotopes carbon-14, carbon-13, oxygen-18, tritium and radon-222, for the dissolved...

J. C. Vogel A. S. Talma T. H. E. Heaton

1980-01-01

91

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

USGS Publications Warehouse

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

Chapman, Duane C.; Deters, Joseph E.

2009-01-01

92

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 3mgl(-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 2mgl(-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

93

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

94

Relationship between the optical properties of chromophoric dissolved organic matter and total concentration of dissolved organic carbon in the southern Baltic Sea region  

Microsoft Academic Search

Absorption and fluorescence of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) measurements were performed during three oceanographic surveys in 1994 in the southern Baltic Sea (Polish area of the Baltic Proper). DOC was measured both by high-temperature catalytic oxidation (HTCO) and low-temperature oxidation (LTO) conventional persulphate methods. CDOM fluorescence was shown to be highly correlated with absorption,

Giovanni M. Ferrari; Mark D. Dowell; Stefania Grossi; Cristina Targa

1996-01-01

95

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

96

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

97

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

EPA Science Inventory

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

98

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

99

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

SciTech Connect

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

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

1990-12-01

100

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

101

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

PubMed Central

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

Garcia, Rolando G.

1972-01-01

102

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

SciTech Connect

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

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

1999-02-01

103

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

NASA Astrophysics Data System (ADS)

Numerous studies of marine environments show that dissolved organic carbon (DOC) concentrations in sediments are typically tenfold higher than in the overlying water. Large concentration gradients near the sediment-water interface suggest that there may be a significant flux of organic carbon from sediments to the water column. Furthermore, accumulation of DOC in the porewater may influence the burial and preservation of organic matter by promoting geopolymerization and/or adsorption reactions. We measured DOC concentration profiles (for porewater collected by centrifugation and "sipping") and benthic fluxes (with in situ and shipboard chambers) at two sites on the North Carolina continental slope to better understand the controls on porewater DOC concentrations and quantify sediment-water exchange rates. We also measured a suite of sediment properties (e.g., sediment accumulation and bioturbation rates, organic carbon content, and mineral surface area) that allow us to examine the relationship between porewater DOC concentrations and organic carbon preservation. Sediment depth-distributions of DOC from a downslope transect (300-1000 m water depth) follow a trend consistent with other porewater constituents (?CO 2 and SO 42-) and a tracer of modern, fine-grained sediment (fallout Pu), suggesting that DOC levels are regulated by organic matter remineralization. However, remineralization rates appear to be relatively uniform across the sediment transect. A simple diagenetic model illustrates that variations in DOC profiles at this site may be due to differences in the depth of the active remineralization zone, which in turn is largely controlled by the intensity of bioturbation. Comparison of porewater DOC concentrations, organic carbon burial efficiency, and organic matter sorption suggest that DOC levels are not a major factor in promoting organic matter preservation or loading on grain surfaces. The DOC benthic fluxes are difficult to detect, but suggest that only 2% of the dissolved organic carbon escapes remineralization in the sediments by transport across the sediment-water interface.

Alperin, Marc J.; Martens, Christopher S.; Albert, Daniel B.; Suayah, Ismail B.; Benninger, Larry K.; Blair, Neal E.; Jahnke, Richard A.

1999-02-01

104

[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

105

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

PubMed

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

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

2012-11-01

106

Effect of dissolved oxygen concentrations on fish and invertebrates in large experimental channels  

SciTech Connect

The responses of fish (smallmouth bass, channel catfish, golden shiners, and bluegill), zooplankton, and benthic macroinvertebrates to various levels of dissolved oxygen (DO) were monitored in six large outdoor channels at TVA's Aquatic Research Laboratory at Browns Ferry Nuclear Plant. Nitrogen stripping was used to remove oxygen from the water, and aquatic organisms were exposed to target levels of 5, 4, 3, and 2 mg/L (2 channels) and to an untreated control from July 24, 1984 until September 24, 1984. Responses of adult golden shiners, bluegill, and channel catfish to DO were not consistent, probably because of predation by smallmouth bass on golden shiners and competition between bluegill and channel catfish. Bluegill spawned successfully only in the control. Cleaned nests were found in the 5 mg/L treatment and partially cleaned nests in the 3 and 4 mg/L treatments, but no evidence of nesting was found in the 2 mg/L treatment. 14 refs., 8 figs., 7 tabs.

Heuer, J.H.; Seawell, W.M.

1987-07-01

107

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

108

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

109

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

Microsoft Academic Search

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

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

2011-01-01

110

EFFECTS OF MINERAL ACID DEPOSITION ON CONCENTRATIONS OF DISSOLVED ORGANIC ACIDS IN SURFACE WATERS  

EPA Science Inventory

Data have accumulated in recent years from a variety of sources suggesting that concentrations of organic acids may have decreased in surface waters in response to increased mineral acidity. These include laboratory studies, paleoecological investigations, theoretical considerati...

111

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

PubMed

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

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

2012-06-15

112

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

113

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

114

Concentrations of dissolved and suspended particulate Cd, Cu, Mn, Ni, Pb and Zn in surface waters around the coasts of England and Wales and in adjacent seas  

NASA Astrophysics Data System (ADS)

Trace metal concentrations in British coastal waters were determined during the summers of 1991 and 1992. The measured concentrations of Cd, Cu, Ni, Pb and Zn are in general agreement with those previously reported in the literature. Higher offshore dissolved Mn concentrations (mean = 1·2 ?g l -1) are attributed to summertime increases in benthic Mn fluxes to the water column. Concentrations of all determinands were generally higher in the Irish Sea and North Sea than in the English Channel. This reflects the larger riverine component of the North and Irish Seas, and the stronger influence of North Atlantic water in the English Channel. Elevated dissolved and suspended particulate Pb concentrations in the Dogger Bank region are tentatively attributed to atmospheric inputs, and reduced removal by the lower concentrations of suspended particulate matter at these stations. Of the six major estuaries sampled, the Tweed was regarded as a reference site since it has a sparsely populated catchment area with little industry. Dissolved Mn concentrations in the Tweed were generally lower than those in the other estuaries, although the highest suspended particulate Mn (6600 ?g g -1) and Ni (69 ?g g -1) concentrations were found there. These high particulate concentrations are attributed to the oxidation of Mn(II) and the subsequent scavenging of Ni by the newly precipitated Mn-oxyhydroxides. Highest suspended particulate Cd (6·1 ?g g -1), Cu (200 ?g g -1), Pb (650 ?g g -1) and Zn (1400 ?g g -1), and dissolved Pb (1·1 ?g g -1) and Zn (25 ?g l -1) concentrations were observed in the Tyne. The Tees had the highest dissolved Cu (10 ?g l -1) concentration, while the Humber and Mersey had the highest dissolved Cd (220 ng l -1) and Ni concentrations (9·4 ?g l -1), respectively. The high concentrations are attributed to anthropogenic inputs.

Laslett, R. E.

1995-01-01

115

Hydrogen peroxide automatic dosing based on dissolved oxygen concentration during solar photo-Fenton  

Microsoft Academic Search

Nowadays the potential of photo-Fenton process for decontamination of biologically persistent wastewater is widely recognized. In this process, hydrogen peroxide consumption could be considered as one of the factors that considerably affects costs. This highlights that an automatically hydrogen peroxide dosing system to keep the concentration optimized throughout the process would be a valuable tool for industrial wastewater remediation plants.

L. Prieto-Rodríguez; I. Oller; A. Zapata; A. Agüera; S. Malato

2011-01-01

116

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

NASA Astrophysics Data System (ADS)

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

Derx, J.; Blaschke, A. P.

2012-04-01

117

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 ...

118

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

119

Concentration and transport of dissolved and suspended substances in the Orinoco River  

Microsoft Academic Search

The Orinoco River, which is hydrologically unregulated and has a minimally disturbed watershed, was sampled quantitatively\\u000a over a four-year interval. In conjunction with the sampling, a method was developed for quantifying statistical uncertainty\\u000a in the estimates of annual transport. The discharge-weighted mean concentration of total suspended solids in the Orinoco River\\u000a is 80 mg\\/l, which corresponds to total annual transport

William M. Lewis; James F. Saunders

1989-01-01

120

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

121

Dissolved organic carbon concentrations vary with season and land use - investigations from two fens in Northeastern Germany over two years  

NASA Astrophysics Data System (ADS)

The rising export of dissolved organic carbon (DOC) from peatlands during the last 20 years is of great environmental concern, as DOC harms drinking water quality and diminishes the carbon storage of peatlands. Lack of knowledge particularly exists for fens. The aim of our study was to determine DOC concentrations at an agriculturally used fen and a rewetted fen throughout the year. We measured DOC concentrations in ditch water of these fens in 2011 and 2012. Furthermore, discharge measurements were condcucted to detect DOC export. Overall DOC concentrations at our agriculturally used site and at our rewetted site were 35 mg L-1 and 26 mg L-1 (median), respectively. The maximum DOC concentration at our agriculturally used site was twice as high as at the rewetted site (134 mg L-1 vs. 61 mg L-1). Annual DOC export was calculated for the rewetted site, amounting to 200 kg C ha-1 on average. Our results suggest that rewetting of degraded fens reduces DOC export in the long-term, while agricultural use of fens leads to enhanced decomposition and thus, elevates DOC export.

Schwalm, M.; Zeitz, J.

2014-05-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

123

A Record of Dissolved Metal Concentrations in the Lena River During the Period of Ice Breakup  

NASA Astrophysics Data System (ADS)

The PARTNERS project is a 5-year research program (2002-2007) funded by the Arctic System Science Program of the U.S. National Science Foundation. The objective of the PARTNERS project is to measure several biogeochemical parameters in the six largest rivers that drain the watershed of the Arctic Ocean (Yenisey, Lena, Ob, Mackenzie, Yukon, and Kolyma) as a means to study the origins and fates of continental runoff. As part of the PARTNERS field program for 2004, samples were collected on the Lena River in the spring (May-June) during the period of peak discharge and ice breakup. Samples were collected from the bank at the town of Zhigansk (66.75 N, 23.38 E) once daily from May 28th through June 7th, 2004. The river was completely ice covered at the beginning of this period. The river level rose dramatically each day until ice breakup, which occurred on May 30th. Following breakup, the river level began to drop steadily. Visual observation of daily water samples indicated a darkening of the tannic brown color of the river water as discharge levels increased up until breakup, suggesting an increase in DOC concentrations associated with the peak discharge and ice breakup period. Water samples for metals analyses were syringe filtered in the field through 0.45 um polypropylene and 0.02 um Anotop filter discs and acidified under clean conditions upon return to the laboratory. The samples were analyzed by high-resolution ICPMS for a suite of metals including Ba, Cd, Ce, Co, Cr, Cs, Cu, Fe, Li, Mn, Mo, Ni, Pb, Rb, Re, Sr, Tl, U, V, and Zn. Here we report the results from these analyses as a daily time series of metal concentrations bracketing the ice breakup and peak discharge events. During this relatively short amount of time, significant fluctuations in metal concentrations were observed, which are likely related to concurrent fluctuations in DOC concentrations and other changes in river chemistry occurring during this dynamic period of the annual hydrologic cycle in the watershed.

Monson, O. D.; Guay, C. K.; Holmes, R. M.; Zhulidov, A. V.

2004-12-01

124

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

125

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

126

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

127

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

128

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

129

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

130

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.

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

2014-01-01

131

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

132

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

NASA Astrophysics Data System (ADS)

Falling of rivers into the seas or surging in shallow aquatoria cause the violation of the balance between living and dead matter occurring in the open ocean ( Pelevin and Rostovtseva, 2001). That means in littoral arias the one-parameter model of sea waters optical properties developed for the open ocean (Pelevin and Rostovtseva, 1997) is not valid. We suggest to use the three-parameters model of light scattering and absorbing prop- erties of sea water for the most arias on shelves. The three parameters are: the coeffi- cient of light absorption by coloured matter at 500 nm (coloured matter includes both chlorophyll pigments and "yellow substance"), the coefficient of light absorption by suspended matter and the coefficient of light backscattering by suspended matter. For some specific shelf arias with coloured suspended matter we suggest to add the fourth parameter taking into account the spectral dependence of backscattering by suspended matter. The method of such type arias determination is also given. The algorithm of solution of the inverse problem of these parameters estimation using optical remote sensing data obtained from satellites is developed. It consists of two steps: the rough determination of the parameters values by some spectral characteris- tics and then the minimization of real and model spectra discrepancy. The suggested algorithm was used for spectral distribution of upward radiation mea- sured in the Black, Marmora and Baltic Seas. Comparison of the obtained results with some data of direct measurements carried out in these aquatoria proved the validity of the model for these shelf waters and showed the efficiency of the suggested approach. V.N.Pelevin and V.V.Rostovtseva , 1997, Estimation of lightscattering and lightabsorb- ing admixture concentration in open ocean waters of different types.- Atmospheric and Oceanic Optics, 10(9), 989-995. V.N.Pelevin and V.V.Rostovtseva, 2001, Modelling of optic- biological parameters of open ocean waters. - OCEANOLOGIA, 43(4).

Pelevin, V.; Rostovtseva, V.

133

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, the chemical and physical processes occurring after atmospheric deposition are 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 within 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 (Mn), iron (Fe) and aluminum (Al) concentrations were followed immediately after the seeding with dust and over the following week. The Mn, Fe and Al inventories and loss or dissolution rates were determined. The evolution of the inventories after the two consecutive additions of dust showed distinct behaviors for dissolved Mn, Al and Fe. Even though the mixing conditions differed from one seeding to the other, Mn and Al showed clear increases directly after both seedings due to dissolution processes. Three days after the dust additions, Al concentrations decreased as a consequence of scavenging on sinking particles. Al 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. In the case of dissolved Fe, it appears that the first dust addition resulted in a decrease as it was scavenged by sinking dust particles, whereas the second seeding induced dissolution of Fe from the dust particles due to the excess Fe binding ligand concentrations present at that time. 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 the fractional solubility of metals from dust particles in seawater were 1.44 ± 0.19% and 0.91 ± 0.83% for Al and 41 ± 9% and 27 ± 19% for Mn for the first and the second dust addition. These values are in good agreement with laboratory-based estimates. For Fe no fractional solubility was obtained after the first seeding, but 0.12 ± 0.03% was estimated after the second seeding. Overall, the trace metal dataset presented here makes a significant contribution to enhancing our knowledge on the processes influencing trace metal 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.

2013-04-01

134

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

135

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

136

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

137

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

PubMed

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

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

2012-09-01

138

Morphological and metabolic shifts of Yarrowia lipolytica induced by alteration of the dissolved oxygen concentration in the growth environment.  

PubMed

Yarrowia lipolytica, an ascomycete with biotechnological potential, is able to form either yeast cells or hyphae and pseudohyphae in response to environmental conditions. This study shows that the morphology of Y. lipolytica, cultivated in batch cultures on hydrophilic (glucose and glycerol) and hydrophobic (olive oil) media, was not affected by the nature of the carbon source, nor by the nature or the concentration of the nitrogen source. By contrast, dissolved oxygen concentration (DOC) should be considered as the major factor affecting yeast morphology. Specifically, when growth occurred at low or zero DOC the mycelial and/or pseudomycelial forms predominated over the yeast form independently of the carbon and nitrogen sources used. Experimental data obtained from a continuous culture of Y. lipolytica on glycerol, being used as carbon and energy source, demonstrated that the mycelium-to-yeast form transition occurs when DOC increases from 0.1 to 1.5 mg l(-1). DOC also affected the yeast physiology, as the activity of enzymes implicated in lipid biosynthesis (i.e. ATP-citrate lyase, malic enzyme) was upregulated at high DOC whereas the activity of enzymes implicated in glycerol assimilation (such as glycerol dehydrogenase and kinase) remained fundamentally unaffected in the cell-free extract. PMID:24509502

Bellou, Stamatia; Makri, Anna; Triantaphyllidou, Irene-Eva; Papanikolaou, Seraphim; Aggelis, George

2014-04-01

139

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

140

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

141

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

142

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

NASA Astrophysics Data System (ADS)

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

Barringer, Julia L.; Wilson, Timothy P.; Szabo, Zoltan; Bonin, Jennifer L.; Fischer, Jeffrey M.; Smith, Nicholas P.

2008-01-01

143

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

144

Challenges of using polyethylene passive samplers to determine dissolved concentrations of parent and alkylated PAHs under cold and saline conditions.  

PubMed

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

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

2013-09-17

145

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

146

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

147

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

148

Superovulation in ewes by a single injection of pFSH dissolved in polyvinylpyrrolidone (PVP): effects of PVP molecular weight, concentration and schedule of treatment  

Microsoft Academic Search

Three experiments were carried out to evaluate induction in ewes of superovulation and embryo production by a single injection of a porcine pituitary extract (pFSH) dissolved in polyvinylpyrrolidone (PVP), investigating the effects of PVP molecular weight and its concentration (Experiment I), time and method of treatment (Experiments II and III). All ewes were synchronized for estrus by vaginal sponges impregnated

A. G D’Alessandro; G Martemucci; M. A Colonna; A Borghese; M. G Terzano; A Bellitti

2001-01-01

149

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

National Technical Information Service (NTIS)

The U.S. Geological Survey, Washington State Department of Ecology, and Puyallup Tribe of Indians monitored water temperature, specific conductance, pH, and dissolved-oxygen concentrations in the White River at river miles 4.9 and 1.8 from August until mi...

J. C. Ebbert

2003-01-01

150

Distribution of dissolved-solids concentrations and temperature in ground water of the gulf coast aquifer systems, south-central United States  

USGS Publications Warehouse

The distribution of dissolved-solids concentrations and temperature in waters of 10 of the aquifers comprising the gulf coast aquifer systems of the Gulf Mexico Coastal Plain are mapped at a scale of 1:3,500,000. Dissolved solids concentration in the aquifers of the Tertiary System ranges from less than 500 mg/L at the outcrop and subcrop areas to as much as 150,000 mg/L at the downdip extent of these aquifers. A distinct band of sharply increasing concentration of dissolved-solids occurs at about middip of each aquifer of the Tertiary System. Dissolved-solids concentration in younger aquifers ranges from less than 500 mg/L in outcrop and subcrop areas to about 70,000 mg/L at the downdip extent of these aquifers. Temperature of waters in permeable Tertiary deposits ranges from about 18 C at the outcrop and subcrop areas to 90 C at the downdip extent of these aquifers. Temperature of waters in younger deposits ranges from about 14 C at the outcrop and subcrop areas to 30 C at their downdip extent. (USGS)

Pettijohn, Robert A.; Weiss, Jonathan S.; Williamson, Alex K.

1988-01-01

151

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

152

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

153

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

EPA Science Inventory

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

154

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

PubMed

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

Yanagida, Hirotaka

2008-04-01

155

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

156

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

PubMed

Agriculture often is considered to be a contributor of soluble reactive phosphorus (SRP) and nitrate-N (NO3- -N) to surface waters. This research analyzed SRP and NO3- -N concentrations in groundwater and in a creek fed by groundwater on a valley dairy farm in the Cannonsville basin of the New York City (NYC) watershed. A total of 37 groundwater piezometers were installed to depths of 0.3 to 1.5 m. Water-table depth and concentrations of SRP, NO3- -N, dissolved organic carbon (DOC), and dissolved oxygen were measured at regular intervals over a three-year period. A multivariate mixed model analysis of variance indicated that the SRP and NO3- -N concentrations were controlled primarily by three classes of variables: environmental variables, including precipitation and water table depth; source variables, including manure applied and crop type; and chemical variables, including DOC and dissolved oxygen concentrations in groundwater. The highest groundwater concentrations of N03- -N and SRP were found at the shallowest water-table depths, which has implications for agricultural nutrient management in areas with shallow groundwater. PMID:21449473

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

2011-02-01

157

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

PubMed

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

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

2012-05-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

159

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

Microsoft Academic Search

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

Marley J. Waiser

2006-01-01

160

Increased Concentrations of Dissolved Organic Carbon During the Spring Floods in the Sagavanirktok, Kuparuk and Colville Rivers in the Alaskan Arctic  

NASA Astrophysics Data System (ADS)

Arctic rivers discharge 40 to 80% of their annual water volume during the spring floods in May, June and July. During May and June 2001 and 2002, intensive sampling of the Sagavanirktok, Kuparuk and Colville rivers in the Alaskan Arctic was carried out to address questions related to the transport of dissolved and particulate organic carbon to the coastal Beaufort Sea. In June 2001, water flow increased by approximately 250% during peak discharge in the Sagavanirktok River, at the same time concentrations of dissolved organic carbon (DOC) increased from 167 to 742 micromolar. As water flow decreased in the 4 days following peak discharge, concentrations of DOC decreased to <300 micromolar. Similar results were found for the Kuparuk and Colville rivers. In May 2002, concentrations of DOC in the Kuparuk River increased from 670 to >1140 micromolar in 3 days and decreased with water discharge to 600 micromolar within 6 days of peak water discharge. In the Sagavanirktok River, concentrations of DOC increased from 420 to >600 micromolar during the first two days of water discharge in 2002. However, during the next 4 days, temperature dropped to below freezing and surface water flow in the Sagavanirktok River stopped. Consequently, concentrations of DOC decreased to 440 micromolar. However, when water flow resumed, concentrations of DOC increased to >850 micromolar before dropping to 200 micromolar within 9 days. Concentrations of particulate organic carbon averaged >5% (dry weight) in the Kuparuk River during 2002 and were significantly higher than concentrations found in the Sagavanirktok River (1.6%) during that same period. However, Based on these data, Alaskan Arctic rivers discharge >83% and >88% of the dissolved and particulate carbon, respectively, during the spring floods. These results suggest that the storage and subsequent flushing of organic carbon from arctic soils during the spring floods is an important component of the flux of organic carbon to the coastal Beaufort Sea.

Rember, R. D.; Trefry, J. H.

2003-12-01

161

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

Microsoft Academic Search

Sources and concentrations of dissolved solids and selenium in the San Joaquin River and its tributaries, California, were assessed by a mass-balance approach to determine the effects of tile-drain water and irrigation-return flows on the river. The study included low-flow periods from October 1985 to mid-February 1986 and mid-May 1986 through March 1987, and a high-flow period from mid-February to

D. G. Clifton; R. J. Gilliom

1989-01-01

162

Effect of nitrate concentration on filamentous bulking under low level of dissolved oxygen in an airlift inner circular anoxic-aerobic incorporate reactor.  

PubMed

This laboratory research investigated a possible cause of filamentous bulking under low level of dissolved oxygen conditions (dissolved oxygen value in aerobic zone maintained between 0.6-0.8 mg O2/L) in an airlift inner-circular anoxic-aerobic reactor. During the operating period, it was observed that low nitrate concentrations affected sludge volume index significantly. Unlike the existing hypothesis, the batch tests indicated that filamentous bacteria (mainly Thiothrix sp.) could store nitrate temporarily under carbon restricted conditions. When nitrate concentration was below 4 mg/L, low levels of carbon substrates and dissolved oxygen in the aerobic zone stimulated the nitrate-storing capacity of filaments. When filamentous bacteria riched in nitrate reached the anoxic zone, where they were exposed to high levels of carbon but limited nitrate, they underwent denitrification. However, when nonfilamentous bacteria were exposed to similar conditions, denitrification was restrained due to their intrinsic nitrate limitation. Hence, in order to avoid filamentous bulking, the nitrate concentration in the return sludge (from aerobic zone to the anoxic zone) should be above 4 mg/L, or alternatively, the nitrate load in the anoxic zone should be kept at levels above 2.7 mg NO(3-)-N/g SS. PMID:24520715

Su, Yiming; Zhang, Yalei; Zhou, Xuefei; Jiang, Ming

2013-09-01

163

Coastal sediments in the Gulf of Bothnia as a source of dissolved PCDD/Fs and PCBs to water and fish.  

PubMed

High levels of PCDD/Fs and PCBs in Baltic Sea biota have been a matter of great concern during the last decades. We measured the freely dissolved concentrations of PCDD/Fs and PCBs in sediment pore water and bottom water in eight areas along the Swedish coast of the Gulf of Bothnia, by using state-of-the-art passive samplers. Chemical activity ratios (calculated from freely dissolved concentrations in pore water and bottom water based on chemical activity ratios) for PCDD/Fs were higher than 1 at all stations (PCDD/Fs average 27; stdev 22). High activity ratios suggest that the sediments have a potential to act as a source of dissolved PCDD/Fs to the water column. Activity ratios for PCBs varied between 0.3 and 17 (average 2; stdev 4). The concentrations of PCDD/Fs and PCBs in bottom water were significantly correlated with concentrations in sediment pore water (p<0.00001 to p=0.03) as well as with concentrations in juvenile perch caught in the same areas (p<0.00001 to p=0.02). To our knowledge, this is the first study demonstrating a correlation between in-situ measured freely dissolved PCDD/F concentrations and lipid-normalized contents in stationary fish. Our results confirm that freely dissolved concentrations should be used as chemical predictors of bioaccumulation. The results from this study imply that continued efforts to reduce levels of PCDD/Fs and PCBs in coastal sediments will have positive effects on concentrations of these contaminants in lower trophic levels of Baltic Sea ecosystems. PMID:24802269

Sobek, A; Wiberg, K; Sundqvist, K L; Haglund, P; Jonsson, P; Cornelissen, G

2014-07-15

164

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

165

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

166

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

167

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

SciTech Connect

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

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

1993-04-01

168

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

USGS Publications Warehouse

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

Orlando, James L.; Kuivila, Kathryn M.

2006-01-01

169

Concentrations of total dissolved organic carbon and humic and hydrophilic sub-fractions extracted from major Dutch soil types and their relation with soil properties  

NASA Astrophysics Data System (ADS)

Measurements of the concentrations of dissolved organic carbon (DOC) and its humic and hydrophilic sub-fractions in different soil types, and our understanding of the underlying processes, are still limited. This knowledge gap strongly hampers adequate modelling of the speciation, mobility and bioavailability of trace elements in soils, the reactive DOC concentration being a major controlling parameter, as well as assessments of carbon cycling between soil and water. In this study, we have analysed the concentration of DOC and its humic and hydrophilic sub-fractions in 10-3M CaCl2 extractions of approximately 100 top- and sub-soil samples from major Dutch soil types (sand, peat and clay). A rapid batch fractionation procedure (van Zomeren & Comans, 2007) was used to distinguish the concentrations of dissolved humic acids (HA), fulvic acids (FA), hydrophobic neutrals (HON) and hydrophilic acids (Hy). Field-moist samples were used, as well as dried samples from the archive of samples collected for the realisation of the recently published geochemical soil atlas of The Netherlands (Mol et al., 2012). The latter samples have been incubated for one month, after being re-moisturised to field capacity, prior to the extraction and fractionation procedure, in order to limit previously observed effects of soil-drying on DOC concentration and composition. Substantial differences in the concentration and composition of DOC between dried, re-moisturised and field-moist samples were indeed observed and will be discussed. In addition, and as a first step towards a model for the partitioning of DOC and its humic sub-fractions, empirical partition functions have been derived, which relate their dissolved concentrations to potentially controlling soil properties such as pH, total soil organic matter (SOM) and the reactive surface area of iron- and aluminium(hydr)oxides, as estimated from selective extractions. The resulting empirical functions are discussed in light of current mechanistic views on chemical processes contributing to the solid/liquid partitioning of humic substances in soils. References van Zomeren, A. & Comans, R.N.J. (2007) Measurement of humic and fulvic acid concentrations and dissolution properties by a rapid batch procedure. Environ. Sci. Technol. 41, 6755-6761. Mol, G., Spijker, J., van Gaans, P. & Römkens, P. (eds.). Geochemische bodematlas van Nederland. Wageningen Academic Publishers, 2012, 276 p (in Dutch).

Comans, Rob N. J.; van Zomeren, Andre; Groenenberg, Jan E.

2013-04-01

170

A synthesis of light absorption properties of the Arctic Ocean: application to semianalytical estimates of dissolved organic carbon concentrations from space  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

171

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

PubMed

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

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

2014-03-01

172

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

USGS Publications Warehouse

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

Ebbert, James C.

2003-01-01

173

Model for Evaporation of Freely Falling Droplets.  

National Technical Information Service (NTIS)

Results of theoretical investigations concerning the quasistationary evaporation of freely falling droplets in the continuum regime are presented. The mathematical model is based on simultaneous numerical solution of equations governing mass and heat tran...

T. Vesala J. Kukkonen M. Kulmala

1989-01-01

174

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

175

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

PubMed

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

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

2011-07-01

176

Effects of Lowered Dissolved Oxygen Concentration on the Toxicity of 1,2,4-Trichlorobenzene to Fathead Minnows.  

National Technical Information Service (NTIS)

Fathead minnows Pimephales promelas were exposed for 32 days, starting with embryos and continuing through early juvenile development, to five concentrations of 1,2,4-trichlorobenzene (1,2,4-TCB) with a control. Each series of treatments was completed at ...

A. R. Carlson

1987-01-01

177

Spatial and temporal variations of dissolved organic carbon and inorganic carbon concentrations and ?13C in a peatland-stream continuum: implications of peatland invasion by vascular plants  

NASA Astrophysics Data System (ADS)

Dissolved fluxes of C which are an important component of the global C budget of peatlands may be affected by global change in different ways. The evolution of peatland vegetation is an issue caused by the indirect effect of global change that still needs to be addressed. The aim of this study was to study the temporal and spatial variations in the quantity and the characteristics of dissolved C within in a peatland stream continuum, the peatland being invaded by Molinia caerulea and Betula spp. The study highlighted the following key points: (i) Vegetation change tends to increase the DOC concentration of peat surface water. (ii) DOC exports were in the range of those found in the literature, and it was clearly established that peatland DOC can reach second order streams. (iii) Peat water was supersaturated in CO2 especially in summer during the peak of microbial activity. (iv) the CO2 critical layer at the surface of the soil may promote CO2 excess build-up in the peat water. This critical layer may promote CO2 export out of the peatland. The effect of vegetation change on the DOC content of peat water deserves further attention as it may have a deep impact on downstream river water quality. In particular, it is necessary to clarify whether the concentration of C dynamics is affected by the invading species. More attention should be paid to hydrological processes (e.g. pumping capacity of the different plants) and the microbial activity in the rhizosphere of the invading plants. Also, the relation between the CO2 critical zone at the surface of the soil and the CO2 concentration in water should be studied in detail.

Gogo, S.; Albéric, P.; Laggoun-Défarge, F.; Binet, S.; Aurouet, A.

2012-03-01

178

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

179

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

USGS Publications Warehouse

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

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

2013-01-01

180

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

181

Concentration polarization effects in the use of micellar-enhanced ultrafiltration to remove dissolved organic pollutants from wastewater  

SciTech Connect

Micellar-enhanced ultrafiltration (MEUF) is used to remove 4-tert-butylphenol (TBP) from aqueous solution, a separation for which traditional ultrafiltration is ineffective. A micelle-forming surfactant is added to the solution. The micelles solubilize a high fraction of the TBP. The stream is then forced through an ultrafilter. Overall rejection of TBP was greater than 99% under all conditions studied and did not decrease with increasing pressure drop. Micelles were completely rejected by membranes with pore size 10,000 Dalton MWCD and below. Concentration polarization affects MEUF fluxes under conditions of interest. Gel polarization theory does not completely explain MEUF flux behavior. Selection of optimum operating parameters in MEUF application are discussed.

Dunn, R.O. Jr.; Scamehorn, J.F.; Christian, S.D.

1987-01-01

182

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

PubMed

Maintaining stability of low concentration (< 1 g L(-1)) floccular biomass in the nitritation-anaerobic ammonium oxidation (anammox) process in the sequencing batch reactor (SBR) system for the treatment of high COD (> 15,000 mg O2 L(-1)) to N (1680 mg N L(-1)) ratio real wastewater streams coming from the food industry is challenging. The anammox process was suitable for the treatment of yeast factory wastewater containing relatively high and abruptly increased organic C/N ratio and dissolved oxygen (DO) concentrations. Maximum specific total inorganic nitrogen (TIN) loading and removal rates applied were 600 and 280 mg N g(-1) VSS d(-1), respectively. Average TIN removal efficiency over the operation period of 270 days was 70%. Prior to simultaneous reduction of high organics (total organic carbon > 600mg L(-1)) and N concentrations > 400 mg L(-1), hydraulic retention time of 15 h and DO concentrations of 3.18 (+/- 1.73) mg O2 L(-1) were applied. Surprisingly, higher DO concentrations did not inhibit the anammox process efficiency demonstrating a wider application of cultivated anammox biomass. The SBR was fed rapidly over 5% of the cycle time at 50% volumetric exchange ratio. It maintained high free ammonia concentration, suppressing growth of nitrite-oxidizing bacteria. Partial least squares and response surface modelling revealed two periods of SBR operation and the SBR performances change at different periods with different total nitrogen (TN) loadings. Anammox activity tests showed yeast factory-specific organic N compound-betaine and inorganic N simultaneous biodegradation. Among other microorganisms determined by pyrosequencing, anammox microorganism (uncultured Planctomycetales bacterium clone P4) was determined by polymerase chain reaction also after applying high TN loading rates. PMID:24701957

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

2014-01-01

183

Bioaccumulation of 2,2{prime},5,5{prime}-tetrachlorobiphenyl and pyrene by picoplankton (Synechococcus leopoliensis, Cyanophyceae): Influence of variable humic acid concentrations and pH  

SciTech Connect

Natural dissolved organic matter (DOM) controls the aqueous phase partitioning of hydrophobic organic contaminants (HOCs), where the sum of aqueous HOCs is distributed between the bound and free forms of HOCs, that is [HOC-DOM] {leftrightarrow} [HOC] + [DOM]. The hypothesis that the bioavailability of aqueous HOCs can be attributed solely to the concentration of the free form of HOCs was tested. Bioavailability was measured as accumulation of [{sup 14}C]-PCB (IUPAC 52) and [{sup 14}C]-pyrene over 48 h by the phytoplanktonic cyanobacterium Synechococcus leopoliensis. The phytoplankton were exposed within dialysis sacs to freely dissolved HOC at concentrations that were similar in all sacs. However, humic acid concentrations were varied among the sacs. The experiment was designed to vary the concentrations of HOC-HA and HA while keeping the concentration of freely dissolved HOCs at the same levels in all the sacs. Sorption mechanism were probed by manipulating the pH of the exposure medium; the hydrophobicities of the cell surface and the humic acid are pH-sensitive, whereas the freely dissolved concentration of HOCs is pH-invariant. Bioaccumulation was predominantly controlled by the freely dissolved concentration of HOC and was greater at pH 4.3 than at pH 7.3. Although sorption of the PCB-HA and pyrene-HA complexes by S. leopoliensis occurred, this mechanism did not contribute significantly to the total accumulation of PCB of pyrene. These results suggest that the accumulation of HOCs by planktonic microorganisms can be predicted on the basis of the concentration of freely dissolved HOC molecules.

Twiss, M.R.; Granier, L.; Lafrance, P.; Campbell, P.G.C.

1999-09-01

184

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

185

Effect of benthic-pelagic coupling on dissolved organic carbon concentrations in permeable sediments and water column in the northeastern Gulf of Mexico  

NASA Astrophysics Data System (ADS)

Large areas of the continental shelf are covered by permeable sand beds that filter substantial volumes of coastal water. This study investigated the temporal changes in and coupling between dissolved organic carbon (DOC) concentrations in the water column and pore water of nearshore permeable sediments in the northeastern Gulf of Mexico. Time series samples, collected in the nearshore environments at an exposed and a nearby protected site, showed very similar patterns of sedimentary DOC concentrations at both sites indicating that large-scale, seasonal, and weather-related processes controlled these distributions. A summer situation, with the sediment surface layer depleted in DOC and upward diffusion of recalcitrant DOC from deeper layers, was separated by a fall transition phase, where increasing winds and waves caused a mixing of the sedimentary DOC, resulting in relatively even concentrations over the investigated sediment depth (0-12 cm). The subsequent winter situation was characterized by increased DOC in the surface layer caused by filtration of degradable organic material into the sands and subsurface removal of degradable DOC. A second transition phase in early spring marked the end of the winter situation, with strong winds and waves and thorough pore water mixing, leading again to even DOC distribution in the investigated sediment layer. This transition phase initiated the next summer situation with depletion of DOC in the sediment surface layers. Our results indicate that DOC in the upper layer (?12 cm) of the shallow sands is controlled by benthic-pelagic coupling facilitated by relatively rapid solute and particle exchange in the highly permeable sediments at our study sites. The prompt responses of the surface layer DOC concentrations to the changes in the overlying water underline the dynamic character of substrate supply in the permeable sediments, setting them apart from fine-grained cohesive beds characterized by relatively stable DOC distributions.

Chipman, Lindsay; Huettel, Markus; Laschet, Matthias

2012-08-01

186

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

187

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

USGS Publications Warehouse

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

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

2003-01-01

188

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

PubMed

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 GD1(T), 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 GD1(T) 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

2014-02-01

189

Accuracy of different sensors for the estimation of pollutant concentrations (total suspended solids, total and dissolved chemical oxygen demand) in wastewater and stormwater.  

PubMed

Many field investigations have used continuous sensors (turbidimeters and/or ultraviolet (UV)-visible spectrophotometers) to estimate with a short time step pollutant concentrations in sewer systems. Few, if any, publications compare the performance of various sensors for the same set of samples. Different surrogate sensors (turbidity sensors, UV-visible spectrophotometer, pH meter, conductivity meter and microwave sensor) were tested to link concentrations of total suspended solids (TSS), total and dissolved chemical oxygen demand (COD), and sensors' outputs. In the combined sewer at the inlet of a wastewater treatment plant, 94 samples were collected during dry weather, 44 samples were collected during wet weather, and 165 samples were collected under both dry and wet weather conditions. From these samples, triplicate standard laboratory analyses were performed and corresponding sensors outputs were recorded. Two outlier detection methods were developed, based, respectively, on the Mahalanobis and Euclidean distances. Several hundred regression models were tested, and the best ones (according to the root mean square error criterion) are presented in order of decreasing performance. No sensor appears as the best one for all three investigated pollutants. PMID:23863442

Lepot, Mathieu; Aubin, Jean-Baptiste; Bertrand-Krajewski, Jean-Luc

2013-01-01

190

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

PubMed

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

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

2014-04-01

191

A freely-moving monkey treadmill model.  

PubMed

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. PMID:24995476

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

2014-08-01

192

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

NASA Astrophysics Data System (ADS)

We present an application of the INCA-C (Integrated Catchments model for Carbon) to the Svartberget catchment in central Sweden. The INCA-C model is a catchment-scale, semi-distributed, process-based model of dissolved organic carbon (DOC) that has been used previously to simulate intra- and inter-annual patterns in surface water DOC concentration and flux in boreal and temperate forested catchments (Futter et al. 2007). The 50 ha Svartberget catchment provides an ideal location for evaluating the performance of INCA-C as it contains two mire and upland landscape elements, where the output from each element has been monitored separately for a decade. Previous work has shown that these two landscape elements have markedly different intra-annual patterns of DOC concentration and export as well as the importance of the riparian zone in controlling surface water DOC concentration from the forested sub-catchment (Köhler et al. 2008). The 19 ha mire sub-catchment is dominated by bog communities with Scots pine in the upland areas. The 13 ha forested sub-catchment stream joins the main stem of the stream just above the confluence. It is dominated by Scots pine and Norway spruce. A third sub-catchment between the mire and the catchment outflow has a similar vegetation cover to that of the forested sub-catchment. INCA is designed to model different landscape elements, and combine them to simulate downstream locations. Like most complex, process-based models, however, INCA-C is over-determined. Insufficient data are available to constrain all processes and pool-sizes. As a result, similar in-stream DOC concentrations may be obtained by varying either aquatic or terrestrial rate parameters. The Svartberget catchment provides an opportunity to constrain the model parameter space for the entire catchment as there is information for the two major constituent elements, forest and mire. Additionally soil solution data from the riparian zone in the forest area together with a large set of physical parameters such as water content and soil temperature allow to constrain the range of the major driving variables and quantify the riparian zone effect on DOC mobilisation. The INCA-C model was able to capture the seasonal patterns in DOC concentration at the three sub-catchments. Using parameter sets derived from the forested sub-catchment, it was possible to constrain the simulations for the catchment outflow. The approach presented can be used in other modelling applications where data are available for multiple sub-catchments and extended to the lower lying higher order catchments. Further work is required to incorporate riparian zone dynamics into INCA-C. M.N. Futter, D. Butterfield, B.J. Cosby, P.J. Dillon, A.J. Wade and P.G. Whitehead. 2007. Modelling the mechanisms that control in-stream dissolved organic carbon dynamics in upland and forested catchments. Water Resources Research 43, W02424, doi:10.1029/2006WR004960 S.J. Köhler, I. Buffam, H. Laudon and K.H. Bishop 2008. Climate's control of intra-annual and interannual variability of total organic carbon concentration and flux in two contrasting boreal landscape elements. Journal of Geophysical Research 113, G03012, doi:10.1029/2007JG000629.

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

2009-04-01

193

Evaluation Of High-Frequency Mean Streamwater Transit-Time Estimates Using Groundwater Age And Dissolved Silica Concentrations In A Small, Forested Watershed  

NASA Astrophysics Data System (ADS)

Many previous investigations of mean streamwater transit times (MTT) have been limited by an inability to quantify their dynamic nature. Here, we draw on (1) a linear relationship (r2 = 0.97) between groundwater 3H/3He ages and dissolved silica (Si) concentrations, combined with (2) predicted streamwater Si concentrations from a multiple regression relation (R2 = 0.87) to estimate MTT at 5-min intervals for a 23 yr time series of streamflow (water year (WY) 1986 thru 2008) at the Panola Mountain Research Watershed, Georgia. The time-based average MTT derived from the 5-min data was ~8.4×2.9 years and the volume-weighted (VW) MTT was ~4.7 years for the study period, reflecting the importance of younger runoff water during high flow. The 5-min MTTs are normally distributed and ranged from 0 to 15 years. Monthly VW MTTs averaged 7.0 × 3.3 years and ranged from 4-6 years during the typically high streamflow period in winter to 8-10 years during the low streamflow period in summer. The annual VW MTTs averaged 5.6×2.0 years, and ranged from ~5 years during wet years (2003, 2005) to >10 years during dry years (2002, 2008). Stormflows are composed of much younger water than baseflow, and although stormflow only occurs ~17% of the time, this runoff fraction contributed 39% of the runoff over the 23 year study period. Combining the 23-yr VW MTT (including stormflow) with the annual average baseflow for the period (~212 mm) indicates that active groundwater storage is ~1000 mm However, the groundwater storage ranged from 1040 to 1950 mm using WY baseflow and WY VW MTT. The approach described herein may be applicable in other watersheds underlain by granitoid bedrock, where weathering is the dominant control on Si concentrations in soils, groundwater, and streamwater.

Peters, N. E.; Burns, D. A.; Aulenbach, B. T.

2013-12-01

194

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...

195

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

196

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

PubMed

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

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

2013-01-01

197

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

198

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

USGS Publications Warehouse

Concentrations of total dissolved solids (TDS) and nutrients in selected Santa Ana Basin streams were examined as a function of water source. The principal water sources are mountain runoff, wastewater, urban runoff, and stormflow. Rising ground water also enters basin streams in some reaches. Data were collected from October 1998 to September 2001 from 6 fixed sites (including a mountain site), 6 additional mountain sites (including an alpine indicator site), and more than 20 synoptic sites. The fixed mountain site on the Santa Ana River near Mentone appears to be a good representative of reference conditions for water entering the basin. TDS can be related to water source. The median TDS concentration in base-flow samples from mountain sites was 200 mg/L (milligrams per liter). Base-flow TDS concentrations from sites on the valley floor typically ranged from 400 to 600 mg/L; base flow to most of these sites is predominantly treated wastewater, with minor contributions of rising ground water and urban runoff. Sparse data suggest that TDS concentrations in urban runoff are about 300 mg/L. TDS concentrations appear to increase on a downstream gradient along the main stem of the Santa Ana River, regardless of source inputs. The major-ion compositions observed in samples from the different sites can be related to water source, as well as to in-stream processes in the basin. Water compositions from mountain sites are categorized into two groups: one group had a composition close to that of the alpine indicator site high in the watershed, and another group had ionic characteristics closer to those in tributaries on the valley floor. The water composition at Warm Creek, a tributary urban indicator site, was highly variable but approximately intermediate to the compositions of the upgradient mountain sites. Water compositions at the Prado Dam and Imperial Highway sites, located 11 miles apart on the Santa Ana River, were similar to one another and appeared to be a mixture of the waters of the upstream sites, Santa Ana River at MWD Crossing, Cucamonga Creek, and Warm Creek. Rainfall usually dilutes stream TDS concentrations. The median TDS concentration in all storm-event discrete samples was 260 mg/L. The median flow-weighted average TDS concentration for stormflow, based on continuous measurement of specific conductance and hydrograph separation of the continuous discharge record, was 190 mg/L. However, stormflow TDS concentrations were variable, and depended on whether the storm was associated with a relatively small or large rainfall event. TDS concentrations in stormflow associated with relatively small events ranged from about 50 to 600 mg/L with a median of 220 mg/L, whereas concentrations in stormflow associated with relatively large events ranged from about 40 to 300 mg/L with a median of 100 mg/L. From the perspective of water managers, the nutrient species of highest concern in Santa Ana Basin streams is nitrate. Most mountain streams had median base-flow concentrations of nitrate below 0.3 mg/L as nitrogen. Nitrate concentrations in both urban runoff and stormflow were near 1 mg/L, which is close to the level found in rainfall for the region. In fact, results from this study suggest that much of the nitrate load in urban storm runoff comes from rainwater. Nitrate concentrations in the Santa Ana River and its major tributaries are highest downstream from wastewater inputs, where median base-flow concentrations of nitrite+nitrate ranged from about 5 to 7 mg/L. About 4 percent of samples collected from sites receiving treated wastewater had nitrate concentrations greater than 10 mg/L. Rising ground water also appears to have high nitrate concentrations (greater than 10 mg/L) in some reaches of the river. Concentrations of other nitrogen species were much lower than nitrate concentrations in base-flow samples. However, storm events increased concentrations and the proportion of organic nitro

Kent, Robert; Belitz, Kenneth

2004-01-01

199

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

200

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

201

METHOD OF DISSOLVING URANIUM METAL  

Microsoft Academic Search

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

Slotin

1958-01-01

202

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

NASA Astrophysics Data System (ADS)

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. High spatial variability in surface mixed layer (ML) [CH4] was observed, ranging from 2.2 nmol L-1 to 17.8 nmol L-1. ML-[CH4] was supersaturated at all BA stations during both cruises. The highest [CH4] was 72.4 nmol L-1 (2819 % supersaturated) measured at 10 m depth during S2, about 3 km southwest of the discharge point of the South Bay Ocean Outfall (SBOO). Our results show an apparent connection between wastewater treatment discharges and [CH4]. Application of a sewer CH4 production model suggests that the SBOO may be a large source of CH4 to the BA and points to the need to consider point sources in developing coastal marine CH4 budgets for highly populated areas. Based on our data, the SCBMex appears to be a relatively strong source of CH4 to the atmosphere compared to other Pacific Basin areas. The average BA sea-to-air CH4 flux (F) during S1 was (15.5 ± 8.6) × 10-2 nmol m-2 s-1, about 1.5 times higher than F during S2, which had a flux of (9.5 ± 6.9) × 10-2 nmol m-2 s-1 mainly due to the higher wind speed during S1.

Castro-Morales, Karel; Macías-Zamora, J. Vinicio; Canino-Herrera, S. Raúl; Burke, Roger A.

2014-05-01

203

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

204

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

205

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

206

Statistical physics of the freely jointed chain  

NASA Astrophysics Data System (ADS)

Using the method of constraints proposed by S. F. Edwards and A. G. Goodyear [J. Phys. A 5, 965 (1972); 5, 1188 (1972)], we do a complete calculation of the canonical partition function of a freely jointed chain (FJC) from its classical Hamiltonian. We show how the constraints reduce the phase space of an ideal gas of monomers to the phase space of a FJC, and how they permit one to find the canonical partition function. By using this function, it is possible to study thermodynamical properties of FJC's and to build other thermodynamical ensembles via Laplace transforms. Thus we define a grand canonical ensemble where the monomer number of the FJC can fluctuate; in this ensemble, the FJC of infinite length is the asymptotic state at low and high temperatures. The critical exponents ? and ? for FJC's are calculated and found to be equal to the Gaussian polymer exponents. Connections between the properties of FJC's and random walks on regular lattices are also discussed.

Mazars, Martial

1996-06-01

207

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

USGS Publications Warehouse

Decadal-scale changes in groundwater quality were evaluated by the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program. Samples of groundwater collected from wells during 1988-2000 - a first sampling event representing the decade ending the 20th century - were compared on a pair-wise basis to samples from the same wells collected during 2001-2010 - a second sampling event representing the decade beginning the 21st century. The data set consists of samples from 1,236 wells in 56 well networks, representing major aquifers and urban and agricultural land-use areas, with analytical results for chloride, dissolved solids, and nitrate. Statistical analysis was done on a network basis rather than by individual wells. Although spanning slightly more or less than a 10-year period, the two-sample comparison between the first and second sampling events is referred to as an analysis of decadal-scale change based on a step-trend analysis. The 22 principal aquifers represented by these 56 networks account for nearly 80 percent of the estimated withdrawals of groundwater used for drinking-water supply in the Nation. Well networks where decadal-scale changes in concentrations were statistically significant were identified using the Wilcoxon-Pratt signed-rank test. For the statistical analysis of chloride, dissolved solids, and nitrate concentrations at the network level, more than half revealed no statistically significant change over the decadal period. However, for networks that had statistically significant changes, increased concentrations outnumbered decreased concentrations by a large margin. Statistically significant increases of chloride concentrations were identified for 43 percent of 56 networks. Dissolved solids concentrations increased significantly in 41 percent of the 54 networks with dissolved solids data, and nitrate concentrations increased significantly in 23 percent of 56 networks. At least one of the three - chloride, dissolved solids, or nitrate - had a statistically significant increase in concentration in 66 percent of the networks. Statistically significant decreases in concentrations were identified in 4 percent of the networks for chloride, 2 percent of the networks for dissolved solids, and 9 percent of the networks for nitrate. A larger percentage of urban land-use networks had statistically significant increases in chloride, dissolved solids, and nitrate concentrations than agricultural land-use networks. In order to assess the magnitude of statistically significant changes, the median of the differences between constituent concentrations from the first full-network sampling event and those from the second full-network sampling event was calculated using the Turnbull method. The largest median decadal increases in chloride concentrations were in networks in the Upper Illinois River Basin (67 mg/L) and in the New England Coastal Basins (34 mg/L), whereas the largest median decadal decrease in chloride concentrations was in the Upper Snake River Basin (1 mg/L). The largest median decadal increases in dissolved solids concentrations were in networks in the Rio Grande Valley (260 mg/L) and the Upper Illinois River Basin (160 mg/L). The largest median decadal decrease in dissolved solids concentrations was in the Apalachicola-Chattahoochee-Flint River Basin (6.0 mg/L). The largest median decadal increases in nitrate as nitrogen (N) concentrations were in networks in the South Platte River Basin (2.0 mg/L as N) and the San Joaquin-Tulare Basins (1.0 mg/L as N). The largest median decadal decrease in nitrate concentrations was in the Santee River Basin and Coastal Drainages (0.63 mg/L). The magnitude of change in networks with statistically significant increases typically was much larger than the magnitude of change in networks with statistically significant decreases. The magnitude of change was greatest for chloride in the urban land-use networks and greatest for dissolved solids and nitrate in the agricultural land-use networks. Analysis of data from all networks combined indicated statistic

Lindsey, Bruce D.; Rupert, Michael G.

2012-01-01

208

Crank inertial load affects freely chosen pedal rate duringcycling  

Microsoft Academic Search

Cyclists seek to maximize performance duringcompetition, and g ross efficiency is an important factor affectingperformance. Gross efficiency is itself affected by pedal rate. Thus, it is important to understand factors that affect freely chosen pedal rate. Crank inertial load varies greatly during road cycling based on the selected gear ratio. Nevertheless, the possible influence of crank inertial load on freely

Ernst Albin Hansen; Lars Vincents Jrgensen; Kurt Jensen; Benjamin Jon Fregly; Gisela Sjgaarda

209

Predicting polycyclic aromatic hydrocarbon concentrations in resident aquatic organisms using passive samplers and partial least-squares calibration.  

PubMed

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

Forsberg, Norman D; Smith, Brian W; Sower, Greg J; Anderson, Kim A

2014-06-01

210

Determination of free copper concentrations in natural waters by using supported liquid membrane extraction under equilibrium conditions  

Microsoft Academic Search

A method is described for measurement of freely dissolved copper concentrations in natural water samples using supported liquid membrane (SLM) extraction under equilibrium conditions, a technique denoted “equilibrium sampling through membranes” (ESTM). For this purpose, 1,10-dibenzyl-1,10-diaza-18-crown-6 as neutral carrier and oleic acid were used in the membrane phase. The main variables optimised were the carrier used to form the metal

Roberto Romero; Jan Åke Jönsson

2005-01-01

211

Modification of Carrier Gas Stream to Improve 13C/12C Isotopic Accuracy in Cavity Ring-Down Spectroscopy-Based Measurements of Low-Concentration Dissolved Carbon Samples  

NASA Astrophysics Data System (ADS)

Determining isotopic composition of dissolved organic and inorganic carbon in natural waters is of critical importance to a broad set of scientific objectives. The routine analysis of these sample types can be expensive and in the past has been limited predominantly to laboratories capable of high-precision isotope ratio mass spectrometric analysis. More recently, cavity ring-down spectroscopy (CRDS) has provided an alternative instrumental means for characterizing these samples. One challenge with these types of is that the CRDS can show a non-linear response in d13C at low carbon concentrations (<0.5 mM). Here we present a new approach using a modification of a total organic carbon-cavity ring-down spectroscopy (TOC-CRDS) continuous flow system by adding a background stream of carbon dioxide of known isotopic composition to the CRDS analytical train. The isotopic carbon values generated by the CRDS are then corrected using a two-component isotopic mixing model. This modification is useful in reducing bias towards lighter carbon isotopic values when measuring samples with low carbon concentration, such as natural waters with either dissolved organic or inorganic carbon concentrations of less than 0.5 mM, and does not introduce substantial bias for higher concentration samples.

Conaway, C. H.; Morkner, P.; Thomas, B.; Saad, N.

2013-12-01

212

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

PubMed

The ubiquity of dissolved organic matter (DOM) in an aqueous environment may have influence on the carbonaceous material's impact on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) to benthonic organisms in contaminated sediment. In the present study, 1 multiwalled carbon nanotube (MWNT); 2 types of DOM (fulvic acid and tannic acid), and 2 PAHs (pyrene and chrysene) were selected to study the influence of MWNT with preloaded and coexisting DOM on the bioaccumulation of PAHs to Chironomus plumosus larvae in sediment. Moreover, the freely dissolved concentrations of PAHs were measured to explore the influence mechanisms. The results showed that despite the presence or absence of preloaded or coexisting DOM, the presence of 1% MWNT in sediments suppressed the biota-sediment accumulation factor (BSAF) and elevated the water-based bioaccumulation factor (BAF) of PAHs. However, the BSAF and BAF values generally decreased with the increase of 2 forms of both DOM; this was caused by the combined impact of DOM and MWNT on the freely dissolved concentrations of PAHs and the ingestion behavior of benthic organisms. PMID:24123323

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

2014-01-01

213

Sediment–dissolved organic matter equilibrium partitioning of pentachlorophenol  

Microsoft Academic Search

The dissolved humic matter (HM) has an essential influence on the release of the bound pentachlorophenol (PCP) from the solid sediment. It was studied how the increase of the dissolved HM concentration affects the equilibrium partitioning of PCP between the solid sediment matter and dissolved HM. The lake sedimentary and dissolved HM were isolated and their structural compositions were compared

Nina Paaso; Juhani Peuravuori; Tero Lehtonen; Kalevi Pihlaja

2002-01-01

214

Chemistry Review: Dissolving  

NSDL National Science Digital Library

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

Kessler, James; Galvan, Patti

2010-01-01

215

Concentration  

NSDL National Science Digital Library

Watch your solution change color as you mix chemicals with water. Then check molarity with the concentration meter. What are all the ways you can change the concentration of your solution? Switch solutes to compare different chemicals and find out how concentrated you can go before you hit saturation!

Simulations, Phet I.; Chamberlain, Julia; Malley, Chris; Lancaster, Kelly; Moore, Emily B.; Perkins, Kathy

2012-03-09

216

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

217

Evaluations of combined zebrafish (Danio rerio) embryo and marine phytoplankton (Diacronema lutheri) toxicity of dissolved organic contaminants in the Ythan catchment, Scotland, UK.  

PubMed

A wide variety of organic contaminants including pesticides, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) have previously been detected in surface waters in the river Ythan catchment, North East Scotland UK. While the concentrations detected were below Water Framework Directive Environmental Quality Standards (WFD-EQSs) environmental exposures to the diverse mixtures of contaminants, known and unknown, may pose chronic and/or sublethal effects to non target organisms. The present study assessed the embryo and algal toxicity potential of freely dissolved organic contaminants from the Ythan catchment using silicone rubber passive sampling devices (SR-PSDs) and miniaturised bioassay techniques. Zebrafish (Danio rerio) embryos and marine phytoplankton species (Diacronema lutheri) were exposed to extracts from SR-PSDs deployed at different locations along the river Ythan and an undeployed procedural blank. Statistically significant developmental and algal toxicities were measured in all tests of extracts from deployed samples compared with the procedural blanks. This indicates environmental exposure to, and the combined toxicity potential of, freely dissolved organic contaminants in the catchment. The present and previous studies in the Ythan catchment, coupling SR-PSDs and bioassay techniques, have both helped to understand the interactions and combined effects of dissolved organic contaminants in the catchment. They have further revealed the need for improvement in the techniques currently used to assess environmental impact. PMID:24407789

Emelogu, Emmanuel S; Seiler, Thomas-Benjamin; Pollard, Pat; Robinson, Craig D; Webster, Lynda; McKenzie, Craig; Heger, Sebastian; Hollert, Henner; Bresnan, Eileen; Best, Jennifer; Moffat, Colin F

2014-04-01

218

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

PubMed

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

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

2012-11-01

219

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

Microsoft Academic Search

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

Dieke Postma

1985-01-01

220

Concentration  

NSDL National Science Digital Library

This NCTM iOS app of the familiar online Illuminations game, "Concentration" (cataloged separately) 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.

2011-09-15

221

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

222

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

223

The motion of a freely falling chain tip: Force measurements  

NASA Astrophysics Data System (ADS)

A chain is firmly attached at one end while the other falls freely in the gravitational field. We report careful time-resolved measurements of the horizontal and vertical components of the force applied by the chain on the mount. Our results complement previous laboratory measurements and simulations of the free end dynamics.

Géminard, Jean-Christophe; Vanel, Loïc

2008-06-01

224

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

225

Hippocampal cellular and network activity in freely moving echolocating bats  

Microsoft Academic Search

The hippocampus is crucial for episodic and spatial memory. In freely moving rodents, hippocampal pyramidal neurons show spatially selective firing when the animal passes through a neuron's 'place-field', and theta-band oscillation is continuously present during locomotion. Here we report the first hippocampal recordings from echolocating bats, mammals phylogenetically distant from rodents, which showed place cells very similar to those of

Cynthia F Moss; Nachum Ulanovsky

2007-01-01

226

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

227

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

Microsoft Academic Search

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

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

2009-01-01

228

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

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.

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

2013-01-01

230

Elastomer damper for a freely precessing dual-spin seeker  

NASA Astrophysics Data System (ADS)

The damping performance of an elastomer damper for a freely precessing dual-spin seeker, such as those used in the guidance of radiation seeking missiles, is analyzed. An approximate expression for the decay time constant of the coning motion is obtained using perturbation techniques. It is noted that the time constant of the Kelvin material damper is always less than that of the three-parameter material damper irrespective of the magnitude of the material constants in the constitutive equation.

Chang, C. O.; Chen, M. P.

1993-02-01

231

Soot Formation in Freely-Propagating Laminar Premixed Flames  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

232

Photobleaching of humic rich dissolved organic matter  

Microsoft Academic Search

Humic rich dissolved organic matter (DOM) from a bog lake in the Northern Black Forest was treated with simulated solar UV-light. The effects of irradiation time, initial pH values, and dissolved iron and copper on photobleaching were investigated. The DOC concentration and the UV\\/VIS absorption decreased with increasing amounts of absorbed light energy. The wavelengths of the maximum bleaching effect

Thomas Brinkmann; Daniel Sartorius; Fritz H. Frimmel

2003-01-01

233

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

234

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

235

Method for dissolving delta-phase plutonium  

Microsoft Academic Search

This patent describes a process for dissolving plutonium metal, the process. It comprises: heating a mixture of nitric acid, hydroxylammonium nitrate and potassium fluoride; and immersing the plutonium in the mixture; the nitric acid having a concentration of not more than 2M, the hydroxylammonium nitrate having a concentration of between approximately 0.33 M and 1 M, and the potassium fluoride

Karraker

1992-01-01

236

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

237

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

EPA Science Inventory

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

238

Amphetamine releases GABA in striatum of the freely moving rat: involvement of calcium and high affinity transporter mechanisms  

Microsoft Academic Search

Using microdialysis the effect was investigated of amphetamine (AMPH) infusions into the striatum on the release of GABA in the freely moving rat. AMPH (5, 10 and 20 ?g\\/?l), infused through a microdialysis probe at the rate of 2.5 ?l\\/min, produced a dose-related increase in extracellular concentrations of GABA. At the highest dose (20 ?g\\/?l), AMPH increased GABA from 0.08±0.01

Alberto Del Arco; Tamara R. Castaneda; Francisco Mora

1998-01-01

239

Diffusion of a freely water-soluble drug in aqueous enteric-coated pellets.  

PubMed

The effects of filler used in the pellet cores (ie, waxy cornstarch or lactose) and the enteric film coat thickness on the diffusion and dissolution of a freely soluble drug were studied. Two kinds of pellet cores containing riboflavin sodium phosphate as a model drug, microcrystalline cellulose (MCC) as a basic filler, and waxy cornstarch or lactose as a cofiller were film coated (theoretically weight increase 20% or 30%) with an aqueous dispersion of cellulose acetate phthalate (CAP). The diffusion of riboflavin sodium phosphate in aqueous enteric-coated pellets was investigated using noninvasive confocal laser scanning microscopy (CLSM). The in vitro release tests were performed using a USP apparatus I (basket method). Diffusion of drug from the core to the film coat was found to be greater with lactose-containing pellets than with waxy cornstarch-containing pellets. The dissolution test showed that 30% enteric-coated waxy cornstarch pellets had a good acidic resistance in 0.1 N HCl solution for at least 1 hour, while the other enteric pellet formulations failed the test. The waxy cornstarch-containing enteric pellets dissolved at SIF in less than 10 minutes. Confocal images of film-coated pellets showed that waxy cornstarch-containing pellets had less drug dissolved than respective lactose-containing pellets. The observations were further confirmed by measurement of fluorescence intensity of riboflavin sodium phosphate in the film coat. The dissolution test was consistent with the confocal microscopy results. In conclusion, waxy cornstarch as a cofiller in the pellet cores minimizes premature drug diffusion from the core into the film coat layer. PMID:12916953

Guo, H X; Heinämäki, J; Yliruusi, J

2002-01-01

240

Wireless neural stimulation in freely behaving small animals.  

PubMed

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

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

2009-07-01

241

Optogenetic Control of Targeted Peripheral Axons in Freely Moving Animals  

PubMed Central

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

Iyer, Shrivats M.; Deisseroth, Karl; Delp, Scott L.

2013-01-01

242

Photopolymerized Elastomer Stripes in the Freely Suspended Liquid Crystal Films  

NASA Astrophysics Data System (ADS)

We report the polarized light microscopy study of a freely suspended liquid crystal film in which an elastomeric stripe is generated by photopolymerized crosslinking through a mask. The ferroelectric liquid crystal elastomer (CT90) is composed of liquid crystal monomers in SmC* connected to a polysiloxane backbone decorated with crosslinkable groups. We are able to make thin freely suspended films 2-10 layers thick. After crosslinking, we applied an AC field, and found that the liquid crystal monomer in the uncrosslinked area is switchable as a normal SmC*. In the crosslinked stripe, the liquid crystal monomers are bound by a restoring force to the original crosslinking direction. The monomers are only able to rotate partially when a field is applied in the opposite direction. It is also observed that the force restricting the movement of the monomers depends on the length of time the material is exposed to the UV light. This work is supported by NASA Grant NAG 3-2457 and DMR MRSEC-9809555

Chattham, Nattaporn; Tolksdorf, Christian; Zentel, Rudolf; Clark, Noel

2003-03-01

243

Towards direct numerical simulation of freely swimming fish.  

NASA Astrophysics Data System (ADS)

Swimming mechanisms employed by fish are currently inspiring unique underwater vehicles and robotic devices as well as basic science research into the neural control of movement. Key engineering issues include propulsion efficiency, precise motion control and maneuverability. A numerical scheme that simulates the motion of freely swimming fish will be a valuable design and research tool. We are working towards this goal. In particular we are interested in simulating the motion of a gymnotiform fish that swims by producing undulations of a ventral ribbon fin while keeping its body rigid. We model the fish as a rigid body with an attached undulating membrane. In our numerical scheme the key idea is to assume that the entire fluid-fish domain is a fluid. Then we impose two constraints: the first requires that the fluid in the region occupied by the fish body moves rigidly (a fictitious domain approach), and the second requires that the fluid at the location of the fin has the traveling wave velocity of the fin (an immersed boundary approach). Given the traveling wave form of the fin, the objective is for the numerical scheme to give the swimming velocity of the fish by solving the coupled fluid-fish problem. We will present results for the forces generated by a fin attached to a fixed body and preliminary results for freely swimming fish.

Curet, Oscar; Patankar, Neelesh; Maciver, Malcolm

2006-11-01

244

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

245

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

PubMed

Perfluoroalkyl substances (PFASs) are sometimes regarded as proteinophilic compounds, however, there is no research report about the effect of environmental protein on the bioaccumulation of PFASs in waters. In the present study we investigated influences of protein on the bioaccumulation of six kinds of PFASs by Daphnia magna in water; it included perfluorooctane sulfonate, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, and perfluorododecanoic acid. Two types of protein including bovine albumin from animal and soy peptone from plant were compared and the effects of protein concentration were investigated. Both types of protein at high concentrations (10 and 20 mg L(-1)) suppressed the bioaccumulation of PFASs. When protein concentration increased from 0 to 20 mg L(-1), the decreasing ratios of the PFAS body burden (35.3-52.9%) in Daphnia magna induced by bovine albumin were significantly higher than those (22.0-36.6%) by soy peptone. The dialysis bag experiment results showed that the binding of PFASs to protein followed the Freundlich isotherm, suggesting it is not a linear partitioning process but an adsorption-like process. The partition coefficients of PFASs between bovine albumin and water were higher compared to soy peptone; this resulted in higher reducing rates of freely dissolved concentrations of PFASs with increasing bovine albumin concentration, leading to a stronger suppression of PFAS bioaccumulation. However, the presence of both types of protein with a low concentration (1 mg L(-1)) enhanced the bioaccumulation of PFASs. Furthermore, the water-based bioaccumulation factor based on the freely dissolved concentrations of PFASs even increased with and the depuration rate constants of PFASs from Daphnia magna decreased with protein concentration, suggesting that protein would not only reduce the bioavailable concentrations and uptake rates of PFASs but also lower the elimination rates of PFASs in Daphnia magna. Because these two opposite effects would change with different protein concentrations in water, the net effect of protein on PFAS bioaccumulation would also vary with protein concentration. PMID:23968486

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

2013-10-01

246

Dissolved aluminum in the Mediterranean  

SciTech Connect

Three vertical profiles of dissolved Al and nutrients are reported from the eastern basin of the Mediterranean. Profiles of Al concentrations resemble those of the nutrient elements, except that a proportionally higher residual concentration remains in the surface layer. Concentrations of Al in the surface water inflow from the North Atlantic, which contains between 10 and 20 nM around Gibraltar, are elevated to 55, 59 and 75 nM at the stations occupied. Calculations indicate that these concentrations are probably produced by dissolution Al from aeolian dust and advective mixing of Al-rich deep waters into the surface layer, balance by a biologically-associated removal process. The Al removed from the surface layer redissolves in the deep water to raise Al concentrations to about 160 nM. Samples were also recovered from anoxic deep brines in the Tyro and Bannock basins. In the brines, Al concentrations fall to about 15 nM while Si concentrations approach 270 nM.

Hydes, D.J. (Institute of Oceanographic Sciences Deacon Lab., Surrey (England)); De Lange, G.J.; De Baar, H.J.W. (Univ. of Utrecht (Netherlands))

1988-08-01

247

Method for dissolving delta-phase plutonium  

SciTech Connect

This patent describes a process for dissolving plutonium metal, the process. It comprises: heating a mixture of nitric acid, hydroxylammonium nitrate and potassium fluoride; and immersing the plutonium in the mixture; the nitric acid having a concentration of not more than 2M, the hydroxylammonium nitrate having a concentration of between approximately 0.33 M and 1 M, and the potassium fluoride having a concentration between approximately 0.05 M approximately 0.1 M.

Karraker, D.G.

1992-08-04

248

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

249

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

250

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

251

Functional Brain Mapping in Freely Moving Rats During Treadmill Walking  

PubMed Central

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

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

2014-01-01

252

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

253

Evaporation rates of freely falling liquid nitrogen droplets in air  

SciTech Connect

The rates of heat transfer to individual droplets of liquid nitrogen falling freely in air were measured under different air temperatures similar to the conditions in a cryogenic freezing system. High-speed cinephotography was used to measure drop size and velocity. Experimental results of heat transfer rates to individual droplets were analyzed and the data were compared to those obtainable using other types of dimensionless correlations. Droplets of initial size range investigated (2.5-0.72 mm diameter) attained terminal velocities at distances of 4-6 cm freefall away from the drop generator tip. The velocity values used in the correlation of heat transfer data were averaged over the time traveled by individual droplet.

Awonorin, S.O.

1989-01-01

254

Firing rate homeostasis in visual cortex of freely behaving rodents.  

PubMed

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 day of MD but then rebounded to baseline over the next 2-3 days despite continued MD. This drop and rebound in firing was accompanied by bidirectional 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 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

2013-10-16

255

Observation of two Dimensional Smectic Order in Freely Suspended Films  

NASA Astrophysics Data System (ADS)

We report the polarized light microscopy study of freely suspended film of T-shaped bolaamphiphiles, with hydroxy terminated cores and semi-fluorinated lateral chains. In one material (CT2), we observe with decreasing temperature (1) a regular SmA phase; (2) a biaxial SmA phase; and (3) a fan-shaped focal conic texture indicative of a two dimensional smectic structure, where the "heads" (cores) of the molecules which are oriented parallel to the smectic layer plane, order in rows. This novel phase shows a strongly temperature-dependent birefringence, whose origins are under investigation. These optical studies are supported by earlier bulk x-ray measurements. This work is supported by NASA Grant NAG 3-2457 and NSF Grants DMR MRSEC 9809555 and DMR 0072989.

Chattham, Nattaporn; Maclennan, Joseph; Clark, Noel; Tschierske, Carsten

2002-03-01

256

Freely chosen cadence during a covert manipulation of ambient temperature.  

PubMed

The present study investigated relationships between changes in power output (PO) to torque (TOR) or freely chosen cadence (FCC) during thermal loading. Twenty participants cycled at a constant rating of perceived exertion while ambient temperature (Ta) was covertly manipulated at 20-min intervals of 20 °C, 35 °C, and 20 °C. The magnitude responses of PO, FCC and TOR were analyzed using repeated-measures ANOVA, while the temporal correlations were analyzed using Auto-Regressive Integrated Moving Averages (ARIMA). Increases in Ta caused significant thermal strain (p < .01), and subsequently, a decrease in PO and TOR magnitude (p < .01), whereas FCC remained unchanged (p = .51). ARIMA indicates that changes in PO were highly correlated to TOR (stationary r2 = .954, p = .04), while FCC was moderately correlated (stationary r2 = .717, p = .01) to PO. In conclusion, changes in PO are caused by a modulation in TOR, whereas FCC remains unchanged and therefore, unaffected by thermal stressors. PMID:22964755

Hartley, Geoffrey L; Cheung, Stephen S

2013-01-01

257

Neural circuit activity in freely behaving zebrafish (Danio rerio).  

PubMed

Examining neuronal network activity in freely behaving animals is advantageous for probing the function of the vertebrate central nervous system. Here, we describe a simple, robust technique for monitoring the activity of neural circuits in unfettered, freely behaving zebrafish (Danio rerio). Zebrafish respond to unexpected tactile stimuli with short- or long-latency escape behaviors, which are mediated by distinct neural circuits. Using dipole electrodes immersed in the aquarium, we measured electric field potentials generated in muscle during short- and long-latency escapes. We found that activation of the underlying neural circuits produced unique field potential signatures that are easily recognized and can be repeatedly monitored. In conjunction with behavioral analysis, we used this technique to track changes in the pattern of circuit activation during the first week of development in animals whose trigeminal sensory neurons were unilaterally ablated. One day post-ablation, the frequency of short- and long-latency responses was significantly lower on the ablated side than on the intact side. Three days post-ablation, a significant fraction of escapes evoked by stimuli on the ablated side was improperly executed, with the animal turning towards rather than away from the stimulus. However, the overall response rate remained low. Seven days post-ablation, the frequency of escapes increased dramatically and the percentage of improperly executed escapes declined. Our results demonstrate that trigeminal ablation results in rapid reconfiguration of the escape circuitry, with reinnervation by new sensory neurons and adaptive changes in behavior. This technique is valuable for probing the activity, development, plasticity and regeneration of neural circuits under natural conditions. PMID:21346131

Issa, Fadi A; O'Brien, Georgeann; Kettunen, Petronella; Sagasti, Alvaro; Glanzman, David L; Papazian, Diane M

2011-03-15

258

Numerical simulation of dissolved oxygen in Jakarta Bay  

NASA Astrophysics Data System (ADS)

In this paper, an ecosystem model is proposed to study interaction between ecosystem compartment such as nutrient, phytoplankton, zooplankton and detritus on dissolved oxygen (DO) in Jakarta Bay. Three-Dimensional NPZD model with adding DO compartment is applied in this region. The average of current circulation in west and east season is used as input in the model. It is assumed that the nutrients are discharged into water body with constant rates. The analysis of the model shows that the concentration of dissolved oxygen was distributed with range value 3 - 4 ppm in the bay. The air-sea interaction plays important role in decrease of dissolved oxygen than the nutrient discharge from the river. Over all the decrease of dissolved oxygen mainly due to decrease of saturated dissolved oxygen which is caused by high water temperature. There is no significant variation of dissolved oxygen concentration in west and east seasons.

Nurdjaman, Susanna; Radjawane, Ivonne M.; Jamelina, Sripardi

2014-03-01

259

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

260

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

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

261

SOME FACTORS AFFECTING THE STA)~ILITY OF CERTAIN MILK PROPERTIES. VI. RELATION OF THE CONCENTRATION OF DISSOLVED OXYGEN TO THE OXIDATION OF ASCORBIC ACID AND TO THE DEVELOP MENT OF OXIDIZED FLAVOR IN MILK  

Microsoft Academic Search

Tile destruction of ascorbic acid and the devclopment of oxidized flavor in milk are oxidative reactions that are of paramount importance to the dairy industry. Research work has shown that dissolved oxygen is the prin- cipal agent (3, 4, 5, 7, 10) responsible for these chemical reactions. Re- search has shown further that both reactions are catalyzed by the presence

O. F. GARRETT

262

Developing Standards for Dissolved Iron in Seawater  

Microsoft Academic Search

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

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

2007-01-01

263

Modeling Fish Growth in Low Dissolved Oxygen  

ERIC Educational Resources Information Center

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

Neilan, Rachael Miller

2013-01-01

264

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

265

Spectroscopic characterization of dissolved organic matter isolated from rainwater  

Microsoft Academic Search

Rainwater is a matrix containing extremely low concentrations (in the range of ?M C) of dissolved organic carbon (DOC) and for its characterization, an efficient extraction procedure is essential. A recently developed procedure based on adsorption onto XAD-8 and XAD-4 resins in series was used in this work for the extraction and isolation of rainwater dissolved organic matter (DOM). Prior

Patrícia S. M. Santos; Marta Otero; Regina M. B. O. Duarte; Armando C. Duarte

2009-01-01

266

3-D Worm Tracker for Freely Moving C. elegans  

PubMed Central

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

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

2013-01-01

267

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

268

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

269

Stability and separation of freely interacting boundary layers  

NASA Astrophysics Data System (ADS)

The triple-deck theory to describe boundary-layer free interaction and separation is carefully investigated from the viewpoint of how it predicts stability properties of a viscous flow. The linearized version of this theory gives the same results as the linear stability theory based on the Orr-Sommerfeld equation if the flow is incompressible and the wave number of small disturbances goes to zero. Hence, a rather general criterion results to fix limits for a subsonic boundary layer to be stable. On the contrary, the linear approximation to the triple-deck theory leads to discouraging conclusions when the velocity of the oncoming stream exceeds the speed of sound, since it fails to reveal the boundary-layer instability. The Prandtl equations with a self-induced pressure gradient included are used to formulate a nonlinear approach for elucidating stability properties of freely inter acting boundary layers both for subsonic and supersonic cases. The shock-wave boundary-layer interaction and separation on a moving wall is numerically studied, the formation of two recirculation bubbles being the most striking feature. With the shock strength increasing, both bubbles tend to divide into smaller vortex cells whence the nonsteady process of velocity field "breathing" stems.

Ryzhov, Oleg S.; Zhuk, Vladimir I.

270

Universal extremal statistics in a freely expanding Jepsen gas.  

PubMed

We study the extremal dynamics emerging in an out-of-equilibrium one-dimensional Jepsen gas of (N+1) hard-point particles. The particles undergo binary elastic collisions, but move ballistically in between collisions. The gas is initially uniformly distributed in a box [-L,0] with the "leader" (or the rightmost particle) at X=0 , and a random positive velocity, independently drawn from a distribution phi(V) , is assigned to each particle. The gas expands freely at subsequent times. We compute analytically the distribution of the leader's velocity at time t , and also the mean and the variance of the number of collisions that are undergone by the leader up to time t . We show that in the thermodynamic limit and at fixed time t>1 (the so-called "growing regime"), when interactions are strongly manifest, the velocity distribution exhibits universal scaling behavior of only three possible varieties, depending on the tail of phi(V) . The associated scaling functions are entirely different from the usual extreme-value distributions of uncorrelated random variables. In this growing regime the mean and the variance of the number of collisions of the leader up to time t increase logarithmically with t , with universal prefactors that are computed exactly. The implications of our results in the context of biological evolution modeling are pointed out. PMID:17677018

Bena, Ioana; Majumdar, Satya N

2007-05-01

271

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

272

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

PubMed

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

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

2013-01-01

273

Dissolved Nitrogen Measurements at Clarks Hill Reservoir, Georgia-South Carolina.  

National Technical Information Service (NTIS)

Several oxygen injection systems have been investigated to enhance the dissolved oxygen distribution in the withdrawal zone of a reservoir, thereby increasing the dissolved oxygen concentration in the downstream area. Additionally, oxygen injection could ...

D. H. Merritt D. Leggett

1981-01-01

274

A Dissolving Challenge  

NSDL National Science Digital Library

In this activity, students add objects and substances to carbonated water to discover that added objects also increase the rate dissolved gas comes out of solution. Students are then challenged to make a lemon soda that retains as much carbonation as possible by using carbonated water, sugar, and lemon juice. There is a downloadable activity sheet that will be very helpful to educators, and will help students stay on track. An assessment sheet is also available on the activity page to keep track of students progress. There is also a step by step guide as to how to perform the experiment, and how to introduce it t the students.

Kessler, James; Galvan, Patti

2010-01-01

275

Turbulent Rayleigh-Benard convection with freely moving boundary  

NASA Astrophysics Data System (ADS)

In thermal convection, coherent flow structures emerge at high Rayleigh numbers as a result of intrinsic hydrodynamic instability and self-organization. They range from small-scale thermal plumes that are produced near both the top and the bottom boundaries to large-scale circulations across the entire convective volume. These flow structures exert viscous forces upon any boundary. Such forces will affect a boundary which is free to deform or change position. In our experiment, we study the dynamics of a free boundary that floats on the upper surface of a convective fluid. This seemingly passive boundary is subjected solely to viscous stress underneath. However, the boundary thermally insulates the fluid, modifying the bulk flow. As a consequence, the interaction between the free boundary and the convective fluid results in rich dynamics including periodic evolution of thr flow structures and predictable motions of the free boundary. Here I present two sets of experiments on thermal convection with freely moving top boundary. The first experiment is conducted in a rectangular geometry. We discover that as the sizes of the free boundary increases, the convection system transits from a nearly-periodic oscillation state into a local trapped state. A phenomenological numerical model explains this dynamcal transition. The second set of experiment is conducted in an annular geometry, where a periodic boundary condition is satisfied for both the flow structures and the free boundary. In a long time scale, persistent rotations of the free boundary along the circular path inside the convection cell are observed. In short time scales, the free boundary rotates in a hopping fashion. Consequently, through temperature distribution measurements, we observe the regular evolutions of the flow patterns in the convective fluid.

Zhong, Jin-Qiang

276

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

277

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

278

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...

279

Selective Isolation of Dissolved Organic Matter from Aquatic Systems.  

National Technical Information Service (NTIS)

A chromatographic ion-exchange procedure for fractionation, isolation and concentration of dissolved organic matter (DOM) in surface waters was developed and applied to samples from Illinois lakes. Recoveries of DOM from five humic-containing (colored) su...

J. R. Tuschall G. George

1984-01-01

280

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 ...

281

Determination of free copper concentrations in natural waters by using supported liquid membrane extraction under equilibrium conditions.  

PubMed

A method is described for measurement of freely dissolved copper concentrations in natural water samples using supported liquid membrane (SLM) extraction under equilibrium conditions, a technique denoted "equilibrium sampling through membranes" (ESTM). For this purpose, 1,10-dibenzyl-1,10-diaza-18-crown-6 as neutral carrier and oleic acid were used in the membrane phase. The main variables optimised were the carrier used to form the metal complexes, the organic solvent used in the membrane, the countercation, pH, the ligand used in the acceptor phase, the extraction time, and the flow rate of the donor phase. After the optimisation process an enrichment factor of 18.5 was obtained. Equilibrium conditions were reached after extraction for 60 min if a flow rate of 1.0 mL min(-1) or greater was used. When different ligands such as humic acids, phthalic acid, and EDTA were added to the sample solution, and sample pH ranged from 6 to 8, the results obtained for freely dissolved copper concentrations were in a good agreement with results from speciation calculations performed with Visual Minteq V 2.30, Cheaqs V L20.1, and WinHumic V. The developed technique was applied to analysis of stream and leachate water. PMID:15759138

Romero, Roberto; Jönsson, Jan Ake

2005-04-01

282

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

PubMed

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

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

2012-03-15

283

Fast dissolving films made of maltodextrins  

Microsoft Academic Search

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

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

2008-01-01

284

Method of dissolving organic filter cake  

Microsoft Academic Search

A method of dissolving a polysaccharide-containing filter cake present in a subterranean formation is described, comprising: injecting an effective amount of a treatment fluid comprising a water soluble source of fluoride ions present in an amount sufficient to provide a molar concentration of from about 0.01 to about 0.5 and a source of hydrogen ions present in an amount sufficient

K. H. Hollenbeck; L. R. Norman

1989-01-01

285

Method for dissolving delta-phase plutonium  

Microsoft Academic Search

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

Karraker

1992-01-01

286

Method for dissolving delta-phase plutonium  

Microsoft Academic Search

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

Karraker; David G

1992-01-01

287

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

SciTech Connect

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

Orians, K.J.; Bruland, K.W. (Univ. of California, Santa Cruz (USA))

1988-12-01

288

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

289

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

290

ICPP custom dissolver explosion recovery  

Microsoft Academic Search

This report discusses the recovery from the February 9, 1991 small scale explosion in a custom processing dissolver at the Idaho Chemical Processing Plant. Custom processing is a small scale dissolution facility which processes nuclear material in an economical fashion. The material dissolved in this facility was uranium metal, uranium oxides, and uranium\\/fissium alloy in nitric acid. The paper explained

R. Demmer; R. Hawk

1992-01-01

291

Differential pressure experiment to probe hole growth in freely standing polymer films  

NASA Astrophysics Data System (ADS)

We have developed a sensitive experiment which allows the measurement of the growth of holes in thin freely standing polystyrene (PS) films at elevated temperatures. In the experiment, a constant small pressure difference is applied and maintained across the freely standing film, and the formation and growth of holes is detected as a flow of air through the film. From measurements of freely standing PS films for which the glass transition temperature Tg is equal to the bulk value Tgbulk, as well as for films that are sufficiently thin that Tg is 30 °C less than Tgbulk, we find that substantial chain mobility occurs only at temperatures that are comparable to Tgbulk. The results can be interpreted as a shear thinning effect, which is consistent with previous optical microscopy measurements of hole growth in freely standing PS films.

Roth, C. B.; Nickel, B. G.; Dutcher, J. R.; Dalnoki-Veress, K.

2003-05-01

292

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

293

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

National Technical Information Service (NTIS)

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

O. D. Velev

2004-01-01

294

Quantitative studies of the wakes of freely flying birds in a low-turbulence wind tunnel  

NASA Astrophysics Data System (ADS)

A novel application of DPIV methods is presented for measuring velocity and vorticity distributions in vertical cross sections through the wake of a freely flying bird (thrush nightingale) in a wind tunnel. A dual-camera system is used, and successive cross-correlation operations remove lens/camera distortions, and then the undisturbed background flow, so that the final operation simply examines the disturbance effect of the bird alone. The concentration and tuning of processing methods to the disturbance quantities allows full exploitation of the correlation calculation and estimation algorithms. Since the ultimate objective is to deduce forces and power requirements on the bird itself from the wake structure, the analytical procedure is followed through an example on a fixed airfoil, before sample results from extensive bird flight tests are described. The wake structure of the thrush nightingale in slow (5-m/s) flight is qualitatively quite similar to those previously described in the literature, but certain quantitative details are different in important respects.

Spedding, G. R.; Hedenström, A.; Rosén, M.

2003-02-01

295

Revised Procedure for Converting Total Recoverable Water Quality Criteria for Metals to Dissolved Criteria.  

National Technical Information Service (NTIS)

The correct conversion factor should include an additional factor which is the ratio of the acidification concentration to the total recoverable concentration. This factor when multiplied by the ratio of the dissolved concentration to the acidification co...

1995-01-01

296

Method of dissolving organic filter cake  

SciTech Connect

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

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

1989-03-07

297

Kinetics and equilibrium of dissolved oxygen adsorption on activated carbon  

Microsoft Academic Search

The macroscopic adsorption behavior of dissolved oxygen on a coconut shell-derived granular activated carbon has been studied in batch mode at 301 and 313K for initial dissolved oxygen concentrations of 10–30mg\\/l and oxygen\\/carbon ratios of 2–180mg\\/g. BET (Brunauer, Emmett, and Teller) surface area, micropore volume, and pore size distribution were determined from N2 isotherm data for fresh and used samples

Vassileios M. Matsis; Helen P. Grigoropoulou

2008-01-01

298

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

299

Characterization of Urban Runoff Pollution between Dissolved and Particulate Phases  

PubMed Central

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.

Wei, Zhang; Simin, Li; Fengbing, Tang

2013-01-01

300

Hypolimnetic Dissolved-Oxygen Dynamics within Selected White River Reservoirs, Northern Arkansas-Southern Missouri, 1974-2008.  

National Technical Information Service (NTIS)

Dissolved oxygen is a critical constituent in reservoirs and lakes because it is essential for metabolism by all aerobic aquatic organisms. In general, hypolimnetic temperature and dissolved-oxygen concentrations vary from summer to summer in reservoirs, ...

J. L. De Lanois W. R. Green

2011-01-01

301

Predicting Diel Dissolved Oxygen Dynamics in the Carson River, Nevada  

NASA Astrophysics Data System (ADS)

The Carson River originates in eastern Alpine County California, flows northeast into western Nevada through Carson City, and terminates in the Carson Sink. Elevated nutrient levels from agricultural return flows allow for excess attached algal (periphyton) growth. Periods of low flow, coupled with an abundance of periphyton, harbor an environment capable of producing dissolved oxygen concentrations less than 5 mg L-1. Algal biomass sampling, water quality constituent sampling, and YSI Sonde deployments were performed during low flow months of 2003 and 2004 to investigate dissolved oxygen dynamics and relative amounts of periphyton present in a 33 kilometer reach of the Carson River. A significantly augmented version of the Water Quality Analysis and Simulation Program (WASP5) was calibrated and verified. Preliminary results from this version of WASP5 track observed periphyton biomass and dissolved oxygen data fairly consistently throughout both the temporal and spatial model domains. Dissolved oxygen calibration was constrained through the use of observed periphyton biomass, water quality constituents, and temperature data. Finally, the calibrated input file will also be used as an input file for an updated version of the EPA water quality model, WASP7, and a comparison of the simulated periphyton biomass and dissolved oxygen dynamics from these models will be accomplished. The uniqueness of this study stems from the coupling of algal biomass, water quality constituents, temperature, dissolved oxygen field data and the comparison of results from two water quality simulation models, in order to understand the underlying reasons for observed dissolved oxygen variations.

Latham, Z. B.; Warwick, J. J.; Fritsen, C. H.

2005-12-01

302

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

303

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

PubMed

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

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

2010-08-11

304

Friction-based stabilization of juxtacellular recordings in freely moving rats  

PubMed Central

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

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

2012-01-01

305

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

306

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

PubMed

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

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

2013-04-01

307

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

308

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

USGS Publications Warehouse

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

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

2003-01-01

309

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

310

Science Shorts: The Dynamics of Dissolving  

NSDL National Science Digital Library

Dissolving is as much about the substance doing the dissolving (the solvent) as it is about the substance being dissolved (the solute). Dissolving depends on the interaction between the molecules of solvents and solutes. This article looks at the molecular structure of water, the universal solvent and includes a corresponding activity.

Kessler, James; Galvan, Patti

2006-02-01

311

Interactions Among Dissolved Nitrogen, Phosphate, and Dissolved Oxygen at Several Sites in Chesapeake Bay in 2000  

NSDL National Science Digital Library

We looked at the correlation between dissolved oxygen and two water quality variables: dissolved nitrogen and dissolved phosphorus. We thought that, if dissolved oxygen were highly correlated with dissolved nitrogen (for example), then that would imply that dissolved nitrogen was limiting or otherwise important at that site. Likewise for dissolved phosphorus. We found that different sites in the bay had different levels of correlation, but there was no spatial pattern to the data.

Charlie Hunter (Southwestern College;); Sarah Kenick (University of New Hampshire;); Brian White (University of Massachusettes ;); ;

2006-06-18

312

Dynamics of dissolved organic nitrogen in subalpine Castle Lake, California  

Microsoft Academic Search

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

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

1988-01-01

313

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

EPA Science Inventory

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

314

The relationship between chromophoric dissolved organic matter and dissolved organic carbon in the European Atlantic coastal area and in the West Mediterranean Sea (Gulf of Lions)  

Microsoft Academic Search

The absorption coefficient of chromophoric dissolved organic matter (aCDOM) has been found to be correlated with fluorescence emission (excitation at 355 nm). In the coastal European Atlantic area and in the Western Mediterranean Sea (Gulf of Lions), a significant statistical dependence has been found between aCDOM and fluorescence with dissolved organic carbon (DOC) concentration. The relationship shows that, in the

Giovanni M. Ferrari

2000-01-01

315

A Small, Dilute-Cytoplasm, High-Affinity, Novel Bacterium Isolated by Extinction Culture and Having Kinetic Constants Compatible with Growth at Ambient Concentrations of Dissolved Nutrients in Seawater  

PubMed Central

Dilutions of raw seawater produced a bacterial isolate capable of extended growth in unamended seawater. Its 2.9-Mb genome size and 40-fg dry mass were similar to values for many naturally occurring aquatic organotrophs, but water and DNA comprised a large portion of this small chemoheterotroph, as compared to Escherichia coli. The isolate used only a few aromatic hydrocarbons and acetate, and glucose and amino acid incorporation were entirely absent, although many membrane and cytoplasmic proteins were inducible; it was named Cycloclasticus oligotrophus. A general rate equation that incorporates saturation phenomena into specific affinity theory is derived. It is used to relate the kinetic constants for substrate uptake by the isolate to its cellular proteins. The affinity constant KA for toluene was low at 1.3 ?g/liter under optimal conditions, similar to those measured in seawater, and the low value was ascribed to an unknown slow step such as limitation by a cytoplasmic enzyme; KA increased with increasing specific affinities. Specific affinities, a°s, were protocol sensitive, but under optimal conditions were 47.4 liters/mg of cells/h, the highest reported in the literature and a value sufficient for growth in seawater at concentrations sometimes found. Few rRNA operons, few cytoplasmic proteins, a small genome size, and a small cell size, coupled with a high a°s and a low solids content and the ability to grow without intentionally added substrate, are consistent with the isolation of a marine bacterium with properties typical of the bulk of those present.

Button, D. K.; Robertson, Betsy R.; Lepp, Paul W.; Schmidt, Thomas M.

1998-01-01

316

Comparison of SLN-evoked swallows during rest and chewing in the freely behaving rabbit  

Microsoft Academic Search

Interactions between the swallowing central neural pathway and the chewing central neural pathway were examined in freely behaving, unanesthetized rabbits. Pharyngeal swallows were elicited by electrical stimulation of the superior laryngeal nerve (SLN) and defined by thyrohyoid muscle (TH) activity in the electromyogram (EMG). Recordings were obtained from rabbits at rest and during chewing. The number of swallows elicited by

Masamichi Takagi; Tadashi Noda; Yoshiaki Yamada

2002-01-01

317

Amplification of light in a linear chain of freely expanding plasma spheres  

Microsoft Academic Search

An analysis is made of the amplification of light in a linear chain of freely expanding plasma spheres. It is shown that an optimal distribution of these spheres on a straight line ensures more effective amplification of light due to transitions in hydrogen-like ions in the case of recombination pumping of such a system than the amplification that can be

A V Borovski?; V V Korobkin; V B Mokrov; Ch K Mukhtarov

1989-01-01

318

Freely accessible water does not decrease consumption of ethanol liquid diets  

Microsoft Academic Search

In experimental studies, liquid ethanol diets are usually given as the sole source of nutrition and fluid. Two series of experiments were conducted to examine the effect of freely accessible water on the consumption of ethanol liquid diets in male Long–Evans rats. The consumption of diets and subsequent learning ability of rats were first examined in animals given twice-daily saline

NancyEllen C de Fiebre; Christopher M de Fiebre

2003-01-01

319

A multichannel system for recording and analysis of cortical field potentials in freely moving rats  

Microsoft Academic Search

A system has been developed to record and analyze the cortical electrical activity from 16 different sites in freely moving rats. The hardware includes a 16-channel amplifier system whose high input impedance, low noise, small size, light weight and shielded multistrand connecting cable allow high quality multichannel recording of field potentials. The software developed for this system consists of data

Fu-Zen Shaw; Ruei-Feng Chen; Hen-Wai Tsao; Chen-Tung Yen

1999-01-01

320

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

321

State of Coral Reef Ecosystems of the United States and Pacific Freely Associated States: 2008.  

National Technical Information Service (NTIS)

This report is the third in an ongoing series of assessments of the condition of coral reef ecosystems in the United States and Pacific Freely Associated states, and the second report to focus specifically on summarizing the results of coral reef ecosyste...

A. M. Clarke J. E. Waddell

2008-01-01

322

METABOLIC RATES OF FREELY DIVING WEDDELL SEALS: CORRELATIONS WITH OXYGEN STORES, SWIM VELOCITY AND DIVING DURATION  

Microsoft Academic Search

Summary The metabolic rates of freely diving Weddell seals were measured using modern methods of on-line computer analysis coupled to oxygen consumption instrumen- tation. Oxygen consumption values were collected during sleep, resting periods while awake and during diving periods with the seals breathing at the surface of the water in an experimental sea-ice hole in Antarctica. Oxygen consumption during diving

MICHAEL A. CASTELLINI; GERALD L. KOOYMAN

323

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

NASA Astrophysics Data System (ADS)

Molecular level characterizations of dissolved lignin were conducted in Mississippi River plume waters to study the impact of various removal mechanisms (photooxidation, microbial degradation, and flocculation) on dissolved organic material (DOM) concentrations and compositions. Prior to analysis, dissolved (<0.2-?m pore size) samples were size fractionated by ultrafiltration into high molecular weight (HMW; >1 kDalton) and low molecular weight (LMW; <1 kDalton) components. At salinities <25 psu, flocculation and microbial degradation were the primary factors affecting lignin concentrations. At salinities >25 psu, photooxidation was a dominant factor influencing lignin compositions and concentrations. Diagnostic indicators of photooxidation include a sharp decrease in the percentage of lignin in the HMW size fraction, changes in ratios of syringyl to vanillyl phenols, and increases in LMW acid:aldehyde ratios for both vanillyl and syringyl phenols. A 10-day incubation experiment with plume water indicated rates of microbial degradation of dissolved lignin that were ˜30% of photooxidation rates in surface waters. These results highlight the importance of microbial as well as photochemical processes in the cycling of terrigenous DOM in coastal waters. Neither flocculation nor microbial degradation significantly altered lignin composition, suggesting that composition is primarily determined by source and photochemical transformation. Overall, high removal rates indicate the potential importance of terrigenous DOM as a carbon and nutrient source in the coastal ocean. Strong correlations between absorption coefficients at 350 nm and dissolved lignin demonstrate the potential for using absorption to trace terrigenous DOM in coastal environments with significant riverine input.

Hernes, Peter J.; Benner, Ronald

2003-09-01

324

ICPP custom dissolver explosion recovery  

Microsoft Academic Search

This paper discusses the recovery from the February 9, 1991, small scale explosion in a custom processing dissolver at the Idaho Chemical Processing Plant (ICPP) a Department of Energy facility at the Idaho National Engineering Laboratory. The custom processing facility is a limited production area designed to recover unirradiated uranium fuel. A small amount of the nuclear material received and

R. Demmer; R. Hawk

1992-01-01

325

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...

326

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

327

Manual for Dissolved Oxygen Analysis.  

National Technical Information Service (NTIS)

Three methods covering the determination of dissolved oxygen in seawater are given. Depending upon the method used, accuracies on the order of 0.5 ppb to 5 ppb are possible. Seawater samples are analyzed by an optimized Winkler procedure. Reagents used, t...

H. C. Edgington

1971-01-01

328

Optimization of Dissolved Oxygen Measurements.  

National Technical Information Service (NTIS)

The report describes the work that was carried out in the optimization of dissolved oxygen (DO) measurements. The purpose was to evaluate the effect of the various parameters affecting the precision and accuracy of the Winkler method and to develop an opt...

H. C. Edgington

1971-01-01

329

Geochemistry of dissolved trace metals (cadmium, copper, zinc) in the Scheldt estuary, southwestern Netherlands: Impact of seasonal variability  

Microsoft Academic Search

The distribution of dissolved Cd, Cu, and Zn in the Scheldt estuary has been studied during eight axial surveys, carried out between February 1987 and February 1988. The observed metal-salinity profiles depend on the season. During spring and summer, when the river water is anoxic (containing traces of dissolved sulfide), the dissolved metal concentrations in the riverine endmember are extremely

John J. G. Zwolsman; Bert T. M. Van Eck; Cornelis H. Van Der Weijden

1997-01-01

330

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

Microsoft Academic Search

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

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

1999-01-01

331

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

332

Comparing the desorption and biodegradation of low concentrations of phenanthrene sorbed to activated carbon, biochar and compost.  

PubMed

Carbonaceous soil amendments are applied to contaminated soils and sediments to strongly sorb hydrophobic organic contaminants (HOCs) and reduce their freely dissolved concentrations. This limits biouptake and toxicity, but also biodegradation. To investigate whether HOCs sorbed to such amendments can be degraded at all, the desorption and biodegradation of low concentrations of (14)C-labelled phenanthrene (?5 ?g L(-1)) freshly sorbed to suspensions of the pure soil amendments activated carbon (AC), biochar (charcoal) and compost were compared. Firstly, the maximum abiotic desorption of phenanthrene from soil amendment suspensions in water, minimal salts medium (MSM) or tryptic soy broth (TSB) into a dominating silicone sink were measured. Highest fractions remained sorbed to AC (84±2.3%, 87±4.1%, and 53±1.2% for water, MSM and TSB, respectively), followed by charcoal (35±2.2%, 32±1.7%, and 12±0.3%, respectively) and compost (1.3±0.21%, similar for all media). Secondly, the mineralization of phenanthrene sorbed to AC, charcoal and compost by Sphingomonas sp. 10-1 (DSM 12247) was determined. In contrast to the amounts desorbed, phenanthrene mineralization was similar for all the soil amendments at about 56±11% of the initially applied radioactivity. Furthermore, HPLC analyses showed only minor amounts (<5%) of residual phenanthrene remaining in the suspensions, indicating almost complete biodegradation. Fitting the data to a coupled desorption and biodegradation model revealed that desorption did not limit biodegradation for any of the amendments, and that degradation could proceed due to the high numbers of bacteria and/or the production of biosurfactants or biofilms. Therefore, reduced desorption of phenanthrene from AC or charcoal did not inhibit its biodegradation, which implies that under the experimental conditions these amendments can reduce freely dissolved concentration without hindering biodegradation. In contrast, phenanthrene sorbed to compost was fully desorbed and biodegraded. PMID:22921652

Marchal, Geoffrey; Smith, Kilian E C; Rein, Arno; Winding, Anne; Trapp, Stefan; Karlson, Ulrich G

2013-02-01

333

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

334

Speaking Freely  

ERIC Educational Resources Information Center

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

Watson, Jamal Eric

2012-01-01

335

Amylopectin as a subcoating material improves the acidic resistance of enteric-coated pellets containing a freely soluble drug.  

PubMed

The effect of an aqueous amylopectin subcoating on the acidic resistance and dissolution behaviour of enteric-coated pellets was studied. Freely water-soluble riboflavin sodium phosphate (RSP) was used as a model drug, and microcrystalline cellulose (MCC) and lactose as fillers in the pellet cores. The pellets were subcoated with 5% aqueous amylopectin solution or with 5% hydroxypropyl methylcellulose (HPMC) solution, and subsequently film-coated with aqueous dispersion of cellulose acetate phthalate (CAP). Drug release of enteric-coated pellets was investigated by confocal laser scanning microscopy (CLSM). Dissolution tests showed that amylopectin subcoating improved the acidic resistance of the enteric-coated pellets in 0.1 N hydrochloric acid (HCl) compared with HPMC subcoating. As the amylopectin subcoating load was increased to 4% and the aqueous CAP coating load to 35%, the coated pellets resisted in 0.1 N HCl solution for approximately 1 h (the amount of drug released was below 10%), and they dissolved in the SIF without enzymes in less than 10 min. Confocal microscopy images and profiles of mean fluorescence intensities of RSP (obtained in the range of the interface of the pellet core and the film and the film coating surface) showed consistent results with dissolution tests. It seems that amylopectin subcoating can prevent the influx of the dissolution medium into the pellet core, and thus decrease the premature dissolution and release of the drug from the enteric-coated pellets in 0.1 N HCl solution. The drug release mechanism appeared to be osmotically driven release, and followed by diffusion through the polymer film. PMID:11879742

Guo, H X; Heinämäki, J; Yliruusi, J

2002-03-20

336

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

337

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.

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

2012-01-01

338

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...

339

The mechanisms of dissolved solids transport in flysch drainage basins  

Microsoft Academic Search

The transformation of precipitation input into runoff is accompanied by a continuous change in the chemical properties of water involved in the water circulation cycle. These range from slightly acid precip­ itation water, through neutral stream water to alkaline underground waters. The relationship between discharge and total dissolved solids concentration conforms to a curved regression equation, in the form y

W. FROEHLICH

340

Separation of oil from water by dissolved air flotation  

Microsoft Academic Search

Synthetic industrial effluent was prepared by stabilising low concentrations of oil (Catenex 11, Shell, UK) in aqueous dispersion with a non-ionic surfactant (Span 20) and dissolved air flotation (DAF) was used to clarify this wastewater. Operating parameters including saturator pressure, recycle ratio, and air to oil ratio, were investigated to find conditions that would enhance the efficiency of the DAF

A. A Al-Shamrani; A James; H Xiao

2002-01-01

341

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...

342

Adaptive dissolved oxygen control based on dynamic structure neural network  

Microsoft Academic Search

Activated sludge wastewater treatment processes (WWTPs) are difficult to control because of their complex nonlinear behavior. In this paper, an adaptive controller based on a dynamic structure neural network (ACDSNN) is proposed to control the dissolved oxygen (DO) concentration in a wastewater treatment process (WWTP). The proposed ACDSNN incorporates a structure variable feedforward neural network (FNN), where the FNN can

Hong-Gui Han; Jun-Fei Qiao

2011-01-01

343

U-shaped plastic optical fiber dissolved oxygen sensor  

Microsoft Academic Search

A dissolved oxygen sensor based on U-shape plastic optical fiber (POF) was described. Analyte-sensitive fluorophore are entrapped into ormosil film by using Sol-gel method. Phase modulation technique is used to measure fluorescence lifetime. The influence of oxygen indictor concentration, annealing time and U-shaped POF curve radius on the systems sensitivity is studied.

Haiwen Cai; Fenghong Chu; Ronghui Qu; Zujie Fang

2008-01-01

344

A polarographic method for measuring dissolved nitric oxide  

Microsoft Academic Search

A polarographic method for measuring the concentration of authentic nitric oxide (NO) in aqueous solutions is described. When solutions of NO were injected into aqueous solutions containing dissolved oxygen, NO reacted with oxygen to give nitrite. The amount of nitrite formed in this reaction (analyzed by capillary electrophoresis) was compared with the amount of oxygen consumed (measured by polarography). We

B. O Jensen; J Skeidsvoll; H Holmsen

1997-01-01

345

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...

346

REDUCED DISSOLVED OXYGEN TEST SYSTEM FOR MARINE ORGANISMS  

EPA Science Inventory

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

347

Dissolved gas concentrations of the geothermal fluids in Taiwan  

Microsoft Academic Search

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,

Ai-Ti Chen; Tsanyao Frank Yang

2010-01-01

348

Effects of Phytoplankton on Dissolved Oxygen Concentration in Catfish Ponds.  

National Technical Information Service (NTIS)

Dense populations of blue-green algae frequently develop in fish ponds at Auburn, Alabama, during windy weather in March and early April. Massive die-offs of the algae can be expected when surface scums form during prolonged periods of calm, clear, warm w...

C. E. Boyd E. Johnston C. S. Tucker R. Romaire J. Davis

1977-01-01

349

Measurement of Relative Dissolved Gas Concentrations Using Underwater Mass Spectrometry  

Microsoft Academic Search

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

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

2004-01-01

350

Thermodynamic properties of gases dissolved in electrolyte solutions.  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

351

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

PubMed Central

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.

2012-01-01

352

Coarse-grained dynamics of the freely cooling granular gas in one dimension.  

PubMed

We study the dynamics and structure of clusters in the inhomogeneous clustered regime of a freely cooling granular gas of point particles in one dimension. The coefficient of restitution is modeled as r(0)<1 or 1, depending on whether the relative speed is greater or smaller than a velocity scale ?. The effective fragmentation rate of a cluster is shown to rise sharply beyond a ?-dependent time scale. This crossover is coincident with the velocity fluctuations within a cluster becoming order ?. Beyond this crossover time, the cluster-size distribution develops a nontrivial power-law distribution, whose scaling properties are related to those of the velocity fluctuations. We argue that these underlying features are responsible for the recently observed nontrivial coarsening behavior in the one-dimensional freely cooling granular gas. PMID:22060364

Shinde, Mahendra; Das, Dibyendu; Rajesh, R

2011-09-01

353

Chronic, wireless recordings of large-scale brain activity in freely moving rhesus monkeys.  

PubMed

Advances in techniques for recording large-scale brain activity contribute to both the elucidation of neurophysiological principles and the development of brain-machine interfaces (BMIs). Here we describe a neurophysiological paradigm for performing tethered and wireless large-scale recordings based on movable volumetric three-dimensional (3D) multielectrode implants. This approach allowed us to isolate up to 1,800 neurons (units) per animal and simultaneously record the extracellular activity of close to 500 cortical neurons, distributed across multiple cortical areas, in freely behaving rhesus monkeys. The method is expandable, in principle, to thousands of simultaneously recorded channels. It also allows increased recording longevity (5 consecutive years) and recording of a broad range of behaviors, such as social interactions, and BMI paradigms in freely moving primates. We propose that wireless large-scale recordings could have a profound impact on basic primate neurophysiology research while providing a framework for the development and testing of clinically relevant neuroprostheses. PMID:24776634

Schwarz, David A; Lebedev, Mikhail A; Hanson, Timothy L; Dimitrov, Dragan F; Lehew, Gary; Meloy, Jim; Rajangam, Sankaranarayani; Subramanian, Vivek; Ifft, Peter J; Li, Zheng; Ramakrishnan, Arjun; Tate, Andrew; Zhuang, Katie Z; Nicolelis, Miguel A L

2014-06-01

354

Dual-modal (OIS/LSCI) imager of cerebral cortex in freely moving animals  

NASA Astrophysics Data System (ADS)

Optical intrinsic signals (OIS) and laser speckle contrast imaging (LSCI) have been used for years in the study of the cerebral blood flow (CBF) and hemodynamic responses to the neural activity under functional stimulation. So far, most in vivo rodent experiments are based on the anesthesia model when the animals are in unconscious and restrained conditions. The influences of anesthesia on the neural activity have been documented in literature. In this study, we designed a miniature head-mounted dual-modal imager in freely moving animals that could monitor in real time the coupling of local oxygen consumption and blood perfusion of CBF by integrating different imaging modalities of OIS and LSCI. The system facilitates the study the cortical hemodynamics and neural-hemodynamic coupling in real time in freely moving animals.

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

2011-11-01

355

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

PubMed

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

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

2013-01-01

356

2D Brownian motion of inclusions in low pressure environment on freely suspended liquid crystal film  

NASA Astrophysics Data System (ADS)

The homogeneous freely suspended fluid SmA liquid crystal film of several nanometer thickness provides a very good system for studying 2D hydrodynamics. Using microscope and high-speed camera, we track the motion of inclusions of about 2-20?m in diameter that doing Brownian motion on the film. We report 2D Brownian motion experiment of drops in different air pressure environment. We found that at ambient pressure, the Hughes, Pailthorpe, and White (HPW) theory can perfectly predict the diffusion coefficient of those inclusions, while under low pressure when the mean free path of the air molecules is comparable with the size of inclusions, the HPW theory fails. We propose a model, based on freely diffused air molecules with Maxwell distribution, to explain the elevated diffusion coefficient in low pressure.

Qi, Zhiyuan; Park, Cheol; Maclennan, Joseph; Glaser, Matthew; Clark, Noel

2013-03-01

357

External optical imaging of freely moving mice with green fluorescent protein-expressing metastatic tumors  

NASA Astrophysics Data System (ADS)

We report here a new approach to genetically engineering tumors to become fluorescence such that they can be imaged externally in freely-moving animals. We describe here external high-resolution real-time fluorescent optical imaging of metastatic tumors in live mice. Stable high-level green flourescent protein (GFP)-expressing human and rodent cell lines enable tumors and metastasis is formed from them to be externally imaged from freely-moving mice. Real-time tumor and metastatic growth were quantitated from whole-body real-time imaging in GFP-expressing melanoma and colon carcinoma models. This GFP optical imaging system is highly appropriate for high throughput in vivo drug screening.

Yang, Meng; Baranov, Eugene; Shimada, Hiroshi; Moossa, A. R.; Hoffman, Robert M.

2000-04-01

358

Head fixed field coil system for measuring eye movements in freely moving monkeys.  

PubMed

Coil systems have been a standard for measuring eye movements since they were first introduced. These systems, which have been designed to work at low frequencies (20 KHz), generally require large field coils so that a uniform field can be established at the eye coil site. This configuration makes it virtually impossible to study eye movements in freely moving animals. In this paper, we describe the design of a coil system, which operates at radio frequencies (10 MHz). This system allows the use of compact coils with radii of 10 mm that are capable of accurately measuring eye movements in three dimensions during head free locomotion. This system opens the possibility for studying eye movements in freely moving monkeys under a wide range of conditions. PMID:17946708

Ogorodnikov, Dmitri; Tarasenko, Sergey; Yakushin, Sergei; Cohen, Bernard; Raphan, Theodore

2006-01-01

359

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

NASA Astrophysics Data System (ADS)

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 that the ecosystem in the South China Sea may be limited by bioavailable nitrogen or some trace nutrient rather than DIP. Nutrient enrichment experiments using either nitrate, phosphate or both indicate that nitrogen limits the net growth of phytoplankton in the South China Sea, at least during March and July 2000. The fixed nitrogen limitation may result from the excess phosphate (N:P<16) transported into the South China Sea from the North Pacific relative to microbial population needs, or from iron control of nitrogen fixation. The iron-limited nitrogen fixation hypothesis is supported by the observation of low population densities of Trichodesmium spp. (<48 × 103 trichomes/m3), the putative N2 fixing cyanobacterium, and with low concentrations of dissolved iron (˜0.2-0.3 nM) in the South China Sea surface water. Our results suggest that nitrogen fixation can be limited by available iron even in regions with a high rate of atmospheric dust deposition such as in the South China Sea.

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

2003-03-01

360

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

361

Ecosystem Modulation of Dissolved Carbon Age in a Temperate Marsh-Dominated Estuary  

Microsoft Academic Search

We measured the concentrations and isotopic values (? 14C and d 13C) of dissolved inorganic, dissolved organic, and particulate organic carbon (DIC, DOC, and POC, respectively) in the Parker River watershed and estuary in Massachusetts, USA, to determine the age of carbon (C) entering the estuary and how estuarine processing affects the quantity and apparent age of C transported to

Peter A. Raymond; Charles S. Hopkinson

2003-01-01

362

UNDERSTANDING AND MANAGING RISKS POSED BY BRINES CONTAINING DISSOLVED CARBON DIOXIDE  

EPA Science Inventory

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

363

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...

364

Distribution of chromophoric dissolved organic matter in the North Atlantic: Implications for biogeochemistry and tracer studies  

Microsoft Academic Search

Chromophoric dissolved organic material (CDOM), the colored fraction of the dissolved organic material (DOM) pool, is a highly dynamic property found throughout the open ocean. Most CDOM found away from continental margins is of open ocean origin and is not derived from riverine input or coastal runoff. CDOM is an optical property; hence, its concentration can be easily detected over

N. B. Nelson; D. A. Siegel; C. A. Carlson; J. Klamberg; S. J. Goldberg; C. Swan

2004-01-01

365

URINE RELEASE IN FREELY MOVING CATHETERISED LOBSTERS (HOMARUS AMERICANUS) WITH REFERENCE TO FEEDING AND SOCIAL ACTIVITIES  

Microsoft Academic Search

Previous studies suggest that urine-borne pheromones play an important role in lobster agonistic and sexual behaviour. This paper investigates the pattern of urine release in catheterised, but otherwise freely moving, adult lobsters with respect to feeding, social and non-social activities. Lobsters on average released 4.1 ml (1 % of body mass) of urine over a 12 h period; this more

THOMAS BREITHAUPT; DANIEL P. LINDSTROM; JELLE ATEMA

1999-01-01

366

Quantitative studies of the wakes of freely flying birds in a low-turbulence wind tunnel  

Microsoft Academic Search

A novel application of DPIV methods is presented for measuring velocity and vorticity distributions in vertical cross sections\\u000a through the wake of a freely flying bird (thrush nightingale) in a wind tunnel. A dual-camera system is used, and successive\\u000a cross-correlation operations remove lens\\/camera distortions, and then the undisturbed background flow, so that the final operation\\u000a simply examines the disturbance effect

G. R. Spedding; A. Hedenström; M. Rosén

2003-01-01

367

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

368

Diffusion of a freely water-soluble drug in aqueous enteric-coated pellets  

Microsoft Academic Search

The effects of filler used in the pellet cores (ie, waxy cornstarch or lactose) and the enteric film coat thickness on the\\u000a diffusion and dissolution of a freely soluble drug were studied. Two kinds of pellet cores containing riboflavin sodium phosphate\\u000a as a model drug, microcrystalline cellulose (MCC) as a basic filler, and waxy cornstarch or lactose as a cofiller

HX Guo; J Heinämäki; J Yliruusi

2002-01-01

369

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

370

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

371

A procedure for recording electroretinogram and visual evoked potential in freely moving cats.  

PubMed

A procedure for recording the electroretinogram (ERG) and the visual evoked potential (VEP) in freely moving cats was developed and used to test the visual toxicity of nalidixic acid. The electrodes for recording the ERG and VEP were implanted chronically in the sclera of the eye and on the surface of the visual cortex, respectively. Both the ERG and VEP were simultaneously recorded in freely moving cats using a slip ring that allows the cat to move freely without twisting the cables. After a 15-min dark-adaptation period, 20 responses to repetitive photic stimulation with an intensity of 2 joules and a 10-sec interstimulus interval were averaged by means of a minicomputer. The waveform of the ERG consisted of a negative wave (a-wave) followed by a positive wave (b-wave) with 2 to 3 oscillatory potentials on the rising slope. The VEP consisted of initial positive wave (P1 wave) followed by a negative wave (N1 wave) and late positive and negative deflections. The amplitude of the components of the ERG and VEP varied considerably from animal to animal, whereas within the same animal they were very stable. Using this technique, the effects of nalidixic acid, a retinotoxic compound, on the ERG and VEP were studied. Nalidixic acid produced a marked, but transient, decrease in the amplitude of the ERG b-wave after a single intravenous injection at a dose of 10 mg/kg. After repeated doses at 40 mg/kg/day for 2 weeks, the reduction in the amplitude of the b-wave was stronger, but remained transient. Upon ophthalmologic and histopathologic examination of the retina, no abnormalities indicating visual toxicity were observed. These results indicate that this procedure for recording the ERG and VEP is useful for evaluating the visual toxicity of drugs in freely moving cats. PMID:2082023

Imai, R; Sugimoto, S; Ando, T; Sato, S

1990-11-01

372

Effect of dissolved gas on bubble nucleation  

Microsoft Academic Search

Experiments studying the extinction of a gas bubble in a liquid droplet and the possibility of bubble formation in a droplet containing dissolved gas are used to investigate the effect of dissolved gas on liquid-gas phase transitions (boiling, caviation, etc.). The superheat limit of the liquid was studied using a technique in which a droplet containing a dissolved gas was

Y. Mori; K. Hijikata; T. Nagatani

1976-01-01

373

Methods for chronic neural recording in the telencephalon of freely behaving fish.  

PubMed

We have adapted for use in fish several of the procedures employed for recording single neuron activity in freely behaving rodents. Developing a method for single unit chronic recording in freely behaving fish was motivated by a need for a comparison across taxa of telencephalic neural activity evoked during spatial navigation by animals of their environments. However, the procedures outlined here can be modified easily for underwater recording from most aquatic species and from other brain areas. Under anesthesia, bundles of stereotrodes or tetrodes were implanted into the dorsolateral region of the goldfish or cichlid telencephalon. An infrared light emitting diode (LED) was also fixed to the fish's head at the time of surgery. After recovery from anesthesia, fish were allowed to swim freely within a large aquarium. Single unit activity was analyzed and correlated with stimulus conditions, behavior, and the location and movement of the LED recorded by a camera tracking system. The value of this technique is demonstrated by providing the first evidence in fish for navigation-related neural firing, including "place cells" that display location-specific discharge. PMID:14757353

Canfield, James G; Mizumori, Sheri J Y

2004-02-15

374

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.

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

2012-01-01

375

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

376

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

377

Simultaneous recording of hippocampal oxygen and glucose in real time using constant potential amperometry in the freely-moving rat.  

PubMed

Amperometric sensors for oxygen and glucose allow for real time recording from the brain in freely-moving animals. These sensors have been used to detect activity- and drug-induced changes in metabolism in a number of brain regions but little attention has been given over to the hippocampus despite its importance in cognition and disease. Sensors for oxygen and glucose were co-implanted into the hippocampus and allowed to record for several days. Baseline recordings show that basal concentrations of hippocampal oxygen and glucose are 100.26±5.76 ?M and 0.60±0.06 mM respectively. Furthermore, stress-induced changes in neural activity have been shown to significantly alter concentrations of both analytes in the hippocampus. Administration of O2 gas to the animals' snouts results in significant increases in hippocampal oxygen and glucose and administration of N2 gas results in a significant decrease in hippocampal oxygen. Chloral hydrate-induced anaesthesia causes a significant increase in hippocampal oxygen whereas treatment with the carbonic anhydrase inhibitor acetazolamide significantly increases hippocampal oxygen and glucose. These findings provide real time electrochemical data for the hippocampus which has been previously impossible with traditional methods such as microdialysis or ex vivo analysis. As such, these sensors provide a window into hippocampal function which can be used in conjunction with behavioural and pharmacological interventions to further elucidate the functions and mechanisms of action of the hippocampus in normal and disease states. PMID:23499196

Kealy, John; Bennett, Rachel; Lowry, John P

2013-04-30

378

Quantification of dissolved iron sources to the North Atlantic Ocean.  

PubMed

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

Conway, Tim M; John, Seth G

2014-07-10

379

Wormhole formation in dissolving fractures  

NASA Astrophysics Data System (ADS)

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 effects of flow rate, mineral dissolution rate, and geometrical properties of the fracture were investigated, and the optimal conditions for wormhole formation were determined.

Szymczak, P.; Ladd, A. J. C.

2009-06-01

380

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

381

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

382

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

PubMed

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

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

2012-11-28

383

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

384

Transient Dissolved Organic Carbon Through Soils  

NASA Astrophysics Data System (ADS)

Dissolved organic carbon (DOC) is an important constituent of soil solution that plays a role in many chemical and biological processes in soils; it is also an important energy source for bacteria in the soil ecosystem. Hydrology has a significant control on the transport and fate of dissolved organic carbon in the soil but mechanisms that affect said transport are not well understood. In particular, dynamic information on DOC transport through forest soils on short time scales (one or two precipitation event) is lacking at present. DOC is a very complex mix of organic compounds. A key to quantifying DOC dynamics is to establish useful approximations for behavior of this complex mixture. Biodegradable dissolved organic carbon (BDOC) is an important part of DOC. It is reported that between 12 and 44% of DOC released from the forest floor can be decomposed in solutions by indigenous microbes. In our study, we considered how DOC, BDOC, and flow interact in soil columns. In-situ soil cores with two different lengths were installed under a mixed deciduous canopy. The effects of artificial rain on DOC and BDOC transport were examined by dripping nano pure water amended with bromide on the top of soil cores and sampling the water collected at the bottom of the cores for DOC and BDOC. We used plug-flow biofilm reactors to measure the BDOC concentration. It is likely that reduced rates of decomposition in dry soils will cause microbial products of DOC to accumulate; hence DOC concentration should be high at the first flush of rain and decline as the event proceeds. The experimental results show the expected pattern, that is, the first samples we collected always had the highest DOC and BDOC concentrations. The concentrations tend to decline through the simulated precipitation event. Application of a second “storm” forty minutes after the cessation of the first application of water resulted in effluent DOC concentration increasing a small amount initially and then declining with time. A model based on a one-dimensional Richards’ equation coupled with reactive convection-dispersion equations and a heat transport model to characterize the temperature pattern along the core was developed to explore the experimental results mechanistically. Parameters for both the flow and transport models were selected using trial and error calibration first, and then refined using UCODE (USGS). The results show that the model can match the main features of the observed DOC and BDOC patterns under transient soil water flux conditions. These results indicate that future work to extend the model to two and three dimensions to describe hillslope and catchment processes is a reasonable goal, although additional processes (e.g. bacterial growth) will have to be incorporated to achieve an appropriate degree of realism.

Mei, Y.; Hornberger, G. M.; Kaplan, L. A.; Newbold, J. D.; Aufdenkampe, A. K.; Tsang, Y.

2009-12-01

385